fix(mcp): keep SSE client session alive after connect

internal/mcp/client_sdk.go

@@ -44,11 +44,12 @@ func newSDKClientFromSession(session *mcp.ClientSession, client *mcp.Client, log
 
 // lazySDKClient 延迟连接：Initialize() 时才调用官方 SDK 建立连接，对外实现 ExternalMCPClient
 type lazySDKClient struct {
-	serverCfg config.ExternalMCPServerConfig
-	logger    *zap.Logger
-	inner     ExternalMCPClient // 连接成功后为 *sdkClient
-	mu        sync.RWMutex
-	status    string
+	serverCfg     config.ExternalMCPServerConfig
+	logger        *zap.Logger
+	sessionCancel context.CancelFunc
+	inner         ExternalMCPClient // connected SDK client
+	mu            sync.RWMutex
+	status        string
 }
 
 func newLazySDKClient(serverCfg config.ExternalMCPServerConfig, logger *zap.Logger) *lazySDKClient {
@@ -92,14 +93,61 @@ func (c *lazySDKClient) Initialize(ctx context.Context) error {
 	}
 	c.mu.Unlock()
 
-	inner, err := createSDKClient(ctx, c.serverCfg, c.logger)
-	if err != nil {
+	sessionCtx, sessionCancel := context.WithCancel(context.Background())
+	type connectResult struct {
+		inner ExternalMCPClient
+		err   error
+	}
+	resultCh := make(chan connectResult)
+	abandoned := make(chan struct{})
+	go func() {
+		inner, err := createSDKClient(sessionCtx, c.serverCfg, c.logger)
+		select {
+		case resultCh <- connectResult{inner: inner, err: err}:
+		case <-abandoned:
+			if inner != nil {
+				_ = inner.Close()
+			}
+			sessionCancel()
+		}
+	}()
+
+	var result connectResult
+	select {
+	case result = <-resultCh:
+	case <-ctx.Done():
+		close(abandoned)
+		sessionCancel()
+		c.setStatus("error")
+		return ctx.Err()
+	}
+
+	if err := ctx.Err(); err != nil {
+		sessionCancel()
+		if result.inner != nil {
+			_ = result.inner.Close()
+		}
 		c.setStatus("error")
 		return err
 	}
 
+	if result.err != nil {
+		sessionCancel()
+		c.setStatus("error")
+		return result.err
+	}
+
 	c.mu.Lock()
-	c.inner = inner
+	if c.inner != nil {
+		c.mu.Unlock()
+		sessionCancel()
+		if result.inner != nil {
+			_ = result.inner.Close()
+		}
+		return nil
+	}
+	c.inner = result.inner
+	c.sessionCancel = sessionCancel
 	c.mu.Unlock()
 	c.setStatus("connected")
 	return nil
@@ -128,9 +176,14 @@ func (c *lazySDKClient) CallTool(ctx context.Context, name string, args map[stri
 func (c *lazySDKClient) Close() error {
 	c.mu.Lock()
 	inner := c.inner
+	sessionCancel := c.sessionCancel
 	c.inner = nil
+	c.sessionCancel = nil
 	c.mu.Unlock()
 	c.setStatus("disconnected")
+	if sessionCancel != nil {
+		sessionCancel()
+	}
 	if inner != nil {
 		return inner.Close()
 	}