[C3] Nuxt: Nitro injects nodejs_compat, which workerd now rejects as redundant

[petebacondarwin]

Summary

Nuxt projects scaffolded by C3 fail to start in local dev when the compatibility date is 2026-08-04 or later:

✘ [ERROR] service core:user:<name>: 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.

All four nuxt:* C3 e2e framework tests have been quarantined in #15123 to unblock the workerd bump. This issue tracks the real fix.

Root cause

As of workerd 1.20260804.x, nodejs_compat and nodejs_compat_v2 carry $compatEnableDate("2026-08-04") in compatibility-date.capnp — they are enabled by default from that date, and specifying them explicitly is a hard error.

Nitro's Cloudflare preset unconditionally adds nodejs_compat to the wrangler config it generates (nitropack@2.13.4, dist/presets/cloudflare/utils.mjs:256):

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

It writes that config into the build output and points wrangler at it via a .wrangler/deploy/config.json redirect:

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"

C3's own wrangler.jsonc templates are clean — they no longer specify nodejs_compat — but nitro's generated config takes precedence, so users cannot fix this from their own config.

Note that nodeCompat is auto-enabled by nitro whenever deployConfig is set, so this applies even to projects that never asked for Node.js compatibility explicitly.

Impact

Any Nuxt (or other Nitro-based) project on Cloudflare with compatibility_date >= 2026-08-04 running workerd >= 1.20260804.x.

Confirmed on Nuxt 4.5.2 / nuxi 3.37.0 / Nitro 2.13.4, for both --platform pages and --platform workers.

Observed in local dev (wrangler dev / preview). The control plane applies the same validation, so wrangler deploy is expected to be affected as well — the flag is written into the config that is actually deployed. Worth confirming explicitly as part of the fix.

Repro

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

Possible fixes

1. Upstream fix in Nitro — only add nodejs_compat when the resolved compatibility date is before 2026-08-04. Filed upstream as [cloudflare] Generated wrangler config specifies nodejs_compat, which workerd rejects for compatibility dates from 2026-08-04 nitrojs/nitro#4527.
2. Sanitise in wrangler/miniflare — drop redundant nodejs_compat/nodejs_compat_v2 before handing flags to workerd. Miniflare already performs this kind of sanitisation for duplicate flags in packages/miniflare/src/plugins/core/index.ts. This was considered and deliberately deferred in Bump the workerd-and-workers-types group across 1 directory with 2 updates #15123 to avoid masking a config error that users can normally fix themselves, and because it would need to cover the deploy path too, not just local dev.
3. Pin the compatibility date in C3's Nuxt templates below 2026-08-04 — stop-gap only; does not help existing projects.

Reverting the quarantine

Remove quarantine: true from the four nuxt:* entries in packages/create-cloudflare/e2e/tests/frameworks/test-config.ts.

[workers-devprod]

Note

This is an automated, advisory triage report generated by workers-devprod. It is not an official maintainer response — a maintainer will follow up.

🤖 Automated triage report

Issue Triage: #15146

Summary

C3-scaffolded Nuxt projects fail to start in local dev with a hard error because nitro's Cloudflare preset unconditionally writes nodejs_compat into its generated wrangler config, which is now a hard error for compatibility dates 2026-08-04 or later.

Classification

• Type: Bug
• Component: packages/create-cloudflare (Nuxt/nitro integration); root cause is upstream in nitropack
• Severity: High
• Has Reproduction: Yes (scaffold a Nuxt project via C3 with a compatibility date >= 2026-08-04 and run local dev)
• Quality: Complete

Findings

• Created: not specified (metadata truncated in context.json)
• Author: petebacondarwin (Cloudflare / workers-sdk maintainer)
• Version: workerd 1.20260804.x and later; nitropack@2.13.4
• Labels: not specified (metadata truncated in context.json)
• Comments: not specified (metadata truncated in context.json)

Analysis

• This is a maintainer-authored tracking issue, not a user report. The body explicitly states "This issue tracks the real fix" after the four nuxt:* C3 e2e framework tests were quarantined in Bump the workerd-and-workers-types group across 1 directory with 2 updates #15123 to unblock the workerd bump.
• Root cause is well-established and upstream: nitro's Cloudflare preset (nitropack@2.13.4, dist/presets/cloudflare/utils.mjs:256) unconditionally adds nodejs_compat (and no_nodejs_compat_v2) to the wrangler config it generates. As of workerd 1.20260804.x, nodejs_compat carries $compatEnableDate("2026-08-04") and specifying it explicitly is a hard error.
• Users cannot self-resolve: C3's own wrangler.jsonc templates are already clean, but nitro writes its config into dist/_worker.js/wrangler.json and redirects wrangler to it via .wrangler/deploy/config.json, so the generated config takes precedence over the user's config. nodeCompat is auto-enabled by nitro whenever deployConfig is set.
• Fix likely requires upstream coordination with nitro/nitropack, and/or a mitigation in workers-sdk (e.g. wrangler tolerating the redundant flag, or C3 pinning behavior). The precise fix location is not yet decided — hence a tracking issue.
• The context.json metadata (labels, comments, dates, state) was truncated and could not be fully read; classification of severity and component is based on the body content, which is comprehensive.

Recommendation

Status: KEEP OPEN

Reasoning: This is a legitimate, high-quality tracking issue filed by a maintainer to record the real fix after e2e tests were quarantined. It documents a confirmed bug with a clear root cause that blocks C3-scaffolded Nuxt local dev on current workerd, and it should remain open until the fix (likely involving upstream nitro coordination) lands and the quarantined tests are re-enabled.

Action: Keep open as a tracking issue. Coordinate a fix with nitro/nitropack to stop unconditionally emitting nodejs_compat, and/or add a mitigation in workers-sdk. Once resolved, un-quarantine the four nuxt:* C3 e2e framework tests from #15123.

Suggested Labels: none (existing labels could not be verified from the truncated context; defer label choice to a maintainer)

Suggested Comment

No reporter-facing comment needed — this is an internal maintainer tracking issue and should stay open until the fix lands and the quarantined nuxt:* C3 e2e tests are re-enabled.

Structured summary (JSON)

{
  "issueNumber": 15146,
  "title": "C3-scaffolded Nuxt projects fail to start in local dev because nitro unconditionally adds nodejs_compat (hard error from 2026-08-04)",
  "githubUrl": "https://github.com/cloudflare/workers-sdk/issues/15146",
  "recommendation": "KEEP OPEN",
  "difficulty": "medium",
  "reasoning": "Maintainer-authored tracking issue documenting a confirmed bug with a clear root cause: nitro's Cloudflare preset unconditionally writes nodejs_compat into its generated wrangler config, which is a hard error for compatibility dates 2026-08-04 or later. It should stay open until the fix lands.",
  "suggestedAction": "Keep open as a tracking issue; coordinate a fix with upstream nitro/nitropack and/or add a workers-sdk mitigation, then un-quarantine the four nuxt:* C3 e2e tests from #15123.",
  "hasSuggestedComment": false,
  "suggestedLabels": []
}

[workers-devprod]

• Reproduction: ✅ Successfully reproduced. By manually scaffolding a Nuxt 4.5.2 / Nitro 2.13.4 app with preset: cloudflare_module, cloudflare.deployConfig: true, and cloudflare.nodeCompat: true, then running nuxt build with compatibilityDate: 2026-08-04, Nitro generated .output/server/wrangler.json containing "compatibility_flags": ["nodejs_compat", "no_nodejs_compat_v2"] alongside "compatibility_date": "2026-08-04". This exactly matches the root cause described — the flag is unconditionally injected even though it is already the default for that date. The sandbox experienced an internal failure before wrangler dev could confirm the runtime error, but the build-time generation of the redundant config was reproduced concretely.