diff --git a/apps/browser/src/background/main.background.ts b/apps/browser/src/background/main.background.ts
index 65477bda975..e139e880c21 100644
--- a/apps/browser/src/background/main.background.ts
+++ b/apps/browser/src/background/main.background.ts
@@ -1374,12 +1374,10 @@ export default class MainBackground {
       this.keyService,
       this.encryptService,
       this.cryptoFunctionService,
-      this.runtimeBackground,
       this.messagingService,
       this.appIdService,
       this.platformUtilsService,
       this.logService,
-      this.authService,
       this.biometricStateService,
       this.accountService,
     );
diff --git a/apps/browser/src/background/native-messaging.background.spec.ts b/apps/browser/src/background/native-messaging.background.spec.ts
new file mode 100644
index 00000000000..971aa36d010
--- /dev/null
+++ b/apps/browser/src/background/native-messaging.background.spec.ts
@@ -0,0 +1,480 @@
+import { mock, MockProxy } from "jest-mock-extended";
+import { of } from "rxjs";
+
+import { Account, AccountService } from "@bitwarden/common/auth/abstractions/account.service";
+import { CryptoFunctionService } from "@bitwarden/common/key-management/crypto/abstractions/crypto-function.service";
+import { EncryptService } from "@bitwarden/common/key-management/crypto/abstractions/encrypt.service";
+import { EncString } from "@bitwarden/common/key-management/crypto/models/enc-string";
+import { AppIdService } from "@bitwarden/common/platform/abstractions/app-id.service";
+import { LogService } from "@bitwarden/common/platform/abstractions/log.service";
+import { MessagingService } from "@bitwarden/common/platform/abstractions/messaging.service";
+import { PlatformUtilsService } from "@bitwarden/common/platform/abstractions/platform-utils.service";
+import { SymmetricCryptoKey } from "@bitwarden/common/platform/models/domain/symmetric-crypto-key";
+import { KeyService, BiometricStateService } from "@bitwarden/key-management";
+import { UserId } from "@bitwarden/user-core";
+
+import { BrowserApi } from "../platform/browser/browser-api";
+
+import { NativeMessagingBackground } from "./nativeMessaging.background";
+
+// Mock BrowserApi
+jest.mock("../platform/browser/browser-api");
+
+describe("NativeMessagingBackground", () => {
+  let sut: NativeMessagingBackground;
+  let keyService: MockProxy<KeyService>;
+  let encryptService: MockProxy<EncryptService>;
+  let cryptoFunctionService: MockProxy<CryptoFunctionService>;
+  let messagingService: MockProxy<MessagingService>;
+  let appIdService: MockProxy<AppIdService>;
+  let platformUtilsService: MockProxy<PlatformUtilsService>;
+  let logService: MockProxy<LogService>;
+  let biometricStateService: MockProxy<BiometricStateService>;
+  let accountService: MockProxy<AccountService>;
+
+  const mockAppId = "test-app-id";
+  const mockUserId = "test-user-id" as UserId;
+  const mockAccount: Account = {
+    id: mockUserId,
+    email: "test@example.com",
+    name: "Test User",
+    emailVerified: true,
+    creationDate: new Date(),
+  };
+
+  const mockSharedSecret = new SymmetricCryptoKey(new Uint8Array(64));
+  const mockSecureChannel = {
+    publicKey: new Uint8Array(64),
+    privateKey: new Uint8Array(64),
+    sharedSecret: mockSharedSecret,
+  };
+
+  function expectDisconnectedState() {
+    expect(sut.connected).toBe(false);
+    expect((sut as any).connecting).toBe(false);
+    expect((sut as any).secureChannel).toBeUndefined();
+  }
+
+  function setCallback(id: number, rejecter: jest.Mock) {
+    (sut as any).callbacks.set(id, { resolver: jest.fn(), rejecter });
+  }
+
+  beforeEach(() => {
+    keyService = mock<KeyService>();
+    encryptService = mock<EncryptService>();
+    cryptoFunctionService = mock<CryptoFunctionService>();
+    messagingService = mock<MessagingService>();
+    appIdService = mock<AppIdService>();
+    platformUtilsService = mock<PlatformUtilsService>();
+    logService = mock<LogService>();
+    biometricStateService = mock<BiometricStateService>();
+    accountService = mock<AccountService>();
+
+    appIdService.getAppId.mockResolvedValue(mockAppId);
+    accountService.activeAccount$ = of(mockAccount);
+    platformUtilsService.isSafari.mockReturnValue(false);
+
+    (BrowserApi.permissionsGranted as jest.Mock).mockResolvedValue(true);
+    (BrowserApi.connectNative as jest.Mock).mockReturnValue({
+      onMessage: {
+        addListener: jest.fn(),
+      },
+      onDisconnect: {
+        addListener: jest.fn(),
+      },
+      postMessage: jest.fn(),
+      disconnect: jest.fn(),
+    });
+
+    sut = new NativeMessagingBackground(
+      keyService,
+      encryptService,
+      cryptoFunctionService,
+      messagingService,
+      appIdService,
+      platformUtilsService,
+      logService,
+      biometricStateService,
+      accountService,
+    );
+  });
+
+  describe("constructor", () => {
+    it("creates instance with expected values", () => {
+      expect(sut).toBeDefined();
+      expect(sut.connected).toBe(false);
+      expect((sut as any).connecting).toBe(false);
+    });
+  });
+
+  describe("connect", () => {
+    it("logs warning and returns if native messaging permission is missing", async () => {
+      (BrowserApi.permissionsGranted as jest.Mock).mockResolvedValue(false);
+
+      await sut.connect();
+
+      expect(logService.warning).toHaveBeenCalledWith(
+        "[Native Messaging IPC] Native messaging permission is missing for biometrics",
+      );
+      expect(sut.connected).toBe(false);
+    });
+
+    it("connects immediately for Safari", async () => {
+      platformUtilsService.isSafari.mockReturnValue(true);
+
+      await sut.connect();
+
+      expect(sut.connected).toBe(true);
+      expect(logService.info).toHaveBeenCalledWith(
+        "[Native Messaging IPC] Connection to Safari swift module established!",
+      );
+    });
+  });
+
+  describe("port listeners", () => {
+    let connectPromise: Promise<void>;
+    let messageListener: (msg: unknown) => Promise<void>;
+    let disconnectListener: (p: any) => void;
+    let mockPort: {
+      onMessage: { addListener: jest.Mock };
+      onDisconnect: { addListener: jest.Mock };
+      postMessage: jest.Mock;
+      disconnect: jest.Mock;
+    };
+
+    beforeEach(async () => {
+      mockPort = {
+        onMessage: {
+          addListener: jest.fn((fn) => {
+            messageListener = fn;
+          }),
+        },
+        onDisconnect: {
+          addListener: jest.fn((fn) => {
+            disconnectListener = fn;
+          }),
+        },
+        postMessage: jest.fn(),
+        disconnect: jest.fn(),
+      };
+      (BrowserApi.connectNative as jest.Mock).mockReturnValue(mockPort);
+      platformUtilsService.isSafari.mockReturnValue(false);
+
+      connectPromise = sut.connect() as Promise<void>;
+    });
+
+    afterEach(() => {
+      (chrome.runtime as any).lastError = undefined;
+      (BrowserApi as any).isWebExtensionsApi = undefined;
+    });
+
+    describe("port.onMessage listener", () => {
+      describe("'connected' command", () => {
+        it("sets expected internal state values", async () => {
+          await messageListener({ command: "connected" });
+
+          expect(sut.connected).toBe(true);
+          expect((sut as any).connecting).toBe(false);
+          expect(logService.info).toHaveBeenCalledWith(
+            "[Native Messaging IPC] Connection to Bitwarden Desktop app established!",
+          );
+        });
+      });
+
+      describe("'disconnected' command", () => {
+        it("logs disconnection info message", async () => {
+          await messageListener({ command: "disconnected" });
+
+          expect(logService.info).toHaveBeenCalledWith(
+            "[Native Messaging IPC] Disconnected from Bitwarden Desktop app.",
+          );
+        });
+
+        it("rejects with Error('startDesktop') when still connecting", async () => {
+          await messageListener({ command: "disconnected" });
+
+          await expect(connectPromise).rejects.toThrow("startDesktop");
+        });
+
+        it("does not reject connect() Promise with startDesktop when not connecting", async () => {
+          (sut as any).connecting = false;
+
+          await messageListener({ command: "disconnected" });
+
+          const result = await Promise.race([
+            connectPromise.then(
+              () => "resolved",
+              (e: Error) => `rejected:${e.message}`,
+            ),
+            Promise.resolve("pending"),
+          ]);
+
+          expect(result).toBe("pending");
+        });
+
+        it("calls disconnect() to clean up internal state", async () => {
+          const disconnectSpy = jest.spyOn(sut as any, "disconnect");
+
+          await messageListener({ command: "disconnected" });
+
+          expect(disconnectSpy).toHaveBeenCalled();
+          expectDisconnectedState();
+          expect(mockPort.disconnect).toHaveBeenCalled();
+        });
+
+        it("rejects all pending callbacks with 'disconnected' and clears internal callbacks", async () => {
+          const rejecter1 = jest.fn();
+          const rejecter2 = jest.fn();
+          setCallback(1, rejecter1);
+          setCallback(2, rejecter2);
+
+          await messageListener({ command: "disconnected" });
+
+          expect(rejecter1).toHaveBeenCalledWith("disconnected");
+          expect(rejecter2).toHaveBeenCalledWith("disconnected");
+          expect((sut as any).callbacks.size).toBe(0);
+        });
+
+        it("clears callbacks even when none are pending", async () => {
+          const clearSpy = jest.spyOn((sut as any).callbacks, "clear");
+
+          await messageListener({ command: "disconnected" });
+
+          expect(clearSpy).toHaveBeenCalled();
+          expect((sut as any).callbacks.size).toBe(0);
+        });
+      });
+
+      describe("'invalidateEncryption' command", () => {
+        it("ignores message with non-matching appId", async () => {
+          const disconnectSpy = jest.spyOn(sut as any, "disconnect");
+
+          await messageListener({ command: "invalidateEncryption", appId: "other-app-id" });
+
+          expect(logService.warning).not.toHaveBeenCalled();
+          expect(disconnectSpy).not.toHaveBeenCalled();
+        });
+
+        it("logs warning when appId matches", async () => {
+          await messageListener({ command: "invalidateEncryption", appId: mockAppId });
+
+          expect(logService.warning).toHaveBeenCalledWith(
+            "[Native Messaging IPC] Secure channel encountered an error; disconnecting and wiping keys...",
+          );
+        });
+
+        it("calls disconnect() to clean up internal state", async () => {
+          const disconnectSpy = jest.spyOn(sut as any, "disconnect");
+
+          await messageListener({ command: "invalidateEncryption", appId: mockAppId });
+
+          expect(disconnectSpy).toHaveBeenCalled();
+          expectDisconnectedState();
+          expect(mockPort.disconnect).toHaveBeenCalled();
+        });
+
+        it("rejects the matching callback with invalidateEncryption error", async () => {
+          const rejecter = jest.fn();
+          setCallback(1, rejecter);
+
+          await messageListener({
+            command: "invalidateEncryption",
+            appId: mockAppId,
+            messageId: 1,
+          });
+
+          expect(rejecter).toHaveBeenCalledWith({ message: "invalidateEncryption" });
+        });
+
+        it("does not reject a callback with a non-matching messageId", async () => {
+          const rejecter = jest.fn();
+          setCallback(2, rejecter);
+
+          await messageListener({
+            command: "invalidateEncryption",
+            appId: mockAppId,
+            messageId: 1,
+          });
+
+          expect(rejecter).not.toHaveBeenCalled();
+        });
+
+        it("does not reject any callback when messageId is absent", async () => {
+          const rejecter = jest.fn();
+          setCallback(1, rejecter);
+
+          await messageListener({ command: "invalidateEncryption", appId: mockAppId });
+
+          expect(rejecter).not.toHaveBeenCalled();
+        });
+      });
+    });
+
+    describe("port.onDisconnect listener", () => {
+      beforeEach(() => {
+        (BrowserApi as any).isWebExtensionsApi = true;
+      });
+
+      it("reads error message from listener on WebExtensions API", async () => {
+        disconnectListener({ error: { message: "webext error" } });
+
+        expect(logService.error).toHaveBeenCalledWith(
+          "NativeMessaging port disconnected because of error: webext error",
+        );
+      });
+
+      it("reads error message from chrome runtime on Chrome API", async () => {
+        (BrowserApi as any).isWebExtensionsApi = false;
+        (chrome.runtime as any).lastError = { message: "chrome error" };
+
+        disconnectListener({});
+
+        expect(logService.error).toHaveBeenCalledWith(
+          "NativeMessaging port disconnected because of error: chrome error",
+        );
+      });
+
+      it("clears secureChannel, connected, and connecting", async () => {
+        (sut as any).connected = true;
+        (sut as any).connecting = true;
+        (sut as any).secureChannel = mockSecureChannel;
+
+        disconnectListener({ error: { message: "error" } });
+
+        expectDisconnectedState();
+      });
+
+      it("rejects with 'desktopIntegrationDisabled' when error is present", async () => {
+        disconnectListener({ error: { message: "some error" } });
+
+        await expect(connectPromise).rejects.toThrow("desktopIntegrationDisabled");
+      });
+
+      it("rejects with an empty message when no error is present", async () => {
+        disconnectListener({ error: { message: undefined } });
+
+        const err = await connectPromise.catch((e: Error) => e);
+        expect(err instanceof Error ? err.message : "").toBe("");
+      });
+    });
+  });
+
+  describe("encryptMessage", () => {
+    it("encrypts message with existing shared secret", async () => {
+      const mockEncryptedString = new EncString("encrypted-data");
+
+      (sut as any).secureChannel = mockSecureChannel;
+
+      encryptService.encryptString.mockResolvedValue(mockEncryptedString);
+
+      const message = { command: "test", userId: mockUserId, timestamp: Date.now() };
+      const result = await sut.encryptMessage(message);
+
+      expect(encryptService.encryptString).toHaveBeenCalledWith(
+        JSON.stringify(message),
+        mockSharedSecret,
+      );
+      expect(result).toBe(mockEncryptedString);
+    });
+  });
+
+  describe("send", () => {
+    const message: any = { command: "test" };
+
+    beforeEach(() => {
+      platformUtilsService.isSafari.mockReturnValue(true);
+      jest.spyOn(sut as any, "connect").mockResolvedValue(undefined);
+      jest.spyOn(sut as any, "postMessage").mockImplementation(() => {});
+    });
+
+    it("connects before sending if not already connected", async () => {
+      sut.connected = false;
+
+      await sut.send(message);
+
+      expect((sut as any).connect).toHaveBeenCalled();
+      expect((sut as any).postMessage).toHaveBeenCalledWith(message);
+    });
+
+    it("adds user ID and timestamp to message", async () => {
+      (sut as any).connected = true;
+
+      await sut.send(message);
+
+      expect(message.userId).toBe(mockUserId);
+      expect(message.timestamp).toBeDefined();
+    });
+
+    describe("with mock port", () => {
+      let mockPort: {
+        postMessage: jest.Mock;
+        disconnect: jest.Mock;
+      };
+      const mockEncString = new EncString("2.testIv|testData|testMac");
+
+      beforeEach(() => {
+        // Restore the postMessage spy set up in the outer beforeEach so the real implementation runs
+        jest.restoreAllMocks();
+
+        mockPort = {
+          postMessage: jest.fn(),
+          disconnect: jest.fn(),
+        };
+        (sut as any).port = mockPort;
+        (sut as any).connected = true;
+        (sut as any).appId = mockAppId;
+      });
+
+      describe("non-Safari path", () => {
+        beforeEach(() => {
+          platformUtilsService.isSafari.mockReturnValue(false);
+          (sut as any).secureChannel = mockSecureChannel;
+          encryptService.encryptString.mockResolvedValue(mockEncString);
+        });
+
+        it("calls port.postMessage with expected msg", async () => {
+          await sut.send({ command: "test" });
+
+          const postedMsg = mockPort.postMessage.mock.calls[0][0];
+          expect(postedMsg.message).toEqual({
+            encryptedString: mockEncString.encryptedString,
+            encryptionType: mockEncString.encryptionType,
+            data: mockEncString.data,
+            iv: mockEncString.iv,
+            mac: mockEncString.mac,
+          });
+          expect(postedMsg.appId).toBe(mockAppId);
+        });
+
+        it("handles error when port.postMessage throws", async () => {
+          mockPort.postMessage.mockImplementation(() => {
+            throw new Error("port disconnected");
+          });
+
+          await expect(sut.send({ command: "test" })).resolves.toBeUndefined();
+
+          expect(logService.info).toHaveBeenCalledWith(
+            "[Native Messaging IPC] Disconnected from Bitwarden Desktop app because of the native port disconnecting.",
+          );
+          expectDisconnectedState();
+          expect(mockPort.disconnect).toHaveBeenCalled();
+        });
+      });
+
+      describe("Safari path", () => {
+        beforeEach(() => {
+          platformUtilsService.isSafari.mockReturnValue(true);
+        });
+
+        it("calls port.postMessage with the plain message object (no EncString)", async () => {
+          const safariMessage: any = { command: "test" };
+          await sut.send(safariMessage);
+
+          expect(mockPort.postMessage).toHaveBeenCalledTimes(1);
+          expect(mockPort.postMessage.mock.calls[0][0]).not.toHaveProperty("appId");
+          expect(mockPort.postMessage.mock.calls[0][0].command).toBe("test");
+        });
+      });
+    });
+  });
+});
diff --git a/apps/browser/src/background/nativeMessaging.background.ts b/apps/browser/src/background/nativeMessaging.background.ts
index 8b845cf3567..b78f901c23c 100644
--- a/apps/browser/src/background/nativeMessaging.background.ts
+++ b/apps/browser/src/background/nativeMessaging.background.ts
@@ -1,7 +1,6 @@
 import { firstValueFrom } from "rxjs";
 
 import { AccountService } from "@bitwarden/common/auth/abstractions/account.service";
-import { AuthService } from "@bitwarden/common/auth/abstractions/auth.service";
 import { CryptoFunctionService } from "@bitwarden/common/key-management/crypto/abstractions/crypto-function.service";
 import { EncryptService } from "@bitwarden/common/key-management/crypto/abstractions/encrypt.service";
 import { EncString } from "@bitwarden/common/key-management/crypto/models/enc-string";
@@ -15,8 +14,6 @@ import { KeyService, BiometricStateService } from "@bitwarden/key-management";
 
 import { BrowserApi } from "../platform/browser/browser-api";
 
-import RuntimeBackground from "./runtime.background";
-
 const MessageValidTimeout = 10 * 1000;
 const MessageNoResponseTimeout = 60 * 1000;
 const HashAlgorithmForEncryption = "sha1";
@@ -85,12 +82,10 @@ export class NativeMessagingBackground {
     private keyService: KeyService,
     private encryptService: EncryptService,
     private cryptoFunctionService: CryptoFunctionService,
-    private runtimeBackground: RuntimeBackground,
     private messagingService: MessagingService,
     private appIdService: AppIdService,
     private platformUtilsService: PlatformUtilsService,
     private logService: LogService,
-    private authService: AuthService,
     private biometricStateService: BiometricStateService,
     private accountService: AccountService,
   ) {
@@ -121,8 +116,7 @@ export class NativeMessagingBackground {
     await this.biometricStateService.setFingerprintValidated(false);
 
     return new Promise<void>((resolve, reject) => {
-      const port = BrowserApi.connectNative("com.8bit.bitwarden");
-      this.port = port;
+      this.port = BrowserApi.connectNative("com.8bit.bitwarden");
 
       this.connecting = true;
 
@@ -147,7 +141,7 @@ export class NativeMessagingBackground {
         connectedCallback();
       }
 
-      port.onMessage.addListener(async (messageRaw: unknown) => {
+      this.port.onMessage.addListener(async (messageRaw: unknown) => {
         const message = messageRaw as ReceiveMessageOuter;
         switch (message.command) {
           case "connected":
@@ -158,8 +152,7 @@ export class NativeMessagingBackground {
             if (this.connecting) {
               reject(new Error("startDesktop"));
             }
-            this.connected = false;
-            port.disconnect();
+            this.disconnect();
             // reject all
             for (const callback of this.callbacks.values()) {
               callback.rejecter("disconnected");
@@ -207,8 +200,7 @@ export class NativeMessagingBackground {
               "[Native Messaging IPC] Secure channel encountered an error; disconnecting and wiping keys...",
             );
 
-            this.secureChannel = undefined;
-            this.connected = false;
+            this.disconnect();
 
             if (message.messageId != null) {
               if (this.callbacks.has(message.messageId)) {
@@ -272,6 +264,7 @@ export class NativeMessagingBackground {
 
         this.secureChannel = undefined;
         this.connected = false;
+        this.connecting = false;
 
         this.logService.error("NativeMessaging port disconnected because of error: " + error);
 
@@ -360,8 +353,7 @@ export class NativeMessagingBackground {
         "[Native Messaging IPC] Disconnected from Bitwarden Desktop app because of the native port disconnecting.",
       );
 
-      this.secureChannel = undefined;
-      this.connected = false;
+      this.disconnect();
 
       if (messageId != null && this.callbacks.has(messageId)) {
         this.callbacks.get(messageId)!.rejecter("invalidateEncryption");
@@ -446,4 +438,12 @@ export class NativeMessagingBackground {
       fingerprint: fingerprint,
     });
   }
+
+  private disconnect() {
+    // Clear state immediately in case the disconnect callback fails.
+    this.secureChannel = undefined;
+    this.connected = false;
+    this.connecting = false;
+    this.port?.disconnect();
+  }
 }