Context

The SessionMemoryObserverActor was added in #410 as a spike. It works — it watches the conversation stream and distills memories when the session goes idle. But it needs formalization as a first-class framework component, particularly now that #411 introduced the Passivating state with the plumbing for passivation-triggered distillation.

What needs to happen

Passivation-triggered distillation

The observer currently only distills on its own idle timer (90s). When the parent session enters Passivating, it sends DistillMemories to the observer (added in #411). The observer already handles this message, but the interaction protocol needs formal specification:

• Observer receives DistillMemories → triggers immediate distillation regardless of idle state
• Observer sends SessionDistillationCompleted back to parent with proposals
• Parent waits up to 5s grace period, then stops (already implemented in refactor: formalize LlmSessionActor state machine for composable lifecycle states #411)
• If observer is mid-distillation when passivation arrives, it should complete and respond

Protocol formalization

• SessionPhaseChanged(Passivating) notification (already sent by TransitionTo() in refactor: formalize LlmSessionActor state machine for composable lifecycle states #411)
• DistillMemories request → SessionDistillationCompleted response
• Define what happens when the observer receives messages after passivation starts

Own OpenSpec

The observer has its own persistence identity (memory-observer-{sessionId}), its own protocol, and its own lifecycle. It deserves its own OpenSpec spec rather than being a subsection of netclaw-session.

Prerequisite work (done)

• SessionPhase.Passivating state (refactor: formalize LlmSessionActor state machine for composable lifecycle states #411)
• TransitionTo() sends SessionPhaseChanged to observer (refactor: formalize LlmSessionActor state machine for composable lifecycle states #411)
• Passivating behavior sends DistillMemories and waits for SessionDistillationCompleted (refactor: formalize LlmSessionActor state machine for composable lifecycle states #411)
• Observer already handles DistillMemories (feat(memory): session-level memory observer actor (spike) #410)

Refs

• Depends on: refactor: formalize LlmSessionActor state machine for composable lifecycle states #411 (state machine formalization — merged in PR refactor: decompose LlmSessionActor for composability (#411, #414) #417)
• Built on: feat(memory): session-level memory observer actor (spike) #410 (memory observer spike — merged)
• Related: bug: graceful daemon restart on config change — drain active sessions before restart #326 (graceful daemon restart — this is a prerequisite)