Anthropic LLM Big Closed weights

Claude Opus 4.1

464 days since Anthropic announced it · 5 Aug 2025

Claude Opus 4.1 is a closed-weights LLM from Anthropic, announced 5 Aug 2025. It costs $15 per 1M input tokens and $75 per 1M output tokens.

Input: $15; per 1M tokens
Cache write: $18.75; per 1M tokens
Cache read: $1.50; per 1M tokens
Output: $75; per 1M tokens
Context window: —; tokens
Parameters: —; not disclosed

Announcement: anthropic.com/news/claude-opus-4-1

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Anthropic · Big · Opus

closed weights

A new one every ~60 days — due in ~9d.

Claude Opus 5.5 +60d 22 Sep 2026
Claude Opus 5 +57d 24 Jul 2026
Claude Opus 4.8 +42d 28 May 2026
Claude Opus 4.7 +70d 16 Apr 2026
Claude Opus 4.6 +73d 5 Feb 2026
Claude Opus 4.5 +111d 24 Nov 2025
Claude Opus 4.1 5 Aug 2025

More from Anthropic

All models

Claude Mythos 5.2 9 Nov 2026
Claude Fable 5.2 9 Nov 2026
Claude Haiku 5.5 7 Oct 2026
Claude Sonnet 5.5 28 Sep 2026
Claude Mythos 5.1 15 Sep 2026
Claude Fable 5.1 1 Sep 2026
Claude Sonnet 5 30 Jun 2026
Claude Mythos 5 9 Jun 2026

Facts last updated 1 Nov 2026, from Anthropic’s own pages.