tsox

Fast TypeScript runner for Node.js. Like tsx but uses Rolldown/Oxc (Rust) instead of esbuild (Go) for transforms.

Install

pnpm add tsox

Usage

tsox file.ts                       # run a ts file
tsox watch server.ts               # watch mode
tsox -e "const x: number = 1"      # eval
tsox -p "1 + 2"                    # eval + print
tsox --test                        # node test runner w/ ts
tsox                               # repl

All node flags pass through (--env-file, --inspect, etc).

As a loader

Skip the CLI overhead entirely:

node --import tsox/loader file.ts

Benchmarks

Measured with hyperfine on Node v25.6.1, macOS arm64. 30 runs, 3 warmup.

Hooks-only (no CLI process, just the loader -- apples-to-apples transform comparison):

| | tsx | tsox | | |---|--:|--:|---| | 1 file | 177ms | 126ms | 1.4x | | 5 modules | 193ms | 120ms | 1.6x | | 100 modules | 303ms | 148ms | 2.1x |

E2E (full tsox file.ts vs tsx file.ts):

| | tsx | tsox | | |---|--:|--:|---| | 1 file | 190ms | 153ms | 1.2x | | types-heavy | 208ms | 151ms | 1.4x | | enums | 207ms | 146ms | 1.4x | | 5 modules | 171ms | 143ms | 1.2x | | 100 modules | 226ms | 164ms | 1.4x |

The gap grows with more modules since Oxc's per-file transform cost is way lower than esbuild's (~0.02ms vs ~0.31ms). E2E numbers are closer because both tools pay the same child-process spawn cost.

Run bash bench/run.sh to reproduce (needs hyperfine + tsx).

How it works

Same architecture as tsx -- CLI spawns node --no-strip-types --import <loader> file.ts, loader registers ESM hooks via module.register(), hooks intercept .ts/.tsx/.mts/.cts imports and run them through Oxc's transformSync. CJS support via Module._extensions patching.

We import from rolldown/utils instead of rolldown/experimental which avoids loading the full bundler engine (~9ms vs ~44ms import time).

Also handles .js -> .ts remapping, extensionless resolution, directory/index resolution, and tsconfig paths (lazy-loaded so there's zero cost if you don't use them).

Requirements

• Node >= 22.12.0
• Works as a drop-in tsx replacement (same CLI flags, same loader interface)

License

MIT