Salvage of PR #8018 by @alt-glitch onto current main.
On sandbox teardown, FileSyncManager now downloads the remote .hermes/
directory, diffs against SHA-256 hashes of what was originally pushed,
and applies only changed files back to the host.
Core (tools/environments/file_sync.py):
- sync_back(): orchestrates download -> unpack -> diff -> apply with:
- Retry with exponential backoff (3 attempts, 2s/4s/8s)
- SIGINT trap + defer (prevents partial writes on Ctrl-C)
- fcntl.flock serialization (concurrent gateway sandboxes)
- Last-write-wins conflict resolution with warning
- New remote files pulled back via _infer_host_path prefix matching
Backends:
- SSH: _ssh_bulk_download — tar cf - piped over SSH
- Modal: _modal_bulk_download — exec tar cf - -> proc.stdout.read
- Daytona: _daytona_bulk_download — exec tar cf -> SDK download_file
- All three call sync_back() at the top of cleanup()
Fixes applied during salvage (vs original PR #8018):
| # | Issue | Fix |
|---|-------|-----|
| C1 | import fcntl unconditional — crashes Windows | try/except with fallback; _sync_back_locked skips locking when fcntl=None |
| W1 | assert for runtime guard (stripped by -O) | Replaced with proper if/raise RuntimeError |
| W2 | O(n*m) from _get_files_fn() called per file | Cache mapping once at start of _sync_back_impl, pass to resolve/infer |
| W3 | Dead BulkDownloadFn imports in 3 backends | Removed unused imports |
| W4 | Modal hardcodes root/.hermes, no explanation | Added docstring comment explaining Modal always runs as root |
| S1 | SHA-256 computed for new files where pushed_hash=None | Skip hashing when pushed_hash is None (comparison always False) |
| S2 | Daytona /tmp/.hermes_sync.tar never cleaned up | Added rm -f after download (best-effort) |
Tests: 49 passing (17 new: _infer_host_path edge cases, SIGINT
main/worker thread, Windows fcntl=None fallback, Daytona tar cleanup).
Based on #8018 by @alt-glitch.
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