• websocket.php crashes at startup. The EspoCRM log shows:
Error: Class "ZMQContext" not found at /app/code/10.0.8/vendor/react/zmq/src/Context.php:37
• The browser retries /wss every few seconds and gets a 503. The Apache log shows:
AH00957: WS: attempt to connect to 127.0.0.1:8080 (127.0.0.1:8080) failed
• As a result, real-time notifications and VoIP call popups stop working.

Cause:
The package switched from cloudron/base:5.0.0 to cloudron/php-base:8.4 in commit 0d5ac2af (7 August).
In the 3.0.8 image, the generic php-zmq package from the sury PPA depends on the build for the newest PHP, so it installs php8.5-zmq (plus about 13 other php8.5-* packages). PHP 8.4's extension_dir is /usr/lib/php/20240924, which has no zmq.so, so the extension is never loaded. Loading the 8.5 build into PHP 8.4 manually also fails, because of the ABI mismatch.
We also checked the base the package now uses on master, cloudron/php-base:8.4-20260920. It has no zmq package at all, so a 3.0.9 build from the current master would still have no WebSocket.

Suggested fix:
Install the version-specific package in the EspoCRM Dockerfile, or in php-base:

apt-get install -y php8.4-zmq

php8.4-zmq (1.1.3-32+ubuntu24.04.1+deb.sury.org+1) is available in the same repository. Pinning to the PHP version, rather than using the php-zmq metapackage, also keeps the next PHP release on sury from breaking it again.
To reproduce:

docker run --rm --platform linux/amd64 --entrypoint /bin/bash cloudron/com.espocrm.cloudronapp:202609090034540000 -c 'php -v | head -1; php -m | grep -i zmq || echo "zmq not loaded"; dpkg -l | grep -i zmq; find / -name zmq.so -not -path "/proc/*" 2>/dev/null'

Workaround for others: stay on 3.0.3 (EspoCRM 10.0.3), or turn off useWebSocket in Administration > Settings so the client falls back to polling.
Thanks!