diff --git a/packages/cli-workflow/src/__tests__/adapter-json-roundtrip.test.ts b/packages/cli-workflow/src/__tests__/adapter-json-roundtrip.test.ts
new file mode 100644
index 0000000..250241d
--- /dev/null
+++ b/packages/cli-workflow/src/__tests__/adapter-json-roundtrip.test.ts
@@ -0,0 +1,174 @@
+import { execFileSync } from "node:child_process";
+import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { putSchema } from "@uncaged/json-cas";
+import { createFsStore } from "@uncaged/json-cas-fs";
+import type { CasRef, StepNodePayload, ThreadId } from "@uncaged/workflow-protocol";
+import { afterEach, beforeEach, describe, expect, test } from "vitest";
+import { registerUwfSchemas } from "../schemas.js";
+import { saveThreadsIndex } from "../store.js";
+
+// ── schemas ──────────────────────────────────────────────────────────────────
+
+const OUTPUT_SCHEMA = {
+  type: "object" as const,
+  properties: {
+    $status: { type: "string" as const, enum: ["done", "failed"] },
+    result: { type: "string" as const },
+  },
+  required: ["$status"],
+  additionalProperties: false,
+};
+
+// ── fixture ──────────────────────────────────────────────────────────────────
+
+let tmpDir: string;
+
+beforeEach(async () => {
+  tmpDir = await mkdtemp(join(tmpdir(), "cli-uwf-roundtrip-test-"));
+});
+
+afterEach(async () => {
+  await rm(tmpDir, { recursive: true, force: true });
+});
+
+describe("C1: adapter JSON round-trip integration", () => {
+  test("mock agent outputs JSON, CLI parses it and updates thread head in CAS", async () => {
+    // 1. Set up CAS store with workflow, start node, and output schema
+    const casDir = join(tmpDir, "cas");
+    await mkdir(casDir, { recursive: true });
+    const store = createFsStore(casDir);
+    const schemas = await registerUwfSchemas(store);
+
+    const outputSchemaHash = await putSchema(store, OUTPUT_SCHEMA);
+
+    const workflowHash = await store.put(schemas.workflow, {
+      name: "test-roundtrip",
+      description: "roundtrip integration test",
+      roles: {
+        worker: {
+          description: "Worker role",
+          goal: "Do work",
+          capabilities: [],
+          procedure: "work",
+          output: "result",
+          frontmatter: outputSchemaHash,
+        },
+      },
+      graph: {
+        $START: { _: { role: "worker", prompt: "Do the work", location: null } },
+        worker: { done: { role: "$END", prompt: "completed", location: null } },
+      },
+    });
+
+    const startHash = await store.put(schemas.startNode, {
+      workflow: workflowHash,
+      prompt: "Test round-trip task",
+    });
+
+    const threadId = "01ROUNDTRIPTEST0000000000" as ThreadId;
+    await saveThreadsIndex(tmpDir, { [threadId]: startHash });
+
+    // 2. Pre-create CAS nodes that the mock agent would produce
+    const outputHash = await store.put(outputSchemaHash, {
+      $status: "done",
+      result: "test-ok",
+    });
+
+    // Use text schema for detail (simple placeholder)
+    const detailHash = await store.put(schemas.text, "mock detail");
+
+    const startedAtMs = 1716600000000;
+    const completedAtMs = 1716600001500;
+
+    const stepHash = await store.put(schemas.stepNode, {
+      start: startHash,
+      prev: null,
+      role: "worker",
+      output: outputHash,
+      detail: detailHash,
+      agent: "uwf-mock",
+      edgePrompt: "Do the work",
+      startedAtMs,
+      completedAtMs,
+      cwd: tmpDir,
+    });
+
+    // 3. Create a minimal mock agent shell script that just outputs JSON
+    //    The step node is already in CAS — the agent just needs to print the JSON line
+    const mockAgentPath = join(tmpDir, "mock-agent.sh");
+    const adapterJson = JSON.stringify({
+      stepHash,
+      detailHash,
+      role: "worker",
+      frontmatter: { $status: "done", result: "test-ok" },
+      body: "",
+      startedAtMs,
+      completedAtMs,
+    });
+    await writeFile(mockAgentPath, `#!/bin/sh\necho '${adapterJson}'\n`, { mode: 0o755 });
+
+    // 4. Write config.yaml
+    const configPath = join(tmpDir, "config.yaml");
+    await writeFile(
+      configPath,
+      `defaultAgent: uwf-hermes\ndefaultModel: test-model\nagentOverrides: null\nagents: {}\nproviders: {}\nmodels: {}\n`,
+    );
+
+    // 5. Run CLI with agent override pointing to our mock
+    const cliPath = join(import.meta.dirname, "..", "cli.js");
+    let stdout: string;
+    let stderr: string;
+    let exitCode: number;
+
+    try {
+      stdout = execFileSync(
+        "bun",
+        ["run", cliPath, "thread", "exec", threadId, "--agent", mockAgentPath],
+        {
+          encoding: "utf8",
+          stdio: ["ignore", "pipe", "pipe"],
+          env: { ...process.env, WORKFLOW_STORAGE_ROOT: tmpDir },
+          cwd: tmpDir,
+          timeout: 30000,
+        },
+      );
+      stderr = "";
+      exitCode = 0;
+    } catch (e: unknown) {
+      const err = e as NodeJS.ErrnoException & {
+        stdout?: string;
+        stderr?: string;
+        status?: number;
+      };
+      stdout = err.stdout ?? "";
+      stderr = err.stderr ?? "";
+      exitCode = err.status ?? 1;
+    }
+
+    // 6. Verify
+    if (exitCode !== 0) {
+      throw new Error(`CLI exited with code ${exitCode}\nstdout: ${stdout}\nstderr: ${stderr}`);
+    }
+
+    // Parse CLI output
+    const cliOutput = JSON.parse(stdout.trim());
+    expect(cliOutput).toHaveProperty("thread", threadId);
+    expect(cliOutput).toHaveProperty("head", stepHash);
+    expect(cliOutput.head).toMatch(/^[0-9A-HJ-NP-TV-Z]{13}$/);
+
+    // Verify the CAS step node exists and has correct metadata
+    const storeAfter = createFsStore(casDir);
+    const stepNode = storeAfter.get(cliOutput.head as CasRef);
+    expect(stepNode).not.toBeNull();
+
+    const payload = stepNode!.payload as StepNodePayload;
+    expect(payload.role).toBe("worker");
+    expect(payload.agent).toBe("uwf-mock");
+    expect(payload.startedAtMs).toBe(1716600000000);
+    expect(payload.completedAtMs).toBe(1716600001500);
+    expect(payload.output).toBe(outputHash);
+    expect(payload.detail).toBe(detailHash);
+  });
+});
diff --git a/packages/cli-workflow/src/__tests__/spawn-agent-json.test.ts b/packages/cli-workflow/src/__tests__/spawn-agent-json.test.ts
new file mode 100644
index 0000000..3d03091
--- /dev/null
+++ b/packages/cli-workflow/src/__tests__/spawn-agent-json.test.ts
@@ -0,0 +1,100 @@
+import { describe, expect, test } from "vitest";
+
+/**
+ * B-group tests: validate JSON parsing logic used by spawnAgent.
+ *
+ * We test the parsing logic inline since spawnAgent is a private function.
+ * These tests verify the contract: last line of stdout must be valid JSON
+ * with a valid stepHash CasRef.
+ */
+
+const CASREF_PATTERN = /^[0-9A-HJ-NP-TV-Z]{13}$/;
+
+function isCasRef(s: string): boolean {
+  return CASREF_PATTERN.test(s);
+}
+
+type AdapterOutput = {
+  stepHash: string;
+  detailHash: string;
+  role: string;
+  frontmatter: Record<string, unknown>;
+  body: string;
+  startedAtMs: number;
+  completedAtMs: number;
+};
+
+function parseAgentStdout(stdout: string): AdapterOutput {
+  const line = stdout.trim().split("\n").pop()?.trim() ?? "";
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(line);
+  } catch {
+    throw new Error(`agent stdout last line is not valid JSON: ${line || "(empty)"}`);
+  }
+  const obj = parsed as Record<string, unknown>;
+  if (
+    typeof obj !== "object" ||
+    obj === null ||
+    typeof obj.stepHash !== "string" ||
+    !isCasRef(obj.stepHash as string)
+  ) {
+    throw new Error(`agent stdout JSON missing valid stepHash: ${line}`);
+  }
+  return obj as unknown as AdapterOutput;
+}
+
+const VALID_OUTPUT: AdapterOutput = {
+  stepHash: "0123456789ABC",
+  detailHash: "DEFGH12345678",
+  role: "planner",
+  frontmatter: { $status: "ready", plan: "somehash" },
+  body: "Plan body",
+  startedAtMs: 1000,
+  completedAtMs: 2000,
+};
+
+describe("spawnAgent JSON parsing", () => {
+  test("B1. parses valid JSON from agent stdout", () => {
+    const stdout = JSON.stringify(VALID_OUTPUT) + "\n";
+    const result = parseAgentStdout(stdout);
+    expect(result.stepHash).toBe("0123456789ABC");
+    expect(result.detailHash).toBe("DEFGH12345678");
+    expect(result.role).toBe("planner");
+    expect(result.frontmatter).toEqual({ $status: "ready", plan: "somehash" });
+    expect(result.body).toBe("Plan body");
+    expect(result.startedAtMs).toBe(1000);
+    expect(result.completedAtMs).toBe(2000);
+  });
+
+  test("B2. extracts stepHash for head pointer", () => {
+    const stdout = JSON.stringify(VALID_OUTPUT) + "\n";
+    const result = parseAgentStdout(stdout);
+    expect(result.stepHash).toBe("0123456789ABC");
+    expect(isCasRef(result.stepHash)).toBe(true);
+  });
+
+  test("B3. handles debug lines before JSON", () => {
+    const debugLines = "[debug] loading context...\n[debug] running agent...\n";
+    const stdout = debugLines + JSON.stringify(VALID_OUTPUT) + "\n";
+    const result = parseAgentStdout(stdout);
+    expect(result.stepHash).toBe("0123456789ABC");
+  });
+
+  test("B4. rejects non-JSON last line", () => {
+    const stdout = "not-json-at-all\n";
+    expect(() => parseAgentStdout(stdout)).toThrow("not valid JSON");
+  });
+
+  test("B5. rejects JSON missing stepHash", () => {
+    const incomplete = { detailHash: "DEFGH12345678", role: "planner" };
+    const stdout = JSON.stringify(incomplete) + "\n";
+    expect(() => parseAgentStdout(stdout)).toThrow("missing valid stepHash");
+  });
+
+  test("B6. rejects JSON with invalid stepHash", () => {
+    const bad = { ...VALID_OUTPUT, stepHash: "not-a-hash" };
+    const stdout = JSON.stringify(bad) + "\n";
+    expect(() => parseAgentStdout(stdout)).toThrow("missing valid stepHash");
+  });
+});
diff --git a/packages/cli-workflow/src/commands/thread.ts b/packages/cli-workflow/src/commands/thread.ts
index 2418321..c3b245d 100644
--- a/packages/cli-workflow/src/commands/thread.ts
+++ b/packages/cli-workflow/src/commands/thread.ts
@@ -23,6 +23,7 @@ import {
   generateUlid,
   type ProcessLogger,
 } from "@uncaged/workflow-util";
+import type { AdapterOutput } from "@uncaged/workflow-util-agent";
 import { getEnvPath, loadWorkflowConfig } from "@uncaged/workflow-util-agent";
 import { config as loadDotenv } from "dotenv";
 import { parse } from "yaml";
@@ -788,7 +789,7 @@ function spawnAgent(
   role: string,
   edgePrompt: string,
   cwd: string,
-): CasRef {
+): AdapterOutput {
   const argv = [...agent.args, "--thread", threadId, "--role", role, "--prompt", edgePrompt];
   let stdout: string;
   try {
@@ -811,10 +812,22 @@ function spawnAgent(
   }
 
   const line = stdout.trim().split("\n").pop()?.trim() ?? "";
-  if (!isCasRef(line)) {
-    failStep(plog, `agent stdout is not a valid CAS hash: ${line || "(empty)"}`);
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(line);
+  } catch {
+    failStep(plog, `agent stdout last line is not valid JSON: ${line || "(empty)"}`);
   }
-  return line;
+  const obj = parsed as Record<string, unknown>;
+  if (
+    typeof obj !== "object" ||
+    obj === null ||
+    typeof obj.stepHash !== "string" ||
+    !isCasRef(obj.stepHash as string)
+  ) {
+    failStep(plog, `agent stdout JSON missing valid stepHash: ${line}`);
+  }
+  return obj as unknown as AdapterOutput;
 }
 
 async function archiveThread(
@@ -1019,7 +1032,8 @@ async function cmdThreadStepOnce(
   });
 
   loadDotenv({ path: getEnvPath(storageRoot) });
-  const newHead = spawnAgent(plog, agent, threadId, role, edgePrompt, effectiveCwd);
+  const agentResult = spawnAgent(plog, agent, threadId, role, edgePrompt, effectiveCwd);
+  const newHead = agentResult.stepHash as CasRef;
 
   plog.log(PL_AGENT_DONE, `agent returned head=${newHead}`, null);
 
diff --git a/packages/workflow-util-agent/__tests__/adapter-retry.test.ts b/packages/workflow-util-agent/__tests__/adapter-retry.test.ts
new file mode 100644
index 0000000..f9a35cf
--- /dev/null
+++ b/packages/workflow-util-agent/__tests__/adapter-retry.test.ts
@@ -0,0 +1,72 @@
+import { createMemoryStore, putSchema } from "@uncaged/json-cas";
+import { describe, expect, test } from "vitest";
+
+import { tryFrontmatterFastPath } from "../src/frontmatter.js";
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+
+const PLANNER_SCHEMA = {
+  type: "object",
+  properties: {
+    $status: { type: "string", enum: ["ready", "failed"] },
+    plan: { type: "string" },
+  },
+  required: ["$status"],
+  additionalProperties: false,
+};
+
+describe("adapter-stdout: A4 retry loop survives JSON output", () => {
+  test("A4. first extraction fails, second succeeds — final result has correct data", async () => {
+    const store = createMemoryStore();
+    const schemaHash = await putSchema(store, PLANNER_SCHEMA);
+
+    // Simulate the retry loop from createAgent (run.ts lines 163-173):
+    // First attempt: agent outputs garbage (no frontmatter)
+    const badOutput = "Here is my response without frontmatter.\nJust plain text.";
+    const firstAttempt = await tryFrontmatterFastPath(badOutput, schemaHash, store);
+    expect(firstAttempt).toBeNull();
+
+    // Second attempt (after correction message): agent outputs valid frontmatter
+    const goodOutput = `---\n$status: ready\nplan: corrected-hash\n---\nCorrected body with valid frontmatter.`;
+    const secondAttempt = await tryFrontmatterFastPath(goodOutput, schemaHash, store);
+
+    expect(secondAttempt).not.toBeNull();
+    expect(secondAttempt!.outputHash).toMatch(/^[0-9A-Z]{13}$/);
+    expect(secondAttempt!.frontmatter).toEqual({ $status: "ready", plan: "corrected-hash" });
+    expect(secondAttempt!.body).toBe("Corrected body with valid frontmatter.");
+
+    // Verify the final AdapterOutput shape would be correct
+    const adapterOutput = {
+      stepHash: "MOCK_STEP_HASH",
+      detailHash: "MOCK_DETAIL_HA",
+      role: "planner",
+      frontmatter: secondAttempt!.frontmatter,
+      body: secondAttempt!.body,
+      startedAtMs: 1000,
+      completedAtMs: 2000,
+    };
+
+    const json = JSON.stringify(adapterOutput);
+    const parsed = JSON.parse(json);
+    expect(parsed.frontmatter).toEqual({ $status: "ready", plan: "corrected-hash" });
+    expect(parsed.body).toBe("Corrected body with valid frontmatter.");
+    expect(parsed.completedAtMs).toBeGreaterThanOrEqual(parsed.startedAtMs);
+  });
+
+  test("A4. all retries fail — extraction returns null on every attempt", async () => {
+    const store = createMemoryStore();
+    const schemaHash = await putSchema(store, PLANNER_SCHEMA);
+
+    const MAX_RETRIES = 2;
+    const badOutput = "No frontmatter here";
+
+    // Simulate MAX_FRONTMATTER_RETRIES iterations all failing
+    let extracted = await tryFrontmatterFastPath(badOutput, schemaHash, store);
+    for (let retry = 0; retry < MAX_RETRIES && extracted === null; retry++) {
+      // Each retry also gets bad output
+      extracted = await tryFrontmatterFastPath(badOutput, schemaHash, store);
+    }
+
+    expect(extracted).toBeNull();
+  });
+});
diff --git a/packages/workflow-util-agent/__tests__/adapter-stdout.test.ts b/packages/workflow-util-agent/__tests__/adapter-stdout.test.ts
new file mode 100644
index 0000000..a724c98
--- /dev/null
+++ b/packages/workflow-util-agent/__tests__/adapter-stdout.test.ts
@@ -0,0 +1,105 @@
+import { createMemoryStore, putSchema } from "@uncaged/json-cas";
+import { describe, expect, test } from "vitest";
+
+import { tryFrontmatterFastPath } from "../src/frontmatter.js";
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+
+const PLANNER_SCHEMA = {
+  type: "object",
+  properties: {
+    $status: { type: "string", enum: ["ready", "failed"] },
+    plan: { type: "string" },
+  },
+  required: ["$status"],
+  additionalProperties: false,
+};
+
+const FRONTMATTER_SCHEMA = {
+  type: "object",
+  properties: {
+    status: { anyOf: [{ type: "string" }, { type: "null" }] },
+    next: { anyOf: [{ type: "string" }, { type: "null" }] },
+    confidence: { anyOf: [{ type: "number" }, { type: "null" }] },
+    artifacts: { type: "array", items: { type: "string" } },
+    scope: { type: "string" },
+  },
+  required: ["status", "next", "confidence", "artifacts", "scope"],
+  additionalProperties: false,
+};
+
+describe("adapter-stdout: FrontmatterFastPathResult includes frontmatter", () => {
+  test("A2. frontmatter field contains the parsed YAML frontmatter object", async () => {
+    const store = createMemoryStore();
+    const schemaHash = await putSchema(store, PLANNER_SCHEMA);
+
+    const raw = `---\n$status: ready\nplan: abc123\n---\nSome body text`;
+    const result = await tryFrontmatterFastPath(raw, schemaHash, store);
+
+    expect(result).not.toBeNull();
+    expect(result!.frontmatter).toEqual({ $status: "ready", plan: "abc123" });
+  });
+
+  test("A3. body field contains the markdown body after frontmatter", async () => {
+    const store = createMemoryStore();
+    const schemaHash = await putSchema(store, PLANNER_SCHEMA);
+
+    const raw = `---\n$status: ready\nplan: hash123\n---\nHere is the body.\n\nWith multiple paragraphs.`;
+    const result = await tryFrontmatterFastPath(raw, schemaHash, store);
+
+    expect(result).not.toBeNull();
+    expect(result!.body).toBe("Here is the body.\n\nWith multiple paragraphs.");
+  });
+
+  test("A1. result contains outputHash as valid CasRef", async () => {
+    const store = createMemoryStore();
+    const schemaHash = await putSchema(store, FRONTMATTER_SCHEMA);
+
+    const raw = `---\nstatus: done\nnext: null\nconfidence: 0.9\nartifacts: []\nscope: test\n---\nBody`;
+    const result = await tryFrontmatterFastPath(raw, schemaHash, store);
+
+    expect(result).not.toBeNull();
+    expect(result!.outputHash).toMatch(/^[0-9A-Z]{13}$/);
+    expect(result!.frontmatter).toBeDefined();
+    expect(result!.body).toBe("Body");
+  });
+});
+
+describe("adapter-stdout: AdapterOutput JSON shape", () => {
+  test("A5. JSON.stringify produces valid parseable JSON with all fields", () => {
+    const output = {
+      stepHash: "0123456789ABC",
+      detailHash: "DEFGH12345678",
+      role: "planner",
+      frontmatter: { $status: "ready", plan: "somehash" },
+      body: "Plan body text",
+      startedAtMs: 1000,
+      completedAtMs: 2000,
+    };
+
+    const json = JSON.stringify(output);
+    const parsed = JSON.parse(json);
+
+    expect(parsed.stepHash).toBe("0123456789ABC");
+    expect(parsed.detailHash).toBe("DEFGH12345678");
+    expect(parsed.role).toBe("planner");
+    expect(parsed.frontmatter).toEqual({ $status: "ready", plan: "somehash" });
+    expect(parsed.body).toBe("Plan body text");
+    expect(parsed.startedAtMs).toBe(1000);
+    expect(parsed.completedAtMs).toBe(2000);
+  });
+
+  test("completedAtMs >= startedAtMs", () => {
+    const output = {
+      stepHash: "0123456789ABC",
+      detailHash: "DEFGH12345678",
+      role: "planner",
+      frontmatter: {},
+      body: "",
+      startedAtMs: 1000,
+      completedAtMs: 2000,
+    };
+
+    expect(output.completedAtMs).toBeGreaterThanOrEqual(output.startedAtMs);
+  });
+});
diff --git a/packages/workflow-util-agent/src/frontmatter.ts b/packages/workflow-util-agent/src/frontmatter.ts
index 3b926b3..5000b33 100644
--- a/packages/workflow-util-agent/src/frontmatter.ts
+++ b/packages/workflow-util-agent/src/frontmatter.ts
@@ -20,6 +20,7 @@ type StandardKey = (typeof STANDARD_KEYS)[number];
 export type FrontmatterFastPathResult = {
   body: string;
   outputHash: CasRef;
+  frontmatter: Record<string, unknown>;
 };
 
 function extractYamlBlock(raw: string): string | null {
@@ -176,5 +177,5 @@ export async function tryFrontmatterFastPath(
     return null;
   }
 
-  return { body, outputHash };
+  return { body, outputHash, frontmatter: candidate };
 }
diff --git a/packages/workflow-util-agent/src/index.ts b/packages/workflow-util-agent/src/index.ts
index bd32100..dfdfcdc 100644
--- a/packages/workflow-util-agent/src/index.ts
+++ b/packages/workflow-util-agent/src/index.ts
@@ -15,6 +15,7 @@ export { createAgent, parseArgv } from "./run.js";
 export { getCachedSessionId, getCachePath, setCachedSessionId } from "./session-cache.js";
 export { getConfigPath, getEnvPath, loadWorkflowConfig, resolveStorageRoot } from "./storage.js";
 export type {
+  AdapterOutput,
   AgentContext,
   AgentContinueFn,
   AgentOptions,
diff --git a/packages/workflow-util-agent/src/run.ts b/packages/workflow-util-agent/src/run.ts
index 1090ccb..b6d08f6 100644
--- a/packages/workflow-util-agent/src/run.ts
+++ b/packages/workflow-util-agent/src/run.ts
@@ -6,7 +6,7 @@ import { buildContextWithMeta } from "./context.js";
 import { tryFrontmatterFastPath } from "./frontmatter.js";
 import type { AgentStore } from "./storage.js";
 import { getEnvPath, resolveStorageRoot } from "./storage.js";
-import type { AgentOptions } from "./types.js";
+import type { AdapterOutput, AgentOptions } from "./types.js";
 
 const MAX_FRONTMATTER_RETRIES = 2;
 
@@ -85,14 +85,24 @@ async function writeStepNode(options: {
   return hash;
 }
 
+type ExtractedOutput = {
+  outputHash: CasRef;
+  frontmatter: Record<string, unknown>;
+  body: string;
+};
+
 async function tryExtractOutput(
   rawOutput: string,
   outputSchema: CasRef,
   ctx: Awaited<ReturnType<typeof buildContextWithMeta>>,
-): Promise<CasRef | null> {
+): Promise<ExtractedOutput | null> {
   const fastPath = await tryFrontmatterFastPath(rawOutput, outputSchema, ctx.meta.store);
   if (fastPath !== null) {
-    return fastPath.outputHash;
+    return {
+      outputHash: fastPath.outputHash,
+      frontmatter: fastPath.frontmatter,
+      body: fastPath.body,
+    };
   }
   return null;
 }
@@ -148,9 +158,9 @@ export function createAgent(options: AgentOptions): () => Promise<void> {
     const primaryDetailHash = agentResult.detailHash;
 
     // Try to extract frontmatter; retry via continue if it fails
-    let outputHash = await tryExtractOutput(agentResult.output, roleDef.frontmatter, ctx);
+    let extracted = await tryExtractOutput(agentResult.output, roleDef.frontmatter, ctx);
 
-    for (let retry = 0; retry < MAX_FRONTMATTER_RETRIES && outputHash === null; retry++) {
+    for (let retry = 0; retry < MAX_FRONTMATTER_RETRIES && extracted === null; retry++) {
       const correctionMessage =
         "Your previous response did not contain valid YAML frontmatter matching the role schema.\n" +
         "You MUST begin your response with a YAML frontmatter block (--- delimited).\n" +
@@ -159,10 +169,10 @@ export function createAgent(options: AgentOptions): () => Promise<void> {
       agentResult = await runWithMessage("agent continue failed", () =>
         options.continue(agentResult.sessionId, correctionMessage, ctx.meta.store),
       );
-      outputHash = await tryExtractOutput(agentResult.output, roleDef.frontmatter, ctx);
+      extracted = await tryExtractOutput(agentResult.output, roleDef.frontmatter, ctx);
     }
 
-    if (outputHash === null) {
+    if (extracted === null) {
       fail(
         "Agent output does not contain valid YAML frontmatter matching the role schema " +
           `after ${MAX_FRONTMATTER_RETRIES} retries.\n` +
@@ -172,13 +182,22 @@ export function createAgent(options: AgentOptions): () => Promise<void> {
     const completedAtMs = Date.now();
     const stepHash = await persistStep({
       ctx,
-      outputHash,
+      outputHash: extracted.outputHash,
       detailHash: primaryDetailHash,
       agentName: agentLabel(options.name),
       startedAtMs,
       completedAtMs,
     });
 
-    process.stdout.write(`${stepHash}\n`);
+    const adapterOutput: AdapterOutput = {
+      stepHash,
+      detailHash: primaryDetailHash,
+      role,
+      frontmatter: extracted.frontmatter,
+      body: extracted.body,
+      startedAtMs,
+      completedAtMs,
+    };
+    process.stdout.write(`${JSON.stringify(adapterOutput)}\n`);
   };
 }
diff --git a/packages/workflow-util-agent/src/types.ts b/packages/workflow-util-agent/src/types.ts
index 42f8c1e..dbff5e3 100644
--- a/packages/workflow-util-agent/src/types.ts
+++ b/packages/workflow-util-agent/src/types.ts
@@ -37,6 +37,16 @@ export type AgentContinueFn = (
 
 export type AgentRunFn = (ctx: AgentContext) => Promise<AgentRunResult>;
 
+export type AdapterOutput = {
+  stepHash: string;
+  detailHash: string;
+  role: string;
+  frontmatter: Record<string, unknown>;
+  body: string;
+  startedAtMs: number;
+  completedAtMs: number;
+};
+
 export type AgentOptions = {
   name: string;
   run: AgentRunFn;