diff --git a/frontend/src/api/angular-client.ts b/frontend/src/api/angular-client.ts
index add41c1..6befb53 100644
--- a/frontend/src/api/angular-client.ts
+++ b/frontend/src/api/angular-client.ts
@@ -1,4 +1,13 @@
-import type { ApiFailure, ApiResult, HealthResponse, SessionDetailResponse } from './types';
+import type {
+  ApiFailure,
+  ApiResult,
+  HealthResponse,
+  JoinSessionRequest,
+  JoinSessionResponse,
+  SessionDetailResponse,
+  StartRoundRequest,
+  StartRoundResponse
+} from './types';
 
 export interface AngularHttpError {
   status?: number;
@@ -8,11 +17,14 @@ export interface AngularHttpError {
 
 export interface AngularHttpClientLike {
   get<T>(url: string, options?: { withCredentials?: boolean }): Promise<T>;
+  post<T>(url: string, body: unknown, options?: { withCredentials?: boolean }): Promise<T>;
 }
 
 export interface AngularApiClient {
   health(): Promise<ApiResult<HealthResponse>>;
   getSession(code: string): Promise<ApiResult<SessionDetailResponse>>;
+  joinSession(payload: JoinSessionRequest): Promise<ApiResult<JoinSessionResponse>>;
+  startRound(code: string, payload: StartRoundRequest): Promise<ApiResult<StartRoundResponse>>;
 }
 
 function toFailure(error: unknown): ApiFailure {
@@ -40,23 +52,46 @@ function normalizeCode(code: string): string {
   return code.trim().toUpperCase();
 }
 
-async function wrapGet<T>(call: () => Promise<T>): Promise<ApiResult<T>> {
+async function wrap<T>(call: () => Promise<T>): Promise<ApiResult<T>> {
   try {
     const data = await call();
     return { ok: true, status: 200, data };
   } catch (error: unknown) {
-    return { ok: false, status: typeof (error as AngularHttpError)?.status === 'number' ? (error as AngularHttpError).status! : 0, error: toFailure(error) };
+    return {
+      ok: false,
+      status: typeof (error as AngularHttpError)?.status === 'number' ? (error as AngularHttpError).status! : 0,
+      error: toFailure(error)
+    };
   }
 }
 
 export function createAngularApiClient(http: AngularHttpClientLike, baseUrl = ''): AngularApiClient {
   return {
-    health: () => wrapGet(() => http.get<HealthResponse>(`${baseUrl}/healthz`, { withCredentials: true })),
+    health: () => wrap(() => http.get<HealthResponse>(`${baseUrl}/healthz`, { withCredentials: true })),
     getSession: (code: string) =>
-      wrapGet(() =>
+      wrap(() =>
         http.get<SessionDetailResponse>(`${baseUrl}/lobby/sessions/${encodeURIComponent(normalizeCode(code))}`, {
           withCredentials: true
         })
+      ),
+    joinSession: (payload: JoinSessionRequest) =>
+      wrap(() =>
+        http.post<JoinSessionResponse>(
+          `${baseUrl}/lobby/sessions/join`,
+          {
+            code: normalizeCode(payload.code),
+            nickname: payload.nickname.trim()
+          },
+          { withCredentials: true }
+        )
+      ),
+    startRound: (code: string, payload: StartRoundRequest) =>
+      wrap(() =>
+        http.post<StartRoundResponse>(
+          `${baseUrl}/lobby/sessions/${encodeURIComponent(normalizeCode(code))}/rounds/start`,
+          payload,
+          { withCredentials: true }
+        )
       )
   };
 }
diff --git a/frontend/tests/angular-api-client.test.ts b/frontend/tests/angular-api-client.test.ts
index 1020362..1cc7fc7 100644
--- a/frontend/tests/angular-api-client.test.ts
+++ b/frontend/tests/angular-api-client.test.ts
@@ -49,7 +49,27 @@ describe('createAngularApiClient', () => {
       throw { status: 404, error: { error: 'Not found' } };
     });
 
-    const http = { get };
+    const post = vi.fn<AngularHttpClientLike['post']>(async <T>(url: string, body: unknown) => {
+      if (url === '/lobby/sessions/join') {
+        expect(body).toEqual({ code: 'ABCD12', nickname: 'Maja' });
+        return {
+          player: { id: 9, nickname: 'Maja', session_token: 'token-1', score: 0 },
+          session: { code: 'ABCD12', status: 'lobby' }
+        } as T;
+      }
+
+      if (url === '/lobby/sessions/ABCD12/rounds/start') {
+        expect(body).toEqual({ category_slug: 'history' });
+        return {
+          session: { code: 'ABCD12', status: 'lie', current_round: 1 },
+          round: { number: 1, category: { slug: 'history', name: 'History' } }
+        } as T;
+      }
+
+      throw { status: 404, error: { error: 'Not found' } };
+    });
+
+    const http = { get, post };
     const client = createAngularApiClient(http as AngularHttpClientLike);
 
     const health = await client.health();
@@ -67,26 +87,55 @@ describe('createAngularApiClient', () => {
       expect(session.data.phase_view_model.host.can_start_round).toBe(true);
     }
 
+    const join = await client.joinSession({ code: ' abcd12 ', nickname: ' Maja ' });
+    expect(join.ok).toBe(true);
+
+    const start = await client.startRound(' abcd12 ', { category_slug: 'history' });
+    expect(start.ok).toBe(true);
+
     expect(get).toHaveBeenNthCalledWith(1, '/healthz', { withCredentials: true });
     expect(get).toHaveBeenNthCalledWith(2, '/lobby/sessions/ABCD12', { withCredentials: true });
+    expect(post).toHaveBeenNthCalledWith(
+      1,
+      '/lobby/sessions/join',
+      { code: 'ABCD12', nickname: 'Maja' },
+      { withCredentials: true }
+    );
+    expect(post).toHaveBeenNthCalledWith(
+      2,
+      '/lobby/sessions/ABCD12/rounds/start',
+      { category_slug: 'history' },
+      { withCredentials: true }
+    );
   });
 
   it('maps HttpErrorResponse-style failures to ApiResult errors', async () => {
     const http = {
       get: vi.fn<AngularHttpClientLike['get']>(async () => {
         throw { status: 503, message: 'Service unavailable', error: { error: 'maintenance' } };
+      }),
+      post: vi.fn<AngularHttpClientLike['post']>(async () => {
+        throw { status: 403, message: 'Forbidden', error: { error: 'Only host can start round' } };
       })
     };
 
     const client = createAngularApiClient(http as AngularHttpClientLike);
-    const result = await client.health();
+    const health = await client.health();
 
-    expect(result.ok).toBe(false);
-    if (!result.ok) {
-      expect(result.status).toBe(503);
-      expect(result.error.kind).toBe('http');
-      expect(result.error.payload).toEqual({ error: 'maintenance' });
-      expect(result.error.message).toContain('Service unavailable');
+    expect(health.ok).toBe(false);
+    if (!health.ok) {
+      expect(health.status).toBe(503);
+      expect(health.error.kind).toBe('http');
+      expect(health.error.payload).toEqual({ error: 'maintenance' });
+      expect(health.error.message).toContain('Service unavailable');
+    }
+
+    const start = await client.startRound('ABCD12', { category_slug: 'history' });
+    expect(start.ok).toBe(false);
+    if (!start.ok) {
+      expect(start.status).toBe(403);
+      expect(start.error.kind).toBe('http');
+      expect(start.error.payload).toEqual({ error: 'Only host can start round' });
     }
   });
 });