typescript-sdk/.changeset/custom-methods-minimal.md

@modelcontextprotocol/core-internal	@modelcontextprotocol/client	@modelcontextprotocol/server
minor	minor	minor

Add custom (non-spec) method support: a 3-arg setRequestHandler(method, schemas, handler) / setNotificationHandler(method, schemas, handler) form for vendor-prefixed methods, and a request(req, resultSchema) overload (also on ctx.mcpReq.send) for typed custom-method results. Spec-method calls are unchanged.

Response result-schema validation failure now rejects with SdkError(InvalidResult) instead of a raw ZodError. Adds SdkErrorCode.InvalidResult.