fix(session): serialize canonical file access (#5383)

nanobot/agent/memory.py

@@ -769,28 +769,25 @@ class MemoryStore:
         return f"{prefix}\n\n{diff_body}"
 
     @staticmethod
-    def prune_dream_sessions(sessions_dir: Path, *, keep: int = 10) -> None:
+    def prune_dream_sessions(sessions: SessionManager, *, keep: int = 10) -> None:
         """Remove the oldest Dream session files, keeping only the N most recent.
 
         Only current base64url-encoded Dream session keys are considered.
         Non-dream session files are never touched.
         """
-        dream_files: list[Path] = []
-        for path in sessions_dir.glob("*.jsonl"):
-            decoded_key = SessionManager.decode_storage_key(path.stem)
-            if decoded_key is not None and decoded_key.startswith("dream:"):
-                dream_files.append(path)
-        dream_files.sort(key=lambda p: p.stat().st_mtime)
-        if len(dream_files) <= keep:
-            return
+        with sessions.locked_session_files() as sessions_dir:
+            dream_files: list[tuple[Path, str]] = []
+            for path in sessions_dir.glob("*.jsonl"):
+                decoded_key = SessionManager.decode_storage_key(path.stem)
+                if decoded_key is not None and decoded_key.startswith("dream:"):
+                    dream_files.append((path, decoded_key))
+            dream_files.sort(key=lambda item: item[0].stat().st_mtime)
 
-        to_remove = dream_files[: len(dream_files) - keep]
-        for path in to_remove:
-            try:
-                path.unlink()
-                logger.debug("Pruned old dream session: {}", path.stem)
-            except OSError:
-                logger.warning("Failed to prune dream session {}", path)
+            for path, key in dream_files[: max(0, len(dream_files) - keep)]:
+                if sessions.delete_session(key):
+                    logger.debug("Pruned old dream session: {}", path.stem)
+                else:
+                    logger.warning("Failed to prune dream session {}", path)
 
 
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