test(antigravity): add missing unit tests for upstream and custom model_mapping

- Add GetAccessToken upstream branch tests (success/failure/empty/nil)
- Add mapAntigravityModel wildcard-target-equals-request edge case tests
- Add upstream account smart retry test case
- Add GeminiMessagesCompatService custom model_mapping and empty model tests

backend/internal/service/antigravity_model_mapping_test.go

@@ -265,3 +265,58 @@ func TestAntigravityGatewayService_IsModelSupported(t *testing.T) {
 		})
 	}
 }
+
+// TestMapAntigravityModel_WildcardTargetEqualsRequest 测试通配符映射目标恰好等于请求模型名的 edge case
+// 例如 {"claude-*": "claude-sonnet-4-5"}，请求 "claude-sonnet-4-5" 时应该通过
+func TestMapAntigravityModel_WildcardTargetEqualsRequest(t *testing.T) {
+	tests := []struct {
+		name           string
+		modelMapping   map[string]any
+		requestedModel string
+		expected       string
+	}{
+		{
+			name:           "wildcard target equals request model",
+			modelMapping:   map[string]any{"claude-*": "claude-sonnet-4-5"},
+			requestedModel: "claude-sonnet-4-5",
+			expected:       "claude-sonnet-4-5",
+		},
+		{
+			name:           "wildcard target differs from request model",
+			modelMapping:   map[string]any{"claude-*": "claude-sonnet-4-5"},
+			requestedModel: "claude-opus-4-6",
+			expected:       "claude-sonnet-4-5",
+		},
+		{
+			name:           "wildcard no match",
+			modelMapping:   map[string]any{"claude-*": "claude-sonnet-4-5"},
+			requestedModel: "gpt-4o",
+			expected:       "",
+		},
+		{
+			name:           "explicit passthrough same name",
+			modelMapping:   map[string]any{"claude-sonnet-4-5": "claude-sonnet-4-5"},
+			requestedModel: "claude-sonnet-4-5",
+			expected:       "claude-sonnet-4-5",
+		},
+		{
+			name:           "multiple wildcards target equals one request",
+			modelMapping:   map[string]any{"claude-*": "claude-sonnet-4-5", "gemini-*": "gemini-2.5-flash"},
+			requestedModel: "gemini-2.5-flash",
+			expected:       "gemini-2.5-flash",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			account := &Account{
+				Platform: PlatformAntigravity,
+				Credentials: map[string]any{
+					"model_mapping": tt.modelMapping,
+				},
+			}
+			got := mapAntigravityModel(account, tt.requestedModel)
+			require.Equal(t, tt.expected, got, "mapAntigravityModel(%q) = %q, want %q", tt.requestedModel, got, tt.expected)
+		})
+	}
+}

backend/internal/service/antigravity_rate_limit_test.go

@@ -526,6 +526,7 @@ func TestParseAntigravitySmartRetryInfo(t *testing.T) {
 func TestShouldTriggerAntigravitySmartRetry(t *testing.T) {
 	oauthAccount := &Account{Type: AccountTypeOAuth, Platform: PlatformAntigravity}
 	setupTokenAccount := &Account{Type: AccountTypeSetupToken, Platform: PlatformAntigravity}
+	upstreamAccount := &Account{Type: AccountTypeUpstream, Platform: PlatformAntigravity}
 	apiKeyAccount := &Account{Type: AccountTypeAPIKey}
 
 	tests := []struct {
@@ -587,6 +588,23 @@ func TestShouldTriggerAntigravitySmartRetry(t *testing.T) {
 			expectedShouldRateLimit: true,
 			modelName:               "claude-sonnet-4-5",
 		},
+		{
+			name:    "Upstream account with short delay - smart retry",
+			account: upstreamAccount,
+			body: `{
+				"error": {
+					"status": "RESOURCE_EXHAUSTED",
+					"details": [
+						{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "claude-sonnet-4-5"}, "reason": "RATE_LIMIT_EXCEEDED"},
+						{"@type": "type.googleapis.com/google.rpc.RetryInfo", "retryDelay": "2s"}
+					]
+				}
+			}`,
+			expectedShouldRetry:     true,
+			expectedShouldRateLimit: false,
+			minWait:                 2 * time.Second,
+			modelName:               "claude-sonnet-4-5",
+		},
 		{
 			name:    "API Key account - should not trigger",
 			account: apiKeyAccount,

backend/internal/service/antigravity_token_provider_test.go

@@ -0,0 +1,97 @@
+//go:build unit
+
+package service
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestAntigravityTokenProvider_GetAccessToken_Upstream(t *testing.T) {
+	provider := &AntigravityTokenProvider{}
+
+	t.Run("upstream account with valid api_key", func(t *testing.T) {
+		account := &Account{
+			Platform: PlatformAntigravity,
+			Type:     AccountTypeUpstream,
+			Credentials: map[string]any{
+				"api_key": "sk-test-key-12345",
+			},
+		}
+		token, err := provider.GetAccessToken(context.Background(), account)
+		require.NoError(t, err)
+		require.Equal(t, "sk-test-key-12345", token)
+	})
+
+	t.Run("upstream account missing api_key", func(t *testing.T) {
+		account := &Account{
+			Platform:    PlatformAntigravity,
+			Type:        AccountTypeUpstream,
+			Credentials: map[string]any{},
+		}
+		token, err := provider.GetAccessToken(context.Background(), account)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "upstream account missing api_key")
+		require.Empty(t, token)
+	})
+
+	t.Run("upstream account with empty api_key", func(t *testing.T) {
+		account := &Account{
+			Platform: PlatformAntigravity,
+			Type:     AccountTypeUpstream,
+			Credentials: map[string]any{
+				"api_key": "",
+			},
+		}
+		token, err := provider.GetAccessToken(context.Background(), account)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "upstream account missing api_key")
+		require.Empty(t, token)
+	})
+
+	t.Run("upstream account with nil credentials", func(t *testing.T) {
+		account := &Account{
+			Platform: PlatformAntigravity,
+			Type:     AccountTypeUpstream,
+		}
+		token, err := provider.GetAccessToken(context.Background(), account)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "upstream account missing api_key")
+		require.Empty(t, token)
+	})
+}
+
+func TestAntigravityTokenProvider_GetAccessToken_Guards(t *testing.T) {
+	provider := &AntigravityTokenProvider{}
+
+	t.Run("nil account", func(t *testing.T) {
+		token, err := provider.GetAccessToken(context.Background(), nil)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "account is nil")
+		require.Empty(t, token)
+	})
+
+	t.Run("non-antigravity platform", func(t *testing.T) {
+		account := &Account{
+			Platform: PlatformAnthropic,
+			Type:     AccountTypeOAuth,
+		}
+		token, err := provider.GetAccessToken(context.Background(), account)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "not an antigravity account")
+		require.Empty(t, token)
+	})
+
+	t.Run("unsupported account type", func(t *testing.T) {
+		account := &Account{
+			Platform: PlatformAntigravity,
+			Type:     AccountTypeAPIKey,
+		}
+		token, err := provider.GetAccessToken(context.Background(), account)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "not an antigravity oauth account")
+		require.Empty(t, token)
+	})
+}

backend/internal/service/gemini_multiplatform_test.go

@@ -905,6 +905,39 @@ func TestGeminiMessagesCompatService_isModelSupportedByAccount(t *testing.T) {
 			model:    "gpt-4",
 			expected: false,
 		},
+		{
+			name:     "Antigravity平台-空模型允许",
+			account:  &Account{Platform: PlatformAntigravity},
+			model:    "",
+			expected: true,
+		},
+		{
+			name: "Antigravity平台-自定义映射-支持自定义模型",
+			account: &Account{
+				Platform: PlatformAntigravity,
+				Credentials: map[string]any{
+					"model_mapping": map[string]any{
+						"my-custom-model": "upstream-model",
+						"gpt-4o":          "some-model",
+					},
+				},
+			},
+			model:    "my-custom-model",
+			expected: true,
+		},
+		{
+			name: "Antigravity平台-自定义映射-不在映射中的模型不支持",
+			account: &Account{
+				Platform: PlatformAntigravity,
+				Credentials: map[string]any{
+					"model_mapping": map[string]any{
+						"my-custom-model": "upstream-model",
+					},
+				},
+			},
+			model:    "claude-sonnet-4-5",
+			expected: false,
+		},
 		{
 			name:     "Gemini平台-无映射配置-支持所有模型",
 			account:  &Account{Platform: PlatformGemini},