From b204a11cc03ae699b55944fe6d074b2d87af1f7e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=B0=8F=E7=BA=AA?= <3049035704@qq.com>
Date: Thu, 14 May 2026 02:46:23 +0800
Subject: [PATCH] fix: guard MCP stderr buffer access

---
 internal/extensions/mcp/client.go | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/internal/extensions/mcp/client.go b/internal/extensions/mcp/client.go
index 25cc1ff4..bf34d3d4 100644
--- a/internal/extensions/mcp/client.go
+++ b/internal/extensions/mcp/client.go
@@ -12,6 +12,7 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -297,7 +298,7 @@ func (c *StdioClient) runRPC(ctx context.Context, cfg ServerConfig, requests []r
 	if err != nil {
 		return nil, newClientError(ClientErrorTransport, "failed to open mcp stdout pipe", err)
 	}
-	var stderr bytes.Buffer
+	var stderr lockedBuffer
 	cmd.Stderr = &stderr
 
 	if err := cmd.Start(); err != nil {
@@ -489,6 +490,23 @@ func stopCommand(cmd *exec.Cmd, stdin io.WriteCloser) {
 	<-done
 }
 
+type lockedBuffer struct {
+	mu  sync.Mutex
+	buf bytes.Buffer
+}
+
+func (b *lockedBuffer) Write(p []byte) (int, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.buf.Write(p)
+}
+
+func (b *lockedBuffer) String() string {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.buf.String()
+}
+
 type rpcRequest struct {
 	JSONRPC string `json:"jsonrpc"`
 	ID      any    `json:"id,omitempty"`