diff --git a/apps/api/src/guards/oauth-callback.guard.spec.ts b/apps/api/src/guards/oauth-callback.guard.spec.ts
new file mode 100644
index 000000000..6c8daacde
--- /dev/null
+++ b/apps/api/src/guards/oauth-callback.guard.spec.ts
@@ -0,0 +1,100 @@
+import { Logger } from '@nestjs/common';
+
+import { OAuthCallbackGuard } from './oauth-callback.guard';
+
+describe('OAuthCallbackGuard', () => {
+  let warnSpy: jest.SpyInstance;
+  let errorSpy: jest.SpyInstance;
+
+  beforeEach(() => {
+    warnSpy = jest.spyOn(Logger.prototype, 'warn').mockImplementation(() => undefined as any);
+    errorSpy = jest.spyOn(Logger.prototype, 'error').mockImplementation(() => undefined as any);
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  function getGuardInstance(strategy = 'oidc') {
+    const Guard = OAuthCallbackGuard(strategy);
+    return new (Guard as any)();
+  }
+
+  it('should return user when authentication succeeds', () => {
+    const guard = getGuardInstance('oidc');
+    const user = { jwt: 'token' };
+
+    const result = guard.handleRequest(null, user, null, null, null);
+
+    expect(result).toBe(user);
+    expect(errorSpy).not.toHaveBeenCalled();
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it('should log error when err is provided', () => {
+    const guard = getGuardInstance('oidc');
+    const err = new Error('token exchange failed');
+
+    const result = guard.handleRequest(err, false, null, null, null);
+
+    expect(result).toBe(false);
+    expect(errorSpy).toHaveBeenCalledWith(
+      expect.stringContaining('Authentication with the oidc strategy has failed')
+    );
+  });
+
+  it('should log warn when user is falsy and info is provided (silent failure case)', () => {
+    const guard = getGuardInstance('oidc');
+    const info = new Error('Invalid state');
+
+    const result = guard.handleRequest(null, undefined, info, null, null);
+
+    expect(result).toBeUndefined();
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('Authentication with the oidc strategy has failed')
+    );
+    expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining('Invalid state'));
+  });
+
+  it('should log warn when user is falsy without info (OidcStateStore verify failure)', () => {
+    const guard = getGuardInstance('oidc');
+
+    const result = guard.handleRequest(null, null, null, null, null);
+
+    expect(result).toBeNull();
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('Authentication with the oidc strategy has failed')
+    );
+  });
+
+  it('should log both error and warn when err and !user with info', () => {
+    const guard = getGuardInstance('oidc');
+    const err = new Error('exchange error');
+    const info = 'State mismatch';
+
+    const result = guard.handleRequest(err, undefined, info, null, null);
+
+    expect(result).toBeUndefined();
+    expect(errorSpy).toHaveBeenCalled();
+    expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining('State mismatch'));
+  });
+
+  it('should log warn with stringified info when info is object', () => {
+    const guard = getGuardInstance('oidc');
+    const info = { message: 'invalid_token' };
+
+    guard.handleRequest(null, undefined, info, null, null);
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('invalid_token')
+    );
+  });
+
+  it('should keep generic strategy name in log', () => {
+    const guard = getGuardInstance('google');
+    guard.handleRequest(null, undefined, 'some info', null, null);
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining('google')
+    );
+  });
+});
diff --git a/apps/api/src/guards/oauth-callback.guard.ts b/apps/api/src/guards/oauth-callback.guard.ts
index cedbccde1..3fc6cb695 100644
--- a/apps/api/src/guards/oauth-callback.guard.ts
+++ b/apps/api/src/guards/oauth-callback.guard.ts
@@ -5,10 +5,27 @@ export function OAuthCallbackGuard(strategy: string): Type<IAuthGuard> {
   class OAuthCallbackGuardMixin extends AuthGuard(strategy) {
     private readonly logger = new Logger(OAuthCallbackGuard.name);
 
-    public override handleRequest(error: Error, user: any) {
-      if (error) {
+    public override handleRequest(
+      err: unknown,
+      user: any,
+      info: unknown,
+      context: unknown,
+      status?: unknown
+    ) {
+      if (err) {
         this.logger.error(
-          `Authentication with the ${strategy} strategy has failed: ${error.message}`
+          `Authentication with the ${strategy} strategy has failed: ${(err as Error)?.message ?? err}`
+        );
+      }
+
+      if (!user) {
+        const infoMessage =
+          info !== undefined && info !== null
+            ? `: ${info instanceof Error ? info.message : typeof info === 'string' ? info : JSON.stringify(info)}`
+            : ': no user returned';
+
+        this.logger.warn(
+          `Authentication with the ${strategy} strategy has failed${infoMessage}`
         );
       }