This change was originally proposed as the root-cause fix for the
2026-07-14 DeviceNotFoundError incident. That diagnosis was wrong: it was
subsequently confirmed only one Host Agent process was running at the time,
ruling out the duplicate-process precondition this change addresses. The
actual root cause was execution.py's create_task_runner() omitting manager=
when wiring TaskRunner (see 08cef7c). Reframe the Why section: this change
stands on its own as independent duplicate-process hardening, not as a fix
for an incident it turned out not to have caused.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Proposal, design, spec, and tasks for the per-installation exclusive
instance lock. 15/16 tasks complete; only manual real-environment
verification (5.4) remains, with semantics covered by unit tests in
test_app.py and test_instance_lock.py.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
q792602257andClaude Sonnet 5