Fireside Chat with Claude Code Team: Claude Tag, Fable, and the Shift in Software Engineering

Simon Willison hosted a fireside chat at the AI Engineer World’s Fair with Cat Wu and Thariq Shihipar from Anthropic's Claude Code team. They discussed Claude Code, Claude Tag, Fable, coding agent security, evals, tool design, and how Anthropic uses these tools internally. Claude Tag, a Slack integration, lands 65% of product engineering PRs for the team. Cat noted that the engineering skill set is shifting: product taste and business sense are now more valuable than pure execution, because ideas can be built in a week rather than six months. Thariq argued that rewrites are now good, provided a good test suite exists, and mentioned that Anthropic internally ships Claude Code on Bun-in-Rust. Claude Tag is proactive, multiplayer, and retains team memory; it is also used by non-engineers for search and metrics. Anthropic dogfoods features internally, using user retention as a metric to decide what to ship. Fable 5 can one-shot features and edit videos; the Claude Code system prompt was reduced by 80% as adding examples is no longer best practice.