fix(server): steer Codex turns while native identification is pending

Wait for the accepted foreground turn to receive its native ID before steering it. Returning unavailable in this window replaced the turn even after the manager had waited for startup.

packages/server/src/server/agent/agent-manager.test.ts

@@ -956,6 +956,131 @@ test("unavailable steer interrupts once and starts one replacement turn", async
   }
 });
 
+test("steers a send that arrives while the previous turn is still starting", async () => {
+  const startHeld = deferred<void>();
+  class SlowStartSteeringSession extends SteeringTestSession {
+    override async startTurn(prompt: AgentPromptInput): Promise<{ turnId: string }> {
+      await startHeld.promise;
+      return await super.startTurn(prompt);
+    }
+  }
+  const session = new SlowStartSteeringSession({
+    provider: "codex",
+    cwd: process.cwd(),
+  });
+  const workdir = mkdtempSync(join(tmpdir(), "agent-manager-steer-starting-"));
+  const manager = new AgentManager({
+    clients: {
+      codex: new (class extends TestAgentClient {
+        override async createSession(): Promise<AgentSession> {
+          return session;
+        }
+      })(),
+    },
+    logger,
+  });
+  let agentId: string | null = null;
+  try {
+    const agent = await manager.createAgent({ provider: "codex", cwd: workdir }, undefined, {
+      workspaceId: undefined,
+    });
+    agentId = agent.id;
+    const steerOptions = (clientMessageId: string) => ({
+      replaceRunning: true,
+      activeTurnBehavior: "steer" as const,
+      runOptions: { clientMessageId },
+    });
+    await startAgentRun(manager, agent.id, "FIRST", logger, steerOptions("first-client"));
+    const second = startAgentRun(
+      manager,
+      agent.id,
+      "SECOND",
+      logger,
+      steerOptions("second-client"),
+    );
+
+    startHeld.resolve();
+    await expect(second).resolves.toEqual({ disposition: "steered" });
+
+    expect(session.startPrompts).toEqual(["FIRST"]);
+    expect(session.interruptCount).toBe(0);
+    expect(
+      manager
+        .fetchTimeline(agent.id, { limit: 0 })
+        .rows.filter((row) => row.item.type === "user_message")
+        .map((row) => ({
+          text: row.item.type === "user_message" ? row.item.text : null,
+          turnId: row.turnId,
+        })),
+    ).toEqual([
+      { text: "FIRST", turnId: "active-turn-1" },
+      { text: "SECOND", turnId: "active-turn-1" },
+    ]);
+  } finally {
+    startHeld.resolve();
+    if (agentId) await manager.closeAgent(agentId).catch(() => undefined);
+    rmSync(workdir, { recursive: true, force: true });
+  }
+});
+
+test("starts its own turn when the previous turn fails to start under a steer send", async () => {
+  const startHeld = deferred<void>();
+  class FailingFirstStartSession extends SteeringTestSession {
+    override async startTurn(prompt: AgentPromptInput): Promise<{ turnId: string }> {
+      if (prompt === "FIRST") {
+        this.startPrompts.push(prompt);
+        await startHeld.promise;
+        throw new Error("first start failed");
+      }
+      return await super.startTurn(prompt);
+    }
+  }
+  const session = new FailingFirstStartSession({
+    provider: "codex",
+    cwd: process.cwd(),
+  });
+  const workdir = mkdtempSync(join(tmpdir(), "agent-manager-steer-failed-start-"));
+  const manager = new AgentManager({
+    clients: {
+      codex: new (class extends TestAgentClient {
+        override async createSession(): Promise<AgentSession> {
+          return session;
+        }
+      })(),
+    },
+    logger,
+  });
+  let agentId: string | null = null;
+  try {
+    const agent = await manager.createAgent({ provider: "codex", cwd: workdir }, undefined, {
+      workspaceId: undefined,
+    });
+    agentId = agent.id;
+    const steerOptions = (clientMessageId: string) => ({
+      replaceRunning: true,
+      activeTurnBehavior: "steer" as const,
+      runOptions: { clientMessageId },
+    });
+    await startAgentRun(manager, agent.id, "FIRST", logger, steerOptions("first-client"));
+    const second = startAgentRun(
+      manager,
+      agent.id,
+      "SECOND",
+      logger,
+      steerOptions("second-client"),
+    );
+
+    startHeld.resolve();
+    await expect(second).resolves.toEqual({ disposition: "turn_started" });
+    await vi.waitFor(() => expect(session.startPrompts).toEqual(["FIRST", "SECOND"]));
+    expect(session.interruptCount).toBe(0);
+  } finally {
+    startHeld.resolve();
+    if (agentId) await manager.closeAgent(agentId).catch(() => undefined);
+    rmSync(workdir, { recursive: true, force: true });
+  }
+});
+
 test("orders an accepted steer before output emitted while acknowledgement is pending", async () => {
   const entered = deferred<void>();
   const release = deferred<void>();

packages/server/src/server/agent/agent-manager.ts

@@ -2734,7 +2734,7 @@ export class AgentManager {
         throw error;
       }
       if (isStaleProviderSessionError(error)) {
-        pendingRun.start = { status: "failed", error: error.message };
+        this.runs.settleForegroundStart(pendingRun, { status: "failed", error: error.message });
         agent.pendingReplacement = false;
         if (!agent.activeForegroundTurnId) agent.lifecycle = "idle";
         this.runs.settleForegroundRun(agentId, pendingRun.token);
@@ -2742,20 +2742,24 @@ export class AgentManager {
       }
       agent.pendingReplacement = false;
       const errorMsg = error instanceof Error ? error.message : "Failed to start turn";
-      pendingRun.start = { status: "failed", error: errorMsg };
-      // A terminal rejection belongs after the submitted prompt even though no provider turn exists.
-      if (options?.clientMessageId) {
-        this.recordSubmittedPrompt(agent, prompt, options.clientMessageId, "rejected", {
-          messageId: options.clientMessageId,
+      this.runs.settleForegroundStart(pendingRun, { status: "failed", error: errorMsg });
+      try {
+        // A terminal rejection belongs after the submitted prompt even though no provider turn exists.
+        if (options?.clientMessageId) {
+          this.recordSubmittedPrompt(agent, prompt, options.clientMessageId, "rejected", {
+            messageId: options.clientMessageId,
+          });
+        }
+        await this.handleStreamEvent(agent, {
+          type: "turn_failed",
+          provider: agent.provider,
+          error: errorMsg,
         });
+        this.finalizeForegroundTurn(agent);
+      } finally {
+        // A steer waiting on this start is released only once the run is cleared.
+        this.runs.settleForegroundRun(agentId, pendingRun.token);
       }
-      await this.handleStreamEvent(agent, {
-        type: "turn_failed",
-        provider: agent.provider,
-        error: errorMsg,
-      });
-      this.finalizeForegroundTurn(agent);
-      this.runs.settleForegroundRun(agentId, pendingRun.token);
       throw error;
     }
   }
@@ -2832,7 +2836,7 @@ export class AgentManager {
         agent.pendingReplacement = false;
       }
       const turnStartedAt = new Date();
-      pendingRun.start = { status: "started", turnId };
+      this.runs.settleForegroundStart(pendingRun, { status: "started", turnId });
       agent.activeForegroundTurnId = turnId;
       this.openActiveTurn(agent, turnId, turnStartedAt);
       agent.lifecycle = "running";
@@ -3041,6 +3045,9 @@ export class AgentManager {
     prompt: AgentPromptInput,
     options?: AgentSteerOptions,
   ): Promise<ActiveTurnSteerDispatchResult> {
+    // A turn that is still starting has no id to steer yet. Replacing it would drop its
+    // prompt, so wait until it is accepted (or fails) and steer the turn it became.
+    await this.runs.waitForForegroundStart(agentId);
     const agent = this.requireSessionAgent(agentId);
     const expectedTurnId = agent.activeForegroundTurnId ?? agent.activeTurnId;
     if (!expectedTurnId) {

packages/server/src/server/agent/agent-run-state.test.ts

@@ -0,0 +1,51 @@
+import { describe, expect, test } from "vitest";
+
+import { AgentRunState } from "./agent-run-state.js";
+
+function track(promise: Promise<void>): { readonly resolved: boolean } {
+  const state = { resolved: false };
+  void (async () => {
+    await promise;
+    state.resolved = true;
+  })();
+  return state;
+}
+
+async function flushMicrotasks(): Promise<void> {
+  await new Promise<void>((resolve) => setImmediate(resolve));
+}
+
+describe("waitForForegroundStart", () => {
+  test("resolves once the starting turn has an id", async () => {
+    const runs = new AgentRunState();
+    const run = runs.createPendingRun("agent");
+    const wait = track(runs.waitForForegroundStart("agent"));
+
+    await flushMicrotasks();
+    expect(wait.resolved).toBe(false);
+
+    runs.settleForegroundStart(run, { status: "started", turnId: "turn-1" });
+    await flushMicrotasks();
+    expect(wait.resolved).toBe(true);
+  });
+
+  test("waits for a failed start's run to be cleared", async () => {
+    const runs = new AgentRunState();
+    const run = runs.createPendingRun("agent");
+    const wait = track(runs.waitForForegroundStart("agent"));
+
+    runs.settleForegroundStart(run, { status: "failed", error: "start failed" });
+    await flushMicrotasks();
+    expect(wait.resolved).toBe(false);
+    expect(runs.hasPendingRun("agent")).toBe(true);
+
+    runs.settleForegroundRun("agent", run.token);
+    await flushMicrotasks();
+    expect(wait.resolved).toBe(true);
+  });
+
+  test("resolves at once when no turn is starting", async () => {
+    const runs = new AgentRunState();
+    await expect(runs.waitForForegroundStart("agent")).resolves.toBeUndefined();
+  });
+});

packages/server/src/server/agent/agent-run-state.ts

@@ -10,14 +10,18 @@ export interface ForegroundTurnWaiter {
   resolveSettled: () => void;
 }
 
+type ForegroundRunStart =
+  | { status: "pending" }
+  | { status: "started"; turnId: string }
+  | { status: "failed"; error: string };
+
 export interface PendingForegroundRun {
   token: string;
   kind: "foreground";
   stagedEvents: AgentStreamEvent[];
-  start:
-    | { status: "pending" }
-    | { status: "started"; turnId: string }
-    | { status: "failed"; error: string };
+  start: ForegroundRunStart;
+  turnStartedPromise: Promise<void>;
+  resolveTurnStarted: () => void;
   settled: boolean;
   settledPromise: Promise<void>;
   resolveSettled: () => void;
@@ -54,6 +58,28 @@ export class AgentRunState {
     return run?.kind === "foreground" ? run : null;
   }
 
+  settleForegroundStart(
+    run: PendingForegroundRun,
+    start: Exclude<ForegroundRunStart, { status: "pending" }>,
+  ): void {
+    run.start = start;
+    if (start.status === "started") {
+      run.resolveTurnStarted();
+    }
+  }
+
+  /**
+   * Resolves once the agent's foreground run has a turn id or has ended. A failed start
+   * resolves only once its run is cleared, so callers never see a failed run still tracked.
+   */
+  async waitForForegroundStart(agentId: string): Promise<void> {
+    const run = this.getPendingRun(agentId);
+    if (run?.start.status !== "pending") {
+      return;
+    }
+    await Promise.race([run.turnStartedPromise, run.settledPromise]);
+  }
+
   hasPendingRun(agentId: string): boolean {
     return this.getPendingRun(agentId) !== null;
   }
@@ -277,10 +303,16 @@ export class ForegroundTurnStream {
 }
 
 function createPendingForegroundRun(): PendingForegroundRun {
+  let resolveTurnStarted!: () => void;
+  const turnStartedPromise = new Promise<void>((resolvePromise) => {
+    resolveTurnStarted = resolvePromise;
+  });
   return {
     ...createTrackedRunState(),
     kind: "foreground",
     start: { status: "pending" },
+    turnStartedPromise,
+    resolveTurnStarted,
     stagedEvents: [],
   };
 }

packages/server/src/server/agent/providers/codex-app-server-agent.test.ts

@@ -16,6 +16,7 @@ import type {
   AgentSessionConfig,
   AgentSlashCommand,
   AgentStreamEvent,
+  AgentTimelineItem,
 } from "../agent-sdk-types.js";
 import {
   buildCodexAppServerEnv,
@@ -114,7 +115,6 @@ interface CodexSessionTestAccess {
   ensureThreadLoaded(): Promise<void>;
   handleToolApprovalRequest(params: unknown): Promise<unknown>;
   handleNotification(method: string, params: unknown): Promise<void>;
-  loadPersistedHistory(client: CodexClientLike | null): Promise<void>;
   refreshResolvedCollaborationMode(): void;
   serviceTier: "fast" | null;
   planModeEnabled: boolean;
@@ -226,6 +226,64 @@ function deferred<T>() {
 }
 
 describe("Codex active-turn steering admission", () => {
+  test("steers an accepted turn whose native id arrives after startTurn returns", async () => {
+    const appServer = createFakeCodexAppServer({
+      "turn/steer": () => ({ turn: { id: "native-A" } }),
+    });
+    const session = new CodexAppServerAgentSession(
+      createConfig({ cwd: "/workspace/project" }),
+      null,
+      createTestLogger(),
+      async () => appServer.child,
+    );
+    try {
+      const { turnId } = await session.startTurn("FIRST");
+      const steer = session.steerActiveTurn("SECOND", { expectedTurnId: turnId });
+      appServer.startsTurn({ threadId: "thread-1", turnId: "native-A" });
+
+      await expect(steer).resolves.toEqual({ status: "accepted" });
+      expect(
+        appServer.requests().filter((request) => request.method === "turn/start"),
+      ).toHaveLength(1);
+      expect(appServer.requests().filter((request) => request.method === "turn/interrupt")).toEqual(
+        [],
+      );
+      expect(appServer.requests().find((request) => request.method === "turn/steer")).toMatchObject(
+        {
+          params: {
+            threadId: "thread-1",
+            expectedTurnId: "native-A",
+            input: [{ type: "text", text: "SECOND" }],
+          },
+        },
+      );
+      appServer.assertNoErrors();
+    } finally {
+      await session.close();
+    }
+  });
+
+  test("releases a waiting steer when the accepted turn ends before identification", async () => {
+    const appServer = createFakeCodexAppServer();
+    const session = new CodexAppServerAgentSession(
+      createConfig({ cwd: "/workspace/project" }),
+      null,
+      createTestLogger(),
+      async () => appServer.child,
+    );
+    try {
+      const { turnId } = await session.startTurn("FIRST");
+      const steer = session.steerActiveTurn("SECOND", { expectedTurnId: turnId });
+      appServer.completeTurn();
+
+      await expect(steer).resolves.toEqual({ status: "unavailable" });
+      expect(appServer.requests().filter((request) => request.method === "turn/steer")).toEqual([]);
+      appServer.assertNoErrors();
+    } finally {
+      await session.close();
+    }
+  });
+
   test("a steer without the clearing contract leaves permissions open", async () => {
     const appServer = createFakeCodexAppServer({
       "turn/steer": () => ({ turn: { id: "native-A" } }),
@@ -503,6 +561,81 @@ function archivedThreadErrorMessage(threadId: string): string {
   );
 }
 
+function codexUserItem(id: string, text: string) {
+  return { type: "userMessage", id, content: [{ type: "text", text }] };
+}
+
+function codexAgentItem(text: string) {
+  return { type: "agentMessage", id: `agent-${text}`, text };
+}
+
+// An AgentManager over a real Codex provider whose every spawn gets a fresh fake
+// app-server serving `threads` from thread/read.
+function createReopenableCodexAgent(threads: Record<string, unknown[]>) {
+  const appServers: FakeCodexAppServer[] = [];
+  const provider = new CodexAppServerAgentClient(createTestLogger());
+  const internals = castInternals<{
+    goalsEnabledPromise: Promise<boolean> | null;
+    autoReviewEnabledPromise: Promise<boolean> | null;
+    spawnAppServer: () => Promise<ChildProcessWithoutNullStreams>;
+  }>(provider);
+  internals.goalsEnabledPromise = Promise.resolve(false);
+  internals.autoReviewEnabledPromise = Promise.resolve(false);
+  internals.spawnAppServer = async () => {
+    const appServer = createFakeCodexAppServer({
+      "thread/read": (params) => {
+        const { threadId } = params as { threadId: string };
+        return { thread: { id: threadId, turns: threads[threadId] ?? [] } };
+      },
+    });
+    appServers.push(appServer);
+    return appServer.child;
+  };
+  // The fake app-server stands in for the Codex CLI, which test machines may not have.
+  const client: AgentClient = {
+    provider: "codex",
+    capabilities: provider.capabilities,
+    isAvailable: async () => true,
+    fetchCatalog: async () => ({ models: [], modes: [] }),
+    createSession: async () => {
+      throw new Error("Unexpected create");
+    },
+    resumeSession: (...args) => provider.resumeSession(...args),
+  };
+  const manager = new AgentManager({ clients: { codex: client }, logger: createTestLogger() });
+  const agentId = "00000000-0000-4000-8000-000000000001";
+  const handle = { provider: "codex", sessionId: "saved-thread" };
+  const config = createConfig({ cwd: process.cwd() });
+
+  async function open(): Promise<void> {
+    await manager.resumeAgentFromPersistence(handle, config, agentId);
+    await manager.hydrateTimelineFromProvider(agentId);
+  }
+
+  return {
+    manager,
+    agentId,
+    latestAppServer: () => appServers[appServers.length - 1],
+    threadMethods: (index: number) =>
+      appServers[index]
+        .requests()
+        .map((request) => request.method)
+        .filter((method) => typeof method === "string" && method.startsWith("thread/")),
+    // Cold-loads the agent, closes its runtime, and reopens it while Paseo keeps its timeline.
+    async loadCloseAndReopen(): Promise<AgentTimelineItem[]> {
+      await open();
+      const projected = manager.getTimeline(agentId);
+      await manager.closeAgent(agentId);
+      await open();
+      return projected;
+    },
+    async close(): Promise<void> {
+      await manager.closeAgent(agentId);
+      for (const appServer of appServers) appServer.assertNoErrors();
+    },
+  };
+}
+
 function asInternals(session: CodexTestSession): CodexSessionTestAccess {
   return castInternals<CodexSessionTestAccess>(session);
 }
@@ -1897,12 +2030,147 @@ describe("Codex app-server provider", () => {
       "thread/resume",
       "thread/unarchive",
       "thread/resume",
-      "thread/read",
     ]);
     await session.close();
     appServer.assertNoErrors();
   });
 
+  test("resumes a Codex thread without asking for its turns", async () => {
+    const appServer = createFakeCodexAppServer();
+    const provider = createProviderWithFakeAppServer(appServer);
+
+    const session = await provider.resumeSession({ sessionId: "saved-thread" });
+
+    expect(
+      appServer
+        .requests()
+        .filter((request) => request.method === "thread/resume")
+        .map((request) => request.params),
+    ).toEqual([expect.objectContaining({ threadId: "saved-thread", excludeTurns: true })]);
+    await session.close();
+    appServer.assertNoErrors();
+  });
+
+  test("reopening an agent whose timeline Paseo still holds does not read Codex history", async () => {
+    const codex = createReopenableCodexAgent({
+      "saved-thread": [
+        { id: "turn-1", items: [codexUserItem("user-1", "Hello"), codexAgentItem("Hi there.")] },
+      ],
+    });
+    try {
+      const projected = await codex.loadCloseAndReopen();
+
+      expect(projected).toEqual([
+        expect.objectContaining({ type: "user_message", messageId: "user-1", text: "Hello" }),
+        expect.objectContaining({ type: "assistant_message", text: "Hi there." }),
+      ]);
+      expect(codex.threadMethods(0)).toEqual([
+        "thread/loaded/list",
+        "thread/resume",
+        "thread/read",
+      ]);
+      expect(codex.threadMethods(1)).toEqual(["thread/loaded/list", "thread/resume"]);
+      expect(codex.manager.getTimeline(codex.agentId)).toEqual(projected);
+    } finally {
+      await codex.close();
+    }
+  });
+
+  test("rewinds an agent reopened without reading its Codex history", async () => {
+    const firstTurn = {
+      id: "turn-1",
+      items: [codexUserItem("user-1", "First"), codexAgentItem("First answer.")],
+    };
+    const codex = createReopenableCodexAgent({
+      "saved-thread": [
+        firstTurn,
+        { id: "turn-2", items: [codexUserItem("user-2", "Second"), codexAgentItem("Second.")] },
+      ],
+      "forked-thread": [firstTurn],
+    });
+    try {
+      await codex.loadCloseAndReopen();
+
+      await codex.manager.rewind(codex.agentId, "user-2", "conversation");
+
+      expect(codex.latestAppServer().recordedRollbacks).toEqual([
+        { threadId: "forked-thread", numTurns: 1 },
+      ]);
+      expect(codex.manager.getTimeline(codex.agentId)).toEqual([
+        expect.objectContaining({ type: "user_message", messageId: "user-1", text: "First" }),
+        expect.objectContaining({ type: "assistant_message", text: "First answer." }),
+      ]);
+    } finally {
+      await codex.close();
+    }
+  });
+
+  test("keeps a reopened agent's interaction with an earlier sub-agent on its original card", async () => {
+    const codex = createReopenableCodexAgent({
+      "saved-thread": [
+        {
+          id: "turn-1",
+          items: [
+            codexUserItem("user-1", "Delegate"),
+            {
+              type: "subAgentActivity",
+              id: "spawn-child",
+              kind: "started",
+              agentThreadId: "child-thread",
+              agentPath: "/root/child",
+            },
+          ],
+        },
+      ],
+      "child-thread": [{ id: "child-turn-1", items: [codexAgentItem("Child started.")] }],
+    });
+    try {
+      await codex.loadCloseAndReopen();
+      const appServer = codex.latestAppServer();
+
+      const run = codex.manager.runAgent(codex.agentId, "Ask the child again");
+      await appServer.waitForTurnStart();
+      appServer.startsTurn({ threadId: "saved-thread", turnId: "turn-2" });
+      appServer.beginsSubAgentActivity({
+        callId: "interact-child",
+        threadId: "child-thread",
+        parentThreadId: "saved-thread",
+        kind: "interacted",
+        agentPath: "/root/child",
+      });
+      appServer.says({ threadId: "child-thread", itemId: "child-reply", text: "Child replied." });
+      appServer.completesSubAgentActivity({
+        callId: "interact-child",
+        threadId: "child-thread",
+        parentThreadId: "saved-thread",
+        kind: "interacted",
+        agentPath: "/root/child",
+      });
+      appServer.completeTurn({ threadId: "saved-thread" });
+      await run;
+
+      const toolCalls = codex.manager
+        .getTimeline(codex.agentId)
+        .filter((item) => item.type === "tool_call");
+      expect(new Set(toolCalls.map((item) => item.callId))).toEqual(new Set(["spawn-child"]));
+      expect(toolCalls.at(-1)).toMatchObject({ callId: "spawn-child", status: "completed" });
+      expect(codex.manager.getProviderSubagent(codex.agentId, "child-thread")).toMatchObject({
+        toolCallId: "spawn-child",
+        status: "completed",
+      });
+      expect(
+        codex.manager
+          .fetchProviderSubagentTimeline(codex.agentId, "child-thread")
+          .rows.map((row) => row.item),
+      ).toEqual([
+        expect.objectContaining({ type: "assistant_message", text: "Child started." }),
+        expect.objectContaining({ type: "assistant_message", text: "Child replied." }),
+      ]);
+    } finally {
+      await codex.close();
+    }
+  });
+
   test("closes Codex app-server when an interactive resume fails", async () => {
     const appServer = createFakeCodexAppServer({
       "thread/resume": () => Promise.reject(new Error("thread resume failed")),
@@ -4673,8 +4941,6 @@ describe("Codex app-server provider", () => {
       }),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);
@@ -4727,7 +4993,7 @@ describe("Codex app-server provider", () => {
       })),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
+    await Array.fromAsync(session.streamHistory());
 
     expect(asInternals(session).codexUserMessageTurns().resolve("message-history")).toEqual({
       index: 0,
@@ -4796,8 +5062,6 @@ describe("Codex app-server provider", () => {
       }),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);
@@ -4958,8 +5222,6 @@ describe("Codex app-server provider", () => {
       }),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);
@@ -5023,8 +5285,6 @@ describe("Codex app-server provider", () => {
       }),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);
@@ -5200,8 +5460,6 @@ describe("Codex app-server provider", () => {
       }),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);
@@ -5261,8 +5519,6 @@ describe("Codex app-server provider", () => {
       }),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);
@@ -5564,7 +5820,10 @@ describe("Codex app-server provider", () => {
     expect(session.currentThreadId).toBe("archived-thread-id");
     expect(requests).toEqual([
       { method: "thread/loaded/list", params: {} },
-      { method: "thread/resume", params: { threadId: "archived-thread-id" } },
+      {
+        method: "thread/resume",
+        params: { threadId: "archived-thread-id", excludeTurns: true },
+      },
     ]);
   });
 
@@ -6399,8 +6658,6 @@ describe("Codex app-server provider", () => {
       })),
     };
 
-    await asInternals(session).loadPersistedHistory(session.client);
-
     const history: AgentStreamEvent[] = [];
     for await (const event of session.streamHistory()) {
       history.push(event);

packages/server/src/server/agent/providers/codex-app-server-agent.ts

@@ -496,6 +496,11 @@ interface PersistedTimelineEntry {
   providerTurnId?: string;
 }
 
+interface CodexThreadHistory {
+  timeline: PersistedTimelineEntry[];
+  providerSubagentEvents: AgentStreamEvent[];
+}
+
 interface PersistedSubAgentRoute {
   childThreadId: string;
   toolCall: ToolCallTimelineItem;
@@ -3464,10 +3469,12 @@ export class CodexAppServerAgentSession implements AgentSession {
   private serviceTier: string | null = null;
   private speedModels: CodexModel[] = [];
   private planModeEnabled = false;
-  private historyPending = false;
-  private persistedHistory: PersistedTimelineEntry[] = [];
-  private loadingPersistedHistory = false;
-  private persistedProviderSubagentEvents: AgentStreamEvent[] = [];
+  // History read by rewind or an archived resume, held until streamHistory consumes it.
+  private stagedHistory: CodexThreadHistory | null = null;
+  // Collects provider subagent events emitted while a thread history read rebuilds routes.
+  private historySubagentEvents: AgentStreamEvent[] | null = null;
+  // A resumed thread's earlier turns and sub-agents are known only after reading its history.
+  private historyIndexed = true;
   private pendingPermissions = new Map<string, AgentPermissionRequest>();
   private mcpElicitationPermissionIds = new Map<number, string>();
   private pendingPermissionHandlers = new Map<string, CodexPendingPermissionHandler>();
@@ -3574,7 +3581,7 @@ export class CodexAppServerAgentSession implements AgentSession {
 
     if (this.resumeHandle?.sessionId) {
       this.currentThreadId = this.resumeHandle.sessionId;
-      this.historyPending = true;
+      this.historyIndexed = false;
       // Resuming can start a goal before the caller receives the session.
       if (this.initialResumePurpose === "interactive") this.startupEvents = [];
     }
@@ -3622,7 +3629,7 @@ export class CodexAppServerAgentSession implements AgentSession {
 
   private async establishConnection(): Promise<void> {
     if (this.initialResumePurpose === "history") {
-      await this.readArchivedHistory();
+      this.stagedHistory = await this.readArchivedHistory();
       this.connectionState = "history-ready";
       return;
     }
@@ -3655,7 +3662,6 @@ export class CodexAppServerAgentSession implements AgentSession {
 
       if (this.currentThreadId) {
         await this.ensureThreadLoaded();
-        await this.loadPersistedHistory(this.client);
         await this.applyDefaultModelAndThinking();
       }
 
@@ -3970,39 +3976,40 @@ export class CodexAppServerAgentSession implements AgentSession {
     );
   }
 
-  private async readArchivedHistory(): Promise<void> {
+  private async readArchivedHistory(): Promise<CodexThreadHistory> {
     const child = await this.spawnAppServer();
     const client = new CodexAppServerClient(child, this.logger, () => this.traceContext());
     try {
       await client.request("initialize", buildCodexAppServerInitializeParams());
       client.notify("initialized", {});
-      await this.loadPersistedHistory(client);
+      return await this.readThreadHistory(client);
     } finally {
       await client.dispose();
     }
   }
 
-  private async loadPersistedHistory(client: CodexAppServerClientLike | null): Promise<void> {
-    if (!client || !this.currentThreadId) return;
-    const threadId = this.currentThreadId;
-
-    const history = await loadCodexThreadHistoryTimeline({
-      threadId,
+  // Reads the thread and its sub-agent threads, rebuilding the turn index and
+  // sub-agent routes. The caller owns the returned history; nothing retains it.
+  private async readThreadHistory(
+    client: CodexAppServerClientLike | null,
+  ): Promise<CodexThreadHistory> {
+    if (!client || !this.currentThreadId) {
+      return { timeline: [], providerSubagentEvents: [] };
+    }
+    const { timeline, subAgentRoutes } = await loadCodexThreadHistoryTimeline({
+      threadId: this.currentThreadId,
       cwd: this.config.cwd ?? null,
-      requestThread: (threadIdToRead) => {
-        return readCodexThread(client, threadIdToRead);
-      },
+      requestThread: (threadIdToRead) => readCodexThread(client, threadIdToRead),
     });
-    const { timeline, subAgentRoutes } = history;
     this.subAgentCallsByCallId.clear();
     this.subAgentCallIdByChildThreadId.clear();
     this.pendingSubAgentNotificationsByThreadId.clear();
-    this.persistedProviderSubagentEvents = [];
-    this.loadingPersistedHistory = true;
+    const providerSubagentEvents: AgentStreamEvent[] = [];
+    this.historySubagentEvents = providerSubagentEvents;
     try {
       await this.loadPersistedSubAgentHistories(client, subAgentRoutes);
     } finally {
-      this.loadingPersistedHistory = false;
+      this.historySubagentEvents = null;
     }
     this.resetCodexUserMessageTurns();
     for (const entry of timeline) {
@@ -4013,8 +4020,15 @@ export class CodexAppServerAgentSession implements AgentSession {
         this.rememberCodexUserMessageTurn(entry.item.messageId, entry.providerTurnId);
       }
     }
-    this.persistedHistory = timeline;
-    this.historyPending = timeline.length > 0;
+    this.historyIndexed = true;
+    return { timeline, providerSubagentEvents };
+  }
+
+  // Turns and rewind route by the thread's earlier turns and sub-agents. A resumed
+  // session whose projection Paseo already holds reads them here and drops the rest.
+  private async ensureHistoryIndexed(): Promise<void> {
+    if (this.historyIndexed) return;
+    await this.readThreadHistory(this.client);
   }
 
   private async loadPersistedSubAgentHistories(
@@ -4066,7 +4080,8 @@ export class CodexAppServerAgentSession implements AgentSession {
 
   private async ensureThreadLoaded(): Promise<void> {
     if (!this.client || !this.currentThreadId) return;
-    const params: Record<string, unknown> = { threadId: this.currentThreadId };
+    // Paseo reads history only when it replays it; the resume response needs no turns.
+    const params: Record<string, unknown> = { threadId: this.currentThreadId, excludeTurns: true };
     const developerInstructions = composeSystemPromptParts(
       this.config.systemPrompt,
       this.config.daemonAppendSystemPrompt,
@@ -4386,6 +4401,7 @@ export class CodexAppServerAgentSession implements AgentSession {
 
       if (this.currentThreadId) {
         await this.ensureThreadLoaded();
+        await this.ensureHistoryIndexed();
       } else {
         await this.ensureThread();
       }
@@ -4440,9 +4456,18 @@ export class CodexAppServerAgentSession implements AgentSession {
   ): Promise<SteerResult> {
     const client = this.client;
     const threadId = this.currentThreadId;
-    const nativeTurnId = this.currentTurnId;
+    let nativeTurnId = this.currentTurnId;
     const foregroundTurnId = this.activeForegroundTurnId;
-    if (!client || !threadId || !nativeTurnId || foregroundTurnId !== options.expectedTurnId) {
+    if (!client || !threadId || foregroundTurnId !== options.expectedTurnId) {
+      return { status: "unavailable" };
+    }
+    const pendingIdentification = this.pendingForegroundTurnIdentification;
+    // The start acknowledgement precedes the notification that identifies the native
+    // turn. Keep this steer attached to the accepted foreground turn while it arrives.
+    if (!nativeTurnId && pendingIdentification?.foregroundTurnId === foregroundTurnId) {
+      nativeTurnId = await pendingIdentification.promise;
+    }
+    if (!nativeTurnId) {
       return { status: "unavailable" };
     }
     if (await this.resolveSlashCommandInvocation(prompt)) return { status: "unavailable" };
@@ -4559,21 +4584,12 @@ export class CodexAppServerAgentSession implements AgentSession {
   }
 
   async *streamHistory(): AsyncGenerator<AgentStreamEvent> {
-    if (
-      (!this.historyPending || this.persistedHistory.length === 0) &&
-      this.persistedProviderSubagentEvents.length === 0
-    ) {
-      return;
-    }
-    const history = this.persistedHistory;
-    const providerSubagents = this.persistedProviderSubagentEvents;
-    this.persistedHistory = [];
-    this.persistedProviderSubagentEvents = [];
-    this.historyPending = false;
-    for (const event of providerSubagents) {
+    const history = this.stagedHistory ?? (await this.readThreadHistory(this.client));
+    this.stagedHistory = null;
+    for (const event of history.providerSubagentEvents) {
       yield event;
     }
-    for (const entry of history) {
+    for (const entry of history.timeline) {
       yield {
         type: "timeline",
         provider: CODEX_PROVIDER,
@@ -4956,6 +4972,7 @@ export class CodexAppServerAgentSession implements AgentSession {
     } else {
       await this.ensureThread();
     }
+    await this.ensureHistoryIndexed();
 
     await revertCodexConversation({
       client: this.client,
@@ -4970,10 +4987,8 @@ export class CodexAppServerAgentSession implements AgentSession {
       setThreadId: async (threadId) => {
         this.currentThreadId = threadId;
         this.cachedRuntimeInfo = null;
-        this.persistedHistory = [];
-        this.historyPending = false;
-        await this.loadPersistedHistory(this.client);
-        this.reconcileAsyncQuestionsAfterRewind();
+        this.stagedHistory = await this.readThreadHistory(this.client);
+        this.reconcileAsyncQuestionsAfterRewind(this.stagedHistory.timeline);
       },
     });
   }
@@ -5211,6 +5226,8 @@ export class CodexAppServerAgentSession implements AgentSession {
       await this.connect();
       if (this.currentThreadId) {
         await this.ensureThreadLoaded();
+        // A goal runs turns of its own.
+        await this.ensureHistoryIndexed();
       } else {
         await this.ensureThread();
       }
@@ -5404,8 +5421,8 @@ export class CodexAppServerAgentSession implements AgentSession {
   }
 
   private emitEvent(event: AgentStreamEvent): void {
-    if (this.loadingPersistedHistory && event.type === "provider_subagent") {
-      this.persistedProviderSubagentEvents.push(event);
+    if (this.historySubagentEvents && event.type === "provider_subagent") {
+      this.historySubagentEvents.push(event);
       return;
     }
     this.notifySubscribers(event);
@@ -6583,9 +6600,9 @@ export class CodexAppServerAgentSession implements AgentSession {
     }
   }
 
-  private reconcileAsyncQuestionsAfterRewind(): void {
+  private reconcileAsyncQuestionsAfterRewind(timeline: readonly PersistedTimelineEntry[]): void {
     const retainedIds = new Set(
-      this.persistedHistory.flatMap(({ item }) =>
+      timeline.flatMap(({ item }) =>
         item.type === "tool_call" && item.name === "request_user_input_async" ? [item.callId] : [],
       ),
     );

packages/server/src/server/daemon-e2e/codex-steer-starting.real.e2e.test.ts

@@ -0,0 +1,80 @@
+import { expect, test } from "vitest";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+import pino from "pino";
+
+import { CodexAppServerAgentClient } from "../agent/providers/codex-app-server-agent.js";
+import { DaemonClient } from "../test-utils/daemon-client.js";
+import { createMessageCollector } from "../test-utils/message-collector.js";
+import { createTestPaseoDaemon } from "../test-utils/paseo-daemon.js";
+import { canRunRealProvider } from "./real-provider-test-config.js";
+
+test("keeps two concurrent startup steer messages in one real Codex turn", async (context) => {
+  if (!(await canRunRealProvider("codex"))) {
+    context.skip();
+    return;
+  }
+  const cwd = mkdtempSync(path.join(tmpdir(), "codex-steer-starting-"));
+  const logger = pino({ level: "silent" });
+  const daemon = await createTestPaseoDaemon({
+    agentClients: { codex: new CodexAppServerAgentClient(logger) },
+    logger,
+  });
+  const client = new DaemonClient({ url: `ws://127.0.0.1:${daemon.port}/ws` });
+  const collector = createMessageCollector(client);
+  const subscriptions: ReturnType<DaemonClient["subscribeAgentTimeline"]>[] = [];
+  try {
+    await client.connect();
+    await client.fetchAgents({ subscribe: {} });
+    for (let attempt = 0; attempt < 3; attempt += 1) {
+      const agent = await client.createAgent({
+        cwd,
+        provider: "codex",
+        modeId: "full-access",
+      });
+      const subscription = client.subscribeAgentTimeline(agent.id, () => {});
+      subscriptions.push(subscription);
+      await subscription.ready;
+      await Promise.all([
+        client.sendAgentMessage(agent.id, "Reply exactly: FIRST", {
+          messageId: `first-${attempt}`,
+          activeTurnBehavior: "steer",
+        }),
+        client.sendAgentMessage(agent.id, "Reply exactly: SECOND", {
+          messageId: `second-${attempt}`,
+          activeTurnBehavior: "steer",
+        }),
+      ]);
+      await client.waitForFinish(agent.id, 90_000);
+      const timeline = await client.fetchAgentTimeline(agent.id, { limit: 100 });
+      const users = timeline.entries.filter((entry) => entry.item.type === "user_message");
+      const events = collector.messages.flatMap((message) =>
+        message.type === "agent_stream" && message.payload.agentId === agent.id
+          ? [message.payload.event]
+          : [],
+      );
+      expect(users.map((entry) => entry.item.text).sort()).toEqual([
+        "Reply exactly: FIRST",
+        "Reply exactly: SECOND",
+      ]);
+      expect(new Set(users.map((entry) => entry.turnId)).size).toBe(1);
+      expect(events.filter((event) => event.type === "turn_started")).toHaveLength(1);
+      expect(
+        events.filter((event) => event.type === "turn_canceled" || event.type === "turn_failed"),
+      ).toHaveLength(0);
+      expect(
+        timeline.entries.some(
+          (entry) =>
+            entry.item.type === "assistant_message" && entry.item.text.includes("[System Error]"),
+        ),
+      ).toBe(false);
+    }
+  } finally {
+    await Promise.all(subscriptions.map((subscription) => subscription.release()));
+    collector.unsubscribe();
+    await client.close();
+    await daemon.close();
+    rmSync(cwd, { recursive: true, force: true });
+  }
+}, 300_000);