`_store_cached_client()` refuses an `_AuxProbeClientStub`, but
`_get_cached_client()` assigns to `_client_cache` directly and so never
reaches that guard. check_fns resolve through this path inside
`aux_probe_mode()` during tool-schema assembly, and the cache key carries no
probe/runtime distinction — so the stored stub is returned to the next real
caller sharing that key, which dies on attribute access with
`_AuxProbeClientStub used as a real client (attribute 'chat')`.
The `async_mode` field in the cache key is what kept this latent: the probe
caches the sync variant, so async consumers (`analyze_image`) miss the entry
and build a real client, while sync consumers (`browser_vision`) hit the
poisoned one and fail on every call.
Observed against a local OpenAI-compatible vision endpoint, where
`browser_vision` failed every call with that RuntimeError while
`analyze_image` against the same provider worked.
Guard the inline store the same way `_store_cached_client()` does, and
return the stub to the probe caller without caching it.
The existing `test_probe_stub_never_cached` pins the invariant only on
`_store_cached_client()`, which is why the unguarded door went unnoticed;
the new test exercises `_get_cached_client()` and fails without this change.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Steve Ahlstrom
a714ff9823