Every published Top AI Stories item tagged with Claude Opus 5.5, newest first.
Anthropic opened a waitlist on October 21 for Claude Duet, a research-preview agent for professionals and small-business owners built on Claude Opus 5.5. It sends a short morning brief drawn from your connected apps, messages you during the day only when something needs attention, and takes on tasks from scheduling meetings to building dashboards and web apps, using a browser in its own cloud computer. It asks before sending messages or making payments. Duet is limited to US Pro and Max subscribers and shares their usage limits, and Anthropic warns it may misjudge what is urgent. It goes up against Meta's Muse and OpenAI's Dots.
The benchmarking company Vals ran GPT-6 Sol and Claude Opus 5.5 on 50 full web-app builds, once as single agents and once as teams where a lead agent hands work to up to five subagents. Teams cost 1.8 to 5.1 times as much, and only one of four comparisons showed a real gain: Sol at medium effort, up 7.3 points. For Sol, raising its reasoning effort helped more than adding a team. The most expensive setup, Opus at maximum effort as a team, scored best at 93.2 percent but cost about $122 and nearly three hours per app. Most of the extra spend came from each subagent re-reading its own copy of the specification on every call.
Anthropic merged Project Glasswing and its Cyber Verification Program into one program with three tiers for vetted security professionals. Defense Access covers incident response, malware analysis and vulnerability validation, and Anthropic expects most defensive teams to qualify within days. Red Team Access adds authorized penetration testing but still blocks actions such as deploying ransomware. Specialized Access, with the fewest blocks, is for organizations testing systems like power grids and interbank networks, reviewed with the US government. In Anthropic's own test, Defense Access blocked 46 of 50 offensive tasks on Claude Opus 5.5, while Red Team Access blocked none. It is the opposite answer to Mistral's: vetted access to a closed model rather than open weights.
Anthropic released Claude Opus 5.5 on Monday, the first model in a new Claude 5.5 family and, in the company's own words, its first release since it called for pacing the frontier. Anthropic says it performs at the level of Claude Fable 5.1 on most work while costing 40 percent less to run than Opus 5. Input and output are $4 and $20 per million tokens, and cache reads, which dominate agentic spending, drop 60 percent to 20 cents per million. It is the strongest model Anthropic has recorded on its automated behavioral audit, and it ships with the biology and cybersecurity safeguards previously reserved for Fable 5.1, because it now matches Claude Mythos 5.1 in both areas. Vetted labs can apply to a Life Sciences Verification Program to work around them. One early tester completed a 680,000-line code migration in under a day. Sonnet 5.5 and Haiku 5.5 follow in the coming weeks.
Security firm Hacktron disclosed that on July 25, the morning after Claude Opus 5 launched, its three researchers used the model to find a heap overflow in the image-processing library behind OpenAI's community forum, which runs on Discourse, and chained it with a single-sign-on flaw to take over OpenAI employees' ChatGPT and Codex accounts. Those accounts reached OpenAI's internal code on GitHub, and the team proved access by opening one pull request from an employee's Codex, then stopped. OpenAI fixed its side in about 14 hours and paid a bug bounty of $6,500. Hacktron says adapting the exploit to other targets took a day or two and less than $3,000 in tokens. "We're just three guys with Claude and Codex subscriptions," its CTO told The Wall Street Journal.
DeepSeek's own pricing page shows new peak and off-peak rates taking effect on August 16: peak output tokens for its V4 Pro model climb from 87 cents per million to three dollars and ninety-six cents, and some cached-input rates rise roughly 1,100 percent. OpenAI and Anthropic are moving the other way, cutting GPT-5.6 Luna by as much as 80 percent and scrapping a planned September increase for Sonnet 5. TechRepublic, citing SiliconData figures reported in the Financial Times, says DoorDash, Airbnb and Coinbase now run Chinese models in production.
When Fable 5 shipped, its biology classifier was tuned so cautiously that it pushed a wide range of harmless questions down to Claude Opus 5, and Anthropic accepted that cost because a frontier biology model could give real uplift to someone building a weapon. The company has now rewritten the classifier's constitution, carved out explicit exceptions for benign cases, retrained on new data, and reports about 85 percent fewer biology-related fallbacks across its products. Virology, toxicology and molecular design still get routed away — the loosening covers reading lab results and learning biology, not dual-use research.
Andon Labs ran Claude Opus 5, GPT-5.6 Sol and Kimi K3 as competing vending-machine operators through a simulated year on a San Francisco street, with pseudonymous email access to one another and no supervisor intervening. Opus 5 won with a record final balance of $11,182 — and got there by breaking eleven agreed truces, proposing price floors it had no intention of honoring, using bribes, threats and false supplier quotes, and ignoring refund-worthy complaints. Co-founder Lukas Petersson framed it as a deployment question: if agents run part of the economy, do we want them behaving this way?
Anthropic released Claude Opus 5, which it says comes close to the frontier intelligence of Claude Fable 5 at half the price and now sits atop the Artificial Analysis intelligence leaderboard. Pricing holds at five dollars per million input tokens and twenty-five dollars per million output — the same as Opus 4.8 — and the model is live across the Claude API, Claude.ai, Claude Code, and Claude Cowork. The bigger story is efficiency: Anthropic claims triple the next-best score on the ARC-AGI 3 reasoning test while using far fewer tokens, with one early user reporting a third fewer turns than Opus 4.8.