Re-vendor 2026-07-28 schema at spec ead35b59 (SubscriptionsListenResult)

[maxisbey]

Re-vendors schema/draft/schema.json at spec commit ead35b59 to pick up modelcontextprotocol/modelcontextprotocol#2953, the only schema/draft/ change since the previous vendor pin (2852f30e, set by #2912). Spec main is 20 commits past 2ffc3fa2 (#2953's merge) with no further schema/draft/ changes, so this brings the vendored schema fully up to date.

The schema diff is purely additive: SubscriptionsListenResult and SubscriptionsListenResultMeta are added to $defs, and SubscriptionsListenResult joins the ServerResult union.

Motivation and Context

Part of #2901. The subscriptions/listen runtime work needs the result type to exist before it can land; today the lowlevel on_subscriptions_listen slot is typed to return EmptyResult, which is no longer the spec-correct shape post-#2953.

How Has This Been Tested?

gen_surface_types.py --check, pyright, ruff, and ./scripts/test (full suite, 100% coverage, strict-no-cover clean).

Breaking Changes

None for users — SubscriptionsListenResult is a new type and nothing previously consumed subscriptions/listen results. The lowlevel on_subscriptions_listen callback's return type changes from EmptyResult to SubscriptionsListenResult, but per the design that handler is registered by the entry-side router rather than user code, and there is no runtime caller yet.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

• SubscriptionsListenResultMeta is added to OPEN_CLASSES so the generated wire model preserves arbitrary _meta keys, matching NotificationMetaObject (both are MetaObject extensions; neither carries additionalProperties in the upstream JSON Schema, so the codegen default would have closed them).
• In the monolith the new result follows the existing pattern: _meta stays the lenient dict[str, Any] inherited from Result (so SubscriptionsListenResultMeta is SKIP-listed in tests/types/test_parity.py alongside the other *MetaObject types), and the class sits in the ServerResult union immediately before InputRequiredResult, which must remain last.
• Conformance gap: the conformance suite at b18aa918 (this repo's pin and conformance main HEAD) is itself pinned to spec f817239f — pre-fix: normalize OAuth redirect URI URL subtypes #2953 — and has no scenario asserting the subscriptions/listen result body. Its existing subscriptions/listen checks in server/stateless.ts only inspect notification frames on the stream. I'll raise a conformance issue to bump the spec-types pin and add a result-shape check; this PR does not change conformance behaviour either way (the new type is not yet emitted by any runtime path).

[cubic-dev-ai]

No issues found across 10 files

_{Re-trigger cubic}

[claude]

I didn't find any bugs — the regenerated wire models, method maps, and test updates all follow the established re-vendor pattern from #2912 — but since this changes protocol type definitions (ServerResult union, subscriptions/listen result mapping, the on_subscriptions_listen handler signature) and bumps the vendored spec pin, it's worth a maintainer's confirmation that the vendored schema matches upstream ead35b59.

Extended reasoning...

Overview

This PR re-vendors the 2026-07-28 draft schema at spec commit ead35b59, adding SubscriptionsListenResult / SubscriptionsListenResultMeta to the vendored JSON schema, the generated v2026_07_28 wire models, and the monolith types. It also rewires subscriptions/listen result mappings in methods.py (surface and monolith maps) from EmptyResult to the new type, updates the lowlevel on_subscriptions_listen callback annotation, adds SubscriptionsListenResultMeta to OPEN_CLASSES in the codegen script, and updates the methods/parity tests accordingly. Ten files changed, but most of the diff is generated or follows the prior re-vendor pattern.

Security risks

None apparent. The change is additive type plumbing: no auth, crypto, transport, or input-handling logic is touched, and there is no runtime caller of the new result type yet. The only slightly sensitive knob is marking SubscriptionsListenResultMeta as an open (extra="allow") class, which matches how the other *MetaObject classes are treated and is consistent with the spec's MetaObject semantics.

Level of scrutiny

Moderate. The hand-written pieces (union ordering with InputRequiredResult kept last, methods-map rows, OPEN_CLASSES entry, test fixtures) are internally consistent and verified by gen_surface_types.py --check plus the methods/parity test suites. However, this is a protocol-type definition change for the SDK and includes a vendored-schema pin bump whose fidelity to the upstream spec commit can't be verified from the diff alone — that spec-alignment judgment is best left to a maintainer. The on_subscriptions_listen return-type change is technically a signature change on a public constructor parameter, though the author notes there is no runtime caller yet.

Other factors

The bug-hunting pass found no issues, test coverage of the new type is thorough (result fixtures, required-field rejection, parity skip-list), and the PR description is detailed about the conformance-suite gap. There are no prior reviews or outstanding comments on this PR.