refactor: normalize ModelPack config to Docker format in API responses (#875)

Author: ilopezluna

pkg/distribution/internal/partial/partial.go

@@ -56,10 +56,29 @@ func ConfigFile(i WithRawConfigFile) (*types.ConfigFile, error) {
 }
 
 // Descriptor returns the types.Descriptor for the model.
+// Supports both Docker format (where created is in descriptor.created)
+// and CNCF ModelPack format (where created is in descriptor.createdAt).
 func Descriptor(i WithRawConfigFile) (types.Descriptor, error) {
-	cf, err := ConfigFile(i)
+	raw, err := i.RawConfigFile()
 	if err != nil {
-		return types.Descriptor{}, fmt.Errorf("config file: %w", err)
+		return types.Descriptor{}, fmt.Errorf("get raw config file: %w", err)
+	}
+
+	// ModelPack format: extract createdAt from the ModelPack descriptor.
+	// Docker's types.Descriptor uses "created" (snake_case) while ModelPack
+	// uses "createdAt" (camelCase), so we must parse them separately.
+	if modelpack.IsModelPackConfig(raw) {
+		var mp modelpack.Model
+		if err := json.Unmarshal(raw, &mp); err != nil {
+			return types.Descriptor{}, fmt.Errorf("unmarshal modelpack config: %w", err)
+		}
+		return types.Descriptor{Created: mp.Descriptor.CreatedAt}, nil
+	}
+
+	// Docker format
+	var cf types.ConfigFile
+	if err := json.Unmarshal(raw, &cf); err != nil {
+		return types.Descriptor{}, fmt.Errorf("unmarshal config: %w", err)
 	}
 	return cf.Descriptor, nil
 }

pkg/inference/models/adapter.go

@@ -3,9 +3,29 @@ package models
 import (
 	"fmt"
 
+	"github.com/docker/model-runner/pkg/distribution/modelpack"
 	"github.com/docker/model-runner/pkg/distribution/types"
 )
 
+// normalizeConfig converts a ModelPack config to Docker format types.Config
+// so that the API wire format is always consistent. This ensures clients
+// don't need to understand both config formats.
+func normalizeConfig(cfg types.ModelConfig) types.ModelConfig {
+	if cfg == nil {
+		return nil
+	}
+	if _, ok := cfg.(*modelpack.Model); ok {
+		return &types.Config{
+			Format:       cfg.GetFormat(),
+			Parameters:   cfg.GetParameters(),
+			Quantization: cfg.GetQuantization(),
+			Architecture: cfg.GetArchitecture(),
+			Size:         cfg.GetSize(),
+		}
+	}
+	return cfg
+}
+
 func ToModel(m types.Model) (*Model, error) {
 	desc, err := m.Descriptor()
 	if err != nil {
@@ -31,7 +51,7 @@ func ToModel(m types.Model) (*Model, error) {
 		ID:      id,
 		Tags:    m.Tags(),
 		Created: created,
-		Config:  cfg,
+		Config:  normalizeConfig(cfg),
 	}, nil
 }
 
@@ -62,6 +82,6 @@ func ToModelFromArtifact(artifact types.ModelArtifact) (*Model, error) {
 		ID:      id,
 		Tags:    nil, // Remote models don't have local tags
 		Created: created,
-		Config:  cfg,
+		Config:  normalizeConfig(cfg),
 	}, nil
 }

pkg/inference/models/api_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"testing"
 
+	"github.com/docker/model-runner/pkg/distribution/modelpack"
 	"github.com/docker/model-runner/pkg/distribution/types"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -478,6 +479,100 @@ func TestToOpenAIList(t *testing.T) {
 	assert.Nil(t, result.Data[1].DMR)
 }
 
+func TestNormalizeConfigModelPack(t *testing.T) {
+	// Test that normalizeConfig converts ModelPack config to Docker format.
+	// This simulates what happens in ToModel() when the server normalizes
+	// CNCF configs before serializing the API response.
+	mp := &modelpack.Model{
+		Descriptor: modelpack.ModelDescriptor{
+			Family: "qwen3",
+		},
+		Config: modelpack.ModelConfig{
+			Architecture: "qwen3",
+			Format:       "safetensors",
+			ParamSize:    "0.6B",
+			Quantization: "F16",
+		},
+		ModelFS: modelpack.ModelFS{
+			Type: "layers",
+		},
+	}
+
+	normalized := normalizeConfig(mp)
+	require.NotNil(t, normalized)
+
+	// Should be converted to *types.Config
+	dockerCfg, ok := normalized.(*types.Config)
+	require.True(t, ok, "Normalized config should be *types.Config")
+	assert.Equal(t, types.FormatSafetensors, dockerCfg.Format)
+	assert.Equal(t, "0.6B", dockerCfg.Parameters)
+	assert.Equal(t, "F16", dockerCfg.Quantization)
+	assert.Equal(t, "qwen3", dockerCfg.Architecture)
+	assert.Equal(t, "0.6B", dockerCfg.Size)
+}
+
+func TestNormalizeConfigDocker(t *testing.T) {
+	// Docker format configs should pass through unchanged.
+	dockerCfg := &types.Config{
+		Format:       "gguf",
+		Parameters:   "7B",
+		Quantization: "Q4_K_M",
+		Architecture: "llama",
+		Size:         "7B",
+	}
+
+	normalized := normalizeConfig(dockerCfg)
+	assert.Equal(t, dockerCfg, normalized, "Docker config should pass through unchanged")
+}
+
+func TestNormalizeConfigNil(t *testing.T) {
+	assert.Nil(t, normalizeConfig(nil), "nil config should return nil")
+}
+
+func TestToModelWithModelPackConfig(t *testing.T) {
+	// Test that ToModel properly normalizes a ModelPack config and
+	// the resulting JSON is always in Docker format.
+	mp := &modelpack.Model{
+		Config: modelpack.ModelConfig{
+			Architecture: "qwen3",
+			Format:       "gguf",
+			ParamSize:    "0.6B",
+			Quantization: "Q8_0",
+		},
+	}
+
+	m := &mockModel{
+		id:     "sha256:cncf123456789012",
+		tags:   []string{"aistaging/qwen3-cncf:0.6B"},
+		config: mp,
+		desc:   types.Descriptor{},
+	}
+
+	apiModel, err := ToModel(m)
+	require.NoError(t, err)
+
+	// Config should be normalized to *types.Config
+	dockerCfg, ok := apiModel.Config.(*types.Config)
+	require.True(t, ok, "Config should be normalized to *types.Config")
+	assert.Equal(t, types.FormatGGUF, dockerCfg.Format)
+	assert.Equal(t, "0.6B", dockerCfg.Parameters)
+	assert.Equal(t, "Q8_0", dockerCfg.Quantization)
+	assert.Equal(t, "qwen3", dockerCfg.Architecture)
+	assert.Equal(t, "0.6B", dockerCfg.Size)
+
+	// Verify the JSON output is always Docker format (flat structure)
+	jsonData, err := json.Marshal(apiModel)
+	require.NoError(t, err)
+
+	var unmarshaled Model
+	err = json.Unmarshal(jsonData, &unmarshaled)
+	require.NoError(t, err)
+
+	assert.Equal(t, "0.6B", unmarshaled.Config.GetParameters())
+	assert.Equal(t, "Q8_0", unmarshaled.Config.GetQuantization())
+	assert.Equal(t, "qwen3", unmarshaled.Config.GetArchitecture())
+}
+
 // Helper function to create int32 pointers
 func int32Ptr(i int32) *int32 {
 	return &i