v1.2.1 - Custom Handler Preservation Fix

🔧 Bug Fix Release

What Changed

Fixed a critical issue where registerDefaultHandlers() was unconditionally overriding custom handlers that servers had already registered.

🐛 Problem Solved

• Custom Handler Override: The framework was overwriting custom tools/list, prompts/list, and resources/list handlers
• Claude Desktop Compatibility: Servers couldn't provide custom tool lists, causing "Method not found" errors
• Framework Principle Violation: Custom handlers should take precedence over defaults

✅ Solution

Modified registerDefaultHandlers() to check if handlers already exist before registering defaults:

func (s *Server) registerDefaultHandlers() {
    // Only register default handlers if custom ones don't exist
    if s.toolsListHandler == nil {
        s.toolsListHandler = s.handleToolsList
    }
    if s.promptsListHandler == nil {
        s.promptsListHandler = s.handlePromptsList  
    }
    if s.resourcesListHandler == nil {
        s.resourcesListHandler = s.handleResourcesList
    }
}

🎯 Benefits

1. ✅ Preserves Custom Handlers - Servers can register custom handlers before calling Start()
2. ✅ Backward Compatible - Servers not using custom handlers continue to work unchanged
3. ✅ Follows Best Practices - Custom implementations take precedence over defaults
4. ✅ Enables Advanced Use Cases - Servers can now provide dynamic tool lists, custom prompts, etc.

🧪 Testing

• ✅ All Transport Tests Pass - STDIO, SSE, and HTTP Streams
• ✅ Comprehensive Test Coverage - Added TestServerCustomHandlersPreserved
• ✅ Integration Tests - Echo tool compatibility maintained
• ✅ Backward Compatibility - Existing servers continue to work

📦 What's Included

• Handler Override Fix - Custom handlers are now preserved
• Enhanced Test Coverage - Comprehensive testing for handler preservation
• Echo Tool Fix - Improved compatibility with integration tests
• Full Transport Support - STDIO, SSE, and HTTP Streams all working

🔗 Related Projects

This fix enables projects like mcp-server-devpod to provide custom tools/list handlers that include both framework tools and project-specific tools, resolving Claude Desktop compatibility issues.

📋 Full Changelog

• Fix registerDefaultHandlers() to check for existing handlers before registering defaults
• Add comprehensive test coverage for handler override functionality
• Fix echo tool to prepend "Echo: " to message for test compatibility
• Ensure backward compatibility while enabling custom handler preservation

Full Diff: v1.2.0...v1.2.1