A recorded pid is a claim, not a handle. The containment grant store, the
background-job store and the Cookbook task list all outlive the process that
wrote them — deliberately, so a restart keeps a job and its result — and the
kernel reuses pids. Any teardown driven off one of those records can therefore
land on a process we never started. ODY-86 was exactly this, and the Cookbook
survivor sweep still terminated any process whose full command line matched a
tracked one, which is the same mistake spelled differently.
Identity is (pid, start token). The token comes from /proc/<pid>/stat on Linux,
ps -o lstart= on macOS and the BSDs, and GetProcessTimes on Windows; the kernel
will not hand a pid to a process that started earlier, so comparing the token
recorded at launch against the token read now answers "is this still ours"
without a handle or a supervisor. verify() returns owned, gone, foreign or
unverifiable, and only owned permits a signal.
Keeping "unverifiable" out of the other two is the point. Process inspection
has broken off Linux four times here — ODY-70, -86, -94, -99 — every time
because an absent mechanism read as a successful answer. Folding it into "ours"
signals strangers; folding it into "gone" abandons live processes. It is a
containment failure and every caller treats it as one.
Wired into the three places that signal:
- containment.release() gates a grant recovered from the durable store, and
leaves an in-process teardown alone, where the caller holds the child and no
identity question arises. The verdict lands on the record, so "why is this
grant still here" is answerable afterwards.
- A startup reaper. Nothing read either store before, so a crashed run left
every grant permanently active and every job permanently running, and the
first thing to touch such a record was a teardown aimed at a reassigned pid.
The two stores get opposite treatment: an orphaned grant has no caller left
and is torn down, while a detached job is documented to survive a restart and
is only corrected, never killed.
- The Cookbook sweep takes its ownership from the tmux pane's process tree,
captured before the kill destroys the only link between a surviving model
server and the session that started it. A process that merely matches the
tracked command line is now reported rather than killed: the Cookbook
composed that command line, so an identical one is just as likely to be a
server the user started by hand. The sweep also runs on hosts with no procfs
instead of silently skipping, and says so when it could not look at all.
Alexandre Teixeira