Theo (Chat Engine)
Theo is the default conversational engine — fast, capable, and tuned for everyday chat, drafting, and lightweight tool calling.
In depth
Theo is the engine that powers Fast Mode and most casual conversations. It’s the cheapest option per request, sized for instant replies, and is the default for the dashboard sidebar mascot.
Engine selection happens via the unified Theo catalog — never via raw provider IDs.
Also known as
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Theo Pro
Theo Pro is the higher-quality conversational engine — used for hard reasoning, code, and modes where correctness and depth matter more than latency.
Fast Mode
Fast Mode is Theo’s default conversational engine — instant replies, low credit cost, and the right pick for quick questions, drafts, and lightweight artifact creation.