fix: Allow internal module resolution to access builtin modules#6105
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fix: Allow internal module resolution to access builtin modules#6105
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When resolving modules with INTERNAL_ONLY option (used by extension modules and internal builtins), also allow BUILTIN modules to be resolved as a fallback. This enables extension modules (like miniflare's dispatch-namespace worker) to import public built-in modules like cloudflare:workers. Previously, extension modules could only import INTERNAL modules (like cloudflare-internal:workers), which have a different export structure than the public BUILTIN modules. This forced workarounds in libraries like capnweb that needed to handle both module types. The resolution order is preserved: 1. First try to find an INTERNAL module (preferred) 2. If not found, try to find a BUILTIN module (fallback) 3. Only if neither is found, return none
penalosa
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Feb 18, 2026
Extension workers can now import cloudflare:workers directly instead of needing it rewritten to cloudflare-internal:workers. This simplifies the build by removing: - extensionWorkerPaths list - rewriteCloudflareWorkersToInternalPlugin Note: This change depends on cloudflare/workerd#6105 which allows INTERNAL_ONLY module resolution to also access BUILTIN modules.
mikea
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Feb 18, 2026
anonrig
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Feb 18, 2026
jasnell
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Feb 18, 2026
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A key difference between BUILTIN and INTERNAL_ONLY is that BUILTIN modules can be overriden by the worker bundle...
const helloWorld :Workerd.Worker = (
modules = [
(name = "worker", esModule = embed "worker.js"),
(name = "cloudflare:workers", esModule = "export default 1;")
],
compatibilityDate = "2023-02-28",
);
import * as foo from 'cloudflare:workers';
console.log(foo); // [Module: null prototype] { default: 1 }
We need to evaluate whether this change is correct. The INTERNAL_ONLY behavior here is quite intentional.
penalosa
added a commit
to cloudflare/workers-sdk
that referenced
this pull request
Feb 18, 2026
Extension workers can now import cloudflare:workers directly instead of needing it rewritten to cloudflare-internal:workers. This simplifies the build by removing: - extensionWorkerPaths list - rewriteCloudflareWorkersToInternalPlugin Note: This change depends on cloudflare/workerd#6105 which allows INTERNAL_ONLY module resolution to also access BUILTIN modules.
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When resolving modules with
INTERNAL_ONLYoption, also allow BUILTIN modules to be resolved as a fallback.This enables extension modules (like miniflare's
dispatch-namespace.worker.ts, which sparked this PR) to import public built-in modules likecloudflare:workers.Alternative to cloudflare/capnweb#139