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@koic koic commented Dec 4, 2025

Motivation and Context

When starting an MCP server in Claude Code with protocol_version set to DRAFT-2025-v3, it fails with the following error:

2025-12-04T02:58:01.548Z [DEBUG] MCP server "example": Connection failed after 2093ms: Server's protocol version is not supported: DRAFT-2025-v3
2025-12-04T02:58:01.548Z [ERROR] MCP server "example" Connection failed: Server's protocol version is not supported: DRAFT-2025-v3

This PR changes the default behavior so that if protocol_version is not specified, it uses the latest stable protocol version instead of the draft version.

This PR also updates the README to note that the latest stable protocol version includes new features from the draft version.

How Has This Been Tested?

Existing tests have been updated to pass. I also verified its operation with Claude Code.

Breaking Changes

None.

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

When starting an MCP server in Claude Code with `protocol_version` set to `DRAFT-2025-v3`,
it fails with the following error:

```console
2025-12-04T02:58:01.548Z [DEBUG] MCP server "example": Connection failed after 2093ms: Server's protocol version is not supported: DRAFT-2025-v3
2025-12-04T02:58:01.548Z [ERROR] MCP server "example" Connection failed: Server's protocol version is not supported: DRAFT-2025-v3
```

This PR changes the default behavior so that if `protocol_version` is not specified,
it uses the latest stable protocol version instead of the draft version.

This PR also updates the README to note that the latest stable protocol version includes
new features from the draft version.
@koic koic force-pushed the avoid_draft_protocol_version branch from eb7499c to c786a14 Compare December 4, 2025 05:58
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