ADR 0198: Name every quiet interval on the live activity row

• Status: Accepted
• Date: 2026-09-09
• Related: ADR 0175, ADR 0186, D338, D349, D365

Context

ADR 0175 added a compact runtime status row for three quiet waits: waiting-model, retrying, and waiting-subagents. Users still saw a long-running turn with no explanation when the runtime was compacting context, recovering a silent response, preparing the next provider request, or waiting on subagents whose child work was invisible on that row. The generic Working… fallback also hid starting. A parent wait that only said "Waiting for 2 subagents" for more than a minute looked stuck even when the delegates were reading and searching.

The row must stay a single compact inline status. It must not restore the activity-group current-state capsule removed after ADR 0175, and it must not stream raw child events.

Decision

Extend AgentActivity so every user-visible quiet interval has a named phase, and enrich waiting-subagents with a live snapshot of running targets:

1. starting is rendered instead of generic Working….
2. preparing covers the gap after a tool batch and before the next provider request.
3. compacting covers an in-progress checkpoint and carries the reason (manual / threshold / overflow).
4. recovering covers the silent-turn re-run until the retry request is issued.
5. waiting-subagents keeps subagentCount as the live running count and adds optional agents[] with name, lastPhase (waiting-model | thinking | tool), and lastToolName. The snapshot updates when a child tool starts/ends or thinking begins; token-level child events do not emit a new status.

The renderer still draws one compact localized row with a monotonic phase timer. A one-subagent wait names the agent and its latest action; a multi-agent wait lists each running target. The renderer originally hid the row behind thinking, tool, and answer surfaces. Issue #669 demonstrated that those surfaces can remain unchanged while a turn is still running. The tail row now remains visible until completion or pending user interaction, with a Working or Planning/Goal fallback when no runtime phase is known. No second progress card or percentage is added.

Consequences

• Quiet compaction, recovery, and post-tool gaps are distinguishable from a hung turn.
• A parent wait on delegates shows what those delegates are doing without forwarding their event stream.
• Older waiting-subagents payloads without agents still render the count-only label.
• ADR 0175's coarse-phase rule still holds: child internals stay out of the protocol except as this bounded snapshot.

Alternatives

Restore a current-state capsule on the processing group

Rejected because it duplicated the dedicated runtime row and was already removed as redundant chrome.

Forward raw subagent events onto the parent status row

Rejected because it would expand the renderer protocol and flicker on every thinking token. A coarse lastPhase / lastToolName snapshot is enough to explain the wait.

Keep generic Working… for starting, compaction, and recovery

Rejected because those intervals are the ones users already misread as a stuck turn.

References

• docs/spec/03-runtime/01-ipc-protocol.md
• docs/spec/03-runtime/02-agent-runtime.md
• docs/spec/04-ux/09-interaction-patterns.md
• docs/spec/06-delivery/04-e2e-test-plan.md (E2E-008c, E2E-094)