Snapshot current maintainer-preview application changes and regression fixtures for integration into lab. Excludes local runtime data, evaluation outputs and source backups. Focused Python regression selection: 140 passed; full suite not certified.
_process_is_alive used os.kill(pid, 0). That probe is POSIX-only:
CPython's Windows os.kill calls TerminateProcess(handle, sig) for any
signal other than CTRL_C/CTRL_BREAK, so it terminates the process it is
asked about. This function is only reached when there is no procfs to
read a command line from, which is exactly the macOS and Windows case
the rest of this change exists to handle.
core/platform_compat.py already owns that probe and documents the
hazard; its module docstring asks callers to import from there rather
than spell a POSIX-only call out locally. Delegate to it.
pid_alive answers False where os.kill raises PermissionError — a live
process owned by another user. Both call sites want that reading: the
sweep only unlinks a pid file it wrote itself, and a pid it cannot
confirm is not the daemon it is looking for.
_terminate_owned_daemon() read /proc/<pid>/cmdline and, on FileNotFoundError,
unlinked the pid file on the stated assumption that "the daemon may have
exited". Off Linux that file is always missing, so the branch always fired:
the pid file of a live daemon was deleted and the daemon itself never killed.
_owned_daemon_exists() swallowed the same error and therefore always returned
False, which is precisely the state its own docstring warns about, since a
close against an unrecognised session can bootstrap a fresh daemon and wait on
its browser indefinitely.
Demonstrated on macOS before the change: a pid file holding a live pid is
removed by _terminate_owned_daemon() and _owned_daemon_exists() reports False.
After it, the file survives and the daemon is reported present.
_process_command_line() now returns None for "this host cannot tell" and
_process_is_alive() answers the separate question of whether the pid exists.
Without procfs we decline to kill a process we cannot confirm is ours, and we
only forget a pid file once the pid is genuinely gone. Linux behaviour is
unchanged: the command-line identity check still gates both paths.
_terminate_owned_chrome() walked Path("/proc") unconditionally, so on macOS
and Windows iterdir() raised FileNotFoundError out of private-browser session
shutdown. src/tools/cookbook.py already guards the same kind of scan with
os.path.isdir("/proc").
The sweep only reclaims Chrome trees that agent-browser reparented, so it is
an optimisation rather than a correctness requirement: degrade to a no-op
rather than failing the whole shutdown path.
_PROC_ROOT is a module attribute so both branches are testable on either kind
of host. The procfs-present path had no coverage at all before this.
Alexandre Teixeira