diff --git a/.changeset/loud-lamps-camp.md b/.changeset/loud-lamps-camp.md
new file mode 100644
index 00000000000..79b2e59c205
--- /dev/null
+++ b/.changeset/loud-lamps-camp.md
@@ -0,0 +1,5 @@
+---
+'@firebase/app-check': patch
+---
+
+Fix an error causing App Check to log `HTTP status 429` errors in debug mode.
diff --git a/packages/app-check/src/api.test.ts b/packages/app-check/src/api.test.ts
index 14fb1d86305..894fbde65dd 100644
--- a/packages/app-check/src/api.test.ts
+++ b/packages/app-check/src/api.test.ts
@@ -28,6 +28,7 @@ import {
   getFakeApp,
   getFakeCustomTokenProvider,
   getFakePlatformLoggingProvider,
+  getFakeGreCAPTCHA,
   removegreCAPTCHAScriptsOnPage
 } from '../test/util';
 import { clearState, getState } from './state';
@@ -37,8 +38,12 @@ import * as internalApi from './internal-api';
 import * as client from './client';
 import * as storage from './storage';
 import * as logger from './logger';
+import * as util from './util';
 
 describe('api', () => {
+  beforeEach(() => {
+    stub(util, 'getRecaptcha').returns(getFakeGreCAPTCHA());
+  });
   describe('activate()', () => {
     let app: FirebaseApp;
 
@@ -126,25 +131,29 @@ describe('api', () => {
     });
   });
   describe('onTokenChanged()', () => {
+    const fakePlatformLoggingProvider = getFakePlatformLoggingProvider();
+    const fakeRecaptchaToken = 'fake-recaptcha-token';
+    const fakeRecaptchaAppCheckToken = {
+      token: 'fake-recaptcha-app-check-token',
+      expireTimeMillis: Date.now() + 60000,
+      issuedAtTimeMillis: 0
+    };
+
+    beforeEach(() => {
+      stub(storage, 'readTokenFromStorage').resolves(undefined);
+      stub(storage, 'writeTokenToStorage');
+    });
     afterEach(() => {
       clearState();
       removegreCAPTCHAScriptsOnPage();
     });
     it('Listeners work when using top-level parameters pattern', async () => {
-      const app = getFakeApp({ automaticDataCollectionEnabled: true });
-      activate(app, FAKE_SITE_KEY, true);
-      const fakePlatformLoggingProvider = getFakePlatformLoggingProvider();
-      const fakeRecaptchaToken = 'fake-recaptcha-token';
-      const fakeRecaptchaAppCheckToken = {
-        token: 'fake-recaptcha-app-check-token',
-        expireTimeMillis: 123,
-        issuedAtTimeMillis: 0
-      };
+      const app = getFakeApp();
+      activate(app, FAKE_SITE_KEY, false);
       stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
       stub(client, 'exchangeToken').returns(
         Promise.resolve(fakeRecaptchaAppCheckToken)
       );
-      stub(storage, 'writeTokenToStorage').returns(Promise.resolve(undefined));
 
       const listener1 = (): void => {
         throw new Error();
@@ -183,20 +192,12 @@ describe('api', () => {
     });
 
     it('Listeners work when using Observer pattern', async () => {
-      const app = getFakeApp({ automaticDataCollectionEnabled: true });
-      activate(app, FAKE_SITE_KEY, true);
-      const fakePlatformLoggingProvider = getFakePlatformLoggingProvider();
-      const fakeRecaptchaToken = 'fake-recaptcha-token';
-      const fakeRecaptchaAppCheckToken = {
-        token: 'fake-recaptcha-app-check-token',
-        expireTimeMillis: 123,
-        issuedAtTimeMillis: 0
-      };
+      const app = getFakeApp();
+      activate(app, FAKE_SITE_KEY, false);
       stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
       stub(client, 'exchangeToken').returns(
         Promise.resolve(fakeRecaptchaAppCheckToken)
       );
-      stub(storage, 'writeTokenToStorage').returns(Promise.resolve(undefined));
 
       const listener1 = (): void => {
         throw new Error();
@@ -238,11 +239,8 @@ describe('api', () => {
       stub(logger.logger, 'error');
       const app = getFakeApp();
       activate(app, FAKE_SITE_KEY, false);
-      const fakePlatformLoggingProvider = getFakePlatformLoggingProvider();
-      const fakeRecaptchaToken = 'fake-recaptcha-token';
       stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
       stub(client, 'exchangeToken').rejects('exchange error');
-      stub(storage, 'writeTokenToStorage').returns(Promise.resolve(undefined));
 
       const listener1 = spy();
 
diff --git a/packages/app-check/src/client.test.ts b/packages/app-check/src/client.test.ts
index 78a06f90799..352e511915b 100644
--- a/packages/app-check/src/client.test.ts
+++ b/packages/app-check/src/client.test.ts
@@ -52,7 +52,8 @@ describe('client', () => {
   });
 
   it('returns a AppCheck token', async () => {
-    useFakeTimers();
+    // To get a consistent expireTime/issuedAtTime.
+    const clock = useFakeTimers();
     fetchStub.returns(
       Promise.resolve({
         status: 200,
@@ -77,6 +78,7 @@ describe('client', () => {
       expireTimeMillis: 3600,
       issuedAtTimeMillis: 0
     });
+    clock.restore();
   });
 
   it('throws when there is a network error', async () => {
diff --git a/packages/app-check/src/factory.ts b/packages/app-check/src/factory.ts
index ee27b9a04cf..4173813b52b 100644
--- a/packages/app-check/src/factory.ts
+++ b/packages/app-check/src/factory.ts
@@ -36,18 +36,21 @@ import {
 import { Provider } from '@firebase/component';
 import { PartialObserver } from '@firebase/util';
 
+import { FirebaseService } from '@firebase/app-types/private';
+import { getState } from './state';
+
 export function factory(
   app: FirebaseApp,
   platformLoggerProvider: Provider<'platform-logger'>
-): FirebaseAppCheck {
+): FirebaseAppCheck & FirebaseService {
   return {
+    app,
     activate: (
       siteKeyOrProvider: string | AppCheckProvider,
       isTokenAutoRefreshEnabled?: boolean
     ) => activate(app, siteKeyOrProvider, isTokenAutoRefreshEnabled),
     setTokenAutoRefreshEnabled: (isTokenAutoRefreshEnabled: boolean) =>
       setTokenAutoRefreshEnabled(app, isTokenAutoRefreshEnabled),
-
     getToken: forceRefresh =>
       getToken(app, platformLoggerProvider, forceRefresh),
     onTokenChanged: (
@@ -68,7 +71,16 @@ export function factory(
         onNextOrObserver as (tokenResult: AppCheckTokenResult) => void,
         onError,
         onCompletion
-      )
+      ),
+    INTERNAL: {
+      delete: () => {
+        const { tokenObservers } = getState(app);
+        for (const tokenObserver of tokenObservers) {
+          removeTokenListener(app, tokenObserver.next);
+        }
+        return Promise.resolve();
+      }
+    }
   };
 }
 
diff --git a/packages/app-check/src/internal-api.test.ts b/packages/app-check/src/internal-api.test.ts
index 02c9148901a..c0bf48fcfa3 100644
--- a/packages/app-check/src/internal-api.test.ts
+++ b/packages/app-check/src/internal-api.test.ts
@@ -23,6 +23,7 @@ import {
   FAKE_SITE_KEY,
   getFakeApp,
   getFakeCustomTokenProvider,
+  getFakeGreCAPTCHA,
   getFakePlatformLoggingProvider,
   removegreCAPTCHAScriptsOnPage
 } from '../test/util';
@@ -38,20 +39,26 @@ import * as reCAPTCHA from './recaptcha';
 import * as logger from './logger';
 import * as client from './client';
 import * as storage from './storage';
+import * as util from './util';
 import { getState, clearState, setState, getDebugState } from './state';
-import { AppCheckTokenResult } from '@firebase/app-check-interop-types';
 import { Deferred } from '@firebase/util';
+import { AppCheckTokenResult } from '../../app-check-interop-types';
 
 const fakePlatformLoggingProvider = getFakePlatformLoggingProvider();
 
 describe('internal api', () => {
   let app: FirebaseApp;
+  let storageReadStub: SinonStub;
+  let storageWriteStub: SinonStub;
 
   beforeEach(() => {
     app = getFakeApp();
+    storageReadStub = stub(storage, 'readTokenFromStorage').resolves(undefined);
+    storageWriteStub = stub(storage, 'writeTokenToStorage');
+    stub(util, 'getRecaptcha').returns(getFakeGreCAPTCHA());
   });
 
-  afterEach(() => {
+  afterEach(async () => {
     clearState();
     removegreCAPTCHAScriptsOnPage();
   });
@@ -60,18 +67,19 @@ describe('internal api', () => {
     const fakeRecaptchaToken = 'fake-recaptcha-token';
     const fakeRecaptchaAppCheckToken = {
       token: 'fake-recaptcha-app-check-token',
-      expireTimeMillis: 123,
+      // This makes isValid(token) true.
+      expireTimeMillis: Date.now() + 60000,
       issuedAtTimeMillis: 0
     };
 
     const fakeCachedAppCheckToken = {
       token: 'fake-cached-app-check-token',
-      expireTimeMillis: 123,
+      // This makes isValid(token) true.
+      expireTimeMillis: Date.now() + 60000,
       issuedAtTimeMillis: 0
     };
 
     it('uses customTokenProvider to get an AppCheck token', async () => {
-      const clock = useFakeTimers();
       const customTokenProvider = getFakeCustomTokenProvider();
       const customProviderSpy = spy(customTokenProvider, 'getToken');
 
@@ -82,20 +90,18 @@ describe('internal api', () => {
       expect(token).to.deep.equal({
         token: 'fake-custom-app-check-token'
       });
-
-      clock.restore();
     });
 
     it('uses reCAPTCHA token to exchange for AppCheck token if no customTokenProvider is provided', async () => {
       activate(app, FAKE_SITE_KEY);
 
-      const reCAPTCHASpy = stub(reCAPTCHA, 'getToken').returns(
-        Promise.resolve(fakeRecaptchaToken)
+      const reCAPTCHASpy = stub(reCAPTCHA, 'getToken').resolves(
+        fakeRecaptchaToken
       );
       const exchangeTokenStub: SinonStub = stub(
         client,
         'exchangeToken'
-      ).returns(Promise.resolve(fakeRecaptchaAppCheckToken));
+      ).resolves(fakeRecaptchaAppCheckToken);
 
       const token = await getToken(app, fakePlatformLoggingProvider);
 
@@ -111,12 +117,12 @@ describe('internal api', () => {
       const errorStub = stub(console, 'error');
       activate(app, FAKE_SITE_KEY, true);
 
-      const reCAPTCHASpy = stub(reCAPTCHA, 'getToken').returns(
-        Promise.resolve(fakeRecaptchaToken)
+      const reCAPTCHASpy = stub(reCAPTCHA, 'getToken').resolves(
+        fakeRecaptchaToken
       );
 
       const error = new Error('oops, something went wrong');
-      stub(client, 'exchangeToken').returns(Promise.reject(error));
+      stub(client, 'exchangeToken').rejects(error);
 
       const token = await getToken(app, fakePlatformLoggingProvider);
 
@@ -132,12 +138,8 @@ describe('internal api', () => {
     });
 
     it('notifies listeners using cached token', async () => {
-      activate(app, FAKE_SITE_KEY, true);
-
-      const clock = useFakeTimers();
-      stub(storage, 'readTokenFromStorage').returns(
-        Promise.resolve(fakeCachedAppCheckToken)
-      );
+      activate(app, FAKE_SITE_KEY, false);
+      storageReadStub.resolves(fakeCachedAppCheckToken);
 
       const listener1 = spy();
       const listener2 = spy();
@@ -152,18 +154,13 @@ describe('internal api', () => {
       expect(listener2).to.be.calledWith({
         token: fakeCachedAppCheckToken.token
       });
-
-      clock.restore();
     });
 
     it('notifies listeners using new token', async () => {
-      activate(app, FAKE_SITE_KEY, true);
+      activate(app, FAKE_SITE_KEY, false);
 
-      stub(storage, 'readTokenFromStorage').returns(Promise.resolve(undefined));
-      stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
-      stub(client, 'exchangeToken').returns(
-        Promise.resolve(fakeRecaptchaAppCheckToken)
-      );
+      stub(reCAPTCHA, 'getToken').resolves(fakeRecaptchaToken);
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
 
       const listener1 = spy();
       const listener2 = spy();
@@ -182,8 +179,8 @@ describe('internal api', () => {
 
     it('calls optional error handler if there is an error getting a token', async () => {
       stub(logger.logger, 'error');
-      activate(app, FAKE_SITE_KEY, true);
-      stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
+      activate(app, FAKE_SITE_KEY, false);
+      stub(reCAPTCHA, 'getToken').resolves(fakeRecaptchaToken);
       stub(client, 'exchangeToken').rejects('exchange error');
       const listener1 = spy();
 
@@ -197,35 +194,46 @@ describe('internal api', () => {
       expect(errorFn1.args[0][0].name).to.include('exchange error');
     });
 
+    it('ignores listeners that throw', async () => {
+      activate(app, FAKE_SITE_KEY, false);
+      stub(reCAPTCHA, 'getToken').resolves(fakeRecaptchaToken);
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
+      const listener1 = stub().throws(new Error());
+      const listener2 = spy();
+
+      const errorFn1 = spy();
+
+      addTokenListener(app, fakePlatformLoggingProvider, listener1, errorFn1);
+      addTokenListener(app, fakePlatformLoggingProvider, listener2);
+
+      await getToken(app, fakePlatformLoggingProvider);
+
+      expect(errorFn1).not.to.be.called;
+      expect(listener1).to.be.called;
+      expect(listener2).to.be.called;
+    });
+
     it('loads persisted token to memory and returns it', async () => {
-      const clock = useFakeTimers();
       activate(app, FAKE_SITE_KEY);
 
-      stub(storage, 'readTokenFromStorage').returns(
-        Promise.resolve(fakeCachedAppCheckToken)
-      );
+      storageReadStub.resolves(fakeCachedAppCheckToken);
 
       const clientStub = stub(client, 'exchangeToken');
 
       expect(getState(app).token).to.equal(undefined);
-      expect(await getToken(app, fakePlatformLoggingProvider)).to.deep.equal({
+      const result = await getToken(app, fakePlatformLoggingProvider);
+      expect(result).to.deep.equal({
         token: fakeCachedAppCheckToken.token
       });
       expect(getState(app).token).to.equal(fakeCachedAppCheckToken);
       expect(clientStub).has.not.been.called;
-
-      clock.restore();
     });
 
     it('persists token to storage', async () => {
-      activate(app, FAKE_SITE_KEY);
+      activate(app, FAKE_SITE_KEY, false);
 
-      stub(storage, 'readTokenFromStorage').returns(Promise.resolve(undefined));
-      stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
-      stub(client, 'exchangeToken').returns(
-        Promise.resolve(fakeRecaptchaAppCheckToken)
-      );
-      const storageWriteStub = stub(storage, 'writeTokenToStorage');
+      stub(reCAPTCHA, 'getToken').resolves(fakeRecaptchaToken);
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
       const result = await getToken(app, fakePlatformLoggingProvider);
       expect(result).to.deep.equal({ token: fakeRecaptchaAppCheckToken.token });
       expect(storageWriteStub).has.been.calledWith(
@@ -235,27 +243,23 @@ describe('internal api', () => {
     });
 
     it('returns the valid token in memory without making network request', async () => {
-      const clock = useFakeTimers();
       activate(app, FAKE_SITE_KEY);
       setState(app, { ...getState(app), token: fakeRecaptchaAppCheckToken });
 
       const clientStub = stub(client, 'exchangeToken');
-      expect(await getToken(app, fakePlatformLoggingProvider)).to.deep.equal({
+      const result = await getToken(app, fakePlatformLoggingProvider);
+      expect(result).to.deep.equal({
         token: fakeRecaptchaAppCheckToken.token
       });
       expect(clientStub).to.not.have.been.called;
-
-      clock.restore();
     });
 
     it('force to get new token when forceRefresh is true', async () => {
       activate(app, FAKE_SITE_KEY);
       setState(app, { ...getState(app), token: fakeRecaptchaAppCheckToken });
 
-      stub(reCAPTCHA, 'getToken').returns(Promise.resolve(fakeRecaptchaToken));
-      stub(client, 'exchangeToken').returns(
-        Promise.resolve(fakeRecaptchaAppCheckToken)
-      );
+      stub(reCAPTCHA, 'getToken').resolves(fakeRecaptchaToken);
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
 
       expect(
         await getToken(app, fakePlatformLoggingProvider, true)
@@ -264,11 +268,11 @@ describe('internal api', () => {
       });
     });
 
-    it('exchanges debug token if in debug mode', async () => {
+    it('exchanges debug token if in debug mode and there is no cached token', async () => {
       const exchangeTokenStub: SinonStub = stub(
         client,
         'exchangeToken'
-      ).returns(Promise.resolve(fakeRecaptchaAppCheckToken));
+      ).resolves(fakeRecaptchaAppCheckToken);
       const debugState = getDebugState();
       debugState.enabled = true;
       debugState.token = new Deferred();
@@ -284,8 +288,15 @@ describe('internal api', () => {
   });
 
   describe('addTokenListener', () => {
+    const fakeRecaptchaAppCheckToken = {
+      token: 'fake-recaptcha-app-check-token',
+      // This makes isValid(token) true.
+      expireTimeMillis: Date.now() + 60000,
+      issuedAtTimeMillis: 0
+    };
     it('adds token listeners', () => {
       const listener = (): void => {};
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
 
       addTokenListener(app, fakePlatformLoggingProvider, listener);
 
@@ -294,6 +305,7 @@ describe('internal api', () => {
 
     it('starts proactively refreshing token after adding the first listener', () => {
       const listener = (): void => {};
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
       setState(app, { ...getState(app), isTokenAutoRefreshEnabled: true });
       expect(getState(app).tokenObservers.length).to.equal(0);
       expect(getState(app).tokenRefresher).to.equal(undefined);
@@ -301,86 +313,61 @@ describe('internal api', () => {
       addTokenListener(app, fakePlatformLoggingProvider, listener);
 
       expect(getState(app).tokenRefresher?.isRunning()).to.be.true;
+
+      removeTokenListener(app, listener);
     });
 
-    it('notifies the listener with the valid token in memory immediately', done => {
+    it('notifies the listener with the valid token in memory immediately', async () => {
       const clock = useFakeTimers();
-      const fakeListener = (token: AppCheckTokenResult): void => {
-        expect(token).to.deep.equal({
-          token: `fake-memory-app-check-token`
-        });
-        clock.restore();
-        done();
-      };
+      const listener = stub();
 
       setState(app, {
         ...getState(app),
         token: {
           token: `fake-memory-app-check-token`,
-          expireTimeMillis: 123,
+          expireTimeMillis: Date.now() + 60000,
           issuedAtTimeMillis: 0
         }
       });
 
-      addTokenListener(app, fakePlatformLoggingProvider, fakeListener);
+      addTokenListener(app, fakePlatformLoggingProvider, listener);
+      await clock.runAllAsync();
+      expect(listener).to.be.calledWith({
+        token: 'fake-memory-app-check-token'
+      });
+      clock.restore();
     });
 
     it('notifies the listener with the valid token in storage', done => {
-      const clock = useFakeTimers();
-      activate(app, FAKE_SITE_KEY, true);
-      stub(storage, 'readTokenFromStorage').returns(
-        Promise.resolve({
-          token: `fake-cached-app-check-token`,
-          expireTimeMillis: 123,
-          issuedAtTimeMillis: 0
-        })
-      );
+      activate(app, FAKE_SITE_KEY);
+      storageReadStub.resolves({
+        token: `fake-cached-app-check-token`,
+        expireTimeMillis: Date.now() + 60000,
+        issuedAtTimeMillis: 0
+      });
 
+      // Need to use done() if the callback will be called by the
+      // refresher.
       const fakeListener = (token: AppCheckTokenResult): void => {
         expect(token).to.deep.equal({
           token: `fake-cached-app-check-token`
         });
-        clock.restore();
         done();
       };
 
       addTokenListener(app, fakePlatformLoggingProvider, fakeListener);
-      clock.tick(1);
-    });
-
-    it('notifies the listener with the debug token immediately', done => {
-      const fakeListener = (token: AppCheckTokenResult): void => {
-        expect(token).to.deep.equal({
-          token: `my-debug-token`
-        });
-        done();
-      };
-
-      const debugState = getDebugState();
-      debugState.enabled = true;
-      debugState.token = new Deferred();
-      debugState.token.resolve('my-debug-token');
-
-      activate(app, FAKE_SITE_KEY, true);
-      addTokenListener(app, fakePlatformLoggingProvider, fakeListener);
-    });
-
-    it('does NOT start token refresher in debug mode', () => {
-      const debugState = getDebugState();
-      debugState.enabled = true;
-      debugState.token = new Deferred();
-      debugState.token.resolve('my-debug-token');
-
-      activate(app, FAKE_SITE_KEY, true);
-      addTokenListener(app, fakePlatformLoggingProvider, () => {});
-
-      const state = getState(app);
-      expect(state.tokenRefresher).is.undefined;
     });
   });
 
   describe('removeTokenListener', () => {
+    const fakeRecaptchaAppCheckToken = {
+      token: 'fake-recaptcha-app-check-token',
+      // This makes isValid(token) true.
+      expireTimeMillis: Date.now() + 60000,
+      issuedAtTimeMillis: 0
+    };
     it('should remove token listeners', () => {
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
       const listener = (): void => {};
       addTokenListener(app, fakePlatformLoggingProvider, listener);
       expect(getState(app).tokenObservers.length).to.equal(1);
@@ -390,6 +377,7 @@ describe('internal api', () => {
     });
 
     it('should stop proactively refreshing token after deleting the last listener', () => {
+      stub(client, 'exchangeToken').resolves(fakeRecaptchaAppCheckToken);
       const listener = (): void => {};
       setState(app, { ...getState(app), isTokenAutoRefreshEnabled: true });
 
diff --git a/packages/app-check/src/internal-api.ts b/packages/app-check/src/internal-api.ts
index f7d0767ee9b..ebbe70fe4fd 100644
--- a/packages/app-check/src/internal-api.ts
+++ b/packages/app-check/src/internal-api.ts
@@ -24,7 +24,6 @@ import {
 import {
   AppCheckTokenInternal,
   AppCheckTokenObserver,
-  getDebugState,
   getState,
   setState
 } from './state';
@@ -72,25 +71,17 @@ export async function getToken(
   forceRefresh = false
 ): Promise<AppCheckTokenResult> {
   ensureActivated(app);
-  /**
-   * DEBUG MODE
-   * return the debug token directly
-   */
-  if (isDebugMode()) {
-    const tokenFromDebugExchange: AppCheckTokenInternal = await exchangeToken(
-      getExchangeDebugTokenRequest(app, await getDebugToken()),
-      platformLoggerProvider
-    );
-    return { token: tokenFromDebugExchange.token };
-  }
 
   const state = getState(app);
 
+  /**
+   * First check if there is a token in memory from a previous `getToken()` call.
+   */
   let token: AppCheckTokenInternal | undefined = state.token;
   let error: Error | undefined = undefined;
 
   /**
-   * try to load token from indexedDB if it's the first time this function is called
+   * If there is no token in memory, try to load token from indexedDB.
    */
   if (!token) {
     // readTokenFromStorage() always resolves. In case of an error, it resolves with `undefined`.
@@ -104,13 +95,30 @@ export async function getToken(
     }
   }
 
-  // return the cached token if it's valid
+  // Return the cached token (from either memory or indexedDB) if it's valid
   if (!forceRefresh && token && isValid(token)) {
     return {
       token: token.token
     };
   }
 
+  /**
+   * DEBUG MODE
+   * If debug mode is set, and there is no cached token, fetch a new App
+   * Check token using the debug token, and return it directly.
+   */
+  if (isDebugMode()) {
+    const tokenFromDebugExchange: AppCheckTokenInternal = await exchangeToken(
+      getExchangeDebugTokenRequest(app, await getDebugToken()),
+      platformLoggerProvider
+    );
+    // Write debug token to indexedDB.
+    await writeTokenToStorage(app, tokenFromDebugExchange);
+    // Write debug token to state.
+    setState(app, { ...state, token: tokenFromDebugExchange });
+    return { token: tokenFromDebugExchange.token };
+  }
+
   /**
    * request a new token
    */
@@ -155,7 +163,7 @@ export async function getToken(
     interopTokenResult = {
       token: token.token
     };
-    // write the new token to the memory state as well ashe persistent storage.
+    // write the new token to the memory state as well as the persistent storage.
     // Only do it if we got a valid new token
     setState(app, { ...state, token });
     await writeTokenToStorage(app, token);
@@ -182,48 +190,30 @@ export function addTokenListener(
   };
 
   /**
-   * DEBUG MODE
-   *
-   * invoke the listener once with the debug token.
+   * Invoke the listener with the valid token, then start the token refresher
    */
-  if (isDebugMode()) {
-    const debugState = getDebugState();
-    if (debugState.enabled && debugState.token) {
-      debugState.token.promise
-        .then(token => listener({ token }))
-        .catch(() => {
-          /** Ignore errors in listeners. */
-        });
-    }
-  } else {
-    /**
-     * PROD MODE
-     *
-     * invoke the listener with the valid token, then start the token refresher
-     */
-    if (!newState.tokenRefresher) {
-      const tokenRefresher = createTokenRefresher(app, platformLoggerProvider);
-      newState.tokenRefresher = tokenRefresher;
-    }
+  if (!newState.tokenRefresher) {
+    const tokenRefresher = createTokenRefresher(app, platformLoggerProvider);
+    newState.tokenRefresher = tokenRefresher;
+  }
 
-    // Create the refresher but don't start it if `isTokenAutoRefreshEnabled`
-    // is not true.
-    if (
-      !newState.tokenRefresher.isRunning() &&
-      state.isTokenAutoRefreshEnabled === true
-    ) {
-      newState.tokenRefresher.start();
-    }
+  // Create the refresher but don't start it if `isTokenAutoRefreshEnabled`
+  // is not true.
+  if (
+    !newState.tokenRefresher.isRunning() &&
+    state.isTokenAutoRefreshEnabled === true
+  ) {
+    newState.tokenRefresher.start();
+  }
 
-    // invoke the listener async immediately if there is a valid token
-    if (state.token && isValid(state.token)) {
-      const validToken = state.token;
-      Promise.resolve()
-        .then(() => listener({ token: validToken.token }))
-        .catch(() => {
-          /** Ignore errors in listeners. */
-        });
-    }
+  // invoke the listener async immediately if there is a valid token
+  if (state.token && isValid(state.token)) {
+    const validToken = state.token;
+    Promise.resolve()
+      .then(() => listener({ token: validToken.token }))
+      .catch(() => {
+        /** Ignore errors in listeners. */
+      });
   }
 
   setState(app, newState);
diff --git a/packages/app-check/src/state.ts b/packages/app-check/src/state.ts
index 4c983c835ba..d8fe52b046e 100644
--- a/packages/app-check/src/state.ts
+++ b/packages/app-check/src/state.ts
@@ -54,6 +54,7 @@ export interface ReCAPTCHAState {
 
 export interface DebugState {
   enabled: boolean;
+  // This is the debug token string the user interacts with.
   token?: Deferred<string>;
 }