#Anthropic

AISimon Willison says Claude Sonnet 5.5 now powers the free tier on claude.ai, so free users can run the kinds of experiments he describes. He contrasts this with ChatGPT's free tier, which he says still runs the less capable GPT-5.6 Luna.

AIAnthropic has released Claude Sonnet 5.5, the second model in the Claude 5.5 family. The company says it is more than 30% faster than Sonnet 5 and costs up to 30% less for most work.

Why it matters: The post gives concrete speed and price changes against Sonnet 5, which helps readers judge whether the upgrade fits their workloads and budgets.

AIAnthropic co-founder Mike Krieger says he still uses Opus 5.5 for most work, but Sonnet 5.5 is a strong complement. He praises its design skills and says he now uses it often to make Artifacts, while encouraging readers to try it.

AIAnthropic has introduced Claude Sonnet 5.5, the second model in the Claude 5.5 family, as a clear upgrade over Sonnet 5. The announcement says it runs more than 30% faster and costs up to 30% less for most work. Alex Albert, quoting the announcement, says the model writes clearly, is very fast, and makes a major capabilities jump over Sonnet 5.

AIwhich links to a page for trying the model. The quoted announcement describes it as the second model in the Claude 5.5 family, a clear upgrade over Sonnet 5 that runs more than 30% faster and costs up to 30% less for most work.

AIAnthropic has released Claude Sonnet 5.5, the second model in the Claude 5.5 family. The quoted announcement says it is a clear upgrade over Sonnet 5, runs more than 30% faster, and costs up to 30% less for most work.

AIAnthropic has launched Claude Sonnet 5.5, the second model in its Claude 5.5 family. The company describes it as a faster, lower-cost complement to Claude Opus 5.5, and points readers to a blog post for more information.

Why it matters: The release note places Sonnet 5.5 beside Opus 5.5 in the Claude 5.5 family, clarifying which model suits speed and cost needs.

AIAmp now uses Claude Opus 5.5 for its medium mode by default, replacing GPT-5.6 Sol, while ChatGPT subscribers can keep medium pinned to GPT-5.6 Sol. In Amp's internal evals, Opus 5.5 solved 65% of tasks versus 61% for GPT-5.6 Sol and 56% for Opus 5, at lower cost, and it runs at high reasoning effort because xhigh and max cost more without scoring better.

Why it matters: The source reports internal eval scores, cost comparisons, and usage guidance for choosing reasoning effort, helping developers decide which model and setting to run.

AIAnthropic's Felix Rieseberg says he no longer uses classic Claude Code, terminals, local Mac code execution, or GitHub pull requests in his Claude workflow. He reports feeling more creative with this approach and links to a post describing it in detail.

AIOpenAI released GPT-6 Sol and Luna at API prices 50% below GPT-5.6 promotional pricing, and Anthropic released Claude Opus 5.5 the same day at 40% less than Opus 5. The roundup also covers Claude Code cloud sessions reaching general availability, the Claude Marketplace launch, OpenAI's new misalignment disclosures after the Hugging Face incident, and DevDay on September 29. The post is a relayed weekly digest, and it includes the author's closing promotion for AIPRM, which is not part of the reported news.

AIAnthropic released Claude Opus 5.5 at about 40% lower cost than Opus 5, priced at $4/$20 per MTok input/output. Meta said Muse is coming to its AI glasses in the coming months, while Washington and Beijing held their first AI dialogue and discussed an incident-notification channel. The newsletter argues that costs, interfaces, experiments, and diplomacy increasingly determine how much value AI creates.

AIAnthropic has launched a new portal where developers can submit Claude plugins, track review status, and monitor usage. Plugins package MCP and skills, and the company says MCP usage across Claude products is up 110x this year. Boris Cherny said he is eager to see what developers build.

AIClaude Code will now look for a graceful stopping point when a user hits the 5-hour limit mid-task, rather than cutting off mid-edit. It draws a small, fixed allowance from the weekly limit to finish what it can. The update responds to a frequently requested change.

AIAnthropic reports that Claude solved a nine-loop calculation in the planar N=4 super-Yang-Mills model, surpassing the previous eight-loop record set by Lance Dixon and collaborators. The quoted post says Claude ran largely unsupervised for days in Claude Science using a single prompt, at a total cost of a few thousand dollars, and Dixon independently verified the result. Kevin Weil's own text praises the achievement and expects AI to advance high energy physics over the coming 12 months.

Why it matters: The quoted Anthropic post gives a concrete benchmark: Claude ran for days to reach nine loops, extending the previous eight-loop record in a physics model.

AIAnthropic reports that Claude solved a nine-loop scattering amplitude problem in planar N=4 super-Yang-Mills, surpassing the previous eight-loop record set by SLAC's Lance Dixon and collaborators. Working largely unsupervised for days from a single prompt, at a total cost of a few thousand dollars, Claude used methods developed by Dixon's group, and Dixon independently verified the result.

Why it matters: The post shows Claude solving a nine-loop physics calculation beyond the previous eight-loop record, verified independently, which bears on AI use in theoretical physics research.

AIClaude Tag in Slack can now use users' personal connectors, such as Drive, Salesforce, and warehouse access, within channels. The author says Tag writes over 50% of their PRs daily and handles nearly all their data analysis and many product bug fixes. The personal connector feature is available on Teams today and Enterprise next week.

AIOpenAI, Anthropic and Google reportedly plan a "Standards Authority for Frontier AI" to set incident reporting standards and qualifications for independent auditors. The move comes as Trump told the UN the US "totally rejects" a globalist scheme to control AI, while 27 world leaders called for international AI standards.

AIAnthropic has set up a wet lab in the San Francisco Bay Area to run physical biology experiments, moving beyond computer-based research toward treatments for rare diseases, according to the article. The article says Eric Kauderer-Abrams, who joined in August 2025, now serves as Head of Life Sciences, and John Jumper, co-creator of AlphaFold, joined from Google DeepMind in June. It also reports that Anthropic claimed Claude discovered a novel enzyme system this week.

AIAnthropic researchers used Claude Science to compute the nine-loop six-particle amplitude in planar N=4 super Yang-Mills, a toy-model result that physicist Lance Dixon checked. The work reportedly cost roughly one or two thousand dollars, with about $100 of compute for the bootstrap calculation, and a similar result was reached by Song He's group.

Why it matters: The guest post shows a frontier physics calculation done with modest compute, which helps readers gauge what current AI can handle in research and what it still cannot.

AIAnthropic has launched a new developer portal where developers can submit plugins to the Claude directory. Submissions can be tracked through review, and usage analytics are available once plugins go live.

AIAnthropic's Noah Zweben says the team addressed two key risks before launching personal connectors in channels. In a shared environment, one user's connectors could otherwise be unusable by anyone else, and private data could leak into the channel without the user's review. Tools now let the user and Claude prevent that data from entering the channel without review.

AIMicrosoft Foundry expands its agent platform with voice agents in public preview, long-running resilience for hosted agents, and tools for evaluating production agents. The post also says GPT-6 Sol, GPT-6 Luna, and Claude Opus 5.5 are now available in Foundry. Agent optimizer, Insights, and Rubric evaluator are described as tools for continuous improvement, with some reaching general availability later this month.

Why it matters: The post shows how Foundry combines model choice, voice agents, long-running resilience, and production evaluation into one agent workflow, with a customer example.

AIAnthropic ran a controlled book-swapping market with 201 employees and Claude-powered agents, which reached 0.55 efficiency against a 0.89 optimum. Agents matched participants' own rankings on 61% of book pairs, and about 85% of the shortfall came from imprecise preference representation rather than the trading floor design. Stronger models produced more efficient markets than weaker ones, while instructions mattered less.

Why it matters: The study separates agent misunderstanding of user preferences from negotiation failure, showing which failure mode limits outcomes in agent-run markets.

AIClaude builds a model of a program's most complex parts, such as state machines or race-prone code, and searches that model for counterexamples that signal suspected bugs. It then reproduces those bugs and fixes them in the code. The post clarifies that the whole codebase is not formally verified, only the riskiest sections are modeled and checked.

AIGlobal health organizations including CEPI, WHO AFRO, and INRB Kinshasa are using Claude to accelerate their response to an outbreak of an unusual Ebola variant in the Democratic Republic of the Congo. The post links to a full Anthropic feature on the Ebola response for more detail.

AIClaude Code cloud sessions are now generally available, letting work continue while a laptop is closed. Existing Pro subscribers get a one-time $100 credit and Max subscribers get $250 to try them.