# shell/ — nash, the Nucleic agent shell

Design doc: [docs/NASH.md](../docs/NASH.md). Vendored fork base:
[`third_party/brush/`](../third_party/brush/) (brush, pinned at
`brush-shell-v0.4.0`; fork patches are marked with `// nash:` comments).

- `nash/` — the shell binary (M0: transparent embedding of the brush CLI).
- `nash-observe/` — event model, taps, and transport (lands in M1).
- `corpus/` — transcript-replay compat harness: `replay.py` runs every command
  in `corpus.jsonl` under bash and nash in identical fresh workspaces and diffs
  exit/stdout/filesystem (stderr reported separately). Divergences are tracked
  in `corpus/DIVERGENCES.md`.

Build & test:

```sh
cargo build --release                      # binary: target/release/nash
python3 corpus/replay.py --nash <path>     # M0/M3 gate: >= 99% parity
```