fix(config): PR #1970 lmstudio branch must honor cfg.model.base_url fallback

PR #1970 added a dedicated `elif pid == "lmstudio":` branch in
`get_available_models()` that fetches the live /v1/models list when the
hermes_cli helper doesn't have ids cached. The fallback path inside that
branch only looked at `cfg["providers"]["lmstudio"]["base_url"]`, missing
the historical config shape where the URL lives under `cfg["model"]`:

  model:
    provider: lmstudio
    base_url: http://192.168.1.22:1234/v1   ← here, not under providers.lmstudio
  providers:
    lmstudio:
      api_key: local-key

3 pre-existing tests in tests/test_issue1527_lmstudio_base_url_classification
broke on stage-337 because of this — they passed on master, failed after
the PR #1970 merge.

The simpler fix is to enhance the already-introduced `_get_provider_base_url()`
helper so it falls back to `cfg["model"]["base_url"]` when
`cfg["model"]["provider"] == provider_id`, then use the helper inside the
lmstudio branch instead of a direct lookup. This keeps the previous
behaviour (where the generic configured-provider branch handled lmstudio
via the model block) while preserving PR #1970's live-discovery additions.

Belt-and-suspenders: `_get_provider_base_url()` explicitly does NOT inherit
model.base_url for providers other than the active one — if a user's config
says `model.provider: anthropic` and they have `providers.openai` configured
without a base_url, openai must still resolve to None (use SDK default),
not to the anthropic proxy URL.

6 new regression tests in tests/test_pr1970_lmstudio_base_url_fallback.py
lock the two-location lookup, the precedence rule (explicit providers entry
wins over model fallback), trailing-slash stripping, and the negative case
(model.base_url MUST NOT leak to non-active providers).

All 51 tests in the existing model-resolver + custom-provider banks still
pass.

Caught by maintainer review on stage-337 (full pytest with the new network
isolation in place surfaced the regression that the fork-CI mock-server path
would have hidden).

api/config.py

@@ -1480,9 +1480,31 @@ def _custom_slug_rest_looks_like_host_port(rest: str) -> bool:
 
 
 def _get_provider_base_url(provider_id):
-    """Look up the configured base_url for a provider (e.g. lmstudio)."""
+    """Look up the configured base_url for a provider (e.g. lmstudio).
+
+    Checks two locations, in order:
+      1. ``cfg["providers"][<provider_id>]["base_url"]`` — the explicit
+         per-provider override.
+      2. ``cfg["model"]["base_url"]`` — falls back here when
+         ``cfg["model"]["provider"] == provider_id``. This is the historical
+         shape (the model block carries both the active provider AND the
+         base URL for that provider in a single record).
+
+    Returns the URL stripped of trailing ``/`` if configured, otherwise None.
+    """
     prov_cfg = cfg.get("providers", {}).get(provider_id, {}) or {}
-    return (prov_cfg.get("base_url") or "").rstrip("/") or None
+    explicit = (prov_cfg.get("base_url") or "").strip().rstrip("/")
+    if explicit:
+        return explicit
+    model_cfg = cfg.get("model", {}) or {}
+    if isinstance(model_cfg, dict):
+        model_provider = str(model_cfg.get("provider") or "").strip().lower()
+        if model_provider == str(provider_id).strip().lower():
+            model_base = (model_cfg.get("base_url") or "").strip().rstrip("/")
+            if model_base:
+                return model_base
+    return None
+
 
 def resolve_model_provider(model_id: str) -> tuple:
     """Resolve model name, provider, and base_url for AIAgent.
@@ -3415,7 +3437,7 @@ def get_available_models() -> dict:
                             # the profile's .env has been injected into the process environment.
                             lm_cfg = cfg.get("providers", {}).get("lmstudio", {})
                             if isinstance(lm_cfg, dict):
-                                lm_base_url = str(lm_cfg.get("base_url") or "").strip().rstrip("/")
+                                lm_base_url = _get_provider_base_url("lmstudio") or ""
                                 lm_api_key = str(lm_cfg.get("api_key") or "").strip()
                                 if lm_base_url:
                                     headers = {"User-Agent": "OpenAI/Python 1.0"}

tests/test_pr1970_lmstudio_base_url_fallback.py

@@ -0,0 +1,127 @@
+"""Regression for PR #1970 LM Studio provider × cfg.model.base_url shape.
+
+PR #1970 added `_get_provider_base_url()` + a dedicated lmstudio branch in
+`get_available_models()` for fetching live loaded models via the OpenAI-compatible
+/v1/models endpoint.
+
+The initial implementation only looked at `cfg["providers"]["lmstudio"]["base_url"]`,
+missing the historical shape where users put `base_url` under `cfg["model"]`
+(when `cfg["model"]["provider"] == "lmstudio"`). That shape is what
+`tests/test_issue1527_lmstudio_base_url_classification.py` covers and what real
+users have in their config.yaml — 3 pre-existing tests started failing on stage-337
+because of this gap.
+
+This regression test pins the helper's two-location lookup so a future change
+can't accidentally drop the model.base_url fallback again.
+"""
+from __future__ import annotations
+
+import api.config as config
+
+
+class _RestoreCfg:
+    """Context manager: snapshot cfg, restore on exit (test isolation)."""
+
+    def __enter__(self):
+        import copy
+        self._snapshot = copy.deepcopy(config.cfg)
+        return self
+
+    def __exit__(self, *exc):
+        config.cfg.clear()
+        config.cfg.update(self._snapshot)
+
+
+def test_get_provider_base_url_finds_explicit_providers_entry():
+    """When providers.<id>.base_url is set, return that value."""
+    with _RestoreCfg():
+        config.cfg.clear()
+        config.cfg.update({
+            "providers": {
+                "lmstudio": {"base_url": "http://10.0.0.5:1234/v1", "api_key": "x"},
+            },
+        })
+        assert config._get_provider_base_url("lmstudio") == "http://10.0.0.5:1234/v1"
+
+
+def test_get_provider_base_url_strips_trailing_slash():
+    with _RestoreCfg():
+        config.cfg.clear()
+        config.cfg.update({
+            "providers": {
+                "lmstudio": {"base_url": "http://10.0.0.5:1234/v1/", "api_key": "x"},
+            },
+        })
+        assert config._get_provider_base_url("lmstudio") == "http://10.0.0.5:1234/v1"
+
+
+def test_get_provider_base_url_falls_back_to_model_base_url():
+    """When providers.<id>.base_url is unset but cfg.model.base_url is set
+    AND cfg.model.provider matches, the helper returns model.base_url."""
+    with _RestoreCfg():
+        config.cfg.clear()
+        config.cfg.update({
+            "model": {
+                "provider": "lmstudio",
+                "base_url": "http://192.168.1.22:1234/v1",
+                "default": "qwen3.6-35b-a3b@q6_k",
+            },
+            "providers": {
+                "lmstudio": {"api_key": "local-key"},  # no base_url here
+            },
+        })
+        # Was returning None before the fix — the regression that broke
+        # test_issue1527_lmstudio_base_url_classification.
+        assert config._get_provider_base_url("lmstudio") == "http://192.168.1.22:1234/v1"
+
+
+def test_get_provider_base_url_returns_none_when_unconfigured():
+    """Unconfigured provider returns None (sentinel for 'use SDK default')."""
+    with _RestoreCfg():
+        config.cfg.clear()
+        config.cfg.update({"providers": {}})
+        assert config._get_provider_base_url("openai") is None
+        assert config._get_provider_base_url("anthropic") is None
+        assert config._get_provider_base_url("lmstudio") is None
+
+
+def test_get_provider_base_url_model_block_only_matches_active_provider():
+    """cfg.model.base_url must NOT leak to providers other than cfg.model.provider.
+
+    If model.provider is anthropic but providers.openai exists without base_url,
+    _get_provider_base_url("openai") must still return None — otherwise we'd
+    silently rewrite the OpenAI SDK target to an Anthropic endpoint URL.
+    """
+    with _RestoreCfg():
+        config.cfg.clear()
+        config.cfg.update({
+            "model": {
+                "provider": "anthropic",
+                "base_url": "https://my-anthropic-proxy.example.com/v1",
+            },
+            "providers": {
+                "openai": {"api_key": "ok"},  # no base_url
+                "anthropic": {"api_key": "ak"},  # no base_url
+            },
+        })
+        # Active provider gets the model.base_url fallback.
+        assert config._get_provider_base_url("anthropic") == "https://my-anthropic-proxy.example.com/v1"
+        # OpenAI must NOT inherit it.
+        assert config._get_provider_base_url("openai") is None
+
+
+def test_get_provider_base_url_explicit_wins_over_model_fallback():
+    """If both providers.<id>.base_url AND cfg.model.base_url are set with matching
+    provider, the explicit providers entry wins."""
+    with _RestoreCfg():
+        config.cfg.clear()
+        config.cfg.update({
+            "model": {
+                "provider": "lmstudio",
+                "base_url": "http://wrong:1234/v1",
+            },
+            "providers": {
+                "lmstudio": {"base_url": "http://correct:1234/v1", "api_key": "x"},
+            },
+        })
+        assert config._get_provider_base_url("lmstudio") == "http://correct:1234/v1"