diff --git a/src/client/environment.test.ts b/src/client/environment.test.ts
index d3c9ae17..c0579d14 100644
--- a/src/client/environment.test.ts
+++ b/src/client/environment.test.ts
@@ -1,10 +1,23 @@
+import { AsyncLocalStorage } from "node:async_hooks";
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
 import {
   patchMath,
   createDeterministicDate,
   createConsole,
+  setupEnvironment,
+  runWithWorkflowEnvironment,
 } from "./environment.js";
 
+// The workflow environment expects AsyncLocalStorage on globalThis (as provided by
+// convex-backend's async_hooks runtime). Polyfill it here so tests run in Node.js.
+if (
+  (globalThis as { AsyncLocalStorage?: typeof AsyncLocalStorage })
+    .AsyncLocalStorage === undefined
+) {
+  (globalThis as { AsyncLocalStorage?: typeof AsyncLocalStorage }).AsyncLocalStorage =
+    AsyncLocalStorage;
+}
+
 describe("environment patching units", () => {
   describe("patchMath", () => {
     it("should preserve all Math methods except random", () => {
@@ -503,4 +516,68 @@ describe("environment patching units", () => {
       expect(mockConsole.info).not.toHaveBeenCalled();
     });
   });
+
+  describe("workflow-scoped patching", () => {
+    it("keeps patched globals out of non-workflow execution", async () => {
+      const originalSetTimeout = globalThis.setTimeout;
+      const originalSetInterval = globalThis.setInterval;
+      const originalFetch = globalThis.fetch;
+      const originalDateNow = Date.now;
+
+      setupEnvironment();
+
+      await runWithWorkflowEnvironment(
+        () => ({ now: 12345, latest: true }),
+        "workflow-1",
+        async () => {
+          expect(Date.now()).toBe(12345);
+          expect(() => setTimeout(() => {}, 0)).toThrow(
+            /setTimeout isn't supported within workflows yet/,
+          );
+          expect(() => setInterval(() => {}, 0)).toThrow(
+            /setInterval isn't supported within workflows yet/,
+          );
+          expect(() => fetch("https://example.com")).toThrow(
+            /Fetch isn't currently supported within workflows/,
+          );
+
+          await Promise.resolve();
+          expect(() => setTimeout(() => {}, 0)).toThrow(
+            /setTimeout isn't supported within workflows yet/,
+          );
+        },
+      );
+
+      expect(globalThis.setTimeout).toBe(originalSetTimeout);
+      expect(globalThis.setInterval).toBe(originalSetInterval);
+      expect(globalThis.fetch).toBe(originalFetch);
+      expect(Date.now).toBe(originalDateNow);
+
+      const timeout = setTimeout(() => {}, 0);
+      clearTimeout(timeout);
+    });
+
+    it("keeps restricted globals available outside workflow execution", () => {
+      setupEnvironment();
+
+      const hasProcessOutside = "process" in globalThis;
+      const hasCryptoOutside = "crypto" in globalThis;
+
+      runWithWorkflowEnvironment(
+        () => ({ now: 5, latest: true }),
+        "workflow-2",
+        () => {
+          expect((globalThis as { process?: unknown }).process).toBeUndefined();
+          expect((globalThis as { crypto?: unknown }).crypto).toBeUndefined();
+        },
+      );
+
+      if (hasProcessOutside) {
+        expect((globalThis as { process?: unknown }).process).toBeDefined();
+      }
+      if (hasCryptoOutside) {
+        expect((globalThis as { crypto?: unknown }).crypto).toBeDefined();
+      }
+    });
+  });
 });
diff --git a/src/client/environment.ts b/src/client/environment.ts
index cd1bcc2a..c28b34c1 100644
--- a/src/client/environment.ts
+++ b/src/client/environment.ts
@@ -1,5 +1,48 @@
 type GenerationState = { now: number; latest: boolean };
 
+type WorkflowEnvironment = {
+  math: typeof Math;
+  date: typeof Date;
+  console: Console;
+  fetch: typeof globalThis.fetch;
+  setTimeout: typeof globalThis.setTimeout;
+  setInterval: typeof globalThis.setInterval;
+};
+
+type AsyncLocalStorageLike<T> = {
+  run<R>(store: T, callback: () => R): R;
+  getStore(): T | undefined;
+};
+
+type AsyncLocalStorageConstructor = new <T>() => AsyncLocalStorageLike<T>;
+
+let workflowEnvironmentStorage: AsyncLocalStorageLike<WorkflowEnvironment> | undefined;
+let globalsPatched = false;
+
+// Capture original globals before any patching occurs so createWorkflowEnvironment
+// always wraps the true originals, even if called from within an active workflow context.
+const originalGlobals = {
+  Math: globalThis.Math,
+  Date: globalThis.Date,
+  console: globalThis.console,
+};
+
+function ensureWorkflowEnvironmentStorage() {
+  if (workflowEnvironmentStorage !== undefined) {
+    return;
+  }
+
+  const global = globalThis as {
+    AsyncLocalStorage?: AsyncLocalStorageConstructor;
+  };
+  if (global.AsyncLocalStorage === undefined) {
+    throw new Error(
+      "AsyncLocalStorage is not available in this runtime. Update convex-backend to a build with async_hooks support.",
+    );
+  }
+  workflowEnvironmentStorage = new global.AsyncLocalStorage<WorkflowEnvironment>();
+}
+
 // Simple hash function to convert a string to a 32-bit seed
 function hashString(str: string): number {
   let hash = 0;
@@ -82,41 +125,106 @@ export function createDeterministicDate(
   return DeterministicDate as typeof Date;
 }
 
-export function setupEnvironment(
+const unsupportedFetch: typeof globalThis.fetch = (
+  _input: RequestInfo | URL,
+  _init?: RequestInit,
+) => {
+  throw new Error(
+    `Fetch isn't currently supported within workflows. Perform the fetch within an action and call it with step.runAction().`,
+  );
+};
+
+const unsupportedSetTimeout = ((..._args: any[]) => {
+  throw new Error("setTimeout isn't supported within workflows yet");
+}) as unknown as typeof globalThis.setTimeout;
+
+const unsupportedSetInterval = ((..._args: any[]) => {
+  throw new Error("setInterval isn't supported within workflows yet");
+}) as unknown as typeof globalThis.setInterval;
+
+function defineWorkflowAwareGlobal<T>(
+  globalObject: Record<string, unknown>,
+  key: string,
+  getWorkflowValue: (environment: WorkflowEnvironment) => T,
+): void {
+  const descriptor = Object.getOwnPropertyDescriptor(globalObject, key);
+  if (descriptor?.configurable === false) {
+    return;
+  }
+
+  let outsideValue = globalObject[key] as T;
+  Object.defineProperty(globalObject, key, {
+    configurable: true,
+    enumerable: descriptor?.enumerable ?? true,
+    get() {
+      const environment = workflowEnvironmentStorage?.getStore();
+      if (environment !== undefined) {
+        return getWorkflowValue(environment);
+      }
+      return outsideValue;
+    },
+    set(value: T) {
+      outsideValue = value;
+    },
+  });
+}
+
+function createWorkflowEnvironment(
   getGenerationState: () => GenerationState,
   workflowId: string,
-): void {
-  const global = globalThis as Record<string, unknown>;
+): WorkflowEnvironment {
+  return {
+    math: patchMath(originalGlobals.Math, workflowId),
+    date: createDeterministicDate(originalGlobals.Date, getGenerationState),
+    console: createConsole(originalGlobals.console, getGenerationState),
+    fetch: unsupportedFetch,
+    setTimeout: unsupportedSetTimeout,
+    setInterval: unsupportedSetInterval,
+  };
+}
 
-  // Patch Math with seeded random based on workflowId
-  global.Math = patchMath(global.Math as typeof Math, workflowId);
+export function setupEnvironment(): void {
+  if (globalsPatched) {
+    return;
+  }
 
-  // Patch Date
-  const originalDate = global.Date as typeof Date;
-  global.Date = createDeterministicDate(originalDate, getGenerationState);
+  ensureWorkflowEnvironmentStorage();
 
-  // Patch console
-  global.console = createConsole(global.console as Console, getGenerationState);
+  const global = globalThis as Record<string, unknown>;
+  defineWorkflowAwareGlobal(global, "Math", (environment) => environment.math);
+  defineWorkflowAwareGlobal(global, "Date", (environment) => environment.date);
+  defineWorkflowAwareGlobal(global, "console", (environment) => environment.console);
+  defineWorkflowAwareGlobal(global, "fetch", (environment) => environment.fetch);
+  defineWorkflowAwareGlobal(global, "setTimeout", (environment) => environment.setTimeout);
+  defineWorkflowAwareGlobal(global, "setInterval", (environment) => environment.setInterval);
 
-  // Patch fetch
-  global.fetch = (_input: RequestInfo | URL, _init?: RequestInit) => {
-    throw new Error(
-      `Fetch isn't currently supported within workflows. Perform the fetch within an action and call it with step.runAction().`,
-    );
-  };
+  const restrictedGlobals = [
+    "process",
+    "Crypto",
+    "crypto",
+    "CryptoKey",
+    "SubtleCrypto",
+  ];
+  for (const key of restrictedGlobals) {
+    defineWorkflowAwareGlobal(global, key, () => undefined);
+  }
 
-  // Remove non-deterministic globals
-  delete global.process;
-  delete global.Crypto;
-  delete global.crypto;
-  delete global.CryptoKey;
-  delete global.SubtleCrypto;
-  global.setTimeout = () => {
-    throw new Error("setTimeout isn't supported within workflows yet");
-  };
-  global.setInterval = () => {
-    throw new Error("setInterval isn't supported within workflows yet");
-  };
+  globalsPatched = true;
+}
+
+export function runWithWorkflowEnvironment<T>(
+  getGenerationState: () => GenerationState,
+  workflowId: string,
+  run: () => T,
+): T {
+  setupEnvironment();
+  if (workflowEnvironmentStorage === undefined) {
+    throw new Error("AsyncLocalStorage is not initialized");
+  }
+  return workflowEnvironmentStorage.run(
+    createWorkflowEnvironment(getGenerationState, workflowId),
+    run,
+  );
 }
 
 function noop() {}
diff --git a/src/client/workflowMutation.ts b/src/client/workflowMutation.ts
index 5afb2a6b..d85c2fb0 100644
--- a/src/client/workflowMutation.ts
+++ b/src/client/workflowMutation.ts
@@ -15,7 +15,7 @@ import {
 } from "convex/values";
 import { createLogger } from "../component/logging.js";
 import { type JournalEntry } from "../component/schema.js";
-import { setupEnvironment } from "./environment.js";
+import { runWithWorkflowEnvironment } from "./environment.js";
 import type { WorkflowDefinition } from "./index.js";
 import { StepExecutor, type StepRequest, type WorkerResult } from "./step.js";
 import { createWorkflowCtx } from "./workflowContext.js";
@@ -128,8 +128,6 @@ export function workflowMutation<ArgsValidator extends PropertyValidators>(
         Date.now(),
         workpoolOptions,
       );
-      setupEnvironment(executor.getGenerationState.bind(executor), workflowId);
-
       const handlerWorker = async (): Promise<WorkerResult> => {
         let runResult: RunResult;
         try {
@@ -167,7 +165,11 @@ export function workflowMutation<ArgsValidator extends PropertyValidators>(
       const executorWorker = async (): Promise<WorkerResult> => {
         return await executor.run();
       };
-      const result = await Promise.race([handlerWorker(), executorWorker()]);
+      const result = await runWithWorkflowEnvironment(
+        executor.getGenerationState.bind(executor),
+        workflowId,
+        () => Promise.race([handlerWorker(), executorWorker()]),
+      );
       switch (result.type) {
         case "handlerDone": {
           await ctx.runMutation(component.workflow.complete, {