fix: start Xvfb before Node so Chrome has a display

Without Xvfb running, Chrome exits immediately with code 1.
The base sitespeedio image normally handles this via its own
entrypoint script; we now replicate that with start.sh.
Also drop --headless (breaks visual metrics) and add --disable-gpu
for stable Chrome rendering inside Docker.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -17,6 +17,8 @@ RUN npm install --omit=dev
 
 COPY . .
 
+RUN chmod +x /app/start.sh
+
 # Create persistent directories
 RUN mkdir -p /data/reports
 
@@ -33,8 +35,6 @@ ENV PORT=3132 \
 
 EXPOSE 3132
 
-# Override the base image's ENTRYPOINT (which is "sitespeed.io") so that
-# Docker doesn't prepend it to our CMD, causing sitespeed.io to treat
-# "node" as a URL to test.
-ENTRYPOINT ["node"]
-CMD ["app.js"]
+# start.sh boots Xvfb (virtual display for Chrome/Firefox) then runs the app.
+# This mirrors what the base image's own entrypoint does.
+ENTRYPOINT ["/app/start.sh"]

runner.js

@@ -22,17 +22,18 @@ export function runTest(job, onLine) {
       '--sustainable.enable',
       '--axe.enable',
       '--coach',
-      '--headless',
     ];
 
     if (job.mobile) {
       args.push('--mobile');
     }
 
-    // In Docker we need --xvfb false and --browsertime.chrome.args=no-sandbox
+    // Chrome needs these flags when running inside Docker
     if (process.env.IN_DOCKER) {
       args.push('--browsertime.chrome.args', 'no-sandbox');
       args.push('--browsertime.chrome.args', 'disable-dev-shm-usage');
+      // Disable GPU compositing — not needed in Xvfb and can cause crashes
+      args.push('--browsertime.chrome.args', 'disable-gpu');
     }
 
     onLine(`[runner] Starting: node ${args.slice(0, 3).join(' ')} ...`);

start.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -e
+
+# Start virtual framebuffer so Chrome/Firefox have a display to render into.
+# This is what the base sitespeedio/sitespeed.io image's entrypoint does.
+Xvfb :99 -ac -screen 0 1920x1080x24 +extension RANDR &
+export DISPLAY=:99
+
+# Give Xvfb a moment to initialise
+sleep 1
+
+exec node /app/app.js