Bundler error in Cloudflare Workers: Cannot resolve "@react-email/render" when using resend.emails.send with html only (React not used)

[nexckycort]

Describe the Bug

I'm experiencing a bundling error when deploying to Cloudflare Workers using Wrangler v4.32.0. Even though I’m only sending HTML emails via the html prop (without any React component), the build fails with:

ERROR: Could not resolve "@react-email/render"

This happens despite using the latest resend version (v6.0.1). If I downgrade resend to an older version (4.8.0), the error disappears.

Link to the code that reproduces this issue

https://github.com/resend

To Reproduce

Steps to Reproduce

1. Install latest resend (e.g., resend@6.0.1).

2. In a Cloudflare Worker, call:

   await resend.emails.send({
     from: "noreply@...com",
     to: email,
     subject: `...`,
     html: "<div>Some HTML</div>",
   });

3. Run wrangler deploy — even without using react at all — results in:

   ERROR: Could not resolve "@react-email/render"
   

Expected Behavior

The Worker should bundle and deploy successfully when using plain HTML only.

What's your node version? (if relevant)

No response

[jayanratna]

I believe installing @react-email/render will fix this issue for you. npm install @react-email/render :)

[gabrielmfern]

Couldn't reproduce with our Cloudflare Workers example, even after updating to wrangler@4.32.0 and removing @react-email completely.

Can you please share a reproduction for this?

[gabrielmfern]

Was able to reproduce this when bundling with esbuild, seems like it happens because the bundler tries to bundle in @react-email/render. Workaround is to just set @react-email/render as external

[astanciu]

Having the same issue. @gabrielmfern where did you set it as external?

[gabrielmfern]

@astanciu I'm afraid there's no external for the wrangler CLI, this only works when doing bundling yourself, or using something more customizable. The simplest thing you can do, for Cloudflare Workers, is installing @react-email/render so that the error goes away.

[chakravarthi-bb]

Couldn't reproduce with our Cloudflare Workers example, even after updating to wrangler@4.32.0 and removing @react-email completely.

Can you please share a reproduction for this?

Why would you add package that's not needed for your repo?

Facing same issue with docker builds where it requires react email, whereas I only need html

[emiliosheinz]

Just a heads-up. I opened a discussion about this issue here. You might be interested in taking a look and sharing your thoughts.

[gabrielmfern]

Why would you add package that's not needed for your repo?

@chakravarthi-bb it's not added, we just support it conditionally, and it only gets truly imported when the react prop is present. The problem is that esbuild (the cloudflare bundler) tries to bundle in those dynamic imports as well, which causes the errors

[gabrielmfern]

Since Cloudflare Workers uses esbuild, seems like we can rely on the heuristics it uses evanw/esbuild#3216 (comment) and things should work. Will look into this soon.

You want to try this out @emiliosheinz?

[emiliosheinz]

Sorry @gabrielmfern, I had a busy week and didn't have time to look into it. But seems like you have already figured it out. Let me know if I can help with anything else.

[Akryum]

But seems like you have already figured it out.

Has a fix been released somewhere?