Does not run with bun (dev only)

[medz]

Environment

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• Operating System: Darwin
• Node Version: v22.19.0
• Nuxt Version: 4.1.3
• CLI Version: 3.29.3
• Nitro Version: 2.12.7
• Package Manager: bun@1.3.0
• Builder: -
• User Config: compatibilityDate, devtools, nitro
• Runtime Modules: -
• Build Modules: -

---

Reproduction

https://github.com/medz/github-fmzbfj/tree/main/bun-1.3-nuxt-post-500

Describe the bug

When using bun --bun run nuxt dev or nitro: { preset: "bun" }, all requests except GET return 400 errors.

Additional context

This problem only occurs during dev. There will be no problem running it using bun after build.

Logs

There are no errors in your output

[github-actions]

Stackblitz link for the reproduction: Stackblitz

[medz]

[Flo0806]

Hi. I think that's a bun bug. If I start with --bun I can't see any response with CURL.
Since the request doesn't even reach Nitro (no handler logs, no response body, just a 400 with Content-Length: 0 from Bun's HTTP server), I believe this is definitely a Bun bug rather than a Nuxt/Nitro issue.

Evidence:

• bun --bun run dev → POST returns 400 ❌
• bun run dev (uses Node.js) → POST works perfectly ✅
• The handler is never executed (no console logs)
• Bun's server returns the 400 before the request reaches Nitro

Workaround:
Use bun run dev without the --bun flag until this is fixed in Bun.

Am I missing something, or should this be reported to the Bun repository instead?

[medz]

Hi. I think that's a bun bug. If I start with --bun I can't see any response with CURL. Since the request doesn't even reach Nitro (no handler logs, no response body, just a 400 with Content-Length: 0 from Bun's HTTP server), I believe this is definitely a Bun bug rather than a Nuxt/Nitro issue.

Evidence:

• bun --bun run dev → POST returns 400 ❌
• bun run dev (uses Node.js) → POST works perfectly ✅
• The handler is never executed (no console logs)
• Bun's server returns the 400 before the request reaches Nitro

Workaround: Use bun run dev without the --bun flag until this is fixed in Bun.

Am I missing something, or should this be reported to the Bun repository instead?

Temporary solution is not feasible because I use Bun Runtime APIs extensively in the Server part.

[huang-julien]

I think this is related to the CLI moving to socket a few versions ago