po-et/dsh-session-snapshot

Rolling, integrity-verified backups of every DeepSeek Harness session — so corruption costs at most the in-flight turn.

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Part of a three-piece session-integrity suite:

Stage	Plugin	Role
Prevent	dsh-session-guard	stop two dsh processes from corrupting one session
Snapshot	dsh-session-snapshot (this)	keep a verified good copy at every turn boundary
Repair	dsh-session-rescue	fix or salvage a log that already broke

Why it exists

dsh-session-guard prevents the common concurrent-write corruption, but two cases stay outside any plugin's reach: a crash mid-write, and dsh's own cold-load repair path that runs before any agent step. This plugin closes that residual gap from the other side. After each turn ends it verifies the live log still loads and, if so, promotes it to a snapshot. When a turn ends with the log already corrupt, it does not overwrite the last good snapshot and tells you how to recover — losing at most the one turn in flight.

Install

Not on npm yet, so install straight from GitHub. pnpm will ask you to allow this package's build script once (dsh prints the exact line to add); that's the prepare step compiling TypeScript.

dsh plugin --profile web add github:po-et/dsh-session-snapshot

That's it — the plugin snapshots automatically at turn boundaries. Using an AI agent? Tell it: "Install the dsh-session-snapshot plugin."

Recover a broken session

The CLI works even when dsh itself won't boot:

npx github:po-et/dsh-session-snapshot                 # list snapshots + live health for every session
npx github:po-et/dsh-session-snapshot list 37374e34   # snapshots for one session (id fragment)
npx github:po-et/dsh-session-snapshot restore 37374e34   # restore the newest verified snapshot
npx github:po-et/dsh-session-snapshot snapshot 37374e34  # take one right now

restore always preserves the current file as <artifact>.pre-restore-<time> first, and refuses any snapshot that does not itself verify as loadable. Use --at <epoch> (shown in list) to restore a specific snapshot instead of the newest.

Configuration

- id: session-snapshot
  name: dsh-session-snapshot
  config:
    keep: 5            # snapshots kept per session before the oldest is pruned
    minIntervalMs: 0   # minimum ms between snapshots of one session (0 = every changed turn)
    # home: /custom    # default: $DSH_HOME (~/.dsh)

Snapshots live under $DSH_HOME/session-snapshots/<session-id>/ and are only taken when the log grew and still verifies, so an unchanged or already-corrupt session never spends I/O or overwrites a good copy.

Cost & honest scope

• Each snapshot is a file copy plus one verification scan of the session log. Turns are seconds-to-minutes apart, so this is cheap in practice; raise minIntervalMs for very large sessions if you want to bound it further.
• Snapshots are point-in-time copies of the session log only — they do not snapshot your workspace files. For conversation+file rollback, that's a different tool.
• Supports session format version 0 (current dsh developer preview), .jsonl and .jsonl.zstd, JSONL backend. Compression is detected by content, so renamed/backup copies verify correctly. dsh is pre-1.0 with no format-compatibility promise; on an unknown version the tool refuses loudly rather than guessing.

Zero runtime dependencies (zstd via Node's built-in zlib). MIT.