fix(maestro): re-read session before sidecar write in mark_session_dead

mark_session_dead_with_worktree_settlement cloned the session under the
lock, dropped it, did async work, then wrote the stale clone to the
sidecar. A haiku rename (or any other metadata update) that landed
between the clone and the write was silently overwritten, so the sidecar
reverted to name_source: Generated and the next daemon recovery
re-triggered autoname.

Re-read record.session under the lock at write time so the sidecar
always reflects the latest state.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/maestro-daemon/src/session.rs

@@ -2916,17 +2916,16 @@ async fn mark_session_dead_with_worktree_settlement(
                 // Release anyone attached; the scrollback survives for a later
                 // attach.
                 record.bridge.seal();
-                let session = record.session.clone();
                 let worktree = record
                     .worktree_base_repo
                     .clone()
                     .zip(record.worktree_path.clone());
-                Some((session, worktree))
+                Some(worktree)
             }
             _ => None,
         }
     };
-    let Some((mut session, worktree)) = flipped else {
+    let Some(worktree) = flipped else {
         return false;
     };
     let stream = inner
@@ -2943,9 +2942,6 @@ async fn mark_session_dead_with_worktree_settlement(
     if settle_worktree {
         if let Some(wt) = &worktree {
             if settle_worktree_on_exit(inner, id, wt).await {
-                // The tree is settled (removed); a stale "in the way" would
-                // describe something the session no longer holds.
-                session.blocked_work = None;
                 let mut sessions = inner.sessions.lock().await;
                 if let Some(record) = sessions.get_mut(&id) {
                     record.session.worktree = None;
@@ -2957,13 +2953,17 @@ async fn mark_session_dead_with_worktree_settlement(
         }
     }
     // Settle has now been applied or refused either way (#115): from here on
-    // its outcomes are safe to observe.
-    {
+    // its outcomes are safe to observe. Re-read the session from the record
+    // so the sidecar write includes any updates (e.g. a haiku rename) that
+    // landed between the initial clone and now.
+    let session = {
         let mut sessions = inner.sessions.lock().await;
-        if let Some(record) = sessions.get_mut(&id) {
-            record.settled = true;
-        }
-    }
+        let Some(record) = sessions.get_mut(&id) else {
+            return false;
+        };
+        record.settled = true;
+        record.session.clone()
+    };
 
     let _ = inner.sidecar.write(&session);
     let _ = inner.events.send(CatalogEvent::SessionUpdated { session });

crates/maestro-daemon/tests/autoname.rs

@@ -11,14 +11,14 @@ use common::TmuxFixture;
 use maestro_daemon::sidecar::SidecarStore;
 use maestro_daemon::worktree::WorktreeManager;
 use maestro_daemon::SessionManager;
-use maestro_protocol::{display, CatalogEvent, CreateSessionRequest, NameSource};
+use maestro_protocol::{display, CatalogEvent, CreateSessionRequest, NameSource, SessionStatus};
 use tempfile::TempDir;
 use uuid::Uuid;
 
 struct Fixture {
     manager: SessionManager,
     sidecar: SidecarStore,
-    _tmux: TmuxFixture,
+    tmux: TmuxFixture,
     _state_dir: TempDir,
 }
 
@@ -35,7 +35,7 @@ fn fixture() -> Fixture {
     Fixture {
         manager,
         sidecar,
-        _tmux: tmux,
+        tmux,
         _state_dir: state_dir,
     }
 }
@@ -171,3 +171,37 @@ async fn a_blank_name_changes_nothing() {
     let live = fx.sidecar.read(id).unwrap().unwrap();
     assert_eq!(display::name_source(&live), NameSource::Generated);
 }
+
+/// A session that dies naturally (liveness watcher marks it dead) must not
+/// overwrite a haiku rename that landed before the death. Regression test for
+/// the stale-clone sidecar write in `mark_session_dead`.
+#[tokio::test]
+async fn session_death_preserves_the_haiku_name() {
+    let fx = fixture();
+    let id = spawn(&fx.manager, None).await;
+
+    fx.manager.claim_autoname(id).await.unwrap();
+    fx.manager.apply_autoname(id, "haiku-name").await.unwrap();
+
+    // Verify the sidecar has Haiku before the session dies.
+    let before = fx.sidecar.read(id).unwrap().unwrap();
+    assert_eq!(display::name_source(&before), NameSource::Haiku);
+
+    // Kill the tmux session directly so the liveness watcher picks it up.
+    fx.tmux.tmux.kill_session(id).expect("kill tmux directly");
+    fx.manager
+        .start_liveness_watcher(std::time::Duration::from_millis(25));
+
+    common::wait_for_async(std::time::Duration::from_secs(3), || async {
+        fx.manager.status(id).await == Some(SessionStatus::Dead)
+    })
+    .await;
+
+    let after = fx.sidecar.read(id).unwrap().unwrap();
+    assert_eq!(
+        display::name_source(&after),
+        NameSource::Haiku,
+        "mark_session_dead must not overwrite a haiku rename in the sidecar"
+    );
+    assert_eq!(display::custom_name(&after), Some("haiku-name"));
+}

web/src/components/daemon/DaemonLink.test.ts

@@ -0,0 +1,215 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { GRACE_MS, POLL_MS, compareIdentity, createDaemonLinkStore, formatRelease, type Scheduler } from "./DaemonLink.js";
+import type { DaemonInfo } from "../../types.js";
+
+function info(commit: string, instance: string, date = "2026-09-02T14:03:11+01:00"): DaemonInfo {
+  return {
+    hostname: "konishi",
+    version: "0.1.0",
+    presets: [],
+    build: { commit, commit_date: date, dirty: false },
+    instance,
+  };
+}
+
+/** Scheduler whose timers only fire when the test says so, recording the
+ *  delay each was scheduled with. */
+function manual(): Scheduler & { run(): void; pending(): number; delays: number[] } {
+  let next = 1;
+  const timers = new Map<number, () => void>();
+  const delays: number[] = [];
+  return {
+    delays,
+    setTimer(fn, ms) {
+      const h = next++;
+      timers.set(h, fn);
+      delays.push(ms);
+      return h;
+    },
+    clearTimer(h) {
+      timers.delete(h);
+    },
+    run() {
+      const due = [...timers.entries()];
+      timers.clear();
+      for (const [, fn] of due) fn();
+    },
+    pending: () => timers.size,
+  };
+}
+
+describe("compareIdentity", () => {
+  it("reads a changed commit as an upgrade", () => {
+    expect(compareIdentity(info("aaa", "i1"), info("bbb", "i2"))).toBe("upgraded");
+  });
+
+  it("reads a changed instance on the same commit as a plain restart", () => {
+    expect(compareIdentity(info("aaa", "i1"), info("aaa", "i2"))).toBe("restarted");
+  });
+
+  it("reads an unchanged process as no event at all", () => {
+    expect(compareIdentity(info("aaa", "i1"), info("aaa", "i1"))).toBe("same");
+  });
+
+  it("falls back to the instance when the build is unknown", () => {
+    // A daemon built outside a checkout reports empty commits; the instance is
+    // still enough to see the restart, and never claims a phantom upgrade.
+    expect(compareIdentity(info("", "i1"), info("", "i2"))).toBe("restarted");
+    expect(compareIdentity(info("", "i1"), info("", "i1"))).toBe("same");
+  });
+});
+
+describe("formatRelease", () => {
+  it("pairs the short hash with a readable date", () => {
+    expect(formatRelease({ commit: "f89be4a716c7", commit_date: "2026-09-02T14:03:11Z", dirty: false })).toBe(
+      "f89be4a716c7 · 2026-09-02",
+    );
+  });
+
+  it("marks a dirty build", () => {
+    expect(formatRelease({ commit: "f89be4a", commit_date: "", dirty: true })).toBe("f89be4a (dirty)");
+  });
+
+  it("says so when the release is unknown", () => {
+    expect(formatRelease(undefined)).toBe("unknown release");
+  });
+});
+
+describe("daemon link store", () => {
+  it("starts in the connecting state until the first probe lands", async () => {
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => info("aaa", "i1"),
+      scheduler: manual(),
+      reload: () => {},
+    });
+    expect(store.getState().state).toBe("connecting");
+    await store.getState().probe();
+    expect(store.getState().state).toBe("online");
+    expect(store.getState().build?.commit).toBe("aaa");
+  });
+
+  it("holds the modal back during the grace period, then blocks", async () => {
+    const sched = manual();
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => {
+        throw new Error("down");
+      },
+      scheduler: sched,
+      reload: () => {},
+      graceMs: 1000,
+    });
+    store.getState().noteDisconnected();
+    // Still inside the grace window: the dot goes amber, nothing blocks.
+    expect(store.getState().state).toBe("reconnecting");
+    sched.run();
+    await Promise.resolve();
+    expect(store.getState().state).toBe("down");
+  });
+
+  it("unlocks without reloading when the same build comes back", async () => {
+    const sched = manual();
+    const reload = vi.fn();
+    let reply: DaemonInfo | null = info("aaa", "i1");
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => {
+        if (!reply) throw new Error("down");
+        return reply;
+      },
+      scheduler: sched,
+      reload,
+    });
+    await store.getState().probe();
+
+    reply = null;
+    store.getState().noteDisconnected();
+    sched.run(); // grace expires → blocked, poll scheduled
+    await Promise.resolve();
+    expect(store.getState().state).toBe("down");
+
+    // Same commit, new process: a restart, not an upgrade — the page stays.
+    reply = info("aaa", "i2");
+    await store.getState().probe();
+    expect(reload).not.toHaveBeenCalled();
+    expect(store.getState().state).toBe("online");
+  });
+
+  it("reloads the page when the daemon comes back on a new commit", async () => {
+    const sched = manual();
+    const reload = vi.fn();
+    let reply = info("aaa", "i1");
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => reply,
+      scheduler: sched,
+      reload,
+    });
+    await store.getState().probe();
+
+    store.getState().noteDisconnected();
+    reply = info("bbb", "i2");
+    await store.getState().probe();
+    expect(reload).toHaveBeenCalledTimes(1);
+    // Left blocked deliberately: the reload is what ends this page's life, and
+    // flashing an unlocked UI in between would let the user act on stale code.
+    expect(store.getState().state).toBe("updating");
+  });
+
+  it("keeps polling on a scheduled cadence while the daemon is unreachable", async () => {
+    const sched = manual();
+    let attempts = 0;
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => {
+        attempts += 1;
+        throw new Error("down");
+      },
+      scheduler: sched,
+      reload: () => {},
+    });
+    store.getState().noteDisconnected();
+    sched.run(); // grace → first poll
+    await Promise.resolve();
+    await Promise.resolve();
+    const first = attempts;
+    expect(first).toBeGreaterThan(0);
+    sched.run(); // next poll tick
+    await Promise.resolve();
+    await Promise.resolve();
+    expect(attempts).toBeGreaterThan(first);
+    store.getState().stop();
+  });
+
+  it("notifies subscribers on every state change", async () => {
+    const sched = manual();
+    const seen: string[] = [];
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => info("aaa", "i1"),
+      scheduler: sched,
+      reload: () => {},
+    });
+    store.subscribe((s) => seen.push(s.state));
+    await store.getState().probe();
+    store.getState().noteDisconnected();
+    sched.run();
+    await Promise.resolve();
+    expect(seen).toContain("reconnecting");
+  });
+
+  it("schedules the grace timer and poll at the documented defaults", async () => {
+    const sched = manual();
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => {
+        throw new Error("down");
+      },
+      scheduler: sched,
+      reload: () => {},
+    });
+    expect(GRACE_MS).toBe(1200);
+    expect(POLL_MS).toBe(700);
+    store.getState().noteDisconnected();
+    expect(sched.delays).toEqual([GRACE_MS]);
+    sched.run(); // grace fires → schedules the first poll
+    await Promise.resolve();
+    await Promise.resolve();
+    expect(sched.delays).toEqual([GRACE_MS, POLL_MS]);
+  });
+});

web/src/components/daemon/DaemonLink.test.tsx

@@ -0,0 +1,71 @@
+// @vitest-environment happy-dom
+import { cleanup, render } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { createDaemonLinkStore } from "./DaemonLink.js";
+import { DaemonLink } from "./DaemonLink.js";
+
+afterEach(() => cleanup());
+
+describe("DaemonLink", () => {
+  it("probes once on mount, regardless of the initial connected value", async () => {
+    const fetchInfo = vi.fn().mockResolvedValue({ hostname: "h", version: "1", presets: [] });
+    const store = createDaemonLinkStore({ fetchInfo, scheduler: { setTimer: () => 0, clearTimer: () => {} } });
+    render(<DaemonLink store={store} connected={false} />);
+    await Promise.resolve();
+    expect(fetchInfo).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not treat the initial connected value as a transition", async () => {
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => ({ hostname: "h", version: "1", presets: [] }),
+      scheduler: { setTimer: () => 0, clearTimer: () => {} },
+    });
+    render(<DaemonLink store={store} connected={true} />);
+    await Promise.resolve();
+    // Only the mount probe ran — no extra noteConnected() probe on top of it.
+    expect(store.getState().state).toBe("online");
+  });
+
+  it("forwards a later connected drop to noteDisconnected", async () => {
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => ({ hostname: "h", version: "1", presets: [] }),
+      scheduler: { setTimer: () => 0, clearTimer: () => {} },
+    });
+    const { rerender } = render(<DaemonLink store={store} connected={true} />);
+    await Promise.resolve();
+    expect(store.getState().state).toBe("online");
+
+    rerender(<DaemonLink store={store} connected={false} />);
+    expect(store.getState().state).toBe("reconnecting");
+  });
+
+  it("forwards a later connected recovery to noteConnected", async () => {
+    const fetchInfo = vi.fn().mockResolvedValue({ hostname: "h", version: "1", presets: [] });
+    const store = createDaemonLinkStore({ fetchInfo, scheduler: { setTimer: () => 0, clearTimer: () => {} } });
+    const { rerender } = render(<DaemonLink store={store} connected={true} />);
+    await Promise.resolve();
+    expect(store.getState().state).toBe("online");
+
+    // The socket dropped: noteDisconnected() moves off "online" so the coming
+    // recovery isn't a no-op.
+    rerender(<DaemonLink store={store} connected={false} />);
+    expect(store.getState().state).toBe("reconnecting");
+    fetchInfo.mockClear();
+
+    rerender(<DaemonLink store={store} connected={true} />);
+    await Promise.resolve();
+    expect(fetchInfo).toHaveBeenCalledTimes(1);
+    expect(store.getState().state).toBe("online");
+  });
+
+  it("stops the store's polling on unmount", () => {
+    const store = createDaemonLinkStore({
+      fetchInfo: async () => ({ hostname: "h", version: "1", presets: [] }),
+    });
+    const stop = vi.spyOn(store.getState(), "stop");
+    const { unmount } = render(<DaemonLink store={store} connected={false} />);
+    unmount();
+    expect(stop).toHaveBeenCalledTimes(1);
+  });
+});

web/src/components/daemon/DaemonLink.tsx

@@ -0,0 +1,234 @@
+// React port of ../../daemonLink.ts. The link to the daemon behind this page:
+// is it up, and which release is it? `RestartOverlay` (./RestartOverlay.tsx)
+// renders what this reports. See docs/RESTART.md for the restart contract.
+
+import { useEffect, useRef } from "react";
+import { create } from "zustand";
+
+import { getDaemonInfo } from "../../api.js";
+import type { BuildInfo, DaemonInfo } from "../../types.js";
+
+/**
+ * - `connecting` — first probe hasn't landed yet.
+ * - `online` — the daemon answered and is the same process, or a resolved new one.
+ * - `reconnecting` — the socket dropped, but within the grace window; a blip
+ *   shouldn't throw a modal in the user's face.
+ * - `down` — unreachable past the grace window: the overlay blocks the UI and
+ *   the poll runs until it answers.
+ * - `updating` — it answered on a different commit; the page is reloading and
+ *   stays blocked until it does.
+ */
+export type LinkState = "connecting" | "online" | "reconnecting" | "down" | "updating";
+
+/** What happened between two `/api/info` replies. */
+export type RestartKind = "same" | "restarted" | "upgraded";
+
+/** How long a dropped socket may stay dropped before the UI blocks. Long enough
+ *  to ride out a wifi hiccup, short enough that a real restart is visible. */
+export const GRACE_MS = 1200;
+/** Cadence of the `/api/info` poll while the daemon is unreachable. */
+export const POLL_MS = 700;
+
+/**
+ * Compare two daemon replies.
+ *
+ * The commit decides first: a different one means new code, which for a browser
+ * means new assets. The per-process `instance` catches the rest — a restart of
+ * the same build, which needs no reload. A daemon built outside a git checkout
+ * reports an empty commit, so an empty-vs-empty pair never counts as an
+ * upgrade; the instance still reports the restart.
+ */
+export function compareIdentity(before: DaemonInfo, after: DaemonInfo): RestartKind {
+  const a = before.build?.commit ?? "";
+  const b = after.build?.commit ?? "";
+  if (a && b && a !== b) return "upgraded";
+  if (before.instance && after.instance && before.instance !== after.instance) return "restarted";
+  return "same";
+}
+
+/** One line naming a release: `f89be4a716c7 · 2026-09-02`, with `(dirty)` when
+ *  the build carried uncommitted changes. Empty builds say so rather than
+ *  rendering a blank tooltip. */
+export function formatRelease(build: BuildInfo | undefined): string {
+  if (!build?.commit) return "unknown release";
+  const day = build.commit_date ? build.commit_date.slice(0, 10) : "";
+  const parts = [build.commit];
+  if (day) parts.push(`· ${day}`);
+  if (build.dirty) parts.push("(dirty)");
+  return parts.join(" ");
+}
+
+/** Schedules a probe/grace timer; returns a handle `clearTimer` understands. */
+export interface Scheduler {
+  setTimer(fn: () => void, ms: number): number;
+  clearTimer(handle: number): void;
+}
+
+const browserScheduler: Scheduler = {
+  setTimer: (fn, ms) => window.setTimeout(fn, ms),
+  clearTimer: (h) => window.clearTimeout(h),
+};
+
+export interface DaemonLinkState {
+  state: LinkState;
+  /** The release the daemon last reported. Undefined until the first probe,
+   *  and on a daemon too old to carry one. */
+  build?: BuildInfo;
+  /** Hostname the daemon reports, for the indicator's tooltip. */
+  hostname?: string;
+  /** How many probes have failed in the current outage — the overlay counts
+   *  attempts so a long restart doesn't look frozen. */
+  attempts: number;
+}
+
+export interface DaemonLinkActions {
+  /** One `/api/info` round-trip. Resolves `true` when the daemon answered. */
+  probe(): Promise<boolean>;
+  /** The events socket dropped. Starts the grace timer and the poll. */
+  noteDisconnected(): void;
+  /** The events socket came back. It carries no identity of its own, so the
+   *  state only clears once a probe confirms *which* daemon answered — a
+   *  reconnect to an upgraded daemon must reload, not resume. */
+  noteConnected(): void;
+  /** Stop polling. */
+  stop(): void;
+}
+
+export type DaemonLinkStore = DaemonLinkState & DaemonLinkActions;
+
+export interface DaemonLinkOptions {
+  /** Injectable for tests; defaults to `GET /api/info`. */
+  fetchInfo?: () => Promise<DaemonInfo>;
+  scheduler?: Scheduler;
+  /** What an upgrade does. Injectable so tests don't navigate. */
+  reload?: () => void;
+  graceMs?: number;
+  pollMs?: number;
+}
+
+/** Builds an isolated daemon-link store — same shape as
+ *  {@link ../../stores/catalogStore.js!createCatalogStore}: both a React hook
+ *  and a plain object (`getState`/`subscribe`), so it drives the overlay
+ *  whether or not React is the one calling `noteConnected`/`noteDisconnected`. */
+export function createDaemonLinkStore(opts: DaemonLinkOptions = {}) {
+  const fetchInfo = opts.fetchInfo ?? getDaemonInfo;
+  const scheduler = opts.scheduler ?? browserScheduler;
+  const reload = opts.reload ?? (() => window.location.reload());
+  const graceMs = opts.graceMs ?? GRACE_MS;
+  const pollMs = opts.pollMs ?? POLL_MS;
+
+  let identity: DaemonInfo | null = null;
+  let graceTimer: number | null = null;
+  let pollTimer: number | null = null;
+
+  return create<DaemonLinkStore>((set, get) => {
+    function clearTimers(): void {
+      if (graceTimer !== null) {
+        scheduler.clearTimer(graceTimer);
+        graceTimer = null;
+      }
+      if (pollTimer !== null) {
+        scheduler.clearTimer(pollTimer);
+        pollTimer = null;
+      }
+    }
+
+    async function probe(): Promise<boolean> {
+      let info: DaemonInfo;
+      try {
+        info = await fetchInfo();
+      } catch {
+        set((s) => ({ attempts: s.attempts + 1 }));
+        return false;
+      }
+      const before = identity;
+      identity = info;
+      if (before && compareIdentity(before, info) === "upgraded") {
+        // Stay blocked through the reload: an unlocked frame here would let the
+        // user drive new server code from the bundle it just replaced.
+        set({ state: "updating", build: info.build, hostname: info.hostname });
+        reload();
+        return true;
+      }
+      clearTimers();
+      set({ state: "online", build: info.build, hostname: info.hostname, attempts: 0 });
+      return true;
+    }
+
+    async function poll(): Promise<void> {
+      const state = get().state;
+      if (state === "online" || state === "updating") return;
+      const ok = await probe();
+      if (ok || pollTimer !== null) return;
+      pollTimer = scheduler.setTimer(() => {
+        pollTimer = null;
+        void poll();
+      }, pollMs);
+    }
+
+    return {
+      state: "connecting",
+      build: undefined,
+      hostname: undefined,
+      attempts: 0,
+
+      probe,
+
+      noteDisconnected() {
+        const state = get().state;
+        if (state === "down" || state === "updating") return;
+        set({ state: "reconnecting", attempts: 0 });
+        if (graceTimer === null) {
+          graceTimer = scheduler.setTimer(() => {
+            graceTimer = null;
+            if (get().state === "reconnecting") set({ state: "down" });
+            void poll();
+          }, graceMs);
+        }
+      },
+
+      noteConnected() {
+        const state = get().state;
+        if (state === "online" || state === "updating") return;
+        void probe();
+      },
+
+      stop: clearTimers,
+    };
+  });
+}
+
+export type DaemonLinkStoreApi = ReturnType<typeof createDaemonLinkStore>;
+
+export interface DaemonLinkProps {
+  /** The link store this instance drives — `RestartOverlay` (and, later, the
+   *  sidebar's status indicator) read the same one. */
+  store: DaemonLinkStoreApi;
+  /** The catalog store's `connected` field (docs/RESTART.md): the events
+   *  socket dying is the earliest signal a restart happened, ahead of any
+   *  poll. Pass `useStore(catalogStore, (s) => s.connected)`. */
+  connected: boolean;
+}
+
+/**
+ * Renders nothing — the controller that wires a `DaemonLinkStore` to the
+ * catalog's socket state. Mount once near the app root; `RestartOverlay`
+ * reads the store it drives.
+ */
+export function DaemonLink({ store, connected }: DaemonLinkProps): null {
+  const mounted = useRef(false);
+
+  useEffect(() => {
+    if (!mounted.current) {
+      mounted.current = true;
+      void store.getState().probe();
+      return;
+    }
+    if (connected) store.getState().noteConnected();
+    else store.getState().noteDisconnected();
+  }, [store, connected]);
+
+  useEffect(() => () => store.getState().stop(), [store]);
+
+  return null;
+}

web/src/components/daemon/RestartOverlay.test.tsx

@@ -0,0 +1,78 @@
+// @vitest-environment happy-dom
+import { cleanup, fireEvent, render, screen } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { createDaemonLinkStore, type DaemonLinkStoreApi } from "./DaemonLink.js";
+import { RestartOverlay } from "./RestartOverlay.js";
+
+afterEach(() => cleanup());
+
+function storeAt(state: "connecting" | "online" | "reconnecting" | "down" | "updating"): DaemonLinkStoreApi {
+  const store = createDaemonLinkStore({ scheduler: { setTimer: () => 0, clearTimer: () => {} } });
+  store.setState({ state });
+  return store;
+}
+
+describe("RestartOverlay", () => {
+  it("renders nothing while connecting, online, or reconnecting", () => {
+    for (const state of ["connecting", "online", "reconnecting"] as const) {
+      const { unmount } = render(<RestartOverlay store={storeAt(state)} />);
+      expect(screen.queryByRole("alertdialog")).toBeNull();
+      unmount();
+    }
+  });
+
+  it("blocks with a restarting message when down", () => {
+    render(<RestartOverlay store={storeAt("down")} />);
+    const dialog = screen.getByRole("alertdialog");
+    expect(dialog.textContent).toContain("Maestro is restarting");
+    expect(dialog.textContent).toContain("Waiting for the daemon to come back…");
+  });
+
+  it("counts attempts once more than one probe has failed", () => {
+    const store = storeAt("down");
+    store.setState({ attempts: 3 });
+    render(<RestartOverlay store={store} />);
+    expect(screen.getByRole("alertdialog").textContent).toContain("(3 attempts)");
+  });
+
+  it("says it is reloading when updating", () => {
+    render(<RestartOverlay store={storeAt("updating")} />);
+    const dialog = screen.getByRole("alertdialog");
+    expect(dialog.textContent).toContain("Maestro was updated");
+    expect(dialog.textContent).toContain("Reloading this page onto the new release…");
+  });
+
+  it("names the release from the store's build", () => {
+    const store = storeAt("down");
+    store.setState({ build: { commit: "f89be4a", commit_date: "2026-09-02T00:00:00Z", dirty: false } });
+    render(<RestartOverlay store={store} />);
+    expect(screen.getByRole("alertdialog").textContent).toContain("f89be4a · 2026-09-02");
+  });
+
+  it("clears the moment the store reports the link is back", () => {
+    const store = storeAt("down");
+    const { rerender } = render(<RestartOverlay store={store} />);
+    expect(screen.queryByRole("alertdialog")).not.toBeNull();
+    store.setState({ state: "online" });
+    rerender(<RestartOverlay store={store} />);
+    expect(screen.queryByRole("alertdialog")).toBeNull();
+  });
+
+  it("swallows keyboard shortcuts while blocking, but not once cleared", () => {
+    const store = storeAt("down");
+    const handler = vi.fn();
+    window.addEventListener("keydown", handler);
+    const { rerender } = render(<RestartOverlay store={store} />);
+
+    fireEvent.keyDown(window, { key: "n" });
+    expect(handler).not.toHaveBeenCalled();
+
+    store.setState({ state: "online" });
+    rerender(<RestartOverlay store={store} />);
+    fireEvent.keyDown(window, { key: "n" });
+    expect(handler).toHaveBeenCalledTimes(1);
+
+    window.removeEventListener("keydown", handler);
+  });
+});

web/src/components/daemon/RestartOverlay.tsx

@@ -0,0 +1,62 @@
+// React port of ../../restartOverlay.ts. Blocking overlay for a daemon that
+// went away — see docs/RESTART.md.
+//
+// Rendered while the link is `down` or `updating`, gone the moment it is
+// back. It owns no polling of its own: `DaemonLink` polls, this only renders
+// what the store reports.
+
+import { useEffect } from "react";
+import { useStore } from "zustand";
+
+import { formatRelease, type DaemonLinkStoreApi } from "./DaemonLink.js";
+
+export interface RestartOverlayProps {
+  /** The same store a sibling `DaemonLink` drives. */
+  store: DaemonLinkStoreApi;
+}
+
+/** The poll runs while this is up; saying how many tries have gone by is what
+ *  separates "still restarting" from "wedged" for someone staring at it. */
+function attemptText(attempts: number): string {
+  if (attempts <= 1) return "Waiting for the daemon to come back…";
+  return `Waiting for the daemon to come back… (${attempts} attempts)`;
+}
+
+function swallow(e: KeyboardEvent): void {
+  e.stopImmediatePropagation();
+}
+
+export function RestartOverlay({ store }: RestartOverlayProps) {
+  const state = useStore(store, (s) => s.state);
+  const build = useStore(store, (s) => s.build);
+  const attempts = useStore(store, (s) => s.attempts);
+
+  const blocking = state === "down" || state === "updating";
+
+  // The app's shortcuts live on `window`, so hiding the UI behind a backdrop
+  // does not stop them: `n` would still open a spawn form against a daemon
+  // that is not there. Swallow keys in the capture phase until the link is
+  // back, without `preventDefault` so the browser's own chords still work.
+  useEffect(() => {
+    if (!blocking) return;
+    window.addEventListener("keydown", swallow, true);
+    return () => window.removeEventListener("keydown", swallow, true);
+  }, [blocking]);
+
+  if (!blocking) return null;
+
+  const updating = state === "updating";
+
+  return (
+    <div className="modal-backdrop restart-backdrop">
+      <div className="modal restart-modal" role="alertdialog" aria-modal="true" aria-labelledby="restart-title">
+        <div className="restart-spinner" aria-hidden="true" />
+        <h2 id="restart-title">{updating ? "Maestro was updated" : "Maestro is restarting"}</h2>
+        <p className="restart-detail">
+          {updating ? "Reloading this page onto the new release…" : attemptText(attempts)}
+        </p>
+        <p className="restart-release">{formatRelease(build)}</p>
+      </div>
+    </div>
+  );
+}

web/src/hooks/useHashRouter.test.tsx

@@ -0,0 +1,82 @@
+// @vitest-environment happy-dom
+import { act, cleanup, render, waitFor } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+
+import { useHashRouter, type Route, type UseHashRouterResult } from "./useHashRouter.js";
+
+let controls: UseHashRouterResult;
+
+function Probe() {
+  controls = useHashRouter();
+  return <div>{controls.route.kind === "attach" ? `attach:${controls.route.sessionId}` : "catalog"}</div>;
+}
+
+beforeEach(() => {
+  location.hash = "";
+});
+
+afterEach(cleanup);
+
+describe("useHashRouter", () => {
+  it("starts on catalog for an empty hash", () => {
+    const view = render(<Probe />);
+    expect(view.container.textContent).toBe("catalog");
+  });
+
+  it("resolves #/attach/:id to the attach route", () => {
+    location.hash = "#/attach/s1";
+    const view = render(<Probe />);
+    expect(view.container.textContent).toBe("attach:s1");
+  });
+
+  it("decodes an encoded session id", () => {
+    location.hash = `#/attach/${encodeURIComponent("weird id/x")}`;
+    const view = render(<Probe />);
+    expect(view.container.textContent).toBe("attach:weird id/x");
+  });
+
+  it("falls back to catalog for an unknown route", () => {
+    location.hash = "#/nonsense";
+    const view = render(<Probe />);
+    expect(view.container.textContent).toBe("catalog");
+  });
+
+  it("follows a hashchange fired outside the hook", async () => {
+    const view = render(<Probe />);
+    // happy-dom dispatches `hashchange` on a real timer, like a browser — not
+    // synchronously with the assignment.
+    location.hash = "#/attach/s9";
+    await waitFor(() => expect(view.container.textContent).toBe("attach:s9"));
+  });
+
+  it("navigate updates the hash and the route", async () => {
+    const view = render(<Probe />);
+    act(() => controls.navigate({ kind: "attach", sessionId: "s2" } satisfies Route));
+    expect(location.hash).toBe("#/attach/s2");
+    await waitFor(() => expect(view.container.textContent).toBe("attach:s2"));
+  });
+
+  it("navigate back to catalog sets the root hash", async () => {
+    location.hash = "#/attach/s1";
+    const view = render(<Probe />);
+    act(() => controls.navigate({ kind: "catalog" }));
+    expect(location.hash).toBe("#/");
+    await waitFor(() => expect(view.container.textContent).toBe("catalog"));
+  });
+
+  it("navigating to the already-current route still updates state", () => {
+    location.hash = "#/attach/s1";
+    const view = render(<Probe />);
+    act(() => controls.navigate({ kind: "attach", sessionId: "s1" } satisfies Route));
+    expect(view.container.textContent).toBe("attach:s1");
+  });
+
+  it("stops listening after unmount", async () => {
+    const view = render(<Probe />);
+    view.unmount();
+    location.hash = "#/attach/s3";
+    // No assertion beyond "doesn't throw" — a leaked listener would only ever
+    // surface as noise in a later test's act() warnings.
+    await new Promise((r) => setTimeout(r, 0));
+  });
+});

web/src/hooks/useHashRouter.ts

@@ -0,0 +1,47 @@
+// React port of main.ts's `parseRoute`/`dispatch` pair (issue #240). Same two
+// routes, same hash shape (`#/`, `#/attach/:id`) — kept so a deep link or a
+// bookmark from the vanilla shell still resolves.
+
+import { useCallback, useEffect, useState } from "react";
+
+export type Route = { kind: "catalog" } | { kind: "attach"; sessionId: string };
+
+function parseHash(hash: string): Route {
+  const raw = hash.replace(/^#/, "");
+  if (raw === "" || raw === "/") return { kind: "catalog" };
+  const m = raw.match(/^\/attach\/([^/?#]+)$/);
+  if (m) return { kind: "attach", sessionId: decodeURIComponent(m[1]) };
+  return { kind: "catalog" };
+}
+
+function routeToHash(route: Route): string {
+  return route.kind === "catalog" ? "#/" : `#/attach/${encodeURIComponent(route.sessionId)}`;
+}
+
+export interface UseHashRouterResult {
+  route: Route;
+  navigate(route: Route): void;
+}
+
+export function useHashRouter(): UseHashRouterResult {
+  const [route, setRoute] = useState<Route>(() => parseHash(location.hash));
+
+  useEffect(() => {
+    const onHashChange = () => setRoute(parseHash(location.hash));
+    window.addEventListener("hashchange", onHashChange);
+    return () => window.removeEventListener("hashchange", onHashChange);
+  }, []);
+
+  const navigate = useCallback((next: Route) => {
+    const hash = routeToHash(next);
+    // Setting an unchanged hash never fires `hashchange`, so the state update
+    // that would otherwise ride on that event has to happen here instead.
+    if (location.hash === hash) {
+      setRoute(next);
+    } else {
+      location.hash = hash;
+    }
+  }, []);
+
+  return { route, navigate };
+}