> ## Documentation Index
> Fetch the complete documentation index at: https://docs.anpord.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Harnesses

> The agents that can run a case

A harness is the coding agent itself. Every harness runs the same cases, so switching one is a variant change rather than a rewrite.

| Harness      | `harness`  | Credential                           | Reports                 |
| ------------ | ---------- | ------------------------------------ | ----------------------- |
| Codex        | `codex`    | API key, or ChatGPT                  | Commands, files, tokens |
| Claude Code  | `claude`   | API key                              | Commands, files, tokens |
| OpenCode     | `opencode` | Auth file                            | Commands, files, tokens |
| Pi           | `pi`       | Auth file                            | Commands, files, tokens |
| Gemini CLI   | `gemini`   | API key                              | Commands, files, tokens |
| Qwen Code    | `qwen`     | API key                              | Commands, files, tokens |
| Cursor Agent | `cursor`   | API key                              | Commands, files         |
| FX           | `fx`       | AI Gateway key, or ChatGPT auth file | Verdict only            |

Each needs a [connection](/connections) before it can run. A harness that reports less still passes or fails on its verifier; it just leaves a thinner trajectory, and no cost.

## Models

Model ids are per harness — `opus` for Claude Code, `provider/model` for OpenCode, a bare id for Codex. `codex` and `opencode` list theirs live, the rest come from a fixed set.

```ts theme={null}
const { models } = await anpord.evals.models({ harness: "claude" });
```

## Compare two

Same case, same sandbox, one field apart:

```ts theme={null}
tasks: [
  { harness: "codex", model: "gpt-5.6-sol", provider: "daytona" },
  { harness: "claude", model: "opus", provider: "daytona" },
]
```

Each is its own cell with its own baseline, so their histories never mix.