fix: session security and correctness — path traversal, turn count restore, incognito quality leak

- store: validate session ID against store root to block path traversal in Load/Save
- local: seed turnCount from LocalConfig.TurnCount so resumed sessions keep correct turn count
- main: pass TurnCount from snapshot to LocalConfig on resume
- main: suppress quality.json save when --incognito is active
- main: handle UserConfigDir error in quality save defer instead of silently using wrong path
- test: add TestSessionStore_Load/Save_RejectsPathTraversal

cmd/gnoma/main.go

@@ -196,14 +196,21 @@ func main() {
 		}
 	}
 
-	// Save QualityTracker data on exit (best-effort)
+	// Save QualityTracker data on exit (best-effort, suppressed in incognito)
 	defer func() {
+		if *incognito {
+			return
+		}
 		snap := rtr.QualityTracker().Snapshot()
 		data, err := json.Marshal(snap)
 		if err != nil {
 			return
 		}
-		userCfgDir, _ := os.UserConfigDir()
+		userCfgDir, err := os.UserConfigDir()
+		if err != nil {
+			logger.Warn("quality save skipped: no user config dir", "error", err)
+			return
+		}
 		dir := filepath.Join(userCfgDir, "gnoma")
 		os.MkdirAll(dir, 0o755)
 		os.WriteFile(filepath.Join(dir, "quality.json"), data, 0o644)
@@ -409,6 +416,7 @@ func main() {
 	}
 
 	// Resume logic: --resume/-r flag
+	resumedTurnCount := 0
 	resumeRequested := isFlagSet("resume") || isFlagSet("r")
 	if resumeRequested {
 		var snap session.Snapshot
@@ -439,6 +447,7 @@ func main() {
 		eng.SetHistory(snap.Messages)
 		eng.SetUsage(snap.Metadata.Usage)
 		sessionID = snap.ID
+		resumedTurnCount = snap.Metadata.TurnCount
 		logger.Info("session resumed", "id", snap.ID, "turns", snap.Metadata.TurnCount)
 	}
 
@@ -504,6 +513,7 @@ func main() {
 			Provider:  *providerName,
 			Model:     armModel,
 			SessionID: sessionID,
+			TurnCount: resumedTurnCount,
 			Store:     sessStore,
 			Incognito: fw.Incognito(),
 			Logger:    logger,

internal/session/local.go

@@ -18,6 +18,7 @@ type LocalConfig struct {
 	Provider   string
 	Model      string
 	SessionID  string                  // identifies this session on disk
+	TurnCount  int                     // seed from restored snapshot; 0 for new sessions
 	Store      *SessionStore           // nil = no persistence
 	Incognito  *security.IncognitoMode // nil = always persist
 	Logger     *slog.Logger            // nil = slog.Default()
@@ -60,6 +61,7 @@ func NewLocal(cfg LocalConfig) *Local {
 		state:     StateIdle,
 		provider:  cfg.Provider,
 		model:     cfg.Model,
+		turnCount: cfg.TurnCount,
 		sessionID: cfg.SessionID,
 		store:     cfg.Store,
 		incognito: cfg.Incognito,

internal/session/store.go

@@ -7,6 +7,7 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
+	"strings"
 
 	"somegit.dev/Owlibou/gnoma/internal/message"
 )
@@ -27,8 +28,25 @@ func NewSessionStore(projectRoot string, maxKeep int, logger *slog.Logger) *Sess
 	}
 }
 
+// sessionDir validates a session ID and returns its absolute path within the store.
+// Rejects empty IDs and path traversal attempts.
+func (s *SessionStore) sessionDir(id string) (string, error) {
+	if id == "" {
+		return "", fmt.Errorf("session ID must not be empty")
+	}
+	dir := filepath.Join(s.dir, id)
+	storeRoot := filepath.Clean(s.dir) + string(os.PathSeparator)
+	if !strings.HasPrefix(dir+string(os.PathSeparator), storeRoot) {
+		return "", fmt.Errorf("invalid session ID %q", id)
+	}
+	return dir, nil
+}
+
 func (s *SessionStore) Save(snap Snapshot) error {
-	dir := filepath.Join(s.dir, snap.ID)
+	dir, err := s.sessionDir(snap.ID)
+	if err != nil {
+		return fmt.Errorf("session save: %w", err)
+	}
 	if err := os.MkdirAll(dir, 0o755); err != nil {
 		return fmt.Errorf("session %q: create dir: %w", snap.ID, err)
 	}
@@ -45,7 +63,10 @@ func (s *SessionStore) Save(snap Snapshot) error {
 }
 
 func (s *SessionStore) Load(id string) (Snapshot, error) {
-	dir := filepath.Join(s.dir, id)
+	dir, err := s.sessionDir(id)
+	if err != nil {
+		return Snapshot{}, fmt.Errorf("session load: %w", err)
+	}
 
 	metaBytes, err := os.ReadFile(filepath.Join(dir, "metadata.json"))
 	if err != nil {

internal/session/store_test.go

@@ -106,6 +106,25 @@ func TestSessionStore_List_SortedByUpdatedAt(t *testing.T) {
 	}
 }
 
+func TestSessionStore_Load_RejectsPathTraversal(t *testing.T) {
+	store := makeStore(t)
+	cases := []string{"../../etc/passwd", "../sibling", ""}
+	for _, id := range cases {
+		_, err := store.Load(id)
+		if err == nil {
+			t.Errorf("Load(%q): expected error for invalid ID", id)
+		}
+	}
+}
+
+func TestSessionStore_Save_RejectsPathTraversal(t *testing.T) {
+	store := makeStore(t)
+	snap := makeSnap("../../evil", time.Now().UTC())
+	if err := store.Save(snap); err == nil {
+		t.Error("Save with traversal ID: expected error")
+	}
+}
+
 func TestSessionStore_Prune_RemovesOldest(t *testing.T) {
 	store := makeStore(t) // maxKeep = 3
 	now := time.Now().UTC()