[Task][RFC]: Qualify attached and managed Agent session modes

[huangruiteng]

Outcome / 目标

验收 attached / managed 会话模式。One task tracks this RFC's delivery; keep implementation PRs and milestone evidence here instead of creating a parallel task tree.

Canonical design: RFC. Roadmap: S4/R2, under #4574. Design acceptance is distinct from implementation, live qualification and promotion.

Current boundary

Source audit: main at ce3862e33 (2026-09-28). This is source/PR inspection, not a new test or live-qualification claim.

Attached bindings, broker/fencing and managed process supervision exist. Merged #5144 adds a shared TS managed-host process owner. Registration or a successful segment does not prove cross-host lifecycle qualification.

Work remaining

• Complete the RFC M1–M4 admission and lifecycle matrix using existing host bindings: explicit persisted mode, one executor and typed unsupported-capability results.
• Carry mode and effective launch context through restart, attached-host parity and frontend readback without inferring or silently switching ownership.

Ownership and ongoing work

Reuse #5051/#5039 and PRs #5130/#5188 where relevant. Desktop owns onboarding/UX; this RFC owns session admission. Do not launch a second executor or duplicate the active supervision work.

Contribution route: implementation/integration overlaps active work. Start from the linked current owners/PRs and identify an unowned acceptance gap in a claim comment; do not begin a competing rewrite.

Acceptance

• Real supported-host tests cover bind/start/resume/interrupt/close, crash, stale binding and duplicate completion.
• Off-state preserves native host behavior; conversation text cannot substitute for canonical validation and settlement.
• CLI and packaged frontend report the same mode and availability; qualify each advertised host independently.
• Reconcile the RFC's current delivery checkpoint and this issue with the integrated revision, commands, passed/failed/untested evidence and remaining gates. Close the accepted scope only; no claim that a merged PR alone completes the RFC.

Starting points and delivery boundary

• loopx/control_plane/turn_driver
• loopx/control_plane/turn_driver/host_binding.py
• apps/desktop/loopx-control-plane

Base: latest main. Reuse the existing typed owner and provider boundaries. Include affected CLI/frontend/Lark companions; verify real entrypoints and backend where changed. Preserve existing first-screen review and maintainer merge gates. Public artifacts contain only synthetic/public-safe evidence, no private operational state. This task does not authorize provider promotion, benchmark launches, release/deployment or unrelated protected effects.