feat: Dashboard workflow graph visualization with React Flow (#198)

Phase 1: API + static graph rendering

Backend:
- GET /workflows/:name now returns descriptor (with graph) from bundle YAML
- Graceful fallback to null if YAML missing/invalid

Frontend:
- New workflow-graph/ component module (7 files)
- React Flow + dagre auto-layout (TB direction)
- Custom nodes: RoleNode (rounded rect) + TerminalNode (circle for START/END)
- Custom edges: dashed for FALLBACK, solid with label for conditions
- Self-loop edges supported (e.g. coder → coder)
- Node states: default/completed/active with color-coded borders
- Active node pulse animation
- Collapsible graph panel (300px) above thread records
- Dark theme using existing CSS variables

Integration:
- ThreadDetail extracts workflow name → fetches descriptor → computes node states → renders graph
- Node states derived from ThreadRecord[] (completed/active/default)

docs/plans/2026-05-12-dashboard-workflow-graph.md

@@ -1,68 +1,53 @@
 # Dashboard Workflow Graph Visualization
 
 **Issue**: #198
-**Status**: Draft
+**Status**: In Progress
 **Author**: xingyue
 
 ## Overview
 
 在 Dashboard 的 ThreadDetail 页面中嵌入一个交互式流程图，将 workflow 的 `ModeratorTable` 可视化为有向图。用户可以一眼看到角色流转结构和当前执行进度。
 
-## 数据流
+## 数据层（✅ 已完成 — PR #201）
 
-### 问题：ModeratorTable 在 bundle 端，Dashboard 在前端
+### WorkflowGraph 类型
 
-`ModeratorTable` 是运行时数据结构（包含 JS 函数引用如 `check`），无法直接序列化给前端。需要一个**静态图描述格式**作为中间层。
-
-### 方案：扩展 WorkflowDescriptor
-
-当前 `WorkflowDescriptor` 只有 roles + description，不包含转换图信息：
+`WorkflowDefinition.moderator`（函数）已替换为 `WorkflowDefinition.table`（声明式 `ModeratorTable`），`buildDescriptor` 自动从 table 提取 graph：
 
 ```ts
-type WorkflowDescriptor = {
-  description: string;
-  roles: Record<string, WorkflowRoleDescriptor>;
-};
-```
-
-**扩展为**：
-
-```ts
-type TransitionEdge = {
-  condition: string;        // condition.name，或 "FALLBACK"
-  description: string | null; // condition.description，FALLBACK 为 null
-  target: string;           // role name 或 "__end__"
+type WorkflowGraphEdge = {
+  from: string;              // source role 或 "__start__"
+  to: string;                // target role 或 "__end__"
+  condition: string;         // condition.name 或 "FALLBACK"
+  conditionDescription: string | null;
 };
 
-type WorkflowGraph = Record<string, TransitionEdge[]>;
-// key = source role name 或 "__start__"
+type WorkflowGraph = {
+  edges: readonly WorkflowGraphEdge[];
+};
 
 type WorkflowDescriptor = {
   description: string;
   roles: Record<string, WorkflowRoleDescriptor>;
-  graph: WorkflowGraph | null;  // null = legacy bundles without graph
+  graph: WorkflowGraph;      // 必填，新 bundle 自动生成
 };
 ```
 
-在 `buildDescriptor`（`workflow-register`）中，从 `ModeratorTable` 提取静态图结构。`condition.check` 函数不序列化，只保留 `name` 和 `description`。
-
-### 数据暴露路径
+### 数据流
 
 ```
-ModeratorTable (runtime)
-  → buildDescriptor() 提取 graph
-    → descriptor.yaml 持久化
-      → CLI serve /workflows API 返回
+ModeratorTable (WorkflowDefinition.table)
+  → buildDescriptor() 自动提取 graph
+    → descriptor.yaml 持久化（hash.yaml）
+      → CLI serve /workflows/:name API 返回 descriptor
         → Dashboard 前端拿到 graph
 ```
 
-同时需要新增或扩展一个 API，让 Dashboard 能拿到指定 workflow 的 descriptor（含 graph）：
+### 剩余数据层工作
 
-```
-GET /workflows/:name → { descriptor: WorkflowDescriptor }
-```
+**serve API 需要返回 descriptor**：当前 `GET /workflows/:name` 只返回 registry entry（hash + timestamp），不含 descriptor。需要从 `bundles/{hash}.yaml` 读取 descriptor 并返回给前端。
 
-或者在现有 `listWorkflows` 返回中附带。
+方案：在 `routes-workflow.ts` 的 `GET /workflows/:name` 响应中附带 `descriptor` 字段。或者：thread-detail 发现 workflow name 后，请求 `GET /workflows/:name/descriptor` 拿到 graph。
 
 ## 前端渲染
 
@@ -87,17 +72,17 @@ GET /workflows/:name → { descriptor: WorkflowDescriptor }
 ### 图结构映射
 
 ```
-WorkflowGraph → React Flow nodes + edges
+WorkflowGraph.edges → React Flow nodes + edges
 
-节点:
+节点（自动从 edges 推导）:
   - __start__  → 圆形小节点（入口）
   - role       → 圆角矩形，显示 role name + description
   - __end__    → 圆形小节点（终止）
 
 边:
   - FALLBACK   → 虚线（dashed），无 label
-  - condition  → 实线，label = condition.name
-                  hover tooltip = condition.description
+  - condition  → 实线，label = condition
+                  hover tooltip = conditionDescription
 ```
 
 ### 布局
@@ -172,7 +157,7 @@ function getNodeStates(records: ThreadRecord[]): Map<string, "completed" | "acti
 workflow-dashboard/src/
   components/
     workflow-graph/
-      types.ts           — TransitionEdge, NodeState 等前端类型
+      types.ts           — NodeState 等前端类型
       index.ts           — export { WorkflowGraph }
       workflow-graph.tsx  — 主组件，React Flow canvas
       role-node.tsx       — 自定义 role 节点
@@ -196,15 +181,22 @@ workflow-dashboard/src/
 
 图高度固定 300px，React Flow 支持 pan + zoom，不影响下方 records 滚动。
 
-## 分阶段实施
+## 实施计划
 
-### Phase 1: 数据层 + 静态图
+### ~~Phase 0: 数据层~~ ✅ Done (PR #201)
 
-1. 在 `workflow-protocol` 中新增 `TransitionEdge` / `WorkflowGraph` 类型
-2. 在 `workflow-register` 的 `buildDescriptor` 中从 `ModeratorTable` 提取 graph
-3. `stringifyWorkflowDescriptor` / `validateWorkflowDescriptor` 支持 graph 字段
-4. CLI serve 的 `/workflows` API 返回 descriptor（含 graph）
-5. Dashboard 新增 `WorkflowGraph` 组件，静态渲染图
+- [x] `WorkflowDefinition.moderator` → `table` (ModeratorTable)
+- [x] `WorkflowDescriptor` 新增 `graph: WorkflowGraph`
+- [x] `buildDescriptor` 自动提取 graph
+- [x] `validateWorkflowDescriptor` 校验 graph
+
+### Phase 1: API + 静态图渲染
+
+1. serve API：`GET /workflows/:name` 返回 descriptor（含 graph），或新增 `GET /workflows/:name/descriptor`
+2. Dashboard `api.ts` 新增 `getWorkflowDescriptor(agent, name)` 函数
+3. 安装 `@xyflow/react` + `@dagrejs/dagre`
+4. 实现 `workflow-graph/` 组件集
+5. ThreadDetail 中集成：从 thread-start record 拿 workflow name → 请求 descriptor → 渲染图
 
 **产出**：打开 ThreadDetail 看到 workflow 流程图，无高亮。
 
@@ -219,21 +211,14 @@ workflow-dashboard/src/
 ### Phase 3: 交互增强
 
 1. 点击节点滚动到对应 role 的 RecordCard
-2. 边 hover 显示 condition description tooltip
+2. 边 hover 显示 conditionDescription tooltip
 3. 节点 hover 显示 role description + schema summary
 
 **产出**：图和记录列表联动。
 
 ## 注意事项
 
-- **向后兼容**：`graph` 字段为 `null` 时（旧 bundle），不渲染图，只显示 records
 - **自循环边**：如 `coder → coder (FALLBACK)`，React Flow 支持自循环，dagre 需要特殊处理（self-edge 用 loop 路径）
 - **大图性能**：dagre 在 <50 节点时性能无忧，workflow 通常 <10 个 role
 - **暗色主题**：Dashboard 已使用 CSS variables，节点/边样式复用现有色板
 - **不提交 pnpm-lock.yaml**
-
-## 开放问题
-
-1. **graph 放 descriptor 还是独立字段？** — 建议放 descriptor，因为它描述的就是 workflow 结构
-2. **是否需要 WorkflowList 页也展示图？** — Phase 1 先只在 ThreadDetail，后续按需扩展
-3. **`buildDescriptor` 需要 `ModeratorTable` 参数** — 当前 `buildDescriptor` 只接收 roles，需要扩展签名或在 bundle 注册时额外传入 table

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

@@ -45,8 +45,8 @@ describe("gc cli and garbageCollectCas", () => {
       {
         name: "demo",
         hash: bundleHash,
-
         depth: 0,
+        parentState: null,
       },
       promptHash,
     );
@@ -100,8 +100,8 @@ describe("gc cli and garbageCollectCas", () => {
       {
         name: "demo",
         hash: bundleHash,
-
         depth: 0,
+        parentState: null,
       },
       promptHash,
     );
@@ -135,8 +135,8 @@ describe("gc cli and garbageCollectCas", () => {
       {
         name: "demo",
         hash: bundleHash,
-
         depth: 0,
+        parentState: null,
       },
       promptHash,
     );

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

@@ -1,9 +1,14 @@
+import { readFile } from "node:fs/promises";
+import { join } from "node:path";
+import type { WorkflowDescriptor } from "@uncaged/workflow-protocol";
 import {
   getRegisteredWorkflow,
   listRegisteredWorkflowNames,
   readWorkflowRegistry,
+  validateWorkflowDescriptor,
 } from "@uncaged/workflow-register";
 import { Hono } from "hono";
+import { parse as parseYaml } from "yaml";
 
 export function createWorkflowRoutes(storageRoot: string): Hono {
   const app = new Hono();
@@ -35,7 +40,17 @@ export function createWorkflowRoutes(storageRoot: string): Hono {
     if (entry === null) {
       return c.json({ error: `workflow not found: ${name}` }, 404);
     }
-    return c.json({ name, ...entry });
+    let descriptor: WorkflowDescriptor | null = null;
+    try {
+      const yamlPath = join(storageRoot, "bundles", `${entry.hash}.yaml`);
+      const yamlText = await readFile(yamlPath, "utf8");
+      const parsed: unknown = parseYaml(yamlText);
+      const validated = validateWorkflowDescriptor(parsed);
+      descriptor = validated.ok ? validated.value : null;
+    } catch {
+      descriptor = null;
+    }
+    return c.json({ name, ...entry, descriptor });
   });
 
   app.get("/:name/history", async (c) => {

packages/workflow-agent-llm/__tests__/create-llm-adapter.test.ts

@@ -12,6 +12,7 @@ function makeCtx(userContent: string): AgentContext {
       timestamp: 1,
     },
     depth: 0,
+    bundleHash: "TESTHASH00001",
     steps: [],
     threadId: "01TEST000000000000000000TR",
     currentRole: { name: "planner", systemPrompt: "system instructions" },

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

@@ -14,6 +14,7 @@ function payload(
     ancestors: partial.ancestors ?? [],
     compact: partial.compact ?? null,
     timestamp: partial.timestamp ?? 0,
+    childThread: partial.childThread ?? null,
   };
 }
 
@@ -62,4 +63,32 @@ describe("collectRefs", () => {
     );
     expect(refs).toEqual(["S2", "C2"]);
   });
+
+  test("includes childThread hash when childThread is non-null", () => {
+    const refs = collectRefs(
+      payload({
+        role: "developer",
+        start: "S3",
+        content: "C3",
+        ancestors: ["A3"],
+        compact: null,
+        childThread: "CHILDEND000000000000001",
+      }),
+    );
+    expect(refs).toEqual(["S3", "C3", "A3", "CHILDEND000000000000001"]);
+  });
+
+  test("does not include childThread when childThread is null", () => {
+    const refs = collectRefs(
+      payload({
+        role: "developer",
+        start: "S4",
+        content: "C4",
+        ancestors: [],
+        compact: null,
+        childThread: null,
+      }),
+    );
+    expect(refs).toEqual(["S4", "C4"]);
+  });
 });

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

@@ -0,0 +1,161 @@
+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 { stringify } from "yaml";
+
+import { createCasStore } from "../src/cas.js";
+import { parseCasThreadNode, putStartNode, putStateNode } from "../src/nodes.js";
+
+describe("putStartNode — parentState in refs", () => {
+  let dir: string;
+
+  beforeEach(async () => {
+    dir = await mkdtemp(join(tmpdir(), "wf-cas-nodes-"));
+  });
+
+  afterEach(async () => {
+    await rm(dir, { recursive: true, force: true });
+  });
+
+  test("refs contains only promptHash when parentState is null", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const promptHash = await cas.put("hello");
+    const startHash = await putStartNode(
+      cas,
+      { name: "demo", hash: "BUNDLEAAAAAAAAA", depth: 0, parentState: null },
+      promptHash,
+    );
+
+    const blob = await cas.get(startHash);
+    expect(blob).not.toBeNull();
+    const parsed = parseCasThreadNode(blob ?? "");
+    expect(parsed).not.toBeNull();
+    expect(parsed?.kind).toBe("start");
+    if (parsed?.kind !== "start") return;
+
+    expect(parsed.node.refs).toEqual([promptHash]);
+    expect(parsed.node.payload.parentState).toBeNull();
+  });
+
+  test("refs contains [promptHash, parentStateHash] when parentState is set", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const parentStateHash = await cas.put("fake-parent-state");
+    const promptHash = await cas.put("child-prompt");
+    const startHash = await putStartNode(
+      cas,
+      { name: "develop", hash: "BUNDLEBBBBBBBBB", depth: 1, parentState: parentStateHash },
+      promptHash,
+    );
+
+    const blob = await cas.get(startHash);
+    expect(blob).not.toBeNull();
+    const parsed = parseCasThreadNode(blob ?? "");
+    expect(parsed).not.toBeNull();
+    expect(parsed?.kind).toBe("start");
+    if (parsed?.kind !== "start") return;
+
+    expect(parsed.node.refs).toEqual([promptHash, parentStateHash]);
+    expect(parsed.node.payload.parentState).toBe(parentStateHash);
+  });
+});
+
+describe("putStateNode — childThread in refs", () => {
+  let dir: string;
+
+  beforeEach(async () => {
+    dir = await mkdtemp(join(tmpdir(), "wf-cas-nodes-state-"));
+  });
+
+  afterEach(async () => {
+    await rm(dir, { recursive: true, force: true });
+  });
+
+  test("refs does not include childThread when childThread is null", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const startHash = await cas.put("start");
+    const contentHash = await cas.put("content");
+    const stateHash = await putStateNode(cas, {
+      role: "planner",
+      meta: {},
+      start: startHash,
+      content: contentHash,
+      ancestors: [],
+      compact: null,
+      timestamp: 1000,
+      childThread: null,
+    });
+
+    const blob = await cas.get(stateHash);
+    expect(blob).not.toBeNull();
+    const parsed = parseCasThreadNode(blob ?? "");
+    expect(parsed?.kind).toBe("state");
+    if (parsed?.kind !== "state") return;
+
+    expect(parsed.node.refs).not.toContain("anything-else");
+    expect(parsed.node.refs).toEqual([startHash, contentHash]);
+    expect(parsed.node.payload.childThread).toBeNull();
+  });
+
+  test("refs includes childThread hash when childThread is set", async () => {
+    const cas = createCasStore(join(dir, "cas"));
+    const startHash = await cas.put("start");
+    const contentHash = await cas.put("content");
+    const childEndHash = await cas.put("child-end-state");
+    const stateHash = await putStateNode(cas, {
+      role: "developer",
+      meta: { pr: 42 },
+      start: startHash,
+      content: contentHash,
+      ancestors: [],
+      compact: null,
+      timestamp: 2000,
+      childThread: childEndHash,
+    });
+
+    const blob = await cas.get(stateHash);
+    expect(blob).not.toBeNull();
+    const parsed = parseCasThreadNode(blob ?? "");
+    expect(parsed?.kind).toBe("state");
+    if (parsed?.kind !== "state") return;
+
+    expect(parsed.node.refs).toContain(childEndHash);
+    expect(parsed.node.payload.childThread).toBe(childEndHash);
+  });
+});
+
+describe("parseCasThreadNode — legacy node compatibility", () => {
+  test("start node without parentState field defaults to null", () => {
+    const yaml = stringify({
+      type: "start",
+      payload: { name: "demo", hash: "BUNDLEAAAAAAAAA", depth: 0 },
+      refs: ["PROMPTHASH00001"],
+    });
+    const parsed = parseCasThreadNode(yaml);
+    expect(parsed).not.toBeNull();
+    expect(parsed?.kind).toBe("start");
+    if (parsed?.kind !== "start") return;
+    expect(parsed.node.payload.parentState).toBeNull();
+  });
+
+  test("state node without childThread field defaults to null", () => {
+    const yaml = stringify({
+      type: "state",
+      payload: {
+        role: "planner",
+        meta: {},
+        start: "STARTHASH00001",
+        content: "CONTENTHASH0001",
+        ancestors: [],
+        compact: null,
+        timestamp: 1000,
+      },
+      refs: ["STARTHASH00001", "CONTENTHASH0001"],
+    });
+    const parsed = parseCasThreadNode(yaml);
+    expect(parsed).not.toBeNull();
+    expect(parsed?.kind).toBe("state");
+    if (parsed?.kind !== "state") return;
+    expect(parsed.node.payload.childThread).toBeNull();
+  });
+});

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

@@ -9,5 +9,8 @@ export function collectRefs(payload: StateNode["payload"]): string[] {
   if (payload.compact !== null) {
     out.push(payload.compact);
   }
+  if (payload.childThread !== null) {
+    out.push(payload.childThread);
+  }
   return out;
 }

packages/workflow-cas/src/nodes.ts

@@ -18,6 +18,10 @@ function isStartPayload(value: unknown): value is StartNodePayload {
   if (!isRecord(value)) {
     return false;
   }
+  const parentState = value.parentState;
+  if (parentState !== undefined && parentState !== null && typeof parentState !== "string") {
+    return false;
+  }
   return (
     typeof value.name === "string" &&
     typeof value.hash === "string" &&
@@ -25,6 +29,16 @@ function isStartPayload(value: unknown): value is StartNodePayload {
   );
 }
 
+/** Normalizes a raw start payload, defaulting `parentState` to `null` for legacy nodes. */
+function normalizeStartPayload(raw: StartNodePayload): StartNodePayload {
+  return {
+    name: raw.name,
+    hash: raw.hash,
+    depth: raw.depth,
+    parentState: raw.parentState ?? null,
+  };
+}
+
 function isStatePayload(value: unknown): value is StateNodePayload {
   if (!isRecord(value)) {
     return false;
@@ -41,6 +55,10 @@ function isStatePayload(value: unknown): value is StateNodePayload {
   if (!isRecord(meta)) {
     return false;
   }
+  const childThread = value.childThread;
+  if (childThread !== undefined && childThread !== null && typeof childThread !== "string") {
+    return false;
+  }
   return (
     typeof value.role === "string" &&
     typeof value.start === "string" &&
@@ -49,6 +67,20 @@ function isStatePayload(value: unknown): value is StateNodePayload {
   );
 }
 
+/** Normalizes a raw state payload, defaulting `childThread` to `null` for legacy nodes. */
+function normalizeStatePayload(raw: StateNodePayload): StateNodePayload {
+  return {
+    role: raw.role,
+    meta: raw.meta,
+    start: raw.start,
+    content: raw.content,
+    ancestors: raw.ancestors,
+    compact: raw.compact,
+    timestamp: raw.timestamp,
+    childThread: raw.childThread ?? null,
+  };
+}
+
 /** 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;
@@ -86,14 +118,22 @@ export function parseCasThreadNode(yamlText: string): ParsedCasThreadNode | null
     if (!isStartPayload(raw.payload)) {
       return null;
     }
-    const node: StartNode = { type: "start", payload: raw.payload, refs: [...refs] };
+    const node: StartNode = {
+      type: "start",
+      payload: normalizeStartPayload(raw.payload),
+      refs: [...refs],
+    };
     return { kind: "start", node };
   }
 
   if (!isStatePayload(raw.payload)) {
     return null;
   }
-  const node: StateNode = { type: "state", payload: raw.payload, refs: [...refs] };
+  const node: StateNode = {
+    type: "state",
+    payload: normalizeStatePayload(raw.payload),
+    refs: [...refs],
+  };
   return { kind: "state", node };
 }
 
@@ -143,10 +183,14 @@ export async function putStartNode(
   payload: StartNode["payload"],
   promptHash: string,
 ): Promise<string> {
+  const refs = [promptHash];
+  if (payload.parentState !== null) {
+    refs.push(payload.parentState);
+  }
   const node: StartNode = {
     type: "start",
     payload,
-    refs: [promptHash],
+    refs,
   };
   return store.put(serializeCasNode(node));
 }

packages/workflow-dashboard/package.json

@@ -9,6 +9,8 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "@dagrejs/dagre": "^3.0.0",
+    "@xyflow/react": "^12.10.2",
     "react": "^19.2.6",
     "react-dom": "^19.2.6",
     "react-markdown": "^10.1.0",

packages/workflow-dashboard/src/api.ts

@@ -104,6 +104,36 @@ export type WorkflowResultRecord = {
 
 export type ThreadRecord = ThreadStartRecord | RoleRecord | WorkflowResultRecord;
 
+export type WorkflowGraphEdge = {
+  from: string;
+  to: string;
+  condition: string;
+  conditionDescription: string | null;
+};
+
+export type WorkflowGraph = {
+  edges: readonly WorkflowGraphEdge[];
+};
+
+export type WorkflowRoleDescriptor = {
+  description: string;
+  schema: Record<string, unknown>;
+};
+
+export type WorkflowDescriptor = {
+  description: string;
+  roles: Record<string, WorkflowRoleDescriptor>;
+  graph: WorkflowGraph;
+};
+
+export type WorkflowDetail = {
+  name: string;
+  hash: string;
+  timestamp: number;
+  history: unknown[];
+  descriptor: WorkflowDescriptor | null;
+};
+
 // ── Gateway endpoints ───────────────────────────────────────────────
 
 export function listAgents(): Promise<AgentEndpoint[]> {
@@ -117,6 +147,15 @@ export function listWorkflows(agent: string): Promise<{ workflows: WorkflowSumma
   return fetchJson(agentBase(agent), "/workflows");
 }
 
+export function getWorkflowDescriptor(
+  agent: string,
+  name: string,
+): Promise<WorkflowDescriptor | null> {
+  return fetchJson<WorkflowDetail>(agentBase(agent), `/workflows/${encodeURIComponent(name)}`).then(
+    (res) => res.descriptor,
+  );
+}
+
 export function listThreads(agent: string): Promise<{ threads: ThreadSummary[] }> {
   return fetchJson(agentBase(agent), "/threads");
 }

packages/workflow-dashboard/src/components/thread-detail.tsx

@@ -1,8 +1,17 @@
-import { useEffect, useRef, useState } from "react";
-import { getThread, killThread, pauseThread, resumeThread } from "../api.ts";
+import { useEffect, useMemo, useRef, useState } from "react";
+import {
+  getThread,
+  getWorkflowDescriptor,
+  killThread,
+  pauseThread,
+  resumeThread,
+  type ThreadRecord,
+  type WorkflowDescriptor,
+} from "../api.ts";
 import { useFetch } from "../hooks.ts";
 import { useSSE } from "../use-sse.ts";
 import { RecordCard } from "./record-card.tsx";
+import { type NodeState, WorkflowGraph } from "./workflow-graph/index.ts";
 
 type Props = {
   agent: string;
@@ -10,6 +19,84 @@ type Props = {
   onBack: () => void;
 };
 
+function extractWorkflowName(records: readonly ThreadRecord[]): string | null {
+  for (const r of records) {
+    if (r.type === "thread-start") return r.workflow;
+  }
+  return null;
+}
+
+type GraphPanelProps = {
+  descriptor: WorkflowDescriptor;
+  workflowName: string | null;
+  nodeStates: Map<string, NodeState>;
+};
+
+function GraphPanel({ descriptor, workflowName, nodeStates }: GraphPanelProps) {
+  const [open, setOpen] = useState(true);
+  const edgeCount = descriptor.graph.edges.length;
+  return (
+    <div
+      className="mb-4 rounded-lg border overflow-hidden"
+      style={{ borderColor: "var(--color-border)", background: "var(--color-surface)" }}
+    >
+      <button
+        type="button"
+        onClick={() => setOpen((v) => !v)}
+        className="w-full flex items-center justify-between px-3 py-2 text-xs"
+        style={{ color: "var(--color-text-muted)" }}
+      >
+        <span className="font-mono">
+          {open ? "▼" : "▶"} Workflow graph
+          {workflowName !== null && (
+            <span className="ml-2" style={{ color: "var(--color-text)" }}>
+              {workflowName}
+            </span>
+          )}
+        </span>
+        <span>
+          {edgeCount} edge{edgeCount === 1 ? "" : "s"}
+        </span>
+      </button>
+      {open && (
+        <div style={{ height: 300, width: "100%" }}>
+          <WorkflowGraph
+            graph={descriptor.graph}
+            roles={descriptor.roles}
+            nodeStates={nodeStates}
+          />
+        </div>
+      )}
+    </div>
+  );
+}
+
+function computeNodeStates(records: readonly ThreadRecord[]): Map<string, NodeState> {
+  const states = new Map<string, NodeState>();
+  const roleRecords = records.filter(
+    (r): r is Extract<ThreadRecord, { type: "role" }> => r.type === "role",
+  );
+  const hasResult = records.some((r) => r.type === "workflow-result");
+
+  for (let i = 0; i < roleRecords.length; i++) {
+    const role = roleRecords[i].role;
+    const isLast = i === roleRecords.length - 1;
+    states.set(role, !hasResult && isLast ? "active" : "completed");
+  }
+
+  if (roleRecords.length > 0) {
+    states.set("__start__", "completed");
+  }
+  if (hasResult) {
+    states.set("__end__", "completed");
+    for (const [k, v] of states) {
+      if (v === "active") states.set(k, "completed");
+    }
+  }
+
+  return states;
+}
+
 export function ThreadDetail({ agent, threadId, onBack }: Props) {
   const sse = useSSE(agent, threadId);
   const { status, data, error } = useFetch(() => getThread(agent, threadId), [agent, threadId]);
@@ -23,6 +110,17 @@ export function ThreadDetail({ agent, threadId, onBack }: Props) {
       ? data.records
       : ([] as typeof sse.records);
 
+  const workflowName = useMemo(() => extractWorkflowName(records), [records]);
+
+  const descriptorFetch = useFetch<WorkflowDescriptor | null>(
+    () =>
+      workflowName === null ? Promise.resolve(null) : getWorkflowDescriptor(agent, workflowName),
+    [agent, workflowName],
+  );
+
+  const descriptor = descriptorFetch.status === "ok" ? descriptorFetch.data : null;
+  const nodeStates = useMemo(() => computeNodeStates(records), [records]);
+
   // biome-ignore lint/correctness/useExhaustiveDependencies: scroll when the rendered record list grows
   useEffect(() => {
     recordsEndRef.current?.scrollIntoView({ behavior: "smooth" });
@@ -95,6 +193,10 @@ export function ThreadDetail({ agent, threadId, onBack }: Props) {
         </p>
       )}
 
+      {descriptor !== null && descriptor.graph.edges.length > 0 && (
+        <GraphPanel descriptor={descriptor} workflowName={workflowName} nodeStates={nodeStates} />
+      )}
+
       {status === "loading" && !liveActive && records.length === 0 && (
         <p style={{ color: "var(--color-text-muted)" }}>Loading...</p>
       )}

packages/workflow-dashboard/src/components/workflow-graph/condition-edge.tsx

@@ -0,0 +1,76 @@
+import {
+  BaseEdge,
+  EdgeLabelRenderer,
+  type EdgeProps,
+  getBezierPath,
+  getSmoothStepPath,
+} from "@xyflow/react";
+import type { ConditionEdgeData } from "./types.ts";
+
+export function ConditionEdge(props: EdgeProps) {
+  const {
+    id,
+    source,
+    target,
+    sourceX,
+    sourceY,
+    targetX,
+    targetY,
+    sourcePosition,
+    targetPosition,
+    data,
+    markerEnd,
+  } = props;
+  const edgeData = data as ConditionEdgeData | undefined;
+  const isFallback = edgeData?.isFallback ?? false;
+  const isSelfLoop = source === target;
+
+  const [path, labelX, labelY] = isSelfLoop
+    ? getSmoothStepPath({
+        sourceX,
+        sourceY,
+        targetX,
+        targetY,
+        sourcePosition,
+        targetPosition,
+        borderRadius: 20,
+      })
+    : getBezierPath({
+        sourceX,
+        sourceY,
+        targetX,
+        targetY,
+        sourcePosition,
+        targetPosition,
+      });
+
+  const stroke = isFallback ? "var(--color-text-muted)" : "var(--color-text)";
+  const strokeDasharray = isFallback ? "5 4" : undefined;
+
+  return (
+    <>
+      <BaseEdge
+        id={id}
+        path={path}
+        markerEnd={markerEnd}
+        style={{ stroke, strokeWidth: 1.5, strokeDasharray }}
+      />
+      {edgeData && !isFallback && edgeData.condition !== "" && (
+        <EdgeLabelRenderer>
+          <div
+            className="absolute px-1.5 py-0.5 rounded text-[10px] font-mono pointer-events-auto"
+            style={{
+              transform: `translate(-50%, -50%) translate(${labelX}px, ${labelY}px)`,
+              background: "var(--color-bg)",
+              border: "1px solid var(--color-border)",
+              color: "var(--color-text)",
+            }}
+            title={edgeData.conditionDescription ?? undefined}
+          >
+            {edgeData.condition}
+          </div>
+        </EdgeLabelRenderer>
+      )}
+    </>
+  );
+}

packages/workflow-dashboard/src/components/workflow-graph/index.ts

@@ -0,0 +1,2 @@
+export type { NodeState } from "./types.ts";
+export { WorkflowGraph } from "./workflow-graph.tsx";

packages/workflow-dashboard/src/components/workflow-graph/role-node.tsx

@@ -0,0 +1,69 @@
+import { Handle, type NodeProps, Position } from "@xyflow/react";
+import type { RoleNodeData } from "./types.ts";
+
+function borderColor(state: RoleNodeData["state"]): string {
+  switch (state) {
+    case "completed":
+      return "var(--color-success)";
+    case "active":
+      return "var(--color-accent)";
+    default:
+      return "var(--color-border)";
+  }
+}
+
+function stateIcon(state: RoleNodeData["state"]): string | null {
+  if (state === "completed") return "✓";
+  if (state === "active") return "●";
+  return null;
+}
+
+export function RoleNode(props: NodeProps) {
+  const data = props.data as RoleNodeData;
+  const icon = stateIcon(data.state);
+  const isActive = data.state === "active";
+  const handleStyle = {
+    background: "var(--color-text-muted)",
+    width: 6,
+    height: 6,
+    border: "none",
+  } as const;
+
+  return (
+    <div
+      className={`px-3 py-2 rounded-md border-2 text-xs font-medium ${isActive ? "wf-node-pulse" : ""}`}
+      style={{
+        width: 180,
+        height: 60,
+        background: "var(--color-surface)",
+        borderColor: borderColor(data.state),
+        color: "var(--color-text)",
+        display: "flex",
+        flexDirection: "column",
+        justifyContent: "center",
+        boxSizing: "border-box",
+      }}
+      title={data.description}
+    >
+      <Handle type="target" position={Position.Top} style={handleStyle} isConnectable={false} />
+      <div className="flex items-center gap-1.5 font-mono">
+        {icon !== null && (
+          <span
+            style={{
+              color: data.state === "active" ? "var(--color-accent)" : "var(--color-success)",
+            }}
+          >
+            {icon}
+          </span>
+        )}
+        <span className="truncate">{data.label}</span>
+      </div>
+      {data.description !== "" && (
+        <div className="text-[10px] truncate mt-0.5" style={{ color: "var(--color-text-muted)" }}>
+          {data.description}
+        </div>
+      )}
+      <Handle type="source" position={Position.Bottom} style={handleStyle} isConnectable={false} />
+    </div>
+  );
+}

packages/workflow-dashboard/src/components/workflow-graph/terminal-node.tsx

@@ -0,0 +1,57 @@
+import { Handle, type NodeProps, Position } from "@xyflow/react";
+import type { TerminalNodeData } from "./types.ts";
+
+function borderColor(state: TerminalNodeData["state"]): string {
+  switch (state) {
+    case "completed":
+      return "var(--color-success)";
+    case "active":
+      return "var(--color-accent)";
+    default:
+      return "var(--color-border)";
+  }
+}
+
+function bgColor(state: TerminalNodeData["state"]): string {
+  if (state === "completed") return "var(--color-success)";
+  if (state === "active") return "var(--color-accent)";
+  return "var(--color-surface)";
+}
+
+export function TerminalNode(props: NodeProps) {
+  const data = props.data as TerminalNodeData;
+  const isStart = data.kind === "start";
+  const isActive = data.state === "active";
+  const handleStyle = {
+    background: "var(--color-text-muted)",
+    width: 6,
+    height: 6,
+    border: "none",
+  } as const;
+
+  return (
+    <div
+      className={`rounded-full border-2 flex items-center justify-center text-[10px] font-bold ${isActive ? "wf-node-pulse" : ""}`}
+      style={{
+        width: 40,
+        height: 40,
+        background: bgColor(data.state),
+        borderColor: borderColor(data.state),
+        color: data.state === "default" ? "var(--color-text-muted)" : "var(--color-bg)",
+      }}
+      title={isStart ? "Start" : "End"}
+    >
+      {isStart ? (
+        <Handle
+          type="source"
+          position={Position.Bottom}
+          style={handleStyle}
+          isConnectable={false}
+        />
+      ) : (
+        <Handle type="target" position={Position.Top} style={handleStyle} isConnectable={false} />
+      )}
+      {isStart ? "▶" : "■"}
+    </div>
+  );
+}

packages/workflow-dashboard/src/components/workflow-graph/types.ts

@@ -0,0 +1,29 @@
+import type { WorkflowGraphEdge } from "../../api.ts";
+
+export type NodeState = "default" | "completed" | "active";
+
+export type TerminalKind = "start" | "end";
+
+export type RoleNodeData = {
+  label: string;
+  description: string;
+  state: NodeState;
+  [key: string]: unknown;
+};
+
+export type TerminalNodeData = {
+  kind: TerminalKind;
+  state: NodeState;
+  [key: string]: unknown;
+};
+
+export type ConditionEdgeData = {
+  condition: string;
+  conditionDescription: string | null;
+  isFallback: boolean;
+  [key: string]: unknown;
+};
+
+export type GraphInput = {
+  edges: readonly WorkflowGraphEdge[];
+};

packages/workflow-dashboard/src/components/workflow-graph/use-layout.ts

@@ -0,0 +1,127 @@
+import Dagre from "@dagrejs/dagre";
+import type { Edge, Node } from "@xyflow/react";
+import { useMemo } from "react";
+import type { WorkflowGraphEdge } from "../../api.ts";
+import type { ConditionEdgeData, NodeState, RoleNodeData, TerminalNodeData } from "./types.ts";
+
+const START_ID = "__start__";
+const END_ID = "__end__";
+const ROLE_NODE_WIDTH = 180;
+const ROLE_NODE_HEIGHT = 60;
+const TERMINAL_NODE_SIZE = 40;
+
+type LayoutInput = {
+  edges: readonly WorkflowGraphEdge[];
+  roles: Record<string, { description: string }>;
+  nodeStates: Map<string, NodeState>;
+};
+
+type LayoutResult = {
+  nodes: Node[];
+  edges: Edge[];
+};
+
+function collectNodeIds(edges: readonly WorkflowGraphEdge[]): Set<string> {
+  const ids = new Set<string>();
+  for (const e of edges) {
+    ids.add(e.from);
+    ids.add(e.to);
+  }
+  return ids;
+}
+
+function nodeSize(id: string): { width: number; height: number } {
+  if (id === START_ID || id === END_ID) {
+    return { width: TERMINAL_NODE_SIZE, height: TERMINAL_NODE_SIZE };
+  }
+  return { width: ROLE_NODE_WIDTH, height: ROLE_NODE_HEIGHT };
+}
+
+function buildRoleNode(
+  id: string,
+  pos: { x: number; y: number },
+  roles: Record<string, { description: string }>,
+  state: NodeState,
+): Node<RoleNodeData> {
+  const description = roles[id]?.description ?? "";
+  return {
+    id,
+    type: "role",
+    position: pos,
+    data: { label: id, description, state },
+    draggable: false,
+  };
+}
+
+function buildTerminalNode(
+  id: string,
+  pos: { x: number; y: number },
+  state: NodeState,
+): Node<TerminalNodeData> {
+  return {
+    id,
+    type: "terminal",
+    position: pos,
+    data: { kind: id === START_ID ? "start" : "end", state },
+    draggable: false,
+    selectable: false,
+  };
+}
+
+function edgeKey(e: WorkflowGraphEdge): string {
+  return `${e.from}->${e.to}::${e.condition}`;
+}
+
+function buildEdge(e: WorkflowGraphEdge): Edge<ConditionEdgeData> {
+  const isFallback = e.condition === "FALLBACK";
+  return {
+    id: edgeKey(e),
+    source: e.from,
+    target: e.to,
+    type: "condition",
+    data: {
+      condition: e.condition,
+      conditionDescription: e.conditionDescription,
+      isFallback,
+    },
+  };
+}
+
+export function useLayout(input: LayoutInput): LayoutResult {
+  return useMemo(() => {
+    const ids = collectNodeIds(input.edges);
+
+    const g = new Dagre.graphlib.Graph({ multigraph: true }).setDefaultEdgeLabel(() => ({}));
+    g.setGraph({ rankdir: "TB", nodesep: 60, ranksep: 80 });
+
+    for (const id of ids) {
+      const size = nodeSize(id);
+      g.setNode(id, { width: size.width, height: size.height });
+    }
+    for (const e of input.edges) {
+      if (e.from === e.to) {
+        continue;
+      }
+      g.setEdge(e.from, e.to, {}, edgeKey(e));
+    }
+
+    Dagre.layout(g);
+
+    const nodes: Node[] = [];
+    for (const id of ids) {
+      const dagNode = g.node(id);
+      const size = nodeSize(id);
+      const pos = { x: dagNode.x - size.width / 2, y: dagNode.y - size.height / 2 };
+      const state = input.nodeStates.get(id) ?? "default";
+      if (id === START_ID || id === END_ID) {
+        nodes.push(buildTerminalNode(id, pos, state));
+      } else {
+        nodes.push(buildRoleNode(id, pos, input.roles, state));
+      }
+    }
+
+    const edges: Edge[] = input.edges.map(buildEdge);
+
+    return { nodes, edges };
+  }, [input.edges, input.roles, input.nodeStates]);
+}

packages/workflow-dashboard/src/components/workflow-graph/workflow-graph.tsx

@@ -0,0 +1,61 @@
+import { Background, type EdgeTypes, MarkerType, type NodeTypes, ReactFlow } from "@xyflow/react";
+import "@xyflow/react/dist/style.css";
+import { useMemo } from "react";
+import type { WorkflowGraph as WorkflowGraphData } from "../../api.ts";
+import { ConditionEdge } from "./condition-edge.tsx";
+import { RoleNode } from "./role-node.tsx";
+import { TerminalNode } from "./terminal-node.tsx";
+import type { NodeState } from "./types.ts";
+import { useLayout } from "./use-layout.ts";
+
+type Props = {
+  graph: WorkflowGraphData;
+  roles: Record<string, { description: string }>;
+  nodeStates: Map<string, NodeState>;
+};
+
+const nodeTypes: NodeTypes = {
+  role: RoleNode,
+  terminal: TerminalNode,
+};
+
+const edgeTypes: EdgeTypes = {
+  condition: ConditionEdge,
+};
+
+export function WorkflowGraph({ graph, roles, nodeStates }: Props) {
+  const layout = useLayout({ edges: graph.edges, roles, nodeStates });
+
+  const styledEdges = useMemo(
+    () =>
+      layout.edges.map((e) => ({
+        ...e,
+        markerEnd: {
+          type: MarkerType.ArrowClosed,
+          width: 14,
+          height: 14,
+          color: "var(--color-text)",
+        },
+      })),
+    [layout.edges],
+  );
+
+  return (
+    <ReactFlow
+      nodes={layout.nodes}
+      edges={styledEdges}
+      nodeTypes={nodeTypes}
+      edgeTypes={edgeTypes}
+      fitView
+      fitViewOptions={{ padding: 0.15 }}
+      nodesDraggable={false}
+      nodesConnectable={false}
+      elementsSelectable={false}
+      proOptions={{ hideAttribution: true }}
+      colorMode="dark"
+      style={{ background: "var(--color-bg)" }}
+    >
+      <Background color="var(--color-border)" gap={20} size={1} />
+    </ReactFlow>
+  );
+}

packages/workflow-dashboard/src/index.css

@@ -19,3 +19,17 @@ body {
   color: var(--color-text);
   font-family: "Inter", system-ui, -apple-system, sans-serif;
 }
+
+@keyframes wf-node-pulse {
+  0%,
+  100% {
+    box-shadow: 0 0 0 0 rgba(124, 109, 240, 0.55);
+  }
+  50% {
+    box-shadow: 0 0 0 6px rgba(124, 109, 240, 0);
+  }
+}
+
+.wf-node-pulse {
+  animation: wf-node-pulse 1.6s ease-in-out infinite;
+}

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

@@ -35,6 +35,7 @@ function noLogger(): (tag: string, content: string) => void {
 function makeOptions(overrides: Partial<ExecuteThreadOptions>): ExecuteThreadOptions {
   return {
     depth: 0,
+    parentStateHash: null,
     signal: new AbortController().signal,
     awaitAfterEachYield: async () => {},
     forkSourceThreadId: null,
@@ -144,9 +145,9 @@ describe("executeThread (Phase 2 — CAS thread storage)", () => {
       runtime: WorkflowRuntime,
     ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
       const h1 = await runtime.cas.put("plan-text");
-      yield { role: "planner", contentHash: h1, meta: { plan: 1 }, refs: [h1] };
+      yield { role: "planner", contentHash: h1, meta: { plan: 1 }, refs: [h1], childThread: null };
       const h2 = await runtime.cas.put("code-text");
-      yield { role: "coder", contentHash: h2, meta: { diff: "y" }, refs: [h2] };
+      yield { role: "coder", contentHash: h2, meta: { diff: "y" }, refs: [h2], childThread: null };
       return { returnCode: 0, summary: "done" };
     };
 
@@ -210,7 +211,7 @@ describe("executeThread (Phase 2 — CAS thread storage)", () => {
       runtime: WorkflowRuntime,
     ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
       const h = await runtime.cas.put("only-step");
-      yield { role: "only", contentHash: h, meta: {}, refs: [h] };
+      yield { role: "only", contentHash: h, meta: {}, refs: [h], childThread: null };
       return { returnCode: 0, summary: "completed" };
     };
 
@@ -261,7 +262,7 @@ describe("executeThread (Phase 2 — CAS thread storage)", () => {
       runtime: WorkflowRuntime,
     ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
       const h = await runtime.cas.put("step");
-      yield { role: "only", contentHash: h, meta: {}, refs: [h] };
+      yield { role: "only", contentHash: h, meta: {}, refs: [h], childThread: null };
       return { returnCode: 0, summary: "done" };
     };
 

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

@@ -46,6 +46,7 @@ describe("garbageCollectCas (mark-and-sweep)", () => {
         name: "demo",
         hash: bundleHash,
         depth: 0,
+        parentState: null,
       },
       promptHash,
     );
@@ -59,6 +60,7 @@ describe("garbageCollectCas (mark-and-sweep)", () => {
       ancestors: [],
       compact: null,
       timestamp: 1,
+      childThread: null,
     } satisfies StateNodePayload);
 
     const c2 = await putContentNodeWithRefs(cas, "c1", []);
@@ -70,6 +72,7 @@ describe("garbageCollectCas (mark-and-sweep)", () => {
       ancestors: [h1],
       compact: null,
       timestamp: 2,
+      childThread: null,
     } satisfies StateNodePayload);
 
     const ec = await putContentNodeWithRefs(cas, "", []);
@@ -81,6 +84,7 @@ describe("garbageCollectCas (mark-and-sweep)", () => {
       ancestors: [h1],
       compact: null,
       timestamp: 3,
+      childThread: null,
     } satisfies StateNodePayload);
 
     await upsertThreadEntry(bundleDir, "THREAD_AAAAAAA", {

packages/workflow-execute/__tests__/merkle-call-stack.test.ts

@@ -0,0 +1,306 @@
+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 type { CasStore } from "@uncaged/workflow-cas";
+import { createCasStore, parseCasThreadNode } from "@uncaged/workflow-cas";
+import type { StartNode, StateNode } from "@uncaged/workflow-protocol";
+import type {
+  RoleOutput,
+  ThreadContext,
+  WorkflowCompletion,
+  WorkflowFn,
+  WorkflowRuntime,
+} from "@uncaged/workflow-runtime";
+
+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 {
+    depth: 0,
+    parentStateHash: null,
+    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;
+}> {
+  const storageRoot = await mkdtemp(join(tmpdir(), "uncaged-wf-merkle-"));
+  await writeFile(join(storageRoot, "workflow.yaml"), TEST_REGISTRY_YAML, "utf8");
+  const casDir = join(storageRoot, "cas");
+  await mkdir(casDir, { recursive: true });
+  return { storageRoot, casDir };
+}
+
+async function loadStartNode(cas: CasStore, endHash: string): Promise<StartNode> {
+  const endBlob = await cas.get(endHash);
+  const endParsed = parseCasThreadNode(endBlob ?? "");
+  if (endParsed?.kind !== "state") throw new Error("expected state node");
+  const startBlob = await cas.get(endParsed.node.payload.start);
+  const startParsed = parseCasThreadNode(startBlob ?? "");
+  if (startParsed?.kind !== "start") throw new Error("expected start node");
+  return startParsed.node;
+}
+
+async function loadStateNode(cas: CasStore, hash: string): Promise<StateNode> {
+  const blob = await cas.get(hash);
+  const parsed = parseCasThreadNode(blob ?? "");
+  if (parsed?.kind !== "state") throw new Error("expected state node");
+  return parsed.node;
+}
+
+describe("Merkle call stack — cross-thread DAG linking (Phase 2)", () => {
+  let storageRoot: string;
+  let casDir: string;
+
+  beforeEach(async () => {
+    const setup = await setupStorage();
+    storageRoot = setup.storageRoot;
+    casDir = setup.casDir;
+  });
+
+  afterEach(async () => {
+    await rm(storageRoot, { recursive: true, force: true });
+  });
+
+  test("parentStateHash is written into child start node's parentState and refs", async () => {
+    const cas = createCasStore(casDir);
+
+    // biome-ignore lint/correctness/useYield: testing start-only path
+    const parentWf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      _runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      return { returnCode: 0, summary: "parent done" };
+    };
+
+    const parentResult = await executeThread(
+      parentWf,
+      "parent-wf",
+      { prompt: "parent task", steps: [] },
+      makeOptions({ storageRoot }),
+      {
+        threadId: "P_THREAD_01",
+        hash: "PARENTHASH0001",
+        infoJsonlPath: join(storageRoot, "logs", "PARENTHASH0001", "P1.info.jsonl"),
+        cas,
+      },
+      noLogger(),
+    );
+
+    // biome-ignore lint/correctness/useYield: testing start-only path
+    const childWf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      _runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      return { returnCode: 0, summary: "child done" };
+    };
+
+    const childResult = await executeThread(
+      childWf,
+      "child-wf",
+      { prompt: "child task", steps: [] },
+      makeOptions({ storageRoot, depth: 1, parentStateHash: parentResult.rootHash }),
+      {
+        threadId: "C_THREAD_01",
+        hash: "CHILDHASH00001",
+        infoJsonlPath: join(storageRoot, "logs", "CHILDHASH00001", "C1.info.jsonl"),
+        cas,
+      },
+      noLogger(),
+    );
+
+    const childStart = await loadStartNode(cas, childResult.rootHash);
+    expect(childStart.payload.parentState).toBe(parentResult.rootHash);
+    expect(childStart.refs).toContain(parentResult.rootHash);
+  });
+
+  test("childThread on parent state node points to child's final state and is in refs", async () => {
+    const cas = createCasStore(casDir);
+    const childFinalHash = "CHILD_FINAL_001";
+
+    const parentWf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      const h = await runtime.cas.put("developer output");
+      yield {
+        role: "developer",
+        contentHash: h,
+        meta: { action: "delegate" },
+        refs: [h],
+        childThread: childFinalHash,
+      };
+      return { returnCode: 0, summary: "parent complete" };
+    };
+
+    const result = await executeThread(
+      parentWf,
+      "parent-wf",
+      { prompt: "parent task", steps: [] },
+      makeOptions({ storageRoot }),
+      {
+        threadId: "P_THREAD_02",
+        hash: "CTHREAD_TEST01",
+        infoJsonlPath: join(storageRoot, "logs", "CTHREAD_TEST01", "P2.info.jsonl"),
+        cas,
+      },
+      noLogger(),
+    );
+
+    const endNode = await loadStateNode(cas, result.rootHash);
+    const devStateHash = endNode.payload.ancestors[0] ?? "";
+    const devNode = await loadStateNode(cas, devStateHash);
+
+    expect(devNode.payload.role).toBe("developer");
+    expect(devNode.payload.childThread).toBe(childFinalHash);
+    expect(devNode.refs).toContain(childFinalHash);
+  });
+
+  test("parent state with no child has childThread: null", async () => {
+    const cas = createCasStore(casDir);
+
+    const wf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      const h = await runtime.cas.put("prep output");
+      yield { role: "preparer", contentHash: h, meta: {}, refs: [h], childThread: null };
+      return { returnCode: 0, summary: "done" };
+    };
+
+    const result = await executeThread(
+      wf,
+      "test-wf",
+      { prompt: "task", steps: [] },
+      makeOptions({ storageRoot }),
+      {
+        threadId: "NULL_CT_01",
+        hash: "NULLCT_TEST001",
+        infoJsonlPath: join(storageRoot, "logs", "NULLCT_TEST001", "N1.info.jsonl"),
+        cas,
+      },
+      noLogger(),
+    );
+
+    const endNode = await loadStateNode(cas, result.rootHash);
+    const prepHash = endNode.payload.ancestors[0] ?? "";
+    const prepNode = await loadStateNode(cas, prepHash);
+
+    expect(prepNode.payload.childThread).toBeNull();
+    expect(prepNode.refs).not.toContain(null);
+  });
+
+  test("full bidirectional: child parentState is traversable to parent's context", async () => {
+    const cas = createCasStore(casDir);
+    const parentHash = "BIDIR_PARENT01";
+
+    const parentWf: WorkflowFn = async function* (
+      _thread: ThreadContext,
+      runtime: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      const h1 = await runtime.cas.put("preparation output");
+      yield {
+        role: "preparer",
+        contentHash: h1,
+        meta: { repoPath: "/test" },
+        refs: [h1],
+        childThread: null,
+      };
+      const h2 = await runtime.cas.put("developer output");
+      yield {
+        role: "developer",
+        contentHash: h2,
+        meta: { action: "code" },
+        refs: [h2],
+        childThread: "CHILD_END_HASH1",
+      };
+      return { returnCode: 0, summary: "all done" };
+    };
+
+    const observedHeads: string[] = [];
+    const opts = makeOptions({
+      storageRoot,
+      awaitAfterEachYield: async () => {
+        const bundleDir = join(storageRoot, "bundles", parentHash);
+        const text = await readFile(join(bundleDir, "threads.json"), "utf8");
+        const parsed = JSON.parse(text) as Record<string, { head: string }>;
+        const head = parsed.BIDIR_T_001?.head ?? null;
+        if (head !== null) observedHeads.push(head);
+      },
+    });
+
+    await executeThread(
+      parentWf,
+      "bidir-wf",
+      { prompt: "bidir test", steps: [] },
+      opts,
+      {
+        threadId: "BIDIR_T_001",
+        hash: parentHash,
+        infoJsonlPath: join(storageRoot, "logs", parentHash, "BD1.info.jsonl"),
+        cas,
+      },
+      noLogger(),
+    );
+
+    expect(observedHeads.length).toBe(2);
+    const preparerStateHash = observedHeads[0] ?? "";
+
+    // Execute child with parentState pointing to parent's preparer state
+    // biome-ignore lint/correctness/useYield: testing start-only path
+    const childWf: WorkflowFn = async function* (
+      _t: ThreadContext,
+      _r: WorkflowRuntime,
+    ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
+      return { returnCode: 0, summary: "child ok" };
+    };
+
+    const childResult = await executeThread(
+      childWf,
+      "bidir-child",
+      { prompt: "child bidir", steps: [] },
+      makeOptions({ storageRoot, depth: 1, parentStateHash: preparerStateHash }),
+      {
+        threadId: "BIDIR_C_001",
+        hash: "BIDIR_CHILD001",
+        infoJsonlPath: join(storageRoot, "logs", "BIDIR_CHILD001", "BC1.info.jsonl"),
+        cas,
+      },
+      noLogger(),
+    );
+
+    // Upward traversal: child start → parentState → preparer state → meta.repoPath
+    const childStart = await loadStartNode(cas, childResult.rootHash);
+    expect(childStart.payload.parentState).toBe(preparerStateHash);
+
+    const parentPrep = await loadStateNode(cas, preparerStateHash);
+    expect(parentPrep.payload.meta.repoPath).toBe("/test");
+  });
+});

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

@@ -94,6 +94,7 @@ async function appendStateForStep(params: {
   meta: Record<string, unknown>;
   refs: readonly string[];
   timestamp: number;
+  childThread: string | null;
 }): Promise<{ stateHash: string; chain: ChainState }> {
   const text = await getContentMerklePayload(params.cas, params.contentHash);
   if (text === null) {
@@ -112,6 +113,7 @@ async function appendStateForStep(params: {
     ancestors,
     compact: null,
     timestamp: params.timestamp,
+    childThread: params.childThread,
   };
   const stateHash = await putStateNode(params.cas, payload);
   return {
@@ -137,6 +139,7 @@ async function appendEndState(params: {
     ancestors,
     compact: null,
     timestamp: params.timestamp,
+    childThread: null,
   };
   return putStateNode(params.cas, payload);
 }
@@ -329,6 +332,7 @@ async function driveWorkflowGenerator(params: {
       meta: step.meta,
       refs: step.refs,
       timestamp: ts,
+      childThread: step.childThread ?? null,
     });
     chain = written_.chain;
     await publishHead({ bundleDir, threadId, startHash, headHash: written_.stateHash });
@@ -439,6 +443,7 @@ export async function executeThread(
         name: workflowName,
         hash: io.hash,
         depth: options.depth,
+        parentState: options.parentStateHash,
       },
       promptHash,
     );
@@ -466,6 +471,7 @@ export async function executeThread(
         meta: row.meta,
         refs: row.refs,
         timestamp: row.timestamp,
+        childThread: null,
       });
       chain = written.chain;
       await publishHead({
@@ -487,6 +493,7 @@ export async function executeThread(
   const thread: ThreadContext = {
     threadId: io.threadId,
     depth: options.depth,
+    bundleHash: io.hash,
     start: {
       role: START,
       content: input.prompt,

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

@@ -144,6 +144,7 @@ async function payloadToRoleOutput(cas: CasStore, payload: StateNodePayload): Pr
     contentHash: payload.content,
     meta: payload.meta,
     refs,
+    childThread: payload.childThread,
   };
 }
 
@@ -240,6 +241,7 @@ async function buildForkContinuation(params: {
     ancestors: ancestorsMarker,
     compact: null,
     timestamp: Date.now(),
+    childThread: null,
   };
   const markerHash = await putStateNode(cas, markerPayload);
 

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

@@ -41,6 +41,8 @@ export type PrefilledDiskStep = {
 export type ExecuteThreadOptions = {
   /** Passed to the bundle thread context as `ThreadContext.depth`. */
   depth: number;
+  /** Parent thread's head state hash at spawn time; `null` for top-level threads. */
+  parentStateHash: string | null;
   signal: AbortSignal;
   /** Invoked after each successful yield (and outer-loop checks); used for pause/resume. */
   awaitAfterEachYield: () => Promise<void>;

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

@@ -72,11 +72,13 @@ function parseRoleOutputRecord(obj: Record<string, unknown>): RoleOutput | null
   if (meta === null || typeof meta !== "object") {
     return null;
   }
+  const childThread = obj.childThread;
   return {
     role,
     contentHash,
     meta: meta as Record<string, unknown>,
     refs: normalizeRefsField(obj.refs),
+    childThread: typeof childThread === "string" ? childThread : null,
   };
 }
 
@@ -497,6 +499,7 @@ async function main(): Promise<void> {
         { prompt: cmd.prompt, steps: cmd.steps },
         {
           ...cmd.options,
+          parentStateHash: null,
           signal: ac.signal,
           awaitAfterEachYield: () => pauseGate.awaitAfterYield(),
           forkSourceThreadId: cmd.forkSourceThreadId,

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

@@ -6,7 +6,7 @@ import {
   getRegisteredWorkflow,
   readWorkflowRegistry,
 } from "@uncaged/workflow-register";
-import type { AgentContext, AgentFn } from "@uncaged/workflow-runtime";
+import type { AgentContext, AgentFn, AgentFnResult } from "@uncaged/workflow-runtime";
 import {
   createLogger,
   generateUlid,
@@ -14,7 +14,7 @@ import {
   getGlobalCasDir,
 } from "@uncaged/workflow-util";
 import type { ExecuteThreadIo } from "./engine/index.js";
-import { executeThread } from "./engine/index.js";
+import { executeThread, getBundleDir, readThreadsIndex } from "./engine/index.js";
 
 const DEFAULT_WORKFLOW_AS_AGENT_MAX_DEPTH = 3;
 
@@ -37,6 +37,13 @@ function resolveWorkflowAsAgentStorageRoot(options: WorkflowAsAgentOptions | nul
   return getDefaultWorkflowStorageRoot();
 }
 
+async function readParentHeadState(storageRoot: string, ctx: AgentContext): Promise<string | null> {
+  const bundleDir = getBundleDir(storageRoot, ctx.bundleHash);
+  const index = await readThreadsIndex(bundleDir);
+  const entry = index[ctx.threadId] ?? null;
+  return entry !== null ? entry.head : null;
+}
+
 /**
  * Returns an {@link AgentFn} that runs another registered workflow in a new thread,
  * using the parent thread's initial prompt (`ctx.start.content`) as the child prompt.
@@ -45,7 +52,7 @@ export function workflowAsAgent(
   workflowName: string,
   options: WorkflowAsAgentOptions | null = null,
 ): AgentFn {
-  return async (ctx: AgentContext): Promise<string> => {
+  return async (ctx: AgentContext): Promise<AgentFnResult> => {
     const nextDepth = ctx.depth + 1;
 
     const storageRoot = resolveWorkflowAsAgentStorageRoot(options);
@@ -89,6 +96,8 @@ export function workflowAsAgent(
     const logger = createLogger({ sink: { kind: "file", path: infoJsonlPath } });
     const signalNever = new AbortController();
 
+    const parentHeadState = await readParentHeadState(storageRoot, ctx);
+
     try {
       const result = await executeThread(
         bundleExportsResult.value.run,
@@ -96,6 +105,7 @@ export function workflowAsAgent(
         input,
         {
           depth: nextDepth,
+          parentStateHash: parentHeadState,
           signal: signalNever.signal,
           awaitAfterEachYield: async () => {},
           forkSourceThreadId: ctx.threadId,
@@ -107,7 +117,8 @@ export function workflowAsAgent(
         io,
         logger,
       );
-      return `Child workflow "${workflowName}" completed (returnCode=${result.returnCode}).\n\nSummary: ${result.summary}\n\nChild thread root hash: ${result.rootHash}`;
+      const summary = `Child workflow "${workflowName}" completed (returnCode=${result.returnCode}).\n\nSummary: ${result.summary}\n\nChild thread root hash: ${result.rootHash}`;
+      return { output: summary, childThread: result.rootHash };
     } catch (e) {
       const message = e instanceof Error ? e.message : String(e);
       return `ERROR: ${message}`;

packages/workflow-protocol/__tests__/moderator-table.test.ts

@@ -21,6 +21,7 @@ function makeCtx(roles: (keyof TestMeta & string)[]): ModeratorContext<TestMeta>
   return {
     threadId: "test-thread",
     depth: 0,
+    bundleHash: "TESTHASH00001",
     start: {
       role: START,
       content: "test",

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

@@ -4,6 +4,8 @@ export type StartNodePayload = {
   name: string;
   hash: string;
   depth: number;
+  /** Parent thread's head state hash at spawn time. `null` for top-level workflows. */
+  parentState: string | null;
 };
 
 export type StartNode = {
@@ -20,6 +22,8 @@ export type StateNodePayload = {
   ancestors: string[];
   compact: string | null;
   timestamp: number;
+  /** Child thread's final state hash (workflow-as-agent). `null` when no child spawned. */
+  childThread: string | null;
 };
 
 export type StateNode = {

packages/workflow-protocol/src/index.ts

@@ -13,6 +13,7 @@ export type {
   AgentBinding,
   AgentContext,
   AgentFn,
+  AgentFnResult,
   CasStore,
   ExtractFn,
   ExtractResult,

packages/workflow-protocol/src/types.ts

@@ -54,6 +54,7 @@ export type RoleOutput = {
   contentHash: string;
   meta: Record<string, unknown>;
   refs: string[];
+  childThread: string | null;
 };
 
 export type StartStep = {
@@ -76,6 +77,7 @@ export type RoleStep<M extends RoleMeta> = {
 export type ThreadContext<M extends RoleMeta = RoleMeta> = {
   threadId: string;
   depth: number;
+  bundleHash: string;
   start: StartStep;
   steps: RoleStep<M>[];
 };
@@ -140,7 +142,9 @@ export type ExtractFn = <T extends Record<string, unknown>>(
   contentHash: string,
 ) => Promise<ExtractResult<T>>;
 
-export type AgentFn = (ctx: AgentContext) => Promise<string>;
+export type AgentFnResult = string | { output: string; childThread: string | null };
+
+export type AgentFn = (ctx: AgentContext) => Promise<AgentFnResult>;
 
 export type AgentBinding = {
   agent: AgentFn;

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

@@ -27,7 +27,7 @@ describe("buildThreadContext", () => {
     const bundleHash = "BHAAAAAAAAAAA";
     const startHash = await putStartNode(
       cas,
-      { name: "demo", hash: bundleHash, depth: 2 },
+      { name: "demo", hash: bundleHash, depth: 2, parentState: null },
       promptHash,
     );
 
@@ -41,6 +41,7 @@ describe("buildThreadContext", () => {
       ancestors: [],
       compact: null,
       timestamp: 1000,
+      childThread: null,
     });
 
     const chCode = await putContentNodeWithRefs(cas, "code body", []);
@@ -52,6 +53,7 @@ describe("buildThreadContext", () => {
       ancestors: [statePlan],
       compact: null,
       timestamp: 2000,
+      childThread: null,
     });
 
     const ctx = await buildThreadContext(stateCode, cas);
@@ -71,7 +73,7 @@ describe("buildThreadContext", () => {
     const promptHash = await cas.put("only-prompt");
     const startHash = await putStartNode(
       cas,
-      { name: "solo", hash: "BHBBBBBBBBBBB", depth: 1 },
+      { name: "solo", hash: "BHBBBBBBBBBBB", depth: 1, parentState: null },
       promptHash,
     );
 
@@ -87,7 +89,7 @@ describe("buildThreadContext", () => {
     const bundleHash = "BHCCCCCCCCCCC";
     const startHash = await putStartNode(
       cas,
-      { name: "demo", hash: bundleHash, depth: 0 },
+      { name: "demo", hash: bundleHash, depth: 0, parentState: null },
       promptHash,
     );
 
@@ -100,6 +102,7 @@ describe("buildThreadContext", () => {
       ancestors: [],
       compact: null,
       timestamp: 500,
+      childThread: null,
     });
 
     const endContent = await putContentNodeWithRefs(cas, "finished", []);
@@ -111,6 +114,7 @@ describe("buildThreadContext", () => {
       ancestors: [state1],
       compact: null,
       timestamp: 600,
+      childThread: null,
     });
 
     const ctx = await buildThreadContext(endState, cas);

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

@@ -54,6 +54,7 @@ async function threadFromStartHead<M extends RoleMeta>(
   return {
     threadId: "",
     depth: p.depth,
+    bundleHash: p.hash,
     start: {
       role: START,
       content: prompt,
@@ -113,6 +114,7 @@ async function threadFromStateHead<M extends RoleMeta>(
   return {
     threadId: "",
     depth: sp.depth,
+    bundleHash: sp.hash,
     start: {
       role: START,
       content: prompt,

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

@@ -7,6 +7,7 @@ import {
   type AgentBinding,
   type AgentContext,
   type AgentFn,
+  type AgentFnResult,
   END,
   type ModeratorContext,
   type RoleDefinition,
@@ -50,6 +51,16 @@ function mergeUniqueHashes(a: readonly string[], b: readonly string[]): string[]
   return out;
 }
 
+function normalizeAgentResult(result: AgentFnResult): {
+  output: string;
+  childThread: string | null;
+} {
+  if (typeof result === "string") {
+    return { output: result, childThread: null };
+  }
+  return result;
+}
+
 function agentForRole(binding: AgentBinding, roleName: string): AgentFn {
   const overrides = binding.overrides;
   const overrideFn: AgentFn | undefined =
@@ -89,9 +100,9 @@ async function advanceOneRound<M extends RoleMeta>(
   };
 
   const agent = agentForRole(binding, next);
-  const raw = await agent(agentCtx as unknown as AgentContext);
+  const agentResult = normalizeAgentResult(await agent(agentCtx as unknown as AgentContext));
 
-  const agentContentHash = await putContentNodeWithRefs(runtime.cas, raw, []);
+  const agentContentHash = await putContentNodeWithRefs(runtime.cas, agentResult.output, []);
 
   const extracted = await runtime.extract(
     roleDef.schema as z.ZodType<Record<string, unknown>>,
@@ -125,6 +136,7 @@ async function advanceOneRound<M extends RoleMeta>(
       contentHash: step.contentHash,
       meta: step.meta,
       refs: step.refs,
+      childThread: agentResult.childThread,
     },
     step,
   };

packages/workflow-runtime/src/index.ts

@@ -5,6 +5,7 @@ export type {
   AgentBinding,
   AgentContext,
   AgentFn,
+  AgentFnResult,
   CasStore,
   ExtractFn,
   ExtractResult,

packages/workflow-runtime/src/types.ts

@@ -7,6 +7,7 @@ export type {
   AgentBinding,
   AgentContext,
   AgentFn,
+  AgentFnResult,
   CasStore,
   ExtractFn,
   ExtractResult,

packages/workflow-template-develop/__tests__/develop-template.test.ts

@@ -29,6 +29,7 @@ function makeCtx(steps: ModeratorContext<DevelopMeta>["steps"]): ModeratorContex
   return {
     threadId: "01TEST000000000000000000TR",
     depth: 0,
+    bundleHash: "TESTHASH00001",
     start: makeStart(),
     steps,
   };

packages/workflow-template-solve-issue/__tests__/solve-issue-template.test.ts

@@ -116,6 +116,7 @@ function makeCtx(
   return {
     threadId: "01TEST000000000000000000TR",
     depth: 0,
+    bundleHash: "TESTHASH00001",
     start: makeStart(),
     steps,
   };
@@ -181,6 +182,7 @@ function makeThread(prompt: string) {
   return {
     threadId: "01TEST000000000000000000TR",
     depth: 0,
+    bundleHash: "TESTHASH00001",
     start: {
       role: START,
       content: prompt,

packages/workflow-util-agent/__tests__/build-agent-prompt.test.ts

@@ -17,6 +17,7 @@ describe("buildAgentPrompt", () => {
     const ctx: AgentContext = {
       start: startTask("fix the bug"),
       depth: 0,
+      bundleHash: "TESTHASH00001",
       steps: [],
       threadId: "01TEST000000000000000000TR",
       currentRole: { name: START, systemPrompt: "You are an agent." },
@@ -33,6 +34,7 @@ describe("buildAgentPrompt", () => {
     const ctx: AgentContext = {
       start: startTask("user task"),
       depth: 0,
+      bundleHash: "TESTHASH00001",
       threadId: "01TEST000000000000000000TR",
       currentRole: { name: "coder", systemPrompt: "Be helpful." },
       steps: [
@@ -61,6 +63,7 @@ describe("buildAgentPrompt", () => {
     const ctx: AgentContext = {
       start: startTask("first message full: task content here"),
       depth: 0,
+      bundleHash: "TESTHASH00001",
       threadId: "01TEST000000000000000000TR",
       currentRole: { name: "coder", systemPrompt: "System." },
       steps: [
@@ -99,6 +102,7 @@ describe("buildAgentPrompt", () => {
     const ctx: AgentContext = {
       start: startTask("start"),
       depth: 0,
+      bundleHash: "TESTHASH00001",
       threadId: "01TEST000000000000000000TR",
       currentRole: { name: "c", systemPrompt: "S" },
       steps: [