The Precious Eyeblink

Why IDE feedback loops kill flow state—and how 400ms matters

Modern tools optimize for completeness over speed, leaving engineers waiting through delays that shatter focus. The Doherty Threshold—established in 1982—shows that feedback arriving after 400 milliseconds starts pulling attention away from the task. Fast, partial answers that keep you in flow beat slow, perfect ones that don't.

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Questions this essay answers

  • How does IDE latency affect developer productivity and flow state?
  • Should tools prioritize fast partial feedback over slow complete feedback?
  • What's the optimal speed for test runners and linters to maintain focus?
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