feat(HAI-078): add configurable task prefix to settings

- Add taskPrefix field to Settings type and use it in allocateId
- Update store listTasks and handleFsChange to support any task prefix
- Update triage duplicate regex to match configurable prefix
- Add Task Prefix input to dashboard SettingsModal UI
- Add tests for prefix-aware task allocation and settings modal

packages/dashboard/app/components/SettingsModal.tsx

@@ -12,6 +12,7 @@ import type { ToastType } from "../hooks/useToast";
  *   2. Add a corresponding case in renderSectionFields()
  */
 const SETTINGS_SECTIONS = [
+  { id: "general", label: "General" },
   { id: "scheduling", label: "Scheduling" },
   { id: "worktrees", label: "Worktrees" },
   { id: "commands", label: "Commands" },
@@ -29,6 +30,7 @@ export function SettingsModal({ onClose, addToast }: SettingsModalProps) {
   const [form, setForm] = useState<Settings & { worktreeInitCommand?: string }>({ maxConcurrent: 2, maxWorktrees: 4, pollIntervalMs: 15000, groupOverlappingFiles: false, autoMerge: false, recycleWorktrees: false, worktreeInitCommand: "" });
   const [loading, setLoading] = useState(true);
   const [activeSection, setActiveSection] = useState<SectionId>(SETTINGS_SECTIONS[0].id);
+  const [prefixError, setPrefixError] = useState<string | null>(null);
 
   useEffect(() => {
     fetchSettings()
@@ -58,10 +60,12 @@ export function SettingsModal({ onClose, addToast }: SettingsModalProps) {
   );
 
   const handleSave = useCallback(async () => {
+    if (prefixError) return;
     try {
       const payload = {
         ...form,
         worktreeInitCommand: form.worktreeInitCommand?.trim() || undefined,
+        taskPrefix: form.taskPrefix?.trim() || undefined,
       };
       await updateSettings(payload);
       addToast("Settings saved", "success");
@@ -69,10 +73,36 @@ export function SettingsModal({ onClose, addToast }: SettingsModalProps) {
     } catch (err: any) {
       addToast(err.message, "error");
     }
-  }, [form, onClose, addToast]);
+  }, [form, prefixError, onClose, addToast]);
 
   const renderSectionFields = () => {
     switch (activeSection) {
+      case "general":
+        return (
+          <>
+            <h4 className="settings-section-heading">General</h4>
+            <div className="form-group">
+              <label htmlFor="taskPrefix">Task Prefix</label>
+              <input
+                id="taskPrefix"
+                type="text"
+                placeholder="HAI"
+                value={form.taskPrefix || ""}
+                onChange={(e) => {
+                  const val = e.target.value;
+                  setForm((f) => ({ ...f, taskPrefix: val || undefined }));
+                  if (val && !/^[A-Z]{1,10}$/.test(val)) {
+                    setPrefixError("Prefix must be 1–10 uppercase letters");
+                  } else {
+                    setPrefixError(null);
+                  }
+                }}
+              />
+              {prefixError && <small className="field-error" style={{ color: "var(--color-error, #e74c3c)" }}>{prefixError}</small>}
+              {!prefixError && <small>Prefix for new task IDs (e.g. HAI, PROJ)</small>}
+            </div>
+          </>
+        );
       case "scheduling":
         return (
           <>

packages/dashboard/app/components/__tests__/SettingsModal.test.tsx

@@ -35,6 +35,7 @@ describe("SettingsModal", () => {
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
     // Each label appears in the sidebar nav
+    expect(screen.getAllByText("General").length).toBeGreaterThanOrEqual(1);
     const nav = screen.getAllByText("Scheduling");
     expect(nav.length).toBeGreaterThanOrEqual(1);
     expect(screen.getAllByText("Worktrees").length).toBeGreaterThanOrEqual(1);
@@ -42,21 +43,25 @@ describe("SettingsModal", () => {
     expect(screen.getAllByText("Merge").length).toBeGreaterThanOrEqual(1);
   });
 
-  it("shows Scheduling fields by default", async () => {
+  it("shows General fields by default", async () => {
     render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
-    expect(screen.getByLabelText("Max Concurrent Tasks")).toBeTruthy();
-    expect(screen.getByLabelText("Poll Interval (ms)")).toBeTruthy();
+    expect(screen.getByLabelText("Task Prefix")).toBeTruthy();
     // Fields from other sections should not be visible
+    expect(screen.queryByLabelText("Max Concurrent Tasks")).toBeNull();
     expect(screen.queryByLabelText("Max Worktrees")).toBeNull();
-    expect(screen.queryByLabelText("Test Command")).toBeNull();
   });
 
   it("switches section when clicking sidebar item", async () => {
     render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
+    // Click Scheduling
+    fireEvent.click(screen.getByText("Scheduling"));
+    expect(screen.getByLabelText("Max Concurrent Tasks")).toBeTruthy();
+    expect(screen.queryByLabelText("Task Prefix")).toBeNull();
+
     // Click Commands
     fireEvent.click(screen.getByText("Commands"));
     expect(screen.getByLabelText("Test Command")).toBeTruthy();
@@ -68,7 +73,11 @@ describe("SettingsModal", () => {
     render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
-    // Scheduling (default)
+    // General (default)
+    expect(screen.getByLabelText("Task Prefix")).toBeTruthy();
+
+    // Scheduling
+    fireEvent.click(screen.getByText("Scheduling"));
     expect(screen.getByLabelText("Max Concurrent Tasks")).toBeTruthy();
     expect(screen.getByLabelText("Poll Interval (ms)")).toBeTruthy();
 
@@ -113,10 +122,62 @@ describe("SettingsModal", () => {
     expect(payload.recycleWorktrees).toBe(true);
   });
 
+  it("Task Prefix field saves correctly when set", async () => {
+    render(<SettingsModal onClose={onClose} addToast={addToast} />);
+    await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
+
+    const input = screen.getByLabelText("Task Prefix") as HTMLInputElement;
+    fireEvent.change(input, { target: { value: "PROJ" } });
+    expect(input.value).toBe("PROJ");
+
+    fireEvent.click(screen.getByText("Save"));
+    await waitFor(() => expect(updateSettings).toHaveBeenCalledTimes(1));
+
+    const payload = (updateSettings as ReturnType<typeof vi.fn>).mock.calls[0][0];
+    expect(payload.taskPrefix).toBe("PROJ");
+  });
+
+  it("Task Prefix field submits undefined when empty (uses default)", async () => {
+    render(<SettingsModal onClose={onClose} addToast={addToast} />);
+    await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
+
+    const input = screen.getByLabelText("Task Prefix") as HTMLInputElement;
+    fireEvent.change(input, { target: { value: "" } });
+
+    fireEvent.click(screen.getByText("Save"));
+    await waitFor(() => expect(updateSettings).toHaveBeenCalledTimes(1));
+
+    const payload = (updateSettings as ReturnType<typeof vi.fn>).mock.calls[0][0];
+    expect(payload.taskPrefix).toBeUndefined();
+  });
+
+  it("Task Prefix shows validation error for invalid input", async () => {
+    render(<SettingsModal onClose={onClose} addToast={addToast} />);
+    await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
+
+    const input = screen.getByLabelText("Task Prefix") as HTMLInputElement;
+    fireEvent.change(input, { target: { value: "bad" } });
+
+    expect(screen.getByText("Prefix must be 1–10 uppercase letters")).toBeTruthy();
+  });
+
+  it("Task Prefix validation error prevents save", async () => {
+    render(<SettingsModal onClose={onClose} addToast={addToast} />);
+    await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
+
+    const input = screen.getByLabelText("Task Prefix") as HTMLInputElement;
+    fireEvent.change(input, { target: { value: "bad" } });
+
+    fireEvent.click(screen.getByText("Save"));
+    // Should not have called updateSettings due to validation error
+    expect(updateSettings).not.toHaveBeenCalled();
+  });
+
   it("groupOverlappingFiles input has type checkbox", async () => {
     render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
+    fireEvent.click(screen.getByText("Scheduling"));
     const checkbox = screen.getByLabelText("Serialize tasks with overlapping files");
     expect(checkbox).toBeTruthy();
     expect(checkbox.getAttribute("type")).toBe("checkbox");