Reference › Version matrix

Version matrix

Verified against the npm registry on 2026-08-02. The canonical copy lives in builder/versions.js, which is what the generator uses.

#Pick a row and use everything in it

Do not mix generations.

#Scramjet 2.x, what you should be installing

{
	"@mercuryworkshop/scramjet": "2.0.67-alpha.2",
	"@mercuryworkshop/scramjet-controller": "0.0.14",
	"@mercuryworkshop/scramjet-utils": "0.0.3",
	"@mercuryworkshop/libcurl-transport": "^2.0.5",
	"@mercuryworkshop/epoxy-transport": "^3.0.1",
	"@mercuryworkshop/wisp-js": "^0.4.1"
}

Or let @mercuryworkshop/proxy-bootstrap@0.0.5 fetch all of it at runtime.

Add "@mercuryworkshop/bare-transport": "^1.0.0" and a Bare server instead of wisp-js if you want Scramjet without a WebSocket. Not bare-as-module3, which is the bare-mux-era package and will not work here. See the two Bare packages.

#Ultraviolet 3.x, for reference only

Not a recommendation. This is here so you can tell at a glance whether a codebase you have inherited is on the old generation, and so you do not accidentally install half of it alongside Scramjet. See proxy engines.

{
	"@titaniumnetwork-dev/ultraviolet": "^3.2.10",
	"@mercuryworkshop/bare-mux": "^2.1.9",
	"@mercuryworkshop/libcurl-transport": "^1.5.2",
	"@mercuryworkshop/epoxy-transport": "^2.1.28",
	"@mercuryworkshop/wisp-js": "^0.4.1",

	"@mercuryworkshop/bare-as-module3": "^2.2.5",
	"@tomphttp/bare-server-node": "^2.0.3"
}

Note the transport majors: libcurl ^1 and epoxy ^2, against Scramjet's ^2 and ^3. That is the mismatch that bites people who copy one line out of an old package.json.

#The trap: latest is not the newest Scramjet

npm install @mercuryworkshop/scramjet     # installs 1.1.0, not 2.x

Scramjet 2.x is published under the alpha dist-tag. latest still points at the 1.x line, which uses a completely different API ($scramjetLoadController and bare-mux). Ask for the version explicitly:

npm install @mercuryworkshop/scramjet@2.0.67-alpha.2

Pin the Scramjet packages exactly. These are alphas and the controller API has changed more than once between them.

Older guides install from a GitHub release URL:

https://github.com/MercuryWorkshop/scramjet/releases/download/latest/mercuryworkshop-scramjet-2.0.0-alpha.tgz

latest there is a rolling continuous build, so that URL no longer resolves to the version the guide was written against. Everything is on npm now; use npm.

#Transport compatibility

The interface these implement changed, and the package majors track it:

Mismatched versions sometimes appear to work, because the two interfaces are structurally similar. That is worse than failing outright, you get errors on specific sites rather than at startup.

#Node-side path helpers

Which packages export a helper for serving their browser assets:

For the ones without a helper:

import { createRequire } from "node:module";
import path from "node:path";

const require = createRequire(import.meta.url);
const dirOf = specifier => path.dirname(require.resolve(specifier));

app.use(
	"/controller/",
	express.static(dirOf("@mercuryworkshop/scramjet-controller"))
);
app.use(
	"/libcurl/",
	express.static(dirOf("@mercuryworkshop/libcurl-transport"))
);

require.resolve only resolves a path; it does not execute the module. That matters because the newer transports are browser-only and throw if you import them in Node. libcurl throws "environment detection error" from its Emscripten runtime, epoxy with something else from wasm-bindgen.

"None" above means none you can reach: epoxy 3.x still ships a lib/index.cjs exporting epoxyPath, but its exports map only declares ".", so no import specifier resolves to it.

#What each package contains

The generated server gives each package a distinct prefix so the same routes work in Express and Fastify.

#Release timeline

Two things to read off this table: Ultraviolet has not shipped since October 2024, and its README now calls it superseded by Scramjet, though the repository is not archived, and main has commits newer than 3.2.10. And bare-mux 2.1.9 carries a deprecation notice pointing at proxy-transports, even though UV 3.x still depends on it.

#Checking for yourself

npm view @mercuryworkshop/scramjet dist-tags
npm view @mercuryworkshop/scramjet-controller version
npm view @mercuryworkshop/libcurl-transport versions --json | tail -20

If this page and npm disagree, npm is right and this page is stale. Please open a PR.

Source: docs/reference/versions.md
Verified against Scramjet 2.0.67-alpha.2, controller 0.0.14, and Ultraviolet undefined on 2026-08-02. If this page and upstream disagree, upstream is right.