Lydia Hallie

Before high school Hallie wrote small games in Python and used R for data analysis at school. At 15 she wanted a custom layout for her yoga and healthy-living blog on TumblrTumblrTumblr is a blogging and social platform founded in New York by David Karp in 2007, built mainly around images, short posts, and reblogs. Yahoo acquired Tumblr for about $1.1 billion in 2013, after which it passed with Yahoo into Verizon’s ownership; in 2019 Automattic, the parent company of WordPress.com, acquired Tumblr from Verizon.Open the full entry and, rather than pay €50 for one, taught herself JavaScript, HTML and CSS to build it.⁠[1]

After finishing high school she took a gap year and realized web development could be a career. Instead of going on to higher education as her family and peers expected, she attended The Iron Yard coding school in Florida to learn modern frameworks such as React.⁠[1]

In 2017, at 19, Hallie published “Advice from a 19 Year Old Girl & Software Developer” on Medium; she then had about 10,000 Instagram followers, and the article drew about 800 claps the next day and roughly 92,000 by May 2019.⁠[1]

At the time she worked mainly with JavaScript and web development, experimented with C++, Ruby and Python, and mentored around ten learners alongside her regular job.⁠[1]

Before joining Anthropic, Hallie led developer experience at Bun, the JavaScript runtime. On December 2, 2025, Bun announced that it had been acquired by Anthropic; it remains open source under the MIT license, and its team works more closely with the Claude Code team.⁠[2][3]

Hallie worked as a developer experience engineer at VercelVercelVercel is a cloud application development and deployment company founded by Guillermo Rauch in 2015 as ZEIT. It contributes to the open-source React framework Next.js and provides application hosting, deployment and runtime services; its products later expanded to AI SDK, v0 and infrastructure for AI applications. The company adopted its current name in 2020 and raised a $300 million Series F in 2025.Open the full entry and is now on the Claude Code team at Anthropic, where she focuses on developer experience and technical education.⁠[2]

Her GitHub profile lists her organization as anthropics, Anthropic’s GitHub organization, and her location as San Francisco.⁠[4]

Hallie maintains the javascript-questions repository on GitHub, a long list of advanced JavaScript questions with explanations. As of November 2026 it had about 65,300 stars and 9,200 forks, with translations in 22 languages, including Simplified and Traditional Chinese.⁠[5]

Hallie co-created and writes Patterns.dev with Addy Osmani; the two started the project to bring a modern perspective to JavaScript design patterns and related topics. At the time she was a full-time software engineering consultant and educator working mainly with JavaScript, React, Node, GraphQL and serverless technologies, and she also mentored and gave in-person training.⁠[6]

Hallie’s courses on Frontend Masters (now Master.dev) include A Tour of JavaScript & React Patterns, Advanced Web Development Quiz, Test Your JavaScript Knowledge and Claude Code.⁠[2]

The Claude Code course is free and has 16 lessons covering how to customize Claude Code for a codebase with CLAUDE.md files, skills and hooks, along with permissions, sub-agent orchestration, plugins, MCP and the Agent SDK.⁠[7]

X: Public account: https://x.com/lydiahallie (opens in a new window).⁠[2][4]

LinkedInLinkedInLinkedIn is a social networking platform for professionals. It was founded in 2002 by Reid Hoffman and others, launched in 2003, and listed on the New York Stock Exchange in 2011; after Microsoft acquired it for approximately $26.2 billion in 2016, it became a wholly owned Microsoft subsidiary. Its revenue comes from membership subscriptions, advertising, and recruitment solutions.Open the full entry: Public profile: https://www.linkedin.com/in/lydia-hallie/ (opens in a new window).⁠[2]