Nine Engineers, 1,211 PRs in a Day: Lessons From Building Copilot Cowork
usamawahabkhan · x · 2026-11-11
Microsoft's official blog postmortem on building Copilot Cowork, an agentic execution layer for multi-step workflows by everyday knowledge workers: nine engineers once merged 1,211 pull requests in a single day.
The article distills six lessons on engineering with agents, including how the team migrated its runtime from Python to Rust while the product was live. Started from an empty repo in January, the product reached worldwide GA, integrating Work IQ, Microsoft 365 governance, cloud execution, and a multi-model architecture.
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