Claude Sonnet 5.5 vs GPT-6 Astra

Where it leads

• Lower input and output prices, $2 and $10 vs $10 and $50 per 1M tokens
• Higher Arena Text score, 1477 Elo vs 1476 Elo
• Cheaper cached input, $0.10 vs $1 per 1M tokens
• Batch pricing, $1 input and $5 output per 1M tokens

Best for

• Production workloads that need frontier-adjacent quality at a mid-tier rate
• Latency-sensitive agent steps inside a larger pipeline

Watch out for

• Same list price as Claude Sonnet 5, so the gain is capability and cache economics rather than a cheaper rate card
• Anthropic positions Opus 5.5 rather than this as the default, so reach for Sonnet 5.5 when latency matters more than peak capability

Where it leads

• Higher Arena WebDev score, 1773 Elo vs 1770 Elo
• Higher FrontierMath Tiers 1-3 (v2) score, 93.7% vs 88.8%
• Higher GPQA Diamond score, 95.8% vs 95.6%
• Higher SimpleQA Verified score, 75.6% vs 46.5%
• Larger context window 1,050,000 vs 1,000,000 tokens

Best for

• Frontier reasoning and agentic evaluations where deep-context retrieval accuracy is the binding constraint
• Workloads that can be kept under the long-context threshold, where the effective rate stays at $10 / $50

Watch out for

• Long-context billing is a cliff, not a taper: a request over the long-context threshold is rebilled in full at $20 per million input and $75 per million output, so a prompt that crosses it costs roughly double
• GPT-6 Astra is the first publicly released model OpenAI classifies as crossing the Critical cybersecurity threshold under its own Preparedness Framework, which carries additional deployment safeguards
• Vendor-reported benchmark figures come from OpenAI’s own launch material and its own harness; they are not independently reproduced here