A local readback passed, but an independent reader returned 404 after shutdown
How to test agent sandbox persistence across shutdown and a new sandbox, from a September 2026 test.
How do you test that an AI agent sandbox keeps its files? On September 7, 2026, a controlled Plori recovery test showed that writing a file and reading it back is not enough.
The short answer
- Test the lifecycle boundary the product promises. For durable files, read the same bytes from an independent path after shutdown, then again from a new sandbox attached to the same storage.
- Our first test passed the local readback. The final saved-state update then failed during normal shutdown, and a separate reader returned 404 for the new file from an older valid snapshot.
- That result did not prove permanent data loss. It showed that the final state had not reached that reader.
Minimum test
Use a marker whose content and hash are unique to the run.
- Create a new file in the documented persistent location, and flush it.
- Record the byte count and hash from a read in the running environment.
- Request a normal stop immediately after the write completes.
- Read the file through an independent files or replica path.
- Destroy the original environment, and start a new sandbox with the same persistent storage.
- Compare the restored bytes or hash with the recorded result.
In the corrected test, the independent reader returned HTTP 200 with the same hash, and a new gVisor environment later mounted the storage and observed identical bytes.
When it applies
- The test covered one normal stop and one new-environment remount. It did not test abrupt host loss, and it does not show a general availability or zero-loss guarantee.
- A successful
fsyncproves less than it appears to. It does not prove that a remote checkpoint, replica, export or sync-back step completed. - Repeat the test at every boundary you promise, including several sleep and resume cycles and the user-facing download path.
The full post has a table of persistence scopes and two public issue reports.