diff --git a/cache/refs.go b/cache/refs.go
index 2ddac6d1..2b25235e 100644
--- a/cache/refs.go
+++ b/cache/refs.go
@@ -375,10 +375,8 @@ func (sr *immutableRef) parentRefChain() []*immutableRef {
 }
 
 func (sr *immutableRef) Mount(ctx context.Context, readonly bool, s session.Group) (snapshot.Mountable, error) {
-	if getBlobOnly(sr.md) {
-		if err := sr.Extract(ctx, s); err != nil {
-			return nil, err
-		}
+	if err := sr.Extract(ctx, s); err != nil {
+		return nil, err
 	}
 
 	sr.mu.Lock()
@@ -387,6 +385,10 @@ func (sr *immutableRef) Mount(ctx context.Context, readonly bool, s session.Grou
 }
 
 func (sr *immutableRef) Extract(ctx context.Context, s session.Group) (rerr error) {
+	if !getBlobOnly(sr.md) {
+		return
+	}
+
 	ctx, done, err := leaseutil.WithLease(ctx, sr.cm.LeaseManager, leaseutil.MakeTemporary)
 	if err != nil {
 		return err
diff --git a/solver/edge.go b/solver/edge.go
index f6adca98..6ebf3a74 100644
--- a/solver/edge.go
+++ b/solver/edge.go
@@ -223,6 +223,14 @@ func (e *edge) slowCacheFunc(dep *dep) ResultBasedCacheFunc {
 	return e.cacheMap.Deps[int(dep.index)].ComputeDigestFunc
 }
 
+// preprocessFunc returns result based cache func
+func (e *edge) preprocessFunc(dep *dep) PreprocessFunc {
+	if e.cacheMap == nil {
+		return nil
+	}
+	return e.cacheMap.Deps[int(dep.index)].PreprocessFunc
+}
+
 // allDepsHaveKeys checks if all dependencies have at least one key. used for
 // determining if there is enough data for combining cache key for edge
 func (e *edge) allDepsHaveKeys(matching bool) bool {
@@ -487,17 +495,20 @@ func (e *edge) processUpdate(upt pipe.Receiver) (depChanged bool) {
 					e.err = upt.Status().Err
 				}
 			} else if !dep.slowCacheComplete {
-				k := NewCacheKey(upt.Status().Value.(digest.Digest), -1)
-				dep.slowCacheKey = &ExportableCacheKey{CacheKey: k, Exporter: &exporter{k: k}}
-				slowKeyExp := CacheKeyWithSelector{CacheKey: *dep.slowCacheKey}
-				defKeys := make([]CacheKeyWithSelector, 0, len(dep.result.CacheKeys()))
-				for _, dk := range dep.result.CacheKeys() {
-					defKeys = append(defKeys, CacheKeyWithSelector{CacheKey: dk, Selector: e.cacheMap.Deps[i].Selector})
-				}
-				dep.slowCacheFoundKey = e.probeCache(dep, []CacheKeyWithSelector{slowKeyExp})
+				dgst := upt.Status().Value.(digest.Digest)
+				if e.cacheMap.Deps[int(dep.index)].ComputeDigestFunc != nil && dgst != "" {
+					k := NewCacheKey(dgst, -1)
+					dep.slowCacheKey = &ExportableCacheKey{CacheKey: k, Exporter: &exporter{k: k}}
+					slowKeyExp := CacheKeyWithSelector{CacheKey: *dep.slowCacheKey}
+					defKeys := make([]CacheKeyWithSelector, 0, len(dep.result.CacheKeys()))
+					for _, dk := range dep.result.CacheKeys() {
+						defKeys = append(defKeys, CacheKeyWithSelector{CacheKey: dk, Selector: e.cacheMap.Deps[i].Selector})
+					}
+					dep.slowCacheFoundKey = e.probeCache(dep, []CacheKeyWithSelector{slowKeyExp})
 
-				// connect def key to slow key
-				e.op.Cache().Query(append(defKeys, slowKeyExp), dep.index, e.cacheMap.Digest, e.edge.Index)
+					// connect def key to slow key
+					e.op.Cache().Query(append(defKeys, slowKeyExp), dep.index, e.cacheMap.Digest, e.edge.Index)
+				}
 
 				dep.slowCacheComplete = true
 				e.keysDidChange = true
@@ -583,7 +594,7 @@ func (e *edge) recalcCurrentState() {
 	stHigh := edgeStatusCacheSlow // maximum possible state
 	if e.cacheMap != nil {
 		for _, dep := range e.deps {
-			isSlowIncomplete := e.slowCacheFunc(dep) != nil && (dep.state == edgeStatusCacheSlow || (dep.state == edgeStatusComplete && !dep.slowCacheComplete))
+			isSlowIncomplete := (e.slowCacheFunc(dep) != nil || e.preprocessFunc(dep) != nil) && (dep.state == edgeStatusCacheSlow || (dep.state == edgeStatusComplete && !dep.slowCacheComplete))
 
 			if dep.state > stLow && len(dep.keyMap) == 0 && !isSlowIncomplete {
 				stLow = dep.state
@@ -804,15 +815,16 @@ func (e *edge) createInputRequests(desiredState edgeStatusType, f *pipeFactory,
 			}
 		}
 		// initialize function to compute cache key based on dependency result
-		if dep.state == edgeStatusComplete && dep.slowCacheReq == nil && e.slowCacheFunc(dep) != nil && e.cacheMap != nil {
+		if dep.state == edgeStatusComplete && dep.slowCacheReq == nil && (e.slowCacheFunc(dep) != nil || e.preprocessFunc(dep) != nil) && e.cacheMap != nil {
+			pfn := e.preprocessFunc(dep)
 			fn := e.slowCacheFunc(dep)
 			res := dep.result
-			func(fn ResultBasedCacheFunc, res Result, index Index) {
+			func(pfn PreprocessFunc, fn ResultBasedCacheFunc, res Result, index Index) {
 				dep.slowCacheReq = f.NewFuncRequest(func(ctx context.Context) (interface{}, error) {
-					v, err := e.op.CalcSlowCache(ctx, index, fn, res)
+					v, err := e.op.CalcSlowCache(ctx, index, pfn, fn, res)
 					return v, errors.Wrap(err, "failed to compute cache key")
 				})
-			}(fn, res, dep.index)
+			}(pfn, fn, res, dep.index)
 			addedNew = true
 		}
 	}
diff --git a/solver/jobs.go b/solver/jobs.go
index 99e31b23..d34db5e7 100644
--- a/solver/jobs.go
+++ b/solver/jobs.go
@@ -268,6 +268,17 @@ func (jl *Solver) setEdge(e Edge, newEdge *edge) {
 	st.setEdge(e.Index, newEdge)
 }
 
+func (jl *Solver) getState(e Edge) *state {
+	jl.mu.RLock()
+	defer jl.mu.RUnlock()
+
+	st, ok := jl.actives[e.Vertex.Digest()]
+	if !ok {
+		return nil
+	}
+	return st
+}
+
 func (jl *Solver) getEdge(e Edge) *edge {
 	jl.mu.RLock()
 	defer jl.mu.RUnlock()
@@ -547,7 +558,7 @@ type activeOp interface {
 	Exec(ctx context.Context, inputs []Result) (outputs []Result, exporters []ExportableCacheKey, err error)
 	IgnoreCache() bool
 	Cache() CacheManager
-	CalcSlowCache(context.Context, Index, ResultBasedCacheFunc, Result) (digest.Digest, error)
+	CalcSlowCache(context.Context, Index, PreprocessFunc, ResultBasedCacheFunc, Result) (digest.Digest, error)
 }
 
 func newSharedOp(resolver ResolveOpFunc, cacheManager CacheManager, st *state) *sharedOp {
@@ -606,14 +617,14 @@ func (s *sharedOp) LoadCache(ctx context.Context, rec *CacheRecord) (Result, err
 	return res, err
 }
 
-func (s *sharedOp) CalcSlowCache(ctx context.Context, index Index, f ResultBasedCacheFunc, res Result) (dgst digest.Digest, err error) {
+func (s *sharedOp) CalcSlowCache(ctx context.Context, index Index, p PreprocessFunc, f ResultBasedCacheFunc, res Result) (dgst digest.Digest, err error) {
 	defer func() {
 		err = errdefs.WrapVertex(err, s.st.origDigest)
 	}()
 	key, err := s.g.Do(ctx, fmt.Sprintf("slow-compute-%d", index), func(ctx context.Context) (interface{}, error) {
 		s.slowMu.Lock()
 		// TODO: add helpers for these stored values
-		if res := s.slowCacheRes[index]; res != "" {
+		if res, ok := s.slowCacheRes[index]; ok {
 			s.slowMu.Unlock()
 			return res, nil
 		}
@@ -622,9 +633,23 @@ func (s *sharedOp) CalcSlowCache(ctx context.Context, index Index, f ResultBased
 			return err, nil
 		}
 		s.slowMu.Unlock()
-		ctx = opentracing.ContextWithSpan(progress.WithProgress(ctx, s.st.mpw), s.st.mspan)
-		key, err := f(withAncestorCacheOpts(ctx, s.st), res, s.st)
+
 		complete := true
+		if p != nil {
+			st := s.st.solver.getState(s.st.vtx.Inputs()[index])
+			ctx2 := opentracing.ContextWithSpan(progress.WithProgress(ctx, st.mpw), st.mspan)
+			err = p(ctx2, res, st)
+			if err != nil {
+				f = nil
+				ctx = ctx2
+			}
+		}
+
+		var key digest.Digest
+		if f != nil {
+			ctx = opentracing.ContextWithSpan(progress.WithProgress(ctx, s.st.mpw), s.st.mspan)
+			key, err = f(withAncestorCacheOpts(ctx, s.st), res, s.st)
+		}
 		if err != nil {
 			select {
 			case <-ctx.Done():
diff --git a/solver/llbsolver/ops/build.go b/solver/llbsolver/ops/build.go
index 45f0d41a..5e7fbc7a 100644
--- a/solver/llbsolver/ops/build.go
+++ b/solver/llbsolver/ops/build.go
@@ -54,6 +54,7 @@ func (b *buildOp) CacheMap(ctx context.Context, g session.Group, index int) (*so
 		Deps: make([]struct {
 			Selector          digest.Digest
 			ComputeDigestFunc solver.ResultBasedCacheFunc
+			PreprocessFunc    solver.PreprocessFunc
 		}, len(b.v.Inputs())),
 	}, true, nil
 }
diff --git a/solver/llbsolver/ops/exec.go b/solver/llbsolver/ops/exec.go
index 5938df7a..1ad18903 100644
--- a/solver/llbsolver/ops/exec.go
+++ b/solver/llbsolver/ops/exec.go
@@ -118,6 +118,7 @@ func (e *execOp) CacheMap(ctx context.Context, g session.Group, index int) (*sol
 		Deps: make([]struct {
 			Selector          digest.Digest
 			ComputeDigestFunc solver.ResultBasedCacheFunc
+			PreprocessFunc    solver.PreprocessFunc
 		}, e.numInputs),
 	}
 
@@ -137,6 +138,7 @@ func (e *execOp) CacheMap(ctx context.Context, g session.Group, index int) (*sol
 		if !dep.NoContentBasedHash {
 			cm.Deps[i].ComputeDigestFunc = llbsolver.NewContentHashFunc(toSelectors(dedupePaths(dep.Selectors)))
 		}
+		cm.Deps[i].PreprocessFunc = llbsolver.UnlazyResultFunc
 	}
 
 	return cm, true, nil
diff --git a/solver/llbsolver/ops/file.go b/solver/llbsolver/ops/file.go
index f2f0f387..78b0c031 100644
--- a/solver/llbsolver/ops/file.go
+++ b/solver/llbsolver/ops/file.go
@@ -120,6 +120,7 @@ func (f *fileOp) CacheMap(ctx context.Context, g session.Group, index int) (*sol
 		Deps: make([]struct {
 			Selector          digest.Digest
 			ComputeDigestFunc solver.ResultBasedCacheFunc
+			PreprocessFunc    solver.PreprocessFunc
 		}, f.numInputs),
 	}
 
@@ -138,6 +139,9 @@ func (f *fileOp) CacheMap(ctx context.Context, g session.Group, index int) (*sol
 
 		cm.Deps[idx].ComputeDigestFunc = llbsolver.NewContentHashFunc(dedupeSelectors(m))
 	}
+	for idx := range cm.Deps {
+		cm.Deps[idx].PreprocessFunc = llbsolver.UnlazyResultFunc
+	}
 
 	return cm, true, nil
 }
diff --git a/solver/llbsolver/result.go b/solver/llbsolver/result.go
index 069b3025..a36891c7 100644
--- a/solver/llbsolver/result.go
+++ b/solver/llbsolver/result.go
@@ -21,6 +21,17 @@ type Selector struct {
 	FollowLinks bool
 }
 
+func UnlazyResultFunc(ctx context.Context, res solver.Result, g session.Group) error {
+	ref, ok := res.Sys().(*worker.WorkerRef)
+	if !ok {
+		return errors.Errorf("invalid reference: %T", res)
+	}
+	if ref.ImmutableRef == nil {
+		return nil
+	}
+	return ref.ImmutableRef.Extract(ctx, g)
+}
+
 func NewContentHashFunc(selectors []Selector) solver.ResultBasedCacheFunc {
 	return func(ctx context.Context, res solver.Result, s session.Group) (digest.Digest, error) {
 		ref, ok := res.Sys().(*worker.WorkerRef)
diff --git a/solver/scheduler_test.go b/solver/scheduler_test.go
index 84067e8c..96a6dc39 100644
--- a/solver/scheduler_test.go
+++ b/solver/scheduler_test.go
@@ -3517,6 +3517,7 @@ func (v *vertex) makeCacheMap() *CacheMap {
 		Deps: make([]struct {
 			Selector          digest.Digest
 			ComputeDigestFunc ResultBasedCacheFunc
+			PreprocessFunc    PreprocessFunc
 		}, len(v.Inputs())),
 	}
 	for i, f := range v.opt.slowCacheCompute {
diff --git a/solver/types.go b/solver/types.go
index 892beb35..76e4c911 100644
--- a/solver/types.go
+++ b/solver/types.go
@@ -148,6 +148,7 @@ type Op interface {
 }
 
 type ResultBasedCacheFunc func(context.Context, Result, session.Group) (digest.Digest, error)
+type PreprocessFunc func(context.Context, Result, session.Group) error
 
 // CacheMap is a description for calculating the cache key of an operation.
 type CacheMap struct {
@@ -173,6 +174,9 @@ type CacheMap struct {
 		// For example, in LLB this is invoked to calculate the cache key based on
 		// the checksum of file contents from input snapshots.
 		ComputeDigestFunc ResultBasedCacheFunc
+
+		// PreprocessFunc is a function that runs on an input before it is passed to op
+		PreprocessFunc PreprocessFunc
 	}
 
 	// Opts specifies generic options that will be passed to cache load calls if/when