Fix session cookie being recreated on every export

functions/src/common/auth.ts

@@ -65,19 +65,22 @@ export async function getDecodedIdToken(
 
 /**
  * Generates and sets a session cookie for the current user into the provided response.
+ * Returns the absolute expiry timestamp (ms since epoch) of the created cookie.
  */
 export async function setSessionCookie(
   req: Request,
   res: Response
-): Promise<void> {
+): Promise<number> {
   const token = getAuthBearer(req);
   const expiresIn = 60 * 60 * 24 * 5 * 1000; // 5 days
   const cookie = await getAuth().createSessionCookie(token!, { expiresIn });
+  const expiresAt = Date.now() + expiresIn;
   res.cookie(SESSION_COOKIE_NAME, cookie, {
     maxAge: expiresIn,
     httpOnly: true,
     secure: true,
   });
+  return expiresAt;
 }
 
 function isEmulatorIdToken(user: DecodedIdToken): boolean {

functions/src/session-login.spec.ts

@@ -0,0 +1,86 @@
+/**
+ * Copyright 2026 The Ground Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as adminAuth from 'firebase-admin/auth';
+import type { Auth } from 'firebase-admin/auth';
+import { Request } from 'firebase-functions/v2/https';
+import type { Response } from 'express';
+import { StatusCodes } from 'http-status-codes';
+import { sessionLoginHandler } from './session-login';
+
+const FIVE_DAYS_MS = 60 * 60 * 24 * 5 * 1000;
+
+describe('sessionLoginHandler', () => {
+  let req: Request;
+  let res: jasmine.SpyObj<Response>;
+  let createSessionCookieSpy: jasmine.Spy;
+
+  beforeEach(() => {
+    req = {
+      headers: { authorization: 'Bearer fake-id-token' },
+      cookies: {},
+    } as unknown as Request;
+
+    res = jasmine.createSpyObj<Response>('response', [
+      'setHeader',
+      'cookie',
+      'json',
+      'status',
+      'send',
+    ]);
+    res.status.and.returnValue(res);
+
+    createSessionCookieSpy = jasmine
+      .createSpy('createSessionCookie')
+      .and.resolveTo('fake-session-cookie');
+    spyOn(adminAuth, 'getAuth').and.returnValue({
+      createSessionCookie: createSessionCookieSpy,
+    } as unknown as Auth);
+  });
+
+  it('returns expiresAt approximately 5 days in the future', async () => {
+    const before = Date.now();
+    await sessionLoginHandler(req, res);
+    const after = Date.now();
+
+    expect(res.json).toHaveBeenCalledOnceWith(
+      jasmine.objectContaining({ expiresAt: jasmine.any(Number) })
+    );
+    const { expiresAt } = (res.json as jasmine.Spy).calls.mostRecent().args[0];
+    expect(expiresAt).toBeGreaterThanOrEqual(before + FIVE_DAYS_MS);
+    expect(expiresAt).toBeLessThanOrEqual(after + FIVE_DAYS_MS);
+  });
+
+  it('sets httpOnly secure session cookie', async () => {
+    await sessionLoginHandler(req, res);
+
+    // Cast needed: Express's `cookie` overloads cause TS to resolve it as a
+    // 2-param function, but `setSessionCookie` calls the 3-param overload.
+    expect(res.cookie as jasmine.Spy).toHaveBeenCalledOnceWith(
+      '__session',
+      'fake-session-cookie',
+      jasmine.objectContaining({ httpOnly: true, secure: true })
+    );
+  });
+
+  it('returns 401 on auth error', async () => {
+    createSessionCookieSpy.and.rejectWith(new Error('invalid token'));
+
+    await sessionLoginHandler(req, res);
+
+    expect(res.status).toHaveBeenCalledWith(StatusCodes.UNAUTHORIZED);
+  });
+});

functions/src/session-login.ts

@@ -28,8 +28,8 @@ export async function sessionLoginHandler(req: Request, res: Response) {
     // Required for CDN:
     // https://stackoverflow.com/questions/44929653/firebase-cloud-function-wont-store-cookie-named-other-than-session/44935288#44935288
     res.setHeader('Cache-Control', 'private');
-    await setSessionCookie(req, res);
-    res.end('OK');
+    const expiresAt = await setSessionCookie(req, res);
+    res.json({ expiresAt });
   } catch (err) {
     logger.error(err);
     res.status(StatusCodes.UNAUTHORIZED).send('Authorization error');

web/src/app/components/shared/job-list-item/job-list-item.component.ts

@@ -125,7 +125,6 @@ export class JobListItemComponent implements OnInit {
   }
 
   async onDownloadCsvClick() {
-    // TODO(#1160): This can be optimized to only create a cookie when missing or expired.
     await this.authService.createSessionCookie();
     window.open(
       `${environment.cloudFunctionsUrl}/exportCsv?` +
@@ -135,7 +134,6 @@ export class JobListItemComponent implements OnInit {
   }
 
   async onDownloadGeoJsonClick() {
-    // TODO(#1160): This can be optimized to only create a cookie when missing or expired.
     await this.authService.createSessionCookie();
     window.open(
       `${environment.cloudFunctionsUrl}/exportGeojson?` +

web/src/app/services/auth/auth.service.spec.ts

@@ -16,17 +16,60 @@
 
 import { TestBed } from '@angular/core/testing';
 import { initializeApp, provideFirebaseApp } from '@angular/fire/app';
-import { getAuth, provideAuth } from '@angular/fire/auth';
+import {
+  Auth,
+  User as FirebaseUser,
+  getAuth,
+  provideAuth,
+} from '@angular/fire/auth';
 import { Firestore } from '@angular/fire/firestore';
 import { Functions } from '@angular/fire/functions';
 import { Router } from '@angular/router';
 import { of } from 'rxjs';
 
 import { AuthService } from 'app/services/auth/auth.service';
 import { DataStoreService } from 'app/services/data-store/data-store.service';
+import { User } from 'app/models/user.model';
+import { environment } from 'environments/environment';
 
 import { HttpClientService } from '../http-client/http-client.service';
 
+const SESSION_COOKIE_EXPIRES_AT_KEY = 'sessionCookieExpiresAt';
+const FIVE_DAYS_MS = 60 * 60 * 24 * 5 * 1000;
+
+/** Providers shared by all describe blocks that use a mock Auth. */
+function mockAuthProviders(mockAuth: Partial<Auth>, postWithAuth: jasmine.Spy) {
+  return [
+    { provide: Auth, useValue: mockAuth },
+    { provide: Firestore, useValue: {} },
+    { provide: Functions, useValue: {} },
+    {
+      provide: DataStoreService,
+      useValue: {
+        user$: () =>
+          of({
+            id: 'user-1',
+            email: 'test@test.com',
+            displayName: 'Test User',
+            isAuthenticated: true,
+          } as User),
+      },
+    },
+    { provide: Router, useValue: { events: of() } },
+    { provide: HttpClientService, useValue: { postWithAuth } },
+  ];
+}
+
+/** Returns a minimal Auth mock where onAuthStateChanged is a no-op. */
+function createMockAuth(onIdTokenChanged: jasmine.Spy): Partial<Auth> {
+  return {
+    onIdTokenChanged,
+    onAuthStateChanged: jasmine
+      .createSpy('onAuthStateChanged')
+      .and.returnValue(() => {}),
+  };
+}
+
 describe('AuthService', () => {
   beforeEach(() => {
     TestBed.configureTestingModule({
@@ -50,3 +93,104 @@ describe('AuthService', () => {
     expect(service).toBeTruthy();
   });
 });
+
+describe('AuthService createSessionCookie()', () => {
+  let service: AuthService;
+  let postWithAuthSpy: jasmine.Spy;
+  const futureExpiry = Date.now() + FIVE_DAYS_MS;
+
+  beforeEach(() => {
+    localStorage.clear();
+
+    postWithAuthSpy = jasmine
+      .createSpy('postWithAuth')
+      .and.resolveTo({ expiresAt: futureExpiry });
+
+    const mockAuth = createMockAuth(
+      jasmine.createSpy('onIdTokenChanged').and.returnValue(() => {})
+    );
+
+    TestBed.configureTestingModule({
+      providers: mockAuthProviders(mockAuth, postWithAuthSpy),
+    });
+
+    service = TestBed.inject(AuthService);
+  });
+
+  afterEach(() => localStorage.clear());
+
+  it('calls sessionLogin and persists expiresAt in localStorage on first call', async () => {
+    await service.createSessionCookie();
+
+    expect(postWithAuthSpy).toHaveBeenCalledOnceWith(
+      `${environment.cloudFunctionsUrl}/sessionLogin`,
+      {}
+    );
+    expect(localStorage.getItem(SESSION_COOKIE_EXPIRES_AT_KEY)).toBe(
+      String(futureExpiry)
+    );
+  });
+
+  it('skips sessionLogin when a valid cookie already exists in localStorage', async () => {
+    localStorage.setItem(SESSION_COOKIE_EXPIRES_AT_KEY, String(futureExpiry));
+
+    await service.createSessionCookie();
+
+    expect(postWithAuthSpy).not.toHaveBeenCalled();
+  });
+
+  it('calls sessionLogin again when the stored cookie has expired', async () => {
+    localStorage.setItem(SESSION_COOKIE_EXPIRES_AT_KEY, String(Date.now() - 1));
+
+    await service.createSessionCookie();
+
+    expect(postWithAuthSpy).toHaveBeenCalledTimes(1);
+  });
+});
+
+describe('AuthService session cookie invalidation', () => {
+  let service: AuthService;
+  let capturedIdTokenCallback: (user: FirebaseUser | null) => void;
+
+  beforeEach(() => {
+    localStorage.setItem(
+      SESSION_COOKIE_EXPIRES_AT_KEY,
+      String(Date.now() + FIVE_DAYS_MS)
+    );
+
+    const onIdTokenChangedSpy = jasmine
+      .createSpy('onIdTokenChanged')
+      .and.callFake((cb: (user: FirebaseUser | null) => void) => {
+        capturedIdTokenCallback = cb;
+        return () => {};
+      });
+
+    const mockAuth = createMockAuth(onIdTokenChangedSpy);
+
+    TestBed.configureTestingModule({
+      providers: mockAuthProviders(mockAuth, jasmine.createSpy('postWithAuth')),
+    });
+
+    service = TestBed.inject(AuthService);
+  });
+
+  afterEach(() => localStorage.clear());
+
+  it('clears localStorage entry when user signs out', () => {
+    expect(localStorage.getItem(SESSION_COOKIE_EXPIRES_AT_KEY)).not.toBeNull();
+
+    capturedIdTokenCallback!(null);
+
+    expect(localStorage.getItem(SESSION_COOKIE_EXPIRES_AT_KEY)).toBeNull();
+  });
+
+  it('preserves localStorage entry on token refresh for the same user', () => {
+    // Spy on callProfileRefresh to prevent it from calling httpsCallable with
+    // the mock Functions instance, which would fail with a missing _url error.
+    spyOn(service, 'callProfileRefresh').and.resolveTo();
+
+    capturedIdTokenCallback!({ uid: 'user-1' } as FirebaseUser);
+
+    expect(localStorage.getItem(SESSION_COOKIE_EXPIRES_AT_KEY)).not.toBeNull();
+  });
+});

web/src/app/services/auth/auth.service.ts

@@ -63,6 +63,8 @@ export const ROLE_OPTIONS = [
   },
 ];
 
+const SESSION_COOKIE_EXPIRES_AT_KEY = 'sessionCookieExpiresAt';
+
 @Injectable({
   providedIn: 'root',
 })
@@ -90,7 +92,10 @@ export class AuthService {
     // import { user } from '@angular/fire/auth'; --> corresponds to onIdTokenChanged.
     // But I didn't import 'user' in the top block, I imported 'User as FirebaseUser'.
     // Let's just use the strict SDK method in constructor.
-    this.auth.onIdTokenChanged(user => this.tokenChanged$.next(user));
+    this.auth.onIdTokenChanged(user => {
+      if (!user) localStorage.removeItem(SESSION_COOKIE_EXPIRES_AT_KEY);
+      this.tokenChanged$.next(user);
+    });
 
     this.user$ = authState(this.auth).pipe(
       mergeWith(this.tokenChanged$),
@@ -107,14 +112,22 @@ export class AuthService {
    * backend functions which require session auth. Namely, this is necessary for functions which
    * download arbitrarily large files (namely, "/exportCsv"). These functions can only be invoked via
    * HTTP GET, since browser do not allow streaming directly to disk via POST or other methods.
+   *
+   * Skips the server call if a valid session cookie was already created in this browser. The expiry
+   * timestamp is persisted in localStorage (sourced from the server response) so the check survives
+   * page refreshes. The entry is cleared when the user signs out (tracked via onIdTokenChanged).
    */
   async createSessionCookie() {
+    const stored = localStorage.getItem(SESSION_COOKIE_EXPIRES_AT_KEY);
+    if (stored !== null && Date.now() < parseInt(stored, 10)) {
+      return;
+    }
     try {
       // TODO(#1159): Refactor access to Cloud Functions into new service.
-      await this.httpClientService.postWithAuth(
-        `${environment.cloudFunctionsUrl}/sessionLogin`,
-        {}
-      );
+      const { expiresAt } = await this.httpClientService.postWithAuth<{
+        expiresAt: number;
+      }>(`${environment.cloudFunctionsUrl}/sessionLogin`, {});
+      localStorage.setItem(SESSION_COOKIE_EXPIRES_AT_KEY, String(expiresAt));
     } catch (err) {
       console.error(
         'Session login failed. Some features may be unavailable',