The command wrapper prints the cwd marker after the command returns. A
killed or timed-out command emits no marker, so ``env.cwd`` still holds the
directory of the last command to FINISH. One local environment serves every
session, because ``_resolve_container_task_id`` collapses cwd-only overrides
to ``"default"``. That leftover directory is therefore routinely another
session's.
The post-command dual-write copied ``env.cwd`` into the interrupted session's
durable record. Every later command in that session then ran in the foreign
directory, and the cwd echo told the model it had moved there. A desktop chat
silently re-homed into a worktree that another chat had opened.
Report the observation instead of inferring it. The marker parse now sets
``result["cwd_observed"]``, and both the record write and the echo read that
flag. The local override clears the flag when it rolls back a path that does
not exist, because the restored value is also unobserved. When a command
reports no cwd, the session keeps the directory it already had.
This needs no second session to be wrong: a lone session that interrupts a
command re-adopts a stale value too. A second session only makes the wrong
directory belong to somebody else.
The same class of write exists in the file-tools rescue for a reaped
environment (#26211). That rescue copied the cached snapshot of the shared
``env.cwd`` into the session record. The rescue is now fill-only: it writes
the snapshot when the session has no record, and it never overwrites a
record that the session wrote for itself.
The tests drive ``terminal_tool`` itself through an interrupt, not a copy of
its gate. Review found that a revert of either call site passed the first
version of the tests. Each gate now has a test that fails when the gate is
removed (verified by mutation).
Two exact-dict assertions in the Vercel sandbox tests now assert the two
fields they care about, so a new result key does not fail them.
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