[ci] Cache Chrome binary across CI runs for Browser Run tests

.github/workflows/test-and-check.yml

@@ -136,6 +136,33 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ github.token }}
 
+      # Browser Run tests in `packages/miniflare/test/plugins/browser/index.spec.ts`
+      # and the `fixtures/browser-run` fixture use `@puppeteer/browsers` to
+      # download Chrome into the global Wrangler cache. Caching that binary
+      # across CI runs avoids ~150 MB of repeat downloads per run and reduces
+      # the surface area for the intermittent partial-extraction race that
+      # surfaces as `The browser folder (...) exists but the executable (...)
+      # is missing` (see #13971, #13980).
+      #
+      # The Browser Run fixture is skipped on Ubuntu (AppArmor), but the
+      # miniflare browser spec runs everywhere, so the cache is needed on all
+      # three OSes for `packages-and-tools` and on Windows + macOS for
+      # `fixtures`.
+      - name: Restore Chrome browser cache (Browser Run)
+        if: steps.changes.outputs.everything_but_markdown == 'true' && (matrix.suite == 'packages-and-tools' || (matrix.suite == 'fixtures' && matrix.os != 'ubuntu-latest'))
+        uses: actions/cache@v4
+        with:
+          # The Chrome version lives in
+          # `packages/miniflare/src/plugins/browser-rendering/browser-version.ts`.
+          # Bumping that constant invalidates this cache automatically via
+          # `hashFiles()` — a cache miss only triggers a fresh download, no
+          # functional impact.
+          key: chrome-${{ runner.os }}-${{ hashFiles('packages/miniflare/src/plugins/browser-rendering/browser-version.ts') }}
+          path: |
+            ~/.cache/.wrangler/chrome
+            ~/Library/Caches/.wrangler/chrome
+            ~/AppData/Local/xdg.cache/.wrangler/chrome
+
       - name: Run tests (tools only)
         # tools _only_ needs to be tested on Linux because they're only intended to run in CI
         if: steps.changes.outputs.everything_but_markdown == 'true' && matrix.suite == 'packages-and-tools' && matrix.os == 'ubuntu-latest'

packages/miniflare/src/index.ts

@@ -63,6 +63,7 @@ import {
 	WORKFLOWS_PLUGIN_NAME,
 } from "./plugins";
 import { RPC_PROXY_SERVICE_NAME } from "./plugins/assets/constants";
+import { BROWSER_VERSION } from "./plugins/browser-rendering/browser-version";
 import {
 	CUSTOM_SERVICE_KNOWN_OUTBOUND,
 	CustomServiceKind,
@@ -1550,13 +1551,7 @@ export class Miniflare {
 				);
 				const { sessionId, browserProcess, startTime, wsEndpoint } =
 					await launchBrowser({
-						// Puppeteer v22.13.1 supported chrome version:
-						// https://pptr.dev/supported-browsers#supported-browser-version-list
-						//
-						// It should match the supported chrome version for the upstream puppeteer
-						// version from which @cloudflare/puppeteer branched off, which is specified in:
-						// https://github.com/cloudflare/puppeteer/?tab=readme-ov-file#workers-version-of-puppeteer-core
-						browserVersion: "126.0.6478.182",
+						browserVersion: BROWSER_VERSION,
 						log: this.#log,
 						tmpPath: this.#tmpPath,
 						headful,

packages/miniflare/src/plugins/browser-rendering/browser-version.ts

@@ -0,0 +1,14 @@
+/**
+ * The Chrome browser version downloaded by Miniflare's Browser Run binding.
+ *
+ * Puppeteer v22.13.1 supported chrome version:
+ * https://pptr.dev/supported-browsers#supported-browser-version-list
+ *
+ * It should match the supported chrome version for the upstream puppeteer
+ * version from which @cloudflare/puppeteer branched off, which is specified in:
+ * https://github.com/cloudflare/puppeteer/?tab=readme-ov-file#workers-version-of-puppeteer-core
+ *
+ * Bumping this value also invalidates the Chrome binary cache in
+ * `.github/workflows/test-and-check.yml` (which uses `hashFiles()` on this file).
+ */
+export const BROWSER_VERSION = "126.0.6478.182";