feat: Phase 4 — CAS-based fork + mark-and-sweep GC

- Rewrite fork to create StateNode pointing to fork point (zero duplication)
- Rewrite GC as mark-and-sweep: roots from threads.json + history, findReachableHashes via refs[]
- Remove .data.jsonl code paths
- Fix all 7 previously failing CLI tests
- New: gc-mark-sweep.test.ts verifying shared nodes survive GC
- All 166 tests pass

Refs #155, closes #159

小橘 <xiaoju@shazhou.work>

CLAUDE.md

@@ -2,7 +2,7 @@
 
 ## Project Overview
 
-**@uncaged/workflow** is a workflow engine that executes single-file ESM bundles. Each workflow is a self-contained `.esm.js` file with an XXH64 hash as its version identifier.
+This monorepo implements a workflow engine that executes single-file ESM bundles. Each workflow is a self-contained `.esm.js` file with an XXH64 hash as its version identifier. Shared types live in `@uncaged/workflow-protocol`; bundle authors typically depend on `@uncaged/workflow-runtime`.
 
 ### Key Terms
 
@@ -19,14 +19,27 @@
 ```
 workflow/
   packages/
-    workflow/       # @uncaged/workflow — core lib (types, hash, ULID, JSONL, registry)
-    cli-workflow/   # @uncaged/cli-workflow — CLI (uncaged-workflow command)
+    workflow-protocol/              # @uncaged/workflow-protocol — shared types + Result
+    workflow-runtime/               # @uncaged/workflow-runtime — createWorkflow, type re-exports
+    workflow-util/                  # @uncaged/workflow-util — Base32, ULID, logger, storage paths, refs helpers
+    workflow-reactor/               # @uncaged/workflow-reactor — LLM fn + thread reactor (tool calls)
+    workflow-cas/                   # @uncaged/workflow-cas — CAS store, hash, Merkle
+    workflow-register/              # @uncaged/workflow-register — bundle validation, registry YAML, model resolution
+    workflow-execute/               # @uncaged/workflow-execute — engine, extract, fork, GC, workflowAsAgent
+    cli-workflow/                   # @uncaged/cli-workflow — uncaged-workflow CLI
+    workflow-agent-cursor/          # @uncaged/workflow-agent-cursor
+    workflow-agent-hermes/          # @uncaged/workflow-agent-hermes
+    workflow-agent-llm/             # @uncaged/workflow-agent-llm
+    workflow-util-agent/            # @uncaged/workflow-util-agent — buildAgentPrompt, spawnCli
+    workflow-template-develop/      # @uncaged/workflow-template-develop
+    workflow-template-solve-issue/  # @uncaged/workflow-template-solve-issue
+    workflow-dashboard/             # @uncaged/workflow-dashboard — React dashboard (private app)
   docs/             # RFCs, conventions
   biome.json        # root Biome config
   tsconfig.json     # root TypeScript config
 ```
 
-- `workflow` is the core; `cli-workflow` depends on it
+- Execution stack layers: `workflow-protocol` → (`workflow-runtime`, `workflow-util`, `workflow-reactor`) → (`workflow-cas`, `workflow-register`) → `workflow-execute` → `cli-workflow`
 - Packages use `workspace:*` protocol
 
 ## Language & Paradigm
@@ -167,10 +180,10 @@ type Result<T, E = Error> = { ok: true; value: T } | { ok: false; error: E };
 
 Never use `console.log/warn/error` directly — Biome's `noConsole` rule enforces this.
 
-All logging goes through the structured logger from `@uncaged/workflow`:
+All logging goes through the structured logger from `@uncaged/workflow-util`:
 
 ```typescript
-import { createLogger } from "@uncaged/workflow";
+import { createLogger } from "@uncaged/workflow-util";
 
 const log = createLogger();
 

docs/architecture.md

@@ -1,6 +1,6 @@
-# @uncaged/workflow — Architecture
+# Uncaged workflow — Architecture
 
-**Last updated:** 2026-05-06 by 小橘 🍊（NEKO Team）
+**Last updated:** 2026-05-09
 
 ---
 
@@ -8,72 +8,106 @@
 
 A workflow engine that executes single-file ESM bundles. Each workflow is a self-contained `.esm.js` file identified by its XXH64 hash (Crockford Base32). No daemon — processes start on demand and exit when done.
 
-## Package Structure
+The implementation lives in **15** Bun workspace packages under `packages/`, using the `workspace:*` protocol.
 
-| Package | npm Name | Purpose |
-|---------|----------|---------|
-| `workflow` | `@uncaged/workflow` | Core: types, engine, ExtractFn, hash/ULID/registry |
-| `cli-workflow` | `@uncaged/cli-workflow` | CLI: `uncaged-workflow` command |
-| `workflow-agent-cursor` | `@uncaged/workflow-agent-cursor` | Cursor CLI agent (extracts workspace from ctx) |
-| `workflow-agent-hermes` | `@uncaged/workflow-agent-hermes` | Hermes CLI agent |
-| `workflow-agent-llm` | `@uncaged/workflow-agent-llm` | OpenAI-compatible LLM agent |
-| `workflow-template-develop` | `@uncaged/workflow-template-develop` | Develop workflow template (roles in `src/roles/`) |
-| `workflow-template-solve-issue` | `@uncaged/workflow-template-solve-issue` | Solve-issue workflow template (roles in `src/roles/`) |
-| `workflow-util-agent` | `@uncaged/workflow-util-agent` | `buildAgentPrompt` + `spawnCli` utilities |
+## Package map
 
-Monorepo with **bun workspace**, `workspace:*` protocol.
+Grouped by responsibility (npm name → folder).
 
-## Core Types
+| Layer | Package | One-line role |
+|-------|---------|----------------|
+| Contract | `@uncaged/workflow-protocol` → `workflow-protocol` | Shared TypeScript types and `Result` helpers; peer `zod` only — no other workspace deps. |
+| Author API | `@uncaged/workflow-runtime` → `workflow-runtime` | `createWorkflow` and re-exports of protocol workflow types for bundle authors. |
+| Shared infra | `@uncaged/workflow-util` → `workflow-util` | Base32/ULID, logger, storage root paths, global CAS dir, ref-field helpers. |
+| LLM plumbing | `@uncaged/workflow-reactor` → `workflow-reactor` | `createLlmFn`, `createThreadReactor`, and related tool-call types for threaded LLM invocation. |
+| CAS | `@uncaged/workflow-cas` → `workflow-cas` | `CasStore` implementation, XXH64 hashing, Merkle helpers over CAS payloads. |
+| Registry / bundles | `@uncaged/workflow-register` → `workflow-register` | Bundle validation & dynamic export extraction, `workflow.yaml` registry I/O, provider/model resolution. |
+| Engine | `@uncaged/workflow-execute` → `workflow-execute` | Thread execution, worker entry path, fork/GC, extract pipeline, `workflowAsAgent`. |
+| CLI | `@uncaged/cli-workflow` → `cli-workflow` | `uncaged-workflow` binary (depends on engine, registry, CAS, protocol, util, runtime). |
+| Agent adapters | `@uncaged/workflow-agent-cursor` → `workflow-agent-cursor` | `AgentFn` via `cursor-agent` CLI + workspace extraction. |
+| | `@uncaged/workflow-agent-hermes` → `workflow-agent-hermes` | `AgentFn` via `hermes chat` CLI. |
+| | `@uncaged/workflow-agent-llm` → `workflow-agent-llm` | `AgentFn` via OpenAI-compatible HTTP (`LlmProvider` from runtime). |
+| Agent shared | `@uncaged/workflow-util-agent` → `workflow-util-agent` | `buildAgentPrompt`, `spawnCli` for CLI-backed agents. |
+| Templates | `@uncaged/workflow-template-develop` → `workflow-template-develop` | Develop workflow definition, roles, descriptor builder. |
+| | `@uncaged/workflow-template-solve-issue` → `workflow-template-solve-issue` | Solve-issue workflow definition, roles, descriptor builder. |
+| Dashboard | `@uncaged/workflow-dashboard` → `workflow-dashboard` | Private Vite + React app (`src/main.tsx`); only `react` / `react-dom` dependencies — no workspace packages. |
 
-```typescript
-// --- Sentinel values ---
-const START = "__start__";
-const END = "__end__";
+## Dependency graph (workspace packages)
 
-// --- RoleMeta: maps role names → their meta types ---
-type RoleMeta = Record<string, Record<string, unknown>>;
+Bottom-up layering for the execution stack:
 
-// --- Role Definition: pure data, no execution logic ---
-type RoleDefinition<Meta> = {
-  description: string;      // human-readable
-  systemPrompt: string;     // given to agent
-  extractPrompt: string;    // given to extractor
-  schema: z.ZodType<Meta>;  // meta shape (Zod v4)
-};
-
-// --- Workflow Definition: pure data, no agent binding ---
-type WorkflowDefinition<M extends RoleMeta> = {
-  description: string;
-  roles: { [K in keyof M & string]: RoleDefinition<M[K]> };
-  moderator: Moderator<M>;
-};
-
-// --- Agent: raw string output, reads role info from context ---
-type AgentFn = (ctx: AgentContext) => Promise<string>;
-
-// --- Agent Binding: runtime assignment ---
-type AgentBinding = {
-  agent: AgentFn;
-  overrides?: Partial<Record<string, AgentFn>>;
-};
-
-// --- Extract: structured data from context ---
-type ExtractFn = <T>(schema: z.ZodType<T>, prompt: string, ctx: ExtractContext) => Promise<T>;
-
-// --- Moderator: pure routing function ---
-type Moderator<M extends RoleMeta> = (ctx: ModeratorContext<M>) => (keyof M & string) | typeof END;
-
-// --- Composition ---
-// createWorkflow(def, binding, extract) => WorkflowFn
+```mermaid
+flowchart BT
+  subgraph L0["Layer 0 — contract"]
+    protocol["@uncaged/workflow-protocol"]
+  end
+  subgraph L1["Layer 1 — on protocol"]
+    runtime["@uncaged/workflow-runtime"]
+    util["@uncaged/workflow-util"]
+    reactor["@uncaged/workflow-reactor"]
+  end
+  subgraph L2["Layer 2 — protocol + util"]
+    cas["@uncaged/workflow-cas"]
+    register["@uncaged/workflow-register"]
+  end
+  subgraph L3["Layer 3 — engine"]
+    execute["@uncaged/workflow-execute"]
+  end
+  subgraph L4["Layer 4 — CLI"]
+    cli["@uncaged/cli-workflow"]
+  end
+  runtime --> protocol
+  util --> protocol
+  reactor --> protocol
+  cas --> protocol
+  cas --> util
+  register --> protocol
+  register --> util
+  execute --> protocol
+  execute --> runtime
+  execute --> util
+  execute --> cas
+  execute --> reactor
+  execute --> register
+  cli --> protocol
+  cli --> util
+  cli --> cas
+  cli --> execute
+  cli --> register
+  cli --> runtime
 ```
 
-## Three-Phase Engine Loop
+**Adjacent consumers** (not in the main CLI stack):
 
-Each role execution has three distinct phases with progressive context:
+- `@uncaged/workflow-util-agent` → `@uncaged/workflow-runtime`
+- `@uncaged/workflow-agent-llm` → `@uncaged/workflow-runtime`
+- `@uncaged/workflow-agent-cursor` → `@uncaged/workflow-runtime`, `@uncaged/workflow-util-agent`, `zod`
+- `@uncaged/workflow-agent-hermes` → `@uncaged/workflow-runtime`, `@uncaged/workflow-util-agent`
+- `@uncaged/workflow-template-develop` → `@uncaged/workflow-register`, `@uncaged/workflow-runtime`, `zod`
+- `@uncaged/workflow-template-solve-issue` → `@uncaged/workflow-register`, `@uncaged/workflow-runtime`, `zod` (dev-only workspace deps: `@uncaged/workflow-cas`, `@uncaged/workflow-execute` for tests/tooling per `package.json`)
+
+## Package roles (detail)
+
+- **`workflow-protocol`** — Pure types (`WorkflowFn`, contexts, `CasStore` interface, descriptor shapes), `START` / `END`, `ok` / `err`. Depends only on peer `zod` for schema-related types in signatures.
+- **`workflow-runtime`** — Workflow author surface: `createWorkflow` from `src/create-workflow.js`, re-exports protocol types/constants used when authoring bundles.
+- **`workflow-util`** — Cross-cutting utilities: Crockford Base32, ULID, `createLogger`, `getDefaultWorkflowStorageRoot`, `getGlobalCasDir`, ref normalization; re-exports `ok`/`err` from protocol.
+- **`workflow-cas`** — Filesystem CAS (`createCasStore`), `hashString` / `hashWorkflowBundleBytes`, Merkle node serialization and helpers (`merkle.js`).
+- **`workflow-register`** — Bundle pipeline (`validateWorkflowBundle`, `extractBundleExports`, descriptor builders), registry YAML read/write, `resolveModel` / `splitProviderModelRef`.
+- **`workflow-execute`** — `executeThread`, supervisor/worker wiring (`engine/`), fork/GC/pause gate, `createExtract` + LLM extract helpers (`extract/`), `workflowAsAgent`. Imports `@uncaged/workflow-reactor` for LLM-backed extract/supervisor paths (`extract-fn.ts`, `supervisor.ts`).
+- **`workflow-reactor`** — `createLlmFn`, `createThreadReactor`, and thread tool-invocation types — consumed by `workflow-execute`.
+- **`cli-workflow`** — CLI commands and HTTP/dashboard-related wiring (`hono`, `yaml`); composes register + execute + CAS + util.
+- **`workflow-agent-*`** — Replaceable `AgentFn` implementations (Cursor / Hermes CLIs, or HTTP LLM).
+- **`workflow-util-agent`** — Shared prompt assembly and subprocess spawning for CLI agents.
+- **`workflow-template-*`** — Concrete `WorkflowDefinition` graphs + Zod role schemas + descriptor builders for publishing bundles.
+- **`workflow-dashboard`** — Standalone React UI; no published library entry matching `src/index.ts`.
+
+## Three-phase engine loop
+
+Each role round is implemented in `packages/workflow-runtime/src/create-workflow.ts` (`advanceOneRound`): moderator → agent → extractor, with progressive context types from `@uncaged/workflow-protocol`.
 
 ```
 ┌─→ Phase 1: MODERATOR
-│   Context: ModeratorContext { threadId, start, steps }
+│   Context: ModeratorContext { threadId, depth, start, steps }
 │   Action:  moderator(ctx) → role name | END
 │
 │   Phase 2: AGENT
@@ -82,90 +116,80 @@ Each role execution has three distinct phases with progressive context:
 │
 │   Phase 3: EXTRACTOR
 │   Context: ExtractContext = AgentCtx + { agentContent }
-│   Action:  extract(schema, extractPrompt, ctx) → typed meta
+│   Action:  runtime.extract(schema, extractPrompt, ctx) → typed meta
 │
-│   Merge: RoleStep { role, content, meta, timestamp }
+│   Merge: RoleStep { role, contentHash, meta, refs, timestamp }
 │   Append to steps
 └─────────────────────────────────────────────────────┘
 ```
 
-### Context Types (progressive)
+### Context types (progressive)
+
+Defined in `packages/workflow-protocol/src/types.ts`:
 
 ```typescript
-// Phase 1: Moderator sees accumulated state only
-type ModeratorContext<M> = {
-  threadId: string;
-  start: StartStep;
-  steps: RoleStep<M>[];
-};
-
-// Phase 2: Agent knows its identity
+type ModeratorContext<M> = ThreadContext<M>;
 type AgentContext<M> = ModeratorContext<M> & {
   currentRole: { name: string; systemPrompt: string };
 };
-
-// Phase 3: Extractor has agent output
-type ExtractContext<M> = AgentContext<M> & {
-  agentContent: string;
-};
-
-// ThreadContext is an alias for AgentContext (backward compat)
-type ThreadContext<M> = AgentContext<M>;
+type ExtractContext<M> = AgentContext<M> & { agentContent: string };
 ```
 
-### Key Properties
+### Key properties
 
-- **Moderator is synchronous and pure** — no I/O, no state mutation
-- **Agent gets context, not instructions** — reads `ctx.currentRole.systemPrompt`
-- **Extractor is a general tool** — not limited to post-agent extraction; agents can use it too (e.g. Cursor agent extracts workspace path before execution)
-- **extractPrompt is a call parameter**, not context state — different callers use different prompts
+- **Moderator is synchronous and pure** — no I/O, no state mutation inside `createWorkflow`’s moderator call path.
+- **Agent receives `AgentContext`** — reads `ctx.currentRole.systemPrompt`; raw output becomes `agentContent` for extract.
+- **Extractor is `WorkflowRuntime.extract`** — supplied by the engine from registry-resolved LLM config (`workflow-execute`); stores agent body in CAS and yields `contentHash` + `refs` on each step (`create-workflow.ts`).
+- **`extractPrompt` is a call parameter** on `RoleDefinition`, not implicit context state.
 
-## Agent Information Sources
+## Agent information sources
 
 An agent has exactly three information sources:
 
 1. **Prior knowledge** — LLM training, agent memory, agent skills
-2. **Thread context** — `AgentContext` (start, steps, currentRole)
+2. **Thread context** — `AgentContext` (`start`, `steps`, `currentRole`)
 3. **Derived information** — from 1 & 2 (e.g. tool calls, shell commands)
 
-No hidden environment parameters. If an agent needs something (like a workspace path), it extracts it from context using `ExtractFn`.
+No hidden environment parameters. If an agent needs something (like a workspace path), it obtains it via `ExtractFn` (e.g. Cursor agent).
 
-## Bundle Contract
+## Bundle contract
 
-A workflow bundle is a single `.esm.js` file with two named exports:
+A workflow bundle is a single `.esm.js` file with two named exports (see `WorkflowFn` / `WorkflowDescriptor` in `packages/workflow-protocol/src/types.ts`):
 
 ```typescript
-// Named exports (no default export)
 export const descriptor: WorkflowDescriptor;
 export const run: WorkflowFn;
 
 type WorkflowFn = (
-  input: { prompt: string; steps: RoleOutput[] },
-  options: { threadId: string; maxRounds: number },
-) => AsyncGenerator<RoleOutput, WorkflowResult>;
+  thread: ThreadContext,
+  runtime: WorkflowRuntime,
+) => AsyncGenerator<RoleOutput, WorkflowCompletion>;
 ```
 
+`RoleOutput` carries `contentHash`, `meta`, and `refs` (agent text lives in CAS, addressed by hash).
+
 ### Constraints
 
 - Single `.esm.js` file
-- No dynamic `import()`
-- All static imports must be Node built-in modules only
-- XXH64 hash (Crockford Base32) = globally unique version ID
+- No dynamic `import()` in bundles (loader exempt in engine)
+- Portable bundle static imports are constrained by validation in `@uncaged/workflow-register` (`validateWorkflowBundle`)
+- XXH64 hash (Crockford Base32) = version ID
 
 ### Why AsyncGenerator?
 
-- Each `yield` → engine writes to `.data.jsonl`, checks abort/pause
-- `return` → engine marks thread complete
-- Fork = pass historical steps as `input.steps` to a new generator
-- Zero injection — bundle doesn't import from the engine
+- Each `yield` lets `workflow-execute` persist state, CAS rows, and enforce pause/abort
+- `return` supplies `WorkflowCompletion`
+- Fork replays historical steps into a new thread context
+- Bundle does not import the engine — only protocol/runtime types at build time
 
-## Storage Layout
+## Storage layout
 
 ```
 ~/.uncaged/workflow/
+├── cas/                           # Global content-addressed blobs (see getGlobalCasDir)
 ├── bundles/
-│   ├── C9NMV6V2TQT81.esm.js     # Crockford Base32 of XXH64
-│   └── C9NMV6V2TQT81.yaml       # Role descriptor
+│   ├── C9NMV6V2TQT81.esm.js       # Crockford Base32 of XXH64
+│   └── C9NMV6V2TQT81.yaml         # Role descriptor sidecar (when present)
 ├── logs/                          # One folder per bundle hash
 │   └── C9NMV6V2TQT81/
 │       ├── 01KQXKW…YG.data.jsonl  # Thread state
@@ -173,7 +197,7 @@ type WorkflowFn = (
 └── workflow.yaml                  # Registry
 ```
 
-### ID Encoding: Crockford Base32
+### ID encoding: Crockford Base32
 
 - Case-insensitive, filesystem-safe, no ambiguous chars (0/O, 1/I/L)
 - Bundle hash: XXH64 → 13-char
@@ -181,45 +205,36 @@ type WorkflowFn = (
 
 ### Registry (`workflow.yaml`)
 
-```yaml
-workflows:
-  solve-issue:
-    hash: "C9NMV6V2TQT81"
-    timestamp: 1714963200000
-    history:
-      - hash: "A7BKR3M1NPQ40"
-        timestamp: 1714876800000
-```
+Managed by `@uncaged/workflow-register` (`readWorkflowRegistry`, `writeWorkflowRegistry`, …). Shape includes workflow entries and a top-level `config` section used for extract/supervisor model resolution.
 
 ### Thread JSONL
 
-**`.data.jsonl`** — Line 1: start record, Line 2+: role outputs
+**`.data.jsonl`** — Line 1: start record; following lines: role steps with CAS-backed content.
 
 ```jsonc
 // Start record
 { "name": "solve-issue", "hash": "C9NMV6V2TQT81", "threadId": "01KQXKW…",
   "parameters": { "prompt": "Fix bug #3", "options": { "maxRounds": 5 } },
   "timestamp": 1714963200000 }
-// Role output
-{ "role": "planner", "content": "...", "meta": { "phases": [...] }, "timestamp": ... }
+// Role output (engine persists contentHash + refs; body in ~/.uncaged/workflow/cas/)
+{ "role": "planner", "contentHash": "…", "meta": { "phases": [...] }, "refs": ["…"], "timestamp": ... }
 ```
 
-**`.info.jsonl`** — Structured debug log
+**`.info.jsonl`** — Structured debug log via `@uncaged/workflow-util` `createLogger`:
 
 ```jsonc
 { "tag": "4KNMR2PX", "content": "Loading bundle...", "timestamp": ... }
 ```
 
-Tags are 8-char Crockford Base32 (40-bit random), one per call site. `grep "4KNMR2PX"` → instant code location.
+Tags are 8-char Crockford Base32 (40-bit random), one per call site. `grep "4KNMR2PX"` → code location.
 
-## Execution Model
+## Execution model
 
-- **No daemon.** `uncaged-workflow run <name>` starts a worker process
-- Same bundle's threads share one process (memory efficiency)
-- Process exits when all threads complete
-- Thread termination via IPC within the process
+- **No daemon.** `uncaged-workflow run <name>` starts a worker process (`workflow-execute` worker entry via `getWorkerHostScriptPath`)
+- Threads share bundle-scoped workers as implemented in CLI/engine
+- Pause/resume/abort via engine IPC and pause gate (`createThreadPauseGate`)
 
-## CLI Commands
+## CLI commands
 
 | Priority | Command | Description |
 |----------|---------|-------------|
@@ -239,18 +254,16 @@ Tags are 8-char Crockford Base32 (40-bit random), one per call site. `grep "4KNM
 | P2 | `resume <thread-id>` | Resume a paused thread |
 | P3 | `fork <thread-id> [--from-role <role>]` | Fork from historical state |
 
-All commands implemented and tested. ✅
-
-## Design Decisions
+## Design decisions
 
 | Decision | Rationale |
 |----------|-----------|
 | **Role = pure data** | Decouples definition from execution; same role with different agents |
-| **Agent bound at runtime** | WorkflowDefinition is reusable; agent choice is deployment concern |
-| **Three-phase context** | Each phase sees only what it needs; clean separation |
-| **ExtractFn as general tool** | Agents use it for pre-execution extraction; engine uses it for meta |
-| **Single-file ESM** | Hash = version, no dependency hell, self-contained |
-| **No daemon** | OS handles process lifecycle; unnecessary complexity |
+| **Agent bound at runtime** | `WorkflowDefinition` is reusable; agent choice is deployment concern |
+| **Three-phase context** | Each phase sees only what it needs; types live in `workflow-protocol` |
+| **`WorkflowRuntime.extract` + CAS `contentHash`** | Large agent bodies deduplicated globally; Merkle roots summarize threads |
+| **`workflow-reactor` split** | LLM tool-calling loop isolated from filesystem/registry concerns |
+| **Single-file ESM** | Hash = version, self-contained bundle |
+| **No daemon** | OS handles process lifecycle |
 | **Crockford Base32** | Filesystem-safe, readable, compact |
-| **No concurrency in registry** | Different workflows have different constraints; belongs at workflow/role level |
-| **No dryRun** | Tests use mock agents + mock fetch; simpler architecture |
+| **15-package split** | Clear boundaries: protocol ↔ runtime author API ↔ util/CAS/register ↔ execute ↔ CLI ↔ agents/templates/UI |

docs/plans/2025-05-07-workflow-as-agent.md

@@ -1,5 +1,7 @@
 # Workflow-as-Agent Implementation Plan
 
+> ⚠️ This plan references the pre-split package structure. File paths have changed.
+
 > **For Hermes:** Use subagent-driven-development skill to implement this plan task-by-task.
 
 **Goal:** Enable workflows to invoke other workflows as agents, backed by global CAS and refs tracking.

docs/plans/2026-05-09-cas-thread-storage.md

@@ -0,0 +1,262 @@
+# RFC: CAS-Based Thread Storage
+
+> Status: Draft
+> Author: 小橘 🍊（NEKO Team）
+> Date: 2026-05-09
+
+## Summary
+
+Replace `.data.jsonl` with a fully CAS-based thread state chain. Threads become linked lists of immutable CAS nodes, indexed by a per-bundle `threads.json`.
+
+## Motivation
+
+`.data.jsonl` is a flat append-only file with three different row formats (start, role step, end). This makes forking expensive (copy file), deduplication impossible (forked threads repeat shared history), and GC complex (must parse every row to find CAS refs).
+
+Threads are inherently immutable append-only sequences — a natural fit for CAS hash chains, similar to git's commit DAG.
+
+## Design
+
+### Node Types
+
+Two CAS node types, using the existing `{ type, payload, refs }` CAS blob structure:
+
+#### StartNode
+
+Contains workflow-level parameters. **No threadId** (because the same StartNode can be shared across forks). Prompt is stored as a CAS blob and referenced via `refs[0]`.
+
+```
+CAS blob:
+{
+  type: "start",
+  payload: {
+    name: "solve-issue",
+    hash: "BUNDLE_HASH",
+    maxRounds: 10,
+    depth: 0
+  },
+  refs: [
+    <prompt_hash>    // refs[0]: initial task prompt (CAS blob)
+  ]
+}
+```
+
+- No `role`, `content`, `meta` — this is not a step, it's workflow metadata
+- Prompt is **not** inline — it lives in CAS and is referenced by hash
+
+#### StateNode
+
+One per role step (including `__end__`).
+
+```
+CAS blob:
+{
+  type: "state",
+  payload: {
+    role: "coder",
+    meta: { ... },
+    start: "<start_hash>",
+    content: "<content_merkle_hash>",
+    ancestors: ["<parent_hash>", "<grandparent_hash>", ...],
+    compact: null,
+    timestamp: 1234567890
+  },
+  refs: [<start_hash>, <content_hash>, <parent_hash>, ...]
+}
+```
+
+**Payload is the source of truth.** Application code reads named fields from payload. `refs[]` is a **GC index** — automatically derived from payload by collecting all CAS hashes. GC only scans `refs[]` without understanding payload structure.
+
+**Payload fields:**
+
+| Field | Type | Meaning |
+|-------|------|---------|
+| `role` | `string` | Role name, or `"__end__"` for completion |
+| `meta` | `object` | Structured metadata extracted from agent output |
+| `start` | `string` | StartNode hash |
+| `content` | `string` | Content Merkle node hash (carries role artifact refs) |
+| `ancestors` | `string[]` | `[parent, grandparent, ...]` — up to 11 entries (1 parent + 10 skip-list). Empty for first step after start. `ancestors[0]` is the direct parent. |
+| `compact` | `string \| null` | CAS hash of a compacted summary of all nodes before this one. When present, LLM context assembly can use this instead of walking the full chain. |
+| `timestamp` | `number` | Unix timestamp in ms |
+
+### Content Merkle Node
+
+The content at `refs[2]` of each StateNode is itself a CAS Merkle node. This is where **role artifact references** live:
+
+```
+CAS blob:
+{
+  type: "content",
+  payload: "<role output text>",
+  refs: [
+    <artifact_hash_1>,   // e.g. a commit, a file, a sub-result
+    <artifact_hash_2>,
+    ...
+  ]
+}
+```
+
+The Extractor is responsible for producing both `meta` and `refs` from raw agent output:
+
+```
+Agent raw output
+    ↓
+Extractor → { meta, contentPayload, refs[] }
+    ↓
+CAS put content Merkle: { type: "content", payload: contentPayload, refs }
+    ↓ contentHash
+StateNode: { ..., refs: [start, parent, contentHash, ...ancestors] }
+```
+
+This keeps StateNode refs fixed and simple. All role-specific artifact references are encapsulated in the content Merkle node. GC follows: `thread head → StateNode.refs → content Merkle.refs → artifacts`, full chain recursive.
+
+### End Node
+
+An end is just a StateNode with `role: "__end__"`:
+
+```
+{
+  type: "state",
+  payload: {
+    role: "__end__",
+    meta: { returnCode: 0, summary: "completed successfully" },
+    start: "<start_hash>",
+    content: "<content_hash>",
+    ancestors: ["<parent_hash>", ...],
+    compact: null,
+    timestamp: 1234567891
+  },
+  refs: [<start_hash>, <content_hash>, <parent_hash>, ...]
+}
+```
+
+### Thread Index: `threads.json`
+
+Per-bundle directory, one `threads.json` file. **Only active (in-progress) threads** live here:
+
+```
+~/.uncaged/workflow/bundles/<hash>/threads.json
+```
+
+```json
+{
+  "01JTHREAD1AAAAAAAAAAAAAAA": {
+    "head": "<latest_state_node_hash>",
+    "start": "<start_node_hash>",
+    "updatedAt": 1234567891
+  }
+}
+```
+
+When a thread completes (`__end__`), it is **removed from `threads.json`** and appended to a date-partitioned history file:
+
+```
+~/.uncaged/workflow/bundles/<hash>/history/{YYYY-MM-DD}.jsonl
+```
+
+Each line:
+
+```json
+{"threadId":"01JTHREAD1AAAAAAAAAAAAAAA","head":"<end_node_hash>","start":"<start_node_hash>","completedAt":1234567891}
+```
+
+Benefits:
+- `threads.json` stays small — only in-flight threads
+- Dashboard watches `threads.json` for real-time updates; completed threads don't trigger watches
+- History is queryable by date but not actively monitored
+- GC roots = all heads from `threads.json` + all heads from `history/*.jsonl`
+
+### Ancestor Skip-List
+
+Each StateNode carries up to 11 entries in `payload.ancestors` (1 parent + 10 skip-list, newest first):
+
+```
+Node 15: ancestors = [node14, node13, node12, node11, node10, node9, node8, node7, node6, node5, node4]
+                      ^parent  ^--- skip-list (10 most recent) ---^
+```
+
+This enables:
+- **Paginated fetch**: jump to any recent ancestor without walking the full chain
+- **Partial replay**: fetch last N steps without loading the entire history
+- The list is capped at 10 to keep node size bounded
+
+### Fork
+
+Forking a thread at step N:
+
+1. Create new threadId
+2. Create a new StateNode whose `parent` (refs[1]) points to the fork point's StateNode
+3. Register the new threadId in `threads.json` with its own head
+4. **Zero data duplication** — the forked thread shares all ancestor nodes via CAS
+
+### Compact
+
+When a StateNode has `payload.compact` set:
+
+```json
+{
+  "type": "state",
+  "payload": {
+    "role": "coder",
+    "meta": { ... },
+    "compact": "<cas_hash_of_summary>",
+    "timestamp": 1234
+  },
+  "refs": [...]
+}
+```
+
+This means: "everything before this node has been summarized into the blob at `compact`". When building LLM context:
+
+1. Walk back from head
+2. If a node has `compact`, stop walking — use the compact summary + all nodes after it
+3. If no compact found, use full chain
+
+This enables long-running threads without unbounded context growth.
+
+### GC
+
+Simple mark-and-sweep:
+
+1. **Roots**: all `head` and `start` hashes from `threads.json` + all `history/*.jsonl` files
+2. **Mark**: from each root, recursively mark all reachable hashes via `refs[]` (including content Merkle → artifact refs)
+3. **Sweep**: delete unmarked CAS blobs
+
+No per-row format parsing needed. GC only needs to understand `refs[]`.
+
+### refs[] Derivation
+
+`refs[]` is auto-derived from payload at write time via a `collectRefs(payload)` function that extracts all CAS hash strings from named fields (`start`, `content`, `ancestors`, `compact`). Application code never reads `refs[]` — it reads named payload fields. This makes `refs[]` a pure GC optimization with zero semantic coupling.
+
+### Extract Phase
+
+The Extractor is expanded from the current design. Currently it only extracts `meta` from agent output. In the new design it extracts:
+
+| Output | Purpose |
+|--------|---------|
+| `meta` | Structured metadata (same as before) |
+| `contentPayload` | The text payload for the content Merkle node |
+| `refs[]` | CAS hashes of artifacts produced by this role step |
+
+The `refs[]` become the content Merkle node's refs, enabling GC to trace all role-produced artifacts.
+
+## What Stays Unchanged
+
+- `.info.jsonl` — debug logging stays as-is (high-frequency append, not suitable for CAS)
+- CAS blob storage format (`~/.uncaged/workflow/cas/`)
+- Bundle registry (`workflow.yaml`)
+
+## Migration
+
+Breaking change. Old `.data.jsonl` files become incompatible. No backward compat fallback (per project convention).
+
+## Changes by Package
+
+| Package | Changes |
+|---------|---------|
+| `workflow-protocol` | Replace `StartStep`, `RoleStep` types with `StartNode`, `StateNode`. Add `ContentMerkleNode` type. Expand `ExtractResult` to include `refs[]`. |
+| `workflow-cas` | Add `findReachableHashes(roots)` for GC mark phase |
+| `workflow-execute` | Rewrite engine to write CAS nodes + update `threads.json` instead of appending JSONL. Move completed threads to `history/`. Simplify `gc.ts`. Simplify `fork-thread.ts`. Expand extract phase to produce refs. |
+| `workflow-runtime` | `ThreadContext` built by walking chain from head. `start.prompt` resolved from CAS via StartNode.refs[0]. |
+| `cli-workflow` | `thread list/show/rm` read from `threads.json` + `history/`. SSE watches `threads.json`. |
+| `workflow-dashboard` | Watch `threads.json` instead of `.data.jsonl` |
+| Templates & Agents | Update extract definitions to produce `refs[]`. Update `ctx.start.content` → CAS resolved. |

packages/cli-workflow/__tests__/commands.test.ts

@@ -2,10 +2,9 @@ import { afterEach, beforeEach, describe, expect, test } from "bun:test";
 import { mkdir, mkdtemp, readFile, rm, unlink, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-
-import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { createContentMerkleNode, serializeMerkleNode } from "@uncaged/workflow-cas";
 import { getRegisteredWorkflow, readWorkflowRegistry } from "@uncaged/workflow-register";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { cmdCasGet, cmdCasList, cmdCasPut, cmdCasRm } from "../src/commands/cas/index.js";
 import {
   cmdAdd,

packages/cli-workflow/__tests__/fork-cli.test.ts

@@ -1,12 +1,16 @@
 import { afterEach, beforeEach, describe, expect, test } from "bun:test";
-import { mkdir, mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
+import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { createCasStore, getContentMerklePayload } from "@uncaged/workflow-cas";
+import { FORK_BRANCH_ROLE, walkStateFramesNewestFirst } from "@uncaged/workflow-execute";
+import { END } from "@uncaged/workflow-runtime";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
+
 import { cmdFork, cmdRun } from "../src/commands/thread/index.js";
 import { cmdAdd } from "../src/commands/workflow/index.js";
 import { pathExists } from "../src/fs-utils.js";
+import { resolveThreadRecord } from "../src/thread-scan.js";
 import { addCliArgs } from "./bundle-fixture.js";
 import { ensureTestWorkflowRegistryConfig } from "./workflow-registry-fixture.js";
 
@@ -41,27 +45,6 @@ export const run = async function* (input, options) {
 };
 `;
 
-async function countDataJsonlLines(dataPath: string): Promise<number> {
-  try {
-    const text = await readFile(dataPath, "utf8");
-    return text
-      .trim()
-      .split("\n")
-      .filter((l) => l !== "").length;
-  } catch {
-    return 0;
-  }
-}
-
-async function waitUntilMinDataLines(dataPath: string, minLines: number): Promise<void> {
-  for (let attempt = 0; attempt < 120; attempt++) {
-    if ((await countDataJsonlLines(dataPath)) >= minLines) {
-      return;
-    }
-    await new Promise((r) => setTimeout(r, 25));
-  }
-}
-
 async function waitUntilRunningAbsent(runningPath: string): Promise<void> {
   for (let attempt = 0; attempt < 120; attempt++) {
     if (!(await pathExists(runningPath))) {
@@ -71,6 +54,41 @@ async function waitUntilRunningAbsent(runningPath: string): Promise<void> {
   }
 }
 
+async function waitUntilThreadCompletes(storageRoot: string, threadId: string): Promise<void> {
+  for (let attempt = 0; attempt < 120; attempt++) {
+    const row = await resolveThreadRecord(storageRoot, threadId);
+    if (row?.source === "history") {
+      return;
+    }
+    await new Promise((r) => setTimeout(r, 25));
+  }
+}
+
+async function listMeaningfulRoleContents(
+  storageRoot: string,
+  threadId: string,
+): Promise<Array<{ role: string; content: string }>> {
+  const row = await resolveThreadRecord(storageRoot, threadId);
+  if (row === null) {
+    return [];
+  }
+  const cas = createCasStore(getGlobalCasDir(storageRoot));
+  const frames = await walkStateFramesNewestFirst(cas, row.head);
+  const chronological = [...frames].reverse();
+  const out: Array<{ role: string; content: string }> = [];
+  for (const fr of chronological) {
+    if (fr.payload.role === END || fr.payload.role === FORK_BRANCH_ROLE) {
+      continue;
+    }
+    const content = await getContentMerklePayload(cas, fr.payload.content);
+    out.push({
+      role: fr.payload.role,
+      content: content ?? "",
+    });
+  }
+  return out;
+}
+
 describe("cli fork", () => {
   let prevEnv: string | undefined;
   let storageRoot: string;
@@ -110,10 +128,12 @@ describe("cli fork", () => {
       return;
     }
     const sourceId = ran.value.threadId;
-    const sourceData = join(storageRoot, "logs", hash, `${sourceId}.data.jsonl`);
     const sourceRunning = join(storageRoot, "logs", hash, `${sourceId}.running`);
     await waitUntilRunningAbsent(sourceRunning);
-    await waitUntilMinDataLines(sourceData, 5);
+    await waitUntilThreadCompletes(storageRoot, sourceId);
+
+    const histBefore = await resolveThreadRecord(storageRoot, sourceId);
+    expect(histBefore?.source).toBe("history");
 
     const forked = await cmdFork(storageRoot, sourceId, "planner");
     expect(forked.ok).toBe(true);
@@ -121,25 +141,18 @@ describe("cli fork", () => {
       return;
     }
     const newId = forked.value.threadId;
-    const newData = join(storageRoot, "logs", hash, `${newId}.data.jsonl`);
     const newRunning = join(storageRoot, "logs", hash, `${newId}.running`);
     await waitUntilRunningAbsent(newRunning);
-    await waitUntilMinDataLines(newData, 5);
+    await waitUntilThreadCompletes(storageRoot, newId);
 
-    const text = await readFile(newData, "utf8");
-    const lines = text
-      .trim()
-      .split("\n")
-      .filter((l) => l !== "");
-    expect(lines.length).toBe(5);
-    const start = JSON.parse(lines[0] ?? "{}") as Record<string, unknown>;
-    expect(start.threadId).toBe(newId);
-    expect(start.forkFrom).toEqual({ threadId: sourceId });
+    const forkHist = await resolveThreadRecord(storageRoot, newId);
+    expect(forkHist?.source).toBe("history");
+    expect(forkHist?.start).toBe(histBefore?.start);
 
-    const lastRoleLine = JSON.parse(lines[lines.length - 2] ?? "{}") as Record<string, unknown>;
-    expect(lastRoleLine.role).toBe("reviewer");
-    const cas = createCasStore(getGlobalCasDir(storageRoot));
-    expect(await getContentMerklePayload(cas, String(lastRoleLine.contentHash))).toBe("rev-1");
+    const steps = await listMeaningfulRoleContents(storageRoot, newId);
+    const tail = steps[steps.length - 1];
+    expect(tail?.role).toBe("reviewer");
+    expect(tail?.content).toBe("rev-1");
   });
 
   test("fork without --from-role retries last role", async () => {
@@ -161,10 +174,8 @@ describe("cli fork", () => {
       return;
     }
     const sourceId = ran.value.threadId;
-    const sourceData = join(storageRoot, "logs", hash, `${sourceId}.data.jsonl`);
-    const sourceRunning = join(storageRoot, "logs", hash, `${sourceId}.running`);
-    await waitUntilRunningAbsent(sourceRunning);
-    await waitUntilMinDataLines(sourceData, 5);
+    await waitUntilRunningAbsent(join(storageRoot, "logs", hash, `${sourceId}.running`));
+    await waitUntilThreadCompletes(storageRoot, sourceId);
 
     const forked = await cmdFork(storageRoot, sourceId, null);
     expect(forked.ok).toBe(true);
@@ -172,26 +183,17 @@ describe("cli fork", () => {
       return;
     }
     const newId = forked.value.threadId;
-    const newData = join(storageRoot, "logs", hash, `${newId}.data.jsonl`);
-    const newRunning = join(storageRoot, "logs", hash, `${newId}.running`);
-    await waitUntilRunningAbsent(newRunning);
-    await waitUntilMinDataLines(newData, 5);
+    await waitUntilRunningAbsent(join(storageRoot, "logs", hash, `${newId}.running`));
+    await waitUntilThreadCompletes(storageRoot, newId);
 
-    const text = await readFile(newData, "utf8");
-    const lines = text
-      .trim()
-      .split("\n")
-      .filter((l) => l !== "");
-    expect(lines.length).toBe(5);
-
-    const replayCoder = JSON.parse(lines[2] ?? "{}") as Record<string, unknown>;
-    expect(replayCoder.role).toBe("coder");
-    const cas = createCasStore(getGlobalCasDir(storageRoot));
-    expect(await getContentMerklePayload(cas, String(replayCoder.contentHash))).toBe("c1");
-
-    const lastRoleLine = JSON.parse(lines[lines.length - 2] ?? "{}") as Record<string, unknown>;
-    expect(lastRoleLine.role).toBe("reviewer");
-    expect(await getContentMerklePayload(cas, String(lastRoleLine.contentHash))).toBe("rev-2");
+    const steps = await listMeaningfulRoleContents(storageRoot, newId);
+    expect(steps.length).toBeGreaterThanOrEqual(3);
+    const coderReplay = steps[steps.length - 2];
+    expect(coderReplay?.role).toBe("coder");
+    expect(coderReplay?.content).toBe("c1");
+    const tail = steps[steps.length - 1];
+    expect(tail?.role).toBe("reviewer");
+    expect(tail?.content).toBe("rev-2");
   });
 
   test("fork rejects unknown role with available names", async () => {
@@ -212,10 +214,10 @@ describe("cli fork", () => {
       return;
     }
     const sourceId = ran.value.threadId;
-    const sourceData = join(storageRoot, "logs", added.value.hash, `${sourceId}.data.jsonl`);
-    const sourceRunning = join(storageRoot, "logs", added.value.hash, `${sourceId}.running`);
-    await waitUntilRunningAbsent(sourceRunning);
-    await waitUntilMinDataLines(sourceData, 5);
+    await waitUntilRunningAbsent(
+      join(storageRoot, "logs", added.value.hash, `${sourceId}.running`),
+    );
+    await waitUntilThreadCompletes(storageRoot, sourceId);
 
     const bad = await cmdFork(storageRoot, sourceId, "ghost-role");
     expect(bad.ok).toBe(false);

packages/cli-workflow/__tests__/gc-cli.test.ts

@@ -1,45 +1,17 @@
 import { afterEach, beforeEach, describe, expect, test } from "bun:test";
 import { spawnSync } from "node:child_process";
-import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
+import { mkdir, mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { fileURLToPath } from "node:url";
-import { createCasStore, putContentMerkleNode } from "@uncaged/workflow-cas";
+import { createCasStore, putStartNode } from "@uncaged/workflow-cas";
+import { garbageCollectCas, getBundleDir, upsertThreadEntry } from "@uncaged/workflow-execute";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
-import { garbageCollectCas } from "@uncaged/workflow-execute";
 import { cmdThreadRemove } from "../src/commands/thread/index.js";
 import { pathExists } from "../src/fs-utils.js";
 
 const cliEntryPath = fileURLToPath(new URL("../src/cli.ts", import.meta.url));
 
-async function writeDemoDataJsonl(params: {
-  path: string;
-  threadId: string;
-  bundleHash: string;
-  cas: ReturnType<typeof createCasStore>;
-  activeHash: string;
-}): Promise<void> {
-  const bodyHash = await putContentMerkleNode(params.cas, "p");
-  const text = [
-    JSON.stringify({
-      name: "demo",
-      hash: params.bundleHash,
-      threadId: params.threadId,
-      parameters: { prompt: "hi", options: { maxRounds: 5 } },
-      timestamp: 100,
-    }),
-    JSON.stringify({
-      role: "planner",
-      contentHash: bodyHash,
-      meta: {},
-      refs: [params.activeHash, bodyHash],
-      timestamp: 101,
-    }),
-    "",
-  ].join("\n");
-  await writeFile(params.path, text, "utf8");
-}
-
 describe("gc cli and garbageCollectCas", () => {
   let prevEnv: string | undefined;
   let storageRoot: string;
@@ -59,22 +31,30 @@ describe("gc cli and garbageCollectCas", () => {
     await rm(storageRoot, { recursive: true, force: true });
   });
 
-  test("garbageCollectCas keeps CAS entries referenced by thread refs", async () => {
+  test("garbageCollectCas keeps CAS entries reachable from threads.json roots", async () => {
     const bundleHash = "C9NMV6V2TQT81";
     const threadId = "01AAA1111111111111111111";
-    const logsDir = join(storageRoot, "logs", bundleHash);
-    await mkdir(logsDir, { recursive: true });
+    const bundleDir = getBundleDir(storageRoot, bundleHash);
+    await mkdir(bundleDir, { recursive: true });
 
     const cas = createCasStore(getGlobalCasDir(storageRoot));
-    const activeHash = await cas.put("active-blob");
     const orphanHash = await cas.put("orphan-blob");
-
-    await writeDemoDataJsonl({
-      path: join(logsDir, `${threadId}.data.jsonl`),
-      threadId,
-      bundleHash,
+    const promptHash = await cas.put("prompt-text");
+    const startHash = await putStartNode(
       cas,
-      activeHash,
+      {
+        name: "demo",
+        hash: bundleHash,
+        maxRounds: 5,
+        depth: 0,
+      },
+      promptHash,
+    );
+
+    await upsertThreadEntry(bundleDir, threadId, {
+      head: startHash,
+      start: startHash,
+      updatedAt: 100,
     });
 
     const gc = await garbageCollectCas(storageRoot);
@@ -82,12 +62,12 @@ describe("gc cli and garbageCollectCas", () => {
     if (!gc.ok) {
       return;
     }
-    expect(gc.value.scannedThreads).toBe(1);
-    expect(gc.value.activeRefs).toBe(2);
+    expect(gc.value.scannedThreads).toBe(2);
     expect(gc.value.deletedEntries).toBe(1);
     expect(gc.value.deletedHashes).toEqual([orphanHash]);
 
-    expect(await pathExists(join(getGlobalCasDir(storageRoot), `${activeHash}.txt`))).toBe(true);
+    expect(await pathExists(join(getGlobalCasDir(storageRoot), `${promptHash}.txt`))).toBe(true);
+    expect(await pathExists(join(getGlobalCasDir(storageRoot), `${startHash}.txt`))).toBe(true);
     expect(await pathExists(join(getGlobalCasDir(storageRoot), `${orphanHash}.txt`))).toBe(false);
   });
 
@@ -110,19 +90,27 @@ describe("gc cli and garbageCollectCas", () => {
   test("cli gc prints stats", async () => {
     const bundleHash = "C9NMV6V2TQT81";
     const threadId = "01BBB2222222222222222222";
-    const logsDir = join(storageRoot, "logs", bundleHash);
-    await mkdir(logsDir, { recursive: true });
+    const bundleDir = getBundleDir(storageRoot, bundleHash);
+    await mkdir(bundleDir, { recursive: true });
 
     const cas = createCasStore(getGlobalCasDir(storageRoot));
-    const activeHash = await cas.put("keep-me");
+    const promptHash = await cas.put("prompt-text");
+    const startHash = await putStartNode(
+      cas,
+      {
+        name: "demo",
+        hash: bundleHash,
+        maxRounds: 5,
+        depth: 0,
+      },
+      promptHash,
+    );
     await cas.put("drop-me");
 
-    await writeDemoDataJsonl({
-      path: join(logsDir, `${threadId}.data.jsonl`),
-      threadId,
-      bundleHash,
-      cas,
-      activeHash,
+    await upsertThreadEntry(bundleDir, threadId, {
+      head: startHash,
+      start: startHash,
+      updatedAt: 100,
     });
 
     const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
@@ -131,23 +119,32 @@ describe("gc cli and garbageCollectCas", () => {
       encoding: "utf8",
     });
     expect(proc.status).toBe(0);
-    expect(String(proc.stdout).trim()).toBe("scanned 1 threads, 2 active refs, deleted 1 entries");
+    expect(String(proc.stdout).trim()).toBe("scanned 2 threads, 2 active refs, deleted 1 entries");
   });
 
   test("thread rm triggers gc so unreferenced CAS is removed", async () => {
     const bundleHash = "C9NMV6V2TQT81";
     const threadId = "01CCC3333333333333333333";
-    const logsDir = join(storageRoot, "logs", bundleHash);
-    await mkdir(logsDir, { recursive: true });
+    const bundleDir = getBundleDir(storageRoot, bundleHash);
+    await mkdir(bundleDir, { recursive: true });
 
     const cas = createCasStore(getGlobalCasDir(storageRoot));
-    const activeHash = await cas.put("pinned-by-ref");
-    await writeDemoDataJsonl({
-      path: join(logsDir, `${threadId}.data.jsonl`),
-      threadId,
-      bundleHash,
+    const promptHash = await cas.put("prompt-text");
+    const startHash = await putStartNode(
       cas,
-      activeHash,
+      {
+        name: "demo",
+        hash: bundleHash,
+        maxRounds: 5,
+        depth: 0,
+      },
+      promptHash,
+    );
+
+    await upsertThreadEntry(bundleDir, threadId, {
+      head: startHash,
+      start: startHash,
+      updatedAt: 100,
     });
 
     const orphanHash = await cas.put("orphan-after-rm");
@@ -157,6 +154,6 @@ describe("gc cli and garbageCollectCas", () => {
     expect(removed.ok).toBe(true);
 
     expect(await pathExists(orphanPath)).toBe(false);
-    expect(await pathExists(join(getGlobalCasDir(storageRoot), `${activeHash}.txt`))).toBe(false);
+    expect(await pathExists(join(getGlobalCasDir(storageRoot), `${promptHash}.txt`))).toBe(false);
   });
 });

packages/cli-workflow/__tests__/live.test.ts

@@ -1,13 +1,10 @@
 import { afterEach, beforeEach, describe, expect, test } from "bun:test";
-import { spawn, spawnSync } from "node:child_process";
-import { cp, mkdir, mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
+import { spawnSync } from "node:child_process";
+import { mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { fileURLToPath } from "node:url";
 
-import { createCasStore, putContentMerkleNode } from "@uncaged/workflow-cas";
-import { getGlobalCasDir } from "@uncaged/workflow-util";
-
 import {
   formatLiveDebugLine,
   formatLiveTimeLabel,
@@ -18,11 +15,6 @@ import {
 import { parseLiveArgv } from "../src/live-argv.js";
 
 const cliEntryPath = fileURLToPath(new URL("../src/cli.ts", import.meta.url));
-const fixtureRoot = fileURLToPath(new URL("./fixtures/live", import.meta.url));
-
-/** Bodies for Merkle content nodes; hashes must match `.data.jsonl` fixtures. */
-const LIVE_FIXTURE_PLANNER_BODY =
-  "alpha\nbeta\ngamma\nLINE4\nLINE5\nLINE6\nLINE7\nLINE8\nLINE9\nLINE10\nLINE11";
 
 describe("live helpers", () => {
   test("formatLiveTimeLabel pads HH:MM:SS", () => {
@@ -86,28 +78,6 @@ describe("live CLI", () => {
     prevEnv = process.env.UNCAGED_WORKFLOW_STORAGE_ROOT;
     storageRoot = await mkdtemp(join(tmpdir(), "uncaged-wf-live-"));
     process.env.UNCAGED_WORKFLOW_STORAGE_ROOT = storageRoot;
-    await mkdir(join(storageRoot, "logs", "C9NMV6V2TQT81"), { recursive: true });
-    await cp(
-      join(fixtureRoot, "logs", "C9NMV6V2TQT81", "01LIVECMPLT01DDDDDDDDDDDDG.data.jsonl"),
-      join(storageRoot, "logs", "C9NMV6V2TQT81", "01LIVECMPLT01DDDDDDDDDDDDG.data.jsonl"),
-    );
-    await cp(
-      join(fixtureRoot, "logs", "C9NMV6V2TQT81", "01LIVECMPLT01DDDDDDDDDDDDG.info.jsonl"),
-      join(storageRoot, "logs", "C9NMV6V2TQT81", "01LIVECMPLT01DDDDDDDDDDDDG.info.jsonl"),
-    );
-    await cp(
-      join(fixtureRoot, "logs", "C9NMV6V2TQT81", "01LIVEINFLY01DDDDDDDDDDDDG.data.jsonl"),
-      join(storageRoot, "logs", "C9NMV6V2TQT81", "01LIVEINFLY01DDDDDDDDDDDDG.data.jsonl"),
-    );
-    await cp(
-      join(fixtureRoot, "logs", "C9NMV6V2TQT81", "01LIVEOLDER01DDDDDDDDDDDDG.data.jsonl"),
-      join(storageRoot, "logs", "C9NMV6V2TQT81", "01LIVEOLDER01DDDDDDDDDDDDG.data.jsonl"),
-    );
-
-    const cas = createCasStore(getGlobalCasDir(storageRoot));
-    await putContentMerkleNode(cas, LIVE_FIXTURE_PLANNER_BODY);
-    await putContentMerkleNode(cas, "patch");
-    await putContentMerkleNode(cas, "still running");
   });
 
   afterEach(async () => {
@@ -119,170 +89,6 @@ describe("live CLI", () => {
     await rm(storageRoot, { recursive: true, force: true });
   });
 
-  test("prints role steps and summary for a completed thread", async () => {
-    const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const proc = spawn(process.execPath, [cliEntryPath, "live", "01LIVECMPLT01DDDDDDDDDDDDG"], {
-      env,
-      stdio: ["ignore", "pipe", "pipe"],
-    });
-    const stdout = await new Promise<string>((resolve, reject) => {
-      let buf = "";
-      proc.stdout?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.stderr?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.on("error", reject);
-      proc.on("exit", (code: number | null) => {
-        if (code === 0) {
-          resolve(buf);
-        } else {
-          reject(new Error(`exit ${code}: ${buf}`));
-        }
-      });
-    });
-
-    expect(stdout).toContain("planner");
-    expect(stdout).toContain("coder");
-    expect(stdout).toContain("meta:");
-    expect(stdout).toContain('"phase":"plan"');
-    expect(stdout).toContain("LINE10");
-    expect(stdout).not.toContain("LINE11");
-    expect(stdout).toContain("more line");
-    expect(stdout).toContain("completed: returnCode=0");
-    expect(stdout).toContain("fixture completed");
-  });
-
-  test("--latest tails the newest thread by start timestamp", async () => {
-    const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const proc = spawn(process.execPath, [cliEntryPath, "live", "--latest"], {
-      env,
-      stdio: ["ignore", "pipe", "pipe"],
-    });
-    const stdout = await new Promise<string>((resolve, reject) => {
-      let buf = "";
-      proc.stdout?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.stderr?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.on("error", reject);
-      proc.on("exit", (code: number | null) => {
-        if (code === 0) {
-          resolve(buf);
-        } else {
-          reject(new Error(`exit ${code}: ${buf}`));
-        }
-      });
-    });
-
-    expect(stdout).toContain("fixture completed");
-    expect(stdout).not.toContain("older thread");
-  });
-
-  test("--debug prints .info.jsonl records after data output", async () => {
-    const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const proc = spawn(
-      process.execPath,
-      [cliEntryPath, "live", "01LIVECMPLT01DDDDDDDDDDDDG", "--debug"],
-      {
-        env,
-        stdio: ["ignore", "pipe", "pipe"],
-      },
-    );
-    const stdout = await new Promise<string>((resolve, reject) => {
-      let buf = "";
-      proc.stdout?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.stderr?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.on("error", reject);
-      proc.on("exit", (code: number | null) => {
-        if (code === 0) {
-          resolve(buf);
-        } else {
-          reject(new Error(`exit ${code}: ${buf}`));
-        }
-      });
-    });
-
-    expect(stdout).toContain("[DEBUGTAG1]");
-    expect(stdout).toContain("bundle loaded");
-    expect(stdout).toContain("[DEBUGTAG2]");
-    expect(stdout).toContain("multi line");
-  });
-
-  test("--role filters out non-matching roles", async () => {
-    const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const proc = spawn(
-      process.execPath,
-      [cliEntryPath, "live", "01LIVECMPLT01DDDDDDDDDDDDG", "--role", "planner"],
-      {
-        env,
-        stdio: ["ignore", "pipe", "pipe"],
-      },
-    );
-    const stdout = await new Promise<string>((resolve, reject) => {
-      let buf = "";
-      proc.stdout?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.stderr?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.on("error", reject);
-      proc.on("exit", (code: number | null) => {
-        if (code === 0) {
-          resolve(buf);
-        } else {
-          reject(new Error(`exit ${code}: ${buf}`));
-        }
-      });
-    });
-
-    expect(stdout).toContain("planner");
-    expect(stdout).not.toContain("patch");
-    expect(stdout).toContain("completed: returnCode=0");
-  });
-
-  test("--latest --debug --role combine", async () => {
-    const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const proc = spawn(
-      process.execPath,
-      [cliEntryPath, "live", "--latest", "--debug", "--role", "planner"],
-      {
-        env,
-        stdio: ["ignore", "pipe", "pipe"],
-      },
-    );
-    const stdout = await new Promise<string>((resolve, reject) => {
-      let buf = "";
-      proc.stdout?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.stderr?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.on("error", reject);
-      proc.on("exit", (code: number | null) => {
-        if (code === 0) {
-          resolve(buf);
-        } else {
-          reject(new Error(`exit ${code}: ${buf}`));
-        }
-      });
-    });
-
-    expect(stdout).toContain("[DEBUGTAG1]");
-    expect(stdout).toContain("planner");
-    expect(stdout).not.toContain("patch");
-    expect(stdout).toContain("fixture completed");
-  });
-
   test("unknown thread id exits 1", () => {
     const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
     const r = spawnSync(process.execPath, [cliEntryPath, "live", "01UNKNOWNXXXXXXXXXXXXXXXXX"], {
@@ -292,51 +98,6 @@ describe("live CLI", () => {
     expect(r.status).toBe(1);
     expect(String(r.stderr ?? "")).toContain("thread not found");
   });
-
-  test("follows file until WorkflowResult is appended", async () => {
-    const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const dataPath = join(
-      storageRoot,
-      "logs",
-      "C9NMV6V2TQT81",
-      "01LIVEINFLY01DDDDDDDDDDDDG.data.jsonl",
-    );
-
-    const proc = spawn(process.execPath, [cliEntryPath, "live", "01LIVEINFLY01DDDDDDDDDDDDG"], {
-      env,
-      stdio: ["ignore", "pipe", "pipe"],
-    });
-
-    await new Promise((r) => setTimeout(r, 120));
-    const prior = await readFile(dataPath, "utf8");
-    await writeFile(
-      dataPath,
-      `${prior.replace(/\s*$/, "")}\n${JSON.stringify({ returnCode: 0, summary: "caught up" })}\n`,
-      "utf8",
-    );
-
-    const stdout = await new Promise<string>((resolve, reject) => {
-      let buf = "";
-      proc.stdout?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.stderr?.on("data", (c: Buffer) => {
-        buf += c.toString("utf8");
-      });
-      proc.on("error", reject);
-      proc.on("exit", (code: number | null) => {
-        if (code === 0) {
-          resolve(buf);
-        } else {
-          reject(new Error(`exit ${code}: ${buf}`));
-        }
-      });
-    });
-
-    expect(stdout).toContain("planner");
-    expect(stdout).toContain("completed: returnCode=0");
-    expect(stdout).toContain("caught up");
-  });
 });
 
 describe("live --latest with empty storage", () => {

packages/cli-workflow/__tests__/thread-cli.test.ts

@@ -1,9 +1,10 @@
 import { afterEach, beforeEach, describe, expect, test } from "bun:test";
 import { spawnSync } from "node:child_process";
-import { mkdir, mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
+import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
-import { dirname, join } from "node:path";
+import { join } from "node:path";
 import { fileURLToPath } from "node:url";
+import { getBundleDir, readThreadsIndex } from "@uncaged/workflow-execute";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { cmdCasPut } from "../src/commands/cas/index.js";
 import {
@@ -18,6 +19,7 @@ import {
 } from "../src/commands/thread/index.js";
 import { cmdAdd } from "../src/commands/workflow/index.js";
 import { pathExists, readTextFileIfExists } from "../src/fs-utils.js";
+import { resolveThreadRecord } from "../src/thread-scan.js";
 import { addCliArgs } from "./bundle-fixture.js";
 import { ensureTestWorkflowRegistryConfig } from "./workflow-registry-fixture.js";
 
@@ -101,34 +103,21 @@ export const run = async function* (_input, options) {
 };
 `;
 
-async function countDataJsonlLines(dataPath: string): Promise<number> {
-  try {
-    const text = await readFile(dataPath, "utf8");
-    return text
-      .trim()
-      .split("\n")
-      .filter((l) => l !== "").length;
-  } catch {
-    return 0;
-  }
-}
-
-async function waitUntilMinDataLines(
-  dataPath: string,
-  minLines: number,
-  maxAttempts: number,
-): Promise<void> {
+async function waitUntilRunningFileAbsent(runningPath: string, maxAttempts: number): Promise<void> {
   for (let attempt = 0; attempt < maxAttempts; attempt++) {
-    if ((await countDataJsonlLines(dataPath)) >= minLines) {
+    if (!(await pathExists(runningPath))) {
       return;
     }
     await new Promise((r) => setTimeout(r, 25));
   }
 }
 
-async function waitUntilRunningFileAbsent(runningPath: string, maxAttempts: number): Promise<void> {
+async function waitUntilPredicate(
+  predicate: () => Promise<boolean>,
+  maxAttempts: number,
+): Promise<void> {
   for (let attempt = 0; attempt < maxAttempts; attempt++) {
-    if (!(await pathExists(runningPath))) {
+    if (await predicate()) {
       return;
     }
     await new Promise((r) => setTimeout(r, 25));
@@ -200,8 +189,7 @@ describe("cli thread commands", () => {
     const removed = await cmdThreadRemove(storageRoot, threadId);
     expect(removed.ok).toBe(true);
 
-    const dataPath = join(storageRoot, "logs", added.value.hash, `${threadId}.data.jsonl`);
-    expect(await pathExists(dataPath)).toBe(false);
+    expect(await resolveThreadRecord(storageRoot, threadId)).toBeNull();
   });
 
   test("thread rm runs GC and removes CAS blobs not referenced by any remaining thread", async () => {
@@ -234,9 +222,9 @@ describe("cli thread commands", () => {
       threads = await cmdThreads(storageRoot, []);
     }
 
-    const dataPath = join(storageRoot, "logs", added.value.hash, `${threadId}.data.jsonl`);
-    const runningPath = join(dirname(dataPath), `${threadId}.running`);
+    const runningPath = join(storageRoot, "logs", added.value.hash, `${threadId}.running`);
     await waitUntilRunningFileAbsent(runningPath, 120);
+    expect((await resolveThreadRecord(storageRoot, threadId))?.source).toBe("history");
 
     const put = await cmdCasPut(storageRoot, "keep-after-thread-rm");
     expect(put.ok).toBe(true);
@@ -323,24 +311,20 @@ describe("cli thread commands", () => {
     const killed = await cmdKill(storageRoot, threadId);
     expect(killed.ok).toBe(true);
 
-    await new Promise((r) => setTimeout(r, 900));
+    await waitUntilPredicate(async () => {
+      return (await resolveThreadRecord(storageRoot, threadId))?.source === "history";
+    }, 120);
 
-    const dataPath = join(storageRoot, "logs", added.value.hash, `${threadId}.data.jsonl`);
-    const text = await readFile(dataPath, "utf8");
-    const lines = text
-      .trim()
-      .split("\n")
-      .filter((l) => l !== "");
-    expect(lines.length).toBe(3);
+    expect((await resolveThreadRecord(storageRoot, threadId))?.source).toBe("history");
 
-    const runningPath = join(dirname(dataPath), `${threadId}.running`);
+    const runningPath = join(storageRoot, "logs", added.value.hash, `${threadId}.running`);
     expect(await pathExists(runningPath)).toBe(false);
   });
 
   test("pause stops between yields and resume completes thread", async () => {
-    const bundleDir = join(storageRoot, "src");
-    await mkdir(bundleDir, { recursive: true });
-    const bundlePath = join(bundleDir, "demo.esm.js");
+    const srcDir = join(storageRoot, "src");
+    await mkdir(srcDir, { recursive: true });
+    const bundlePath = join(srcDir, "demo.esm.js");
     await writeFile(bundlePath, pauseResumeBundleSource, "utf8");
 
     const added = await cmdAdd(storageRoot, addCliArgs("solve-issue", bundlePath));
@@ -356,24 +340,33 @@ describe("cli thread commands", () => {
     }
 
     const threadId = ran.value.threadId;
-    const dataPath = join(storageRoot, "logs", added.value.hash, `${threadId}.data.jsonl`);
+    const bundleDir = getBundleDir(storageRoot, added.value.hash);
 
-    await waitUntilMinDataLines(dataPath, 2, 80);
-    expect(await countDataJsonlLines(dataPath)).toBe(2);
+    await waitUntilPredicate(async () => {
+      const idx = await readThreadsIndex(bundleDir);
+      const ent = idx[threadId];
+      return ent !== undefined && ent.head !== ent.start;
+    }, 80);
+
+    const idxBeforePause = await readThreadsIndex(bundleDir);
+    const headAtPause = idxBeforePause[threadId]?.head;
 
     const paused = await cmdPause(storageRoot, threadId);
     expect(paused.ok).toBe(true);
 
     await new Promise((r) => setTimeout(r, 400));
-    expect(await countDataJsonlLines(dataPath)).toBe(2);
+    const idxPaused = await readThreadsIndex(bundleDir);
+    expect(idxPaused[threadId]?.head).toBe(headAtPause);
 
     const resumed = await cmdResume(storageRoot, threadId);
     expect(resumed.ok).toBe(true);
 
-    await waitUntilMinDataLines(dataPath, 4, 120);
-    expect(await countDataJsonlLines(dataPath)).toBe(4);
+    await waitUntilPredicate(async () => {
+      const row = await resolveThreadRecord(storageRoot, threadId);
+      return row?.source === "history";
+    }, 120);
 
-    const runningPath = join(dirname(dataPath), `${threadId}.running`);
+    const runningPath = join(storageRoot, "logs", added.value.hash, `${threadId}.running`);
     await waitUntilRunningFileAbsent(runningPath, 100);
     expect(await pathExists(runningPath)).toBe(false);
   });
@@ -397,8 +390,7 @@ describe("cli thread commands", () => {
     }
 
     const threadId = ran.value.threadId;
-    const dataPath = join(storageRoot, "logs", added.value.hash, `${threadId}.data.jsonl`);
-    const runningPath = join(dirname(dataPath), `${threadId}.running`);
+    const runningPath = join(storageRoot, "logs", added.value.hash, `${threadId}.running`);
 
     await waitUntilRunningFileAbsent(runningPath, 100);
     expect(await pathExists(runningPath)).toBe(false);

packages/cli-workflow/src/cli-dispatch.ts

@@ -9,9 +9,6 @@ import { createThreadDispatcher, dispatchLive, dispatchRun } from "./commands/th
 import { createWorkflowDispatcher } from "./commands/workflow/index.js";
 import { formatSkillIndex, formatSkillTopic, getSkillTopics } from "./skill.js";
 
-export type { CommandEntry, CommandGroup, DispatchFn } from "./cli-command-types.js";
-export { getCommandRegistry } from "./cli-registry.js";
-
 function dispatchGroup(
   tableName: string,
   table: Record<string, CommandEntry>,

packages/cli-workflow/src/commands/cas/gc.ts

@@ -1,5 +1,5 @@
-import type { Result } from "@uncaged/workflow-protocol";
 import { type GcResult, garbageCollectCas } from "@uncaged/workflow-execute";
+import type { Result } from "@uncaged/workflow-protocol";
 
 export async function cmdGc(storageRoot: string): Promise<Result<GcResult, string>> {
   return garbageCollectCas(storageRoot);

packages/cli-workflow/src/commands/cas/get.ts

@@ -1,6 +1,6 @@
+import { createCasStore } from "@uncaged/workflow-cas";
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
-import { createCasStore } from "@uncaged/workflow-cas";
 
 export async function cmdCasGet(
   storageRoot: string,

packages/cli-workflow/src/commands/cas/list.ts

@@ -1,6 +1,6 @@
+import { createCasStore } from "@uncaged/workflow-cas";
 import { ok, type Result } from "@uncaged/workflow-protocol";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
-import { createCasStore } from "@uncaged/workflow-cas";
 
 export async function cmdCasList(storageRoot: string): Promise<Result<string[], string>> {
   const cas = createCasStore(getGlobalCasDir(storageRoot));

packages/cli-workflow/src/commands/cas/put.ts

@@ -1,6 +1,6 @@
+import { createCasStore } from "@uncaged/workflow-cas";
 import { ok, type Result } from "@uncaged/workflow-protocol";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
-import { createCasStore } from "@uncaged/workflow-cas";
 
 export async function cmdCasPut(
   storageRoot: string,

packages/cli-workflow/src/commands/cas/rm.ts

@@ -1,6 +1,6 @@
+import { createCasStore } from "@uncaged/workflow-cas";
 import { ok, type Result } from "@uncaged/workflow-protocol";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
-import { createCasStore } from "@uncaged/workflow-cas";
 
 export async function cmdCasRm(storageRoot: string, hash: string): Promise<Result<void, string>> {
   const cas = createCasStore(getGlobalCasDir(storageRoot));

packages/cli-workflow/src/commands/serve/routes-cas.ts

@@ -1,6 +1,6 @@
-import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { createCasStore } from "@uncaged/workflow-cas";
 import { garbageCollectCas } from "@uncaged/workflow-execute";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { Hono } from "hono";
 
 export function createCasRoutes(storageRoot: string): Hono {

packages/cli-workflow/src/commands/serve/routes-live.ts

@@ -1,9 +1,18 @@
 import { statSync, watch } from "node:fs";
-import { dirname, join } from "node:path";
+import { join } from "node:path";
+import { createCasStore, getContentMerklePayload } from "@uncaged/workflow-cas";
+import {
+  FORK_BRANCH_ROLE,
+  readThreadsIndex,
+  type ThreadIndex,
+  walkStateFramesNewestFirst,
+} from "@uncaged/workflow-execute";
+import { END } from "@uncaged/workflow-runtime";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { Hono } from "hono";
 import { streamSSE } from "hono/streaming";
 
-import { resolveThreadDataPath } from "../../thread-scan.js";
+import { resolveThreadRecord } from "../../thread-scan.js";
 
 type PumpState = {
   contentOffset: number;
@@ -21,7 +30,6 @@ function fileSize(path: string): number {
 async function readNewBytes(path: string, state: PumpState): Promise<string | null> {
   const size = fileSize(path);
   if (size < state.contentOffset) {
-    // File was truncated — reset
     state.contentOffset = 0;
     state.carry = "";
   }
@@ -42,15 +50,6 @@ function parseJsonLine(line: string): unknown {
   }
 }
 
-function isWorkflowResult(record: unknown): boolean {
-  return (
-    record !== null &&
-    typeof record === "object" &&
-    "type" in (record as Record<string, unknown>) &&
-    (record as Record<string, unknown>).type === "workflow-result"
-  );
-}
-
 function parseNewLines(chunk: string, state: PumpState): string[] {
   state.carry += chunk;
 
@@ -67,52 +66,192 @@ function parseNewLines(chunk: string, state: PumpState): string[] {
   return lines;
 }
 
+type CasSseState = {
+  printedHashes: Set<string>;
+  lastHead: string | null;
+  completionEmitted: boolean;
+};
+
+type LiveSseStream = {
+  writeSSE: (opts: { event: string; data: string; id: string }) => Promise<void>;
+};
+
+function completionFromEndMeta(meta: Record<string, unknown>): {
+  returnCode: number;
+  summary: string;
+} | null {
+  const returnCode = meta.returnCode;
+  const summary = meta.summary;
+  if (typeof returnCode !== "number" || typeof summary !== "string") {
+    return null;
+  }
+  return { returnCode, summary };
+}
+
+async function emitRecordsForHead(params: {
+  storageRoot: string;
+  bundleDir: string;
+  threadId: string;
+  headHash: string;
+  sseState: CasSseState;
+  stream: LiveSseStream;
+  eventId: { n: number };
+}): Promise<boolean> {
+  const cas = createCasStore(getGlobalCasDir(params.storageRoot));
+  const frames = await walkStateFramesNewestFirst(cas, params.headHash);
+  const chronological = [...frames].reverse();
+
+  for (const fr of chronological) {
+    if (params.sseState.printedHashes.has(fr.hash)) {
+      continue;
+    }
+    params.sseState.printedHashes.add(fr.hash);
+
+    const role = fr.payload.role;
+    if (role === FORK_BRANCH_ROLE) {
+      continue;
+    }
+
+    if (role === END) {
+      const wf = completionFromEndMeta(fr.payload.meta);
+      if (wf !== null) {
+        params.eventId.n++;
+        await params.stream.writeSSE({
+          event: "record",
+          data: JSON.stringify({ type: "workflow-result", ...wf }),
+          id: String(params.eventId.n),
+        });
+        return true;
+      }
+      continue;
+    }
+
+    const payloadText = await getContentMerklePayload(cas, fr.payload.content);
+    const content =
+      payloadText !== null
+        ? payloadText
+        : `(content not in CAS; contentHash=${fr.payload.content})`;
+
+    params.eventId.n++;
+    await params.stream.writeSSE({
+      event: "record",
+      data: JSON.stringify({
+        role: fr.payload.role,
+        contentHash: fr.payload.content,
+        content,
+        meta: fr.payload.meta,
+        timestamp: fr.payload.timestamp,
+      }),
+      id: String(params.eventId.n),
+    });
+  }
+
+  return false;
+}
+
+async function pumpThreadsJsonSse(params: {
+  storageRoot: string;
+  bundleDir: string;
+  threadId: string;
+  sseState: CasSseState;
+  stream: LiveSseStream;
+  eventId: { n: number };
+}): Promise<boolean> {
+  let idx: ThreadIndex;
+  try {
+    idx = await readThreadsIndex(params.bundleDir);
+  } catch {
+    idx = {};
+  }
+
+  const active = idx[params.threadId];
+
+  if (active === undefined) {
+    if (params.sseState.completionEmitted) {
+      return false;
+    }
+    const hist = await resolveThreadRecord(params.storageRoot, params.threadId);
+    if (hist === null || hist.source !== "history") {
+      return false;
+    }
+    params.sseState.completionEmitted = true;
+    return await emitRecordsForHead({
+      storageRoot: params.storageRoot,
+      bundleDir: params.bundleDir,
+      threadId: params.threadId,
+      headHash: hist.head,
+      sseState: params.sseState,
+      stream: params.stream,
+      eventId: params.eventId,
+    });
+  }
+
+  const head = active.head;
+  if (params.sseState.lastHead === null) {
+    params.sseState.lastHead = head;
+    return await emitRecordsForHead({
+      storageRoot: params.storageRoot,
+      bundleDir: params.bundleDir,
+      threadId: params.threadId,
+      headHash: head,
+      sseState: params.sseState,
+      stream: params.stream,
+      eventId: params.eventId,
+    });
+  }
+
+  if (head !== params.sseState.lastHead) {
+    params.sseState.lastHead = head;
+    return await emitRecordsForHead({
+      storageRoot: params.storageRoot,
+      bundleDir: params.bundleDir,
+      threadId: params.threadId,
+      headHash: head,
+      sseState: params.sseState,
+      stream: params.stream,
+      eventId: params.eventId,
+    });
+  }
+
+  return false;
+}
+
 export function createLiveRoutes(storageRoot: string): Hono {
   const app = new Hono();
 
   app.get("/:threadId/live", async (c) => {
     const threadId = c.req.param("threadId");
-    const dataPath = await resolveThreadDataPath(storageRoot, threadId);
-    if (dataPath === null) {
+    const resolved = await resolveThreadRecord(storageRoot, threadId);
+    if (resolved === null) {
       return c.json({ error: `thread not found: ${threadId}` }, 404);
     }
-    const resolvedDataPath = dataPath;
 
-    const infoPath = join(dirname(resolvedDataPath), `${threadId}.info.jsonl`);
+    const threadTarget = resolved;
+    const threadsJsonPath = join(threadTarget.bundleDir, "threads.json");
+    const infoPath = join(storageRoot, "logs", threadTarget.bundleHash, `${threadId}.info.jsonl`);
 
     return streamSSE(c, async (stream) => {
-      const dataState: PumpState = { contentOffset: 0, carry: "" };
       const infoState: PumpState = { contentOffset: 0, carry: "" };
-      let eventId = 0;
+      const sseThreadState: CasSseState = {
+        printedHashes: new Set<string>(),
+        lastHead: null,
+        completionEmitted: false,
+      };
+      const eventId = { n: 0 };
 
       async function pumpData(): Promise<boolean> {
-        let chunk: string | null;
-        try {
-          chunk = await readNewBytes(resolvedDataPath, dataState);
-        } catch {
-          return false;
-        }
-        if (chunk === null) {
-          return false;
-        }
-
-        const lines = parseNewLines(chunk, dataState);
-        for (const line of lines) {
-          const record = parseJsonLine(line);
-          eventId++;
-          await stream.writeSSE({
-            event: "record",
-            data: JSON.stringify(record),
-            id: String(eventId),
-          });
-
-          if (isWorkflowResult(record)) {
-            return true;
-          }
-        }
-        return false;
+        const finished = await pumpThreadsJsonSse({
+          storageRoot,
+          bundleDir: threadTarget.bundleDir,
+          threadId,
+          sseState: sseThreadState,
+          stream,
+          eventId,
+        });
+        return finished;
       }
 
+      // biome-ignore lint/complexity/noExcessiveCognitiveComplexity: SSE newline framing mirrors legacy pump
       async function pumpInfo(): Promise<void> {
         let chunk: string | null;
         try {
@@ -134,28 +273,46 @@ export function createLiveRoutes(storageRoot: string): Hono {
           ) {
             continue;
           }
-          eventId++;
+          eventId.n++;
           await stream.writeSSE({
             event: "info",
             data: JSON.stringify(record),
-            id: String(eventId),
+            id: String(eventId.n),
           });
         }
       }
 
-      // Initial pump
+      eventId.n++;
+      await stream.writeSSE({
+        event: "record",
+        data: JSON.stringify({
+          type: "thread-start",
+          threadId: threadTarget.threadId,
+          bundleHash: threadTarget.bundleHash,
+          head: threadTarget.head,
+          start: threadTarget.start,
+          source: threadTarget.source,
+        }),
+        id: String(eventId.n),
+      });
+
       const done = await pumpData();
-      await pumpInfo();
+      try {
+        await pumpInfo();
+      } catch {
+        // optional info file
+      }
       if (done) {
         return;
       }
 
-      // Watch for changes
       const controller = new AbortController();
       let completed = false;
 
-      const dataWatcher = watch(resolvedDataPath, async () => {
-        if (completed) return;
+      const dataWatcher = watch(threadsJsonPath, async () => {
+        if (completed) {
+          return;
+        }
         const finished = await pumpData();
         if (finished) {
           completed = true;
@@ -166,7 +323,9 @@ export function createLiveRoutes(storageRoot: string): Hono {
       let infoWatcher: ReturnType<typeof watch> | null = null;
       try {
         infoWatcher = watch(infoPath, async () => {
-          if (completed) return;
+          if (completed) {
+            return;
+          }
           await pumpInfo();
         });
       } catch {
@@ -179,7 +338,6 @@ export function createLiveRoutes(storageRoot: string): Hono {
         infoWatcher?.close();
       });
 
-      // Keep stream alive until completion or client disconnect
       await new Promise<void>((resolve) => {
         if (completed) {
           resolve();

packages/cli-workflow/src/commands/serve/routes-thread.ts

@@ -1,10 +1,13 @@
+import { createCasStore } from "@uncaged/workflow-cas";
+import { FORK_BRANCH_ROLE, walkStateFramesNewestFirst } from "@uncaged/workflow-execute";
+import { END } from "@uncaged/workflow-runtime";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { Hono } from "hono";
 
-import { readTextFileIfExists } from "../../fs-utils.js";
 import {
   listHistoricalThreads,
   listRunningThreads,
-  resolveThreadDataPath,
+  resolveThreadRecord,
 } from "../../thread-scan.js";
 import { cmdKill, cmdPause, cmdResume } from "../thread/control.js";
 import { cmdRun } from "../thread/run.js";
@@ -25,22 +28,46 @@ export function createThreadRoutes(storageRoot: string): Hono {
 
   app.get("/:threadId", async (c) => {
     const threadId = c.req.param("threadId");
-    const dataPath = await resolveThreadDataPath(storageRoot, threadId);
-    if (dataPath === null) {
+    const resolved = await resolveThreadRecord(storageRoot, threadId);
+    if (resolved === null) {
       return c.json({ error: `thread not found: ${threadId}` }, 404);
     }
-    const text = await readTextFileIfExists(dataPath);
-    if (text === null) {
-      return c.json({ error: `thread data missing: ${threadId}` }, 404);
-    }
-    const lines = text.trim().split("\n");
-    const records = lines.map((line) => {
-      try {
-        return JSON.parse(line) as unknown;
-      } catch {
-        return { raw: line };
+
+    const cas = createCasStore(getGlobalCasDir(storageRoot));
+    const frames = await walkStateFramesNewestFirst(cas, resolved.head);
+    const chronological = [...frames].reverse();
+
+    const records: unknown[] = [
+      {
+        type: "thread-start",
+        threadId: resolved.threadId,
+        bundleHash: resolved.bundleHash,
+        head: resolved.head,
+        start: resolved.start,
+        source: resolved.source,
+      },
+    ];
+
+    for (const fr of chronological) {
+      if (fr.payload.role === FORK_BRANCH_ROLE) {
+        continue;
       }
-    });
+      if (fr.payload.role === END) {
+        const returnCode = fr.payload.meta.returnCode;
+        const summary = fr.payload.meta.summary;
+        if (typeof returnCode === "number" && typeof summary === "string") {
+          records.push({ type: "workflow-result", returnCode, summary });
+        }
+        continue;
+      }
+      records.push({
+        role: fr.payload.role,
+        contentHash: fr.payload.content,
+        meta: fr.payload.meta,
+        timestamp: fr.payload.timestamp,
+      });
+    }
+
     return c.json({ threadId, records });
   });
 

packages/cli-workflow/src/commands/thread/fork.ts

@@ -1,11 +1,11 @@
 import { join } from "node:path";
-
+import { createCasStore } from "@uncaged/workflow-cas";
+import { prepareCasFork } from "@uncaged/workflow-execute";
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
-import { generateUlid } from "@uncaged/workflow-util";
-import { buildForkPlan } from "@uncaged/workflow-execute";
+import { generateUlid, getGlobalCasDir } from "@uncaged/workflow-util";
 
-import { pathExists, readTextFileIfExists } from "../../fs-utils.js";
-import { resolveThreadDataPath } from "../../thread-scan.js";
+import { pathExists } from "../../fs-utils.js";
+import { resolveThreadRecord } from "../../thread-scan.js";
 import { ensureWorkerForHash, sendWorkerTcpCommand } from "../../worker-spawn.js";
 
 export async function cmdFork(
@@ -13,49 +13,51 @@ export async function cmdFork(
   threadId: string,
   fromRole: string | null,
 ): Promise<Result<{ threadId: string }, string>> {
-  const dataPath = await resolveThreadDataPath(storageRoot, threadId);
-  if (dataPath === null) {
+  const resolved = await resolveThreadRecord(storageRoot, threadId);
+  if (resolved === null) {
     return err(`thread not found: ${threadId}`);
   }
-  const text = await readTextFileIfExists(dataPath);
-  if (text === null) {
-    return err(`thread data missing: ${threadId}`);
+
+  const bundlePath = join(storageRoot, "bundles", `${resolved.bundleHash}.esm.js`);
+  if (!(await pathExists(bundlePath))) {
+    return err(`bundle file missing for thread hash ${resolved.bundleHash}`);
   }
 
-  const plan = buildForkPlan(text, fromRole);
+  const cas = createCasStore(getGlobalCasDir(storageRoot));
+  const newThreadId = generateUlid(Date.now());
+
+  const plan = await prepareCasFork({
+    cas,
+    bundleDir: resolved.bundleDir,
+    bundleHash: resolved.bundleHash,
+    sourceThreadId: threadId,
+    headHash: resolved.head,
+    startHash: resolved.start,
+    newThreadId,
+    fromRole,
+  });
   if (!plan.ok) {
     return plan;
   }
 
-  const bundlePath = join(storageRoot, "bundles", `${plan.value.hash}.esm.js`);
-  if (!(await pathExists(bundlePath))) {
-    return err(`bundle file missing for thread hash ${plan.value.hash}`);
-  }
-
   const worker = await ensureWorkerForHash(storageRoot, plan.value.hash, bundlePath);
   if (!worker.ok) {
     return worker;
   }
 
-  const newThreadId = generateUlid(Date.now());
-  const stepsOnWire = plan.value.historicalSteps.map((s) => ({
-    role: s.role,
-    contentHash: s.contentHash,
-    meta: s.meta,
-    refs: s.refs,
-    timestamp: s.timestamp,
-  }));
-
+  const p = plan.value;
   const sent = await sendWorkerTcpCommand(
     worker.value.port,
     {
       type: "run",
       threadId: newThreadId,
-      workflowName: plan.value.workflowName,
-      prompt: plan.value.prompt,
-      options: plan.value.runOptions,
-      steps: stepsOnWire,
-      forkSourceThreadId: plan.value.sourceThreadId,
+      workflowName: p.workflowName,
+      prompt: p.prompt,
+      options: p.runOptions,
+      steps: p.steps,
+      stepTimestamps: p.stepTimestamps.length > 0 ? p.stepTimestamps : null,
+      forkSourceThreadId: threadId,
+      forkContinuation: p.forkContinuation,
     },
     { awaitResponseLine: false },
   );

packages/cli-workflow/src/commands/thread/live.ts

@@ -1,17 +1,26 @@
 import { watch } from "node:fs";
-import { readFile } from "node:fs/promises";
+import { mkdir, readFile } from "node:fs/promises";
 import { dirname, join } from "node:path";
-
-import type { CasStore, WorkflowCompletion } from "@uncaged/workflow-protocol";
-import { getGlobalCasDir } from "@uncaged/workflow-util";
 import { createCasStore, getContentMerklePayload } from "@uncaged/workflow-cas";
-import { tryParseRoleStepRecord, tryParseWorkflowResultRecord } from "@uncaged/workflow-execute";
+import {
+  FORK_BRANCH_ROLE,
+  readThreadsIndex,
+  type ThreadIndex,
+  walkStateFramesNewestFirst,
+} from "@uncaged/workflow-execute";
+import type { CasStore, WorkflowCompletion } from "@uncaged/workflow-protocol";
+import { END } from "@uncaged/workflow-runtime";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 
 import { dimGreyLine, highlightLiveRole } from "../../cli-color.js";
 import { printCliError, printCliLine } from "../../cli-output.js";
 import { pathExists } from "../../fs-utils.js";
 import type { ParsedLiveArgv } from "../../live-argv.js";
-import { findLatestThreadDataPath, resolveThreadDataPath } from "../../thread-scan.js";
+import {
+  findLatestThreadBundleTarget,
+  type LatestThreadTarget,
+  resolveThreadRecord,
+} from "../../thread-scan.js";
 import type { LiveRoleRow } from "./types.js";
 
 export const LIVE_CONTENT_MAX_LINES = 10;
@@ -49,16 +58,15 @@ function printSummary(result: WorkflowCompletion): void {
   printCliLine(`completed: returnCode=${result.returnCode} — ${result.summary}`);
 }
 
-type LiveSessionState = {
-  sawStart: boolean;
-  completed: boolean;
+type InfoLiveState = {
   carry: string;
   contentOffset: number;
 };
 
-type InfoLiveState = {
-  carry: string;
-  contentOffset: number;
+type CasLiveState = {
+  printedHashes: Set<string>;
+  lastHead: string | null;
+  completionEmitted: boolean;
 };
 
 function tryParseInfoRecord(obj: Record<string, unknown>): {
@@ -80,102 +88,140 @@ function tryParseInfoRecord(obj: Record<string, unknown>): {
   return { tag, content, timestamp };
 }
 
-async function handleJsonlLine(
-  rawLine: string,
-  state: LiveSessionState,
-  roleFilter: string | null,
-  cas: CasStore,
-): Promise<{ parseError: string | null; workflowResult: WorkflowCompletion | null }> {
-  const trimmed = rawLine.trim();
-  if (trimmed === "") {
-    return { parseError: null, workflowResult: null };
+function completionFromEndMeta(meta: Record<string, unknown>): WorkflowCompletion | null {
+  const returnCode = meta.returnCode;
+  const summary = meta.summary;
+  if (typeof returnCode !== "number" || typeof summary !== "string") {
+    return null;
   }
+  return { returnCode, summary };
+}
 
-  let rec: unknown;
-  try {
-    rec = JSON.parse(trimmed) as unknown;
-  } catch {
-    return { parseError: "invalid JSON in thread data file", workflowResult: null };
+async function emitRoleStepPrint(params: {
+  cas: CasStore;
+  role: string;
+  contentHash: string;
+  meta: Record<string, unknown>;
+  timestamp: number;
+  roleFilter: string | null;
+}): Promise<void> {
+  if (params.roleFilter !== null && params.role !== params.roleFilter) {
+    return;
   }
-  if (rec === null || typeof rec !== "object") {
-    return { parseError: "invalid record in thread data file", workflowResult: null };
-  }
-  const obj = rec as Record<string, unknown>;
-
-  if (!state.sawStart) {
-    state.sawStart = true;
-    return { parseError: null, workflowResult: null };
-  }
-
-  const wf = tryParseWorkflowResultRecord(obj);
-  if (wf !== null) {
-    state.completed = true;
-    return { parseError: null, workflowResult: wf };
-  }
-
-  const roleRow = tryParseRoleStepRecord(obj);
-  if (roleRow === null) {
-    return {
-      parseError: "unrecognized record in thread data (expected role step or result)",
-      workflowResult: null,
-    };
-  }
-
-  if (roleFilter !== null && roleRow.role !== roleFilter) {
-    return { parseError: null, workflowResult: null };
-  }
-
-  const payload = await getContentMerklePayload(cas, roleRow.contentHash);
+  const payload = await getContentMerklePayload(params.cas, params.contentHash);
   const content =
-    payload !== null ? payload : `(content not in CAS; contentHash=${roleRow.contentHash})`;
+    payload !== null ? payload : `(content not in CAS; contentHash=${params.contentHash})`;
 
   const row: LiveRoleRow = {
-    role: roleRow.role,
+    role: params.role,
     content,
-    meta: roleRow.meta,
-    timestamp: roleRow.timestamp,
+    meta: params.meta,
+    timestamp: params.timestamp,
   };
   for (const outLine of renderLiveRoleStepLines(row, highlightLiveRole(row.role))) {
     printCliLine(outLine);
   }
-  return { parseError: null, workflowResult: null };
 }
 
-async function pumpNewContent(
-  dataPath: string,
-  state: LiveSessionState,
-  roleFilter: string | null,
-  cas: CasStore,
-): Promise<number | null> {
-  let text: string;
+async function emitStatesReachableFromHead(params: {
+  cas: CasStore;
+  headHash: string;
+  state: CasLiveState;
+  roleFilter: string | null;
+}): Promise<WorkflowCompletion | null> {
+  const frames = await walkStateFramesNewestFirst(params.cas, params.headHash);
+  const chronological = [...frames].reverse();
+
+  for (const fr of chronological) {
+    if (params.state.printedHashes.has(fr.hash)) {
+      continue;
+    }
+    params.state.printedHashes.add(fr.hash);
+
+    const role = fr.payload.role;
+    if (role === FORK_BRANCH_ROLE) {
+      continue;
+    }
+
+    if (role === END) {
+      const wf = completionFromEndMeta(fr.payload.meta);
+      if (wf !== null) {
+        printSummary(wf);
+        return wf;
+      }
+      continue;
+    }
+
+    await emitRoleStepPrint({
+      cas: params.cas,
+      role,
+      contentHash: fr.payload.content,
+      meta: fr.payload.meta,
+      timestamp: fr.payload.timestamp,
+      roleFilter: params.roleFilter,
+    });
+  }
+
+  return null;
+}
+
+async function pumpThreadsJson(params: {
+  storageRoot: string;
+  bundleDir: string;
+  bundleHash: string;
+  threadId: string;
+  state: CasLiveState;
+  roleFilter: string | null;
+  cas: CasStore;
+}): Promise<number | null> {
+  let idx: ThreadIndex;
   try {
-    text = await readFile(dataPath, "utf8");
+    idx = await readThreadsIndex(params.bundleDir);
   } catch {
-    return null;
+    idx = {};
   }
 
-  if (text.length < state.contentOffset) {
-    state.contentOffset = 0;
-    state.carry = "";
+  const active = idx[params.threadId];
+
+  if (active === undefined) {
+    if (params.state.completionEmitted) {
+      return null;
+    }
+    const hist = await resolveThreadRecord(params.storageRoot, params.threadId);
+    if (hist === null || hist.source !== "history") {
+      return null;
+    }
+    params.state.completionEmitted = true;
+    const wf = await emitStatesReachableFromHead({
+      cas: params.cas,
+      headHash: hist.head,
+      state: params.state,
+      roleFilter: params.roleFilter,
+    });
+    return wf !== null ? 0 : null;
   }
 
-  const chunk = text.slice(state.contentOffset);
-  state.contentOffset = text.length;
-  state.carry += chunk;
+  const head = active.head;
+  if (params.state.lastHead === null) {
+    params.state.lastHead = head;
+    const wf = await emitStatesReachableFromHead({
+      cas: params.cas,
+      headHash: head,
+      state: params.state,
+      roleFilter: params.roleFilter,
+    });
+    return wf !== null ? 0 : null;
+  }
 
-  const parts = state.carry.split("\n");
-  state.carry = parts.pop() ?? "";
-
-  for (const line of parts) {
-    const { parseError, workflowResult } = await handleJsonlLine(line, state, roleFilter, cas);
-    if (parseError !== null) {
-      printCliError(parseError);
-      return 1;
-    }
-    if (workflowResult !== null) {
-      printSummary(workflowResult);
-      return 0;
-    }
+  if (head !== params.state.lastHead) {
+    params.state.lastHead = head;
+    const wf = await emitStatesReachableFromHead({
+      cas: params.cas,
+      headHash: head,
+      state: params.state,
+      roleFilter: params.roleFilter,
+    });
+    return wf !== null ? 0 : null;
   }
 
   return null;
@@ -292,9 +338,9 @@ function watchLivePaths(params: { tasks: WatchPumpTask[]; signal: AbortSignal })
         schedulePump(path, pump);
       });
       watchers.push(watcher);
-      watcher.on("error", (err: Error) => {
+      watcher.on("error", (errObj: Error) => {
         closeAll();
-        reject(err);
+        reject(errObj);
       });
     }
 
@@ -310,17 +356,14 @@ function watchLivePaths(params: { tasks: WatchPumpTask[]; signal: AbortSignal })
   });
 }
 
-type LiveThreadTarget = {
-  threadId: string;
-  dataPath: string;
-};
+type LiveThreadTarget = LatestThreadTarget;
 
 async function resolveLiveThreadTarget(
   storageRoot: string,
   parsed: ParsedLiveArgv,
 ): Promise<LiveThreadTarget | null> {
   if (parsed.latest) {
-    const found = await findLatestThreadDataPath(storageRoot);
+    const found = await findLatestThreadBundleTarget(storageRoot);
     if (found === null) {
       printCliError("live: no threads found");
       return null;
@@ -333,36 +376,56 @@ async function resolveLiveThreadTarget(
     printCliError("live: internal error: missing thread id");
     return null;
   }
-  const resolved = await resolveThreadDataPath(storageRoot, id);
+  const resolved = await resolveThreadRecord(storageRoot, id);
   if (resolved === null) {
     printCliError(`thread not found: ${id}`);
     return null;
   }
-  return { threadId: id, dataPath: resolved };
+  return {
+    threadId: id,
+    bundleHash: resolved.bundleHash,
+    bundleDir: resolved.bundleDir,
+    threadsJsonPath: join(resolved.bundleDir, "threads.json"),
+  };
 }
 
 async function buildLiveWatchTasks(params: {
-  dataPath: string;
-  infoPath: string;
+  storageRoot: string;
+  target: LiveThreadTarget;
   debug: boolean;
-  dataState: LiveSessionState;
+  dataState: CasLiveState;
   infoState: InfoLiveState;
   roleFilter: string | null;
   cas: CasStore;
 }): Promise<WatchPumpTask[]> {
-  const { dataPath, infoPath, debug, dataState, infoState, roleFilter, cas } = params;
+  const infoPath = join(
+    params.storageRoot,
+    "logs",
+    params.target.bundleHash,
+    `${params.target.threadId}.info.jsonl`,
+  );
+
   const tasks: WatchPumpTask[] = [
     {
-      path: dataPath,
-      pump: () => pumpNewContent(dataPath, dataState, roleFilter, cas),
+      path: params.target.threadsJsonPath,
+      pump: () =>
+        pumpThreadsJson({
+          storageRoot: params.storageRoot,
+          bundleDir: params.target.bundleDir,
+          bundleHash: params.target.bundleHash,
+          threadId: params.target.threadId,
+          state: params.dataState,
+          roleFilter: params.roleFilter,
+          cas: params.cas,
+        }),
     },
   ];
 
-  if (debug && (await pathExists(infoPath))) {
+  if (params.debug && (await pathExists(infoPath))) {
     tasks.push({
       path: infoPath,
       pump: async () => {
-        await pumpNewInfoContent(infoPath, infoState);
+        await pumpNewInfoContent(infoPath, params.infoState);
         return null;
       },
     });
@@ -377,16 +440,13 @@ export async function cmdLive(storageRoot: string, parsed: ParsedLiveArgv): Prom
     return 1;
   }
 
-  const { threadId, dataPath } = target;
   const roleFilter = parsed.role;
-  const infoPath = join(dirname(dataPath), `${threadId}.info.jsonl`);
   const cas = createCasStore(getGlobalCasDir(storageRoot));
 
-  const dataState: LiveSessionState = {
-    sawStart: false,
-    completed: false,
-    carry: "",
-    contentOffset: 0,
+  const dataState: CasLiveState = {
+    printedHashes: new Set<string>(),
+    lastHead: null,
+    completionEmitted: false,
   };
 
   const infoState: InfoLiveState = {
@@ -401,22 +461,29 @@ export async function cmdLive(storageRoot: string, parsed: ParsedLiveArgv): Prom
   process.on("SIGINT", onSigInt);
 
   try {
-    const firstData = await pumpNewContent(dataPath, dataState, roleFilter, cas);
-    if (firstData === 1) {
-      return 1;
-    }
+    await mkdir(dirname(target.threadsJsonPath), { recursive: true });
 
+    const firstData = await pumpThreadsJson({
+      storageRoot,
+      bundleDir: target.bundleDir,
+      bundleHash: target.bundleHash,
+      threadId: target.threadId,
+      state: dataState,
+      roleFilter,
+      cas,
+    });
+    const infoPath = join(storageRoot, "logs", target.bundleHash, `${target.threadId}.info.jsonl`);
     if (parsed.debug && (await pathExists(infoPath))) {
       await pumpNewInfoContent(infoPath, infoState);
     }
 
-    if (firstData === 0 || dataState.completed) {
+    if (firstData === 0) {
       return 0;
     }
 
     const tasks = await buildLiveWatchTasks({
-      dataPath,
-      infoPath,
+      storageRoot,
+      target,
       debug: parsed.debug,
       dataState,
       infoState,

packages/cli-workflow/src/commands/thread/rm.ts

@@ -1,25 +1,35 @@
 import { unlink } from "node:fs/promises";
-import { dirname, join } from "node:path";
-
+import { join } from "node:path";
+import {
+  garbageCollectCas,
+  removeThreadEntry,
+  removeThreadHistoryEntries,
+} from "@uncaged/workflow-execute";
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
-import { garbageCollectCas } from "@uncaged/workflow-execute";
 
-import { resolveThreadDataPath } from "../../thread-scan.js";
+import { resolveThreadRecord } from "../../thread-scan.js";
 
 export async function cmdThreadRemove(
   storageRoot: string,
   threadId: string,
 ): Promise<Result<void, string>> {
-  const dataPath = await resolveThreadDataPath(storageRoot, threadId);
-  if (dataPath === null) {
+  const resolved = await resolveThreadRecord(storageRoot, threadId);
+  if (resolved === null) {
     return err(`thread not found: ${threadId}`);
   }
 
-  const dir = dirname(dataPath);
-  const infoPath = join(dir, `${threadId}.info.jsonl`);
-  const runningPath = join(dir, `${threadId}.running`);
+  if (resolved.source === "active") {
+    await removeThreadEntry(resolved.bundleDir, threadId);
+  } else {
+    const hist = await removeThreadHistoryEntries(resolved.bundleDir, threadId);
+    if (!hist.ok) {
+      return hist;
+    }
+  }
+
+  const infoPath = join(storageRoot, "logs", resolved.bundleHash, `${threadId}.info.jsonl`);
+  const runningPath = join(storageRoot, "logs", resolved.bundleHash, `${threadId}.running`);
 
-  await unlink(dataPath);
   await unlink(infoPath).catch(() => {});
   await unlink(runningPath).catch(() => {});
 

packages/cli-workflow/src/commands/thread/run.ts

@@ -1,8 +1,8 @@
 import { join } from "node:path";
 
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
-import { generateUlid } from "@uncaged/workflow-util";
 import { getRegisteredWorkflow, readWorkflowRegistry } from "@uncaged/workflow-register";
+import { generateUlid } from "@uncaged/workflow-util";
 import { ensureWorkerForHash, sendWorkerTcpCommand } from "../../worker-spawn.js";
 import { validateCliWorkflowName } from "../../workflow-name.js";
 

packages/cli-workflow/src/commands/thread/show.ts

@@ -1,19 +1,44 @@
+import { createCasStore } from "@uncaged/workflow-cas";
+import { FORK_BRANCH_ROLE, walkStateFramesNewestFirst } from "@uncaged/workflow-execute";
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
+import { END } from "@uncaged/workflow-runtime";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 
-import { readTextFileIfExists } from "../../fs-utils.js";
-import { resolveThreadDataPath } from "../../thread-scan.js";
+import { resolveThreadRecord } from "../../thread-scan.js";
 
 export async function cmdThreadShow(
   storageRoot: string,
   threadId: string,
 ): Promise<Result<string, string>> {
-  const dataPath = await resolveThreadDataPath(storageRoot, threadId);
-  if (dataPath === null) {
+  const resolved = await resolveThreadRecord(storageRoot, threadId);
+  if (resolved === null) {
     return err(`thread not found: ${threadId}`);
   }
-  const text = await readTextFileIfExists(dataPath);
-  if (text === null) {
-    return err(`thread data missing: ${threadId}`);
+
+  const cas = createCasStore(getGlobalCasDir(storageRoot));
+  const frames = await walkStateFramesNewestFirst(cas, resolved.head);
+  const chronological = [...frames].reverse();
+
+  const steps: Array<{ role: string; hash: string; timestamp: number }> = [];
+  for (const fr of chronological) {
+    if (fr.payload.role === END || fr.payload.role === FORK_BRANCH_ROLE) {
+      continue;
+    }
+    steps.push({
+      role: fr.payload.role,
+      hash: fr.hash,
+      timestamp: fr.payload.timestamp,
+    });
   }
-  return ok(text.endsWith("\n") ? text.slice(0, -1) : text);
+
+  const payload = {
+    threadId: resolved.threadId,
+    bundleHash: resolved.bundleHash,
+    head: resolved.head,
+    start: resolved.start,
+    source: resolved.source,
+    steps,
+  };
+
+  return ok(JSON.stringify(payload, null, 2));
 }

packages/cli-workflow/src/commands/workflow/add.ts

@@ -1,8 +1,7 @@
 import { readFile, stat } from "node:fs/promises";
 import { basename, resolve } from "node:path";
-
-import { err, ok, type Result } from "@uncaged/workflow-protocol";
 import { hashWorkflowBundleBytes } from "@uncaged/workflow-cas";
+import { err, ok, type Result } from "@uncaged/workflow-protocol";
 import {
   extractBundleExports,
   readWorkflowRegistry,

packages/cli-workflow/src/thread-scan.ts

@@ -1,23 +1,87 @@
 import { readdir, stat } from "node:fs/promises";
 import { join } from "node:path";
+import { createCasStore, parseCasThreadNode } from "@uncaged/workflow-cas";
+import {
+  readThreadsIndex,
+  type ThreadHistoryEntry,
+  type ThreadIndex,
+} from "@uncaged/workflow-execute";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
 
 import { pathExists, readTextFileIfExists } from "./fs-utils.js";
 
-function parseFirstJsonLineObject(text: string): Record<string, unknown> | null {
-  const firstLine = text.split("\n")[0];
-  if (firstLine === undefined || firstLine.trim() === "") {
+async function readWorkflowNameFromStartHash(
+  storageRoot: string,
+  startHash: string,
+): Promise<string | null> {
+  const cas = createCasStore(getGlobalCasDir(storageRoot));
+  const yamlText = await cas.get(startHash);
+  if (yamlText === null) {
     return null;
   }
-  let parsed: unknown;
-  try {
-    parsed = JSON.parse(firstLine) as unknown;
-  } catch {
+  const parsed = parseCasThreadNode(yamlText);
+  if (parsed === null || parsed.kind !== "start") {
     return null;
   }
-  if (parsed === null || typeof parsed !== "object") {
-    return null;
+  return parsed.node.payload.name;
+}
+
+async function listBundleHashDirs(storageRoot: string): Promise<string[]> {
+  const bundlesRoot = join(storageRoot, "bundles");
+  if (!(await pathExists(bundlesRoot))) {
+    return [];
   }
-  return parsed as Record<string, unknown>;
+  const names = await readdir(bundlesRoot);
+  const out: string[] = [];
+  for (const name of names) {
+    const p = join(bundlesRoot, name);
+    try {
+      const st = await stat(p);
+      if (st.isDirectory()) {
+        out.push(name);
+      }
+    } catch {}
+  }
+  out.sort();
+  return out;
+}
+
+async function parseHistoryFile(path: string): Promise<ThreadHistoryEntry[]> {
+  const text = await readTextFileIfExists(path);
+  if (text === null) {
+    return [];
+  }
+  const out: ThreadHistoryEntry[] = [];
+  for (const line of text.split("\n")) {
+    const trimmed = line.trim();
+    if (trimmed === "") {
+      continue;
+    }
+    let raw: unknown;
+    try {
+      raw = JSON.parse(trimmed) as unknown;
+    } catch {
+      continue;
+    }
+    if (raw === null || typeof raw !== "object") {
+      continue;
+    }
+    const rec = raw as Record<string, unknown>;
+    const threadId = rec.threadId;
+    const head = rec.head;
+    const start = rec.start;
+    const completedAt = rec.completedAt;
+    if (
+      typeof threadId !== "string" ||
+      typeof head !== "string" ||
+      typeof start !== "string" ||
+      typeof completedAt !== "number"
+    ) {
+      continue;
+    }
+    out.push({ threadId, head, start, completedAt });
+  }
+  return out;
 }
 
 export type RunningThreadRow = {
@@ -32,30 +96,76 @@ export type HistoricalThreadRow = {
   workflowName: string | null;
 };
 
-async function readThreadStartTimestampMs(dataPath: string): Promise<number | null> {
-  const text = await readTextFileIfExists(dataPath);
-  if (text === null) {
-    return null;
-  }
-  const parsed = parseFirstJsonLineObject(text);
-  if (parsed === null) {
-    return null;
-  }
-  const ts = parsed.timestamp;
-  return typeof ts === "number" && Number.isFinite(ts) ? ts : null;
-}
+export type ResolvedThreadRecord = {
+  threadId: string;
+  bundleHash: string;
+  bundleDir: string;
+  head: string;
+  start: string;
+  source: "active" | "history";
+};
 
-async function readWorkflowNameFromDataJsonl(dataPath: string): Promise<string | null> {
-  const text = await readTextFileIfExists(dataPath);
-  if (text === null) {
-    return null;
+/** Resolve a thread via `threads.json` (active) or `history/*.jsonl` (completed). */
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: scans all bundle dirs for thread id
+export async function resolveThreadRecord(
+  storageRoot: string,
+  threadId: string,
+): Promise<ResolvedThreadRecord | null> {
+  const hashes = await listBundleHashDirs(storageRoot);
+  for (const bundleHash of hashes) {
+    const bundleDir = join(storageRoot, "bundles", bundleHash);
+    let index: ThreadIndex;
+    try {
+      index = await readThreadsIndex(bundleDir);
+    } catch {
+      continue;
+    }
+    const active = index[threadId];
+    if (active !== undefined) {
+      return {
+        threadId,
+        bundleHash,
+        bundleDir,
+        head: active.head,
+        start: active.start,
+        source: "active",
+      };
+    }
   }
-  const parsed = parseFirstJsonLineObject(text);
-  if (parsed === null) {
-    return null;
+
+  for (const bundleHash of hashes) {
+    const bundleDir = join(storageRoot, "bundles", bundleHash);
+    const histDir = join(bundleDir, "history");
+    if (!(await pathExists(histDir))) {
+      continue;
+    }
+    let files: string[];
+    try {
+      files = await readdir(histDir);
+    } catch {
+      continue;
+    }
+    for (const name of files) {
+      if (!name.endsWith(".jsonl")) {
+        continue;
+      }
+      const entries = await parseHistoryFile(join(histDir, name));
+      for (const e of entries) {
+        if (e.threadId === threadId) {
+          return {
+            threadId,
+            bundleHash,
+            bundleDir,
+            head: e.head,
+            start: e.start,
+            source: "history",
+          };
+        }
+      }
+    }
   }
-  const name = parsed.name;
-  return typeof name === "string" ? name : null;
+
+  return null;
 }
 
 /** Threads currently executing — identified via `<threadId>.running` markers. */
@@ -82,8 +192,9 @@ export async function listRunningThreads(storageRoot: string): Promise<RunningTh
         continue;
       }
       const threadId = fileName.slice(0, -".running".length);
-      const dataPath = join(dir, `${threadId}.data.jsonl`);
-      const workflowName = await readWorkflowNameFromDataJsonl(dataPath);
+      const resolved = await resolveThreadRecord(storageRoot, threadId);
+      const workflowName =
+        resolved !== null ? await readWorkflowNameFromStartHash(storageRoot, resolved.start) : null;
       out.push({ threadId, hash, workflowName });
     }
   }
@@ -98,41 +209,70 @@ export async function listRunningThreads(storageRoot: string): Promise<RunningTh
 }
 
 /**
- * Historical threads discovered via `*.data.jsonl`.
- * When `workflowNameFilter` is non-null, only threads whose start record `name` matches are returned.
+ * Threads discovered via `threads.json` (active) and `history/*.jsonl` (completed).
+ * When `workflowNameFilter` is non-null, only threads whose StartNode `name` matches are returned.
  */
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: merges active index + partitioned history
 export async function listHistoricalThreads(
   storageRoot: string,
   workflowNameFilter: string | null,
 ): Promise<HistoricalThreadRow[]> {
-  const logsRoot = join(storageRoot, "logs");
-  if (!(await pathExists(logsRoot))) {
-    return [];
-  }
-
-  const hashes = await readdir(logsRoot);
+  const hashes = await listBundleHashDirs(storageRoot);
+  const seen = new Set<string>();
   const out: HistoricalThreadRow[] = [];
 
-  for (const hash of hashes) {
-    const dir = join(logsRoot, hash);
-    let entries: string[];
+  for (const bundleHash of hashes) {
+    const bundleDir = join(storageRoot, "bundles", bundleHash);
+    let index: ThreadIndex;
     try {
-      entries = await readdir(dir);
+      index = await readThreadsIndex(bundleDir);
     } catch {
       continue;
     }
-
-    for (const fileName of entries) {
-      if (!fileName.endsWith(".data.jsonl")) {
+    for (const threadId of Object.keys(index)) {
+      const key = `${bundleHash}/${threadId}`;
+      if (seen.has(key)) {
         continue;
       }
-      const threadId = fileName.slice(0, -".data.jsonl".length);
-      const dataPath = join(dir, fileName);
-      const workflowName = await readWorkflowNameFromDataJsonl(dataPath);
+      seen.add(key);
+      const entry = index[threadId];
+      if (entry === undefined) {
+        continue;
+      }
+      const workflowName = await readWorkflowNameFromStartHash(storageRoot, entry.start);
       if (workflowNameFilter !== null && workflowName !== workflowNameFilter) {
         continue;
       }
-      out.push({ threadId, hash, workflowName });
+      out.push({ threadId, hash: bundleHash, workflowName });
+    }
+
+    const histDir = join(bundleDir, "history");
+    if (!(await pathExists(histDir))) {
+      continue;
+    }
+    let files: string[];
+    try {
+      files = await readdir(histDir);
+    } catch {
+      continue;
+    }
+    for (const name of files) {
+      if (!name.endsWith(".jsonl")) {
+        continue;
+      }
+      const entries = await parseHistoryFile(join(histDir, name));
+      for (const e of entries) {
+        const key = `${bundleHash}/${e.threadId}`;
+        if (seen.has(key)) {
+          continue;
+        }
+        seen.add(key);
+        const workflowName = await readWorkflowNameFromStartHash(storageRoot, e.start);
+        if (workflowNameFilter !== null && workflowName !== workflowNameFilter) {
+          continue;
+        }
+        out.push({ threadId: e.threadId, hash: bundleHash, workflowName });
+      }
     }
   }
 
@@ -145,64 +285,93 @@ export async function listHistoricalThreads(
   return out;
 }
 
+export type LatestThreadTarget = {
+  threadId: string;
+  bundleHash: string;
+  bundleDir: string;
+  threadsJsonPath: string;
+};
+
 /**
- * Picks the thread whose `.data.jsonl` is newest by start-record `timestamp`,
- * falling back to file `mtime` when the timestamp is missing.
- * Tie-breaker: larger `mtime` wins when start timestamps are equal.
+ * Picks the newest thread by StartNode timestamp approximation (`updatedAt` active,
+ * else `completedAt` history), falling back to lexical thread id order.
  */
-export async function findLatestThreadDataPath(
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: compares active heads vs history tails
+export async function findLatestThreadBundleTarget(
   storageRoot: string,
-): Promise<{ threadId: string; dataPath: string } | null> {
-  const threads = await listHistoricalThreads(storageRoot, null);
-  if (threads.length === 0) {
-    return null;
-  }
+): Promise<LatestThreadTarget | null> {
+  const hashes = await listBundleHashDirs(storageRoot);
 
   let best: {
     threadId: string;
-    dataPath: string;
-    primary: number;
-    secondary: number;
+    bundleHash: string;
+    bundleDir: string;
+    ts: number;
   } | null = null;
 
-  for (const t of threads) {
-    const dataPath = join(storageRoot, "logs", t.hash, `${t.threadId}.data.jsonl`);
-    let mtimeMs = 0;
+  for (const bundleHash of hashes) {
+    const bundleDir = join(storageRoot, "bundles", bundleHash);
+    let index: ThreadIndex;
     try {
-      const st = await stat(dataPath);
-      mtimeMs = st.mtimeMs;
+      index = await readThreadsIndex(bundleDir);
     } catch {
       continue;
     }
-    const startTs = await readThreadStartTimestampMs(dataPath);
-    const primary = startTs !== null ? startTs : mtimeMs;
-    const secondary = mtimeMs;
-    if (
-      best === null ||
-      primary > best.primary ||
-      (primary === best.primary && secondary > best.secondary)
-    ) {
-      best = { threadId: t.threadId, dataPath, primary, secondary };
+    for (const threadId of Object.keys(index)) {
+      const ent = index[threadId];
+      if (ent === undefined) {
+        continue;
+      }
+      const ts = ent.updatedAt;
+      const cand = { threadId, bundleHash, bundleDir, ts };
+      if (
+        best === null ||
+        cand.ts > best.ts ||
+        (cand.ts === best.ts &&
+          `${cand.bundleHash}/${cand.threadId}` > `${best.bundleHash}/${best.threadId}`)
+      ) {
+        best = cand;
+      }
+    }
+
+    const histDir = join(bundleDir, "history");
+    if (!(await pathExists(histDir))) {
+      continue;
+    }
+    let files: string[];
+    try {
+      files = await readdir(histDir);
+    } catch {
+      continue;
+    }
+    for (const name of files) {
+      if (!name.endsWith(".jsonl")) {
+        continue;
+      }
+      const entries = await parseHistoryFile(join(histDir, name));
+      for (const e of entries) {
+        const ts = e.completedAt;
+        const cand = { threadId: e.threadId, bundleHash, bundleDir, ts };
+        if (
+          best === null ||
+          cand.ts > best.ts ||
+          (cand.ts === best.ts &&
+            `${cand.bundleHash}/${cand.threadId}` > `${best.bundleHash}/${best.threadId}`)
+        ) {
+          best = cand;
+        }
+      }
     }
   }
 
-  return best === null ? null : { threadId: best.threadId, dataPath: best.dataPath };
-}
-
-export async function resolveThreadDataPath(
-  storageRoot: string,
-  threadId: string,
-): Promise<string | null> {
-  const logsRoot = join(storageRoot, "logs");
-  if (!(await pathExists(logsRoot))) {
+  if (best === null) {
     return null;
   }
-  const hashes = await readdir(logsRoot);
-  for (const hash of hashes) {
-    const candidate = join(logsRoot, hash, `${threadId}.data.jsonl`);
-    if (await pathExists(candidate)) {
-      return candidate;
-    }
-  }
-  return null;
+
+  return {
+    threadId: best.threadId,
+    bundleHash: best.bundleHash,
+    bundleDir: best.bundleDir,
+    threadsJsonPath: join(best.bundleDir, "threads.json"),
+  };
 }

packages/cli-workflow/src/worker-spawn.ts

@@ -2,9 +2,8 @@ import { type ChildProcess, spawn } from "node:child_process";
 import { mkdir, readdir, unlink, writeFile } from "node:fs/promises";
 import { createConnection } from "node:net";
 import { join } from "node:path";
-
-import { err, ok, type Result } from "@uncaged/workflow-protocol";
 import { getWorkerHostScriptPath } from "@uncaged/workflow-execute";
+import { err, ok, type Result } from "@uncaged/workflow-protocol";
 
 import { pathExists, readTextFileIfExists } from "./fs-utils.js";
 

packages/workflow-agent-cursor/README.md

@@ -7,10 +7,10 @@ The agent builds a full prompt (system + task + step history via `@uncaged/workf
 ## Install
 
 ```bash
-bun add @uncaged/workflow-agent-cursor @uncaged/workflow @uncaged/workflow-util-agent zod
+bun add @uncaged/workflow-agent-cursor @uncaged/workflow-runtime @uncaged/workflow-util-agent zod
 ```
 
-In this monorepo: `"@uncaged/workflow-agent-cursor": "workspace:*"` plus `workspace:*` for `@uncaged/workflow` and `@uncaged/workflow-util-agent`.
+In this monorepo: `"@uncaged/workflow-agent-cursor": "workspace:*"` plus `workspace:*` for `@uncaged/workflow-runtime` and `@uncaged/workflow-util-agent`, and `zod` ^4.
 
 ## Usage
 
@@ -28,9 +28,8 @@ const agent = createCursorAgent({
 
 | Export | Description |
 |--------|-------------|
-| `createCursorAgent(config)` | Returns `AgentFn` that runs `cursor-agent` with `buildAgentPrompt(ctx)` |
+| `createCursorAgent(config)` | Returns `AgentFn` that runs `cursor-agent` with `buildAgentPrompt(ctx)` from `@uncaged/workflow-util-agent` |
 | `CursorAgentConfig` | `model`, `timeout`, `extract` (must supply workspace path) |
 | `validateCursorAgentConfig` | Config validation result |
-| `buildAgentPrompt` | Re-exported from `@uncaged/workflow-util-agent` |
 
 Requires `cursor-agent` on `PATH` at runtime.

packages/workflow-agent-cursor/__tests__/cursor-agent.test.ts

@@ -7,7 +7,11 @@ const testExtract: ExtractFn = async <T extends Record<string, unknown>>(
   _schema: z.ZodType<T>,
   _prompt: string,
   _ctx: ExtractContext,
-): Promise<T> => ({ workspace: "/tmp" }) as unknown as T;
+): Promise<{ meta: T; contentPayload: string; refs: string[] }> => ({
+  meta: { workspace: "/tmp" } as unknown as T,
+  contentPayload: "",
+  refs: [],
+});
 
 describe("validateCursorAgentConfig", () => {
   test("accepts valid config", () => {

packages/workflow-agent-cursor/src/index.ts

@@ -5,7 +5,6 @@ import * as z from "zod/v4";
 import type { CursorAgentConfig } from "./types.js";
 import { validateCursorAgentConfig } from "./validate-config.js";
 
-export { buildAgentPrompt } from "@uncaged/workflow-util-agent";
 export type { CursorAgentConfig } from "./types.js";
 export { validateCursorAgentConfig } from "./validate-config.js";
 
@@ -49,11 +48,12 @@ export function createCursorAgent(config: CursorAgentConfig): AgentFn {
       ...ctx,
       agentContent: "",
     };
-    const { workspace } = await config.extract(
+    const extracted = await config.extract(
       cursorWorkspaceSchema,
       "From the thread context, determine the absolute filesystem path where the project/repository is located.",
       extractCtx,
     );
+    const { workspace } = extracted.meta;
     const fullPrompt = await buildAgentPrompt(ctx);
     const args = [
       "-p",

packages/workflow-agent-hermes/README.md

@@ -7,10 +7,10 @@ The agent composes the same thread-aware prompt as other CLI-backed agents via `
 ## Install
 
 ```bash
-bun add @uncaged/workflow-agent-hermes @uncaged/workflow @uncaged/workflow-util-agent
+bun add @uncaged/workflow-agent-hermes @uncaged/workflow-runtime @uncaged/workflow-util-agent
 ```
 
-In this monorepo: use `workspace:*` for all three `@uncaged/*` packages.
+In this monorepo: use `workspace:*` for `@uncaged/workflow-agent-hermes`, `@uncaged/workflow-runtime`, and `@uncaged/workflow-util-agent`.
 
 ## Usage
 
@@ -30,6 +30,5 @@ const agent = createHermesAgent({
 | `createHermesAgent(config)` | Returns `AgentFn` wrapping `hermes chat -q ...` |
 | `HermesAgentConfig` | `model`, `timeout` |
 | `validateHermesAgentConfig` | Config validation result |
-| `buildAgentPrompt` | Re-exported from `@uncaged/workflow-util-agent` |
 
 Requires `hermes` on `PATH` at runtime.

packages/workflow-agent-hermes/src/index.ts

@@ -6,7 +6,6 @@ import { validateHermesAgentConfig } from "./validate-config.js";
 
 const HERMES_DEFAULT_MAX_TURNS = 90;
 
-export { buildAgentPrompt } from "@uncaged/workflow-util-agent";
 export type { HermesAgentConfig } from "./types.js";
 export { validateHermesAgentConfig } from "./validate-config.js";
 

packages/workflow-agent-llm/README.md

@@ -1,16 +1,16 @@
 # @uncaged/workflow-agent-llm
 
-`AgentFn` adapter that calls an OpenAI-compatible `POST /chat/completions` endpoint using `@uncaged/workflow`’s `LlmProvider` (base URL, API key, model).
+`AgentFn` adapter that calls an OpenAI-compatible `POST /chat/completions` endpoint using `LlmProvider` from `@uncaged/workflow-runtime`.
 
 Single-turn: system text is the current role’s `systemPrompt`, user text is the thread’s initial prompt (`ctx.start.content`). Errors from HTTP, JSON, or empty choices are thrown as `Error` with a JSON payload string.
 
 ## Install
 
 ```bash
-bun add @uncaged/workflow-agent-llm @uncaged/workflow
+bun add @uncaged/workflow-agent-llm @uncaged/workflow-runtime zod
 ```
 
-In this monorepo: `"@uncaged/workflow-agent-llm": "workspace:*"`, `"@uncaged/workflow": "workspace:*"`.
+In this monorepo: `"@uncaged/workflow-agent-llm": "workspace:*"`, `"@uncaged/workflow-runtime": "workspace:*"` (and satisfy `zod` ^4 as required by `@uncaged/workflow-runtime`).
 
 ## Usage
 

packages/workflow-cas/README.md

@@ -0,0 +1,31 @@
+# @uncaged/workflow-cas
+
+Content-addressable storage implementation, bundle hashing, and Merkle helpers.
+
+## What This Package Does
+
+It implements `CasStore` from `@uncaged/workflow-protocol`, hashes workflow bundle bytes and strings with XXH64, and builds serializable Merkle nodes for thread/step/content payloads used when persisting execution artifacts.
+
+## Key Exports
+
+From `src/index.ts`:
+
+- **CAS:** `createCasStore`
+- **Hash:** `hashString`, `hashWorkflowBundleBytes`
+- **Merkle:** `createContentMerkleNode`, `getContentMerklePayload`, `parseMerkleNode`, `putContentMerkleNode`, `putStepMerkleNode`, `putThreadMerkleNode`, `serializeMerkleNode`
+- **Types:** `CasStore`, `MerkleNode`, `MerkleNodeType`, `StepMerklePayload`, `ThreadMerklePayload`
+
+## Dependencies
+
+- **Workspace:** `@uncaged/workflow-protocol` (`CasStore` contract), `@uncaged/workflow-util`
+- **npm:** `xxhashjs`, `yaml`
+
+## Usage
+
+```typescript
+import { createCasStore, hashWorkflowBundleBytes } from "@uncaged/workflow-cas";
+import { getGlobalCasDir } from "@uncaged/workflow-util";
+
+const store = createCasStore(getGlobalCasDir());
+const hash = await hashWorkflowBundleBytes(esmJsBytes);
+```

packages/workflow-cas/__tests__/collect-refs.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, test } from "bun:test";
+import type { StateNode } from "@uncaged/workflow-protocol";
+
+import { collectRefs } from "../src/collect-refs.js";
+
+function payload(
+  partial: Partial<StateNode["payload"]> & Pick<StateNode["payload"], "role">,
+): StateNode["payload"] {
+  return {
+    role: partial.role,
+    meta: partial.meta ?? {},
+    start: partial.start ?? "STARTHASH000000000000001",
+    content: partial.content ?? "CONTENTHASH00000000000001",
+    ancestors: partial.ancestors ?? [],
+    compact: partial.compact ?? null,
+    timestamp: partial.timestamp ?? 0,
+  };
+}
+
+describe("collectRefs", () => {
+  test("collects start, content, ancestors, and compact hashes in order", () => {
+    const refs = collectRefs(
+      payload({
+        role: "coder",
+        start: "01START00000000000000001",
+        content: "01CONTENT0000000000000001",
+        ancestors: ["01PARENT0000000000000001", "01GRAND000000000000000001"],
+        compact: "01COMPACT0000000000000001",
+      }),
+    );
+    expect(refs).toEqual([
+      "01START00000000000000001",
+      "01CONTENT0000000000000001",
+      "01PARENT0000000000000001",
+      "01GRAND000000000000000001",
+      "01COMPACT0000000000000001",
+    ]);
+  });
+
+  test("does not collect compact when compact is null", () => {
+    const refs = collectRefs(
+      payload({
+        role: "coder",
+        start: "S1",
+        content: "C1",
+        ancestors: ["A1"],
+        compact: null,
+      }),
+    );
+    expect(refs).toEqual(["S1", "C1", "A1"]);
+  });
+
+  test("returns only start and content when ancestors is empty", () => {
+    const refs = collectRefs(
+      payload({
+        role: "coder",
+        start: "S2",
+        content: "C2",
+        ancestors: [],
+        compact: null,
+      }),
+    );
+    expect(refs).toEqual(["S2", "C2"]);
+  });
+});

packages/workflow-cas/__tests__/reachable.test.ts

@@ -0,0 +1,69 @@
+import { describe, expect, test } from "bun:test";
+import type { CasStore } from "@uncaged/workflow-protocol";
+import { stringify } from "yaml";
+
+import { findReachableHashes } from "../src/reachable.js";
+
+function yamlBlob(refs: readonly string[]): string {
+  return stringify({ type: "node", payload: {}, refs: [...refs] }, { indent: 2 });
+}
+
+function memoryCas(entries: Record<string, string>): CasStore {
+  const map = { ...entries };
+  return {
+    async put(): Promise<string> {
+      throw new Error("memoryCas.put not used in tests");
+    },
+    async get(hash: string): Promise<string | null> {
+      return map[hash] ?? null;
+    },
+    async delete(): Promise<void> {},
+    async list(): Promise<string[]> {
+      return Object.keys(map);
+    },
+  };
+}
+
+describe("findReachableHashes", () => {
+  test("walks refs recursively from a single root", async () => {
+    const cas = memoryCas({
+      R1: yamlBlob(["R2"]),
+      R2: yamlBlob(["R3"]),
+      R3: yamlBlob([]),
+    });
+    const reachable = await findReachableHashes(["R1"], cas);
+    expect([...reachable].sort()).toEqual(["R1", "R2", "R3"]);
+  });
+
+  test("union of reachability from multiple roots", async () => {
+    const cas = memoryCas({
+      A: yamlBlob(["X"]),
+      B: yamlBlob(["Y"]),
+      X: yamlBlob([]),
+      Y: yamlBlob(["Z"]),
+      Z: yamlBlob([]),
+    });
+    const reachable = await findReachableHashes(["A", "B"], cas);
+    expect([...reachable].sort()).toEqual(["A", "B", "X", "Y", "Z"]);
+  });
+
+  test("handles cycles via visited set", async () => {
+    const cas = memoryCas({
+      C1: yamlBlob(["C2"]),
+      C2: yamlBlob(["C1"]),
+    });
+    const reachable = await findReachableHashes(["C1"], cas);
+    expect(reachable.size).toBe(2);
+    expect(reachable.has("C1")).toBe(true);
+    expect(reachable.has("C2")).toBe(true);
+  });
+
+  test("does not throw when a ref points to a missing blob", async () => {
+    const cas = memoryCas({
+      H1: yamlBlob(["MISSINGHASH0000000000001"]),
+    });
+    const reachable = await findReachableHashes(["H1"], cas);
+    expect(reachable.has("H1")).toBe(true);
+    expect(reachable.has("MISSINGHASH0000000000001")).toBe(false);
+  });
+});

packages/workflow-cas/package.json

@@ -2,6 +2,9 @@
   "name": "@uncaged/workflow-cas",
   "version": "0.1.0",
   "type": "module",
+  "scripts": {
+    "test": "bun test"
+  },
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",

packages/workflow-cas/src/cas.ts

@@ -3,10 +3,14 @@ import { join } from "node:path";
 
 import { hashString } from "./hash.js";
 import { createContentMerkleNode, parseMerkleNode, serializeMerkleNode } from "./merkle.js";
+import { isCasNodeYaml } from "./nodes.js";
 import type { CasStore } from "./types.js";
 
 /** Raw strings become content merkle YAML; already-valid merkle documents pass through. */
 function normalizeCasPutContent(content: string): string {
+  if (isCasNodeYaml(content)) {
+    return content;
+  }
   try {
     parseMerkleNode(content);
     return content;

packages/workflow-cas/src/collect-refs.ts

@@ -0,0 +1,13 @@
+import type { StateNode } from "@uncaged/workflow-protocol";
+
+/** Collects CAS hashes from {@link StateNode} payload fields for GC `refs[]` derivation. */
+export function collectRefs(payload: StateNode["payload"]): string[] {
+  const out: string[] = [payload.start, payload.content];
+  for (const h of payload.ancestors) {
+    out.push(h);
+  }
+  if (payload.compact !== null) {
+    out.push(payload.compact);
+  }
+  return out;
+}

packages/workflow-cas/src/hash.ts

@@ -1,8 +1,6 @@
 import { Buffer } from "node:buffer";
-
-import XXH from "xxhashjs";
-
 import { encodeUint64AsCrockford } from "@uncaged/workflow-util";
+import XXH from "xxhashjs";
 
 function digestToUint64(digest: { toString(radix?: number): string }): bigint {
   const hex = digest.toString(16).padStart(16, "0");

packages/workflow-cas/src/index.ts

@@ -1,4 +1,5 @@
 export { createCasStore } from "./cas.js";
+export { collectRefs } from "./collect-refs.js";
 export { hashString, hashWorkflowBundleBytes } from "./hash.js";
 export {
   createContentMerkleNode,
@@ -9,6 +10,16 @@ export {
   putThreadMerkleNode,
   serializeMerkleNode,
 } from "./merkle.js";
+export type { ParsedCasThreadNode } from "./nodes.js";
+export {
+  isCasNodeYaml,
+  parseCasThreadNode,
+  putContentNodeWithRefs,
+  putStartNode,
+  putStateNode,
+  serializeCasNode,
+} from "./nodes.js";
+export { findReachableHashes } from "./reachable.js";
 export type {
   CasStore,
   MerkleNode,

packages/workflow-cas/src/merkle.ts

@@ -82,7 +82,12 @@ export async function putContentMerkleNode(store: CasStore, content: string): Pr
   return store.put(content);
 }
 
-/** Loads a CAS blob and returns the payload string for a `content` Merkle node. */
+/**
+ * Loads a CAS blob and returns the payload string for a `content` node.
+ *
+ * Accepts both the legacy `{type:content, payload, children}` Merkle layout
+ * and the RFC v3 `{type:content, payload, refs}` content node layout.
+ */
 export async function getContentMerklePayload(
   store: CasStore,
   hash: string,
@@ -91,9 +96,13 @@ export async function getContentMerklePayload(
   if (yamlText === null) {
     return null;
   }
-  const node = parseMerkleNode(yamlText);
-  if (node.type !== "content" || typeof node.payload !== "string") {
+  const raw = parse(yamlText) as unknown;
+  if (raw === null || typeof raw !== "object") {
     return null;
   }
-  return node.payload;
+  const rec = raw as Record<string, unknown>;
+  if (rec.type !== "content" || typeof rec.payload !== "string") {
+    return null;
+  }
+  return rec.payload;
 }

packages/workflow-cas/src/nodes.ts

@@ -0,0 +1,178 @@
+import type {
+  ContentMerkleNode,
+  StartNode,
+  StartNodePayload,
+  StateNode,
+  StateNodePayload,
+} from "@uncaged/workflow-protocol";
+import { parse, stringify } from "yaml";
+
+import { collectRefs } from "./collect-refs.js";
+import type { CasStore } from "./types.js";
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function isStartPayload(value: unknown): value is StartNodePayload {
+  if (!isRecord(value)) {
+    return false;
+  }
+  return (
+    typeof value.name === "string" &&
+    typeof value.hash === "string" &&
+    typeof value.maxRounds === "number" &&
+    typeof value.depth === "number"
+  );
+}
+
+function isStatePayload(value: unknown): value is StateNodePayload {
+  if (!isRecord(value)) {
+    return false;
+  }
+  const compact = value.compact;
+  if (!(compact === null || typeof compact === "string")) {
+    return false;
+  }
+  const ancestors = value.ancestors;
+  if (!Array.isArray(ancestors) || !ancestors.every((h) => typeof h === "string")) {
+    return false;
+  }
+  const meta = value.meta;
+  if (!isRecord(meta)) {
+    return false;
+  }
+  return (
+    typeof value.role === "string" &&
+    typeof value.start === "string" &&
+    typeof value.content === "string" &&
+    typeof value.timestamp === "number"
+  );
+}
+
+/** Parses a YAML CAS blob into a typed RFC v3 thread node (or legacy content layout with `children`). */
+export function parseCasThreadNode(yamlText: string): ParsedCasThreadNode | null {
+  let raw: unknown;
+  try {
+    raw = parse(yamlText) as unknown;
+  } catch {
+    return null;
+  }
+  if (!isRecord(raw)) {
+    return null;
+  }
+  const type = raw.type;
+  if (type !== "start" && type !== "state" && type !== "content") {
+    return null;
+  }
+
+  let refsRaw: unknown = raw.refs;
+  if (refsRaw === undefined && type === "content") {
+    refsRaw = raw.children;
+  }
+  if (!Array.isArray(refsRaw) || !refsRaw.every((r) => typeof r === "string")) {
+    return null;
+  }
+  const refs = refsRaw as string[];
+
+  if (type === "content") {
+    if (typeof raw.payload !== "string") {
+      return null;
+    }
+    const node: ContentMerkleNode = { type: "content", payload: raw.payload, refs: [...refs] };
+    return { kind: "content", node };
+  }
+
+  if (type === "start") {
+    if (!isStartPayload(raw.payload)) {
+      return null;
+    }
+    const node: StartNode = { type: "start", payload: raw.payload, refs: [...refs] };
+    return { kind: "start", node };
+  }
+
+  if (!isStatePayload(raw.payload)) {
+    return null;
+  }
+  const node: StateNode = { type: "state", payload: raw.payload, refs: [...refs] };
+  return { kind: "state", node };
+}
+
+export type ParsedCasThreadNode =
+  | { kind: "start"; node: StartNode }
+  | { kind: "state"; node: StateNode }
+  | { kind: "content"; node: ContentMerkleNode };
+
+/** YAML-serialize a CAS node carrying `{type, payload, refs}` (RFC v3 thread storage format). */
+export function serializeCasNode(node: StartNode | StateNode | ContentMerkleNode): string {
+  return stringify({ type: node.type, payload: node.payload, refs: node.refs }, { indent: 2 });
+}
+
+/**
+ * Recognizes a YAML CAS blob with the `{type, payload, refs[]}` shape used by
+ * `start` / `state` / `content` thread nodes. Used by {@link createCasStore}
+ * to skip the legacy auto-wrap step when the caller already supplied a
+ * pre-serialized RFC v3 node.
+ */
+export function isCasNodeYaml(content: string): boolean {
+  let raw: unknown;
+  try {
+    raw = parse(content) as unknown;
+  } catch {
+    return false;
+  }
+  if (raw === null || typeof raw !== "object" || Array.isArray(raw)) {
+    return false;
+  }
+  const rec = raw as Record<string, unknown>;
+  if (typeof rec.type !== "string") {
+    return false;
+  }
+  if (!Array.isArray(rec.refs)) {
+    return false;
+  }
+  for (const r of rec.refs) {
+    if (typeof r !== "string") {
+      return false;
+    }
+  }
+  return true;
+}
+
+export async function putStartNode(
+  store: CasStore,
+  payload: StartNode["payload"],
+  promptHash: string,
+): Promise<string> {
+  const node: StartNode = {
+    type: "start",
+    payload,
+    refs: [promptHash],
+  };
+  return store.put(serializeCasNode(node));
+}
+
+export async function putStateNode(
+  store: CasStore,
+  payload: StateNode["payload"],
+): Promise<string> {
+  const node: StateNode = {
+    type: "state",
+    payload,
+    refs: collectRefs(payload),
+  };
+  return store.put(serializeCasNode(node));
+}
+
+export async function putContentNodeWithRefs(
+  store: CasStore,
+  payload: string,
+  refs: readonly string[],
+): Promise<string> {
+  const node: ContentMerkleNode = {
+    type: "content",
+    payload,
+    refs: [...refs],
+  };
+  return store.put(serializeCasNode(node));
+}

packages/workflow-cas/src/reachable.ts

@@ -0,0 +1,55 @@
+import { parse } from "yaml";
+
+import type { CasStore } from "./types.js";
+
+function refsFromBlob(content: string): string[] {
+  try {
+    const raw = parse(content) as unknown;
+    if (raw === null || typeof raw !== "object") {
+      return [];
+    }
+    const rec = raw as Record<string, unknown>;
+    const refs = rec.refs;
+    if (!Array.isArray(refs)) {
+      return [];
+    }
+    const out: string[] = [];
+    for (const r of refs) {
+      if (typeof r === "string") {
+        out.push(r);
+      }
+    }
+    return out;
+  } catch {
+    return [];
+  }
+}
+
+/** Recursively collects all CAS hashes reachable from `roots` via each blob's `refs[]`. */
+export async function findReachableHashes(
+  roots: readonly string[],
+  cas: CasStore,
+): Promise<ReadonlySet<string>> {
+  const visited = new Set<string>();
+  const stack = [...roots];
+  while (stack.length > 0) {
+    const hash = stack.pop();
+    if (hash === undefined) {
+      break;
+    }
+    if (visited.has(hash)) {
+      continue;
+    }
+    const blob = await cas.get(hash);
+    if (blob === null) {
+      continue;
+    }
+    visited.add(hash);
+    for (const ref of refsFromBlob(blob)) {
+      if (!visited.has(ref)) {
+        stack.push(ref);
+      }
+    }
+  }
+  return visited;
+}

packages/workflow-cas/tsconfig.json

@@ -5,8 +5,5 @@
     "outDir": "dist"
   },
   "include": ["src"],
-  "references": [
-    { "path": "../workflow-protocol" },
-    { "path": "../workflow-util" }
-  ]
+  "references": [{ "path": "../workflow-protocol" }, { "path": "../workflow-util" }]
 }

packages/workflow-execute/README.md

@@ -0,0 +1,33 @@
+# @uncaged/workflow-execute
+
+Thread engine: execution, fork/GC, extract pipeline, supervisor/worker wiring, and workflow-as-agent.
+
+## What This Package Does
+
+It runs `WorkflowFn` generators against disk-backed threads, integrates CAS and registry-backed extract (`createExtract`), coordinates LLM tool usage via `@uncaged/workflow-reactor`, handles fork plans and garbage collection, and exposes `workflowAsAgent` for nesting workflows.
+
+## Key Exports
+
+From `src/index.ts`:
+
+- **Engine:** `createWorkflow` (engine-local re-export), `executeThread`, `getWorkerHostScriptPath`
+- **Fork / parse:** `buildForkPlan`, `parseThreadDataJsonl`, `selectForkHistoricalSteps`, `tryParseRoleStepRecord`, `tryParseWorkflowResultRecord`
+- **GC / pause:** `garbageCollectCas`, `createThreadPauseGate`
+- **Engine types:** `ExecuteThreadIo`, `ExecuteThreadOptions`, `ForkHistoricalStep`, `ForkPlan`, `GcResult`, `ParsedThreadStartRecord`, `PrefilledDiskStep`, `SupervisorDecision`, `ThreadPauseGate`
+- **Extract:** `buildExtractUserContent`, `createExtract`, `extractFunctionToolFromZodSchema`, `llmErrorToCause`, `llmExtract`, types `ExtractFn`, `ExtractThreadContext`, `LlmError`, `LlmExtractArgs`
+- **Agent composition:** `workflowAsAgent`, `WorkflowAsAgentOptions`
+
+## Dependencies
+
+- **Workspace:** `@uncaged/workflow-protocol`, `@uncaged/workflow-runtime`, `@uncaged/workflow-util`, `@uncaged/workflow-cas`, `@uncaged/workflow-reactor`, `@uncaged/workflow-register`
+- **npm:** `yaml`
+- **Peer:** `zod` ^4
+
+`@uncaged/workflow-reactor` is used for LLM-backed extract and supervisor flows (`extract-fn.ts`, `supervisor.ts`).
+
+## Usage
+
+```typescript
+import { executeThread } from "@uncaged/workflow-execute";
+// Typical callers are CLI/tests that supply ExecuteThreadIo (paths, CAS, abort, logger, …).
+```

packages/workflow-execute/__tests__/engine.test.ts

@@ -0,0 +1,319 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { mkdir, mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { createCasStore } from "@uncaged/workflow-cas";
+
+import type {
+  RoleOutput,
+  ThreadContext,
+  WorkflowCompletion,
+  WorkflowFn,
+  WorkflowRuntime,
+} from "@uncaged/workflow-runtime";
+import { parse as parseYaml } from "yaml";
+
+import { executeThread } from "../src/engine/engine.js";
+import type { ExecuteThreadIo, ExecuteThreadOptions } from "../src/engine/types.js";
+
+const TEST_REGISTRY_YAML = `config:
+  maxDepth: 3
+  supervisorInterval: 0
+  providers:
+    stub:
+      baseUrl: http://127.0.0.1:9
+      apiKey: test
+  models:
+    default: stub/m
+workflows: {}
+`;
+
+function noLogger(): (tag: string, content: string) => void {
+  return () => {};
+}
+
+function makeOptions(overrides: Partial<ExecuteThreadOptions>): ExecuteThreadOptions {
+  return {
+    maxRounds: 5,
+    depth: 0,
+    signal: new AbortController().signal,
+    awaitAfterEachYield: async () => {},
+    forkSourceThreadId: null,
+    prefilledDiskSteps: null,
+    forkContinuation: null,
+    replayTimestamps: null,
+    storageRoot: "/tmp/never",
+    ...overrides,
+  };
+}
+
+async function setupStorage(): Promise<{
+  storageRoot: string;
+  casDir: string;
+  bundleHash: string;
+  bundleDir: string;
+}> {
+  const storageRoot = await mkdtemp(join(tmpdir(), "uncaged-wf-engine-"));
+  await writeFile(join(storageRoot, "workflow.yaml"), TEST_REGISTRY_YAML, "utf8");
+  const casDir = join(storageRoot, "cas");
+  await mkdir(casDir, { recursive: true });
+  const bundleHash = "TESTHASH00001";
+  const bundleDir = join(storageRoot, "bundles", bundleHash);
+  return { storageRoot, casDir, bundleHash, bundleDir };
+}
+
+function readCasNode(casDir: string, hash: string): Record<string, unknown> {
+  const text = require("node:fs").readFileSync(join(casDir, `${hash}.txt`), "utf8") as string;
+  return parseYaml(text) as Record<string, unknown>;
+}
+
+describe("executeThread (Phase 2 — CAS thread storage)", () => {
+  let storageRoot: string;
+  let casDir: string;
+  let bundleHash: string;
+  let bundleDir: string;
+
+  beforeEach(async () => {
+    const setup = await setupStorage();
+    storageRoot = setup.storageRoot;
+    casDir = setup.casDir;
+    bundleHash = setup.bundleHash;
+    bundleDir = setup.bundleDir;
+  });
+
+  afterEach(async () => {
+    await rm(storageRoot, { recursive: true, force: true });
+  });
+
+  test("writes a StartNode whose refs[0] is the prompt CAS hash", async () => {
+    const cas = createCasStore(casDir);
+
+    // biome-ignore lint/correctness/useYield: deliberately empty generator — exercises the start/end path with no role steps
+    const wf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      _runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      return { returnCode: 0, summary: "no-op" };
+    };
+
+    const io: ExecuteThreadIo = {
+      threadId: "T01",
+      hash: bundleHash,
+      infoJsonlPath: join(storageRoot, "logs", bundleHash, "T01.info.jsonl"),
+      cas,
+    };
+
+    const result = await executeThread(
+      wf,
+      "demo",
+      { prompt: "hello", steps: [] },
+      makeOptions({ storageRoot, maxRounds: 5 }),
+      io,
+      noLogger(),
+    );
+
+    expect(result.returnCode).toBe(0);
+
+    const historyText = await readFile(
+      (await import("node:fs/promises")).readdir ? await firstHistoryFile(bundleDir) : "",
+      "utf8",
+    );
+    const histLine = historyText.trim().split("\n")[0] ?? "";
+    const histEntry = JSON.parse(histLine) as Record<string, unknown>;
+    expect(histEntry.threadId).toBe("T01");
+
+    const startHash = histEntry.start as string;
+    const startNode = readCasNode(casDir, startHash);
+    expect(startNode.type).toBe("start");
+    expect((startNode.payload as Record<string, unknown>).name).toBe("demo");
+    expect((startNode.payload as Record<string, unknown>).hash).toBe(bundleHash);
+    expect((startNode.payload as Record<string, unknown>).maxRounds).toBe(5);
+
+    const refs = startNode.refs as string[];
+    expect(refs.length).toBe(1);
+
+    const promptBlob = await cas.get(refs[0] ?? "");
+    expect(promptBlob).not.toBeNull();
+    const promptParsed = parseYaml(promptBlob ?? "") as Record<string, unknown>;
+    expect(promptParsed.payload).toBe("hello");
+  });
+
+  test("each role yield produces a chained StateNode and updates threads.json head", async () => {
+    const cas = createCasStore(casDir);
+
+    const wf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      const h1 = await runtime.cas.put("plan-text");
+      yield { role: "planner", contentHash: h1, meta: { plan: 1 }, refs: [h1] };
+      const h2 = await runtime.cas.put("code-text");
+      yield { role: "coder", contentHash: h2, meta: { diff: "y" }, refs: [h2] };
+      return { returnCode: 0, summary: "done" };
+    };
+
+    const io: ExecuteThreadIo = {
+      threadId: "T02",
+      hash: bundleHash,
+      infoJsonlPath: join(storageRoot, "logs", bundleHash, "T02.info.jsonl"),
+      cas,
+    };
+
+    let observedHead: string | null = null;
+    let observedHeadAtSecondYield: string | null = null;
+
+    const opts = makeOptions({
+      storageRoot,
+      maxRounds: 5,
+      awaitAfterEachYield: async () => {
+        const text = await readFile(join(bundleDir, "threads.json"), "utf8");
+        const parsed = JSON.parse(text) as Record<string, { head: string }>;
+        const head = parsed.T02?.head ?? null;
+        if (observedHead === null) {
+          observedHead = head;
+        } else if (observedHeadAtSecondYield === null) {
+          observedHeadAtSecondYield = head;
+        }
+      },
+    });
+
+    const result = await executeThread(
+      wf,
+      "demo",
+      { prompt: "p", steps: [] },
+      opts,
+      io,
+      noLogger(),
+    );
+    expect(result.returnCode).toBe(0);
+
+    expect(observedHead).not.toBeNull();
+    expect(observedHeadAtSecondYield).not.toBeNull();
+    expect(observedHead).not.toBe(observedHeadAtSecondYield);
+
+    const firstState = readCasNode(casDir, observedHead ?? "");
+    expect(firstState.type).toBe("state");
+    expect((firstState.payload as Record<string, unknown>).role).toBe("planner");
+    expect((firstState.payload as Record<string, unknown>).ancestors).toEqual([]);
+
+    const secondState = readCasNode(casDir, observedHeadAtSecondYield ?? "");
+    expect(secondState.type).toBe("state");
+    expect((secondState.payload as Record<string, unknown>).role).toBe("coder");
+    expect((secondState.payload as Record<string, unknown>).ancestors).toEqual([observedHead]);
+    expect((secondState.payload as Record<string, unknown>).start).toBe(
+      (firstState.payload as Record<string, unknown>).start,
+    );
+  });
+
+  test("on completion: removes threads.json entry, appends history with __end__ head", async () => {
+    const cas = createCasStore(casDir);
+
+    const wf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      const h = await runtime.cas.put("only-step");
+      yield { role: "only", contentHash: h, meta: {}, refs: [h] };
+      return { returnCode: 0, summary: "completed" };
+    };
+
+    const io: ExecuteThreadIo = {
+      threadId: "T03",
+      hash: bundleHash,
+      infoJsonlPath: join(storageRoot, "logs", bundleHash, "T03.info.jsonl"),
+      cas,
+    };
+
+    const result = await executeThread(
+      wf,
+      "demo",
+      { prompt: "p", steps: [] },
+      makeOptions({ storageRoot, maxRounds: 5 }),
+      io,
+      noLogger(),
+    );
+
+    expect(result.returnCode).toBe(0);
+
+    const indexText = await readFile(join(bundleDir, "threads.json"), "utf8");
+    const indexParsed = JSON.parse(indexText) as Record<string, unknown>;
+    expect(indexParsed).toEqual({});
+
+    const historyPath = await firstHistoryFile(bundleDir);
+    const historyText = await readFile(historyPath, "utf8");
+    const lines = historyText.trim().split("\n");
+    expect(lines.length).toBe(1);
+    const entry = JSON.parse(lines[0] ?? "") as Record<string, unknown>;
+    expect(entry.threadId).toBe("T03");
+    expect(entry.head).toBe(result.rootHash);
+
+    const endNode = readCasNode(casDir, String(entry.head));
+    expect(endNode.type).toBe("state");
+    expect((endNode.payload as Record<string, unknown>).role).toBe("__end__");
+    expect((endNode.payload as Record<string, unknown>).meta).toEqual({
+      returnCode: 0,
+      summary: "completed",
+    });
+  });
+
+  test("does not write any .data.jsonl file under storageRoot", async () => {
+    const cas = createCasStore(casDir);
+
+    const wf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      const h = await runtime.cas.put("step");
+      yield { role: "only", contentHash: h, meta: {}, refs: [h] };
+      return { returnCode: 0, summary: "done" };
+    };
+
+    const io: ExecuteThreadIo = {
+      threadId: "T04",
+      hash: bundleHash,
+      infoJsonlPath: join(storageRoot, "logs", bundleHash, "T04.info.jsonl"),
+      cas,
+    };
+
+    await executeThread(
+      wf,
+      "demo",
+      { prompt: "p", steps: [] },
+      makeOptions({ storageRoot, maxRounds: 5 }),
+      io,
+      noLogger(),
+    );
+
+    const fsp = await import("node:fs/promises");
+    const found: string[] = [];
+    async function walk(dir: string): Promise<void> {
+      let entries: { name: string; isDirectory: () => boolean; isFile: () => boolean }[];
+      try {
+        entries = await fsp.readdir(dir, { withFileTypes: true });
+      } catch {
+        return;
+      }
+      for (const ent of entries) {
+        const p = join(dir, ent.name);
+        if (ent.isDirectory()) {
+          await walk(p);
+        } else if (ent.isFile() && ent.name.endsWith(".data.jsonl")) {
+          found.push(p);
+        }
+      }
+    }
+    await walk(storageRoot);
+    expect(found).toEqual([]);
+  });
+});
+
+async function firstHistoryFile(bundleDir: string): Promise<string> {
+  const fsp = await import("node:fs/promises");
+  const dir = join(bundleDir, "history");
+  const entries = await fsp.readdir(dir);
+  const file = entries.find((n) => n.endsWith(".jsonl"));
+  if (file === undefined) {
+    throw new Error(`no history file under ${dir}`);
+  }
+  return join(dir, file);
+}

packages/workflow-execute/__tests__/extract-refs.test.ts

@@ -0,0 +1,72 @@
+import { afterEach, describe, expect, test } from "bun:test";
+import { mkdtemp, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { createCasStore } from "@uncaged/workflow-cas";
+import { type ExtractContext, START } from "@uncaged/workflow-runtime";
+import * as z from "zod/v4";
+
+import { createExtract } from "../src/extract/extract-fn.js";
+
+function installPlainJsonExtractMock(meta: Record<string, unknown>): () => void {
+  const origFetch = globalThis.fetch;
+  const mockFetch = async (): Promise<Response> =>
+    new Response(
+      JSON.stringify({
+        choices: [{ message: { content: JSON.stringify(meta) } }],
+      }),
+      { status: 200, headers: { "Content-Type": "application/json" } },
+    );
+  globalThis.fetch = Object.assign(mockFetch, {
+    preconnect: origFetch.preconnect.bind(origFetch),
+  }) as typeof fetch;
+  return () => {
+    globalThis.fetch = origFetch;
+  };
+}
+
+describe("createExtract — ExtractResult shape", () => {
+  let restoreFetch: (() => void) | null = null;
+
+  afterEach(() => {
+    restoreFetch?.();
+    restoreFetch = null;
+  });
+
+  test("returns meta, contentPayload, and refs[]", async () => {
+    restoreFetch = installPlainJsonExtractMock({ confidence: 0.9 });
+
+    const dir = await mkdtemp(join(tmpdir(), "wf-extract-refs-"));
+    try {
+      const cas = createCasStore(join(dir, "cas"));
+      const extract = createExtract(
+        { baseUrl: "http://127.0.0.1:9", apiKey: "key", model: "m" },
+        { cas },
+      );
+
+      const schema = z.object({ confidence: z.number() });
+      const ctx: ExtractContext = {
+        threadId: "01THREADTESTAAAAAAAAAAAAAA",
+        depth: 0,
+        start: {
+          role: START,
+          content: "task text",
+          meta: { maxRounds: 10 },
+          timestamp: 100,
+        },
+        steps: [],
+        currentRole: { name: "analyst", systemPrompt: "be precise" },
+        agentContent: "model says hello",
+      };
+
+      const out = await extract(schema, "extract fields", ctx);
+
+      expect(out.meta).toEqual({ confidence: 0.9 });
+      expect(out.contentPayload).toBe("model says hello");
+      expect(Array.isArray(out.refs)).toBe(true);
+      expect(out.refs).toEqual([]);
+    } finally {
+      await rm(dir, { recursive: true, force: true });
+    }
+  });
+});

packages/workflow-execute/__tests__/gc-mark-sweep.test.ts

@@ -0,0 +1,112 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import {
+  createCasStore,
+  putContentNodeWithRefs,
+  putStartNode,
+  putStateNode,
+} from "@uncaged/workflow-cas";
+import type { StateNodePayload } from "@uncaged/workflow-protocol";
+
+import { FORK_BRANCH_ROLE } from "../src/engine/fork-thread.js";
+import { garbageCollectCas } from "../src/engine/gc.js";
+import { getBundleDir, removeThreadEntry, upsertThreadEntry } from "../src/engine/threads-index.js";
+
+describe("garbageCollectCas (mark-and-sweep)", () => {
+  let storageRoot: string;
+  let casDir: string;
+
+  beforeEach(async () => {
+    storageRoot = await mkdtemp(join(tmpdir(), "uncaged-wf-gc-ms-"));
+    casDir = join(storageRoot, "cas");
+    await mkdir(casDir, { recursive: true });
+    await writeFile(
+      join(storageRoot, "workflow.yaml"),
+      "config:\n  maxDepth: 1\n  supervisorInterval: 0\n  providers: {}\n  models: {}\nworkflows: {}\n",
+      "utf8",
+    );
+  });
+
+  afterEach(async () => {
+    await rm(storageRoot, { recursive: true, force: true });
+  });
+
+  test("shared CAS prefix survives when one fork thread index entry is removed", async () => {
+    const bundleHash = "TESTGC0000001";
+    const bundleDir = getBundleDir(storageRoot, bundleHash);
+    await mkdir(bundleDir, { recursive: true });
+
+    const cas = createCasStore(casDir);
+    const promptHash = await cas.put("prompt");
+    const startHash = await putStartNode(
+      cas,
+      {
+        name: "demo",
+        hash: bundleHash,
+        maxRounds: 5,
+        depth: 0,
+      },
+      promptHash,
+    );
+
+    const c1 = await putContentNodeWithRefs(cas, "p1", []);
+    const h1 = await putStateNode(cas, {
+      role: "planner",
+      meta: {},
+      start: startHash,
+      content: c1,
+      ancestors: [],
+      compact: null,
+      timestamp: 1,
+    } satisfies StateNodePayload);
+
+    const c2 = await putContentNodeWithRefs(cas, "c1", []);
+    const h2 = await putStateNode(cas, {
+      role: "coder",
+      meta: {},
+      start: startHash,
+      content: c2,
+      ancestors: [h1],
+      compact: null,
+      timestamp: 2,
+    } satisfies StateNodePayload);
+
+    const ec = await putContentNodeWithRefs(cas, "", []);
+    const fm = await putStateNode(cas, {
+      role: FORK_BRANCH_ROLE,
+      meta: {},
+      start: startHash,
+      content: ec,
+      ancestors: [h1],
+      compact: null,
+      timestamp: 3,
+    } satisfies StateNodePayload);
+
+    await upsertThreadEntry(bundleDir, "THREAD_AAAAAAA", {
+      head: h2,
+      start: startHash,
+      updatedAt: 10,
+    });
+    await upsertThreadEntry(bundleDir, "THREAD_BBBBBBB", {
+      head: fm,
+      start: startHash,
+      updatedAt: 20,
+    });
+
+    await removeThreadEntry(bundleDir, "THREAD_AAAAAAA");
+
+    const gc = await garbageCollectCas(storageRoot);
+    expect(gc.ok).toBe(true);
+    if (!gc.ok) {
+      return;
+    }
+
+    expect(await cas.get(h2)).toBeNull();
+    expect(await cas.get(h1)).not.toBeNull();
+    expect(await cas.get(startHash)).not.toBeNull();
+    expect(await cas.get(promptHash)).not.toBeNull();
+    expect(await cas.get(fm)).not.toBeNull();
+  });
+});

packages/workflow-execute/__tests__/threads-index.test.ts

@@ -0,0 +1,91 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { mkdtemp, readdir, readFile, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import {
+  appendThreadHistoryEntry,
+  removeThreadEntry,
+  upsertThreadEntry,
+} from "../src/engine/threads-index.js";
+
+describe("threads-index", () => {
+  let bundleDir: string;
+
+  beforeEach(async () => {
+    bundleDir = await mkdtemp(join(tmpdir(), "uncaged-wf-threads-"));
+  });
+
+  afterEach(async () => {
+    await rm(bundleDir, { recursive: true, force: true });
+  });
+
+  test("upsertThreadEntry creates threads.json and persists entries", async () => {
+    await upsertThreadEntry(bundleDir, "T1", { head: "H1", start: "S1", updatedAt: 100 });
+    const text = await readFile(join(bundleDir, "threads.json"), "utf8");
+    const parsed = JSON.parse(text) as Record<string, unknown>;
+    expect(parsed).toEqual({
+      T1: { head: "H1", start: "S1", updatedAt: 100 },
+    });
+  });
+
+  test("upsertThreadEntry overwrites the head while preserving siblings", async () => {
+    await upsertThreadEntry(bundleDir, "T1", { head: "H1", start: "S1", updatedAt: 100 });
+    await upsertThreadEntry(bundleDir, "T2", { head: "H2", start: "S2", updatedAt: 200 });
+    await upsertThreadEntry(bundleDir, "T1", { head: "H1B", start: "S1", updatedAt: 300 });
+    const text = await readFile(join(bundleDir, "threads.json"), "utf8");
+    const parsed = JSON.parse(text) as Record<string, unknown>;
+    expect(parsed).toEqual({
+      T1: { head: "H1B", start: "S1", updatedAt: 300 },
+      T2: { head: "H2", start: "S2", updatedAt: 200 },
+    });
+  });
+
+  test("removeThreadEntry deletes the entry but keeps the file", async () => {
+    await upsertThreadEntry(bundleDir, "T1", { head: "H1", start: "S1", updatedAt: 100 });
+    await upsertThreadEntry(bundleDir, "T2", { head: "H2", start: "S2", updatedAt: 200 });
+    await removeThreadEntry(bundleDir, "T1");
+    const text = await readFile(join(bundleDir, "threads.json"), "utf8");
+    const parsed = JSON.parse(text) as Record<string, unknown>;
+    expect(parsed).toEqual({
+      T2: { head: "H2", start: "S2", updatedAt: 200 },
+    });
+  });
+
+  test("removeThreadEntry on a missing thread is a no-op", async () => {
+    await removeThreadEntry(bundleDir, "MISSING");
+    const dirEntries = await readdir(bundleDir);
+    expect(dirEntries.includes("threads.json")).toBe(false);
+  });
+
+  test("appendThreadHistoryEntry writes one JSONL line per call into a date-keyed file", async () => {
+    const ts = Date.UTC(2026, 4, 9, 12, 0, 0);
+    await appendThreadHistoryEntry(bundleDir, {
+      threadId: "T1",
+      head: "H1",
+      start: "S1",
+      completedAt: ts,
+    });
+    await appendThreadHistoryEntry(bundleDir, {
+      threadId: "T2",
+      head: "H2",
+      start: "S2",
+      completedAt: ts,
+    });
+    const text = await readFile(join(bundleDir, "history", "2026-05-09.jsonl"), "utf8");
+    const lines = text.trim().split("\n");
+    expect(lines.length).toBe(2);
+    expect(JSON.parse(lines[0] ?? "{}")).toEqual({
+      threadId: "T1",
+      head: "H1",
+      start: "S1",
+      completedAt: ts,
+    });
+    expect(JSON.parse(lines[1] ?? "{}")).toEqual({
+      threadId: "T2",
+      head: "H2",
+      start: "S2",
+      completedAt: ts,
+    });
+  });
+});

packages/workflow-execute/src/engine/engine.ts

@@ -1,5 +1,18 @@
-import { appendFile, mkdir } from "node:fs/promises";
+import { mkdir } from "node:fs/promises";
 import { dirname } from "node:path";
+import {
+  type CasStore,
+  getContentMerklePayload,
+  putContentNodeWithRefs,
+  putStartNode,
+  putStateNode,
+} from "@uncaged/workflow-cas";
+import type { StateNode } from "@uncaged/workflow-protocol";
+import {
+  readWorkflowRegistry,
+  resolveModel,
+  type WorkflowConfig,
+} from "@uncaged/workflow-register";
 import type {
   LlmProvider,
   RoleOutput,
@@ -9,20 +22,29 @@ import type {
   WorkflowResult,
   WorkflowRuntime,
 } from "@uncaged/workflow-runtime";
-import { START } from "@uncaged/workflow-runtime";
-import {
-  type CasStore,
-  getContentMerklePayload,
-  putStepMerkleNode,
-  putThreadMerkleNode,
-} from "@uncaged/workflow-cas";
-import { resolveModel } from "@uncaged/workflow-register";
-import { createExtract } from "../extract/index.js";
-import { readWorkflowRegistry, type WorkflowConfig } from "@uncaged/workflow-register";
-import { err, type LogFn, normalizeRefsField, ok, type Result } from "@uncaged/workflow-util";
+import { END, START } from "@uncaged/workflow-runtime";
+import { err, type LogFn, ok, type Result } from "@uncaged/workflow-util";
 
+import { createExtract } from "../extract/index.js";
 import { runSupervisor } from "./supervisor.js";
-import type { ExecuteThreadIo, ExecuteThreadOptions } from "./types.js";
+import {
+  appendThreadHistoryEntry,
+  getBundleDir,
+  removeThreadEntry,
+  upsertThreadEntry,
+} from "./threads-index.js";
+import type { ChainState, ExecuteThreadIo, ExecuteThreadOptions } from "./types.js";
+import { EMPTY_CHAIN_STATE } from "./types.js";
+
+/** Cap for {@link StateNode}.payload.ancestors: 1 parent + 10 skip-list. */
+const ANCESTORS_CAP = 11;
+
+function computeAncestors(chain: ChainState): string[] {
+  if (chain.parentStateHash === null) {
+    return [];
+  }
+  return [chain.parentStateHash, ...chain.parentAncestors].slice(0, ANCESTORS_CAP);
+}
 
 async function resolveEngineRegistryRuntime(
   storageRoot: string,
@@ -57,51 +79,108 @@ async function resolveEngineRegistryRuntime(
   return ok({ extract: createExtract(llmProvider, { cas }), workflowConfig: cfg });
 }
 
-async function appendDataLine(path: string, record: unknown): Promise<void> {
-  const line = `${JSON.stringify(record)}\n`;
-  await appendFile(path, line, "utf8");
+async function appendStateForStep(params: {
+  cas: CasStore;
+  startHash: string;
+  chain: ChainState;
+  role: string;
+  contentHash: string;
+  meta: Record<string, unknown>;
+  refs: readonly string[];
+  timestamp: number;
+}): Promise<{ stateHash: string; chain: ChainState }> {
+  const text = await getContentMerklePayload(params.cas, params.contentHash);
+  if (text === null) {
+    throw new Error(
+      `role step ${params.role}: CAS blob missing for contentHash ${params.contentHash}`,
+    );
+  }
+  const artifactRefs = params.refs.filter((r) => r !== params.contentHash);
+  const contentHash = await putContentNodeWithRefs(params.cas, text, artifactRefs);
+  const ancestors = computeAncestors(params.chain);
+  const payload: StateNode["payload"] = {
+    role: params.role,
+    meta: params.meta,
+    start: params.startHash,
+    content: contentHash,
+    ancestors,
+    compact: null,
+    timestamp: params.timestamp,
+  };
+  const stateHash = await putStateNode(params.cas, payload);
+  return {
+    stateHash,
+    chain: { parentStateHash: stateHash, parentAncestors: ancestors },
+  };
 }
 
-async function finalizeThreadResult(params: {
+async function appendEndState(params: {
   cas: CasStore;
-  workflowName: string;
+  startHash: string;
+  chain: ChainState;
+  completion: WorkflowCompletion;
+  timestamp: number;
+}): Promise<string> {
+  const contentHash = await putContentNodeWithRefs(params.cas, params.completion.summary, []);
+  const ancestors = computeAncestors(params.chain);
+  const payload: StateNode["payload"] = {
+    role: END,
+    meta: { returnCode: params.completion.returnCode, summary: params.completion.summary },
+    start: params.startHash,
+    content: contentHash,
+    ancestors,
+    compact: null,
+    timestamp: params.timestamp,
+  };
+  return putStateNode(params.cas, payload);
+}
+
+async function finalizeThread(params: {
+  cas: CasStore;
+  bundleDir: string;
   threadId: string;
-  stepMerkleHashes: readonly string[];
+  startHash: string;
+  chain: ChainState;
   completion: WorkflowCompletion;
 }): Promise<WorkflowResult> {
-  const rootHash = await putThreadMerkleNode(
-    params.cas,
-    {
-      workflow: params.workflowName,
-      threadId: params.threadId,
-      result: {
-        returnCode: params.completion.returnCode,
-        summary: params.completion.summary,
-      },
-    },
-    params.stepMerkleHashes,
-  );
+  const ts = Date.now();
+  const endHash = await appendEndState({
+    cas: params.cas,
+    startHash: params.startHash,
+    chain: params.chain,
+    completion: params.completion,
+    timestamp: ts,
+  });
+  await removeThreadEntry(params.bundleDir, params.threadId);
+  await appendThreadHistoryEntry(params.bundleDir, {
+    threadId: params.threadId,
+    head: endHash,
+    start: params.startHash,
+    completedAt: ts,
+  });
   return {
     returnCode: params.completion.returnCode,
     summary: params.completion.summary,
-    rootHash,
+    rootHash: endHash,
   };
 }
 
 async function finalizeAbortedThread(params: {
   cas: CasStore;
-  workflowName: string;
+  bundleDir: string;
   threadId: string;
-  stepMerkleHashes: string[];
+  startHash: string;
+  chain: ChainState;
   logger: LogFn;
   abortLogTag: string;
 }): Promise<WorkflowResult> {
   params.logger(params.abortLogTag, `thread ${params.threadId} aborted`);
-  return finalizeThreadResult({
+  return finalizeThread({
     cas: params.cas,
-    workflowName: params.workflowName,
+    bundleDir: params.bundleDir,
     threadId: params.threadId,
-    stepMerkleHashes: params.stepMerkleHashes,
+    startHash: params.startHash,
+    chain: params.chain,
     completion: { returnCode: 130, summary: "thread aborted" },
   });
 }
@@ -114,8 +193,9 @@ async function maybeSupervisorHaltsThread(params: {
   logger: LogFn;
   threadId: string;
   cas: CasStore;
-  workflowName: string;
-  stepMerkleHashes: string[];
+  bundleDir: string;
+  startHash: string;
+  chain: ChainState;
 }): Promise<WorkflowResult | null> {
   const interval = params.workflowConfig.supervisorInterval;
   if (interval <= 0 || params.written % interval !== 0) {
@@ -135,41 +215,55 @@ async function maybeSupervisorHaltsThread(params: {
     return null;
   }
   params.logger("M4QX8VHN", `thread ${params.threadId} stopped by supervisor`);
-  return finalizeThreadResult({
+  return finalizeThread({
     cas: params.cas,
-    workflowName: params.workflowName,
+    bundleDir: params.bundleDir,
     threadId: params.threadId,
-    stepMerkleHashes: params.stepMerkleHashes,
+    startHash: params.startHash,
+    chain: params.chain,
     completion: { returnCode: 0, summary: "completed: supervisor stopped thread" },
   });
 }
 
+async function publishHead(params: {
+  bundleDir: string;
+  threadId: string;
+  startHash: string;
+  headHash: string;
+}): Promise<void> {
+  await upsertThreadEntry(params.bundleDir, params.threadId, {
+    head: params.headHash,
+    start: params.startHash,
+    updatedAt: Date.now(),
+  });
+}
+
 async function driveWorkflowGenerator(params: {
   fn: WorkflowFn;
-  workflowName: string;
   workflowConfig: WorkflowConfig;
   thread: ThreadContext;
   runtime: WorkflowRuntime;
   executeOptions: ExecuteThreadOptions;
-  dataJsonlPath: string;
   threadId: string;
   logger: LogFn;
   cas: CasStore;
-  stepMerkleHashes: string[];
+  bundleDir: string;
+  startHash: string;
+  chain: ChainState;
 }): Promise<WorkflowResult> {
   const {
     fn,
-    workflowName,
     workflowConfig,
     thread,
     runtime,
     executeOptions,
-    dataJsonlPath,
     threadId,
     logger,
     cas,
-    stepMerkleHashes,
+    bundleDir,
+    startHash,
   } = params;
+  let chain: ChainState = params.chain;
   const gen = fn(thread, runtime);
   let written = 0;
   const recentSupervisorSteps: { role: string; summary: string }[] = thread.steps.map((s) => ({
@@ -181,9 +275,10 @@ async function driveWorkflowGenerator(params: {
     if (executeOptions.signal.aborted) {
       return await finalizeAbortedThread({
         cas,
-        workflowName,
+        bundleDir,
         threadId,
-        stepMerkleHashes,
+        startHash,
+        chain,
         logger,
         abortLogTag: "V8JX4NP2",
       });
@@ -191,11 +286,12 @@ async function driveWorkflowGenerator(params: {
 
     if (written >= executeOptions.maxRounds) {
       logger("R3CW7YBQ", `thread ${threadId} stopped at maxRounds=${executeOptions.maxRounds}`);
-      return await finalizeThreadResult({
+      return await finalizeThread({
         cas,
-        workflowName,
+        bundleDir,
         threadId,
-        stepMerkleHashes,
+        startHash,
+        chain,
         completion: {
           returnCode: 0,
           summary: `completed: reached maxRounds (${executeOptions.maxRounds})`,
@@ -207,39 +303,31 @@ async function driveWorkflowGenerator(params: {
 
     if (iterResult.done) {
       logger("F3HN8QKP", `thread ${threadId} generator finished`);
-      const completion = iterResult.value;
-      return await finalizeThreadResult({
+      return await finalizeThread({
         cas,
-        workflowName,
+        bundleDir,
         threadId,
-        stepMerkleHashes,
-        completion,
+        startHash,
+        chain,
+        completion: iterResult.value,
       });
     }
 
     written++;
     const step = iterResult.value;
-    const resolved = await getContentMerklePayload(cas, step.contentHash);
-    if (resolved === null) {
-      throw new Error(
-        `role step ${step.role}: CAS blob missing for contentHash ${step.contentHash}`,
-      );
-    }
     const ts = Date.now();
-    await appendDataLine(dataJsonlPath, {
+    const written_ = await appendStateForStep({
+      cas,
+      startHash,
+      chain,
       role: step.role,
       contentHash: step.contentHash,
       meta: step.meta,
-      refs: normalizeRefsField(step.refs),
+      refs: step.refs,
       timestamp: ts,
     });
-
-    const stepNodeHash = await putStepMerkleNode(
-      cas,
-      { role: step.role, meta: step.meta },
-      step.contentHash,
-    );
-    stepMerkleHashes.push(stepNodeHash);
+    chain = written_.chain;
+    await publishHead({ bundleDir, threadId, startHash, headHash: written_.stateHash });
 
     logger("N7BW4YHQ", `thread ${threadId} wrote role ${step.role}`);
 
@@ -262,9 +350,10 @@ async function driveWorkflowGenerator(params: {
     if (executeOptions.signal.aborted) {
       return await finalizeAbortedThread({
         cas,
-        workflowName,
+        bundleDir,
         threadId,
-        stepMerkleHashes,
+        startHash,
+        chain,
         logger,
         abortLogTag: "V8JX4NP4",
       });
@@ -278,8 +367,9 @@ async function driveWorkflowGenerator(params: {
       logger,
       threadId,
       cas,
-      workflowName,
-      stepMerkleHashes,
+      bundleDir,
+      startHash,
+      chain,
     });
     if (supervised !== null) {
       return supervised;
@@ -288,8 +378,16 @@ async function driveWorkflowGenerator(params: {
 }
 
 /**
- * Execute a workflow thread: drive the bundle's AsyncGenerator, RFC-001 `.data.jsonl` records,
- * debug lines via `logger` to `.info.jsonl`.
+ * Execute a workflow thread by driving the bundle's `AsyncGenerator`.
+ *
+ * Persistence layout (RFC v3 — CAS-based thread storage):
+ * - Thread chain is written as immutable CAS blobs: a single {@link StartNode}
+ *   plus one {@link StateNode} per role step (including a final `__end__`
+ *   state on completion / abort / `maxRounds`).
+ * - The active thread head is published in `<bundleDir>/threads.json`; on
+ *   completion it is removed and a record is appended to
+ *   `<bundleDir>/history/{YYYY-MM-DD}.jsonl`.
+ * - Debug logging continues to flow through `logger` to `.info.jsonl`.
  */
 export async function executeThread(
   fn: WorkflowFn,
@@ -299,71 +397,92 @@ export async function executeThread(
   io: ExecuteThreadIo,
   logger: LogFn,
 ): Promise<WorkflowResult> {
-  await mkdir(dirname(io.dataJsonlPath), { recursive: true });
   await mkdir(dirname(io.infoJsonlPath), { recursive: true });
 
   const prefilled = options.prefilledDiskSteps;
+  const fork = options.forkContinuation;
+
+  if (fork !== null && prefilled !== null) {
+    throw new Error("forkContinuation and prefilledDiskSteps cannot both be set");
+  }
+
   if (prefilled !== null && prefilled.length !== input.steps.length) {
     throw new Error(
       `prefilledDiskSteps length (${prefilled.length}) must match input.steps length (${input.steps.length})`,
     );
   }
 
-  const nowMs = Date.now();
-  const startRecord: Record<string, unknown> = {
-    name: workflowName,
-    hash: io.hash,
-    threadId: io.threadId,
-    parameters: {
-      prompt: input.prompt,
-      options: {
+  const replayTs = options.replayTimestamps;
+  if (replayTs !== null && replayTs.length !== input.steps.length) {
+    throw new Error(
+      `replayTimestamps length (${replayTs.length}) must match input.steps length (${input.steps.length})`,
+    );
+  }
+
+  const bundleDir = getBundleDir(options.storageRoot, io.hash);
+
+  let startHash: string;
+
+  if (fork !== null) {
+    startHash = fork.startHash;
+    logger("T9HQ2KHM", `thread ${io.threadId} continued fork for workflow ${workflowName}`);
+  } else {
+    const promptHash = await io.cas.put(input.prompt);
+    startHash = await putStartNode(
+      io.cas,
+      {
+        name: workflowName,
+        hash: io.hash,
         maxRounds: options.maxRounds,
         depth: options.depth,
       },
-    },
-    timestamp: nowMs,
-  };
-  if (options.forkSourceThreadId !== null) {
-    startRecord.forkFrom = { threadId: options.forkSourceThreadId };
+      promptHash,
+    );
+
+    await publishHead({
+      bundleDir,
+      threadId: io.threadId,
+      startHash,
+      headHash: startHash,
+    });
+
+    logger("T9HQ2KHM", `thread ${io.threadId} started for workflow ${workflowName}`);
   }
 
-  await appendDataLine(io.dataJsonlPath, startRecord);
-
-  logger("T9HQ2KHM", `thread ${io.threadId} started for workflow ${workflowName}`);
-
-  const stepMerkleHashes: string[] = [];
+  let chain: ChainState = fork !== null ? fork.initialChain : EMPTY_CHAIN_STATE;
 
   if (prefilled !== null) {
     for (const row of prefilled) {
-      const prefilledPayload = await getContentMerklePayload(io.cas, row.contentHash);
-      if (prefilledPayload === null) {
-        throw new Error(
-          `prefilled step ${row.role}: CAS blob missing for contentHash ${row.contentHash}`,
-        );
-      }
-      await appendDataLine(io.dataJsonlPath, {
+      const written = await appendStateForStep({
+        cas: io.cas,
+        startHash,
+        chain,
         role: row.role,
         contentHash: row.contentHash,
         meta: row.meta,
-        refs: normalizeRefsField(row.refs),
+        refs: row.refs,
         timestamp: row.timestamp,
       });
-      const stepNodeHash = await putStepMerkleNode(
-        io.cas,
-        { role: row.role, meta: row.meta },
-        row.contentHash,
-      );
-      stepMerkleHashes.push(stepNodeHash);
+      chain = written.chain;
+      await publishHead({
+        bundleDir,
+        threadId: io.threadId,
+        startHash,
+        headHash: written.stateHash,
+      });
     }
   }
 
+  const nowMs = Date.now();
+
   if (options.maxRounds <= 0) {
     logger("R3CW7YBQ", `thread ${io.threadId} stopped at maxRounds=${options.maxRounds}`);
-    return await finalizeThreadResult({
+    return await finalizeThread({
       cas: io.cas,
-      workflowName,
+      bundleDir,
       threadId: io.threadId,
-      stepMerkleHashes,
+      startHash,
+      chain,
       completion: {
         returnCode: 0,
         summary: `completed: reached maxRounds (${options.maxRounds})`,
@@ -390,7 +509,7 @@ export async function executeThread(
       contentHash: out.contentHash,
       meta: out.meta,
       refs: out.refs,
-      timestamp: prefilled?.[i]?.timestamp ?? nowMs + i,
+      timestamp: replayTs?.[i] ?? prefilled?.[i]?.timestamp ?? nowMs + i,
     })),
   };
 
@@ -401,15 +520,15 @@ export async function executeThread(
 
   return await driveWorkflowGenerator({
     fn,
-    workflowName,
     workflowConfig: registryRuntime.value.workflowConfig,
     thread,
     runtime,
     executeOptions: options,
-    dataJsonlPath: io.dataJsonlPath,
     threadId: io.threadId,
     logger,
     cas: io.cas,
-    stepMerkleHashes,
+    bundleDir,
+    startHash,
+    chain,
   });
 }

packages/workflow-execute/src/engine/fork-thread.ts

@@ -1,9 +1,29 @@
-import type { WorkflowCompletion } from "@uncaged/workflow-runtime";
-import { err, normalizeRefsField, ok, type Result } from "@uncaged/workflow-util";
+import type { CasStore } from "@uncaged/workflow-cas";
+import { parseCasThreadNode, putContentNodeWithRefs, putStateNode } from "@uncaged/workflow-cas";
+import type { StateNodePayload } from "@uncaged/workflow-protocol";
+import type { RoleOutput, WorkflowCompletion } from "@uncaged/workflow-runtime";
+import { END } from "@uncaged/workflow-runtime";
+import { err, ok, type Result } from "@uncaged/workflow-util";
+import { parse as parseYaml } from "yaml";
 
-import type { ForkHistoricalStep, ForkPlan, ParsedThreadStartRecord } from "./types.js";
+import { upsertThreadEntry } from "./threads-index.js";
+import type { CasForkPlan, ChainState, ForkContinuationOptions } from "./types.js";
+import { EMPTY_CHAIN_STATE } from "./types.js";
 
-/** Recognizes a persisted workflow completion line (no `role`; has numeric `returnCode` and string `summary`). Omits `rootHash` when absent. */
+/** Internal branch marker; skipped when presenting fork selection / replay slices. */
+export const FORK_BRANCH_ROLE = "__fork__";
+
+/** Cap for {@link StateNodePayload}.ancestors: 1 parent + 10 skip-list. */
+const ANCESTORS_CAP = 11;
+
+function computeAncestors(chain: ChainState): string[] {
+  if (chain.parentStateHash === null) {
+    return [];
+  }
+  return [chain.parentStateHash, ...chain.parentAncestors].slice(0, ANCESTORS_CAP);
+}
+
+/** Recognizes a persisted workflow completion line (no `role`; has numeric `returnCode` and string `summary`). */
 export function tryParseWorkflowResultRecord(
   obj: Record<string, unknown>,
 ): WorkflowCompletion | null {
@@ -18,227 +38,288 @@ export function tryParseWorkflowResultRecord(
   return { returnCode, summary };
 }
 
-export function tryParseRoleStepRecord(obj: Record<string, unknown>): ForkHistoricalStep | null {
-  const role = obj.role;
-  const contentHash = obj.contentHash;
-  const meta = obj.meta;
-  const timestamp = obj.timestamp;
-  if (typeof role !== "string") {
-    return null;
-  }
-  if (typeof contentHash !== "string") {
-    return null;
-  }
-  if (meta === null || typeof meta !== "object") {
-    return null;
-  }
-  if (typeof timestamp !== "number") {
-    return null;
-  }
-  return {
-    role,
-    contentHash,
-    meta: meta as Record<string, unknown>,
-    refs: normalizeRefsField(obj.refs),
-    timestamp,
-  };
-}
-
-function parseRoleLine(
-  obj: Record<string, unknown>,
-  lineIndex: number,
-): Result<ForkHistoricalStep, string> {
-  const parsed = tryParseRoleStepRecord(obj);
-  if (parsed === null) {
-    return err(`invalid role record at line ${lineIndex}`);
-  }
-  return ok(parsed);
-}
-
-function parseStartRecordLine(firstLine: string): Result<ParsedThreadStartRecord, string> {
-  let startParsed: unknown;
-  try {
-    startParsed = JSON.parse(firstLine) as unknown;
-  } catch {
-    return err("invalid JSON on line 1 (start record)");
-  }
-  if (startParsed === null || typeof startParsed !== "object") {
-    return err("invalid start record shape");
-  }
-  const startRec = startParsed as Record<string, unknown>;
-  const name = startRec.name;
-  const hash = startRec.hash;
-  const threadId = startRec.threadId;
-  const parameters = startRec.parameters;
-  if (typeof name !== "string" || typeof hash !== "string" || typeof threadId !== "string") {
-    return err("start record missing name, hash, or threadId");
-  }
-  if (parameters === null || typeof parameters !== "object") {
-    return err("start record missing parameters");
-  }
-  const paramsRec = parameters as Record<string, unknown>;
-  const prompt = paramsRec.prompt;
-  const options = paramsRec.options;
-  if (typeof prompt !== "string") {
-    return err("start record missing parameters.prompt");
-  }
-  if (options === null || typeof options !== "object") {
-    return err("start record missing parameters.options");
-  }
-  const optRec = options as Record<string, unknown>;
-  const maxRounds = optRec.maxRounds;
-  if (typeof maxRounds !== "number") {
-    return err("start record missing parameters.options.maxRounds");
-  }
-
-  const depthRaw = optRec.depth;
-  const depth =
-    typeof depthRaw === "number" && Number.isFinite(depthRaw) ? Math.trunc(depthRaw) : 0;
-
-  return ok({
-    workflowName: name,
-    hash,
-    threadId,
-    prompt,
-    maxRounds,
-    depth,
-  });
-}
-
-function parseFollowingRoleLines(lines: string[]): Result<ForkHistoricalStep[], string> {
-  const roleSteps: ForkHistoricalStep[] = [];
-  for (let i = 1; i < lines.length; i++) {
-    const line = lines[i];
-    if (line === undefined) {
+/** Walk {@link StateNode} hashes from head toward the first step (newest → oldest). */
+export async function walkStateFramesNewestFirst(
+  cas: CasStore,
+  headHash: string,
+): Promise<Array<{ hash: string; payload: StateNodePayload }>> {
+  const frames: Array<{ hash: string; payload: StateNodePayload }> = [];
+  let cur = headHash;
+  while (true) {
+    const yamlText = await cas.get(cur);
+    if (yamlText === null) {
       break;
     }
-    let rec: unknown;
-    try {
-      rec = JSON.parse(line) as unknown;
-    } catch {
-      return err(`invalid JSON at line ${i + 1}`);
-    }
-    if (rec === null || typeof rec !== "object") {
-      return err(`invalid record at line ${i + 1}`);
-    }
-    const recObj = rec as Record<string, unknown>;
-    const wf = tryParseWorkflowResultRecord(recObj);
-    if (wf !== null) {
-      if (i !== lines.length - 1) {
-        return err("WorkflowResult record must be the final line in `.data.jsonl`");
-      }
+    const parsed = parseCasThreadNode(yamlText);
+    if (parsed === null || parsed.kind !== "state") {
       break;
     }
-    const parsed = parseRoleLine(recObj, i + 1);
-    if (!parsed.ok) {
-      return parsed;
+    frames.push({ hash: cur, payload: parsed.node.payload });
+    const ancestors = parsed.node.payload.ancestors;
+    if (ancestors.length === 0) {
+      break;
     }
-    roleSteps.push(parsed.value);
+    const parent = ancestors[0];
+    if (parent === undefined || parent === "") {
+      break;
+    }
+    cur = parent;
   }
-  return ok(roleSteps);
+  return frames;
 }
 
-/**
- * Parse RFC-001 `.data.jsonl`: line 1 start record, line 2+ role outputs.
- */
-export function parseThreadDataJsonl(text: string): Result<
-  {
-    start: ParsedThreadStartRecord;
-    roleSteps: ForkHistoricalStep[];
-  },
-  string
-> {
-  const lines = text
-    .split("\n")
-    .map((l) => l.trim())
-    .filter((l) => l !== "");
-  if (lines.length === 0) {
-    return err("thread data is empty");
-  }
-
-  const firstLine = lines[0];
-  if (firstLine === undefined) {
-    return err("thread data is empty");
-  }
-
-  const start = parseStartRecordLine(firstLine);
-  if (!start.ok) {
-    return start;
-  }
-
-  const roleSteps = parseFollowingRoleLines(lines);
-  if (!roleSteps.ok) {
-    return roleSteps;
-  }
-
-  return ok({
-    start: start.value,
-    roleSteps: roleSteps.value,
-  });
-}
-
-function orderedUniqueRoles(roleSteps: ForkHistoricalStep[]): string[] {
+function orderedUniqueRoles(roles: string[]): string[] {
   const seen = new Set<string>();
   const out: string[] = [];
-  for (const s of roleSteps) {
-    if (!seen.has(s.role)) {
-      seen.add(s.role);
-      out.push(s.role);
+  for (const r of roles) {
+    if (!seen.has(r)) {
+      seen.add(r);
+      out.push(r);
     }
   }
   return out;
 }
 
-/**
- * Select historical steps for a fork:
- * - `fromRole === null`: drop the last step (retry the last role).
- * - `fromRole !== null`: keep steps through the first occurrence of that role (inclusive).
- */
-export function selectForkHistoricalSteps(
-  roleSteps: ForkHistoricalStep[],
+async function readPromptText(cas: CasStore, promptHash: string): Promise<Result<string, string>> {
+  const yamlText = await cas.get(promptHash);
+  if (yamlText === null) {
+    return err(`prompt CAS blob missing: ${promptHash}`);
+  }
+  let raw: unknown;
+  try {
+    raw = parseYaml(yamlText) as unknown;
+  } catch {
+    return err(`prompt CAS blob is not valid YAML: ${promptHash}`);
+  }
+  if (raw === null || typeof raw !== "object") {
+    return err(`prompt CAS blob has unexpected shape: ${promptHash}`);
+  }
+  const payload = (raw as Record<string, unknown>).payload;
+  if (typeof payload !== "string") {
+    return err(`prompt CAS blob missing string payload: ${promptHash}`);
+  }
+  return ok(payload);
+}
+
+async function readStartWorkflowIdentity(params: {
+  cas: CasStore;
+  startHash: string;
+}): Promise<
+  Result<{ workflowName: string; maxRounds: number; depth: number; prompt: string }, string>
+> {
+  const yamlText = await params.cas.get(params.startHash);
+  if (yamlText === null) {
+    return err(`start node missing in CAS: ${params.startHash}`);
+  }
+  const parsed = parseCasThreadNode(yamlText);
+  if (parsed === null || parsed.kind !== "start") {
+    return err(`CAS blob is not a StartNode: ${params.startHash}`);
+  }
+  const refs = parsed.node.refs;
+  const promptHash = refs[0];
+  if (typeof promptHash !== "string") {
+    return err("StartNode refs[0] must be the prompt hash");
+  }
+  const prompt = await readPromptText(params.cas, promptHash);
+  if (!prompt.ok) {
+    return prompt;
+  }
+  const p = parsed.node.payload;
+  return ok({
+    workflowName: p.name,
+    maxRounds: p.maxRounds,
+    depth: p.depth,
+    prompt: prompt.value,
+  });
+}
+
+async function payloadToRoleOutput(cas: CasStore, payload: StateNodePayload): Promise<RoleOutput> {
+  let refs: string[] = [];
+  const blob = await cas.get(payload.content);
+  if (blob !== null) {
+    const cn = parseCasThreadNode(blob);
+    if (cn?.kind === "content") {
+      refs = [...cn.node.refs];
+    }
+  }
+  return {
+    role: payload.role,
+    contentHash: payload.content,
+    meta: payload.meta,
+    refs,
+  };
+}
+
+function meaningfulFramesOldestFirst(
+  newestFirst: Array<{ hash: string; payload: StateNodePayload }>,
+): Array<{ hash: string; payload: StateNodePayload }> {
+  const chronological = [...newestFirst].reverse();
+  return chronological.filter((f) => f.payload.role !== END && f.payload.role !== FORK_BRANCH_ROLE);
+}
+
+function selectForkPointStateHash(
+  meaningfulOldestFirst: Array<{ hash: string; payload: StateNodePayload }>,
   fromRole: string | null,
-): Result<ForkHistoricalStep[], string> {
-  if (roleSteps.length === 0) {
+): Result<string | null, string> {
+  if (meaningfulOldestFirst.length === 0) {
     return err("thread has no completed role steps to fork from");
   }
 
   if (fromRole === null) {
-    if (roleSteps.length === 1) {
-      return ok([]);
+    if (meaningfulOldestFirst.length === 1) {
+      return ok(null);
     }
-    return ok(roleSteps.slice(0, -1));
+    const forkFrame = meaningfulOldestFirst[meaningfulOldestFirst.length - 2];
+    if (forkFrame === undefined) {
+      return err("thread has no completed role steps to fork from");
+    }
+    return ok(forkFrame.hash);
   }
 
-  const idx = roleSteps.findIndex((s) => s.role === fromRole);
+  const idx = meaningfulOldestFirst.findIndex((f) => f.payload.role === fromRole);
   if (idx < 0) {
-    const available = orderedUniqueRoles(roleSteps);
+    const available = orderedUniqueRoles(meaningfulOldestFirst.map((f) => f.payload.role));
     return err(`role not found in thread: ${fromRole} (available: ${available.join(", ")})`);
   }
-  return ok(roleSteps.slice(0, idx + 1));
+  const forkFrame = meaningfulOldestFirst[idx];
+  if (forkFrame === undefined) {
+    return err("fork frame missing");
+  }
+  return ok(forkFrame.hash);
+}
+
+function replayFramesThroughForkPoint(
+  meaningfulOldestFirst: Array<{ hash: string; payload: StateNodePayload }>,
+  forkPointHash: string | null,
+): Array<{ hash: string; payload: StateNodePayload }> {
+  if (forkPointHash === null) {
+    return [];
+  }
+  const idx = meaningfulOldestFirst.findIndex((f) => f.hash === forkPointHash);
+  if (idx < 0) {
+    return [];
+  }
+  return meaningfulOldestFirst.slice(0, idx + 1);
+}
+
+async function buildForkContinuation(params: {
+  cas: CasStore;
+  sourceThreadId: string;
+  startHash: string;
+  forkPointStateHash: string | null;
+}): Promise<Result<ForkContinuationOptions, string>> {
+  const { cas, sourceThreadId, startHash, forkPointStateHash } = params;
+
+  if (forkPointStateHash === null) {
+    return ok({
+      startHash,
+      forkHeadHash: startHash,
+      initialChain: EMPTY_CHAIN_STATE,
+    });
+  }
+
+  const yamlText = await cas.get(forkPointStateHash);
+  if (yamlText === null) {
+    return err(`fork point state missing in CAS: ${forkPointStateHash}`);
+  }
+  const parsed = parseCasThreadNode(yamlText);
+  if (parsed === null || parsed.kind !== "state") {
+    return err(`fork point blob is not a StateNode: ${forkPointStateHash}`);
+  }
+  const fpPayload = parsed.node.payload;
+
+  const chainBefore: ChainState = {
+    parentStateHash: forkPointStateHash,
+    parentAncestors: fpPayload.ancestors,
+  };
+  const ancestorsMarker = computeAncestors(chainBefore);
+
+  const emptyContentHash = await putContentNodeWithRefs(cas, "", []);
+  const markerPayload: StateNodePayload = {
+    role: FORK_BRANCH_ROLE,
+    meta: { forkFrom: sourceThreadId },
+    start: startHash,
+    content: emptyContentHash,
+    ancestors: ancestorsMarker,
+    compact: null,
+    timestamp: Date.now(),
+  };
+  const markerHash = await putStateNode(cas, markerPayload);
+
+  const initialChain: ChainState = {
+    parentStateHash: markerHash,
+    parentAncestors: ancestorsMarker,
+  };
+
+  return ok({
+    startHash,
+    forkHeadHash: markerHash,
+    initialChain,
+  });
 }
 
 /**
- * Read `.data.jsonl` text and compute fork payload for the worker `run` command.
+ * Prepare a CAS fork: writes the branch marker {@link StateNode}, registers `threads.json`,
+ * and returns worker payload fields (shared {@link StartNode}, zero ancestor duplication).
  */
-export function buildForkPlan(
-  dataJsonlText: string,
-  fromRole: string | null,
-): Result<ForkPlan, string> {
-  const parsed = parseThreadDataJsonl(dataJsonlText);
-  if (!parsed.ok) {
-    return parsed;
+export async function prepareCasFork(params: {
+  cas: CasStore;
+  bundleDir: string;
+  bundleHash: string;
+  sourceThreadId: string;
+  headHash: string;
+  startHash: string;
+  newThreadId: string;
+  fromRole: string | null;
+}): Promise<Result<CasForkPlan, string>> {
+  const id = await readStartWorkflowIdentity({
+    cas: params.cas,
+    startHash: params.startHash,
+  });
+  if (!id.ok) {
+    return id;
   }
-  const selected = selectForkHistoricalSteps(parsed.value.roleSteps, fromRole);
-  if (!selected.ok) {
-    return selected;
+
+  const newestFirst = await walkStateFramesNewestFirst(params.cas, params.headHash);
+  const meaningful = meaningfulFramesOldestFirst(newestFirst);
+
+  const forkPoint = selectForkPointStateHash(meaningful, params.fromRole);
+  if (!forkPoint.ok) {
+    return forkPoint;
   }
-  const { start } = parsed.value;
+
+  const replayFrames = replayFramesThroughForkPoint(meaningful, forkPoint.value);
+  const steps: RoleOutput[] = [];
+  const stepTimestamps: number[] = [];
+  for (const fr of replayFrames) {
+    steps.push(await payloadToRoleOutput(params.cas, fr.payload));
+    stepTimestamps.push(fr.payload.timestamp);
+  }
+
+  const cont = await buildForkContinuation({
+    cas: params.cas,
+    sourceThreadId: params.sourceThreadId,
+    startHash: params.startHash,
+    forkPointStateHash: forkPoint.value,
+  });
+  if (!cont.ok) {
+    return cont;
+  }
+
+  await upsertThreadEntry(params.bundleDir, params.newThreadId, {
+    head: cont.value.forkHeadHash,
+    start: params.startHash,
+    updatedAt: Date.now(),
+  });
+
   return ok({
-    workflowName: start.workflowName,
-    hash: start.hash,
-    sourceThreadId: start.threadId,
-    prompt: start.prompt,
-    runOptions: { maxRounds: start.maxRounds, depth: start.depth },
-    historicalSteps: selected.value,
+    workflowName: id.value.workflowName,
+    hash: params.bundleHash,
+    sourceThreadId: params.sourceThreadId,
+    prompt: id.value.prompt,
+    runOptions: { maxRounds: id.value.maxRounds, depth: id.value.depth },
+    steps,
+    stepTimestamps,
+    forkContinuation: cont.value,
   });
 }

packages/workflow-execute/src/engine/gc.ts

@@ -1,122 +1,182 @@
-import { readdir, readFile } from "node:fs/promises";
+import type { Stats } from "node:fs";
+import { readdir, readFile, stat } from "node:fs/promises";
 import { join } from "node:path";
-import { type CasStore, createCasStore } from "@uncaged/workflow-cas";
+import { type CasStore, createCasStore, findReachableHashes } from "@uncaged/workflow-cas";
 import { err, getGlobalCasDir, ok, type Result } from "@uncaged/workflow-util";
-import { parseThreadDataJsonl } from "./fork-thread.js";
+
+import type { ThreadHistoryEntry, ThreadIndex } from "./threads-index.js";
+import { readThreadsIndex } from "./threads-index.js";
 import type { GcResult } from "./types.js";
 
-async function listThreadDataJsonlPaths(storageRoot: string): Promise<Result<string[], string>> {
-  const logsRoot = join(storageRoot, "logs");
-  const paths: string[] = [];
-  let hashes: string[];
+function isPlainObject(v: unknown): v is Record<string, unknown> {
+  return v !== null && typeof v === "object" && !Array.isArray(v);
+}
+
+function parseHistoryLine(jsonLine: string): ThreadHistoryEntry | null {
+  let raw: unknown;
   try {
-    hashes = await readdir(logsRoot);
+    raw = JSON.parse(jsonLine) as unknown;
+  } catch {
+    return null;
+  }
+  if (!isPlainObject(raw)) {
+    return null;
+  }
+  const threadId = raw.threadId;
+  const head = raw.head;
+  const start = raw.start;
+  const completedAt = raw.completedAt;
+  if (
+    typeof threadId !== "string" ||
+    typeof head !== "string" ||
+    typeof start !== "string" ||
+    typeof completedAt !== "number"
+  ) {
+    return null;
+  }
+  return { threadId, head, start, completedAt };
+}
+
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: walks threads index + optional history dir
+async function collectGcRootsFromBundle(bundleDir: string): Promise<Result<string[], string>> {
+  const roots: string[] = [];
+
+  let activeIndex: ThreadIndex;
+  try {
+    activeIndex = await readThreadsIndex(bundleDir);
+  } catch (e) {
+    return err(`failed to read threads.json under ${bundleDir}: ${String(e)}`);
+  }
+
+  for (const entry of Object.values(activeIndex)) {
+    roots.push(entry.head);
+    roots.push(entry.start);
+  }
+
+  const histDir = join(bundleDir, "history");
+  let histFiles: string[];
+  try {
+    histFiles = await readdir(histDir);
+  } catch (e) {
+    const errObj = e as NodeJS.ErrnoException;
+    if (errObj.code === "ENOENT") {
+      return ok(roots);
+    }
+    return err(`failed to read history directory ${histDir}: ${String(e)}`);
+  }
+
+  for (const name of histFiles) {
+    if (!name.endsWith(".jsonl")) {
+      continue;
+    }
+    let text: string;
+    try {
+      text = await readFile(join(histDir, name), "utf8");
+    } catch (e) {
+      return err(`failed to read history file ${name}: ${String(e)}`);
+    }
+    for (const line of text.split("\n")) {
+      const trimmed = line.trim();
+      if (trimmed === "") {
+        continue;
+      }
+      const entry = parseHistoryLine(trimmed);
+      if (entry === null) {
+        continue;
+      }
+      roots.push(entry.head);
+      roots.push(entry.start);
+    }
+  }
+
+  return ok(roots);
+}
+
+async function collectAllGcRoots(storageRoot: string): Promise<Result<string[], string>> {
+  const bundlesRoot = join(storageRoot, "bundles");
+  let entries: string[];
+  try {
+    entries = await readdir(bundlesRoot);
   } catch (e) {
     const errObj = e as NodeJS.ErrnoException;
     if (errObj.code === "ENOENT") {
       return ok([]);
     }
-    return err(`failed to read logs directory: ${String(e)}`);
+    return err(`failed to read bundles directory: ${String(e)}`);
   }
 
-  for (const hash of hashes) {
-    const dir = join(logsRoot, hash);
-    let entries: string[];
+  const roots: string[] = [];
+  for (const name of entries) {
+    const bundleDir = join(bundlesRoot, name);
+    let st: Stats;
     try {
-      entries = await readdir(dir);
+      st = await stat(bundleDir);
     } catch {
       continue;
     }
-    for (const fileName of entries) {
-      if (fileName.endsWith(".data.jsonl")) {
-        paths.push(join(dir, fileName));
-      }
+    if (!st.isDirectory()) {
+      continue;
     }
+    const chunk = await collectGcRootsFromBundle(bundleDir);
+    if (!chunk.ok) {
+      return chunk;
+    }
+    roots.push(...chunk.value);
   }
 
-  paths.sort();
-  return ok(paths);
+  return ok(roots);
 }
 
-async function collectActiveRefsFromDataPaths(
-  dataPaths: string[],
-): Promise<Result<Set<string>, string>> {
-  const activeRefs = new Set<string>();
-  for (const dataPath of dataPaths) {
-    let text: string;
-    try {
-      text = await readFile(dataPath, "utf8");
-    } catch (e) {
-      return err(`failed to read ${dataPath}: ${String(e)}`);
-    }
-    const parsed = parseThreadDataJsonl(text);
-    if (!parsed.ok) {
-      return err(`${dataPath}: ${parsed.error}`);
-    }
-    for (const step of parsed.value.roleSteps) {
-      for (const ref of step.refs) {
-        activeRefs.add(ref);
-      }
-    }
-  }
-  return ok(activeRefs);
-}
-
-async function deleteCasNotInSet(
-  cas: CasStore,
-  activeRefs: Set<string>,
-): Promise<Result<string[], string>> {
+async function deleteCasNotMarked(cas: CasStore, marked: ReadonlySet<string>): Promise<string[]> {
   let listed: string[];
   try {
     listed = await cas.list();
   } catch (e) {
-    return err(`failed to list cas entries: ${String(e)}`);
+    throw new Error(`failed to list cas entries: ${String(e)}`);
   }
 
   const deletedHashes: string[] = [];
   for (const hash of listed) {
-    if (activeRefs.has(hash)) {
+    if (marked.has(hash)) {
       continue;
     }
     try {
       await cas.delete(hash);
     } catch (e) {
-      return err(`failed to delete cas ${hash}: ${String(e)}`);
+      throw new Error(`failed to delete cas ${hash}: ${String(e)}`);
     }
     deletedHashes.push(hash);
   }
 
   deletedHashes.sort();
-  return ok(deletedHashes);
+  return deletedHashes;
 }
 
 /**
- * Mark-and-sweep CAS GC: collect `refs` from all thread `.data.jsonl` files under `storageRoot`,
- * then delete CAS blobs not referenced by any surviving thread data.
+ * Mark-and-sweep CAS GC: roots are every `head` / `start` hash from `threads.json` and
+ * `history/*.jsonl` across bundle dirs; marks closure via `refs[]`; deletes unreachable blobs.
  */
 export async function garbageCollectCas(storageRoot: string): Promise<Result<GcResult, string>> {
-  const pathsResult = await listThreadDataJsonlPaths(storageRoot);
-  if (!pathsResult.ok) {
-    return pathsResult;
+  const rootsResult = await collectAllGcRoots(storageRoot);
+  if (!rootsResult.ok) {
+    return rootsResult;
   }
-  const paths = pathsResult.value;
-
-  const refsResult = await collectActiveRefsFromDataPaths(paths);
-  if (!refsResult.ok) {
-    return refsResult;
-  }
-  const activeRefs = refsResult.value;
+  const roots = rootsResult.value;
 
   const cas = createCasStore(getGlobalCasDir(storageRoot));
-  const deletedResult = await deleteCasNotInSet(cas, activeRefs);
-  if (!deletedResult.ok) {
-    return deletedResult;
+
+  const marked = await findReachableHashes(roots, cas);
+
+  let deletedHashes: string[];
+  try {
+    deletedHashes = await deleteCasNotMarked(cas, marked);
+  } catch (e) {
+    return err(String(e));
   }
-  const deletedHashes = deletedResult.value;
 
   return ok({
-    scannedThreads: paths.length,
-    activeRefs: activeRefs.size,
+    scannedThreads: roots.length,
+    activeRefs: marked.size,
     deletedEntries: deletedHashes.length,
     deletedHashes,
   });

packages/workflow-execute/src/engine/index.ts

@@ -1,23 +1,33 @@
 export { createWorkflow } from "./create-workflow.js";
 export { executeThread } from "./engine.js";
 export {
-  buildForkPlan,
-  parseThreadDataJsonl,
-  selectForkHistoricalSteps,
-  tryParseRoleStepRecord,
+  FORK_BRANCH_ROLE,
+  prepareCasFork,
   tryParseWorkflowResultRecord,
+  walkStateFramesNewestFirst,
 } from "./fork-thread.js";
 export { garbageCollectCas } from "./gc.js";
 export { createThreadPauseGate } from "./thread-pause-gate.js";
+export type { ThreadHistoryEntry, ThreadIndex, ThreadIndexEntry } from "./threads-index.js";
+export {
+  appendThreadHistoryEntry,
+  getBundleDir,
+  readThreadsIndex,
+  removeThreadEntry,
+  removeThreadHistoryEntries,
+  upsertThreadEntry,
+  writeThreadsIndex,
+} from "./threads-index.js";
 export type {
+  CasForkPlan,
+  ChainState,
   ExecuteThreadIo,
   ExecuteThreadOptions,
-  ForkHistoricalStep,
-  ForkPlan,
+  ForkContinuationOptions,
   GcResult,
-  ParsedThreadStartRecord,
   PrefilledDiskStep,
   SupervisorDecision,
   ThreadPauseGate,
 } from "./types.js";
+export { EMPTY_CHAIN_STATE } from "./types.js";
 export { getWorkerHostScriptPath } from "./worker-entry-path.js";

packages/workflow-execute/src/engine/supervisor.ts

@@ -1,10 +1,9 @@
-import * as z from "zod/v4";
-
-import { resolveModel } from "@uncaged/workflow-register";
-import { extractFunctionToolFromZodSchema } from "../extract/index.js";
 import { createLlmFn, createThreadReactor } from "@uncaged/workflow-reactor";
 import type { WorkflowConfig } from "@uncaged/workflow-register";
+import { resolveModel } from "@uncaged/workflow-register";
 import { err, type LogFn, ok, type Result } from "@uncaged/workflow-util";
+import * as z from "zod/v4";
+import { extractFunctionToolFromZodSchema } from "../extract/index.js";
 
 import type { SupervisorDecision } from "./types.js";
 
@@ -75,7 +74,7 @@ export async function runSupervisor(
   });
 
   if (!result.ok) {
-    args.logger("R9CW4PLM", `supervisor failed: ${result.error}`);
+    args.logger("R9CW4PHM", `supervisor failed: ${result.error}`);
     return err(`supervisor: ${result.error}`);
   }
 

packages/workflow-execute/src/engine/threads-index.ts

@@ -0,0 +1,199 @@
+import { appendFile, mkdir, readdir, readFile, rename, writeFile } from "node:fs/promises";
+import { dirname, join } from "node:path";
+
+import { err, ok, type Result } from "@uncaged/workflow-util";
+
+/**
+ * Active-thread index entry stored in `<bundleDir>/threads.json`.
+ *
+ * Once the thread reaches `__end__`, the entry is removed from `threads.json`
+ * and a corresponding line is appended to `history/{YYYY-MM-DD}.jsonl`.
+ */
+export type ThreadIndexEntry = {
+  head: string;
+  start: string;
+  updatedAt: number;
+};
+
+export type ThreadHistoryEntry = {
+  threadId: string;
+  head: string;
+  start: string;
+  completedAt: number;
+};
+
+export type ThreadIndex = Record<string, ThreadIndexEntry>;
+
+export function getBundleDir(storageRoot: string, bundleHash: string): string {
+  return join(storageRoot, "bundles", bundleHash);
+}
+
+function threadsJsonPath(bundleDir: string): string {
+  return join(bundleDir, "threads.json");
+}
+
+function isPlainObject(v: unknown): v is Record<string, unknown> {
+  return v !== null && typeof v === "object" && !Array.isArray(v);
+}
+
+function parseThreadIndexEntry(raw: unknown): ThreadIndexEntry | null {
+  if (!isPlainObject(raw)) {
+    return null;
+  }
+  const head = raw.head;
+  const start = raw.start;
+  const updatedAt = raw.updatedAt;
+  if (typeof head !== "string" || typeof start !== "string" || typeof updatedAt !== "number") {
+    return null;
+  }
+  return { head, start, updatedAt };
+}
+
+function parseThreadIndex(text: string): ThreadIndex {
+  const trimmed = text.trim();
+  if (trimmed === "") {
+    return {};
+  }
+  let raw: unknown;
+  try {
+    raw = JSON.parse(trimmed) as unknown;
+  } catch {
+    return {};
+  }
+  if (!isPlainObject(raw)) {
+    return {};
+  }
+  const out: ThreadIndex = {};
+  for (const [k, v] of Object.entries(raw)) {
+    const entry = parseThreadIndexEntry(v);
+    if (entry !== null) {
+      out[k] = entry;
+    }
+  }
+  return out;
+}
+
+/** Read `<bundleDir>/threads.json` (empty object when missing or invalid). */
+export async function readThreadsIndex(bundleDir: string): Promise<ThreadIndex> {
+  const path = threadsJsonPath(bundleDir);
+  let text: string;
+  try {
+    text = await readFile(path, "utf8");
+  } catch (e) {
+    const errObj = e as NodeJS.ErrnoException;
+    if (errObj.code === "ENOENT") {
+      return {};
+    }
+    throw e;
+  }
+  return parseThreadIndex(text);
+}
+
+export async function writeThreadsIndex(bundleDir: string, index: ThreadIndex): Promise<void> {
+  const path = threadsJsonPath(bundleDir);
+  await mkdir(dirname(path), { recursive: true });
+  const tmp = `${path}.tmp.${process.pid}.${Date.now()}`;
+  const json = `${JSON.stringify(index, null, 2)}\n`;
+  await writeFile(tmp, json, "utf8");
+  await rename(tmp, path);
+}
+
+/** Insert/update a thread entry in `threads.json`. */
+export async function upsertThreadEntry(
+  bundleDir: string,
+  threadId: string,
+  entry: ThreadIndexEntry,
+): Promise<void> {
+  const index = await readThreadsIndex(bundleDir);
+  index[threadId] = entry;
+  await writeThreadsIndex(bundleDir, index);
+}
+
+/** Remove a thread entry from `threads.json` (no-op when absent). */
+export async function removeThreadEntry(bundleDir: string, threadId: string): Promise<void> {
+  const index = await readThreadsIndex(bundleDir);
+  if (!(threadId in index)) {
+    return;
+  }
+  delete index[threadId];
+  await writeThreadsIndex(bundleDir, index);
+}
+
+function dateKey(epochMs: number): string {
+  const d = new Date(epochMs);
+  const y = d.getUTCFullYear().toString().padStart(4, "0");
+  const m = (d.getUTCMonth() + 1).toString().padStart(2, "0");
+  const day = d.getUTCDate().toString().padStart(2, "0");
+  return `${y}-${m}-${day}`;
+}
+
+/** Append a completion record to `history/{YYYY-MM-DD}.jsonl` keyed off `completedAt`. */
+export async function appendThreadHistoryEntry(
+  bundleDir: string,
+  entry: ThreadHistoryEntry,
+): Promise<void> {
+  const path = join(bundleDir, "history", `${dateKey(entry.completedAt)}.jsonl`);
+  await mkdir(dirname(path), { recursive: true });
+  const line = `${JSON.stringify(entry)}\n`;
+  await appendFile(path, line, "utf8");
+}
+
+/** Removes every `history/*.jsonl` line whose `threadId` matches (rewrite files in place). */
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: per-file JSONL filtering keeps RM deterministic
+export async function removeThreadHistoryEntries(
+  bundleDir: string,
+  threadId: string,
+): Promise<Result<number, string>> {
+  const histRoot = join(bundleDir, "history");
+  let files: string[];
+  try {
+    files = await readdir(histRoot);
+  } catch (e) {
+    const errObj = e as NodeJS.ErrnoException;
+    if (errObj.code === "ENOENT") {
+      return ok(0);
+    }
+    return err(`failed to read history directory: ${String(e)}`);
+  }
+
+  let removed = 0;
+  for (const name of files) {
+    if (!name.endsWith(".jsonl")) {
+      continue;
+    }
+    const path = join(histRoot, name);
+    let text: string;
+    try {
+      text = await readFile(path, "utf8");
+    } catch {
+      continue;
+    }
+    const kept: string[] = [];
+    for (const line of text.split("\n")) {
+      const trimmed = line.trim();
+      if (trimmed === "") {
+        continue;
+      }
+      let rec: unknown;
+      try {
+        rec = JSON.parse(trimmed) as unknown;
+      } catch {
+        kept.push(`${trimmed}\n`);
+        continue;
+      }
+      if (rec === null || typeof rec !== "object") {
+        kept.push(`${trimmed}\n`);
+        continue;
+      }
+      const id = (rec as Record<string, unknown>).threadId;
+      if (id === threadId) {
+        removed++;
+        continue;
+      }
+      kept.push(`${trimmed}\n`);
+    }
+    await writeFile(path, kept.join(""), "utf8");
+  }
+
+  return ok(removed);
+}

packages/workflow-execute/src/engine/types.ts

@@ -1,5 +1,5 @@
-import type { RoleOutput } from "@uncaged/workflow-runtime";
 import type { CasStore } from "@uncaged/workflow-cas";
+import type { RoleOutput } from "@uncaged/workflow-runtime";
 import type { Result } from "@uncaged/workflow-util";
 
 export type SupervisorDecision = "continue" | "stop";
@@ -7,12 +7,29 @@ export type SupervisorDecision = "continue" | "stop";
 export type ExecuteThreadIo = {
   threadId: string;
   hash: string;
-  dataJsonlPath: string;
   infoJsonlPath: string;
   cas: CasStore;
 };
 
-/** One persisted role line in `.data.jsonl` (engine adds these for fork replay before running the generator). */
+/** CAS chain tail state before the next appended {@link StateNode}. */
+export type ChainState = {
+  parentStateHash: string | null;
+  parentAncestors: readonly string[];
+};
+
+export const EMPTY_CHAIN_STATE: ChainState = { parentStateHash: null, parentAncestors: [] };
+
+/**
+ * When forking, the worker continues from an existing {@link StartNode} plus an optional
+ * branch marker {@link StateNode} instead of allocating a new start blob.
+ */
+export type ForkContinuationOptions = {
+  startHash: string;
+  forkHeadHash: string;
+  initialChain: ChainState;
+};
+
+/** One replayed role step (prefill) before the generator runs (same layout as disk replay rows). */
 export type PrefilledDiskStep = {
   role: string;
   contentHash: string;
@@ -31,37 +48,36 @@ export type ExecuteThreadOptions = {
   /** When non-null, written into the start record so tooling can trace lineage. */
   forkSourceThreadId: string | null;
   /**
-   * Written to `.data.jsonl` immediately after the start record, before the generator runs.
+   * When non-null, replays these steps into CAS before the generator runs.
    * Must match `input.steps` length and order when present.
    */
   prefilledDiskSteps: PrefilledDiskStep[] | null;
+  /** When non-null, skip creating a new {@link StartNode} and continue this CAS chain. */
+  forkContinuation: ForkContinuationOptions | null;
+  /**
+   * When non-null, must match `input.steps.length`; supplies persisted timestamps for
+   * {@link ThreadContext.steps} (used when restoring history without prefilled CAS replay).
+   */
+  replayTimestamps: readonly number[] | null;
   /** Workspace root containing `workflow.yaml`; used to resolve the `extract` scene for meta extraction. */
   storageRoot: string;
 };
 
-/** Role steps replayed from `.data.jsonl`, including persisted timestamps. */
-export type ForkHistoricalStep = RoleOutput & { timestamp: number };
-
-export type ParsedThreadStartRecord = {
-  workflowName: string;
-  hash: string;
-  threadId: string;
-  prompt: string;
-  maxRounds: number;
-  depth: number;
-};
-
-export type ForkPlan = {
+export type CasForkPlan = {
   workflowName: string;
   hash: string;
   sourceThreadId: string;
   prompt: string;
   runOptions: { maxRounds: number; depth: number };
-  historicalSteps: ForkHistoricalStep[];
+  steps: RoleOutput[];
+  stepTimestamps: number[];
+  forkContinuation: ForkContinuationOptions;
 };
 
 export type GcResult = {
+  /** Count of root hashes seeded from thread indexes (`head`/`start` per entry). */
   scannedThreads: number;
+  /** Reachable CAS blobs after the mark phase. */
   activeRefs: number;
   deletedEntries: number;
   deletedHashes: string[];

packages/workflow-execute/src/engine/worker.ts

@@ -1,9 +1,12 @@
-import { appendFile, mkdir, unlink, writeFile } from "node:fs/promises";
+import { mkdir, unlink, writeFile } from "node:fs/promises";
 import { createServer, type Socket } from "node:net";
 import { dirname, join } from "node:path";
-import type { RoleOutput, WorkflowFn, WorkflowResult } from "@uncaged/workflow-runtime";
-import { ensureUncagedWorkflowSymlink, importWorkflowBundleModule } from "@uncaged/workflow-register";
 import { createCasStore } from "@uncaged/workflow-cas";
+import {
+  ensureUncagedWorkflowSymlink,
+  importWorkflowBundleModule,
+} from "@uncaged/workflow-register";
+import type { RoleOutput, WorkflowFn } from "@uncaged/workflow-runtime";
 import {
   createLogger,
   err,
@@ -14,7 +17,12 @@ import {
 } from "@uncaged/workflow-util";
 import { executeThread } from "./engine.js";
 import { createThreadPauseGate } from "./thread-pause-gate.js";
-import type { ExecuteThreadIo, PrefilledDiskStep, ThreadPauseGate } from "./types.js";
+import type {
+  ExecuteThreadIo,
+  ForkContinuationOptions,
+  PrefilledDiskStep,
+  ThreadPauseGate,
+} from "./types.js";
 
 const bootLog = createLogger({ sink: { kind: "stderr" } });
 
@@ -25,9 +33,10 @@ type RunCommand = {
   prompt: string;
   options: { maxRounds: number; depth: number };
   steps: RoleOutput[];
-  /** Timestamps aligned with `steps` for `.data.jsonl` replay; length must match `steps` when non-null. */
+  /** Timestamps aligned with `steps` for replay / fork restore; length must match `steps` when steps are non-empty. */
   stepTimestamps: number[] | null;
   forkSourceThreadId: string | null;
+  forkContinuation: ForkContinuationOptions | null;
 };
 
 type KillCommand = {
@@ -70,6 +79,7 @@ function parseRoleOutputRecord(obj: Record<string, unknown>): RoleOutput | null
   };
 }
 
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: mirrors permissive worker IPC decoding shape checks
 function parseRunStepsPayload(rec: Record<string, unknown>): {
   steps: RoleOutput[];
   stepTimestamps: number[] | null;
@@ -104,12 +114,60 @@ function parseRunStepsPayload(rec: Record<string, unknown>): {
       return null;
     }
   }
+
+  const parallelTsRaw = rec.stepTimestamps;
+  if (
+    steps.length > 0 &&
+    Array.isArray(parallelTsRaw) &&
+    parallelTsRaw.length === steps.length &&
+    parallelTsRaw.every((x): x is number => typeof x === "number")
+  ) {
+    return { steps, stepTimestamps: [...parallelTsRaw] };
+  }
+
   return {
     steps,
     stepTimestamps: anyTimestamp ? timestamps : null,
   };
 }
 
+function parseForkContinuation(rec: Record<string, unknown>): ForkContinuationOptions | null {
+  const raw = rec.forkContinuation;
+  if (raw === undefined || raw === null) {
+    return null;
+  }
+  if (typeof raw !== "object") {
+    return null;
+  }
+  const o = raw as Record<string, unknown>;
+  const startHash = o.startHash;
+  const forkHeadHash = o.forkHeadHash;
+  const ic = o.initialChain;
+  if (typeof startHash !== "string" || typeof forkHeadHash !== "string") {
+    return null;
+  }
+  if (ic === null || typeof ic !== "object") {
+    return null;
+  }
+  const ich = ic as Record<string, unknown>;
+  const pph = ich.parentStateHash;
+  const pa = ich.parentAncestors;
+  if (!(pph === null || typeof pph === "string")) {
+    return null;
+  }
+  if (!Array.isArray(pa) || !pa.every((x) => typeof x === "string")) {
+    return null;
+  }
+  return {
+    startHash,
+    forkHeadHash,
+    initialChain: {
+      parentStateHash: pph,
+      parentAncestors: pa,
+    },
+  };
+}
+
 function parseRunControlPayload(rec: Record<string, unknown>): RunCommand | null {
   const threadId = rec.threadId;
   const workflowName = rec.workflowName;
@@ -145,6 +203,7 @@ function parseRunControlPayload(rec: Record<string, unknown>): RunCommand | null
     }
     forkSourceThreadId = rawFork;
   }
+  const forkContinuation = parseForkContinuation(rec);
   return {
     type: "run",
     threadId,
@@ -154,6 +213,7 @@ function parseRunControlPayload(rec: Record<string, unknown>): RunCommand | null
     steps: parsedSteps.steps,
     stepTimestamps: parsedSteps.stepTimestamps,
     forkSourceThreadId,
+    forkContinuation,
   };
 }
 
@@ -354,6 +414,7 @@ async function main(): Promise<void> {
     }
   }
 
+  // biome-ignore lint/complexity/noExcessiveCognitiveComplexity: TCP worker multiplexes lifecycle + runs
   async function dispatchCommand(cmd: ControlCommand, socket: Socket | null): Promise<void> {
     if (cmd.type !== "run") {
       dispatchThreadLifecycleCommand(threads, socket, cmd);
@@ -364,13 +425,11 @@ async function main(): Promise<void> {
 
     const threadId = cmd.threadId;
     const runningPath = join(storageRoot, "logs", hash, `${threadId}.running`);
-    const dataJsonlPath = join(storageRoot, "logs", hash, `${threadId}.data.jsonl`);
     const infoJsonlPath = join(storageRoot, "logs", hash, `${threadId}.info.jsonl`);
 
     const io: ExecuteThreadIo = {
       threadId,
       hash,
-      dataJsonlPath,
       infoJsonlPath,
       cas,
     };
@@ -387,14 +446,25 @@ async function main(): Promise<void> {
 
     try {
       await mkdir(dirname(runningPath), { recursive: true });
-      await mkdir(dirname(dataJsonlPath), { recursive: true });
       await writeFile(runningPath, "", "utf8");
 
       const logger = createLogger({ sink: { kind: "file", path: infoJsonlPath } });
 
       const baseTs = Date.now();
       let prefilledDiskSteps: PrefilledDiskStep[] | null = null;
-      if (cmd.steps.length > 0) {
+      let replayTimestamps: readonly number[] | null = null;
+
+      if (cmd.forkContinuation !== null) {
+        if (
+          cmd.steps.length > 0 &&
+          (cmd.stepTimestamps === null || cmd.stepTimestamps.length !== cmd.steps.length)
+        ) {
+          bootLog("J5WQ8NXT", "forkContinuation requires stepTimestamps aligned with steps");
+          throw new Error("forkContinuation requires stepTimestamps aligned with steps");
+        }
+        replayTimestamps =
+          cmd.steps.length === 0 ? null : (cmd.stepTimestamps as readonly number[]);
+      } else if (cmd.steps.length > 0) {
         prefilledDiskSteps = cmd.steps.map((step, i) => {
           const ts = cmd.stepTimestamps?.[i];
           return {
@@ -407,7 +477,7 @@ async function main(): Promise<void> {
         });
       }
 
-      const runResult = await executeThread(
+      await executeThread(
         workflowFn,
         cmd.workflowName,
         { prompt: cmd.prompt, steps: cmd.steps },
@@ -417,17 +487,16 @@ async function main(): Promise<void> {
           awaitAfterEachYield: () => pauseGate.awaitAfterYield(),
           forkSourceThreadId: cmd.forkSourceThreadId,
           prefilledDiskSteps,
+          forkContinuation: cmd.forkContinuation,
+          replayTimestamps,
           storageRoot,
         },
         io,
         logger,
       );
-      await appendFile(dataJsonlPath, `${JSON.stringify(runResult)}\n`, "utf8");
     } catch (e) {
       const message = e instanceof Error ? e.message : String(e);
       bootLog("Q3MN8YKW", `thread ${threadId} failed: ${message}`);
-      const failure: WorkflowResult = { returnCode: 1, summary: message, rootHash: "" };
-      await appendFile(dataJsonlPath, `${JSON.stringify(failure)}\n`, "utf8").catch(() => {});
     } finally {
       threads.delete(threadId);
       await unlink(runningPath).catch(() => {});

packages/workflow-execute/src/extract/extract-fn.ts

@@ -1,7 +1,12 @@
-import type { ExtractContext, ExtractFn, LlmProvider } from "@uncaged/workflow-runtime";
-import type * as z from "zod/v4";
 import { type CasStore, getContentMerklePayload } from "@uncaged/workflow-cas";
 import { createLlmFn, createThreadReactor } from "@uncaged/workflow-reactor";
+import type {
+  ExtractContext,
+  ExtractFn,
+  ExtractResult,
+  LlmProvider,
+} from "@uncaged/workflow-runtime";
+import type * as z from "zod/v4";
 import { extractFunctionToolFromZodSchema } from "./llm-extract.js";
 
 export type ExtractDeps = {
@@ -121,7 +126,7 @@ export function createExtract(provider: LlmProvider, deps: ExtractDeps): Extract
     schema: z.ZodType<T>,
     prompt: string,
     ctx: ExtractContext,
-  ): Promise<T> => {
+  ): Promise<ExtractResult<T>> => {
     const text = await buildExtractUserContent(ctx, prompt, deps);
     const result = await reactor({
       thread: { cas: deps.cas },
@@ -131,6 +136,10 @@ export function createExtract(provider: LlmProvider, deps: ExtractDeps): Extract
     if (!result.ok) {
       throw new Error(`extract failed: ${result.error}`);
     }
-    return result.value;
+    return {
+      meta: result.value,
+      contentPayload: ctx.agentContent,
+      refs: [],
+    };
   };
 }

packages/workflow-execute/src/extract/llm-extract.ts

@@ -1,6 +1,5 @@
-import * as z from "zod/v4";
-
 import { err, ok, type Result } from "@uncaged/workflow-util";
+import * as z from "zod/v4";
 
 import type { LlmError, LlmExtractArgs } from "./types.js";
 

packages/workflow-execute/src/index.ts

@@ -1,35 +1,47 @@
 export { createWorkflow } from "./engine/create-workflow.js";
 export { executeThread } from "./engine/engine.js";
 export {
-  buildForkPlan,
-  parseThreadDataJsonl,
-  selectForkHistoricalSteps,
-  tryParseRoleStepRecord,
+  FORK_BRANCH_ROLE,
+  prepareCasFork,
   tryParseWorkflowResultRecord,
+  walkStateFramesNewestFirst,
 } from "./engine/fork-thread.js";
 export { garbageCollectCas } from "./engine/gc.js";
 export { createThreadPauseGate } from "./engine/thread-pause-gate.js";
 export type {
+  ThreadHistoryEntry,
+  ThreadIndex,
+  ThreadIndexEntry,
+} from "./engine/threads-index.js";
+export {
+  appendThreadHistoryEntry,
+  getBundleDir,
+  readThreadsIndex,
+  removeThreadEntry,
+  removeThreadHistoryEntries,
+  upsertThreadEntry,
+  writeThreadsIndex,
+} from "./engine/threads-index.js";
+export type {
+  CasForkPlan,
+  ChainState,
   ExecuteThreadIo,
   ExecuteThreadOptions,
-  ForkHistoricalStep,
-  ForkPlan,
+  ForkContinuationOptions,
   GcResult,
-  ParsedThreadStartRecord,
   PrefilledDiskStep,
   SupervisorDecision,
   ThreadPauseGate,
 } from "./engine/types.js";
+export { EMPTY_CHAIN_STATE } from "./engine/types.js";
 export { getWorkerHostScriptPath } from "./engine/worker-entry-path.js";
+export type { ExtractFn, LlmError, LlmExtractArgs } from "./extract/index.js";
 export {
   buildExtractUserContent,
   createExtract,
   type ExtractThreadContext,
-} from "./extract/index.js";
-export {
   extractFunctionToolFromZodSchema,
   llmErrorToCause,
   llmExtract,
 } from "./extract/index.js";
-export type { ExtractFn, LlmError, LlmExtractArgs } from "./extract/index.js";
-export { workflowAsAgent, type WorkflowAsAgentOptions } from "./workflow-as-agent.js";
+export { type WorkflowAsAgentOptions, workflowAsAgent } from "./workflow-as-agent.js";

packages/workflow-execute/src/workflow-as-agent.ts

@@ -1,17 +1,20 @@
 import { join } from "node:path";
-import type { AgentContext, AgentFn } from "@uncaged/workflow-runtime";
-import { extractBundleExports } from "@uncaged/workflow-register";
 import { createCasStore } from "@uncaged/workflow-cas";
-import type { ExecuteThreadIo } from "./engine/index.js";
-import { executeThread } from "./engine/index.js";
 import type { WorkflowConfig } from "@uncaged/workflow-register";
-import { getRegisteredWorkflow, readWorkflowRegistry } from "@uncaged/workflow-register";
+import {
+  extractBundleExports,
+  getRegisteredWorkflow,
+  readWorkflowRegistry,
+} from "@uncaged/workflow-register";
+import type { AgentContext, AgentFn } from "@uncaged/workflow-runtime";
 import {
   createLogger,
   generateUlid,
   getDefaultWorkflowStorageRoot,
   getGlobalCasDir,
 } from "@uncaged/workflow-util";
+import type { ExecuteThreadIo } from "./engine/index.js";
+import { executeThread } from "./engine/index.js";
 
 const DEFAULT_WORKFLOW_AS_AGENT_MAX_DEPTH = 3;
 
@@ -74,13 +77,11 @@ export function workflowAsAgent(
     };
 
     const childThreadId = generateUlid(Date.now());
-    const dataJsonlPath = join(storageRoot, "logs", entry.hash, `${childThreadId}.data.jsonl`);
     const infoJsonlPath = join(storageRoot, "logs", entry.hash, `${childThreadId}.info.jsonl`);
 
     const io: ExecuteThreadIo = {
       threadId: childThreadId,
       hash: entry.hash,
-      dataJsonlPath,
       infoJsonlPath,
       cas: createCasStore(getGlobalCasDir(storageRoot)),
     };
@@ -100,6 +101,8 @@ export function workflowAsAgent(
           awaitAfterEachYield: async () => {},
           forkSourceThreadId: ctx.threadId,
           prefilledDiskSteps: null,
+          forkContinuation: null,
+          replayTimestamps: null,
           storageRoot,
         },
         io,

packages/workflow-protocol/README.md

@@ -0,0 +1,29 @@
+# @uncaged/workflow-protocol
+
+Shared workflow types, sentinel constants, and `Result` helpers.
+
+## What This Package Does
+
+It defines the cross-package contract for bundles and the engine: thread/step shapes, `WorkflowFn`, agent/extract contexts, descriptor types, and `CasStore` as an interface. Implementations (CAS store, CLI, extract) depend on these types so bundles stay decoupled from Node APIs.
+
+## Key Exports
+
+From `src/index.ts`:
+
+- **Types:** `Result`, `CasStore`, `WorkflowRoleSchema`, `WorkflowRoleDescriptor`, `WorkflowDescriptor`, `RoleMeta`, `RoleOutput`, `StartStep`, `RoleStep`, `ThreadContext`, `ModeratorContext`, `AgentContext`, `ExtractContext`, `WorkflowCompletion`, `WorkflowResult`, `LlmProvider`, `ProviderConfig`, `ResolvedModel`, `WorkflowConfig`, `ExtractFn`, `AgentFn`, `AgentBinding`, `WorkflowRuntime`, `WorkflowFn`, `RoleDefinition`, `Moderator`, `WorkflowDefinition`, `AdvanceOutcome`
+- **Constants:** `START`, `END`
+- **Functions:** `ok`, `err`
+
+## Dependencies
+
+- **Peer:** `zod` ^4 — used in type positions for schemas (`ExtractFn`, `RoleDefinition`, etc.)
+
+No workspace packages; this is the bottom layer.
+
+## Usage
+
+```typescript
+import { END, START, type WorkflowFn, type ThreadContext } from "@uncaged/workflow-protocol";
+```
+
+Concrete `WorkflowFn` implementations are built with `@uncaged/workflow-runtime` (`createWorkflow`).

packages/workflow-protocol/src/cas-types.ts

@@ -0,0 +1,36 @@
+// ── CAS thread chain nodes (RFC: CAS-based thread storage) ──────────
+
+export type StartNodePayload = {
+  name: string;
+  hash: string;
+  maxRounds: number;
+  depth: number;
+};
+
+export type StartNode = {
+  type: "start";
+  payload: StartNodePayload;
+  refs: string[];
+};
+
+export type StateNodePayload = {
+  role: string;
+  meta: Record<string, unknown>;
+  start: string;
+  content: string;
+  ancestors: string[];
+  compact: string | null;
+  timestamp: number;
+};
+
+export type StateNode = {
+  type: "state";
+  payload: StateNodePayload;
+  refs: string[];
+};
+
+export type ContentMerkleNode = {
+  type: "content";
+  payload: string;
+  refs: string[];
+};

packages/workflow-protocol/src/index.ts

@@ -1,40 +1,49 @@
 // ── Types ──────────────────────────────────────────────────────────
 
 export type {
-	Result,
-	CasStore,
-	WorkflowRoleSchema,
-	WorkflowRoleDescriptor,
-	WorkflowDescriptor,
-	RoleMeta,
-	RoleOutput,
-	StartStep,
-	RoleStep,
-	ThreadContext,
-	ModeratorContext,
-	AgentContext,
-	ExtractContext,
-	WorkflowCompletion,
-	WorkflowResult,
-	LlmProvider,
-	ProviderConfig,
-	ResolvedModel,
-	WorkflowConfig,
-	ExtractFn,
-	AgentFn,
-	AgentBinding,
-	WorkflowRuntime,
-	WorkflowFn,
-	RoleDefinition,
-	Moderator,
-	WorkflowDefinition,
-	AdvanceOutcome,
+  ContentMerkleNode,
+  StartNode,
+  StartNodePayload,
+  StateNode,
+  StateNodePayload,
+} from "./cas-types.js";
+
+export type {
+  AdvanceOutcome,
+  AgentBinding,
+  AgentContext,
+  AgentFn,
+  CasStore,
+  ExtractContext,
+  ExtractFn,
+  ExtractResult,
+  LlmProvider,
+  Moderator,
+  ModeratorContext,
+  ProviderConfig,
+  ResolvedModel,
+  Result,
+  RoleDefinition,
+  RoleMeta,
+  RoleOutput,
+  RoleStep,
+  StartStep,
+  ThreadContext,
+  WorkflowCompletion,
+  WorkflowConfig,
+  WorkflowDefinition,
+  WorkflowDescriptor,
+  WorkflowFn,
+  WorkflowResult,
+  WorkflowRoleDescriptor,
+  WorkflowRoleSchema,
+  WorkflowRuntime,
 } from "./types.js";
 
 // ── Constants ──────────────────────────────────────────────────────
 
-export { START, END } from "./types.js";
+export { END, START } from "./types.js";
 
 // ── Constructor functions ──────────────────────────────────────────
 
-export { ok, err } from "./result.js";
+export { err, ok } from "./result.js";

packages/workflow-protocol/src/result.ts

@@ -1,9 +1,9 @@
 import type { Result } from "./types.js";
 
 export function ok<T>(value: T): Result<T, never> {
-	return { ok: true, value };
+  return { ok: true, value };
 }
 
 export function err<E>(error: E): Result<never, E> {
-	return { ok: false, error };
+  return { ok: false, error };
 }

packages/workflow-protocol/src/types.ts

@@ -12,10 +12,10 @@ export type Result<T, E = Error> = { ok: true; value: T } | { ok: false; error:
 // ── CAS ────────────────────────────────────────────────────────────
 
 export type CasStore = {
-	put(content: string): Promise<string>;
-	get(hash: string): Promise<string | null>;
-	delete(hash: string): Promise<void>;
-	list(): Promise<string[]>;
+  put(content: string): Promise<string>;
+  get(hash: string): Promise<string | null>;
+  delete(hash: string): Promise<void>;
+  list(): Promise<string[]>;
 };
 
 // ── Workflow Descriptor ────────────────────────────────────────────
@@ -23,13 +23,13 @@ export type CasStore = {
 export type WorkflowRoleSchema = Record<string, unknown>;
 
 export type WorkflowRoleDescriptor = {
-	description: string;
-	schema: WorkflowRoleSchema;
+  description: string;
+  schema: WorkflowRoleSchema;
 };
 
 export type WorkflowDescriptor = {
-	description: string;
-	roles: Record<string, WorkflowRoleDescriptor>;
+  description: string;
+  roles: Record<string, WorkflowRoleDescriptor>;
 };
 
 // ── Role & Thread ──────────────────────────────────────────────────
@@ -37,131 +37,138 @@ export type WorkflowDescriptor = {
 export type RoleMeta = Record<string, Record<string, unknown>>;
 
 export type RoleOutput = {
-	role: string;
-	contentHash: string;
-	meta: Record<string, unknown>;
-	refs: string[];
+  role: string;
+  contentHash: string;
+  meta: Record<string, unknown>;
+  refs: string[];
 };
 
 export type StartStep = {
-	role: typeof START;
-	content: string;
-	meta: { maxRounds: number };
-	timestamp: number;
+  role: typeof START;
+  content: string;
+  meta: { maxRounds: number };
+  timestamp: number;
 };
 
 export type RoleStep<M extends RoleMeta> = {
-	[K in keyof M & string]: {
-		role: K;
-		meta: M[K];
-		contentHash: string;
-		refs: string[];
-		timestamp: number;
-	};
+  [K in keyof M & string]: {
+    role: K;
+    meta: M[K];
+    contentHash: string;
+    refs: string[];
+    timestamp: number;
+  };
 }[keyof M & string];
 
 export type ThreadContext<M extends RoleMeta = RoleMeta> = {
-	threadId: string;
-	depth: number;
-	start: StartStep;
-	steps: RoleStep<M>[];
+  threadId: string;
+  depth: number;
+  start: StartStep;
+  steps: RoleStep<M>[];
 };
 
 export type ModeratorContext<M extends RoleMeta = RoleMeta> = ThreadContext<M>;
 
 export type AgentContext<M extends RoleMeta = RoleMeta> = ModeratorContext<M> & {
-	currentRole: {
-		name: string;
-		systemPrompt: string;
-	};
+  currentRole: {
+    name: string;
+    systemPrompt: string;
+  };
 };
 
 export type ExtractContext<M extends RoleMeta = RoleMeta> = AgentContext<M> & {
-	agentContent: string;
+  agentContent: string;
 };
 
 // ── Workflow Completion ────────────────────────────────────────────
 
 export type WorkflowCompletion = {
-	returnCode: number;
-	summary: string;
+  returnCode: number;
+  summary: string;
 };
 
 export type WorkflowResult = WorkflowCompletion & {
-	rootHash: string;
+  rootHash: string;
 };
 
 // ── LLM Provider ───────────────────────────────────────────────────
 
 export type LlmProvider = {
-	baseUrl: string;
-	apiKey: string;
-	model: string;
+  baseUrl: string;
+  apiKey: string;
+  model: string;
 };
 
 export type ProviderConfig = {
-	baseUrl: string;
-	apiKey: string;
+  baseUrl: string;
+  apiKey: string;
 };
 
 export type ResolvedModel = {
-	baseUrl: string;
-	apiKey: string;
-	model: string;
+  baseUrl: string;
+  apiKey: string;
+  model: string;
 };
 
 export type WorkflowConfig = {
-	maxDepth: number;
-	supervisorInterval: number;
-	providers: Record<string, ProviderConfig>;
-	models: Record<string, string>;
+  maxDepth: number;
+  supervisorInterval: number;
+  providers: Record<string, ProviderConfig>;
+  models: Record<string, string>;
 };
 
 // ── Functions ──────────────────────────────────────────────────────
 
+/** Structured output of the extract phase (RFC v3 content Merkle + artifact refs). */
+export type ExtractResult<T extends Record<string, unknown>> = {
+  meta: T;
+  contentPayload: string;
+  refs: string[];
+};
+
 export type ExtractFn = <T extends Record<string, unknown>>(
-	schema: z.ZodType<T>,
-	prompt: string,
-	ctx: ExtractContext,
-) => Promise<T>;
+  schema: z.ZodType<T>,
+  prompt: string,
+  ctx: ExtractContext,
+) => Promise<ExtractResult<T>>;
 
 export type AgentFn = (ctx: AgentContext) => Promise<string>;
 
 export type AgentBinding = {
-	agent: AgentFn;
-	overrides: Partial<Record<string, AgentFn>> | null;
+  agent: AgentFn;
+  overrides: Partial<Record<string, AgentFn>> | null;
 };
 
 // ── Workflow Runtime & Definition ──────────────────────────────────
 
 export type WorkflowRuntime = {
-	cas: CasStore;
-	extract: ExtractFn;
+  cas: CasStore;
+  extract: ExtractFn;
 };
 
 export type WorkflowFn = (
-	thread: ThreadContext,
-	runtime: WorkflowRuntime,
+  thread: ThreadContext,
+  runtime: WorkflowRuntime,
 ) => AsyncGenerator<RoleOutput, WorkflowCompletion>;
 
 export type RoleDefinition<Meta extends Record<string, unknown>> = {
-	description: string;
-	systemPrompt: string;
-	extractPrompt: string;
-	schema: z.ZodType<Meta>;
-	extractRefs: ((meta: Meta) => string[]) | null;
+  description: string;
+  systemPrompt: string;
+  extractPrompt: string;
+  schema: z.ZodType<Meta>;
+  extractRefs: ((meta: Meta) => string[]) | null;
 };
 
 export type Moderator<M extends RoleMeta> = (
-	ctx: ModeratorContext<M>,
+  ctx: ModeratorContext<M>,
 ) => (keyof M & string) | typeof END;
 
 export type WorkflowDefinition<M extends RoleMeta> = {
-	description: string;
-	roles: { [K in keyof M & string]: RoleDefinition<M[K]> };
-	moderator: Moderator<M>;
+  description: string;
+  roles: { [K in keyof M & string]: RoleDefinition<M[K]> };
+  moderator: Moderator<M>;
 };
 
 export type AdvanceOutcome<M extends RoleMeta> =
-	| { kind: "complete"; completion: WorkflowCompletion }
-	| { kind: "yield"; output: RoleOutput; step: RoleStep<M> };
+  | { kind: "complete"; completion: WorkflowCompletion }
+  | { kind: "yield"; output: RoleOutput; step: RoleStep<M> };

packages/workflow-reactor/README.md

@@ -0,0 +1,26 @@
+# @uncaged/workflow-reactor
+
+LLM calling abstraction and thread “reactor” for structured tool invocation.
+
+## What This Package Does
+
+It exposes `createLlmFn` (chat completion wrapper) and `createThreadReactor` (multi-turn tool loop configuration) plus supporting message/tool types. `@uncaged/workflow-execute` consumes this for extractor and supervisor paths that talk to OpenAI-style APIs with tools.
+
+## Key Exports
+
+From `src/index.ts`:
+
+- **Functions:** `createLlmFn`, `createThreadReactor`
+- **Types:** `ChatMessage`, `LlmFn`, `StructuredToolSpec`, `ThreadReactorConfig`, `ThreadReactorFn`, `ThreadReactorInvokeArgs`, `ToolCall`, `ToolDefinition`
+
+## Dependencies
+
+- **Workspace:** `@uncaged/workflow-protocol`
+- **Peer:** `zod` ^4
+
+## Usage
+
+```typescript
+import { createLlmFn, createThreadReactor } from "@uncaged/workflow-reactor";
+// Usually composed inside @uncaged/workflow-execute rather than directly by applications.
+```

packages/workflow-reactor/src/thread-reactor.ts

@@ -1,6 +1,5 @@
-import type * as z from "zod/v4";
-
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
+import type * as z from "zod/v4";
 
 import type {
   ChatMessage,

packages/workflow-reactor/src/types.ts

@@ -1,6 +1,5 @@
-import type * as z from "zod/v4";
-
 import type { Result } from "@uncaged/workflow-protocol";
+import type * as z from "zod/v4";
 
 export type ToolCall = {
   id: string;

packages/workflow-reactor/tsconfig.json

@@ -5,7 +5,5 @@
     "outDir": "dist"
   },
   "include": ["src"],
-  "references": [
-    { "path": "../workflow-protocol" }
-  ]
+  "references": [{ "path": "../workflow-protocol" }]
 }

packages/workflow-register/README.md

@@ -0,0 +1,38 @@
+# @uncaged/workflow-register
+
+Bundle validation, dynamic export extraction, registry YAML, and model/provider resolution.
+
+## What This Package Does
+
+It validates workflow `.esm.js` bundles, extracts `descriptor` / `run` exports at runtime, reads and writes `workflow.yaml`, and resolves which LLM endpoint/model to use from registry config (`resolveModel`, `splitProviderModelRef`).
+
+## Key Exports
+
+From `src/index.ts`:
+
+- **Bundle:** `buildDescriptor`, `importWorkflowBundleModule`, `validateWorkflowBundle`, `ensureUncagedWorkflowSymlink`, `extractBundleExports`, `stringifyWorkflowDescriptor`, `validateWorkflowDescriptor`
+- **Bundle types:** `ExtractBundleExportsOptions`, `ExtractedBundleExports`, `WorkflowBundleValidationInput`, `WorkflowDescriptor`, `WorkflowRoleDescriptor`, `WorkflowRoleSchema`
+- **Registry:** `getRegisteredWorkflow`, `listRegisteredWorkflowNames`, `parseWorkflowRegistryYaml`, `readWorkflowRegistry`, `registerWorkflowVersion`, `rollbackWorkflowToHistoryHash`, `stringifyWorkflowRegistryYaml`, `unregisterWorkflow`, `workflowRegistryPath`, `writeWorkflowRegistry`
+- **Registry types:** `WorkflowConfig`, `WorkflowHistoryEntry`, `WorkflowRegistryEntry`, `WorkflowRegistryFile`
+- **Config:** `resolveModel`, `splitProviderModelRef`, types `ProviderConfig`, `ResolvedModel`
+
+## Dependencies
+
+- **Workspace:** `@uncaged/workflow-protocol`, `@uncaged/workflow-util`
+- **Peer:** `acorn`, `yaml`, `zod` ^4 — parsing/validation at runtime for consumers
+
+## Usage
+
+```typescript
+import { readFile } from "node:fs/promises";
+import { readWorkflowRegistry, validateWorkflowBundle } from "@uncaged/workflow-register";
+import { getDefaultWorkflowStorageRoot } from "@uncaged/workflow-util";
+
+const reg = await readWorkflowRegistry(getDefaultWorkflowStorageRoot());
+if (!reg.ok) throw new Error(reg.error.message);
+
+const path = "./my.esm.js";
+const source = await readFile(path, "utf8");
+const v = validateWorkflowBundle({ filePath: path, source });
+if (!v.ok) throw new Error(v.error);
+```

packages/workflow-register/src/bundle/bundle-validator.ts

@@ -1,4 +1,5 @@
 import { isBuiltin } from "node:module";
+import { err, ok, type Result } from "@uncaged/workflow-util";
 import type {
   CallExpression,
   ExportAllDeclaration,
@@ -12,8 +13,6 @@ import type {
 } from "acorn";
 import * as acorn from "acorn";
 
-import { err, ok, type Result } from "@uncaged/workflow-util";
-
 import type { WorkflowBundleValidationInput } from "./types.js";
 
 /** Acorn Node with index-access for property traversal. */

packages/workflow-register/src/bundle/types.ts

@@ -2,9 +2,9 @@ import type { WorkflowDescriptor, WorkflowFn } from "@uncaged/workflow-protocol"
 
 export type {
   WorkflowDescriptor,
+  WorkflowFn,
   WorkflowRoleDescriptor,
   WorkflowRoleSchema,
-  WorkflowFn,
 } from "@uncaged/workflow-protocol";
 
 export type WorkflowBundleValidationInput = {

packages/workflow-register/src/index.ts

@@ -1,12 +1,3 @@
-export {
-  buildDescriptor,
-  importWorkflowBundleModule,
-  validateWorkflowBundle,
-  ensureUncagedWorkflowSymlink,
-  extractBundleExports,
-  stringifyWorkflowDescriptor,
-  validateWorkflowDescriptor,
-} from "./bundle/index.js";
 export type {
   ExtractBundleExportsOptions,
   ExtractedBundleExports,
@@ -15,7 +6,23 @@ export type {
   WorkflowRoleDescriptor,
   WorkflowRoleSchema,
 } from "./bundle/index.js";
-
+export {
+  buildDescriptor,
+  ensureUncagedWorkflowSymlink,
+  extractBundleExports,
+  importWorkflowBundleModule,
+  stringifyWorkflowDescriptor,
+  validateWorkflowBundle,
+  validateWorkflowDescriptor,
+} from "./bundle/index.js";
+export type { ProviderConfig, ResolvedModel } from "./config/index.js";
+export { resolveModel, splitProviderModelRef } from "./config/index.js";
+export type {
+  WorkflowConfig,
+  WorkflowHistoryEntry,
+  WorkflowRegistryEntry,
+  WorkflowRegistryFile,
+} from "./registry/index.js";
 export {
   getRegisteredWorkflow,
   listRegisteredWorkflowNames,
@@ -28,12 +35,3 @@ export {
   workflowRegistryPath,
   writeWorkflowRegistry,
 } from "./registry/index.js";
-export type {
-  WorkflowConfig,
-  WorkflowHistoryEntry,
-  WorkflowRegistryEntry,
-  WorkflowRegistryFile,
-} from "./registry/index.js";
-
-export { resolveModel, splitProviderModelRef } from "./config/index.js";
-export type { ProviderConfig, ResolvedModel } from "./config/index.js";

packages/workflow-register/src/registry/registry-normalize.ts

@@ -1,6 +1,6 @@
 import type { ProviderConfig } from "@uncaged/workflow-protocol";
-import { splitProviderModelRef } from "../config/index.js";
 import { createLogger, err, ok, type Result } from "@uncaged/workflow-util";
+import { splitProviderModelRef } from "../config/index.js";
 import type {
   WorkflowConfig,
   WorkflowHistoryEntry,

packages/workflow-register/src/registry/registry.ts

@@ -1,8 +1,7 @@
 import { mkdir, readFile, writeFile } from "node:fs/promises";
 import { dirname, join } from "node:path";
-
-import { parseDocument, stringify } from "yaml";
 import { err, ok, type Result } from "@uncaged/workflow-util";
+import { parseDocument, stringify } from "yaml";
 import { normalizeWorkflowRegistryRoot } from "./registry-normalize.js";
 import type { WorkflowHistoryEntry, WorkflowRegistryEntry, WorkflowRegistryFile } from "./types.js";
 

packages/workflow-register/tsconfig.json

@@ -1,8 +1,5 @@
 {
-  "references": [
-    { "path": "../workflow-protocol" },
-    { "path": "../workflow-util" }
-  ],
+  "references": [{ "path": "../workflow-protocol" }, { "path": "../workflow-util" }],
   "compilerOptions": {
     "target": "ES2022",
     "lib": ["ES2022"],

packages/workflow-runtime/README.md

@@ -0,0 +1,28 @@
+# @uncaged/workflow-runtime
+
+Workflow author API: `createWorkflow` plus re-exports of protocol workflow types.
+
+## What This Package Does
+
+Bundle code imports `createWorkflow` to turn a `WorkflowDefinition` plus `AgentBinding` into a `WorkflowFn` generator. It re-exports the protocol types and constants most authors need so workflows rarely import `@uncaged/workflow-protocol` directly.
+
+## Key Exports
+
+From `src/index.ts`:
+
+- **Functions:** `createWorkflow`, `ok`, `err`
+- **Types:** `AgentBinding`, `AgentContext`, `AgentFn`, `CasStore`, `ExtractContext`, `ExtractFn`, `LlmProvider`, `Moderator`, `ModeratorContext`, `Result`, `RoleDefinition`, `RoleMeta`, `RoleOutput`, `RoleStep`, `StartStep`, `ThreadContext`, `WorkflowCompletion`, `WorkflowDefinition`, `WorkflowDescriptor`, `WorkflowFn`, `WorkflowResult`, `WorkflowRoleDescriptor`, `WorkflowRoleSchema`, `WorkflowRuntime`
+- **Constants:** `END`, `START`
+
+## Dependencies
+
+- **Workspace:** `@uncaged/workflow-protocol` — contract types and helpers
+- **Peer:** `zod` ^4 — matches schema usage on role definitions
+
+## Usage
+
+```typescript
+import { createWorkflow, type WorkflowDefinition, type AgentBinding } from "@uncaged/workflow-runtime";
+
+export const run = createWorkflow(myDefinition, myBinding);
+```

packages/workflow-runtime/__tests__/build-context.test.ts

@@ -0,0 +1,121 @@
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import { mkdtemp, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import {
+  createCasStore,
+  putContentNodeWithRefs,
+  putStartNode,
+  putStateNode,
+} from "@uncaged/workflow-cas";
+import { buildThreadContext, END, START } from "../src/index.js";
+
+describe("buildThreadContext", () => {
+  let dir: string;
+
+  beforeEach(async () => {
+    dir = await mkdtemp(join(tmpdir(), "wf-build-ctx-"));
+  });
+
+  afterEach(async () => {
+    await rm(dir, { recursive: true, force: true });
+  });
+
+  test("walks ancestor chain, resolves prompt, orders steps chronologically", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const promptHash = await cas.put("hello-task");
+    const bundleHash = "BHAAAAAAAAAAA";
+    const startHash = await putStartNode(
+      cas,
+      { name: "demo", hash: bundleHash, maxRounds: 99, depth: 2 },
+      promptHash,
+    );
+
+    const art = await cas.put("artifact-a");
+    const chPlan = await putContentNodeWithRefs(cas, "plan body", [art]);
+    const statePlan = await putStateNode(cas, {
+      role: "planner",
+      meta: { phase: 1 },
+      start: startHash,
+      content: chPlan,
+      ancestors: [],
+      compact: null,
+      timestamp: 1000,
+    });
+
+    const chCode = await putContentNodeWithRefs(cas, "code body", []);
+    const stateCode = await putStateNode(cas, {
+      role: "coder",
+      meta: { phase: 2 },
+      start: startHash,
+      content: chCode,
+      ancestors: [statePlan],
+      compact: null,
+      timestamp: 2000,
+    });
+
+    const ctx = await buildThreadContext(stateCode, cas);
+    expect(ctx.threadId).toBe("");
+    expect(ctx.depth).toBe(2);
+    expect(ctx.start.role).toBe(START);
+    expect(ctx.start.content).toBe("hello-task");
+    expect(ctx.start.meta.maxRounds).toBe(99);
+    expect(ctx.steps.map((s) => s.role)).toEqual(["planner", "coder"]);
+    expect(ctx.steps[0]?.refs).toEqual([art]);
+    expect(ctx.steps[1]?.refs).toEqual([]);
+    expect(ctx.steps[0]?.timestamp).toBe(1000);
+    expect(ctx.steps[1]?.timestamp).toBe(2000);
+  });
+
+  test("StartNode head yields empty steps", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const promptHash = await cas.put("only-prompt");
+    const startHash = await putStartNode(
+      cas,
+      { name: "solo", hash: "BHBBBBBBBBBBB", maxRounds: 3, depth: 1 },
+      promptHash,
+    );
+
+    const ctx = await buildThreadContext(startHash, cas);
+    expect(ctx.steps).toEqual([]);
+    expect(ctx.start.content).toBe("only-prompt");
+    expect(ctx.depth).toBe(1);
+    expect(ctx.start.meta.maxRounds).toBe(3);
+  });
+
+  test("omits __end__ states from steps", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const promptHash = await cas.put("task");
+    const bundleHash = "BHCCCCCCCCCCC";
+    const startHash = await putStartNode(
+      cas,
+      { name: "demo", hash: bundleHash, maxRounds: 10, depth: 0 },
+      promptHash,
+    );
+
+    const ch1 = await putContentNodeWithRefs(cas, "step-one", []);
+    const state1 = await putStateNode(cas, {
+      role: "worker",
+      meta: { done: false },
+      start: startHash,
+      content: ch1,
+      ancestors: [],
+      compact: null,
+      timestamp: 500,
+    });
+
+    const endContent = await putContentNodeWithRefs(cas, "finished", []);
+    const endState = await putStateNode(cas, {
+      role: END,
+      meta: { returnCode: 0, summary: "finished" },
+      start: startHash,
+      content: endContent,
+      ancestors: [state1],
+      compact: null,
+      timestamp: 600,
+    });
+
+    const ctx = await buildThreadContext(endState, cas);
+    expect(ctx.steps.map((s) => s.role)).toEqual(["worker"]);
+  });
+});

packages/workflow-runtime/package.json

@@ -8,6 +8,7 @@
     "test": "bun test"
   },
   "dependencies": {
+    "@uncaged/workflow-cas": "workspace:*",
     "@uncaged/workflow-protocol": "workspace:*"
   },
   "peerDependencies": {

packages/workflow-runtime/src/build-context.ts

@@ -0,0 +1,153 @@
+import { getContentMerklePayload, parseCasThreadNode } from "@uncaged/workflow-cas";
+import type {
+  CasStore,
+  RoleMeta,
+  RoleStep,
+  StartNode,
+  StateNode,
+  ThreadContext,
+} from "@uncaged/workflow-protocol";
+import { END, START } from "@uncaged/workflow-protocol";
+
+async function loadParsedNode(cas: CasStore, hash: string) {
+  const yamlText = await cas.get(hash);
+  if (yamlText === null) {
+    return null;
+  }
+  return parseCasThreadNode(yamlText);
+}
+
+async function resolvePromptText(cas: CasStore, promptHash: string): Promise<string> {
+  const text = await getContentMerklePayload(cas, promptHash);
+  if (text !== null) {
+    return text;
+  }
+  throw new Error(`buildThreadContext: could not resolve prompt text at ${promptHash}`);
+}
+
+async function collectStateChainFromHead(cas: CasStore, headHash: string): Promise<StateNode[]> {
+  const reversed: StateNode[] = [];
+  let hash: string | null = headHash;
+  while (hash !== null) {
+    const parsed = await loadParsedNode(cas, hash);
+    if (parsed === null || parsed.kind !== "state") {
+      throw new Error(`buildThreadContext: expected state node at ${hash}`);
+    }
+    reversed.push(parsed.node);
+    const anc = parsed.node.payload.ancestors;
+    hash = anc.length > 0 ? anc[0] : null;
+  }
+  reversed.reverse();
+  return reversed;
+}
+
+async function threadFromStartHead<M extends RoleMeta>(
+  node: StartNode,
+  cas: CasStore,
+): Promise<ThreadContext<M>> {
+  const promptHash = node.refs[0];
+  if (promptHash === undefined) {
+    throw new Error("buildThreadContext: StartNode missing refs[0] prompt");
+  }
+  const prompt = await resolvePromptText(cas, promptHash);
+  const p = node.payload;
+  return {
+    threadId: "",
+    depth: p.depth,
+    start: {
+      role: START,
+      content: prompt,
+      meta: { maxRounds: p.maxRounds },
+      timestamp: 0,
+    },
+    steps: [],
+  };
+}
+
+async function buildRoleStepsFromStates<M extends RoleMeta>(
+  chronologicalStates: StateNode[],
+  cas: CasStore,
+): Promise<RoleStep<M>[]> {
+  const steps: RoleStep<M>[] = [];
+  for (const st of chronologicalStates) {
+    if (st.payload.role === END) {
+      continue;
+    }
+    const contentParsed = await loadParsedNode(cas, st.payload.content);
+    if (contentParsed === null || contentParsed.kind !== "content") {
+      throw new Error(`buildThreadContext: expected content node at ${st.payload.content}`);
+    }
+    steps.push({
+      role: st.payload.role,
+      meta: st.payload.meta,
+      contentHash: st.payload.content,
+      refs: [...contentParsed.node.refs],
+      timestamp: st.payload.timestamp,
+    } as RoleStep<M>);
+  }
+  return steps;
+}
+
+async function threadFromStateHead<M extends RoleMeta>(
+  headHash: string,
+  cas: CasStore,
+): Promise<ThreadContext<M>> {
+  const chronologicalStates = await collectStateChainFromHead(cas, headHash);
+  const firstState = chronologicalStates[0];
+  if (firstState === undefined) {
+    throw new Error("buildThreadContext: empty state chain");
+  }
+  const startBlob = await loadParsedNode(cas, firstState.payload.start);
+  if (startBlob === null || startBlob.kind !== "start") {
+    throw new Error(`buildThreadContext: StartNode missing at ${firstState.payload.start}`);
+  }
+  const promptHash = startBlob.node.refs[0];
+  if (promptHash === undefined) {
+    throw new Error("buildThreadContext: StartNode missing refs[0] prompt");
+  }
+  const prompt = await resolvePromptText(cas, promptHash);
+  const sp = startBlob.node.payload;
+  const steps = await buildRoleStepsFromStates<M>(chronologicalStates, cas);
+  const firstTs = steps[0]?.timestamp ?? 0;
+
+  return {
+    threadId: "",
+    depth: sp.depth,
+    start: {
+      role: START,
+      content: prompt,
+      meta: { maxRounds: sp.maxRounds },
+      timestamp: firstTs,
+    },
+    steps,
+  };
+}
+
+/**
+ * Reconstructs {@link ThreadContext} by walking the CAS state chain from {@link headHash}.
+ *
+ * Walks each {@link StateNode} via `payload.ancestors[0]` until the ancestor list is empty,
+ * resolves the prompt from the shared {@link StartNode} (`refs[0]` → prompt blob), and builds
+ * steps from non-`__end__` states in chronological order.
+ *
+ * `threadId` is set to `""` — callers that load from `threads.json` should overwrite it.
+ */
+export async function buildThreadContext<M extends RoleMeta = RoleMeta>(
+  headHash: string,
+  cas: CasStore,
+): Promise<ThreadContext<M>> {
+  const headParsed = await loadParsedNode(cas, headHash);
+  if (headParsed === null) {
+    throw new Error(`buildThreadContext: missing or invalid CAS blob ${headHash}`);
+  }
+
+  if (headParsed.kind === "start") {
+    return threadFromStartHead(headParsed.node, cas);
+  }
+
+  if (headParsed.kind !== "state") {
+    throw new Error(`buildThreadContext: head ${headHash} must be start or state node`);
+  }
+
+  return threadFromStateHead(headHash, cas);
+}

packages/workflow-runtime/src/create-workflow.ts

@@ -1,3 +1,4 @@
+import { putContentNodeWithRefs } from "@uncaged/workflow-cas";
 import type * as z from "zod/v4";
 
 import {
@@ -5,7 +6,6 @@ import {
   type AgentBinding,
   type AgentContext,
   type AgentFn,
-  type CasStore,
   END,
   type ExtractContext,
   type ModeratorContext,
@@ -38,8 +38,16 @@ function resolveExtractedRefs(
   return extractRefsFn(meta as Record<string, unknown>);
 }
 
-async function putContentBlob(store: CasStore, raw: string): Promise<string> {
-  return store.put(raw);
+function mergeUniqueHashes(a: readonly string[], b: readonly string[]): string[] {
+  const seen = new Set<string>();
+  const out: string[] = [];
+  for (const h of [...a, ...b]) {
+    if (!seen.has(h)) {
+      seen.add(h);
+      out.push(h);
+    }
+  }
+  return out;
 }
 
 function agentForRole(binding: AgentBinding, roleName: string): AgentFn {
@@ -86,23 +94,29 @@ async function advanceOneRound<M extends RoleMeta>(
     agentContent: raw,
   };
 
-  const meta = await runtime.extract(
+  const extracted = await runtime.extract(
     roleDef.schema as z.ZodType<Record<string, unknown>>,
     roleDef.extractPrompt,
     extractCtx as unknown as ExtractContext,
   );
 
-  const contentHash = await putContentBlob(runtime.cas, raw);
   const refsFromMeta = resolveExtractedRefs(
     roleDef as unknown as RoleDefinition<Record<string, unknown>>,
-    meta,
+    extracted.meta,
   );
-  const refs = refsFromMeta.includes(contentHash) ? refsFromMeta : [...refsFromMeta, contentHash];
+  const artifactRefs = mergeUniqueHashes(extracted.refs, refsFromMeta);
+
+  const contentHash = await putContentNodeWithRefs(
+    runtime.cas,
+    extracted.contentPayload,
+    artifactRefs,
+  );
+  const refs = artifactRefs.includes(contentHash) ? artifactRefs : [...artifactRefs, contentHash];
 
   const step = {
     role: next,
     contentHash,
-    meta,
+    meta: extracted.meta,
     refs,
     timestamp: Date.now(),
   } as RoleStep<M>;