release_notes/release-notes-v1.0.0.md
Status: STABLE Release date: 12 May 2026
We're thrilled to announce that Pyrefly has reached its stable 1.0.0 release! Since our beta release in November 2025, we've fixed hundreds of bugs, improved performance, and added lots of new functionality. Pyrefly is already the default type checker for Instagram at Meta and has been adopted by other large production codebases like PyTorch and JAX. Today, we're making it official: Pyrefly is production ready.
This would not have been possible without our amazing open-source community. To everyone who filed GitHub issues, submitted pull requests, gave us feedback at conferences, or joined us on Discord: thank you. Your contributions shaped this release.
These release notes cover the major highlights since our beta release. For the full history, see our past weekly release notes.
We've continued to push Pyrefly's performance since the speed improvements we shared in February. Since beta:
(Tested on an M4 Macbook Pro using open-source benchmarks from type_coverage_py and ty_benchmark.)
Compare the performance of Pyrefly and other Python type checkers on our regularly updated benchmarking suite, which runs against 53 popular Python packages.
A new preset configuration option provides named bundles of error severities and behavior settings.
| Preset | Description |
|---|---|
off | Silences all diagnostics. Useful for IDE-only users or if you want total control of which errors are enabled. |
basic | Low-noise, high-confidence diagnostics only (syntax errors, missing imports, unknown names, etc.). Ideal for unconfigured projects or IDE-first users. |
legacy | For codebases migrating from mypy. Disables checks mypy doesn't have. pyrefly init now emits this preset automatically when migrating from a mypy config. |
default | The standard Pyrefly experience. Equivalent to having no preset. |
strict | Enables additional strict checks on top of the default preset. For users who want to avoid Any types in their codebase. |
See the configuration docs for details.
We’ve made improvements to the out-of-the-box experience for projects without a pyrefly.toml.
pyrefly init would commit to disk.)We've been hard at work making the type checker robust and feature-complete, with a focus on driving down false positives and improving type quality in real-world code bases. Here are some highlights:
source.fixAll.RootModel, pydantic-settings, and pydantic.dataclasses..ipynb IDE support has reached full parity with .py files, with rename, find references, code actions, and document symbols all supported.Pyrefly ships with tools to aid with adopting type checking in an existing codebase. Two new tools since beta:
pyrefly report** outputs a JSON report with annotation completeness and type completeness metrics per function, class, and module, so you can track coverage over time.Going forward, we’ll switch from a weekly to monthly cadence for minor (1.x.0) releases, with patch releases in between as-needed for critical fixes. We’ll continue providing release notes for minor versions, so you can see what’s new in each release.
The following people have directly contributed at least once to the development of Pyrefly since our first Alpha release.
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