Block uses Claude Fable 5 to orchestrate code migrations across thousands of pull requests
In a Claude Blog Q&A published October 8, 2026, Block's head of AI capabilities Bradley Axen described how the company uses Claude Fable 5 to orchestrate company-wide code migrations: the model does high-level design work such as data models, API specs and algorithms, then directs up to dozens of cheaper models like Opus or Sonnet to make file edits and run tests. A single migration can span multiple repos and millions of lines of code, with as many as roughly a thousand pull requests merged, all coordinated in Buzz, Block's open-source workspace for human-agent teams. Axen said merges to main and production deploys still require two human approvals, and that in Block's own testing Claude refuses to try to bypass that dual-approval system.
It gives a concrete enterprise account of frontier models moving from single coding assistants to multi-model orchestration, including the cost and safeguard trade-offs.