From 246fdf3f33d48b7361f9623f1566a020c894a32c Mon Sep 17 00:00:00 2001
From: yuchou87 <yuchou87@gmail.com>
Date: Sat, 21 Feb 2026 13:40:55 +0800
Subject: [PATCH] fix(mcp): guard against nil result from CallTool

CallTool can return (nil, nil) if the underlying MCP library misbehaves.
Without a nil check, result.IsError would panic. Return an explicit error
ToolResult instead.
---
 pkg/tools/mcp_tool.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/pkg/tools/mcp_tool.go b/pkg/tools/mcp_tool.go
index c29ab8525..6bd3d75e3 100644
--- a/pkg/tools/mcp_tool.go
+++ b/pkg/tools/mcp_tool.go
@@ -119,6 +119,11 @@ func (t *MCPTool) Execute(ctx context.Context, args map[string]interface{}) *Too
 		return ErrorResult(fmt.Sprintf("MCP tool execution failed: %v", err)).WithError(err)
 	}
 
+	if result == nil {
+		nilErr := fmt.Errorf("MCP tool returned nil result without error")
+		return ErrorResult("MCP tool execution failed: nil result").WithError(nilErr)
+	}
+
 	// Handle error result from server
 	if result.IsError {
 		errMsg := extractContentText(result.Content)