fix(client): preserve _meta on input_required results - #2862
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felixweinberger merged 4 commits intoSep 28, 2026
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felixweinberger merged 4 commits into
felixweinberger merged 4 commits into
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The 2026-07-28 decode seam rebuilt the input_required payload from inputRequests and requestState only, so result-level `_meta` — including the `io.modelcontextprotocol/serverInfo` stamp servers send — was dropped before an `allowInputRequired: true` caller could see it. `Result._meta` is a result-level field, so `input_required` carries it like any other result, and the encode side already stamps it in `stampServerInfoMeta`. Pass it through the seam in `decodeResult` and `manualInputRequiredValue`, and cover both with tests that fail without the src change.
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@modelcontextprotocol/client
@modelcontextprotocol/codemod
@modelcontextprotocol/core
@modelcontextprotocol/server
@modelcontextprotocol/server-legacy
@modelcontextprotocol/express
@modelcontextprotocol/fastify
@modelcontextprotocol/hono
@modelcontextprotocol/node
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Fixes #2861.
A server that puts result-level
_metaon aninput_requiredresult loses it before the client can see it: withallowInputRequired: truethe caller receives{ resultType, inputRequests, requestState }and nothing else.The 2026-07-28 decode seam rebuilds that payload by hand instead of lifting the body, in two places:
packages/core-internal/src/wire/rev2026-07-28/codec.ts—decodeResult, theinput_requiredbranchpackages/core-internal/src/shared/inputRequiredEngine.ts—manualInputRequiredValueResult._metais a result-level field —stampServerInfoMetaruns "for every result regardless ofresultType" — and the wireInputRequiredResultSchemacarries it, so the loss is decode-only and the encode side already ships it.Changes
DecodedResult'sinput_requiredvariant carries_meta?: ResultMetaObject.Testing
packages/core-internal/test/shared/inputRequiredFunnel.test.ts: new case asserting the handed-back value keeps the server's_meta.packages/client/test/client/inputRequiredEngine.test.ts: new manual-mode case through a scripted 2026-07-28 server.expected undefined to deeply equal …) and pass with it.pnpm typecheck:all,pnpm lint:all,pnpm build:allandpnpm -r --filter '!@modelcontextprotocol/test-e2e' testpass locally.Changeset included. If you want this covered in
modelcontextprotocol/conformancetoo, I can add a scenario that round-trips_metaon aninput_requiredresult.Note on how this was written: an agent drafted the change and tests; I read every line of the diff and can answer for it in review.