Claude Opus 5.5: what the leak says and what Anthropic has confirmed
Claude Opus 5.5 is out. Anthropic's $4/$20 price, 1M context and always-on thinking, scored against the claude-wafer-eap leak that called it.
Anthropic released Claude Opus 5.5 on Tuesday 22 September 2026, the day the leaks said it would come. Most of what leaked held up: the model id, the day, the price down to the cache rates, and the switch to thinking that stays on. The context-window figures were wrong, and the rumoured Sonnet and Fable releases did not arrive with it.
Public status on 22 September 2026 at 21:30 UTC: Claude Opus 5.5 is released. It is on the Claude API as claude-opus-5-5 at $4 per million input tokens and $20 per million output tokens, and on Amazon Bedrock, Google Cloud and Microsoft Foundry. Claude Opus 5 remains available.
This page opened on 21 September as a tracker of the leak. Every claim from that version is below, now scored against Anthropic's launch post, its models overview and its notes for developers. Post times are in UTC.
Claude Opus 5.5 at a glance
Claude Opus 5.5 | |
|---|---|
Released | Tuesday 22 September 2026 |
API id |
|
API price per million tokens | $4 input, $20 output, $0.20 cache reads, $5 cache writes (5-minute) |
Context window | 1,000,000 tokens, with up to 128,000 output tokens |
Thinking | Always on. The effort setting controls how deep it goes, and the default is medium |
Reliable knowledge cutoff | June 2026 |
Speed | Output more than 30% faster than Opus 5, per Anthropic |
Where | Claude apps, Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry |
Anthropic calls it "the first model in our new Claude 5.5 family" and says it "performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5."
The tracker, scored after launch
Claim | Verdict | Who said it, and when | What Anthropic confirmed |
|---|---|---|---|
Anthropic is weighing a new model to answer GPT-6 Astra | Right | Reuters, citing three sources, 18 September | Opus 5.5 launched four days later |
Some Claude Code users are being routed to an "Opus 5.2" | Wrong name | @pankajkumar_dev, 14 September, 18:57 | Anthropic never announced an Opus 5.2. The next Opus was 5.5 |
New Fable, Opus and Sonnet versions are in stealth testing | Partly right | @synthwavedd, 18 September, 22:16 | Opus 5.5 shipped. Sonnet 5.5 and Haiku 5.5 are due "in the coming weeks". No new Fable was announced |
The model is Opus 5.5, id | Right, codename unconfirmed | @lyraxana, 20 September, 13:43 | The id is exact. Anthropic has not used the codename publicly |
Release on Tuesday 22 September, possibly Monday | Right | @lyraxana, 20 September, 15:35 | Released on the Tuesday |
API price of $4 input and $20 output per million tokens | Right | @synaptized, 20 September, 15:30 | Exact, including the $0.20 cache read and $5 cache write |
Context window "872K down from 936K" | Wrong | @pankajkumar_dev, 20 September, 18:58 | 1,000,000 tokens, the same as Opus 5 |
Thinking is always adaptive, forced tool use is retired | Right | @lyraxana, 20 September, 15:35 | Both are listed as breaking changes for developers |
Opus 5.5 beats GPT-6 Sol | Right on one independent index | @pankajkumar_dev, 20 September | Artificial Analysis scores Opus 5.5 at 58 and GPT-6 Sol at 48. Neither company compared the two |
Sonnet 5.5 and Fable 5.5 are rolling out too | Wrong on the day | r/ClaudeAI thread, 21 September | Sonnet 5.5 is announced for the coming weeks. Nothing on Fable 5.5 or 5.2 |
MultiChats carries Opus 5.5 | In progress | Our model registry, 22 September | We are adding it |
What Anthropic announced
Performance. Anthropic calls Opus 5.5 "the new leading model". On its own benchmark table it scores 66.4% on Terminal-Bench 4.0, against 52.3% for Opus 5 and 57.9% for GPT-6 Astra, and 1846 on GDPval-AA v2.1, a test of real-world work across 44 occupations, against 1735 for Claude Fable 5.1.
Cost. Per token, Opus 5.5 is 20% cheaper than Opus 5, and cache reads are 60% cheaper. Anthropic says it also uses fewer tokens per task, which "nets out to a 40% drop in costs" on typical workloads at default settings.
Writing. Anthropic says Opus 5.5 "communicates more naturally than prior models" and "puts the most important information up front", after feedback that Opus 5 could be hard to follow over long sessions.
Usage limits. Anthropic is raising five-hour usage limits on its Pro, Max, Team and seat-based Enterprise plans, and giving subscribers a rate-limit reset they can save and use when they choose. The old version of this page noted that nothing about limits had leaked; this is the answer.
Safeguards. Opus 5.5 launches with protections similar to those on Claude Fable 5.1 for cybersecurity, biology and distillation. Anthropic says "most cybersecurity tasks will be re-routed to Opus 4.8", and organisations doing biology research can apply to a new Life Sciences Verification Program for fuller access.
The leaked price, confirmed
Model | Input | Output | Cache read | Cache write |
|---|---|---|---|---|
Claude Opus 5 | $5.00 | $25.00 | $0.50 | $6.25 |
Claude Opus 5.5 (leaked 20 September) | $4.00 | $20.00 | $0.20 | $5.00 |
Claude Opus 5.5 (published 22 September) | $4.00 | $20.00 | $0.20 | $5.00 |
GPT-6 Sol (published 22 September) | $2.00 | $10.00 | $0.20 | $2.50 |
Per million tokens. Cache writes are the 5-minute rate for Claude and the standard rate for OpenAI.
The leak matched to the cent. Yesterday's version of this page pointed out that the leaked Opus price equalled GPT-5.6 Sol's promotional price. That comparison lasted a few hours: OpenAI launched GPT-6 Sol the same day at half of it.
The independent check tells a more nuanced story on cost. Artificial Analysis scores Opus 5.5 at 58 on its Intelligence Index at max effort, up from Opus 5's 51 and above GPT-6 Astra's 53. At that setting, though, Opus 5.5 wrote about 119,000 output tokens per task against Opus 5's 73,000, and its cost per task came out level with Opus 5's, $5.98 against $5.86. Anthropic's 40% saving is measured at default effort, and the gap between the two shrinks as you turn effort up.
Three details the leak got wrong
The comparison model did not exist. The most-quoted post called Opus 5.5 "around 20% cheaper than Opus 5.1". There is no Opus 5.1. The 20% figure holds against Opus 5, which Anthropic confirmed.
The context numbers matched nothing. "872K down from 936K" implied a shrinking window. Opus 5.5 keeps Opus 5's one million tokens and 128,000 output tokens.
The lineup was early. The r/ClaudeAI thread said Opus, Fable and Sonnet 5.5 were all rolling out. Anthropic released one model and said: "Claude Sonnet 5.5 and Claude Haiku 5.5 will follow in the coming weeks." Fable was not mentioned.
How the Opus 5.5 story took shape
On 14 September a few accounts said Claude Code sessions set to Opus 5 were being answered by something newer, which @pankajkumar_dev called Opus 5.2.
On 18 September Reuters reported that Anthropic was "considering rolling out a new AI model to counter OpenAI's momentum since its launch of GPT-6 Astra", with one source saying its safety was still being evaluated. That evening @synthwavedd posted that "new versions of Fable, Opus and Sonnet are now being stealth tested".
On Sunday 20 September Lyra supplied the specifics: a version number, an id, a codename and a day. At 15:30 UTC @synaptized posted a price list, and Lyra added that partners "only got access for 24h". On Tuesday 22 September, Anthropic published the model.
Why the timing drew attention
Six days before the rumours peaked, chief executive Dario Amodei published an essay arguing that "We must slow the pace at which we improve the capabilities of AI models." Anthropic addresses that directly: "Claude Opus 5.5 is our first release since we called for pacing the frontier." It says the model was tested before release by outside evaluators including METR and Frontier Design, and that it beat every recent Claude model on nearly every measure of misaligned behaviour in its automated audit.
OpenAI released GPT-6 Sol and GPT-6 Luna the same day. Our GPT-6 Sol page covers that launch, and Opus 5.5 vs GPT-6 Sol puts the two side by side.
What changes for Claude users
A new default Opus. Anthropic's developer docs now say to "start with Claude Opus 5.5 for most workloads".
Thinking that stays on. Opus 5.5 "is no longer available with 'thinking' mode switched off". You choose how hard it thinks, and the default is medium, one step below Opus 5's.
Higher limits on paid plans, plus a rate-limit reset you can save.
Stricter safeguards. Some cybersecurity and biology requests are handled by other Claude models or declined.
For developers there are four breaking changes: thinking cannot be disabled, forced tool use returns an error, thinking blocks only carry over between certain models, and computer use needs the newer toolset on the Claude API and Google Cloud.
Where MultiChats stands
We are adding Claude Opus 5.5 to MultiChats on our paid plans, alongside GPT-6 Sol and GPT-6 Luna from OpenAI's launch the same day. We do not carry a Fable model.
Frequently asked questions
Is Claude Opus 5.5 out?
Yes. Anthropic released it on Tuesday 22 September 2026. It is on the Claude API as claude-opus-5-5, in the Claude apps, and on Amazon Bedrock, Google Cloud and Microsoft Foundry.
How much does Claude Opus 5.5 cost?
In the API, $4 per million input tokens and $20 per million output tokens, against $5 and $25 for Opus 5. Cache reads cost $0.20 and batch processing is half price. On Claude subscriptions, Anthropic raised five-hour usage limits on Pro, Max, Team and seat-based Enterprise plans.
Is Claude Opus 5.5 better than Opus 5?
On Anthropic's benchmarks and on Artificial Analysis' index (58 against 51 at max effort), yes. It is also cheaper per token and faster at generating text.
What is claude-wafer-eap?
The codename a leaks account gave for the model on 20 September. The model id in that post was exact, but Anthropic has not used the codename publicly.
Is there a Claude Sonnet 5.5?
Announced, not yet released. Anthropic says Claude Sonnet 5.5 and Claude Haiku 5.5 will follow in the coming weeks. The current Sonnet is Claude Sonnet 5.
Can I still use Claude Opus 5?
Yes. Anthropic's deprecations page lists Opus 5 as active, with retirement no sooner than 24 July 2027.
Update log
22 September 2026, 21:30 UTC. Anthropic released Claude Opus 5.5. Tracker scored against the launch post, the models overview and the developer notes. Added launch facts and Artificial Analysis scores.
21 September 2026, 20:22 UTC. Page opened. No claude-opus-5-5 in Anthropic's API, model documentation or newsroom.