Lamplit

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What it is

Lamplit is a single-page app for collaborative fiction: you write a line, a model writes the next passage, and the two of you keep going. It is built around one idea that most tools of this kind leave out — a story is written in chapters.

Each chapter opens on a scene you write yourself, runs for as long as it wants to, and is then closed: the model folds it into a running summary of everything that has happened, and the next chapter starts from there. Only the current chapter is ever sent to the model, so a story that runs for months still costs the same per reply as one that started this morning.

There is no account, no cloud, and no server between you and the model. The browser talks to your endpoint directly. A small local server sits behind the app to hold your stories — plain JSON files, and the only copy there is.

It is deliberately not a configuration tool. No character cards, no extensions, no prompt manager, no images. One bar across the top, and everything in it is something you will actually use. If you want to know exactly what will be sent, one click shows you the whole assembled prompt, block by block.

Why

Tools for this are usually built for people who enjoy tuning them. This one is built for people who want to read what comes out. Two things follow from that:

• Reading comes first. Speech is set apart, actions are italicised, prose is set in a serif at a readable measure, and the page is never taken away from you — everything else opens over it.
• Nothing is hidden. The whole prompt is rebuilt from your documents on every single request. There is no accumulated state, no invisible history, nothing that drifted three hours ago. What you can see in "What the model sees" is exactly what goes on the wire.

What it does

Chapters with scenes	A chapter cannot be written into until its scene is written — the one thing the app insists on. The scene goes to the model verbatim and stays editable.
Close a chapter	The model is handed the story so far and asked to give the whole thing back with this chapter folded in. You edit the result before it lands.
A world that fires on keywords	Facts, people and places that are only sent when the story mentions them, plus a "story so far" that is always sent.
Narrator or role-play	One omniscient voice, or a named cast the model plays while never writing for you.
Book-style reading	Markdown, quoted speech set apart, *actions* in italics, adjustable text size, light and dark.
Per-message control	Edit, regenerate, replay from here, copy, delete. Stop mid-stream keeps the partial answer.
Every provider on the list, or your own	OpenAI, Anthropic, Google, OpenRouter, NanoGPT, Ollama and the rest, each filling in its own URL and linking to where it hands out keys — or paste any URL that answers /models and /chat/completions. Streaming, with the provider's real token usage shown after each reply.
Plain files on disk	settings.json, stories/<id>.json, chapters/<id>.json — read once when the app starts and written straight back, with no second copy in the browser to fall out of step with them. Copy the folder and you have copied everything. Zipped to backups/ once a day.

A look around

Every chapter opens on a scene	Nothing is hidden
A world that only speaks when spoken to	Close a chapter and carry the story forward

Quick start

Nothing below is needed to use Lamplit — the download page has installers that carry Node inside them. This is the way in for people who want the source.

Node 22.22+, 24.15+ or 26+ — what Angular 22 asks for.

npm install
npm start

Then open http://localhost:4200. The app asks for a model first, then who tells the story and who you play, then the opening scene — and you are writing.

npm run package

builds a self-contained folder and a ~1 MB zip — the same one every release publishes as Lamplit.zip. Unzip it anywhere, run start.bat (Windows), start.command (macOS) or ./start.sh (Linux), and the app opens in your browser with no install step at all. See Running it anywhere.

npm run desktop:dist

builds the desktop installers for whatever OS you are on. See The desktop app.

Documentation

Read the docs →

Getting started	Installing, the first run, writing your first chapter
Reading and writing	The page, the composer, what each message can do
Chapters	Scenes, closing a chapter, the chapters list
Story and world	Narrator or role-play, your persona, the world and its lore
The prompt	How every request is assembled, and how to look at it
Models and parameters	Connecting, picking a model, sampling settings
Your data	Where files live, backups, offline, several stories
The desktop app	One download, one icon, and where it keeps your stories
Running it anywhere	Building the zip and running it on another machine
Development	Repo layout, scripts, tests, how the pictures are made

A note on your API key

Your key is stored in plain text, in data/settings.json on your own machine. That is deliberate: Lamplit is a single-user tool on your own computer, and a local file you control beats a secret store you have to unlock every time. The server listens on 127.0.0.1 only — nothing else on your network can reach it — unless you turn sharing on under Preferences → Advanced, which opens a second listener your phone can reach after it has scanned a code. A phone that has scanned it can read the key, so share on a network you trust. Don't run Lamplit on a machine you share, and don't put it on the open internet.

Status

Written in four steps, all done: streaming chat and the model connection, then chapters and the world, then persistence and packaging, then a desktop build and a way for people to find it. PLAN.md is the plan of record and records why each decision went the way it did.

Windows and Linux builds are not signed — Windows will warn about an unfamiliar app the first time, and the download page shows the two clicks past it. macOS is not built at all: a build that opens without a fight needs Apple's developer licence, which this project does not hold. If you have one and would like to contribute those builds, an issue would be very welcome.

Not here, on purpose: images, group chats, swipes and variants, an extensions system, text completion (non-chat) endpoints.

Built with

Angular 22 (standalone, signals, zoneless) · Angular Material · Express 5 · Playwright · Vitest. No state library, no HTTP client, no model SDK — fetch and a hand-written SSE reader.

License

MIT. Do what you like with it.

The book in the icon is Lucide’s book-open-text, under the ISC licence — see NOTICE.