Use a fixed default compatibility date derived from the pinned workerd

[jamesopstad]

When no compatibility date is set, Wrangler, C3 and the Vitest pool all defaulted to the current date. workerd only accepts a compatibility date up to 7 days beyond its own release, so the default could get ahead of the runtime that had been installed and local development would fail to start.

This adds a single DEFAULT_COMPAT_DATE constant to @cloudflare/workers-utils, committed to the repo and derived from the workerd version pinned in the pnpm catalog. That leaves a week of headroom and can never exceed what the shipped runtime supports.

Keeping it current is automated. pnpm check:compat-date, which runs as part of pnpm check, fails if the constant and the pin drift apart. Dependabot's workerd bump PRs refresh the constant in the same commit.

--latest is affected too. wrangler deploy --latest, wrangler versions upload --latest and wrangler pages download config (for projects set to always use the latest compatibility date) all wrote the current date into a config file for later commands to use, which could leave a project unable to run wrangler dev. These now resolve to the same fixed default, and the flag's help text and warning have been reworded to match.

getTodaysCompatDate() is deliberately retained for validation in packages/miniflare/src/plugins/core/index.ts, which must keep comparing against the real current date.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: compatible with existing documentation

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[changeset-bot]

🦋 Changeset detected

Latest commit: 6567b08

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
wrangler	Patch
create-cloudflare	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-pool-workers	Patch

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[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/wrangler

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[github-actions]

✅ All changesets look good

[ask-bonk]

All consistent. I've completed a thorough review of the changes across all 45 files. The PR:

• Introduces a single committed DEFAULT_COMPAT_DATE constant derived from pinned workerd
• Correctly replaces getTodaysCompatDate() at all default-value sites while retaining it for the miniflare validation comparison (line 271, which legitimately needs the real current date)
• The --latest resolution and pages download-config changes are consistent
• The automation tooling (update-default-compat-date.ts) has a robust cross-check that gracefully degrades and only asserts when the installed workerd matches the pinned version
• The dependabot integration guards correctly (only refreshes on workerd bumps, safe timing with the version-equality check)
• Tests are comprehensive and the "not in the future" assertion is non-flaky
• The deleted build-constants.ts is fully cleaned up with no stale references

The logic is sound, backward compatibility is preserved (unstable_getDevCompatibilityDate still works, deprecation note updated appropriately), and there are no security or API-behavior issues. No actionable issues found.

LGTM

github run

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@cloudflare/autoconfig

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commit: 6567b08

[workers-devprod]

Codeowners reviews satisfied