This release includes several enhancements and bugfixes. Worth mentioning is the addition of schema caching, which significantly improves the performance in some stateless server deployment scenarios.

Dependency updates

• go.mod: upgrade to jsonschema v0.4.2 by @jba in https://github.com/modelcontextprotocol/go-sdk/pull/732

Enhancements

• perf: add schema caching to avoid repeated reflection by @SamMorrowDrums in https://github.com/modelcontextprotocol/go-sdk/pull/685
• mcp: add DisableListening option to StreamableClientTransport by @zxxf18 in https://github.com/modelcontextprotocol/go-sdk/pull/729
• feat: deprecated logger in client & add Logger in ClientOption by @CocaineCong in https://github.com/modelcontextprotocol/go-sdk/pull/738
• feat: deleted the old logger in client by @CocaineCong in https://github.com/modelcontextprotocol/go-sdk/pull/744
• Export GetError and SetError methods by @jba in https://github.com/modelcontextprotocol/go-sdk/pull/753

Bugfixes

• fix: connectStandaloneSSE checking Content-Type header by @liushuangls in https://github.com/modelcontextprotocol/go-sdk/pull/736
• mcp: fix SSEClientTransport to report HTTP errors properly by @hassan123789 in https://github.com/modelcontextprotocol/go-sdk/pull/740
• mcp: add Allow header to 405 responses per RFC 9110 §15.5.6 by @SamMorrowDrums in https://github.com/modelcontextprotocol/go-sdk/pull/757
• mcp: fix a race condition in logging by @maciej-kisiel in https://github.com/modelcontextprotocol/go-sdk/pull/761

Chores

• docs: adds SDK version support matrix by @La002 in https://github.com/modelcontextprotocol/go-sdk/pull/737
• .github/workflows: add nightly conformance tests by @findleyr in https://github.com/modelcontextprotocol/go-sdk/pull/752

New Contributors

• @La002 made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/737
• @hassan123789 made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/740
• @liushuangls made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/736
• @CocaineCong made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/738
• @zxxf18 made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/729
• @SamMorrowDrums made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/685
• @maciej-kisiel made their first contribution in https://github.com/modelcontextprotocol/go-sdk/pull/761

Full Changelog: https://github.com/modelcontextprotocol/go-sdk/compare/v1.2.0...v1.3.0-pre.1