Production `state.db` files accumulate zero-message "open" gateway session
rows carrying test-fixture identities (`chat-1` / `user-1` / `wx-chat`), with
matching `gateway_routing` scopes pointing at `pytest-of-*` temp directories.
The escape is structural. Hermetic isolation rides entirely on the process
environment: `HERMES_HOME` says *where* to write, `PYTEST_CURRENT_TEST` /
`PYTEST_VERSION` say *whether the guard is armed*. Both travel in the same
carrier, so a child spawned with a rebuilt environment loses them together —
it resolves the developer's real `state.db` *and* silences the only check
that would have stopped it, in one step. The guard is a no-op in precisely
the situation it was written for.
Back the env probe with process ancestry, which survives an env rebuild:
* `_process_looks_like_pytest()` matches a pytest launcher by argv token
basename, so `/tmp/pytest-of-dev/...` paths in real argv cannot
false-positive, and an unreadable process is never assumed to be a test.
* `_has_pytest_ancestor()` walks parents via psutil, memoised, and fails
open when psutil is unavailable — a real `hermes` run pays for at most
one walk and keeps the previous behaviour if the walk errors.
* `_in_test_context()` checks env first (two dict lookups, covers the
in-process case) and only then ancestry.
`_STATE_DB_GUARD_BYPASS` is a module global and cannot cross a process
boundary, so ancestry-armed children would have had no way to opt out at
all; `HERMES_STATE_DB_GUARD_BYPASS=1` is the env-carried twin.
Also sweeps the rows already written. Bulk prune/archive cannot reach them:
their shared selector is pinned to `ended_at IS NOT NULL` so a live session
is never picked, which permanently excludes every never-closed row. Adds a
narrower selector — keyed, still open, and with no messages, tokens, tool
calls, API calls, activity or title — behind
`hermes sessions prune --never-active` (default floor 30 days, honours
--dry-run/--yes). Routing entries naming a deleted row go with it, so the
gateway is never left resuming a session id that no longer exists; `pinned`
and `archived` rows are excluded as explicit user intent.
Closes#82770
joaomarcos