diff --git a/server/pkg/agent/claude.go b/server/pkg/agent/claude.go
index 3c5c19a94..ae75c1c18 100644
--- a/server/pkg/agent/claude.go
+++ b/server/pkg/agent/claude.go
@@ -52,14 +52,21 @@ func (b *claudeBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 		cancel()
 		return nil, fmt.Errorf("claude stdin pipe: %w", err)
 	}
+	closeStdin := func() {
+		if stdin != nil {
+			_ = stdin.Close()
+			stdin = nil
+		}
+	}
 	cmd.Stderr = newLogWriter(b.cfg.Logger, "[claude:stderr] ")
 
 	if err := cmd.Start(); err != nil {
+		closeStdin()
 		cancel()
 		return nil, fmt.Errorf("start claude: %w", err)
 	}
 	if err := writeClaudeInput(stdin, prompt); err != nil {
-		_ = stdin.Close()
+		closeStdin()
 		cancel()
 		_ = cmd.Wait()
 		return nil, fmt.Errorf("write claude input: %w", err)
@@ -70,7 +77,7 @@ func (b *claudeBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 	resCh := make(chan Result, 1)
 
 	go func() {
-		defer stdin.Close()
+		defer closeStdin()
 		defer cancel()
 		defer close(msgCh)
 		defer close(resCh)
@@ -107,6 +114,7 @@ func (b *claudeBackend) Execute(ctx context.Context, prompt string, opts ExecOpt
 				}
 				trySend(msgCh, Message{Type: MessageStatus, Status: "running"})
 			case "result":
+				closeStdin()
 				sessionID = msg.SessionID
 				if msg.ResultText != "" {
 					output.Reset()