diff --git a/src-tauri/src/proxy/forwarder.rs b/src-tauri/src/proxy/forwarder.rs
index 9c0a0fc96..f16375fad 100644
--- a/src-tauri/src/proxy/forwarder.rs
+++ b/src-tauri/src/proxy/forwarder.rs
@@ -561,12 +561,19 @@ impl RequestForwarder {
         // 检查是否需要格式转换
         let needs_transform = adapter.needs_transform(provider);
 
-        let effective_endpoint =
-            if needs_transform && adapter.name() == "Claude" && endpoint == "/v1/messages" {
+        // 确定有效端点：
+        // - 如果需要转换且是 Claude 的 /v1/messages 端点，改写为 /v1/chat/completions
+        // - 但如果 base_url 已包含 chat/completions，则不再自动添加
+        let effective_endpoint = if needs_transform && adapter.name() == "Claude" {
+            let base_has_chat_completions = base_url.contains("chat/completions");
+            if endpoint == "/v1/messages" && !base_has_chat_completions {
                 "/v1/chat/completions"
             } else {
                 endpoint
-            };
+            }
+        } else {
+            endpoint
+        };
 
         // 使用适配器构建 URL
         let url = adapter.build_url(&base_url, effective_endpoint);
diff --git a/src-tauri/src/proxy/providers/claude.rs b/src-tauri/src/proxy/providers/claude.rs
index 04d4ec6ff..ea71790f3 100644
--- a/src-tauri/src/proxy/providers/claude.rs
+++ b/src-tauri/src/proxy/providers/claude.rs
@@ -23,10 +23,16 @@ impl ClaudeAdapter {
     /// 获取供应商类型
     ///
     /// 根据 base_url 和 auth_mode 检测具体的供应商类型：
+    /// - ChatCompletions: chat_completions_mode 为 true（优先级最高）
     /// - OpenRouter: base_url 包含 openrouter.ai
     /// - ClaudeAuth: auth_mode 为 bearer_only
     /// - Claude: 默认 Anthropic 官方
     pub fn provider_type(&self, provider: &Provider) -> ProviderType {
+        // 检测 ChatCompletions 模式（优先级最高）
+        if self.is_chat_completions_mode(provider) {
+            return ProviderType::ChatCompletions;
+        }
+
         // 检测 OpenRouter
         if self.is_openrouter(provider) {
             return ProviderType::OpenRouter;
@@ -48,6 +54,20 @@ impl ClaudeAdapter {
         false
     }
 
+    /// 检测是否启用 ChatCompletions 兼容模式
+    fn is_chat_completions_mode(&self, provider: &Provider) -> bool {
+        let raw = provider.settings_config.get("chat_completions_mode");
+        match raw {
+            Some(serde_json::Value::Bool(enabled)) => *enabled,
+            Some(serde_json::Value::Number(num)) => num.as_i64().unwrap_or(0) != 0,
+            Some(serde_json::Value::String(value)) => {
+                let normalized = value.trim().to_lowercase();
+                normalized == "true" || normalized == "1"
+            }
+            _ => false,
+        }
+    }
+
     /// 检测 OpenRouter 是否启用兼容模式
     fn is_openrouter_compat_enabled(&self, provider: &Provider) -> bool {
         if !self.is_openrouter(provider) {
@@ -253,13 +273,9 @@ impl ProviderAdapter for ClaudeAdapter {
         }
     }
 
-    fn needs_transform(&self, _provider: &Provider) -> bool {
-        // NOTE:
-        // OpenRouter 已推出 Claude Code 兼容接口（可直接处理 `/v1/messages`），默认不再启用
-        // Anthropic ↔ OpenAI 的格式转换。
-        //
-        // 如果未来需要回退到旧的 OpenAI Chat Completions 方案，可恢复下面这行：
-        self.is_openrouter_compat_enabled(_provider)
+    fn needs_transform(&self, provider: &Provider) -> bool {
+        // ChatCompletions 模式或 OpenRouter 兼容模式都需要转换
+        self.is_chat_completions_mode(provider) || self.is_openrouter_compat_enabled(provider)
     }
 
     fn transform_request(
diff --git a/src-tauri/src/proxy/providers/mod.rs b/src-tauri/src/proxy/providers/mod.rs
index 61be1087e..8621b9954 100644
--- a/src-tauri/src/proxy/providers/mod.rs
+++ b/src-tauri/src/proxy/providers/mod.rs
@@ -50,6 +50,8 @@ pub enum ProviderType {
     GeminiCli,
     /// OpenRouter（已支持 Claude Code 兼容接口，默认透传；保留旧转换逻辑备用）
     OpenRouter,
+    /// ChatCompletions 兼容模式（Anthropic ↔ OpenAI 格式转换，不限制上游地址）
+    ChatCompletions,
 }
 
 impl ProviderType {
@@ -75,6 +77,7 @@ impl ProviderType {
                 "https://generativelanguage.googleapis.com"
             }
             ProviderType::OpenRouter => "https://openrouter.ai/api",
+            ProviderType::ChatCompletions => "https://api.openai.com",
         }
     }
 
@@ -148,6 +151,7 @@ impl ProviderType {
             ProviderType::Gemini => "gemini",
             ProviderType::GeminiCli => "gemini_cli",
             ProviderType::OpenRouter => "openrouter",
+            ProviderType::ChatCompletions => "chat_completions",
         }
     }
 }
@@ -169,6 +173,9 @@ impl std::str::FromStr for ProviderType {
             "gemini" => Ok(ProviderType::Gemini),
             "gemini_cli" | "gemini-cli" => Ok(ProviderType::GeminiCli),
             "openrouter" => Ok(ProviderType::OpenRouter),
+            "chat_completions" | "chat-completions" | "chatcompletions" => {
+                Ok(ProviderType::ChatCompletions)
+            }
             _ => Err(format!("Invalid provider type: {s}")),
         }
     }
@@ -191,9 +198,10 @@ pub fn get_adapter(app_type: &AppType) -> Box<dyn ProviderAdapter> {
 #[allow(dead_code)]
 pub fn get_adapter_for_provider_type(provider_type: &ProviderType) -> Box<dyn ProviderAdapter> {
     match provider_type {
-        ProviderType::Claude | ProviderType::ClaudeAuth | ProviderType::OpenRouter => {
-            Box::new(ClaudeAdapter::new())
-        }
+        ProviderType::Claude
+        | ProviderType::ClaudeAuth
+        | ProviderType::OpenRouter
+        | ProviderType::ChatCompletions => Box::new(ClaudeAdapter::new()),
         ProviderType::Codex => Box::new(CodexAdapter::new()),
         ProviderType::Gemini | ProviderType::GeminiCli => Box::new(GeminiAdapter::new()),
     }
diff --git a/src-tauri/src/proxy/providers/streaming.rs b/src-tauri/src/proxy/providers/streaming.rs
index a3fd590c2..5f111aaef 100644
--- a/src-tauri/src/proxy/providers/streaming.rs
+++ b/src-tauri/src/proxy/providers/streaming.rs
@@ -115,16 +115,22 @@ pub fn create_anthropic_sse_stream(
 
                                     if let Some(choice) = chunk.choices.first() {
                                         if !has_sent_message_start {
+                                            // 构建完整的 message_start 事件，与原生 Anthropic 格式一致
                                             let event = json!({
                                                 "type": "message_start",
                                                 "message": {
                                                     "id": message_id.clone().unwrap_or_default(),
                                                     "type": "message",
                                                     "role": "assistant",
+                                                    "content": [],
                                                     "model": current_model.clone().unwrap_or_default(),
+                                                    "stop_reason": null,
+                                                    "stop_sequence": null,
                                                     "usage": {
-                                                        "input_tokens": 0,
-                                                        "output_tokens": 0
+                                                        "input_tokens": chunk.usage.as_ref().map(|u| u.prompt_tokens).unwrap_or(1),
+                                                        "output_tokens": 0,
+                                                        "cache_creation_input_tokens": 0,
+                                                        "cache_read_input_tokens": 0
                                                     }
                                                 }
                                             });
@@ -272,18 +278,17 @@ pub fn create_anthropic_sse_stream(
                                             }
 
                                             let stop_reason = map_stop_reason(Some(finish_reason));
-                                            // 构建 usage 信息，包含 input_tokens 和 output_tokens
-                                            let usage_json = chunk.usage.as_ref().map(|u| json!({
-                                                "input_tokens": u.prompt_tokens,
-                                                "output_tokens": u.completion_tokens
-                                            }));
+                                            // 构建 usage 信息，Anthropic 格式只需要 output_tokens
+                                            let output_tokens = chunk.usage.as_ref().map(|u| u.completion_tokens).unwrap_or(0);
                                             let event = json!({
                                                 "type": "message_delta",
                                                 "delta": {
                                                     "stop_reason": stop_reason,
                                                     "stop_sequence": null
                                                 },
-                                                "usage": usage_json
+                                                "usage": {
+                                                    "output_tokens": output_tokens
+                                                }
                                             });
                                             let sse_data = format!("event: message_delta\ndata: {}\n\n",
                                                 serde_json::to_string(&event).unwrap_or_default());
diff --git a/src/config/claudeProviderPresets.ts b/src/config/claudeProviderPresets.ts
index 5eda7f8d4..d42c2569b 100644
--- a/src/config/claudeProviderPresets.ts
+++ b/src/config/claudeProviderPresets.ts
@@ -430,6 +430,20 @@ export const providerPresets: ProviderPreset[] = [
     icon: "openrouter",
     iconColor: "#6566F1",
   },
+  {
+    name: "ChatCompletions",
+    websiteUrl: "",
+    settingsConfig: {
+      env: {
+        ANTHROPIC_BASE_URL: "",
+        ANTHROPIC_AUTH_TOKEN: "",
+      },
+      chat_completions_mode: true,
+    },
+    category: "third_party",
+    icon: "openai",
+    iconColor: "#10A37F",
+  },
   {
     name: "Xiaomi MiMo",
     websiteUrl: "https://platform.xiaomimimo.com",