Choosing the Right AI Model for Your Agent

atbot.run currently supports three AI models via OpenRouter: Qwen3.5 Flash, Claude Sonnet 4.6, and GPT-4o Mini. Each has different characteristics in terms of speed, cost, and reasoning quality. Here's how to choose.

Qwen3.5 Flash — the default

Qwen3.5 Flash is fast and cost-efficient. For most everyday use cases — answering questions, casual conversation, basic task assistance — it performs well and keeps costs low. This is the default on atbot.run and the right choice for most people starting out.

Choose Qwen3.5 Flash if:
- You're building a general-purpose assistant
- Response time matters (it's the fastest option)
- You're processing high message volume on a tight budget

Claude Sonnet 4.6 — for complex reasoning

Claude Sonnet 4.6 is Anthropic's mid-tier model. It excels at tasks requiring multi-step reasoning, nuanced writing, and careful instruction-following. If your agent needs to analyze text, summarize long documents, or handle sensitive customer interactions, Sonnet's thoughtfulness pays off.

Choose Claude Sonnet 4.6 if:
- Your agent does analysis or document processing
- Tone and nuance matter (support bots, writing assistants)
- You're willing to pay slightly more for better reasoning quality

GPT-4o Mini — familiar reliability

GPT-4o Mini is OpenAI's fast, affordable model. It's a strong all-rounder and many people are familiar with the GPT "style" of responses. If you've used ChatGPT and want similar behavior in your agent, this is a natural fit.

Choose GPT-4o Mini if:
- You want a well-tested model with broad knowledge
- Your use case is general-purpose
- You prefer OpenAI's response style

The practical answer

Start with Qwen3.5 Flash. Test your use case thoroughly. If you notice quality problems — missed nuance, shallow reasoning, poor instruction-following — switch to Claude Sonnet 4.6. Model choice is easy to change in your agent's settings; it takes effect immediately with no restart needed.