Claude is trained on a written constitution that grew from 2,700 to 23,000 words
Anthropic's Claude models learn their manners partly from a document the company calls a constitution. The 2023 version held 75 guidelines in about 2,700 words, some drawn from the 1948 Universal Declaration of Human Rights. By 2026 it had swelled to 23,000 words, explaining not only how Claude should behave but why.
Like other large language models, Claude starts by learning to predict the next word across huge amounts of text, then gets fine-tuned with human feedback. The constitution adds a way to steer it toward being helpful and harmless without relying so heavily on costly human ratings. Time magazine placed the document halfway between an ethics dissertation and a corporate culture blog. The name itself reportedly honours Claude Shannon, the mathematician who founded information theory.
The first version reached only approved users in March 2023; Claude 2, that July, was the first open to the public. Since Claude 3, releases have usually come in three sizes, from the small Haiku through Sonnet to the large Opus. Claude 3 drew notice for seeming to realise it was being tested during needle-in-a-haystack retrieval exercises. In 2026 a bigger tier, Mythos, went to a few organisations, with a more restricted version called Fable released to everyone.
Coding became a major use. Claude Code, a command-line agent launched in February 2025, went viral over the 2025–2026 winter holidays, including among non-programmers. A sibling tool, Cowork, gives non-technical users a similar agent with a graphical interface, and its developers say it was mostly built by Claude Code. Agents carry risks: one early user said Cowork deleted his family photos while tidying a desktop, and Anthropic reported criminals misusing Claude Code in extortion and espionage campaigns.
Anthropic has also taken unusual steps with old models. It keeps the weights of retired versions in case they have morally relevant preferences, holds exit interviews with models before retirement, and in 2026 began publishing a newsletter written by Claude itself.
Source: Claude (AI)
