[wangtsiao]

Summary

Desktop hides child sessions from the main sidebar and previously had no child roster. Cold child lookup also scanned a root-only list, so an existing child could be reported missing after restart or a missed event.

• Add a compact Subagents popover in the existing session header, using current style tokens and icon sizing.
• List saved direct children from canonical session/list with includeChildren: true; distinguish working, approval/input waits, queued work and idle. Idle is explicitly not a completion claim.
• Open the selected child's existing conversation. Resolve cold IDs through session/read, without scanning the root roster or resuming work just to identify the session.
• Read only on open/refresh/check-more. Bound each scan to five 200-row pages, expose remaining pages, reject repeated cursors, prevent overlapping refreshes, and discard stale results after close/navigation.

Relationship to #272

Independent Desktop slice based on main 4228c9dc. No runtime or public Native schema change, and no prerequisite code copied from #272. Its Python collect/progress/end-turn APIs are not exposed as invented UI RPCs. This is not a complete subagent control center.

Validation

• 22 new SDK, hook and mounted real Base UI popover regression cases passed.
• The cold-child regression fails against main's original SDK and passes with this change.
• Full Desktop suite: 948 passed, 1 existing macOS tray skip, 0 failed with a writable test XDG_CONFIG_HOME.
• TypeScript tsc --noEmit: passed.
• Canonical protocol generation: passed; generated Native TS/schema match the tracked TUI artifacts exactly.
• electron-vite build, new-file Biome lint, and git diff --check: passed.
• Independent final static review found no remaining blocker.
• Exact head 9355edbc351651ca6991b1216f06611f91feadf5: 8 successful checks, 10 path-filter skips, no failures. Desktop CI and all six runtime bundles passed. Unaffected Rust/TUI/kernel jobs were skipped, not revalidated.
• Merge-tree compatibility with feat(rlm): complete subagent controls and independent root sessions #272 at 05495fc4: clean. This is a conflict check, not a combined runtime end-to-end test.

Limits

This is an on-demand snapshot, not continuously live polling. Native pagination is not transactional and has no parent filter; each page still enumerates the server roster, so the page cap does not bound total server enumeration. No completion/recovery inference, retained-answer collection, progress-note display, bulk steering/cancellation, model calls or approval-policy changes.

Chromium visual verification could not run because this container denies its required socket operation, including after an allowed escalation. Real popover DOM tests verify close/Escape, focus restoration and navigation; packaged Electron and screenshot checks are not claimed.

Details: docs/desktop-subagent-roster.md. Published to the user fork first. Draft for review; no merge, auto-merge or deployment.