# Loop de loop.

> This DeepSeek Harness plugin stops Qwen's unrecoverable loopiness.

- Published: 2026-09-04
- Tags: ai
- Page: https://gustavo.is/blog/agent-circuit-breaker

Perplexity has been my Google replacement for search and deep research for a while
but I wasn't getting the depth I wanted, so I decided to replace it with a locally
run solution. I've been running Qwen 3.8 with Opencode and Hermes,
and I noticed early on that 3.8 agents would go into these tool call loops you couldn't
recover from even by interrupting them. I tried changing the llama.cpp flags thinking
something might help with no luck. After looking into it, this is what I found out:

<Blockquote icon="🤖">
  <p>
    Repetition self-reinforces into a loop no instruction can break, and Qwen's
    linear-attention layers, with their lossy precision-sensitive recall, fall in
    more easily. Agent loops repeat whole tool calls, too far apart for any sampler
    penalty to notice.
  </p>
</Blockquote>

So that's why setting up a deep research skill using this model will leave your harness
making thousands of tool calls and getting nowhere.

## Breaking the cycle [#breaking-the-cycle]

I could probably fix this by using `tool.execute.before` in Opencode, but I'd been
wanting to try [DeepSeek Harness](https://deepseekharness.io/) to see if its plugin
system is as easy and powerful as 11,000 overenthusiastic tech bros will tell you on
YouTube without backing it up with examples. And it was.

It only took 100 lines of code. The plugin sits between the harness and its tools and
fires before each tool call. The same call with the same significant
arguments six times inside a sliding window gets denied, with an explanation
handed back to the model. A per-agent lifetime cap stops loops that vary
their arguments. It also strips annotation-only fields like bash's
`description` before comparing, because the model rewrites those every call,
and it can log each first denial to a JSONL file so a supervising agent can
notice a stuck child and interrupt it.

There's probably a plugin for this already but this was a fun project for understanding how to make one.
I can see why DSH is getting so much traction. There have been many times when I've wanted to switch the
plumbing in the Claude Code harness outside of hooks and skills.

## Try it out [#try-it-out]

Find it here: [dsh-circuit-breaker](https://github.com/pricklywiggles/dsh-circuit-breaker),
to install:

```sh
dsh plugin --profile web add github:pricklywiggles/dsh-circuit-breaker
```

Knobs (limits, exemptions, the incident log) are documented in the
readme, and the defaults are loose: normal repeats pass, only
degenerate ones die. It's not specific to Qwen 3.8 but it works well with it.