v1.7.0-pre.2

This is a follow-up pre-release on top of v1.7.0-pre.1, still targeting protocol version 2026-07-28. It rounds out the previous release with conformance-test coverage on both client and server, tightens spec compliance and introduces first-class support for custom JSON-RPC methods.

Custom JSON-RPC methods

The SDK now supports registering non-standard JSON-RPC methods end-to-end. Servers can register handlers with AddReceivingCustomMethod and clients can invoke them via AddSendingCustomMethod.

• mcp: Allow registration of custom JSON-RPC methods by @guglielmo-san (#956)

Conformance tests

Both the client and server implementations are now exercised by the official MCP conformance test suite as part of CI.

• mcp: add integration for server conformance tests by @guglielmo-san (#1054)
• mcp: add conformance tests on client by @guglielmo-san (#1063)

Protection agains OOM attacks

The streamable HTTP transport now enforces a configurable request body size limit to protect servers against OOM-style attacks from oversized payloads.

• mcp: enforce body size limit in Streamable connection by @guglielmo-san (#1055)

Spec compliance fixes

Several smaller fixes bring the implementation closer to the spec.

• mcp: do not exclude Notifications from carrying InitializeParams in Meta by @guglielmo-san (#1049)
• mcp: cap negotiated protocolVersion in legacy initialize to protocolVersion20251125 by @guglielmo-san (#1051)
• mcp: make NotificationSubscriptions a mandatory field by @guglielmo-san (#1050)
• fix: extra wrapper for input response map by @yarolegovich (#1045)
• mcp: do not enforce TTL on cached tool by @guglielmo-san (#1053)
• mcp: block server initiated requests (SEP-2322) by @guglielmo-san (#1057)

Full Changelog: https://github.com/modelcontextprotocol/go-sdk/compare/v1.7.0-pre.1...v1.7.0-pre.2