Microsoft says nine engineers merged 1,211 pull requests in one day
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Microsoft says nine engineers merged 1,211 pull requests into the Copilot Cowork backend’s main branch on October 21. The company says it took the product from an empty repository to worldwide general availability in about four and a half months, with agents writing most of the code. Copilot Cowork reached its first enterprise customers through the Frontier program on March 30 and general availability on June 16, according to Microsoft.
The team began requiring a Markdown specification before each change, covering the task’s purpose, how success would be measured and what could not break. Agents handled narrow tasks within defined boundaries, while engineers reviewed higher-risk changes and retained responsibility for decisions. Microsoft also says it moved the live runtime from Python to Rust between September 23 and October 10 without interrupting the service.
Why it matters · editorial interpretation
The case suggests a development model in which agents extend the capacity of a small team, but with upfront specifications, scope limits and human review for higher-risk changes. The migration from Python to Rust without interrupting service also illustrates the technical coordination required when systems are developed at this pace.
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