feat: replace infer_target_type with capability-based model selection and validation

tests/test_config.py

@@ -10,11 +10,11 @@ import yaml
 from bulkgen.config import (
     Defaults,
     TargetConfig,
-    TargetType,
-    infer_target_type,
+    infer_required_capabilities,
     load_config,
     resolve_model,
 )
+from bulkgen.providers.models import Capability
 
 
 class TestLoadConfig:
@@ -88,34 +88,88 @@ class TestLoadConfig:
             _ = load_config(config_path)
 
 
-class TestInferTargetType:
-    """Test target type inference from file extensions."""
+class TestInferRequiredCapabilities:
+    """Test capability inference from file extensions and target config."""
 
-    @pytest.mark.parametrize(
-        "name", ["photo.png", "photo.jpg", "photo.jpeg", "photo.webp"]
-    )
+    def test_plain_image(self) -> None:
+        target = TargetConfig(prompt="x")
+        assert infer_required_capabilities("out.png", target) == frozenset(
+            {Capability.TEXT_TO_IMAGE}
+        )
+
+    @pytest.mark.parametrize("name", ["out.png", "out.jpg", "out.jpeg", "out.webp"])
     def test_image_extensions(self, name: str) -> None:
-        assert infer_target_type(name) is TargetType.IMAGE
+        target = TargetConfig(prompt="x")
+        caps = infer_required_capabilities(name, target)
+        assert Capability.TEXT_TO_IMAGE in caps
 
-    @pytest.mark.parametrize("name", ["PHOTO.PNG", "PHOTO.JPG"])
+    @pytest.mark.parametrize("name", ["OUT.PNG", "OUT.JPG"])
     def test_case_insensitive(self, name: str) -> None:
-        assert infer_target_type(name) is TargetType.IMAGE
+        target = TargetConfig(prompt="x")
+        caps = infer_required_capabilities(name, target)
+        assert Capability.TEXT_TO_IMAGE in caps
+
+    def test_image_with_reference_images(self) -> None:
+        target = TargetConfig(prompt="x", reference_images=["ref.png"])
+        assert infer_required_capabilities("out.png", target) == frozenset(
+            {Capability.TEXT_TO_IMAGE, Capability.REFERENCE_IMAGES}
+        )
+
+    def test_image_with_control_images(self) -> None:
+        target = TargetConfig(prompt="x", control_images=["ctrl.png"])
+        assert infer_required_capabilities("out.png", target) == frozenset(
+            {Capability.TEXT_TO_IMAGE, Capability.CONTROL_IMAGES}
+        )
+
+    def test_image_with_both(self) -> None:
+        target = TargetConfig(
+            prompt="x", reference_images=["ref.png"], control_images=["ctrl.png"]
+        )
+        assert infer_required_capabilities("out.png", target) == frozenset(
+            {
+                Capability.TEXT_TO_IMAGE,
+                Capability.REFERENCE_IMAGES,
+                Capability.CONTROL_IMAGES,
+            }
+        )
 
     @pytest.mark.parametrize("name", ["doc.md", "doc.txt"])
     def test_text_extensions(self, name: str) -> None:
-        assert infer_target_type(name) is TargetType.TEXT
+        target = TargetConfig(prompt="x")
+        caps = infer_required_capabilities(name, target)
+        assert caps == frozenset({Capability.TEXT_GENERATION})
+
+    def test_text_with_text_inputs(self) -> None:
+        target = TargetConfig(prompt="x", inputs=["data.txt"])
+        assert infer_required_capabilities("out.md", target) == frozenset(
+            {Capability.TEXT_GENERATION}
+        )
+
+    def test_text_with_image_input(self) -> None:
+        target = TargetConfig(prompt="x", inputs=["photo.png"])
+        assert infer_required_capabilities("out.txt", target) == frozenset(
+            {Capability.TEXT_GENERATION, Capability.VISION}
+        )
+
+    def test_text_with_image_reference(self) -> None:
+        target = TargetConfig(prompt="x", reference_images=["ref.jpg"])
+        assert infer_required_capabilities("out.md", target) == frozenset(
+            {Capability.TEXT_GENERATION, Capability.VISION}
+        )
 
     def test_unsupported_extension_raises(self) -> None:
+        target = TargetConfig(prompt="x")
         with pytest.raises(ValueError, match="unsupported extension"):
-            _ = infer_target_type("data.csv")
+            _ = infer_required_capabilities("data.csv", target)
 
     def test_no_extension_raises(self) -> None:
+        target = TargetConfig(prompt="x")
         with pytest.raises(ValueError, match="unsupported extension"):
-            _ = infer_target_type("Makefile")
+            _ = infer_required_capabilities("Makefile", target)
 
 
 class TestResolveModel:
-    """Test model resolution (explicit vs. default)."""
+    """Test model resolution with capability validation."""
 
     def test_explicit_model_wins(self) -> None:
         target = TargetConfig(prompt="x", model="mistral-small-latest")
@@ -138,3 +192,30 @@ class TestResolveModel:
         target = TargetConfig(prompt="x", model="nonexistent-model")
         with pytest.raises(ValueError, match="Unknown model"):
             _ = resolve_model("out.txt", target, Defaults())
+
+    def test_explicit_model_missing_capability_raises(self) -> None:
+        # flux-dev does not support reference images
+        target = TargetConfig(prompt="x", model="flux-dev", reference_images=["r.png"])
+        with pytest.raises(ValueError, match="lacks required capabilities"):
+            _ = resolve_model("out.png", target, Defaults())
+
+    def test_default_fallback_for_reference_images(self) -> None:
+        # Default flux-dev lacks reference_images, should fall back to a capable model
+        target = TargetConfig(prompt="x", reference_images=["r.png"])
+        defaults = Defaults(image_model="flux-dev")
+        result = resolve_model("out.png", target, defaults)
+        assert Capability.REFERENCE_IMAGES in result.capabilities
+
+    def test_default_fallback_for_vision(self) -> None:
+        # Default mistral-large-latest lacks vision, should fall back to a pixtral model
+        target = TargetConfig(prompt="x", inputs=["photo.png"])
+        defaults = Defaults(text_model="mistral-large-latest")
+        result = resolve_model("out.txt", target, defaults)
+        assert Capability.VISION in result.capabilities
+
+    def test_default_preferred_when_capable(self) -> None:
+        # Default flux-2-pro already supports reference_images, should be used directly
+        target = TargetConfig(prompt="x", reference_images=["r.png"])
+        defaults = Defaults(image_model="flux-2-pro")
+        result = resolve_model("out.png", target, defaults)
+        assert result.name == "flux-2-pro"