pending_changes.agent stamped at every queue site (native -> 'boocode', dispatched external -> task.agent, manual RightRail -> NULL) + flows through listPending. New GET /api/sessions/:id/agent-sessions -> [{agent,status,has_session,last_active_at}] per (chat,agent). opencode warm server consumes session.next.step.ended, accumulating input_tokens/output_tokens/cost onto agent_sessions (new idempotent columns) via a pure opencode-usage.ts mapper. Tests: agent-sessions.routes (3) + opencode-usage (6); tsc clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>