Client should expose the internal sender or provide a method to send async message to the server about opamp-go HOT 2 CLOSED

Generally, I do not think we should expose Sender directly. If we need to send a message then it should be exposed in the OpAMPClient interface, similar to for example SetEffectiveConfig. Let's keep Sender in internal.

Report failing health of the agent or worse, termination status of the agent.
Report agent restart metrics.

I think these are both expected to be reported via own telemetry, so shouldn't be done via OpAMP. What OpAMP message do you want to send for these 2 cases?

Report agent package or addon download progress.

This should happen in response to the OnAddonsAvailable/OnAgentPackageAvailable callbacks. The AddonSyncer and AgentPackageSyncer are supposed to have the context to report the progress. Are these not sufficient?

from opamp-go.

I think you are right. I was thinking that there might be separate telemetry needs from the supervisor -- reporting the up/down stats of the collector, but the spec as it stands today doesn't talk about this at least not in the context of the supervisor. And as to the agent/addon download status, etc, the syncer should be a good place.

from opamp-go.