Highlight

This is the core Lumis workflow: choose a language, choose a formatter, then render output.

Simple example

JavaScript

import {highlight} from '@lumis-sh/lumis';
import {htmlInline} from '@lumis-sh/lumis/formatters';
import javascript from '@lumis-sh/lumis/langs/javascript';
import dracula from '@lumis-sh/themes/dracula';

const html = await highlight(
  'const x = 1',
  htmlInline({language: javascript, theme: dracula})
);

Rust

use lumis::{highlight, HtmlInlineBuilder, languages::Language, themes};

let theme = themes::get("dracula").unwrap();

let formatter = HtmlInlineBuilder::new()
    .language(Language::Javascript)
    .theme(Some(theme))
    .build()
    .unwrap();

let html = highlight("const x = 1", formatter);

Elixir

Lumis.highlight!(
  "const x = 1",
  formatter: {:html_inline, language: "javascript", theme: "dracula"}
)

Java

import io.roastedroot.lumis4j.core.Lang;
import io.roastedroot.lumis4j.core.Lumis;
import io.roastedroot.lumis4j.core.Theme;

var lumis = Lumis.builder().build();

var highlighter = lumis.highlighter()
    .withLang(Lang.JAVASCRIPT)
    .withTheme(Theme.DRACULA)
    .build();

var html = highlighter.highlight("const x = 1").string();

CLI

lumis highlight index.js \
  --language javascript \
  --theme dracula

Options by runtime

Need	CLI	Rust	Elixir	JavaScript	Java
Set language	--language	.language(...)	language: "..."	language: ...	withLang(...)
Set theme	--theme	.theme(...)	theme: "..."	theme: ...	withTheme(...)
Choose output	--formatter	builder type	formatter: ...	formatter factory	runtime-specific

Language detection

If you omit the language, Lumis tries to detect it using:

• file extensions (.rs, .js, .ex, etc.)
• filenames (Makefile, Dockerfile, Caddyfile)
• shebangs (#!/usr/bin/env python)
• Emacs mode lines (-*- mode: ruby -*-)

If detection fails, it falls back to plaintext.

Incomplete code

Lumis handles incomplete or malformed code without crashing. Tree-sitter produces a partial syntax tree and Lumis highlights what it can. This is useful for streaming scenarios where code arrives in chunks (e.g., LLM output).

Next steps

• choose an output mode in Formatters
• pick or generate colors in Themes
• emphasize lines in Line Highlighting