perf: add preloadSchemas() and warm wire schemas eagerly on workerd (#2483)

packages/server/src/index.ts

@@ -99,5 +99,11 @@ export type { CacheHint, CacheScope } from '@modelcontextprotocol/core-internal'
 export type { ElicitInputParams, InputRequiredSpec, InputResponseView } from '@modelcontextprotocol/core-internal';
 export { acceptedContent, inputRequired, inputResponse } from '@modelcontextprotocol/core-internal';
 
+// Explicit opt-in to eager wire-schema construction, for platforms that bill
+// request CPU but not module evaluation (isolate-based edge/serverless
+// runtimes). The package's workerd build calls it automatically at module
+// scope; other builds stay lazy unless the application calls it itself.
+export { preloadSchemas } from '@modelcontextprotocol/core-internal';
+
 // re-export curated public API from core
 export * from '@modelcontextprotocol/core-internal/public';

packages/server/src/shimsBrowser.ts

@@ -0,0 +1,27 @@
+/**
+ * Browser runtime shims for server package
+ *
+ * This file is selected via package.json export conditions when bundling for
+ * browsers. It binds the same platform choices as the workerd shim (the
+ * cfWorker validator, the process stub) WITHOUT the module-scope
+ * `preloadSchemas()` call: in a browser, module evaluation is page load —
+ * boot latency — so schema construction stays lazy, exactly like Node.
+ */
+export { CfWorkerJsonSchemaValidator as DefaultJsonSchemaValidator } from '@modelcontextprotocol/core-internal/validators/cfWorker';
+
+/**
+ * Stub process object for non-Node.js environments.
+ * StdioServerTransport is not supported in Cloudflare Workers/browser environments.
+ */
+function notSupported(): never {
+    throw new Error('StdioServerTransport is not supported in this environment. Use StreamableHTTPServerTransport instead.');
+}
+
+export const process = {
+    get stdin(): never {
+        return notSupported();
+    },
+    get stdout(): never {
+        return notSupported();
+    }
+};

packages/server/src/shimsWorkerd.ts

@@ -3,8 +3,17 @@
  *
  * This file is selected via package.json export conditions when running in workerd.
  */
+import { preloadSchemas } from '@modelcontextprotocol/core-internal';
+
 export { CfWorkerJsonSchemaValidator as DefaultJsonSchemaValidator } from '@modelcontextprotocol/core-internal/validators/cfWorker';
 
+// Platform asymmetry: isolate platforms like workerd evaluate module scope
+// during deployment/isolate warm-up, outside any request's billed CPU, while
+// lazy construction would land inside the first request each fresh isolate
+// serves. The Node and browser shims stay lazy — there, module evaluation is
+// process/page startup and boot latency is the cost that matters.
+preloadSchemas();
+
 /**
  * Stub process object for non-Node.js environments.
  * StdioServerTransport is not supported in Cloudflare Workers/browser environments.