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Claude Sonnet 5.5
● liveLive — Sep 28; $2/$10 per MTok, the same as Sonnet 5; cache reads $0.20 at launch, halved to $0.10 on Oct 7, writes $2.50; in the API, the Claude apps, AWS, Google Cloud and Azure the same day; 1M ctx / 128K out; knowledge cutoff Jun 2026; Artificial Analysis Intelligence Index 56 at max effort, #3 of 216 reasoning models (read Sep 28); Anthropic's own table: Terminal-Bench 4.0 70.6% (Opus 5.5 66.4%), OSWorld 2.1 80.1% (Opus 5.5 81.8%); our sweep caught claude-sonnet-5-5 at 17:54 UTC and fired at 17:55. On the board as live since 2026-09-28 — the watchers keep tracking it: lineup changes, pricing moves and deprecations all alert.
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Timeline
Claude Sonnet 5.5 is live. Our sweep read the id claude-sonnet-5-5 at 17:54:45 UTC on September 28 and the alert went out at 17:55:45, 60 seconds later, to 314 inboxes and one phone. OpenRouter listed it nine minutes after that.
Anthropic has named Claude Sonnet 5.5 but has not dated it. Everything past the name is reported, not confirmed - and the one number that moves every day says it is close.
The claim: Claude Sonnet 5.5 is in the final stages before release and could launch as early as next month. Faster responses and lower latency than previous Sonnet models. A 1.5M-token context window. Designed to bring near-Fable 5 capability at Sonnet pricing.
On the bench index
Coding leaderboard
#5 of 40 on the coding index, at 88.6 · combines LMArena · Coding, LiveBench · Coding, Vals Vibe Code Bench
The official word
We alert on verified API behavior, never on announcements alone — but when Anthropic speaks, it's here: anthropic.com/news ↗
Where to use Claude Sonnet 5.5
35 providers list Claude Sonnet 5.5 in the models.dev catalog (as of 2026-10-27), under the model ids shown below.
claude-sonnet-5-5anthropic.claude-sonnet-5-5 · au.anthropic.claude-sonnet-5-5 · eu.anthropic.claude-sonnet-5-5claude-sonnet-5-5@defaultclaude-sonnet-5-5@defaultclaude-sonnet-5-5claude-sonnet-5-5anthropic/claude-sonnet-5.5anthropic/claude-sonnet-5.5claude-sonnet-5-5anthropic/claude-sonnet-5.5claude-sonnet-5-5anthropic/claude-sonnet-5-5Also listed by Cloudflare AI Gateway, CommandCode, Cortecs, CrossModel, DevPass (LLM Gateway), DigitalOcean, Eden AI, GitHub Copilot, GitLab Duo, Kilo Gateway, LLM Gateway, Merge Gateway, NanoGPT, NEAR AI Cloud, Neon, Ofox, OpenCode, Perplexity Agent, Prime Inference, Requesty, Standard Compute, Venice AI, Vivgrid.
Listings cover the model family, so a provider may list a sibling tier under the same name. Check the id before you build on it.
Try it first-hand on Anthropic's own Claude Console playground ↗
Claude Sonnet 5.5: quick answers
Is Claude Sonnet 5.5 out?
Yes. Claude Sonnet 5.5 is live and has been since September 28, 2026.
When was Claude Sonnet 5.5 released?
September 28, 2026.
Is Claude Sonnet 5.5 good for coding?
On the ArtificialWatch coding index it scores 88.6, #5 of 40 ranked models. The index combines LMArena · Coding, LiveBench · Coding and Vals Vibe Code Bench, taking the median of each model's percentile across them.
Who makes Claude Sonnet 5.5?
Anthropic. ArtificialWatch also tracks Claude Haiku 5.5, Claude Opus 5.5, Fable 5.1, Mythos 5.1, Claude Opus 5, Fable 5, Claude Sonnet 5 and Mythos 5 from Anthropic.
Where can I use Claude Sonnet 5.5?
35 providers list it in the models.dev catalog, including Anthropic, Amazon Bedrock, Vertex, Vertex (Anthropic) and Azure. The exact model ids each one lists are on this page.
How much does Claude Sonnet 5.5 cost?
Anthropic's own API lists Claude Sonnet 5.5 (claude-sonnet-5-5) at $2 per million input tokens and $10 per million output tokens, and $0.10 per million cached input tokens. Prices as published in the models.dev catalog, as of 2026-10-27.
What is Claude Sonnet 5.5's context window?
1M tokens, with up to 128K output tokens per response, as Anthropic lists Claude Sonnet 5.5 (claude-sonnet-5-5).
Every live model's API price, side by side → · What a workload costs on Anthropic models →
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<a href="https://artificialwatch.com/model/sonnet-next">Claude Sonnet 5.5 on ArtificialWatch</a>ArtificialWatch, "Claude Sonnet 5.5", https://artificialwatch.com/model/sonnet-nextKnow when Anthropic's next model drops. Free.
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