diff --git a/packages/google-cloud-gkeconnect-gateway/.jsdoc.js b/packages/google-cloud-gkeconnect-gateway/.jsdoc.js
index dac3006fadb..009c138bd99 100644
--- a/packages/google-cloud-gkeconnect-gateway/.jsdoc.js
+++ b/packages/google-cloud-gkeconnect-gateway/.jsdoc.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -40,7 +40,7 @@ module.exports = {
     includePattern: '\\.js$'
   },
   templates: {
-    copyright: 'Copyright 2024 Google LLC',
+    copyright: 'Copyright 2025 Google LLC',
     includeDate: false,
     sourceFiles: false,
     systemName: '@google-cloud/gke-connect-gateway',
diff --git a/packages/google-cloud-gkeconnect-gateway/.mocharc.js b/packages/google-cloud-gkeconnect-gateway/.mocharc.js
index 7e843ab5a75..eef6173ab44 100644
--- a/packages/google-cloud-gkeconnect-gateway/.mocharc.js
+++ b/packages/google-cloud-gkeconnect-gateway/.mocharc.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/.prettierrc.js b/packages/google-cloud-gkeconnect-gateway/.prettierrc.js
index 120c6aa3e6e..b189724933b 100644
--- a/packages/google-cloud-gkeconnect-gateway/.prettierrc.js
+++ b/packages/google-cloud-gkeconnect-gateway/.prettierrc.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/README.md b/packages/google-cloud-gkeconnect-gateway/README.md
index 7a0b98d15ce..4bbd12d37d1 100644
--- a/packages/google-cloud-gkeconnect-gateway/README.md
+++ b/packages/google-cloud-gkeconnect-gateway/README.md
@@ -44,7 +44,7 @@ Google APIs Client Libraries, in [Client Libraries Explained][explained].
 1.  [Select or create a Cloud Platform project][projects].
 1.  [Enable billing for your project][billing].
 1.  [Enable the GKE Connect Gateway API][enable_api].
-1.  [Set up authentication with a service account][auth] so you can access the
+1.  [Set up authentication][auth] so you can access the
     API from your local workstation.
 
 ### Installing the client library
@@ -150,4 +150,4 @@ See [LICENSE](https://github.com/googleapis/google-cloud-node/blob/main/LICENSE)
 [projects]: https://console.cloud.google.com/project
 [billing]: https://support.google.com/cloud/answer/6293499#enable-billing
 [enable_api]: https://console.cloud.google.com/flows/enableapi?apiid=connectgateway.googleapis.com
-[auth]: https://cloud.google.com/docs/authentication/getting-started
+[auth]: https://cloud.google.com/docs/authentication/external/set-up-adc-local
diff --git a/packages/google-cloud-gkeconnect-gateway/protos/protos.d.ts b/packages/google-cloud-gkeconnect-gateway/protos/protos.d.ts
index 76c80bd714f..7546a107a27 100644
--- a/packages/google-cloud-gkeconnect-gateway/protos/protos.d.ts
+++ b/packages/google-cloud-gkeconnect-gateway/protos/protos.d.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/protos/protos.js b/packages/google-cloud-gkeconnect-gateway/protos/protos.js
index f72f654f6bc..03d2ede0f52 100644
--- a/packages/google-cloud-gkeconnect-gateway/protos/protos.js
+++ b/packages/google-cloud-gkeconnect-gateway/protos/protos.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/protos/protos.json b/packages/google-cloud-gkeconnect-gateway/protos/protos.json
index e5cc54242c4..857992fce85 100644
--- a/packages/google-cloud-gkeconnect-gateway/protos/protos.json
+++ b/packages/google-cloud-gkeconnect-gateway/protos/protos.json
@@ -1,4 +1,7 @@
 {
+  "options": {
+    "syntax": "proto3"
+  },
   "nested": {
     "google": {
       "nested": {
diff --git a/packages/google-cloud-gkeconnect-gateway/samples/generated/v1/gateway_control.generate_credentials.js b/packages/google-cloud-gkeconnect-gateway/samples/generated/v1/gateway_control.generate_credentials.js
index 5cd5b80a7f5..6dff1506e17 100644
--- a/packages/google-cloud-gkeconnect-gateway/samples/generated/v1/gateway_control.generate_credentials.js
+++ b/packages/google-cloud-gkeconnect-gateway/samples/generated/v1/gateway_control.generate_credentials.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/samples/generated/v1beta1/gateway_control.generate_credentials.js b/packages/google-cloud-gkeconnect-gateway/samples/generated/v1beta1/gateway_control.generate_credentials.js
index d4c5fbd5e97..4fb4efa3df9 100644
--- a/packages/google-cloud-gkeconnect-gateway/samples/generated/v1beta1/gateway_control.generate_credentials.js
+++ b/packages/google-cloud-gkeconnect-gateway/samples/generated/v1beta1/gateway_control.generate_credentials.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/src/index.ts b/packages/google-cloud-gkeconnect-gateway/src/index.ts
index d56e850fea9..aa49dc0e5a1 100644
--- a/packages/google-cloud-gkeconnect-gateway/src/index.ts
+++ b/packages/google-cloud-gkeconnect-gateway/src/index.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/src/v1/gateway_control_client.ts b/packages/google-cloud-gkeconnect-gateway/src/v1/gateway_control_client.ts
index bf48e8d0ef2..35e6de9c107 100644
--- a/packages/google-cloud-gkeconnect-gateway/src/v1/gateway_control_client.ts
+++ b/packages/google-cloud-gkeconnect-gateway/src/v1/gateway_control_client.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -133,6 +133,12 @@ export class GatewayControlClient {
     );
     const port = opts?.port || staticMembers.port;
     const clientConfig = opts?.clientConfig ?? {};
+    // Implicitly enable HTTP transport for the APIs that use REST as transport (e.g. Google Cloud Compute).
+    if (!opts) {
+      opts = {fallback: true};
+    } else {
+      opts.fallback = opts.fallback ?? true;
+    }
     const fallback =
       opts?.fallback ??
       (typeof window !== 'undefined' && typeof window?.fetch === 'function');
diff --git a/packages/google-cloud-gkeconnect-gateway/src/v1/index.ts b/packages/google-cloud-gkeconnect-gateway/src/v1/index.ts
index 58f2810e2db..dd818f3b743 100644
--- a/packages/google-cloud-gkeconnect-gateway/src/v1/index.ts
+++ b/packages/google-cloud-gkeconnect-gateway/src/v1/index.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/src/v1beta1/gateway_control_client.ts b/packages/google-cloud-gkeconnect-gateway/src/v1beta1/gateway_control_client.ts
index 8cc2910c798..27c4ad35923 100644
--- a/packages/google-cloud-gkeconnect-gateway/src/v1beta1/gateway_control_client.ts
+++ b/packages/google-cloud-gkeconnect-gateway/src/v1beta1/gateway_control_client.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -133,6 +133,12 @@ export class GatewayControlClient {
     );
     const port = opts?.port || staticMembers.port;
     const clientConfig = opts?.clientConfig ?? {};
+    // Implicitly enable HTTP transport for the APIs that use REST as transport (e.g. Google Cloud Compute).
+    if (!opts) {
+      opts = {fallback: true};
+    } else {
+      opts.fallback = opts.fallback ?? true;
+    }
     const fallback =
       opts?.fallback ??
       (typeof window !== 'undefined' && typeof window?.fetch === 'function');
diff --git a/packages/google-cloud-gkeconnect-gateway/src/v1beta1/index.ts b/packages/google-cloud-gkeconnect-gateway/src/v1beta1/index.ts
index 58f2810e2db..dd818f3b743 100644
--- a/packages/google-cloud-gkeconnect-gateway/src/v1beta1/index.ts
+++ b/packages/google-cloud-gkeconnect-gateway/src/v1beta1/index.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.js b/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.js
index 78439a18c9e..8dc0c97ee46 100644
--- a/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.js
+++ b/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.js
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.ts b/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.ts
index 2801297f835..1fc62d81f20 100644
--- a/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.ts
+++ b/packages/google-cloud-gkeconnect-gateway/system-test/fixtures/sample/src/index.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/system-test/install.ts b/packages/google-cloud-gkeconnect-gateway/system-test/install.ts
index 83b83f332c3..d927b34361d 100644
--- a/packages/google-cloud-gkeconnect-gateway/system-test/install.ts
+++ b/packages/google-cloud-gkeconnect-gateway/system-test/install.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1.ts b/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1.ts
index 9f8661479ea..83c4adea94f 100644
--- a/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1.ts
+++ b/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -20,10 +20,10 @@ import * as protos from '../protos/protos';
 import * as assert from 'assert';
 import * as sinon from 'sinon';
 import {SinonStub} from 'sinon';
-import {describe, it} from 'mocha';
+import {describe, it, beforeEach, afterEach} from 'mocha';
 import * as gatewaycontrolModule from '../src';
 
-import {protobuf} from 'google-gax';
+import {GoogleAuth, protobuf} from 'google-gax';
 
 // Dynamically loaded proto JSON is needed to get the type information
 // to fill in default values for request objects
@@ -65,6 +65,19 @@ function stubSimpleCallWithCallback<ResponseType>(
 }
 
 describe('v1.GatewayControlClient', () => {
+  let googleAuth: GoogleAuth;
+  beforeEach(() => {
+    googleAuth = {
+      getClient: sinon.stub().resolves({
+        getRequestHeaders: sinon
+          .stub()
+          .resolves({Authorization: 'Bearer SOME_TOKEN'}),
+      }),
+    } as unknown as GoogleAuth;
+  });
+  afterEach(() => {
+    sinon.restore();
+  });
   describe('Common methods', () => {
     it('has apiEndpoint', () => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient();
@@ -179,7 +192,7 @@ describe('v1.GatewayControlClient', () => {
 
     it('has initialize method and supports deferred initialization', async () => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       assert.strictEqual(client.gatewayControlStub, undefined);
@@ -189,7 +202,7 @@ describe('v1.GatewayControlClient', () => {
 
     it('has close method for the initialized client', done => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -201,7 +214,7 @@ describe('v1.GatewayControlClient', () => {
 
     it('has close method for the non-initialized client', done => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       assert.strictEqual(client.gatewayControlStub, undefined);
@@ -213,7 +226,7 @@ describe('v1.GatewayControlClient', () => {
     it('has getProjectId method', async () => {
       const fakeProjectId = 'fake-project-id';
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.auth.getProjectId = sinon.stub().resolves(fakeProjectId);
@@ -225,7 +238,7 @@ describe('v1.GatewayControlClient', () => {
     it('has getProjectId method with callback', async () => {
       const fakeProjectId = 'fake-project-id';
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.auth.getProjectId = sinon
@@ -248,7 +261,7 @@ describe('v1.GatewayControlClient', () => {
   describe('generateCredentials', () => {
     it('invokes generateCredentials without error', async () => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -280,7 +293,7 @@ describe('v1.GatewayControlClient', () => {
 
     it('invokes generateCredentials without error using callback', async () => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -327,7 +340,7 @@ describe('v1.GatewayControlClient', () => {
 
     it('invokes generateCredentials with error', async () => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -358,7 +371,7 @@ describe('v1.GatewayControlClient', () => {
 
     it('invokes generateCredentials with closed client', async () => {
       const client = new gatewaycontrolModule.v1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
diff --git a/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1beta1.ts b/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1beta1.ts
index 1d5b83fe506..c1c056a4792 100644
--- a/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1beta1.ts
+++ b/packages/google-cloud-gkeconnect-gateway/test/gapic_gateway_control_v1beta1.ts
@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2025 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -20,10 +20,10 @@ import * as protos from '../protos/protos';
 import * as assert from 'assert';
 import * as sinon from 'sinon';
 import {SinonStub} from 'sinon';
-import {describe, it} from 'mocha';
+import {describe, it, beforeEach, afterEach} from 'mocha';
 import * as gatewaycontrolModule from '../src';
 
-import {protobuf} from 'google-gax';
+import {GoogleAuth, protobuf} from 'google-gax';
 
 // Dynamically loaded proto JSON is needed to get the type information
 // to fill in default values for request objects
@@ -65,6 +65,19 @@ function stubSimpleCallWithCallback<ResponseType>(
 }
 
 describe('v1beta1.GatewayControlClient', () => {
+  let googleAuth: GoogleAuth;
+  beforeEach(() => {
+    googleAuth = {
+      getClient: sinon.stub().resolves({
+        getRequestHeaders: sinon
+          .stub()
+          .resolves({Authorization: 'Bearer SOME_TOKEN'}),
+      }),
+    } as unknown as GoogleAuth;
+  });
+  afterEach(() => {
+    sinon.restore();
+  });
   describe('Common methods', () => {
     it('has apiEndpoint', () => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient();
@@ -180,7 +193,7 @@ describe('v1beta1.GatewayControlClient', () => {
 
     it('has initialize method and supports deferred initialization', async () => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       assert.strictEqual(client.gatewayControlStub, undefined);
@@ -190,7 +203,7 @@ describe('v1beta1.GatewayControlClient', () => {
 
     it('has close method for the initialized client', done => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -202,7 +215,7 @@ describe('v1beta1.GatewayControlClient', () => {
 
     it('has close method for the non-initialized client', done => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       assert.strictEqual(client.gatewayControlStub, undefined);
@@ -214,7 +227,7 @@ describe('v1beta1.GatewayControlClient', () => {
     it('has getProjectId method', async () => {
       const fakeProjectId = 'fake-project-id';
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.auth.getProjectId = sinon.stub().resolves(fakeProjectId);
@@ -226,7 +239,7 @@ describe('v1beta1.GatewayControlClient', () => {
     it('has getProjectId method with callback', async () => {
       const fakeProjectId = 'fake-project-id';
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.auth.getProjectId = sinon
@@ -249,7 +262,7 @@ describe('v1beta1.GatewayControlClient', () => {
   describe('generateCredentials', () => {
     it('invokes generateCredentials without error', async () => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -281,7 +294,7 @@ describe('v1beta1.GatewayControlClient', () => {
 
     it('invokes generateCredentials without error using callback', async () => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -328,7 +341,7 @@ describe('v1beta1.GatewayControlClient', () => {
 
     it('invokes generateCredentials with error', async () => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();
@@ -359,7 +372,7 @@ describe('v1beta1.GatewayControlClient', () => {
 
     it('invokes generateCredentials with closed client', async () => {
       const client = new gatewaycontrolModule.v1beta1.GatewayControlClient({
-        credentials: {client_email: 'bogus', private_key: 'bogus'},
+        auth: googleAuth,
         projectId: 'bogus',
       });
       client.initialize();