typescript-sdk/.changeset/hide-wire-only-members.md

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

Hide wire-only protocol members from the public surface, at the type level and at runtime. resultType (the 2026-07-28 result discrimination field) is no longer declared on any public result type — the wire schemas keep parsing it, and the client funnel now consumes it raw-first: 'complete' results are stripped to the public shape and any other kind (e.g. input_required) rejects with the new SdkErrorCode.UnsupportedResultType instead of masking into an empty success. The reserved _meta envelope keys are lifted out of inbound requests and notifications before handlers run, and the multi-round-trip retry fields (inputResponses, requestState) out of inbound requests only (the spec reserves those names on client-initiated requests; notification params keep them), so handler params keep the 2025-era shape; for requests the lifted material surfaces at ctx.mcpReq.envelope, ctx.mcpReq.inputResponses, and ctx.mcpReq.requestState (notifications have no ctx — their lifted envelope keys are not surfaced). High-level client/server methods now return the named public result types (Promise<CallToolResult> etc.). Task wire vocabulary stays importable but is @deprecated and excluded from the typed method maps (RequestMethod/RequestTypeMap/ResultTypeMap/NotificationTypeMap), and callTool is typed as plain CallToolResult. See docs/migration/support-2026-07-28.md "Wire-only members hidden from public types".