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

# Agents & models

> Choose which coding agent and model runs each task — Claude Code, Codex, or OpenCode.

Twill orchestrates the CLI coding agents you'd use in your own terminal, rather than reinventing one. Pick per task in the composer, set workspace defaults with [routing configs](/agent-config/routing), or run the same task with several agents in parallel and keep the best PR.

## Available agents

| Agent           | By          | Models                                                                    |
| --------------- | ----------- | ------------------------------------------------------------------------- |
| **Claude Code** | Anthropic   | Claude Fable, Opus, Sonnet, Haiku                                         |
| **Codex**       | OpenAI      | GPT 5.6 Sol, GPT 5.6 Terra, GPT 5.6 Luna, GPT 5.5, GPT 5.4, GPT 5.3 Codex |
| **OpenCode**    | Open source | Multi-provider — see below                                                |

OpenCode runs frontier and open-weight models side by side: DeepSeek V4 Pro, GLM 5.2, Kimi K2.6, GPT 5.6 Sol / Terra / Luna, GPT 5.5 / 5.4 / 5.3 Codex, Gemini 3.1 Pro, Claude Opus 4.7, Claude Sonnet 4.6 — plus any OpenRouter model via the **OpenRouter…** picker.

<Tip>
  A pragmatic split: frontier models for hard tasks, open-weight models for
  routine ones. With [BYOK](/agent-config/byok) you pay provider rates for both.
</Tip>

## Reasoning effort

Every model runs at an effort level: `low`, `medium`, `high`, or `xhigh` — higher effort means deeper reasoning and longer runs. Claude Code adds `ultracode`, which combines maximum effort with multi-agent workflows for the hardest tasks.

## Defaults

Set what runs when you don't choose explicitly in **Settings → Routing**: the `default` routing config defines the workspace's standard agent, model, and effort, and `/trigger` keywords let a single message opt into something else. See [Routing](/agent-config/routing).

## Memory

Agents persist non-obvious learnings — setup quirks, conventions, gotchas — to `CLAUDE.md` or `AGENTS.md` in the relevant repo, and read those files at the start of every task. Memory is plain Markdown in your repo: reviewable in PRs, portable across all three agents, and yours to edit.