diff --git a/vtex/__tests__/client-segment-cookie.test.ts b/vtex/__tests__/client-segment-cookie.test.ts
index f165d20..f0de476 100644
--- a/vtex/__tests__/client-segment-cookie.test.ts
+++ b/vtex/__tests__/client-segment-cookie.test.ts
@@ -18,12 +18,45 @@ function mockResponse(body: unknown = {}, status = 200): Response {
 	} as Response;
 }
 
-/** Run `fn` inside a fake request context with the given cookie header. */
+/**
+ * Run `fn` inside a fake request context with the given cookie header.
+ *
+ * Two problems prevented a naive `RequestContext.run(new Request(...))`
+ * approach from working:
+ *
+ *  1. Under the Fetch spec a Request's headers are in the "request"
+ *     guard mode, which silently drops forbidden request headers —
+ *     including `cookie` — at construction time. Node 22 / undici
+ *     enforces this strictly, so the cookie never reaches
+ *     `request.headers.get("cookie")`.
+ *  2. `@decocms/start`'s `RequestContext` is backed by a
+ *     `RequestStore` that defaults to a NOOP implementation. The
+ *     ALS-backed store is installed by site code at worker boot, not
+ *     in unit tests. So `RequestContext.run(req, fn)` calls
+ *     `fn()` without any propagation, and `RequestContext.current`
+ *     inside `fn` still returns `null` — production code under test
+ *     never sees the test's cookie.
+ *
+ * Fix: build a fresh `Headers` object (which uses the "none" guard,
+ * so `set("cookie", ...)` works), wrap it in a minimal `Ctx`-shaped
+ * object, and override the `RequestContext.current` getter via
+ * `vi.spyOn`. The spy is restored after `fn` resolves to keep tests
+ * isolated. Nothing here depends on undici or ALS internals.
+ */
 function withRequest<T>(cookieHeader: string | null, fn: () => Promise<T>): Promise<T> {
-	const request = new Request("http://localhost/", {
-		headers: cookieHeader ? { cookie: cookieHeader } : {},
-	});
-	return RequestContext.run(request, fn);
+	const headers = new Headers();
+	if (cookieHeader) headers.set("cookie", cookieHeader);
+	const fakeCtx = {
+		request: { headers } as unknown as Request,
+		signal: new AbortController().signal,
+		responseHeaders: new Headers(),
+		bag: new Map(),
+		startedAt: Date.now(),
+	};
+	const spy = vi
+		.spyOn(RequestContext, "current", "get")
+		.mockReturnValue(fakeCtx as unknown as ReturnType<typeof Reflect.get>);
+	return fn().finally(() => spy.mockRestore());
 }
 
 describe("vtexFetchResponse — vtex_segment cookie forwarding", () => {