diff --git a/packages/server/src/server/agent/agent-mcp.e2e.test.ts b/packages/server/src/server/agent/agent-mcp.e2e.test.ts
index 9d231bd06..d36412b6b 100644
--- a/packages/server/src/server/agent/agent-mcp.e2e.test.ts
+++ b/packages/server/src/server/agent/agent-mcp.e2e.test.ts
@@ -11,6 +11,14 @@ import pino from "pino";
 import { withTimeout } from "../../utils/promise-timeout.js";
 import { createPaseoDaemon, type PaseoDaemonConfig } from "../bootstrap.js";
 import { createTestAgentClients } from "../test-utils/fake-agent-client.js";
+import type {
+  AgentClient,
+  AgentPersistenceHandle,
+  AgentRunResult,
+  AgentSession,
+  AgentSessionConfig,
+  AgentStreamEvent,
+} from "./agent-sdk-types.js";
 
 interface StructuredContent {
   [key: string]: unknown;
@@ -19,6 +27,7 @@ interface StructuredContent {
 interface McpToolResult {
   structuredContent?: StructuredContent;
   content?: Array<{ structuredContent?: StructuredContent } | StructuredContent>;
+  isError?: boolean;
 }
 
 interface McpClient {
@@ -276,6 +285,222 @@ describe("agent MCP end-to-end (offline)", () => {
     }
   }, 30_000);
 
+  test("create_agent with background initialPrompt reflects running state once the first turn starts", async () => {
+    const paseoHome = await mkdtemp(path.join(os.tmpdir(), "paseo-home-"));
+    const staticDir = await mkdtemp(path.join(os.tmpdir(), "paseo-static-"));
+    const agentCwd = await mkdtemp(path.join(os.tmpdir(), "paseo-agent-cwd-"));
+    const port = await getAvailablePort();
+
+    const daemonConfig: PaseoDaemonConfig = {
+      listen: `127.0.0.1:${port}`,
+      paseoHome,
+      corsAllowedOrigins: [],
+      hostnames: true,
+      mcpEnabled: true,
+      staticDir,
+      mcpDebug: false,
+      agentClients: createTestAgentClients(),
+      agentStoragePath: path.join(paseoHome, "agents"),
+    };
+
+    const daemon = await createPaseoDaemon(daemonConfig, pino({ level: "silent" }));
+    await daemon.start();
+
+    const client = await createMcpClient(`http://127.0.0.1:${port}/mcp/agents`);
+
+    let agentId: string | null = null;
+    try {
+      const result = await client.callTool({
+        name: "create_agent",
+        args: {
+          cwd: agentCwd,
+          title: "MCP background create",
+          provider: "codex/gpt-5.4-mini",
+          mode: "full-access",
+          initialPrompt: "Run exactly: sleep 30",
+          background: true,
+        },
+      });
+
+      const payload = getStructuredContent(result);
+      agentId = typeof payload?.agentId === "string" ? payload.agentId : null;
+      expect(agentId).toBeTruthy();
+      expect(payload?.status).toBe("running");
+
+      const statusResult = await client.callTool({
+        name: "get_agent_status",
+        args: { agentId },
+      });
+      const statusPayload = getStructuredContent(statusResult);
+      expect(statusPayload?.status).toBe("running");
+    } finally {
+      if (agentId) {
+        await client.callTool({ name: "kill_agent", args: { agentId } });
+      }
+      await client.close();
+      await daemon.stop();
+      await rm(paseoHome, { recursive: true, force: true });
+      await rm(staticDir, { recursive: true, force: true });
+      await rm(agentCwd, { recursive: true, force: true });
+    }
+  }, 30_000);
+
+  test("create_agent propagates initial-turn start failure instead of returning success", async () => {
+    class StartTurnFailureSession implements AgentSession {
+      readonly provider = "codex" as const;
+      readonly id = "mcp-start-turn-failure-session";
+      readonly capabilities = {
+        supportsStreaming: false,
+        supportsSessionPersistence: true,
+        supportsDynamicModes: false,
+        supportsMcpServers: false,
+        supportsReasoningStream: false,
+        supportsToolInvocations: false,
+        supportsRewindConversation: false,
+        supportsRewindFiles: false,
+        supportsRewindBoth: false,
+      } as const;
+
+      async run(): Promise<AgentRunResult> {
+        return {
+          sessionId: this.id,
+          finalText: "",
+          timeline: [],
+        };
+      }
+
+      async startTurn(): Promise<{ turnId: string }> {
+        throw new Error("Initial turn failed to start");
+      }
+
+      subscribe(_callback: (event: AgentStreamEvent) => void): () => void {
+        return () => undefined;
+      }
+
+      async *streamHistory(): AsyncGenerator<AgentStreamEvent> {
+        yield* [];
+      }
+
+      async getRuntimeInfo() {
+        return {
+          provider: "codex" as const,
+          sessionId: this.id,
+          model: "gpt-5.4-mini",
+          modeId: "full-access",
+        };
+      }
+
+      async getAvailableModes(): Promise<
+        Array<{ id: string; label: string; description: string }>
+      > {
+        return [{ id: "full-access", label: "Full access", description: "No prompts" }];
+      }
+
+      async getCurrentMode(): Promise<string | null> {
+        return "full-access";
+      }
+
+      async setMode(): Promise<void> {}
+
+      getPendingPermissions() {
+        return [];
+      }
+
+      async respondToPermission(): Promise<void> {}
+
+      describePersistence(): AgentPersistenceHandle | null {
+        return { provider: "codex", sessionId: this.id };
+      }
+
+      async interrupt(): Promise<void> {}
+
+      async close(): Promise<void> {}
+    }
+
+    class StartTurnFailureClient implements AgentClient {
+      readonly provider = "codex" as const;
+      readonly capabilities = {
+        supportsStreaming: false,
+        supportsSessionPersistence: true,
+        supportsDynamicModes: false,
+        supportsMcpServers: false,
+        supportsReasoningStream: false,
+        supportsToolInvocations: false,
+        supportsRewindConversation: false,
+        supportsRewindFiles: false,
+        supportsRewindBoth: false,
+      } as const;
+
+      async isAvailable(): Promise<boolean> {
+        return true;
+      }
+
+      async createSession(_config: AgentSessionConfig): Promise<AgentSession> {
+        return new StartTurnFailureSession();
+      }
+
+      async resumeSession(
+        _handle: AgentPersistenceHandle,
+        _config?: Partial<AgentSessionConfig>,
+      ): Promise<AgentSession> {
+        return new StartTurnFailureSession();
+      }
+    }
+
+    const paseoHome = await mkdtemp(path.join(os.tmpdir(), "paseo-home-"));
+    const staticDir = await mkdtemp(path.join(os.tmpdir(), "paseo-static-"));
+    const agentCwd = await mkdtemp(path.join(os.tmpdir(), "paseo-agent-cwd-"));
+    const port = await getAvailablePort();
+
+    const daemonConfig: PaseoDaemonConfig = {
+      listen: `127.0.0.1:${port}`,
+      paseoHome,
+      corsAllowedOrigins: [],
+      hostnames: true,
+      mcpEnabled: true,
+      staticDir,
+      mcpDebug: false,
+      agentClients: {
+        ...createTestAgentClients(),
+        codex: new StartTurnFailureClient(),
+      },
+      agentStoragePath: path.join(paseoHome, "agents"),
+    };
+
+    const daemon = await createPaseoDaemon(daemonConfig, pino({ level: "silent" }));
+    await daemon.start();
+
+    const client = await createMcpClient(`http://127.0.0.1:${port}/mcp/agents`);
+
+    try {
+      const result = await client.callTool({
+        name: "create_agent",
+        args: {
+          cwd: agentCwd,
+          title: "MCP start failure",
+          provider: "codex/gpt-5.4-mini",
+          mode: "full-access",
+          initialPrompt: "Run exactly: sleep 30",
+          background: true,
+        },
+      });
+
+      expect(result.isError).toBe(true);
+      const contentItem = result.content?.[0];
+      const contentText: string | undefined =
+        contentItem != null && typeof contentItem === "object"
+          ? Reflect.get(contentItem, "text")
+          : undefined;
+      expect(contentText ?? "").toContain("Initial turn failed to start");
+    } finally {
+      await client.close();
+      await daemon.stop();
+      await rm(paseoHome, { recursive: true, force: true });
+      await rm(staticDir, { recursive: true, force: true });
+      await rm(agentCwd, { recursive: true, force: true });
+    }
+  }, 30_000);
+
   test("create_agent with worktree is async and boots terminals only after setup success", async () => {
     const paseoHome = await mkdtemp(path.join(os.tmpdir(), "paseo-home-"));
     const staticDir = await mkdtemp(path.join(os.tmpdir(), "paseo-static-"));
diff --git a/packages/server/src/server/agent/agent-prompt.ts b/packages/server/src/server/agent/agent-prompt.ts
index 97d4afc52..2c4a7c016 100644
--- a/packages/server/src/server/agent/agent-prompt.ts
+++ b/packages/server/src/server/agent/agent-prompt.ts
@@ -1,7 +1,7 @@
 import type { Logger } from "pino";
 
 import type { AgentPromptInput, AgentRunOptions } from "./agent-sdk-types.js";
-import type { AgentManager } from "./agent-manager.js";
+import type { AgentManager, ManagedAgent } from "./agent-manager.js";
 import type { AgentStorage } from "./agent-storage.js";
 import { ensureAgentLoaded } from "./agent-loading.js";
 
@@ -137,6 +137,31 @@ export interface SendPromptToAgentParams {
   logger: Logger;
 }
 
+export interface StartCreatedAgentInitialPromptParams {
+  agentManager: AgentManager;
+  agentId: string;
+  snapshot?: ManagedAgent;
+  prompt: AgentPromptInput | null;
+  runOptions?: AgentRunOptions;
+  logger: Logger;
+}
+
+const AGENT_RUN_START_TIMEOUT_MS = 15_000;
+
+export async function waitForAgentRunStartWithTimeout(
+  agentManager: AgentManager,
+  agentId: string,
+): Promise<void> {
+  const startAbort = new AbortController();
+  const startTimeout = setTimeout(() => startAbort.abort("timeout"), AGENT_RUN_START_TIMEOUT_MS);
+
+  try {
+    await agentManager.waitForAgentRunStart(agentId, { signal: startAbort.signal });
+  } finally {
+    clearTimeout(startTimeout);
+  }
+}
+
 /**
  * Full send-prompt orchestration: (optional unarchive) → load → (optional
  * mode change) → start run.
@@ -177,6 +202,39 @@ export async function sendPromptToAgent(
   });
 }
 
+export async function startCreatedAgentInitialPrompt(
+  params: StartCreatedAgentInitialPromptParams,
+): Promise<ManagedAgent> {
+  const currentSnapshot = params.agentManager.getAgent(params.agentId) ?? params.snapshot ?? null;
+  if (!currentSnapshot) {
+    throw new Error(`Agent ${params.agentId} not found`);
+  }
+
+  if (params.prompt === null) {
+    return currentSnapshot;
+  }
+
+  const dispatchResult = startAgentRun(
+    params.agentManager,
+    params.agentId,
+    params.prompt,
+    params.logger,
+    {
+      runOptions: params.runOptions,
+    },
+  );
+
+  if (!dispatchResult.outOfBand) {
+    await waitForAgentRunStartWithTimeout(params.agentManager, params.agentId);
+  }
+
+  const refreshedSnapshot = params.agentManager.getAgent(params.agentId) ?? params.snapshot ?? null;
+  if (!refreshedSnapshot) {
+    throw new Error(`Agent ${params.agentId} not found`);
+  }
+  return refreshedSnapshot;
+}
+
 export interface SetupFinishNotificationParams {
   agentManager: AgentManager;
   agentStorage: AgentStorage;
diff --git a/packages/server/src/server/agent/mcp-server.test.ts b/packages/server/src/server/agent/mcp-server.test.ts
index 7cba061a1..5eefbfabb 100644
--- a/packages/server/src/server/agent/mcp-server.test.ts
+++ b/packages/server/src/server/agent/mcp-server.test.ts
@@ -124,7 +124,11 @@ interface TestDeps {
 function buildAgentManagerSpies() {
   return {
     createAgent: vi.fn(),
-    waitForAgentEvent: vi.fn(),
+    waitForAgentEvent: vi.fn().mockResolvedValue({
+      status: "idle",
+      permission: null,
+      lastMessage: null,
+    }),
     setAgentMode: vi.fn().mockResolvedValue(undefined),
     setAgentModel: vi.fn().mockResolvedValue(undefined),
     setAgentThinkingOption: vi.fn().mockResolvedValue(undefined),
@@ -141,8 +145,10 @@ function buildAgentManagerSpies() {
     appendTimelineItem: vi.fn().mockResolvedValue(undefined),
     emitLiveTimelineItem: vi.fn().mockResolvedValue(undefined),
     hasInFlightRun: vi.fn().mockReturnValue(false),
+    tryRunOutOfBand: vi.fn().mockReturnValue(false),
     subscribe: vi.fn().mockReturnValue(() => {}),
     streamAgent: vi.fn(() => (async function* noop() {})()),
+    waitForAgentRunStart: vi.fn().mockResolvedValue(undefined),
     respondToPermission: vi.fn(),
     cancelAgentRun: vi.fn(),
     getPendingPermissions: vi.fn(),
diff --git a/packages/server/src/server/agent/mcp-server.ts b/packages/server/src/server/agent/mcp-server.ts
index a146d31ca..8d24b6139 100644
--- a/packages/server/src/server/agent/mcp-server.ts
+++ b/packages/server/src/server/agent/mcp-server.ts
@@ -75,7 +75,11 @@ import {
   toScheduleSummary,
   waitForAgentWithTimeout,
 } from "./mcp-shared.js";
-import { sendPromptToAgent, setupFinishNotification, startAgentRun } from "./agent-prompt.js";
+import {
+  sendPromptToAgent,
+  setupFinishNotification,
+  startCreatedAgentInitialPrompt,
+} from "./agent-prompt.js";
 import type { GitHubService } from "../../services/github-service.js";
 import type { WorkspaceGitService } from "../workspace-git-service.js";
 import type { CreatePaseoWorktreeInput } from "../paseo-worktree-service.js";
@@ -1105,8 +1109,15 @@ export async function createAgentMcpServer(options: AgentMcpServerOptions): Prom
         logger: childLogger,
       });
 
+      let liveSnapshot = snapshot;
       try {
-        startAgentRun(agentManager, snapshot.id, trimmedPrompt, childLogger);
+        liveSnapshot = await startCreatedAgentInitialPrompt({
+          agentManager,
+          agentId: snapshot.id,
+          snapshot,
+          prompt: trimmedPrompt,
+          logger: childLogger,
+        });
         if (notifyOnFinish && callerAgentId) {
           setupFinishNotification({
             agentManager,
@@ -1124,12 +1135,12 @@ export async function createAgentMcpServer(options: AgentMcpServerOptions): Prom
           });
 
           const responseData = {
-            agentId: snapshot.id,
+            agentId: liveSnapshot.id,
             type: provider,
             status: result.status,
-            cwd: snapshot.cwd,
-            currentModeId: snapshot.currentModeId,
-            availableModes: snapshot.availableModes,
+            cwd: liveSnapshot.cwd,
+            currentModeId: liveSnapshot.currentModeId,
+            availableModes: liveSnapshot.availableModes,
             lastMessage: result.lastMessage,
             permission: sanitizePermissionRequest(result.permission),
           };
@@ -1143,18 +1154,20 @@ export async function createAgentMcpServer(options: AgentMcpServerOptions): Prom
         }
       } catch (error) {
         childLogger.error({ err: error, agentId: snapshot.id }, "Failed to run initial prompt");
+        throw error;
       }
 
       // Return immediately if background=true
+      const currentSnapshot = agentManager.getAgent(snapshot.id) ?? liveSnapshot;
       const response = {
         content: [],
         structuredContent: ensureValidJson({
-          agentId: snapshot.id,
+          agentId: currentSnapshot.id,
           type: provider,
-          status: snapshot.lifecycle,
-          cwd: snapshot.cwd,
-          currentModeId: snapshot.currentModeId,
-          availableModes: snapshot.availableModes,
+          status: currentSnapshot.lifecycle,
+          cwd: currentSnapshot.cwd,
+          currentModeId: currentSnapshot.currentModeId,
+          availableModes: currentSnapshot.availableModes,
           lastMessage: null,
           permission: null,
         }),
diff --git a/packages/server/src/server/daemon-client.e2e.test.ts b/packages/server/src/server/daemon-client.e2e.test.ts
index b6b864a21..ad9d78aa8 100644
--- a/packages/server/src/server/daemon-client.e2e.test.ts
+++ b/packages/server/src/server/daemon-client.e2e.test.ts
@@ -121,6 +121,192 @@ test("DaemonClient surfaces password auth failures from WebSocket close reasons"
   }
 });
 
+test("createAgent without an initial prompt returns an idle snapshot", async () => {
+  const daemon = await createTestPaseoDaemon();
+  const client = new DaemonClient({
+    url: `ws://127.0.0.1:${daemon.port}/ws`,
+    appVersion: "0.1.82",
+  });
+
+  try {
+    await client.connect();
+    await client.fetchAgents({ subscribe: { subscriptionId: "create-no-prompt" } });
+
+    const agent = await client.createAgent({
+      provider: "codex",
+      cwd: tmpCwd(),
+      title: "No prompt agent",
+      modeId: "full-access",
+      model: "gpt-5.4-mini",
+    });
+
+    expect(agent.status).toBe("idle");
+  } finally {
+    await client.close();
+    await daemon.close();
+  }
+});
+
+test("createAgent with background initialPrompt returns a running snapshot before turn completion", async () => {
+  const daemon = await createTestPaseoDaemon();
+  const client = new DaemonClient({
+    url: `ws://127.0.0.1:${daemon.port}/ws`,
+    appVersion: "0.1.82",
+  });
+
+  try {
+    await client.connect();
+    await client.fetchAgents({ subscribe: { subscriptionId: "create-background-prompt" } });
+
+    const agent = await client.createAgent({
+      provider: "codex",
+      cwd: tmpCwd(),
+      title: "Background prompt agent",
+      modeId: "full-access",
+      model: "gpt-5.4-mini",
+      initialPrompt: "Run exactly: sleep 30",
+    });
+
+    expect(agent.status).toBe("running");
+
+    const fetchedWhileRunning = await client.fetchAgent(agent.id);
+    expect(fetchedWhileRunning?.agent.status).toBe("running");
+
+    await new Promise((resolve) => setTimeout(resolve, 350));
+
+    const fetchedAfterCompletion = await client.fetchAgent(agent.id);
+    expect(fetchedAfterCompletion?.agent.status).toBe("idle");
+  } finally {
+    await client.close();
+    await daemon.close();
+  }
+});
+
+test("createAgent fails when the initial turn cannot start", async () => {
+  class StartTurnFailureSession implements AgentSession {
+    readonly provider = "codex" as const;
+    readonly id = "start-turn-failure-session";
+    readonly capabilities = {
+      supportsStreaming: false,
+      supportsSessionPersistence: true,
+      supportsDynamicModes: false,
+      supportsMcpServers: false,
+      supportsReasoningStream: false,
+      supportsToolInvocations: false,
+      supportsRewindConversation: false,
+      supportsRewindFiles: false,
+      supportsRewindBoth: false,
+    } as const;
+
+    async run(): Promise<AgentRunResult> {
+      return {
+        sessionId: this.id,
+        finalText: "",
+        timeline: [],
+      };
+    }
+
+    async startTurn(): Promise<{ turnId: string }> {
+      throw new Error("Initial turn failed to start");
+    }
+
+    subscribe(): () => void {
+      return () => undefined;
+    }
+
+    async *streamHistory(): AsyncGenerator<AgentStreamEvent> {
+      yield* [];
+    }
+
+    async getRuntimeInfo() {
+      return {
+        provider: "codex" as const,
+        sessionId: this.id,
+        model: "gpt-5.4-mini",
+        modeId: "full-access",
+      };
+    }
+
+    async getAvailableModes(): Promise<Array<{ id: string; label: string; description: string }>> {
+      return [{ id: "full-access", label: "Full access", description: "No prompts" }];
+    }
+
+    async getCurrentMode(): Promise<string | null> {
+      return "full-access";
+    }
+
+    async setMode(): Promise<void> {}
+
+    getPendingPermissions() {
+      return [];
+    }
+
+    async respondToPermission(): Promise<void> {}
+
+    describePersistence(): AgentPersistenceHandle | null {
+      return { provider: "codex", sessionId: this.id };
+    }
+
+    async interrupt(): Promise<void> {}
+
+    async close(): Promise<void> {}
+  }
+
+  class StartTurnFailureClient implements AgentClient {
+    readonly provider = "codex" as const;
+    readonly capabilities = {
+      supportsStreaming: false,
+      supportsSessionPersistence: true,
+      supportsDynamicModes: false,
+      supportsMcpServers: false,
+      supportsReasoningStream: false,
+      supportsToolInvocations: false,
+      supportsRewindConversation: false,
+      supportsRewindFiles: false,
+      supportsRewindBoth: false,
+    } as const;
+
+    async isAvailable(): Promise<boolean> {
+      return true;
+    }
+
+    async createSession(_config: AgentSessionConfig): Promise<AgentSession> {
+      return new StartTurnFailureSession();
+    }
+
+    async resumeSession(): Promise<AgentSession> {
+      return new StartTurnFailureSession();
+    }
+  }
+
+  const daemon = await createTestPaseoDaemon({
+    agentClients: { codex: new StartTurnFailureClient() },
+  });
+  const client = new DaemonClient({
+    url: `ws://127.0.0.1:${daemon.port}/ws`,
+    appVersion: "0.1.82",
+  });
+
+  try {
+    await client.connect();
+    await client.fetchAgents({ subscribe: { subscriptionId: "create-start-failure" } });
+
+    await expect(
+      client.createAgent({
+        provider: "codex",
+        cwd: tmpCwd(),
+        title: "Start failure agent",
+        modeId: "full-access",
+        model: "gpt-5.4-mini",
+        initialPrompt: "Run exactly: sleep 30",
+      }),
+    ).rejects.toThrow("Initial turn failed to start");
+  } finally {
+    await client.close();
+    await daemon.close();
+  }
+});
+
 function waitForSignal<T>(
   timeoutMs: number,
   setup: (resolve: (value: T) => void, reject: (error: Error) => void) => () => void,
diff --git a/packages/server/src/server/session.ts b/packages/server/src/server/session.ts
index e4c392cde..460d62c2e 100644
--- a/packages/server/src/server/session.ts
+++ b/packages/server/src/server/session.ts
@@ -68,6 +68,8 @@ import { ensureAgentLoaded } from "./agent/agent-loading.js";
 import {
   formatSystemNotificationPrompt,
   sendPromptToAgent,
+  startCreatedAgentInitialPrompt,
+  waitForAgentRunStartWithTimeout,
   unarchiveAgentState,
 } from "./agent/agent-prompt.js";
 import { experimental_createMCPClient } from "ai";
@@ -3188,7 +3190,7 @@ export class Session {
         createdWorktree,
       });
 
-      await this.sendInitialCreateAgentPrompt({
+      const liveSnapshot = await this.sendInitialCreateAgentPrompt({
         snapshot,
         trimmedPrompt,
         images,
@@ -3199,12 +3201,12 @@ export class Session {
       });
 
       if (requestId) {
-        const agentPayload = await this.buildAgentPayload(snapshot);
+        const agentPayload = await this.buildAgentPayload(liveSnapshot);
         this.emit({
           type: "status",
           payload: {
             status: "agent_created",
-            agentId: snapshot.id,
+            agentId: liveSnapshot.id,
             requestId,
             agent: agentPayload,
           },
@@ -3250,20 +3252,20 @@ export class Session {
   }
 
   private async sendInitialCreateAgentPrompt(params: {
-    snapshot: { id: string; cwd: string };
+    snapshot: ManagedAgent;
     trimmedPrompt: string | undefined;
     images: Array<{ data: string; mimeType: string }> | undefined;
     attachments: AgentAttachment[] | undefined;
     clientMessageId: string | undefined;
     outputSchema: Record<string, unknown> | undefined;
     explicitTitle: string | null;
-  }): Promise<void> {
+  }): Promise<ManagedAgent> {
     const { snapshot, trimmedPrompt, images, attachments, clientMessageId, outputSchema } = params;
     const hasPrompt = Boolean(trimmedPrompt);
     const hasImages = (images?.length ?? 0) > 0;
     const hasAttachments = (attachments?.length ?? 0) > 0;
     if (!hasPrompt && !hasImages && !hasAttachments) {
-      return;
+      return snapshot;
     }
     scheduleAgentMetadataGeneration({
       agentManager: this.agentManager,
@@ -3275,18 +3277,18 @@ export class Session {
       paseoHome: this.paseoHome,
       logger: this.sessionLogger,
     });
+    const prompt = this.buildAgentPrompt(trimmedPrompt || "", images, attachments);
 
-    const started = await this.handleSendAgentMessage(
-      snapshot.id,
-      trimmedPrompt || "",
-      resolveClientMessageId(clientMessageId),
-      images,
-      attachments,
-      outputSchema ? { outputSchema } : undefined,
-    );
-    if (!started.ok) {
-      throw new Error(started.error);
-    }
+    return await startCreatedAgentInitialPrompt({
+      agentManager: this.agentManager,
+      agentId: snapshot.id,
+      snapshot,
+      prompt,
+      runOptions: outputSchema ? { outputSchema } : undefined,
+      logger: this.sessionLogger.child({
+        clientMessageId: resolveClientMessageId(clientMessageId),
+      }),
+    });
   }
 
   private async handleResumeAgentRequest(
@@ -7814,11 +7816,8 @@ export class Session {
         return;
       }
 
-      const startAbort = new AbortController();
-      const startTimeoutMs = 15_000;
-      const startTimeout = setTimeout(() => startAbort.abort("timeout"), startTimeoutMs);
       try {
-        await this.agentManager.waitForAgentRunStart(agentId, { signal: startAbort.signal });
+        await waitForAgentRunStartWithTimeout(this.agentManager, agentId);
       } catch (error) {
         this.emit({
           type: "send_agent_message_response",
@@ -7830,8 +7829,6 @@ export class Session {
           },
         });
         return;
-      } finally {
-        clearTimeout(startTimeout);
       }
 
       this.emit({