Closer to production quality Python notebooks with `marimo check`

Summary

In this blog post, we introduce marimo check, a linter that enables agents and humans alike to write high-quality notebooks, pipelines, and apps with marimo. We discuss the motivations behind its creation, the principles guiding its design, and how it integrates seamlessly into modern software development workflows, including CI pipelines and AI-assisted coding. When writing traditional software, developers use linters to find bugs, errors, and code smells; because marimo notebooks are actually just Python programs, we believe they deserve similar tooling. As one of our users put it: “I think the right approach (to notebooks) is using things like IDEs, Git, uv, ruff, pre-commit etc. which in my opinion greatly helps any type of professional and should be a non-optional standard.” This insight captures what we’re seeing across disciplines—professionals recognizing that software engineering practices are essential for anyone writing code that matters. Engineers in machine learning, data engineering, and AI, are already bought in to the idea of using linters, and want to bring that experience to marimo. The demand became so strong that developers started building their own solutions. One community member even created a custom Pylint plugin specifically for marimo notebooks, checking for unused parameters in cell functions—clear evidence that the community was ready for better tooling. Program validation tools like linters aren’t just for humans. In the age of coding agents, linters provide critical feedback to Claude Code, Gemini, and other agents, allowing them to iterate and self-correct without human intervention. While we’ve long understood that our community was interested in a marimo linter, it was this line of reasoning that motivated us to prioritize its development — especially given that more and more organizations are using Claude Code in conjunction with marimo to rapidly create new data workflows. Today, we’re excited to introduce marimo check, our compreh...