fix: load ngspice engine without blob: import (fixes schematic simulation)

[rushabhcodes]

Important

This PR is a proof / stopgap, not the real fix. It patches a dependency's
built output in node_modules so schematic simulation works on the server
today. The actual defect lives in @tscircuit/ngspice-spice-engine

Problem

Schematic simulation fails on the server with:

Only URLs with a scheme in: file, data, and node are supported by the default ESM loader. Received protocol 'blob:'

Root cause: @tscircuit/ngspice-spice-engine@0.0.18 loads its WASM engine via an unconditional URL.createObjectURL + import("blob:..."):

// node_modules/@tscircuit/ngspice-spice-engine/dist/index.js
const source = await response.text();
const moduleUrl = URL.createObjectURL(new Blob([source], { type: "text/javascript" }));
return import(moduleUrl); // ← Node ESM loader rejects blob:

Node's ESM loader only accepts file:, data:, and node: schemes, so this throws the moment ngspice loads. It is the missing piece of #1686: preloadNgspice() hits this same import and silently fails, so the error only surfaces at simulate time.

What this PR does (the workaround)

• Patches the package in postinstall (scripts/apply-dependency-patches.mjs, mirroring the existing occt-import-js patch with idempotency + "upstream changed" guards) to import the bundled @tscircuit/eecircuit-engine directly instead of fetching + blob-importing. This removes the blob import and the runtime CDN fetch (matching Prevent CDN fallback in production by preloading bundled ngspice #1686's goal).
• Promotes @tscircuit/eecircuit-engine to a runtime dependency (pinned to 1.7.4, the same version the package's hardcoded CDN URL referenced) since a runtime dependency now imports it.
• Adds a Node-level regression test (tests/ngspice-node-loader.test.ts). The existing bun tests can't catch this — bun accepts blob: imports — so the test spawns a real Node process to run simulate().

The real fix

The proper fix belongs in @tscircuit/ngspice-spice-engine (lib/import-eecircuit-engine.ts). Today it loads the engine the same way in every environment:

const source = await response.text();
const moduleUrl = URL.createObjectURL(new Blob([source], { type: "text/javascript" }));
return import(moduleUrl);

blob: URLs only resolve in browsers/bun; the Node ESM loader rejects them — so the package is broken for any Node consumer, not just this repo. It should be environment-aware. Either:

1. Branch on environment — keep the CDN fetch, but in non-browser environments use a data: URL (which the Node loader accepts) instead of a blob URL. This is the minimal change and matches the pattern @tscircuit/eval already uses:

   const dataUrl = `data:text/javascript;base64,${Buffer.from(source, "utf8").toString("base64")}`;
   return import(dataUrl);

2. (Preferred) Import the package directly — declare @tscircuit/eecircuit-engine as a real dependency and return import("@tscircuit/eecircuit-engine"), optionally falling back to the CDN. This avoids the network round-trip entirely and is exactly what this PR forces via the patch.

Once a fixed @tscircuit/ngspice-spice-engine is published, the follow-up here is trivial: bump the dependency and remove patchNgspiceSpiceEngine() from scripts/apply-dependency-patches.mjs.

Verification

• ✅ Patch applies and is idempotent (re-run → "already patched")
• ✅ New guard fails without the patch (exact production error) and passes with it
• ✅ Existing schematic-simulation-svg test still passes
• ✅ Formatted with biome

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
svg-tscircuit-com	Ready	Preview, Comment	Jun 27, 2026 9:30pm
svg-tscircuit-com-wke7	Ready	Preview, Comment	Jun 27, 2026 9:30pm