dsh-plugin-anti-rot

Readme

# dsh-plugin-anti-rot

A [DeepSeek Harness](https://github.com/deepseek-ai/deepseek-harness) plugin
developed to remove a common source of **context rot** in long-running agent
sessions: verbose tool error payloads piling up in the context window. When a
child process dies mid-traceback, its raw stack dump would otherwise spend the
whole error — often dozens of noise lines — against the session's context
budget, and repeated failures compound over hours of work. This plugin
compresses those payloads before they reach model context and the session log. A failed call's text is reduced to its first `maxLines` message
lines, indented `at …` stack-frame lines are dropped, and an elision marker names
what was removed:

```
Error: boom
[…anti-rot: dropped 8 stack-frame lines, omitted 0 of 8 message lines…]
```

## How it works

The plugin hooks the `tools/post-execute` waterfall and rewrites error text in
place. It recognizes two failure signals and nothing else:

- an `isError` result (infrastructure failures — spawn errors, aborts), or
- a trailing non-zero `[exit code: N]` marker per the shell tools' shared
  rendering contract (failing commands are model-interpreted SUCCESS results,
  so the marker is the only failing-command signal).

A clean exit leaves the result untouched. The exit marker is always re-appended
as the final line of a compressed payload, because the model is instructed to
check it and the terminal UI parses it from the end of the text.

Bounding oversized *successful* text is a different concern, owned by
`@deepseek-ai/dsh-spill-policy`; both plugins delegate through `next()` and
compose.

## Install

From a checkout of this repository:

```sh
pnpm dsh plugin --profile web add /path/to/dsh-plugin-anti-rot
```

Or run it transiently with an overlay:

```sh
pnpm dsh web --patch /path/to/dsh-plugin-anti-rot/overlay.yml
```

## Configuration

| Field | Type | Description |
| --- | --- | --- |
| `maxLines` | `number` | Maximum message lines kept in a compressed error payload. Must be a positive integer; load fails loudly otherwise. |

Example entry in `cordis.patch.yml`:

```yaml
- insert:
    - id: anti-rot
      name: dsh-plugin-anti-rot
      config:
        maxLines: 15
```

## Development

```sh
npm install
npm run build                                        # tsc → lib/
node --import tsx/esm tests/anti-rot.smoke.ts        # keyless smoke tests
npx tsc -p tsconfig.json                             # strict typecheck
```

## License

[MIT](./LICENSE) © Orangelightening