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A Fireside Chat with Cat and Thariq from the Claude Code team

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  • Transcript from an AI Engineer World’s Fair fireside chat with two members of Anthropic’s Claude Code team, covering how internal engineering practice has shifted as models improved.
  • Concrete stat: their coding agent (“Claude Tag”) now lands 65% of Anthropic’s own product engineering PRs; system prompts shrank 80% for newer models (Fable 5, Opus 4.8) because dropping hand-crafted examples let the model be “more creative than the examples we gave it.”
  • Few-shot examples and long lists of “do not do this” constraints are no longer best practice — conflicting directives confuse strong models more than they help.
  • Full rewrites are now considered viable (not just incremental patches) given a solid test suite, since the codebase itself acts as the spec.
  • Code review is increasingly automated for outer-layer changes, humans retained only for core/critical code; the team also built behavioral evals for softer UX preferences (e.g., users dislike Claude Code announcing it’s “going to sleep”).