Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war
Simon Willison @simonw · blog · 2026-09-22 · ★★★ · archived
Same-day comparison of the two simultaneous frontier launches, framing them as a price war.
Summary
Willison covers Anthropic's Claude Opus 5.5 and, about an hour later, OpenAI's GPT-6 Sol and GPT-6 Luna. Reported pricing: Opus 5.5 at $4/$20 per million input/output tokens (~20% cut, cached reads $0.20), GPT-6 Luna at $0.10/$0.50. Includes pelican-SVG comparison grids across reasoning levels. Announced in his tweet x.com/simonw/status/2102546103984079131 (verified via syndication, 2026-09-22T23:50Z). Title/date from his September archive.
Archived text
Page title: Claude Opus 5.5, GPT-6 Sol, GPT-6 Luna, and a new price war
Page description: Yesterday was Grok 4.7 (pelicans) and MiMo v2.6 Flash/Pro (more pelicans). Today Anthropic released Claude Opus 5.5, and around an hour later OpenAI released GPT-6 Sol and GPT-6 Luna. It’s …
Metadata archived 2026-09-29; see Summary for content.
Related events
- Anthropic releases Claude Opus 5.5 — Fable-5.1-level performance at $4/$20, first model of the Claude 5.5 family 2026-09-22
- OpenAI launches GPT-6 Sol and GPT-6 Luna at half the price of GPT-5.6 2026-09-22
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