test: cover constrained browser concurrency

CHANGELOG.md

@@ -25,6 +25,8 @@ Follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) · versioned wi
   headers so browser and intermediary caches cannot retain the client-visible access-key handoff.
 - **Navigation Race Protection.** Rehearser phase requests now survive late feature-module initialization, and
   overlapping character-library refreshes cannot overwrite a newer table/card view.
+- **Constrained Browser Smoke Coverage.** Added a 4 GB `navigator.deviceMemory` regression that verifies shared
+  batch work is capped at two concurrent operations.
 - **API Boundary Hardening.** External API authentication is enabled by default, request and mutation limits are
   enforced, and settings responses redact provider credentials for non-browser callers.
 - **Server-side Provider Credentials.** Provider keys are now masked even for same-origin Settings responses, are

TODO.md

@@ -60,7 +60,8 @@ the first block before investing in architecture or polish.
 - [x] **M — Add explicit cache invalidation and eviction.** Fish.audio search responses, persisted synthesized
   audio, image-generation job mappings, and browser object URLs have bounded cleanup.
 - [ ] **M — Add constrained-device validation.** Test with Chrome CPU/memory throttling,
-  a 4 GB VM/container, and measure browser, Docker and temporary-disk usage.
+  a 4 GB VM/container, and measure browser, Docker and temporary-disk usage. Automated browser emulation now proves
+  the 4 GB shared-pool cap; physical VM/container and resource measurements remain.
 - [ ] **L — Add background jobs and bounded queues.** Give voice design, transcription,
   casting and image generation IDs, progress, cancellation, timeout, retry and
   idempotency support.

static/js/utils.js

@@ -367,6 +367,7 @@ async function runPool(items, worker, concurrency = 4, onProgress) {
   }
   await Promise.all(Array.from({ length: Math.min(effectiveConcurrency, arr.length) }, run));
 }
+window.runPool = runPool;
 async function copyText(text) {
   try {
     await navigator.clipboard.writeText(text);

tests/constrained.spec.js

@@ -0,0 +1,22 @@
+// @ts-check
+// Lightweight constrained-device regression: the browser's 4 GB profile must
+// reduce shared batch concurrency before multiple audio/image operations run.
+const { test, expect } = require('@playwright/test');
+
+test('4 GB browser profile caps shared batch concurrency at two', async ({ page }) => {
+  await page.goto('/', { waitUntil: 'domcontentloaded' });
+  await page.waitForFunction(() => typeof window.runPool === 'function', null, { timeout: 15_000 });
+  const maxActive = await page.evaluate(async () => {
+    Object.defineProperty(navigator, 'deviceMemory', { configurable: true, value: 4 });
+    let active = 0;
+    let max = 0;
+    await window.runPool(Array.from({ length: 8 }, (_, i) => i), async () => {
+      active += 1;
+      max = Math.max(max, active);
+      await new Promise(resolve => setTimeout(resolve, 15));
+      active -= 1;
+    }, 4);
+    return max;
+  });
+  expect(maxActive).toBeLessThanOrEqual(2);
+});