# Use any model and any harness - Docs

PostHog Code is harness-agnostic. You can run tasks against [Claude Code](https://www.anthropic.com/claude-code) (the default) or [Codex](https://github.com/openai/codex), and pick a specific model within each.

## Picking a harness

Choose a harness when you start a task. PostHog Code ships with two adapters today:

| Harness | Default model | Best for |
| --- | --- | --- |
| Claude Code | Claude Opus | General-purpose code generation, long-context refactors |
| Codex | GPT‑5.x | Reasoning-heavy debugging, alternative second opinion |

More harnesses are on the roadmap – let us know on [Discord](https://discord.gg/posthog) which one you'd like next.

## Picking a model

Each harness exposes its provider's model list. Open the model picker in the task composer to switch before sending a prompt.

Both harnesses also expose a reasoning effort level, which trades latency for deeper reasoning. The available levels differ by harness:

| Harness | Effort levels |
| --- | --- |
| Claude Code | low, medium, high, plus extra high and max on supported models |
| Codex | low, medium, high |

## Authentication

Both harnesses authenticate through PostHog Code. You don't need to manage API keys directly.

### Community questions

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