Cache notes in one place, and serialise a project's writes

Implements the design spec's §2 — "notes cached in zustand keyed by
project id" — which the plan substituted with a hook-local `useState`.

Sharing the `NotesPanel` *component* between the Project Home sub-tab and
the dock did not share the *cache*. Both resolve to the same project, so
two panels mount two `useNotes(P)`, each with its own list. Edit a note
in the dock and blur; the tab's copy is still pre-edit, and the tab's
next blur commits `{...staleRecord, title, body}` — the dock's edit gone
from disk with no error and no indicator. That is the feature's own
primary workflow: take notes in the dock while the agent runs, which is
the reason the dock exists, then go back to the tab.

`notesByProject` plus a per-project in-flight flag now hold the list.
Both surfaces render from one array; two panels mounting for one project
make one read; and because the write is keyed by project, a response
that lands after the user has moved on updates the project it belongs to
rather than whichever is on screen. This is also the boundary §8 says a
detached notes window needs.

Three more bugs in the same code, fixed with it:

- Delete-after-edit could resurrect the note. Clicking Delete with the
  textarea focused fires blur first, so `save_note` and `delete_note` go
  out back to back; Rust's `write_lock` stops them interleaving but does
  not order them, and a delete that wins the lock is undone by the
  upsert behind it. A project's mutations now go through one promise
  chain, module-scoped for the reason `useTerminal`'s input queue is.
- An unsaved draft vanished when any other note was saved, because the
  re-read replaced the list with the backend's. "New note" now persists,
  so the backend owns the row from the start — chosen over merging local
  drafts because a local-only row in a *shared* cache would exist in the
  panel that made it and nowhere else.
- The save outcome was reported for the wrong project after a switch:
  the guard covered only the list replacement, so the new project's
  SaveIndicator flashed "Saved ✓" for the old project's write. The
  indicator now resets on a project change and reports only its own.

`NotesPanel` also re-seeds its draft when the *stored* text of the note
it has selected changes, so an edit made in the other surface reaches
the editor and not only the list. It never overwrites something
half-typed; that still blurs into a last-writer-wins save, as any
blur-commit editor does.

NotesPanel.shared.test.tsx is the configuration none of the existing
tests had: two panels, one project, the real hook. Four of its six
assertions fail against the previous implementation.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HjL1E2JFNctUqCYotUwqqb

app/src/components/notes/NotesPanel.shared.test.tsx

@@ -0,0 +1,167 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, within, fireEvent, waitFor } from "@testing-library/react";
+import NotesPanel from "./NotesPanel";
+import { useAppState } from "../../store/appState";
+import type { Note } from "../../lib/types";
+
+/**
+ * Two panels, one project — the configuration the app actually runs in.
+ *
+ * `NotesTab` and `NotesDock` both mount a `NotesPanel`, and the dock follows
+ * the active tab's project, so opening the dock over a Project Home tab mounts
+ * two panels for the *same* project. Every other notes test mounts exactly
+ * one, which is precisely the configuration in which a per-panel cache looks
+ * correct: it is only with two that an edit made in one is seen — or lost — by
+ * the other. `useNotes` is deliberately **not** mocked here; the cache is what
+ * is under test.
+ */
+
+const files: Record<string, Note[]> = {};
+
+vi.mock("../../lib/tauri-commands", () => ({
+  listNotes: async (p: string) => [...(files[p] ?? [])],
+  saveNote: async (p: string, n: Note) => {
+    const list = files[p] ?? (files[p] = []);
+    const at = list.findIndex((x) => x.id === n.id);
+    if (at === -1) list.unshift(n);
+    else list[at] = n;
+    return n;
+  },
+  deleteNote: async (p: string, id: string) => {
+    files[p] = (files[p] ?? []).filter((x) => x.id !== id);
+  },
+}));
+
+vi.mock("./SendToAgentButton", () => ({
+  default: () => <button type="button">Send to agent</button>,
+}));
+
+const note = (over: Partial<Note> = {}): Note => ({
+  id: "n1",
+  title: "Deploy steps",
+  body: "one",
+  pinned: false,
+  created_at: "2026-09-01T00:00:00Z",
+  updated_at: "2026-09-01T00:00:00Z",
+  ...over,
+});
+
+/** The tab and the dock, mounted together the way `App` mounts them. */
+function renderBothSurfaces() {
+  render(
+    <>
+      <div data-testid="tab">
+        <NotesPanel projectId="p1" />
+      </div>
+      <div data-testid="dock">
+        <NotesPanel projectId="p1" />
+      </div>
+    </>,
+  );
+  return {
+    tab: () => within(screen.getByTestId("tab")),
+    dock: () => within(screen.getByTestId("dock")),
+  };
+}
+
+beforeEach(() => {
+  for (const key of Object.keys(files)) delete files[key];
+  files.p1 = [note()];
+  useAppState.setState({ notesByProject: {}, notesLoading: {}, toasts: [] });
+});
+
+describe("NotesPanel with the tab and the dock both open", () => {
+  it("shows an edit made in one surface in the other", async () => {
+    const { tab, dock } = renderBothSurfaces();
+    await waitFor(() => expect(tab().getByLabelText("Note body")).toHaveValue("one"));
+
+    const dockTitle = dock().getByLabelText("Note title");
+    fireEvent.change(dockTitle, { target: { value: "Deploy steps v2" } });
+    fireEvent.blur(dockTitle);
+
+    // The other surface's list *and* its editor, not just one of them.
+    await waitFor(() =>
+      expect(tab().getByRole("button", { name: /deploy steps v2/i })).toBeInTheDocument(),
+    );
+    expect(tab().getByLabelText("Note title")).toHaveValue("Deploy steps v2");
+  });
+
+  it("does not write one surface's stale copy over the other's edit", async () => {
+    // The reported repro: edit in the dock, then go back to the tab and edit
+    // there. With a cache per panel, the tab committed `{...staleNote, ...}`
+    // and the dock's edit was gone from disk with no error and no indicator.
+    const { tab, dock } = renderBothSurfaces();
+    await waitFor(() => expect(tab().getByLabelText("Note body")).toHaveValue("one"));
+
+    const dockTitle = dock().getByLabelText("Note title");
+    fireEvent.change(dockTitle, { target: { value: "Deploy steps v2" } });
+    fireEvent.blur(dockTitle);
+    await waitFor(() => expect(files.p1[0].title).toBe("Deploy steps v2"));
+
+    const tabBody = tab().getByLabelText("Note body");
+    fireEvent.change(tabBody, { target: { value: "two" } });
+    fireEvent.blur(tabBody);
+
+    await waitFor(() => expect(files.p1[0].body).toBe("two"));
+    expect(files.p1).toHaveLength(1);
+    expect(files.p1[0].title).toBe("Deploy steps v2");
+  });
+
+  it("reads the project once for both surfaces", async () => {
+    // Two panels are two `useNotes`, but the in-flight flag is per project, so
+    // mounting the dock over an open Notes tab does not re-read the file.
+    const listNotes = vi.spyOn(
+      await import("../../lib/tauri-commands"),
+      "listNotes",
+    );
+    renderBothSurfaces();
+    await waitFor(() =>
+      expect(screen.getAllByLabelText("Note body")[0]).toHaveValue("one"),
+    );
+    expect(listNotes).toHaveBeenCalledTimes(1);
+    listNotes.mockRestore();
+  });
+
+  it("keeps text the user is part-way through typing when the other surface saves", async () => {
+    // Showing a remote edit must never mean discarding an unsaved local one.
+    const { tab, dock } = renderBothSurfaces();
+    await waitFor(() => expect(tab().getByLabelText("Note body")).toHaveValue("one"));
+
+    const tabBody = tab().getByLabelText("Note body");
+    fireEvent.change(tabBody, { target: { value: "half-typed" } });
+
+    const dockBody = dock().getByLabelText("Note body");
+    fireEvent.change(dockBody, { target: { value: "saved in the dock" } });
+    fireEvent.blur(dockBody);
+    await waitFor(() => expect(files.p1[0].body).toBe("saved in the dock"));
+
+    expect(tabBody).toHaveValue("half-typed");
+  });
+
+  it("falls back to another note when the selected one is deleted", async () => {
+    // The claim a differently-named test in NotesPanel.test.tsx used to make
+    // and could not keep: `useNotes` is mocked there and its list never
+    // changes, so the fallback was invisible. Here the list is real.
+    files.p1 = [note(), note({ id: "n2", title: "Gotchas", body: "beware" })];
+    const { tab } = renderBothSurfaces();
+    await waitFor(() => expect(tab().getByLabelText("Note body")).toHaveValue("one"));
+
+    fireEvent.click(tab().getByRole("button", { name: /delete note/i }));
+
+    await waitFor(() => expect(tab().getByLabelText("Note body")).toHaveValue("beware"));
+    expect(tab().queryByRole("button", { name: /deploy steps/i })).not.toBeInTheDocument();
+    expect(files.p1).toHaveLength(1);
+  });
+
+  it("shows a note created in one surface in the other", async () => {
+    const { tab, dock } = renderBothSurfaces();
+    await waitFor(() => expect(tab().getByLabelText("Note body")).toHaveValue("one"));
+
+    fireEvent.click(dock().getByRole("button", { name: /new note/i }));
+
+    await waitFor(() =>
+      expect(tab().getAllByRole("button", { name: /untitled note/i })).toHaveLength(1),
+    );
+    expect(files.p1).toHaveLength(2);
+  });
+});

app/src/components/notes/NotesPanel.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useState } from "react";
+import { useEffect, useMemo, useRef, useState } from "react";
 import { useNotes } from "../../hooks/useNotes";
 import NoteEditor from "./NoteEditor";
 import Button from "../ui/Button";
@@ -30,22 +30,44 @@ export default function NotesPanel({ projectId }: Props) {
     [notes, selectedId],
   );
 
-  // Load the selected note's stored text into the draft. Keyed on the id, not
-  // the note object, so a save round trip does not stomp what is being typed.
+  // What was last copied out of the store into the draft fields. The draft is
+  // "untouched" exactly while it still matches this, which is how an edit made
+  // somewhere else can be shown without ever discarding something half-typed.
+  const seeded = useRef<{ id: string | null; title: string; body: string }>({
+    id: null,
+    title: "",
+    body: "",
+  });
+
+  // Load the selected note's stored text into the draft — on a change of note,
+  // and on a change to the *stored* text of the note already selected. The
+  // second case is the dock and the tab showing one project at once: an edit
+  // committed in one surface has to reach the other's editor, not just its
+  // list. It never overwrites text the user is part-way through typing; that
+  // blurs into a last-writer-wins save, as any blur-commit editor does.
   useEffect(() => {
     if (!selected) {
+      seeded.current = { id: null, title: "", body: "" };
       setTitle("");
       setBody("");
       return;
     }
-    setTitle(selected.title);
-    setBody(selected.body);
-  }, [selected?.id]); // eslint-disable-line react-hooks/exhaustive-deps
+    const untouched =
+      title === seeded.current.title && body === seeded.current.body;
+    if (seeded.current.id !== selected.id || untouched) {
+      seeded.current = { id: selected.id, title: selected.title, body: selected.body };
+      setTitle(selected.title);
+      setBody(selected.body);
+    }
+  }, [selected?.id, selected?.title, selected?.body]); // eslint-disable-line react-hooks/exhaustive-deps
 
   const commit = () => {
     if (!selected) return;
     // Reading is not editing: clicking through notes must not rewrite the file.
     if (title === selected.title && body === selected.body) return;
+    // Mark the draft as matching what was just committed, so the store update
+    // this save produces reads as "no change" rather than as a stale re-seed.
+    seeded.current = { id: selected.id, title, body };
     void saveNote({ ...selected, title, body });
   };