Bug 1 of #55048: when the MCP connection dropped (driver crash / restart),
_lifecycle_coro exited but left _started=True, so the next list_apps/capture
passed _require_started() and then operated on a None session — hanging
forever instead of reconnecting.
- _lifecycle_coro's finally now resets _started=False on ANY exit, so a dead
session is re-enterable (idempotent no-op on the normal stop() path; atomic
bool write, safe from the bridge-loop thread without the lock stop() holds).
- call_tool() re-enters start() when the session isn't active, rebuilding it
before the call. The start_session/end_session handshake (driven by start()/
stop() themselves) is exempted so bootstrap doesn't recurse.
Tests: two cases in test_computer_use_delivery_ladder.py — finally resets
_started, and call_tool restarts a dead session exactly once. Full
computer_use suite green (233).
Refs #55048 (Bug 1). Bug 2 (expose foreground dispatch) is covered by the
delivery_mode work in #67123.
Hermes' computer_use wrapper dropped cua-driver's structured action verdicts,
exposed no delivery_mode, and injected background-only guidance — so the agent
reported unverified no-ops as success and concluded cua-driver 'cannot drive'
Electron/Chromium surfaces (observed live on tldraw offline). Fixes#67052.
Phase A — preserve the result contract:
- ActionResult carries verified/effect/escalation/path/degraded/code/delivery_mode
- CuaDriverBackend._action() reads structuredContent (was data-only); a helper
normalizes it, additive and None-safe on old drivers
- _text_response surfaces the fields additively (ok stays transport-only)
Phase B — bounded, model-reachable foreground:
- delivery_mode (background|foreground) + bring_to_front on the schema, dispatcher,
ABC, and all input methods
- foreground is capability-gated (input.delivery_mode); old drivers get a
structured foreground_unsupported refusal, never a silent background downgrade
- no automatic/hidden foreground retry — the model selects it from the signal
Phase C — guidance + isolation:
- system prompt (prompt_builder) and bundled skills/computer-use/SKILL.md go from
background-ONLY to background-FIRST, teaching the AX→PX→foreground ladder driven
by returned effect/escalation, not predicted from the app being Electron
- foreground approval scoped by (action, delivery_mode): a background approval
never silently authorizes foreground
- approval state keyed per session_id so concurrent gateway runs don't leak unlocks
Tests: tests/tools/test_computer_use_delivery_ladder.py (15) cover confirmed/
unverifiable/suspected_noop/degraded/old-driver verdicts, delivery_mode gating +
foreground_unsupported, and session-scoped foreground approval. Existing 265
computer_use tests still green.
Live E2E (real cua-driver 0.8.3 + tldraw offline on Linux/X11): a background click
returned effect='unverifiable'/path='ax' (no fabricated success), and a foreground
request returned code='foreground_unsupported' — correct on a driver that predates
the input.delivery_mode capability.
