Svelte 5+

Drop-in replacement.
Native speed.

Rust parser + parallel transforms + tsgo type-checking. Same CLI. Same output. Faster feedback.

$npm install -D svelte-check-rs
svelte-check
svelte-check-rs
faster
ยท

Built for agentic coding

svelte-check is built on Language Server Protocol infrastructure—optimized for IDEs with persistent connections, incremental updates, and interactive editing. Great for autocomplete and hover info. Slow for one-shot CLI checks.

svelte-check-rs is a batch-first CLI. No LSP. No language service overhead. Just fast, parallel diagnostics for CI pipelines and AI coding agents.

Built for
  • AI coding agents (Claude Code, Codex, Cursor)
  • CI/CD pipelines
  • Pre-commit hooks
  • Watch mode iteration
Not a replacement for
  • In-editor diagnostics
  • Autocomplete / IntelliSense
  • Hover documentation
  • Go-to-definition

Keep using the Svelte VS Code extension for IDE features. Use svelte-check-rs when you need fast CLI feedback. Still on Svelte 4? Stick with svelte-check.

Why it's fast

svelte-check
Uses TypeScript's Language Service API with in-memory transforms. Designed for IDEs, not batch compilation. No incremental builds—re-analyzes entire project every run.
vs
svelte-check-rs
Writes real TypeScript files to disk, runs tsgo as a standalone compiler. Enables incremental: true with persistent .tsbuildinfo. Subsequent runs only re-check changed files.
01

Rust Parser

Zero-copy lexer and AST built for Svelte 5 runes. No Node.js startup overhead.

02

Svelte Compiler (bun)

Persistent bun workers run Svelte compiler diagnostics directly on source.

03

Parallel Transform

Svelte to TypeScript via rayon. All CPU cores. Source maps preserved.

04

tsgo Compiler

Microsoft's native Go port of TypeScript. 10x faster than tsc.

Install

npm (recommended)
$npm install -D svelte-check-rs

Uses platform-specific optional dependencies to provide the binary. If you install with --no-optional, re-enable optional deps or use the shell/PowerShell installers below.

macOS / Linux
$curl --proto '=https' --tlsv1.2 -LsSf https://github.com/pheuter/svelte-check-rs/releases/latest/download/svelte-check-rs-installer.sh | sh
Windows (PowerShell)
>irm https://github.com/pheuter/svelte-check-rs/releases/latest/download/svelte-check-rs-installer.ps1 | iex

CLI Reference

Core

--workspace <path> Project root
--tsconfig <path> TypeScript config
--output <fmt> human | json | machine
--watch Re-check on file change

Diagnostics

--threshold error | warning
--fail-on-warnings Exit 1 on warnings
--ignore <glob> Skip matching files
--skip-tsgo Skip TypeScript type-checking

Debug

--timings Print timing breakdown
--timings-format text | json
--debug-paths Show resolved binaries (tsgo, bun)
--emit-ts Print transformed TS

Tooling

--tsgo-version Show installed tsgo version
--bun-version Show installed bun version
--bun-update Update bun to latest
--bun-update=<ver> Install specific version

Benchmark Methodology

Test Project

Production SvelteKit monorepo. Stats are source files checked for diagnostics; TypeScript also loads the full node_modules dependency graph for type resolution.

650 Svelte files
479 Routes
4.2k TS/JS files
640k Source LOC

Scenarios

  • Cold: Cleared .svelte-kit and node_modules/.cache/svelte-check-rs caches before each run
  • Warm: Caches preserved, no file changes between runs
  • Iterative: Single file change with dependent consumer updated

Environment

Machine Apple M4 Max, 48GB RAM
OS macOS 26.1 (25B78)
svelte-check 4.3.5
svelte-check-rs 0.1.0
tsgo 7.0.0-dev.20260101.1
Svelte / Kit 5.46.1 / 2.49.2

Results

Scenario svelte-check svelte-check-rs Speedup
Cold start
Warm cache
Iterative