Fix: Resolve multi-arch tags to platform-specific digests

Co-authored-by: raf <raf@onkernel.com>

Author: cursoragent

lib/images/oci.go

@@ -80,14 +80,21 @@ func (c *ociClient) inspectManifest(ctx context.Context, imageRef string) (strin
 
 	// Use system authentication (reads from ~/.docker/config.json, etc.)
 	// Default retry: only on network errors, max ~1.3s total
-	descriptor, err := remote.Head(ref,
+	// WithPlatform ensures we resolve multi-arch tags/digests to the
+	// platform-specific manifest digest that pullToOCILayout will actually pull.
+	img, err := remote.Image(ref,
 		remote.WithContext(ctx),
-		remote.WithAuthFromKeychain(authn.DefaultKeychain))
+		remote.WithAuthFromKeychain(authn.DefaultKeychain),
+		remote.WithPlatform(currentPlatform()))
 	if err != nil {
-		return "", fmt.Errorf("fetch manifest: %w", wrapRegistryError(err))
+		return "", fmt.Errorf("fetch image manifest: %w", wrapRegistryError(err))
 	}
 
-	return descriptor.Digest.String(), nil
+	d, err := img.Digest()
+	if err != nil {
+		return "", fmt.Errorf("compute image digest: %w", err)
+	}
+	return d.String(), nil
 }
 
 // pullResult contains the metadata and digest from pulling an image

lib/images/oci_inspect_test.go

@@ -0,0 +1,43 @@
+package images
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInspectManifestReturnsPlatformSpecificDigestForMultiArch(t *testing.T) {
+	// alpine:latest is a multi-arch image on Docker Hub; we should resolve the
+	// digest of the platform-specific manifest that we will actually pull.
+	const imageRef = "docker.io/library/alpine:latest"
+
+	client, err := newOCIClient(t.TempDir())
+	require.NoError(t, err)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+
+	gotDigest, err := client.inspectManifest(ctx, imageRef)
+	require.NoError(t, err)
+	require.NotEmpty(t, gotDigest)
+
+	ref, err := name.ParseReference(imageRef)
+	require.NoError(t, err)
+
+	img, err := remote.Image(ref,
+		remote.WithContext(ctx),
+		remote.WithAuthFromKeychain(authn.DefaultKeychain),
+		remote.WithPlatform(currentPlatform()))
+	require.NoError(t, err)
+
+	want, err := img.Digest()
+	require.NoError(t, err)
+
+	require.Equal(t, want.String(), gotDigest)
+}
+