feat: port to MCP SDK v2 (minimum-diff via compat layer)

Ports ext-apps to @modelcontextprotocol/sdk ^2.0.0-alpha.2 using the v2
backwards-compat layer. Source delta is 4 files +44/-31; the compat layer
keeps v1 deep-import paths and the ZodSchema overloads working.

Unavoidable changes:
- Protocol<X,Y,Z> -> Protocol<ContextT> generic-arity (events.ts)
- assertCapability* override params widened to string (app.ts, app-bridge.ts)
- registerAppTool callback unifies LegacyToolCallback | ToolCallback to
  cover both raw-shape and StandardSchema args (server/index.ts)

CI will fail until @modelcontextprotocol/sdk@2.0.0-alpha.2 is published;
see typescript-sdk milestone v2.0.0-bc. package-lock.json intentionally
not updated in this commit.

Author: felixweinberger

package.json

@@ -76,7 +76,7 @@
   "author": "Olivier Chafik",
   "devDependencies": {
     "@boneskull/typedoc-plugin-mermaid": "^0.2.0",
-    "@modelcontextprotocol/sdk": "^1.29.0",
+    "@modelcontextprotocol/sdk": "^2.0.0-alpha.2",
     "@playwright/test": "1.57.0",
     "@types/bun": "^1.3.2",
     "@types/node": "20.19.27",
@@ -107,7 +107,7 @@
     "zod": "^4.1.13"
   },
   "peerDependencies": {
-    "@modelcontextprotocol/sdk": "^1.29.0",
+    "@modelcontextprotocol/sdk": "^2.0.0-alpha.2",
     "react": "^17.0.0 || ^18.0.0 || ^19.0.0",
     "react-dom": "^17.0.0 || ^18.0.0 || ^19.0.0",
     "zod": "^3.25.0 || ^4.0.0"

src/app-bridge.ts

@@ -1325,7 +1325,7 @@ export class AppBridge extends ProtocolWithEvents<
    * Verify that the guest supports the capability required for the given request method.
    * @internal
    */
-  assertCapabilityForMethod(method: AppRequest["method"]): void {
+  assertCapabilityForMethod(method: string): void {
     // TODO
   }
 
@@ -1341,7 +1341,7 @@ export class AppBridge extends ProtocolWithEvents<
    * Verify that the host supports the capability required for the given notification method.
    * @internal
    */
-  assertNotificationCapability(method: AppNotification["method"]): void {
+  assertNotificationCapability(method: string): void {
     // TODO
   }
 

src/app.ts

@@ -762,7 +762,7 @@ export class App extends ProtocolWithEvents<
    * Verify that the host supports the capability required for the given request method.
    * @internal
    */
-  assertCapabilityForMethod(method: AppRequest["method"]): void {
+  assertCapabilityForMethod(method: string): void {
     // TODO
   }
 
@@ -792,7 +792,7 @@ export class App extends ProtocolWithEvents<
    * Verify that the app supports the capability required for the given notification method.
    * @internal
    */
-  assertNotificationCapability(method: AppNotification["method"]): void {
+  assertNotificationCapability(method: string): void {
     // TODO
   }
 

src/events.ts

@@ -3,7 +3,11 @@ import {
   Request,
   Notification,
   Result,
+  type BaseContext,
+  type LegacyContextFields,
 } from "@modelcontextprotocol/sdk/types.js";
+
+type AppContext = BaseContext & LegacyContextFields;
 import { ZodLiteral, ZodObject } from "zod/v4";
 
 type MethodSchema = ZodObject<{ method: ZodLiteral<string> }>;
@@ -61,7 +65,10 @@ export abstract class ProtocolWithEvents<
   SendNotificationT extends Notification,
   SendResultT extends Result,
   EventMap extends Record<string, unknown>,
-> extends Protocol<SendRequestT, SendNotificationT, SendResultT> {
+> extends Protocol<AppContext> {
+  protected buildContext(ctx: AppContext): AppContext {
+    return ctx;
+  }
   private _registeredMethods = new Set<string>();
   private _eventSlots = new Map<keyof EventMap, EventSlot>();
 
@@ -209,14 +216,11 @@ export abstract class ProtocolWithEvents<
    *
    * @throws {Error} if a handler for this method is already registered.
    */
-  override setRequestHandler: Protocol<
-    SendRequestT,
-    SendNotificationT,
-    SendResultT
-  >["setRequestHandler"] = (schema, handler) => {
-    this._assertMethodNotRegistered(schema, "setRequestHandler");
-    super.setRequestHandler(schema, handler);
-  };
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  override setRequestHandler = ((...args: any) => {
+    this._assertMethodNotRegistered(args[0], "setRequestHandler");
+    super.setRequestHandler(...(args as [MethodSchema, () => Result]));
+  }) as Protocol<AppContext>["setRequestHandler"];
 
   /**
    * Registers a notification handler. Throws if a handler for the same
@@ -225,14 +229,11 @@ export abstract class ProtocolWithEvents<
    *
    * @throws {Error} if a handler for this method is already registered.
    */
-  override setNotificationHandler: Protocol<
-    SendRequestT,
-    SendNotificationT,
-    SendResultT
-  >["setNotificationHandler"] = (schema, handler) => {
-    this._assertMethodNotRegistered(schema, "setNotificationHandler");
-    super.setNotificationHandler(schema, handler);
-  };
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  override setNotificationHandler = ((...args: any) => {
+    this._assertMethodNotRegistered(args[0], "setNotificationHandler");
+    super.setNotificationHandler(...(args as [MethodSchema, () => void]));
+  }) as Protocol<AppContext>["setNotificationHandler"];
 
   /**
    * Warn if a request handler `on*` setter is replacing a previously-set
@@ -255,15 +256,12 @@ export abstract class ProtocolWithEvents<
    * Replace a request handler, bypassing double-set protection. Used by
    * `on*` request-handler setters that need replace semantics.
    */
-  protected replaceRequestHandler: Protocol<
-    SendRequestT,
-    SendNotificationT,
-    SendResultT
-  >["setRequestHandler"] = (schema, handler) => {
-    const method = (schema as MethodSchema).shape.method.value;
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  protected replaceRequestHandler = ((...args: any) => {
+    const method = (args[0] as MethodSchema).shape.method.value;
     this._registeredMethods.add(method);
-    super.setRequestHandler(schema, handler);
-  };
+    super.setRequestHandler(...(args as [MethodSchema, () => Result]));
+  }) as Protocol<AppContext>["setRequestHandler"];
 
   private _assertMethodNotRegistered(schema: unknown, via: string): void {
     const method = (schema as MethodSchema).shape.method.value;

src/server/index.ts

@@ -41,17 +41,27 @@ import {
 } from "../app.js";
 import type {
   BaseToolCallback,
+  LegacyToolCallback,
   McpServer,
   RegisteredTool,
   ResourceMetadata,
-  ToolCallback,
+  ToolCallback as SchemaToolCallback,
   ReadResourceCallback as _ReadResourceCallback,
   RegisteredResource,
 } from "@modelcontextprotocol/sdk/server/mcp.js";
 import type {
   AnySchema,
   ZodRawShapeCompat,
+  StandardSchemaWithJSON,
 } from "@modelcontextprotocol/sdk/server/zod-compat.js";
+import type { ZodRawShape } from "@modelcontextprotocol/sdk";
+
+type ToolCallback<Args extends ZodRawShapeCompat | AnySchema | undefined> =
+  Args extends ZodRawShape
+    ? LegacyToolCallback<Args>
+    : Args extends StandardSchemaWithJSON
+      ? SchemaToolCallback<Args>
+      : SchemaToolCallback<undefined>;
 import type {
   ClientCapabilities,
   ReadResourceResult,
@@ -241,7 +251,12 @@ export function registerAppTool<
     normalizedMeta = { ...meta, ui: { ...uiMeta, resourceUri: legacyUri } };
   }
 
-  return server.registerTool(name, { ...config, _meta: normalizedMeta }, cb);
+  return (server.registerTool as McpServer["registerTool"])(
+    name,
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    { ...config, _meta: normalizedMeta } as any,
+    cb as SchemaToolCallback<undefined>,
+  );
 }
 
 export type McpUiReadResourceResult = ReadResourceResult & {