🚀 Introducing Astryx from Meta – an open source design system that’s AI fluent and fully customizable without dependencies. 150+ accessible components, brand-level theming, ship-ready templates, and a CLI. Built at Meta over 8 years, now yours. Astryx Design → astryx.atmeta.com

Astryx Design System

An open source design system that is fully customizable and agent ready.

astryx.atmeta.com

Python is the most used programming language at Meta. This year marks our 10th consecutive year as a sponsor of the Python Software Foundation, the organization dedicated to advancing and protecting the language and its community. Read more: engineering.fb.com/2026/06/30/o... #Python #OpenSource

We’re thrilled to share that Pyrefly, our open source type checker and language server for Python, has officially reached v1.0! Video: www.youtube.com/watch?v=_o0T... Blog: pyrefly.org/blog/v1.0/ We also want say a huge thank-you to the open-source community for helping us get here. 🙏

Pyrefly v1.0.0 is here!

Pyrefly is a fast, open-source type checker and language server for Python, built by Meta and ready for production Useful links: Get started: pyrefly.org Tips for getting your agent to use Pyrefly:…

youtube.com

The official Python Developers Survey is currently open 📝 🙌 Take the survey now — it takes less than 15 minutes to complete and helps the open source community understand the evolving needs of Python users. Link: surveys.jetbrains.com/s3/python-de...

Python Developers Survey 2026

Hi Pythonista, This is the ninth iteration of the official Python Developers Survey. Its goal is to show how the world of Python development looks today and how it compares to last year. The results serve as a major source of knowledge about the current state of the Python community, and we encourage you to support this initiative by taking 10–15 minutes to fill it out. Once it’s finished, we will publish the aggregated results and randomly draw 20 winners (from those who complete the survey with meaningful responses), who will each receive a USD 100 Amazon Gift Card or a local equivalent. Thank you for contributing to the community’s efforts!

surveys.jetbrains.com

⚡️OSS Project Spotlight⚡️ Yoga is a cross-platform layout engine that brings Flexbox to any environment—not just the web. It powers the layout for massive frameworks like React Native, enabling you to build responsive UIs once and run them anywhere. www.yogalayout.dev

Yoga

Documentation for the Yoga layout engine

yogalayout.dev

🔎 Meta Open Source 101🔎 Need to compress data in real-time without sacrificing speed? Use Zstandard (zstd), a fast compression algorithm designed to provide high compression ratios while maintaining incredibly fast encoding and decoding. Get started: https://facebook.github.io/zstd/

Zstandard - Real-time data compression algorithm

a fast compression algorithm designed to provide high compression ratios while maintaining incredibly fast encoding and decoding.

facebook.github.io

⚡️OSS Project Spotlight⚡️ Fairchem is a centralized repository from FAIR Chemistry that provides state-of-the-art data, models, and tools for materials science and quantum chemistry. It includes several datasets to accelerate renewable energy research. https://fair-chem.github.io/

🔎 Meta Open Source 101🔎 Do you work with survey data that doesn't quite match your target audience? Use Balance, a Python package that adjusts biased data samples (like non-representative surveys) by creating weights to match a target population. https://import-balance.org/

⚡️OSS Project Spotlight⚡️ Folly is a library of C++ components designed with practicality and efficiency. It complements the standard library with optimized utilities—such as fast synchronization primitives and memory-efficient containers. Learn more: https://github.com/facebook/folly

GitHub - facebook/folly: An open-source C++ library developed and used at Facebook.

An open-source C++ library developed and used at Facebook. - facebook/folly

github.com

🔎 Meta Open Source 101🔎 Need speed of a dynamic language but the discipline of a static one? Meet HHVM (HipHop Virtual Machine) and Hack, the engine and language designed to execute PHP code with lightning-fast performance using JIT compilation. Link: https://hhvm.com/

HHVM

The landing page for HHVM and the blog of Hack/HHVM

hhvm.com

⚡️OSS Project Spotlight⚡️ Lexical is an extensible text editor framework designed for reliability, accessibility, and performance. It provides a powerful, framework-agnostic engine for building sophisticated text editing experiences on both the web and iOS. Learn more: https://lexical.dev/

New Meta Open Source Content 🔎 Four type-narrowing patterns that make Python type checking more intuitive. 🐍✨ From tuple length narrowing to hasattr guards, see how Pyrefly helps reduce the need for explicit casts in your code. Learn more here: https://pyrefly.org/blog/type-narrowing/

4 Pyrefly Type Narrowing Patterns that make Type Checking more Intuitive | Pyrefly

Learn about 4 ways Pyrefly narrows types, reducing the need to explicitly cast in your code.

pyrefly.org

🔎 Meta Open Source 101🔎 Want to catch null pointer exceptions and resource leaks before they crash your app? Use Infer, a static analyzer that detects complex bugs in Java, C++, and Objective-C. Learn more at https://fbinfer.com/

Infer Static Analyzer | Infer | Infer

A tool to detect bugs in Java and C/C++/Objective-C code before it ships

fbinfer.com

⚡️OSS Project Spotlight⚡️ IGListKit is a data-driven UICollectionView framework for building fast lists on iOS. It features a decoupled diffing algorithm that handles updates automatically, eliminating reloadData or performBatchUpdates. Learn more: https://instagram.github.io/IGListKit/

IGListKit

A data-driven UICollectionView framework for building fast and flexible lists.

instagram.github.io

Python typing is trending — and the community has spoken! 📊 From improved readability to better tooling support, see what developers love (and struggle with) in 2025: https://engineering.fb.com/2025/12/22/developer-tools/python-typing-survey-2025-code-quality-flexibility-typing-adoption/

Python Typing Survey 2025: Code Quality and Flexibility As Top Reasons for Typing Adoption

The 2025 Typed Python Survey, conducted by contributors from JetBrains, Meta, and the broader Python typing community, offers a comprehensive look at the current state of Python’s type system and d…

engineering.fb.com

🔎 Check out our new video on Pyrefly’s Pydantic support Pyrefly currently offers experimental support for Pydantic, bringing improved static type checking and IDE integration to your data models. ▶️ Watch the video: youtu.be/zXYpSQB57YI #Python #TypeChecking #OpenSource

How Pyrefly Works with Pydantic (v1 experimental support)

YouTube video by Meta Open Source

youtu.be

🚀 New from Meta AI Research: Souper-Model! By smartly averaging multiple model weights using a method called SoCE (Soup Of Category Experts), the team achieved strong performance without retraining a whole new model. Read more here: https://loom.ly/bSbrL70

Souper-Model: How Simple Arithmetic Unlocks State-of-the-Art LLM Performance | Research - AI at Meta

Large Language Models (LLMs) have demonstrated remarkable capabilities across diverse domains, but their training remains resource- and time-intensive,...

ai.meta.com

Announcing Pyrefly is now in Beta 🎉 Pyrefly is a super fast, open source language server and typechecker for Python. We’ve been working closely with our open source community to improve performance, add new features and address bugs. Learn more: https://youtu.be/4o0RLJJ-FAo

🚀 New Blog Post Alert 🚀 Ax, our OS adaptive experimentation platform, uses machine learning to automate and optimize complex experiments. Discover real-world applications of AX across AI, GenAI, infrastructure and even physical engineering. Learn more: https://loom.ly/Djv-f8k

Efficient Optimization With Ax, an Open Platform for Adaptive Experimentation

Efficient Optimization With Ax, an Open Platform for Adaptive Experimentation

engineering.fb.com

⚡️OSS Project Spotlight⚡️ Below is a powerful resource monitoring tool for Linux that provides deep insights into system performance, including CPU, memory, I/O, and more — all from an intuitive terminal interface. Learn more: https://github.com/facebookincubator/below

GitHub - facebookincubator/below: A time traveling resource monitor for modern Linux systems

A time traveling resource monitor for modern Linux systems - facebookincubator/below

github.com

🚀 StyleX: Meta’s Open Source Styling Library for CSS at Scale! StyleX is the styling system that combines the best of CSS-in-JS ergonomics with the performance of static CSS—making styling expressive, type-safe, and lightning fast. Link: https://loom.ly/IEnQjTY

StyleX: A Styling Library for CSS at Scale

StyleX is Meta’s styling system for large-scale applications. It combines the ergonomics of CSS-in-JS with the performance of static CSS, generating collision-free atomic CSS while allowing for expressive, type-safe style authoring.

engineering.fb.com

Did you know that 63% of AI training models today are built on @PyTorch? When Meta first released the framework, we wanted to support developer experiences for AI researchers. Today, PyTorch helps accelerate the path to AI productization around the world: https://youtu.be/g__HkxDEvCg

🚀 New Podcast Episode Alert! Are you passionate about Python typing or developer experience? Check out the latest episode of @talkpython.fm featuring Pyrefly, Meta’s blazing-fast type checker for Python: https://www.youtube.com/watch?v=P4RKxl_giH4&t=2s

🚀 New on the Meta Engineering blog: Branching in a Sapling Monorepo Discover how Meta solved the tradeoffs between scalability and dev experience by introducing directory branching alongside full-repo branching in Sapling. Read more here: https://loom.ly/GgxCxto

Branching in a Sapling Monorepo

Sapling is a scalable, user-friendly, and open-source source control system that powers Meta’s monorepo. As discussed at the GitMerge 2024 conference session on branching, designing and imple…

engineering.fb.com

⚡️OSS Project Spotlight⚡️ Captum is an open source library from Meta for model interpretability in PyTorch. It helps developers understand and visualize the decisions made by deep learning models using attribution methods like Integrated Gradients and DeepLIFT. Learn more: https://captum.ai/

Captum · Model Interpretability for PyTorch

Model Interpretability for PyTorch

captum.ai

🚀 Big news! Today marks the formation of the React Foundation — a new home for React, React Native, JSX, and the broader React ecosystem. Let’s celebrate a new chapter for React and the open web! 🔗 Read more: https://loom.ly/UrW8eeI #React #OpenSource #WebDev #ReactNative

Introducing the React Foundation: The New Home for React & React Native

Meta open-sourced React over a decade ago to help developers build better user experiences. Since then, React has grown into one of the world’s most popular open source projects, powering over 50 m…

engineering.fb.com

🚀 Introducing OpenZL, a new #opensource, format-aware compression framework! It uses a unique “graph model” for compression, enabling modular, high-performance codecs and a universal decoder - perfect for structured data at scale Link: https://loom.ly/z09xoNw #DataCompression

Introducing OpenZL: An Open Source Format-Aware Compression Framework

Introducing OpenZL: An Open Source Format-Aware Compression Framework

engineering.fb.com

How do you make sure your IDE works smoothly when you have more than 20 million lines of python code? 🤔 For devs at Instagram the answer is to use the Pyrefly VSCode extension 👩🏼‍💻 Read our blog about how Pyrefly improves your experience: https://pyrefly.org/blog/2025/09/15/ide-extension/

Give your Python IDE a Glow-Up with Pyrefly | Pyrefly

Learn how Pyrefly's language server capabilities can help you navigate large Python codebases with ease.

pyrefly.org

🔎 Meta Open Source 101🔎 Meet Sapling, Meta’s next-gen source-control system. It’s Git-compatible but designed for massive repos and lightning-fast operations, even at scale. Perfect if you need speed and a smooth developer experience. Learn more 👉 https://sapling-scm.com