feat(providers): add LongCat model provider support (#1317)

* feat(providers): add LongCat model provider support

Add LongCat as an OpenAI-compatible provider with base URL
https://api.longcat.chat/openai and default model LongCat-Flash-Thinking.
Includes provider config, migration, factory routing, example config,
tests, and README entries for all 6 locales.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(providers): address LongCat review feedback

- Add dedicated factory routing test for LongCat provider
- Add longcat to DefaultAPIBase test coverage
- Set default api_base in example config providers section

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* test(providers): add ResolveProviderSelection tests for LongCat

Add two test cases to TestResolveProviderSelection:
- Explicit provider selection with api_base default and proxy wiring
- Fallback inference from model name with api_base default

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/providers/factory.go

@@ -221,6 +221,15 @@ func resolveProviderSelection(cfg *config.Config) (providerSelection, error) {
 					sel.apiBase = "https://api.minimaxi.com/v1"
 				}
 			}
+		case "longcat":
+			if cfg.Providers.LongCat.APIKey != "" {
+				sel.apiKey = cfg.Providers.LongCat.APIKey
+				sel.apiBase = cfg.Providers.LongCat.APIBase
+				sel.proxy = cfg.Providers.LongCat.Proxy
+				if sel.apiBase == "" {
+					sel.apiBase = "https://api.longcat.chat/openai"
+				}
+			}
 		case "github_copilot", "copilot":
 			sel.providerType = providerTypeGitHubCopilot
 			if cfg.Providers.GitHubCopilot.APIBase != "" {
@@ -352,6 +361,13 @@ func resolveProviderSelection(cfg *config.Config) (providerSelection, error) {
 			if sel.apiBase == "" {
 				sel.apiBase = "https://api.avian.io/v1"
 			}
+		case (strings.Contains(lowerModel, "longcat") || strings.HasPrefix(model, "longcat/")) && cfg.Providers.LongCat.APIKey != "":
+			sel.apiKey = cfg.Providers.LongCat.APIKey
+			sel.apiBase = cfg.Providers.LongCat.APIBase
+			sel.proxy = cfg.Providers.LongCat.Proxy
+			if sel.apiBase == "" {
+				sel.apiBase = "https://api.longcat.chat/openai"
+			}
 		case cfg.Providers.VLLM.APIBase != "":
 			sel.apiKey = cfg.Providers.VLLM.APIKey
 			sel.apiBase = cfg.Providers.VLLM.APIBase

pkg/providers/factory_provider.go

@@ -95,7 +95,7 @@ func CreateProviderFromConfig(cfg *config.ModelConfig) (LLMProvider, string, err
 	case "litellm", "openrouter", "groq", "zhipu", "gemini", "nvidia",
 		"ollama", "moonshot", "shengsuanyun", "deepseek", "cerebras",
 		"vivgrid", "volcengine", "vllm", "qwen", "mistral", "avian",
-		"minimax":
+		"minimax", "longcat":
 		// All other OpenAI-compatible HTTP providers
 		if cfg.APIKey == "" && cfg.APIBase == "" {
 			return nil, "", fmt.Errorf("api_key or api_base is required for HTTP-based protocol %q", protocol)
@@ -215,6 +215,8 @@ func getDefaultAPIBase(protocol string) string {
 		return "https://api.avian.io/v1"
 	case "minimax":
 		return "https://api.minimaxi.com/v1"
+	case "longcat":
+		return "https://api.longcat.chat/openai"
 	default:
 		return ""
 	}

pkg/providers/factory_provider_test.go

@@ -113,6 +113,7 @@ func TestCreateProviderFromConfig_DefaultAPIBase(t *testing.T) {
 		{"vllm", "vllm"},
 		{"deepseek", "deepseek"},
 		{"ollama", "ollama"},
+		{"longcat", "longcat"},
 	}
 
 	for _, tt := range tests {
@@ -162,6 +163,29 @@ func TestCreateProviderFromConfig_LiteLLM(t *testing.T) {
 	}
 }
 
+func TestCreateProviderFromConfig_LongCat(t *testing.T) {
+	cfg := &config.ModelConfig{
+		ModelName: "test-longcat",
+		Model:     "longcat/LongCat-Flash-Thinking",
+		APIKey:    "test-key",
+		APIBase:   "https://api.longcat.chat/openai",
+	}
+
+	provider, modelID, err := CreateProviderFromConfig(cfg)
+	if err != nil {
+		t.Fatalf("CreateProviderFromConfig() error = %v", err)
+	}
+	if provider == nil {
+		t.Fatal("CreateProviderFromConfig() returned nil provider")
+	}
+	if modelID != "LongCat-Flash-Thinking" {
+		t.Errorf("modelID = %q, want %q", modelID, "LongCat-Flash-Thinking")
+	}
+	if _, ok := provider.(*HTTPProvider); !ok {
+		t.Fatalf("expected *HTTPProvider, got %T", provider)
+	}
+}
+
 func TestCreateProviderFromConfig_Anthropic(t *testing.T) {
 	cfg := &config.ModelConfig{
 		ModelName: "test-anthropic",

pkg/providers/factory_test.go

@@ -178,6 +178,26 @@ func TestResolveProviderSelection(t *testing.T) {
 			wantAPIBase: "https://api.moonshot.cn/v1",
 			wantProxy:   "http://127.0.0.1:7890",
 		},
+		{
+			name: "explicit longcat provider uses defaults",
+			setup: func(cfg *config.Config) {
+				cfg.Agents.Defaults.Provider = "longcat"
+				cfg.Providers.LongCat.APIKey = "longcat-key"
+				cfg.Providers.LongCat.Proxy = "http://127.0.0.1:7890"
+			},
+			wantType:    providerTypeHTTPCompat,
+			wantAPIBase: "https://api.longcat.chat/openai",
+			wantProxy:   "http://127.0.0.1:7890",
+		},
+		{
+			name: "longcat model fallback uses longcat base default",
+			setup: func(cfg *config.Config) {
+				cfg.Agents.Defaults.Model = "longcat/LongCat-Flash-Thinking"
+				cfg.Providers.LongCat.APIKey = "longcat-key"
+			},
+			wantType:    providerTypeHTTPCompat,
+			wantAPIBase: "https://api.longcat.chat/openai",
+		},
 		{
 			name: "missing keys returns model config error",
 			setup: func(cfg *config.Config) {