feat: add thread steps and thread fork commands

- uwf thread steps <thread-id>: walk CAS chain, list all steps chronologically
- uwf thread fork <thread-id> <step-hash>: create new thread from history point
- New types: StartEntry, StepEntry, ThreadStepsOutput, ThreadForkOutput
- Supports both active and archived threads

Refs #342

packages/cli-uwf/src/cli.ts

@@ -3,11 +3,13 @@
 import { Command } from "commander";
 
 import {
+  cmdThreadFork,
   cmdThreadKill,
   cmdThreadList,
   cmdThreadShow,
   cmdThreadStart,
   cmdThreadStep,
+  cmdThreadSteps,
 } from "./commands/thread.js";
 import { cmdWorkflowList, cmdWorkflowPut, cmdWorkflowShow } from "./commands/workflow.js";
 import { cmdSetup, cmdSetupInteractive } from "./commands/setup.js";
@@ -144,6 +146,31 @@ thread
     });
   });
 
+thread
+  .command("steps")
+  .description("List all steps in a thread")
+  .argument("<thread-id>", "Thread ULID")
+  .action((threadId: string) => {
+    const storageRoot = resolveStorageRoot();
+    runAction(async () => {
+      const result = await cmdThreadSteps(storageRoot, threadId);
+      writeOutput(result);
+    });
+  });
+
+thread
+  .command("fork")
+  .description("Fork a thread from a specific step")
+  .argument("<thread-id>", "Thread ULID")
+  .argument("<step-hash>", "CAS hash of the step to fork from")
+  .action((threadId: string, stepHash: string) => {
+    const storageRoot = resolveStorageRoot();
+    runAction(async () => {
+      const result = await cmdThreadFork(storageRoot, threadId, stepHash);
+      writeOutput(result);
+    });
+  });
+
 program
   .command("setup")
   .description("Configure provider, model, and agent")

packages/cli-uwf/src/commands/thread.ts

@@ -8,13 +8,17 @@ import type {
   AgentConfig,
   CasRef,
   ModeratorContext,
+  StartEntry,
   StartNodePayload,
   StartOutput,
   StepContext,
+  StepEntry,
   StepNodePayload,
   StepOutput,
+  ThreadForkOutput,
   ThreadId,
   ThreadListItem,
+  ThreadStepsOutput,
   WorkflowConfig,
   WorkflowPayload,
 } from "@uncaged/uwf-protocol";
@@ -437,6 +441,131 @@ export async function cmdThreadStep(
   };
 }
 
+async function resolveHeadHash(storageRoot: string, threadId: ThreadId): Promise<CasRef> {
+  const index = await loadThreadsIndex(storageRoot);
+  const activeHead = index[threadId];
+  if (activeHead !== undefined) {
+    return activeHead;
+  }
+  const hist = await findThreadInHistory(storageRoot, threadId);
+  if (hist !== null) {
+    return hist.head;
+  }
+  fail(`thread not found: ${threadId}`);
+}
+
+export async function cmdThreadSteps(
+  storageRoot: string,
+  threadId: ThreadId,
+): Promise<ThreadStepsOutput> {
+  const headHash = await resolveHeadHash(storageRoot, threadId);
+  const uwf = await createUwfStore(storageRoot);
+  const chain = walkChain(uwf, headHash);
+
+  const startNode = uwf.store.get(chain.startHash);
+  if (startNode === null) {
+    fail(`StartNode not found: ${chain.startHash}`);
+  }
+
+  const startEntry: StartEntry = {
+    hash: chain.startHash,
+    workflow: chain.start.workflow,
+    prompt: chain.start.prompt,
+    timestamp: startNode.timestamp,
+  };
+
+  const stepEntries: StepEntry[] = [];
+
+  // Walk again to get hashes for each step
+  let hash: CasRef | null = headHash;
+  const hashToNode = new Map<string, { payload: StepNodePayload; timestamp: number }>();
+  while (hash !== null) {
+    const node = uwf.store.get(hash);
+    if (node === null || node.type !== uwf.schemas.stepNode) {
+      break;
+    }
+    const payload = node.payload as StepNodePayload;
+    hashToNode.set(hash, { payload, timestamp: node.timestamp });
+    hash = payload.prev;
+  }
+
+  // Build chronological list with hashes
+  // Walk from start's next to head
+  let cur: CasRef | null = chain.headIsStart ? null : headHash;
+  const ordered: { hash: CasRef; payload: StepNodePayload; timestamp: number }[] = [];
+  while (cur !== null) {
+    const entry = hashToNode.get(cur);
+    if (entry === undefined) break;
+    ordered.push({ hash: cur, ...entry });
+    cur = entry.payload.prev;
+  }
+  ordered.reverse();
+
+  for (const item of ordered) {
+    stepEntries.push({
+      hash: item.hash,
+      role: item.payload.role,
+      output: expandOutput(uwf, item.payload.output),
+      detail: item.payload.detail,
+      agent: item.payload.agent,
+      timestamp: item.timestamp,
+    });
+  }
+
+  return {
+    thread: threadId,
+    workflow: chain.start.workflow,
+    steps: [startEntry, ...stepEntries],
+  };
+}
+
+export async function cmdThreadFork(
+  storageRoot: string,
+  threadId: ThreadId,
+  stepHash: CasRef,
+): Promise<ThreadForkOutput> {
+  const headHash = await resolveHeadHash(storageRoot, threadId);
+  const uwf = await createUwfStore(storageRoot);
+
+  // Verify stepHash belongs to this thread by walking the chain
+  let found = false;
+  let cur: CasRef | null = headHash;
+  while (cur !== null) {
+    if (cur === stepHash) {
+      found = true;
+      break;
+    }
+    const node = uwf.store.get(cur);
+    if (node === null) break;
+    if (node.type === uwf.schemas.startNode) {
+      // startHash check
+      if (cur === stepHash) {
+        found = true;
+      }
+      break;
+    }
+    const payload = node.payload as StepNodePayload;
+    cur = payload.prev;
+  }
+
+  if (!found) {
+    fail(`step ${stepHash} not found in thread ${threadId}`);
+  }
+
+  const newThreadId = generateUlid(Date.now()) as ThreadId;
+  const index = await loadThreadsIndex(storageRoot);
+  index[newThreadId] = stepHash;
+  await saveThreadsIndex(storageRoot, index);
+
+  return {
+    thread: newThreadId,
+    forkedFrom: {
+      thread: threadId,
+      step: stepHash,
+    },
+  };
+}
+
 export async function cmdThreadKill(storageRoot: string, threadId: ThreadId): Promise<KillOutput> {
   const index = await loadThreadsIndex(storageRoot);
   const head = index[threadId];

packages/uwf-protocol/src/index.ts

@@ -16,14 +16,18 @@ export type {
   RoleDefinition,
   RoleName,
   Scenario,
+  StartEntry,
   StartNodePayload,
   StartOutput,
   StepContext,
+  StepEntry,
   StepNodePayload,
   StepOutput,
   StepRecord,
+  ThreadForkOutput,
   ThreadId,
   ThreadListItem,
+  ThreadStepsOutput,
   ThreadsIndex,
   Transition,
   WorkflowConfig,

packages/uwf-protocol/src/types.ts

@@ -80,6 +80,40 @@ export type StepOutput = {
   done: boolean;
 };
 
+/** uwf thread steps — single step entry */
+export type StepEntry = {
+  hash: CasRef;
+  role: string;
+  output: unknown;
+  detail: CasRef;
+  agent: string;
+  timestamp: number;
+};
+
+/** uwf thread steps — start entry */
+export type StartEntry = {
+  hash: CasRef;
+  workflow: CasRef;
+  prompt: string;
+  timestamp: number;
+};
+
+/** uwf thread steps output */
+export type ThreadStepsOutput = {
+  thread: ThreadId;
+  workflow: CasRef;
+  steps: [StartEntry, ...StepEntry[]];
+};
+
+/** uwf thread fork output */
+export type ThreadForkOutput = {
+  thread: ThreadId;
+  forkedFrom: {
+    thread: ThreadId;
+    step: CasRef;
+  };
+};
+
 /** uwf thread list */
 export type ThreadListItem = {
   thread: ThreadId;