fix(code-runtime): capture worker JSON intrinsics

packages/code-runtime/code-runtime-worker/tests/output-json.spec.ts

@@ -68,4 +68,42 @@ describe('jsonValueBytesUpTo', () => {
     expect(jsonValueBytesUpTo(value, 10_004)).toBe(10_004)
     expect(jsonValueBytesUpTo(value, 10_003)).toBeUndefined()
   })
+
+  it('uses module-captured intrinsics after model-visible globals are mutated', () => {
+    const value: CodeJsonValue = { payload: ['€', 42] }
+    const bytes = Buffer.byteLength(JSON.stringify(value), 'utf8')
+    const arrayIsArrayDescriptor = Object.getOwnPropertyDescriptor(Array, 'isArray')!
+    const arrayPopDescriptor = Object.getOwnPropertyDescriptor(Array.prototype, 'pop')!
+    const arrayPushDescriptor = Object.getOwnPropertyDescriptor(Array.prototype, 'push')!
+    const byteLengthDescriptor = Object.getOwnPropertyDescriptor(Buffer, 'byteLength')!
+    const objectKeysDescriptor = Object.getOwnPropertyDescriptor(Object, 'keys')!
+    const charCodeAtDescriptor = Object.getOwnPropertyDescriptor(String.prototype, 'charCodeAt')!
+    const codePointAtDescriptor = Object.getOwnPropertyDescriptor(String.prototype, 'codePointAt')!
+    const sliceDescriptor = Object.getOwnPropertyDescriptor(String.prototype, 'slice')!
+    let measured: number | undefined
+    let prefix = ''
+    try {
+      Array.isArray = () => false
+      Array.prototype.pop = () => { throw new Error('mutated pop') }
+      Array.prototype.push = () => { throw new Error('mutated push') }
+      Buffer.byteLength = () => 0
+      Object.keys = () => []
+      String.prototype.charCodeAt = () => { throw new Error('mutated charCodeAt') }
+      String.prototype.codePointAt = () => { throw new Error('mutated codePointAt') }
+      String.prototype.slice = () => { throw new Error('mutated slice') }
+      measured = jsonValueBytesUpTo(value, bytes)
+      prefix = truncateJsonStringBytes('€x', 5)
+    } finally {
+      Object.defineProperty(Array, 'isArray', arrayIsArrayDescriptor)
+      Object.defineProperty(Array.prototype, 'pop', arrayPopDescriptor)
+      Object.defineProperty(Array.prototype, 'push', arrayPushDescriptor)
+      Object.defineProperty(Buffer, 'byteLength', byteLengthDescriptor)
+      Object.defineProperty(Object, 'keys', objectKeysDescriptor)
+      Object.defineProperty(String.prototype, 'charCodeAt', charCodeAtDescriptor)
+      Object.defineProperty(String.prototype, 'codePointAt', codePointAtDescriptor)
+      Object.defineProperty(String.prototype, 'slice', sliceDescriptor)
+    }
+    expect(measured).toBe(bytes)
+    expect(prefix).toBe('€')
+  })
 })

packages/code-runtime/code-runtime-worker/tests/runtime.spec.ts

@@ -657,6 +657,41 @@ describe('WorkerCodeRuntime — hostile programs (real workers)', () => {
     })
   })
 
+  it('preserves binding and completion JSON after model code mutates boundary globals', async () => {
+    const { runtime } = await setup()
+    const result = await runtime.run({
+      program: `
+        const arrayPrototype = Array.prototype;
+        const objectPrototype = Object.prototype;
+        const setPrototype = Set.prototype;
+        const stringPrototype = String.prototype;
+        Array.isArray = () => false;
+        arrayPrototype.at = arrayPrototype.includes = arrayPrototype.pop = arrayPrototype.push = () => { throw new Error('mutated array method') };
+        Object.defineProperty = Object.getOwnPropertyDescriptor = Object.getPrototypeOf = Object.keys = () => { throw new Error('mutated object method') };
+        Object.hasOwn = () => false;
+        Object.is = () => true;
+        objectPrototype.propertyIsEnumerable = () => false;
+        Number.isFinite = Number.isSafeInteger = () => false;
+        Reflect.apply = Reflect.ownKeys = () => { throw new Error('mutated reflect method') };
+        setPrototype.add = setPrototype.delete = setPrototype.has = () => { throw new Error('mutated set method') };
+        stringPrototype.charCodeAt = stringPrototype.codePointAt = stringPrototype.slice = () => { throw new Error('mutated string method') };
+        Buffer.byteLength = () => 0;
+        Function.prototype.toString = () => 'mutated';
+        globalThis.Array = globalThis.Buffer = globalThis.Function = globalThis.Number = globalThis.Object = globalThis.Reflect = globalThis.Set = globalThis.String = undefined;
+        const echoed = await tools.echo({ request: ['€', 1] });
+        return { echoed, completion: { ok: true, amount: 42 } };
+      `,
+      bindings: tools({ echo: async args => args }),
+    })
+    expect(result).toEqual({
+      logs: [],
+      value: {
+        echoed: { request: ['€', 1] },
+        completion: { ok: true, amount: 42 },
+      },
+    })
+  })
+
   it('rejects forged lossy binding arguments again at the host boundary', async () => {
     const { runtime } = await setup()
     let calls = 0