From cbb1b577a3c4739d65af6df31e50704d85cf1fa7 Mon Sep 17 00:00:00 2001
From: alighaznavi <alighaznavi@google.com>
Date: Thu, 9 Oct 2025 20:50:49 +0000
Subject: [PATCH 1/5] Add support for App Check

---
 common/api-review/telemetry-react.api.md      |  5 ++
 common/api-review/telemetry.api.md            |  5 ++
 docs-devsite/_toc.yaml                        |  4 +
 .../telemetry_.dynamicheaderprovider.md       | 43 ++++++++++
 docs-devsite/telemetry_.md                    |  1 +
 .../telemetry_react.dynamicheaderprovider.md  | 43 ++++++++++
 docs-devsite/telemetry_react.md               |  1 +
 .../src/logging/appcheck-provider.ts          | 51 ++++++++++++
 .../src/logging/fetch-transport.edge.test.ts  | 78 +++++++++++++++++++
 .../src/logging/fetch-transport.edge.ts       | 22 +++++-
 .../telemetry/src/logging/logger-provider.ts  | 45 ++++++-----
 packages/telemetry/src/public-types.ts        | 17 ++++
 packages/telemetry/src/register.node.ts       |  3 +-
 packages/telemetry/src/register.ts            |  9 ++-
 packages/telemetry/src/service.ts             | 16 +---
 yarn.lock                                     | 31 +-------
 16 files changed, 303 insertions(+), 71 deletions(-)
 create mode 100644 docs-devsite/telemetry_.dynamicheaderprovider.md
 create mode 100644 docs-devsite/telemetry_react.dynamicheaderprovider.md
 create mode 100644 packages/telemetry/src/logging/appcheck-provider.ts

diff --git a/common/api-review/telemetry-react.api.md b/common/api-review/telemetry-react.api.md
index 53e344cc1ab..a57b8027e49 100644
--- a/common/api-review/telemetry-react.api.md
+++ b/common/api-review/telemetry-react.api.md
@@ -8,6 +8,11 @@ import { FirebaseApp } from '@firebase/app';
 import { FirebaseOptions } from '@firebase/app';
 import { LoggerProvider } from '@opentelemetry/sdk-logs';
 
+// @public
+export interface DynamicHeaderProvider {
+    getHeader(): Promise<Record<string, string> | null>;
+}
+
 // @public
 export function FirebaseTelemetry({ firebaseOptions, telemetryOptions }: {
     firebaseOptions?: FirebaseOptions;
diff --git a/common/api-review/telemetry.api.md b/common/api-review/telemetry.api.md
index 6a23ce03b80..ef9fbb27ea2 100644
--- a/common/api-review/telemetry.api.md
+++ b/common/api-review/telemetry.api.md
@@ -12,6 +12,11 @@ import { LoggerProvider } from '@opentelemetry/sdk-logs';
 // @public
 export function captureError(telemetry: Telemetry, error: unknown, attributes?: AnyValueMap): void;
 
+// @public
+export interface DynamicHeaderProvider {
+    getHeader(): Promise<Record<string, string> | null>;
+}
+
 // @public
 export function flush(telemetry: Telemetry): Promise<void>;
 
diff --git a/docs-devsite/_toc.yaml b/docs-devsite/_toc.yaml
index 81078cb2618..e0227cf3c94 100644
--- a/docs-devsite/_toc.yaml
+++ b/docs-devsite/_toc.yaml
@@ -697,6 +697,8 @@ toc:
 - title: telemetry
   path: /docs/reference/js/telemetry_.md
   section:
+  - title: DynamicHeaderProvider
+    path: /docs/reference/js/telemetry_.dynamicheaderprovider.md
   - title: Telemetry
     path: /docs/reference/js/telemetry_.telemetry.md
   - title: TelemetryOptions
@@ -704,6 +706,8 @@ toc:
 - title: telemetry/react
   path: /docs/reference/js/telemetry_react.md
   section:
+  - title: DynamicHeaderProvider
+    path: /docs/reference/js/telemetry_react.dynamicheaderprovider.md
   - title: Telemetry
     path: /docs/reference/js/telemetry_react.telemetry.md
   - title: TelemetryOptions
diff --git a/docs-devsite/telemetry_.dynamicheaderprovider.md b/docs-devsite/telemetry_.dynamicheaderprovider.md
new file mode 100644
index 00000000000..e4d81fd5cd8
--- /dev/null
+++ b/docs-devsite/telemetry_.dynamicheaderprovider.md
@@ -0,0 +1,43 @@
+Project: /docs/reference/js/_project.yaml
+Book: /docs/reference/_book.yaml
+page_type: reference
+
+{% comment %}
+DO NOT EDIT THIS FILE!
+This is generated by the JS SDK team, and any local changes will be
+overwritten. Changes should be made in the source code at
+https://github.com/firebase/firebase-js-sdk
+{% endcomment %}
+
+# DynamicHeaderProvider interface
+An interface for classes that provide dynamic headers.
+
+Classes that implement this interface can be used to supply custom headers for logging.
+
+<b>Signature:</b>
+
+```typescript
+export interface DynamicHeaderProvider 
+```
+
+## Methods
+
+|  Method | Description |
+|  --- | --- |
+|  [getHeader()](./telemetry_.dynamicheaderprovider.md#dynamicheaderprovidergetheader) | Returns a record of headers to be added to a request. |
+
+## DynamicHeaderProvider.getHeader()
+
+Returns a record of headers to be added to a request.
+
+<b>Signature:</b>
+
+```typescript
+getHeader(): Promise<Record<string, string> | null>;
+```
+<b>Returns:</b>
+
+Promise&lt;Record&lt;string, string&gt; \| null&gt;
+
+A  that resolves to a  of header key-value pairs, or null if no headers are to be added.
+
diff --git a/docs-devsite/telemetry_.md b/docs-devsite/telemetry_.md
index ae1f827c9e3..a351203e44a 100644
--- a/docs-devsite/telemetry_.md
+++ b/docs-devsite/telemetry_.md
@@ -27,6 +27,7 @@ https://github.com/firebase/firebase-js-sdk
 
 |  Interface | Description |
 |  --- | --- |
+|  [DynamicHeaderProvider](./telemetry_.dynamicheaderprovider.md#dynamicheaderprovider_interface) | An interface for classes that provide dynamic headers.<!-- -->Classes that implement this interface can be used to supply custom headers for logging. |
 |  [Telemetry](./telemetry_.telemetry.md#telemetry_interface) | An instance of the Firebase Telemetry SDK.<!-- -->Do not create this instance directly. Instead, use [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 |  [TelemetryOptions](./telemetry_.telemetryoptions.md#telemetryoptions_interface) | Options for initialized the Telemetry service using [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 
diff --git a/docs-devsite/telemetry_react.dynamicheaderprovider.md b/docs-devsite/telemetry_react.dynamicheaderprovider.md
new file mode 100644
index 00000000000..b9b56dd56d8
--- /dev/null
+++ b/docs-devsite/telemetry_react.dynamicheaderprovider.md
@@ -0,0 +1,43 @@
+Project: /docs/reference/js/_project.yaml
+Book: /docs/reference/_book.yaml
+page_type: reference
+
+{% comment %}
+DO NOT EDIT THIS FILE!
+This is generated by the JS SDK team, and any local changes will be
+overwritten. Changes should be made in the source code at
+https://github.com/firebase/firebase-js-sdk
+{% endcomment %}
+
+# DynamicHeaderProvider interface
+An interface for classes that provide dynamic headers.
+
+Classes that implement this interface can be used to supply custom headers for logging.
+
+<b>Signature:</b>
+
+```typescript
+export interface DynamicHeaderProvider 
+```
+
+## Methods
+
+|  Method | Description |
+|  --- | --- |
+|  [getHeader()](./telemetry_react.dynamicheaderprovider.md#dynamicheaderprovidergetheader) | Returns a record of headers to be added to a request. |
+
+## DynamicHeaderProvider.getHeader()
+
+Returns a record of headers to be added to a request.
+
+<b>Signature:</b>
+
+```typescript
+getHeader(): Promise<Record<string, string> | null>;
+```
+<b>Returns:</b>
+
+Promise&lt;Record&lt;string, string&gt; \| null&gt;
+
+A  that resolves to a  of header key-value pairs, or null if no headers are to be added.
+
diff --git a/docs-devsite/telemetry_react.md b/docs-devsite/telemetry_react.md
index 40d58284958..84d49ee790d 100644
--- a/docs-devsite/telemetry_react.md
+++ b/docs-devsite/telemetry_react.md
@@ -21,6 +21,7 @@ https://github.com/firebase/firebase-js-sdk
 
 |  Interface | Description |
 |  --- | --- |
+|  [DynamicHeaderProvider](./telemetry_react.dynamicheaderprovider.md#dynamicheaderprovider_interface) | An interface for classes that provide dynamic headers.<!-- -->Classes that implement this interface can be used to supply custom headers for logging. |
 |  [Telemetry](./telemetry_react.telemetry.md#telemetry_interface) | An instance of the Firebase Telemetry SDK.<!-- -->Do not create this instance directly. Instead, use [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 |  [TelemetryOptions](./telemetry_react.telemetryoptions.md#telemetryoptions_interface) | Options for initialized the Telemetry service using [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 
diff --git a/packages/telemetry/src/logging/appcheck-provider.ts b/packages/telemetry/src/logging/appcheck-provider.ts
new file mode 100644
index 00000000000..a961e0cccdc
--- /dev/null
+++ b/packages/telemetry/src/logging/appcheck-provider.ts
@@ -0,0 +1,51 @@
+/**
+ * @license
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *   http://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 { DynamicHeaderProvider } from '../public-types';
+import { Provider } from '@firebase/component';
+import {
+  FirebaseAppCheckInternal,
+  AppCheckInternalComponentName
+} from '@firebase/app-check-interop-types';
+
+export class AppCheckProvider implements DynamicHeaderProvider {
+  appCheck: FirebaseAppCheckInternal | null;
+
+  constructor(appCheckProvider: Provider<AppCheckInternalComponentName>) {
+    this.appCheck = appCheckProvider?.getImmediate({ optional: true });
+    if (!this.appCheck) {
+      void appCheckProvider
+        ?.get()
+        .then(appCheck => (this.appCheck = appCheck))
+        .catch();
+    }
+  }
+
+  async getHeader(): Promise<Record<string, string> | null> {
+    if (!this.appCheck) {
+      return null;
+    }
+
+    const appCheckToken = await this.appCheck.getToken();
+    // If the error field is defined, the token field will be populated with a dummy token
+    if (!appCheckToken || !!appCheckToken.error) {
+      return null;
+    }
+
+    return {'X-Firebase-AppCheck': appCheckToken.token};
+  }
+}
\ No newline at end of file
diff --git a/packages/telemetry/src/logging/fetch-transport.edge.test.ts b/packages/telemetry/src/logging/fetch-transport.edge.test.ts
index 0e954495067..464157e0f3b 100644
--- a/packages/telemetry/src/logging/fetch-transport.edge.test.ts
+++ b/packages/telemetry/src/logging/fetch-transport.edge.test.ts
@@ -20,6 +20,7 @@
 
 import * as sinon from 'sinon';
 import * as assert from 'assert';
+import { DynamicHeaderProvider } from '../public-types';
 import { FetchTransportEdge } from './fetch-transport.edge';
 import {
   ExportResponseRetryable,
@@ -173,5 +174,82 @@ describe('FetchTransportEdge', () => {
       }, done /* catch any rejections */);
       clock.tick(requestTimeout + 100);
     });
+
+    it('attaches static and dynamic headers to the request', done => {
+      // arrange
+      const fetchStub = sinon
+        .stub(globalThis, 'fetch')
+        .resolves(new Response('test response', { status: 200 }));
+
+      const dynamicProvider: DynamicHeaderProvider = {
+        getHeader: sinon.stub().resolves({ 'dynamic-header': 'dynamic-value' })
+      };
+
+      const transport = new FetchTransportEdge({
+        ...testTransportParameters,
+        dynamicHeaders: [dynamicProvider]
+      });
+
+      //act
+      transport.send(testPayload, requestTimeout).then(response => {
+        // assert
+        try {
+          assert.strictEqual(response.status, 'success');
+          sinon.assert.calledOnceWithMatch(
+            fetchStub,
+            testTransportParameters.url,
+            {
+              method: 'POST',
+              headers: {
+                foo: 'foo-value',
+                bar: 'bar-value',
+                'Content-Type': 'application/json',
+                'dynamic-header': 'dynamic-value'
+              },
+              body: testPayload
+            }
+          );
+          done();
+        } catch (e) {
+          done(e);
+        }
+      }, done /* catch any rejections */);
+    });
+
+    it('handles dynamic header providers that return null', done => {
+      // arrange
+      const fetchStub = sinon
+        .stub(globalThis, 'fetch')
+        .resolves(new Response('test response', { status: 200 }));
+
+      const dynamicProvider: DynamicHeaderProvider = {
+        getHeader: sinon.stub().resolves(null)
+      };
+
+      const transport = new FetchTransportEdge({
+        ...testTransportParameters,
+        dynamicHeaders: [dynamicProvider]
+      });
+
+      //act
+      transport.send(testPayload, requestTimeout).then(response => {
+        // assert
+        try {
+          assert.strictEqual(response.status, 'success');
+          sinon.assert.calledOnceWithMatch(
+            fetchStub,
+            testTransportParameters.url,
+            {
+              method: 'POST',
+              headers: testTransportParameters.headers(),
+              body: testPayload
+            }
+          );
+          done();
+        } catch (e) {
+          done(e);
+        }
+      }, done /* catch any rejections */);
+    });
   });
 });
diff --git a/packages/telemetry/src/logging/fetch-transport.edge.ts b/packages/telemetry/src/logging/fetch-transport.edge.ts
index 9b095b779fc..967148ecc72 100644
--- a/packages/telemetry/src/logging/fetch-transport.edge.ts
+++ b/packages/telemetry/src/logging/fetch-transport.edge.ts
@@ -23,6 +23,7 @@ import {
   ExportResponse
 } from '@opentelemetry/otlp-exporter-base';
 import { diag } from '@opentelemetry/api';
+import { DynamicHeaderProvider } from '../public-types';
 
 function isExportRetryable(statusCode: number): boolean {
   const retryCodes = [429, 502, 503, 504];
@@ -53,6 +54,7 @@ function parseRetryAfterToMills(
 export interface FetchTransportParameters {
   url: string;
   headers: () => Record<string, string>;
+  dynamicHeaders?: DynamicHeaderProvider[];
 }
 
 /**
@@ -68,9 +70,27 @@ export class FetchTransportEdge implements IExporterTransport {
     const timeout = setTimeout(() => abortController.abort(), timeoutMillis);
     try {
       const url = new URL(this.parameters.url);
+      const headers = this.parameters.headers();
+
+      if (
+        this.parameters.dynamicHeaders &&
+        this.parameters.dynamicHeaders.length > 0
+      ) {
+        const dynamicHeaderPromises = this.parameters.dynamicHeaders.map(
+          provider => provider.getHeader()
+        );
+        const resolvedHeaders = await Promise.all(dynamicHeaderPromises);
+
+        for (const header of resolvedHeaders) {
+          if (header) {
+            Object.assign(headers, header);
+          }
+        }
+      }
+
       const body = {
         method: 'POST',
-        headers: this.parameters.headers(),
+        headers,
         signal: abortController.signal,
         keepalive: false,
         mode: 'cors',
diff --git a/packages/telemetry/src/logging/logger-provider.ts b/packages/telemetry/src/logging/logger-provider.ts
index cc22e22a297..006997fb56b 100644
--- a/packages/telemetry/src/logging/logger-provider.ts
+++ b/packages/telemetry/src/logging/logger-provider.ts
@@ -23,7 +23,6 @@ import {
 } from '@opentelemetry/sdk-logs';
 import { ATTR_SERVICE_NAME } from '@opentelemetry/semantic-conventions';
 import { resourceFromAttributes } from '@opentelemetry/resources';
-import { OTLPLogExporter } from '@opentelemetry/exporter-logs-otlp-http';
 import { JsonLogsSerializer } from '@opentelemetry/otlp-transformer';
 import type { OTLPExporterConfigBase } from '@opentelemetry/otlp-exporter-base';
 import {
@@ -31,13 +30,17 @@ import {
   createOtlpNetworkExportDelegate
 } from '@opentelemetry/otlp-exporter-base';
 import { FetchTransportEdge } from './fetch-transport.edge';
+import { DynamicHeaderProvider } from '../public-types';
 
 /**
  * Create a logger provider for the current execution environment.
  *
  * @internal
  */
-export function createLoggerProvider(endpointUrl: string): LoggerProvider {
+export function createLoggerProvider(
+  endpointUrl: string,
+  dynamicHeaders: DynamicHeaderProvider[] = []
+): LoggerProvider {
   const resource = resourceFromAttributes({
     [ATTR_SERVICE_NAME]: 'firebase_telemetry_service'
   });
@@ -45,32 +48,27 @@ export function createLoggerProvider(endpointUrl: string): LoggerProvider {
     endpointUrl = endpointUrl.slice(0, -1);
   }
   const otlpEndpoint = `${endpointUrl}/api/v1/logs`;
+  const logExporter = new OTLPLogExporter(
+    { url: otlpEndpoint },
+    dynamicHeaders
+  );
 
-  if (typeof process !== 'undefined' && process?.env?.NEXT_RUNTIME === 'edge') {
-    // We need a slightly custom implementation for the Edge Runtime, because it doesn't have access
-    // to many features available in Node.
-    const logExporter = new OTLPLogExporterEdge({ url: otlpEndpoint });
-    const provider = new LoggerProvider({
-      resource,
-      processors: [new BatchLogRecordProcessor(logExporter)],
-      logRecordLimits: {}
-    });
-    return provider;
-  } else {
-    const logExporter = new OTLPLogExporter({ url: otlpEndpoint });
-    return new LoggerProvider({
-      resource,
-      processors: [new BatchLogRecordProcessor(logExporter)]
-    });
-  }
+  return new LoggerProvider({
+    resource,
+    processors: [new BatchLogRecordProcessor(logExporter)],
+    logRecordLimits: {}
+  });
 }
 
-/** OTLP exporter that uses custom FetchTransport for use in the Edge Runtime. */
-class OTLPLogExporterEdge
+/** OTLP exporter that uses custom FetchTransportEdge. */
+class OTLPLogExporter
   extends OTLPExporterBase<ReadableLogRecord[]>
   implements LogRecordExporter
 {
-  constructor(config: OTLPExporterConfigBase = {}) {
+  constructor(
+    config: OTLPExporterConfigBase = {},
+    dynamicHeaders: DynamicHeaderProvider[] = []
+  ) {
     super(
       createOtlpNetworkExportDelegate(
         {
@@ -83,7 +81,8 @@ class OTLPLogExporterEdge
           url: config.url!,
           headers: () => ({
             'Content-Type': 'application/json'
-          })
+          }),
+          dynamicHeaders
         })
       )
     );
diff --git a/packages/telemetry/src/public-types.ts b/packages/telemetry/src/public-types.ts
index 852c72221fd..a19c2fb04fa 100644
--- a/packages/telemetry/src/public-types.ts
+++ b/packages/telemetry/src/public-types.ts
@@ -47,3 +47,20 @@ export interface TelemetryOptions {
    */
   endpointUrl?: string;
 }
+
+/**
+ * An interface for classes that provide dynamic headers.
+ *
+ * Classes that implement this interface can be used to supply custom headers for logging.
+ *
+ * @public
+ */
+export interface DynamicHeaderProvider {
+  /**
+   * Returns a record of headers to be added to a request.
+   *
+   * @returns A {@link Promise} that resolves to a {@link Record<string, string>} of header
+   * key-value pairs, or null if no headers are to be added.
+   */
+  getHeader(): Promise<Record<string, string> | null>;
+}
diff --git a/packages/telemetry/src/register.node.ts b/packages/telemetry/src/register.node.ts
index 58988dd6f13..8a5b233f960 100644
--- a/packages/telemetry/src/register.node.ts
+++ b/packages/telemetry/src/register.node.ts
@@ -37,9 +37,8 @@ export function registerTelemetry(): void {
         // getImmediate for FirebaseApp will always succeed
         const app = container.getProvider('app').getImmediate();
         const loggerProvider = createLoggerProvider(endpointUrl);
-        const appCheckProvider = container.getProvider('app-check-internal');
 
-        return new TelemetryService(app, loggerProvider, appCheckProvider);
+        return new TelemetryService(app, loggerProvider);
       },
       ComponentType.PUBLIC
     ).setMultipleInstances(true)
diff --git a/packages/telemetry/src/register.ts b/packages/telemetry/src/register.ts
index 8d7fb8d5397..f410a59d8ae 100644
--- a/packages/telemetry/src/register.ts
+++ b/packages/telemetry/src/register.ts
@@ -21,6 +21,7 @@ import { TELEMETRY_TYPE } from './constants';
 import { name, version } from '../package.json';
 import { TelemetryService } from './service';
 import { createLoggerProvider } from './logging/logger-provider';
+import { AppCheckProvider } from './logging/appcheck-provider';
 
 export function registerTelemetry(): void {
   _registerComponent(
@@ -36,10 +37,14 @@ export function registerTelemetry(): void {
 
         // getImmediate for FirebaseApp will always succeed
         const app = container.getProvider('app').getImmediate();
-        const loggerProvider = createLoggerProvider(endpointUrl);
         const appCheckProvider = container.getProvider('app-check-internal');
+        const dynamicHeaders = [new AppCheckProvider(appCheckProvider)];
+        const loggerProvider = createLoggerProvider(
+          endpointUrl,
+          dynamicHeaders
+        );
 
-        return new TelemetryService(app, loggerProvider, appCheckProvider);
+        return new TelemetryService(app, loggerProvider);
       },
       ComponentType.PUBLIC
     ).setMultipleInstances(true)
diff --git a/packages/telemetry/src/service.ts b/packages/telemetry/src/service.ts
index a93059ad9fa..e09e861d3dc 100644
--- a/packages/telemetry/src/service.ts
+++ b/packages/telemetry/src/service.ts
@@ -18,23 +18,9 @@
 import { _FirebaseService, FirebaseApp } from '@firebase/app';
 import { Telemetry } from './public-types';
 import { LoggerProvider } from '@opentelemetry/sdk-logs';
-import { Provider } from '@firebase/component';
-import {
-  AppCheckInternalComponentName,
-  FirebaseAppCheckInternal
-} from '@firebase/app-check-interop-types';
 
 export class TelemetryService implements Telemetry, _FirebaseService {
-  appCheck: FirebaseAppCheckInternal | null;
-
-  constructor(
-    public app: FirebaseApp,
-    public loggerProvider: LoggerProvider,
-    appCheckProvider?: Provider<AppCheckInternalComponentName>
-  ) {
-    const appCheck = appCheckProvider?.getImmediate({ optional: true });
-    this.appCheck = appCheck || null;
-  }
+  constructor(public app: FirebaseApp, public loggerProvider: LoggerProvider) {}
 
   _delete(): Promise<void> {
     return Promise.resolve();
diff --git a/yarn.lock b/yarn.lock
index e6e4692d51e..70c7e806773 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -15718,7 +15718,7 @@ string-argv@~0.3.1:
   resolved "https://registry.npmjs.org/string-argv/-/string-argv-0.3.2.tgz#2b6d0ef24b656274d957d54e0a4bbf6153dc02b6"
   integrity sha512-aqD2Q0144Z+/RqG52NeHEkZauTAUWJO8c6yTftGJKO3Tja5tUgIfmIl6kExvhtxSDP7fXB6DvzkfMpCd/F3G+Q==
 
-"string-width-cjs@npm:string-width@^4.2.0":
+"string-width-cjs@npm:string-width@^4.2.0", "string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.0.0, string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.2, string-width@^4.2.3:
   version "4.2.3"
   resolved "https://registry.npmjs.org/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
   integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
@@ -15736,15 +15736,6 @@ string-width@^1.0.1, string-width@^1.0.2:
     is-fullwidth-code-point "^1.0.0"
     strip-ansi "^3.0.0"
 
-"string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.0.0, string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.2, string-width@^4.2.3:
-  version "4.2.3"
-  resolved "https://registry.npmjs.org/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
-  integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
-  dependencies:
-    emoji-regex "^8.0.0"
-    is-fullwidth-code-point "^3.0.0"
-    strip-ansi "^6.0.1"
-
 string-width@^2.1.1:
   version "2.1.1"
   resolved "https://registry.npmjs.org/string-width/-/string-width-2.1.1.tgz#ab93f27a8dc13d28cac815c462143a6d9012ae9e"
@@ -15808,7 +15799,7 @@ string_decoder@~1.1.1:
   dependencies:
     safe-buffer "~5.1.0"
 
-"strip-ansi-cjs@npm:strip-ansi@^6.0.1":
+"strip-ansi-cjs@npm:strip-ansi@^6.0.1", strip-ansi@^6.0.0, strip-ansi@^6.0.1:
   version "6.0.1"
   resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
   integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
@@ -15829,13 +15820,6 @@ strip-ansi@^4.0.0:
   dependencies:
     ansi-regex "^3.0.0"
 
-strip-ansi@^6.0.0, strip-ansi@^6.0.1:
-  version "6.0.1"
-  resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
-  integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
-  dependencies:
-    ansi-regex "^5.0.1"
-
 strip-ansi@^7.0.1:
   version "7.1.0"
   resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-7.1.0.tgz#d5b6568ca689d8561370b0707685d22434faff45"
@@ -17515,7 +17499,7 @@ workerpool@6.2.0:
   resolved "https://registry.npmjs.org/workerpool/-/workerpool-6.2.0.tgz#827d93c9ba23ee2019c3ffaff5c27fccea289e8b"
   integrity sha512-Rsk5qQHJ9eowMH28Jwhe8HEbmdYDX4lwoMWshiCXugjtHqMD9ZbiqSDLxcsfdqsETPzVUtX5s1Z5kStiIM6l4A==
 
-"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0":
+"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0", wrap-ansi@^7.0.0:
   version "7.0.0"
   resolved "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
   integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
@@ -17549,15 +17533,6 @@ wrap-ansi@^6.0.1, wrap-ansi@^6.2.0:
     string-width "^4.1.0"
     strip-ansi "^6.0.0"
 
-wrap-ansi@^7.0.0:
-  version "7.0.0"
-  resolved "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
-  integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
-  dependencies:
-    ansi-styles "^4.0.0"
-    string-width "^4.1.0"
-    strip-ansi "^6.0.0"
-
 wrap-ansi@^8.1.0:
   version "8.1.0"
   resolved "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-8.1.0.tgz#56dc22368ee570face1b49819975d9b9a5ead214"

From 4d071b54c1dd68432df1cffb12a5da5d95f66856 Mon Sep 17 00:00:00 2001
From: alighaznavi <alighaznavi@google.com>
Date: Fri, 10 Oct 2025 15:51:45 +0000
Subject: [PATCH 2/5] Maked DynamicHeaderProvider an internal interface and
 addresses other comments on PR

---
 common/api-review/telemetry-react.api.md      |  5 ---
 common/api-review/telemetry.api.md            |  5 ---
 docs-devsite/_toc.yaml                        |  4 --
 .../telemetry_.dynamicheaderprovider.md       | 43 -------------------
 docs-devsite/telemetry_.md                    |  1 -
 .../telemetry_react.dynamicheaderprovider.md  | 43 -------------------
 docs-devsite/telemetry_react.md               |  1 -
 .../src/logging/appcheck-provider.ts          | 14 ++++--
 ...t.edge.test.ts => fetch-transport.test.ts} | 20 ++++-----
 ...h-transport.edge.ts => fetch-transport.ts} |  6 +--
 .../telemetry/src/logging/logger-provider.ts  |  8 ++--
 packages/telemetry/src/public-types.ts        | 17 --------
 packages/telemetry/src/types.ts               | 33 ++++++++++++++
 13 files changed, 60 insertions(+), 140 deletions(-)
 delete mode 100644 docs-devsite/telemetry_.dynamicheaderprovider.md
 delete mode 100644 docs-devsite/telemetry_react.dynamicheaderprovider.md
 rename packages/telemetry/src/logging/{fetch-transport.edge.test.ts => fetch-transport.test.ts} (91%)
 rename packages/telemetry/src/logging/{fetch-transport.edge.ts => fetch-transport.ts} (94%)
 create mode 100644 packages/telemetry/src/types.ts

diff --git a/common/api-review/telemetry-react.api.md b/common/api-review/telemetry-react.api.md
index a57b8027e49..53e344cc1ab 100644
--- a/common/api-review/telemetry-react.api.md
+++ b/common/api-review/telemetry-react.api.md
@@ -8,11 +8,6 @@ import { FirebaseApp } from '@firebase/app';
 import { FirebaseOptions } from '@firebase/app';
 import { LoggerProvider } from '@opentelemetry/sdk-logs';
 
-// @public
-export interface DynamicHeaderProvider {
-    getHeader(): Promise<Record<string, string> | null>;
-}
-
 // @public
 export function FirebaseTelemetry({ firebaseOptions, telemetryOptions }: {
     firebaseOptions?: FirebaseOptions;
diff --git a/common/api-review/telemetry.api.md b/common/api-review/telemetry.api.md
index ef9fbb27ea2..6a23ce03b80 100644
--- a/common/api-review/telemetry.api.md
+++ b/common/api-review/telemetry.api.md
@@ -12,11 +12,6 @@ import { LoggerProvider } from '@opentelemetry/sdk-logs';
 // @public
 export function captureError(telemetry: Telemetry, error: unknown, attributes?: AnyValueMap): void;
 
-// @public
-export interface DynamicHeaderProvider {
-    getHeader(): Promise<Record<string, string> | null>;
-}
-
 // @public
 export function flush(telemetry: Telemetry): Promise<void>;
 
diff --git a/docs-devsite/_toc.yaml b/docs-devsite/_toc.yaml
index e0227cf3c94..81078cb2618 100644
--- a/docs-devsite/_toc.yaml
+++ b/docs-devsite/_toc.yaml
@@ -697,8 +697,6 @@ toc:
 - title: telemetry
   path: /docs/reference/js/telemetry_.md
   section:
-  - title: DynamicHeaderProvider
-    path: /docs/reference/js/telemetry_.dynamicheaderprovider.md
   - title: Telemetry
     path: /docs/reference/js/telemetry_.telemetry.md
   - title: TelemetryOptions
@@ -706,8 +704,6 @@ toc:
 - title: telemetry/react
   path: /docs/reference/js/telemetry_react.md
   section:
-  - title: DynamicHeaderProvider
-    path: /docs/reference/js/telemetry_react.dynamicheaderprovider.md
   - title: Telemetry
     path: /docs/reference/js/telemetry_react.telemetry.md
   - title: TelemetryOptions
diff --git a/docs-devsite/telemetry_.dynamicheaderprovider.md b/docs-devsite/telemetry_.dynamicheaderprovider.md
deleted file mode 100644
index e4d81fd5cd8..00000000000
--- a/docs-devsite/telemetry_.dynamicheaderprovider.md
+++ /dev/null
@@ -1,43 +0,0 @@
-Project: /docs/reference/js/_project.yaml
-Book: /docs/reference/_book.yaml
-page_type: reference
-
-{% comment %}
-DO NOT EDIT THIS FILE!
-This is generated by the JS SDK team, and any local changes will be
-overwritten. Changes should be made in the source code at
-https://github.com/firebase/firebase-js-sdk
-{% endcomment %}
-
-# DynamicHeaderProvider interface
-An interface for classes that provide dynamic headers.
-
-Classes that implement this interface can be used to supply custom headers for logging.
-
-<b>Signature:</b>
-
-```typescript
-export interface DynamicHeaderProvider 
-```
-
-## Methods
-
-|  Method | Description |
-|  --- | --- |
-|  [getHeader()](./telemetry_.dynamicheaderprovider.md#dynamicheaderprovidergetheader) | Returns a record of headers to be added to a request. |
-
-## DynamicHeaderProvider.getHeader()
-
-Returns a record of headers to be added to a request.
-
-<b>Signature:</b>
-
-```typescript
-getHeader(): Promise<Record<string, string> | null>;
-```
-<b>Returns:</b>
-
-Promise&lt;Record&lt;string, string&gt; \| null&gt;
-
-A  that resolves to a  of header key-value pairs, or null if no headers are to be added.
-
diff --git a/docs-devsite/telemetry_.md b/docs-devsite/telemetry_.md
index a351203e44a..ae1f827c9e3 100644
--- a/docs-devsite/telemetry_.md
+++ b/docs-devsite/telemetry_.md
@@ -27,7 +27,6 @@ https://github.com/firebase/firebase-js-sdk
 
 |  Interface | Description |
 |  --- | --- |
-|  [DynamicHeaderProvider](./telemetry_.dynamicheaderprovider.md#dynamicheaderprovider_interface) | An interface for classes that provide dynamic headers.<!-- -->Classes that implement this interface can be used to supply custom headers for logging. |
 |  [Telemetry](./telemetry_.telemetry.md#telemetry_interface) | An instance of the Firebase Telemetry SDK.<!-- -->Do not create this instance directly. Instead, use [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 |  [TelemetryOptions](./telemetry_.telemetryoptions.md#telemetryoptions_interface) | Options for initialized the Telemetry service using [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 
diff --git a/docs-devsite/telemetry_react.dynamicheaderprovider.md b/docs-devsite/telemetry_react.dynamicheaderprovider.md
deleted file mode 100644
index b9b56dd56d8..00000000000
--- a/docs-devsite/telemetry_react.dynamicheaderprovider.md
+++ /dev/null
@@ -1,43 +0,0 @@
-Project: /docs/reference/js/_project.yaml
-Book: /docs/reference/_book.yaml
-page_type: reference
-
-{% comment %}
-DO NOT EDIT THIS FILE!
-This is generated by the JS SDK team, and any local changes will be
-overwritten. Changes should be made in the source code at
-https://github.com/firebase/firebase-js-sdk
-{% endcomment %}
-
-# DynamicHeaderProvider interface
-An interface for classes that provide dynamic headers.
-
-Classes that implement this interface can be used to supply custom headers for logging.
-
-<b>Signature:</b>
-
-```typescript
-export interface DynamicHeaderProvider 
-```
-
-## Methods
-
-|  Method | Description |
-|  --- | --- |
-|  [getHeader()](./telemetry_react.dynamicheaderprovider.md#dynamicheaderprovidergetheader) | Returns a record of headers to be added to a request. |
-
-## DynamicHeaderProvider.getHeader()
-
-Returns a record of headers to be added to a request.
-
-<b>Signature:</b>
-
-```typescript
-getHeader(): Promise<Record<string, string> | null>;
-```
-<b>Returns:</b>
-
-Promise&lt;Record&lt;string, string&gt; \| null&gt;
-
-A  that resolves to a  of header key-value pairs, or null if no headers are to be added.
-
diff --git a/docs-devsite/telemetry_react.md b/docs-devsite/telemetry_react.md
index 84d49ee790d..40d58284958 100644
--- a/docs-devsite/telemetry_react.md
+++ b/docs-devsite/telemetry_react.md
@@ -21,7 +21,6 @@ https://github.com/firebase/firebase-js-sdk
 
 |  Interface | Description |
 |  --- | --- |
-|  [DynamicHeaderProvider](./telemetry_react.dynamicheaderprovider.md#dynamicheaderprovider_interface) | An interface for classes that provide dynamic headers.<!-- -->Classes that implement this interface can be used to supply custom headers for logging. |
 |  [Telemetry](./telemetry_react.telemetry.md#telemetry_interface) | An instance of the Firebase Telemetry SDK.<!-- -->Do not create this instance directly. Instead, use [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 |  [TelemetryOptions](./telemetry_react.telemetryoptions.md#telemetryoptions_interface) | Options for initialized the Telemetry service using [getTelemetry()](./telemetry_.md#gettelemetry_448bdc6)<!-- -->. |
 
diff --git a/packages/telemetry/src/logging/appcheck-provider.ts b/packages/telemetry/src/logging/appcheck-provider.ts
index a961e0cccdc..655b55bcfd2 100644
--- a/packages/telemetry/src/logging/appcheck-provider.ts
+++ b/packages/telemetry/src/logging/appcheck-provider.ts
@@ -15,13 +15,18 @@
  * limitations under the License.
  */
 
-import { DynamicHeaderProvider } from '../public-types';
+import { DynamicHeaderProvider } from '../types';
 import { Provider } from '@firebase/component';
 import {
   FirebaseAppCheckInternal,
   AppCheckInternalComponentName
 } from '@firebase/app-check-interop-types';
 
+/**
+ * An implementation of DynamicHeaderProvider that can be used to provide App Check token headers.
+ *
+ * @internal
+ */
 export class AppCheckProvider implements DynamicHeaderProvider {
   appCheck: FirebaseAppCheckInternal | null;
 
@@ -41,11 +46,12 @@ export class AppCheckProvider implements DynamicHeaderProvider {
     }
 
     const appCheckToken = await this.appCheck.getToken();
-    // If the error field is defined, the token field will be populated with a dummy token
+    // The error field must be checked as when there is an error, the token field is populated with
+    // a dummy error.
     if (!appCheckToken || !!appCheckToken.error) {
       return null;
     }
 
-    return {'X-Firebase-AppCheck': appCheckToken.token};
+    return { 'X-Firebase-AppCheck': appCheckToken.token };
   }
-}
\ No newline at end of file
+}
diff --git a/packages/telemetry/src/logging/fetch-transport.edge.test.ts b/packages/telemetry/src/logging/fetch-transport.test.ts
similarity index 91%
rename from packages/telemetry/src/logging/fetch-transport.edge.test.ts
rename to packages/telemetry/src/logging/fetch-transport.test.ts
index 464157e0f3b..a3ae5501a7e 100644
--- a/packages/telemetry/src/logging/fetch-transport.edge.test.ts
+++ b/packages/telemetry/src/logging/fetch-transport.test.ts
@@ -20,8 +20,8 @@
 
 import * as sinon from 'sinon';
 import * as assert from 'assert';
-import { DynamicHeaderProvider } from '../public-types';
-import { FetchTransportEdge } from './fetch-transport.edge';
+import { DynamicHeaderProvider } from '../types';
+import { FetchTransport } from './fetch-transport';
 import {
   ExportResponseRetryable,
   ExportResponseFailure,
@@ -40,7 +40,7 @@ const testTransportParameters = {
 const requestTimeout = 1000;
 const testPayload = Uint8Array.from([1, 2, 3]);
 
-describe('FetchTransportEdge', () => {
+describe('FetchTransport', () => {
   afterEach(() => {
     sinon.restore();
   });
@@ -51,7 +51,7 @@ describe('FetchTransportEdge', () => {
       const fetchStub = sinon
         .stub(globalThis, 'fetch')
         .resolves(new Response('test response', { status: 200 }));
-      const transport = new FetchTransportEdge(testTransportParameters);
+      const transport = new FetchTransport(testTransportParameters);
 
       //act
       transport.send(testPayload, requestTimeout).then(response => {
@@ -88,7 +88,7 @@ describe('FetchTransportEdge', () => {
       sinon
         .stub(globalThis, 'fetch')
         .resolves(new Response('', { status: 404 }));
-      const transport = new FetchTransportEdge(testTransportParameters);
+      const transport = new FetchTransport(testTransportParameters);
 
       //act
       transport.send(testPayload, requestTimeout).then(response => {
@@ -109,7 +109,7 @@ describe('FetchTransportEdge', () => {
         .resolves(
           new Response('', { status: 503, headers: { 'Retry-After': '5' } })
         );
-      const transport = new FetchTransportEdge(testTransportParameters);
+      const transport = new FetchTransport(testTransportParameters);
 
       //act
       transport.send(testPayload, requestTimeout).then(response => {
@@ -133,7 +133,7 @@ describe('FetchTransportEdge', () => {
       abortError.name = 'AbortError';
       sinon.stub(globalThis, 'fetch').rejects(abortError);
       const clock = sinon.useFakeTimers();
-      const transport = new FetchTransportEdge(testTransportParameters);
+      const transport = new FetchTransport(testTransportParameters);
 
       //act
       transport.send(testPayload, requestTimeout).then(response => {
@@ -156,7 +156,7 @@ describe('FetchTransportEdge', () => {
       // arrange
       sinon.stub(globalThis, 'fetch').throws(new Error('fetch failed'));
       const clock = sinon.useFakeTimers();
-      const transport = new FetchTransportEdge(testTransportParameters);
+      const transport = new FetchTransport(testTransportParameters);
 
       //act
       transport.send(testPayload, requestTimeout).then(response => {
@@ -185,7 +185,7 @@ describe('FetchTransportEdge', () => {
         getHeader: sinon.stub().resolves({ 'dynamic-header': 'dynamic-value' })
       };
 
-      const transport = new FetchTransportEdge({
+      const transport = new FetchTransport({
         ...testTransportParameters,
         dynamicHeaders: [dynamicProvider]
       });
@@ -226,7 +226,7 @@ describe('FetchTransportEdge', () => {
         getHeader: sinon.stub().resolves(null)
       };
 
-      const transport = new FetchTransportEdge({
+      const transport = new FetchTransport({
         ...testTransportParameters,
         dynamicHeaders: [dynamicProvider]
       });
diff --git a/packages/telemetry/src/logging/fetch-transport.edge.ts b/packages/telemetry/src/logging/fetch-transport.ts
similarity index 94%
rename from packages/telemetry/src/logging/fetch-transport.edge.ts
rename to packages/telemetry/src/logging/fetch-transport.ts
index 967148ecc72..ad5a4b253a7 100644
--- a/packages/telemetry/src/logging/fetch-transport.edge.ts
+++ b/packages/telemetry/src/logging/fetch-transport.ts
@@ -23,7 +23,7 @@ import {
   ExportResponse
 } from '@opentelemetry/otlp-exporter-base';
 import { diag } from '@opentelemetry/api';
-import { DynamicHeaderProvider } from '../public-types';
+import { DynamicHeaderProvider } from '../types';
 
 function isExportRetryable(statusCode: number): boolean {
   const retryCodes = [429, 502, 503, 504];
@@ -58,11 +58,11 @@ export interface FetchTransportParameters {
 }
 
 /**
- * An implementation of IExporterTransport that can be used in the Edge Runtime.
+ * An implementation of IExporterTransport.
  *
  * @internal
  */
-export class FetchTransportEdge implements IExporterTransport {
+export class FetchTransport implements IExporterTransport {
   constructor(private parameters: FetchTransportParameters) {}
 
   async send(data: Uint8Array, timeoutMillis: number): Promise<ExportResponse> {
diff --git a/packages/telemetry/src/logging/logger-provider.ts b/packages/telemetry/src/logging/logger-provider.ts
index 006997fb56b..24a626e11a9 100644
--- a/packages/telemetry/src/logging/logger-provider.ts
+++ b/packages/telemetry/src/logging/logger-provider.ts
@@ -29,8 +29,8 @@ import {
   OTLPExporterBase,
   createOtlpNetworkExportDelegate
 } from '@opentelemetry/otlp-exporter-base';
-import { FetchTransportEdge } from './fetch-transport.edge';
-import { DynamicHeaderProvider } from '../public-types';
+import { FetchTransport } from './fetch-transport';
+import { DynamicHeaderProvider } from '../types';
 
 /**
  * Create a logger provider for the current execution environment.
@@ -60,7 +60,7 @@ export function createLoggerProvider(
   });
 }
 
-/** OTLP exporter that uses custom FetchTransportEdge. */
+/** OTLP exporter that uses custom FetchTransport. */
 class OTLPLogExporter
   extends OTLPExporterBase<ReadableLogRecord[]>
   implements LogRecordExporter
@@ -77,7 +77,7 @@ class OTLPLogExporter
           compression: 'none'
         },
         JsonLogsSerializer,
-        new FetchTransportEdge({
+        new FetchTransport({
           url: config.url!,
           headers: () => ({
             'Content-Type': 'application/json'
diff --git a/packages/telemetry/src/public-types.ts b/packages/telemetry/src/public-types.ts
index a19c2fb04fa..852c72221fd 100644
--- a/packages/telemetry/src/public-types.ts
+++ b/packages/telemetry/src/public-types.ts
@@ -47,20 +47,3 @@ export interface TelemetryOptions {
    */
   endpointUrl?: string;
 }
-
-/**
- * An interface for classes that provide dynamic headers.
- *
- * Classes that implement this interface can be used to supply custom headers for logging.
- *
- * @public
- */
-export interface DynamicHeaderProvider {
-  /**
-   * Returns a record of headers to be added to a request.
-   *
-   * @returns A {@link Promise} that resolves to a {@link Record<string, string>} of header
-   * key-value pairs, or null if no headers are to be added.
-   */
-  getHeader(): Promise<Record<string, string> | null>;
-}
diff --git a/packages/telemetry/src/types.ts b/packages/telemetry/src/types.ts
new file mode 100644
index 00000000000..f1041e5dbc9
--- /dev/null
+++ b/packages/telemetry/src/types.ts
@@ -0,0 +1,33 @@
+/**
+ * @license
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *   http://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.
+ */
+
+/**
+ * An interface for classes that provide dynamic headers.
+ *
+ * Classes that implement this interface can be used to supply custom headers for logging.
+ *
+ * @internal
+ */
+export interface DynamicHeaderProvider {
+  /**
+   * Returns a record of headers to be added to a request.
+   *
+   * @returns A {@link Promise} that resolves to a {@link Record<string, string>} of header
+   * key-value pairs, or null if no headers are to be added.
+   */
+  getHeader(): Promise<Record<string, string> | null>;
+}

From 10fa5b631c4b0a3e71e122457ccbbf6be594d45a Mon Sep 17 00:00:00 2001
From: alighaznavi <alighaznavi@google.com>
Date: Fri, 10 Oct 2025 15:56:59 +0000
Subject: [PATCH 3/5] Fix typo in comment

---
 packages/telemetry/src/logging/appcheck-provider.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/telemetry/src/logging/appcheck-provider.ts b/packages/telemetry/src/logging/appcheck-provider.ts
index 655b55bcfd2..e2e0b199ebb 100644
--- a/packages/telemetry/src/logging/appcheck-provider.ts
+++ b/packages/telemetry/src/logging/appcheck-provider.ts
@@ -47,7 +47,7 @@ export class AppCheckProvider implements DynamicHeaderProvider {
 
     const appCheckToken = await this.appCheck.getToken();
     // The error field must be checked as when there is an error, the token field is populated with
-    // a dummy error.
+    // a dummy token.
     if (!appCheckToken || !!appCheckToken.error) {
       return null;
     }

From 97888a25312cbbf9e8719ff36b5f0df8d81230bc Mon Sep 17 00:00:00 2001
From: alighaznavi <alighaznavi@google.com>
Date: Tue, 14 Oct 2025 15:41:53 +0000
Subject: [PATCH 4/5] Use the Headers object for better typing

---
 .../telemetry/src/logging/appcheck-provider.ts     |  6 +++---
 .../telemetry/src/logging/fetch-transport.test.ts  | 14 +++++++-------
 packages/telemetry/src/logging/fetch-transport.ts  |  6 +++---
 packages/telemetry/src/logging/logger-provider.ts  |  2 +-
 packages/telemetry/src/types.ts                    |  9 ++++++++-
 5 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/packages/telemetry/src/logging/appcheck-provider.ts b/packages/telemetry/src/logging/appcheck-provider.ts
index e2e0b199ebb..a0a7e78d501 100644
--- a/packages/telemetry/src/logging/appcheck-provider.ts
+++ b/packages/telemetry/src/logging/appcheck-provider.ts
@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-import { DynamicHeaderProvider } from '../types';
+import { DynamicHeaderProvider, HttpHeader } from '../types';
 import { Provider } from '@firebase/component';
 import {
   FirebaseAppCheckInternal,
@@ -40,7 +40,7 @@ export class AppCheckProvider implements DynamicHeaderProvider {
     }
   }
 
-  async getHeader(): Promise<Record<string, string> | null> {
+  async getHeader(): Promise<HttpHeader | null> {
     if (!this.appCheck) {
       return null;
     }
@@ -52,6 +52,6 @@ export class AppCheckProvider implements DynamicHeaderProvider {
       return null;
     }
 
-    return { 'X-Firebase-AppCheck': appCheckToken.token };
+    return ['X-Firebase-AppCheck', appCheckToken.token];
   }
 }
diff --git a/packages/telemetry/src/logging/fetch-transport.test.ts b/packages/telemetry/src/logging/fetch-transport.test.ts
index a3ae5501a7e..d13b6ed9534 100644
--- a/packages/telemetry/src/logging/fetch-transport.test.ts
+++ b/packages/telemetry/src/logging/fetch-transport.test.ts
@@ -30,7 +30,7 @@ import {
 
 const testTransportParameters = {
   url: 'http://example.test',
-  headers: () => ({
+  headers: new Headers({
     foo: 'foo-value',
     bar: 'bar-value',
     'Content-Type': 'application/json'
@@ -68,11 +68,11 @@ describe('FetchTransport', () => {
             testTransportParameters.url,
             {
               method: 'POST',
-              headers: {
+              headers: new Headers({
                 foo: 'foo-value',
                 bar: 'bar-value',
                 'Content-Type': 'application/json'
-              },
+              }),
               body: testPayload
             }
           );
@@ -182,7 +182,7 @@ describe('FetchTransport', () => {
         .resolves(new Response('test response', { status: 200 }));
 
       const dynamicProvider: DynamicHeaderProvider = {
-        getHeader: sinon.stub().resolves({ 'dynamic-header': 'dynamic-value' })
+        getHeader: sinon.stub().resolves(['dynamic-header', 'dynamic-value'])
       };
 
       const transport = new FetchTransport({
@@ -200,12 +200,12 @@ describe('FetchTransport', () => {
             testTransportParameters.url,
             {
               method: 'POST',
-              headers: {
+              headers: new Headers({
                 foo: 'foo-value',
                 bar: 'bar-value',
                 'Content-Type': 'application/json',
                 'dynamic-header': 'dynamic-value'
-              },
+              }),
               body: testPayload
             }
           );
@@ -241,7 +241,7 @@ describe('FetchTransport', () => {
             testTransportParameters.url,
             {
               method: 'POST',
-              headers: testTransportParameters.headers(),
+              headers: testTransportParameters.headers,
               body: testPayload
             }
           );
diff --git a/packages/telemetry/src/logging/fetch-transport.ts b/packages/telemetry/src/logging/fetch-transport.ts
index ad5a4b253a7..f27a9fc90d4 100644
--- a/packages/telemetry/src/logging/fetch-transport.ts
+++ b/packages/telemetry/src/logging/fetch-transport.ts
@@ -53,7 +53,7 @@ function parseRetryAfterToMills(
 /** @internal */
 export interface FetchTransportParameters {
   url: string;
-  headers: () => Record<string, string>;
+  headers: Headers;
   dynamicHeaders?: DynamicHeaderProvider[];
 }
 
@@ -70,7 +70,7 @@ export class FetchTransport implements IExporterTransport {
     const timeout = setTimeout(() => abortController.abort(), timeoutMillis);
     try {
       const url = new URL(this.parameters.url);
-      const headers = this.parameters.headers();
+      const headers = this.parameters.headers;
 
       if (
         this.parameters.dynamicHeaders &&
@@ -83,7 +83,7 @@ export class FetchTransport implements IExporterTransport {
 
         for (const header of resolvedHeaders) {
           if (header) {
-            Object.assign(headers, header);
+            headers.append(...header);
           }
         }
       }
diff --git a/packages/telemetry/src/logging/logger-provider.ts b/packages/telemetry/src/logging/logger-provider.ts
index 24a626e11a9..cf6a02f22a2 100644
--- a/packages/telemetry/src/logging/logger-provider.ts
+++ b/packages/telemetry/src/logging/logger-provider.ts
@@ -79,7 +79,7 @@ class OTLPLogExporter
         JsonLogsSerializer,
         new FetchTransport({
           url: config.url!,
-          headers: () => ({
+          headers: new Headers({
             'Content-Type': 'application/json'
           }),
           dynamicHeaders
diff --git a/packages/telemetry/src/types.ts b/packages/telemetry/src/types.ts
index f1041e5dbc9..95c517148cb 100644
--- a/packages/telemetry/src/types.ts
+++ b/packages/telemetry/src/types.ts
@@ -15,6 +15,13 @@
  * limitations under the License.
  */
 
+/**
+ * A type for HTTP Headers
+ *
+ * @internal
+ */
+export type HttpHeader = [key: string, value: string];
+
 /**
  * An interface for classes that provide dynamic headers.
  *
@@ -29,5 +36,5 @@ export interface DynamicHeaderProvider {
    * @returns A {@link Promise} that resolves to a {@link Record<string, string>} of header
    * key-value pairs, or null if no headers are to be added.
    */
-  getHeader(): Promise<Record<string, string> | null>;
+  getHeader(): Promise<HttpHeader | null>;
 }

From 4c0ebfed56fe777abc9c2741e717f8e849d1adb6 Mon Sep 17 00:00:00 2001
From: alighaznavi <alighaznavi@google.com>
Date: Tue, 14 Oct 2025 15:51:12 +0000
Subject: [PATCH 5/5] Revert changes in yarn.lock

---
 yarn.lock | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/yarn.lock b/yarn.lock
index 70c7e806773..e6e4692d51e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -15718,7 +15718,7 @@ string-argv@~0.3.1:
   resolved "https://registry.npmjs.org/string-argv/-/string-argv-0.3.2.tgz#2b6d0ef24b656274d957d54e0a4bbf6153dc02b6"
   integrity sha512-aqD2Q0144Z+/RqG52NeHEkZauTAUWJO8c6yTftGJKO3Tja5tUgIfmIl6kExvhtxSDP7fXB6DvzkfMpCd/F3G+Q==
 
-"string-width-cjs@npm:string-width@^4.2.0", "string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.0.0, string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.2, string-width@^4.2.3:
+"string-width-cjs@npm:string-width@^4.2.0":
   version "4.2.3"
   resolved "https://registry.npmjs.org/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
   integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
@@ -15736,6 +15736,15 @@ string-width@^1.0.1, string-width@^1.0.2:
     is-fullwidth-code-point "^1.0.0"
     strip-ansi "^3.0.0"
 
+"string-width@^1.0.2 || 2 || 3 || 4", string-width@^4.0.0, string-width@^4.1.0, string-width@^4.2.0, string-width@^4.2.2, string-width@^4.2.3:
+  version "4.2.3"
+  resolved "https://registry.npmjs.org/string-width/-/string-width-4.2.3.tgz#269c7117d27b05ad2e536830a8ec895ef9c6d010"
+  integrity sha512-wKyQRQpjJ0sIp62ErSZdGsjMJWsap5oRNihHhu6G7JVO/9jIB6UyevL+tXuOqrng8j/cxKTWyWUwvSTriiZz/g==
+  dependencies:
+    emoji-regex "^8.0.0"
+    is-fullwidth-code-point "^3.0.0"
+    strip-ansi "^6.0.1"
+
 string-width@^2.1.1:
   version "2.1.1"
   resolved "https://registry.npmjs.org/string-width/-/string-width-2.1.1.tgz#ab93f27a8dc13d28cac815c462143a6d9012ae9e"
@@ -15799,7 +15808,7 @@ string_decoder@~1.1.1:
   dependencies:
     safe-buffer "~5.1.0"
 
-"strip-ansi-cjs@npm:strip-ansi@^6.0.1", strip-ansi@^6.0.0, strip-ansi@^6.0.1:
+"strip-ansi-cjs@npm:strip-ansi@^6.0.1":
   version "6.0.1"
   resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
   integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
@@ -15820,6 +15829,13 @@ strip-ansi@^4.0.0:
   dependencies:
     ansi-regex "^3.0.0"
 
+strip-ansi@^6.0.0, strip-ansi@^6.0.1:
+  version "6.0.1"
+  resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.1.tgz#9e26c63d30f53443e9489495b2105d37b67a85d9"
+  integrity sha512-Y38VPSHcqkFrCpFnQ9vuSXmquuv5oXOKpGeT6aGrr3o3Gc9AlVa6JBfUSOCnbxGGZF+/0ooI7KrPuUSztUdU5A==
+  dependencies:
+    ansi-regex "^5.0.1"
+
 strip-ansi@^7.0.1:
   version "7.1.0"
   resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-7.1.0.tgz#d5b6568ca689d8561370b0707685d22434faff45"
@@ -17499,7 +17515,7 @@ workerpool@6.2.0:
   resolved "https://registry.npmjs.org/workerpool/-/workerpool-6.2.0.tgz#827d93c9ba23ee2019c3ffaff5c27fccea289e8b"
   integrity sha512-Rsk5qQHJ9eowMH28Jwhe8HEbmdYDX4lwoMWshiCXugjtHqMD9ZbiqSDLxcsfdqsETPzVUtX5s1Z5kStiIM6l4A==
 
-"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0", wrap-ansi@^7.0.0:
+"wrap-ansi-cjs@npm:wrap-ansi@^7.0.0":
   version "7.0.0"
   resolved "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
   integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
@@ -17533,6 +17549,15 @@ wrap-ansi@^6.0.1, wrap-ansi@^6.2.0:
     string-width "^4.1.0"
     strip-ansi "^6.0.0"
 
+wrap-ansi@^7.0.0:
+  version "7.0.0"
+  resolved "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-7.0.0.tgz#67e145cff510a6a6984bdf1152911d69d2eb9e43"
+  integrity sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==
+  dependencies:
+    ansi-styles "^4.0.0"
+    string-width "^4.1.0"
+    strip-ansi "^6.0.0"
+
 wrap-ansi@^8.1.0:
   version "8.1.0"
   resolved "https://registry.npmjs.org/wrap-ansi/-/wrap-ansi-8.1.0.tgz#56dc22368ee570face1b49819975d9b9a5ead214"