sigil-lang

Parser, validator, serializer, and converter for the Sigil document format (.sgl).

Sigil is a semantic document format for LLM-native content. Every block has an explicit type — facts, warnings, steps, examples, conditionals — drawn from a fixed vocabulary.

Install

npm install sigil-lang

API

import { parse, validate, serialize } from 'sigil-lang';
import { readFileSync } from 'fs';

const { document, warnings } = parse(readFileSync('skill.sgl', 'utf-8'));

document.header.doctype   // 'skill'
document.blocks           // Block[]

// filter by semantic type
const facts    = document.blocks.filter(b => b.type === 'fact');
const triggers = document.blocks.filter(b => b.type === 'trigger');
const steps    = document.blocks.filter(b => b.type === 'step');

// validate against the spec
const { valid, errors } = validate(document);

// re-serialize to .sgl
const output = serialize(document);

Parser modes:

// strict (default) — throws on any spec violation
const { document } = parse(input, { mode: 'strict' });

// lenient — best-effort, useful for LLM-generated output
const { document, warnings } = parse(input, { mode: 'lenient' });

Markdown conversion:

import { fromMarkdown, toMarkdown } from 'sigil-lang';

const doc = fromMarkdown(markdownString);   // best-effort
const md  = toMarkdown(doc);

CLI

npm install -g sigil-lang

sigil parse skill.sgl --pretty          # parse to JSON AST
sigil validate skill.sgl                # check spec compliance
sigil serialize skill.sgl               # roundtrip check
sigil convert skill.sgl --to markdown   # convert to markdown
sigil convert README.md --to sigil      # convert from markdown
sigil validate skill.sgl --mode lenient # lenient mode

Links

• Spec — full language definition
• Examples — annotated walkthroughs
• Conformance tests — test suite for alternative implementations
• Changelog

License

MIT