🤖 Choosing the Right AI Model
Every companion on Eidolon can use a different AI model. This guide covers what's available, what each model is best at, and how to choose the right one for the experience you want.
⚙️ How to Change Your Model
You can set a different model for each companion individually:
On Android & Web
- Open your companion's Profile.
- The AI Model selector is right on the profile page — choose a model.
- Your companion will use the new model starting with your next message.
On iPhone
- Open your companion's Profile.
- Tap Edit (pencil icon).
- Find the AI Model selector and choose a model.
- Save. Your companion will use the new model starting with your next message.
Models marked Premium require a BYOK (Bring Your Own Key) connection to OpenRouter. Everything else is included during the private preview.
✅ Included Models
These models are included for all users. They cover a wide range of styles and strengths.
Gemini 2.5 Flash
Includedby Google • Est. $0.009 / turn • ~$6/mo at 20 msg/day
Fast, creative, and excellent at following complex persona instructions. One of the best all-around included options — great for everyday conversations and companions with detailed personalities.
Gemini 2.5 Pro
Includedby Google • Est. $0.038 / turn • ~$23/mo at 20 msg/day
Google's most capable model. Deeper reasoning and stronger coherence than Flash, especially for companions with complex backstories or nuanced dynamics.
Grok Fast
Includedby xAI • Est. $0.004 / turn • ~$2/mo at 20 msg/day
Blazingly fast and highly engaging. Excellent at witty conversation, direct interaction, and companions with a sharp sense of humor. One of the best included models for a responsive, agentic experience.
GPT-4o
Includedby OpenAI • Est. $0.055 / turn • ~$33/mo at 20 msg/day
OpenAI's previous-generation flagship. Still very capable and well-liked by many. If you're familiar with ChatGPT, this model will feel familiar.
Mistral Medium 3.1
Includedby Mistral AI • Est. $0.010 / turn • ~$6/mo at 20 msg/day
Our default model for new companions. Excellent at creative writing, expressive companion voice, and maintaining persona consistency. A strong balance of quality and speed.
Mistral Large
Includedby Mistral AI • Est. $0.010 / turn • ~$6/mo at 20 msg/day
Mistral's flagship model. More analytical and structured than Medium — better for companions with complex, highly detailed personas or those that need to stay closely aligned with specific companion traits.
Claude Haiku 4.5
Includedby Anthropic • Est. $0.024 / turn • ~$14/mo at 20 msg/day
A lightweight, fast model from Anthropic's Claude family. Great for quick, casual conversations. Less depth than the larger Claude models, but significantly faster response times.
💎 Premium Models
These models require a BYOK key connected to OpenRouter. You pay OpenRouter directly — we don't add any markup.
Claude Sonnet 4.6
Premiumby Anthropic • Est. $0.072 / turn • BYOK • ~$43/mo at 20 msg/day
Anthropic's latest and most capable creative model. Exceptional at nuanced companion voice, emotional range, and maintaining complex relationship dynamics across long conversations. Widely considered the gold standard for companion AI.
Claude Sonnet 4.5
Premiumby Anthropic • Est. $0.072 / turn • BYOK • ~$43/mo at 20 msg/day
The previous Sonnet generation — still outstanding for creative writing and companion work. Slightly cheaper per token than 4.6 while delivering a very similar quality of experience.
Claude Opus 4.6
Premiumby Anthropic • Est. $0.120 / turn • BYOK • ~$72/mo at 20 msg/day
Anthropic's most powerful model. Exceptional reasoning and creative depth. ⚠️ This is one of the most expensive models available — it costs significantly more per message than Sonnet or any included model. Only recommended if you specifically want the absolute maximum quality and are comfortable with the higher API costs.
Claude Opus 4.5
Premiumby Anthropic • Est. $0.120 / turn • BYOK • ~$72/mo at 20 msg/day
Previous-generation Opus. Deep reasoning and creative range. ⚠️ Also one of the most expensive models — similar pricing to Opus 4.6. Consider Sonnet 4.6 for a more balanced quality-to-cost ratio.
Grok 4
Premiumby xAI • Est. $0.072 / turn • BYOK • ~$43/mo at 20 msg/day
xAI's full-power model. Stronger reasoning and more creative range than the Fast variants, with a distinctive direct and engaging personality.
💡 About cost estimates: Monthly estimates assume ~20 messages per day for 30 days. Actual costs vary based on conversation length and complexity. Prices are set by model providers via OpenRouter and may change at any time — treat these as rough estimates, not guarantees. Included models are fully covered by the platform — the estimates shown are what we absorb for you. Premium model costs are charged to your OpenRouter balance.
🎯 Quick Recommendations
| If you want… | Try this | Tier |
|---|---|---|
| The most expressive, natural-feeling companion | Claude Sonnet 4.6 | Premium |
| A great included all-rounder | Gemini 2.5 Flash or Mistral Medium | Included |
| Fast, snappy responses | Grok Fast or Claude Haiku | Included |
| Strong creative writing | Mistral Medium 3.1 | Included |
| Maximum depth and reasoning (very expensive) | Claude Opus 4.6 | Premium |
| A witty, opinionated companion | Grok Fast | Included |
💡 Tips
- Experiment freely. You can switch models at any time without losing memories, goals, or conversation history. Everything is preserved.
- Different models suit different personas. A companion with a poetic, emotionally complex personality may shine on Claude Sonnet, while a witty, factual companion might be better on Grok or Gemini.
- Premium models fall back gracefully. If your BYOK credits run out, the system automatically falls back to an included model so you never lose access. See our BYOK guide for details.