perf(types): keep default-heap Node 24 typecheck under the heap limit (#2414)

* fix(types): narrow SDK response schema consumers

* perf(types): bound mixed Zod schema comparisons

src/cli/structuredIO.ts

@@ -134,7 +134,8 @@ function buildRequiresActionDetails(
 type PendingRequest<T> = {
   resolve: (result: T) => void
   reject: (error: unknown) => void
-  schema?: z.Schema
+  // Response consumers only parse; avoid comparing Zod's fluent builder types.
+  schema?: Pick<z.Schema, 'parse'>
   request: SDKControlRequest
 }
 
@@ -496,7 +497,7 @@ export class StructuredIO {
 
   private async sendRequest<Response>(
     request: SDKControlRequest['request'],
-    schema: z.Schema,
+    schema: Pick<z.Schema, 'parse'>,
     signal?: AbortSignal,
     requestId: string = randomUUID(),
   ): Promise<Response> {
@@ -798,7 +799,7 @@ export class StructuredIO {
         message,
       },
       z.object({
-        mcp_response: z.any() as z.Schema<JSONRPCMessage>,
+        mcp_response: z.any() as z.core.$ZodType<JSONRPCMessage>,
       }),
     )
     return response.mcp_response

src/utils/zodDependencies.test.ts

@@ -1,6 +1,7 @@
 import { describe, expect, test } from 'bun:test'
 import { zodOutputFormat } from '@anthropic-ai/sdk/helpers/zod'
 import { SandboxRuntimeConfigSchema } from '@anthropic-ai/sandbox-runtime'
+import type { AnySchema } from '@modelcontextprotocol/sdk/server/zod-compat.js'
 import { parseWithCompat, toJsonSchemaCompat } from '@modelcontextprotocol/sdk/server/zod-json-schema-compat.js'
 import { z as legacy } from 'zod/v3'
 import { z } from 'zod/v4'
@@ -14,7 +15,12 @@ describe('dependency schema compatibility', () => {
   })
 
   test('the protocol converter and parser support both packaged schema generations', () => {
-    for (const schema of [z.strictObject({ value: z.string() }), legacy.object({ value: legacy.string() }).strict()]) {
+    // Avoid finding a common type by comparing both versions' fluent builders.
+    const schemas: AnySchema[] = [
+      z.strictObject({ value: z.string() }),
+      legacy.object({ value: legacy.string() }).strict(),
+    ]
+    for (const schema of schemas) {
       expect(toJsonSchemaCompat(schema).type).toBe('object')
       expect(parseWithCompat(schema, { value: 'ok' })).toEqual({ value: 'ok' })
       expect(() => parseWithCompat(schema, { value: 1 })).toThrow()