fix(proxy): bypass circuit breaker for single provider scenario

When failover is disabled (single provider), circuit breaker open state
would block all requests causing poor UX. Now bypasses circuit breaker
check in this scenario. Also integrates model mapping into request flow.

src-tauri/src/proxy/forwarder.rs

@@ -176,14 +176,24 @@ impl RequestForwarder {
         let mut last_provider = None;
         let mut attempted_providers = 0usize;
 
+        // 单 Provider 场景下跳过熔断器检查（故障转移关闭时）
+        let bypass_circuit_breaker = providers.len() == 1;
+
         // 依次尝试每个供应商
         for provider in providers.iter() {
             // 发起请求前先获取熔断器放行许可（HalfOpen 会占用探测名额）
-            let permit = self
-                .router
-                .allow_provider_request(&provider.id, app_type_str)
-                .await;
-            if !permit.allowed {
+            // 单 Provider 场景下跳过此检查，避免熔断器阻塞所有请求
+            let (allowed, used_half_open_permit) = if bypass_circuit_breaker {
+                (true, false)
+            } else {
+                let permit = self
+                    .router
+                    .allow_provider_request(&provider.id, app_type_str)
+                    .await;
+                (permit.allowed, permit.used_half_open_permit)
+            };
+
+            if !allowed {
                 log::debug!(
                     "[{}] Provider {} 熔断器拒绝本次请求，跳过",
                     app_type_str,
@@ -192,8 +202,6 @@ impl RequestForwarder {
                 continue;
             }
 
-            let used_half_open_permit = permit.used_half_open_permit;
-
             attempted_providers += 1;
 
             log::info!(
@@ -435,10 +443,23 @@ impl RequestForwarder {
             serde_json::to_string_pretty(body).unwrap_or_else(|_| body.to_string())
         );
 
+        // 应用模型映射（独立于格式转换）
+        let (mapped_body, _original_model, mapped_model) =
+            super::model_mapper::apply_model_mapping(body.clone(), provider);
+
+        if let Some(ref mapped) = mapped_model {
+            log::info!(
+                "[{}] >>> 模型映射后的请求 JSON:\n{}",
+                adapter.name(),
+                serde_json::to_string_pretty(&mapped_body).unwrap_or_default()
+            );
+            log::info!("[{}] 模型已映射到: {}", adapter.name(), mapped);
+        }
+
         // 转换请求体（如果需要）
         let request_body = if needs_transform {
             log::info!("[{}] 转换请求格式 (Anthropic → OpenAI)", adapter.name());
-            let transformed = adapter.transform_request(body.clone(), provider)?;
+            let transformed = adapter.transform_request(mapped_body, provider)?;
             log::info!(
                 "[{}] >>> 转换后的请求 JSON:\n{}",
                 adapter.name(),
@@ -446,7 +467,7 @@ impl RequestForwarder {
             );
             transformed
         } else {
-            body.clone()
+            mapped_body
         };
 
         log::info!(

src-tauri/src/proxy/provider_router.rs

@@ -91,29 +91,19 @@ impl ProviderRouter {
                 }
             }
         } else {
-            // 故障转移关闭：仅使用当前供应商
-            log::info!("[{app_type}] Failover disabled, using current provider only");
+            // 故障转移关闭：仅使用当前供应商，跳过熔断器检查
+            // 原因：单 Provider 场景下，熔断器打开会导致所有请求失败，用户体验差
+            log::info!("[{app_type}] Failover disabled, using current provider only (circuit breaker bypassed)");
 
             if let Some(current_id) = self.db.get_current_provider(app_type)? {
                 if let Some(current) = self.db.get_provider_by_id(&current_id, app_type)? {
-                    let circuit_key = format!("{}:{}", app_type, current.id);
-                    let breaker = self.get_or_create_circuit_breaker(&circuit_key).await;
-
-                    if breaker.is_available().await {
-                        log::info!(
-                            "[{}] Current provider available: {} ({})",
-                            app_type,
-                            current.name,
-                            current.id
-                        );
-                        result.push(current);
-                    } else {
-                        log::warn!(
-                            "[{}] Current provider {} circuit breaker open",
-                            app_type,
-                            current.name
-                        );
-                    }
+                    log::info!(
+                        "[{}] Current provider: {} ({})",
+                        app_type,
+                        current.name,
+                        current.id
+                    );
+                    result.push(current);
                 }
             }
         }