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New error code H34: All up dynos are quarantined

Change effective on 27 October 2025

We added a new error code for Common Runtime apps: H34: All up dynos are quarantined. When a connection to a dyno fails, the router quarantines that dyno for 5 seconds and retries on another available dyno. This H34 error indicates that the router can’t find an unquarantined dyno after a 75-second timeout while attempting to establish a connection. Previously, we returned these types of errors as the more generic H99 - Platform Error.

See the Error Codes article for more info about the new error code.

PHP updates - October 2025