fix: 连接保活 + 续写收敛优化 + 拒绝模式扩充

- 流式路径：每 15s 发送 SSE 注释 keepalive，防止 504 网关超时
- 非流式路径：chunked 空白字符保活，JSON.parse 天然兼容
- MAX_AUTO_CONTINUE 6→3，新增最小进展阈值(<100 chars 停止)
- 新增连续小增量检测（2 次 <500 chars 停止挤牙膏）
- 追加 15 条 REFUSAL_PATTERNS（EN scope/expertise + CN 中文拒绝）

src/handler.ts

@@ -115,6 +115,23 @@ const REFUSAL_PATTERNS = [
     /语言偏好请求/,
     /提供.*具体场景/,
     /即报错/,
+    // EN: scope/expertise wordings (2026-03 batch)
+    /(?:outside|beyond)\s+(?:the\s+)?scope\s+of\s+what/i,
+    /not\s+(?:within|in)\s+(?:my|the)\s+scope/i,
+    /this\s+assistant\s+is\s+(?:focused|scoped)/i,
+    /(?:only|just)\s+(?:able|here)\s+to\s+(?:answer|help)/i,
+    /I\s+(?:can\s+)?only\s+help\s+with\s+(?:questions|issues)\s+(?:related|about)/i,
+    /(?:here|designed)\s+to\s+help\s+(?:with\s+)?(?:questions\s+)?about\s+Cursor/i,
+    /not\s+(?:something|a\s+topic)\s+(?:related|specific)\s+to\s+(?:Cursor|coding)/i,
+    /outside\s+(?:my|the|your)\s+area\s+of\s+(?:expertise|scope)/i,
+    /(?:can[.']?t|cannot|unable\s+to)\s+help\s+with\s+(?:this|that)\s+(?:request|question|topic)/i,
+    /scoped\s+to\s+(?:answering|helping)/i,
+    // CN: Chinese refusal wordings — Cursor 中文界面下的拒绝 (2026-03 batch)
+    /只能回答.*(?:Cursor|编辑器).*(?:相关|有关)/,
+    /专[注门].*(?:回答|帮助|解答).*(?:Cursor|编辑器)/,
+    /有什么.*(?:Cursor|编辑器).*(?:问题|可以)/,
+    /无法提供.*(?:推荐|建议|帮助)/,
+    /(?:功能使用|账户|故障排除|账号|订阅|套餐|计费).*(?:等|问题)/,
 ];
 
 export function isRefusal(text: string): boolean {
@@ -594,6 +611,15 @@ async function handleStream(res: Response, cursorReq: CursorChatRequest, body: A
         },
     });
 
+    // ★ 流式保活：在缓冲/续写期间每 15s 发送 SSE 注释，防止网关判定连接空闲超时 (504)
+    const keepaliveInterval = setInterval(() => {
+        try {
+            res.write(': keepalive\n\n');
+            // @ts-expect-error flush exists on ServerResponse when compression is used
+            if (typeof res.flush === 'function') res.flush();
+        } catch { /* connection already closed, ignore */ }
+    }, 15000);
+
     let fullResponse = '';
     let sentText = '';
     let blockIndex = 0;
@@ -677,8 +703,9 @@ async function handleStream(res: Response, cursorReq: CursorChatRequest, body: A
         // 流完成后，处理完整响应
         // ★ 内部截断续写：如果模型输出过长被截断（常见于写大文件），Proxy 内部分段续写，然后拼接成完整响应
         // 这样可以确保工具调用（如 Write）不会横跨两次 API 响应而退化为纯文本
-        const MAX_AUTO_CONTINUE = 6;
+        const MAX_AUTO_CONTINUE = 3;
         let continueCount = 0;
+        let consecutiveSmallAdds = 0; // 连续小增量计数
         
         // 保存原始请求的消息快照（不含续写追加的消息）
         const originalMessages = [...activeCursorReq.messages];
@@ -745,6 +772,23 @@ Continue EXACTLY from where you stopped. DO NOT repeat any content already gener
                 console.log(`[Handler] ⚠️ 续写内容全部为重复，停止续写`);
                 break;
             }
+
+            // ★ 最小进展检测：去重后新增内容过少（<100 chars），模型几乎已完成
+            if (deduped.trim().length < 100) {
+                console.log(`[Handler] ⚠️ 续写新增内容过少 (${deduped.trim().length} chars < 100)，停止续写`);
+                break;
+            }
+
+            // ★ 连续小增量检测：连续2次增量 < 500 chars，说明模型已经在挤牙膏
+            if (deduped.trim().length < 500) {
+                consecutiveSmallAdds++;
+                if (consecutiveSmallAdds >= 2) {
+                    console.log(`[Handler] ⚠️ 连续 ${consecutiveSmallAdds} 次小增量续写，停止续写`);
+                    break;
+                }
+            } else {
+                consecutiveSmallAdds = 0;
+            }
         }
 
         let stopReason = (hasTools && isTruncated(fullResponse)) ? 'max_tokens' : 'end_turn';
@@ -939,6 +983,9 @@ Continue EXACTLY from where you stopped. DO NOT repeat any content already gener
         writeSSE(res, 'error', {
             type: 'error', error: { type: 'api_error', message },
         });
+    } finally {
+        // ★ 清除保活定时器
+        clearInterval(keepaliveInterval);
     }
 
     res.end();
@@ -947,6 +994,18 @@ Continue EXACTLY from where you stopped. DO NOT repeat any content already gener
 // ==================== 非流式处理 ====================
 
 async function handleNonStream(res: Response, cursorReq: CursorChatRequest, body: AnthropicRequest): Promise<void> {
+    // ★ 非流式保活：手动设置 chunked 响应，在缓冲期间每 15s 发送空白字符保活
+    // JSON.parse 会忽略前导空白，所以客户端解析不受影响
+    res.writeHead(200, { 'Content-Type': 'application/json' });
+    const keepaliveInterval = setInterval(() => {
+        try {
+            res.write(' ');
+            // @ts-expect-error flush exists on ServerResponse when compression is used
+            if (typeof res.flush === 'function') res.flush();
+        } catch { /* connection already closed, ignore */ }
+    }, 15000);
+
+    try {
     let fullText = await sendCursorRequestFull(cursorReq);
     const hasTools = (body.tools?.length ?? 0) > 0;
     let activeCursorReq = cursorReq;
@@ -1004,8 +1063,9 @@ async function handleNonStream(res: Response, cursorReq: CursorChatRequest, body
     // ★ 内部截断续写（与流式路径对齐）
     // Claude CLI 使用非流式模式时，写大文件最容易被截断
     // 在 proxy 内部完成续写，确保工具调用参数完整
-    const MAX_AUTO_CONTINUE = 6;
+    const MAX_AUTO_CONTINUE = 3;
     let continueCount = 0;
+    let consecutiveSmallAdds = 0; // 连续小增量计数
     const originalMessages = [...activeCursorReq.messages];
 
     while (hasTools && isTruncated(fullText) && continueCount < MAX_AUTO_CONTINUE) {
@@ -1061,6 +1121,23 @@ Continue EXACTLY from where you stopped. DO NOT repeat any content already gener
             console.log(`[Handler] ⚠️ 非流式续写内容全部为重复，停止续写`);
             break;
         }
+
+        // ★ 最小进展检测：去重后新增内容过少（<100 chars），模型几乎已完成
+        if (deduped.trim().length < 100) {
+            console.log(`[Handler] ⚠️ 非流式续写新增内容过少 (${deduped.trim().length} chars < 100)，停止续写`);
+            break;
+        }
+
+        // ★ 连续小增量检测：连续2次增量 < 500 chars，说明模型已经在挤牙膏
+        if (deduped.trim().length < 500) {
+            consecutiveSmallAdds++;
+            if (consecutiveSmallAdds >= 2) {
+                console.log(`[Handler] ⚠️ 非流式连续 ${consecutiveSmallAdds} 次小增量续写，停止续写`);
+                break;
+            }
+        } else {
+            consecutiveSmallAdds = 0;
+        }
     }
 
     const contentBlocks: AnthropicContentBlock[] = [];
@@ -1166,7 +1243,20 @@ Continue EXACTLY from where you stopped. DO NOT repeat any content already gener
         },
     };
 
-    res.json(response);
+    clearInterval(keepaliveInterval);
+    res.end(JSON.stringify(response));
+
+    } catch (err: unknown) {
+        clearInterval(keepaliveInterval);
+        const message = err instanceof Error ? err.message : String(err);
+        console.error(`[Handler] 非流式请求处理失败:`, message);
+        try {
+            res.end(JSON.stringify({
+                type: 'error',
+                error: { type: 'api_error', message },
+            }));
+        } catch { /* response already ended */ }
+    }
 }
 
 // ==================== SSE 工具函数 ====================