``create_openai_client`` was a hardcoded if-ladder: copilot-acp builds an ACP
stdio shim, gemini builds a native client, everything else gets an
``openai.OpenAI``. There was no extension point, so a provider whose wire
protocol is not OpenAI-over-HTTP could only be added by editing this function —
which is exactly why an ACP provider cannot ship outside this tree today, even
though ``providers/__init__.py`` has discovered out-of-tree profiles from
``~/.hermes/plugins/model-providers/`` and pip entry points for a while.
``ProviderProfile.create_client(**client_kwargs)`` closes that gap. It returns
``None`` by default, so every provider that wants the standard client is
unaffected and the existing ladder still runs as the fallback. copilot-acp is
migrated onto it — its hardcoded branch is gone and its profile supplies the
client in three lines, which is the same three lines an external package writes.
Resolution goes by provider name first, then by ``base_url`` prefix, so a
runtime configured only by URL still reaches its profile — matching what the
replaced ``startswith("acp://copilot")`` branch did. A profile that raises is
logged and skipped: a third-party plugin can fail to provide a client, but it
cannot take the turn down.
Also replaces the two ``isinstance`` checks in ``agent/auxiliary_client.py``
that mean "this client is complete, do not wrap it" with capability flags the
client class declares — ``HERMES_SKIP_TRANSPORT_WRAP`` and
``HERMES_SKIP_ASYNC_WRAP``, mirroring ``SUPPORTS_HERMES_TOOL_CALLS`` in
``background_review.py``. Two in-tree consumers (the ACP shim and the Gemini
native client), an out-of-tree client is covered by the same declaration, and
the hot path no longer imports those modules just to type-test.
Co-Authored-By: Junie <junie@jetbrains.com>
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