diff --git a/wavesrv/pkg/scbase/scbase.go b/wavesrv/pkg/scbase/scbase.go
index bc9ab45ba..a4303f00d 100644
--- a/wavesrv/pkg/scbase/scbase.go
+++ b/wavesrv/pkg/scbase/scbase.go
@@ -122,7 +122,7 @@ func createWaveAuthKeyFile(fileName string) (string, error) {
 
 func ReadWaveAuthKey() (string, error) {
 	homeDir := GetWaveHomeDir()
-	err := ensureDir(homeDir)
+	err := EnsureDir(homeDir)
 	if err != nil {
 		return "", fmt.Errorf("cannot find/create WAVETERM_HOME directory %q", homeDir)
 	}
@@ -149,7 +149,7 @@ func ReadWaveAuthKey() (string, error) {
 
 func AcquireWaveLock() (*os.File, error) {
 	homeDir := GetWaveHomeDir()
-	err := ensureDir(homeDir)
+	err := EnsureDir(homeDir)
 	if err != nil {
 		return nil, fmt.Errorf("cannot find/create WAVETERM_HOME directory %q", homeDir)
 	}
@@ -180,7 +180,7 @@ func EnsureSessionDir(sessionId string) (string, error) {
 	}
 	scHome := GetWaveHomeDir()
 	sdir = path.Join(scHome, SessionsDirBaseName, sessionId)
-	err := ensureDir(sdir)
+	err := EnsureDir(sdir)
 	if err != nil {
 		return "", err
 	}
@@ -197,35 +197,13 @@ func GetSessionsDir() string {
 	return sdir
 }
 
-func EnsureScreenDir(screenId string) (string, error) {
-	if screenId == "" {
-		return "", fmt.Errorf("cannot get screen dir for blank sessionid")
-	}
-	BaseLock.Lock()
-	sdir, ok := ScreenDirCache[screenId]
-	BaseLock.Unlock()
-	if ok {
-		return sdir, nil
-	}
-	scHome := GetWaveHomeDir()
-	sdir = path.Join(scHome, ScreensDirBaseName, screenId)
-	err := ensureDir(sdir)
-	if err != nil {
-		return "", err
-	}
-	BaseLock.Lock()
-	ScreenDirCache[screenId] = sdir
-	BaseLock.Unlock()
-	return sdir, nil
-}
-
 func GetScreensDir() string {
 	waveHome := GetWaveHomeDir()
 	sdir := path.Join(waveHome, ScreensDirBaseName)
 	return sdir
 }
 
-func ensureDir(dirName string) error {
+func EnsureDir(dirName string) error {
 	info, err := os.Stat(dirName)
 	if errors.Is(err, fs.ErrNotExist) {
 		err = os.MkdirAll(dirName, 0700)
@@ -259,20 +237,6 @@ func PtyOutFile_Sessions(sessionId string, cmdId string) (string, error) {
 	return fmt.Sprintf("%s/%s.ptyout.cf", sdir, cmdId), nil
 }
 
-func PtyOutFile(screenId string, lineId string) (string, error) {
-	sdir, err := EnsureScreenDir(screenId)
-	if err != nil {
-		return "", err
-	}
-	if screenId == "" {
-		return "", fmt.Errorf("cannot get ptyout file for blank screenid")
-	}
-	if lineId == "" {
-		return "", fmt.Errorf("cannot get ptyout file for blank lineid")
-	}
-	return fmt.Sprintf("%s/%s.ptyout.cf", sdir, lineId), nil
-}
-
 func GenWaveUUID() string {
 	for {
 		rtn := uuid.New().String()
diff --git a/wavesrv/pkg/sstore/fileops.go b/wavesrv/pkg/sstore/fileops.go
index 7b1b9ab17..a58d425b0 100644
--- a/wavesrv/pkg/sstore/fileops.go
+++ b/wavesrv/pkg/sstore/fileops.go
@@ -12,6 +12,7 @@ import (
 	"log"
 	"os"
 	"path"
+	"sync"
 	"time"
 
 	"github.com/google/uuid"
@@ -20,8 +21,11 @@ import (
 	"github.com/wavetermdev/waveterm/wavesrv/pkg/scbase"
 )
 
+var screenDirLock = &sync.Mutex{}
+var screenDirCache = make(map[string]string) // locked with screenDirLock
+
 func CreateCmdPtyFile(ctx context.Context, screenId string, lineId string, maxSize int64) error {
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return err
 	}
@@ -33,7 +37,7 @@ func CreateCmdPtyFile(ctx context.Context, screenId string, lineId string, maxSi
 }
 
 func StatCmdPtyFile(ctx context.Context, screenId string, lineId string) (*cirfile.Stat, error) {
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return nil, err
 	}
@@ -41,7 +45,7 @@ func StatCmdPtyFile(ctx context.Context, screenId string, lineId string) (*cirfi
 }
 
 func ClearCmdPtyFile(ctx context.Context, screenId string, lineId string) error {
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return err
 	}
@@ -68,7 +72,7 @@ func AppendToCmdPtyBlob(ctx context.Context, screenId string, lineId string, dat
 	if pos < 0 {
 		return nil, fmt.Errorf("invalid seek pos '%d' in AppendToCmdPtyBlob", pos)
 	}
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return nil, err
 	}
@@ -99,7 +103,7 @@ func AppendToCmdPtyBlob(ctx context.Context, screenId string, lineId string, dat
 
 // returns (real-offset, data, err)
 func ReadFullPtyOutFile(ctx context.Context, screenId string, lineId string) (int64, []byte, error) {
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return 0, nil, err
 	}
@@ -113,7 +117,7 @@ func ReadFullPtyOutFile(ctx context.Context, screenId string, lineId string) (in
 
 // returns (real-offset, data, err)
 func ReadPtyOutFile(ctx context.Context, screenId string, lineId string, offset int64, maxSize int64) (int64, []byte, error) {
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return 0, nil, err
 	}
@@ -189,7 +193,7 @@ func FullSessionDiskSize() (map[string]SessionDiskSizeType, error) {
 }
 
 func DeletePtyOutFile(ctx context.Context, screenId string, lineId string) error {
-	ptyOutFileName, err := scbase.PtyOutFile(screenId, lineId)
+	ptyOutFileName, err := PtyOutFile(screenId, lineId)
 	if err != nil {
 		return err
 	}
@@ -218,10 +222,46 @@ func deleteScreenDirMakeCtx(screenId string) {
 }
 
 func DeleteScreenDir(ctx context.Context, screenId string) error {
-	screenDir, err := scbase.EnsureScreenDir(screenId)
+	screenDir, err := EnsureScreenDir(screenId)
 	if err != nil {
 		return fmt.Errorf("error getting screendir: %w", err)
 	}
 	log.Printf("delete screen dir, remove-all %s\n", screenDir)
 	return os.RemoveAll(screenDir)
 }
+
+func EnsureScreenDir(screenId string) (string, error) {
+	if screenId == "" {
+		return "", fmt.Errorf("cannot get screen dir for blank sessionid")
+	}
+	screenDirLock.Lock()
+	sdir, ok := screenDirCache[screenId]
+	screenDirLock.Unlock()
+	if ok {
+		return sdir, nil
+	}
+	scHome := scbase.GetWaveHomeDir()
+	sdir = path.Join(scHome, scbase.ScreensDirBaseName, screenId)
+	err := scbase.EnsureDir(sdir)
+	if err != nil {
+		return "", err
+	}
+	screenDirLock.Lock()
+	screenDirCache[screenId] = sdir
+	screenDirLock.Unlock()
+	return sdir, nil
+}
+
+func PtyOutFile(screenId string, lineId string) (string, error) {
+	sdir, err := EnsureScreenDir(screenId)
+	if err != nil {
+		return "", err
+	}
+	if screenId == "" {
+		return "", fmt.Errorf("cannot get ptyout file for blank screenid")
+	}
+	if lineId == "" {
+		return "", fmt.Errorf("cannot get ptyout file for blank lineid")
+	}
+	return fmt.Sprintf("%s/%s.ptyout.cf", sdir, lineId), nil
+}
diff --git a/wavesrv/pkg/sstore/sstore_migrate.go b/wavesrv/pkg/sstore/sstore_migrate.go
index dd370e972..f00ec2b5e 100644
--- a/wavesrv/pkg/sstore/sstore_migrate.go
+++ b/wavesrv/pkg/sstore/sstore_migrate.go
@@ -91,12 +91,12 @@ func RunMigration20() error {
 
 func processMigration20Chunk(ctx context.Context, mchunk []cmdMigration20Type) error {
 	for _, mig := range mchunk {
-		newFile, err := scbase.PtyOutFile(mig.ScreenId, mig.LineId)
+		newFile, err := PtyOutFile(mig.ScreenId, mig.LineId)
 		if err != nil {
 			log.Printf("ptyoutfile(lineid) error: %v\n", err)
 			continue
 		}
-		oldFile, err := scbase.PtyOutFile(mig.ScreenId, mig.CmdId)
+		oldFile, err := PtyOutFile(mig.ScreenId, mig.CmdId)
 		if err != nil {
 			log.Printf("ptyoutfile(cmdid) error: %v\n", err)
 			continue
@@ -158,7 +158,7 @@ func RunMigration13() error {
 
 func processMigration13Chunk(ctx context.Context, mchunk []cmdMigration13Type) error {
 	for _, mig := range mchunk {
-		newFile, err := scbase.PtyOutFile(mig.ScreenId, mig.CmdId)
+		newFile, err := PtyOutFile(mig.ScreenId, mig.CmdId)
 		if err != nil {
 			log.Printf("ptyoutfile error: %v\n", err)
 			continue