FN-5907: harden planning task creation side effects

Keep Planning Mode task creation responses successful when follow-up work fails.

- catch and log planning create-task/create-tasks side-effect failures so the API can still return 201 after task creation succeeds
- safely handle async task lifecycle listener failures in the core store to avoid leaking unhandled rejections during follow-up updates
- add regression coverage for single-task and multi-task Planning Mode creation across live/persisted sessions, branch selection surfaces, and GitHub tracking failures

Files changed:
 .changeset/fn-5907-planning-create-fetch.md        |   5 +
 .../core/src/__tests__/task-creation-hook.test.ts  |  25 ++
 packages/core/src/store.ts                         |  38 ++-
 .../src/__tests__/routes-planning-tracking.test.ts | 108 ++++++++-
 .../src/__tests__/routes-planning.test.ts          | 267 +++++++++++++++++++++
 .../src/routes/register-planning-subtask-routes.ts |  69 +++++-
 6 files changed, 496 insertions(+), 16 deletions(-)

Fusion-Task-Id: FN-5907

Fusion-Task-Lineage: d9f6574b-e19b-4459-a612-7a3d2510836f

.changeset/fn-5907-planning-create-fetch.md

@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Fix a Planning Mode reliability bug where creating a single task could fail with a browser-level `Failed to fetch` error when post-create side effects threw or rejected before the dashboard finished responding.

packages/core/src/__tests__/task-creation-hook.test.ts

@@ -108,6 +108,31 @@ describe("task creation hook", () => {
     expect(created2.id).toMatch(/^FN-/);
   });
 
+  it("does not leak async task:updated listener rejections during create follow-up updates", async () => {
+    const store = harness.store();
+    const unhandledRejections: unknown[] = [];
+    const onUnhandledRejection = (reason: unknown) => {
+      unhandledRejections.push(reason);
+    };
+    process.on("unhandledRejection", onUnhandledRejection);
+
+    store.on("task:updated", async (task) => {
+      if (task.id.startsWith("FN-")) {
+        throw new Error(`listener boom for ${task.id}`);
+      }
+    });
+
+    try {
+      const task = await store.createTask({ description: "planning create listener safety" });
+      await store.updateTask(task.id, { size: "M" });
+      await store.logEntry(task.id, "Created via Planning Mode", "Initial plan: test");
+      await new Promise((resolve) => setImmediate(resolve));
+      expect(unhandledRejections).toHaveLength(0);
+    } finally {
+      process.off("unhandledRejection", onUnhandledRejection);
+    }
+  });
+
   it("can clear hook with undefined", async () => {
     const store = harness.store();
     const hook = vi.fn();

packages/core/src/store.ts

@@ -1224,6 +1224,34 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     this.globalSettingsStore = new GlobalSettingsStore(resolvedGlobalSettingsDir);
   }
 
+  private emitTaskLifecycleEventSafely(
+    event: "task:created" | "task:updated",
+    args: TaskStoreEvents["task:created"] | TaskStoreEvents["task:updated"],
+  ): boolean {
+    const listeners = super.listeners(event) as Array<(...listenerArgs: typeof args) => unknown>;
+    if (listeners.length === 0) {
+      return false;
+    }
+
+    const [task] = args;
+    const taskId = task && typeof task === "object" && "id" in task ? String(task.id) : "unknown";
+
+    for (const listener of listeners) {
+      try {
+        const result = listener(...args);
+        if (result && typeof (result as PromiseLike<unknown>).then === "function") {
+          void Promise.resolve(result).catch((error) => {
+            storeLog.warn(`[${event}] listener failed for ${taskId}: ${getErrorMessage(error)}`);
+          });
+        }
+      } catch (error) {
+        storeLog.warn(`[${event}] listener failed for ${taskId}: ${getErrorMessage(error)}`);
+      }
+    }
+
+    return true;
+  }
+
   /**
    * Get the SQLite database, initializing it on first access.
    * Also performs auto-migration from legacy file-based storage if needed.
@@ -4001,7 +4029,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
 
     await this._maybeAutoArchiveSameAgentDuplicate(task, input);
 
-    this.emit("task:created", task);
+    this.emitTaskLifecycleEventSafely("task:created", [task]);
     if (options?.invokeTaskCreatedHook !== false) {
       await this.invokeTaskCreatedHook(task);
     }
@@ -5850,7 +5878,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       if (movedToTriage) {
         this.emit("task:moved", { task, from: "todo" as Column, to: "triage" as Column, source: "engine" });
       }
-      this.emit("task:updated", task);
+      this.emitTaskLifecycleEventSafely("task:updated", [task]);
       return task;
     });
   }
@@ -6521,7 +6549,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       if (movedToTriage) {
         this.emit("task:moved", { task, from: "todo" as Column, to: "triage" as Column, source: "engine" });
       }
-      this.emit("task:updated", task);
+      this.emitTaskLifecycleEventSafely("task:updated", [task]);
       return task;
     });
   }
@@ -6772,12 +6800,12 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
         if (this.isWatching) {
           this.taskCache.set(id, { ...current });
         }
-        this.emit("task:updated", current);
+        this.emitTaskLifecycleEventSafely("task:updated", [current]);
         return current;
       }
 
       const emittedTask = ({ id, log, updatedAt } as unknown) as Task;
-      this.emit("task:updated", emittedTask);
+      this.emitTaskLifecycleEventSafely("task:updated", [emittedTask]);
       return emittedTask;
     });
   }

packages/dashboard/src/__tests__/routes-planning-tracking.test.ts

@@ -200,7 +200,39 @@ describe("planning routes github tracking background dispatch", () => {
 
     expect(response.status).toBe(201);
     await vi.waitFor(() => {
-      expect(planningWarn).toHaveBeenCalled();
+      expect(planningWarn).toHaveBeenCalledWith(expect.stringContaining("[github-tracking] Failed to create issue"));
+    });
+  });
+
+  it("POST /planning/create-task still returns 201 when createIssue throws synchronously", async () => {
+    createIssueSpy.mockImplementation(() => {
+      throw new Error("sync github crash");
+    });
+
+    sessions.set("plan-2-sync", {
+      summary: {
+        title: "Planned task 2",
+        description: "Planned task description 2",
+        suggestedSize: "M",
+        priority: "normal",
+        suggestedDependencies: [],
+        keyDeliverables: [],
+      },
+      initialPlan: "initial",
+      history: [],
+    });
+
+    const response = await performRequest(
+      app,
+      "POST",
+      "/planning/create-task",
+      JSON.stringify({ sessionId: "plan-2-sync" }),
+      { "content-type": "application/json" },
+    );
+
+    expect(response.status).toBe(201);
+    await vi.waitFor(() => {
+      expect(planningWarn).toHaveBeenCalledWith(expect.stringContaining("[github-tracking] Failed to create issue"));
     });
   });
 
@@ -250,4 +282,78 @@ describe("planning routes github tracking background dispatch", () => {
       expect(createIssueSpy).toHaveBeenCalledTimes(2);
     });
   });
+
+  it("POST /planning/create-tasks still returns 201 when createIssue rejects asynchronously", async () => {
+    createIssueSpy.mockRejectedValue(new Error("github down"));
+
+    sessions.set("plan-3-reject", {
+      summary: {
+        title: "Plan",
+        description: "Plan",
+        suggestedSize: "M",
+        priority: "normal",
+        suggestedDependencies: [],
+        keyDeliverables: [],
+      },
+      initialPlan: "initial",
+      history: [],
+    });
+
+    const response = await performRequest(
+      app,
+      "POST",
+      "/planning/create-tasks",
+      JSON.stringify({
+        planningSessionId: "plan-3-reject",
+        subtasks: [
+          { id: "tmp-1", title: "Subtask 1", description: "D1" },
+          { id: "tmp-2", title: "Subtask 2", description: "D2" },
+        ],
+      }),
+      { "content-type": "application/json" },
+    );
+
+    expect(response.status).toBe(201);
+    await vi.waitFor(() => {
+      expect(planningWarn).toHaveBeenCalledWith(expect.stringContaining("[github-tracking] Failed to create issue"));
+    });
+  });
+
+  it("POST /planning/create-tasks still returns 201 when createIssue throws synchronously", async () => {
+    createIssueSpy.mockImplementation(() => {
+      throw new Error("sync github crash");
+    });
+
+    sessions.set("plan-3-sync", {
+      summary: {
+        title: "Plan",
+        description: "Plan",
+        suggestedSize: "M",
+        priority: "normal",
+        suggestedDependencies: [],
+        keyDeliverables: [],
+      },
+      initialPlan: "initial",
+      history: [],
+    });
+
+    const response = await performRequest(
+      app,
+      "POST",
+      "/planning/create-tasks",
+      JSON.stringify({
+        planningSessionId: "plan-3-sync",
+        subtasks: [
+          { id: "tmp-1", title: "Subtask 1", description: "D1" },
+          { id: "tmp-2", title: "Subtask 2", description: "D2" },
+        ],
+      }),
+      { "content-type": "application/json" },
+    );
+
+    expect(response.status).toBe(201);
+    await vi.waitFor(() => {
+      expect(planningWarn).toHaveBeenCalledWith(expect.stringContaining("[github-tracking] Failed to create issue"));
+    });
+  });
 });

packages/dashboard/src/__tests__/routes-planning.test.ts

@@ -421,6 +421,23 @@ describe("Planning Mode Routes", () => {
       return app;
     }
 
+    async function createCompletedPlanningSession(initialPlan = "Build a user auth system"): Promise<string> {
+      const startRes = await REQUEST(
+        buildApp(),
+        "POST",
+        "/api/planning/start",
+        JSON.stringify({ initialPlan }),
+        { "Content-Type": "application/json" }
+      );
+      const sessionId = startRes.body.sessionId;
+
+      await REQUEST(buildApp(), "POST", "/api/planning/respond", JSON.stringify({ sessionId, responses: { scope: "medium" } }), { "Content-Type": "application/json" });
+      await REQUEST(buildApp(), "POST", "/api/planning/respond", JSON.stringify({ sessionId, responses: { requirements: "Must have login" } }), { "Content-Type": "application/json" });
+      await REQUEST(buildApp(), "POST", "/api/planning/respond", JSON.stringify({ sessionId, responses: { confirm: true } }), { "Content-Type": "application/json" });
+
+      return sessionId;
+    }
+
     async function connectPlanningStreamUntilComplete(sessionId: string): Promise<void> {
       const streamPromise = REQUEST(buildApp(), "GET", `/api/planning/${sessionId}/stream`);
       setTimeout(() => {
@@ -1952,6 +1969,256 @@ describe("Planning Mode Routes", () => {
         });
       });
 
+      it.each([
+        {
+          sessionSource: "live",
+          useSummaryOverride: false,
+          branchSelection: { mode: "project-default" },
+          expectedBranch: undefined,
+          expectedBaseBranch: undefined,
+        },
+        {
+          sessionSource: "live",
+          useSummaryOverride: true,
+          branchSelection: { mode: "auto-new", baseBranch: "develop" },
+          expectedBranch: undefined,
+          expectedBaseBranch: "develop",
+        },
+        {
+          sessionSource: "persisted",
+          useSummaryOverride: false,
+          branchSelection: { mode: "existing", branchName: "feature/shared-auth", baseBranch: "develop" },
+          expectedBranch: "feature/shared-auth",
+          expectedBaseBranch: "develop",
+        },
+        {
+          sessionSource: "persisted",
+          useSummaryOverride: true,
+          branchSelection: { mode: "custom-new", branchName: "feature/planned-auth", baseBranch: "main" },
+          expectedBranch: "feature/planned-auth",
+          expectedBaseBranch: "main",
+        },
+      ])("returns 201 for $sessionSource create-task sessions across branch selection surfaces (summary override: $useSummaryOverride)", async ({
+        sessionSource,
+        useSummaryOverride,
+        branchSelection,
+        expectedBranch,
+        expectedBaseBranch,
+      }) => {
+        (store.createTask as ReturnType<typeof vi.fn>).mockResolvedValue({
+          id: `FN-${sessionSource}-${branchSelection.mode}`,
+          description: "Build auth flow",
+          column: "triage",
+          dependencies: [],
+          createdAt: "2026-01-01T00:00:00.000Z",
+          updatedAt: "2026-01-01T00:00:00.000Z",
+        });
+        (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue({});
+        (store.logEntry as ReturnType<typeof vi.fn>).mockResolvedValue(undefined);
+
+        let app = buildApp();
+        let sessionId: string;
+
+        if (sessionSource === "live") {
+          sessionId = await createCompletedPlanningSession();
+        } else {
+          sessionId = `persisted-${branchSelection.mode}-${useSummaryOverride ? "override" : "default"}`;
+          const persistedSession = {
+            id: sessionId,
+            type: "planning",
+            status: "complete",
+            title: "Build persisted planning",
+            inputPayload: JSON.stringify({ initialPlan: "Build resumable planning sessions" }),
+            conversationHistory: "[]",
+            currentQuestion: null,
+            result: JSON.stringify({
+              title: "Persisted planning output",
+              description: "Persist planning results so users can create tasks later",
+              suggestedSize: "M",
+              priority: "normal",
+              suggestedDependencies: ["FN-100"],
+              keyDeliverables: ["Persist sessions"],
+            }),
+            thinkingOutput: "",
+            error: null,
+            projectId: null,
+            createdAt: "2026-01-01T00:00:00.000Z",
+            updatedAt: "2026-01-01T00:00:00.000Z",
+            archived: 0,
+          };
+          const mockAiSessionStore = {
+            get: vi.fn((id: string) => (id === sessionId ? persistedSession : null)),
+            listAll: vi.fn(() => []),
+            delete: vi.fn(),
+          };
+          app = express();
+          app.use(express.json());
+          app.use("/api", createApiRoutes(store, { aiSessionStore: mockAiSessionStore as any }));
+        }
+
+        const summary = useSummaryOverride
+          ? {
+              title: "Edited auth task",
+              description: "Edited description from summary view",
+              suggestedSize: "S",
+              suggestedDependencies: ["FN-500"],
+              keyDeliverables: ["Login flow"],
+            }
+          : undefined;
+
+        const res = await REQUEST(
+          app,
+          "POST",
+          "/api/planning/create-task",
+          JSON.stringify({ sessionId, branchSelection, ...(summary ? { summary } : {}) }),
+          { "Content-Type": "application/json" }
+        );
+
+        expect(res.status).toBe(201);
+        expect(store.createTask).toHaveBeenCalledWith(
+          expect.objectContaining({
+            title: useSummaryOverride ? "Edited auth task" : expect.any(String),
+            branch: expectedBranch,
+            baseBranch: expectedBaseBranch,
+          }),
+        );
+      });
+
+      it.each([
+        { label: "size update rejection", configure: () => (store.updateTask as ReturnType<typeof vi.fn>).mockRejectedValueOnce(new Error("size update failed")) },
+        { label: "log entry rejection", configure: () => (store.logEntry as ReturnType<typeof vi.fn>).mockRejectedValueOnce(new Error("log entry failed")) },
+      ])("still returns 201 when planning create-task post-create side effects fail (%s)", async ({ configure }) => {
+        (store.createTask as ReturnType<typeof vi.fn>).mockResolvedValue({
+          id: "FN-250",
+          description: "Build a user auth system",
+          column: "triage",
+          dependencies: [],
+          createdAt: "2026-01-01T00:00:00.000Z",
+          updatedAt: "2026-01-01T00:00:00.000Z",
+        });
+        (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue({});
+        (store.logEntry as ReturnType<typeof vi.fn>).mockResolvedValue(undefined);
+        configure();
+
+        const sessionId = await createCompletedPlanningSession();
+        const res = await REQUEST(
+          buildApp(),
+          "POST",
+          "/api/planning/create-task",
+          JSON.stringify({ sessionId }),
+          { "Content-Type": "application/json" }
+        );
+
+        expect(res.status).toBe(201);
+      });
+
+      it("still returns 201 when planning create-task session release throws", async () => {
+        (store.createTask as ReturnType<typeof vi.fn>).mockResolvedValue({
+          id: "FN-251",
+          description: "Build a user auth system",
+          column: "triage",
+          dependencies: [],
+          createdAt: "2026-01-01T00:00:00.000Z",
+          updatedAt: "2026-01-01T00:00:00.000Z",
+        });
+        (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue({});
+        (store.logEntry as ReturnType<typeof vi.fn>).mockResolvedValue(undefined);
+        const releaseSessionSpy = vi.spyOn(planningModule, "releaseSession").mockImplementation(() => {
+          throw new Error("release exploded");
+        });
+
+        try {
+          const sessionId = await createCompletedPlanningSession();
+          const res = await REQUEST(
+            buildApp(),
+            "POST",
+            "/api/planning/create-task",
+            JSON.stringify({ sessionId }),
+            { "Content-Type": "application/json" }
+          );
+
+          expect(res.status).toBe(201);
+        } finally {
+          releaseSessionSpy.mockRestore();
+        }
+      });
+
+      it("still returns 201 when planning create-tasks post-create updates fail", async () => {
+        (store.createTask as ReturnType<typeof vi.fn>)
+          .mockResolvedValueOnce({
+            id: "FN-260",
+            description: "First",
+            column: "triage",
+            dependencies: [],
+            createdAt: "2026-01-01T00:00:00.000Z",
+            updatedAt: "2026-01-01T00:00:00.000Z",
+          })
+          .mockResolvedValueOnce({
+            id: "FN-261",
+            description: "Second",
+            column: "triage",
+            dependencies: [],
+            createdAt: "2026-01-01T00:00:00.000Z",
+            updatedAt: "2026-01-01T00:00:00.000Z",
+          });
+        (store.updateTask as ReturnType<typeof vi.fn>)
+          .mockRejectedValueOnce(new Error("size update failed"))
+          .mockResolvedValueOnce({
+            id: "FN-261",
+            description: "Second",
+            column: "triage",
+            dependencies: ["FN-260"],
+            createdAt: "2026-01-01T00:00:00.000Z",
+            updatedAt: "2026-01-01T00:00:00.000Z",
+          });
+        (store.logEntry as ReturnType<typeof vi.fn>).mockResolvedValue(undefined);
+
+        const planningSessionId = await createCompletedPlanningSession();
+        const breakdownRes = await REQUEST(
+          buildApp(),
+          "POST",
+          "/api/planning/start-breakdown",
+          JSON.stringify({ sessionId: planningSessionId }),
+          { "Content-Type": "application/json" }
+        );
+
+        const generatedSubtasks = breakdownRes.body.subtasks as Array<{
+          id: string;
+          title: string;
+          description: string;
+          suggestedSize: "S" | "M" | "L";
+          dependsOn: string[];
+        }>;
+
+        const res = await REQUEST(
+          buildApp(),
+          "POST",
+          "/api/planning/create-tasks",
+          JSON.stringify({
+            planningSessionId,
+            subtasks: [
+              {
+                id: generatedSubtasks[0]!.id,
+                title: "Auth backend",
+                description: "Implement backend",
+                suggestedSize: "L",
+                dependsOn: [],
+              },
+              {
+                id: generatedSubtasks[1]!.id,
+                title: "Auth frontend",
+                description: "Implement frontend",
+                dependsOn: [generatedSubtasks[0]!.id],
+              },
+            ],
+          }),
+          { "Content-Type": "application/json" }
+        );
+
+        expect(res.status).toBe(201);
+        expect(res.body.tasks).toHaveLength(2);
+      });
+
       it("creates task with explicit summary priority", async () => {
         (store.createTask as ReturnType<typeof vi.fn>).mockResolvedValue({
           id: "FN-100",

packages/dashboard/src/routes/register-planning-subtask-routes.ts

@@ -983,6 +983,25 @@ export function registerPlanningSubtaskRoutes(ctx: ApiRoutesContext, deps: Plann
     };
   };
 
+  const logPlanningCreateWarning = (message: string, error: unknown, metadata?: Record<string, unknown>): void => {
+    planningLogger.warn(message, {
+      ...metadata,
+      error: error instanceof Error ? error.message : String(error),
+    });
+  };
+
+  const runPlanningCreateSideEffect = async (
+    message: string,
+    work: () => Promise<unknown> | unknown,
+    metadata?: Record<string, unknown>,
+  ): Promise<void> => {
+    try {
+      await work();
+    } catch (error) {
+      logPlanningCreateWarning(message, error, metadata);
+    }
+  };
+
   /**
    * POST /api/planning/create-task
    * Create a task from a completed planning session.
@@ -1103,18 +1122,30 @@ export function registerPlanningSubtaskRoutes(ctx: ApiRoutesContext, deps: Plann
         baseBranch: resolvedBaseBranch,
       });
 
-      // Update task with suggested size if provided
+      // Update task with suggested size if provided.
       if (summary.suggestedSize) {
-        await scopedStore.updateTask(task.id, { size: summary.suggestedSize });
+        await runPlanningCreateSideEffect(
+          "Planning create-task size update failed",
+          () => scopedStore.updateTask(task.id, { size: summary.suggestedSize }),
+          { taskId: task.id, sessionId },
+        );
       }
 
-      // Log the planning mode creation
+      // Log the planning mode creation.
-      await scopedStore.logEntry(task.id, "Created via Planning Mode", `Initial plan: ${(initialPlan ?? "").slice(0, 200)}`);
+      await runPlanningCreateSideEffect(
+        "Planning create-task log entry failed",
+        () => scopedStore.logEntry(task.id, "Created via Planning Mode", `Initial plan: ${(initialPlan ?? "").slice(0, 200)}`),
+        { taskId: task.id, sessionId },
+      );
 
       // Release any live in-memory planning runtime for this session, but
       // keep the persisted completed row so planning history can still list
       // and restore the summary after single-task creation.
-      releaseSession(sessionId);
+      await runPlanningCreateSideEffect(
+        "Planning create-task session release failed",
+        () => releaseSession(sessionId),
+        { taskId: task.id, sessionId },
+      );
 
       res.status(201).json(task);
     } catch (err: unknown) {
@@ -1314,7 +1345,11 @@ export function registerPlanningSubtaskRoutes(ctx: ApiRoutesContext, deps: Plann
         createdTasks.push(task);
 
         if (item.suggestedSize === "S" || item.suggestedSize === "M" || item.suggestedSize === "L") {
-          await scopedStore.updateTask(task.id, { size: item.suggestedSize });
+          await runPlanningCreateSideEffect(
+            "Planning create-tasks size update failed",
+            () => scopedStore.updateTask(task.id, { size: item.suggestedSize }),
+            { taskId: task.id, planningSessionId },
+          );
         }
       }
 
@@ -1326,14 +1361,28 @@ export function registerPlanningSubtaskRoutes(ctx: ApiRoutesContext, deps: Plann
           : [];
 
         if (resolvedDependencies.length > 0) {
-          const updated = await scopedStore.updateTask(created.id, { dependencies: resolvedDependencies });
+          await runPlanningCreateSideEffect(
-          createdTasks[index] = updated;
+            "Planning create-tasks dependency update failed",
+            async () => {
+              const updated = await scopedStore.updateTask(created.id, { dependencies: resolvedDependencies });
+              createdTasks[index] = updated;
+            },
+            { taskId: created.id, planningSessionId },
+          );
         }
 
-        await scopedStore.logEntry(created.id, "Created via Planning Mode (multi-task)", logDetails);
+        await runPlanningCreateSideEffect(
+          "Planning create-tasks log entry failed",
+          () => scopedStore.logEntry(created.id, "Created via Planning Mode (multi-task)", logDetails),
+          { taskId: created.id, planningSessionId },
+        );
       }
 
-      cleanupSession(planningSessionId);
+      await runPlanningCreateSideEffect(
+        "Planning create-tasks session cleanup failed",
+        () => cleanupSession(planningSessionId),
+        { planningSessionId },
+      );
 
       res.status(201).json({ tasks: createdTasks });
     } catch (err: unknown) {