diff --git a/src/app/v1/_lib/proxy/response-handler.ts b/src/app/v1/_lib/proxy/response-handler.ts
index 4a4725a49..21e9c048a 100644
--- a/src/app/v1/_lib/proxy/response-handler.ts
+++ b/src/app/v1/_lib/proxy/response-handler.ts
@@ -1355,35 +1355,85 @@ function parseUsageFromResponseText(
   // 2. 纯 data: 格式 - Gemini
   if (!usageMetrics && responseText.includes("data:")) {
     const events = parseSSEData(responseText);
-    for (const event of events) {
-      if (usageMetrics) {
-        break;
-      }
 
+    // Claude SSE 特殊处理：
+    // - message_start 包含 input tokens 和缓存创建字段（5m/1h 区分计费）
+    // - message_delta 包含最终的 output_tokens
+    // 需要分别提取并合并
+    let messageStartUsage: UsageMetrics | null = null;
+    let messageDeltaOutputTokens: number | null = null;
+
+    for (const event of events) {
       if (typeof event.data !== "object" || !event.data) {
         continue;
       }
 
       const data = event.data as Record<string, unknown>;
 
-      // Claude message_start format: data.message.usage (preferred)
-      if (data.message && typeof data.message === "object") {
+      // Claude message_start format: data.message.usage
+      // 提取 input tokens 和缓存字段
+      if (event.event === "message_start" && data.message && typeof data.message === "object") {
         const messageObj = data.message as Record<string, unknown>;
-        applyUsageValue(messageObj.usage, `sse.${event.event}.message.usage`);
+        if (messageObj.usage && typeof messageObj.usage === "object") {
+          const extracted = extractUsageMetrics(messageObj.usage);
+          if (extracted) {
+            messageStartUsage = extracted;
+            logger.debug("[ResponseHandler] Extracted usage from message_start", {
+              source: "sse.message_start.message.usage",
+              usage: extracted,
+            });
+          }
+        }
+      }
+
+      // Claude message_delta format: data.usage.output_tokens
+      // 提取最终的 output_tokens（在流结束时）
+      if (event.event === "message_delta" && data.usage && typeof data.usage === "object") {
+        const deltaUsage = data.usage as Record<string, unknown>;
+        if (typeof deltaUsage.output_tokens === "number") {
+          messageDeltaOutputTokens = deltaUsage.output_tokens;
+          logger.debug("[ResponseHandler] Extracted output_tokens from message_delta", {
+            source: "sse.message_delta.usage.output_tokens",
+            outputTokens: messageDeltaOutputTokens,
+          });
+        }
       }
 
-      // Fallback: Standard usage fields (data.usage)
-      applyUsageValue(data.usage, `sse.${event.event}.usage`);
+      // 非 Claude 格式的 SSE 处理（Gemini 等）
+      if (!messageStartUsage && !messageDeltaOutputTokens) {
+        // Standard usage fields (data.usage)
+        applyUsageValue(data.usage, `sse.${event.event}.usage`);
+
+        // Gemini usageMetadata
+        applyUsageValue(data.usageMetadata, `sse.${event.event}.usageMetadata`);
 
-      // Gemini usageMetadata
-      applyUsageValue(data.usageMetadata, `sse.${event.event}.usageMetadata`);
+        // Handle response wrapping in SSE
+        if (!usageMetrics && data.response && typeof data.response === "object") {
+          const responseObj = data.response as Record<string, unknown>;
+          applyUsageValue(responseObj.usage, `sse.${event.event}.response.usage`);
+          applyUsageValue(responseObj.usageMetadata, `sse.${event.event}.response.usageMetadata`);
+        }
+      }
+    }
 
-      // Handle response wrapping in SSE
-      if (!usageMetrics && data.response && typeof data.response === "object") {
-        const responseObj = data.response as Record<string, unknown>;
-        applyUsageValue(responseObj.usage, `sse.${event.event}.response.usage`);
-        applyUsageValue(responseObj.usageMetadata, `sse.${event.event}.response.usageMetadata`);
+    // 合并 Claude SSE 的 message_start 和 message_delta 数据
+    if (messageStartUsage) {
+      // 使用 message_delta 中的 output_tokens 覆盖 message_start 中的值
+      if (messageDeltaOutputTokens !== null) {
+        messageStartUsage.output_tokens = messageDeltaOutputTokens;
+        logger.debug(
+          "[ResponseHandler] Merged output_tokens from message_delta into message_start usage",
+          {
+            finalOutputTokens: messageDeltaOutputTokens,
+          }
+        );
       }
+      usageMetrics = adjustUsageForProviderType(messageStartUsage, providerType);
+      usageRecord = messageStartUsage as unknown as Record<string, unknown>;
+      logger.debug("[ResponseHandler] Final merged usage from Claude SSE", {
+        providerType,
+        usage: usageMetrics,
+      });
     }
   }