---
title: "The error model"
description: "Michael Arnaldi distinguishes typed failures a program handles from defects it lets escape."
group: concept
terms:
  - "Effect error model"
  - "typed failures"
sources:
  - https://youtu.be/und9h4xiIz4?t=1418
  - https://youtu.be/und9h4xiIz4?t=1512
---

# The error model

Michael says typed errors belong to control flow when the program intends to handle them; defects describe failures the program lets escape. [Why JavaScript Is Broken, 23:38](https://youtu.be/und9h4xiIz4?t=1418) [25:12](https://youtu.be/und9h4xiIz4?t=1512).

He presents this distinction as part of Effect's computation model, not as a wrapper around Promises. [22:11](https://youtu.be/und9h4xiIz4?t=1331).