The GistUI Lang engine: an incremental streaming parser, a patch-based materializer, validation with deterministic repair, a canonical printer, edit-mode merge and a system-prompt generator. It has zero dependencies and works in any JS runtime.

npm install @gistui/core

import { createStream, defineLibrary, generatePrompt } from "@gistui/core";

const lib = defineLibrary({ components: [/* ComponentSpec… */] });
const system = generatePrompt(lib).text;

const stream = createStream(lib);
stream.store.subscribe("root", () => render(stream.store.get("root")));
for await (const chunk of llmResponse) {
  stream.push(chunk); // string or UTF-8 bytes
  stream.flush(); // call once per frame; commits patches and notifies subscribers
}
stream.end(); // auto-closes, drops unresolved refs, reports errors
console.log(stream.errors());

• parse(source, lib): one-shot parse. Returns {root, store, errors, valid: {strict, lenient}}.
• validate(source, lib): validity, errors and the reachable component count.
• autofix(text, lib): repairs a program with mistakes, in code (no model call): unknown props and extra arguments removed, invalid values corrected, missing required props filled, misspelled components renamed, dangling references dropped, unused statements placed. Every change is listed.
• toEditSource / merge: the canonical printout for edit turns, and the merge of an edit into a program.
• generatePrompt(lib, {mode, tools, examples, groups, progressive}): a byte-stable system prompt.

The language is specified in spec/gistui-lang.md in the GistUI repository, with a conformance suite in spec/conformance/.

bun test               # unit, property, conformance and performance tests
bun run bench          # parser benchmarks → bench/results/parser.json

All packages

GistUI is one project in several packages, released together under one version.

| Package | What it is | |---|---| | @gistui/react | React renderer and default components | | @gistui/vue | Vue 3.5+ and Nuxt | | @gistui/svelte | Svelte 5 and SvelteKit | | @gistui/solid | Solid and SolidStart | | @gistui/vanilla | Vanilla JavaScript renderer, no framework | | @gistui/catalog | Component schemas, the system prompt and the agent skill | | @gistui/styles | One stylesheet for every framework | | @gistui/server | Stream reading, validation and repair on the server | | @gistui/chat | Headless chat store, model adapters, React chat layouts | | @gistui/core | The language: streaming parser, validator, autofix, prompt generator | | @gistui/headless | Shared internals: engine, themes, forms | | @gistui/widgets | Shared internals: charts, Markdown |

Licence

MIT