Claude: System Prompts
Anthropic documents the system prompts that Claude's web and mobile apps inject at the start of every conversation — dynamic context such as the current date plus behavioral guidance — and tracks revisions in its release notes. The day's second-highest HN story (561 points, 234 comments), it gives users unusual visibility into the instructions behind a commercial model. Builders get a rare public reference for how a frontier lab structures production system prompts.