diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4166bab3..71a1263e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -103,8 +103,8 @@ jobs:
       - name: Test Windows auth and DPAPI packages
         run: go test -v -count=1 -timeout=10m ./internal/keychain ./internal/auth
 
-      - name: Test Windows auth migration and export diagnostics
-        run: go test -v -count=1 -timeout=5m ./internal/app -run '^TestAuth(MigrateKeychain|StatusDiagnosticReportsCiphertextKeyMismatch|ExportRejectsWindowsDPAPIBackend)'
+      - name: Test Windows auth migration and portable auth diagnostics
+        run: go test -v -count=1 -timeout=5m ./internal/app -run '^Test(CrossPlatformCoverage)?Auth(MigrateKeychain|StatusDiagnosticReportsCiphertextKeyMismatch|ExportRejectsWindowsDPAPIBackend|ImportRejectsWindowsDPAPIBackend)'
 
   coverage-darwin:
     name: Coverage (macOS)
diff --git a/internal/app/auth_command_test.go b/internal/app/auth_command_test.go
index 02d6b607..fb8b89b8 100644
--- a/internal/app/auth_command_test.go
+++ b/internal/app/auth_command_test.go
@@ -102,7 +102,7 @@ func TestAuthExportImportBase64RoundTrip(t *testing.T) {
 	}
 }
 
-func TestAuthExportUnsupportedBackendIsValidationError(t *testing.T) {
+func TestCrossPlatformCoverageAuthExportUnsupportedBackendIsValidationError(t *testing.T) {
 	exportCmd := newAuthExportCommandWithSupport(func() error {
 		return errors.New("portable auth export is unavailable for the test backend")
 	})
@@ -123,7 +123,7 @@ func TestAuthExportUnsupportedBackendIsValidationError(t *testing.T) {
 	}
 }
 
-func TestAuthExportRejectsWindowsDPAPIBackend(t *testing.T) {
+func TestCrossPlatformCoverageAuthExportRejectsWindowsDPAPIBackend(t *testing.T) {
 	if runtime.GOOS != "windows" {
 		t.Skip("Windows DPAPI contract requires a native Windows runner")
 	}
@@ -149,7 +149,7 @@ func TestAuthExportRejectsWindowsDPAPIBackend(t *testing.T) {
 	}
 }
 
-func TestAuthImportUnsupportedBackendIsValidationErrorBeforeReadingInput(t *testing.T) {
+func TestCrossPlatformCoverageAuthImportUnsupportedBackendIsValidationErrorBeforeReadingInput(t *testing.T) {
 	root := t.TempDir()
 	configDir := filepath.Join(root, ".dws")
 	keychainDir := filepath.Join(root, "keychain")
@@ -181,7 +181,7 @@ func TestAuthImportUnsupportedBackendIsValidationErrorBeforeReadingInput(t *test
 	}
 }
 
-func TestAuthImportRejectsWindowsDPAPIBackend(t *testing.T) {
+func TestCrossPlatformCoverageAuthImportRejectsWindowsDPAPIBackend(t *testing.T) {
 	if runtime.GOOS != "windows" {
 		t.Skip("Windows DPAPI contract requires a native Windows runner")
 	}
@@ -222,7 +222,7 @@ func TestAuthImportRejectsWindowsDPAPIBackend(t *testing.T) {
 	}
 }
 
-func TestAuthImportRequiresForceWhenPopulated(t *testing.T) {
+func TestCrossPlatformCoverageAuthImportRequiresForceWhenPopulated(t *testing.T) {
 	t.Setenv(keychain.DisableKeychainEnv, "1")
 	root := t.TempDir()
 	t.Cleanup(CloseFileLogger)
diff --git a/internal/app/test_home_test.go b/internal/app/test_home_test.go
index 50d6fb8a..51a534e7 100644
--- a/internal/app/test_home_test.go
+++ b/internal/app/test_home_test.go
@@ -29,7 +29,7 @@ func setTestHome(t *testing.T, home string) {
 	}
 }
 
-func TestConfigureLogLevelTerminatesReplacedFileLoggers(t *testing.T) {
+func TestCrossPlatformCoverageConfigureLogLevelTerminatesReplacedFileLoggers(t *testing.T) {
 	firstConfig := t.TempDir()
 	secondConfig := t.TempDir()
 	t.Cleanup(CloseFileLogger)
diff --git a/internal/auth/portable_store_test.go b/internal/auth/portable_store_test.go
index e2116ee0..9fc98ec5 100644
--- a/internal/auth/portable_store_test.go
+++ b/internal/auth/portable_store_test.go
@@ -28,7 +28,7 @@ import (
 	"github.com/DingTalk-Real-AI/dingtalk-workspace-cli/internal/keychain"
 )
 
-func TestPortableExportSupported(t *testing.T) {
+func TestCrossPlatformCoveragePortableExportSupported(t *testing.T) {
 	switch runtime.GOOS {
 	case "windows":
 		if PortableExportSupported() {
@@ -60,7 +60,7 @@ func TestPortableExportSupported(t *testing.T) {
 	}
 }
 
-func TestPortableExportSupportError(t *testing.T) {
+func TestCrossPlatformCoveragePortableExportSupportError(t *testing.T) {
 	tests := []struct {
 		name            string
 		goos            string
@@ -89,7 +89,7 @@ func TestPortableExportSupportError(t *testing.T) {
 	}
 }
 
-func TestPortableImportSupportError(t *testing.T) {
+func TestCrossPlatformCoveragePortableImportSupportError(t *testing.T) {
 	tests := []struct {
 		name      string
 		goos      string
@@ -116,7 +116,7 @@ func TestPortableImportSupportError(t *testing.T) {
 	}
 }
 
-func TestImportPortableAuthBundleRejectsWindowsDPAPIWithoutMutation(t *testing.T) {
+func TestCrossPlatformCoverageImportPortableAuthBundleRejectsWindowsDPAPIWithoutMutation(t *testing.T) {
 	if runtime.GOOS != "windows" {
 		t.Skip("Windows DPAPI contract requires a native Windows runner")
 	}
diff --git a/internal/logging/logger_test.go b/internal/logging/logger_test.go
index 326061e4..f5bf7dfe 100644
--- a/internal/logging/logger_test.go
+++ b/internal/logging/logger_test.go
@@ -123,7 +123,7 @@ func TestCloseOnNilLogger(t *testing.T) {
 	}
 }
 
-func TestFileLoggerCloseIsTerminal(t *testing.T) {
+func TestCrossPlatformCoverageFileLoggerCloseIsTerminal(t *testing.T) {
 	t.Parallel()
 
 	dir := t.TempDir()
@@ -136,6 +136,15 @@ func TestFileLoggerCloseIsTerminal(t *testing.T) {
 	if err := os.Remove(logPath); err != nil {
 		t.Fatalf("remove closed log file: %v", err)
 	}
+	if err := fl.writer.open(); !errors.Is(err, os.ErrClosed) {
+		t.Fatalf("open after close = %v, want os.ErrClosed", err)
+	}
+	fl.writer.mu.Lock()
+	err := fl.writer.reopenLocked()
+	fl.writer.mu.Unlock()
+	if !errors.Is(err, os.ErrClosed) {
+		t.Fatalf("reopen after close = %v, want os.ErrClosed", err)
+	}
 
 	n, err := fl.Writer().Write([]byte("late write"))
 	if n != 0 || !errors.Is(err, os.ErrClosed) {