Rezi

TypeScript TUI, Near-Native Performance.
High-level developer experience powered by a deterministic C rendering engine.

Website · Docs · Quickstart · Widgets · API · Benchmarks

Status: Pre-alpha — under active development and changing rapidly. Public APIs, ABI expectations, and behavior may change between releases, and Rezi is not yet recommended for production workloads.

What Rezi Can Do

Rezi is a high-performance terminal UI framework for TypeScript. You write declarative widget trees — a native C engine handles layout diffing and rendering.

56 built-in widgets — layout primitives, form controls, data tables, virtual lists, navigation, overlays, a code editor, diff viewer, and more
Canvas drawing — sub-character resolution via braille (2×4), sextant (2×3), quadrant (2×2), and halfblock (1×2) blitters; draw lines, shapes, and gradients within a single terminal cell grid
Charts & visualization — line charts, scatter plots, heatmaps, sparklines, bar charts, gauges, and mini charts — all rendered at sub-character resolution
Inline image rendering — display PNG, JPEG, and raw RGBA buffers using Kitty, Sixel, or iTerm2 graphics protocols, with automatic blitter fallback
Terminal auto-detection — identifies Kitty, WezTerm, iTerm2, Ghostty, Windows Terminal, and tmux; enables the best graphics protocol automatically, with env-var overrides for any capability
Performance-focused architecture — binary drawlists + native C framebuffer diffing; benchmark details and caveats are documented in the Benchmarks section
Ink compatibility layer — run existing Ink CLIs on Rezi with minimal changes (import swap or dependency aliasing), plus deterministic parity diagnostics; details: Porting guide · Ink Compat architecture
JSX without React — optional @rezi-ui/jsx maps JSX directly to Rezi VNodes with zero React runtime overhead
Deterministic rendering — same state + same events = same frames; versioned binary protocol, pinned Unicode tables
Hot state-preserving reload — swap widget views or route tables in-process during development without losing app state or focus context
Syntax tokenizer utilities — shared lexical highlighters for TypeScript/JS/JSON/Go/Rust/C/C++/C#/Java/Python/Bash with custom-tokenizer hooks
Advanced deterministic layout — intrinsic sizing, flexShrink/flexBasis, alignSelf, wrapped text layout, grid spans/explicit placement, absolute positioning, and stability-signature relayout skipping
6 built-in themes — dark, light, dimmed, high-contrast, nord, dracula; switch at runtime with one call
Declarative animation APIs — numeric hooks (useTransition, useSpring, useSequence, useStagger) and ui.box transition props for position/size/opacity motion
Record & replay — capture input sessions as deterministic bundles for debugging and automated testing

Showcase

EdgeOps Control Plane

A production-style terminal control console built entirely with Rezi.

Visual Stress Test

Image Rendering

How It Works

You write declarative widget trees in TypeScript. Rezi computes layout and emits a compact binary drawlist (ZRDL). A native C engine — Zireael — diffs framebuffers and writes only changed cells to the terminal.

Most JavaScript TUI frameworks generate ANSI escape sequences in userland on every frame. Rezi moves the hot path out of JavaScript — rendering stays ergonomic at the top and fast on real workloads.

Benchmarks

22 scenarios across primitive workloads (tree construction, rerender, layout), terminal-level rendering (full PTY write path), and full-app UI composition. All 8 frameworks run in PTY mode.

Representative numbers

Numbers from a single-replicate full run on Apple M4 Pro (macOS arm64, PTY mode). Directional, not publication-grade.

Scenario	Rezi	Ink	OpenTUI Core	Ratatui	blessed
rerender	330µs	19.22ms	1.26ms	70µs	39µs
tree-construction (100 items)	153µs	24.16ms	1.51ms	913µs	1.70ms
tree-construction (1000 items)	1.31ms	79.60ms	17.35ms	2.33ms	19.14ms
terminal-full-ui	1.14ms	22.34ms	1.32ms	258µs	314µs
terminal-strict-ui	873µs	22.14ms	1.27ms	183µs	302µs
terminal-virtual-list (100K)	644µs	22.32ms	1.28ms	121µs	124µs
scroll-stress (2000 items)	6.99ms	182ms	32.58ms	—	—

Rezi is the fastest TypeScript/JavaScript framework across all measured scenarios. terminal-kit, blessed, and Ratatui are lower-level libraries (no layout engine or no widget system); they are faster on primitive output scenarios, and slower or absent on workloads requiring structured layout and widget composition.

Memory at terminal-full-ui (peak RSS)

Framework	Peak RSS
Ratatui	2.9 MB
Rezi	129 MB
OpenTUI (Core)	131 MB
blessed	260 MB
Ink	301 MB
OpenTUI (React)	1,010 MB

Running benchmarks

# Prerequisites: build Rezi, then ensure bun/cargo are in PATH
npm ci && npm run build && npm run build:native && npx tsc -b packages/bench

# Quick run — all 8 frameworks
PATH="$HOME/.cargo/bin:$HOME/.bun/bin:$PATH" \
REZI_BUN_BIN="$HOME/.bun/bin/bun" \
node --expose-gc packages/bench/dist/run.js \
  --suite all --io pty --quick --output-dir benchmarks/local-all

See BENCHMARKS.md for full results, all scenarios, scenario definitions, methodology caveats, and advanced run options.

Quick Start

Get running in under a minute:

npm create rezi my-app
cd my-app
npm start

Or with Bun:

bun create rezi my-app
cd my-app
bun start

Starter templates: dashboard, stress-test, cli-tool, animation-lab, minimal, and starship (command console).

Example

`ui.*` API

import { ui } from "@rezi-ui/core";
import { createNodeApp } from "@rezi-ui/node";

const app = createNodeApp<{ count: number }>({
  initialState: { count: 0 },
});

app.view((s) =>
  ui.page({
    p: 1,
    gap: 1,
    header: ui.header({ title: "Counter", subtitle: "Beautiful defaults" }),
    body: ui.panel("Count", [
      ui.row({ gap: 1, items: "center" }, [
        ui.text(String(s.count), { variant: "heading" }),
        ui.spacer({ flex: 1 }),
        ui.button("inc", "+1", {
          intent: "primary",
          onPress: () => app.update((prev) => ({ count: prev.count + 1 })),
        }),
      ]),
    ]),
  }),
);

app.keys({ q: () => app.stop() });
await app.start();

Beautiful Defaults

When the active theme provides semantic color tokens, Rezi uses design system recipes by default for: ui.button, ui.input/ui.textarea, ui.select, ui.checkbox, ui.progress, and ui.callout.

Use intent on buttons for common “primary/danger/link” patterns.
Use preset on ui.box (or ui.card/ui.panel) for consistent container defaults.
Use manual style props to override specific attributes (they do not disable recipes).

Docs: Design System · Migration: Beautiful Defaults

Install:

npm install @rezi-ui/core @rezi-ui/node

JSX (No React Runtime)

@rezi-ui/jsx maps JSX directly to Rezi VNodes.

/** @jsxImportSource @rezi-ui/jsx */
import { createNodeApp } from "@rezi-ui/node";
import { Column, Row, Spacer, Text, Button } from "@rezi-ui/jsx";

const app = createNodeApp<{ count: number }>({
  initialState: { count: 0 },
});

app.view((s) => (
  <Column p={1} gap={1}>
    <Text variant="heading">Counter</Text>
    <Row gap={1} items="center">
      <Text variant="heading">{String(s.count)}</Text>
      <Spacer flex={1} />
      <Button
        id="inc"
        label="+1"
        intent="primary"
        onPress={() => app.update((prev) => ({ count: prev.count + 1 }))}
      />
    </Row>
  </Column>
));

app.keys({ q: () => app.stop() });
await app.start();

npm install @rezi-ui/jsx @rezi-ui/core @rezi-ui/node

Features

56 built-in widgets — primitives (box, row, column, text, grid), form inputs (input, button, checkbox, select, slider), data display (table, virtual list, tree), navigation (tabs, accordion, breadcrumb, pagination), overlays (modal, dropdown, toast, command palette), advanced (code editor with built-in/custom syntax tokenization, diff viewer, file picker, logs console), and visualization (canvas, image, line chart, scatter, heatmap, sparkline, bar chart, gauge, mini chart).

Graphics & Visualization

Widget	Description
`ui.canvas`	Programmable drawing surface with braille, sextant, quadrant, halfblock, or ASCII blitters
`ui.image`	Inline images via Kitty, Sixel, iTerm2, or blitter fallback
`ui.lineChart`	Multi-series line charts at sub-character resolution
`ui.scatter`	Scatter plots with configurable point styles
`ui.heatmap`	Heatmap grids with automatic color scaling
`ui.sparkline`	Inline sparklines (text mode or high-res canvas mode)
`ui.barChart`	Horizontal bar charts
`ui.gauge`	Progress and percentage gauges
`ui.miniChart`	Compact inline charts

Terminal Graphics Protocol Support

Rezi auto-detects your terminal emulator and enables the best available graphics protocol:

Terminal	Graphics Protocol	Hyperlinks (OSC 8)
Kitty	Kitty graphics	Yes
WezTerm	Sixel	Yes
iTerm2	iTerm2 inline images	Yes
Ghostty	Kitty graphics	Yes
Windows Terminal	—	Yes

Canvas and chart widgets work in any terminal via Unicode blitters — no graphics protocol required. Image widgets fall back to blitter rendering when no protocol is available.

Override any capability with environment variables: REZI_TERMINAL_SUPPORTS_KITTY, REZI_TERMINAL_SUPPORTS_SIXEL, REZI_TERMINAL_SUPPORTS_ITERM2, REZI_TERMINAL_SUPPORTS_OSC8

Focus & Input

Automatic tab navigation
Focus traps for modals
Global keybindings
Vim-style and chord sequences
Mouse support (click, scroll, drag)

Theming

Six built-in themes: dark, light, dimmed, high-contrast, nord, dracula

Switch at runtime:

app.setTheme("nord");

Deterministic Rendering

Same state + same events = same frames
Versioned binary protocol
Pinned Unicode version
Strict update semantics

Record & Replay

Capture input sessions as deterministic bundles for debugging and testing.

Who is Rezi for?

Rezi is built for:

Real-time dashboards
Developer tooling
Control planes
Log viewers
Terminal-first applications
Teams who want TypeScript ergonomics without sacrificing performance

Architecture

Rezi separates authoring from rendering:

Application Code (TypeScript)
        │
        ▼
@rezi-ui/core      Layout, widgets, protocol builders
        │ ZRDL drawlist
        ▼
@rezi-ui/node      Node.js/Bun backend
        │
        ▼
@rezi-ui/native    N-API binding
        │
        ▼
Zireael (C engine) Framebuffer diff, ANSI emission
        │
        ▼
Terminal

Data flows down as drawlists (ZRDL). Input events flow up as event batches (ZREV). Both are versioned binary formats validated at the boundary.

Packages

Package	Description
`@rezi-ui/core`	Runtime-agnostic widgets, layout, themes
`@rezi-ui/node`	Node.js/Bun backend
`@rezi-ui/native`	N-API binding to Zireael
`@rezi-ui/jsx`	JSX runtime (no React)
`@rezi-ui/testkit`	Testing utilities
`create-rezi`	Project scaffolding CLI

Requirements

Runtime: Node.js 18+ (18.18+ recommended) or Bun 1.3+
Platforms: Linux x64/arm64, macOS x64/arm64, Windows x64/arm64
Terminal: 256-color or true-color support recommended
Graphics: For inline images, a terminal supporting Kitty graphics, Sixel, or iTerm2 inline images. Canvas and chart widgets work in any terminal via Unicode blitters.

Prebuilt native binaries are published for all supported platforms above. The package does not compile from source at install time; for unsupported targets, build from a repository checkout with npm run build:native.

Documentation

Resource	Link
Website & Docs	rezitui.dev
Getting started	Install · Quickstart · JSX
Guides	Concepts · Layout · Input & Focus · Styling
Widget catalog	56 widgets
API reference	TypeDoc
Architecture	Overview · Protocol

Contributing

git clone https://github.com/RtlZeroMemory/Rezi.git
cd Rezi
git submodule update --init --recursive
npm ci
npm run build
npm test

See CONTRIBUTING.md.

License

Apache-2.0

Name		Name	Last commit message	Last commit date
Latest commit History 547 Commits
.claude/skills		.claude/skills
.codex/skills		.codex/skills
.github		.github
Assets		Assets
benchmarks		benchmarks
docs		docs
examples		examples
packages		packages
results		results
scripts		scripts
snapshots		snapshots
vendor		vendor
.editorconfig		.editorconfig
.gitattributes		.gitattributes
.gitignore		.gitignore
.gitmodules		.gitmodules
AGENTS.md		AGENTS.md
BENCHMARKS.md		BENCHMARKS.md
BENCHMARK_VALIDITY.md		BENCHMARK_VALIDITY.md
CHANGELOG.md		CHANGELOG.md
CLAUDE.md		CLAUDE.md
CODEOWNERS		CODEOWNERS
CONTRIBUTING.md		CONTRIBUTING.md
GOVERNANCE.md		GOVERNANCE.md
INK_COMPAT_AUDIT_REPORT.md		INK_COMPAT_AUDIT_REPORT.md
LICENSE		LICENSE
README.md		README.md
RELEASING.md		RELEASING.md
ROADMAP.md		ROADMAP.md
SECURITY.md		SECURITY.md
SUPPORT.md		SUPPORT.md
biome.json		biome.json
mkdocs.yml		mkdocs.yml
package-lock.json		package-lock.json
package.json		package.json
requirements-docs.txt		requirements-docs.txt
tsconfig.base.json		tsconfig.base.json
tsconfig.json		tsconfig.json
typedoc.json		typedoc.json

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RtlZeroMemory/Rezi

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Rezi

What Rezi Can Do

Showcase

EdgeOps Control Plane

Visual Stress Test

Image Rendering

How It Works

Benchmarks

Representative numbers

Memory at terminal-full-ui (peak RSS)

Running benchmarks

Quick Start

Example

ui.* API

Beautiful Defaults

JSX (No React Runtime)

Features

Graphics & Visualization

Terminal Graphics Protocol Support

Focus & Input

Theming

Deterministic Rendering

Record & Replay

Who is Rezi for?

Architecture

Packages

Requirements

Documentation

Contributing

License

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