D-1: Track upstream OpenCode child-to-parent question propagation

[Cho-Geer]

Parent Epic

#138 — Sub-Agent Question Propagation Fix

Phase 4 — Option D: Upstream Enhancement (Tracked)

Task

Track upstream OpenCode support for child-session question propagation.

Required Upstream Changes (from §6 Option D)

1. Child session emits a question event with session metadata.
2. Parent session/TUI renders the prompt in the user-visible context.
3. User response is routed back to the child tool invocation.
4. Permission and audit logs preserve the child agent/session identity.

Acceptance

• When upstream propagation becomes available, the local guard (Phase 1) can be replaced after E2E harness verification (Phase 3).
• The HANDOVER protocol will remain as a fallback.

Current Status

No known upstream support as of 2026-06-21. Official OpenCode docs describe child-session navigation and question permission, but do not document child-to-parent question propagation.

Reference

docs/review/framework-refactor/sub-agent-question-propagation-issue.md §6 Option D