# AN-2026-0690: Cloudflare Workers compatibility date 2026-11-17 (Nov 17, 2026): new module registry by default; invalid import attributes throw, require() of top-level-await modules fails

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- id: AN-2026-0690 (version 1; cite https://breakwire.org/claim/AN-2026-0690/v/1)
- kind: breaking · status: active · review: editor
- source: <https://developers.cloudflare.com/changelog/post/2026-11-02-module-registry-default/>
- more sources: <https://developers.cloudflare.com/workers/configuration/compatibility-flags/#new-module-registry>
- event date: 2026-11-02
- services: cloudflare-workers
- affected: compatibility_date >= 2026-11-17; JavaScript Workers; new_module_registry; legacy_module_registry; nodejs_compat require()
- ACT BY: 2026-11-17
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Cloudflare's changelog (2026-11-02, opened 2026-11-03) says that starting November 17, 2026, JavaScript Workers with a compatibility date of 2026-11-17 or later use the new module registry by default, without the new_module_registry flag; Python Workers keep the legacy registry.  [✓0 ✗0]
1. Existing Workers keep their current behavior until their compatibility date or flags change; to keep the legacy registry with a 2026-11-17 or later date, add the legacy_module_registry flag.  [✓0 ✗0]
2. The new registry rejects invalid import attributes, and require() fails if the module or any of its dependencies use top-level await; the compatibility flags page adds that require() rejects such graphs even after they finished evaluating and says to use dynamic import() instead.  [✓0 ✗0]
3. Per the compatibility flags page, require() of an ES module returns its namespace unless it exports a value named "module.exports", and the legacy-registry flags export_commonjs_default, require_returns_default_export, throw_on_unrecognized_import_assertion and disable_top_level_await_in_require do not control the new registry.  [✓0 ✗0]

## Fix
```text
Before moving compatibility_date to 2026-11-17 or later, test with new_module_registry on your current date. Remove or fix invalid import attributes, and replace require() of modules that use top-level await with dynamic import(). To keep the old behavior on a newer date, add legacy_module_registry to compatibility_flags.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0690/reports_

## History
- v1 2026-11-03 by wire-editor: promoted from candidate #191 (cloudflare-workers-changelog) after review