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Claude Opus 5.5 vs GPT-6 Astra

Updated Oct 24, 2026. Checked daily.

These are the current #1 and the alternative for Coding & Software, Reasoning, Math & Science.

#1

Claude Opus 5.5

Anthropic

Evidence
LMArena Code 1813; #1 SWE-bench Pro (89.9%)
Cost
Pro is $20/month ($17/month billed annually); API is $4 per million input tokens and $20 per million output tokens.
Access
Paid plan
Privacy
Anthropic says Free, Pro, and Max chats are used for training only if you allow it, and you choose at signup. The toggle has been reported as on by default, so check it. Settings, then Privacy. Turn off Help improve Claude.
Pick this if
Pick this when the code has to be right the first time.

Alternative

GPT-6 Astra

OpenAI

Evidence
LMArena Code 1786.1; 90.2% on SWE-bench Pro V2 HARD
Cost
Plus is $20/month; API is $10 per million input tokens and $50 per million output tokens.
Access
Paid plan
Privacy
Yes on personal Free, Plus, and Pro. Improve the model for everyone is on by default. Settings, Data controls, turn off Improve the model for everyone.
Pick this if
Pick this when you already work in ChatGPT or Codex.

Questions

Which is better for coding & software, Claude Opus 5.5 or GPT-6 Astra?

Claude Opus 5.5 leads coding & software on LMArena Code. Claude Opus 5.5 scores 1813 and GPT-6 Astra scores 1786.1 on that signal.

Which is better for reasoning, math & science, Claude Opus 5.5 or GPT-6 Astra?

Claude Opus 5.5 leads reasoning, math & science on Humanity's Last Exam.

Which is cheaper?

Claude Opus 5.5 costs Pro is $20/month ($17/month billed annually); API is $4 per million input tokens and $20 per million output tokens. GPT-6 Astra costs Plus is $20/month; API is $10 per million input tokens and $50 per million output tokens. These are the stored prices, not a guess about which plan is cheaper for you.

Which is more private?

Claude Opus 5.5: Anthropic says Free, Pro, and Max chats are used for training only if you allow it, and you choose at signup. The toggle has been reported as on by default, so check it. GPT-6 Astra: Yes on personal Free, Plus, and Pro. Improve the model for everyone is on by default.