Claude Sonnet 5.5 New Sonnet model from Anthropic today. They say it "runs 30%+ faster, and costs up to 30% less for most work" - it's priced the same as Sonnet 5 but appears to beat it on every benchmark, and should be cheaper to run as well. Here are some pelicans riding bicycles.
Claude Sonnet 5.5
About this summary. This is a short, independently written summary of an article first published by Simon Willison. Cyber Security News did not report or verify the underlying story. Read the original: https://simonwillison.net/2026/Sep/28/claude-sonnet-5-5/
Source attribution: headline and facts are from Simon Willison (simonwillison.net). Summary method: excerpt of the source description. See our source attribution policy.
Related coverage
JadePuffer crims hijacked Azure identities and used them to blow up cloud resources
The cyber criminal behind JadePuffer, the first known agentic ransomware infection reported over the summer, has also used stolen Azure identities to conduct destructive…
How we found 24 Android vulnerabilities using our open source AI security agent
With the rise of AI in the security space, our team created the GitHub Security Lab Taskflow Agent as a way for security researchers to easily automate, package, and…
Subjects, Not Authors: The Authorship Hazard in Agentic Dataspaces
arXiv:2609.30614v1 Announce Type: new Abstract: Dataspace connectors decide whether a transfer may occur, not what the transferred value contains, tolerable for…
A Large-Scale Empirical Study of Modern Phishing Email Content
arXiv:2609.30683v1 Announce Type: new Abstract: Phishing remains one of the most pervasive threats to Internet users, and email remains its predominant delivery channel…
AGATE: Provenance-Based Runtime Defense Against Compositional Attacks on LLM Agents
arXiv:2609.30830v1 Announce Type: new Abstract: LLM agents can produce harmful effects through sequences of ordinary operations. Judging such actions requires…
MetaPermit: Scalable and Auditable Access Control for AI Agents via LLM-Inferred Meta-Attributes
arXiv:2609.31039v1 Announce Type: new Abstract: The rise of autonomous AI agents equipped with tools has introduced significant security risks, ranging from unintended…