`model.openai_runtime: codex_app_server` only ever admitted `openai` /
`openai-codex`: a named custom provider (`providers.<name>`) resolves to
provider="custom" on the named-custom ladder rung, which never ran the
runtime gate, so `/codex-runtime codex_app_server` silently left the main
turn on Hermes' chat-completions client. And even when routed, thread/start
sent only `cwd`, so codex could not know which of its own providers to use.
- `_maybe_apply_codex_app_server_runtime` takes `requested_provider` and
admits provider="custom" only when `codex_model_provider_id()` finds a
configured `providers.<name>` entry (bare `custom`, ollama/vllm aliases
and unknown names have no stable id -> ineligible, unchanged).
- The named-custom rung applies the same opt-in the pool rung already does
for openai/openai-codex.
- `CodexAppServerSession(model=, model_provider=)` -> `thread/start.model` /
`.modelProvider` (fields verified against the codex 0.147 app-server
schema). `_ensure_codex_session` fills them only for custom agents; codex
resolves base_url/env_key from its own `[model_providers.<name>]`, so the
Hermes credential never enters the JSON-RPC payload.
- `tui_gateway/server.py::_make_agent` forwards `requested_provider` so the
Desktop/TUI agent knows the provider id (it otherwise collapses to
"custom" and codex would fall back to its default provider).
- Docs: matching `[model_providers.<name>]` + `env_key` requirement and the
bare-`custom` ineligibility.
Ported and trimmed from #75191 by @cosin2077 (aux-loop `allow_codex_app_server`
plumbing, `cli-config.yaml.example` block and the integration-test suite dropped:
background_review already maps codex_app_server -> codex_responses on main).
Fixes#75186
8b7caf226f