nc://chronos

Chronos Time Travel: snapshots the workspace before each file edit or shell call, so a bad change can be diffed and rolled back. A Nodecode rewrite of DevTarlow/hermes-chronos by DevTarlow.

A write, a refactor or a shell command that goes wrong leaves the workspace in a state nobody asked for. This cell records a checkpoint of the whole workspace before every tool call that can change it, keeps the checkpoints in a private git repository inside the workspace, and puts the files back when asked. The project's own git history never moves, and nothing leaves the machine.

Get it

Tell the agent "add the chronos cell", or run:

nodecode add nc://chronos

Set it up

git on PATH is all it needs, and every setting has a default. All of them are optional, in ~/.nodecode/config.jsonc:

{
  "chronos": {
    "workspace": "/work/project",   // absolute; this process's own directory when unset
    "auto_snapshot": true,         // a checkpoint before every file-editing or shell call
    "max_checkpoints": 50,         // how many /chronos lists
    "clean_untracked": true,        // a rollback deletes files created since the checkpoint
    "ignored": ["node_modules"],    // extra gitignore patterns no checkpoint covers
    "max_diff_chars": 400000,       // how much diff text one answer carries
    "timeout_seconds": 30           // one git run's ceiling; its process tree is killed past it
  }
}

Use it

Nothing to type: before a (write-file ...), an (edit ...), a (sh ...) or an eval, a checkpoint is taken unless the workspace is unchanged since the last one.

The model has four tools:

• chronos_checkpoint(description) — take one before a risky step.
• chronos_list_checkpoints(limit) — id, time, the tool that took it, its description.
• chronos_diff(checkpoint_id | from_checkpoint | to_checkpoint, max_chars) — what one checkpoint changed, what changed between two, or what changed since one up to the files on disk (to_checkpoint: "WORKTREE", the default). The answer carries the diff, its stat, and the untracked files a worktree diff does not cover.
• chronos_rollback(checkpoint_id, clean) — put the files back the way that checkpoint left them. A safety checkpoint of the state now is taken first, so the rollback can itself be rolled back. clean (the default) deletes files created since the checkpoint; clean: false writes them back and leaves them untracked.

The operator types the same:

• /chronos — the checkpoints, newest first.
• /chronos diff ID — what that one changed.
• /chronos rollback ID or /chronos rollback latest — restore it; --no-clean keeps the files created since.
• /chronos help, and (help :chronos) is the manual the model carries.

Every answer is JSON with status (ok or error), so a failed call is a result the model reads, not a condition it has to catch.

What it costs, and what it does not cover

A checkpoint is git add -A plus a commit in the shadow repository: the second one of a quiet workspace costs nothing, because no commit is written when nothing changed. The repository lives at <workspace>/.nodecode-chronos/, holds every non-ignored file -- untracked ones such as .env included, which is why it stays inside the workspace -- and carries a .gitignore of * so the operator's own git status never shows it. .git, .nodecode-chronos, node_modules, .venv, venv and __pycache__ are never covered, nor is anything the ignored setting names.

Not covered: ignored files, empty directories, file modes and symlink targets beyond what git stores; and a shell command that leaves the workspace half-written is only put back by a rollback, never mid-command. A restore runs without a prompt — that is the point of a one-verb undo — and it is safe to run twice, since the second one finds nothing to restore.

Test it

.github/test-cell.sh tools/nodecode-chronos

The tests stub the one git seam, so they need no repository, no git install and no network.