loreline

A modern and open-source scripting language for writing interactive fiction.

Designed so writers can focus on story and dialogue while still having real programming tools (branching, state, functions) when they need them. If you write for games, visual novels, or any kind of branching narrative, this is for you.

Loreline works everywhere: game engines, web apps, or standalone projects. It adapts to your tools, the stories you write stay portable.

Get started

The documentation, an interactive playground and a downloadable editor (Loreline Writer) are available on loreline.app.

Building Loreline

What follows is only needed if you want to modify Loreline from source. If you just want to use Loreline with your favourite engine, check out the integrations guides.

Prerequisites

Building Loreline from source requires Node.js (v18+). The resulting outputs (JS library, C# library, native CLI) have no Node.js dependency.

npm install    # Install Node.js dependencies (esbuild, tsx, etc.)

Building

node ./setup --js          # Build JavaScript library (js/loreline.js)
node ./setup --cs          # Export C# source files (cs/Loreline/)
node ./setup --cs --cs-dll # Export C# + build Loreline.dll
node ./setup --cs-generics # Export C# test runner without erase-generics
node ./setup --py          # Build Python package (py/loreline/)
node ./setup --lua         # Build Lua module (lua/loreline/)
node ./setup --php         # Build PHP package (php/)
node ./setup --php-cli     # Build PHP CLI (build/php-cli/)
node ./setup --cpp         # Build native CLI (loreline / loreline.exe)
node ./setup --cpp-lib     # Build C++ shared library
node ./setup --jvm         # Build JVM jar (jvm/loreline.jar)
node ./setup --gdscript    # Export pure-GDScript Godot addon (godot/gdscript/)

Setting up samples

node ./setup --sample          # Set up all sample projects
node ./setup --sample web      # Set up loreline-web only
node ./setup --sample unity    # Set up loreline-unity only
node ./setup --sample cpp      # Set up loreline-cpp only
node ./setup --sample python   # Set up loreline-python only
node ./setup --sample lua      # Set up loreline-lua only

This copies the built runtime and story files into the sample directories. For loreline-web, run --js first. For loreline-unity, run --cs first. For loreline-cpp, run --cpp first. For loreline-python, run --py first. For loreline-lua, run --lua first.

Testing

Python, Lua, PHP, JS, JVM and GDScript tests require running the corresponding build step first (e.g. node ./setup --py before Python tests). GDScript tests also need a Godot 4 binary on the PATH (or pointed to by the GODOT_BIN environment variable).

node run test ./test                    # Run Neko tests only
python3 py/test-runner.py ./test        # Run Python tests only
lua5.4 lua/test-runner.lua ./test       # Run Lua tests only
php php/test-runner.php ./test          # Run PHP tests only
php build/php-cli/index.php test ./test # Run PHP CLI tests only
npx tsx js/test-runner.ts ./test        # Run JS tests only
java -cp jvm/loreline.jar:build/jvm/test TestRunner ./test  # Run JVM tests only
node ./setup --gdscript-test            # Run GDScript tests only (headless Godot)
node ./setup --test                     # Build and run all test suites (Neko + C# + C# AOT + C# (with generics) + JS + C++ lib + Python + Lua + PHP + PHP CLI + JVM)

Each test/*.lor file ends with a <test> YAML block describing its test cases (choices, beat, expected, …). saveAtDialogue and saveAtChoice take one index or a list of indices (saveAtDialogue: [2, 5]), counted over an uninterrupted run: at each one, the runner saves, restores in a new interpreter and continues, so the saved event shows twice in expected.

On top of the explicit cases, the Haxe runners (Neko, C# with generics, PHP CLI, GDScript) run a save sweep: every test case is saved and restored at each of its events (and at every pair of events in files with insertions), and must give the uninterrupted output with the saved events shown twice. Files relying on randomness are skipped, and a test case can opt out with saveSweep: false.

How Loreline is authored

Loreline’s core runtime (its lexer, parser, interpreter and the overall architecture that ties them together) has been written by hand. The Loreline language is also the result of many design iterations that are essentially human authored.

That said, I have used coding assistants for unit tests, scaffolding, debugging, documenting the code, continuous integration, fixes to the runtime and help implementing new features. All of this improves the overall reliability and quality of Loreline, makes sure that anything tested won’t break in the future, and gives me more bandwidth for the more creative, interesting and trickier parts of Loreline itself. I weighed that this use would benefit the users of the project, and I take entire responsibility for all the code and design choices in this repository.

For some context on where I stand, I don’t endorse the use of generative AI as a general rule: I care a lot about writing code myself, especially the creative parts, and about human authorship in general. I reject the use of any AI-generated asset or content in the games I make.

License

MIT License

Copyright © 2025-2026 Jérémy Faivre

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.