chore: sync schemas.ts to spec @d494db5c; segregate pre-2026 wire schemas

schemas.ts:
- Result/Notification _meta now use plain MetaObject (not RequestMetaSchema)
- ResultTypeSchema, resultType optional on ResultSchema (BC: pre-2026 omits it)
- RequestMetaSchema kept simple {progressToken?}; namespaced io.modelcontextprotocol/*
  keys validated by parseClientMeta in P2, not here (TS2589 depth budget)
- DiscoverRequest/Result, UnsupportedProtocolVersionErrorData,
  MissingRequiredClientCapabilityErrorData
- DiscoverRequest/PaginatedRequest params: .default({}) — spec @d494db5c marks
  params required; .default keeps inferred type required while server-side parse
  stays tolerant of pre-2026 clients (Client._send populates params._meta in P2)
- SubscriptionFilter, SubscriptionsListenRequest/Params,
  SubscriptionsAcknowledgedNotification/Params
- subscriptions/listen has no result type per spec — omitted from resultSchemas
  runtime map; ResultTypeMap['subscriptions/listen'] = never
- InputRequest/Response/s, InputRequiredResult, InputResponseRequestParams
- CacheableResult/CacheScope (SEP-2243), PaginatedResult extends CacheableResult,
  ReadResourceResult extends CacheableResult
- structuredContent: unknown (was Record<string,unknown>)
- Tool inputSchema/outputSchema loosened to match spec (open record + type:object on input)
- ToolExecution removed (only had taskSupport)
- ClientRequest/ServerNotification/etc unions = 2026 spec methods only
- registerLegacySchemas() lets legacyWireSchemas merge into runtime lookup maps
- Dropped Initialize*/Ping/SetLevel/Subscribe/Unsubscribe/RootsListChanged

NEW legacyWireSchemas.ts:
- LegacyRequestParams/Result/RequestMetaObject base types (no namespaced keys, no resultType)
- TS interfaces + zod for Initialize/Ping/SetLevel/Subscribe/Unsubscribe/RootsListChanged
- legacyRequest/Result/NotificationSchemas maps; registerLegacySchemas() side-effect on import

types.ts: re-exports legacy types; RequestTypeMap/NotificationTypeMap/ResultTypeMap
merge legacy methods. Adds Discover*/InputRequired*/Subscriptions*/Cache* types.

guards.ts: isInitializeRequest/isInitializedNotification import from legacyWireSchemas.

specTypeSchema.ts: allowlist updated (drop legacy, add 2026).

spec.types.test.ts: Relax<T> helper makes spec-required PermissiveKeys
(_meta/resultType/ttlMs/cacheScope/inputResponses/requestState/io.modelcontextprotocol/*)
optional so mutual assignability holds for everything else. Dropped checks for
removed types; added 17 checks for 2026 types. Count 176→150.

types.capabilities.test.ts: import InitializeRequestParamsSchema from legacyWireSchemas.
types.test.ts: outputSchema no longer requires type:object.

mcp.ts: drop ToolExecution/execution (removed from spec).
client.ts: assertCapabilityForMethod switches on RequestMethod (includes legacy).

Author: felixweinberger

.changeset/spec-types-d494db5c.md

@@ -0,0 +1,4 @@
+---
+'@modelcontextprotocol/core': major
+---
+Regenerate spec.types.ts and sync schemas to spec @d494db5c. Pre-2026 wire schemas (Initialize/Ping/SetLevel/Subscribe/Unsubscribe) moved to legacyWireSchemas.ts.

packages/client/src/client/client.ts

@@ -4,8 +4,6 @@ import type {
     CallToolRequest,
     ClientCapabilities,
     ClientContext,
-    ClientNotification,
-    ClientRequest,
     CompleteRequest,
     GetPromptRequest,
     Implementation,
@@ -498,7 +496,7 @@ export class Client extends Protocol<ClientContext> {
     }
 
     protected assertCapabilityForMethod(method: RequestMethod | string): void {
-        switch (method as ClientRequest['method']) {
+        switch (method as RequestMethod) {
             case 'logging/setLevel': {
                 if (!this._serverCapabilities?.logging) {
                     throw new SdkError(SdkErrorCode.CapabilityNotSupported, `Server does not support logging (required for ${method})`);
@@ -561,7 +559,7 @@ export class Client extends Protocol<ClientContext> {
     }
 
     protected assertNotificationCapability(method: NotificationMethod | string): void {
-        switch (method as ClientNotification['method']) {
+        switch (method as NotificationMethod) {
             case 'notifications/roots/list_changed': {
                 if (!this._capabilities.roots?.listChanged) {
                     throw new SdkError(

packages/core/src/types/guards.ts

@@ -1,7 +1,7 @@
+import type { InitializedNotification, InitializeRequest } from './legacyWireSchemas.js';
+import { InitializedNotificationSchema, InitializeRequestSchema } from './legacyWireSchemas.js';
 import {
     CallToolResultSchema,
-    InitializedNotificationSchema,
-    InitializeRequestSchema,
     JSONRPCErrorResponseSchema,
     JSONRPCMessageSchema,
     JSONRPCNotificationSchema,
@@ -14,8 +14,6 @@ import type {
     CompleteRequest,
     CompleteRequestPrompt,
     CompleteRequestResourceTemplate,
-    InitializedNotification,
-    InitializeRequest,
     JSONRPCErrorResponse,
     JSONRPCMessage,
     JSONRPCNotification,

packages/core/src/types/index.ts

@@ -4,6 +4,9 @@ export * from './constants.js';
 export * from './enums.js';
 export * from './errors.js';
 export * from './guards.js';
+/* eslint-disable import/export -- legacy type names overlap with types.ts re-exports; TS resolves deterministically. */
+export * from './legacyWireSchemas.js';
 export * from './schemas.js';
 export * from './specTypeSchema.js';
 export * from './types.js';
+/* eslint-enable import/export */

packages/core/src/types/legacyWireSchemas.ts

@@ -0,0 +1,268 @@
+/**
+ * Pre-2026 wire types and schemas.
+ *
+ * These types represent JSON-RPC methods and notifications that were part of
+ * MCP up to and including 2025-11-25 but are removed from the 2026-06 draft
+ * spec. They are NOT in the current `spec.types.ts` (regenerated from the
+ * spec repo) and are SDK-maintained here so `LegacyServer` / `LegacyClient`
+ * can continue to speak the pre-2026 wire protocol.
+ *
+ * Deleted when pre-2026 protocol support is dropped.
+ */
+import * as z from 'zod/v4';
+
+import {
+    ClientCapabilitiesSchema,
+    ImplementationSchema,
+    LoggingLevelSchema,
+    NotificationSchema,
+    ProgressTokenSchema,
+    registerLegacySchemas,
+    ServerCapabilitiesSchema
+} from './schemas.js';
+import type {
+    ClientCapabilities,
+    Implementation,
+    JSONRPCNotification,
+    JSONRPCRequest,
+    LoggingLevel,
+    MetaObject,
+    NotificationParams,
+    ProgressToken,
+    ServerCapabilities
+} from './spec.types.js';
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* Legacy base shapes                                                         */
+/*                                                                            */
+/* The 2026-06 spec's `RequestParams._meta` is required and carries           */
+/* namespaced `io.modelcontextprotocol/*` keys. Pre-2026 requests have an     */
+/* optional `_meta` with only `progressToken`. These local base types let     */
+/* the legacy interfaces below avoid the strict 2026 shape.                   */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+/** Pre-2026 `_meta` shape: only `progressToken`, no namespaced keys. */
+export interface LegacyRequestMetaObject extends MetaObject {
+    progressToken?: ProgressToken;
+}
+
+/** Pre-2026 request params: `_meta` is optional. */
+export interface LegacyRequestParams {
+    _meta?: LegacyRequestMetaObject;
+    [key: string]: unknown;
+}
+
+/** Pre-2026 result: no `resultType`. */
+export interface LegacyResult {
+    _meta?: MetaObject;
+    [key: string]: unknown;
+}
+
+/* Zod base shapes for legacy schemas. Kept separate from `schemas.ts` so the
+ * 2026 file is spec-only at the source level. The shapes here are the pre-2026
+ * wire format (no namespaced `_meta` keys, no `resultType`). */
+
+const LegacyRequestMetaSchema = z.looseObject({
+    progressToken: ProgressTokenSchema.optional()
+});
+
+const LegacyBaseRequestParamsSchema = z.object({
+    _meta: LegacyRequestMetaSchema.optional()
+});
+
+const LegacyRequestSchema = z.object({
+    method: z.string(),
+    params: LegacyBaseRequestParamsSchema.loose().optional()
+});
+
+const LegacyResultSchema = z.looseObject({
+    _meta: z.record(z.string(), z.unknown()).optional()
+});
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* `initialize` / `notifications/initialized`                                 */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+export interface InitializeRequestParams extends LegacyRequestParams {
+    /**
+     * The latest version of the Model Context Protocol that the client
+     * supports. The client MAY decide to support older versions as well.
+     */
+    protocolVersion: string;
+    capabilities: ClientCapabilities;
+    clientInfo: Implementation;
+}
+
+export interface InitializeRequest extends JSONRPCRequest {
+    method: 'initialize';
+    params: InitializeRequestParams;
+}
+
+export interface InitializeResult extends LegacyResult {
+    /**
+     * The version of the Model Context Protocol that the server wants to use.
+     * This may not match the version that the client requested. If the client
+     * cannot support this version, it MUST disconnect.
+     */
+    protocolVersion: string;
+    capabilities: ServerCapabilities;
+    serverInfo: Implementation;
+    /**
+     * Instructions describing how to use the server and its features.
+     */
+    instructions?: string;
+}
+
+export interface InitializedNotification extends JSONRPCNotification {
+    method: 'notifications/initialized';
+    params?: NotificationParams;
+}
+
+export const InitializeRequestParamsSchema = LegacyBaseRequestParamsSchema.extend({
+    protocolVersion: z.string(),
+    capabilities: ClientCapabilitiesSchema,
+    clientInfo: ImplementationSchema
+});
+
+export const InitializeRequestSchema = LegacyRequestSchema.extend({
+    method: z.literal('initialize'),
+    params: InitializeRequestParamsSchema
+});
+
+export const InitializeResultSchema = LegacyResultSchema.extend({
+    protocolVersion: z.string(),
+    capabilities: ServerCapabilitiesSchema,
+    serverInfo: ImplementationSchema,
+    instructions: z.string().optional()
+});
+
+export const InitializedNotificationSchema = NotificationSchema.extend({
+    method: z.literal('notifications/initialized')
+});
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* `ping`                                                                     */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+export interface PingRequest extends JSONRPCRequest {
+    method: 'ping';
+    params?: LegacyRequestParams;
+}
+
+export const PingRequestSchema = LegacyRequestSchema.extend({
+    method: z.literal('ping')
+});
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* `logging/setLevel`                                                         */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+export interface SetLevelRequestParams extends LegacyRequestParams {
+    /**
+     * The level of logging that the client wants to receive from the server.
+     */
+    level: LoggingLevel;
+}
+
+export interface SetLevelRequest extends JSONRPCRequest {
+    method: 'logging/setLevel';
+    params: SetLevelRequestParams;
+}
+
+export const SetLevelRequestParamsSchema = LegacyBaseRequestParamsSchema.extend({
+    level: LoggingLevelSchema
+});
+
+export const SetLevelRequestSchema = LegacyRequestSchema.extend({
+    method: z.literal('logging/setLevel'),
+    params: SetLevelRequestParamsSchema
+});
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* `resources/subscribe` / `resources/unsubscribe`                            */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+export interface SubscribeRequestParams extends LegacyRequestParams {
+    /** The URI of the resource to subscribe to. */
+    uri: string;
+}
+
+export interface SubscribeRequest extends JSONRPCRequest {
+    method: 'resources/subscribe';
+    params: SubscribeRequestParams;
+}
+
+export type UnsubscribeRequestParams = SubscribeRequestParams;
+
+export interface UnsubscribeRequest extends JSONRPCRequest {
+    method: 'resources/unsubscribe';
+    params: UnsubscribeRequestParams;
+}
+
+export const SubscribeRequestParamsSchema = LegacyBaseRequestParamsSchema.extend({
+    uri: z.string()
+});
+
+export const SubscribeRequestSchema = LegacyRequestSchema.extend({
+    method: z.literal('resources/subscribe'),
+    params: SubscribeRequestParamsSchema
+});
+
+export const UnsubscribeRequestParamsSchema = SubscribeRequestParamsSchema;
+
+export const UnsubscribeRequestSchema = LegacyRequestSchema.extend({
+    method: z.literal('resources/unsubscribe'),
+    params: UnsubscribeRequestParamsSchema
+});
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* `notifications/roots/list_changed` (client → server)                       */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+export interface RootsListChangedNotification extends JSONRPCNotification {
+    method: 'notifications/roots/list_changed';
+    params?: NotificationParams;
+}
+
+export const RootsListChangedNotificationSchema = NotificationSchema.extend({
+    method: z.literal('notifications/roots/list_changed')
+});
+
+/* ────────────────────────────────────────────────────────────────────────── */
+/* Maps for legacy method/result/notification dispatch                        */
+/* ────────────────────────────────────────────────────────────────────────── */
+
+/** Legacy request methods that are not in the 2026-06 `RequestTypeMap`. */
+export const legacyRequestSchemas = {
+    initialize: InitializeRequestSchema,
+    ping: PingRequestSchema,
+    'logging/setLevel': SetLevelRequestSchema,
+    'resources/subscribe': SubscribeRequestSchema,
+    'resources/unsubscribe': UnsubscribeRequestSchema
+} as const;
+
+/** Legacy result schemas keyed by request method. */
+export const legacyResultSchemas = {
+    initialize: InitializeResultSchema,
+    ping: LegacyResultSchema,
+    'logging/setLevel': LegacyResultSchema,
+    'resources/subscribe': LegacyResultSchema,
+    'resources/unsubscribe': LegacyResultSchema
+} as const;
+
+/** Legacy notification methods that are not in the 2026-06 `NotificationTypeMap`. */
+export const legacyNotificationSchemas = {
+    'notifications/initialized': InitializedNotificationSchema,
+    'notifications/roots/list_changed': RootsListChangedNotificationSchema
+} as const;
+
+export type LegacyRequestMethod = keyof typeof legacyRequestSchemas;
+export type LegacyNotificationMethod = keyof typeof legacyNotificationSchemas;
+
+// Merge into the runtime lookup maps so `getRequestSchema('initialize')` etc.
+// continue to work. Runs at module load (this file is barrel-imported).
+registerLegacySchemas({
+    requests: legacyRequestSchemas,
+    results: legacyResultSchemas,
+    notifications: legacyNotificationSchemas
+});