[Ubuntu 24.04][Sandbox] Failed snapshot (unreadable file) exits 1 'Snapshot failed' but still registers and lists the incomplete snapshot

[wangericnv]

Description

When nemoclaw {sandbox} snapshot create fails because a captured file is unreadable, the command exits non-zero with Snapshot failed. / Failed files: openclaw.json — but it does not clean up: the incomplete snapshot is left on disk AND registered as a listable snapshot (it appears in nemoclaw {sandbox} snapshot list as a normal versioned entry). Inconsistent fail-closed cleanup: the credential-sanitization-error path removes its incomplete backup, but the failed-files path leaves a listable, restorable, incomplete snapshot behind.

Impact: a later restore could pick up an incomplete snapshot that never completed successfully.

Platform scope: Reproduced on Ubuntu 24.04 x86_64 (A100), NemoClaw v0.0.101. Not believed platform-specific.
Regression: Unknown.

Environment

OS: Ubuntu 24.04.4 LTS   Arch: x86_64   Docker: 29.6.0
OpenShell: 0.0.85   NemoClaw: v0.0.101   OpenClaw: 2026.7.1

Steps to Reproduce

1. Onboard an OpenClaw sandbox {sandbox}; confirm snapshot list is empty.
2. nemoclaw {sandbox} exec -- bash -lc 'chmod 000 /sandbox/.openclaw/openclaw.json'
3. nemoclaw {sandbox} snapshot create --name failtest (capture output + exit code)
4. nemoclaw {sandbox} snapshot list

Expected Result

The failed snapshot is cleaned up — incomplete staging dir removed, snapshot NOT registered/listed (consistent with the credential-sanitization-error path). snapshot list shows no new entry.

Actual Result

# Step 3 -> exit 1
Creating snapshot of '{sandbox}' (--name failtest)...
Snapshot failed.
Failed files: openclaw.json

# Step 4 -> the incomplete snapshot is listed as a valid versioned entry:
v1   failtest   2026-08-04T06-53-38-310Z   /home/.../.nemoclaw/rebuild-ba...

The incomplete snapshot persists on disk and is listable (and restorable), with no cleanup or warning.