Direct child sessions are hidden in parent session UI

[ChamHerry]

Description

Child sessions created directly with session.create(parentID) are not shown in the parent session UI. The session exists and can stream events, but the TUI only discovers subagents from native task tool metadata, so plugin-created child sessions look invisible from the parent.

Plugins

Plugin-created child sessions using the session API.

OpenCode version

Current dev branch.

Steps to reproduce

1. Create a parent session.
2. Create a child session with parentID via the session API, without a native task tool part.
3. Observe the parent session UI.

Expected: the child appears as a subagent/child session entry.
Actual: no subagent entry is shown.

Screenshot and/or share link

Not available.

Operating System

macOS

Terminal

Terminal TUI

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [BUG] Sessions with parent_id are invisible in session listings despite existing in database #27620: Sessions with parent_id are invisible in session listings despite existing in database — covers the same root cause (child sessions with a parent_id being hidden from the UI/listings)
• Task child session can exist without metadata.sessionId after interruption, leaving web UI unable to show subagent activity #22348: Task child session can exist without metadata.sessionId after interruption, leaving web UI unable to show subagent activity — related issue where child sessions created without native task tool metadata are not surfaced in the UI

If your issue is specifically about the TUI not showing plugin-created child sessions as subagent entries (distinct from the session list / CLI filtering in #27620), please clarify that distinction so maintainers can track it separately.

[ChamHerry]

This is distinct from #22348 and #27620.

• Task child session can exist without metadata.sessionId after interruption, leaving web UI unable to show subagent activity #22348 is about native task-created child sessions where the parent task part can lose metadata.sessionId after an interrupted/aborted path. There is still a native task part; the linkage metadata is missing.
• [BUG] Sessions with parent_id are invisible in session listings despite existing in database #27620 is about child sessions being filtered out from session listings because list calls use roots: true.
• This issue is specifically about direct session.create(parentID) children created by plugins/session API. These children have no native task tool part at all, so the parent UI never discovers them as subagents even though they exist and can stream events.

The related PR fixes the direct-child discovery/rendering path without changing native task semantics, and keeps task metadata authoritative when it exists.