diff --git a/client/client_test.go b/client/client_test.go
index 2cbcef37e..1ccb1c88f 100644
--- a/client/client_test.go
+++ b/client/client_test.go
@@ -44,6 +44,7 @@ import (
 	"github.com/moby/buildkit/session/sshforward/sshprovider"
 	"github.com/moby/buildkit/solver/errdefs"
 	"github.com/moby/buildkit/solver/pb"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/moby/buildkit/util/attestation"
 	binfotypes "github.com/moby/buildkit/util/buildinfo/types"
 	"github.com/moby/buildkit/util/contentutil"
@@ -6377,23 +6378,25 @@ func testExportAttestations(t *testing.T, sb integration.Sandbox) {
 			if err != nil {
 				return nil, err
 			}
-			res.AddInTotoAttestation(pk, &attestation.InTotoAttestation{
-				PredicatePath: "/attestation.json",
-				PredicateType: "https://example.com/attestations/v1.0",
-				Subjects: []attestation.InTotoSubject{
-					&attestation.InTotoSubjectSelf{},
+			res.AddAttestation(pk, &result.InTotoAttestation{
+				PredicateRefKey: "foo",
+				PredicatePath:   "/attestation.json",
+				PredicateType:   "https://example.com/attestations/v1.0",
+				Subjects: []result.InTotoSubject{
+					&result.InTotoSubjectSelf{},
 				},
-			}, refAttest)
-			res.AddInTotoAttestation(pk, &attestation.InTotoAttestation{
-				PredicatePath: "/attestation2.json",
-				PredicateType: "https://example.com/attestations2/v1.0",
-				Subjects: []attestation.InTotoSubject{
-					&attestation.InTotoSubjectRaw{
+			}, map[string]gateway.Reference{"foo": refAttest})
+			res.AddAttestation(pk, &result.InTotoAttestation{
+				PredicateRefKey: "bar",
+				PredicatePath:   "/attestation2.json",
+				PredicateType:   "https://example.com/attestations2/v1.0",
+				Subjects: []result.InTotoSubject{
+					&result.InTotoSubjectRaw{
 						Name:   "/attestation.json",
 						Digest: []digest.Digest{successDigest},
 					},
 				},
-			}, refAttest)
+			}, map[string]gateway.Reference{"bar": refAttest})
 		}
 
 		dt, err := json.Marshal(expPlatforms)
diff --git a/exporter/containerimage/export.go b/exporter/containerimage/export.go
index 6f01de233..18b5f4dfc 100644
--- a/exporter/containerimage/export.go
+++ b/exporter/containerimage/export.go
@@ -195,7 +195,7 @@ func (e *imageExporterInstance) Config() exporter.Config {
 	}
 }
 
-func (e *imageExporterInstance) Export(ctx context.Context, src exporter.Source, sessionID string) (map[string]string, error) {
+func (e *imageExporterInstance) Export(ctx context.Context, src *exporter.Source, sessionID string) (map[string]string, error) {
 	if src.Metadata == nil {
 		src.Metadata = make(map[string][]byte)
 	}
@@ -324,7 +324,7 @@ func (e *imageExporterInstance) Export(ctx context.Context, src exporter.Source,
 	return resp, nil
 }
 
-func (e *imageExporterInstance) pushImage(ctx context.Context, src exporter.Source, sessionID string, targetName string, dgst digest.Digest) error {
+func (e *imageExporterInstance) pushImage(ctx context.Context, src *exporter.Source, sessionID string, targetName string, dgst digest.Digest) error {
 	annotations := map[digest.Digest]map[string]string{}
 	mprovider := contentutil.NewMultiProvider(e.opt.ImageWriter.ContentStore())
 	if src.Ref != nil {
@@ -355,7 +355,7 @@ func (e *imageExporterInstance) pushImage(ctx context.Context, src exporter.Sour
 	return push.Push(ctx, e.opt.SessionManager, sessionID, mprovider, e.opt.ImageWriter.ContentStore(), dgst, targetName, e.insecure, e.opt.RegistryHosts, e.pushByDigest, annotations)
 }
 
-func (e *imageExporterInstance) unpackImage(ctx context.Context, img images.Image, src exporter.Source, s session.Group) (err0 error) {
+func (e *imageExporterInstance) unpackImage(ctx context.Context, img images.Image, src *exporter.Source, s session.Group) (err0 error) {
 	unpackDone := progress.OneOff(ctx, "unpacking to "+img.Name)
 	defer func() {
 		unpackDone(err0)
diff --git a/exporter/containerimage/writer.go b/exporter/containerimage/writer.go
index 0d65b5517..f38752d5f 100644
--- a/exporter/containerimage/writer.go
+++ b/exporter/containerimage/writer.go
@@ -22,6 +22,7 @@ import (
 	"github.com/moby/buildkit/session"
 	"github.com/moby/buildkit/snapshot"
 	"github.com/moby/buildkit/solver"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/moby/buildkit/util/attestation"
 	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/buildkit/util/buildinfo"
@@ -54,7 +55,7 @@ type ImageWriter struct {
 	opt WriterOpt
 }
 
-func (ic *ImageWriter) Commit(ctx context.Context, inp exporter.Source, sessionID string, opts *ImageCommitOpts) (*ocispecs.Descriptor, error) {
+func (ic *ImageWriter) Commit(ctx context.Context, inp *exporter.Source, sessionID string, opts *ImageCommitOpts) (*ocispecs.Descriptor, error) {
 	platformsBytes, ok := inp.Metadata[exptypes.ExporterPlatformsKey]
 
 	if len(inp.Refs) > 0 && !ok {
@@ -248,7 +249,7 @@ func (ic *ImageWriter) exportLayers(ctx context.Context, refCfg cacheconfig.RefC
 	return out, err
 }
 
-func (ic *ImageWriter) extractAttestations(ctx context.Context, s session.Group, desc *ocispecs.Descriptor, refs map[string]cache.ImmutableRef, attestations []attestation.Attestation) ([]intoto.Statement, error) {
+func (ic *ImageWriter) extractAttestations(ctx context.Context, s session.Group, desc *ocispecs.Descriptor, refs map[string]cache.ImmutableRef, attestations []result.Attestation) ([]intoto.Statement, error) {
 	eg, ctx := errgroup.WithContext(ctx)
 	statements := make([]intoto.Statement, len(attestations))
 
@@ -260,7 +261,7 @@ func (ic *ImageWriter) extractAttestations(ctx context.Context, s session.Group,
 		i, att := i, att
 		eg.Go(func() error {
 			switch att := att.(type) {
-			case *attestation.InTotoAttestation:
+			case *result.InTotoAttestation:
 				ref, ok := refs[att.PredicateRefKey]
 				if !ok {
 					return errors.Errorf("key %s not found in refs map", att.PredicateRefKey)
@@ -293,12 +294,12 @@ func (ic *ImageWriter) extractAttestations(ctx context.Context, s session.Group,
 				}
 				for _, subject := range att.Subjects {
 					switch subject2 := subject.(type) {
-					case *attestation.InTotoSubjectSelf:
+					case *result.InTotoSubjectSelf:
 						statements[i].Subject = append(statements[i].Subject, intoto.Subject{
 							Name:   "_",
-							Digest: attestation.DigestToDigestMap(desc.Digest),
+							Digest: result.DigestToDigestMap(desc.Digest),
 						})
-					case *attestation.InTotoSubjectRaw:
+					case *result.InTotoSubjectRaw:
 						statements[i].Subject = append(statements[i].Subject, intoto.Subject{
 							Name:   subject2.Name,
 							Digest: subject2.DigestMap(),
diff --git a/exporter/exporter.go b/exporter/exporter.go
index 925c13c21..284cb5615 100644
--- a/exporter/exporter.go
+++ b/exporter/exporter.go
@@ -4,10 +4,12 @@ import (
 	"context"
 
 	"github.com/moby/buildkit/cache"
-	"github.com/moby/buildkit/util/attestation"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/moby/buildkit/util/compression"
 )
 
+type Source = result.Result[cache.ImmutableRef]
+
 type Exporter interface {
 	Resolve(context.Context, map[string]string) (ExporterInstance, error)
 }
@@ -15,16 +17,9 @@ type Exporter interface {
 type ExporterInstance interface {
 	Name() string
 	Config() Config
-	Export(ctx context.Context, src Source, sessionID string) (map[string]string, error)
+	Export(ctx context.Context, src *Source, sessionID string) (map[string]string, error)
 }
 
 type Config struct {
 	Compression compression.Config
 }
-
-type Source struct {
-	Ref          cache.ImmutableRef
-	Refs         map[string]cache.ImmutableRef
-	Metadata     map[string][]byte
-	Attestations map[string][]attestation.Attestation
-}
diff --git a/exporter/local/export.go b/exporter/local/export.go
index a3cd94062..fbd727d87 100644
--- a/exporter/local/export.go
+++ b/exporter/local/export.go
@@ -52,7 +52,7 @@ func (e *localExporter) Config() exporter.Config {
 	return exporter.Config{}
 }
 
-func (e *localExporterInstance) Export(ctx context.Context, inp exporter.Source, sessionID string) (map[string]string, error) {
+func (e *localExporterInstance) Export(ctx context.Context, inp *exporter.Source, sessionID string) (map[string]string, error) {
 	timeoutCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
 	defer cancel()
 
diff --git a/exporter/oci/export.go b/exporter/oci/export.go
index c2ef4b3ab..047d9d5a8 100644
--- a/exporter/oci/export.go
+++ b/exporter/oci/export.go
@@ -93,7 +93,7 @@ func (e *imageExporterInstance) Config() exporter.Config {
 	}
 }
 
-func (e *imageExporterInstance) Export(ctx context.Context, src exporter.Source, sessionID string) (map[string]string, error) {
+func (e *imageExporterInstance) Export(ctx context.Context, src *exporter.Source, sessionID string) (map[string]string, error) {
 	if e.opt.Variant == VariantDocker && len(src.Refs) > 0 {
 		return nil, errors.Errorf("docker exporter does not currently support exporting manifest lists")
 	}
diff --git a/exporter/tar/export.go b/exporter/tar/export.go
index 806dbef7f..82af4404f 100644
--- a/exporter/tar/export.go
+++ b/exporter/tar/export.go
@@ -70,7 +70,7 @@ func (e *localExporterInstance) Config() exporter.Config {
 	return exporter.Config{}
 }
 
-func (e *localExporterInstance) Export(ctx context.Context, inp exporter.Source, sessionID string) (map[string]string, error) {
+func (e *localExporterInstance) Export(ctx context.Context, inp *exporter.Source, sessionID string) (map[string]string, error) {
 	var defers []func()
 
 	defer func() {
diff --git a/frontend/frontend.go b/frontend/frontend.go
index dedda54c6..2409891cb 100644
--- a/frontend/frontend.go
+++ b/frontend/frontend.go
@@ -6,10 +6,14 @@ import (
 	"github.com/moby/buildkit/client/llb"
 	gw "github.com/moby/buildkit/frontend/gateway/client"
 	"github.com/moby/buildkit/session"
+	"github.com/moby/buildkit/solver"
 	"github.com/moby/buildkit/solver/pb"
+	"github.com/moby/buildkit/solver/result"
 	digest "github.com/opencontainers/go-digest"
 )
 
+type Result = result.Result[solver.ResultProxy]
+
 type Frontend interface {
 	Solve(ctx context.Context, llb FrontendLLBBridge, opt map[string]string, inputs map[string]*pb.Definition, sid string, sm *session.Manager) (*Result, error)
 }
diff --git a/frontend/gateway/client/client.go b/frontend/gateway/client/client.go
index 61bc018ff..fe7752238 100644
--- a/frontend/gateway/client/client.go
+++ b/frontend/gateway/client/client.go
@@ -7,12 +7,21 @@ import (
 
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/solver/pb"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/moby/buildkit/util/apicaps"
 	digest "github.com/opencontainers/go-digest"
 	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
 	fstypes "github.com/tonistiigi/fsutil/types"
 )
 
+type Result = result.Result[Reference]
+
+type BuildFunc func(context.Context, Client) (*Result, error)
+
+func NewResult() *Result {
+	return &Result{}
+}
+
 type Client interface {
 	Solve(ctx context.Context, req SolveRequest) (*Result, error)
 	ResolveImageConfig(ctx context.Context, ref string, opt llb.ResolveImageConfigOpt) (digest.Digest, []byte, error)
diff --git a/frontend/gateway/client/result.go b/frontend/gateway/client/result.go
deleted file mode 100644
index 845e3ad58..000000000
--- a/frontend/gateway/client/result.go
+++ /dev/null
@@ -1,68 +0,0 @@
-package client
-
-import (
-	"context"
-	"sync"
-
-	"github.com/moby/buildkit/identity"
-	"github.com/moby/buildkit/util/attestation"
-	"github.com/pkg/errors"
-)
-
-type BuildFunc func(context.Context, Client) (*Result, error)
-
-type Result struct {
-	mu           sync.Mutex
-	Ref          Reference
-	Refs         map[string]Reference
-	Metadata     map[string][]byte
-	Attestations map[string][]attestation.Attestation
-}
-
-func NewResult() *Result {
-	return &Result{}
-}
-
-func (r *Result) AddMeta(k string, v []byte) {
-	r.mu.Lock()
-	if r.Metadata == nil {
-		r.Metadata = map[string][]byte{}
-	}
-	r.Metadata[k] = v
-	r.mu.Unlock()
-}
-
-func (r *Result) AddRef(k string, ref Reference) {
-	r.mu.Lock()
-	if r.Refs == nil {
-		r.Refs = map[string]Reference{}
-	}
-	r.Refs[k] = ref
-	r.mu.Unlock()
-}
-
-func (r *Result) AddInTotoAttestation(k string, v *attestation.InTotoAttestation, predicateRef Reference) {
-	r.mu.Lock()
-	if r.Attestations == nil {
-		r.Attestations = map[string][]attestation.Attestation{}
-	}
-	v.PredicateRefKey = "attestation:" + identity.NewID()
-	r.Refs[v.PredicateRefKey] = predicateRef
-	r.Attestations[k] = append(r.Attestations[k], v)
-	r.mu.Unlock()
-}
-
-func (r *Result) SetRef(ref Reference) {
-	r.Ref = ref
-}
-
-func (r *Result) SingleRef() (Reference, error) {
-	r.mu.Lock()
-	defer r.mu.Unlock()
-
-	if r.Refs != nil && r.Ref == nil {
-		return nil, errors.Errorf("invalid map result")
-	}
-
-	return r.Ref, nil
-}
diff --git a/frontend/gateway/forwarder/forward.go b/frontend/gateway/forwarder/forward.go
index e95449870..e98bf6ed7 100644
--- a/frontend/gateway/forwarder/forward.go
+++ b/frontend/gateway/forwarder/forward.go
@@ -17,6 +17,7 @@ import (
 	"github.com/moby/buildkit/solver/errdefs"
 	llberrdefs "github.com/moby/buildkit/solver/llbsolver/errdefs"
 	opspb "github.com/moby/buildkit/solver/pb"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/moby/buildkit/util/apicaps"
 	"github.com/moby/buildkit/worker"
 	digest "github.com/opencontainers/go-digest"
@@ -66,27 +67,19 @@ func (c *bridgeClient) Solve(ctx context.Context, req client.SolveRequest) (*cli
 		return nil, c.wrapSolveError(err)
 	}
 
-	cRes := &client.Result{}
 	c.mu.Lock()
-	for k, r := range res.Refs {
+	cRes, err := result.ConvertResult(res, func(r solver.ResultProxy) (client.Reference, error) {
 		rr, err := c.newRef(r, session.NewGroup(c.sid))
 		if err != nil {
 			return nil, err
 		}
 		c.refs = append(c.refs, rr)
-		cRes.AddRef(k, rr)
-	}
-	if r := res.Ref; r != nil {
-		rr, err := c.newRef(r, session.NewGroup(c.sid))
-		if err != nil {
-			return nil, err
-		}
-		c.refs = append(c.refs, rr)
-		cRes.SetRef(rr)
-	}
+		return rr, nil
+	})
 	c.mu.Unlock()
-	cRes.Metadata = res.Metadata
-	cRes.Attestations = res.Attestations
+	if err != nil {
+		return nil, err
+	}
 
 	return cRes, nil
 }
@@ -185,28 +178,16 @@ func (c *bridgeClient) toFrontendResult(r *client.Result) (*frontend.Result, err
 		return nil, nil
 	}
 
-	res := &frontend.Result{}
-
-	if r.Refs != nil {
-		res.Refs = make(map[string]solver.ResultProxy, len(r.Refs))
-		for k, r := range r.Refs {
-			rr, ok := r.(*ref)
-			if !ok {
-				return nil, errors.Errorf("invalid reference type for forward %T", r)
-			}
-			res.Refs[k] = rr.acquireResultProxy()
-		}
-	}
-	if r := r.Ref; r != nil {
+	res, err := result.ConvertResult(r, func(r client.Reference) (solver.ResultProxy, error) {
 		rr, ok := r.(*ref)
 		if !ok {
 			return nil, errors.Errorf("invalid reference type for forward %T", r)
 		}
-		res.Ref = rr.acquireResultProxy()
+		return rr.acquireResultProxy(), nil
+	})
+	if err != nil {
+		return nil, err
 	}
-	res.Metadata = r.Metadata
-	res.Attestations = r.Attestations
-
 	return res, nil
 }
 
diff --git a/frontend/gateway/gateway.go b/frontend/gateway/gateway.go
index 598977c21..2154782b7 100644
--- a/frontend/gateway/gateway.go
+++ b/frontend/gateway/gateway.go
@@ -38,7 +38,6 @@ import (
 	llberrdefs "github.com/moby/buildkit/solver/llbsolver/errdefs"
 	opspb "github.com/moby/buildkit/solver/pb"
 	"github.com/moby/buildkit/util/apicaps"
-	"github.com/moby/buildkit/util/attestation"
 	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/buildkit/util/buildinfo"
 	"github.com/moby/buildkit/util/grpcerrors"
@@ -707,7 +706,7 @@ func (lbf *llbBridgeForwarder) Solve(ctx context.Context, req *pb.SolveRequest)
 	}
 
 	if res.Attestations != nil {
-		attestations := map[string]*pb.Attestations{}
+		pbRes.Attestations = map[string]*pb.Attestations{}
 		for k, atts := range res.Attestations {
 			for _, att := range atts {
 				pbAtt, err := pb.ToAttestationPB(att)
@@ -715,13 +714,12 @@ func (lbf *llbBridgeForwarder) Solve(ctx context.Context, req *pb.SolveRequest)
 					return nil, err
 				}
 
-				if attestations[k] == nil {
-					attestations[k] = &pb.Attestations{}
+				if pbRes.Attestations[k] == nil {
+					pbRes.Attestations[k] = &pb.Attestations{}
 				}
-				attestations[k].Attestation = append(attestations[k].Attestation, pbAtt)
+				pbRes.Attestations[k].Attestation = append(pbRes.Attestations[k].Attestation, pbAtt)
 			}
 		}
-		pbRes.Attestations = attestations
 	}
 
 	lbf.mu.Unlock()
@@ -890,44 +888,39 @@ func (lbf *llbBridgeForwarder) Return(ctx context.Context, in *pb.ReturnRequest)
 		if err != nil {
 			return nil, err
 		}
-		r.Ref = ref
+		r.SetRef(ref)
 	case *pb.Result_RefsDeprecated:
-		m := map[string]solver.ResultProxy{}
 		for k, id := range res.RefsDeprecated.Refs {
 			ref, err := lbf.cloneRef(id)
 			if err != nil {
 				return nil, err
 			}
-			m[k] = ref
+			r.AddRef(k, ref)
 		}
-		r.Refs = m
 	case *pb.Result_Ref:
 		ref, err := lbf.cloneRef(res.Ref.Id)
 		if err != nil {
 			return nil, err
 		}
-		r.Ref = ref
+		r.SetRef(ref)
 	case *pb.Result_Refs:
-		m := map[string]solver.ResultProxy{}
 		for k, ref := range res.Refs.Refs {
 			ref, err := lbf.cloneRef(ref.Id)
 			if err != nil {
 				return nil, err
 			}
-			m[k] = ref
+			r.AddRef(k, ref)
 		}
-		r.Refs = m
 	}
 
 	if in.Result.Attestations != nil {
-		r.Attestations = map[string][]attestation.Attestation{}
 		for k, pbAtts := range in.Result.Attestations {
 			for _, pbAtt := range pbAtts.Attestation {
 				att, err := pb.FromAttestationPB(pbAtt)
 				if err != nil {
 					return nil, err
 				}
-				r.Attestations[k] = append(r.Attestations[k], att)
+				r.AddAttestation(k, att, nil)
 			}
 		}
 	}
diff --git a/frontend/gateway/grpcclient/client.go b/frontend/gateway/grpcclient/client.go
index fad0a55e6..3013992d6 100644
--- a/frontend/gateway/grpcclient/client.go
+++ b/frontend/gateway/grpcclient/client.go
@@ -21,7 +21,6 @@ import (
 	"github.com/moby/buildkit/identity"
 	opspb "github.com/moby/buildkit/solver/pb"
 	"github.com/moby/buildkit/util/apicaps"
-	"github.com/moby/buildkit/util/attestation"
 	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/buildkit/util/grpcerrors"
 	"github.com/moby/sys/signal"
@@ -116,7 +115,7 @@ func (c *grpcClient) Run(ctx context.Context, f client.BuildFunc) (retError erro
 			req := &pb.ReturnRequest{}
 			if retError == nil {
 				if res == nil {
-					res = &client.Result{}
+					res = client.NewResult()
 				}
 				pbRes := &pb.Result{
 					Metadata: res.Metadata,
@@ -422,7 +421,7 @@ func (c *grpcClient) Solve(ctx context.Context, creq client.SolveRequest) (res *
 		return nil, err
 	}
 
-	res = &client.Result{}
+	res = client.NewResult()
 	if resp.Result == nil {
 		if id := resp.Ref; id != "" {
 			c.requests[id] = req
@@ -465,14 +464,13 @@ func (c *grpcClient) Solve(ctx context.Context, creq client.SolveRequest) (res *
 		}
 
 		if resp.Result.Attestations != nil {
-			res.Attestations = map[string][]attestation.Attestation{}
 			for p, as := range resp.Result.Attestations {
 				for _, a := range as.Attestation {
 					att, err := pb.FromAttestationPB(a)
 					if err != nil {
 						return nil, err
 					}
-					res.Attestations[p] = append(res.Attestations[p], att)
+					res.AddAttestation(p, att, nil)
 				}
 			}
 		}
diff --git a/frontend/gateway/pb/attestation.go b/frontend/gateway/pb/attestation.go
index 7afe155ae..838d14e3d 100644
--- a/frontend/gateway/pb/attestation.go
+++ b/frontend/gateway/pb/attestation.go
@@ -1,17 +1,17 @@
 package moby_buildkit_v1_frontend //nolint:revive
 
 import (
-	"github.com/moby/buildkit/util/attestation"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/pkg/errors"
 )
 
-func ToAttestationPB(a attestation.Attestation) (*Attestations_Attestation, error) {
+func ToAttestationPB(a result.Attestation) (*Attestations_Attestation, error) {
 	switch a := a.(type) {
-	case *attestation.InTotoAttestation:
+	case *result.InTotoAttestation:
 		subjects := []*InToto_Subject{}
 		for _, subject := range a.Subjects {
 			switch s := subject.(type) {
-			case *attestation.InTotoSubjectRaw:
+			case *result.InTotoSubjectRaw:
 				subjects = append(subjects, &InToto_Subject{
 					Subject: &InToto_Subject_Raw{
 						Raw: &InToto_Subject_RawSubject{
@@ -20,7 +20,7 @@ func ToAttestationPB(a attestation.Attestation) (*Attestations_Attestation, erro
 						},
 					},
 				})
-			case *attestation.InTotoSubjectSelf:
+			case *result.InTotoSubjectSelf:
 				subjects = append(subjects, &InToto_Subject{
 					Subject: &InToto_Subject_Self{
 						Self: &InToto_Subject_SelfSubject{},
@@ -41,29 +41,29 @@ func ToAttestationPB(a attestation.Attestation) (*Attestations_Attestation, erro
 			Attestation: &Attestations_Attestation_Intoto{intoto},
 		}, nil
 	default:
-		return nil, errors.Errorf("unknown attestation type %T", a)
+		return nil, errors.Errorf("unknown result type %T", a)
 	}
 }
 
-func FromAttestationPB(a *Attestations_Attestation) (attestation.Attestation, error) {
+func FromAttestationPB(a *Attestations_Attestation) (result.Attestation, error) {
 	switch a := a.Attestation.(type) {
 	case *Attestations_Attestation_Intoto:
-		subjects := []attestation.InTotoSubject{}
+		subjects := []result.InTotoSubject{}
 		for _, pbSubject := range a.Intoto.Subjects {
 			switch pbSubject := pbSubject.Subject.(type) {
 			case *InToto_Subject_Raw:
-				subjects = append(subjects, &attestation.InTotoSubjectRaw{
+				subjects = append(subjects, &result.InTotoSubjectRaw{
 					Name:   pbSubject.Raw.Name,
 					Digest: pbSubject.Raw.Digest,
 				})
 			case *InToto_Subject_Self:
-				subjects = append(subjects, &attestation.InTotoSubjectSelf{})
+				subjects = append(subjects, &result.InTotoSubjectSelf{})
 			default:
 				return nil, errors.Errorf("unknown in toto subject type %T", pbSubject)
 			}
 		}
 
-		return &attestation.InTotoAttestation{
+		return &result.InTotoAttestation{
 			PredicateType:   a.Intoto.PredicateType,
 			PredicatePath:   a.Intoto.PredicatePath,
 			PredicateRefKey: a.Intoto.PredicateRefKey,
diff --git a/frontend/result.go b/frontend/result.go
deleted file mode 100644
index a85bd46a4..000000000
--- a/frontend/result.go
+++ /dev/null
@@ -1,27 +0,0 @@
-package frontend
-
-import (
-	"github.com/moby/buildkit/solver"
-	"github.com/moby/buildkit/util/attestation"
-)
-
-type Result struct {
-	Ref          solver.ResultProxy
-	Refs         map[string]solver.ResultProxy
-	Metadata     map[string][]byte
-	Attestations map[string][]attestation.Attestation
-}
-
-func (r *Result) EachRef(fn func(solver.ResultProxy) error) (err error) {
-	if r.Ref != nil {
-		err = fn(r.Ref)
-	}
-	for _, r := range r.Refs {
-		if r != nil {
-			if err1 := fn(r); err1 != nil && err == nil {
-				err = err1
-			}
-		}
-	}
-	return err
-}
diff --git a/go.mod b/go.mod
index 2fffcc88c..6622bc87d 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/moby/buildkit
 
-go 1.17
+go 1.18
 
 require (
 	github.com/Microsoft/go-winio v0.5.2
diff --git a/go.sum b/go.sum
index 5cdceec40..303f1f0af 100644
--- a/go.sum
+++ b/go.sum
@@ -245,7 +245,6 @@ github.com/bgentry/speakeasy v0.1.0/go.mod h1:+zsyZBPWlz7T6j88CTgSN5bM796AkVf0kB
 github.com/bitly/go-simplejson v0.5.0/go.mod h1:cXHtHw4XUPsvGaxgjIAn8PhEWG9NfngEKAMDJEczWVA=
 github.com/bits-and-blooms/bitset v1.2.0/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
 github.com/bketelsen/crypt v0.0.3-0.20200106085610-5cbc8cc4026c/go.mod h1:MKsuJmJgSg28kpZDP6UIiPt0e0Oz0kqKNGyRaWEPv84=
-github.com/bketelsen/crypt v0.0.4/go.mod h1:aI6NrJ0pMGgvZKL1iVgXLnfIFJtfV+bKCoqOes/6LfM=
 github.com/blakesmith/ar v0.0.0-20190502131153-809d4375e1fb/go.mod h1:PkYb9DJNAwrSvRx5DYA+gUcOIgTGVMNkfSCbZM8cWpI=
 github.com/blang/semver v3.1.0+incompatible/go.mod h1:kRBLl5iJ+tD4TcOOxsy/0fnwebNt5EWlYSAyrTnjyyk=
 github.com/blang/semver v3.5.0+incompatible/go.mod h1:kRBLl5iJ+tD4TcOOxsy/0fnwebNt5EWlYSAyrTnjyyk=
@@ -272,7 +271,6 @@ github.com/census-instrumentation/opencensus-proto v0.2.0/go.mod h1:f6KPmirojxKA
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/certifi/gocertifi v0.0.0-20191021191039-0944d244cd40/go.mod h1:sGbDF6GwGcLpkNXPUTkMRoywsNa/ol15pxFe6ERfguA=
 github.com/certifi/gocertifi v0.0.0-20200922220541-2c3bb06c6054/go.mod h1:sGbDF6GwGcLpkNXPUTkMRoywsNa/ol15pxFe6ERfguA=
-github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cespare/xxhash/v2 v2.1.1/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cespare/xxhash/v2 v2.1.2 h1:YRXhKfTDauu4ajMg1TPgFO5jnlC2HCbmLXMcTG5cbYE=
@@ -305,7 +303,6 @@ github.com/cockroachdb/errors v1.2.4/go.mod h1:rQD95gz6FARkaKkQXUksEje/d9a6wBJoC
 github.com/cockroachdb/logtags v0.0.0-20190617123548-eb05cc24525f/go.mod h1:i/u985jwjWRlyHXQbwatDASoW0RMlZ/3i9yJHE2xLkI=
 github.com/codahale/hdrhistogram v0.0.0-20160425231609-f8ad88b59a58/go.mod h1:sE/e/2PUdi/liOCUjSTXgM1o87ZssimdTWN964YiIeI=
 github.com/codahale/rfc6979 v0.0.0-20141003034818-6a90f24967eb h1:EDmT6Q9Zs+SbUoc7Ik9EfrFqcylYqgPZ9ANSbTAntnE=
-github.com/codahale/rfc6979 v0.0.0-20141003034818-6a90f24967eb/go.mod h1:ZjrT6AXHbDs86ZSdt/osfBi5qfexBrKUdONk989Wnk4=
 github.com/containerd/aufs v0.0.0-20200908144142-dab0cbea06f4/go.mod h1:nukgQABAEopAHvB6j7cnP5zJ+/3aVcE7hCYqvIwAHyE=
 github.com/containerd/aufs v0.0.0-20201003224125-76a6863f2989/go.mod h1:AkGGQs9NM2vtYHaUen+NljV0/baGCAPELGm2q9ZXpWU=
 github.com/containerd/aufs v0.0.0-20210316121734-20793ff83c97/go.mod h1:kL5kd6KM5TzQjR79jljyi4olc1Vrx6XBlcyj3gNv2PU=
@@ -442,7 +439,6 @@ github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3Ee
 github.com/coreos/go-systemd v0.0.0-20161114122254-48702e0da86b/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd v0.0.0-20180511133405-39ca1b05acc7/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd v0.0.0-20181012123002-c6f51f82210d/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
-github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e h1:Wf6HqHfScWJN9/ZjdUKyjop4mf3Qdd+1TvvltAvM3m8=
 github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/go-systemd/v22 v22.0.0/go.mod h1:xO0FLkIi5MaZafQlIrOotqXZ90ih+1atmu1JpKERPPk=
 github.com/coreos/go-systemd/v22 v22.1.0/go.mod h1:xO0FLkIi5MaZafQlIrOotqXZ90ih+1atmu1JpKERPPk=
@@ -451,7 +447,6 @@ github.com/coreos/go-systemd/v22 v22.3.2/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSV
 github.com/coreos/pkg v0.0.0-20160727233714-3ac0863d7acf/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/coreos/pkg v0.0.0-20180108230652-97fdf19511ea/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
-github.com/cpuguy83/go-md2man v1.0.10 h1:BSKMNlYxDvnunlTymqtgONjNnaRV1sTpcovwwjF22jk=
 github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwcJI5acqYI6dE=
 github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
 github.com/cpuguy83/go-md2man/v2 v2.0.0 h1:EoUDS0afbrsXAZ9YQ9jdu/mZ2sXgT1/2yyNng4PGlyM=
@@ -798,7 +793,6 @@ github.com/grpc-ecosystem/grpc-gateway v1.9.5/go.mod h1:vNeuVxBJEsws4ogUvrchl83t
 github.com/grpc-ecosystem/grpc-gateway v1.16.0 h1:gmcG1KaJ57LophUzW0Hy8NmPhnMZb4M0+kPpLofRdBo=
 github.com/grpc-ecosystem/grpc-gateway v1.16.0/go.mod h1:BDjrQk3hbvj6Nolgz8mAMFbcEtjT1g+wF4CSlocrBnw=
 github.com/grpc-ecosystem/grpc-opentracing v0.0.0-20180507213350-8e809c8a8645/go.mod h1:6iZfnjpejD4L/4DwD7NryNaJyCQdzwWwH2MWhCA90Kw=
-github.com/hanwen/go-fuse v1.0.0 h1:GxS9Zrn6c35/BnfiVsZVWmsG803xwE7eVRDvcf/BEVc=
 github.com/hanwen/go-fuse v1.0.0/go.mod h1:unqXarDXqzAk0rt98O2tVndEPIpUgLD9+rwFisZH3Ok=
 github.com/hanwen/go-fuse/v2 v2.0.3/go.mod h1:0EQM6aH2ctVpvZ6a+onrQ/vaykxh2GH7hy3e13vzTUY=
 github.com/hanwen/go-fuse/v2 v2.1.1-0.20220112183258-f57e95bda82d h1:ibbzF2InxMOS+lLCphY9PHNKPURDUBNKaG6ErSq8gJQ=
@@ -909,7 +903,6 @@ github.com/klauspost/cpuid v1.2.0/go.mod h1:Pj4uuM528wm8OyEC2QMXAi2YiTZ96dNQPGgo
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/konsorten/go-windows-terminal-sequences v1.0.2/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/konsorten/go-windows-terminal-sequences v1.0.3/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
-github.com/kr/fs v0.1.0/go.mod h1:FFnZGqtBN9Gxj7eW1uZ42v5BccTP0vu6NEaFoC2HwRg=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pretty v0.2.0/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
@@ -931,7 +924,6 @@ github.com/linuxkit/virtsock v0.0.0-20201010232012-f8cee7dfc7a3/go.mod h1:3r6x7q
 github.com/logrusorgru/aurora v0.0.0-20181002194514-a7b3b318ed4e/go.mod h1:7rIyQOR62GCctdiQpZ/zOJlFyk6y+94wXzv6RNZgaR4=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/magiconair/properties v1.8.1/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
-github.com/magiconair/properties v1.8.5/go.mod h1:y3VJvCyxH9uVvJTWEGAELF3aiYNyPKd5NZ3oSwXrF60=
 github.com/mailru/easyjson v0.0.0-20160728113105-d5b7844b561a/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
 github.com/mailru/easyjson v0.0.0-20190614124828-94de47d64c63/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
 github.com/mailru/easyjson v0.0.0-20190626092158-b2ccc519800e/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
@@ -977,7 +969,6 @@ github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrk
 github.com/mitchellh/go-ps v0.0.0-20190716172923-621e5597135b/go.mod h1:r1VsdOzOPt1ZSrGZWFoNhsAedKnEd6r9Np1+5blZCWk=
 github.com/mitchellh/go-testing-interface v1.0.0/go.mod h1:kRemZodwjscx+RGhAo8eIhFbs2+BFgRtFPeD/KE+zxI=
 github.com/mitchellh/gox v0.4.0/go.mod h1:Sd9lOJ0+aimLBi73mGofS1ycjY8lL3uZM3JPS42BGNg=
-github.com/mitchellh/hashstructure v1.0.0 h1:ZkRJX1CyOoTkar7p/mLS5TZU4nJ1Rn/F8u9dGS02Q3Y=
 github.com/mitchellh/hashstructure v1.0.0/go.mod h1:QjSHrPWS+BGUVBYkbTZWEnOh3G1DutKwClXU/ABz6AQ=
 github.com/mitchellh/hashstructure/v2 v2.0.2 h1:vGKWl0YJqUNxE8d+h8f6NJLcCJrgbhC4NcD46KavDd4=
 github.com/mitchellh/hashstructure/v2 v2.0.2/go.mod h1:MG3aRVU/N29oo/V/IhBX8GR/zz4kQkprJgF2EVszyDE=
@@ -985,7 +976,6 @@ github.com/mitchellh/iochan v1.0.0/go.mod h1:JwYml1nuB7xOzsp52dPpHFffvOCDupsG0Qu
 github.com/mitchellh/mapstructure v0.0.0-20160808181253-ca63d7c062ee/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
 github.com/mitchellh/mapstructure v1.1.2/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
 github.com/mitchellh/mapstructure v1.3.1/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
-github.com/mitchellh/mapstructure v1.4.1/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
 github.com/mitchellh/osext v0.0.0-20151018003038-5e2d6d41470f/go.mod h1:OkQIRizQZAeMln+1tSwduZz7+Af5oFlKirV/MSYes2A=
 github.com/moby/buildkit v0.8.1/go.mod h1:/kyU1hKy/aYCuP39GZA9MaKioovHku57N6cqlKZIaiQ=
 github.com/moby/locker v1.0.1 h1:fOXqR41zeveg4fFODix+1Ch4mj/gT0NE1XJbp/epuBg=
@@ -1130,7 +1120,6 @@ github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/profile v1.5.0 h1:042Buzk+NhDI+DeSAA62RwJL8VAuZUMQZUjCsRz1Mug=
 github.com/pkg/profile v1.5.0/go.mod h1:qBsxPvzyUincmltOk6iyRVxHYg4adc0OFOv72ZdLa18=
-github.com/pkg/sftp v1.10.1/go.mod h1:lYOWFsE0bwd1+KfKJaKeuokY15vzFx25BLbzYYoAxZI=
 github.com/pmezard/go-difflib v0.0.0-20151028094244-d8ed2627bdf0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
@@ -1195,7 +1184,6 @@ github.com/rogpeppe/go-internal v1.5.2/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTE
 github.com/rs/xid v1.2.1/go.mod h1:+uKXf+4Djp6Md1KODXJxgGQPKngRmWyn10oCKFzNHOQ=
 github.com/rs/xid v1.4.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
 github.com/rubiojr/go-vhd v0.0.0-20160810183302-0bfd3b39853c/go.mod h1:DM5xW0nvfNNm2uytzsvhI3OnX8uzaRAg8UX/CnDqbto=
-github.com/russross/blackfriday v1.5.2 h1:HyvC0ARfnZBqnXwABFeSZHpKvJHJJfPz81GNueLj0oo=
 github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR/rfWxYHBV53g=
 github.com/russross/blackfriday/v2 v2.0.1 h1:lPqVAte+HuHNfhJ/0LC98ESWRz8afy9tM/0RK8m9o+Q=
 github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
@@ -1248,7 +1236,6 @@ github.com/sourcegraph/go-diff v0.5.3/go.mod h1:v9JDtjCE4HHHCZGId75rg8gkKKa98RVj
 github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=
 github.com/spf13/afero v1.2.2/go.mod h1:9ZxEEn6pIJ8Rxe320qSDBk6AsU0r9pR7Q4OcevTdifk=
-github.com/spf13/afero v1.6.0/go.mod h1:Ai8FlHk4v/PARR026UzYexafAt9roJ7LcLMAmO6Z93I=
 github.com/spf13/cast v1.3.0/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
 github.com/spf13/cast v1.3.1/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
 github.com/spf13/cobra v0.0.2-0.20171109065643-2da4a54c5cee/go.mod h1:1l0Ry5zgKvJasoi3XT1TypsSe7PqH0Sj9dhYf7v3XqQ=
@@ -1256,7 +1243,6 @@ github.com/spf13/cobra v0.0.3/go.mod h1:1l0Ry5zgKvJasoi3XT1TypsSe7PqH0Sj9dhYf7v3
 github.com/spf13/cobra v0.0.5/go.mod h1:3K3wKZymM7VvHMDS9+Akkh4K60UwM26emMESw8tLCHU=
 github.com/spf13/cobra v1.0.0/go.mod h1:/6GTrnGXV9HjY+aR4k0oJ5tcvakLuG6EuKReYlHNrgE=
 github.com/spf13/cobra v1.1.3/go.mod h1:pGADOWyqRD/YMrPZigI/zbliZ2wVD/23d+is3pSWzOo=
-github.com/spf13/cobra v1.2.1/go.mod h1:ExllRjgxM/piMAM+3tAZvg8fsklGAf3tPfi+i8t68Nk=
 github.com/spf13/jwalterweatherman v1.0.0/go.mod h1:cQK4TGJAtQXfYWX+Ddv3mKDzgVb68N+wFjFa4jdeBTo=
 github.com/spf13/jwalterweatherman v1.1.0/go.mod h1:aNWZUN0dPAAO/Ljvb5BEdw96iTZ0EXowPYD95IqWIGo=
 github.com/spf13/pflag v0.0.0-20170130214245-9ff6c6923cff/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
@@ -1268,7 +1254,6 @@ github.com/spf13/viper v1.3.2/go.mod h1:ZiWeW+zYFKm7srdB9IoDzzZXaJaI5eL9QjNiN/DM
 github.com/spf13/viper v1.4.0/go.mod h1:PTJ7Z/lr49W6bUbkmS1V3by4uWynFiR9p7+dSq/yZzE=
 github.com/spf13/viper v1.6.1/go.mod h1:t3iDnF5Jlj76alVNuyFBk5oUMCvsrkbvZK0WQdfDi5k=
 github.com/spf13/viper v1.7.0/go.mod h1:8WkrPz2fc9jxqZNCJI/76HCieCp4Q8HaLFoCha5qpdg=
-github.com/spf13/viper v1.8.1/go.mod h1:o0Pch8wJ9BVSWGQMbra6iw0oQ5oktSIBaujf1rJH9Ns=
 github.com/stefanberger/go-pkcs11uri v0.0.0-20201008174630-78d3cae3a980/go.mod h1:AO3tvPzVZ/ayst6UlUKUv6rcPQInYe3IknH3jYhAKu8=
 github.com/stoewer/go-strcase v1.2.0/go.mod h1:IBiWB2sKIp3wVVQ3Y035++gc+knqhUQag1KpM8ahLw8=
 github.com/stretchr/objx v0.0.0-20180129172003-8a3f7159479f/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -1394,7 +1379,6 @@ go.opencensus.io v0.22.4/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.5/go.mod h1:5pWMHQbX5EPX2/62yrJeAkowc+lfs/XD7Uxpq3pI6kk=
 go.opencensus.io v0.23.0 h1:gqCw0LfLxScz8irSi8exQc7fyQ0fKQU/qnC/X8+V/1M=
 go.opencensus.io v0.23.0/go.mod h1:XItmlyltB5F7CS4xOC1DcqMoFqwtC6OG2xF7mCv7P7E=
-go.opentelemetry.io/contrib v0.20.0 h1:ubFQUn0VCZ0gPwIoJfBJVpeBlyRMxu8Mm/huKWYd9p0=
 go.opentelemetry.io/contrib v0.20.0/go.mod h1:G/EtFaa6qaN7+LxqfIAT3GiZa7Wv5DTBUzl5H4LY0Kc=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.20.0/go.mod h1:oVGt1LRbBOBq1A5BQLlUg9UaU/54aiHw8cgjV3aWZ/E=
 go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.28.0/go.mod h1:vEhqr0m4eTc+DWxfsXoXue2GBgV2uUwVznkGIHW/e5w=
@@ -1412,7 +1396,6 @@ go.opentelemetry.io/otel v1.4.1 h1:QbINgGDDcoQUoMJa2mMaWno49lja9sHwp6aoa2n3a4g=
 go.opentelemetry.io/otel v1.4.1/go.mod h1:StM6F/0fSwpd8dKWDCdRr7uRvEPYdW0hBSlbdTiUde4=
 go.opentelemetry.io/otel/exporters/jaeger v1.4.1 h1:VHCK+2yTZDqDaVXj7JH2Z/khptuydo6C0ttBh2bxAbc=
 go.opentelemetry.io/otel/exporters/jaeger v1.4.1/go.mod h1:ZW7vkOu9nC1CxsD8bHNHCia5JUbwP39vxgd1q4Z5rCI=
-go.opentelemetry.io/otel/exporters/otlp v0.20.0 h1:PTNgq9MRmQqqJY0REVbZFvwkYOA85vbdQU/nVfxDyqg=
 go.opentelemetry.io/otel/exporters/otlp v0.20.0/go.mod h1:YIieizyaN77rtLJra0buKiNBOm9XQfkPEKBeuhoMwAM=
 go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.3.0/go.mod h1:VpP4/RMn8bv8gNo9uK7/IMY4mtWLELsS+JIP0inH0h4=
 go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.4.1 h1:imIM3vRDMyZK1ypQlQlO+brE22I9lRhJsBDXpDWjlz8=
@@ -1473,7 +1456,6 @@ golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8U
 golang.org/x/crypto v0.0.0-20190605123033-f99c8df09eb5/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20190701094942-4def268fd1a4/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20190820162420-60c769a6c586/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191002192127-34f69633bfdc/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191206172530-e9b2fee46413/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
@@ -1610,7 +1592,6 @@ golang.org/x/oauth2 v0.0.0-20201208152858-08078c50e5b5/go.mod h1:KelEdhl1UZF7XfJ
 golang.org/x/oauth2 v0.0.0-20210218202405-ba52d332ba99/go.mod h1:KelEdhl1UZF7XfJ4dDtk6s++YSgaE7mD/BuKKDLBl4A=
 golang.org/x/oauth2 v0.0.0-20210220000619-9bb904979d93/go.mod h1:KelEdhl1UZF7XfJ4dDtk6s++YSgaE7mD/BuKKDLBl4A=
 golang.org/x/oauth2 v0.0.0-20210313182246-cd4f82c27b84/go.mod h1:KelEdhl1UZF7XfJ4dDtk6s++YSgaE7mD/BuKKDLBl4A=
-golang.org/x/oauth2 v0.0.0-20210402161424-2e8d93401602/go.mod h1:KelEdhl1UZF7XfJ4dDtk6s++YSgaE7mD/BuKKDLBl4A=
 golang.org/x/oauth2 v0.0.0-20210514164344-f6687ab2804c/go.mod h1:KelEdhl1UZF7XfJ4dDtk6s++YSgaE7mD/BuKKDLBl4A=
 golang.org/x/oauth2 v0.0.0-20210819190943-2bc19b11175f/go.mod h1:KelEdhl1UZF7XfJ4dDtk6s++YSgaE7mD/BuKKDLBl4A=
 golang.org/x/oauth2 v0.0.0-20211104180415-d3ed0bb246c8 h1:RerP+noqYHUQ8CMRcPlC2nvTa4dcBIjegkuWdcUDuqg=
@@ -1735,7 +1716,6 @@ golang.org/x/sys v0.0.0-20210809222454-d867a43fc93e/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20210831042530-f4d43177bf5e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210903071746-97244b99971b/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210906170528-6f6e22806c34/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20210909193231-528a39cd75f3/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211025201205-69cdffdb9359/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211116061358-0a5406a5449c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
@@ -1899,7 +1879,6 @@ google.golang.org/api v0.36.0/go.mod h1:+z5ficQTmoYpPn8LCUNVpK5I7hwkpjbcgqA7I34q
 google.golang.org/api v0.40.0/go.mod h1:fYKFpnQN0DsDSKRVRcQSDQNtqWPfM9i+zNPxepjRCQ8=
 google.golang.org/api v0.41.0/go.mod h1:RkxM5lITDfTzmyKFPt+wGrCJbVfniCr2ool8kTBzRTU=
 google.golang.org/api v0.43.0/go.mod h1:nQsDGjRXMo4lvh5hP0TKqF244gqhGcr/YSIykhUk/94=
-google.golang.org/api v0.44.0/go.mod h1:EBOGZqzyhtvMDoxwS97ctnh0zUmYY6CxqXsc1AvkYD8=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.2.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
 google.golang.org/appengine v1.3.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
@@ -2033,7 +2012,6 @@ gopkg.in/gemnasium/logrus-airbrake-hook.v2 v2.1.2/go.mod h1:Xk6kEKp8OKb+X14hQBKW
 gopkg.in/inf.v0 v0.9.1/go.mod h1:cWUDdTG/fYaXco+Dcufb5Vnc6Gp2YChqWtbxRZE0mXw=
 gopkg.in/ini.v1 v1.51.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/ini.v1 v1.56.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
-gopkg.in/ini.v1 v1.62.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/natefinch/lumberjack.v2 v2.0.0/go.mod h1:l0ndWWf7gzL7RNwBG7wST/UCcT4T24xpD6X8LsfU/+k=
 gopkg.in/resty.v1 v1.12.0/go.mod h1:mDo4pnntr5jdWRML875a/NmxYqAlA73dVijT2AXvQQo=
 gopkg.in/square/go-jose.v2 v2.2.2/go.mod h1:M9dMgbHiYLoDGQrXy7OpJDJWiKiU//h+vD76mk0e1AI=
diff --git a/solver/llbsolver/bridge.go b/solver/llbsolver/bridge.go
index 0bf8ac905..8e6555107 100644
--- a/solver/llbsolver/bridge.go
+++ b/solver/llbsolver/bridge.go
@@ -165,10 +165,7 @@ func (b *llbBridge) Solve(ctx context.Context, req frontend.SolveRequest, sid st
 				return nil, err
 			}
 			if len(dtbi) > 0 {
-				if res.Metadata == nil {
-					res.Metadata = make(map[string][]byte)
-				}
-				res.Metadata[fmt.Sprintf("%s/%s", exptypes.ExporterBuildInfo, p)] = dtbi
+				res.AddMeta(fmt.Sprintf("%s/%s", exptypes.ExporterBuildInfo, p), dtbi)
 			}
 		}
 	} else {
@@ -177,10 +174,7 @@ func (b *llbBridge) Solve(ctx context.Context, req frontend.SolveRequest, sid st
 			return nil, err
 		}
 		if len(dtbi) > 0 {
-			if res.Metadata == nil {
-				res.Metadata = make(map[string][]byte)
-			}
-			res.Metadata[exptypes.ExporterBuildInfo] = dtbi
+			res.AddMeta(exptypes.ExporterBuildInfo, dtbi)
 		}
 	}
 
diff --git a/solver/llbsolver/solver.go b/solver/llbsolver/solver.go
index 0f27b1f7c..ccaea995f 100644
--- a/solver/llbsolver/solver.go
+++ b/solver/llbsolver/solver.go
@@ -19,7 +19,7 @@ import (
 	"github.com/moby/buildkit/identity"
 	"github.com/moby/buildkit/session"
 	"github.com/moby/buildkit/solver"
-	"github.com/moby/buildkit/util/attestation"
+	"github.com/moby/buildkit/solver/result"
 	"github.com/moby/buildkit/util/buildinfo"
 	"github.com/moby/buildkit/util/compression"
 	"github.com/moby/buildkit/util/entitlements"
@@ -176,55 +176,40 @@ func (s *Solver) Solve(ctx context.Context, id string, sessionID string, req fro
 			return nil, err
 		}
 		if len(dtbi) > 0 {
-			if res.Metadata == nil {
-				res.Metadata = make(map[string][]byte)
-			}
-			res.Metadata[exptypes.ExporterBuildInfo] = dtbi
+			res.AddMeta(exptypes.ExporterBuildInfo, dtbi)
 		}
 	}
-	if res.Refs != nil {
-		for k, r := range res.Refs {
-			if r == nil {
-				continue
-			}
-			dtbi, err := buildinfo.Encode(ctx, res.Metadata, fmt.Sprintf("%s/%s", exptypes.ExporterBuildInfo, k), r.BuildSources())
-			if err != nil {
-				return nil, err
-			}
-			if len(dtbi) > 0 {
-				if res.Metadata == nil {
-					res.Metadata = make(map[string][]byte)
-				}
-				res.Metadata[fmt.Sprintf("%s/%s", exptypes.ExporterBuildInfo, k)] = dtbi
-			}
+	for k, r := range res.Refs {
+		if r == nil {
+			continue
+		}
+		dtbi, err := buildinfo.Encode(ctx, res.Metadata, fmt.Sprintf("%s/%s", exptypes.ExporterBuildInfo, k), r.BuildSources())
+		if err != nil {
+			return nil, err
+		}
+		if len(dtbi) > 0 {
+			res.AddMeta(fmt.Sprintf("%s/%s", exptypes.ExporterBuildInfo, k), dtbi)
 		}
 	}
 
 	var exporterResponse map[string]string
 	if e := exp.Exporter; e != nil {
-		inp := exporter.Source{
-			Metadata:     res.Metadata,
-			Attestations: res.Attestations,
+		cached, err := result.ConvertResult(res, func(res solver.ResultProxy) (solver.CachedResult, error) {
+			return res.Result(ctx)
+		})
+		if err != nil {
+			return nil, err
 		}
-		if inp.Metadata == nil {
-			inp.Metadata = make(map[string][]byte)
-		}
-		if inp.Attestations == nil {
-			inp.Attestations = make(map[string][]attestation.Attestation)
-		}
-		var cr solver.CachedResult
-		var crMap = map[string]solver.CachedResult{}
-		if res := res.Ref; res != nil {
-			r, err := res.Result(ctx)
-			if err != nil {
-				return nil, err
-			}
-			workerRef, ok := r.Sys().(*worker.WorkerRef)
+
+		inp, err := result.ConvertResult(cached, func(res solver.CachedResult) (cache.ImmutableRef, error) {
+			workerRef, ok := res.Sys().(*worker.WorkerRef)
 			if !ok {
-				return nil, errors.Errorf("invalid reference: %T", r.Sys())
+				return nil, errors.Errorf("invalid reference: %T", res.Sys())
 			}
-			inp.Ref = workerRef.ImmutableRef
-			cr = r
+			return workerRef.ImmutableRef, nil
+		})
+		if err != nil {
+			return nil, err
 		}
 		if res.Refs != nil {
 			m := make(map[string]cache.ImmutableRef, len(res.Refs))
@@ -241,29 +226,29 @@ func (s *Solver) Solve(ctx context.Context, id string, sessionID string, req fro
 						return nil, errors.Errorf("invalid reference: %T", r.Sys())
 					}
 					m[k] = workerRef.ImmutableRef
-					crMap[k] = r
 				}
 			}
 			inp.Refs = m
 		}
+
 		if _, ok := asInlineCache(exp.CacheExporter); ok {
 			if err := inBuilderContext(ctx, j, "preparing layers for inline cache", j.SessionID+"-cache-inline", func(ctx context.Context, _ session.Group) error {
-				if cr != nil {
-					dtic, err := inlineCache(ctx, exp.CacheExporter, cr, e.Config().Compression, session.NewGroup(sessionID))
+				if cached.Ref != nil {
+					dtic, err := inlineCache(ctx, exp.CacheExporter, cached.Ref, e.Config().Compression, session.NewGroup(sessionID))
 					if err != nil {
 						return err
 					}
 					if dtic != nil {
-						inp.Metadata[exptypes.ExporterInlineCache] = dtic
+						inp.AddMeta(exptypes.ExporterInlineCache, dtic)
 					}
 				}
-				for k, res := range crMap {
+				for k, res := range cached.Refs {
 					dtic, err := inlineCache(ctx, exp.CacheExporter, res, e.Config().Compression, session.NewGroup(sessionID))
 					if err != nil {
 						return err
 					}
 					if dtic != nil {
-						inp.Metadata[fmt.Sprintf("%s/%s", exptypes.ExporterInlineCache, k)] = dtic
+						inp.AddMeta(fmt.Sprintf("%s/%s", exptypes.ExporterInlineCache, k), dtic)
 					}
 				}
 				exp.CacheExporter = nil
diff --git a/util/attestation/attestation.go b/solver/result/attestation.go
similarity index 97%
rename from util/attestation/attestation.go
rename to solver/result/attestation.go
index 8ee67e4d6..2db3dfac4 100644
--- a/util/attestation/attestation.go
+++ b/solver/result/attestation.go
@@ -1,4 +1,4 @@
-package attestation
+package result
 
 import (
 	digest "github.com/opencontainers/go-digest"
diff --git a/solver/result/result.go b/solver/result/result.go
new file mode 100644
index 000000000..1fa6c2ff6
--- /dev/null
+++ b/solver/result/result.go
@@ -0,0 +1,118 @@
+package result
+
+import (
+	"reflect"
+	"strings"
+	"sync"
+
+	"github.com/moby/buildkit/identity"
+	"github.com/pkg/errors"
+)
+
+const (
+	attestationRefPrefix = "attestation:"
+)
+
+type Result[T any] struct {
+	mu           sync.Mutex
+	Ref          T
+	Refs         map[string]T
+	Metadata     map[string][]byte
+	Attestations map[string][]Attestation
+}
+
+func (r *Result[T]) AddMeta(k string, v []byte) {
+	r.mu.Lock()
+	if r.Metadata == nil {
+		r.Metadata = map[string][]byte{}
+	}
+	r.Metadata[k] = v
+	r.mu.Unlock()
+}
+
+func (r *Result[T]) AddRef(k string, ref T) {
+	r.mu.Lock()
+	if r.Refs == nil {
+		r.Refs = map[string]T{}
+	}
+	r.Refs[k] = ref
+	r.mu.Unlock()
+}
+
+func (r *Result[T]) AddAttestation(k string, v Attestation, refs map[string]T) {
+	r.mu.Lock()
+	if r.Attestations == nil {
+		r.Attestations = map[string][]Attestation{}
+	}
+
+	// if the attestation refs aren't already internal, then insert them
+	switch v := v.(type) {
+	case *InTotoAttestation:
+		if !strings.HasPrefix(v.PredicateRefKey, attestationRefPrefix) {
+			internalKey := attestationRefPrefix + identity.NewID()
+			r.Refs[internalKey] = refs[v.PredicateRefKey]
+			v.PredicateRefKey = internalKey
+		}
+	}
+	r.Attestations[k] = append(r.Attestations[k], v)
+
+	r.mu.Unlock()
+}
+
+func (r *Result[T]) SetRef(ref T) {
+	r.Ref = ref
+}
+
+func (r *Result[T]) SingleRef() (T, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if r.Refs != nil && !reflect.ValueOf(r.Ref).IsValid() {
+		var t T
+		return t, errors.Errorf("invalid map result")
+	}
+	return r.Ref, nil
+}
+
+func (r *Result[T]) EachRef(fn func(T) error) (err error) {
+	if reflect.ValueOf(r.Ref).IsValid() {
+		err = fn(r.Ref)
+	}
+	for _, r := range r.Refs {
+		if reflect.ValueOf(r).IsValid() {
+			if err1 := fn(r); err1 != nil && err == nil {
+				err = err1
+			}
+		}
+	}
+	return err
+}
+
+func ConvertResult[U any, V any](r *Result[U], fn func(U) (V, error)) (*Result[V], error) {
+	r2 := &Result[V]{}
+	var err error
+
+	if reflect.ValueOf(r.Ref).IsValid() {
+		r2.Ref, err = fn(r.Ref)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if r.Refs != nil {
+		r2.Refs = map[string]V{}
+	}
+	for k, r := range r.Refs {
+		if reflect.ValueOf(r).IsValid() {
+			r2.Refs[k], err = fn(r)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	r2.Attestations = r.Attestations
+	r2.Metadata = r.Metadata
+
+	return r2, nil
+}