33 read sites across 25 files used BOM-intolerant encoding='utf-8'.
Windows tooling BOMs files it touches; json.load on a BOM'd file fails
with 'Expecting value'. Reads now use utf-8-sig (writes unchanged).
check-windows-footguns.py --all: 33 → 0.
The unit tests share one interpreter, so they cannot exercise the failure the
fence exists to prevent: two SEPARATE gateway processes, each holding its own
snapshot of a conversation, both writing to it. That is how the defect was found
and it is the only way to show it is closed.
This drives two real `python -m tui_gateway.entry` processes over stdio and
checks the whole sequence, including the parts that are easy to get wrong:
session.create claims nothing an idle composer must not hold a session
the lease keys on the STORED id a lease keyed on the runtime handle would
fence nothing, since two processes
resuming one conversation have different
runtime ids by construction
B may still RESUME reading is never fenced; only writing is
B's submit -> SESSION_NOT_OWNED typed, and the registry is unchanged
A killed, B retries -> accepted a dead owner is pruned, not permanent
No provider is needed. The fence is checked before the agent is built, so a
submit that later fails for want of a model still proves who owns the session --
which keeps the probe free of credentials and of inference cost.
Against the parent commit it stops at the second check with an empty registry,
which is the defect stated exactly: with no cap configured, nothing was recorded
and therefore nothing could be refused.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
