Rezi

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

Website · Docs · Quickstart · Widgets · API · Benchmarks

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Status: Alpha — under active development. APIs may change between releases.

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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
• 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
• 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

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Showcase

EdgeOps Control Plane

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

Visual Stress Test

Image Rendering

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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.

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Benchmarks

Two different benchmark datasets are committed and should not be mixed:

1. Rigorous terminal suite (replicates + confidence reporting): benchmarks/2026-02-19-terminal-v3
2. Quick driver/framework matchups (single replicate, directional): benchmarks/2026-02-20-*

From the rigorous suite (benchmarks/2026-02-19-terminal-v3), Rezi is:

• 7.3×–59.1× faster than Ink
• 1.4×–52.5× faster than OpenTUI React
• 1.9×–14.8× slower than native Rust (ratatui) (expected for native baseline)

That suite uses 7 replicates with first-replicate discard (6 measured), framework-order shuffling, CPU pinning, and confidence-aware ratio reporting.

From the quick matchup snapshots (directional only):

• Rezi vs OpenTUI React (benchmarks/2026-02-20-rezi-opentui-react-all-quick-v6): Rezi faster in 21/21 scenarios (geomean ~10.4×)
• Rezi vs OpenTUI Core (benchmarks/2026-02-20-rezi-opentui-core-all-quick-v4): Rezi faster in 19/21 scenarios (geomean ~2.6×)
• OpenTUI Core vs OpenTUI React: Core faster in 21/21 scenarios (geomean ~4.0×)
• Rezi vs Bubble Tea (benchmarks/2026-02-20-rezi-opentui-bubbletea-core-all-quick-v3): Rezi faster in 20/21 scenarios (geomean ~8.5×); Bubble Tea wins scroll-stress

Representative rows below are from the rigorous suite (OpenTUI column here means OpenTUI React):

Scenario	Rezi	Ink	OpenTUI (React)	Ratatui	Rezi vs Ink	Rezi vs OpenTUI (React)	Rezi vs Ratatui
terminal-frame-fill (1 dirty line)	372 µs	21.96 ms	4.03 ms	197 µs	59.1× faster	10.8× faster	1.9× slower
terminal-fps-stream	3.40 ms	24.96 ms	4.66 ms	231 µs	7.3× faster	1.4× faster	14.8× slower
terminal-virtual-list	681 µs	22.82 ms	35.73 ms	127 µs	33.5× faster	52.5× faster	5.4× slower

Full benchmark artifacts (methodology, confidence bands, and raw result tables):

• BENCHMARKS.md
• benchmarks/2026-02-19-terminal-v3/results.md
• benchmarks/2026-02-20-rezi-opentui-react-all-quick-v6/results.md
• benchmarks/2026-02-20-rezi-opentui-core-all-quick-v4/results.md
• benchmarks/2026-02-20-rezi-opentui-bubbletea-core-all-quick-v3/results.md

Full methodology and reproduction steps: 👉 BENCHMARKS.md

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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, and minimal.

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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.column({ p: 1, gap: 1 }, [
    ui.text("Counter", { style: { bold: true } }),
    ui.row({ gap: 2 }, [
      ui.text(`Count: ${s.count}`),
      ui.button("inc", "+1", {
        onPress: () => app.update((prev) => ({ count: prev.count + 1 })),
      }),
    ]),
  ]),
);

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

Install:

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

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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, Text, Button } from "@rezi-ui/jsx";

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

app.view((s) => (
  <Column p={1} gap={1}>
    <Text style={{ bold: true }}>Counter</Text>
    <Row gap={2}>
      <Text>Count: {s.count}</Text>
      <Button
        id="inc"
        label="+1"
        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

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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.

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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

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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.

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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

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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.

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License

Apache-2.0