🛠️Simon Willison: Opus 5.5 vs GPT-6 Sol Sparks LLM Price War
TL;DR
Simon Willison compares Claude Opus 5.5, GPT-6 Sol and GPT-6 Luna hours after launch, with a full price table and hands-on tests. His sharpest finding: Opus 5.5 on max effort burned all 128,000 output tokens reasoning about an SVG and returned nothing, twice.
Simon Willison compares Claude Opus 5.5, GPT-6 Sol and GPT-6 Luna hours after launch, with a full price table and hands-on tests. His sharpest finding: Opus 5.5 on max effort burned all 128,000 output tokens reasoning about an SVG and returned nothing, twice.

Key Points
Side-by-side table puts GPT-6 Luna at $0.10/$0.50 and Grok 4.7 at $2/$6 per million tokens
Two failed Opus 5.5 max runs cost $2.56 each and took nearly 20 minutes
Opus cache-read price fell 60%, which matters most for long agent sessions
GPT-5.6 has a 25% price hike scheduled for November, widening the gap
Willison now defaults to GPT-6 Sol in Codex and Opus 5.5 in Claude Code
Why It Matters
The practical takeaway: pick effort levels deliberately, because max reasoning can overthink simple jobs and cost real money with nothing to show for it.
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