fix(api): reject doubled provider prefixes in agent model ids (#334)

app/core/config.py

@@ -32,8 +32,12 @@ def validate_model_identifier(v: str) -> str:
         The validated model identifier, unchanged.
 
     Raises:
-        ValueError: If the format is invalid, the model name is blank, or the
-            provider is not in :data:`VALID_MODEL_PROVIDERS`.
+        ValueError: If the format is invalid, the model name is blank, the
+            provider is not in :data:`VALID_MODEL_PROVIDERS`, or the model
+            name nests another provider prefix (e.g.
+            ``google-gla:google-gla:gemini-3-flash-preview``). Multi-colon
+            Ollama tag identifiers stay valid (``ollama:llama3.1:8b`` —
+            ``llama3.1`` is not a provider).
     """
     if ":" not in v:
         raise ValueError(
@@ -56,6 +60,19 @@ def validate_model_identifier(v: str) -> str:
         raise ValueError(
             f"Unknown provider '{provider}'. Valid providers: {list(VALID_MODEL_PROVIDERS)}"
         )
+
+    # Reject a nested/doubled provider prefix inside the model name
+    # (issue #334: 'google-gla:google-gla:gemini-…' → Gemini 404 at run time).
+    # Ollama tags ('ollama:llama3.1:8b') stay valid: 'llama3.1' is not a provider.
+    if ":" in model_name:
+        nested = model_name.split(":", 1)[0]
+        if nested in VALID_MODEL_PROVIDERS:
+            suggested = f"{provider}:{model_name.split(':', 1)[1]}"
+            raise ValueError(
+                f"Nested provider prefix '{nested}:' inside the model name of '{v}'. "
+                f"Did you mean '{suggested}'? "
+                "Expected format: 'provider:model-name' with the provider given once."
+            )
     return v
 
 

app/features/agents/tests/test_config_validation.py

@@ -38,6 +38,19 @@ def test_invalid_model_identifier_empty_provider(self):
         with pytest.raises(ValidationError, match="Unknown provider"):
             Settings(agent_default_model=":model-name")
 
+    def test_doubled_prefix_rejected_at_settings_boot(self):
+        """A doubled provider prefix fails Settings construction (issue #334)."""
+        with pytest.raises(ValidationError, match="Nested provider"):
+            Settings(
+                agent_default_model="anthropic:anthropic:claude-sonnet-4-5",
+                _env_file=None,
+            )
+
+    def test_ollama_tag_accepted_at_settings_boot(self):
+        """A multi-colon Ollama name:tag identifier constructs Settings fine."""
+        settings = Settings(agent_default_model="ollama:llama3.1:8b", _env_file=None)
+        assert settings.agent_default_model == "ollama:llama3.1:8b"
+
 
 class TestAPIKeyValidation:
     """Test API key validation for models."""

app/features/config/service.py

@@ -24,7 +24,7 @@
 from sqlalchemy.dialects.postgresql import insert as pg_insert
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from app.core.config import get_settings
+from app.core.config import get_settings, validate_model_identifier
 from app.core.logging import get_logger
 from app.features.agents.agents.base import reset_agent_caches
 from app.features.config.models import AppConfig
@@ -46,6 +46,10 @@
 # Scalar types an ``app_config`` override value may hold.
 OverrideValue = str | int | float | bool
 
+# Override keys holding a "provider:model-name" identifier — re-validated at
+# startup so a malformed persisted row never goes live (issue #334).
+_MODEL_ID_KEYS = frozenset({"agent_default_model", "agent_fallback_model"})
+
 
 # =============================================================================
 # Helpers
@@ -190,6 +194,18 @@ async def apply_overrides_on_startup(db: AsyncSession) -> None:
     for key, value in overrides.items():
         if key not in ALLOWED_OVERRIDE_KEYS:
             continue
+        if key in _MODEL_ID_KEYS and isinstance(value, str):
+            try:
+                validate_model_identifier(value)
+            except ValueError as exc:
+                # Skip-and-warn: leave the env/default value in effect — the
+                # function's no-crash-on-startup contract stands.
+                logger.warning(
+                    "config.override_invalid_model_id",
+                    key=key,
+                    error=str(exc),
+                )
+                continue
         setattr(settings, key, value)
         if key in SECRET_KEYS and isinstance(value, str):
             os.environ[SECRET_ENV_NAMES[key]] = value

app/features/config/tests/test_routes.py

@@ -117,6 +117,18 @@ def test_patch_rejects_invalid_model(self, client):
         response = client.patch("/config/ai", json={"agent_default_model": "nope"})
         assert response.status_code == 422
 
+    def test_patch_rejects_doubled_provider_prefix(self, client):
+        """A doubled provider prefix is a 422 problem+json naming the field (#334)."""
+        response = client.patch(
+            "/config/ai",
+            json={"agent_default_model": "google-gla:google-gla:gemini-3-flash-preview"},
+        )
+        assert response.status_code == 422
+        body = response.json()
+        assert body["code"] == "VALIDATION_ERROR"
+        assert body["errors"][0]["field"] == "agent_default_model"
+        assert "Nested provider prefix" in body["errors"][0]["message"]
+
     def test_patch_surfaces_dimension_conflict(self, client):
         """A 409 from the dimension guard propagates to the caller."""
         with patch(

app/features/config/tests/test_schemas.py

@@ -42,6 +42,44 @@ def test_validate_model_identifier_rejects_unknown_provider(self):
         with pytest.raises(ValueError, match="Unknown provider"):
             validate_model_identifier("pinecone:model")
 
+    @pytest.mark.parametrize(
+        "identifier",
+        [
+            "google-gla:google-gla:gemini-3-flash-preview",
+            "anthropic:anthropic:claude-sonnet-4-5",
+            "openai:openai:gpt-4o",
+            "google-vertex:google-vertex:gemini-2.0",
+            "ollama:ollama:llama3.1",
+        ],
+    )
+    def test_rejects_doubled_provider_prefix(self, identifier):
+        """A doubled provider prefix inside the model name is rejected (issue #334)."""
+        with pytest.raises(ValueError, match="Nested provider prefix"):
+            validate_model_identifier(identifier)
+
+    def test_rejects_mixed_provider_prefix(self):
+        """A different known provider nested in the model name is also rejected."""
+        with pytest.raises(ValueError, match="Nested provider prefix"):
+            validate_model_identifier("openai:anthropic:claude-x")
+
+    def test_error_message_suggests_correction(self):
+        """The rejection message tells the operator the likely intended id."""
+        with pytest.raises(ValueError) as exc:
+            validate_model_identifier("google-gla:google-gla:gemini-3-flash-preview")
+        assert "Did you mean 'google-gla:gemini-3-flash-preview'?" in str(exc.value)
+
+    @pytest.mark.parametrize(
+        "identifier",
+        ["ollama:llama3.1:8b", "ollama:gemma4:e2b", "ollama:qwen3:8b"],
+    )
+    def test_accepts_ollama_tag_identifiers(self, identifier):
+        """Multi-colon Ollama name:tag identifiers stay valid."""
+        assert validate_model_identifier(identifier) == identifier
+
+    def test_accepts_model_named_like_provider(self):
+        """A model literally named like a provider (no colon after it) stays valid."""
+        assert validate_model_identifier("ollama:openai") == "ollama:openai"
+
 
 class TestAIModelConfigUpdate:
     """Tests for the PATCH /config/ai request body."""
@@ -93,6 +131,18 @@ def test_model_validate_json_path(self):
         assert upd.agent_temperature == 0.5
         assert upd.agent_default_model == "ollama:llama3.1"
 
+    def test_rejects_doubled_prefix_via_model_validate(self):
+        """A doubled prefix fails through the validate_python (JSON) path too."""
+        with pytest.raises(ValidationError, match="Nested provider prefix"):
+            AIModelConfigUpdate.model_validate({"agent_default_model": "google-gla:google-gla:x"})
+
+    def test_fallback_model_also_guarded(self):
+        """The fallback-model field is guarded by the same nested-prefix rule."""
+        with pytest.raises(ValidationError, match="Nested provider prefix"):
+            AIModelConfigUpdate.model_validate(
+                {"agent_fallback_model": "anthropic:anthropic:claude-sonnet-4-5"}
+            )
+
 
 class TestResponseSchemas:
     """Tests for the response-only schemas."""

app/features/config/tests/test_service.py

@@ -193,6 +193,49 @@ async def test_update_config_secret_mirrored_to_environment(self):
         assert os.environ["OPENAI_API_KEY"] == "sk-new-openai-key-123"
 
 
+# =============================================================================
+# Unit tests — apply_overrides_on_startup
+# =============================================================================
+
+
+class TestApplyOverridesOnStartup:
+    """Tests for the startup override loader's model-id guard (issue #334)."""
+
+    @pytest.mark.asyncio
+    async def test_startup_skips_invalid_model_id_override(self):
+        """A malformed persisted model id is skipped with a warning; valid keys apply."""
+        settings = get_settings()
+        # Snapshot mutated fields and restore in finally so the mutation never
+        # leaks into another test (settings-singleton precedent, 24ed5cd).
+        original_model = settings.agent_default_model
+        original_temperature = settings.agent_temperature
+        try:
+            with (
+                patch(
+                    "app.features.config.service._load_overrides",
+                    new=AsyncMock(
+                        return_value={
+                            "agent_default_model": "google-gla:google-gla:x",
+                            "agent_temperature": 0.5,
+                        }
+                    ),
+                ),
+                patch.object(service.logger, "warning") as mock_warning,
+            ):
+                await service.apply_overrides_on_startup(_mock_db())
+
+            # Malformed model id skipped — env/default value stays in effect.
+            assert settings.agent_default_model == original_model
+            # Valid keys in the same batch are still applied.
+            assert settings.agent_temperature == 0.5
+            mock_warning.assert_called_once()
+            assert mock_warning.call_args.args[0] == "config.override_invalid_model_id"
+            assert mock_warning.call_args.kwargs["key"] == "agent_default_model"
+        finally:
+            settings.agent_default_model = original_model
+            settings.agent_temperature = original_temperature
+
+
 # =============================================================================
 # Unit tests — provider health + ollama models
 # =============================================================================