Chapter 1: Does JsxCore actually work with no Node?

The setup

mcr.microsoft.com/dotnet/sdk:9.0, verified empty of JS tooling first:

dotnet: 9.0.316
node: absent    npm: absent    npx: absent    yarn: absent    pnpm: absent

This mattered: the host machine has Node v24 and npm 11 installed, so a build there would have succeeded whether or not JsxCore needed them. The claim was untestable until it ran somewhere clean.

Result: it works

Three commands, dotnet new web, dotnet add package JsxCore, dotnet build:

Spike -> /work/Spike/bin/Debug/net9.0/Spike.dll
JsxCore: restoring with native: typescript, esbuild
JsxCore: created /work/Spike/package.json.
JsxCore: fetching @esbuild/linux-x64@0.28.1
JsxCore: fetching @typescript/typescript-linux-x64@7.0.2
JsxCore: fetching esbuild@0.28.1
JsxCore: fetching typescript@7.0.2

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:09.31

Program.cs was 8 lines. Index.tsx was 3. GET / returned 200 OK.

The claim holds. No Node runtime, no npm binary, TypeScript 7.0.2 and esbuild 0.28.1 sourced by the .NET build itself.

The honest nuance: "no npm" means no npm binary. JsxCore still writes a package.json and speaks the registry protocol directly. Practical consequence for CI: the build machine needs egress to registry.npmjs.org. An air-gapped or strictly-allowlisted runner will fail, and the error won't obviously point at JsxCore.

The finding that changes the plan

The default render mode is client-side, not server-side:

<div id="jsxcore-root"></div>
<script type="application/json" id="jsxcore-model">{"name":"World"}</script>
<script type="module">
import Component from "/_jsx/ve801387ae0/views/Home/Index.js";
import { mountView } from "@jsxcore/client";

Response header: X-JsxCore-Framework: preact.

The root div ships empty. The model is serialized into a JSON script tag and the component mounts in the browser.

This cuts two ways:

• Good: the Jint CPU cost I'd been worried about for a free-tier host doesn't apply per-request in this mode. No JavaScript executes server-side. The hosting math gets easier.
• Bad: an empty root div is wrong for an MVC app. No first paint without JS, nothing for crawlers. Server rendering is opt-in per response and has to be verified separately.

Also notable: the generated import map aliases react, react-dom, and react/jsx-runtime onto preact/compat. React-shaped code works, but Preact is what actually runs. The spec's "convert to React components" framing was imprecise.

And: JsxCore generated TypeScript declarations for 0 .NET type(s), expected here, since the model was an anonymous type. Real ViewModels are what exercise the type generation.

Still unverified

The three things the migration actually depends on:

1. Shared layouts. Layouts are a Razor concept; JsxCore registers as an IViewEngine
2. Form POST with [ValidateAntiForgeryToken], needed for all of Customer CRUD
3. ViewComponents. Equinox has Views/Shared/Components/Summary

Plus, now: server-side render mode, which the default output doesn't use.

Time

Under 15 minutes from empty directory to rendered page, including pulling the image. No .NET knowledge was required for any of it. The whole surface was three commands and two files copied from the README.