diff --git a/internal/cloud/workbench-command-proxy.test.ts b/internal/cloud/workbench-command-proxy.test.ts
new file mode 100644
index 00000000..298c66e3
--- /dev/null
+++ b/internal/cloud/workbench-command-proxy.test.ts
@@ -0,0 +1,9 @@
+import { expect, test } from "bun:test";
+
+import { workbenchActivityDispatchRequested } from "./workbench-command-proxy.ts";
+
+test("accepts activity dispatch header from Node and Fetch request shapes", () => {
+  expect(workbenchActivityDispatchRequested({ headers: { "x-workbench-activity-dispatch": "1" } })).toBe(true);
+  expect(workbenchActivityDispatchRequested({ headers: new Headers({ "x-workbench-activity-dispatch": "1" }) })).toBe(true);
+  expect(workbenchActivityDispatchRequested({ headers: new Headers({ "x-workbench-activity-dispatch": "0" }) })).toBe(false);
+});
diff --git a/internal/cloud/workbench-command-proxy.ts b/internal/cloud/workbench-command-proxy.ts
index 89931233..f24e1292 100644
--- a/internal/cloud/workbench-command-proxy.ts
+++ b/internal/cloud/workbench-command-proxy.ts
@@ -5,7 +5,11 @@ export function workbenchTemporalProxyEnabled(env: Record<string, string | undef
 }
 
 export function workbenchActivityDispatchRequested(request: any) {
-  return String(request.headers?.["x-workbench-activity-dispatch"] ?? "").trim() === "1";
+  const headers = request?.headers;
+  const value = typeof headers?.get === "function"
+    ? headers.get("x-workbench-activity-dispatch")
+    : headers?.["x-workbench-activity-dispatch"];
+  return String(value ?? "").trim() === "1";
 }
 
 export async function proxyWorkbenchCommandHttp(request: any, response: any, options: any, route: string) {