An external-process provider is an agent CLI Hermes drives over stdio rather
than an HTTP endpoint. Three things about it were spelled out for one vendor,
and each was a hard stop for any other:
* ``resolve_provider()`` gates on ``PROVIDER_REGISTRY``. Its auto-extend from
``providers/`` covered api-key providers only, so an external-process profile
never entered it and ``hermes -m <that provider>`` died with "Unknown
provider" before a client was ever built.
* ``resolve_runtime_provider()`` keyed the external-process branch on the
literal ``"copilot-acp"``, so anything else silently fell through to the
OpenRouter default instead of its own runtime.
* ``resolve_external_process_provider_credentials()`` hardcoded the binary
(``copilot``), the argv (``--acp --stdio``), the env var names and the
placeholder api_key — so a third-party provider would have been handed
another vendor's CLI.
Now the profile carries what only the provider knows — ``process_command``,
``process_args``, ``process_command_env_vars``, ``process_args_env_var`` — and
the three core paths key on ``auth_type == "external_process"`` instead of a
name. copilot-acp's values move into its profile verbatim, so
``HERMES_COPILOT_ACP_COMMAND`` / ``COPILOT_CLI_PATH`` /
``HERMES_COPILOT_ACP_ARGS`` and its ``copilot-acp`` api_key placeholder behave
exactly as before; the new tests assert that alongside the out-of-tree case at
every step.
The error for a missing binary now names the provider and its own env override
instead of telling every user to install GitHub Copilot CLI.
Co-Authored-By: Junie <junie@jetbrains.com>
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