diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 000000000..52a2cf860
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,20 @@
+# Contributing
+
+Thanks for contributing to this project.
+
+## Setup
+
+1. Fork and clone this repository.
+2. Install dependencies from the project toolchain files.
+3. Run the test suite (or build) before opening a pull request.
+
+## Pull requests
+
+- Keep changes focused and clearly described.
+- Link related issues (for example `Fixes #123`).
+- Include a short test plan.
+- Match existing code style.
+
+## Conduct
+
+Be respectful and constructive in reviews and discussions.
diff --git a/README.md b/README.md
index abf035b21..f7835e9c8 100644
--- a/README.md
+++ b/README.md
@@ -117,3 +117,7 @@ $ pnpm test:sandbox
 ```
 
 The test corpus runs each program under Node and as a compiled native binary, then compares stdout, stderr, and exit codes byte for byte. The full gate also runs the corpus with AddressSanitizer and the runtime reference-count audit.
+
+## Contributing
+
+See [CONTRIBUTING.md](CONTRIBUTING.md).