fix: update userMetadata to use KeyValue

Signed-off-by: Christopher Phillips <32073428+spiffcs@users.noreply.github.com>

schema/json/schema-latest.json

@@ -4129,11 +4129,8 @@
           "description": "ShardCount is the number of .safetensors shards for a sharded model (1 for a\nsingle-file model)."
         },
         "userMetadata": {
-          "additionalProperties": {
+          "$ref": "#/$defs/KeyValues",
-            "type": "string"
+          "description": "UserMetadata is the optional \"__metadata__\" map from a .safetensors file header\n(string-to-string key/values set by the producer). Stored as a sorted KeyValues\nslice rather than a Go map so SBOM output is stable across runs."
-          },
-          "type": "object",
-          "description": "UserMetadata is the optional \"__metadata__\" map from a .safetensors file header\n(string-to-string key/values set by the producer)."
         },
         "metadataHash": {
           "type": "string",

syft/pkg/cataloger/ai/parse_safetensors.go

@@ -9,6 +9,8 @@ import (
 	"strings"
 
 	"github.com/cespare/xxhash/v2"
+
+	"github.com/anchore/syft/syft/pkg"
 )
 
 // SafeTensors file format: [8 bytes u64 LE header size] [N bytes JSON header] [tensor data].
@@ -144,6 +146,27 @@ func (h *safeTensorsHeader) metadataHash() string {
 	return fmt.Sprintf("%016x", xxhash.Sum64(b))
 }
 
+// userMetadataKeyValues converts the safetensors __metadata__ map into a
+// KeyValues slice sorted by key. We do not use the convention of returning a
+// nil slice for an empty input — instead, an empty input maps to an empty
+// (length-0, non-nil) KeyValues — so downstream JSON serialization remains
+// stable: `omitempty` drops the field either way.
+func userMetadataKeyValues(m map[string]string) pkg.KeyValues {
+	if len(m) == 0 {
+		return nil
+	}
+	keys := make([]string, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	out := make(pkg.KeyValues, 0, len(keys))
+	for _, k := range keys {
+		out = append(out, pkg.KeyValue{Key: k, Value: m[k]})
+	}
+	return out
+}
+
 // normalizeDType maps a safetensors/torch dtype label to an uppercase quantization
 // shorthand matching conventions used elsewhere in syft (e.g., BF16, F16, I8).
 func normalizeDType(dtype string) string {

syft/pkg/cataloger/ai/parse_safetensors_model.go

@@ -38,7 +38,7 @@ func parseSafeTensorsFile(_ context.Context, resolver file.Resolver, _ *generic.
 		TensorCount:  uint64(len(header.tensors)),
 		Quantization: normalizeDType(header.dominantDType()),
 		ShardCount:   1,
-		UserMetadata: header.metadata,
+		UserMetadata: userMetadataKeyValues(header.metadata),
 		MetadataHash: header.metadataHash(),
 	}
 	if p := header.parameterCount(); p > 0 {

syft/pkg/cataloger/ai/parse_safetensors_oci.go

@@ -261,7 +261,7 @@ func parseSafeTensorsOCILayer(_ context.Context, _ file.Resolver, _ *generic.Env
 		Format:       "safetensors",
 		TensorCount:  uint64(len(header.tensors)),
 		Quantization: normalizeDType(header.dominantDType()),
-		UserMetadata: header.metadata,
+		UserMetadata: userMetadataKeyValues(header.metadata),
 		MetadataHash: header.metadataHash(),
 	}
 	if p := header.parameterCount(); p > 0 {

syft/pkg/cataloger/ai/parse_safetensors_test.go

@@ -74,7 +74,7 @@ func TestSafeTensorsCataloger_singleFile(t *testing.T) {
 				TorchDtype:          "bfloat16",
 				TransformersVersion: "4.40.0",
 				ShardCount:          1,
-				UserMetadata:        userMeta,
+				UserMetadata:        pkg.KeyValues{{Key: "format", Value: "pt"}},
 				MetadataHash:        wantHash,
 			},
 		},
@@ -276,6 +276,7 @@ func TestParseSafeTensorsOCILayer(t *testing.T) {
 		"layer.1.weight": {DType: "BF16", Shape: []int64{16, 16}, DataOffsets: []int64{32768, 33280}},
 	}
 	userMeta := map[string]string{"format": "pt"}
+	wantUserMetadata := pkg.KeyValues{{Key: "format", Value: "pt"}}
 	blob := buildSafeTensorsFile(t, userMeta, tensors)
 	wantHash := (&safeTensorsHeader{metadata: userMeta, tensors: tensors}).metadataHash()
 
@@ -291,7 +292,7 @@ func TestParseSafeTensorsOCILayer(t *testing.T) {
 		assert.Equal(t, "safetensors", md.Format)
 		assert.Equal(t, uint64(2), md.TensorCount)
 		assert.Equal(t, "BF16", md.Quantization)
-		assert.Equal(t, userMeta, md.UserMetadata)
+		assert.Equal(t, wantUserMetadata, md.UserMetadata)
 		assert.Equal(t, wantHash, md.MetadataHash)
 	})
 
@@ -327,7 +328,7 @@ func TestParseSafeTensorsOCILayer(t *testing.T) {
 		// MetadataHash is cleared on absorbed parts by the existing merge processor.
 		// What survives is the rest of the per-shard metadata (UserMetadata, TensorCount,
 		// header-derived Quantization). Confirm those are intact.
-		assert.Equal(t, userMeta, md.Parts[0].UserMetadata)
+		assert.Equal(t, wantUserMetadata, md.Parts[0].UserMetadata)
 		assert.Equal(t, uint64(2), md.Parts[0].TensorCount)
 		assert.Equal(t, "BF16", md.Parts[0].Quantization, "part keeps the normalized header dtype")
 	})
@@ -357,7 +358,7 @@ func TestParseSafeTensorsOCILayer_realFixture(t *testing.T) {
 	assert.Equal(t, uint64(148), md.TensorCount, "nomic-embed-v2-moe 475M ships 148 tensor entries in this shard")
 	assert.Equal(t, "F32", md.Quantization, "every tensor in the captured shard is F32")
 	assert.Equal(t, "475.29M", md.Parameters)
-	assert.Equal(t, map[string]string{"format": "pt"}, md.UserMetadata)
+	assert.Equal(t, pkg.KeyValues{{Key: "format", Value: "pt"}}, md.UserMetadata)
 	// MetadataHash is locked to the exact value the parser produces for this
 	// captured input. The fixture is immutable on disk; if this value changes
 	// either the hash algorithm or the canonicalization changed, both of which

syft/pkg/safetensors.go

@@ -46,8 +46,9 @@ type SafeTensorsModelInfo struct {
 	ShardCount int `json:"shardCount,omitempty" cyclonedx:"shardCount"`
 
 	// UserMetadata is the optional "__metadata__" map from a .safetensors file header
-	// (string-to-string key/values set by the producer).
+	// (string-to-string key/values set by the producer). Stored as a sorted KeyValues
-	UserMetadata map[string]string `json:"userMetadata,omitempty" cyclonedx:"userMetadata"`
+	// slice rather than a Go map so SBOM output is stable across runs.
+	UserMetadata KeyValues `json:"userMetadata,omitempty" cyclonedx:"userMetadata"`
 
 	// MetadataHash is an xxhash of the normalized header metadata, providing a stable
 	// identifier for identical model content across repositories or filenames.