Which languages and versions can a coding challenge use

A Kendor challenge can run Node.js 22, Python 3.12, Go 1.27 or 1.26, Java 21, Rust 1.98, C++ with Clang 23, or PHP 8.3 or 8.4. You pick the language when you create the challenge and the version with runtime.version in kendor.yaml. A project can add more languages beside the main one with toolchains.

Languages and versions available today

The value in the second column is what you write in runtime.type, and the third what you write in runtime.version, always as a quoted string.

Every language also comes with its language server, so the editor has completion, go-to-definition and errors: typescript-language-server, Pyright, gopls, Eclipse JDT LS, rust-analyzer, clangd and Intelephense. Every sandbox also has git, make, cmake, ninja, sqlite3 and a C compiler, whatever the language.

Go 1.22 also exists, but it's no longer offered for new challenges (see below).

How the Tests tab reads results

The Tests tab runs the service's test.command and lists each test it finds. It reads TAP (Test Anything Protocol) from the command's standard output, which is why the table lists a converter for most languages: kendor-gotest-tap, kendor-junit-tap and kendor-cargo-tap are on the PATH in every sandbox and turn go test -json, JUnit XML and cargo test output into TAP. Send anything else your build prints to standard error. PHP is the exception: write PHPUnit's JUnit report to /tmp/kendor-phpunit.xml with --log-junit /tmp/kendor-phpunit.xml.

version: 1
runtime:
  type: go
  version: "1.27"
services:
  app:
    test:
      command: go test -json ./... | kendor-gotest-tap

Pick a version

When you create a challenge, choose its Language and Version. The language can't change after the challenge is created; the version can.

To change the version later, set runtime.version in kendor.yaml, either in the Runtime configuration dialog or by editing the file, and save. Keep runtime.type the same as the challenge's language: the version in the file is used only when the two match.

Use the short version from the table, such as "1.27", not the exact build. Kendor checks the version when you save and lists the ones it offers if yours isn't one of them.

Add a second language

toolchains puts more languages in the same sandbox, each with its compiler, tools and language server. This Laravel setup uses PHP as the main language and adds Node.js for the Vite asset build:

version: 1
runtime:
  type: php
  version: "8.3"
toolchains:
  - type: node
    version: "22"
install:
  commands:
    - composer install --no-interaction --prefer-dist --no-progress
services:
  app:
    dev:
      command: php artisan serve --host $HOST --port $PORT
      port: 8000
  vite:
    install:
      commands:
        - npm ci
    dev:
      command: npm run dev -- --port $PORT
      port: 5173
preview:
  service: app

Each language can appear only once across runtime and toolchains.

Retired versions

When a version leaves upstream support, Kendor stops offering it for new challenges but keeps it running. A challenge already on that version keeps working and still saves, and its Version list shows it as "no longer offered". You can't choose a retired version for a new challenge. Go 1.22 is retired today.

When you're ready, move the challenge to a current version by changing runtime.version.

Single-file or full project

When you add a coding challenge, you choose between two kinds:

• Single-file challenge: the candidate edits one file, such as solution.py, and runs the tests you wrote from the Tests tab. There is no preview, only the editor, a terminal and the tests. Every language in the table has a single-file starter.
• Coding challenge: a whole project. Start from a starter scaffold or a blank workspace, upload a zip, or import a repository. It can have a preview, several services, databases and more than one language.

The starter scaffolds for a full project today are:

Each starter ships its own kendor.yaml, so it runs as soon as the sandbox starts. Read it to see a working setup for that language, then change what you need.