Plan a Mosquitto or EMQX cutover
Map effective behavior, test an isolated candidate and preserve state and rollback decisions before assigning traffic.
A working broker carries more than a configuration file: client behavior, credentials, topic policy, retained state, pending sessions and destination effects all matter during replacement.
Start with the Mosquitto or EMQX skill. An operator or agent resolves the effective settings and records a private inventory, semantic choices and the next unfinished step. The bundled audit CLI can help classify a source file.
Resolve behavior before choosing a candidate
Check listener/TLS requirements, actual identities, ACL/filter differences, MQTT version/QoS, retained/offline state, rules and sinks. Current-source MQTT 3.1.1 includes QoS 2. MQTT 5 keeps its selected QoS 0/1 profile and bounded application metadata. Enhanced auth and distributed-cluster semantics need an explicit alternative where required.
Verify the state transition
Use isolated targets with one side-effect owner. Replay the intended client contract and confirm destination commitment separately from broker ACKs. Decide how retained state is reseeded, clients reconnect/resubscribe and pending work is reconciled. Rehearse rejection and rollback after target writes.
A passing reference scenario has its recorded scope. The customer’s actual inventory and compatibility decisions still determine cutover readiness. Use the migration guide, scenario contract and cutover skill to retain that distinction.