Version Packages

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Releases

@modelcontextprotocol/server@2.0.0

Major Changes

• #1389 108f2f3 Thanks @DePasqualeOrg! - Fix error handling for
  unknown tools and resources per MCP spec.

  Tools: Unknown or disabled tool calls now return JSON-RPC protocol errors with code -32602 (InvalidParams) instead of CallToolResult with isError: true. Callers who checked result.isError for unknown tools should catch rejected promises instead.

  Resources: Unknown resource reads now return error code -32002 (ResourceNotFound) instead of -32602 (InvalidParams).

  Added ProtocolErrorCode.ResourceNotFound.

Minor Changes

• #1673 462c3fc Thanks @KKonstantinov! - refactor: extract task
  orchestration from Protocol into TaskManager

  Breaking changes:

  • taskStore, taskMessageQueue, defaultTaskPollInterval, and maxTaskQueueSize moved from ProtocolOptions to capabilities.tasks on ClientOptions/ServerOptions

• #1689 0784be1 Thanks @felixweinberger! - Support Standard Schema
  for tool and prompt schemas

  Tool and prompt registration now accepts any schema library that implements the Standard Schema spec: Zod v4, Valibot, ArkType, and others. RegisteredTool.inputSchema, RegisteredTool.outputSchema, and RegisteredPrompt.argsSchema now use
  StandardSchemaWithJSON (requires both ~standard.validate and ~standard.jsonSchema) instead of the Zod-specific AnySchema type.

  Zod v4 schemas continue to work unchanged — Zod v4 implements the required interfaces natively.

  import { type } from 'arktype';
  
  server.registerTool(
      'greet',
      {
          inputSchema: type({ name: 'string' })
      },
      async ({ name }) => ({ content: [{ type: 'text', text: `Hello, ${name}!` }] })
  );

  For raw JSON Schema (e.g. TypeBox output), use the new fromJsonSchema adapter:

  import { fromJsonSchema, AjvJsonSchemaValidator } from '@modelcontextprotocol/core';
  
  server.registerTool(
      'greet',
      {
          inputSchema: fromJsonSchema({ type: 'object', properties: { name: { type: 'string' } } }, new AjvJsonSchemaValidator())
      },
      handler
  );

  Breaking changes:

  • experimental.tasks.getTaskResult() no longer accepts a resultSchema parameter. Returns GetTaskPayloadResult (a loose Result); cast to the expected type at the call site.
  • Removed unused exports from @modelcontextprotocol/core: SchemaInput, schemaToJson, parseSchemaAsync, getSchemaShape, getSchemaDescription, isOptionalSchema, unwrapOptionalSchema. Use the new standardSchemaToJsonSchema and validateStandardSchema instead.
  • completable() remains Zod-specific (it relies on Zod's .shape introspection).

Patch Changes

• #1363 0a75810 Thanks @DevJanderson! - Fix ReDoS vulnerability in
  UriTemplate regex patterns (CVE-2026-0621)

• #1372 3466a9e Thanks @mattzcarey! - missing change for fix(client):
  replace body.cancel() with text() to prevent hanging

• #1761 01954e6 Thanks @felixweinberger! - Convert remaining
  capability-assertion throws to SdkError(SdkErrorCode.CapabilityNotSupported, ...). Follow-up to v2: Errors refactor (ProtocolError, SdkError, OAuthError) #1454 which missed Client.assertCapability(), the task capability helpers in experimental/tasks/helpers.ts, and the sampling/elicitation capability checks in
  experimental/tasks/server.ts.

• #1433 78bae74 Thanks @codewithkenzo! - Fix transport errors being
  silently swallowed by adding missing onerror callback invocations before all createJsonErrorResponse calls in WebStandardStreamableHTTPServerTransport. This ensures errors like parse failures, invalid headers, and session validation errors are properly reported via the
  onerror callback.

• #1568 f1ade75 Thanks @stakeswky! - Handle stdout errors (e.g. EPIPE)
  in StdioServerTransport gracefully instead of crashing. When the client disconnects abruptly, the transport now catches the stdout error, surfaces it via onerror, and closes.

• #1419 dcf708d Thanks @KKonstantinov! - remove deprecated .tool,
  .prompt, .resource method signatures

• #1388 f66a55b Thanks @mattzcarey! - reverting application/json in
  notifications

• #1534 69a0626 Thanks @josefaidt! - remove npm references, use pnpm

• #1534 69a0626 Thanks @josefaidt! - clean up package manager usage, all
  pnpm

• #1419 dcf708d Thanks @KKonstantinov! - deprecated .tool, .prompt,
  .resource method removal

• #1279 71ae3ac Thanks @KKonstantinov! - Initial 2.0.0-alpha.0
  client and server package

@modelcontextprotocol/client@2.0.0

Minor Changes

• #1527 dc896e1 Thanks @felixweinberger! - Add
  discoverOAuthServerInfo() function and unified discovery state caching for OAuth

  • New discoverOAuthServerInfo(serverUrl) export that performs RFC 9728 protected resource metadata discovery followed by authorization server metadata discovery in a single call. Use this for operations like token refresh and revocation that need the authorization server
    URL outside of auth().
  • New OAuthDiscoveryState type and optional OAuthClientProvider methods saveDiscoveryState() / discoveryState() allow providers to persist all discovery results (auth server URL, resource metadata URL, resource metadata, auth server metadata) across sessions. This
    avoids redundant discovery requests and handles browser redirect scenarios where discovery state would otherwise be lost.
  • New 'discovery' scope for invalidateCredentials() to clear cached discovery state.
  • New OAuthServerInfo type exported for the return value of discoverOAuthServerInfo().

• #1673 462c3fc Thanks @KKonstantinov! - refactor: extract task
  orchestration from Protocol into TaskManager

  Breaking changes:

  • taskStore, taskMessageQueue, defaultTaskPollInterval, and maxTaskQueueSize moved from ProtocolOptions to capabilities.tasks on ClientOptions/ServerOptions

• #1689 0784be1 Thanks @felixweinberger! - Support Standard Schema
  for tool and prompt schemas

  Tool and prompt registration now accepts any schema library that implements the Standard Schema spec: Zod v4, Valibot, ArkType, and others. RegisteredTool.inputSchema, RegisteredTool.outputSchema, and RegisteredPrompt.argsSchema now use
  StandardSchemaWithJSON (requires both ~standard.validate and ~standard.jsonSchema) instead of the Zod-specific AnySchema type.

  Zod v4 schemas continue to work unchanged — Zod v4 implements the required interfaces natively.

  import { type } from 'arktype';
  
  server.registerTool(
      'greet',
      {
          inputSchema: type({ name: 'string' })
      },
      async ({ name }) => ({ content: [{ type: 'text', text: `Hello, ${name}!` }] })
  );

  For raw JSON Schema (e.g. TypeBox output), use the new fromJsonSchema adapter:

  import { fromJsonSchema, AjvJsonSchemaValidator } from '@modelcontextprotocol/core';
  
  server.registerTool(
      'greet',
      {
          inputSchema: fromJsonSchema({ type: 'object', properties: { name: { type: 'string' } } }, new AjvJsonSchemaValidator())
      },
      handler
  );

  Breaking changes:

  • experimental.tasks.getTaskResult() no longer accepts a resultSchema parameter. Returns GetTaskPayloadResult (a loose Result); cast to the expected type at the call site.
  • Removed unused exports from @modelcontextprotocol/core: SchemaInput, schemaToJson, parseSchemaAsync, getSchemaShape, getSchemaDescription, isOptionalSchema, unwrapOptionalSchema. Use the new standardSchemaToJsonSchema and validateStandardSchema instead.
  • completable() remains Zod-specific (it relies on Zod's .shape introspection).

• #1710 e563e63 Thanks @felixweinberger! - Add AuthProvider for
  composable bearer-token auth; transports adapt OAuthClientProvider automatically

  • New AuthProvider interface: { token(): Promise<string | undefined>; onUnauthorized?(ctx): Promise<void> }. Transports call token() before every request and onUnauthorized() on 401 (then retry once).

  • Transport authProvider option now accepts AuthProvider | OAuthClientProvider. OAuth providers are adapted internally via adaptOAuthProvider() — no changes needed to existing OAuthClientProvider implementations.

  • For simple bearer tokens (API keys, gateway-managed tokens, service accounts): { authProvider: { token: async () => myKey } } — one-line object literal, no class.

  • New adaptOAuthProvider(provider) export for explicit adaptation.

  • New handleOAuthUnauthorized(provider, ctx) helper — the standard OAuth onUnauthorized behavior.

  • New isOAuthClientProvider() type guard.

  • New UnauthorizedContext type.

  • Exported previously-internal auth helpers for building custom flows: applyBasicAuth, applyPostAuth, applyPublicAuth, executeTokenRequest.

    Transports are simplified internally — ~50 lines of inline OAuth orchestration (auth() calls, WWW-Authenticate parsing, circuit-breaker state) moved into the adapter's onUnauthorized() implementation. OAuthClientProvider itself is unchanged.

• #1614 1a78b01 Thanks @pcarleton! - Apply resolved scope consistently
  to both DCR and the authorization URL (SEP-835)

  When scopes_supported is present in the protected resource metadata (/.well-known/oauth-protected-resource), the SDK already uses it as the default scope for the authorization URL. This change applies the same resolved scope to the dynamic client registration request
  body, ensuring both use a consistent value.

  • registerClient() now accepts an optional scope parameter that overrides clientMetadata.scope in the registration body.
  • auth() now computes the resolved scope once (WWW-Authenticate → PRM scopes_supported → clientMetadata.scope) and passes it to both DCR and the authorization request.

Patch Changes

• #1761 01954e6 Thanks @felixweinberger! - Convert remaining
  capability-assertion throws to SdkError(SdkErrorCode.CapabilityNotSupported, ...). Follow-up to v2: Errors refactor (ProtocolError, SdkError, OAuthError) #1454 which missed Client.assertCapability(), the task capability helpers in experimental/tasks/helpers.ts, and the sampling/elicitation capability checks in
  experimental/tasks/server.ts.

• #1343 4b5fdcb Thanks @christso! - Fix OAuth error handling for servers
  returning errors with HTTP 200 status

  Some OAuth servers (e.g., GitHub) return error responses with HTTP 200 status instead of 4xx. The SDK now checks for an error field in the JSON response before attempting to parse it as tokens, providing users with meaningful error messages.

• #1534 69a0626 Thanks @josefaidt! - remove npm references, use pnpm

• #1386 00249ce Thanks @PederHP! - Respect capability negotiation in list
  methods by returning empty lists when server lacks capability

  The Client now returns empty lists instead of sending requests to servers that don't advertise the corresponding capability:

  • listPrompts() returns { prompts: [] } if server lacks prompts capability

  • listResources() returns { resources: [] } if server lacks resources capability

  • listResourceTemplates() returns { resourceTemplates: [] } if server lacks resources capability

  • listTools() returns { tools: [] } if server lacks tools capability

    This respects the MCP spec requirement that "Both parties SHOULD respect capability negotiation" and avoids unnecessary server warnings and traffic. The existing enforceStrictCapabilities option continues to throw errors when set to true.

• #1534 69a0626 Thanks @josefaidt! - clean up package manager usage, all
  pnpm

• #1595 13a0d34 Thanks @bhosmer-ant! - Don't swallow fetch TypeError
  as CORS in non-browser environments. Network errors (DNS resolution failure, connection refused, invalid URL) in Node.js and Cloudflare Workers now propagate from OAuth discovery instead of being silently misattributed to CORS and returning undefined. This surfaces the real
  error to callers rather than masking it as "metadata not found."

• #1279 71ae3ac Thanks @KKonstantinov! - Initial 2.0.0-alpha.0
  client and server package

@modelcontextprotocol/express@2.0.0

Patch Changes

• #1534 69a0626 Thanks @josefaidt! - remove npm references, use pnpm

• #1534 69a0626 Thanks @josefaidt! - clean up package manager usage, all
  pnpm

• #1625 1fe9eda Thanks @rameshreddy-adutla! - Add jsonLimit
  option to createMcpExpressApp

• Updated dependencies [0a75810, 3466a9e,
  462c3fc, 01954e6,
  78bae74, f1ade75,
  108f2f3, dcf708d,
  f66a55b, 69a0626,
  69a0626, dcf708d,
  0784be1, 71ae3ac]:

  • @modelcontextprotocol/server@2.0.0

@modelcontextprotocol/hono@2.0.0

Patch Changes

• #1534 69a0626 Thanks @josefaidt! - remove npm references, use pnpm

• #1534 69a0626 Thanks @josefaidt! - clean up package manager usage, all
  pnpm

• Updated dependencies [0a75810, 3466a9e,
  462c3fc, 01954e6,
  78bae74, f1ade75,
  108f2f3, dcf708d,
  f66a55b, 69a0626,
  69a0626, dcf708d,
  0784be1, 71ae3ac]:

  • @modelcontextprotocol/server@2.0.0

@modelcontextprotocol/node@2.0.0

Patch Changes

• #1504 327243c Thanks @corvid-agent! - Add missing hono peer
  dependency to @modelcontextprotocol/node. The package already depends on @hono/node-server which requires hono at runtime, but hono was only listed in the workspace root, not as a peer dependency of the package itself.

• #1410 9296459 Thanks @mattzcarey! - Prevent Hono from overriding
  global Response object by passing overrideGlobalObjects: false to getRequestListener(). This fixes compatibility with frameworks like Next.js whose response classes extend the native Response.

• #1419 dcf708d Thanks @KKonstantinov! - remove deprecated .tool,
  .prompt, .resource method signatures

• #1534 69a0626 Thanks @josefaidt! - remove npm references, use pnpm

• #1534 69a0626 Thanks @josefaidt! - clean up package manager usage, all
  pnpm

• #1419 dcf708d Thanks @KKonstantinov! - deprecated .tool, .prompt,
  .resource method removal

• Updated dependencies [0a75810, 3466a9e,
  462c3fc, 01954e6,
  78bae74, f1ade75,
  108f2f3, dcf708d,
  f66a55b, 69a0626,
  69a0626, dcf708d,
  0784be1, 71ae3ac]:

  • @modelcontextprotocol/server@2.0.0

@modelcontextprotocol/core@2.0.0

Minor Changes

• #1673 462c3fc Thanks @KKonstantinov! - refactor: extract task
  orchestration from Protocol into TaskManager

  Breaking changes:

  • taskStore, taskMessageQueue, defaultTaskPollInterval, and maxTaskQueueSize moved from ProtocolOptions to capabilities.tasks on ClientOptions/ServerOptions

• #1389 108f2f3 Thanks @DePasqualeOrg! - Fix error handling for
  unknown tools and resources per MCP spec.

  Tools: Unknown or disabled tool calls now return JSON-RPC protocol errors with code -32602 (InvalidParams) instead of CallToolResult with isError: true. Callers who checked result.isError for unknown tools should catch rejected promises instead.

  Resources: Unknown resource reads now return error code -32002 (ResourceNotFound) instead of -32602 (InvalidParams).

  Added ProtocolErrorCode.ResourceNotFound.

• #1689 0784be1 Thanks @felixweinberger! - Support Standard Schema
  for tool and prompt schemas

  Tool and prompt registration now accepts any schema library that implements the Standard Schema spec: Zod v4, Valibot, ArkType, and others. RegisteredTool.inputSchema, RegisteredTool.outputSchema, and RegisteredPrompt.argsSchema now use
  StandardSchemaWithJSON (requires both ~standard.validate and ~standard.jsonSchema) instead of the Zod-specific AnySchema type.

  Zod v4 schemas continue to work unchanged — Zod v4 implements the required interfaces natively.

  import { type } from 'arktype';
  
  server.registerTool(
      'greet',
      {
          inputSchema: type({ name: 'string' })
      },
      async ({ name }) => ({ content: [{ type: 'text', text: `Hello, ${name}!` }] })
  );

  For raw JSON Schema (e.g. TypeBox output), use the new fromJsonSchema adapter:

  import { fromJsonSchema, AjvJsonSchemaValidator } from '@modelcontextprotocol/core';
  
  server.registerTool(
      'greet',
      {
          inputSchema: fromJsonSchema({ type: 'object', properties: { name: { type: 'string' } } }, new AjvJsonSchemaValidator())
      },
      handler
  );

  Breaking changes:

  • experimental.tasks.getTaskResult() no longer accepts a resultSchema parameter. Returns GetTaskPayloadResult (a loose Result); cast to the expected type at the call site.
  • Removed unused exports from @modelcontextprotocol/core: SchemaInput, schemaToJson, parseSchemaAsync, getSchemaShape, getSchemaDescription, isOptionalSchema, unwrapOptionalSchema. Use the new standardSchemaToJsonSchema and validateStandardSchema instead.
  • completable() remains Zod-specific (it relies on Zod's .shape introspection).

Patch Changes

• #1735 a2e5037 Thanks @felixweinberger! - Abort in-flight request
  handlers when the connection closes. Previously, request handlers would continue running after the transport disconnected, wasting resources and preventing proper cleanup. Also fixes InMemoryTransport.close() firing onclose twice on the initiating side.

• #1574 379392d Thanks @olaservo! - Add missing size field to
  ResourceSchema to match the MCP specification

• #1363 0a75810 Thanks @DevJanderson! - Fix ReDoS vulnerability in
  UriTemplate regex patterns (CVE-2026-0621)

• #1761 01954e6 Thanks @felixweinberger! - Convert remaining
  capability-assertion throws to SdkError(SdkErrorCode.CapabilityNotSupported, ...). Follow-up to v2: Errors refactor (ProtocolError, SdkError, OAuthError) #1454 which missed Client.assertCapability(), the task capability helpers in experimental/tasks/helpers.ts, and the sampling/elicitation capability checks in
  experimental/tasks/server.ts.

• #1486 65bbcea Thanks @localden! - Fix InMemoryTaskStore to enforce
  session isolation. Previously, sessionId was accepted but ignored on all TaskStore methods, allowing any session to enumerate, read, and mutate tasks created by other sessions. The store now persists sessionId at creation time and enforces ownership on all reads and writes.

• #1419 dcf708d Thanks @KKonstantinov! - remove deprecated .tool,
  .prompt, .resource method signatures

• #1534 69a0626 Thanks @josefaidt! - remove npm references, use pnpm

• #1534 69a0626 Thanks @josefaidt! - clean up package manager usage, all
  pnpm

• #1419 dcf708d Thanks @KKonstantinov! - deprecated .tool, .prompt,
  .resource method removal

• #1762 64897f7 Thanks @felixweinberger! -
  ReadBuffer.readMessage() now silently skips non-JSON lines instead of throwing SyntaxError. This prevents noisy onerror callbacks when hot-reload tools (tsx, nodemon) write debug output like "Gracefully restarting..." to stdout. Lines that parse as JSON but fail JSONRPC
  schema validation still throw.

@modelcontextprotocol/test-integration@2.0.0

Patch Changes

• #1419 dcf708d Thanks @KKonstantinov! - remove deprecated .tool,
  .prompt, .resource method signatures

• #1419 dcf708d Thanks @KKonstantinov! - deprecated .tool, .prompt,
  .resource method removal