Cloudflare Workers WebAssembly error with 0.16+

[vladshcherbin]

Bug report

Description / Observed Behavior

Starting with 0.16 there's an error on Cloudflare Workers

Expected Behavior

Expect it to work same as before 0.16

Reproduction

Create any satori call on Cloudflare Workers, check dashboard logs for errors

Additional Context

Satori 0.16+, previous worked with no errors

Wrangler has nodejs_compat flag on:

"compatibility_date": "2025-07-22",
"compatibility_flags": ["nodejs_compat"]

[shuding]

This is likely a bug/limitation in Cloudflare Workers. Do they have a way to allow this?

[kumardeo]

This is likely a bug/limitation in Cloudflare Workers. Do they have a way to allow this?

No, We can't use WebAssembly.instantiate() in Cloudflare Workers.

Also, Nextjs docs says it doesn't support WebAssembly.instantiate() either in edge runtime.

https://nextjs.org/docs/app/api-reference/edge#unsupported-apis

[pavi2410]

Forgive me for breaking Cloudflare Workers support. I am fixing that - shuding/yoga-wasm-web#35

[pavi2410]

This seems to be working for me on both wrangler dev and wrangler dev --remote. Can you please check this?

import satori from 'satori'
-import initYoga from 'yoga-wasm-web'
-import yogaWasm from '../node_modules/yoga-wasm-web/dist/yoga.wasm'

-const yoga = await initYoga(yogaWasm)
-init(yoga)

// Satori should work now.

wrangler.toml

name = "playbadges"
main = "./src/index.ts"
compatibility_date = "2025-08-01"

[kumardeo]

I am still facing this issue in version 1.18.1 when using the following code:

import satori, { init } from 'satori/standalone';

export default {
  async fetch(req, env, ctx) {
    const res = await fetch('https://unpkg.com/satori/yoga.wasm');
    const yogaWasm = await res.arrayBuffer();

    await init(yogaWasm);

    const svg = await satori(
      <div
        style={{
          display: 'flex',
          width: '100%',
          height: '100%',
          alignItems: 'center',
          justifyContent: 'center',
        }}
      >
        Hello
      </div>,
      {
        width: 600,
        height: 600,
        fonts: [
          {
            data: await fetch(
              'https://github.com/JetBrains/JetBrainsMono/raw/cd5227bd1f61dff3bbd6c814ceaf7ffd95e947d9/fonts/ttf/JetBrainsMono-Regular.ttf',
            ).then((res) => res.arrayBuffer()),
            name: 'sans serif',
          },
        ],
      },
    );

    return new Response(svg, {
      headers: {
        'Content-Type': 'image/svg+xml',
      },
    });
  },
} satisfies ExportedHandler<Env>;

▲ [WARNING] failed to asynchronously prepare wasm: CompileError: WebAssembly.instantiate(): Wasm code generation disallowed by embedder


▲ [WARNING] Aborted(CompileError: WebAssembly.instantiate(): Wasm code generation disallowed by embedder)

This is probably because Cloudflare workers does not allow compiling and instantiating WebAssembly code through buffer sources.

Instead it gives WebAssembly.Module when wasm binary is imported using es module syntax

import wasmModule from "./path-to-yoga-wasm.wasm";
//             ^ this is WebAssembly.Module

So, there must be a way to pass this WebAssembly.Module of yoga wasm to initialize yoga.

Before 0.16 we were using the following:

import satori, { init } from 'satori/wasm';
import initYoga from 'yoga-wasm-web';
import yogaWasmModule from './yoga.wasm';

const yoga = await initYoga(yogaWasmModule); // initYoga() accepts both BufferSource and WebAssembly.Module
await init(yoga);

// now we can use satori
await satori(...);

So, I expect that init from satori/standalone accepts WebAssembly.Module also so that usage of WebAssembly.instantiate() is prevented.

import satori, { init } from 'satori/standalone';
import yogaWasmModule from 'satori/yoga.wasm';

await init(yogaWasmModule); // should accept WebAssembly.Module as well and not only BufferSource

[pavi2410]

You should be able to download the wasm file locally from https://unpkg.com/satori/yoga.wasm and import it. I will test it myself later.

[kumardeo]

You should be able to download the wasm file locally from https://unpkg.com/satori/yoga.wasm and import it. I will test it myself later.

The signature for the init function exported in satori/standalone is as follows:

declare function init(wasm: ArrayBuffer | Buffer): Promise<void>;

It expects ArrayBuffer | Buffer and later it is passed to WebAssembly.instantiate() call which is disallowed in Cloudflare Workers.

[shuding]

I expect that init from satori/standalone accepts WebAssembly.Module

Good point! @huozhi ran into it too. Will fix!

[patdx]

Even with the update of #709, I can't figure out how to pass the WebAssembly.Module available in Cloudflare Workers environment into init() from satori/standalone, nor can I figure out how to instantiate it into a WebAssembly.Instance since that seems to need special functionality in the patched version of yoga-layout inside satori. Though this kind of seems like the fault of yoga-layout for bundling their code in a way that is fundamentally incompatible with Cloudflare Workers

Also I think the yoga.wasm inside satori@0.18.3 may be corrupted? This code reproduces an error in Browser and Node.js:

await WebAssembly.compileStreaming(fetch('https://unpkg.com/satori@0.18.3/yoga.wasm'));
// Uncaught: CompileError: WebAssembly.compileStreaming(): section (code 1, "Type") extends past end of the module (length 7299055, remaining bytes 81343) @+8

And same error message when I do import yogaModule from "./yoga.wasm" inside Cloudflare Workers.

[kumardeo]

Any update on this? I am also experiencing the above issue.