`asyncio.gather` propagates the first failure while its siblings run on, and the
caller unwinding from that closes the set through `async with` — so a sibling
still reading reads through a closed session. Seven fan-outs were affected:
lookup, search, image enrichment, multimodal picture loading, context expansion,
document listing and counting, and the sandbox's document load.
`gather_all` cancels and drains the rest, then re-raises the original exception.
A `TaskGroup` would drain them too but raise an `ExceptionGroup`, which every
caller and both CLIs' exception handlers would have to unwrap. The two
`return_exceptions=True` gathers in session opening and teardown already drain
their children and are left alone.
`close()` refused a client covering a set, which left one with no method to
call: `async with` was the only lifecycle it had. `aclose()` runs that teardown
for a caller that owns the client some other way, whatever it covers, and
nothing to release is not an error, so it is safe before entering and after
closing.
`close()` stays what it is, one connection and nothing else, and says so:
draining the background vacuum and releasing the embedder and reranker are
awaitable.
Every client covering a database built its own, so a set of five loaded the same
local model weights five times over, beside the federator's. A client covering a
database for another borrows that one's, and only its owner closes it.
A URI-backed database is constructed with a local `db_path` nothing connects
to, and the info modal reported that, so `--db-name` on an S3 database named a
local directory. `location` reads the configuration instead, and the modal
labels it as one.
`InfoModal`'s `db_path` argument is gone: both callers passed None, so only a
test reached the branch that used it.
`sessions_for` recorded what opened from `gather`'s results, which arrive only
when it runs to completion. Cancelling it discarded them, so a database that
opened while a sibling was still pending was never recorded and `aclose` never
closed it. `return_exceptions=True` covers a failing child, not a cancelled
parent.
`_open` now registers its own session, so what opened is reachable however the
fan-out ends.
Two files of 1,405 and 814 lines become seven: scope resolution, lifecycle,
search, documents, expansion, citations and capabilities. `_config`, `_seed`
and the rest move to `helpers.py`, importable by the sandbox tests that share
them, and the package points VCR back at `tests/cassettes/multi_db/`.
