Tech

[Cloudflare Pages] bun patch Didn't Apply in Production

I had patched a package in node_modules with bun patch, but on closer inspection, the patch was not applied in production. The actual cause was that the project was being installed with npm rather than Bun, so here is how I fixed it.

2026/01/022026/07/24

Note

This article was initially translated with GPT-5.6 and then reviewed and edited by the author.

Conclusion

To build with Bun, this command is not enough:

bun run build

Use this instead:

npm install -g bun && bun install && bun run build

Where to enter the command

This is where you put it.

What I wanted to do

I recently learned that:

bun patch

lets you edit packages inside node_modules. I think you can do the same thing with npm or Yarn.

Tip

To learn more about bun patch, you could read this article or something.

However, although the patch worked properly in local builds and the development environment, it did not work on Cloudflare Pages. That was strange.

So I checked the logs:

23:36:03.477  Cloning repository...
23:36:06.576  From https://github.com/AoSankaku/aosankaku-website-2025
23:36:06.576   * branch            f6c417a0565109496eba7f527d4fb56d27a20a50 -> FETCH_HEAD
23:36:06.576
23:36:06.862  HEAD is now at f6c417a Repatched @astro-community/astro-embed-youtube prefetch
23:36:06.862
23:36:06.932
23:36:06.932  Using v2 root directory strategy
23:36:06.952  Success: Finished cloning repository files
23:36:08.787  Checking for configuration in a Wrangler configuration file (BETA)
23:36:08.787
23:36:09.887  No wrangler.toml file found. Continuing.
23:36:09.951  Detected the following tools from environment: [email protected], [email protected]
23:36:09.952  Installing project dependencies: npm install --progress=false
23:36:43.266  npm warn deprecated [email protected]: Use @exodus/bytes instead for a more spec-conformant and faster implementation
23:36:48.708
23:36:48.709  added 580 packages, and audited 581 packages in 38s
23:36:48.709
23:36:48.709  196 packages are looking for funding
23:36:48.709    run `npm fund` for details
23:36:48.710
23:36:48.710  found 0 vulnerabilities
23:36:48.736  Executing user command: bun run build
23:36:48.958  $ astro build
23:36:51.468  14:36:51 [content] Syncing content
…

It very clearly says [email protected].

In other words, I had convinced myself that Bun was being used throughout the entire process when it actually was not. Scary.

After that, all I had to do was change the command as described at the beginning of the article.

Bonus

As an added benefit, the build—or, more precisely, the package download—became a little faster.

Thirty seconds is a pretty big difference.

Before switching to Bun:

1 minute 42 seconds before switching to Bun

After switching to Bun:

1 minute 18 seconds after switching to Bun

References

Using Bun on Cloudflare Pages

dt.in.th

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