diff --git a/src/signals/ai.test.ts b/src/signals/ai.test.ts
new file mode 100644
index 0000000..36d1d06
--- /dev/null
+++ b/src/signals/ai.test.ts
@@ -0,0 +1,124 @@
+import { afterEach, describe, expect, test, vi } from "vitest";
+import { ai } from "./ai";
+import { ERROR, NA } from "./utils";
+
+const TIMEOUT_MS = 2_500;
+
+function setBrowserGlobals(availability?: (...args: any[]) => Promise<any>, opera = false) {
+    const browserWindow: Record<string, unknown> = {};
+    if (availability) {
+        browserWindow.Summarizer = { availability };
+    }
+    if (opera) {
+        browserWindow.opr = {};
+    }
+    vi.stubGlobal("window", browserWindow);
+    vi.stubGlobal("navigator", { language: "en-US" });
+}
+
+afterEach(() => {
+    vi.useRealTimers();
+    vi.unstubAllGlobals();
+});
+
+describe("ai", () => {
+    test("returns NA when Summarizer is absent", async () => {
+        setBrowserGlobals();
+
+        await expect(ai()).resolves.toEqual({
+            summarizerAvailability: NA,
+            summarizerLanguageAvailability: NA,
+        });
+    });
+
+    test("preserves normally resolved values", async () => {
+        const availability = vi.fn()
+            .mockResolvedValueOnce("readily")
+            .mockResolvedValueOnce("after-download");
+        setBrowserGlobals(availability);
+
+        await expect(ai()).resolves.toEqual({
+            summarizerAvailability: "readily",
+            summarizerLanguageAvailability: "after-download",
+        });
+        expect(availability).toHaveBeenNthCalledWith(1);
+        expect(availability).toHaveBeenNthCalledWith(2, {
+            expectedInputLanguages: ["en-US"],
+        });
+    });
+
+    test("preserves normal rejection handling", async () => {
+        const availability = vi.fn()
+            .mockRejectedValueOnce(new Error("unavailable"))
+            .mockResolvedValueOnce("readily");
+        setBrowserGlobals(availability);
+
+        await expect(ai()).resolves.toEqual({
+            summarizerAvailability: ERROR,
+            summarizerLanguageAvailability: ERROR,
+        });
+    });
+
+    test("times out when the first availability call never settles", async () => {
+        vi.useFakeTimers();
+        const availability = vi.fn()
+            .mockReturnValueOnce(new Promise(() => {}))
+            .mockResolvedValueOnce("readily");
+        setBrowserGlobals(availability);
+
+        const result = ai();
+        await vi.advanceTimersByTimeAsync(TIMEOUT_MS);
+
+        await expect(result).resolves.toEqual({
+            summarizerAvailability: ERROR,
+            summarizerLanguageAvailability: "readily",
+        });
+    });
+
+    test("times out when the language availability call never settles", async () => {
+        vi.useFakeTimers();
+        const availability = vi.fn()
+            .mockResolvedValueOnce("readily")
+            .mockReturnValueOnce(new Promise(() => {}));
+        setBrowserGlobals(availability);
+
+        const result = ai();
+        await vi.advanceTimersByTimeAsync(TIMEOUT_MS);
+
+        await expect(result).resolves.toEqual({
+            summarizerAvailability: "readily",
+            summarizerLanguageAvailability: ERROR,
+        });
+    });
+
+    test("always completes within the timeout when both calls remain pending", async () => {
+        vi.useFakeTimers();
+        const availability = vi.fn(() => new Promise(() => {}));
+        setBrowserGlobals(availability);
+        let settled = false;
+
+        const result = ai().finally(() => {
+            settled = true;
+        });
+        await vi.advanceTimersByTimeAsync(TIMEOUT_MS - 1);
+        expect(settled).toBe(false);
+        await vi.advanceTimersByTimeAsync(1);
+
+        await expect(result).resolves.toEqual({
+            summarizerAvailability: ERROR,
+            summarizerLanguageAvailability: ERROR,
+        });
+        expect(settled).toBe(true);
+    });
+
+    test("keeps the Opera exclusion", async () => {
+        const availability = vi.fn().mockResolvedValue("readily");
+        setBrowserGlobals(availability, true);
+
+        await expect(ai()).resolves.toEqual({
+            summarizerAvailability: NA,
+            summarizerLanguageAvailability: NA,
+        });
+        expect(availability).not.toHaveBeenCalled();
+    });
+});
diff --git a/src/signals/ai.ts b/src/signals/ai.ts
index 9f45e23..73cbe42 100644
--- a/src/signals/ai.ts
+++ b/src/signals/ai.ts
@@ -7,6 +7,25 @@ function isOpera(): boolean {
     return typeof (window as any).opr !== 'undefined';
 }
 
+const AI_AVAILABILITY_TIMEOUT_MS = 2_500;
+
+function boundedAwait<T>(promise: Promise<T>): Promise<T | typeof ERROR> {
+    return new Promise((resolve, reject) => {
+        const timeout = setTimeout(() => resolve(ERROR), AI_AVAILABILITY_TIMEOUT_MS);
+
+        promise.then(
+            (value) => {
+                clearTimeout(timeout);
+                resolve(value);
+            },
+            (error) => {
+                clearTimeout(timeout);
+                reject(error);
+            },
+        );
+    });
+}
+
 export async function ai() {
     const aiResults = {
         summarizerAvailability: INIT,
@@ -16,10 +35,15 @@ export async function ai() {
     // Opera exposes Summarizer but availability() never settles, hanging the entire collection.
     if ('Summarizer' in window && !isOpera()) {
         try {
-            aiResults.summarizerAvailability = await (window as any).Summarizer.availability();
-            aiResults.summarizerLanguageAvailability = await (window as any).Summarizer.availability({
-                expectedInputLanguages: [navigator.language],
-            });
+            [
+                aiResults.summarizerAvailability,
+                aiResults.summarizerLanguageAvailability,
+            ] = await Promise.all([
+                boundedAwait<string>((window as any).Summarizer.availability()),
+                boundedAwait<string>((window as any).Summarizer.availability({
+                    expectedInputLanguages: [navigator.language],
+                })),
+            ]);
         } catch (error) {
             setObjectValues(aiResults, ERROR);
         }