feat(web): port daemonLink and restartOverlay to React (#242)

DaemonLink.tsx holds the link state machine as a Zustand store (same
shape as catalogStore/connectionStore) plus a thin controller component
wiring the catalog store's `connected` field to it. RestartOverlay.tsx
renders the blocking modal for down/updating, reusing the existing CSS.

Closes #242

web/src/components/common/ContextMenu.test.tsx

@@ -0,0 +1,68 @@
+// @vitest-environment happy-dom
+import { cleanup, fireEvent, render, screen } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { ContextMenu } from "./ContextMenu.js";
+
+afterEach(() => {
+  cleanup();
+});
+
+function labels(): string[] {
+  return [...document.querySelectorAll(".context-menu-item")].map((b) => b.textContent ?? "");
+}
+
+describe("ContextMenu (#125)", () => {
+  it("renders one item per entry, in order", () => {
+    render(
+      <ContextMenu
+        x={10}
+        y={20}
+        items={[
+          { label: "Rename…", onSelect: () => {} },
+          { label: "Kill session", onSelect: () => {}, danger: true },
+        ]}
+        onClose={vi.fn()}
+      />,
+    );
+    expect(labels()).toEqual(["Rename…", "Kill session"]);
+    expect(document.querySelector(".context-menu-item.is-danger")?.textContent).toBe("Kill session");
+  });
+
+  it("runs the selected entry and closes", () => {
+    const chosen = vi.fn();
+    const onClose = vi.fn();
+    render(<ContextMenu x={0} y={0} items={[{ label: "Rename…", onSelect: chosen }]} onClose={onClose} />);
+    fireEvent.click(screen.getByRole("menuitem"));
+    expect(chosen).toHaveBeenCalledOnce();
+    expect(onClose).toHaveBeenCalledOnce();
+  });
+
+  it("closes on Escape and on a press outside it", () => {
+    const onClose = vi.fn();
+    render(<ContextMenu x={0} y={0} items={[{ label: "Rename…", onSelect: () => {} }]} onClose={onClose} />);
+    fireEvent.keyDown(document, { key: "Escape" });
+    expect(onClose).toHaveBeenCalledTimes(1);
+
+    fireEvent(document.body, new Event("pointerdown", { bubbles: true }));
+    expect(onClose).toHaveBeenCalledTimes(2);
+  });
+
+  it("stays open for a press inside itself", () => {
+    const onClose = vi.fn();
+    render(<ContextMenu x={0} y={0} items={[{ label: "Rename…", onSelect: () => {} }]} onClose={onClose} />);
+    const menu = document.querySelector(".context-menu") as HTMLElement;
+    fireEvent(menu, new Event("pointerdown", { bubbles: true }));
+    expect(onClose).not.toHaveBeenCalled();
+  });
+
+  it("closes on scroll and on resize", () => {
+    const onClose = vi.fn();
+    render(<ContextMenu x={0} y={0} items={[{ label: "Rename…", onSelect: () => {} }]} onClose={onClose} />);
+    fireEvent.scroll(window);
+    expect(onClose).toHaveBeenCalledTimes(1);
+
+    fireEvent.resize(window);
+    expect(onClose).toHaveBeenCalledTimes(2);
+  });
+});

web/src/components/common/ContextMenu.tsx

@@ -0,0 +1,86 @@
+// React port of ../../contextMenu.ts (#125), the general-purpose version —
+// unlike the sidebar's own menu, this one also closes on scroll/resize, since
+// a menu anchored to coordinates goes stale the moment the page moves under it.
+
+import { useEffect, useLayoutEffect, useRef, useState } from "react";
+import { createPortal } from "react-dom";
+
+export interface ContextMenuItem {
+  label: string;
+  onSelect(): void;
+  /** Renders the entry in the destructive style. */
+  danger?: boolean;
+}
+
+export interface ContextMenuProps {
+  x: number;
+  y: number;
+  items: ContextMenuItem[];
+  onClose(): void;
+}
+
+export function ContextMenu({ x, y, items, onClose }: ContextMenuProps) {
+  const ref = useRef<HTMLDivElement>(null);
+  const [pos, setPos] = useState({ left: x, top: y });
+
+  // Nudge back inside the viewport once the menu has a measurable size.
+  useLayoutEffect(() => {
+    const rect = ref.current?.getBoundingClientRect();
+    if (!rect) return;
+    const maxX = window.innerWidth - rect.width;
+    const maxY = window.innerHeight - rect.height;
+    setPos({ left: Math.max(0, Math.min(x, maxX)), top: Math.max(0, Math.min(y, maxY)) });
+  }, [x, y]);
+
+  useEffect(() => {
+    const onKeyDown = (e: KeyboardEvent) => {
+      if (e.key === "Escape") onClose();
+    };
+    const onPointerDown = (e: Event) => {
+      if (!ref.current?.contains(e.target as Node)) onClose();
+    };
+    document.addEventListener("keydown", onKeyDown, true);
+    window.addEventListener("pointerdown", onPointerDown, true);
+    window.addEventListener("scroll", onClose, true);
+    window.addEventListener("resize", onClose);
+    return () => {
+      document.removeEventListener("keydown", onKeyDown, true);
+      window.removeEventListener("pointerdown", onPointerDown, true);
+      window.removeEventListener("scroll", onClose, true);
+      window.removeEventListener("resize", onClose);
+    };
+  }, [onClose]);
+
+  useEffect(() => {
+    (ref.current?.firstElementChild as HTMLElement | null)?.focus();
+  }, []);
+
+  return createPortal(
+    <div
+      ref={ref}
+      role="menu"
+      className="context-menu fixed z-modal min-w-[160px] rounded-r-2 border border-border-strong bg-surface py-sp-1 shadow-2"
+      style={{ left: pos.left, top: pos.top }}
+    >
+      {items.map((item) => (
+        <button
+          key={item.label}
+          type="button"
+          role="menuitem"
+          className={`context-menu-item block w-full px-sp-3 py-sp-1 text-left text-fs-12 hover:bg-surface-2 ${
+            item.danger ? "is-danger text-danger" : "text-ink"
+          }`}
+          onClick={(e) => {
+            e.preventDefault();
+            e.stopPropagation();
+            onClose();
+            item.onSelect();
+          }}
+        >
+          {item.label}
+        </button>
+      ))}
+    </div>,
+    document.body,
+  );
+}

web/src/components/common/index.ts

@@ -0,0 +1 @@
+export { ContextMenu, type ContextMenuItem, type ContextMenuProps } from "./ContextMenu.js";

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/components/dialogs/HelpOverlay.test.tsx

@@ -0,0 +1,82 @@
+// @vitest-environment happy-dom
+import { cleanup, fireEvent, render, screen } from "@testing-library/react";
+import { afterEach, describe, expect, it } from "vitest";
+
+import { keyCaps } from "../../commands.js";
+import { groupedCommands } from "../../help.js";
+import { HelpOverlay } from "./HelpOverlay.js";
+
+afterEach(() => {
+  cleanup();
+});
+
+function press(key: string, init: KeyboardEventInit = {}): void {
+  fireEvent.keyDown(window, { key, ...init });
+}
+
+describe("HelpOverlay", () => {
+  it("opens on ? and closes on a second ?", () => {
+    render(<HelpOverlay />);
+    expect(screen.queryByRole("dialog")).toBeNull();
+    press("?", { shiftKey: true });
+    expect(screen.queryByRole("dialog")).not.toBeNull();
+    press("?", { shiftKey: true });
+    expect(screen.queryByRole("dialog")).toBeNull();
+  });
+
+  it("ignores ? while typing and when a non-shift modifier is held", () => {
+    render(<HelpOverlay />);
+    const input = document.createElement("input");
+    document.body.appendChild(input);
+    fireEvent.keyDown(input, { key: "?", shiftKey: true });
+    expect(screen.queryByRole("dialog")).toBeNull();
+
+    press("?", { ctrlKey: true });
+    expect(screen.queryByRole("dialog")).toBeNull();
+    input.remove();
+  });
+
+  it("closes on Escape, on the close button, and on a click outside the panel", () => {
+    render(<HelpOverlay />);
+
+    press("?", { shiftKey: true });
+    press("Escape");
+    expect(screen.queryByRole("dialog")).toBeNull();
+
+    press("?", { shiftKey: true });
+    fireEvent.click(screen.getByRole("button", { name: "Close" }));
+    expect(screen.queryByRole("dialog")).toBeNull();
+
+    press("?", { shiftKey: true });
+    fireEvent.click(screen.getByRole("dialog"));
+    expect(screen.queryByRole("dialog")).toBeNull();
+  });
+
+  it("stays open for a click inside the panel", () => {
+    render(<HelpOverlay />);
+    press("?", { shiftKey: true });
+    fireEvent.click(document.querySelector(".help-panel") as HTMLElement);
+    expect(screen.queryByRole("dialog")).not.toBeNull();
+  });
+
+  it("renders exactly the commands the registry has bound, grouped", () => {
+    render(<HelpOverlay />);
+    press("?", { shiftKey: true });
+
+    const groups = groupedCommands();
+    expect([...document.querySelectorAll(".help-group-title")].map((h) => h.textContent)).toEqual(
+      groups.map((g) => g.title),
+    );
+    expect(
+      [...document.querySelectorAll<HTMLElement>(".help-row")].map((r) => r.dataset.commandId),
+    ).toEqual(groups.flatMap((g) => g.items.map((c) => c.id)));
+    expect([...document.querySelectorAll(".help-desc")].map((d) => d.textContent)).toEqual(
+      groups.flatMap((g) => g.items.map((c) => c.label)),
+    );
+    expect(
+      [...document.querySelectorAll(".help-row")].map((r) =>
+        [...r.querySelectorAll("kbd")].map((k) => k.textContent).join(" "),
+      ),
+    ).toEqual(groups.flatMap((g) => g.items.map((c) => keyCaps(c.keys[0]).join(" "))));
+  });
+});

web/src/components/dialogs/HelpOverlay.tsx

@@ -0,0 +1,78 @@
+// React port of ../../help.ts: the `?` overlay renders the command registry
+// (commands.ts) directly — the same list that dispatches the keys — so a
+// binding can never be documented as one thing and do another.
+
+import { useEffect, useState } from "react";
+import { createPortal } from "react-dom";
+
+import { CommandSet, defineCommands, keyCaps } from "../../commands.js";
+import { groupedCommands } from "../../help.js";
+
+export function HelpOverlay() {
+  const [open, setOpen] = useState(false);
+
+  useEffect(() => {
+    const helpKeys = new CommandSet(defineCommands({ "help.toggle": () => setOpen((o) => !o) }));
+    const overlayKeys = new CommandSet(defineCommands({ "help.close": () => setOpen(false) }));
+    const onKeydown = (e: KeyboardEvent) => {
+      if (open && overlayKeys.handle(e)) return;
+      helpKeys.handle(e);
+    };
+    window.addEventListener("keydown", onKeydown);
+    return () => window.removeEventListener("keydown", onKeydown);
+  }, [open]);
+
+  if (!open) return null;
+
+  const close = () => setOpen(false);
+
+  return createPortal(
+    <div
+      role="dialog"
+      aria-modal="true"
+      aria-label="Keyboard shortcuts"
+      className="help-overlay fixed inset-0 z-modal flex items-center justify-center bg-bg/70"
+      onClick={(e) => {
+        if (e.target === e.currentTarget) close();
+      }}
+    >
+      <div className="help-panel max-h-[80vh] w-full max-w-[560px] overflow-auto rounded-r-3 border border-border bg-surface p-sp-4 shadow-2">
+        <header className="help-head flex items-center justify-between">
+          <h2 className="help-title m-0 text-fs-15 font-semibold text-ink">Keyboard shortcuts</h2>
+          <button
+            type="button"
+            aria-label="Close"
+            className="help-close rounded-r-1 px-sp-2 py-1 text-fs-15 text-muted hover:text-ink"
+            onClick={close}
+          >
+            ✕
+          </button>
+        </header>
+        {groupedCommands().map((group) => (
+          <section key={group.title} className="help-group mt-sp-3">
+            <h3 className="help-group-title text-fs-12 font-semibold text-muted">{group.title}</h3>
+            <dl className="help-list mt-sp-1">
+              {group.items.map((cmd) => (
+                <div
+                  key={cmd.id}
+                  className="help-row flex items-center justify-between gap-sp-3 py-sp-1"
+                  data-command-id={cmd.id}
+                >
+                  <dt className="help-keys m-0 flex gap-sp-1">
+                    {keyCaps(cmd.keys[0]).map((cap, i) => (
+                      <kbd key={i} className="rounded-r-1 border border-border px-sp-1 text-fs-11">
+                        {cap}
+                      </kbd>
+                    ))}
+                  </dt>
+                  <dd className="help-desc m-0 text-fs-12 text-ink">{cmd.label}</dd>
+                </div>
+              ))}
+            </dl>
+          </section>
+        ))}
+      </div>
+    </div>,
+    document.body,
+  );
+}

web/src/components/dialogs/KillDialog.test.tsx

@@ -0,0 +1,74 @@
+// @vitest-environment happy-dom
+import { cleanup, fireEvent, render, screen, waitFor } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { KillDialog } from "./KillDialog.js";
+
+afterEach(() => {
+  cleanup();
+});
+
+describe("KillDialog", () => {
+  it("focuses the kill button, so Enter confirms", () => {
+    render(<KillDialog name="alpha" blockers={null} onConfirm={() => Promise.resolve()} onCancel={vi.fn()} />);
+    expect(document.activeElement).toBe(screen.getByRole("button", { name: "Kill" }));
+  });
+
+  it("focuses the force button too", () => {
+    render(
+      <KillDialog
+        name="alpha"
+        blockers={null}
+        force
+        reason="worktree is dirty."
+        onConfirm={() => Promise.resolve()}
+        onCancel={vi.fn()}
+      />,
+    );
+    expect(document.activeElement).toBe(screen.getByRole("button", { name: "Force kill" }));
+  });
+
+  it("names the blockers in the confirm body", () => {
+    render(
+      <KillDialog
+        name="alpha"
+        blockers={{ uncommitted_files: 2, untracked_files: 0, unpushed_commits: 0 }}
+        onConfirm={() => Promise.resolve()}
+        onCancel={vi.fn()}
+      />,
+    );
+    expect(screen.getByText(/will be refused unless it is forced/)).not.toBeNull();
+  });
+
+  it("cancels on Cancel, on Escape and on a backdrop click", () => {
+    const onCancel = vi.fn();
+    const first = render(<KillDialog name="alpha" blockers={null} onConfirm={() => Promise.resolve()} onCancel={onCancel} />);
+    fireEvent.click(screen.getByRole("button", { name: "Cancel" }));
+    expect(onCancel).toHaveBeenCalledTimes(1);
+    first.unmount();
+
+    const second = render(<KillDialog name="alpha" blockers={null} onConfirm={() => Promise.resolve()} onCancel={onCancel} />);
+    fireEvent.keyDown(screen.getByRole("dialog"), { key: "Escape" });
+    expect(onCancel).toHaveBeenCalledTimes(2);
+    second.unmount();
+
+    render(<KillDialog name="alpha" blockers={null} onConfirm={() => Promise.resolve()} onCancel={onCancel} />);
+    fireEvent.click(screen.getByRole("dialog"));
+    expect(onCancel).toHaveBeenCalledTimes(3);
+  });
+
+  it("disables the button while pending and shows a rejection inline, so the press can be retried", async () => {
+    let reject: (e: Error) => void = () => {};
+    const onConfirm = vi.fn(() => new Promise<void>((_, r) => (reject = r)));
+    render(<KillDialog name="alpha" blockers={null} onConfirm={onConfirm} onCancel={vi.fn()} />);
+
+    const kill = screen.getByRole("button", { name: "Kill" }) as HTMLButtonElement;
+    fireEvent.click(kill);
+    expect(onConfirm).toHaveBeenCalledOnce();
+    expect(kill.disabled).toBe(true);
+
+    reject(new Error("daemon unreachable"));
+    await waitFor(() => expect(kill.disabled).toBe(false));
+    expect(screen.getByText("Failed to kill: daemon unreachable")).not.toBeNull();
+  });
+});

web/src/components/dialogs/KillDialog.tsx

@@ -0,0 +1,95 @@
+// React port of ../../killDialog.ts: the two kill prompts (#81, #160). The
+// daemon refuses an unforced kill over a worktree holding unsaved work; the
+// same component in `force` mode is the override that follows that refusal.
+
+import { useEffect, useRef, useState } from "react";
+import { createPortal } from "react-dom";
+
+import { formatInTheWay, type InTheWay } from "../../types.js";
+
+export interface KillDialogProps {
+  /** Session name, as the sidebar shows it. */
+  name: string;
+  /** What the card last saw in the way, when anything was. */
+  blockers: InTheWay | null;
+  /** Set once the daemon has refused an unforced kill: this pass forces it,
+   *  and `reason` carries the daemon's refusal message. */
+  force?: boolean;
+  /** Message from the daemon's refusal, shown when there are no blockers to
+   *  spell out. */
+  reason?: string;
+  /** Run the kill (or the forced kill). A rejection is rendered inline, and
+   *  the dialog stays open so the press can be retried. */
+  onConfirm(): Promise<void>;
+  onCancel(): void;
+}
+
+export function KillDialog(props: KillDialogProps) {
+  const { name, blockers, force, reason, onConfirm, onCancel } = props;
+  const confirmRef = useRef<HTMLButtonElement>(null);
+  const [pending, setPending] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  // The acting button takes the focus in both modes: the operator already
+  // asked for the kill, so Enter confirms it.
+  useEffect(() => confirmRef.current?.focus(), []);
+
+  const handleConfirm = () => {
+    setPending(true);
+    setError(null);
+    void onConfirm().catch((e: unknown) => {
+      setPending(false);
+      setError(`Failed to kill: ${(e as Error).message}`);
+    });
+  };
+
+  const body = blockers
+    ? force
+      ? `Its worktree still has ${formatInTheWay(blockers)}. Forcing the kill removes the session and leaves the worktree on disk.`
+      : `Its worktree still has ${formatInTheWay(blockers)}. The kill will be refused unless it is forced.`
+    : force
+      ? `${reason ?? ""} Forcing the kill removes the session and leaves the worktree on disk.`
+      : "The session and everything running in it go away. Its worktree stays on disk.";
+
+  return createPortal(
+    <div
+      role="dialog"
+      aria-modal="true"
+      aria-label={`Kill ${name}`}
+      className="kill-dialog fixed inset-0 z-modal flex items-center justify-center bg-bg/70"
+      onClick={(e) => {
+        if (e.target === e.currentTarget) onCancel();
+      }}
+      onKeyDown={(e) => {
+        if (e.key === "Escape") onCancel();
+      }}
+    >
+      <div className="kill-dialog-panel min-w-[280px] max-w-[420px] rounded-r-2 border border-border-strong bg-surface p-sp-4 shadow-2">
+        <h2 className="kill-dialog-title m-0 text-fs-15 font-semibold text-ink">Kill &quot;{name}&quot;?</h2>
+        <p className="kill-dialog-body mt-sp-2 text-fs-13 text-ink">{body}</p>
+        {error && <p className="kill-dialog-error mt-sp-2 text-fs-12 text-danger">{error}</p>}
+        <div className="kill-dialog-actions mt-sp-3 flex justify-end gap-sp-2">
+          <button
+            type="button"
+            className="kill-dialog-cancel rounded-r-1 border border-border px-sp-3 py-sp-1 text-fs-12 text-ink"
+            onClick={onCancel}
+          >
+            Cancel
+          </button>
+          <button
+            ref={confirmRef}
+            type="button"
+            disabled={pending}
+            className={`rounded-r-1 bg-danger px-sp-3 py-sp-1 text-fs-12 text-accent-ink disabled:opacity-60 ${
+              force ? "kill-dialog-force" : "kill-dialog-kill"
+            }`}
+            onClick={handleConfirm}
+          >
+            {force ? "Force kill" : "Kill"}
+          </button>
+        </div>
+      </div>
+    </div>,
+    document.body,
+  );
+}

web/src/components/dialogs/index.ts

@@ -0,0 +1,2 @@
+export { KillDialog, type KillDialogProps } from "./KillDialog.js";
+export { HelpOverlay } from "./HelpOverlay.js";

web/src/components/hooks/useViewport.test.tsx

@@ -0,0 +1,79 @@
+// @vitest-environment happy-dom
+import { cleanup, render } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { useViewport } from "./useViewport.js";
+
+function Probe() {
+  useViewport();
+  return null;
+}
+
+class FakeVisualViewport {
+  height = 800;
+  offsetTop = 0;
+  private listeners: Record<string, Array<() => void>> = { resize: [], scroll: [] };
+
+  addEventListener(type: string, cb: () => void): void {
+    this.listeners[type].push(cb);
+  }
+  removeEventListener(type: string, cb: () => void): void {
+    this.listeners[type] = this.listeners[type].filter((l) => l !== cb);
+  }
+  fire(type: "resize" | "scroll"): void {
+    for (const l of this.listeners[type]) l();
+  }
+}
+
+let vv: FakeVisualViewport;
+
+beforeEach(() => {
+  vv = new FakeVisualViewport();
+  vi.stubGlobal("visualViewport", vv);
+  vi.stubGlobal("requestAnimationFrame", (cb: FrameRequestCallback) => {
+    cb(0);
+    return 0;
+  });
+  vi.stubGlobal("cancelAnimationFrame", () => {});
+});
+
+afterEach(() => {
+  cleanup();
+  vi.unstubAllGlobals();
+  document.documentElement.className = "";
+  document.documentElement.removeAttribute("style");
+});
+
+describe("useViewport", () => {
+  it("mirrors the visual viewport's height and offset onto CSS custom properties", () => {
+    vv.height = 640;
+    vv.offsetTop = 12;
+    render(<Probe />);
+    const root = document.documentElement.style;
+    expect(root.getPropertyValue("--app-vh")).toBe("640px");
+    expect(root.getPropertyValue("--app-top")).toBe("12px");
+  });
+
+  it("no-ops when visualViewport is unavailable", () => {
+    vi.stubGlobal("visualViewport", undefined);
+    expect(() => render(<Probe />)).not.toThrow();
+    expect(document.documentElement.style.getPropertyValue("--app-vh")).toBe("");
+  });
+
+  it("marks kb-open once an editable shrinks the viewport well past the baseline", () => {
+    render(<Probe />);
+    const input = document.createElement("input");
+    document.body.appendChild(input);
+    input.focus();
+
+    vv.height = 800 - 200;
+    vv.fire("resize");
+    expect(document.documentElement.classList.contains("kb-open")).toBe(true);
+
+    input.blur();
+    vv.height = 800;
+    vv.fire("resize");
+    expect(document.documentElement.classList.contains("kb-open")).toBe(false);
+    input.remove();
+  });
+});

web/src/components/hooks/useViewport.ts

@@ -0,0 +1,51 @@
+// React port of ../../viewport.ts. Binds the app shell's height and position
+// to the *visual* viewport rather than the layout one, so a pinned bottom bar
+// (the attach view's special-key bar, NAP-342) lands above an open on-screen
+// keyboard instead of behind it. See viewport.ts for the full mechanism.
+
+import { useEffect } from "react";
+
+const KB_OPEN_THRESHOLD = 150;
+
+export function useViewport(): void {
+  useEffect(() => {
+    const vv = window.visualViewport;
+    if (!vv) return;
+
+    const root = document.documentElement;
+    let raf = 0;
+    let baseline = vv.height;
+
+    const isEditing = () => {
+      const a = document.activeElement as HTMLElement | null;
+      if (!a) return false;
+      return a.tagName === "TEXTAREA" || a.tagName === "INPUT" || a.isContentEditable;
+    };
+
+    const sync = () => {
+      raf = 0;
+      root.style.setProperty("--app-vh", `${Math.round(vv.height)}px`);
+      root.style.setProperty("--app-top", `${Math.round(vv.offsetTop)}px`);
+
+      // Nothing focused ⇒ keyboard can't be open ⇒ this height is the baseline.
+      const editing = isEditing();
+      if (!editing) baseline = vv.height;
+      const kbOpen = editing && baseline - vv.height > KB_OPEN_THRESHOLD;
+      root.classList.toggle("kb-open", kbOpen);
+    };
+    const schedule = () => {
+      if (raf) return;
+      raf = requestAnimationFrame(sync);
+    };
+
+    vv.addEventListener("resize", schedule);
+    vv.addEventListener("scroll", schedule);
+    sync();
+
+    return () => {
+      vv.removeEventListener("resize", schedule);
+      vv.removeEventListener("scroll", schedule);
+      if (raf) cancelAnimationFrame(raf);
+    };
+  }, []);
+}

web/src/components/layout/Drawer.test.tsx

@@ -0,0 +1,154 @@
+// @vitest-environment happy-dom
+import { act, cleanup, fireEvent, render } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { OPEN_SPAWN_EVENT, SPAWN_SIMILAR_EVENT } from "../../catalog.js";
+import { TOGGLE_DRAWER_EVENT } from "../../drawer.js";
+import { Drawer } from "./Drawer.js";
+
+/** Force the mobile media query on, whatever happy-dom's viewport says
+ *  (mirrors ../layout/MultiView's own `forceMobile` in multiview.test.ts). */
+function forceMobile(matches: boolean): void {
+  vi.spyOn(window, "matchMedia").mockImplementation(
+    (query: string) =>
+      ({
+        matches: query.includes("859") && matches,
+        media: query,
+        onchange: null,
+        addEventListener() {},
+        removeEventListener() {},
+        addListener() {},
+        removeListener() {},
+        dispatchEvent: () => false,
+      }) as unknown as MediaQueryList,
+  );
+}
+
+function shell(): HTMLElement {
+  return document.querySelector(".app-shell") as HTMLElement;
+}
+
+function touch(type: "touchstart" | "touchend", x: number, y: number): void {
+  const touches = [{ clientX: x, clientY: y }];
+  const event = new Event(type, { bubbles: true }) as unknown as {
+    touches: typeof touches;
+    changedTouches: typeof touches;
+  };
+  event.touches = touches;
+  event.changedTouches = touches;
+  act(() => {
+    document.dispatchEvent(event as unknown as Event);
+  });
+}
+
+beforeEach(() => forceMobile(true));
+
+afterEach(() => {
+  cleanup();
+  vi.restoreAllMocks();
+});
+
+function openViaToggle(): void {
+  act(() => {
+    document.dispatchEvent(new CustomEvent(TOGGLE_DRAWER_EVENT));
+  });
+}
+
+describe("Drawer (#35)", () => {
+  it("toggles open on the toggle event, off on desktop by class alone", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+    openViaToggle();
+    expect(shell().classList.contains("drawer-open")).toBe(true);
+  });
+
+  it("closes when a session row is tapped", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    openViaToggle();
+    fireEvent.click(document.querySelector(".tree-leaf") as HTMLElement);
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+
+  it("closes when a spawn is requested", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    openViaToggle();
+    act(() => {
+      document.dispatchEvent(new CustomEvent(OPEN_SPAWN_EVENT));
+    });
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+
+  it("closes when spawn similar is requested", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    openViaToggle();
+    act(() => {
+      document.dispatchEvent(new CustomEvent(SPAWN_SIMILAR_EVENT, { detail: {} }));
+    });
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+
+  it("closes on a backdrop click", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    openViaToggle();
+    fireEvent.click(document.querySelector(".mv-backdrop") as HTMLElement);
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+
+  it("opens on a rightward swipe and closes on a leftward one, only on mobile", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    touch("touchstart", 0, 100);
+    touch("touchend", 100, 100);
+    expect(shell().classList.contains("drawer-open")).toBe(true);
+
+    touch("touchstart", 100, 100);
+    touch("touchend", 0, 100);
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+
+  it("ignores swipes on desktop", () => {
+    forceMobile(false);
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    touch("touchstart", 0, 100);
+    touch("touchend", 100, 100);
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+
+  it("ignores a mostly-vertical or too-short gesture", () => {
+    render(
+      <Drawer sidebar={<div className="tree-leaf">row</div>}>
+        <div>content</div>
+      </Drawer>,
+    );
+    touch("touchstart", 0, 0);
+    touch("touchend", 10, 100);
+    expect(shell().classList.contains("drawer-open")).toBe(false);
+  });
+});

web/src/components/layout/Drawer.tsx

@@ -0,0 +1,93 @@
+// React port of ../../drawer.ts (#35): the mobile off-canvas sidebar. On
+// desktop the `drawer-open` class is inert — CSS gates the drawer styling to
+// narrow viewports (styles.css, `.app-shell`).
+//
+// Anything that puts a new view in the content area must close the drawer, or
+// it renders behind the sidebar and the tap reads as a dead button — this
+// listens for the same TOGGLE_DRAWER_EVENT/OPEN_SPAWN_EVENT/SPAWN_SIMILAR_EVENT
+// the rest of the shell already raises, so it needs no wiring from callers.
+
+import type { ReactNode } from "react";
+import { useEffect, useRef, useState } from "react";
+
+import { OPEN_SPAWN_EVENT, SPAWN_SIMILAR_EVENT } from "../../catalog.js";
+import { TOGGLE_DRAWER_EVENT } from "../../drawer.js";
+
+export interface DrawerProps {
+  sidebar: ReactNode;
+  children: ReactNode;
+  className?: string;
+}
+
+export function Drawer({ sidebar, children, className }: DrawerProps) {
+  const [open, setOpen] = useState(false);
+  const sidebarRef = useRef<HTMLDivElement>(null);
+
+  useEffect(() => {
+    const onToggle = () => setOpen((o) => !o);
+    const onClose = () => setOpen(false);
+    document.addEventListener(TOGGLE_DRAWER_EVENT, onToggle);
+    document.addEventListener(OPEN_SPAWN_EVENT, onClose);
+    document.addEventListener(SPAWN_SIMILAR_EVENT, onClose);
+    return () => {
+      document.removeEventListener(TOGGLE_DRAWER_EVENT, onToggle);
+      document.removeEventListener(OPEN_SPAWN_EVENT, onClose);
+      document.removeEventListener(SPAWN_SIMILAR_EVENT, onClose);
+    };
+  }, []);
+
+  // Horizontal swipes drive the drawer (right opens, left closes) rather than
+  // the browser's back/forward navigation. Only a clearly horizontal gesture
+  // past a threshold counts, so vertical terminal scrolling (which owns its
+  // own touch handler) is untouched.
+  useEffect(() => {
+    const mobileMq = window.matchMedia("(max-width: 859px)");
+    let sx = 0;
+    let sy = 0;
+    let tracking = false;
+
+    const onTouchStart = (e: TouchEvent) => {
+      tracking = mobileMq.matches && e.touches.length === 1;
+      if (tracking) {
+        sx = e.touches[0].clientX;
+        sy = e.touches[0].clientY;
+      }
+    };
+    const onTouchEnd = (e: TouchEvent) => {
+      if (!tracking) return;
+      tracking = false;
+      const t = e.changedTouches[0];
+      const dx = t.clientX - sx;
+      const dy = t.clientY - sy;
+      if (Math.abs(dx) < 60 || Math.abs(dx) < Math.abs(dy) * 1.5) return;
+      setOpen((o) => {
+        if (dx > 0 && !o) return true;
+        if (dx < 0 && o) return false;
+        return o;
+      });
+    };
+
+    document.addEventListener("touchstart", onTouchStart, { passive: true });
+    document.addEventListener("touchend", onTouchEnd, { passive: true });
+    return () => {
+      document.removeEventListener("touchstart", onTouchStart);
+      document.removeEventListener("touchend", onTouchEnd);
+    };
+  }, []);
+
+  return (
+    <div className={`app-shell flex h-full min-h-0 ${open ? "drawer-open" : ""} ${className ?? ""}`}>
+      <div
+        ref={sidebarRef}
+        className="sidebar flex h-full min-h-0 flex-col bg-surface"
+        onClick={(e) => {
+          if ((e.target as HTMLElement).closest(".tree-leaf")) setOpen(false);
+        }}
+      >
+        {sidebar}
+      </div>
+      <section className="content min-h-0 flex-1">{children}</section>
+      <div className="mv-backdrop" onClick={() => setOpen(false)} />
+    </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 };
+}