Introducing Claude Opus 5.5
Claude @claudeai · x · 2026-09-22 · ★★★★ · archived
Launch post for Opus 5.5, Anthropic's first model after Amodei's call to pace the frontier, performing near Fable 5.1 at lower cost.
Summary
The Claude account introduced Opus 5.5 as the first model of the Claude 5.5 family. It performs at Fable 5.1's level on most tasks and costs 40% less to run than Opus 5 ($4/$20 per MTok, >30% faster output). A thread post says it writes more naturally, addressing feedback on Opus 5 (x.com/claudeai/status/2102435529044250670). @AnthropicAI posted 'Claude Opus 5.5 is available today.' (x.com/AnthropicAI/status/2102435703535939725). Commentators such as Invezz (x.com/InvezzPortal/status/2102451404548010389) noted the timing, ten days after 'We Must Pace the Frontier'. Arena reported Opus 5.5 at #1 in Text Arena (x.com/arena/status/2103893011164017018). Verified via syndication: 2026-09-22T16:31:01Z.
Archived text
Introducing Claude Opus 5.5, the first model in our new Claude 5.5 family.
It performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5. https://t.co/Q9C2VKQ79f
Media: https://pbs.twimg.com/media/HS1aPgYWMAAP9sw.jpg
likes 96884 · replies 3340 (at fetch time)
Archived 2026-09-29 via syndication.
Related events
- Anthropic releases Claude Opus 5.5 — Fable-5.1-level performance at $4/$20, first model of the Claude 5.5 family 2026-09-22
- Dario Amodei publishes "We Must Pace the Frontier", calling for a deliberate slowdown 2026-09-12
All posts · id: 2026-09-22-claudeai-introducing-opus-5-5