feat(web): add durable control-plane event updates

apps/web/package.json

@@ -12,6 +12,7 @@
     "typecheck": "tsc -p tsconfig.json"
   },
   "dependencies": {
+    "@multi-simadmin/contracts": "workspace:*",
     "react": "19.2.4",
     "react-dom": "19.2.4"
   },

apps/web/src/app-shell.tsx

@@ -1,4 +1,8 @@
 import type { ReactNode } from 'react';
+import { useMemo } from 'react';
+
+import { useControlPlaneEvents } from './events/use-control-plane-events.js';
+import { createEventStreamClient, type EventStreamClient } from './events/event-stream-client.js';
 
 import { FleetPage, type FleetDataSource, type FleetSnapshot } from './fleet/fleet-page.js';
 import { createFleetApiDataSource } from './fleet/fleet-api-data-source.js';
@@ -57,6 +61,7 @@ export interface AppShellProps {
   instanceDataSource?: InstanceDataSource;
   capabilities?: InstanceCapabilityMap;
   capabilityDataSource?: CapabilityDataSource;
+  eventStreamClient?: EventStreamClient;
 }
 
 const MODULE_LABELS = INSTANCE_MODULE_LABELS;
@@ -123,6 +128,7 @@ function Page({
   instanceDataSource,
   capabilities,
   capabilityDataSource,
+  fleetRefreshSignal,
 }: {
   route: ResolvedRoute;
   fleetDataSource: FleetDataSource | undefined;
@@ -131,12 +137,14 @@ function Page({
   instanceDataSource: InstanceDataSource | undefined;
   capabilities: InstanceCapabilityMap | undefined;
   capabilityDataSource: CapabilityDataSource | undefined;
+  fleetRefreshSignal: number;
 }): ReactNode {
   if (route.kind === 'fleet')
     return (
       <FleetPage
         {...(fleetDataSource ? { dataSource: fleetDataSource } : {})}
         {...(fleetData ? { initialData: fleetData } : {})}
+        refreshSignal={fleetRefreshSignal}
       />
     );
   if (route.kind === 'instance-new')
@@ -201,9 +209,17 @@ export function AppShell({
   instanceDataSource,
   capabilities,
   capabilityDataSource,
+  eventStreamClient,
 }: AppShellProps) {
+  const defaultEventStreamClient = useMemo(() => createEventStreamClient(), []);
+  const defaultFleetDataSource = useMemo(() => createFleetApiDataSource(), []);
   const resolved = resolveRoute(pathname);
   const route = resolved.kind === 'redirect' ? resolveRoute(resolved.to ?? '/fleet') : resolved;
+  const routeInstanceId = route.params?.instanceId;
+  const refresh = useControlPlaneEvents(
+    routeInstanceId,
+    eventStreamClient ?? defaultEventStreamClient,
+  );
   const currentSection = section(route);
   return (
     <div className="app-shell" data-route={route.kind}>
@@ -239,12 +255,13 @@ export function AppShell({
         <main id="main-content" tabIndex={-1}>
           <Page
             route={route}
-            fleetDataSource={fleetDataSource ?? createFleetApiDataSource()}
+            fleetDataSource={fleetDataSource ?? defaultFleetDataSource}
             fleetData={fleetData}
             instance={instance}
             instanceDataSource={instanceDataSource}
             capabilities={capabilities}
             capabilityDataSource={capabilityDataSource}
+            fleetRefreshSignal={refresh.fleet}
           />
         </main>
       </div>

apps/web/src/events/event-invalidation-controller.test.ts

@@ -0,0 +1,55 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import { createEventInvalidationController } from './event-invalidation-controller.js';
+
+const base = { id: 'event', occurredAt: '2026-07-17T10:00:00.000Z', requestId: 'request' } as const;
+
+describe('event invalidation controller', () => {
+  it('coalesces bursts into the correct global invalidation domains', () => {
+    const callbacks: Array<() => void> = [];
+    const emit = vi.fn();
+    const controller = createEventInvalidationController(emit, {
+      schedule: (callback) => callbacks.push(callback),
+    });
+    controller.push({ ...base, kind: 'job', jobId: 'job-1' });
+    controller.push({ ...base, kind: 'item', jobId: 'job-1', itemId: 'item-1' });
+    controller.push({ ...base, kind: 'audit', auditEventId: 'audit-1' });
+    expect(callbacks).toHaveLength(1);
+    callbacks[0]?.();
+    expect(emit).toHaveBeenCalledWith(
+      expect.objectContaining({ fleet: false, jobs: true, audit: true }),
+    );
+  });
+
+  it('invalidates Fleet for every instance event but detail only for the latest route owner', () => {
+    const callbacks: Array<() => void> = [];
+    const emit = vi.fn();
+    const controller = createEventInvalidationController(emit, {
+      schedule: (callback) => callbacks.push(callback),
+    });
+    controller.setActiveInstance('old');
+    controller.push({ ...base, kind: 'instance', instanceId: 'old' });
+    controller.setActiveInstance('new');
+    controller.push({ ...base, kind: 'instance', instanceId: 'new' });
+    callbacks[0]?.();
+    const batch = emit.mock.calls[0]?.[0];
+    expect(batch.fleet).toBe(true);
+    expect([...batch.instanceIds]).toEqual(['new']);
+  });
+
+  it('cancels pending work and ignores events after disposal', () => {
+    const callback = vi.fn();
+    const cancel = vi.fn();
+    const emit = vi.fn();
+    const controller = createEventInvalidationController(emit, {
+      schedule: () => callback,
+      cancel,
+    });
+    controller.push({ ...base, kind: 'audit', auditEventId: 'audit-1' });
+    controller.dispose();
+    controller.push({ ...base, kind: 'job', jobId: 'job-1' });
+    callback();
+    expect(cancel).toHaveBeenCalledWith(callback);
+    expect(emit).not.toHaveBeenCalled();
+  });
+});

apps/web/src/events/event-invalidation-controller.ts

@@ -0,0 +1,78 @@
+import type { EventEnvelope } from '@multi-simadmin/contracts';
+
+export interface InvalidationBatch {
+  readonly fleet: boolean;
+  readonly instanceIds: ReadonlySet<string>;
+  readonly jobs: boolean;
+  readonly audit: boolean;
+}
+
+export interface EventInvalidationController {
+  push(event: EventEnvelope): void;
+  setActiveInstance(instanceId: string | undefined): void;
+  dispose(): void;
+}
+
+export interface EventInvalidationOptions {
+  readonly delayMs?: number;
+  readonly schedule?: (callback: () => void, delayMs: number) => unknown;
+  readonly cancel?: (handle: unknown) => void;
+}
+
+export function createEventInvalidationController(
+  emit: (batch: InvalidationBatch) => void,
+  options: EventInvalidationOptions = {},
+): EventInvalidationController {
+  const schedule = options.schedule ?? ((callback, delay) => setTimeout(callback, delay));
+  const cancel =
+    options.cancel ?? ((handle) => clearTimeout(handle as ReturnType<typeof setTimeout>));
+  let activeInstanceId: string | undefined;
+  let handle: unknown;
+  let disposed = false;
+  let fleet = false;
+  let jobs = false;
+  let audit = false;
+  const instanceIds = new Set<string>();
+
+  const flush = (): void => {
+    handle = undefined;
+    if (disposed) return;
+    const batch: InvalidationBatch = {
+      fleet,
+      instanceIds: new Set(instanceIds),
+      jobs,
+      audit,
+    };
+    fleet = false;
+    jobs = false;
+    audit = false;
+    instanceIds.clear();
+    emit(batch);
+  };
+  const arm = (): void => {
+    if (handle === undefined) handle = schedule(flush, Math.max(0, options.delayMs ?? 50));
+  };
+
+  return {
+    push(event) {
+      if (disposed) return;
+      if (event.kind === 'instance') {
+        fleet = true;
+        if (event.instanceId === activeInstanceId) instanceIds.add(event.instanceId);
+      } else if (event.kind === 'job' || event.kind === 'item' || event.kind === 'attempt')
+        jobs = true;
+      else if (event.kind === 'audit') audit = true;
+      arm();
+    },
+    setActiveInstance(instanceId) {
+      activeInstanceId = instanceId;
+      for (const id of instanceIds) if (id !== instanceId) instanceIds.delete(id);
+    },
+    dispose() {
+      disposed = true;
+      if (handle !== undefined) cancel(handle);
+      handle = undefined;
+      instanceIds.clear();
+    },
+  };
+}

apps/web/src/events/event-stream-client.test.ts

@@ -0,0 +1,231 @@
+// @vitest-environment jsdom
+import { describe, expect, it, vi } from 'vitest';
+
+import {
+  createEventStreamClient,
+  createSseParser,
+  parseEventEnvelope,
+  type EventStreamState,
+} from './event-stream-client.js';
+
+const instanceEvent = {
+  kind: 'instance',
+  id: 'event-1',
+  occurredAt: '2026-07-17T10:00:00.000Z',
+  requestId: 'request-1',
+  instanceId: 'instance-1',
+} as const;
+
+function streamResponse(chunks: readonly string[], status = 200): Response {
+  const encoder = new TextEncoder();
+  return new Response(
+    new ReadableStream({
+      start(controller) {
+        for (const chunk of chunks) controller.enqueue(encoder.encode(chunk));
+        controller.close();
+      },
+    }),
+    { status, headers: { 'content-type': 'text/event-stream; charset=utf-8' } },
+  );
+}
+
+function deferred(): { promise: Promise<void>; resolve: () => void } {
+  let resolve!: () => void;
+  return { promise: new Promise<void>((done) => (resolve = done)), resolve };
+}
+
+describe('strict EventEnvelope parser', () => {
+  it('accepts every frozen discriminated-union shape', () => {
+    expect(parseEventEnvelope(instanceEvent)).toEqual(instanceEvent);
+    expect(
+      parseEventEnvelope({ ...instanceEvent, occurredAt: '2026-07-17T10:00:00Z' }),
+    ).toMatchObject({
+      occurredAt: '2026-07-17T10:00:00Z',
+    });
+    expect(
+      parseEventEnvelope({ ...instanceEvent, occurredAt: '2026-07-17T18:00:00+08:00' }),
+    ).toMatchObject({
+      occurredAt: '2026-07-17T18:00:00+08:00',
+    });
+    const base = {
+      kind: instanceEvent.kind,
+      id: instanceEvent.id,
+      occurredAt: instanceEvent.occurredAt,
+      requestId: instanceEvent.requestId,
+    };
+    expect(
+      parseEventEnvelope({ ...base, kind: 'item', jobId: 'job-1', itemId: 'item-1' }),
+    ).toMatchObject({ kind: 'item', jobId: 'job-1', itemId: 'item-1' });
+    expect(
+      parseEventEnvelope({ ...base, kind: 'attempt', jobId: 'job-1', attemptId: 'try-1' }),
+    ).toMatchObject({ kind: 'attempt', attemptId: 'try-1' });
+    expect(parseEventEnvelope({ ...base, kind: 'job', jobId: 'job-1' })).toMatchObject({
+      kind: 'job',
+    });
+    expect(parseEventEnvelope({ ...base, kind: 'audit', auditEventId: 'audit-1' })).toMatchObject({
+      kind: 'audit',
+    });
+  });
+
+  it.each([
+    null,
+    [],
+    { ...instanceEvent, kind: 'unknown' },
+    { ...instanceEvent, id: '' },
+    { ...instanceEvent, occurredAt: 'yesterday' },
+    { ...instanceEvent, instanceId: 1 },
+    { ...instanceEvent, secret: 'must-not-pass' },
+    { ...instanceEvent, kind: 'job' },
+    { ...instanceEvent, kind: 'instance', jobId: 'wrong-union-member' },
+  ])('rejects invalid or non-exact envelopes: %j', (value) => {
+    expect(() => parseEventEnvelope(value)).toThrow('Invalid event envelope.');
+  });
+
+  it.each(['2026-02-30T10:00:00Z', '2026-04-31T10:00:00Z', '2026-01-01T24:00:00Z'])(
+    'rejects normalized invalid RFC3339 timestamp %s',
+    (occurredAt) => {
+      expect(() => parseEventEnvelope({ ...instanceEvent, occurredAt })).toThrow(
+        'Invalid event envelope.',
+      );
+    },
+  );
+});
+
+describe('SSE framing', () => {
+  it('handles arbitrary chunk boundaries, CRLF, comments, and multiline data', () => {
+    const records: Array<{ id?: string; data: string }> = [];
+    const parser = createSseParser((record) => records.push(record));
+    parser.push(': keepalive\r');
+    parser.push('\nid: cursor-1\r\nda');
+    parser.push('ta: {"one":\r\ndata: 2}\r\n\r');
+    parser.push('\n');
+    parser.finish();
+    expect(records).toEqual([{ id: 'cursor-1', data: '{"one":\n2}' }]);
+  });
+
+  it('dispatches a final unterminated event and ignores id-only events and NUL ids', () => {
+    const records: Array<{ id?: string; data: string }> = [];
+    const parser = createSseParser((record) => records.push(record));
+    parser.push('id: ignored\n\nid: bad\0id\ndata: final');
+    parser.finish();
+    expect(records).toEqual([{ data: 'final' }]);
+  });
+});
+
+describe('fetch event stream client', () => {
+  it('uses protected same-origin fetch, retains cursor, and reconnects with Last-Event-ID', async () => {
+    const gate = deferred();
+    const fetcher = vi
+      .fn<typeof fetch>()
+      .mockResolvedValueOnce(
+        streamResponse([
+          `id: cursor-7\ndata: ${JSON.stringify(instanceEvent).slice(0, 20)}`,
+          `${JSON.stringify(instanceEvent).slice(20)}\n\n`,
+        ]),
+      )
+      .mockImplementationOnce(async (_input, init) => {
+        await gate.promise;
+        init?.signal?.throwIfAborted();
+        return streamResponse([]);
+      });
+    const sleep = vi.fn(async () => undefined);
+    const events: unknown[] = [];
+    const states: EventStreamState[] = [];
+    const unsubscribe = createEventStreamClient({ fetch: fetcher, sleep }).subscribe(
+      (event) => events.push(event),
+      (state) => states.push(state),
+    );
+
+    await vi.waitFor(() => expect(fetcher).toHaveBeenCalledTimes(2));
+    expect(events).toEqual([instanceEvent]);
+    expect(fetcher.mock.calls[0]?.[0]).toBe('/api/v1/events');
+    expect(fetcher.mock.calls[0]?.[1]).toMatchObject({
+      credentials: 'same-origin',
+      headers: { Accept: 'text/event-stream' },
+    });
+    expect(fetcher.mock.calls[1]?.[1]?.headers).toEqual({
+      Accept: 'text/event-stream',
+      'Last-Event-ID': 'cursor-7',
+    });
+    expect(states).toContain('open');
+    expect(states).toContain('reconnecting');
+    unsubscribe();
+    gate.resolve();
+  });
+
+  it('applies bounded exponential reconnect delay and never exposes response bodies', async () => {
+    const gate = deferred();
+    const fetcher = vi
+      .fn<typeof fetch>()
+      .mockResolvedValueOnce(new Response('password=top-secret', { status: 401 }))
+      .mockResolvedValueOnce(new Response('another-secret', { status: 503 }))
+      .mockImplementationOnce(async (_input, init) => {
+        await gate.promise;
+        init?.signal?.throwIfAborted();
+        return streamResponse([]);
+      });
+    const delays: number[] = [];
+    const errors: string[] = [];
+    const client = createEventStreamClient({
+      fetch: fetcher,
+      initialRetryMs: 10,
+      maxRetryMs: 20,
+      sleep: async (ms) => void delays.push(ms),
+    });
+    const unsubscribe = client.subscribe(
+      () => undefined,
+      (_state, error) => error && errors.push(error.message),
+    );
+
+    await vi.waitFor(() => expect(fetcher).toHaveBeenCalledTimes(3));
+    expect(delays.slice(0, 2)).toEqual([10, 20]);
+    expect(errors.join(' ')).not.toMatch(/secret|password/i);
+    expect(errors[0]).toBe('The event stream connection failed.');
+    unsubscribe();
+    gate.resolve();
+  });
+
+  it('clears an expired cursor and reconnects without Last-Event-ID', async () => {
+    const gate = deferred();
+    const fetcher = vi
+      .fn<typeof fetch>()
+      .mockResolvedValueOnce(
+        streamResponse([`id: cursor-old\ndata: ${JSON.stringify(instanceEvent)}\n\n`]),
+      )
+      .mockResolvedValueOnce(new Response(null, { status: 409 }))
+      .mockImplementationOnce(async (_input, init) => {
+        await gate.promise;
+        init?.signal?.throwIfAborted();
+        return streamResponse([]);
+      });
+    const states: EventStreamState[] = [];
+    const unsubscribe = createEventStreamClient({
+      fetch: fetcher,
+      sleep: async () => undefined,
+    }).subscribe(
+      () => undefined,
+      (state) => states.push(state),
+    );
+    await vi.waitFor(() => expect(fetcher).toHaveBeenCalledTimes(3));
+    expect(fetcher.mock.calls[1]?.[1]?.headers).toMatchObject({ 'Last-Event-ID': 'cursor-old' });
+    expect(fetcher.mock.calls[2]?.[1]?.headers).toEqual({ Accept: 'text/event-stream' });
+    expect(states).toContain('resetting');
+    unsubscribe();
+    gate.resolve();
+  });
+
+  it('rejects cross-origin endpoints before fetching and aborts on unsubscribe', async () => {
+    const fetcher = vi.fn<typeof fetch>();
+    const errors: Error[] = [];
+    const unsubscribe = createEventStreamClient({
+      url: 'https://attacker.example/events',
+      fetch: fetcher,
+    }).subscribe(
+      () => undefined,
+      (_state, error) => error && errors.push(error),
+    );
+    await vi.waitFor(() => expect(errors).toHaveLength(1));
+    expect(fetcher).not.toHaveBeenCalled();
+    unsubscribe();
+  });
+});

apps/web/src/events/event-stream-client.ts

@@ -0,0 +1,266 @@
+import type { EventEnvelope, EventKind } from '@multi-simadmin/contracts';
+
+export type EventStreamState = 'connecting' | 'open' | 'reconnecting' | 'resetting' | 'closed';
+export type EventStreamStateListener = (state: EventStreamState, error?: Error) => void;
+export type EventStreamListener = (event: EventEnvelope) => void;
+
+export interface SseRecord {
+  readonly id?: string;
+  readonly data: string;
+}
+
+export interface SseParser {
+  push(chunk: string): void;
+  finish(): void;
+}
+
+export interface EventStreamClient {
+  subscribe(onEvent: EventStreamListener, onState?: EventStreamStateListener): () => void;
+}
+
+export interface EventStreamClientOptions {
+  readonly url?: string;
+  readonly fetch?: typeof globalThis.fetch;
+  readonly initialRetryMs?: number;
+  readonly maxRetryMs?: number;
+  readonly sleep?: (milliseconds: number, signal: AbortSignal) => Promise<void>;
+  readonly onPositionReset?: () => void;
+}
+
+const KINDS: readonly EventKind[] = ['instance', 'job', 'item', 'attempt', 'audit'];
+const COMMON_KEYS = ['kind', 'id', 'occurredAt', 'requestId'] as const;
+const KIND_KEYS: Readonly<Record<EventKind, readonly string[]>> = {
+  instance: ['instanceId'],
+  job: ['jobId'],
+  item: ['jobId', 'itemId'],
+  attempt: ['jobId', 'attemptId'],
+  audit: ['auditEventId'],
+};
+const CONNECTION_ERROR = 'The event stream connection failed.';
+const INVALID_EVENT_ERROR = 'Invalid event envelope.';
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return value !== null && typeof value === 'object' && !Array.isArray(value);
+}
+
+function isNonEmptyString(value: unknown): value is string {
+  return typeof value === 'string' && value.length > 0;
+}
+
+function isIsoTimestamp(value: unknown): value is string {
+  if (!isNonEmptyString(value)) return false;
+  const match =
+    /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})(?:\.\d+)?(Z|[+-]\d{2}:\d{2})$/u.exec(value);
+  if (!match) return false;
+  const [, year, month, day, hour, minute, second] = match;
+  const parts = [year, month, day, hour, minute, second].map(Number);
+  if (parts.some((part) => !Number.isInteger(part))) return false;
+  const [y, m, d, h, min, s] = parts as [number, number, number, number, number, number];
+  if (m < 1 || m > 12 || d < 1 || h > 23 || min > 59 || s > 59) return false;
+  const daysInMonth = new Date(Date.UTC(y, m, 0)).getUTCDate();
+  if (d > daysInMonth) return false;
+  return Number.isFinite(Date.parse(value));
+}
+
+/** Validates the exact, frozen EventEnvelope union without retaining unknown fields. */
+export function parseEventEnvelope(value: unknown): EventEnvelope {
+  if (
+    !isRecord(value) ||
+    typeof value.kind !== 'string' ||
+    !KINDS.includes(value.kind as EventKind)
+  )
+    throw new Error(INVALID_EVENT_ERROR);
+
+  const kind = value.kind as EventKind;
+  const kindKeys = KIND_KEYS[kind];
+  if (kindKeys === undefined) throw new Error(INVALID_EVENT_ERROR);
+  const expected = [...COMMON_KEYS, ...kindKeys];
+  const actual = Object.keys(value);
+  if (actual.length !== expected.length || actual.some((key) => !expected.includes(key)))
+    throw new Error(INVALID_EVENT_ERROR);
+  if (
+    !isNonEmptyString(value.id) ||
+    !isIsoTimestamp(value.occurredAt) ||
+    !isNonEmptyString(value.requestId) ||
+    kindKeys.some((key) => !isNonEmptyString(value[key]))
+  )
+    throw new Error(INVALID_EVENT_ERROR);
+
+  return value as unknown as EventEnvelope;
+}
+
+/** Incremental SSE field parser implementing LF, CRLF, CR, comments, and multiline data. */
+export function createSseParser(onRecord: (record: SseRecord) => void): SseParser {
+  let buffer = '';
+  let data: string[] = [];
+  let id: string | undefined;
+
+  const dispatch = (): void => {
+    if (data.length > 0)
+      onRecord(id === undefined ? { data: data.join('\n') } : { id, data: data.join('\n') });
+    data = [];
+    id = undefined;
+  };
+  const line = (value: string): void => {
+    if (value === '') {
+      dispatch();
+      return;
+    }
+    if (value.startsWith(':')) return;
+    const colon = value.indexOf(':');
+    const field = colon < 0 ? value : value.slice(0, colon);
+    let fieldValue = colon < 0 ? '' : value.slice(colon + 1);
+    if (fieldValue.startsWith(' ')) fieldValue = fieldValue.slice(1);
+    if (field === 'data') data.push(fieldValue);
+    else if (field === 'id' && !fieldValue.includes('\0')) id = fieldValue;
+  };
+  const consume = (final: boolean): void => {
+    let start = 0;
+    for (let index = 0; index < buffer.length; index += 1) {
+      const character = buffer[index];
+      if (character !== '\r' && character !== '\n') continue;
+      if (character === '\r' && index + 1 === buffer.length && !final) break;
+      line(buffer.slice(start, index));
+      if (character === '\r' && buffer[index + 1] === '\n') index += 1;
+      start = index + 1;
+    }
+    buffer = buffer.slice(start);
+    if (final && buffer.length > 0) {
+      line(buffer);
+      buffer = '';
+    }
+  };
+  return {
+    push(chunk) {
+      buffer += chunk;
+      consume(false);
+    },
+    finish() {
+      consume(true);
+      dispatch();
+    },
+  };
+}
+
+function sameOriginUrl(input: string): string {
+  const base = globalThis.location?.href ?? 'http://localhost/';
+  const url = new URL(input, base);
+  const origin = new URL(base).origin;
+  if (url.origin !== origin || url.username !== '' || url.password !== '')
+    throw new Error('The event stream URL must be same-origin.');
+  return input.startsWith('/') ? `${url.pathname}${url.search}` : url.href;
+}
+
+function defaultSleep(milliseconds: number, signal: AbortSignal): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const timer = setTimeout(resolve, milliseconds);
+    signal.addEventListener(
+      'abort',
+      () => {
+        clearTimeout(timer);
+        reject(signal.reason);
+      },
+      { once: true },
+    );
+  });
+}
+
+function safeConnectionError(): Error {
+  return new Error(CONNECTION_ERROR);
+}
+
+export function createEventStreamClient(options: EventStreamClientOptions = {}): EventStreamClient {
+  const fetcher = options.fetch ?? globalThis.fetch;
+  const initialRetryMs = Math.max(1, options.initialRetryMs ?? 1_000);
+  const maxRetryMs = Math.max(initialRetryMs, options.maxRetryMs ?? 30_000);
+  const sleep = options.sleep ?? defaultSleep;
+
+  return {
+    subscribe(onEvent, onState = () => undefined) {
+      const controller = new AbortController();
+      let cursor: string | undefined;
+      let retryMs = initialRetryMs;
+
+      const run = async (): Promise<void> => {
+        let url: string;
+        try {
+          url = sameOriginUrl(options.url ?? '/api/v1/events');
+        } catch (error) {
+          onState('closed', error instanceof Error ? error : safeConnectionError());
+          return;
+        }
+
+        onState('connecting');
+        while (!controller.signal.aborted) {
+          try {
+            const headers: Record<string, string> = { Accept: 'text/event-stream' };
+            if (cursor !== undefined) headers['Last-Event-ID'] = cursor;
+            const response = await fetcher(url, {
+              credentials: 'same-origin',
+              headers,
+              signal: controller.signal,
+            });
+            if (response.status === 409 && cursor !== undefined) {
+              cursor = undefined;
+              options.onPositionReset?.();
+              onState(
+                'resetting',
+                new Error('The event stream position expired; refreshing current state.'),
+              );
+              continue;
+            }
+            if (!response.ok || response.body === null) throw safeConnectionError();
+            const contentType = response.headers.get('content-type')?.toLowerCase() ?? '';
+            if (!contentType.startsWith('text/event-stream')) throw safeConnectionError();
+
+            onState('open');
+            retryMs = initialRetryMs;
+            const decoder = new TextDecoder();
+            let recordFailure: Error | undefined;
+            const parser = createSseParser((record) => {
+              if (recordFailure !== undefined) return;
+              try {
+                const event = parseEventEnvelope(JSON.parse(record.data) as unknown);
+                onEvent(event);
+                if (record.id !== undefined) cursor = record.id;
+              } catch {
+                recordFailure = new Error(INVALID_EVENT_ERROR);
+              }
+            });
+            const reader = response.body.getReader();
+            try {
+              while (!controller.signal.aborted) {
+                const result = await reader.read();
+                if (result.done) break;
+                parser.push(decoder.decode(result.value, { stream: true }));
+                if (recordFailure !== undefined) throw recordFailure;
+              }
+              parser.push(decoder.decode());
+              parser.finish();
+              if (recordFailure !== undefined) throw recordFailure;
+            } finally {
+              if (controller.signal.aborted) await reader.cancel().catch(() => undefined);
+              reader.releaseLock();
+            }
+          } catch {
+            if (controller.signal.aborted) break;
+          }
+          if (controller.signal.aborted) break;
+          // Deliberately replace fetch/parser errors: response bodies and transport details may be sensitive.
+          onState('reconnecting', safeConnectionError());
+          const delay = retryMs;
+          retryMs = Math.min(maxRetryMs, retryMs * 2);
+          try {
+            await sleep(delay, controller.signal);
+          } catch {
+            break;
+          }
+        }
+        onState('closed');
+      };
+
+      void run();
+      return () => controller.abort();
+    },
+  };
+}

apps/web/src/events/use-control-plane-events.ts

@@ -0,0 +1,70 @@
+import { useEffect, useRef, useState } from 'react';
+import type { EventEnvelope } from '@multi-simadmin/contracts';
+
+import { createEventInvalidationController } from './event-invalidation-controller.js';
+import {
+  createEventStreamClient,
+  type EventStreamClient,
+  type EventStreamState,
+} from './event-stream-client.js';
+
+export interface EventRefreshState {
+  readonly fleet: number;
+  readonly jobs: number;
+  readonly audit: number;
+  readonly detail: number;
+  readonly stream: EventStreamState;
+  readonly positionReset: number;
+}
+
+export function useControlPlaneEvents(
+  activeInstanceId?: string,
+  client: EventStreamClient = createEventStreamClient(),
+): EventRefreshState {
+  const [state, setState] = useState<EventRefreshState>({
+    fleet: 0,
+    jobs: 0,
+    audit: 0,
+    detail: 0,
+    stream: 'connecting',
+    positionReset: 0,
+  });
+
+  const activeInstanceRef = useRef(activeInstanceId);
+  activeInstanceRef.current = activeInstanceId;
+
+  useEffect(() => {
+    const controller = createEventInvalidationController((batch) => {
+      setState((current) => ({
+        ...current,
+        fleet: current.fleet + (batch.fleet ? 1 : 0),
+        jobs: current.jobs + (batch.jobs ? 1 : 0),
+        audit: current.audit + (batch.audit ? 1 : 0),
+        detail: current.detail + (batch.instanceIds.size > 0 ? 1 : 0),
+      }));
+    });
+    controller.setActiveInstance(activeInstanceRef.current);
+    const unsubscribe = client.subscribe(
+      (event: EventEnvelope) => {
+        controller.setActiveInstance(activeInstanceRef.current);
+        controller.push(event);
+      },
+      (stream) =>
+        setState((current) => ({
+          ...current,
+          stream,
+          fleet: current.fleet + (stream === 'resetting' ? 1 : 0),
+          jobs: current.jobs + (stream === 'resetting' ? 1 : 0),
+          audit: current.audit + (stream === 'resetting' ? 1 : 0),
+          detail: current.detail + (stream === 'resetting' && activeInstanceRef.current ? 1 : 0),
+          positionReset: current.positionReset + (stream === 'resetting' ? 1 : 0),
+        })),
+    );
+    return () => {
+      unsubscribe();
+      controller.dispose();
+    };
+  }, [client]);
+
+  return state;
+}

apps/web/src/fleet/fleet-page.tsx

@@ -20,6 +20,7 @@ export interface FleetDataSource {
 export interface FleetPageProps {
   readonly dataSource?: FleetDataSource;
   readonly initialData?: FleetSnapshot;
+  readonly refreshSignal?: number;
 }
 
 const EMPTY_SNAPSHOT: FleetSnapshot = { instances: [], statuses: new Map() };
@@ -54,7 +55,7 @@ export function canonicalHttpOrigin(value: string): string | null {
   }
 }
 
-export function FleetPage({ dataSource, initialData }: FleetPageProps) {
+export function FleetPage({ dataSource, initialData, refreshSignal = 0 }: FleetPageProps) {
   const [snapshot, setSnapshot] = useState<FleetSnapshot | null>(initialData ?? null);
   const [error, setError] = useState<string | null>(null);
   const [attempt, setAttempt] = useState(0);
@@ -76,7 +77,7 @@ export function FleetPage({ dataSource, initialData }: FleetPageProps) {
   const selectAllRef = useRef<HTMLInputElement>(null);
 
   useEffect(() => {
-    if (initialData) {
+    if (initialData && refreshSignal === 0) {
       setSnapshot(initialData);
       setError(null);
       return;
@@ -100,7 +101,7 @@ export function FleetPage({ dataSource, initialData }: FleetPageProps) {
     return () => {
       active = false;
     };
-  }, [attempt, dataSource, initialData]);
+  }, [attempt, dataSource, initialData, refreshSignal]);
 
   const model = useMemo(
     () =>

apps/web/src/index.ts

@@ -34,4 +34,23 @@ export {
   type PasswordUpdate,
 } from './instances/instance-api-data-source.js';
 
+export {
+  createEventStreamClient,
+  createSseParser,
+  parseEventEnvelope,
+  type EventStreamClient,
+  type EventStreamClientOptions,
+  type EventStreamListener,
+  type EventStreamState,
+  type EventStreamStateListener,
+  type SseParser,
+  type SseRecord,
+} from './events/event-stream-client.js';
+export {
+  createEventInvalidationController,
+  type EventInvalidationController,
+  type EventInvalidationOptions,
+  type InvalidationBatch,
+} from './events/event-invalidation-controller.js';
+
 export const webWorkspaceReady = true;

pnpm-lock.yaml

@@ -61,6 +61,9 @@ importers:
 
   apps/web:
     dependencies:
+      '@multi-simadmin/contracts':
+        specifier: workspace:*
+        version: link:../../packages/contracts
       react:
         specifier: 19.2.4
         version: 19.2.4