Reference · Sessions and engines
Engines and their models
What each engine is, which models and reasoning efforts it offers, and what a new session picks by default.
Five engines: Claude Code, Codex, Gemini, DeepSeek and Claude API. An engine is the program a session runs, chosen on the new-session screen alongside the mode and the working directory. A Gemini session runs on the same background process a DeepSeek session does, speaking Google's own wire vocabulary.
Claude API is Claude on the Turret Android and iPhone apps, where Claude Code cannot run. It runs on the same background process DeepSeek does, billed to an Anthropic API key stored on the phone. Its models are the Claude models that process offers, read from it when Turret starts. Only a phone offers it: a desktop has Claude Code, and its new-session screen does not list Claude API at all.
| Engine | Models | Thinking efforts | Can be forked |
|---|---|---|---|
| Claude Code | Sonnet, Opus, Fable | low, medium, high, xhigh, max | Yes |
| Codex | GPT-6-Astra, GPT-6.1-Sol, GPT-6-Luna | low, medium, high, xhigh, max | No |
| Gemini | — | — | No |
| DeepSeek | — | — | No |
| Claude API | — | — | No |
Every engine appears on the new-session screen even when it cannot be picked. A disabled card's tooltip names the reason, printed on no other part of the card:
- No binary found, for any engine
- Claude Code signed out, as
claude auth statusreports it - Codex signed out, as
codex login statusreports it - No Gemini API key set in Settings → Gemini
- No DeepSeek API key set in Settings → DeepSeek
- No Anthropic API key set on the phone, under Settings → API keys
Claude Code and Codex each have an engine card. It offers Install while no copy is installed and Sign in while a copy is signed out. It offers Fix… while a copy does not start and Update while a newer version is out. A working engine offers Sign out, which asks first.
The card sits on the Set up an engine screen, in the Vendors modal, and under Settings → Claude or Codex. Gemini, DeepSeek and Claude API take a key and have none of these buttons.
A ready Gemini, DeepSeek or Claude API engine can still carry a notice beside it, shown when its binary is an unpinned development build.
An engine, its model and its reasoning effort are fixed once a session starts, the same way its mode is. The composer shows the model and effort under the message box for the rest of the session's life, and nothing there changes them.