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1 | 1 | # @modelcontextprotocol/client |
2 | 2 |
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| 3 | +## 2.0.0-alpha.3 |
| 4 | + |
| 5 | +### Major Changes |
| 6 | + |
| 7 | +- [#2128](https://github.com/modelcontextprotocol/typescript-sdk/pull/2128) [`c8d7401`](https://github.com/modelcontextprotocol/typescript-sdk/commit/c8d7401b46f34b6c49b7cfb7b321714d0d4048f6) Thanks [@felixweinberger](https://github.com/felixweinberger)! - SEP-2663: remove |
| 8 | + 2025-11 experimental tasks (TaskManager, experimental.tasks.\* accessors). Tasks are now Extensions Track. |
| 9 | + |
| 10 | +### Minor Changes |
| 11 | + |
| 12 | +- [#2049](https://github.com/modelcontextprotocol/typescript-sdk/pull/2049) [`4f226c1`](https://github.com/modelcontextprotocol/typescript-sdk/commit/4f226c1e35200616d62f1d7e46a2daa33d91172a) Thanks [@KKonstantinov](https://github.com/KKonstantinov)! - Add `SdkHttpError` subclass |
| 13 | + with typed `.status` / `.statusText` accessors for HTTP transport failures. `StreamableHTTPClientTransport` now throws `SdkHttpError` (which extends `SdkError`) for non-OK HTTP responses; `SSEClientTransport` throws `SdkHttpError` for 401-after-reauth (circuit breaker). |
| 14 | + |
| 15 | +- [#1974](https://github.com/modelcontextprotocol/typescript-sdk/pull/1974) [`db83829`](https://github.com/modelcontextprotocol/typescript-sdk/commit/db83829c5bd5d6659c5e7b96638b11953b0e262d) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add custom (non-spec) |
| 16 | + method support: a 3-arg `setRequestHandler(method, schemas, handler)` / `setNotificationHandler(method, schemas, handler)` form for vendor-prefixed methods, and a `request(req, resultSchema)` overload (also on `ctx.mcpReq.send`) for typed custom-method results. Spec-method |
| 17 | + calls are unchanged. |
| 18 | + |
| 19 | + Response result-schema validation failure now rejects with `SdkError(InvalidResult)` instead of a raw `ZodError`. Adds `SdkErrorCode.InvalidResult`. |
| 20 | + |
| 21 | +- [#1653](https://github.com/modelcontextprotocol/typescript-sdk/pull/1653) [`6bec24a`](https://github.com/modelcontextprotocol/typescript-sdk/commit/6bec24a14cb7e3dbe9f5e04aeb893cd0d6e8cb83) Thanks [@rechedev9](https://github.com/rechedev9)! - Add `validateClientMetadataUrl()` |
| 22 | + utility for early validation of `clientMetadataUrl` |
| 23 | + |
| 24 | + Exports a `validateClientMetadataUrl()` function that `OAuthClientProvider` implementations can call in their constructors to fail fast on invalid URL-based client IDs, instead of discovering the error deep in the auth flow. |
| 25 | + |
| 26 | +- [#2248](https://github.com/modelcontextprotocol/typescript-sdk/pull/2248) [`db28156`](https://github.com/modelcontextprotocol/typescript-sdk/commit/db28156a23032290b3ce3bae00a17544c4807b8f) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Restore the 2025-11-25 |
| 27 | + task wire types that were removed together with the task feature: the task schemas and inferred types, task members of the request/result/notification unions, the `task` request-params augmentation, the `tasks` capability key, the `isTaskAugmentedRequestParams` guard, and |
| 28 | + `RELATED_TASK_META_KEY`. The task feature itself remains removed — servers do not advertise the `tasks` capability and inbound `tasks/*` requests receive `-32601` — but the wire surface stays so SDKs interoperate cleanly with peers on the 2025-11-25 revision. |
| 29 | + |
| 30 | +- [#1887](https://github.com/modelcontextprotocol/typescript-sdk/pull/1887) [`96db044`](https://github.com/modelcontextprotocol/typescript-sdk/commit/96db044fe965f0b7d5109e6d68598eaddce961c9) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Export `isSpecType` and |
| 31 | + `specTypeSchemas` records for runtime validation of any MCP spec type by name. `isSpecType.ContentBlock(value)` is a type predicate; `specTypeSchemas.ContentBlock` is a `StandardSchemaV1Sync<ContentBlock>` validator — `validate()` returns the result synchronously. Guards are |
| 32 | + standalone functions, so `arr.filter(isSpecType.ContentBlock)` works. Also export the `SpecTypeName`, `SpecTypes`, and `StandardSchemaV1Sync` types. |
| 33 | + |
| 34 | +- [#1871](https://github.com/modelcontextprotocol/typescript-sdk/pull/1871) [`9fc9070`](https://github.com/modelcontextprotocol/typescript-sdk/commit/9fc9070b7b8e18227127aaee9869f8809a87fdb1) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Move stdio transports |
| 35 | + to a `./stdio` subpath export. Import `StdioClientTransport`, `getDefaultEnvironment`, `DEFAULT_INHERITED_ENV_VARS`, and `StdioServerParameters` from `@modelcontextprotocol/client/stdio`, and `StdioServerTransport` from `@modelcontextprotocol/server/stdio`. The |
| 36 | + `@modelcontextprotocol/client` root entry no longer pulls in `node:child_process`, `node:stream`, or `cross-spawn`, fixing bundling for browser and Cloudflare Workers targets; the `@modelcontextprotocol/server` root entry drops its `node:stream` reference. Node.js, Bun, and |
| 37 | + Deno consumers update the import path; runtime behavior is unchanged. |
| 38 | + |
| 39 | +### Patch Changes |
| 40 | + |
| 41 | +- [#1897](https://github.com/modelcontextprotocol/typescript-sdk/pull/1897) [`434b2f1`](https://github.com/modelcontextprotocol/typescript-sdk/commit/434b2f11ecec452f3dca0199f68afccd8b119dd4) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Stop bundling |
| 42 | + `@cfworker/json-schema` into the main package barrel. Previously `CfWorkerJsonSchemaValidator` was re-exported from the core internal barrel, so tsdown inlined the `@cfworker/json-schema` dependency into every consumer's bundle even when it was never used. The named validator |
| 43 | + classes are now reachable only via the explicit `@modelcontextprotocol/{client,server}/validators/{ajv,cf-worker}` subpaths and the runtime `_shims` conditional, so consumers that import only from the root entry point no longer ship the validator dep. |
| 44 | + |
| 45 | +- [#1834](https://github.com/modelcontextprotocol/typescript-sdk/pull/1834) [`42cb6b2`](https://github.com/modelcontextprotocol/typescript-sdk/commit/42cb6b2b728347d8b58a0d1940b7e63366a29ab9) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Export |
| 46 | + `InMemoryTransport` for in-process testing. |
| 47 | + |
| 48 | +- [#1898](https://github.com/modelcontextprotocol/typescript-sdk/pull/1898) [`2a7611d`](https://github.com/modelcontextprotocol/typescript-sdk/commit/2a7611d46b0d4f4e7bd4147c7a3ad3da00e57e52) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Add top-level `types` |
| 49 | + field (and `typesVersions` on client/server for their subpath exports) so consumers on legacy `moduleResolution: "node"` can resolve type declarations. The `exports` map remains the source of truth for `nodenext`/`bundler` resolution. The `typesVersions` map includes entries |
| 50 | + for subpaths added by sibling PRs in this series (`zod-schemas`, `stdio`); those entries are no-ops until the corresponding `dist/*.d.mts` files exist. |
| 51 | + |
| 52 | +- [#1655](https://github.com/modelcontextprotocol/typescript-sdk/pull/1655) [`1eb3123`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1eb31236e707c4f4ab9234d87db21ab3f34bf0bc) Thanks [@nielskaspers](https://github.com/nielskaspers)! - fix(client): append custom |
| 53 | + Accept headers to spec-required defaults in StreamableHTTPClientTransport |
| 54 | + |
| 55 | + Custom Accept headers provided via `requestInit.headers` are now appended to the spec-mandated Accept types instead of being overwritten. This ensures the required media types (`application/json, text/event-stream` for POST; `text/event-stream` for GET SSE) are always present |
| 56 | + while allowing users to include additional types for proxy/gateway routing. |
| 57 | + |
| 58 | +- [#2275](https://github.com/modelcontextprotocol/typescript-sdk/pull/2275) [`1b53a41`](https://github.com/modelcontextprotocol/typescript-sdk/commit/1b53a415ea2c33aa11ac413fc9c2d68ccffde784) Thanks [@KKonstantinov](https://github.com/KKonstantinov)! - Add a configurable |
| 59 | + `maxBufferSize` (default 10 MB) to the stdio transports. When a single message would push the read buffer past the limit, the transport now emits an `onerror` and closes instead of growing the buffer unbounded. Configure via `new StdioClientTransport({ ..., maxBufferSize })` or |
| 60 | + `new StdioServerTransport(stdin, stdout, { maxBufferSize })`. The default is exported from `@modelcontextprotocol/core` as `STDIO_DEFAULT_MAX_BUFFER_SIZE`. |
| 61 | + |
| 62 | +- [#2088](https://github.com/modelcontextprotocol/typescript-sdk/pull/2088) [`16d13ab`](https://github.com/modelcontextprotocol/typescript-sdk/commit/16d13abf78b5dba5de73dfa284325b13d4219bb2) Thanks [@mattzcarey](https://github.com/mattzcarey)! - Bundle automatic JSON Schema |
| 63 | + validator defaults in `@modelcontextprotocol/client` and `@modelcontextprotocol/server` runtime shims. |
| 64 | + |
| 65 | + Client and server pick the right validator automatically based on the runtime: the Node shim uses AJV, the browser/workerd shim uses `@cfworker/json-schema`. Both backends are bundled into the shim chunks that select them, so the default code path needs no extra installs — |
| 66 | + `import { McpServer } from '@modelcontextprotocol/server'` does not pull `ajv` or `@cfworker/json-schema` into the root entry chunk. |
| 67 | + |
| 68 | + The named validator classes remain part of the public surface for consumers who want to customize the built-in backend (pre-register schemas by `$id`, register custom AJV formats, switch dialects, change `@cfworker/json-schema` draft). They are exposed through explicit |
| 69 | + subpaths so they do not bloat the root index chunk: |
| 70 | + - `import { AjvJsonSchemaValidator } from '@modelcontextprotocol/{client,server}/validators/ajv'` |
| 71 | + - `import { CfWorkerJsonSchemaValidator } from '@modelcontextprotocol/{client,server}/validators/cf-worker'` |
| 72 | + |
| 73 | + Importing from one of these subpaths means the corresponding peer dep (`ajv` + `ajv-formats`, or `@cfworker/json-schema`) must be in your `package.json`. The shim keeps its own vendored copy for the default path, so a project can use the subpath in some files and rely on the |
| 74 | + default in others. |
| 75 | + |
| 76 | + The `jsonSchemaValidator` interface remains the public extension point for replacing validation entirely with a custom implementation. |
| 77 | + |
| 78 | +- [#1976](https://github.com/modelcontextprotocol/typescript-sdk/pull/1976) [`55b1f06`](https://github.com/modelcontextprotocol/typescript-sdk/commit/55b1f06cd4569e334f3435b7971f0446f1ef9be9) Thanks [@felixweinberger](https://github.com/felixweinberger)! - refactor: subclasses |
| 79 | + override `_wrapHandler` hook instead of redeclaring `setRequestHandler`. |
| 80 | + |
| 81 | +- [#1895](https://github.com/modelcontextprotocol/typescript-sdk/pull/1895) [`b256546`](https://github.com/modelcontextprotocol/typescript-sdk/commit/b256546750277faeb7c886792aae5ed26e6904d5) Thanks [@felixweinberger](https://github.com/felixweinberger)! - Fix runtime crash on |
| 82 | + `tools/list` when a tool's `inputSchema` comes from zod 4.0–4.1. The SDK requires `~standard.jsonSchema` (StandardJSONSchemaV1, added in zod 4.2.0); previously a missing `jsonSchema` crashed at `undefined[io]`. `standardSchemaToJsonSchema` now detects zod 4 schemas lacking |
| 83 | + `jsonSchema` and falls back to the SDK-bundled `z.toJSONSchema()`, emitting a one-time console warning. zod 3 schemas (which the bundled zod 4 converter cannot introspect) and non-zod schema libraries without `jsonSchema` get a clear error pointing to `fromJsonSchema()`. The |
| 84 | + workspace zod catalog is also bumped to `^4.2.0`. |
| 85 | + |
3 | 86 | ## 2.0.0-alpha.2 |
4 | 87 |
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5 | 88 | ### Patch Changes |
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