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Version Packages (alpha) (#2375)

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Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
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272
.changeset/pre.json
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@ -1,106 +1,170 @@
{
"mode": "pre",
"tag": "alpha",
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"@modelcontextprotocol/core-internal": "2.0.0-alpha.0",
"@modelcontextprotocol/express": "2.0.0-alpha.0",
"@modelcontextprotocol/fastify": "2.0.0-alpha.0",
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"@modelcontextprotocol/node": "2.0.0-alpha.0",
"@modelcontextprotocol/server": "2.0.0-alpha.0",
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"@modelcontextprotocol/test-integration": "2.0.0-alpha.0",
"@modelcontextprotocol/test-e2e": "2.0.0-alpha.0"
},
"changesets": [
"abort-handlers-on-close",
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"add-core-public-package",
"add-e2e-test-suite",
"add-fastify-middleware",
"add-hono-peer-dep",
"add-resource-size-field",
"add-sdk-http-error",
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"drop-zod-peer-dep",
"export-inmemory-transport",
"expose-auth-server-discovery",
"expose-icons-on-tools-and-prompts",
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"add-consumer-sse-e2e",
"add-core-public-package",
"add-e2e-test-suite",
"add-fastify-middleware",
"add-hono-peer-dep",
"add-request-state-codec",
"add-resource-size-field",
"add-sdk-http-error",
"add-server-legacy-package",
"add-version-negotiation-option",
"auth-dcr-hygiene",
"auth-iss-server-and-overload",
"auth-iss-validation",
"auth-sep-2352-credential-isolation",
"auth-surface-delta",
"bound-resumability-version-gates",
"brave-lions-glow",
"busy-rice-smoke",
"busy-weeks-hang",
"cacheable-result-cache-fields",
"cfworker-out-of-barrel",
"client-honor-cache-hints",
"client-http-stream-close-cancel",
"client-modern-era-inbound-drop",
"client-response-cache-substrate",
"codec-era-gates",
"codec-split-wire-break",
"codemod-backlog-batch",
"codemod-bigpatient-batch",
"codemod-completable-protocol",
"codemod-context-and-status",
"codemod-core-routing",
"codemod-flag-removed-task-options",
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"codemod-longtail-batch",
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"codemod-resolve-legacy-imports",
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"codemod-streamablehttperror-sdkhttperror",
"codemod-task-handler-methods",
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"core-subscription-schemas",
"create-mcp-handler-legacy-revision",
"create-mcp-handler",
"custom-methods-minimal",
"cyan-cycles-pump",
"deprecate-client-identity-accessors",
"dist-types-skiplibcheck",
"draft-spec-non-sep-conformance",
"drop-zod-peer-dep",
"envelope-auto-emission",
"export-inmemory-transport",
"expose-auth-server-discovery",
"expose-icons-on-tools-and-prompts",
"express-resource-server-auth",
"fast-dragons-lead",
"finish-sdkerror-capability",
"fix-abort-listener-leak",
"fix-conformance-server-leak",
"fix-oauth-5xx-discovery",
"fix-onerror-callbacks",
"fix-server-protocol-version",
"fix-stdio-epipe-crash",
"fix-stdio-windows-hide",
"fix-streamable-close-reentrant",
"fix-streamable-http-error-response",
"fix-transport-exact-optional-property-types",
"fix-unknown-tool-protocol-error",
"fix-validate-client-metadata-url",
"funky-baths-attack",
"gentle-planets-rest",
"handler-drop-node-face",
"heavy-walls-swim",
"hide-wire-only-members",
"hono-peer-optional",
"idjag-spec-type-export",
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"legacy-module-resolution-types",
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"missing-client-capability-error",
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"mrtr-server-seam",
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"node-forward-supported-versions",
"oauth-error-http200",
"odd-forks-enjoy",
"origin-validation-middleware",
"pin-modern-rejection-codes",
"protocol-pre-aborted-signal-wrap",
"quick-islands-occur",
"reconnection-scheduler",
"register-rawshape-compat",
"remove-websocket-transport",
"resource-not-found-32602",
"respect-capability-negotiation",
"restore-task-wire-types",
"rich-hounds-report",
"schema-object-type-for-unions",
"sep-2106-dialect-posture",
"sep-2243-mcp-param-client",
"sep-2243-mcp-param-server",
"sep-2243-std-header-server",
"sep-2350-scope-step-up",
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"sep-2577-deprecate-type-stacks",
"sep-2663-tasks-removal",
"sep-414-trace-context-meta-keys",
"server-ctx-log-request-related",
"server-serve-stdio",
"server-streamablehttp-store-first",
"shy-times-learn",
"spec-2907-error-code-renumber",
"spec-anchor-repin-2fb207da",
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"spec-type-schema",
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"spotty-cats-tickle",
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"stdio-subpath-export",
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"subscriptions-listen-result",
"subscriptions-listen-server",
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"tame-camels-greet",
"tender-snails-fold",
"token-provider-composable-auth",
"twelve-dodos-taste",
"use-scopes-supported-in-dcr",
"wire-public-separation",
"wire-server-discover",
"workerd-shim-vendors-cfworker",
"wraphandler-hook",
"zod-json-schema-compat",
"zod-jsonschema-fallback"
]
}

128
packages/client/CHANGELOG.md
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# @modelcontextprotocol/client
## 2.0.0-alpha.4
### Major Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `Client.listTools()` / `listPrompts()` / `listResources()` / `listResourceTemplates()` now **auto-aggregate every page** when called without a `cursor` and return the complete result with `nextCursor: undefined` (matching the C#, Java, and mcp.d SDKs). Pass an explicit `{ cursor }` string to fetch a single page; the per-page path is unchanged. Existing manual pagination loops keep working — the first iteration returns everything and the loop exits — but can be deleted. The aggregated result is written to the new pluggable `ResponseCacheStore` (default: a fresh per-instance `InMemoryResponseCacheStore`); a `ClientResponseCache` collaborator owns the eviction-generation guard and the derived `tools/list` index that `callTool`'s output validation and SEP-2243 `Mcp-Param-*` mirroring read. New exports: `ResponseCacheStore`, `CacheKey`, `CacheEntry`, `CacheScope`, `MaybePromise`, `InMemoryResponseCacheStore`; new `ClientOptions.responseCacheStore` / `ClientOptions.listMaxPages` (caps the auto-aggregate walk at 64 pages by default; throws `SdkError` with `SdkErrorCode.ListPaginationExceeded` on overrun so a partial aggregate is never cached). The store interface is async-ready (`MaybePromise<…>`); the in-memory default stays synchronous. Entries are automatically scoped by the connected server's identity and (when set) the consumer-supplied `cachePartition`, so a shared store does not collide across servers or principals; evictions are likewise scoped to the connected server's partitions.
**Behavior change (every era):** output-schema validator compilation is now lazy — validators are compiled on the first `callTool()` against the cached `tools/list` entry, not eagerly inside `listTools()`. `listTools()` no longer throws on an uncompilable `outputSchema` (every tool stays listed; the compile failure is captured per-tool); calling `callTool()` on the affected tool throws `ProtocolError(InvalidParams, "Tool 'X' has an invalid outputSchema: …")` before the request is sent — output-schema validation is never silently skipped. A pluggable `jsonSchemaValidator` provider therefore observes compilation at `callTool` time, not `listTools` time. The legacy-era `listTools()` path is unchanged at the wire level but is observably different at the validator-lifecycle level.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Split the wire layer into per-era codecs and make protocol-revision deletions physical. Deliberate wire/schema behavior changes (see docs/migration/support-2026-07-28.md "Per-era wire codecs"):
- `resultType` is no longer modeled by any neutral wire schema: `EmptyResultSchema` (strict) now rejects `{resultType}` bodies; on 2025-era connections a foreign `resultType` is stripped before validation instead of rejected; the member exists only inside the 2026-era codec, which requires it.
- `CallToolResult.content` / `ToolResultContent.content` are required at the wire boundary (`content.default([])` removed): handler results without `content` are rejected with `-32602` instead of silently defaulted, and content-less wire results fail the client parse loudly.
- Custom (3-arg) handlers now receive `_meta` minus the reserved envelope keys instead of having it deleted before params validation.
- `specTypeSchemas` re-scoped to the neutral model: result validators no longer accept `resultType`; task message-type validators and `RequestMetaEnvelope` left the public set (`SpecTypeName` narrowed).
- Role aggregate types/schemas (`ClientRequest`, `ServerResult`, …) no longer carry task vocabulary; the deprecated `Task*` types remain importable unchanged.
- Era-mismatched spec methods fail physically: inbound era-deleted methods get `-32601` even with a handler registered; outbound sends throw `SdkErrorCode.MethodNotSupportedByProtocolVersion` locally.
- Value guards (`isCallToolResult`, …) are documented as neutral-shape consumer checks, not wire validators.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - 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".
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-1613 / SEP-2106 (JSON Schema 2020-12 posture): the Node default JSON Schema validator is now `Ajv2020` (true draft 2020-12) instead of the draft-07 `Ajv` class — `$defs`/`prefixItems`/`unevaluatedProperties`/`dependentRequired` are now enforced where they were previously silently ignored; to opt back, construct the draft-07 instance with the v1 defaults — `const ajv = new Ajv({ strict: false, validateFormats: true, validateSchema: false, allErrors: true }); addFormats(ajv);` — and pass `new AjvJsonSchemaValidator(ajv)`. Schemas declaring a `$schema` other than 2020-12 are rejected with a clear error rather than mis-validating. `outputSchema` may now have a non-object root and `CallToolResult.structuredContent` is widened to `unknown` (a deliberate source-level break for typed consumers — see the migration guide for the narrowing pattern). Toward 2025-era clients McpServer wraps a non-object `outputSchema` (and the matching `structuredContent`) in a `{result: …}` envelope so the tool stays callable, with same-document `$ref`/`$dynamicRef` pointers rewritten to keep resolving — low-level `Server` users (those bypassing `McpServer` and registering a `tools/call` handler directly) get the same wrap by routing the result through the new `Server.projectCallToolResult(result, advertisedOutputSchema)`. Independently, on every era (the SEP's MUST applies regardless of client version), McpServer auto-appends a `TextContent` JSON serialisation when a handler returns non-object `structuredContent` without its own text block. The `structuredContent` presence check is `!== undefined` (not falsy) on both sides. Thanks @mattzcarey (#2249).
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `connect(transport, { prior: DiscoverResult })` for zero-round-trip reconnect (the gateway / distributed-client pattern). Supplying a previously-obtained `DiscoverResult` skips the `server/discover` probe: on a 2026-era server `connect()` sends nothing on the wire and `callTool()` etc. work immediately. Pair with the new `client.getDiscoverResult()` (populated by the `'auto'`-mode probe, by `client.discover()`, and by `connect({ prior })` itself) — the value round-trips through `JSON.stringify`, so a gateway can probe once, persist the blob, and feed it to every worker. Only reuse a persisted `DiscoverResult` across clients that present the same authorization context as the client that obtained it.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add opt-in protocol version negotiation on `ClientOptions.versionNegotiation`. The default is unchanged: without the option (or with `mode: 'legacy'`) the client performs today's 2025 connect sequence byte-identically. `mode: 'auto'` probes the server with `server/discover` at
connect time and conservatively falls back to the plain legacy `initialize` handshake on the same connection unless the outcome is definitive modern evidence (with a supported-versions list that has no 2025-era entry there is nothing to fall back to, and connect rejects
with a typed error instead); a network outage rejects with a typed connect error, and a probe timeout is transport-aware — on stdio it indicates
a legacy server and falls back to `initialize` on the same stream, on HTTP it rejects with a typed timeout error.
`mode: { pin: '<version>' }` negotiates exactly the pinned modern revision with no fallback. Probe policy lives under `probe: { timeoutMs? }` — the probe inherits the standard request timeout. The probe's `MCP-Protocol-Version`/`Mcp-Method` headers derive from the probe
message body; the transport version slot is never touched during negotiation, so legacy-era traffic carries zero 2026 headers by construction. Adds the `SdkErrorCode.EraNegotiationFailed` code for negotiation-phase connect failures.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Dynamic Client Registration hygiene for the 2026-07-28 authorization requirements (SEP-837, SEP-2207). New `resolveClientMetadata(provider)` reads `provider.clientMetadata` and applies the spec defaults — `application_type` derived from the redirect URIs (loopback or custom scheme → `'native'`, otherwise `'web'`), `grant_types: ['authorization_code', 'refresh_token']` when omitted — and `auth()` feeds the resolved document to DCR only (scope selection still reads the raw consumer-supplied `clientMetadata` so statically-registered/CIMD clients are not pushed into `offline_access` + `prompt=consent`); consumer-set values are never overwritten. DCR rejection now throws the new `RegistrationRejectedError` carrying the HTTP status, raw body, and submitted metadata — **breaking for direct `registerClient()` callers**: rejection no longer throws `OAuthError`, so update `instanceof` checks. `OAuthClientMetadata` gains a typed `application_type?: string` field (expected `'native'` / `'web'`; tolerant on parse). `OAuthErrorCode` adds `InvalidRedirectUri`. The token-exchange, refresh, and Cross-App Access (`requestJwtAuthorizationGrant` / `exchangeJwtAuthGrant`) paths now throw the new `InsecureTokenEndpointError` for a non-`https:` token endpoint (`localhost` / `127.0.0.1` / `::1` exempt), and `auth()` surfaces it on the refresh branch instead of silently re-authorizing.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2468 follow-up: `transport.finishAuth()` gains a `URLSearchParams` overload (preferred) that extracts `code`/`iss`, validates `iss` first, and on mismatch throws a sanitized `IssuerMismatchError` (no callback `error_description` text); callers remain responsible for `state`. **Behavior change for `@modelcontextprotocol/server-legacy`:** `mcpAuthRouter` now advertises `authorization_response_iss_parameter_supported` (default `true`; `ProxyOAuthServerProvider` reports `false`) and the bundled authorize handler appends `iss` (RFC 9207) to every `res.redirect(...)` your `OAuthServerProvider.authorize()` issues to the client's `redirect_uri`. If your provider redirects another way (`res.writeHead`, a separate consent-page response, or a standalone `authorizationHandler({provider})` without `issuerUrl`), append `params.issuer` as `iss` yourself or set `authorizationResponseIssParameterSupported: false` — otherwise RFC 9207-compliant clients (including this SDK) will reject the callback.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Implement RFC 9207 / RFC 8414 §3.3 OAuth issuer validation (SEP-2468). `discoverAuthorizationServerMetadata()` now rejects metadata whose `issuer` does not match the discovery URL (opt out via `skipIssuerValidation` / `AuthOptions.skipIssuerMetadataValidation` — security-weakening). `auth()`, `exchangeAuthorization()`, `fetchToken()`, and `transport.finishAuth(code, iss?)` now validate the authorization-callback `iss` against the recorded issuer before redeeming the code; new `IssuerMismatchError` and `validateAuthorizationResponseIssuer()` are exported.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Per-authorization-server credential isolation (SEP-2352). `auth()` now stamps an `issuer` field onto every value it passes to `saveTokens()` / `saveClientInformation()` and threads `{ issuer }` to `tokens()` / `clientInformation()`; on read, a stored credential whose stamp names a different authorization server is treated as `undefined`, so a `client_id` / `refresh_token` issued by one AS is never sent to another. Providers that round-trip stored values verbatim are protected with no code change; multi-AS providers may key storage on `ctx.issuer`. New `AuthorizationServerMismatchError` (callback-leg gate). `OAuthClientProvider.saveAuthorizationServerUrl()` / `authorizationServerUrl()` are deprecated (still written, never read). `ClientCredentialsProvider`, `PrivateKeyJwtProvider`, `StaticPrivateKeyJwtProvider`, and `CrossAppAccessProvider` gain `expectedIssuer` and no longer define `saveClientInformation()`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add the public surface for the 2026-07-28 authorization requirements. New `AuthOptions` type names the `auth()` options object and adds `iss` and `skipIssuerMetadataValidation` fields. `OAuthClientProvider.clientInformation()` / `.saveClientInformation()` / `.tokens()` / `.saveTokens()` accept an optional `OAuthClientInformationContext` carrying the authorization server's `issuer` so providers can key persisted credentials per authorization server. New `StoredOAuthTokens` / `StoredOAuthClientInformation` aliases add an `issuer` stamp field on top of the wire types (kept off the wire schemas so an authorization server cannot populate it) and become the parameter/return types of the credential methods. New `OAuthClientFlowError` base class in `authErrors.ts` for the flow-specific error classes that follow. All changes are additive — existing `OAuthClientProvider` implementations compile unchanged; the new fields are inert until the behavior changes that follow wire them up.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `Client` now **honours** the server-stamped SEP-2549 `ttlMs`/`cacheScope` cache hints on the cacheable verbs (`listTools()`, `listPrompts()`, `listResources()`, `listResourceTemplates()`, `readResource()`): a still-fresh held entry is served without a round trip. New `CacheableRequestOptions.cacheMode` (`'use'` — the default; `'refresh'` — always fetch and re-store; `'bypass'` — fetch without consulting or writing the cache) gives per-call control. The behaviour is opt-in by hint: a server that sends `ttlMs: 0` (the conservative default this SDK's server stamps) sees byte-identical behaviour — every call fetches.
Entries are automatically scoped by connected-server identity (derived from `serverInfo` after connect, encoded collision-free via `JSON.stringify`); `ClientOptions.cachePartition` is the opaque per-principal slot for `'private'`-scoped entries — set it to your principal identifier (e.g. the auth subject) when one `responseCacheStore` backs several principals. With the default `''` every entry lives at the connected server's shared partition (the safe single-tenant posture). `ClientOptions.defaultCacheTtlMs` (default `0`) supplies the TTL when a result lacks one (e.g. a legacy-era response); the server-supplied `ttlMs` is clamped at 24 h (`MAX_CACHE_TTL_MS`). The list verbs always store the aggregate (so `callTool`'s mirroring/output-validation index keeps working at any TTL); `readResource` stores only when the resolved TTL is positive. `notifications/resources/updated` evicts the cached `resources/read` body for that URI. `ResponseCacheStore` gained `delete(key)`; `InMemoryResponseCacheStore` is now bounded (`{ maxEntries }`, default 512, oldest-first eviction). New exports: `CacheMode`, `CacheableRequestOptions`, `InMemoryResponseCacheStoreOptions`, `MAX_CACHE_TTL_MS`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Client request cancellation on a 2026-07-28 Streamable HTTP connection now closes that request's SSE response stream — the spec cancellation signal — instead of POSTing `notifications/cancelled`. Cancellation on a 2025-era connection, and on stdio at any era, still sends `notifications/cancelled` as before. Adds the optional `Transport.hasPerRequestStream` capability flag (set on `StreamableHTTPClientTransport`) for the protocol layer to route the per-transport cancel path.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `SdkErrorCode.MethodNotSupportedByProtocolVersion`: a typed local error raised before anything reaches the transport when a spec method is sent toward a peer whose negotiated protocol version's wire era does not define it (for example `tasks/get` toward a 2026-07-28 peer). The protocol layer now resolves a per-era wire codec from the connection's negotiated protocol version (instance state on `Client`/`Server`, with the legacy era as the pre-negotiation default) and resolves per-method schemas at dispatch time instead of registration time; an edge classification on an inbound message is validated against that instance era, and a mismatch is rejected as an entry/routing error. Behavior on existing (2025-era) connections is unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Per-request `_meta` envelope auto-emission on modern-era connections: once a client negotiates a 2026-07-28+ protocol revision (via `versionNegotiation: { mode: 'auto' }` or `{ pin }`), it automatically attaches the reserved protocol-version / client-info / client-capabilities
`_meta` keys to every outgoing request and notification — you no longer set the envelope by hand. User-supplied `_meta` keys take precedence over the auto-attached ones; the auto-attached client-capabilities reflect what the client actually registered. Legacy-era connections
(the default, and the `'auto'`-mode fallback) never gain these keys, so 2025-era outbound traffic is byte-identical to before.
Adds `Client.getProtocolEra()` (`'legacy' | 'modern' | undefined`), the `ProtocolEra` type, `Client.setVersionNegotiation()` for configuring negotiation pre-connect on an already-constructed instance, and the `probe.maxRetries` knob (default `0`) which governs probe-timeout
re-sends only — the spec-mandated `-32022` corrective continuation is never counted against it. The `versionNegotiation` default remains `'legacy'`: absent (or `mode: 'legacy'`), `connect()` runs the plain 2025 sequence, byte-identical to a v1.x client.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `MissingRequiredClientCapabilityError`, the typed error class for the 2026-07-28 `-32021` protocol error (processing a request requires a capability the client did not declare). Its `data.requiredCapabilities` lists the missing capabilities and `ProtocolError.fromError` recognizes the code/data shape. The 2026-07-28 HTTP entry gains a pre-dispatch gate that refuses a request requiring an undeclared client capability with this error and HTTP status `400`; no method served on the 2026-07-28 registry currently carries such a requirement, so observable behavior is unchanged until methods with capability requirements exist.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add the client side of multi round-trip requests (protocol revision 2026-07-28, SEP-2322). The neutral `InputRequest`/`InputResponse`/`InputRequests`/`InputResponses`/`InputRequiredResult` types and the `isInputRequiredResult()` guard ship as the neutral surface (the
`inputRequired()` builder family and the `acceptedContent()` reader are exported by the server package as part of the server-side change); the 2026-07-28 wire codec models the in-band vocabulary (embedded requests and bare responses) and the retry-channel request fields. On the
client, an `input_required` answer to `tools/call`, `prompts/get`, or `resources/read` on a 2026-07-28 connection is now fulfilled automatically by default: the embedded requests are dispatched to the client's already-registered elicitation/sampling/roots handlers, and the
original call is retried with the collected `inputResponses`, a byte-exact echo of the opaque `requestState`, and a fresh request id, up to `inputRequired.maxRounds` rounds (default 10; exhaustion raises a typed `InputRequiredRoundsExceeded` error carrying the last result).
`client.callTool()` and its siblings keep returning their plain result types. `ClientOptions.inputRequired` (`autoFulfill`, `maxRounds`) configures the driver; manual mode is `autoFulfill: false` plus the per-call `allowInputRequired: true` request option and the
`withInputRequired()` schema wrapper. Retried requests surface their `inputResponses` to server handlers as bare response objects — entries in a wrapped `{method, result}` shape are dropped and reported via `ctx.mcpReq.droppedInputResponseKeys`. 2025-era behavior is unchanged:
the legacy wire has no `input_required` vocabulary and the legacy server-to-client request flow is untouched.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `resources/read` for an unknown URI now answers with JSON-RPC error code `-32602`
(Invalid Params) on every protocol revision, with `error.data.uri` echoing the
requested URI. The 2026-07-28 specification requires `-32602`; the v1.x SDK already
emitted `-32602` on earlier revisions, so v1.x peers see no change.
This supersedes an interim `-32002` emission that shipped in earlier v2 alphas. The
era-aware encode seam (`WireCodec.encodeErrorCode`) maps any handler-thrown `-32002`
to `-32602` on the wire; note that a `-32002` thrown without `data.uri` is emitted as
a bare `-32602` and is no longer recognizable as resource-not-found — throw
`ResourceNotFoundError` (or include `data: { uri }`) to preserve the classification.
`ProtocolErrorCode.ResourceNotFound` (`-32002`) remains importable as receive-tolerated
vocabulary; clients should accept both `-32602` and `-32002` from peers (the
specification's backwards-compatibility clause). The new typed `ResourceNotFoundError`
class carries `data.uri`, and `ProtocolError.fromError` reconstructs it from a `-32602`
only when `error.data` is exactly `{ uri: string }` (and nothing else), and from a
legacy `-32002` whenever `data.uri` is a string; a bare `-32002` without `data.uri`
stays a generic `ProtocolError`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2243 `Mcp-Param-*` client-side mirroring (protocol revision 2026-07-28). On a 2026-07-28 connection over Streamable HTTP, `Client.callTool()` now mirrors tool arguments designated with `x-mcp-header` in the tool's `inputSchema` into `Mcp-Param-{Name}` HTTP headers (with the spec's `=?base64?…?=` sentinel encoding for values that are not safe plain-ASCII field values), and on a non-stdio modern connection `Client.listTools()` (and the client's internal `tools/list` cache) exclude tool definitions whose `x-mcp-header` declarations violate the spec's constraints, logging a warning naming the tool and the reason. The legacy-era `callTool` and `listTools` paths are unchanged at the wire level. Browser environments skip mirroring (dynamically named headers cannot be statically allow-listed for credentialed CORS); a conforming SEP-2243 server will reject a `tools/call` whose body carries a non-null value for an `x-mcp-header` parameter when the matching header is absent, so calling such a tool with that argument from a browser is a known limitation. New `CallToolRequestOptions.toolDefinition` lets callers supply the tool definition directly so mirroring and output-schema validation can run without a prior `tools/list`. `TransportSendOptions.headers` is added (additive, optional) for per-request HTTP headers; the Streamable HTTP transport skips reserved standard/auth header names (`authorization`, `mcp-protocol-version`, `mcp-method`, `mcp-name`, `mcp-session-id`, `content-type`); transports that share a single channel (stdio, in-memory) ignore it.
The Streamable HTTP transport now emits the `Mcp-Name` standard header on every modern-enveloped request (`params.name` for `tools/call`/`prompts/get`, `params.uri` for `resources/read`), sentinel-encoded.
**Behavior change (modern era only):** on a modern-enveloped request the Streamable HTTP transport now surfaces an HTTP `400` whose body is a well-formed JSON-RPC error response addressed to the pending request id in-band as a `ProtocolError` (instead of `SdkHttpError`), so the `HEADER_MISMATCH` recovery retry can fire. Legacy-era exchanges are unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2350 scope step-up: on `403 insufficient_scope`, `StreamableHTTPClientTransport` now re-authorizes with the **union** of the previously-requested and challenged scopes (`computeScopeUnion`), bypassing the refresh-token branch when the union is a strict superset of the current token's granted scope (`isStrictScopeSuperset`, `AuthOptions.forceReauthorization`). New `onInsufficientScope: 'reauthorize' | 'throw'` (default `'reauthorize'`) and `maxStepUpRetries` (default 1) on `StreamableHTTPClientTransportOptions`; `'throw'` raises the new `InsufficientScopeError`. The GET listen-stream open path now applies the same step-up handling. The previous verbatim-header retry guard is replaced by the bounded per-send counter.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Align the 2026-07-28 protocol error codes to the spec renumber: `HeaderMismatch` is now `-32020` (was `-32001`), `MissingRequiredClientCapability` is now `-32021` (was `-32003`), and `UnsupportedProtocolVersion` is now `-32022` (was `-32004`). These codes are part of the draft 2026-07-28 protocol revision only and have never appeared on a 2025-era wire — the 2025 serving paths and the SDK-conventional `-32001` (`Session not found`) on the stateful Streamable HTTP transport are unchanged. `ProtocolErrorCode.MissingRequiredClientCapability`, `ProtocolErrorCode.UnsupportedProtocolVersion`, the `HEADER_MISMATCH_ERROR_CODE` constant, and the `HEADER_MISMATCH` / `MISSING_REQUIRED_CLIENT_CAPABILITY` / `UNSUPPORTED_PROTOCOL_VERSION` spec-type constants now carry the renumbered values; the `UnsupportedProtocolVersionError` and `MissingRequiredClientCapabilityError` classes (and `ProtocolError.fromError` recognition) follow. The client probe classifier recognizes `-32022` for the corrective continuation and the SEP-2243 one-refresh-on-miss retry triggers on `-32020`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `Client.listen(filter)` opens a `subscriptions/listen` stream on a 2026-07-28-era connection, resolving once the server's acknowledged notification arrives with an `McpSubscription { honoredFilter, close(), closed }`. `closed` is a `Promise<'local' | 'remote'>` that resolves exactly once when the subscription terminates (`'local'` = you called `close()`; `'remote'` = the server cancelled, the stream ended, or the transport dropped — re-listen if you still want events) and never rejects. Change notifications delivered on the stream dispatch to the existing `setNotificationHandler` registrations — the same handlers the 2025-era unsolicited notifications fire on a legacy connection — so `listen()` is era-transparent for consumers that already register those. `close()` aborts the listen request's stream (where the transport supports it) and sends `notifications/cancelled` referencing the listen id — both, on every transport; no automatic re-listen. On a 2025-era connection `listen()` throws a typed `MethodNotSupportedByProtocolVersion` steering to `resources/subscribe` and `ClientOptions.listChanged`. `ClientOptions.listChanged` now auto-opens a listen stream on a modern connection — the filter is the intersection of the configured sub-options and the server-advertised `listChanged` capabilities; auto-open is skipped (`client.autoOpenedSubscription` stays `undefined`) when that intersection is empty; otherwise the auto-opened subscription is exposed at `client.autoOpenedSubscription`. `TransportSendOptions` gains `requestSignal` (per-request abort) and `onRequestStreamEnd` (fires when a per-request response stream ends or errors for any non-deliberate reason) on the Streamable HTTP transport.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `subscriptions/listen` graceful close: per spec PR #2953, a server-side graceful close (`createMcpHandler` / `serveStdio` `close()`) now emits the empty `subscriptions/listen` JSON-RPC result (the new `SubscriptionsListenResult` — `_meta` carries the subscriptionId) before closing the stream, replacing the previous server-originated `notifications/cancelled`. On the client, `McpSubscription.closed` now resolves `'graceful'` for this signal (added alongside `'local'` and `'remote'`); a stream close without a result remains `'remote'` (unexpected disconnect).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Wire `server/discover` (protocol revision 2026-07-28) into the typed request funnel and serve it era-aware. The request joins `ClientRequestSchema`/`ServerResultSchema`/`ResultTypeMap` (per-era availability stays with the wire registries: only the 2026-era registry serves
it), and `Client.discover()` issues it as a typed request on 2026-era connections. A `Server` whose `supportedProtocolVersions` list carries a modern (2026-07-28+) revision installs the `server/discover` handler, advertising ONLY its modern revisions and excluding the
listChanged/subscribe-class capabilities until the `subscriptions/listen` flow ships; servers with today's default list are unchanged and keep answering `-32601`. The `initialize` handshake is now era-aware in the other direction: its accept check and counter-offer consult
only the legacy subset of the supported versions — a 2026-era revision is never negotiated via `initialize` — so a 2025-era client can never be offered a 2026 version string; with the default list this is byte-identical to previous behavior. Serving the 2026 revision to
ordinary HTTP/stdio traffic arrives with an upcoming server-side entry point: today the negotiation surface is client-side, and `mode: 'auto'` falls back cleanly against current SDK servers.
### Patch Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Drop inbound JSON-RPC requests on connections that negotiated the 2026-07-28 draft revision instead of answering them: the modern era has no server→client request channel (server-initiated interactions are carried in `input_required` results), and the stdio transport forbids the
client from writing JSON-RPC responses. Dropped requests are surfaced via `onerror`. Legacy-era connections, responses, and notifications are unchanged.
- [#2394](https://github.com/modelcontextprotocol/typescript-sdk/pull/2394) [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Fix the published declaration files for consumers compiling with `skipLibCheck: false`: the bundled `.d.mts` no longer leaves a dangling `URIComponent` reference (ajv's published types import it from `fast-uri`, whose export-assigned namespace the dts bundler cannot link — the type is now inlined via a dts-only path mapping), and no longer imports `json-schema-typed` from an undeclared dependency (it is inlined via `dts.resolve`). `@modelcontextprotocol/node` and `@modelcontextprotocol/server` drop stale `typesVersions` entries pointing at subpaths that never shipped. Package READMEs note that TypeScript >=6.0 requires `"types": ["node"]` since the published declarations reference `Buffer`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Complete the SEP-2577 `@deprecated` sweep on the public type surface (SEP-2596 Tier-1 obligation). Marks the full Logging type stack (`LoggingLevel`, `SetLevelRequest`, `LoggingMessageNotification` and params), the full Sampling type stack (`CreateMessageRequest`/`Result`, `SamplingMessage`, `ModelPreferences`/`ModelHint`, `ToolChoice`, `ToolUseContent`/`ToolResultContent`, and the `includeContext` enum values), the full Roots type stack (`Root`, `ListRootsRequest`/`Result`, `RootsListChangedNotification`), and `registerClient` (Dynamic Client Registration; prefer Client ID Metadata Documents per SEP-991). Mirrors the markers already present on the per-revision reference types. JSDoc only — wire behavior is unchanged; everything remains fully functional during the deprecation window (at least twelve months).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Re-pin the 2026-07-28 draft references (spec reference types, vendored schema.json twins, example corpus) to the latest spec commit and align the 2026-era wire surface with it. Deliberate 2026-era wire behavior changes (the released 2025-11-25 surface is untouched):
- `notifications/elicitation/complete` is no longer part of the 2026-07-28 wire registry (the draft removed the notification together with `elicitationId` on URL-mode elicitation). On connections negotiated at 2026-07-28, sending it — including via `Server.createElicitationCompletionNotifier()` — now fails locally with `SdkErrorCode.MethodNotSupportedByProtocolVersion`, and inbound copies are dropped as unknown notifications. Both remain fully supported on 2025-11-25.
- `notifications/cancelled` on 2026-era connections now parses with a revision-exact schema that requires `requestId` (the draft made it required); the notification `_meta` shape types the `io.modelcontextprotocol/subscriptionId` key. 2025-era parsing is unchanged.
- The error code `-32001` emitted for HTTP header/body mismatches is now defined by the draft schema (`HEADER_MISMATCH`); the emitted behavior is unchanged (documentation only).
No public API surface changes; the regenerated reference artifacts are internal/test-only.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Internal: regenerate the 2026-07-28 spec reference types from the latest draft schema (`DiscoverResult` now extends `CacheableResult`; `ElicitationCompleteNotificationParams` extracted as a named interface) and document the anchor lifecycle policy. Released-revision spec-type generation is now pinned to a fixed spec commit; draft anchors keep floating via the nightly refresh PRs. No public API or runtime behavior changes.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Freeze the per-era wire schemas as self-contained copies decoupled from the public types layer, and convert `WireCodec` to a function-only interface. Two small spec-conformance fixes ride along with the otherwise-pure refactor:
- The 2026 wire-true `resultType` member now defaults to `'complete'` when absent (the spec's receiver-side back-compat rule); the inbound `decodeResult` step continues to require it. The `server/discover` result accepts absent or malformed `ttlMs`/`cacheScope` (falling back to `0`/`'private'` per the spec's receiver leniency in caching.mdx) so the version-negotiation probe classifier stays behavior-neutral. Other cacheable result schemas are unchanged here; general receiver leniency for those belongs to the response-cache surface.
- The sampling `hasTools` discriminant now keys on `tools || toolChoice` (previously `tools` only), aligning the client and server selection of the with-tools result variant with `clientCapabilityRequirements`.
## 2.0.0-alpha.3
### Major Changes

2
packages/client/package.json
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@ -1,6 +1,6 @@
{
"name": "@modelcontextprotocol/client",
"version": "2.0.0-alpha.3",
"version": "2.0.0-alpha.4",
"description": "Model Context Protocol implementation for TypeScript - Client package",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

28
packages/codemod/CHANGELOG.md
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@ -1,5 +1,33 @@
# @modelcontextprotocol/codemod
## 2.0.0-alpha.2
### Minor Changes
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Three migration-sweep fixes. `completable()` calls whose first argument is an optional-wrapped schema are rewritten to apply `.optional()` to the `completable(...)` result — v2 resolves completion metadata after unwrapping an outer optional wrapper, so the v1 nesting produced empty completion lists without an error; wrapper shapes the codemod cannot invert get an action-required marker instead. Imports of `Protocol` and `mergeCapabilities` from v1's `shared/protocol.js` are no longer rewritten to a member the v2 packages do not export: the symbols are dropped from the rewritten import and an action-required marker explains the replacement (`fallbackRequestHandler` for unrouted inbound requests; a plain object spread for capability merging). The manifest zod-range warning now describes the symptom by vintage — zod 4.0–4.1 ranges fail type-checking (TS2769), while zod-3 ranges fail type-checking or at the first `tools/list` depending on the imported zod entry point.
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Migration-sweep batch. The ErrorCode split now coordinates with the surrounding check: an all-SDK condition's `instanceof ProtocolError`/`McpError` guard is rewritten to `SdkError`, a guard covering both enums gets a marker asking for a split, and an `ErrorCode` import with no rewritable member access on a v2 specifier is dropped with a marker instead of failing at module link time. Wrapping a raw shape with `z.object()` adds `import { z } from 'zod'` when the file has no `z` value binding (a non-import `z` binding gets a marker instead). The context-parameter rewrite finds the trailing `extra` parameter, covering the three-argument `registerResource` template callback without flagging its `variables` argument. Resource-server auth helpers routed to the frozen server-legacy copy get a marker on value imports and barrel re-exports (an info note for type-only imports), every rewritten `SdkHttpError` constructor site gets a marker, and single-argument `finishAuth(...)` calls in files the run changes get a run-log note (the one-argument `URLSearchParams` form is valid v2, so the note never re-fires on already-migrated trees). The codemod accepts a single source file as target — source rewrites scope to that file and manifest changes are reported, not applied — and the no-changes summary distinguishes "already on the v2 packages", "still on the v1 SDK under a transform subset", and "no MCP SDK imports found".
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Overhaul manifest handling. The codemod now discovers workspace-member manifests (npm/yarn/bun `workspaces` and `pnpm-workspace.yaml`), writes only the nearest `package.json`, and reports the exact dependency changes every other affected manifest needs, so you can apply them deliberately. The v2 additions are computed from the post-transform import state of the files each manifest owns, so already-migrated packages still receive the packages their imports need when the v1 dependency is removed; in hoisted monorepos, member usage counts toward the manifest that declares the SDK dependency, with a note naming the contributing members. File collection no longer follows symbolic links (pnpm `node_modules` layouts contain cycles that previously aborted the run) and honors `--ignore` patterns during directory descent. Manifests whose `zod` range cannot satisfy the v2 floor get a warning describing the runtime failure mode. `RunnerResult.packageJsonChanges` is now an array of per-manifest changes with optional `warnings` and `notes`.
### Patch Changes
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Backlog fixes. When the zod import injection fires in a package that declares no zod, the manifest pass adds it (devDependencies when only tests import it) so strict node_modules layouts install cleanly. The ErrorCode-split pairing re-points stale `as ProtocolError`/`as McpError` casts bound to subjects whose assertions it moves to `SdkError`. Handler registration resolves one same-file variable hop (`const S = ListToolsRequestSchema`) before declaring a schema custom. Shorthand and aliased destructures of SDK dynamic imports rename with the static-import pass. Call-shape assertions pinning a registration schema (`expect.objectContaining({ inputSchema: … })`) get an advisory. The guide covers dist-text pins (no CJS-resolvable subpaths, content-hashed chunks, changed quote style, ESM-only output).
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Fixes from migrating two large consumers. Registrations nested inside another handler's body no longer crash the transform with a whole-file rollback (calls process inner-first). Legacy `.tool()`/`.prompt()`/`.resource()` calls migrate without a direct `McpServer` import when their shape matches the v1 signature AND the receiver is named like an MCP server (`server`, `harness.mcp`, `this.mockServer`); other receivers are left alone, without hard markers, since their type is unknown to the codemod. `setRequestHandler`/`setNotificationHandler` with a schema _expression_ first argument get a marker pointing at the typed two-argument or custom three-argument form instead of being skipped silently, and `removeRequestHandler`/`removeNotificationHandler` with `Schema.shape.method.value` arguments rewrite to the method string. Destructured trailing callback parameters only count as the context when their keys look like context members, so template-variable destructures stop collecting false markers. The manifest zod note only appears for manifests that actually take part in the migration.
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Two long-standing intervention classes now migrate mechanically. `.code` reads on values an `instanceof SdkHttpError` check proves — in the same condition or the guarded block — rewrite to `.status` (v2 carries the HTTP status there; `.code` is an `SdkErrorCode` string); unprovable reads keep the existing warning. The context-property remap reaches three shapes the call-site scan missed: functions assigned to `fallbackRequestHandler`, parameters annotated with a context type directly or via a same-file alias (accesses remap in place, the parameter keeps its name), and contexts forwarded wholesale to helpers, which get an advisory naming the callee.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - The v1→v2 codemod no longer rewrites `taskStore`/`taskMessageQueue` McpServer constructor options into `capabilities.tasks` — that target does not exist in v2 (the experimental tasks runtime was removed, SEP-2663). The codemod now leaves the code untouched and emits an action-required diagnostic telling migrators to remove the option, matching the removal guidance already given for `experimental/tasks` imports and the migration guide.
- [#2386](https://github.com/modelcontextprotocol/typescript-sdk/pull/2386) [`36055d5`](https://github.com/modelcontextprotocol/typescript-sdk/commit/36055d5bbd1d078922aa025acea6880e61a20577) Thanks [@KKonstantinov](https://github.com/KKonstantinov)! - Preserve a leading `#!` shebang (and the blank lines after it) when migrating a file. Some transforms drop the shebang because it is leading trivia of the first import they rewrite; the codemod now captures it before transforms and restores it before saving, so CLI packages whose `bin` points at the migrated entry keep working.
- [#2393](https://github.com/modelcontextprotocol/typescript-sdk/pull/2393) [`e4e8b22`](https://github.com/modelcontextprotocol/typescript-sdk/commit/e4e8b22dff6c48b9a46fd960c9171aed44a996a8) Thanks [@felixweinberger](https://github.com/felixweinberger)! - The explicit-`undefined` result-schema removal now requires the same proof as the schema-identifier path: `request()` calls must carry a provably literal spec method, and `callTool()` calls whose first argument is a primitive are left alone. Previously, any file importing an MCP package could have the middle argument deleted from an unrelated `.request()` / `.callTool()` member call on a non-SDK receiver (e.g. a bespoke `end.request('ping', undefined, id)` helper), corrupting the call.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - v1-to-v2: now wraps `outputSchema` raw shapes with `z.object()`; importMap covers `sdk/server/express.js`, `sdk/server/middleware/hostHeaderValidation.js`, and `sdk/client/auth-extensions.js`. The unreachable `expressMiddleware` transform is removed.
- [#2383](https://github.com/modelcontextprotocol/typescript-sdk/pull/2383) [`9f8ba61`](https://github.com/modelcontextprotocol/typescript-sdk/commit/9f8ba6127989c371cccf0dbb72ef0cbf4726f9b0) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Keep the result-schema argument on `request()` calls unless the method is a literal spec method, and keep the generic passthrough `ResultSchema` even then. Schema-less v2 `request()` enforces the spec result schema for spec methods and throws a `TypeError` for non-spec methods, so dropping the schema from a dynamic-method call site (the proxy/forwarder shape, `request({ method, params }, ResultSchema)`) or from a custom-method call broke the call. `callTool()` is unaffected — v2 `callTool()` has no schema parameter.
## 2.0.0-alpha.1
### Minor Changes

2
packages/codemod/package.json
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@ -1,6 +1,6 @@
{
"name": "@modelcontextprotocol/codemod",
"version": "2.0.0-alpha.1",
"version": "2.0.0-alpha.2",
"description": "Codemod to migrate MCP TypeScript SDK code from v1 to v2",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

146
packages/core-internal/CHANGELOG.md
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@ -1,5 +1,151 @@
# @modelcontextprotocol/core-internal
## 2.0.0-alpha.3
### Major Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Split the wire layer into per-era codecs and make protocol-revision deletions physical. Deliberate wire/schema behavior changes (see docs/migration/support-2026-07-28.md "Per-era wire codecs"):
- `resultType` is no longer modeled by any neutral wire schema: `EmptyResultSchema` (strict) now rejects `{resultType}` bodies; on 2025-era connections a foreign `resultType` is stripped before validation instead of rejected; the member exists only inside the 2026-era codec, which requires it.
- `CallToolResult.content` / `ToolResultContent.content` are required at the wire boundary (`content.default([])` removed): handler results without `content` are rejected with `-32602` instead of silently defaulted, and content-less wire results fail the client parse loudly.
- Custom (3-arg) handlers now receive `_meta` minus the reserved envelope keys instead of having it deleted before params validation.
- `specTypeSchemas` re-scoped to the neutral model: result validators no longer accept `resultType`; task message-type validators and `RequestMetaEnvelope` left the public set (`SpecTypeName` narrowed).
- Role aggregate types/schemas (`ClientRequest`, `ServerResult`, …) no longer carry task vocabulary; the deprecated `Task*` types remain importable unchanged.
- Era-mismatched spec methods fail physically: inbound era-deleted methods get `-32601` even with a handler registered; outbound sends throw `SdkErrorCode.MethodNotSupportedByProtocolVersion` locally.
- Value guards (`isCallToolResult`, …) are documented as neutral-shape consumer checks, not wire validators.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - 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".
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add opt-in protocol version negotiation on `ClientOptions.versionNegotiation`. The default is unchanged: without the option (or with `mode: 'legacy'`) the client performs today's 2025 connect sequence byte-identically. `mode: 'auto'` probes the server with `server/discover` at
connect time and conservatively falls back to the plain legacy `initialize` handshake on the same connection unless the outcome is definitive modern evidence (with a supported-versions list that has no 2025-era entry there is nothing to fall back to, and connect rejects
with a typed error instead); a network outage rejects with a typed connect error, and a probe timeout is transport-aware — on stdio it indicates
a legacy server and falls back to `initialize` on the same stream, on HTTP it rejects with a typed timeout error.
`mode: { pin: '<version>' }` negotiates exactly the pinned modern revision with no fallback. Probe policy lives under `probe: { timeoutMs? }` — the probe inherits the standard request timeout. The probe's `MCP-Protocol-Version`/`Mcp-Method` headers derive from the probe
message body; the transport version slot is never touched during negotiation, so legacy-era traffic carries zero 2026 headers by construction. Adds the `SdkErrorCode.EraNegotiationFailed` code for negotiation-phase connect failures.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Dynamic Client Registration hygiene for the 2026-07-28 authorization requirements (SEP-837, SEP-2207). New `resolveClientMetadata(provider)` reads `provider.clientMetadata` and applies the spec defaults — `application_type` derived from the redirect URIs (loopback or custom scheme → `'native'`, otherwise `'web'`), `grant_types: ['authorization_code', 'refresh_token']` when omitted — and `auth()` feeds the resolved document to DCR only (scope selection still reads the raw consumer-supplied `clientMetadata` so statically-registered/CIMD clients are not pushed into `offline_access` + `prompt=consent`); consumer-set values are never overwritten. DCR rejection now throws the new `RegistrationRejectedError` carrying the HTTP status, raw body, and submitted metadata — **breaking for direct `registerClient()` callers**: rejection no longer throws `OAuthError`, so update `instanceof` checks. `OAuthClientMetadata` gains a typed `application_type?: string` field (expected `'native'` / `'web'`; tolerant on parse). `OAuthErrorCode` adds `InvalidRedirectUri`. The token-exchange, refresh, and Cross-App Access (`requestJwtAuthorizationGrant` / `exchangeJwtAuthGrant`) paths now throw the new `InsecureTokenEndpointError` for a non-`https:` token endpoint (`localhost` / `127.0.0.1` / `::1` exempt), and `auth()` surfaces it on the refresh branch instead of silently re-authorizing.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Implement RFC 9207 / RFC 8414 §3.3 OAuth issuer validation (SEP-2468). `discoverAuthorizationServerMetadata()` now rejects metadata whose `issuer` does not match the discovery URL (opt out via `skipIssuerValidation` / `AuthOptions.skipIssuerMetadataValidation` — security-weakening). `auth()`, `exchangeAuthorization()`, `fetchToken()`, and `transport.finishAuth(code, iss?)` now validate the authorization-callback `iss` against the recorded issuer before redeeming the code; new `IssuerMismatchError` and `validateAuthorizationResponseIssuer()` are exported.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add the public surface for the 2026-07-28 authorization requirements. New `AuthOptions` type names the `auth()` options object and adds `iss` and `skipIssuerMetadataValidation` fields. `OAuthClientProvider.clientInformation()` / `.saveClientInformation()` / `.tokens()` / `.saveTokens()` accept an optional `OAuthClientInformationContext` carrying the authorization server's `issuer` so providers can key persisted credentials per authorization server. New `StoredOAuthTokens` / `StoredOAuthClientInformation` aliases add an `issuer` stamp field on top of the wire types (kept off the wire schemas so an authorization server cannot populate it) and become the parameter/return types of the credential methods. New `OAuthClientFlowError` base class in `authErrors.ts` for the flow-specific error classes that follow. All changes are additive — existing `OAuthClientProvider` implementations compile unchanged; the new fields are inert until the behavior changes that follow wire them up.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Results of the cacheable 2026-07-28 operations (`tools/list`, `prompts/list`, `resources/list`, `resources/templates/list`, `resources/read`, `server/discover`) now always carry the revision's required `ttlMs`/`cacheScope` fields when served on that revision, defaulting to `ttlMs: 0` / `cacheScope: 'private'`. Servers can configure the emitted values with the new `ServerOptions.cacheHints` option (per operation) and the new `cacheHint` member of the `registerResource` config (per resource); resolution is per field, most specific author first: cache fields returned by a handler win over the per-resource hint, which wins over the per-operation hint, and configured hints are validated at construction/registration time (`RangeError` on invalid values). Responses on 2025-era connections are unchanged and never carry these fields. Note for untyped callers: `registerResource` now interprets a `cacheHint` key in its config object — it is validated and kept out of the resource's list metadata, where it was previously passed through as ordinary metadata.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Client request cancellation on a 2026-07-28 Streamable HTTP connection now closes that request's SSE response stream — the spec cancellation signal — instead of POSTing `notifications/cancelled`. Cancellation on a 2025-era connection, and on stdio at any era, still sends `notifications/cancelled` as before. Adds the optional `Transport.hasPerRequestStream` capability flag (set on `StreamableHTTPClientTransport`) for the protocol layer to route the per-transport cancel path.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `SdkErrorCode.MethodNotSupportedByProtocolVersion`: a typed local error raised before anything reaches the transport when a spec method is sent toward a peer whose negotiated protocol version's wire era does not define it (for example `tasks/get` toward a 2026-07-28 peer). The protocol layer now resolves a per-era wire codec from the connection's negotiated protocol version (instance state on `Client`/`Server`, with the legacy era as the pre-negotiation default) and resolves per-method schemas at dispatch time instead of registration time; an edge classification on an inbound message is validated against that instance era, and a mismatch is rejected as an entry/routing error. Behavior on existing (2025-era) connections is unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Per-request `_meta` envelope auto-emission on modern-era connections: once a client negotiates a 2026-07-28+ protocol revision (via `versionNegotiation: { mode: 'auto' }` or `{ pin }`), it automatically attaches the reserved protocol-version / client-info / client-capabilities
`_meta` keys to every outgoing request and notification — you no longer set the envelope by hand. User-supplied `_meta` keys take precedence over the auto-attached ones; the auto-attached client-capabilities reflect what the client actually registered. Legacy-era connections
(the default, and the `'auto'`-mode fallback) never gain these keys, so 2025-era outbound traffic is byte-identical to before.
Adds `Client.getProtocolEra()` (`'legacy' | 'modern' | undefined`), the `ProtocolEra` type, `Client.setVersionNegotiation()` for configuring negotiation pre-connect on an already-constructed instance, and the `probe.maxRetries` knob (default `0`) which governs probe-timeout
re-sends only — the spec-mandated `-32022` corrective continuation is never counted against it. The `versionNegotiation` default remains `'legacy'`: absent (or `mode: 'legacy'`), `connect()` runs the plain 2025 sequence, byte-identical to a v1.x client.
- [#2381](https://github.com/modelcontextprotocol/typescript-sdk/pull/2381) [`f0bf785`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f0bf785239af67f0cfce24575fec9c1193deaff1) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Serve `input_required` handlers on 2025-era connections: the legacy shim (on by default) converts each embedded request of an `input_required` return into a real server→client request (`elicitation/create`, `sampling/createMessage`, `roots/list`) over the live session — stamped with the originating request's id for stream association — and re-enters the handler with the collected `inputResponses` until a final result. Handlers are written once in the 2026 `inputRequired(...)` style and serve both eras; the previous loud `-32603` failure remains available via `ServerOptions.inputRequired.legacyShim: false`. Knobs: `inputRequired.maxRounds` (default 8) and `inputRequired.roundTimeoutMs` (default 600 000 ms per leg; legs carry a progressToken so a client reporting progress mid-leg resets the leg timeout). Semantics mirror the modern client driver exactly: per-round replaced `inputResponses`, byte-exact `requestState` echo with the verify hook running every round, paced requestState-only rounds, and elicitation accepted content passed through UNVALIDATED (the handler validates via the schema-aware `acceptedContent` overload, exactly as on the 2026 era). URL-mode legs synthesize the `elicitationId` the 2025-11-25 wire requires. Failures surface per family (`tools/call` → `isError` tool result; `prompts/get` / `resources/read` → JSON-RPC error); stateless legacy HTTP degrades to a clean capability refusal; the shim emits no progress of its own (the originating progressToken is the handler's single must-increase stream — the shim never adds a second author to it).
`ctx.mcpReq.requestState` is now a typed accessor: `ctx.mcpReq.requestState<T>()` returns the payload the configured `requestState.verify` hook resolved with (e.g. `createRequestStateCodec.verify` — the hook's return value is now load-bearing; verifiers that are not also decoders should resolve `undefined`), the raw wire string when no hook is configured, or `undefined` when the round carried no state. Code that read the property directly becomes a call: `ctx.mcpReq.requestState` → `ctx.mcpReq.requestState<string>()`. Note the member is now always present (a function), so truthiness no longer means "has state", and it is dropped by JSON serialization of the context.
New typed readers for `inputResponses`, exported from `@modelcontextprotocol/server`: a schema-aware `acceptedContent(responses, key, schema)` overload (validates untrusted accepted content against any synchronous Standard Schema) and `inputResponse(responses, key)` (discriminated `missing | elicit | sampling | roots` view, for decline/cancel detection and the non-elicitation kinds). Content conveniences like text extraction stay in application code as one-liners over the discriminated view.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `MissingRequiredClientCapabilityError`, the typed error class for the 2026-07-28 `-32021` protocol error (processing a request requires a capability the client did not declare). Its `data.requiredCapabilities` lists the missing capabilities and `ProtocolError.fromError` recognizes the code/data shape. The 2026-07-28 HTTP entry gains a pre-dispatch gate that refuses a request requiring an undeclared client capability with this error and HTTP status `400`; no method served on the 2026-07-28 registry currently carries such a requirement, so observable behavior is unchanged until methods with capability requirements exist.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add the client side of multi round-trip requests (protocol revision 2026-07-28, SEP-2322). The neutral `InputRequest`/`InputResponse`/`InputRequests`/`InputResponses`/`InputRequiredResult` types and the `isInputRequiredResult()` guard ship as the neutral surface (the
`inputRequired()` builder family and the `acceptedContent()` reader are exported by the server package as part of the server-side change); the 2026-07-28 wire codec models the in-band vocabulary (embedded requests and bare responses) and the retry-channel request fields. On the
client, an `input_required` answer to `tools/call`, `prompts/get`, or `resources/read` on a 2026-07-28 connection is now fulfilled automatically by default: the embedded requests are dispatched to the client's already-registered elicitation/sampling/roots handlers, and the
original call is retried with the collected `inputResponses`, a byte-exact echo of the opaque `requestState`, and a fresh request id, up to `inputRequired.maxRounds` rounds (default 10; exhaustion raises a typed `InputRequiredRoundsExceeded` error carrying the last result).
`client.callTool()` and its siblings keep returning their plain result types. `ClientOptions.inputRequired` (`autoFulfill`, `maxRounds`) configures the driver; manual mode is `autoFulfill: false` plus the per-call `allowInputRequired: true` request option and the
`withInputRequired()` schema wrapper. Retried requests surface their `inputResponses` to server handlers as bare response objects — entries in a wrapped `{method, result}` shape are dropped and reported via `ctx.mcpReq.droppedInputResponseKeys`. 2025-era behavior is unchanged:
the legacy wire has no `input_required` vocabulary and the legacy server-to-client request flow is untouched.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add the server side of multi round-trip requests (protocol revision 2026-07-28, SEP-2322). Handlers for `tools/call`, `prompts/get`, and `resources/read` can return the value built by `inputRequired()` (exported from the server package together with `acceptedContent()`)
to request additional client input in-band; the structured-content requirement and the tools/call result-schema validation are skipped for that return, the encode seam emits it as `resultType: 'input_required'`, and the handler reads the responses on re-entry from
`ctx.mcpReq.inputResponses` (with non-bare entries reported via `ctx.mcpReq.droppedInputResponseKeys`). The seam re-checks the at-least-one rule for hand-built results, checks every embedded request against the capabilities the client declared on that request's envelope
(answering the typed `-32021` error on violation), and fails loudly — never emitting a mis-typed result — when an input-required value is returned from any other method. Toward a 2025-era request the return is served by the default-on legacy shim (real server→client requests plus handler re-entry); the loud failure for that case remains available via `ServerOptions.inputRequired.legacyShim: false`. A `UrlElicitationRequiredError` escaping a handler on a 2026-era request
fails as an internal error with a clear steer to `inputRequired.elicitUrl(...)`, so the `-32042` error never reaches the 2026-07-28 wire; 2025-era serving keeps today's `-32042` behavior
exactly. The typed local error raised when push-style server-to-client request APIs are used while serving a 2026-era request now steers to `inputRequired(...)`. Tool, prompt, and resource callback types accept the new return alongside their existing result types; 2025-era
wire behavior is unchanged. An optional `ServerOptions.requestState.verify` hook lets a server integrity-check the echoed `requestState` before the handler runs — a throw answers the wire-level `-32602` Invalid Params error with `data.reason: 'invalid_request_state'`; the SDK provides no default verification.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `resources/read` for an unknown URI now answers with JSON-RPC error code `-32602`
(Invalid Params) on every protocol revision, with `error.data.uri` echoing the
requested URI. The 2026-07-28 specification requires `-32602`; the v1.x SDK already
emitted `-32602` on earlier revisions, so v1.x peers see no change.
This supersedes an interim `-32002` emission that shipped in earlier v2 alphas. The
era-aware encode seam (`WireCodec.encodeErrorCode`) maps any handler-thrown `-32002`
to `-32602` on the wire; note that a `-32002` thrown without `data.uri` is emitted as
a bare `-32602` and is no longer recognizable as resource-not-found — throw
`ResourceNotFoundError` (or include `data: { uri }`) to preserve the classification.
`ProtocolErrorCode.ResourceNotFound` (`-32002`) remains importable as receive-tolerated
vocabulary; clients should accept both `-32602` and `-32002` from peers (the
specification's backwards-compatibility clause). The new typed `ResourceNotFoundError`
class carries `data.uri`, and `ProtocolError.fromError` reconstructs it from a `-32602`
only when `error.data` is exactly `{ uri: string }` (and nothing else), and from a
legacy `-32002` whenever `data.uri` is a string; a bare `-32002` without `data.uri`
stays a generic `ProtocolError`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-1613 / SEP-2106 (JSON Schema 2020-12 posture): the Node default JSON Schema validator is now `Ajv2020` (true draft 2020-12) instead of the draft-07 `Ajv` class — `$defs`/`prefixItems`/`unevaluatedProperties`/`dependentRequired` are now enforced where they were previously silently ignored; to opt back, construct the draft-07 instance with the v1 defaults — `const ajv = new Ajv({ strict: false, validateFormats: true, validateSchema: false, allErrors: true }); addFormats(ajv);` — and pass `new AjvJsonSchemaValidator(ajv)`. Schemas declaring a `$schema` other than 2020-12 are rejected with a clear error rather than mis-validating. `outputSchema` may now have a non-object root and `CallToolResult.structuredContent` is widened to `unknown` (a deliberate source-level break for typed consumers — see the migration guide for the narrowing pattern). Toward 2025-era clients McpServer wraps a non-object `outputSchema` (and the matching `structuredContent`) in a `{result: …}` envelope so the tool stays callable, with same-document `$ref`/`$dynamicRef` pointers rewritten to keep resolving — low-level `Server` users (those bypassing `McpServer` and registering a `tools/call` handler directly) get the same wrap by routing the result through the new `Server.projectCallToolResult(result, advertisedOutputSchema)`. Independently, on every era (the SEP's MUST applies regardless of client version), McpServer auto-appends a `TextContent` JSON serialisation when a handler returns non-object `structuredContent` without its own text block. The `structuredContent` presence check is `!== undefined` (not falsy) on both sides. Thanks @mattzcarey (#2249).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2243 `Mcp-Param-*` client-side mirroring (protocol revision 2026-07-28). On a 2026-07-28 connection over Streamable HTTP, `Client.callTool()` now mirrors tool arguments designated with `x-mcp-header` in the tool's `inputSchema` into `Mcp-Param-{Name}` HTTP headers (with the spec's `=?base64?…?=` sentinel encoding for values that are not safe plain-ASCII field values), and on a non-stdio modern connection `Client.listTools()` (and the client's internal `tools/list` cache) exclude tool definitions whose `x-mcp-header` declarations violate the spec's constraints, logging a warning naming the tool and the reason. The legacy-era `callTool` and `listTools` paths are unchanged at the wire level. Browser environments skip mirroring (dynamically named headers cannot be statically allow-listed for credentialed CORS); a conforming SEP-2243 server will reject a `tools/call` whose body carries a non-null value for an `x-mcp-header` parameter when the matching header is absent, so calling such a tool with that argument from a browser is a known limitation. New `CallToolRequestOptions.toolDefinition` lets callers supply the tool definition directly so mirroring and output-schema validation can run without a prior `tools/list`. `TransportSendOptions.headers` is added (additive, optional) for per-request HTTP headers; the Streamable HTTP transport skips reserved standard/auth header names (`authorization`, `mcp-protocol-version`, `mcp-method`, `mcp-name`, `mcp-session-id`, `content-type`); transports that share a single channel (stdio, in-memory) ignore it.
The Streamable HTTP transport now emits the `Mcp-Name` standard header on every modern-enveloped request (`params.name` for `tools/call`/`prompts/get`, `params.uri` for `resources/read`), sentinel-encoded.
**Behavior change (modern era only):** on a modern-enveloped request the Streamable HTTP transport now surfaces an HTTP `400` whose body is a well-formed JSON-RPC error response addressed to the pending request id in-band as a `ProtocolError` (instead of `SdkHttpError`), so the `HEADER_MISMATCH` recovery retry can fire. Legacy-era exchanges are unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2243 standard-header server-side validation (protocol revision 2026-07-28). On the modern (2026-07-28) serving path, `createMcpHandler` now enforces the required `Mcp-Method` and `Mcp-Name` standard request headers in addition to the existing `MCP-Protocol-Version` and `Mcp-Method` cross-checks: a modern request without an `Mcp-Method` header, a `tools/call` / `prompts/get` / `resources/read` request without an `Mcp-Name` header, an `Mcp-Name` header carrying an invalid `=?base64?…?=` sentinel, and an `Mcp-Name` header whose (decoded) value disagrees with the body's `params.name` / `params.uri` are all rejected with `400 Bad Request` and JSON-RPC `-32020` (`HeaderMismatch`). The 2025-era serving paths are unchanged.
New public surface:
- `@modelcontextprotocol/server`: the `mcpNameHeader` field on `InboundHttpRequest`, and the `'standard-header-validation'` member of `InboundValidationRung` (with `client-capabilities` / `param-header-validation` renumbered).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Align the 2026-07-28 protocol error codes to the spec renumber: `HeaderMismatch` is now `-32020` (was `-32001`), `MissingRequiredClientCapability` is now `-32021` (was `-32003`), and `UnsupportedProtocolVersion` is now `-32022` (was `-32004`). These codes are part of the draft 2026-07-28 protocol revision only and have never appeared on a 2025-era wire — the 2025 serving paths and the SDK-conventional `-32001` (`Session not found`) on the stateful Streamable HTTP transport are unchanged. `ProtocolErrorCode.MissingRequiredClientCapability`, `ProtocolErrorCode.UnsupportedProtocolVersion`, the `HEADER_MISMATCH_ERROR_CODE` constant, and the `HEADER_MISMATCH` / `MISSING_REQUIRED_CLIENT_CAPABILITY` / `UNSUPPORTED_PROTOCOL_VERSION` spec-type constants now carry the renumbered values; the `UnsupportedProtocolVersionError` and `MissingRequiredClientCapabilityError` classes (and `ProtocolError.fromError` recognition) follow. The client probe classifier recognizes `-32022` for the corrective continuation and the SEP-2243 one-refresh-on-miss retry triggers on `-32020`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `Client.listen(filter)` opens a `subscriptions/listen` stream on a 2026-07-28-era connection, resolving once the server's acknowledged notification arrives with an `McpSubscription { honoredFilter, close(), closed }`. `closed` is a `Promise<'local' | 'remote'>` that resolves exactly once when the subscription terminates (`'local'` = you called `close()`; `'remote'` = the server cancelled, the stream ended, or the transport dropped — re-listen if you still want events) and never rejects. Change notifications delivered on the stream dispatch to the existing `setNotificationHandler` registrations — the same handlers the 2025-era unsolicited notifications fire on a legacy connection — so `listen()` is era-transparent for consumers that already register those. `close()` aborts the listen request's stream (where the transport supports it) and sends `notifications/cancelled` referencing the listen id — both, on every transport; no automatic re-listen. On a 2025-era connection `listen()` throws a typed `MethodNotSupportedByProtocolVersion` steering to `resources/subscribe` and `ClientOptions.listChanged`. `ClientOptions.listChanged` now auto-opens a listen stream on a modern connection — the filter is the intersection of the configured sub-options and the server-advertised `listChanged` capabilities; auto-open is skipped (`client.autoOpenedSubscription` stays `undefined`) when that intersection is empty; otherwise the auto-opened subscription is exposed at `client.autoOpenedSubscription`. `TransportSendOptions` gains `requestSignal` (per-request abort) and `onRequestStreamEnd` (fires when a per-request response stream ends or errors for any non-deliberate reason) on the Streamable HTTP transport.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `subscriptions/listen` graceful close: per spec PR #2953, a server-side graceful close (`createMcpHandler` / `serveStdio` `close()`) now emits the empty `subscriptions/listen` JSON-RPC result (the new `SubscriptionsListenResult` — `_meta` carries the subscriptionId) before closing the stream, replacing the previous server-originated `notifications/cancelled`. On the client, `McpSubscription.closed` now resolves `'graceful'` for this signal (added alongside `'local'` and `'remote'`); a stream close without a result remains `'remote'` (unexpected disconnect).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `subscriptions/listen` (SEP-1865) is served by both serving entries on protocol revision 2026-07-28. The entry owns ack-first, per-stream filtering, subscription-id stamping, keepalive (HTTP), the pre-ack `-32603` capacity guard, and teardown (HTTP stream close; one
`notifications/cancelled` per subscription on stdio). `server/discover` now advertises `listChanged`/`subscribe` capability bits — the rider that suppressed them until listen was served is discharged.
Under `createMcpHandler` the consumer's factory **is** constructed for `subscriptions/listen` (a capabilities-only probe so the acknowledged filter reflects what the server advertises; the instance is never connected and is closed immediately). Per-request authorization performed inside the factory therefore sees listen requests; token verification still belongs at the middleware layer mounted in front of the entry.
New public surface:
- `@modelcontextprotocol/server`: `ServerEventBus`, `ServerEvent`, `ServerNotifier` (types); `InMemoryServerEventBus` (class).
- `McpHttpHandler` gains `.notify` (`ServerNotifier`: `toolsChanged()`, `promptsChanged()`, `resourcesChanged()`, `resourceUpdated(uri)`) and `.bus` (the `ServerEventBus` listen streams subscribe to).
- `CreateMcpHandlerOptions` gains `bus?: ServerEventBus` (an in-process `InMemoryServerEventBus` is created when omitted), `maxSubscriptions?: number` (default 1024), and `keepAliveMs?: number` (default 15000).
- `ServeStdioOptions` gains `maxSubscriptions?: number` (default 1024). On a modern-pinned connection `serveStdio` routes the pinned instance's existing `send*ListChanged()` calls onto active subscriptions; legacy connections are unchanged.
- `@modelcontextprotocol/server`: `SUBSCRIPTION_ID_META_KEY` (const); `SubscriptionFilter`, `SubscriptionsListenRequest`, `SubscriptionsListenRequestParams`, `SubscriptionsAcknowledgedNotification`, `SubscriptionsAcknowledgedNotificationParams` (types).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Wire `server/discover` (protocol revision 2026-07-28) into the typed request funnel and serve it era-aware. The request joins `ClientRequestSchema`/`ServerResultSchema`/`ResultTypeMap` (per-era availability stays with the wire registries: only the 2026-era registry serves
it), and `Client.discover()` issues it as a typed request on 2026-era connections. A `Server` whose `supportedProtocolVersions` list carries a modern (2026-07-28+) revision installs the `server/discover` handler, advertising ONLY its modern revisions and excluding the
listChanged/subscribe-class capabilities until the `subscriptions/listen` flow ships; servers with today's default list are unchanged and keep answering `-32601`. The `initialize` handshake is now era-aware in the other direction: its accept check and counter-offer consult
only the legacy subset of the supported versions — a 2026-era revision is never negotiated via `initialize` — so a 2025-era client can never be offered a 2026 version string; with the default list this is byte-identical to previous behavior. Serving the 2026 revision to
ordinary HTTP/stdio traffic arrives with an upcoming server-side entry point: today the negotiation surface is client-side, and `mode: 'auto'` falls back cleanly against current SDK servers.
### Patch Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Pin the modern (2026-07-28) HTTP serving path's rejection codes to the assignments the published conformance suite asserts: a header/body cross-check mismatch (`MCP-Protocol-Version` or `Mcp-Method` disagreeing with the request body) is now rejected with `-32020` (HeaderMismatch), and a request whose protocol-version header names a modern revision but whose body is missing the `_meta` envelope (or its required protocol-version key) is rejected with `-32602` invalid params naming the missing key(s). Both keep HTTP 400. These cells previously emitted a provisional `-32004` while the upstream error-code discussion was open. The envelope-less rejection on a modern-only endpoint (`-32022` with the supported-versions list), the 2025-era serving paths, and the client-side probe handling are unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `Protocol.request()` now rejects with `SdkError(RequestTimeout, reason)` when called with an already-aborted signal, matching in-flight aborts. Previously the raw `signal.reason` was thrown.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Complete the SEP-2577 `@deprecated` sweep on the public type surface (SEP-2596 Tier-1 obligation). Marks the full Logging type stack (`LoggingLevel`, `SetLevelRequest`, `LoggingMessageNotification` and params), the full Sampling type stack (`CreateMessageRequest`/`Result`, `SamplingMessage`, `ModelPreferences`/`ModelHint`, `ToolChoice`, `ToolUseContent`/`ToolResultContent`, and the `includeContext` enum values), the full Roots type stack (`Root`, `ListRootsRequest`/`Result`, `RootsListChangedNotification`), and `registerClient` (Dynamic Client Registration; prefer Client ID Metadata Documents per SEP-991). Mirrors the markers already present on the per-revision reference types. JSDoc only — wire behavior is unchanged; everything remains fully functional during the deprecation window (at least twelve months).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Re-pin the 2026-07-28 draft references (spec reference types, vendored schema.json twins, example corpus) to the latest spec commit and align the 2026-era wire surface with it. Deliberate 2026-era wire behavior changes (the released 2025-11-25 surface is untouched):
- `notifications/elicitation/complete` is no longer part of the 2026-07-28 wire registry (the draft removed the notification together with `elicitationId` on URL-mode elicitation). On connections negotiated at 2026-07-28, sending it — including via `Server.createElicitationCompletionNotifier()` — now fails locally with `SdkErrorCode.MethodNotSupportedByProtocolVersion`, and inbound copies are dropped as unknown notifications. Both remain fully supported on 2025-11-25.
- `notifications/cancelled` on 2026-era connections now parses with a revision-exact schema that requires `requestId` (the draft made it required); the notification `_meta` shape types the `io.modelcontextprotocol/subscriptionId` key. 2025-era parsing is unchanged.
- The error code `-32001` emitted for HTTP header/body mismatches is now defined by the draft schema (`HEADER_MISMATCH`); the emitted behavior is unchanged (documentation only).
No public API surface changes; the regenerated reference artifacts are internal/test-only.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Test-only hardening, no runtime changes: a spec example corpus harness (the draft revision's 86 example directories vendored from the specification repository plus a frozen hand-built 2025-11-25 corpus, with rejection-side fixtures routed through real dispatch), a cross-bundle typed-error recognition guard, and extended end-to-end draft-vocabulary leak coverage for hosted transports, SSE streams, and compatibility fallback paths.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Internal: regenerate the 2026-07-28 spec reference types from the latest draft schema (`DiscoverResult` now extends `CacheableResult`; `ElicitationCompleteNotificationParams` extracted as a named interface) and document the anchor lifecycle policy. Released-revision spec-type generation is now pinned to a fixed spec commit; draft anchors keep floating via the nightly refresh PRs. No public API or runtime behavior changes.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Freeze the per-era wire schemas as self-contained copies decoupled from the public types layer, and convert `WireCodec` to a function-only interface. Two small spec-conformance fixes ride along with the otherwise-pure refactor:
- The 2026 wire-true `resultType` member now defaults to `'complete'` when absent (the spec's receiver-side back-compat rule); the inbound `decodeResult` step continues to require it. The `server/discover` result accepts absent or malformed `ttlMs`/`cacheScope` (falling back to `0`/`'private'` per the spec's receiver leniency in caching.mdx) so the version-negotiation probe classifier stays behavior-neutral. Other cacheable result schemas are unchanged here; general receiver leniency for those belongs to the response-cache surface.
- The sampling `hasTools` discriminant now keys on `tools || toolChoice` (previously `tools` only), aligning the client and server selection of the with-tools result variant with `clientCapabilityRequirements`.
## 2.0.0-alpha.2
### Major Changes

2
packages/core-internal/package.json
View file

@ -1,7 +1,7 @@
{
"name": "@modelcontextprotocol/core-internal",
"private": true,
"version": "2.0.0-alpha.2",
"version": "2.0.0-alpha.3",
"description": "Model Context Protocol implementation for TypeScript - Core package",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

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@ -1,5 +1,16 @@
# @modelcontextprotocol/core
## 2.0.0-alpha.2
### Major Changes
- [#2400](https://github.com/modelcontextprotocol/typescript-sdk/pull/2400) [`3c02ffb`](https://github.com/modelcontextprotocol/typescript-sdk/commit/3c02ffb5d9bb4da59028c70cc58987303b310074) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Align the published schema set with the 2026-07-28 surface: removes the
`RequestMetaEnvelopeSchema` export; adds `SubscriptionFilterSchema`, the
`SubscriptionsListen*` request/result schemas, and the
`SubscriptionsAcknowledged*` notification schemas. The bundled schemas now
match `@modelcontextprotocol/client` and `@modelcontextprotocol/server` of
the same release.
## 2.0.0-alpha.1
### Minor Changes

2
packages/core/package.json
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@ -1,6 +1,6 @@
{
"name": "@modelcontextprotocol/core",
"version": "2.0.0-alpha.1",
"version": "2.0.0-alpha.2",
"description": "Model Context Protocol for TypeScript — public Zod schemas (spec + OAuth/OpenID)",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

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@ -1,5 +1,19 @@
# @modelcontextprotocol/express
## 2.0.0-alpha.4
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add Origin header validation alongside the existing Host header validation. The server package gains framework-agnostic helpers (`validateOriginHeader`, `localhostAllowedOrigins`, `originValidationResponse`); the Express, Hono and Fastify adapters gain `originValidation` /
`localhostOriginValidation` middleware and a new `allowedOrigins` option on their app factories, which now arm Origin validation by default for localhost-class binds (mirroring the Host validation ladder; the 0.0.0.0-without-allowlist warning is unchanged). Requests
without an `Origin` header pass — non-browser MCP clients are unaffected — while a present `Origin` that is not allowed or cannot be parsed (including the opaque `null` origin) is rejected with `403`. The Node adapter ships `hostHeaderValidation` / `originValidation`
request guards for plain `node:http` servers, which previously had no validation helpers.
### Patch Changes
- Updated dependencies [[`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`6cc7b1c`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6cc7b1cb66cabf23423ba0fdf06e2d1c2fcf936f), [`f0bf785`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f0bf785239af67f0cfce24575fec9c1193deaff1), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771)]:
- @modelcontextprotocol/server@2.0.0-alpha.4
## 2.0.0-alpha.3
### Minor Changes

2
packages/middleware/express/package.json
View file

@ -1,7 +1,7 @@
{
"name": "@modelcontextprotocol/express",
"private": false,
"version": "2.0.0-alpha.3",
"version": "2.0.0-alpha.4",
"description": "Express adapters for the Model Context Protocol TypeScript server SDK - Express middleware",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

14
packages/middleware/fastify/CHANGELOG.md
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@ -1,5 +1,19 @@
# @modelcontextprotocol/fastify
## 2.0.0-alpha.4
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add Origin header validation alongside the existing Host header validation. The server package gains framework-agnostic helpers (`validateOriginHeader`, `localhostAllowedOrigins`, `originValidationResponse`); the Express, Hono and Fastify adapters gain `originValidation` /
`localhostOriginValidation` middleware and a new `allowedOrigins` option on their app factories, which now arm Origin validation by default for localhost-class binds (mirroring the Host validation ladder; the 0.0.0.0-without-allowlist warning is unchanged). Requests
without an `Origin` header pass — non-browser MCP clients are unaffected — while a present `Origin` that is not allowed or cannot be parsed (including the opaque `null` origin) is rejected with `403`. The Node adapter ships `hostHeaderValidation` / `originValidation`
request guards for plain `node:http` servers, which previously had no validation helpers.
### Patch Changes
- Updated dependencies [[`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`6cc7b1c`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6cc7b1cb66cabf23423ba0fdf06e2d1c2fcf936f), [`f0bf785`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f0bf785239af67f0cfce24575fec9c1193deaff1), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771)]:
- @modelcontextprotocol/server@2.0.0-alpha.4
## 2.0.0-alpha.3
### Patch Changes

2
packages/middleware/fastify/package.json
View file

@ -1,7 +1,7 @@
{
"name": "@modelcontextprotocol/fastify",
"private": false,
"version": "2.0.0-alpha.3",
"version": "2.0.0-alpha.4",
"description": "Fastify adapters for the Model Context Protocol TypeScript server SDK - Fastify middleware",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

14
packages/middleware/hono/CHANGELOG.md
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@ -1,5 +1,19 @@
# @modelcontextprotocol/hono
## 2.0.0-alpha.4
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add Origin header validation alongside the existing Host header validation. The server package gains framework-agnostic helpers (`validateOriginHeader`, `localhostAllowedOrigins`, `originValidationResponse`); the Express, Hono and Fastify adapters gain `originValidation` /
`localhostOriginValidation` middleware and a new `allowedOrigins` option on their app factories, which now arm Origin validation by default for localhost-class binds (mirroring the Host validation ladder; the 0.0.0.0-without-allowlist warning is unchanged). Requests
without an `Origin` header pass — non-browser MCP clients are unaffected — while a present `Origin` that is not allowed or cannot be parsed (including the opaque `null` origin) is rejected with `403`. The Node adapter ships `hostHeaderValidation` / `originValidation`
request guards for plain `node:http` servers, which previously had no validation helpers.
### Patch Changes
- Updated dependencies [[`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`6cc7b1c`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6cc7b1cb66cabf23423ba0fdf06e2d1c2fcf936f), [`f0bf785`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f0bf785239af67f0cfce24575fec9c1193deaff1), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771)]:
- @modelcontextprotocol/server@2.0.0-alpha.4
## 2.0.0-alpha.3
### Patch Changes

2
packages/middleware/hono/package.json
View file

@ -1,7 +1,7 @@
{
"name": "@modelcontextprotocol/hono",
"private": false,
"version": "2.0.0-alpha.3",
"version": "2.0.0-alpha.4",
"description": "Hono adapters for the Model Context Protocol TypeScript server SDK - Hono middleware",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

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packages/middleware/node/CHANGELOG.md
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@ -1,5 +1,30 @@
# @modelcontextprotocol/node
## 2.0.0-alpha.4
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `createMcpHandler` now returns a web-standards-only `{ fetch, close, notify, bus }` handler — the shape Workers/Bun/Deno expect from `export default`. The duck-typed `.node(req, res, parsedBody?)` face is removed; Node frameworks (Express, Fastify, plain `node:http`) wrap the
handler once with the new `toNodeHandler(handler, { onerror? })` exported from `@modelcontextprotocol/node`, which converts the Node request to a web-standard `Request`, calls `handler.fetch`, and writes the `Response` back honoring write backpressure. The optional `onerror`
receives the adapter-level error fallback (request conversion / `handler.fetch` throw) before the `500` response is written, restoring observability parity with the removed `.node` face. `NodeIncomingMessageLike` and `NodeServerResponseLike` move from
`@modelcontextprotocol/server` to `@modelcontextprotocol/node`.
- [#2390](https://github.com/modelcontextprotocol/typescript-sdk/pull/2390) [`6cc7b1c`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6cc7b1cb66cabf23423ba0fdf06e2d1c2fcf936f) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Export `toWebRequest(req, parsedBody?, options?)` — the Node `IncomingMessage` → web-standard `Request` conversion `toNodeHandler` already performs internally. Use it to feed `isLegacyRequest()` (or `handler.fetch()`) from a hand-wired Node/Express `(req, res)` handler instead of assembling a `globalThis.Request` from `req.headers` by hand. When a body parser already consumed the Node stream (`express.json()`), pass the parsed value as `parsedBody`; pass `options.signal` to tie the constructed request to client disconnect, the way `toNodeHandler` does.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add Origin header validation alongside the existing Host header validation. The server package gains framework-agnostic helpers (`validateOriginHeader`, `localhostAllowedOrigins`, `originValidationResponse`); the Express, Hono and Fastify adapters gain `originValidation` /
`localhostOriginValidation` middleware and a new `allowedOrigins` option on their app factories, which now arm Origin validation by default for localhost-class binds (mirroring the Host validation ladder; the 0.0.0.0-without-allowlist warning is unchanged). Requests
without an `Origin` header pass — non-browser MCP clients are unaffected — while a present `Origin` that is not allowed or cannot be parsed (including the opaque `null` origin) is rejected with `403`. The Node adapter ships `hostHeaderValidation` / `originValidation`
request guards for plain `node:http` servers, which previously had no validation helpers.
### Patch Changes
- [#2394](https://github.com/modelcontextprotocol/typescript-sdk/pull/2394) [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Fix the published declaration files for consumers compiling with `skipLibCheck: false`: the bundled `.d.mts` no longer leaves a dangling `URIComponent` reference (ajv's published types import it from `fast-uri`, whose export-assigned namespace the dts bundler cannot link — the type is now inlined via a dts-only path mapping), and no longer imports `json-schema-typed` from an undeclared dependency (it is inlined via `dts.resolve`). `@modelcontextprotocol/node` and `@modelcontextprotocol/server` drop stale `typesVersions` entries pointing at subpaths that never shipped. Package READMEs note that TypeScript >=6.0 requires `"types": ["node"]` since the published declarations reference `Buffer`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Forward `setSupportedProtocolVersions` from `NodeStreamableHTTPServerTransport` to the wrapped Web Standard transport. Previously a server's `supportedProtocolVersions` option never reached the Node adapter's `MCP-Protocol-Version` header validation, which silently kept
validating against the default version list.
- Updated dependencies [[`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`6cc7b1c`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6cc7b1cb66cabf23423ba0fdf06e2d1c2fcf936f), [`f0bf785`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f0bf785239af67f0cfce24575fec9c1193deaff1), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771), [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771)]:
- @modelcontextprotocol/server@2.0.0-alpha.4
## 2.0.0-alpha.3
### Patch Changes

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@ -1,6 +1,6 @@
{
"name": "@modelcontextprotocol/node",
"version": "2.0.0-alpha.3",
"version": "2.0.0-alpha.4",
"description": "Model Context Protocol implementation for TypeScript - Node.js middleware",
"license": "MIT",
"author": "Anthropic, PBC (https://anthropic.com)",

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# @modelcontextprotocol/server-legacy
## 2.0.0-alpha.4
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2468 follow-up: `transport.finishAuth()` gains a `URLSearchParams` overload (preferred) that extracts `code`/`iss`, validates `iss` first, and on mismatch throws a sanitized `IssuerMismatchError` (no callback `error_description` text); callers remain responsible for `state`. **Behavior change for `@modelcontextprotocol/server-legacy`:** `mcpAuthRouter` now advertises `authorization_response_iss_parameter_supported` (default `true`; `ProxyOAuthServerProvider` reports `false`) and the bundled authorize handler appends `iss` (RFC 9207) to every `res.redirect(...)` your `OAuthServerProvider.authorize()` issues to the client's `redirect_uri`. If your provider redirects another way (`res.writeHead`, a separate consent-page response, or a standalone `authorizationHandler({provider})` without `issuerUrl`), append `params.issuer` as `iss` yourself or set `authorizationResponseIssParameterSupported: false` — otherwise RFC 9207-compliant clients (including this SDK) will reject the callback.
## 2.0.0-alpha.3
### Minor Changes

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{
"name": "@modelcontextprotocol/server-legacy",
"private": false,
"version": "2.0.0-alpha.3",
"version": "2.0.0-alpha.4",
"description": "Frozen v1 SSE transport and OAuth Authorization Server helpers for the Model Context Protocol TypeScript SDK. Deprecated; use StreamableHTTP and a dedicated OAuth server in production.",
"deprecated": "This package is a frozen copy of v1's SSE transport and OAuth Authorization Server helpers for migration purposes only. Use StreamableHTTP from @modelcontextprotocol/server and a dedicated OAuth server in production. Will not receive new features.",
"license": "MIT",

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# @modelcontextprotocol/server
## 2.0.0-alpha.4
### Major Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Split the wire layer into per-era codecs and make protocol-revision deletions physical. Deliberate wire/schema behavior changes (see docs/migration/support-2026-07-28.md "Per-era wire codecs"):
- `resultType` is no longer modeled by any neutral wire schema: `EmptyResultSchema` (strict) now rejects `{resultType}` bodies; on 2025-era connections a foreign `resultType` is stripped before validation instead of rejected; the member exists only inside the 2026-era codec, which requires it.
- `CallToolResult.content` / `ToolResultContent.content` are required at the wire boundary (`content.default([])` removed): handler results without `content` are rejected with `-32602` instead of silently defaulted, and content-less wire results fail the client parse loudly.
- Custom (3-arg) handlers now receive `_meta` minus the reserved envelope keys instead of having it deleted before params validation.
- `specTypeSchemas` re-scoped to the neutral model: result validators no longer accept `resultType`; task message-type validators and `RequestMetaEnvelope` left the public set (`SpecTypeName` narrowed).
- Role aggregate types/schemas (`ClientRequest`, `ServerResult`, …) no longer carry task vocabulary; the deprecated `Task*` types remain importable unchanged.
- Era-mismatched spec methods fail physically: inbound era-deleted methods get `-32601` even with a handler registered; outbound sends throw `SdkErrorCode.MethodNotSupportedByProtocolVersion` locally.
- Value guards (`isCallToolResult`, …) are documented as neutral-shape consumer checks, not wire validators.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `createMcpHandler` now returns a web-standards-only `{ fetch, close, notify, bus }` handler — the shape Workers/Bun/Deno expect from `export default`. The duck-typed `.node(req, res, parsedBody?)` face is removed; Node frameworks (Express, Fastify, plain `node:http`) wrap the
handler once with the new `toNodeHandler(handler, { onerror? })` exported from `@modelcontextprotocol/node`, which converts the Node request to a web-standard `Request`, calls `handler.fetch`, and writes the `Response` back honoring write backpressure. The optional `onerror`
receives the adapter-level error fallback (request conversion / `handler.fetch` throw) before the `500` response is written, restoring observability parity with the removed `.node` face. `NodeIncomingMessageLike` and `NodeServerResponseLike` move from
`@modelcontextprotocol/server` to `@modelcontextprotocol/node`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - 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".
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `resources/read` for an unknown URI now answers with JSON-RPC error code `-32602`
(Invalid Params) on every protocol revision, with `error.data.uri` echoing the
requested URI. The 2026-07-28 specification requires `-32602`; the v1.x SDK already
emitted `-32602` on earlier revisions, so v1.x peers see no change.
This supersedes an interim `-32002` emission that shipped in earlier v2 alphas. The
era-aware encode seam (`WireCodec.encodeErrorCode`) maps any handler-thrown `-32002`
to `-32602` on the wire; note that a `-32002` thrown without `data.uri` is emitted as
a bare `-32602` and is no longer recognizable as resource-not-found — throw
`ResourceNotFoundError` (or include `data: { uri }`) to preserve the classification.
`ProtocolErrorCode.ResourceNotFound` (`-32002`) remains importable as receive-tolerated
vocabulary; clients should accept both `-32602` and `-32002` from peers (the
specification's backwards-compatibility clause). The new typed `ResourceNotFoundError`
class carries `data.uri`, and `ProtocolError.fromError` reconstructs it from a `-32602`
only when `error.data` is exactly `{ uri: string }` (and nothing else), and from a
legacy `-32002` whenever `data.uri` is a string; a bare `-32002` without `data.uri`
stays a generic `ProtocolError`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-1613 / SEP-2106 (JSON Schema 2020-12 posture): the Node default JSON Schema validator is now `Ajv2020` (true draft 2020-12) instead of the draft-07 `Ajv` class — `$defs`/`prefixItems`/`unevaluatedProperties`/`dependentRequired` are now enforced where they were previously silently ignored; to opt back, construct the draft-07 instance with the v1 defaults — `const ajv = new Ajv({ strict: false, validateFormats: true, validateSchema: false, allErrors: true }); addFormats(ajv);` — and pass `new AjvJsonSchemaValidator(ajv)`. Schemas declaring a `$schema` other than 2020-12 are rejected with a clear error rather than mis-validating. `outputSchema` may now have a non-object root and `CallToolResult.structuredContent` is widened to `unknown` (a deliberate source-level break for typed consumers — see the migration guide for the narrowing pattern). Toward 2025-era clients McpServer wraps a non-object `outputSchema` (and the matching `structuredContent`) in a `{result: …}` envelope so the tool stays callable, with same-document `$ref`/`$dynamicRef` pointers rewritten to keep resolving — low-level `Server` users (those bypassing `McpServer` and registering a `tools/call` handler directly) get the same wrap by routing the result through the new `Server.projectCallToolResult(result, advertisedOutputSchema)`. Independently, on every era (the SEP's MUST applies regardless of client version), McpServer auto-appends a `TextContent` JSON serialisation when a handler returns non-object `structuredContent` without its own text block. The `structuredContent` presence check is `!== undefined` (not falsy) on both sides. Thanks @mattzcarey (#2249).
### Minor Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `createRequestStateCodec({ key, ttlSeconds?, bind? })`, an opt-in HMAC-SHA256 sealing helper for the multi-round-trip `requestState`: `mint` seals a JSON-serializable payload (with TTL and optional context binding) and `verify` drops directly into `ServerOptions.requestState.verify`. WebCrypto-based and runtime-neutral; verification is fail-closed and constant-time. The `ServerOptions.requestState.verify` hook's return type is widened to `unknown | Promise<unknown>` so the codec's `verify` is directly assignable; the seam captures the hook's resolved value (the decoded payload) and hands it to handlers via the typed `ctx.mcpReq.requestState<T>()` accessor.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Results of the cacheable 2026-07-28 operations (`tools/list`, `prompts/list`, `resources/list`, `resources/templates/list`, `resources/read`, `server/discover`) now always carry the revision's required `ttlMs`/`cacheScope` fields when served on that revision, defaulting to `ttlMs: 0` / `cacheScope: 'private'`. Servers can configure the emitted values with the new `ServerOptions.cacheHints` option (per operation) and the new `cacheHint` member of the `registerResource` config (per resource); resolution is per field, most specific author first: cache fields returned by a handler win over the per-resource hint, which wins over the per-operation hint, and configured hints are validated at construction/registration time (`RangeError` on invalid values). Responses on 2025-era connections are unchanged and never carry these fields. Note for untyped callers: `registerResource` now interprets a `cacheHint` key in its config object — it is validated and kept out of the resource's list metadata, where it was previously passed through as ordinary metadata.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `SdkErrorCode.MethodNotSupportedByProtocolVersion`: a typed local error raised before anything reaches the transport when a spec method is sent toward a peer whose negotiated protocol version's wire era does not define it (for example `tasks/get` toward a 2026-07-28 peer). The protocol layer now resolves a per-era wire codec from the connection's negotiated protocol version (instance state on `Client`/`Server`, with the legacy era as the pre-negotiation default) and resolves per-method schemas at dispatch time instead of registration time; an edge classification on an inbound message is validated against that instance era, and a mismatch is rejected as an entry/routing error. Behavior on existing (2025-era) connections is unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Revise `createMcpHandler`'s legacy handling (a behavior change to the unreleased entry). The entry now serves 2025-era (non-envelope) traffic **by default** through per-request stateless serving from the same factory — `legacy: 'stateless'` is the default rather than an
opt-in — and the strict, modern-only posture is selected with the new `legacy: 'reject'` value (the earlier alpha's default). The handler-valued `legacy` option (bring-your-own legacy serving) is removed: existing legacy deployments (for example a sessionful streamable
HTTP wiring) keep serving 2025 traffic by routing in user land with the new `isLegacyRequest(request, parsedBody?)` export, which runs the entry's own classification step — it returns `true` only for requests with no per-request `_meta` envelope claim, while malformed or
incomplete modern claims are NOT legacy and must be routed to the modern handler, which answers them with the documented validation errors. The predicate classifies a clone, so the routed request body stays readable. `legacyStatelessFallback` remains exported as a
standalone fetch-shaped handler with the same stateless serving as the default.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `createMcpHandler(factory, { legacy?, onerror?, responseMode? })`, an HTTP entry point that serves the 2026-07-28 draft revision per request: each envelope-carrying request is classified once, served on a fresh instance from the factory bound to the claimed revision,
and answered with a JSON body or a lazily-upgraded SSE stream. 2025-era serving is selected with the `legacy` option (`'stateless'` — the default — for per-request stateless serving via the existing streamable HTTP transport, `'reject'` for a modern-only strict endpoint
that answers 2025-era requests with the unsupported-protocol-version error naming its supported revisions). The handler is a web-standard `{ fetch, close, notify, bus }` object: `fetch(request, { authInfo?, parsedBody? })` is the only request face (Node frameworks wrap it with
`toNodeHandler(handler)` from `@modelcontextprotocol/node`), and `close()` tears down in-flight modern exchanges. Also exported: `legacyStatelessFallback` (the same stateless legacy serving as a standalone fetch-shaped handler), the `PerRequestHTTPServerTransport` single-exchange transport and the
`classifyInboundRequest` classifier for hand-wired compositions, and the supporting types. `responseMode: 'json'` never streams and drops mid-call notifications (progress, logging and other related messages emitted before the result); listen-class subscription streams are
always served over SSE. The entry performs no Origin/Host validation (use the middleware packages) and no token verification — `authInfo` is pass-through and never derived from request headers.
- [#2381](https://github.com/modelcontextprotocol/typescript-sdk/pull/2381) [`f0bf785`](https://github.com/modelcontextprotocol/typescript-sdk/commit/f0bf785239af67f0cfce24575fec9c1193deaff1) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Serve `input_required` handlers on 2025-era connections: the legacy shim (on by default) converts each embedded request of an `input_required` return into a real server→client request (`elicitation/create`, `sampling/createMessage`, `roots/list`) over the live session — stamped with the originating request's id for stream association — and re-enters the handler with the collected `inputResponses` until a final result. Handlers are written once in the 2026 `inputRequired(...)` style and serve both eras; the previous loud `-32603` failure remains available via `ServerOptions.inputRequired.legacyShim: false`. Knobs: `inputRequired.maxRounds` (default 8) and `inputRequired.roundTimeoutMs` (default 600 000 ms per leg; legs carry a progressToken so a client reporting progress mid-leg resets the leg timeout). Semantics mirror the modern client driver exactly: per-round replaced `inputResponses`, byte-exact `requestState` echo with the verify hook running every round, paced requestState-only rounds, and elicitation accepted content passed through UNVALIDATED (the handler validates via the schema-aware `acceptedContent` overload, exactly as on the 2026 era). URL-mode legs synthesize the `elicitationId` the 2025-11-25 wire requires. Failures surface per family (`tools/call` → `isError` tool result; `prompts/get` / `resources/read` → JSON-RPC error); stateless legacy HTTP degrades to a clean capability refusal; the shim emits no progress of its own (the originating progressToken is the handler's single must-increase stream — the shim never adds a second author to it).
`ctx.mcpReq.requestState` is now a typed accessor: `ctx.mcpReq.requestState<T>()` returns the payload the configured `requestState.verify` hook resolved with (e.g. `createRequestStateCodec.verify` — the hook's return value is now load-bearing; verifiers that are not also decoders should resolve `undefined`), the raw wire string when no hook is configured, or `undefined` when the round carried no state. Code that read the property directly becomes a call: `ctx.mcpReq.requestState` → `ctx.mcpReq.requestState<string>()`. Note the member is now always present (a function), so truthiness no longer means "has state", and it is dropped by JSON serialization of the context.
New typed readers for `inputResponses`, exported from `@modelcontextprotocol/server`: a schema-aware `acceptedContent(responses, key, schema)` overload (validates untrusted accepted content against any synchronous Standard Schema) and `inputResponse(responses, key)` (discriminated `missing | elicit | sampling | roots` view, for decline/cancel detection and the non-elicitation kinds). Content conveniences like text extraction stay in application code as one-liners over the discriminated view.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `MissingRequiredClientCapabilityError`, the typed error class for the 2026-07-28 `-32021` protocol error (processing a request requires a capability the client did not declare). Its `data.requiredCapabilities` lists the missing capabilities and `ProtocolError.fromError` recognizes the code/data shape. The 2026-07-28 HTTP entry gains a pre-dispatch gate that refuses a request requiring an undeclared client capability with this error and HTTP status `400`; no method served on the 2026-07-28 registry currently carries such a requirement, so observable behavior is unchanged until methods with capability requirements exist.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add the server side of multi round-trip requests (protocol revision 2026-07-28, SEP-2322). Handlers for `tools/call`, `prompts/get`, and `resources/read` can return the value built by `inputRequired()` (exported from the server package together with `acceptedContent()`)
to request additional client input in-band; the structured-content requirement and the tools/call result-schema validation are skipped for that return, the encode seam emits it as `resultType: 'input_required'`, and the handler reads the responses on re-entry from
`ctx.mcpReq.inputResponses` (with non-bare entries reported via `ctx.mcpReq.droppedInputResponseKeys`). The seam re-checks the at-least-one rule for hand-built results, checks every embedded request against the capabilities the client declared on that request's envelope
(answering the typed `-32021` error on violation), and fails loudly — never emitting a mis-typed result — when an input-required value is returned from any other method. Toward a 2025-era request the return is served by the default-on legacy shim (real server→client requests plus handler re-entry); the loud failure for that case remains available via `ServerOptions.inputRequired.legacyShim: false`. A `UrlElicitationRequiredError` escaping a handler on a 2026-era request
fails as an internal error with a clear steer to `inputRequired.elicitUrl(...)`, so the `-32042` error never reaches the 2026-07-28 wire; 2025-era serving keeps today's `-32042` behavior
exactly. The typed local error raised when push-style server-to-client request APIs are used while serving a 2026-era request now steers to `inputRequired(...)`. Tool, prompt, and resource callback types accept the new return alongside their existing result types; 2025-era
wire behavior is unchanged. An optional `ServerOptions.requestState.verify` hook lets a server integrity-check the echoed `requestState` before the handler runs — a throw answers the wire-level `-32602` Invalid Params error with `data.reason: 'invalid_request_state'`; the SDK provides no default verification.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add Origin header validation alongside the existing Host header validation. The server package gains framework-agnostic helpers (`validateOriginHeader`, `localhostAllowedOrigins`, `originValidationResponse`); the Express, Hono and Fastify adapters gain `originValidation` /
`localhostOriginValidation` middleware and a new `allowedOrigins` option on their app factories, which now arm Origin validation by default for localhost-class binds (mirroring the Host validation ladder; the 0.0.0.0-without-allowlist warning is unchanged). Requests
without an `Origin` header pass — non-browser MCP clients are unaffected — while a present `Origin` that is not allowed or cannot be parsed (including the opaque `null` origin) is rejected with `403`. The Node adapter ships `hostHeaderValidation` / `originValidation`
request guards for plain `node:http` servers, which previously had no validation helpers.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2243 `Mcp-Param-*` server-side validation (protocol revision 2026-07-28). On the modern (2026-07-28) serving path, `createMcpHandler` now validates `Mcp-Param-{Name}` headers against the named tool's `x-mcp-header` declarations and the body `arguments` before dispatch: a missing header for a present body value, a header that decodes to a different value than the body, or an invalid `=?base64?…?=` sentinel is rejected with `400 Bad Request` and JSON-RPC `-32020` (`HeaderMismatch`) — the same shape the existing standard-header cross-checks emit. A `null`/absent body value passes regardless of any header (the spec's "server MUST NOT expect the header" rows). `McpServer.registerTool` now warns at registration time when an `x-mcp-header` declaration violates the spec's constraints. The 2025-era serving paths and the low-level `Server` factory shape are unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2243 standard-header server-side validation (protocol revision 2026-07-28). On the modern (2026-07-28) serving path, `createMcpHandler` now enforces the required `Mcp-Method` and `Mcp-Name` standard request headers in addition to the existing `MCP-Protocol-Version` and `Mcp-Method` cross-checks: a modern request without an `Mcp-Method` header, a `tools/call` / `prompts/get` / `resources/read` request without an `Mcp-Name` header, an `Mcp-Name` header carrying an invalid `=?base64?…?=` sentinel, and an `Mcp-Name` header whose (decoded) value disagrees with the body's `params.name` / `params.uri` are all rejected with `400 Bad Request` and JSON-RPC `-32020` (`HeaderMismatch`). The 2025-era serving paths are unchanged.
New public surface:
- `@modelcontextprotocol/server`: the `mcpNameHeader` field on `InboundHttpRequest`, and the `'standard-header-validation'` member of `InboundValidationRung` (with `client-capabilities` / `param-header-validation` renumbered).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add `serveStdio(factory, options?)` (exported from `@modelcontextprotocol/server/stdio`), the connection-pinned stdio entry point for serving the 2026-07-28 draft revision on long-lived connections. The entry owns the transport and the era decision: the client's opening
exchange selects the era (a 2025 `initialize` handshake, 2026-07-28 per-request `_meta` envelope traffic, or a `server/discover` probe followed by either), and ONE instance from the factory is pinned to the connection and serves only that era — mirroring how
`createMcpHandler` classifies each HTTP request before constructing an instance. 2025-era openings are served by default; `legacy: 'reject'` answers them with the unsupported-protocol-version error naming the supported modern revisions instead. A `transport` option
accepts a bring-your-own `StdioServerTransport` (for example over a Unix domain socket); `onerror` reports out-of-band errors; the returned handle's `close()` tears the connection down.
Removed: `ServerOptions.eraSupport` (introduced in an earlier 2.0 alpha, never in a stable release). A hand-constructed `Server`/`McpServer` serves only the 2025-era protocol it was written for; serving the 2026-07-28 revision always goes through a serving entry. Migrate
`new McpServer(info, { eraSupport: 'dual-era' })` + `connect(new StdioServerTransport())` to `serveStdio(() => new McpServer(info))`, and `eraSupport: 'modern'` to `serveStdio(factory, { legacy: 'reject' })`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Align the 2026-07-28 protocol error codes to the spec renumber: `HeaderMismatch` is now `-32020` (was `-32001`), `MissingRequiredClientCapability` is now `-32021` (was `-32003`), and `UnsupportedProtocolVersion` is now `-32022` (was `-32004`). These codes are part of the draft 2026-07-28 protocol revision only and have never appeared on a 2025-era wire — the 2025 serving paths and the SDK-conventional `-32001` (`Session not found`) on the stateful Streamable HTTP transport are unchanged. `ProtocolErrorCode.MissingRequiredClientCapability`, `ProtocolErrorCode.UnsupportedProtocolVersion`, the `HEADER_MISMATCH_ERROR_CODE` constant, and the `HEADER_MISMATCH` / `MISSING_REQUIRED_CLIENT_CAPABILITY` / `UNSUPPORTED_PROTOCOL_VERSION` spec-type constants now carry the renumbered values; the `UnsupportedProtocolVersionError` and `MissingRequiredClientCapabilityError` classes (and `ProtocolError.fromError` recognition) follow. The client probe classifier recognizes `-32022` for the corrective continuation and the SEP-2243 one-refresh-on-miss retry triggers on `-32020`.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `subscriptions/listen` graceful close: per spec PR #2953, a server-side graceful close (`createMcpHandler` / `serveStdio` `close()`) now emits the empty `subscriptions/listen` JSON-RPC result (the new `SubscriptionsListenResult` — `_meta` carries the subscriptionId) before closing the stream, replacing the previous server-originated `notifications/cancelled`. On the client, `McpSubscription.closed` now resolves `'graceful'` for this signal (added alongside `'local'` and `'remote'`); a stream close without a result remains `'remote'` (unexpected disconnect).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `subscriptions/listen` (SEP-1865) is served by both serving entries on protocol revision 2026-07-28. The entry owns ack-first, per-stream filtering, subscription-id stamping, keepalive (HTTP), the pre-ack `-32603` capacity guard, and teardown (HTTP stream close; one
`notifications/cancelled` per subscription on stdio). `server/discover` now advertises `listChanged`/`subscribe` capability bits — the rider that suppressed them until listen was served is discharged.
Under `createMcpHandler` the consumer's factory **is** constructed for `subscriptions/listen` (a capabilities-only probe so the acknowledged filter reflects what the server advertises; the instance is never connected and is closed immediately). Per-request authorization performed inside the factory therefore sees listen requests; token verification still belongs at the middleware layer mounted in front of the entry.
New public surface:
- `@modelcontextprotocol/server`: `ServerEventBus`, `ServerEvent`, `ServerNotifier` (types); `InMemoryServerEventBus` (class).
- `McpHttpHandler` gains `.notify` (`ServerNotifier`: `toolsChanged()`, `promptsChanged()`, `resourcesChanged()`, `resourceUpdated(uri)`) and `.bus` (the `ServerEventBus` listen streams subscribe to).
- `CreateMcpHandlerOptions` gains `bus?: ServerEventBus` (an in-process `InMemoryServerEventBus` is created when omitted), `maxSubscriptions?: number` (default 1024), and `keepAliveMs?: number` (default 15000).
- `ServeStdioOptions` gains `maxSubscriptions?: number` (default 1024). On a modern-pinned connection `serveStdio` routes the pinned instance's existing `send*ListChanged()` calls onto active subscriptions; legacy connections are unchanged.
- `@modelcontextprotocol/server`: `SUBSCRIPTION_ID_META_KEY` (const); `SubscriptionFilter`, `SubscriptionsListenRequest`, `SubscriptionsListenRequestParams`, `SubscriptionsAcknowledgedNotification`, `SubscriptionsAcknowledgedNotificationParams` (types).
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Wire `server/discover` (protocol revision 2026-07-28) into the typed request funnel and serve it era-aware. The request joins `ClientRequestSchema`/`ServerResultSchema`/`ResultTypeMap` (per-era availability stays with the wire registries: only the 2026-era registry serves
it), and `Client.discover()` issues it as a typed request on 2026-era connections. A `Server` whose `supportedProtocolVersions` list carries a modern (2026-07-28+) revision installs the `server/discover` handler, advertising ONLY its modern revisions and excluding the
listChanged/subscribe-class capabilities until the `subscriptions/listen` flow ships; servers with today's default list are unchanged and keep answering `-32601`. The `initialize` handshake is now era-aware in the other direction: its accept check and counter-offer consult
only the legacy subset of the supported versions — a 2026-era revision is never negotiated via `initialize` — so a 2025-era client can never be offered a 2026 version string; with the default list this is byte-identical to previous behavior. Serving the 2026 revision to
ordinary HTTP/stdio traffic arrives with an upcoming server-side entry point: today the negotiation surface is client-side, and `mode: 'auto'` falls back cleanly against current SDK servers.
### Patch Changes
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Deprecate `Server.getClientCapabilities()`, `Server.getClientVersion()` and `Server.getNegotiatedProtocolVersion()` in favor of the per-request handler context: on 2026-07-28 requests the validated `_meta` envelope carries the client's identity (`ctx.mcpReq.envelope`),
and instances serving that revision through `createMcpHandler` are backfilled per request so the accessors keep answering. Behavior on 2025-era connections is unchanged; the accessors remain functional.
- [#2394](https://github.com/modelcontextprotocol/typescript-sdk/pull/2394) [`801111e`](https://github.com/modelcontextprotocol/typescript-sdk/commit/801111ea152c1ba08f6dda0b27d712759aeb46bf) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Fix the published declaration files for consumers compiling with `skipLibCheck: false`: the bundled `.d.mts` no longer leaves a dangling `URIComponent` reference (ajv's published types import it from `fast-uri`, whose export-assigned namespace the dts bundler cannot link — the type is now inlined via a dts-only path mapping), and no longer imports `json-schema-typed` from an undeclared dependency (it is inlined via `dts.resolve`). `@modelcontextprotocol/node` and `@modelcontextprotocol/server` drop stale `typesVersions` entries pointing at subpaths that never shipped. Package READMEs note that TypeScript >=6.0 requires `"types": ["node"]` since the published declarations reference `Buffer`.
- [#2390](https://github.com/modelcontextprotocol/typescript-sdk/pull/2390) [`6cc7b1c`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6cc7b1cb66cabf23423ba0fdf06e2d1c2fcf936f) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `isLegacyRequest` docs: lead with the single-argument form. `isLegacyRequest(request)` is the whole API — the body is read from an internal clone, so the request you pass stays readable for whichever handler you route it to. `parsedBody` is an optional perf escape for a body you already hold parsed (and the way in for an already-consumed stream, e.g. behind `express.json()`), not a required companion. Documentation only; no behavior change.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Pin the modern (2026-07-28) HTTP serving path's rejection codes to the assignments the published conformance suite asserts: a header/body cross-check mismatch (`MCP-Protocol-Version` or `Mcp-Method` disagreeing with the request body) is now rejected with `-32020` (HeaderMismatch), and a request whose protocol-version header names a modern revision but whose body is missing the `_meta` envelope (or its required protocol-version key) is rejected with `-32602` invalid params naming the missing key(s). Both keep HTTP 400. These cells previously emitted a provisional `-32004` while the upstream error-code discussion was open. The envelope-less rejection on a modern-only endpoint (`-32022` with the supported-versions list), the 2025-era serving paths, and the client-side probe handling are unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `ctx.mcpReq.log()` now emits its `notifications/message` notification request-related (like progress and `ctx.mcpReq.notify`), so handler-emitted log messages are delivered when the server is hosted per request via `createMcpHandler` instead of being silently dropped. On a 2026-07-28 request the level filter consults the per-request `_meta` `io.modelcontextprotocol/logLevel` key (the modern equivalent of `logging/setLevel`); per the spec, an absent key means no `notifications/message` is sent for that request.
**2025-era delivery-channel change (spec-conformance correction).** On a 2025-era sessionful Streamable HTTP transport, handler-emitted log messages now ride the per-request POST response stream instead of the standalone GET stream. This is a correction to the 2025-11-25 specification: `docs/specification/2025-11-25/basic/transports.mdx` §"Sending Messages to the Server" item 6 says JSON-RPC messages on the POST response stream SHOULD relate to the originating client request, and §"Listening for Messages from the Server" item 4 says messages on the GET stream SHOULD be unrelated to any concurrently-running client request — so a log emitted from a handler context belongs on the POST stream. Clients reading handler logs off the standalone GET stream will now see them on the per-request POST stream instead. The eventStore-resumable case (a log emitted after `closeSSE()` while the client has not yet reconnected) is handled by the store-first persistence behavior in `WebStandardStreamableHTTPServerTransport.send()`. The session-scoped `Server.sendLoggingMessage()` API is unchanged.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - `WebStandardStreamableHTTPServerTransport`: request-related events (progress, `ctx.mcpReq.notify`, handler-emitted log) and the final response are now persisted to the configured `eventStore` whenever the request is in flight, regardless of whether a live SSE writer currently exists — mirroring the standalone-SSE path's store-first semantics. This fixes the `closeSSE()` poll-and-replay drop (events emitted after `closeSSE()` were previously silently lost) and aligns with the 2025-11-25 specification ("disconnection SHOULD NOT be interpreted as the client cancelling its request"). When an `eventStore` is configured, a final response sent while no per-request stream is connected is stored for replay and returns cleanly instead of throwing "No connection established"; a `Last-Event-ID` reconnect after the request has been retired replays the stored response and then closes the resumed stream. When no `eventStore` is configured, the same condition is surfaced via `onerror` (the response is undeliverable) and the request id is retired.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Re-pin the 2026-07-28 draft references (spec reference types, vendored schema.json twins, example corpus) to the latest spec commit and align the 2026-era wire surface with it. Deliberate 2026-era wire behavior changes (the released 2025-11-25 surface is untouched):
- `notifications/elicitation/complete` is no longer part of the 2026-07-28 wire registry (the draft removed the notification together with `elicitationId` on URL-mode elicitation). On connections negotiated at 2026-07-28, sending it — including via `Server.createElicitationCompletionNotifier()` — now fails locally with `SdkErrorCode.MethodNotSupportedByProtocolVersion`, and inbound copies are dropped as unknown notifications. Both remain fully supported on 2025-11-25.
- `notifications/cancelled` on 2026-era connections now parses with a revision-exact schema that requires `requestId` (the draft made it required); the notification `_meta` shape types the `io.modelcontextprotocol/subscriptionId` key. 2025-era parsing is unchanged.
- The error code `-32001` emitted for HTTP header/body mismatches is now defined by the draft schema (`HEADER_MISMATCH`); the emitted behavior is unchanged (documentation only).
No public API surface changes; the regenerated reference artifacts are internal/test-only.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Internal: regenerate the 2026-07-28 spec reference types from the latest draft schema (`DiscoverResult` now extends `CacheableResult`; `ElicitationCompleteNotificationParams` extracted as a named interface) and document the anchor lifecycle policy. Released-revision spec-type generation is now pinned to a fixed spec commit; draft anchors keep floating via the nightly refresh PRs. No public API or runtime behavior changes.
- [#2286](https://github.com/modelcontextprotocol/typescript-sdk/pull/2286) [`1823aae`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1823aae891837ebb5e3db885ec635f9efefd5771) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Freeze the per-era wire schemas as self-contained copies decoupled from the public types layer, and convert `WireCodec` to a function-only interface. Two small spec-conformance fixes ride along with the otherwise-pure refactor:
- The 2026 wire-true `resultType` member now defaults to `'complete'` when absent (the spec's receiver-side back-compat rule); the inbound `decodeResult` step continues to require it. The `server/discover` result accepts absent or malformed `ttlMs`/`cacheScope` (falling back to `0`/`'private'` per the spec's receiver leniency in caching.mdx) so the version-negotiation probe classifier stays behavior-neutral. Other cacheable result schemas are unchanged here; general receiver leniency for those belongs to the response-cache surface.
- The sampling `hasTools` discriminant now keys on `tools || toolChoice` (previously `tools` only), aligning the client and server selection of the with-tools result variant with `clientCapabilityRequirements`.
## 2.0.0-alpha.3
### Major Changes

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