diff --git a/.github/workflows/unit_tests.yml b/.github/workflows/unit_tests.yml
index ee5fd660..3db1f824 100644
--- a/.github/workflows/unit_tests.yml
+++ b/.github/workflows/unit_tests.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-13]
+        os: [macos-15]
         podspec: [GoogleSignIn.podspec, GoogleSignInSwiftSupport.podspec]
         flag: [
           "",
diff --git a/GoogleSignIn/Sources/GIDSignIn.m b/GoogleSignIn/Sources/GIDSignIn.m
index 1c043735..015c68c5 100644
--- a/GoogleSignIn/Sources/GIDSignIn.m
+++ b/GoogleSignIn/Sources/GIDSignIn.m
@@ -119,8 +119,7 @@
 // Error string for user cancelations.
 static NSString *const kUserCanceledError = @"The user canceled the sign-in flow.";
 
-// User preference key to detect fresh install of the app.
-static NSString *const kAppHasRunBeforeKey = @"GID_AppHasRunBefore";
+NSString *const kAppHasRunBeforeKey = @"GID_AppHasRunBefore";
 
 // Maximum retry interval in seconds for the fetcher.
 static const NSTimeInterval kFetcherMaxRetryInterval = 15.0;
@@ -553,6 +552,11 @@ - (instancetype)initWithKeychainStore:(GTMKeychainStore *)keychainStore
 
     // Check to see if the 3P app is being run for the first time after a fresh install.
     BOOL isFreshInstall = [self isFreshInstall];
+    
+    // If this is a fresh install, ensure that any pre-existing keychain data is purged.
+    if (isFreshInstall) {
+      [self removeAllKeychainEntries];
+    }
 
     NSString *authorizationEnpointURL = [NSString stringWithFormat:kAuthorizationURLTemplate,
                                          [GIDSignInPreferences googleAuthorizationServer]];
diff --git a/GoogleSignIn/Sources/GIDSignIn_Private.h b/GoogleSignIn/Sources/GIDSignIn_Private.h
index bb642cb7..803cc10e 100644
--- a/GoogleSignIn/Sources/GIDSignIn_Private.h
+++ b/GoogleSignIn/Sources/GIDSignIn_Private.h
@@ -32,6 +32,9 @@ NS_ASSUME_NONNULL_BEGIN
 @class GIDAppCheck;
 @class GIDAuthStateMigration;
 
+/// User preference key to detect fresh install of the app.
+extern NSString *const kAppHasRunBeforeKey;
+
 /// Represents a completion block that takes a `GIDSignInResult` on success or an error if the
 /// operation was unsuccessful.
 typedef void (^GIDSignInCompletion)(GIDSignInResult *_Nullable signInResult,
diff --git a/GoogleSignIn/Tests/Unit/GIDSignInTest.m b/GoogleSignIn/Tests/Unit/GIDSignInTest.m
index b36e197a..8db96b41 100644
--- a/GoogleSignIn/Tests/Unit/GIDSignInTest.m
+++ b/GoogleSignIn/Tests/Unit/GIDSignInTest.m
@@ -119,8 +119,6 @@
      @"com.google.UnitTests:///emmcallback?action=unrecognized";
 static NSString * const kDevicePolicyAppBundleID = @"com.google.DevicePolicy";
 
-static NSString * const kAppHasRunBeforeKey = @"GPP_AppHasRunBefore";
-
 static NSString * const kFingerprintKeychainName = @"fingerprint";
 static NSString * const kVerifierKeychainName = @"verifier";
 static NSString * const kVerifierKey = @"verifier";
@@ -993,6 +991,19 @@ - (void)testNotHandleWrongPath {
   XCTAssertFalse(_completionCalled, @"should not call delegate");
 }
 
+#pragma mark - Test Fresh Install
+
+- (void)testFreshInstall_removesKeychainEntries {
+  // Simulate that the app has been deleted and user defaults removed.
+  [NSUserDefaults.standardUserDefaults removeObjectForKey:kAppHasRunBeforeKey];
+  // Initialization should check `isFreshInstall`.
+  GIDSignIn *signIn = [[GIDSignIn alloc] initWithKeychainStore:_keychainStore
+                                     authStateMigrationService:_authStateMigrationService];
+  // If `isFreshInstall`, keychain entries should be removed.
+  XCTAssertNotNil(signIn);
+  XCTAssertTrue(self->_keychainRemoved);
+}
+
 #pragma mark - Tests - disconnectWithCallback:
 
 // Verifies disconnect calls callback with no errors if access token is present.