diff --git a/streaming/README.md b/streaming/README.md
index eeff25e..1dfab01 100644
--- a/streaming/README.md
+++ b/streaming/README.md
@@ -44,6 +44,7 @@ in secure contexts.
 
 | Endpoint | Caller | Purpose |
 |---|---|---|
+| `GET :8080/games/<id>` | flashpoint-web backend, `Authorization: Bearer <API_TOKEN>` | Returns the game's `{width, height}`, or 422 if it can't be streamed |
 | `POST :8080/sessions {gameId}` | flashpoint-web backend, `Authorization: Bearer <API_TOKEN>` | Creates a session; returns `{id, path, width, height}`, or 422 if the game can't be streamed |
 | `POST /stream/<id>/_fp/start {files}` | browser | Starts the container with the player's saves |
 | `GET /stream/<id>/_fp/saves` | browser | Server-sent events carrying `{files}` whenever saves change, then `end` |
diff --git a/streaming/session-manager/src/main.ts b/streaming/session-manager/src/main.ts
index 06f6fa7..4113ec5 100644
--- a/streaming/session-manager/src/main.ts
+++ b/streaming/session-manager/src/main.ts
@@ -18,14 +18,11 @@ const driver = new DockerDriver({
   uid: Number(env('PUID', '1000')),
   gid: Number(env('PGID', '1000')),
 });
-const sessions = new SessionManager(
-  driver,
-  new GameCatalog(env('FLASHPOINT_PATH', '/flashpoint')),
-  Number(env('MAX_SESSIONS', '4')),
-);
+const catalog = new GameCatalog(env('FLASHPOINT_PATH', '/flashpoint'));
+const sessions = new SessionManager(driver, catalog, Number(env('MAX_SESSIONS', '4')));
 
 await driver.removeAll();
-const api = createApiServer(sessions, env('API_TOKEN')).listen(Number(env('API_PORT', '8080')));
+const api = createApiServer(sessions, catalog, env('API_TOKEN')).listen(Number(env('API_PORT', '8080')));
 const stream = createStreamServer(sessions, driver).listen(Number(env('STREAM_PORT', '8081')));
 console.log('Session manager started');
 
diff --git a/streaming/session-manager/src/server.ts b/streaming/session-manager/src/server.ts
index 15378ea..f78eddc 100644
--- a/streaming/session-manager/src/server.ts
+++ b/streaming/session-manager/src/server.ts
@@ -3,6 +3,7 @@ import { text } from 'node:stream/consumers';
 import { timingSafeEqual } from 'node:crypto';
 import httpProxy from 'http-proxy';
 import { streamPath, type Driver } from './docker.ts';
+import type { GameCatalog } from './games.ts';
 import { parseSaveFiles } from './saves.ts';
 import { SessionError, type SessionManager } from './sessions.ts';
 
@@ -10,16 +11,24 @@ const STREAM_URL = /^\/stream\/([0-9a-f]{32})(\/.*)$/;
 const HEARTBEAT_MS = 25_000;
 const MAX_BODY_BYTES = 16 * 1024 * 1024;
 
-/** Internal API for flashpoint-web's backend: creates sessions. */
-export function createApiServer(sessions: SessionManager, token: string): http.Server {
+/** Internal API for flashpoint-web's backend: reports streamable games and creates sessions. */
+export function createApiServer(sessions: SessionManager, catalog: Pick<GameCatalog, 'streamSize'>, token: string): http.Server {
   return http.createServer((req, res) => {
     handle(res, async () => {
-      if (req.method !== 'POST' || req.url !== '/sessions') {
-        throw new SessionError(404, 'not found');
-      }
       if (!tokenMatches(req.headers.authorization, token)) {
         throw new SessionError(401, 'unauthorized');
       }
+      const [, lookupId] = req.url?.match(/^\/games\/([0-9a-f-]{36})$/) ?? [];
+      if (req.method === 'GET' && lookupId) {
+        const size = await catalog.streamSize(lookupId);
+        if (!size) {
+          throw new SessionError(422, 'game is not streamable');
+        }
+        return sendJson(res, 200, size);
+      }
+      if (req.method !== 'POST' || req.url !== '/sessions') {
+        throw new SessionError(404, 'not found');
+      }
       const { gameId } = await readJson(req);
       if (typeof gameId !== 'string') {
         throw new SessionError(400, 'gameId is required');
diff --git a/streaming/session-manager/test/fakes.ts b/streaming/session-manager/test/fakes.ts
index 734c35e..d845633 100644
--- a/streaming/session-manager/test/fakes.ts
+++ b/streaming/session-manager/test/fakes.ts
@@ -48,7 +48,7 @@ export class FakeDriver implements Driver {
 
 export const catalog = {
   async streamSize(gameId: string): Promise<Size | null> {
-    return gameId === 'java' ? { width: 472, height: 354 } : null;
+    return gameId === 'java' || gameId === '247a4c93-c252-49c8-8bc9-fb43d5c039df' ? { width: 472, height: 354 } : null;
   },
 };
 
diff --git a/streaming/session-manager/test/server.test.ts b/streaming/session-manager/test/server.test.ts
index 30304fc..90c68af 100644
--- a/streaming/session-manager/test/server.test.ts
+++ b/streaming/session-manager/test/server.test.ts
@@ -8,8 +8,9 @@ import { catalog, FakeDriver, fastTimings, sleep } from './fakes.ts';
 
 const driver = new FakeDriver();
 const sessions = new SessionManager(driver, catalog, 4, fastTimings);
-const api = createApiServer(sessions, 'secret');
+const api = createApiServer(sessions, catalog, 'secret');
 const stream = createStreamServer(sessions, driver);
+const JAVA_ID = '247a4c93-c252-49c8-8bc9-fb43d5c039df';
 let apiUrl: string;
 let streamUrl: string;
 
@@ -37,6 +38,14 @@ function createSession(gameId: string, token = 'secret') {
   });
 }
 
+test('the API reports whether a game is streamable', async () => {
+  const get = (gameId: string, token = 'secret') =>
+    fetch(`${apiUrl}/games/${gameId}`, { headers: { Authorization: `Bearer ${token}` } });
+  assert.equal((await get(JAVA_ID, 'wrong')).status, 401);
+  assert.deepEqual(await (await get(JAVA_ID)).json(), { width: 472, height: 354 });
+  assert.equal((await get('00000000-0000-0000-0000-000000000000')).status, 422);
+});
+
 test('the API requires the token and reports unstreamable games', async () => {
   assert.equal((await createSession('java', 'wrong')).status, 401);
   assert.equal((await createSession('flash')).status, 422);