dsh-plugin-anti-rot

A 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:

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

Or run it transiently with an overlay:

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:

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

Development

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 © DeepSeek