Chapter 6Why there are different sizes
A family of sizes
Bigger models are more capable but slower and pricier, and most jobs don't need the biggest one. So AI companies sell families of sizes, the way carmakers sell scooters, sedans and trucks.12
| Model | Released | Price per 1M tokens (in / out) | What it's for |
|---|---|---|---|
| Haiku 5.5 | Oct. 7, 2026 | $0.10 / $0.50 For prompts up to 100K tokens; $0.50 / $2.50 above. | Anthropic's lowest-latency, lowest-price model, for high-volume jobs. Access: Everyone.3456 |
| Sonnet 5.5 | Sept. 28, 2026 | $2 / $10 | Balanced speed and capability for everyday coding, writing, analysis and agents. Access: Everyone.357 |
| Opus 5.5 | Sept. 22, 2026 | $4 / $20 | Long, complex agentic coding and knowledge work. Anthropic says most workloads start here. Access: Everyone.358 |
| Fable 5.1 | Sept. 1, 2026 | $10 / $50 | Anthropic's most capable model open to everyone, released with added safeguards. At Fable 5's launch the safeguarded areas were cybersecurity, biology and chemistry, and distillation (copying the model). Access: Everyone (with added safeguards).391011 |
| Mythos 5.1 | Sept. 1, 2026 | $10 / $50 Limited availability. | The same model as Fable 5.1 with different (more permissive) safeguards, offered only to vetted individuals and organizations through trusted-access programs. Access: Vetted individuals and organizations only (trusted-access programs).10549 |
Every word a model writes costs computing power. Larger models generally do harder work better but cost more and respond more slowly, so providers offer a ladder, and good systems send each job to the cheapest model that does it well.5 Anthropic's guidance says most workloads start with Opus 5.5, and that tuning a model's effort setting is often a better lever than switching models.5
Go deeper: every company has a ladder
Last verified Oct. 26, 2026.
- GPT-6 Luna Fast, high-volume, $0.10 / $0.50
- GPT-6.1 Sol Workhorse, $2 / $10
- GPT-6 Astra Flagship, $10 / $50
Notes (15)
- 1Anthropic, “Introducing the next generation of Claude,” March 4, 2024, https://anthropic.com/news/claude-3-family (accessed October 26, 2026).
- 2OpenAI, “GPT-6 Family Model Guide,” October 2, 2026, https://openai.com/index/practical-guide-building-gpt-6/ (accessed October 26, 2026).
- 3Anthropic, “Models overview,” Claude Platform Docs, https://platform.claude.com/docs/en/models/overview (accessed October 26, 2026).
- 4Anthropic, “Pricing,” Claude Platform Docs, https://platform.claude.com/docs/en/about-claude/pricing (accessed October 26, 2026).
- 5Anthropic, “Choosing the right model,” Claude Platform Docs, https://platform.claude.com/docs/en/about-claude/models/choosing-a-model (accessed October 26, 2026).
- 6Anthropic, “Introducing Claude Haiku 5.5,” October 7, 2026, https://www.anthropic.com/claude-haiku-5-5 (accessed October 26, 2026).
- 7Anthropic, “Introducing Claude Sonnet 5.5,” September 28, 2026, https://www.anthropic.com/claude-sonnet-5-5 (accessed October 26, 2026).
- 8Anthropic, “Introducing Claude Opus 5.5,” September 22, 2026, https://www.anthropic.com/claude-opus-5-5 (accessed October 26, 2026).
- 9Anthropic, “Release notes — Claude Platform,” Claude Platform Docs, https://platform.claude.com/docs/release-notes/overview (accessed October 26, 2026).
- 10Anthropic, “Introducing Claude Fable 5.1 and Claude Mythos 5.1,” September 2026, https://www.anthropic.com/claude-fable-and-mythos-5-1 (accessed October 26, 2026).
- 11Anthropic, “Claude Fable 5 and Claude Mythos 5,” June 9, 2026, https://www.anthropic.com/news/claude-fable-5-mythos-5 (accessed October 26, 2026).
- 12OpenAI, “GPT-6 Astra: A new generation of intelligence,” September 2026, https://openai.com/index/gpt-6-astra/ (accessed October 26, 2026).
- 13OpenAI, “Pricing,” OpenAI (developer docs), https://developers.openai.com/api/docs/pricing (accessed October 26, 2026).
- 14Google, “Gemini API pricing,” Google AI for Developers, https://ai.google.dev/gemini-api/docs/pricing (accessed October 26, 2026).
- 15K. Kavukcuoglu, “Gemini 4 Argon: our next era of frontier intelligence,” Google, September 30, 2026, https://blog.google/innovation-and-ai/models-and-research/gemini-models/gemini-4-argon/ (accessed October 26, 2026).
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