Claude Opus 5.5 is the easier default to recommend for many coding-agent and knowledge-work teams because Anthropic cut the API rate to $4 per million input tokens and $20 per million output tokens, positioned the model for long-running coding and knowledge work, and published strong agentic-coding results against GPT-6 Astra.[1][2] That does not mean GPT-6 Astra is obsolete. OpenAI describes Astra as its most capable model for complex reasoning, coding, computer use, research and document creation, and the official model page lists a 1,050,000-token context window, 128,000-token maximum output, image input, tool use, web search, file search and reasoning-effort levels from low through max.[5]
The practical answer is not “Opus wins” or “Astra wins.” It is workload routing.[6] Opus 5.5 currently looks attractive when cache-heavy coding agents need many attempts per dollar, but Astra still has defensible advantages in computer-use benchmarks, hard science/math claims, security-gated capability, certain long-context retrieval reports, and token efficiency at high effort.[3][4][7]