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

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

Refs #155, closes #159

小橘 <xiaoju@shazhou.work>

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

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

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

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

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

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

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

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

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

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

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

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

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

@@ -1,10 +1,11 @@
 import { join } from "node:path";
-import { buildForkPlan } from "@uncaged/workflow-execute";
+import { createCasStore } from "@uncaged/workflow-cas";
+import { prepareCasFork } from "@uncaged/workflow-execute";
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
-import { generateUlid } from "@uncaged/workflow-util";
+import { generateUlid, getGlobalCasDir } from "@uncaged/workflow-util";
 
-import { pathExists, readTextFileIfExists } from "../../fs-utils.js";
+import { pathExists } from "../../fs-utils.js";
-import { resolveThreadDataPath } from "../../thread-scan.js";
+import { resolveThreadRecord } from "../../thread-scan.js";
 import { ensureWorkerForHash, sendWorkerTcpCommand } from "../../worker-spawn.js";
 
 export async function cmdFork(
@@ -12,49 +13,51 @@ export async function cmdFork(
   threadId: string,
   fromRole: string | null,
 ): Promise<Result<{ threadId: string }, string>> {
-  const dataPath = await resolveThreadDataPath(storageRoot, threadId);
+  const resolved = await resolveThreadRecord(storageRoot, threadId);
-  if (dataPath === null) {
+  if (resolved === null) {
     return err(`thread not found: ${threadId}`);
   }
-  const text = await readTextFileIfExists(dataPath);
+
-  if (text === null) {
+  const bundlePath = join(storageRoot, "bundles", `${resolved.bundleHash}.esm.js`);
-    return err(`thread data missing: ${threadId}`);
+  if (!(await pathExists(bundlePath))) {
+    return err(`bundle file missing for thread hash ${resolved.bundleHash}`);
   }
 
-  const plan = buildForkPlan(text, fromRole);
+  const cas = createCasStore(getGlobalCasDir(storageRoot));
+  const newThreadId = generateUlid(Date.now());
+
+  const plan = await prepareCasFork({
+    cas,
+    bundleDir: resolved.bundleDir,
+    bundleHash: resolved.bundleHash,
+    sourceThreadId: threadId,
+    headHash: resolved.head,
+    startHash: resolved.start,
+    newThreadId,
+    fromRole,
+  });
   if (!plan.ok) {
     return plan;
   }
 
-  const bundlePath = join(storageRoot, "bundles", `${plan.value.hash}.esm.js`);
-  if (!(await pathExists(bundlePath))) {
-    return err(`bundle file missing for thread hash ${plan.value.hash}`);
-  }
-
   const worker = await ensureWorkerForHash(storageRoot, plan.value.hash, bundlePath);
   if (!worker.ok) {
     return worker;
   }
 
-  const newThreadId = generateUlid(Date.now());
+  const p = plan.value;
-  const stepsOnWire = plan.value.historicalSteps.map((s) => ({
-    role: s.role,
-    contentHash: s.contentHash,
-    meta: s.meta,
-    refs: s.refs,
-    timestamp: s.timestamp,
-  }));
-
   const sent = await sendWorkerTcpCommand(
     worker.value.port,
     {
       type: "run",
       threadId: newThreadId,
-      workflowName: plan.value.workflowName,
+      workflowName: p.workflowName,
-      prompt: plan.value.prompt,
+      prompt: p.prompt,
-      options: plan.value.runOptions,
+      options: p.runOptions,
-      steps: stepsOnWire,
+      steps: p.steps,
-      forkSourceThreadId: plan.value.sourceThreadId,
+      stepTimestamps: p.stepTimestamps.length > 0 ? p.stepTimestamps : null,
+      forkSourceThreadId: threadId,
+      forkContinuation: p.forkContinuation,
     },
     { awaitResponseLine: false },
   );

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

@@ -1,16 +1,26 @@
 import { watch } from "node:fs";
-import { readFile } from "node:fs/promises";
+import { mkdir, readFile } from "node:fs/promises";
 import { dirname, join } from "node:path";
 import { createCasStore, getContentMerklePayload } from "@uncaged/workflow-cas";
-import { tryParseRoleStepRecord, tryParseWorkflowResultRecord } from "@uncaged/workflow-execute";
+import {
+  FORK_BRANCH_ROLE,
+  readThreadsIndex,
+  type ThreadIndex,
+  walkStateFramesNewestFirst,
+} from "@uncaged/workflow-execute";
 import type { CasStore, WorkflowCompletion } from "@uncaged/workflow-protocol";
+import { END } from "@uncaged/workflow-runtime";
 import { getGlobalCasDir } from "@uncaged/workflow-util";
 
 import { dimGreyLine, highlightLiveRole } from "../../cli-color.js";
 import { printCliError, printCliLine } from "../../cli-output.js";
 import { pathExists } from "../../fs-utils.js";
 import type { ParsedLiveArgv } from "../../live-argv.js";
-import { findLatestThreadDataPath, resolveThreadDataPath } from "../../thread-scan.js";
+import {
+  findLatestThreadBundleTarget,
+  type LatestThreadTarget,
+  resolveThreadRecord,
+} from "../../thread-scan.js";
 import type { LiveRoleRow } from "./types.js";
 
 export const LIVE_CONTENT_MAX_LINES = 10;
@@ -48,16 +58,15 @@ function printSummary(result: WorkflowCompletion): void {
   printCliLine(`completed: returnCode=${result.returnCode} — ${result.summary}`);
 }
 
-type LiveSessionState = {
+type InfoLiveState = {
-  sawStart: boolean;
-  completed: boolean;
   carry: string;
   contentOffset: number;
 };
 
-type InfoLiveState = {
+type CasLiveState = {
-  carry: string;
+  printedHashes: Set<string>;
-  contentOffset: number;
+  lastHead: string | null;
+  completionEmitted: boolean;
 };
 
 function tryParseInfoRecord(obj: Record<string, unknown>): {
@@ -79,102 +88,140 @@ function tryParseInfoRecord(obj: Record<string, unknown>): {
   return { tag, content, timestamp };
 }
 
-async function handleJsonlLine(
+function completionFromEndMeta(meta: Record<string, unknown>): WorkflowCompletion | null {
-  rawLine: string,
+  const returnCode = meta.returnCode;
-  state: LiveSessionState,
+  const summary = meta.summary;
-  roleFilter: string | null,
+  if (typeof returnCode !== "number" || typeof summary !== "string") {
-  cas: CasStore,
+    return null;
-): Promise<{ parseError: string | null; workflowResult: WorkflowCompletion | null }> {
-  const trimmed = rawLine.trim();
-  if (trimmed === "") {
-    return { parseError: null, workflowResult: null };
   }
+  return { returnCode, summary };
+}
 
-  let rec: unknown;
+async function emitRoleStepPrint(params: {
-  try {
+  cas: CasStore;
-    rec = JSON.parse(trimmed) as unknown;
+  role: string;
-  } catch {
+  contentHash: string;
-    return { parseError: "invalid JSON in thread data file", workflowResult: null };
+  meta: Record<string, unknown>;
+  timestamp: number;
+  roleFilter: string | null;
+}): Promise<void> {
+  if (params.roleFilter !== null && params.role !== params.roleFilter) {
+    return;
   }
-  if (rec === null || typeof rec !== "object") {
+  const payload = await getContentMerklePayload(params.cas, params.contentHash);
-    return { parseError: "invalid record in thread data file", workflowResult: null };
-  }
-  const obj = rec as Record<string, unknown>;
-
-  if (!state.sawStart) {
-    state.sawStart = true;
-    return { parseError: null, workflowResult: null };
-  }
-
-  const wf = tryParseWorkflowResultRecord(obj);
-  if (wf !== null) {
-    state.completed = true;
-    return { parseError: null, workflowResult: wf };
-  }
-
-  const roleRow = tryParseRoleStepRecord(obj);
-  if (roleRow === null) {
-    return {
-      parseError: "unrecognized record in thread data (expected role step or result)",
-      workflowResult: null,
-    };
-  }
-
-  if (roleFilter !== null && roleRow.role !== roleFilter) {
-    return { parseError: null, workflowResult: null };
-  }
-
-  const payload = await getContentMerklePayload(cas, roleRow.contentHash);
   const content =
-    payload !== null ? payload : `(content not in CAS; contentHash=${roleRow.contentHash})`;
+    payload !== null ? payload : `(content not in CAS; contentHash=${params.contentHash})`;
 
   const row: LiveRoleRow = {
-    role: roleRow.role,
+    role: params.role,
     content,
-    meta: roleRow.meta,
+    meta: params.meta,
-    timestamp: roleRow.timestamp,
+    timestamp: params.timestamp,
   };
   for (const outLine of renderLiveRoleStepLines(row, highlightLiveRole(row.role))) {
     printCliLine(outLine);
   }
-  return { parseError: null, workflowResult: null };
 }
 
-async function pumpNewContent(
+async function emitStatesReachableFromHead(params: {
-  dataPath: string,
+  cas: CasStore;
-  state: LiveSessionState,
+  headHash: string;
-  roleFilter: string | null,
+  state: CasLiveState;
-  cas: CasStore,
+  roleFilter: string | null;
-): Promise<number | null> {
+}): Promise<WorkflowCompletion | null> {
-  let text: string;
+  const frames = await walkStateFramesNewestFirst(params.cas, params.headHash);
+  const chronological = [...frames].reverse();
+
+  for (const fr of chronological) {
+    if (params.state.printedHashes.has(fr.hash)) {
+      continue;
+    }
+    params.state.printedHashes.add(fr.hash);
+
+    const role = fr.payload.role;
+    if (role === FORK_BRANCH_ROLE) {
+      continue;
+    }
+
+    if (role === END) {
+      const wf = completionFromEndMeta(fr.payload.meta);
+      if (wf !== null) {
+        printSummary(wf);
+        return wf;
+      }
+      continue;
+    }
+
+    await emitRoleStepPrint({
+      cas: params.cas,
+      role,
+      contentHash: fr.payload.content,
+      meta: fr.payload.meta,
+      timestamp: fr.payload.timestamp,
+      roleFilter: params.roleFilter,
+    });
+  }
+
+  return null;
+}
+
+async function pumpThreadsJson(params: {
+  storageRoot: string;
+  bundleDir: string;
+  bundleHash: string;
+  threadId: string;
+  state: CasLiveState;
+  roleFilter: string | null;
+  cas: CasStore;
+}): Promise<number | null> {
+  let idx: ThreadIndex;
   try {
-    text = await readFile(dataPath, "utf8");
+    idx = await readThreadsIndex(params.bundleDir);
   } catch {
+    idx = {};
+  }
+
+  const active = idx[params.threadId];
+
+  if (active === undefined) {
+    if (params.state.completionEmitted) {
       return null;
     }
-
+    const hist = await resolveThreadRecord(params.storageRoot, params.threadId);
-  if (text.length < state.contentOffset) {
+    if (hist === null || hist.source !== "history") {
-    state.contentOffset = 0;
+      return null;
-    state.carry = "";
+    }
+    params.state.completionEmitted = true;
+    const wf = await emitStatesReachableFromHead({
+      cas: params.cas,
+      headHash: hist.head,
+      state: params.state,
+      roleFilter: params.roleFilter,
+    });
+    return wf !== null ? 0 : null;
   }
 
-  const chunk = text.slice(state.contentOffset);
+  const head = active.head;
-  state.contentOffset = text.length;
+  if (params.state.lastHead === null) {
-  state.carry += chunk;
+    params.state.lastHead = head;
-
+    const wf = await emitStatesReachableFromHead({
-  const parts = state.carry.split("\n");
+      cas: params.cas,
-  state.carry = parts.pop() ?? "";
+      headHash: head,
-
+      state: params.state,
-  for (const line of parts) {
+      roleFilter: params.roleFilter,
-    const { parseError, workflowResult } = await handleJsonlLine(line, state, roleFilter, cas);
+    });
-    if (parseError !== null) {
+    return wf !== null ? 0 : null;
-      printCliError(parseError);
-      return 1;
-    }
-    if (workflowResult !== null) {
-      printSummary(workflowResult);
-      return 0;
   }
+
+  if (head !== params.state.lastHead) {
+    params.state.lastHead = head;
+    const wf = await emitStatesReachableFromHead({
+      cas: params.cas,
+      headHash: head,
+      state: params.state,
+      roleFilter: params.roleFilter,
+    });
+    return wf !== null ? 0 : null;
   }
 
   return null;
@@ -291,9 +338,9 @@ function watchLivePaths(params: { tasks: WatchPumpTask[]; signal: AbortSignal })
         schedulePump(path, pump);
       });
       watchers.push(watcher);
-      watcher.on("error", (err: Error) => {
+      watcher.on("error", (errObj: Error) => {
         closeAll();
-        reject(err);
+        reject(errObj);
       });
     }
 
@@ -309,17 +356,14 @@ function watchLivePaths(params: { tasks: WatchPumpTask[]; signal: AbortSignal })
   });
 }
 
-type LiveThreadTarget = {
+type LiveThreadTarget = LatestThreadTarget;
-  threadId: string;
-  dataPath: string;
-};
 
 async function resolveLiveThreadTarget(
   storageRoot: string,
   parsed: ParsedLiveArgv,
 ): Promise<LiveThreadTarget | null> {
   if (parsed.latest) {
-    const found = await findLatestThreadDataPath(storageRoot);
+    const found = await findLatestThreadBundleTarget(storageRoot);
     if (found === null) {
       printCliError("live: no threads found");
       return null;
@@ -332,36 +376,56 @@ async function resolveLiveThreadTarget(
     printCliError("live: internal error: missing thread id");
     return null;
   }
-  const resolved = await resolveThreadDataPath(storageRoot, id);
+  const resolved = await resolveThreadRecord(storageRoot, id);
   if (resolved === null) {
     printCliError(`thread not found: ${id}`);
     return null;
   }
-  return { threadId: id, dataPath: resolved };
+  return {
+    threadId: id,
+    bundleHash: resolved.bundleHash,
+    bundleDir: resolved.bundleDir,
+    threadsJsonPath: join(resolved.bundleDir, "threads.json"),
+  };
 }
 
 async function buildLiveWatchTasks(params: {
-  dataPath: string;
+  storageRoot: string;
-  infoPath: string;
+  target: LiveThreadTarget;
   debug: boolean;
-  dataState: LiveSessionState;
+  dataState: CasLiveState;
   infoState: InfoLiveState;
   roleFilter: string | null;
   cas: CasStore;
 }): Promise<WatchPumpTask[]> {
-  const { dataPath, infoPath, debug, dataState, infoState, roleFilter, cas } = params;
+  const infoPath = join(
+    params.storageRoot,
+    "logs",
+    params.target.bundleHash,
+    `${params.target.threadId}.info.jsonl`,
+  );
+
   const tasks: WatchPumpTask[] = [
     {
-      path: dataPath,
+      path: params.target.threadsJsonPath,
-      pump: () => pumpNewContent(dataPath, dataState, roleFilter, cas),
+      pump: () =>
+        pumpThreadsJson({
+          storageRoot: params.storageRoot,
+          bundleDir: params.target.bundleDir,
+          bundleHash: params.target.bundleHash,
+          threadId: params.target.threadId,
+          state: params.dataState,
+          roleFilter: params.roleFilter,
+          cas: params.cas,
+        }),
     },
   ];
 
-  if (debug && (await pathExists(infoPath))) {
+  if (params.debug && (await pathExists(infoPath))) {
     tasks.push({
       path: infoPath,
       pump: async () => {
-        await pumpNewInfoContent(infoPath, infoState);
+        await pumpNewInfoContent(infoPath, params.infoState);
         return null;
       },
     });
@@ -376,16 +440,13 @@ export async function cmdLive(storageRoot: string, parsed: ParsedLiveArgv): Prom
     return 1;
   }
 
-  const { threadId, dataPath } = target;
   const roleFilter = parsed.role;
-  const infoPath = join(dirname(dataPath), `${threadId}.info.jsonl`);
   const cas = createCasStore(getGlobalCasDir(storageRoot));
 
-  const dataState: LiveSessionState = {
+  const dataState: CasLiveState = {
-    sawStart: false,
+    printedHashes: new Set<string>(),
-    completed: false,
+    lastHead: null,
-    carry: "",
+    completionEmitted: false,
-    contentOffset: 0,
   };
 
   const infoState: InfoLiveState = {
@@ -400,22 +461,29 @@ export async function cmdLive(storageRoot: string, parsed: ParsedLiveArgv): Prom
   process.on("SIGINT", onSigInt);
 
   try {
-    const firstData = await pumpNewContent(dataPath, dataState, roleFilter, cas);
+    await mkdir(dirname(target.threadsJsonPath), { recursive: true });
-    if (firstData === 1) {
-      return 1;
-    }
 
+    const firstData = await pumpThreadsJson({
+      storageRoot,
+      bundleDir: target.bundleDir,
+      bundleHash: target.bundleHash,
+      threadId: target.threadId,
+      state: dataState,
+      roleFilter,
+      cas,
+    });
+    const infoPath = join(storageRoot, "logs", target.bundleHash, `${target.threadId}.info.jsonl`);
     if (parsed.debug && (await pathExists(infoPath))) {
       await pumpNewInfoContent(infoPath, infoState);
     }
 
-    if (firstData === 0 || dataState.completed) {
+    if (firstData === 0) {
       return 0;
     }
 
     const tasks = await buildLiveWatchTasks({
-      dataPath,
+      storageRoot,
-      infoPath,
+      target,
       debug: parsed.debug,
       dataState,
       infoState,

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

@@ -1,24 +1,35 @@
 import { unlink } from "node:fs/promises";
-import { dirname, join } from "node:path";
+import { join } from "node:path";
-import { garbageCollectCas } from "@uncaged/workflow-execute";
+import {
+  garbageCollectCas,
+  removeThreadEntry,
+  removeThreadHistoryEntries,
+} from "@uncaged/workflow-execute";
 import { err, ok, type Result } from "@uncaged/workflow-protocol";
 
-import { resolveThreadDataPath } from "../../thread-scan.js";
+import { resolveThreadRecord } from "../../thread-scan.js";
 
 export async function cmdThreadRemove(
   storageRoot: string,
   threadId: string,
 ): Promise<Result<void, string>> {
-  const dataPath = await resolveThreadDataPath(storageRoot, threadId);
+  const resolved = await resolveThreadRecord(storageRoot, threadId);
-  if (dataPath === null) {
+  if (resolved === null) {
     return err(`thread not found: ${threadId}`);
   }
 
-  const dir = dirname(dataPath);
+  if (resolved.source === "active") {
-  const infoPath = join(dir, `${threadId}.info.jsonl`);
+    await removeThreadEntry(resolved.bundleDir, threadId);
-  const runningPath = join(dir, `${threadId}.running`);
+  } else {
+    const hist = await removeThreadHistoryEntries(resolved.bundleDir, threadId);
+    if (!hist.ok) {
+      return hist;
+    }
+  }
+
+  const infoPath = join(storageRoot, "logs", resolved.bundleHash, `${threadId}.info.jsonl`);
+  const runningPath = join(storageRoot, "logs", resolved.bundleHash, `${threadId}.running`);
 
-  await unlink(dataPath);
   await unlink(infoPath).catch(() => {});
   await unlink(runningPath).catch(() => {});
 

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

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

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

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

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

@@ -40,6 +40,8 @@ function makeOptions(overrides: Partial<ExecuteThreadOptions>): ExecuteThreadOpt
     awaitAfterEachYield: async () => {},
     forkSourceThreadId: null,
     prefilledDiskSteps: null,
+    forkContinuation: null,
+    replayTimestamps: null,
     storageRoot: "/tmp/never",
     ...overrides,
   };

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

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

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

@@ -33,20 +33,12 @@ import {
   removeThreadEntry,
   upsertThreadEntry,
 } from "./threads-index.js";
-import type { ExecuteThreadIo, ExecuteThreadOptions } from "./types.js";
+import type { ChainState, ExecuteThreadIo, ExecuteThreadOptions } from "./types.js";
+import { EMPTY_CHAIN_STATE } from "./types.js";
 
 /** Cap for {@link StateNode}.payload.ancestors: 1 parent + 10 skip-list. */
 const ANCESTORS_CAP = 11;
 
-type ChainState = {
-  /** State hash of the most recently written {@link StateNode}, or `null` before the first step. */
-  parentStateHash: string | null;
-  /** Ancestors recorded on the most recently written {@link StateNode}. */
-  parentAncestors: readonly string[];
-};
-
-const EMPTY_CHAIN: ChainState = { parentStateHash: null, parentAncestors: [] };
-
 function computeAncestors(chain: ChainState): string[] {
   if (chain.parentStateHash === null) {
     return [];
@@ -408,16 +400,35 @@ export async function executeThread(
   await mkdir(dirname(io.infoJsonlPath), { recursive: true });
 
   const prefilled = options.prefilledDiskSteps;
+  const fork = options.forkContinuation;
+
+  if (fork !== null && prefilled !== null) {
+    throw new Error("forkContinuation and prefilledDiskSteps cannot both be set");
+  }
+
   if (prefilled !== null && prefilled.length !== input.steps.length) {
     throw new Error(
       `prefilledDiskSteps length (${prefilled.length}) must match input.steps length (${input.steps.length})`,
     );
   }
 
+  const replayTs = options.replayTimestamps;
+  if (replayTs !== null && replayTs.length !== input.steps.length) {
+    throw new Error(
+      `replayTimestamps length (${replayTs.length}) must match input.steps length (${input.steps.length})`,
+    );
+  }
+
   const bundleDir = getBundleDir(options.storageRoot, io.hash);
 
+  let startHash: string;
+
+  if (fork !== null) {
+    startHash = fork.startHash;
+    logger("T9HQ2KHM", `thread ${io.threadId} continued fork for workflow ${workflowName}`);
+  } else {
     const promptHash = await io.cas.put(input.prompt);
-  const startHash = await putStartNode(
+    startHash = await putStartNode(
       io.cas,
       {
         name: workflowName,
@@ -436,8 +447,9 @@ export async function executeThread(
     });
 
     logger("T9HQ2KHM", `thread ${io.threadId} started for workflow ${workflowName}`);
+  }
 
-  let chain: ChainState = EMPTY_CHAIN;
+  let chain: ChainState = fork !== null ? fork.initialChain : EMPTY_CHAIN_STATE;
 
   if (prefilled !== null) {
     for (const row of prefilled) {
@@ -497,7 +509,7 @@ export async function executeThread(
       contentHash: out.contentHash,
       meta: out.meta,
       refs: out.refs,
-      timestamp: prefilled?.[i]?.timestamp ?? nowMs + i,
+      timestamp: replayTs?.[i] ?? prefilled?.[i]?.timestamp ?? nowMs + i,
     })),
   };
 

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

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

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

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

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

@@ -1,11 +1,10 @@
 export { createWorkflow } from "./create-workflow.js";
 export { executeThread } from "./engine.js";
 export {
-  buildForkPlan,
+  FORK_BRANCH_ROLE,
-  parseThreadDataJsonl,
+  prepareCasFork,
-  selectForkHistoricalSteps,
-  tryParseRoleStepRecord,
   tryParseWorkflowResultRecord,
+  walkStateFramesNewestFirst,
 } from "./fork-thread.js";
 export { garbageCollectCas } from "./gc.js";
 export { createThreadPauseGate } from "./thread-pause-gate.js";
@@ -13,18 +12,22 @@ export type { ThreadHistoryEntry, ThreadIndex, ThreadIndexEntry } from "./thread
 export {
   appendThreadHistoryEntry,
   getBundleDir,
+  readThreadsIndex,
   removeThreadEntry,
+  removeThreadHistoryEntries,
   upsertThreadEntry,
+  writeThreadsIndex,
 } from "./threads-index.js";
 export type {
+  CasForkPlan,
+  ChainState,
   ExecuteThreadIo,
   ExecuteThreadOptions,
-  ForkHistoricalStep,
+  ForkContinuationOptions,
-  ForkPlan,
   GcResult,
-  ParsedThreadStartRecord,
   PrefilledDiskStep,
   SupervisorDecision,
   ThreadPauseGate,
 } from "./types.js";
+export { EMPTY_CHAIN_STATE } from "./types.js";
 export { getWorkerHostScriptPath } from "./worker-entry-path.js";

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

@@ -1,6 +1,8 @@
-import { appendFile, mkdir, readFile, rename, writeFile } from "node:fs/promises";
+import { appendFile, mkdir, readdir, readFile, rename, writeFile } from "node:fs/promises";
 import { dirname, join } from "node:path";
 
+import { err, ok, type Result } from "@uncaged/workflow-util";
+
 /**
  * Active-thread index entry stored in `<bundleDir>/threads.json`.
  *
@@ -71,7 +73,8 @@ function parseThreadIndex(text: string): ThreadIndex {
   return out;
 }
 
-async function readThreadIndex(bundleDir: string): Promise<ThreadIndex> {
+/** Read `<bundleDir>/threads.json` (empty object when missing or invalid). */
+export async function readThreadsIndex(bundleDir: string): Promise<ThreadIndex> {
   const path = threadsJsonPath(bundleDir);
   let text: string;
   try {
@@ -86,7 +89,7 @@ async function readThreadIndex(bundleDir: string): Promise<ThreadIndex> {
   return parseThreadIndex(text);
 }
 
-async function writeThreadIndex(bundleDir: string, index: ThreadIndex): Promise<void> {
+export async function writeThreadsIndex(bundleDir: string, index: ThreadIndex): Promise<void> {
   const path = threadsJsonPath(bundleDir);
   await mkdir(dirname(path), { recursive: true });
   const tmp = `${path}.tmp.${process.pid}.${Date.now()}`;
@@ -101,19 +104,19 @@ export async function upsertThreadEntry(
   threadId: string,
   entry: ThreadIndexEntry,
 ): Promise<void> {
-  const index = await readThreadIndex(bundleDir);
+  const index = await readThreadsIndex(bundleDir);
   index[threadId] = entry;
-  await writeThreadIndex(bundleDir, index);
+  await writeThreadsIndex(bundleDir, index);
 }
 
 /** Remove a thread entry from `threads.json` (no-op when absent). */
 export async function removeThreadEntry(bundleDir: string, threadId: string): Promise<void> {
-  const index = await readThreadIndex(bundleDir);
+  const index = await readThreadsIndex(bundleDir);
   if (!(threadId in index)) {
     return;
   }
   delete index[threadId];
-  await writeThreadIndex(bundleDir, index);
+  await writeThreadsIndex(bundleDir, index);
 }
 
 function dateKey(epochMs: number): string {
@@ -134,3 +137,63 @@ export async function appendThreadHistoryEntry(
   const line = `${JSON.stringify(entry)}\n`;
   await appendFile(path, line, "utf8");
 }
+
+/** Removes every `history/*.jsonl` line whose `threadId` matches (rewrite files in place). */
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: per-file JSONL filtering keeps RM deterministic
+export async function removeThreadHistoryEntries(
+  bundleDir: string,
+  threadId: string,
+): Promise<Result<number, string>> {
+  const histRoot = join(bundleDir, "history");
+  let files: string[];
+  try {
+    files = await readdir(histRoot);
+  } catch (e) {
+    const errObj = e as NodeJS.ErrnoException;
+    if (errObj.code === "ENOENT") {
+      return ok(0);
+    }
+    return err(`failed to read history directory: ${String(e)}`);
+  }
+
+  let removed = 0;
+  for (const name of files) {
+    if (!name.endsWith(".jsonl")) {
+      continue;
+    }
+    const path = join(histRoot, name);
+    let text: string;
+    try {
+      text = await readFile(path, "utf8");
+    } catch {
+      continue;
+    }
+    const kept: string[] = [];
+    for (const line of text.split("\n")) {
+      const trimmed = line.trim();
+      if (trimmed === "") {
+        continue;
+      }
+      let rec: unknown;
+      try {
+        rec = JSON.parse(trimmed) as unknown;
+      } catch {
+        kept.push(`${trimmed}\n`);
+        continue;
+      }
+      if (rec === null || typeof rec !== "object") {
+        kept.push(`${trimmed}\n`);
+        continue;
+      }
+      const id = (rec as Record<string, unknown>).threadId;
+      if (id === threadId) {
+        removed++;
+        continue;
+      }
+      kept.push(`${trimmed}\n`);
+    }
+    await writeFile(path, kept.join(""), "utf8");
+  }
+
+  return ok(removed);
+}

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

@@ -11,7 +11,25 @@ export type ExecuteThreadIo = {
   cas: CasStore;
 };
 
-/** One persisted role line in `.data.jsonl` (engine adds these for fork replay before running the generator). */
+/** CAS chain tail state before the next appended {@link StateNode}. */
+export type ChainState = {
+  parentStateHash: string | null;
+  parentAncestors: readonly string[];
+};
+
+export const EMPTY_CHAIN_STATE: ChainState = { parentStateHash: null, parentAncestors: [] };
+
+/**
+ * When forking, the worker continues from an existing {@link StartNode} plus an optional
+ * branch marker {@link StateNode} instead of allocating a new start blob.
+ */
+export type ForkContinuationOptions = {
+  startHash: string;
+  forkHeadHash: string;
+  initialChain: ChainState;
+};
+
+/** One replayed role step (prefill) before the generator runs (same layout as disk replay rows). */
 export type PrefilledDiskStep = {
   role: string;
   contentHash: string;
@@ -30,37 +48,36 @@ export type ExecuteThreadOptions = {
   /** When non-null, written into the start record so tooling can trace lineage. */
   forkSourceThreadId: string | null;
   /**
-   * Written to `.data.jsonl` immediately after the start record, before the generator runs.
+   * When non-null, replays these steps into CAS before the generator runs.
    * Must match `input.steps` length and order when present.
    */
   prefilledDiskSteps: PrefilledDiskStep[] | null;
+  /** When non-null, skip creating a new {@link StartNode} and continue this CAS chain. */
+  forkContinuation: ForkContinuationOptions | null;
+  /**
+   * When non-null, must match `input.steps.length`; supplies persisted timestamps for
+   * {@link ThreadContext.steps} (used when restoring history without prefilled CAS replay).
+   */
+  replayTimestamps: readonly number[] | null;
   /** Workspace root containing `workflow.yaml`; used to resolve the `extract` scene for meta extraction. */
   storageRoot: string;
 };
 
-/** Role steps replayed from `.data.jsonl`, including persisted timestamps. */
+export type CasForkPlan = {
-export type ForkHistoricalStep = RoleOutput & { timestamp: number };
-
-export type ParsedThreadStartRecord = {
-  workflowName: string;
-  hash: string;
-  threadId: string;
-  prompt: string;
-  maxRounds: number;
-  depth: number;
-};
-
-export type ForkPlan = {
   workflowName: string;
   hash: string;
   sourceThreadId: string;
   prompt: string;
   runOptions: { maxRounds: number; depth: number };
-  historicalSteps: ForkHistoricalStep[];
+  steps: RoleOutput[];
+  stepTimestamps: number[];
+  forkContinuation: ForkContinuationOptions;
 };
 
 export type GcResult = {
+  /** Count of root hashes seeded from thread indexes (`head`/`start` per entry). */
   scannedThreads: number;
+  /** Reachable CAS blobs after the mark phase. */
   activeRefs: number;
   deletedEntries: number;
   deletedHashes: string[];

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

@@ -17,7 +17,12 @@ import {
 } from "@uncaged/workflow-util";
 import { executeThread } from "./engine.js";
 import { createThreadPauseGate } from "./thread-pause-gate.js";
-import type { ExecuteThreadIo, PrefilledDiskStep, ThreadPauseGate } from "./types.js";
+import type {
+  ExecuteThreadIo,
+  ForkContinuationOptions,
+  PrefilledDiskStep,
+  ThreadPauseGate,
+} from "./types.js";
 
 const bootLog = createLogger({ sink: { kind: "stderr" } });
 
@@ -28,9 +33,10 @@ type RunCommand = {
   prompt: string;
   options: { maxRounds: number; depth: number };
   steps: RoleOutput[];
-  /** Timestamps aligned with `steps` for `.data.jsonl` replay; length must match `steps` when non-null. */
+  /** Timestamps aligned with `steps` for replay / fork restore; length must match `steps` when steps are non-empty. */
   stepTimestamps: number[] | null;
   forkSourceThreadId: string | null;
+  forkContinuation: ForkContinuationOptions | null;
 };
 
 type KillCommand = {
@@ -73,6 +79,7 @@ function parseRoleOutputRecord(obj: Record<string, unknown>): RoleOutput | null
   };
 }
 
+// biome-ignore lint/complexity/noExcessiveCognitiveComplexity: mirrors permissive worker IPC decoding shape checks
 function parseRunStepsPayload(rec: Record<string, unknown>): {
   steps: RoleOutput[];
   stepTimestamps: number[] | null;
@@ -107,12 +114,60 @@ function parseRunStepsPayload(rec: Record<string, unknown>): {
       return null;
     }
   }
+
+  const parallelTsRaw = rec.stepTimestamps;
+  if (
+    steps.length > 0 &&
+    Array.isArray(parallelTsRaw) &&
+    parallelTsRaw.length === steps.length &&
+    parallelTsRaw.every((x): x is number => typeof x === "number")
+  ) {
+    return { steps, stepTimestamps: [...parallelTsRaw] };
+  }
+
   return {
     steps,
     stepTimestamps: anyTimestamp ? timestamps : null,
   };
 }
 
+function parseForkContinuation(rec: Record<string, unknown>): ForkContinuationOptions | null {
+  const raw = rec.forkContinuation;
+  if (raw === undefined || raw === null) {
+    return null;
+  }
+  if (typeof raw !== "object") {
+    return null;
+  }
+  const o = raw as Record<string, unknown>;
+  const startHash = o.startHash;
+  const forkHeadHash = o.forkHeadHash;
+  const ic = o.initialChain;
+  if (typeof startHash !== "string" || typeof forkHeadHash !== "string") {
+    return null;
+  }
+  if (ic === null || typeof ic !== "object") {
+    return null;
+  }
+  const ich = ic as Record<string, unknown>;
+  const pph = ich.parentStateHash;
+  const pa = ich.parentAncestors;
+  if (!(pph === null || typeof pph === "string")) {
+    return null;
+  }
+  if (!Array.isArray(pa) || !pa.every((x) => typeof x === "string")) {
+    return null;
+  }
+  return {
+    startHash,
+    forkHeadHash,
+    initialChain: {
+      parentStateHash: pph,
+      parentAncestors: pa,
+    },
+  };
+}
+
 function parseRunControlPayload(rec: Record<string, unknown>): RunCommand | null {
   const threadId = rec.threadId;
   const workflowName = rec.workflowName;
@@ -148,6 +203,7 @@ function parseRunControlPayload(rec: Record<string, unknown>): RunCommand | null
     }
     forkSourceThreadId = rawFork;
   }
+  const forkContinuation = parseForkContinuation(rec);
   return {
     type: "run",
     threadId,
@@ -157,6 +213,7 @@ function parseRunControlPayload(rec: Record<string, unknown>): RunCommand | null
     steps: parsedSteps.steps,
     stepTimestamps: parsedSteps.stepTimestamps,
     forkSourceThreadId,
+    forkContinuation,
   };
 }
 
@@ -357,6 +414,7 @@ async function main(): Promise<void> {
     }
   }
 
+  // biome-ignore lint/complexity/noExcessiveCognitiveComplexity: TCP worker multiplexes lifecycle + runs
   async function dispatchCommand(cmd: ControlCommand, socket: Socket | null): Promise<void> {
     if (cmd.type !== "run") {
       dispatchThreadLifecycleCommand(threads, socket, cmd);
@@ -394,7 +452,19 @@ async function main(): Promise<void> {
 
       const baseTs = Date.now();
       let prefilledDiskSteps: PrefilledDiskStep[] | null = null;
-      if (cmd.steps.length > 0) {
+      let replayTimestamps: readonly number[] | null = null;
+
+      if (cmd.forkContinuation !== null) {
+        if (
+          cmd.steps.length > 0 &&
+          (cmd.stepTimestamps === null || cmd.stepTimestamps.length !== cmd.steps.length)
+        ) {
+          bootLog("J5WQ8NXT", "forkContinuation requires stepTimestamps aligned with steps");
+          throw new Error("forkContinuation requires stepTimestamps aligned with steps");
+        }
+        replayTimestamps =
+          cmd.steps.length === 0 ? null : (cmd.stepTimestamps as readonly number[]);
+      } else if (cmd.steps.length > 0) {
         prefilledDiskSteps = cmd.steps.map((step, i) => {
           const ts = cmd.stepTimestamps?.[i];
           return {
@@ -417,6 +487,8 @@ async function main(): Promise<void> {
           awaitAfterEachYield: () => pauseGate.awaitAfterYield(),
           forkSourceThreadId: cmd.forkSourceThreadId,
           prefilledDiskSteps,
+          forkContinuation: cmd.forkContinuation,
+          replayTimestamps,
           storageRoot,
         },
         io,

packages/workflow-execute/src/index.ts

@@ -1,25 +1,39 @@
 export { createWorkflow } from "./engine/create-workflow.js";
 export { executeThread } from "./engine/engine.js";
 export {
-  buildForkPlan,
+  FORK_BRANCH_ROLE,
-  parseThreadDataJsonl,
+  prepareCasFork,
-  selectForkHistoricalSteps,
-  tryParseRoleStepRecord,
   tryParseWorkflowResultRecord,
+  walkStateFramesNewestFirst,
 } from "./engine/fork-thread.js";
 export { garbageCollectCas } from "./engine/gc.js";
 export { createThreadPauseGate } from "./engine/thread-pause-gate.js";
 export type {
+  ThreadHistoryEntry,
+  ThreadIndex,
+  ThreadIndexEntry,
+} from "./engine/threads-index.js";
+export {
+  appendThreadHistoryEntry,
+  getBundleDir,
+  readThreadsIndex,
+  removeThreadEntry,
+  removeThreadHistoryEntries,
+  upsertThreadEntry,
+  writeThreadsIndex,
+} from "./engine/threads-index.js";
+export type {
+  CasForkPlan,
+  ChainState,
   ExecuteThreadIo,
   ExecuteThreadOptions,
-  ForkHistoricalStep,
+  ForkContinuationOptions,
-  ForkPlan,
   GcResult,
-  ParsedThreadStartRecord,
   PrefilledDiskStep,
   SupervisorDecision,
   ThreadPauseGate,
 } from "./engine/types.js";
+export { EMPTY_CHAIN_STATE } from "./engine/types.js";
 export { getWorkerHostScriptPath } from "./engine/worker-entry-path.js";
 export type { ExtractFn, LlmError, LlmExtractArgs } from "./extract/index.js";
 export {

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

@@ -101,6 +101,8 @@ export function workflowAsAgent(
           awaitAfterEachYield: async () => {},
           forkSourceThreadId: ctx.threadId,
           prefilledDiskSteps: null,
+          forkContinuation: null,
+          replayTimestamps: null,
           storageRoot,
         },
         io,