feat(FN-990): add task spec rebuild endpoint and UI

- Add POST /tasks/:id/spec/rebuild API endpoint to regenerate task specifications
- Add rebuildTaskSpec client function in dashboard API layer
- Add respecify button to task detail modal for triggering spec rebuilds
- Add comprehensive tests for the spec/rebuild endpoint covering success, error, and edge cases

packages/dashboard/app/api.ts

@@ -334,6 +334,12 @@ export function requestSpecRevision(id: string, feedback: string, projectId?: st
   });
 }
 
+export function rebuildTaskSpec(id: string, projectId?: string): Promise<Task> {
+  return api<Task>(withProjectId(`/tasks/${id}/spec/rebuild`, projectId), {
+    method: "POST",
+  });
+}
+
 export function refineTask(id: string, feedback: string, projectId?: string): Promise<Task> {
   return api<Task>(withProjectId(`/tasks/${id}/refine`, projectId), {
     method: "POST",

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -4,7 +4,7 @@ import ReactMarkdown from "react-markdown";
 import remarkGfm from "remark-gfm";
 import type { Task, TaskDetail, TaskAttachment, Column, MergeResult, PrInfo, Settings, AgentLogEntry } from "@fusion/core";
 import { COLUMN_LABELS, VALID_TRANSITIONS } from "@fusion/core";
-import { uploadAttachment, deleteAttachment, updateTask, pauseTask, unpauseTask, fetchTaskDetail, fetchSettings, requestSpecRevision, approvePlan, rejectPlan, refineTask, fetchWorkflowResults } from "../api";
+import { uploadAttachment, deleteAttachment, updateTask, pauseTask, unpauseTask, fetchTaskDetail, fetchSettings, requestSpecRevision, rebuildTaskSpec, approvePlan, rejectPlan, refineTask, fetchWorkflowResults } from "../api";
 import type { WorkflowStepResult } from "@fusion/core";
 import type { ToastType } from "../hooks/useToast";
 import { useAgentLogs } from "../hooks/useAgentLogs";
@@ -524,6 +524,17 @@ export function TaskDetailModal({
     }
   }, [task.id, onClose, addToast]);
 
+  const handleRespecify = useCallback(async () => {
+    if (!confirm("Rebuild the specification for this task? The task will move to triage for re-specification.")) return;
+    try {
+      await rebuildTaskSpec(task.id, projectId);
+      onClose();
+      addToast(`Respecifying ${task.id}...`, "info");
+    } catch (err: any) {
+      addToast(err.message, "error");
+    }
+  }, [task.id, projectId, onClose, addToast]);
+
   const handleOpenRefineModal = useCallback(() => {
     setShowRefineModal(true);
     setRefineFeedback("");
@@ -1245,6 +1256,11 @@ export function TaskDetailModal({
               Refine
             </button>
           )}
+          {task.column !== "triage" && (
+            <button className="btn btn-sm" onClick={handleRespecify}>
+              Respecify
+            </button>
+          )}
           {(task.status === "failed" || task.status === "stuck-killed") && onRetryTask && (
             <button className="btn btn-warning btn-sm" onClick={handleRetry}>
               Retry

packages/dashboard/src/routes.test.ts

@@ -3884,6 +3884,108 @@ describe("POST /tasks/:id/spec/revise", () => {
 });
 
 
+// --- Spec Rebuild route tests ---
+
+describe("POST /tasks/:id/spec/rebuild", () => {
+  let store: TaskStore;
+
+  beforeEach(() => {
+    store = createMockStore({
+      getTask: vi.fn(),
+      moveTask: vi.fn(),
+      updateTask: vi.fn(),
+      logEntry: vi.fn().mockResolvedValue(undefined),
+    });
+  });
+
+  function buildApp() {
+    const app = express();
+    app.use(express.json());
+    app.use("/api", createApiRoutes(store));
+    return app;
+  }
+
+  it("rebuilds spec and moves task from todo to triage", async () => {
+    const todoTask = { ...FAKE_TASK_DETAIL, column: "todo" as const };
+    const movedTask = { ...FAKE_TASK_DETAIL, column: "triage" as const };
+
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(todoTask);
+    (store.moveTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+    (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/KB-001/spec/rebuild");
+
+    expect(res.status).toBe(200);
+    expect(store.logEntry).toHaveBeenCalledWith(
+      "FN-001",
+      "Specification rebuild requested by user"
+    );
+    expect(store.moveTask).toHaveBeenCalledWith("FN-001", "triage");
+    expect(store.updateTask).toHaveBeenCalledWith("FN-001", { status: "needs-respecify" });
+  });
+
+  it("rebuilds spec and moves task from in-progress to triage", async () => {
+    const inProgressTask = { ...FAKE_TASK_DETAIL, column: "in-progress" as const };
+    const movedTask = { ...FAKE_TASK_DETAIL, column: "triage" as const };
+
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(inProgressTask);
+    (store.moveTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+    (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/KB-001/spec/rebuild");
+
+    expect(res.status).toBe(200);
+    expect(store.moveTask).toHaveBeenCalledWith("FN-001", "triage");
+    expect(store.updateTask).toHaveBeenCalledWith("FN-001", { status: "needs-respecify" });
+  });
+
+  it("rebuilds spec and moves task from done to triage", async () => {
+    const doneTask = { ...FAKE_TASK_DETAIL, column: "done" as const };
+    const movedTask = { ...FAKE_TASK_DETAIL, column: "triage" as const };
+
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(doneTask);
+    (store.moveTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+    (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/KB-001/spec/rebuild");
+
+    expect(res.status).toBe(200);
+    expect(store.moveTask).toHaveBeenCalledWith("FN-001", "triage");
+  });
+
+  it("returns 400 when task is already in triage", async () => {
+    const triageTask = { ...FAKE_TASK_DETAIL, column: "triage" as const };
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(triageTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/KB-001/spec/rebuild");
+
+    expect(res.status).toBe(400);
+    expect(res.body.error).toContain("Cannot rebuild spec");
+    expect(store.moveTask).not.toHaveBeenCalled();
+  });
+
+  it("returns 400 when task is in in-review (cannot transition to triage)", async () => {
+    const inReviewTask = { ...FAKE_TASK_DETAIL, column: "in-review" as const };
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(inReviewTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/KB-001/spec/rebuild");
+
+    expect(res.status).toBe(400);
+    expect(res.body.error).toContain("in-review");
+    expect(store.moveTask).not.toHaveBeenCalled();
+  });
+
+  it("returns 404 when task not found", async () => {
+    const error = new Error("Task not found") as Error & { code?: string };
+    error.code = "ENOENT";
+    (store.getTask as ReturnType<typeof vi.fn>).mockRejectedValue(error);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/KB-999/spec/rebuild");
+
+    expect(res.status).toBe(404);
+  });
+});
+
 // --- Plan Approval route tests ---
 
 describe("POST /tasks/:id/approve-plan", () => {

packages/dashboard/src/routes.ts

@@ -2506,6 +2506,42 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
     }
   });
 
+  // Rebuild task spec without feedback
+  router.post("/tasks/:id/spec/rebuild", async (req, res) => {
+    try {
+      const scopedStore = await getScopedStore(req);
+
+      // Get current task state
+      const task = await scopedStore.getTask(req.params.id);
+
+      // Check if task can transition to triage
+      const canTransition = VALID_TRANSITIONS[task.column]?.includes("triage");
+      if (!canTransition) {
+        res.status(400).json({
+          error: `Cannot rebuild spec for tasks in '${task.column}' column. ` +
+                 `Move task to a valid column first.`,
+        });
+        return;
+      }
+
+      // Log the rebuild request
+      await scopedStore.logEntry(task.id, "Specification rebuild requested by user");
+
+      // Move to triage for re-specification
+      const updated = await scopedStore.moveTask(task.id, "triage");
+
+      // Update status to indicate needs re-specification
+      await scopedStore.updateTask(task.id, { status: "needs-respecify" });
+
+      res.json(updated);
+    } catch (err: any) {
+      const status = err.code === "ENOENT" ? 404
+        : err.message?.includes("Invalid transition") ? 400
+        : 500;
+      res.status(status).json({ error: err.message });
+    }
+  });
+
   // Update task
   router.patch("/tasks/:id", async (req, res) => {
     try {