diff --git a/packages/cli-workflow/src/commands/init/workspace.ts b/packages/cli-workflow/src/commands/init/workspace.ts
index 16c3f87..ba6acae 100644
--- a/packages/cli-workflow/src/commands/init/workspace.ts
+++ b/packages/cli-workflow/src/commands/init/workspace.ts
@@ -107,7 +107,7 @@ Init 生成的骨架：\`templates/\` 下放可复用定义，\`workflows/\` 下
 2. **编写 RoleDefinition**：为每个角色写 Zod \`schema\`，补齐 \`systemPrompt\` / \`extractPrompt\` / \`description\`。
 3. **编写 Moderator**：根据 \`ctx.steps\` 与业务状态返回下一个角色名或 \`END\`。
 4. **组装 WorkflowDefinition**：在模板 \`index\` 中导出 definition（以及必要的角色 / moderator 导出）。
-5. **实例化**：在 workflow 包中使用 \`createWorkflow(def, binding)\`（或项目约定的封装）绑定 **AgentFn**；**ExtractFn** 由引擎从 **workflow.yaml** 注入 \`WorkflowFnOptions\`。
+5. **实例化**：在 workflow 包中使用 \`createWorkflow(def, binding)\`（或项目约定的封装）绑定 **AgentFn**；**ExtractFn** 由引擎从 **workflow.yaml** 注入 \`WorkflowRuntime\`。
 6. **构建**：打包为单个 **.esm.js** bundle，使用 **uncaged-workflow add** 注册。
 
 ## 4. 编码规范
diff --git a/packages/workflow-agent-llm/__tests__/create-llm-adapter.test.ts b/packages/workflow-agent-llm/__tests__/create-llm-adapter.test.ts
index 6459909..0065f40 100644
--- a/packages/workflow-agent-llm/__tests__/create-llm-adapter.test.ts
+++ b/packages/workflow-agent-llm/__tests__/create-llm-adapter.test.ts
@@ -3,14 +3,14 @@ import { mkdtempSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { createCasStore } from "@uncaged/workflow";
-import { START, type ThreadContext } from "@uncaged/workflow-runtime";
+import { START, type AgentContext } from "@uncaged/workflow-runtime";
 
 import { createLlmAdapter } from "../src/create-llm-adapter.js";
 
 const casDir = mkdtempSync(join(tmpdir(), "wf-llm-adapter-cas-"));
 const testCas = createCasStore(casDir);
 
-function makeCtx(userContent: string): ThreadContext {
+function makeCtx(userContent: string): AgentContext {
   return {
     start: {
       role: START,
diff --git a/packages/workflow-runtime/src/engine/create-workflow.ts b/packages/workflow-runtime/src/engine/create-workflow.ts
index 8be5ded..4da2983 100644
--- a/packages/workflow-runtime/src/engine/create-workflow.ts
+++ b/packages/workflow-runtime/src/engine/create-workflow.ts
@@ -13,11 +13,11 @@ import {
   type RoleOutput,
   type RoleStep,
   START,
-  type ThreadInput,
+  type ThreadContext,
   type WorkflowCompletion,
   type WorkflowDefinition,
   type WorkflowFn,
-  type WorkflowFnOptions,
+  type WorkflowRuntime,
 } from "../types.js";
 import { mergeRefsWithContentHash } from "../util/index.js";
 
@@ -57,18 +57,12 @@ async function advanceOneRound<M extends RoleMeta>(
   def: Pick<WorkflowDefinition<M>, "roles" | "moderator">,
   binding: AgentBinding,
   params: {
-    start: ModeratorContext<M>["start"];
-    steps: RoleStep<M>[];
-    options: WorkflowFnOptions;
+    thread: ModeratorContext<M>;
+    runtime: WorkflowRuntime;
   },
 ): Promise<AdvanceOutcome<M>> {
-  const { start, steps, options } = params;
-  const modCtx: ModeratorContext<M> = {
-    threadId: options.threadId,
-    depth: options.depth,
-    start,
-    steps,
-  };
+  const { thread, runtime } = params;
+  const modCtx: ModeratorContext<M> = thread;
 
   const next = def.moderator(modCtx);
   if (!isRoleNext(next)) {
@@ -86,7 +80,7 @@ async function advanceOneRound<M extends RoleMeta>(
   const agentCtx: AgentContext<M> = {
     ...modCtx,
     currentRole: { name: next, systemPrompt: roleDef.systemPrompt },
-    cas: options.cas,
+    cas: runtime.cas,
   };
 
   const agent = agentForRole(binding, next);
@@ -97,13 +91,13 @@ async function advanceOneRound<M extends RoleMeta>(
     agentContent: raw,
   };
 
-  const meta = await options.extract(
-    roleDef.schema as unknown as z.ZodType<Record<string, unknown>>,
+  const meta = await runtime.extract(
+    roleDef.schema as z.ZodType<Record<string, unknown>>,
     roleDef.extractPrompt,
     extractCtx as unknown as ExtractContext,
   );
 
-  const contentHash = await putContentBlob(options.cas, raw);
+  const contentHash = await putContentBlob(runtime.cas, raw);
   const refs = mergeRefsWithContentHash(
     resolveExtractedRefs(roleDef as unknown as RoleDefinition<Record<string, unknown>>, meta),
     contentHash,
@@ -133,7 +127,7 @@ async function advanceOneRound<M extends RoleMeta>(
  * Binds pure role definitions + moderator to runtime agents.
  * Assign with `export const run = createWorkflow(def, binding)`.
  *
- * Structured meta extraction is delegated to {@link WorkflowFnOptions.extract}, which the
+ * Structured meta extraction is delegated to {@link WorkflowRuntime.extract}, which the
  * engine resolves from the workflow registry's `extract` scene.
  */
 export function createWorkflow<M extends RoleMeta>(
@@ -141,38 +135,26 @@ export function createWorkflow<M extends RoleMeta>(
   binding: AgentBinding,
 ): WorkflowFn {
   return async function* workflowLoop(
-    input: ThreadInput,
-    options: WorkflowFnOptions,
+    thread: ThreadContext,
+    runtime: WorkflowRuntime,
   ): AsyncGenerator<RoleOutput, WorkflowCompletion> {
-    const nowMs = Date.now();
-    const start: ModeratorContext<M>["start"] = {
-      role: START,
-      content: input.prompt,
-      meta: { maxRounds: options.maxRounds },
-      timestamp: nowMs,
-    };
-
-    const baseTs = Date.now();
-    let steps: RoleStep<M>[] = input.steps.map((out, i) => ({
-      role: out.role,
-      contentHash: out.contentHash,
-      meta: out.meta,
-      refs: out.refs,
-      timestamp: baseTs + i,
-    })) as RoleStep<M>[];
+    if (thread.start.role !== START) {
+      throw new Error(`workflow loop expected start role to be ${START}`);
+    }
+    const maxRounds = thread.start.meta.maxRounds;
+    let currentThread = thread as ModeratorContext<M>;
 
     while (true) {
-      if (steps.length >= options.maxRounds) {
+      if (currentThread.steps.length >= maxRounds) {
         return {
           returnCode: 0,
-          summary: `completed: reached maxRounds (${options.maxRounds})`,
+          summary: `completed: reached maxRounds (${maxRounds})`,
         };
       }
 
       const outcome = await advanceOneRound(def, binding, {
-        start,
-        steps,
-        options,
+        thread: currentThread,
+        runtime,
       });
 
       if (outcome.kind === "complete") {
@@ -180,7 +162,10 @@ export function createWorkflow<M extends RoleMeta>(
       }
 
       yield outcome.output;
-      steps = [...steps, outcome.step];
+      currentThread = {
+        ...currentThread,
+        steps: [...currentThread.steps, outcome.step],
+      };
     }
   };
 }
diff --git a/packages/workflow-runtime/src/index.ts b/packages/workflow-runtime/src/index.ts
index 9fa7afa..f853d5e 100644
--- a/packages/workflow-runtime/src/index.ts
+++ b/packages/workflow-runtime/src/index.ts
@@ -21,11 +21,10 @@ export type {
   RoleStep,
   StartStep,
   ThreadContext,
-  ThreadInput,
   WorkflowCompletion,
   WorkflowDefinition,
   WorkflowFn,
-  WorkflowFnOptions,
+  WorkflowRuntime,
   WorkflowResult,
 } from "./types.js";
 export { END, START } from "./types.js";
diff --git a/packages/workflow-runtime/src/types.ts b/packages/workflow-runtime/src/types.ts
index 5142874..68caefb 100644
--- a/packages/workflow-runtime/src/types.ts
+++ b/packages/workflow-runtime/src/types.ts
@@ -38,18 +38,8 @@ export type WorkflowResult = WorkflowCompletion & {
   rootHash: string;
 };
 
-/** Input to a workflow — prompt plus optional historical steps for fork/resume. */
-export type ThreadInput = {
-  prompt: string;
-  steps: RoleOutput[];
-};
-
-/** Options passed to a workflow bundle's `run` export (engine-provided). */
-export type WorkflowFnOptions = {
-  threadId: string;
-  maxRounds: number;
-  /** Nesting depth for workflow-as-agent chains; root threads use `0`. */
-  depth: number;
+/** Runtime dependencies passed to a workflow bundle's `run` export (engine-provided). */
+export type WorkflowRuntime = {
   /** Global CAS store for Merkle content blobs (role step bodies). */
   cas: CasStore;
   /** Structured meta extraction; resolved from workflow.yaml `extract` scene by the engine. */
@@ -58,8 +48,8 @@ export type WorkflowFnOptions = {
 
 /** Bundle contract — named export `run` is a function returning an AsyncGenerator. */
 export type WorkflowFn = (
-  input: ThreadInput,
-  options: WorkflowFnOptions,
+  thread: ThreadContext,
+  runtime: WorkflowRuntime,
 ) => AsyncGenerator<RoleOutput, WorkflowCompletion>;
 
 /** Engine start frame: initial prompt + thread identity. */
@@ -81,15 +71,18 @@ export type RoleStep<M extends RoleMeta> = {
   };
 }[keyof M & string];
 
-/** Phase 1: Moderator decides next role. */
-export type ModeratorContext<M extends RoleMeta = RoleMeta> = {
+/** Thread runtime context shared by moderator/agent/extractor phases. */
+export type ThreadContext<M extends RoleMeta = RoleMeta> = {
   threadId: string;
-  /** Same as `WorkflowFnOptions.depth` for the active thread. */
+  /** Nesting depth for workflow-as-agent chains; root threads use `0`. */
   depth: number;
   start: StartStep;
   steps: RoleStep<M>[];
 };
 
+/** Phase 1: Moderator decides next role. */
+export type ModeratorContext<M extends RoleMeta = RoleMeta> = ThreadContext<M>;
+
 /** Phase 2: Agent executes — knows its role and prompt. */
 export type AgentContext<M extends RoleMeta = RoleMeta> = ModeratorContext<M> & {
   currentRole: {
@@ -104,9 +97,6 @@ export type ExtractContext<M extends RoleMeta = RoleMeta> = AgentContext<M> & {
   agentContent: string;
 };
 
-/** Alias — most external consumers see the agent-phase context. */
-export type ThreadContext<M extends RoleMeta = RoleMeta> = AgentContext<M>;
-
 /** Raw string output from an LLM/CLI adapter; meta is extracted by the engine. */
 export type AgentFn = (ctx: AgentContext) => Promise<string>;
 
diff --git a/packages/workflow-template-develop/README.md b/packages/workflow-template-develop/README.md
index 614d991..5b75815 100644
--- a/packages/workflow-template-develop/README.md
+++ b/packages/workflow-template-develop/README.md
@@ -2,7 +2,7 @@
 
 Reference **develop** workflow template: plan phases, implement in a loop, review, test, then commit.
 
-Export a `WorkflowDefinition` and `createDevelopRun` so a host can bind agents/LLM and run the same graph the bundled `.esm.js` would use. Use `buildDevelopDescriptor()` when assembling `descriptor` metadata for a bundle.
+Export a pure `WorkflowDefinition` (`developWorkflowDefinition`) and role/moderator pieces. Workflow instantiation (`createWorkflow(definition, binding)`) happens in the workflow instance layer, not in this template package.
 
 ## Install
 
@@ -15,10 +15,10 @@ In this monorepo: `workspace:*` for `@uncaged/workflow-template-develop` and `@u
 ## Usage
 
 ```typescript
-import { createDevelopRun, developWorkflowDefinition } from "@uncaged/workflow-template-develop";
+import { createWorkflow } from "@uncaged/workflow";
+import { developWorkflowDefinition } from "@uncaged/workflow-template-develop";
 
-const run = createDevelopRun(binding);
-// run(...) executes the develop moderator graph with your AgentBinding
+const run = createWorkflow(developWorkflowDefinition, binding);
 ```
 
 ## Roles
@@ -46,7 +46,6 @@ Also exported: role factories/meta schemas (`plannerRole`, `coderRole`, …), `D
 
 | Export | Description |
 |--------|-------------|
-| `createDevelopRun` | `createWorkflow(developWorkflowDefinition, …)` factory |
 | `developWorkflowDefinition` | `description`, `roles`, `developModerator` |
 | `developModerator` | `Moderator<DevelopMeta>` |
 | `buildDevelopDescriptor` | `buildDescriptor({ … })` for bundle metadata |
diff --git a/packages/workflow-template-develop/src/index.ts b/packages/workflow-template-develop/src/index.ts
index 1f307f7..64937b3 100644
--- a/packages/workflow-template-develop/src/index.ts
+++ b/packages/workflow-template-develop/src/index.ts
@@ -1,5 +1,4 @@
-import { createWorkflow } from "@uncaged/workflow";
-import type { AgentBinding, WorkflowDefinition, WorkflowFn } from "@uncaged/workflow-runtime";
+import type { WorkflowDefinition } from "@uncaged/workflow-runtime";
 
 import { developModerator } from "./moderator.js";
 import { DEVELOP_WORKFLOW_DESCRIPTION, type DevelopMeta, developRoles } from "./roles.js";
@@ -36,7 +35,3 @@ export const developWorkflowDefinition: WorkflowDefinition<DevelopMeta> = {
   roles: developRoles,
   moderator: developModerator,
 };
-
-export function createDevelopRun(binding: AgentBinding): WorkflowFn {
-  return createWorkflow(developWorkflowDefinition, binding);
-}
diff --git a/packages/workflow-template-solve-issue/README.md b/packages/workflow-template-solve-issue/README.md
index f5f056c..7d55e44 100644
--- a/packages/workflow-template-solve-issue/README.md
+++ b/packages/workflow-template-solve-issue/README.md
@@ -2,7 +2,7 @@
 
 Reference **solve-issue** workflow template: prepare a repo, delegate implementation to the **develop** workflow, then submit (e.g. open a PR).
 
-`createSolveIssueRun` wires the `developer` role to `workflowAsAgent("develop")` by default; `binding.overrides.developer` wins if you pass one (for tests or custom hosts).
+This package exports a pure `WorkflowDefinition` (`solveIssueWorkflowDefinition`). Workflow instantiation (`createWorkflow(definition, binding)`) and any role-specific agent wiring (for example delegating `developer` to `workflowAsAgent("develop")`) are done in the workflow instance layer.
 
 ## Install
 
@@ -15,9 +15,10 @@ In this monorepo: `workspace:*` for this package and `@uncaged/workflow`.
 ## Usage
 
 ```typescript
-import { createSolveIssueRun, solveIssueWorkflowDefinition } from "@uncaged/workflow-template-solve-issue";
+import { createWorkflow } from "@uncaged/workflow";
+import { solveIssueWorkflowDefinition } from "@uncaged/workflow-template-solve-issue";
 
-const run = createSolveIssueRun(binding);
+const run = createWorkflow(solveIssueWorkflowDefinition, binding);
 ```
 
 ## Roles
@@ -41,7 +42,6 @@ Also exported: `preparerRole`, `developerRole`, `submitterRole` and their Zod me
 
 | Export | Description |
 |--------|-------------|
-| `createSolveIssueRun` | Merges `developer` override with `workflowAsAgent("develop")`, then `createWorkflow` |
 | `solveIssueWorkflowDefinition` | `description`, `roles`, `solveIssueModerator` |
 | `solveIssueModerator` | Linear `Moderator<SolveIssueMeta>` |
 | `buildSolveIssueDescriptor` | Descriptor helper for bundles |
diff --git a/packages/workflow-template-solve-issue/__tests__/solve-issue-template.test.ts b/packages/workflow-template-solve-issue/__tests__/solve-issue-template.test.ts
index 2ea355c..b38298c 100644
--- a/packages/workflow-template-solve-issue/__tests__/solve-issue-template.test.ts
+++ b/packages/workflow-template-solve-issue/__tests__/solve-issue-template.test.ts
@@ -2,7 +2,7 @@ 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, createExtract } from "@uncaged/workflow";
+import { createCasStore, createExtract, createWorkflow } from "@uncaged/workflow";
 import {
   END,
   type ModeratorContext,
@@ -12,7 +12,7 @@ import {
 } from "@uncaged/workflow-runtime";
 import { buildSolveIssueDescriptor } from "../src/descriptor.js";
 import type { DeveloperMeta } from "../src/developer.js";
-import { createSolveIssueRun, solveIssueModerator } from "../src/index.js";
+import { solveIssueModerator, solveIssueWorkflowDefinition } from "../src/index.js";
 import type { PreparerMeta, SubmitterMeta } from "../src/roles/index.js";
 import type { SolveIssueMeta } from "../src/roles.js";
 
@@ -123,6 +123,20 @@ const stubExtract = createExtract({
   model: "test",
 });
 
+function makeThread(prompt: string) {
+  return {
+    threadId: "01TEST000000000000000000TR",
+    depth: 0,
+    start: {
+      role: START,
+      content: prompt,
+      meta: { maxRounds: 20 },
+      timestamp: Date.now(),
+    },
+    steps: [],
+  };
+}
+
 describe("solveIssueModerator", () => {
   test("routes initial → preparer → developer → submitter → END", () => {
     expect(solveIssueModerator(makeCtx(20, []))).toBe("preparer");
@@ -169,7 +183,7 @@ describe("solveIssueModerator", () => {
   });
 });
 
-describe("createSolveIssueRun", () => {
+describe("solveIssueWorkflowDefinition + createWorkflow", () => {
   let restoreFetch: (() => void) | null = null;
   let casDir: string | undefined;
 
@@ -199,17 +213,13 @@ describe("createSolveIssueRun", () => {
     casDir = await mkdtemp(join(tmpdir(), "solve-issue-cas-"));
     const cas = createCasStore(casDir);
 
-    // Override developer so the test does not spin up a child workflow.
-    const run = createSolveIssueRun({
+    const run = createWorkflow(solveIssueWorkflowDefinition, {
       agent: async () => "",
       overrides: { developer: async () => "stub-root-hash" },
     });
     const gen = run(
-      { prompt: "task", steps: [] },
+      makeThread("task"),
       {
-        threadId: "01TEST000000000000000000TR",
-        maxRounds: 20,
-        depth: 0,
         cas,
         extract: stubExtract,
       },
@@ -246,7 +256,7 @@ describe("createSolveIssueRun", () => {
     const cas = createCasStore(casDir);
 
     const calls: string[] = [];
-    const run = createSolveIssueRun({
+    const run = createWorkflow(solveIssueWorkflowDefinition, {
       agent: async () => {
         calls.push("default");
         return "";
@@ -267,11 +277,8 @@ describe("createSolveIssueRun", () => {
       },
     });
     const gen = run(
-      { prompt: "task", steps: [] },
+      makeThread("task"),
       {
-        threadId: "01TEST000000000000000000TR",
-        maxRounds: 20,
-        depth: 0,
         cas,
         extract: stubExtract,
       },
@@ -288,56 +295,6 @@ describe("createSolveIssueRun", () => {
     expect(calls).toEqual(["submitter"]);
   });
 
-  test("developer defaults to workflowAsAgent override (caller override still wins)", async () => {
-    const PREPARER_META: PreparerMeta = {
-      repoPath: "/tmp/r",
-      defaultBranch: "main",
-      conventions: null,
-      toolchain: { packageManager: null, testCommand: null, lintCommand: null, buildCommand: null },
-    };
-    const DEVELOPER_META: DeveloperMeta = {
-      branch: "feat/y",
-      commitSha: "def5678",
-      filesChanged: ["b.ts"],
-      summary: "more work",
-    };
-    restoreFetch = installMockChatCompletions([PREPARER_META, DEVELOPER_META]);
-
-    casDir = await mkdtemp(join(tmpdir(), "solve-issue-cas-"));
-    const cas = createCasStore(casDir);
-
-    let developerInvocations = 0;
-    const run = createSolveIssueRun({
-      agent: async () => "",
-      overrides: {
-        developer: async () => {
-          developerInvocations += 1;
-          return "stub-root-hash";
-        },
-      },
-    });
-    const gen = run(
-      { prompt: "task", steps: [] },
-      {
-        threadId: "01TEST000000000000000000TR",
-        maxRounds: 20,
-        depth: 0,
-        cas,
-        extract: stubExtract,
-      },
-    );
-    // preparer
-    await gen.next();
-    // developer (caller override should be invoked, NOT workflowAsAgent default)
-    const devYield = await gen.next();
-    expect(devYield.done).toBe(false);
-    if (devYield.done) {
-      throw new Error("expected yield");
-    }
-    expect(devYield.value.role).toBe("developer");
-    expect(devYield.value.meta).toEqual(DEVELOPER_META);
-    expect(developerInvocations).toBe(1);
-  });
 });
 
 describe("buildSolveIssueDescriptor", () => {
diff --git a/packages/workflow-template-solve-issue/src/index.ts b/packages/workflow-template-solve-issue/src/index.ts
index c7840b7..6323d0a 100644
--- a/packages/workflow-template-solve-issue/src/index.ts
+++ b/packages/workflow-template-solve-issue/src/index.ts
@@ -1,5 +1,4 @@
-import { createWorkflow, workflowAsAgent } from "@uncaged/workflow";
-import type { AgentBinding, WorkflowDefinition, WorkflowFn } from "@uncaged/workflow-runtime";
+import type { WorkflowDefinition } from "@uncaged/workflow-runtime";
 
 import { solveIssueModerator } from "./moderator.js";
 import { SOLVE_ISSUE_WORKFLOW_DESCRIPTION, type SolveIssueMeta, solveIssueRoles } from "./roles.js";
@@ -31,22 +30,3 @@ export const solveIssueWorkflowDefinition: WorkflowDefinition<SolveIssueMeta> =
   roles: solveIssueRoles,
   moderator: solveIssueModerator,
 };
-
-/**
- * Build the solve-issue {@link WorkflowFn}.
- *
- * The `developer` role always delegates to the registered `develop` workflow via
- * {@link workflowAsAgent}; if the caller supplies their own `developer` override in
- * `binding.overrides`, it takes precedence so tests and custom hosts can stub it.
- */
-export function createSolveIssueRun(binding: AgentBinding): WorkflowFn {
-  const developerOverride = binding.overrides?.developer ?? workflowAsAgent("develop");
-  const mergedBinding: AgentBinding = {
-    agent: binding.agent,
-    overrides: {
-      ...(binding.overrides ?? {}),
-      developer: developerOverride,
-    },
-  };
-  return createWorkflow(solveIssueWorkflowDefinition, mergedBinding);
-}
diff --git a/packages/workflow-util-agent/__tests__/build-agent-prompt.test.ts b/packages/workflow-util-agent/__tests__/build-agent-prompt.test.ts
index b940551..bbd5199 100644
--- a/packages/workflow-util-agent/__tests__/build-agent-prompt.test.ts
+++ b/packages/workflow-util-agent/__tests__/build-agent-prompt.test.ts
@@ -3,11 +3,11 @@ import { mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { createCasStore, putContentMerkleNode } from "@uncaged/workflow";
-import { START, type ThreadContext } from "@uncaged/workflow-runtime";
+import { START, type AgentContext } from "@uncaged/workflow-runtime";
 
 import { buildAgentPrompt } from "../src/index.js";
 
-function startTask(content: string): ThreadContext["start"] {
+function startTask(content: string): AgentContext["start"] {
   return {
     role: START,
     content,
@@ -29,7 +29,7 @@ describe("buildAgentPrompt", () => {
 
   test("includes system prompt and full task; omits tools when there are no steps", async () => {
     const cas = createCasStore(casRoot);
-    const ctx: ThreadContext = {
+    const ctx: AgentContext = {
       start: startTask("fix the bug"),
       depth: 0,
       steps: [],
@@ -47,7 +47,7 @@ describe("buildAgentPrompt", () => {
   test("single step shows full content and meta, and includes tools", async () => {
     const cas = createCasStore(casRoot);
     const onlyHash = await putContentMerkleNode(cas, "only step full body");
-    const ctx: ThreadContext = {
+    const ctx: AgentContext = {
       start: startTask("user task"),
       depth: 0,
       threadId: "01TEST000000000000000000TR",
@@ -77,7 +77,7 @@ describe("buildAgentPrompt", () => {
     const cas = createCasStore(casRoot);
     const plannerHash = await putContentMerkleNode(cas, "PLANNER_SECRET_FULL_TEXT");
     const coderHash = await putContentMerkleNode(cas, "last step full content");
-    const ctx: ThreadContext = {
+    const ctx: AgentContext = {
       start: startTask("first message full: task content here"),
       depth: 0,
       threadId: "01TEST000000000000000000TR",
@@ -118,7 +118,7 @@ describe("buildAgentPrompt", () => {
     const ha = await putContentMerkleNode(cas, "HIDDEN_A");
     const hb = await putContentMerkleNode(cas, "HIDDEN_B_MIDDLE");
     const hc = await putContentMerkleNode(cas, "VISIBLE_LAST");
-    const ctx: ThreadContext = {
+    const ctx: AgentContext = {
       start: startTask("start"),
       depth: 0,
       threadId: "01TEST000000000000000000TR",
diff --git a/packages/workflow/__tests__/engine.test.ts b/packages/workflow/__tests__/engine.test.ts
index c217e48..9dbaf6c 100644
--- a/packages/workflow/__tests__/engine.test.ts
+++ b/packages/workflow/__tests__/engine.test.ts
@@ -304,7 +304,7 @@ describe("executeThread", () => {
     }
   });
 
-  test("pre-filled ThreadInput.steps skips roles already present", async () => {
+  test("pre-filled input.steps skips roles already present", async () => {
     restoreFetch = installMockChatCompletions([{ diff: "+ok" }]);
 
     const root = await mkdtemp(join(tmpdir(), "wf-engine-fork-"));
diff --git a/packages/workflow/__tests__/workflow-as-agent-integration.test.ts b/packages/workflow/__tests__/workflow-as-agent-integration.test.ts
index 3d55c3e..bb690a8 100644
--- a/packages/workflow/__tests__/workflow-as-agent-integration.test.ts
+++ b/packages/workflow/__tests__/workflow-as-agent-integration.test.ts
@@ -72,11 +72,11 @@ export const descriptor = {
     },
   },
 };
-export async function* run(input, options) {
-  const cas = options.cas;
+export async function* run(thread, runtime) {
+  const cas = runtime.cas;
   const h = await putContentMerkleNode(cas, "child-body");
   yield { role: "agent", contentHash: h, meta: {}, refs: [h] };
-  return { returnCode: 0, summary: "child-done:" + input.prompt };
+  return { returnCode: 0, summary: "child-done:" + thread.start.content };
 }
 `;
 
diff --git a/packages/workflow/__tests__/workflow-as-agent.test.ts b/packages/workflow/__tests__/workflow-as-agent.test.ts
index 0002eeb..daa90bb 100644
--- a/packages/workflow/__tests__/workflow-as-agent.test.ts
+++ b/packages/workflow/__tests__/workflow-as-agent.test.ts
@@ -49,11 +49,11 @@ export const descriptor = {
     },
   },
 };
-export async function* run(input, options) {
-  const cas = options.cas;
+export async function* run(thread, runtime) {
+  const cas = runtime.cas;
   const h = await putContentMerkleNode(cas, "child-body");
   yield { role: "agent", contentHash: h, meta: {}, refs: [h] };
-  return { returnCode: 0, summary: "child-done:" + input.prompt };
+  return { returnCode: 0, summary: "child-done:" + thread.start.content };
 }
 `;
 
diff --git a/packages/workflow/src/engine/create-workflow.ts b/packages/workflow/src/engine/create-workflow.ts
index c4628ff..b7fc2a7 100644
--- a/packages/workflow/src/engine/create-workflow.ts
+++ b/packages/workflow/src/engine/create-workflow.ts
@@ -2,7 +2,7 @@
  * Re-export of {@link createWorkflow} from `@uncaged/workflow-runtime`.
  *
  * The runtime's `createWorkflow` already binds role definitions + agents to a workflow loop
- * and delegates structured meta extraction to `WorkflowFnOptions.extract`, which the engine
+ * and delegates structured meta extraction to `WorkflowRuntime.extract`, which the engine
  * supplies (resolved from the `extract` scene in workflow.yaml).
  */
 export { createWorkflow } from "@uncaged/workflow-runtime";
diff --git a/packages/workflow/src/engine/engine.ts b/packages/workflow/src/engine/engine.ts
index 653c4cc..10b28f8 100644
--- a/packages/workflow/src/engine/engine.ts
+++ b/packages/workflow/src/engine/engine.ts
@@ -2,12 +2,14 @@ import { appendFile, mkdir } from "node:fs/promises";
 import { dirname } from "node:path";
 import type {
   LlmProvider,
-  ThreadInput,
+  RoleOutput,
+  ThreadContext,
   WorkflowCompletion,
   WorkflowFn,
-  WorkflowFnOptions,
+  WorkflowRuntime,
   WorkflowResult,
 } from "@uncaged/workflow-runtime";
+import { START } from "@uncaged/workflow-runtime";
 import {
   type CasStore,
   getContentMerklePayload,
@@ -103,7 +105,7 @@ async function finalizeAbortedThread(params: {
 
 async function maybeSupervisorHaltsThread(params: {
   workflowConfig: WorkflowConfig;
-  input: ThreadInput;
+  thread: ThreadContext;
   written: number;
   recentSupervisorSteps: readonly { role: string; summary: string }[];
   logger: LogFn;
@@ -118,7 +120,7 @@ async function maybeSupervisorHaltsThread(params: {
   }
   const sup = await runSupervisor({
     config: params.workflowConfig,
-    prompt: params.input.prompt,
+    prompt: params.thread.start.content,
     recentSteps: params.recentSupervisorSteps,
     logger: params.logger,
   });
@@ -143,8 +145,8 @@ async function driveWorkflowGenerator(params: {
   fn: WorkflowFn;
   workflowName: string;
   workflowConfig: WorkflowConfig;
-  input: ThreadInput;
-  bundleOptions: WorkflowFnOptions;
+  thread: ThreadContext;
+  runtime: WorkflowRuntime;
   executeOptions: ExecuteThreadOptions;
   dataJsonlPath: string;
   threadId: string;
@@ -156,8 +158,8 @@ async function driveWorkflowGenerator(params: {
     fn,
     workflowName,
     workflowConfig,
-    input,
-    bundleOptions,
+    thread,
+    runtime,
     executeOptions,
     dataJsonlPath,
     threadId,
@@ -165,9 +167,9 @@ async function driveWorkflowGenerator(params: {
     cas,
     stepMerkleHashes,
   } = params;
-  const gen = fn(input, bundleOptions);
+  const gen = fn(thread, runtime);
   let written = 0;
-  const recentSupervisorSteps: { role: string; summary: string }[] = input.steps.map((s) => ({
+  const recentSupervisorSteps: { role: string; summary: string }[] = thread.steps.map((s) => ({
     role: s.role,
     summary: JSON.stringify(s.meta),
   }));
@@ -267,7 +269,7 @@ async function driveWorkflowGenerator(params: {
 
     const supervised = await maybeSupervisorHaltsThread({
       workflowConfig,
-      input,
+      thread,
       written,
       recentSupervisorSteps,
       logger,
@@ -289,7 +291,7 @@ async function driveWorkflowGenerator(params: {
 export async function executeThread(
   fn: WorkflowFn,
   workflowName: string,
-  input: ThreadInput,
+  input: { prompt: string; steps: RoleOutput[] },
   options: ExecuteThreadOptions,
   io: ExecuteThreadIo,
   logger: LogFn,
@@ -371,10 +373,25 @@ export async function executeThread(
     throw new Error(registryRuntime.error);
   }
 
-  const bundleOptions: WorkflowFnOptions = {
+  const thread: ThreadContext = {
     threadId: io.threadId,
-    maxRounds: options.maxRounds,
     depth: options.depth,
+    start: {
+      role: START,
+      content: input.prompt,
+      meta: { maxRounds: options.maxRounds },
+      timestamp: nowMs,
+    },
+    steps: input.steps.map((out, i) => ({
+      role: out.role,
+      contentHash: out.contentHash,
+      meta: out.meta,
+      refs: out.refs,
+      timestamp: prefilled?.[i]?.timestamp ?? nowMs + i,
+    })),
+  };
+
+  const runtime: WorkflowRuntime = {
     cas: io.cas,
     extract: registryRuntime.value.extract,
   };
@@ -383,8 +400,8 @@ export async function executeThread(
     fn,
     workflowName,
     workflowConfig: registryRuntime.value.workflowConfig,
-    input,
-    bundleOptions,
+    thread,
+    runtime,
     executeOptions: options,
     dataJsonlPath: io.dataJsonlPath,
     threadId: io.threadId,
diff --git a/packages/workflow/src/engine/types.ts b/packages/workflow/src/engine/types.ts
index 9228547..8788096 100644
--- a/packages/workflow/src/engine/types.ts
+++ b/packages/workflow/src/engine/types.ts
@@ -23,7 +23,7 @@ export type PrefilledDiskStep = {
 
 export type ExecuteThreadOptions = {
   maxRounds: number;
-  /** Passed to the bundle as `WorkflowFnOptions.depth`. */
+  /** Passed to the bundle thread context as `ThreadContext.depth`. */
   depth: number;
   signal: AbortSignal;
   /** Invoked after each successful yield (and outer-loop checks); used for pause/resume. */
diff --git a/packages/workflow/src/workflow-as-agent.ts b/packages/workflow/src/workflow-as-agent.ts
index 86a8130..d6ac8b1 100644
--- a/packages/workflow/src/workflow-as-agent.ts
+++ b/packages/workflow/src/workflow-as-agent.ts
@@ -1,5 +1,5 @@
 import { join } from "node:path";
-import type { AgentContext, AgentFn, ThreadInput } from "@uncaged/workflow-runtime";
+import type { AgentContext, AgentFn } from "@uncaged/workflow-runtime";
 import { extractBundleExports } from "./bundle/index.js";
 import { createCasStore } from "./cas/index.js";
 import type { ExecuteThreadIo } from "./engine/index.js";
@@ -36,7 +36,7 @@ function resolveWorkflowAsAgentStorageRoot(options: WorkflowAsAgentOptions | nul
 
 /**
  * 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 {@link ThreadInput.prompt}.
+ * using the parent thread's initial prompt (`ctx.start.content`) as the child prompt.
  */
 export function workflowAsAgent(
   workflowName: string,
@@ -68,7 +68,7 @@ export function workflowAsAgent(
       return `ERROR: ${bundleExportsResult.error}`;
     }
 
-    const input: ThreadInput = {
+    const input = {
       prompt: ctx.start.content,
       steps: [],
     };