[cloudflare] Generated wrangler config specifies nodejs_compat, which workerd rejects for compatibility dates from 2026-08-04

[petebacondarwin]

Environment

• nitropack 2.13.4 (also reproduces via Nuxt 4.5.2 / nuxi 3.37.0)
• workerd >= 1.20260804.x (shipped in recent wrangler releases)
• Presets: both cloudflare_pages and cloudflare_module

Describe the bug

As of workerd 1.20260804.x, the nodejs_compat and nodejs_compat_v2 compatibility flags are enabled by default from compatibility date 2026-08-04 ($compatEnableDate("2026-08-04") in compatibility-date.capnp).

Once a flag becomes the default, specifying it explicitly is a hard error in workerd — not a warning:

✘ [ERROR] service core:user:my-app: The compatibility flag nodejs_compat became the default as of 2026-08-04 so does not need to be specified anymore.

✘ [ERROR] The Workers runtime failed to start. There was likely a problem with the workerd binary or your configuration.

Nitro's Cloudflare preset adds nodejs_compat unconditionally to the wrangler config it generates, so any Nitro project with compatibility_date >= 2026-08-04 fails to start:

https://github.com/nitrojs/nitro/blob/main/src/presets/cloudflare/utils.ts

if (nitro.options.cloudflare?.nodeCompat) {
  // ...
  } else {
    compatFlags.add("nodejs_compat");
    compatFlags.add("no_nodejs_compat_v2");
  }
}
wranglerConfig.compatibility_flags = [...compatFlags];

Because this config is written into the build output and wrangler is pointed at it through a .wrangler/deploy/config.json redirect, it overrides the user's own wrangler.jsonc:

Using redirected Wrangler configuration.
 - Configuration being used: "dist/_worker.js/wrangler.json"
 - Original user's configuration: "wrangler.jsonc"
 - Deploy configuration file: ".wrangler/deploy/config.json"

So users cannot work around this from their own wrangler config — removing nodejs_compat there has no effect, since Nitro re-adds it at build time.

Note also that enableNodeCompat() turns nodeCompat on automatically whenever deployConfig is set, so this affects projects that never explicitly opted into Node.js compatibility.

Reproduction

pnpm create cloudflare@latest my-nuxt-app --framework=nuxt --platform=workers
cd my-nuxt-app
pnpm run preview

C3 scaffolds with today's date as compatibility_date (>= 2026-08-04) and does not specify nodejs_compat. The build succeeds; the dev server fails to boot with the error above.

Suggested fix

Only add nodejs_compat when the resolved compatibility_date is before 2026-08-04; from that date the flag is implicit and must be omitted:

const NODEJS_COMPAT_DEFAULT_ON_DATE = "2026-08-04";

if (wranglerConfig.compatibility_date < NODEJS_COMPAT_DEFAULT_ON_DATE) {
  compatFlags.add("nodejs_compat");
}
compatFlags.add("no_nodejs_compat_v2");

(Plain string comparison is safe for YYYY-MM-DD dates.)

no_nodejs_compat_v2 is unaffected — disable flags are not rejected — so it can still be added unconditionally if that is the intended behaviour.

It would also be worth reviewing the nodejs_compat_v2 branch just above, since that flag has the same 2026-08-04 default-on date and will hit the identical error.

Additional context

We have quarantined our Nuxt end-to-end tests in cloudflare/workers-sdk while this is outstanding, and are tracking it on our side in cloudflare/workers-sdk#15146. Happy to help review or test a fix.

[pi0]

Thanks for notice @petebacondarwin! Is it v2 only?

[petebacondarwin]

The compat date turns on both the v1 and v2 flags so adding either of those flags explicitly with a date after 2026-08-04 will error.

[pi0]

i meant nitropack v2 (vs nitro v2)

[petebacondarwin]

Ah - I am not sure what the difference between the nitro versions is. Do they both turn on nodejs_compat(_v2)?
We are actually going to land a fix to Wrangler to strip unnecessary nodejs_compat flags for the time being so this should actually become moot.

[petebacondarwin]

We just closed cloudflare/workers-sdk#15146 so probably nothing to do here.
Although if you wanted you could remove the adding of nodejs_compat if you select a new enough compat date