AI model
Claude Sonnet 4 is an Anthropic large language model used for coding, reasoning, and multi-agent AI tasks, offered via Claude Code and the Claude API.
Anthropic retires the claude-sonnet-4-5-20250929 model id on November 30, 61 days after its deprecation notice, according to a dev.to walkthrough. Its replacement, claude-sonnet-5-5, costs the same, so the remaining work is finding every key and config that still pins the old string.
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The study counts only complexity and dead code, because those are the two pyscn metrics that stay exact when you analyze just the files a patch touched. The human's own commit trips the same rule 24% of the time.
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Anthropic says multi-agent systems introduce their new problems in coordination, evaluation and reliability, and its own token arithmetic explains why picking a model is the cheaper half of the decision.
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Anthropic's 0.97 PGR belongs to small open-weights models, but the plumbing that produced it is copyable at roughly $22 per agent-hour, and the ten tests that judged the work still came from humans.
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A Samsung and University of Warsaw preprint tracks the names large language models keep inventing, Elena Vasquez and Marcus Chen among them, into hundreds of AI-generated papers that scholarly aggregators index without checking whether the author exists.
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Anthropic's temporary weekly headroom lapses at 11:59 PM PT with prices unchanged. Teams that wired CI pipelines and sprint plans to borrowed capacity now pay the same for roughly a third less work.
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