ros1_bridge in ROS 2 Humble Requires Explicit Topic Types, Replacing Implicit Auto-Discovery

Goal: Determine whether explicit topic type declarations are mandatory for all ros1_bridge topics in ROS 2 Humble, and whether QoS profiles must be aligned across the RMW boundary to prevent silent message loss.

Constraint: ROS 2 Humble's 2022.2 release removed implicit type auto-discovery from ros1_bridge shims and stabilized default QoS profiles. QoS mismatches between RMW implementations such as Fast RTPS and OpenSplice can cause silent message loss during cross-platform migration.

Uncertainty: It is unresolved whether explicit topic type support alone satisfies the compatibility boundary, or whether QoS policy reconciliation is also required for each bridged topic when default profiles differ between RMW vendors.

Is explicit topic type registration required for every topic bridged by ros1_bridge in ROS 2 Humble?

Must QoS policies be manually reconciled between ROS 1 and ROS 2 endpoints when crossing the RMW boundary?

Does default QoS alignment prevent silent message loss, or is explicit per-topic QoS configuration still necessary?