fix: split SSE chunks per event to avoid JSON parse errors

src/routes/standardGeminiRoutes.js

@@ -547,64 +547,94 @@ async function handleStandardStreamGenerateContent(req, res) {
 
     heartbeatTimer = setInterval(sendHeartbeat, HEARTBEAT_INTERVAL)
 
+    // 缓冲区：有些 chunk 内会包含多条 SSE 事件，需要拆分
+    let sseBuffer = ''
+
+    // 处理单个 SSE 事件块（不含结尾空行）
+    const handleEventBlock = (evt) => {
+      if (!evt.trim()) {
+        return
+      }
+
+      // 取出所有 data 行并拼接（兼容多行 data）
+      const dataLines = evt.split(/\r?\n/).filter((line) => line.startsWith('data:'))
+      if (dataLines.length === 0) {
+        // 非 data 事件，直接原样转发
+        if (!res.destroyed) {
+          res.write(`${evt}\n\n`)
+        }
+        return
+      }
+
+      const dataPayload = dataLines.map((line) => line.replace(/^data:\s?/, '')).join('\n')
+
+      let processedPayload = null
+      let parsed = null
+
+      if (dataPayload === '[DONE]') {
+        processedPayload = '[DONE]'
+      } else {
+        try {
+          parsed = JSON.parse(dataPayload)
+
+          // 捕获 usage（如果在顶层或 response 内都有可能）
+          if (parsed.usageMetadata) {
+            totalUsage = parsed.usageMetadata
+          } else if (parsed.response?.usageMetadata) {
+            totalUsage = parsed.response.usageMetadata
+          }
+
+          // 提取 response 并重新包装
+          processedPayload = JSON.stringify(parsed.response || parsed)
+        } catch (e) {
+          // 解析失败，直接转发原始 data
+        }
+      }
+
+      const outputChunk = processedPayload === null ? `${evt}\n\n` : `data: ${processedPayload}\n\n`
+
+      // 1️⃣ 立即转发处理后的数据
+      if (!res.destroyed) {
+        res.write(outputChunk)
+      }
+
+      // 2️⃣ 异步提取 usage 数据（兜底，防止上面解析失败未捕获）
+      setImmediate(() => {
+        try {
+          const usageSource =
+            processedPayload && processedPayload !== '[DONE]' ? processedPayload : dataPayload
+
+          if (!usageSource || !usageSource.includes('usageMetadata')) {
+            return
+          }
+
+          // 再尝试一次解析
+          const usageObj = JSON.parse(usageSource)
+          const usage = usageObj.usageMetadata || usageObj.response?.usageMetadata || usageObj.usage
+
+          if (usage && typeof usage === 'object') {
+            totalUsage = usage
+            logger.debug('📊 Captured Gemini usage data (async):', totalUsage)
+          }
+        } catch (error) {
+          // 提取用量失败时忽略
+        }
+      })
+    }
+
     streamResponse.on('data', (chunk) => {
       try {
         // 更新最后数据时间
         lastDataTime = Date.now()
 
-        const chunkStr = chunk.toString()
+        // 追加到缓冲区后按双换行拆分事件
+        sseBuffer += chunk.toString()
+        const events = sseBuffer.split(/\r?\n\r?\n/)
+        sseBuffer = events.pop() || ''
 
-        // 尝试解析 SSE 数据
-        // upstream 返回格式: data: {"response": {...}}
-        // standard API 期望格式: data: {...}
-
-        let processedChunk = chunk
-
-        if (chunkStr.startsWith('data: ')) {
-          try {
-            const jsonStr = chunkStr.substring(6).trim()
-            if (jsonStr !== '[DONE]') {
-              const data = JSON.parse(jsonStr)
-              if (data.response) {
-                // 提取内部的 response 对象并重新包装为 SSE
-                const newPayload = JSON.stringify(data.response)
-                processedChunk = Buffer.from(`data: ${newPayload}\n\n`)
+        for (const evt of events) {
+          handleEventBlock(evt)
         }
-            }
-          } catch (e) {
-            // 解析失败，直接转发原始数据
-            // logger.warn('Failed to parse SSE chunk:', e)
-          }
-        }
-
-        // 1️⃣ 立即转发处理后的数据
-        if (!res.destroyed) {
-          res.write(processedChunk)
-        }
-
-        // 2️⃣ 异步提取 usage 数据（不阻塞转发）
-        setImmediate(() => {
-          try {
-            const str = processedChunk.toString()
-            if (!str.trim() || !str.includes('usageMetadata')) {
-              return
-            }
-
-            // 简单的解析尝试
-            const match = str.match(/"usageMetadata":\s*({[^}]+})/)
-            if (match && match[1]) {
-              try {
-                const usage = JSON.parse(match[1])
-                totalUsage = usage
-                logger.debug('📊 Captured Gemini usage data:', totalUsage)
-              } catch (e) {
-                // ignore
-              }
-            }
-          } catch (error) {
-            logger.warn('⚠️ Error extracting usage data:', error.message)
-          }
-        })
       } catch (error) {
         logger.error('Error processing stream chunk:', error)
       }
@@ -613,6 +643,16 @@ async function handleStandardStreamGenerateContent(req, res) {
     streamResponse.on('end', () => {
       logger.info('Stream completed successfully')
 
+      // 处理可能残留在缓冲区的事件（上游未以空行结尾的情况）
+      if (sseBuffer.trim()) {
+        try {
+          handleEventBlock(sseBuffer)
+        } catch (flushError) {
+          // 忽略 flush 期间的异常
+        }
+        sseBuffer = ''
+      }
+
       // 清理心跳定时器
       if (heartbeatTimer) {
         clearInterval(heartbeatTimer)