diff --git a/hypervisor/baseconfig.go b/hypervisor/baseconfig.go
index b2a39345..bdec370b 100644
--- a/hypervisor/baseconfig.go
+++ b/hypervisor/baseconfig.go
@@ -5,7 +5,6 @@ import (
 	"time"
 
 	"github.com/cocoonstack/cocoon/config"
-	"github.com/cocoonstack/cocoon/types"
 	"github.com/cocoonstack/cocoon/utils"
 )
 
@@ -76,7 +75,7 @@ func (c *BaseConfig) LoadAndValidateMeta(dir string) (*SnapshotMeta, error) {
 }
 
 // PreflightRestore runs the shared restore preflight against this backend's managed roots.
-func (c *BaseConfig) PreflightRestore(srcDir string, rec *VMRecord, integrity func(srcDir string, sidecar []*types.StorageConfig) error) (*SnapshotMeta, error) {
+func (c *BaseConfig) PreflightRestore(srcDir string, rec *VMRecord, integrity IntegrityCheck) (*SnapshotMeta, error) {
 	return PreflightRestore(srcDir, c.RootDir, c.Config.RunDir, rec, integrity)
 }
 
diff --git a/hypervisor/firecracker/relay.go b/hypervisor/firecracker/relay.go
index a4308cbe..cf23af7e 100644
--- a/hypervisor/firecracker/relay.go
+++ b/hypervisor/firecracker/relay.go
@@ -68,6 +68,33 @@ func (b *broadcaster) readLoop() {
 	}
 }
 
+// cloneLeaseControl is the parent's half of the relay lease protocol; a nil control (no leases held) no-ops.
+type cloneLeaseControl struct {
+	commands  *os.File
+	responses *os.File
+}
+
+func (c *cloneLeaseControl) close() {
+	if c == nil {
+		return
+	}
+	closeFile(c.commands)
+	closeFile(c.responses)
+	c.commands = nil
+	c.responses = nil
+}
+
+func (c *cloneLeaseControl) commit() error {
+	if c == nil {
+		return nil
+	}
+	defer c.close()
+	if _, err := c.commands.Write([]byte{relayCommitLeasesCommand}); err != nil {
+		return err
+	}
+	return waitRelayLeaseResponse(c.responses, relayLeaseCommitAck, "commit")
+}
+
 // IsRelayMode returns true when the process was started as a console relay.
 func IsRelayMode() bool {
 	return os.Getenv(relayEnvKey) == "1"
diff --git a/hypervisor/firecracker/start.go b/hypervisor/firecracker/start.go
index 036f8564..2642d3ee 100644
--- a/hypervisor/firecracker/start.go
+++ b/hypervisor/firecracker/start.go
@@ -122,33 +122,6 @@ func (fc *Firecracker) configureVM(ctx context.Context, hc *http.Client, rec *hy
 	return nil
 }
 
-// cloneLeaseControl is the parent's half of the relay lease protocol; a nil control (no leases held) no-ops.
-type cloneLeaseControl struct {
-	commands  *os.File
-	responses *os.File
-}
-
-func (c *cloneLeaseControl) close() {
-	if c == nil {
-		return
-	}
-	closeFile(c.commands)
-	closeFile(c.responses)
-	c.commands = nil
-	c.responses = nil
-}
-
-func (c *cloneLeaseControl) commit() error {
-	if c == nil {
-		return nil
-	}
-	defer c.close()
-	if _, err := c.commands.Write([]byte{relayCommitLeasesCommand}); err != nil {
-		return err
-	}
-	return waitRelayLeaseResponse(c.responses, relayLeaseCommitAck, "commit")
-}
-
 func (fc *Firecracker) launchProcess(ctx context.Context, rec *hypervisor.VMRecord, sockPath, netnsPath string, deferQuota bool) (int, error) {
 	pid, _, err := fc.launchProcessWithLeases(ctx, rec, sockPath, netnsPath, nil, deferQuota)
 	return pid, err
diff --git a/hypervisor/snapshot.go b/hypervisor/snapshot.go
index 61f59e60..0f70b995 100644
--- a/hypervisor/snapshot.go
+++ b/hypervisor/snapshot.go
@@ -23,6 +23,9 @@ type SnapshotMeta struct {
 	BootConfig     *types.BootConfig      `json:"boot_config,omitempty"`
 }
 
+// IntegrityCheck verifies the snapshot files under srcDir against the sidecar's storage configs.
+type IntegrityCheck func(srcDir string, sidecar []*types.StorageConfig) error
+
 // RecordSnapshot generates a snapshot ID and records it on the VM's record.
 func (b *Backend) RecordSnapshot(ctx context.Context, vmID string) (string, error) {
 	snapID := utils.GenerateID()
@@ -235,7 +238,7 @@ func PopulateFromSrc(runDir, srcDir string, clean func(string) error, clone func
 }
 
 // PreflightRestore loads and validates the sidecar, runs the backend integrity check and asserts the snapshot role sequence prefixes rec; the validated meta is returned so later phases skip re-reading it.
-func PreflightRestore(srcDir, rootDir, runDir string, rec *VMRecord, integrity func(srcDir string, sidecar []*types.StorageConfig) error) (*SnapshotMeta, error) {
+func PreflightRestore(srcDir, rootDir, runDir string, rec *VMRecord, integrity IntegrityCheck) (*SnapshotMeta, error) {
 	meta, err := LoadAndValidateMeta(srcDir, rootDir, runDir)
 	if err != nil {
 		return nil, err