Claude Opus 5.5 vs GPT-6 Astra

Claude Opus 5.5 in brief

Claude Opus 5.5 specs and pricing: Anthropic's September 2026 default model, $4/$20 per million tokens with a 1M-token context, and how it compares with GPT-6 Astra.

• Anthropic's recommended starting point for most workloads
• Long-running agentic coding
• 1M-token context and 128K output
• Cheaper prompt caching (5% of input price)

GPT-6 Astra in brief

GPT-6 Astra specs and pricing: OpenAI's flagship SI model (September 2026) with a 1.05M-token context window at $10/$50 per million tokens, plus how it compares.

• Long-horizon agentic work and computer use
• Software engineering
• About 1.05M-token context with 128K output
• First model rated "Critical" for cyber capability under OpenAI's framework

Which should you choose?

Choose Claude Opus 5.5 if you need: software engineering and coding agents; knowledge work such as analysis and writing; most production workloads that need top-tier quality.

Choose GPT-6 Astra if you need: the hardest multi-step agent tasks; large codebases and complex engineering; research and analysis where quality matters more than cost.

For most teams the best test is your own workload: run the same 20–50 real prompts through both models and compare quality, speed and cost. Benchmarks published by labs use different settings and rarely match everyday use.