test(models): add regression coverage for Z.AI coding endpoint probing (#2244)

Add focused tests for the z.ai/api/coding path override:
- _match_provider_curated: 5 tests verifying coding vs base key
- _probe_endpoint: 3 tests verifying model preservation, curated
  append on partial response, and base-zai exclusion

Rebased onto dev per reviewer request.

Fixes #2230

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>

tests/test_model_routes.py

@@ -193,6 +193,87 @@ class TestMatchProviderCurated:
     def test_none_url_safe(self):
         assert _match_provider_curated(None, "openai") == "openai"
 
+    # ── Z.AI coding plan path override (#2230) ──
+
+    def test_zai_coding_path_returns_coding_curated(self):
+        """z.ai/api/coding must return 'zai-coding', not the base 'zai' list."""
+        assert _match_provider_curated("https://z.ai/api/coding", "openai") == "zai-coding"
+
+    def test_zai_coding_path_differs_from_base_zai(self):
+        """The coding plan and the base plan must resolve to different curated keys."""
+        base = _match_provider_curated("https://z.ai/v1", "openai")
+        coding = _match_provider_curated("https://z.ai/api/coding", "openai")
+        assert base == "zai"
+        assert coding == "zai-coding"
+        assert base != coding
+
+    def test_zai_coding_with_trailing_slash(self):
+        assert _match_provider_curated("https://z.ai/api/coding/", "openai") == "zai-coding"
+
+    def test_zai_base_does_not_match_coding(self):
+        """z.ai without the /api/coding path must NOT return 'zai-coding'."""
+        assert _match_provider_curated("https://z.ai/v1", "openai") != "zai-coding"
+
+    def test_zai_coding_none_provider(self):
+        """Path-based override fires even when provider is None."""
+        assert _match_provider_curated("https://z.ai/api/coding", None) == "zai-coding"
+
+
+# ── _probe_endpoint: Z.AI coding plan (#2230) ──
+
+class TestProbeZaiCoding:
+    """Regression coverage for the Z.AI coding endpoint probing path."""
+
+    def _patch(self, monkeypatch):
+        monkeypatch.setattr(endpoint_resolver, "resolve_url", lambda url: url, raising=False)
+        monkeypatch.setattr(model_routes, "_normalize_base", lambda url: url.rstrip("/"))
+
+    def test_probe_preserves_models_from_server(self, monkeypatch):
+        """Models returned by /models are kept in the result."""
+        self._patch(monkeypatch)
+        server_models = [{"id": "glm-5.1"}, {"id": "custom-finetune"}]
+
+        def fake_get(url, headers=None, timeout=None, verify=None, **kwargs):
+            return httpx.Response(200, json={"data": server_models},
+                                 request=httpx.Request("GET", url))
+
+        monkeypatch.setattr(model_routes.httpx, "get", fake_get)
+        result = _probe_endpoint("https://z.ai/api/coding", "key")
+        assert "glm-5.1" in result
+        assert "custom-finetune" in result
+
+    def test_probe_appends_curated_on_partial_response(self, monkeypatch):
+        """When /models returns a partial list, curated-only models are appended."""
+        self._patch(monkeypatch)
+        # Server only returns one model; the curated list has more
+        server_models = [{"id": "glm-5.1"}]
+
+        def fake_get(url, headers=None, timeout=None, verify=None, **kwargs):
+            return httpx.Response(200, json={"data": server_models},
+                                 request=httpx.Request("GET", url))
+
+        monkeypatch.setattr(model_routes.httpx, "get", fake_get)
+        result = _probe_endpoint("https://z.ai/api/coding", "key")
+        assert "glm-5.1" in result
+        # At least one curated model should be appended
+        coding_curated = _PROVIDER_CURATED.get("zai-coding", [])
+        appended = [m for m in coding_curated if m in result and m != "glm-5.1"]
+        assert len(appended) > 0, "curated-only models should be appended"
+
+    def test_probe_does_not_use_base_zai_curated(self, monkeypatch):
+        """The coding endpoint must use zai-coding, NOT the base zai list."""
+        self._patch(monkeypatch)
+
+        def fake_get(url, headers=None, timeout=None, verify=None, **kwargs):
+            return httpx.Response(200, json={"data": [{"id": "glm-5.1"}]},
+                                 request=httpx.Request("GET", url))
+
+        monkeypatch.setattr(model_routes.httpx, "get", fake_get)
+        result = _probe_endpoint("https://z.ai/api/coding", "key")
+        base_only = set(_PROVIDER_CURATED.get("zai", [])) - set(_PROVIDER_CURATED.get("zai-coding", []))
+        for model in base_only:
+            assert model not in result, f"base-zai-only model {model} should not appear for coding endpoint"
+
 
 # ── _curate_models ──