setup-koja

GitHub Action that installs the Koja compiler toolchain and adds it to PATH.

The action downloads a prebuilt release tarball, verifies its checksum, installs koja and koja-lsp into the runner tool cache, and registers a problem matcher. With the matcher, compile diagnostics annotate pull request diffs inline.

Usage

steps:
  - uses: actions/checkout@v6
  - uses: koja-lang/setup-koja@v1
    with:
      koja-version: 0.16.0
  - run: koja deps get
  - run: koja test

Install the latest release by omitting the version:

- uses: koja-lang/setup-koja@v1

Read the version from a file:

- uses: koja-lang/setup-koja@v1
  with:
    koja-version-file: .tool-versions

Inputs

Input	Default	Description
koja-version	latest release	Version to install: exact (0.16.0), partial (0.16), or latest.
koja-version-file	none	File that names the version: .tool-versions or koja.toml.
token	github.token	Token for the releases API when resolving versions.

If both koja-version and koja-version-file are set, koja-version wins and the action prints a warning.

A version like 0.16 installs the newest 0.16.x release.

For koja.toml, the action reads the [project] koja key, which declares a minimum compiler version.

Outputs

Output	Description
koja-version	The resolved version that was installed.
koja-path	Directory the toolchain was installed into.

Supported runners

• Linux x86_64 and arm64 (ubuntu-24.04, ubuntu-24.04-arm, and compatible)
• macOS arm64 (macos-14 and newer)

Intel macOS runners and Windows are not supported because no prebuilt binaries exist for them. The earliest installable version is 0.12.1, the first release with prebuilt binaries.

Problem matcher

Koja prints one-line diagnostics in CI (path:line:col: severity: message). The action registers a matcher for that format, so errors and warnings from koja build, koja run, and koja test appear as annotations on the pull request.

License

Copyright (c) 2026 Henry Popp

This project is MIT licensed. See the LICENSE for details.