0.4.0 — fix queue-add race + per-item remove button (#10, #11)

AGENTS.md

@@ -51,10 +51,10 @@ history/
 │   └── countries.geo.json  # 177 features, id=ISO_A3 (committed; Vite copies to dist/)
 ├── shared/                 # NO runtime deps — the single source of truth
 │   ├── types.ts            #   domain types (Nation, GameState, RoundItem, Preset, …)
-│   └── protocol.ts         #   LLM TurnResult schema + AddAction/AddDiplomacy/Jump request types + pure helpers
+│   └── protocol.ts         #   LLM TurnResult schema + AddAction/AddDiplomacy/RemoveQueueItem/Jump request types + pure helpers
 ├── server/
-│   ├── index.ts            # Express: /api/* (action|diplomacy|jump|advisor|games|presets), /sse/:id; reads PORT/LLM_*/DATA_DIR
-│   ├── engine.ts           # pure: buildPrompt / parse+validate / applyTurnResult / runTurn / queueRoundItem / advisor
+│   ├── index.ts            # Express: /api/* (action|diplomacy|queue/remove|jump|advisor|games|presets), /sse/:id; reads PORT/LLM_*/DATA_DIR
+│   ├── engine.ts           # pure: buildPrompt / parse+validate / applyTurnResult / runTurn / queueRoundItem / removeRoundItem / advisor
 │   ├── llm.ts              # LlmClient (injectable transport, retry+backoff, logging) + env config
 │   ├── stub.ts             # deterministic LLM transport (tests/e2e) + ADVISOR_MARKER
 │   ├── map.ts              # GameState → RegionMap (ISO_A3 → owner + stable color)
@@ -74,7 +74,7 @@ history/
         ├── PresetPicker.tsx / NationSelect.tsx   # home + nation pick screens
         ├── WorldMap.tsx     # MapLibre basemap + choropleth + click popup + player highlight
         ├── NationPanel.tsx  # a nation's stats/territory/diplomacy dossier
-        ├── ActionPanel.tsx  # tabs: Action / Diplomacy / Advisor + pending-queue list + "Jump forward"
+        ├── ActionPanel.tsx  # tabs: Action / Diplomacy / Advisor + pending-queue list (per-item trash button + confirm dialog) + "Jump forward"
         ├── EventFeed.tsx    # scrolling event log (newest first)
         ├── StatBar.tsx
         └── ui/              # 14 shadcn/ui primitives
@@ -87,7 +87,7 @@ history/
 | `npm run dev` | Express on :4321 (tsx watch) + Vite on :5173 (proxies `/api`,`/sse`) concurrently |
 | `npm run build` | `vite build` (client → `dist/`) then `tsup server/index.ts` → `server/dist/index.js` |
 | `npm start` | run the compiled server (`node server/dist/index.js`) on :4321 |
-| `npm test` | vitest unit tests in `server/` (19 tests) |
+| `npm test` | vitest unit tests in `server/` (39 tests) |
 | `npm run typecheck` | `tsc --noEmit` (strict) across src/server/shared/e2e/configs |
 | `npm run lint` | ESLint flat config |
 | `npm run e2e` | Playwright, fully deterministic (`LLM_STUB=1`); **runs in CI on every PR** (see below) |
@@ -117,6 +117,17 @@ history/
   sends the entire `pending` array to the model, applies the `TurnResult`, clears `pending`, and
   advances the turn. An empty round (no items queued) is allowed and lets the world advance on its
   own. This design reduces LLM call frequency and makes each call a coherent batch of work.
+  Queued items can be removed again via `POST /queue/remove` (by index — the client offers a
+  trash button per row with a confirm dialog); like the adds it never advances the turn.
+- **Monotonic `GameState.version` — clients "never go backwards".** Every mutation (queue
+  add/remove, turn commit) bumps `state.version` in the engine (`queueRoundItem` /
+  `removeRoundItem` / `applyTurnResult`); it starts at 1 on game creation, is persisted in SQLite,
+  and legacy games without the field are treated as version 0. ALL state ingestion on the client —
+  SSE `state`/`turn` events, REST responses (add/remove/jump), and game loads — flows through the
+  single `applyState` in `App.tsx`: a *different* game id is always adopted, the *same* game only
+  when the incoming version is not older than the current one (compared inside the functional
+  `setGame` updater, so it can't act on a stale closure). This is what stops a late-arriving stale
+  SSE snapshot from clobbering the UI (see Gotchas, #10).
 - **Defensive turn handling, never crash.** `engine.runTurn` strips fences, extracts the first
   balanced `{...}`, `JSON.parse`s, validates (ignores invalid ops, clamps stats to 0–100), retries
   once with a nudge if the result is empty/invalid, and if it's still unusable emits a generic
@@ -170,6 +181,16 @@ history/
 
 ## Gotchas
 
+- **Stale SSE snapshots can arrive *after* a fresher REST response — the version guard is what
+  keeps the UI honest (#10).** The SSE `state` event sent on connect/resync is a snapshot taken at
+  the moment the request is handled, and the SSE stream and the REST responses ride different
+  connections (Vite proxy in dev, Traefik in prod) with no delivery-order guarantee. A snapshot
+  taken just before a mutation is saved (e.g. the on-connect resync racing a quick "Add action")
+  can reach the browser *after* that mutation's REST response. Pre-v0.4.0 the client applied any
+  incoming state unconditionally, so a just-queued item could vanish ("add one: nothing happened,
+  add another: both appears" — issue #10). Now every state carries a monotonic `version` and
+  `App.tsx`'s `applyState` drops same-game states whose version is older than the current one.
+  Don't add unguarded `setGame` calls or remove the version comparison.
 - **502s were the reasoning model exhausting its output budget.** The original client sent only
   `max_tokens: 4000`; `qwen3.8-27b`'s chain-of-thought alone often exceeded 4000 tokens, so
   `content` came back `null`, which the client treated as fatal → HTTP 502 (~half of turns),

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 All notable changes to **History** are listed here, newest first.
 
+## v0.4.0 — 2026-10-11 16:02
+
+- **Fix: queued items disappearing from the pending list (#10).** Root cause: SSE `state` events carried no freshness information, and the client's `onState`/`onTurn` handlers applied any incoming snapshot unconditionally. A stale snapshot — e.g. the SSE on-connect resync taken just before an add was saved, or an EventSource auto-reconnect — could arrive *after* the add's REST response and clobber it, so "add one: nothing happens, add another: both appear". Fix: every mutation now bumps a monotonic `GameState.version` (persisted in SQLite, started at 1 on create, bumped by `queueRoundItem`, the new `removeRoundItem`, and `applyTurnResult`; legacy games without the field are treated as version 0), and the client routes *every* state ingestion (SSE events, add/remove/jump responses, game loads) through a single "never go backwards" rule: a different game id is always adopted, the same game only when the incoming version is not older than the current one (compared inside the functional `setGame` updater, so it is stale-closure-proof).
+- **New: remove button for queued items (#11).** Each pending-queue row in "Your move" has a small trash-icon button that opens a shadcn `Dialog` confirmation (item quoted, Cancel / destructive Remove, dark command-center styling). Confirming calls the new `POST /api/games/:id/queue/remove` (body `{ index }`) — same fast save → broadcast → respond order as the add routes, no LLM, no turn advance; invalid indices get a 400. The client `api.removeQueueItem(id, index)` is version-gated like every other state update, so the list can never regress after a removal.
+- **Unit tests** — new `removeRoundItem` tests (valid removal + version bump, out-of-bounds/non-integer → `null`), version-bump assertions for `queueRoundItem`/`applyTurnResult`/stub turn, a legacy-no-version case, and version round-trip in `db.test.ts` (39 tests, up from 35).
+- **E2E** — new "queue add is never clobbered by a stale SSE snapshot" test (one add appears immediately, still there after a 1s grace period for late SSE events, version strictly increases across adds, queue survives a full page reload) and a "remove with confirmation" test (cancel keeps the item, confirm removes it, no turn advance, version persisted) — all deterministic under `LLM_STUB=1`.
+
 ## v0.3.0 — 2026-10-11 15:29
 
 - **Deep-linking** — the active game's id now lives in the URL (`#/game/<id>`), so a link opens that exact game and two tabs can run two different games; a bad or missing id falls back to the home screen. Fixes #3.

e2e/sim.spec.ts

@@ -181,6 +181,142 @@ test.describe('History — save / resume across a page refresh', () => {
   });
 });
 
+/**
+ * Queue reliability — issue #10. A queued item must appear in the pending list
+ * right after its REST response AND stay there: before the fix, a stale SSE
+ * `state` snapshot (the on-connect resync taken just before the add was saved,
+ * carrying no freshness marker) could arrive after the REST response and
+ * clobber it — "add one: nothing happens, add another: both appear". The fix
+ * gives every mutation a monotonic `GameState.version` and the client applies
+ * an incoming state only when it is not older than the current one.
+ */
+test.describe('History — queue add is never clobbered by a stale SSE snapshot (#10)', () => {
+  test('one added action appears immediately and survives late SSE snapshots', async ({
+    page,
+  }) => {
+    test.setTimeout(90000);
+    const id = await createUkGame(page);
+    const origin = await page.evaluate(() => location.origin);
+
+    // Game screen at turn 1, nothing queued yet.
+    await expect(page.getByTestId('world-map')).toBeVisible();
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+    await expect(page.getByTestId('game-date')).toHaveText('1939-09-01');
+    await expect(page.getByTestId('pending-empty')).toBeVisible();
+
+    // Queue exactly ONE action and assert it appears immediately (turn/date
+    // unchanged, no events yet).
+    await page.getByTestId('action-textarea').fill('Hold the line at the channel');
+    const [addResp] = await Promise.all([
+      page.waitForResponse(
+        (r) => r.request().method() === 'POST' && new URL(r.url()).pathname === `/api/games/${id}/action`,
+      ),
+      page.getByTestId('add-action').click(),
+    ]);
+    const addBody = (await addResp.json()) as { game: { version: number; pending: unknown[] } };
+    expect(addBody.game.pending).toHaveLength(1);
+
+    await expect(page.getByTestId('pending-item')).toHaveCount(1);
+    await expect(page.getByTestId('pending-item').first()).toHaveAttribute('data-kind', 'action');
+    await expect(page.getByTestId('pending-item').first()).toContainText('Hold the line at the channel');
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+    await expect(page.getByTestId('game-date')).toHaveText('1939-09-01');
+    await expect(page.getByTestId('event-item')).toHaveCount(0);
+    await expect(page.getByTestId('title-queued')).toHaveText('1 queued');
+
+    // Let any in-flight / late SSE snapshot (on-connect resync, auto-reconnect)
+    // have its chance to arrive. Under the stub these settle in milliseconds;
+    // a second is generous. Before the version fix, a stale one could clobber
+    // the just-added item here.
+    await page.waitForTimeout(1000);
+
+    // The item is still there — the stale snapshot was dropped, not applied.
+    await expect(page.getByTestId('pending-item')).toHaveCount(1);
+    await expect(page.getByTestId('pending-item').first()).toContainText('Hold the line at the channel');
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+
+    // Protocol-level check: a later mutation (a second queued item) must carry
+    // a strictly higher version than the one we just saw.
+    await page.getByTestId('action-textarea').fill('Scramble the night fighters');
+    const [add2Resp] = await Promise.all([
+      page.waitForResponse(
+        (r) => r.request().method() === 'POST' && new URL(r.url()).pathname === `/api/games/${id}/action`,
+      ),
+      page.getByTestId('add-action').click(),
+    ]);
+    const add2Body = (await add2Resp.json()) as { game: { version: number } };
+    expect(add2Body.game.version).toBeGreaterThan(addBody.game.version);
+    await expect(page.getByTestId('pending-item')).toHaveCount(2);
+
+    // The game persisted with a version survives a full page reload.
+    await page.goto(`${origin}/#/game/${id}`);
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+    await expect(page.getByTestId('pending-item')).toHaveCount(2, { timeout: 15000 });
+  });
+});
+
+/**
+ * Per-item removal — issue #11. Each queued row has a small trash button that
+ * opens a confirmation dialog; confirming removes the item server-side
+ * (POST /api/games/:id/queue/remove, no turn advance) and cancelling keeps it.
+ */
+test.describe('History — remove a queued item with confirmation (#11)', () => {
+  test('cancel keeps the item; confirm removes it', async ({ page }) => {
+    test.setTimeout(90000);
+    const id = await createUkGame(page);
+
+    await expect(page.getByTestId('world-map')).toBeVisible();
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+
+    // Queue one action.
+    await page.getByTestId('action-textarea').fill('Open the back channel with Vichy');
+    await page.getByTestId('add-action').click();
+    await expect(page.getByTestId('pending-item')).toHaveCount(1);
+
+    // Trash icon → confirmation dialog.
+    await page.getByTestId('remove-queue-item').click();
+    const dialog = page.getByTestId('remove-confirm-dialog');
+    await expect(dialog).toBeVisible();
+    await expect(dialog).toContainText('Open the back channel with Vichy');
+
+    // Cancel: the item stays queued.
+    await page.getByTestId('remove-cancel').click();
+    await expect(dialog).not.toBeVisible();
+    await expect(page.getByTestId('pending-item')).toHaveCount(1);
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+
+    // Open again and confirm: the item is removed server-side.
+    await page.getByTestId('remove-queue-item').click();
+    await expect(dialog).toBeVisible();
+    const [removeResp] = await Promise.all([
+      page.waitForResponse(
+        (r) =>
+          r.request().method() === 'POST' &&
+          new URL(r.url()).pathname === `/api/games/${id}/queue/remove`,
+      ),
+      page.getByTestId('remove-confirm').click(),
+    ]);
+    const removeBody = (await removeResp.json()) as { game: { version: number; pending: unknown[] } };
+    expect(removeBody.game.pending).toHaveLength(0);
+
+    await expect(dialog).not.toBeVisible();
+    await expect(page.getByTestId('pending-empty')).toBeVisible();
+    await expect(page.getByTestId('title-queued')).not.toBeVisible();
+    // Still turn 1, no events — removing never advances the round.
+    await expect(page.getByTestId('turn-count')).toHaveText('1');
+    await expect(page.getByTestId('game-date')).toHaveText('1939-09-01');
+    await expect(page.getByTestId('event-item')).toHaveCount(0);
+
+    // The bumped version is persisted with the game (it survives a reload).
+    const after = await page.evaluate(
+      async (gameId) =>
+        ((await fetch(`/api/games/${gameId}`)).json()) as Promise<{ game: { version: number } }>,
+      id,
+    );
+    expect(after.game.version).toBe(removeBody.game.version);
+  });
+});
+
 /**
  * URL deep-linking (issue #3). The active game's id lives in the URL fragment:
  * home is `#/` and an active game is `#/game/<id>`. A fresh page navigated to

package.json

@@ -1,6 +1,6 @@
 {
   "name": "history",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "private": true,
   "type": "module",
   "description": "AI-driven alternate-history simulator — the LLM is the world engine (Pax Historia style).",

server/db.test.ts

@@ -22,6 +22,7 @@ function makeState(id: string): GameState {
     },
     events: [],
     pending: [],
+    version: 1,
   };
 }
 
@@ -54,6 +55,11 @@ describe('openDb', () => {
     expect(db.load('a')?.events).toHaveLength(1);
     expect([...db.listIds()].sort()).toEqual(['a', 'b']); // still two rows
 
+    // the monotonic version is persisted with the state and round-trips
+    s.version = 3;
+    db.save(s);
+    expect(db.load('a')?.version).toBe(3);
+
     db.close();
   });
 

server/engine.test.ts

@@ -9,6 +9,7 @@ import {
   isMeaningful,
   parseTurnResult,
   queueRoundItem,
+  removeRoundItem,
   runTurn,
   validateTurnResult,
 } from './engine';
@@ -72,6 +73,7 @@ function baseState(): GameState {
     },
     events: [],
     pending: [],
+    version: 1,
   };
 }
 
@@ -206,8 +208,11 @@ describe('runTurn (batched round, deterministic stub)', () => {
     expect(state.events[0].nation).toBe('uk');
     expect(state.events[0].outcome).toBe('success');
     expect(result.stateChanges).toEqual([{ nation: 'uk', stat: 'military', op: 'set', value: 85 }]);
+    // committing a turn is a new revision too
+    expect(state.version).toBe(2);
     // the original object is not mutated (a fresh queue was consumed)
     expect(original.pending).toHaveLength(1);
+    expect(original.version).toBe(1);
   });
 
   it('an empty round: turn advances, one political "world moves on" event, pending stays empty', async () => {
@@ -286,6 +291,61 @@ describe('queueRoundItem', () => {
     expect(after.pending[0]).toEqual({ kind: 'diplomacy', to: 'us', text: 'hello' });
     // the original state is not mutated
     expect(before.pending).toHaveLength(0);
+    expect(before.version).toBe(1);
+  });
+
+  it('bumps the monotonic version on each queue mutation', () => {
+    const a = queueRoundItem(baseState(), { kind: 'action', text: 'one' });
+    expect(a.version).toBe(2);
+    const b = queueRoundItem(a, { kind: 'action', text: 'two' });
+    expect(b.version).toBe(3);
+    // and never backwards: two consecutive adds from the same base both
+    // advance past it, so a late snapshot of the older state is always older.
+    const b2 = queueRoundItem(baseState(), { kind: 'action', text: 'two' });
+    expect(b2.version).toBe(2);
+    expect(b.version).toBeGreaterThan(b2.version);
+  });
+
+  it('treats a legacy state without a version field as version 0', () => {
+    const legacy = { ...baseState() } as Omit<GameState, 'version'> & { version?: number };
+    delete legacy.version; // a row saved before the version field existed
+    // simulate a legacy row coming back from SQLite: the JSON has no field.
+    const after = queueRoundItem(legacy as unknown as GameState, {
+      kind: 'action',
+      text: 'first after upgrade',
+    });
+    expect(after.version).toBe(1);
+  });
+});
+
+describe('removeRoundItem', () => {
+  it('removes the item at the index, bumps the version, and leaves the input untouched', () => {
+    const state = baseState();
+    state.pending = [
+      { kind: 'action', text: 'one' },
+      { kind: 'diplomacy', to: 'us', text: 'two' },
+      { kind: 'action', text: 'three' },
+    ];
+    const next = removeRoundItem(state, 1);
+    expect(next).not.toBeNull();
+    expect(next!.version).toBe(2);
+    expect(next!.pending).toEqual([
+      { kind: 'action', text: 'one' },
+      { kind: 'action', text: 'three' },
+    ]);
+    expect(state.pending).toHaveLength(3); // original untouched
+    expect(state.version).toBe(1);
+  });
+
+  it('returns null for out-of-bounds or non-integer indices (route answers 400, nothing mutates)', () => {
+    const state = baseState();
+    state.pending = [{ kind: 'action', text: 'one' }];
+    expect(removeRoundItem(state, -1)).toBeNull();
+    expect(removeRoundItem(state, 1)).toBeNull(); // == length
+    expect(removeRoundItem(state, 5)).toBeNull();
+    expect(removeRoundItem(state, 0.5)).toBeNull();
+    expect(removeRoundItem(state, Number.NaN)).toBeNull();
+    expect(state.pending).toHaveLength(1); // still untouched
   });
 });
 
@@ -346,7 +406,7 @@ describe('applyTurnResult', () => {
     expect(JSON.stringify(state)).toBe(snapshot);
   });
 
-  it('clears the pending round on commit', () => {
+  it('clears the pending round on commit and bumps the version', () => {
     const state = baseState();
     state.pending = [{ kind: 'action', text: 'x' }];
     const result: TurnResult = {
@@ -358,7 +418,9 @@ describe('applyTurnResult', () => {
     };
     const next = applyTurnResult(state, result);
     expect(next.pending).toEqual([]);
+    expect(next.version).toBe(2);
     expect(state.pending).toHaveLength(1); // original untouched
+    expect(state.version).toBe(1);
   });
 });
 

server/engine.ts

@@ -284,6 +284,7 @@ function genericUnclearEvent(state: GameState): TurnEventSpec {
  */
 export function applyTurnResult(state: GameState, result: TurnResult): GameState {
   const next: GameState = JSON.parse(JSON.stringify(state));
+  next.version = (state.version ?? 0) + 1; // every mutation is a new revision
   const actingTurn = state.turn; // this action resolves the current turn
   next.turn = state.turn + 1; // then we advance to the next turn to play
   next.date = isDateLike(result.date) ? result.date : addDays(state.date, 2);
@@ -325,15 +326,34 @@ export function applyTurnResult(state: GameState, result: TurnResult): GameState
 /**
  * Immutably queue one item onto a round: append it to `pending` and return a new
  * state. This never advances the turn or the date — that only happens when a
- * round is committed via runTurn. Exported so the append-without-advance behavior
- * is unit-testable, and reused by the server's /action and /diplomacy routes.
+ * round is committed via runTurn. Bumps `version` (a new revision, so stale SSE
+ * snapshots can never clobber it client-side). Exported so the append-without-
+ * advance behavior is unit-testable, and reused by the /action and /diplomacy
+ * routes.
  */
 export function queueRoundItem(state: GameState, item: RoundItem): GameState {
   const next: GameState = JSON.parse(JSON.stringify(state));
+  next.version = (state.version ?? 0) + 1;
   next.pending.push(item);
   return next;
 }
 
+/**
+ * Immutably remove one item from the pending round by index and return a new
+ * state (bumping `version`). Returns `null` when the index is missing or not a
+ * valid, in-bounds integer position, so the route can answer 400 without
+ * mutating anything. Reused by the server's /queue/remove route.
+ */
+export function removeRoundItem(state: GameState, index: number | undefined): GameState | null {
+  if (index === undefined || !Number.isInteger(index) || index < 0 || index >= state.pending.length) {
+    return null;
+  }
+  const next: GameState = JSON.parse(JSON.stringify(state));
+  next.version = (state.version ?? 0) + 1;
+  next.pending.splice(index, 1);
+  return next;
+}
+
 /**
  * Run one turn end-to-end against the (injectable) LLM: build prompts, call the
  * model ONCE over the whole pending batch, parse/validate, retry once with a

server/index.ts

@@ -9,11 +9,16 @@ import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 
 import { deepClone } from '../shared/protocol';
-import type { AddActionRequest, AddDiplomacyRequest, CreateGameRequest } from '../shared/protocol';
+import type {
+  AddActionRequest,
+  AddDiplomacyRequest,
+  CreateGameRequest,
+  RemoveQueueItemRequest,
+} from '../shared/protocol';
 import type { GameState } from '../shared/types';
 import { createLlmClient } from './llm';
 import { makeStubLlmClient } from './stub';
-import { askAdvisor, queueRoundItem, runTurn } from './engine';
+import { askAdvisor, queueRoundItem, removeRoundItem, runTurn } from './engine';
 import { buildRegionMap } from './map';
 import { createPresetStore } from './presets';
 import { openDb, type Db } from './db';
@@ -114,6 +119,7 @@ app.post('/api/games', (req: Request, res) => {
     nations: Object.fromEntries(preset.nations.map((n) => [n.id, deepClone(n)])),
     events: [],
     pending: [],
+    version: 1, // the first saved revision; every later mutation bumps it
   };
   db.save(state);
   res.json({ game: state });
@@ -179,6 +185,22 @@ app.post('/api/games/:id/diplomacy', (req, res) => {
   res.json({ game: next });
 });
 
+// Remove one item from the pending round, by its index in `game.pending`. No
+// LLM call, no turn advance — same fast save → broadcast → respond order as the
+// add routes above. The mutated state bumps `version`, so clients (which apply
+// states "never go backwards") always reconcile to it.
+app.post('/api/games/:id/queue/remove', (req, res) => {
+  const id = req.params.id;
+  const game = db.load(id);
+  if (!game) return res.status(404).json({ error: 'game not found' });
+  const index = (req.body as RemoveQueueItemRequest | undefined)?.index;
+  const next = removeRoundItem(game, index);
+  if (!next) return res.status(400).json({ error: 'invalid queue index' });
+  db.save(next);
+  broadcast(id, 'state', { state: next });
+  res.json({ game: next });
+});
+
 // Jump forward: commit the whole pending round (or an empty one) to the model
 // in a single turn. applyTurnResult clears the pending queue on the returned
 // state. 404 for not-found/preset-missing; 502 for LLM/model (transport) errors.

server/map.test.ts

@@ -30,6 +30,7 @@ const state: GameState = {
   },
   events: [],
   pending: [],
+  version: 1,
 };
 
 describe('buildRegionMap', () => {

shared/protocol.ts

@@ -99,6 +99,14 @@ export interface TurnResponse {
   result: TurnResult;
 }
 
+/** Remove one queued item from the pending round, by its index in `game.pending`. */
+export interface RemoveQueueItemRequest {
+  index: number;
+}
+export interface RemoveQueueItemResponse {
+  game: GameState;
+}
+
 export interface AdvisorRequest {
   /** Optional prompt to steer the brainstorm. */
   prompt?: string;

shared/types.ts

@@ -85,6 +85,17 @@ export type RoundItem = {
   to?: string;
 };
 
+/**
+ * Monotonic revision counter for a game, bumped by the server on every
+ * mutation (queue add/remove, turn commit) and persisted with the state.
+ * Clients use it to tell a fresh state from a stale one: an SSE `state`/`turn`
+ * snapshot (e.g. the on-connect resync) that arrives *after* a fresher REST
+ * response carries a lower version and must be ignored, never applied
+ * (see the client's "never go backwards" rule in src/App.tsx). Legacy games
+ * saved before this field existed are treated as version 0 by consumers.
+ */
+export type GameVersion = number;
+
 /** The full, persisted state of one game. Saved to SQLite by id. */
 export interface GameState {
   id: string;
@@ -101,6 +112,12 @@ export interface GameState {
    * batch in a single turn and clears this back to `[]`.
    */
   pending: RoundItem[];
+  /**
+   * Monotonic revision counter (see GameVersion). Bumped on every mutation so
+   * clients can reject stale SSE snapshots; see the "never go backwards" rule
+   * in src/App.tsx. Starts at 1 on game creation.
+   */
+  version: GameVersion;
 }
 
 /**

src/App.tsx

@@ -153,6 +153,26 @@ export default function App() {
   // never acts on a stale closure. Written each render (same pattern as sse.ts).
   const latestRef = useRef<{ game: GameState | null; goHome: () => void; loadGame: (id: string) => void } | null>(null);
 
+  // The single entry point for adopting a full game state — SSE `state`/`turn`
+  // events AND the REST responses (add/remove/jump) AND game loads all flow
+  // through here. Two rules:
+  //   • a *different* game id (new game, deep link, resume) is always adopted;
+  //   • the *same* game is adopted only when its `version` is not older than
+  //     the current state's ("never go backwards").
+  // The comparison happens inside the functional updater, so it always reads
+  // the latest committed state — never a stale closure. This is what makes a
+  // late-arriving stale SSE snapshot (e.g. the on-connect resync taken just
+  // before an add was saved, or an EventSource auto-reconnect) harmless: it
+  // carries a lower version than the fresher state the REST response already
+  // applied, so it is dropped instead of clobbering the queued item (#10).
+  // Legacy games saved before `version` existed are treated as version 0.
+  const applyState = useCallback((s: GameState) => {
+    setGame((cur) => {
+      if (!cur || cur.id !== s.id) return s;
+      return (s.version ?? 0) >= (cur.version ?? 0) ? s : cur;
+    });
+  }, []);
+
   // On the home screen: load the scenario manifest and the list of saved games
   // (newest-updated first) so the user can resume a prior game.
   useEffect(() => {
@@ -192,7 +212,7 @@ export default function App() {
         if (!alive) return;
         persistActiveGameId(id); // remember it so a future bare `/` load resumes it
         setActiveGameId(id);
-        setGame(game);
+        applyState(game);
         setScreen({ name: 'game' });
       } catch {
         if (!alive) return;
@@ -250,10 +270,9 @@ export default function App() {
   }, [game]);
 
   // Resync from the persisted server state on connect and after every turn.
-  // Handlers only call the stable setGame, so no stale-closure concerns.
   useSse(game?.id ?? null, {
-    onState: (s) => setGame(s),
-    onTurn: (s) => setGame(s),
+    onState: applyState,
+    onTurn: applyState,
   });
 
   const play = useCallback(async (presetId: string) => {
@@ -282,7 +301,7 @@ export default function App() {
         // Remember this as the active game so a refresh resumes it.
         persistActiveGameId(game.id);
         setActiveGameId(game.id);
-        setGame(game);
+        applyState(game);
         setAdvisors([]);
         setScreen({ name: 'game' });
       } catch (e) {
@@ -295,18 +314,20 @@ export default function App() {
   );
 
   // Add an action to the pending round. Fast, non-LLM — no `busy`; the pending
-  // list updates from the response and the SSE `state` event.
+  // list updates from the response and the SSE `state` event. Both are
+  // version-gated via applyState, so the item can never be clobbered by a
+  // stale snapshot (#10).
   const runAddAction = useCallback(
     async (text: string) => {
       if (!game) return;
       try {
         const { game: g } = await api.addAction(game.id, text);
-        setGame(g);
+        applyState(g);
       } catch (e) {
         toastError(e);
       }
     },
-    [game],
+    [game, applyState],
   );
 
   // Add a diplomatic message to the pending round. Fast, non-LLM — no `busy`.
@@ -315,12 +336,27 @@ export default function App() {
       if (!game) return;
       try {
         const { game: g } = await api.addDiplomacy(game.id, to, message);
-        setGame(g);
+        applyState(g);
       } catch (e) {
         toastError(e);
       }
     },
-    [game],
+    [game, applyState],
+  );
+
+  // Remove a queued item by index. Fast, non-LLM — no `busy`; the pending list
+  // updates from the response and the SSE `state` event (version-gated).
+  const runRemoveQueueItem = useCallback(
+    async (index: number) => {
+      if (!game) return;
+      try {
+        const { game: g } = await api.removeQueueItem(game.id, index);
+        applyState(g);
+      } catch (e) {
+        toastError(e);
+      }
+    },
+    [game, applyState],
   );
 
   // Jump forward: the single LLM call that commits the pending round. Only this
@@ -330,13 +366,13 @@ export default function App() {
     setBusy(true);
     try {
       const { state } = await api.jump(game.id);
-      setGame(state);
+      applyState(state);
     } catch (e) {
       toastError(e);
     } finally {
       setBusy(false);
     }
-  }, [game]);
+  }, [game, applyState]);
 
   const askAdvisor = useCallback(
     async (prompt?: string) => {
@@ -362,7 +398,7 @@ export default function App() {
       // Make this the active game so a bare `/` reload keeps resuming it.
       persistActiveGameId(id);
       setActiveGameId(id);
-      setGame(game);
+      applyState(game);
       setAdvisors([]);
       setScreen({ name: 'game' });
     } catch (e) {
@@ -401,6 +437,7 @@ export default function App() {
           advisors={advisors}
           onAddAction={runAddAction}
           onAddDiplomacy={runAddDiplomacy}
+          onRemoveQueueItem={runRemoveQueueItem}
           onAdvisor={askAdvisor}
           onJump={runJump}
           onHome={goHome}
@@ -440,6 +477,7 @@ interface GameScreenProps {
   advisors: string[];
   onAddAction: (a: string) => void;
   onAddDiplomacy: (to: string, m: string) => void;
+  onRemoveQueueItem: (index: number) => void;
   onAdvisor: (p?: string) => void;
   onJump: () => void;
   onHome: () => void;
@@ -463,6 +501,7 @@ function GameScreen({
   advisors,
   onAddAction,
   onAddDiplomacy,
+  onRemoveQueueItem,
   onAdvisor,
   onJump,
   onHome,
@@ -663,6 +702,7 @@ function GameScreen({
           advisors={advisors}
           onAddAction={onAddAction}
           onAddDiplomacy={onAddDiplomacy}
+          onRemoveQueueItem={onRemoveQueueItem}
           onAdvisor={onAdvisor}
           onJump={onJump}
           inWindow

src/components/ActionPanel.tsx

@@ -1,13 +1,21 @@
 import { useState } from 'react';
-import { Loader2, MessageSquare, Radar, Zap } from 'lucide-react';
+import { Loader2, MessageSquare, Radar, Trash2, Zap } from 'lucide-react';
 import { Badge } from './ui/badge';
 import { Button } from './ui/button';
 import { Card, CardContent, CardHeader, CardTitle } from './ui/card';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from './ui/dialog';
 import { Input } from './ui/input';
 import { Textarea } from './ui/textarea';
 import { Tabs, TabsContent, TabsList, TabsTrigger } from './ui/tabs';
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from './ui/select';
-import type { GameState } from '@shared/types';
+import type { GameState, RoundItem } from '@shared/types';
 
 interface Props {
   game: GameState;
@@ -19,6 +27,8 @@ interface Props {
   onAddAction: (text: string) => void;
   /** Queue a diplomatic message onto the pending round (no turn advance). */
   onAddDiplomacy: (to: string, message: string) => void;
+  /** Remove one queued item by its index in `game.pending` (no turn advance). */
+  onRemoveQueueItem: (index: number) => void;
   onAdvisor: (prompt?: string) => void;
   /** Commit the whole pending round in a single LLM turn. */
   onJump: () => void;
@@ -29,13 +39,22 @@ interface Props {
   inWindow?: boolean;
 }
 
+/** One-line, display-safe rendering of a queued item (text truncated). */
+function describeItem(item: RoundItem, nationName: (id?: string) => string): string {
+  const who = item.kind === 'diplomacy' ? ` to ${nationName(item.to)}` : '';
+  const text = item.text.length > 72 ? `${item.text.slice(0, 71)}…` : item.text;
+  return `${who ? `${who}:` : 'Action:'} “${text}”`;
+}
+
 /**
  * The player's command deck ("Your move"). Three tabs — Action, Diplomacy,
  * Advisor — each with a small "Add" button that queues an item onto the pending
  * round (these never advance the turn). Below the tabs a visible pending-queue
- * list and one prominent "Jump forward" button commit the whole round in a
- * single LLM turn. While a jump is in flight the commit is disabled and a hint
- * is shown; an empty jump (nothing queued) is allowed and advances time.
+ * list — each row has a small trash button that removes that item (with a
+ * confirmation dialog) — and one prominent "Jump forward" button that commits
+ * the whole round in a single LLM turn. While a jump is in flight the commit
+ * is disabled (as is queue editing) and a hint is shown; an empty jump
+ * (nothing queued) is allowed and advances time.
  */
 export default function ActionPanel({
   game,
@@ -43,6 +62,7 @@ export default function ActionPanel({
   advisors,
   onAddAction,
   onAddDiplomacy,
+  onRemoveQueueItem,
   onAdvisor,
   onJump,
   inWindow = false,
@@ -52,6 +72,8 @@ export default function ActionPanel({
   const [target, setTarget] = useState('');
   const [message, setMessage] = useState('');
   const [prompt, setPrompt] = useState('');
+  // Index of the queued item the user is about to remove, or null (dialog closed).
+  const [confirmRemoveIndex, setConfirmRemoveIndex] = useState<number | null>(null);
 
   const others = Object.entries(game.nations)
     .filter(([id]) => id !== game.playerNationId)
@@ -79,6 +101,10 @@ export default function ActionPanel({
   };
 
   const pending = game.pending;
+  // The item the confirmation dialog is about (re-derived from the live list,
+  // so if the queue changes while the dialog is open it tracks the current
+  // item at that index — or the dialog closes if the index went out of range).
+  const removeTarget = confirmRemoveIndex !== null ? pending[confirmRemoveIndex] : undefined;
   const queuedLabel = busy
     ? 'Simulating…'
     : `Jump forward${pending.length > 0 ? ` · ${pending.length} queued` : ''}`;
@@ -227,6 +253,18 @@ export default function ActionPanel({
                       </span>
                     )}
                     <span className="min-w-0 flex-1 truncate text-foreground/85">{item.text}</span>
+                    <Button
+                      variant="ghost"
+                      size="icon-sm"
+                      className="shrink-0 text-muted-foreground hover:text-destructive"
+                      onClick={() => setConfirmRemoveIndex(i)}
+                      disabled={busy}
+                      title="Remove from this round"
+                      aria-label="Remove this queued item"
+                      data-testid="remove-queue-item"
+                    >
+                      <Trash2 className="size-3.5" />
+                    </Button>
                   </li>
                 ))}
               </ul>
@@ -234,6 +272,39 @@ export default function ActionPanel({
           )}
         </div>
 
+        {/* Confirmation for removing a queued item (never removes without asking). */}
+        <Dialog open={removeTarget !== undefined} onOpenChange={(open) => !open && setConfirmRemoveIndex(null)}>
+          <DialogContent className="max-w-sm" data-testid="remove-confirm-dialog">
+            <DialogHeader>
+              <DialogTitle>Remove queued item?</DialogTitle>
+              <DialogDescription>
+                {removeTarget ? (
+                  <>
+                    {describeItem(removeTarget, nationName)} will be removed from this round and
+                    won’t be simulated on the next jump.
+                  </>
+                ) : null}
+              </DialogDescription>
+            </DialogHeader>
+            <DialogFooter>
+              <Button variant="outline" onClick={() => setConfirmRemoveIndex(null)} data-testid="remove-cancel">
+                Cancel
+              </Button>
+              <Button
+                variant="destructive"
+                onClick={() => {
+                  if (confirmRemoveIndex !== null) onRemoveQueueItem(confirmRemoveIndex);
+                  setConfirmRemoveIndex(null);
+                }}
+                data-testid="remove-confirm"
+              >
+                <Trash2 className="size-4" />
+                Remove
+              </Button>
+            </DialogFooter>
+          </DialogContent>
+        </Dialog>
+
         <Button className="h-11 w-full" onClick={onJump} disabled={busy} data-testid="jump-forward">
           {busy ? <Loader2 className="size-4 animate-spin" /> : <Radar className="size-4" />}
           {queuedLabel}

src/lib/api.ts

@@ -8,6 +8,7 @@ import type {
   AdvisorResponse,
   CreateGameResponse,
   GameSummary,
+  RemoveQueueItemResponse,
   TurnResponse,
 } from '@shared/protocol';
 
@@ -48,6 +49,13 @@ export const api = {
       method: 'POST',
       body: JSON.stringify({ to, message }),
     }),
+  // Remove one queued item from the pending round, by its index in `game.pending`.
+  // Fast, non-LLM — no turn advance. Returns the updated game.
+  removeQueueItem: (id: string, index: number) =>
+    req<RemoveQueueItemResponse>(`/api/games/${id}/queue/remove`, {
+      method: 'POST',
+      body: JSON.stringify({ index }),
+    }),
   // Commit the whole pending round (or an empty one) in a single LLM turn.
   jump: (id: string) =>
     req<TurnResponse>(`/api/games/${id}/jump`, {