Pin discovered Codex model id verbatim; clarify Databricks fallback m…

src/ucode/agents/codex.py

@@ -68,13 +68,6 @@
 
 _GPT_RE = re.compile(r"(?:databricks-)?gpt-(\d+)(?:[.-](\d+))?(?:[.-](\d+))?(-.+|[a-z].*)?")
 
-# These models should use the Databricks ID, not the OpenAI ID, as the OpenAI
-# ID is incompatible with Codex.
-CODEX_OPENAI_ID_INCOMPATIBLE_MODELS = {
-    "databricks-gpt-5-2-codex",
-    "databricks-gpt-5-4-nano",
-}
-
 
 def is_update_available() -> tuple[str, str] | None:
     return available_npm_package_update(SPEC["package"])
@@ -274,30 +267,6 @@ def revert_legacy_shared_config() -> bool:
     return _strip_legacy_ucode_entries(_legacy_config_path())
 
 
-def _openai_model_id(model: str | None) -> str | None:
-    """Map Databricks GPT endpoint ids to OpenAI model ids for Codex metadata."""
-    parsed = _parse_gpt(model)
-    if parsed is None:
-        return model
-    major, minor, patch, suffix = parsed
-    version = str(major)
-    if minor is not None:
-        version += f".{minor}"
-    if patch is not None:
-        version += f".{patch}"
-    return f"gpt-{version}{suffix}"
-
-
-def _codex_model_id(model: str | None) -> str | None:
-    # UC model-services ids (`system.ai.gpt-5`) route by name through the
-    # gateway, so they must be sent verbatim — not rewritten to an OpenAI id.
-    if model and model.startswith("system.ai."):
-        return model
-    if model in CODEX_OPENAI_ID_INCOMPATIBLE_MODELS:
-        return model
-    return _openai_model_id(model)
-
-
 def _parse_gpt(model: str | None) -> tuple[int, int | None, int | None, str] | None:
     if not model:
         return None
@@ -322,8 +291,12 @@ def write_tool_config(state: dict, model: str | None = None, provider: str | Non
     workspace = state["workspace"]
     # With a Model Provider Service the gateway routes by header and Codex sends
     # its own canonical model name (e.g. `gpt-5`) — leave `model` unset so no
-    # Databricks endpoint id is pinned.
-    chosen_model = None if provider else _codex_model_id(model or default_model(state))
+    # Databricks endpoint id is pinned. Otherwise pin the discovered endpoint id
+    # verbatim: the gateway routes by that exact name (whether `databricks-gpt-5`
+    # from the AI Gateway listing or `system.ai.gpt-5` from UC model-services), so
+    # rewriting it to an OpenAI id (`gpt-5`) makes the gateway resolve a
+    # non-existent `system.ai.*` alias and 404.
+    chosen_model = None if provider else (model or default_model(state))
     databricks_profile = state.get("profile")
 
     if _use_legacy_layout():

src/ucode/cli.py

@@ -629,7 +629,7 @@ def _use_databricks() -> dict:
         return _use_databricks()
     if not names:
         # Feature is on but no service matches this tool's provider type.
-        print_note(f"No model provider services available for {display}; using Databricks models.")
+        print_note(f"Using Databricks models for {display}.")
         return _use_databricks()
 
     choice = prompt_for_selection(

tests/test_agent_codex.py

@@ -109,7 +109,10 @@ def test_writes_ucode_profile_config_file(self, tmp_path, monkeypatch):
         assert doc["model"] == "gpt-5"
         assert "profiles" not in doc
 
-    def test_writes_openai_model_id_for_databricks_gpt_endpoint(self, tmp_path, monkeypatch):
+    def test_pins_discovered_databricks_model_id_verbatim(self, tmp_path, monkeypatch):
+        # The gateway routes by the discovered endpoint name, so the id is
+        # written as-is (not rewritten to an OpenAI id like `gpt-5.5`, which the
+        # gateway would resolve to a non-existent `system.ai.*` alias and 404).
         config_path = tmp_path / ".codex" / "ucode.config.toml"
         backup_path = tmp_path / "codex-ucode-config.backup.toml"
         monkeypatch.setattr(codex, "CODEX_CONFIG_PATH", config_path)
@@ -122,11 +125,9 @@ def test_writes_openai_model_id_for_databricks_gpt_endpoint(self, tmp_path, monk
         )
 
         doc = read_toml_safe(config_path)
-        assert doc["model"] == "gpt-5.5"
+        assert doc["model"] == "databricks-gpt-5-5"
 
-    def test_preserves_databricks_model_id_when_openai_id_is_incompatible(
-        self, tmp_path, monkeypatch
-    ):
+    def test_pins_uc_model_services_id_verbatim(self, tmp_path, monkeypatch):
         config_path = tmp_path / ".codex" / "ucode.config.toml"
         backup_path = tmp_path / "codex-ucode-config.backup.toml"
         monkeypatch.setattr(codex, "CODEX_CONFIG_PATH", config_path)
@@ -135,12 +136,11 @@ def test_preserves_databricks_model_id_when_openai_id_is_incompatible(
         monkeypatch.setattr(codex, "save_state", lambda state: None)
 
         codex.write_tool_config(
-            {"workspace": WS, "codex_models": ["databricks-gpt-5-2-codex"]},
-            "databricks-gpt-5-2-codex",
+            {"workspace": WS, "codex_models": ["system.ai.gpt-5", "system.ai.gpt-5-5"]}
         )
 
         doc = read_toml_safe(config_path)
-        assert doc["model"] == "databricks-gpt-5-2-codex"
+        assert doc["model"] == "system.ai.gpt-5-5"
 
     def test_provider_writes_header_and_drops_stale_model(self, tmp_path, monkeypatch):
         config_path = tmp_path / ".codex" / "ucode.config.toml"
@@ -522,28 +522,10 @@ def test_codex_default_model_wins_over_allowlist(self):
         }
         assert codex.default_model(state) == "admin-chosen-default"
 
-    def test_openai_model_id_maps_databricks_naming(self):
-        assert codex._openai_model_id("databricks-gpt-5-5") == "gpt-5.5"
-        assert codex._openai_model_id("databricks-gpt-5-5-mini") == "gpt-5.5-mini"
-        assert codex._openai_model_id("databricks-gpt-4o") == "gpt-4o"
-        assert codex._openai_model_id("served-models/databricks-gpt-5-5") == "gpt-5.5"
-        assert codex._openai_model_id("gpt-5.5") == "gpt-5.5"
-
-    def test_codex_model_id_preserves_openai_incompatible_models(self):
-        assert codex._codex_model_id("databricks-gpt-5-2-codex") == "databricks-gpt-5-2-codex"
-        assert codex._codex_model_id("databricks-gpt-5-4-nano") == "databricks-gpt-5-4-nano"
-
-    def test_codex_model_id_passes_model_services_id_verbatim(self):
-        # UC model-services ids route by name, so they must not be rewritten
-        # to the OpenAI id form.
-        assert codex._codex_model_id("system.ai.gpt-5") == "system.ai.gpt-5"
-        assert codex._codex_model_id("system.ai.gpt-5-2-codex") == "system.ai.gpt-5-2-codex"
-
     def test_default_model_selects_model_services_gpt(self):
         models = ["system.ai.gpt-5", "system.ai.gpt-5-5", "system.ai.claude-opus-4-8"]
 
         assert codex.default_model({"codex_models": models}) == "system.ai.gpt-5-5"
-        assert codex._codex_model_id("databricks-gpt-5-5") == "gpt-5.5"
 
 
 class TestCodexValidateCmd: