Make node:worker_threads independent of expose_global_message_channel flag#6069
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petebacondarwin merged 1 commit intomainfrom Feb 13, 2026
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… flag The node:worker_threads module was previously importing MessageChannel and MessagePort from globalThis, which meant it only worked when the expose_global_message_channel compatibility flag was enabled. This change introduces a new internal module (cloudflare-internal:messagechannel) that exposes MessageChannel and MessagePort for use by built-in modules, independent of the global flag. Changes: - Add MessageChannelModule C++ class in messagechannel.h - Register cloudflare-internal:messagechannel as an internal module - Update node:worker_threads to import from the internal module - Add TypeScript type definitions for the internal module - Remove expose_global_message_channel from worker_threads tests This unblocks cloudflare/workers-sdk#12043 which needs worker_threads to work without requiring the global flag.
petebacondarwin
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jasnell
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Feb 13, 2026
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> Make node:worker_threads independent of expose_global_message_channel flag by @petebacondarwin in cloudflare/workerd#6069
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> Make node:worker_threads independent of expose_global_message_channel flag by @petebacondarwin in cloudflare/workerd#6069
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> Make node:worker_threads independent of expose_global_message_channel flag by @petebacondarwin in cloudflare/workerd#6069
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> Make node:worker_threads independent of expose_global_message_channel flag by @petebacondarwin in cloudflare/workerd#6069
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Summary
The
node:worker_threadsmodule was previously importingMessageChannelandMessagePortfromglobalThis, which meant it only worked when theexpose_global_message_channelcompatibility flag was enabled.This change introduces a new internal module (
cloudflare-internal:messagechannel) that exposesMessageChannelandMessagePortfor use by built-in modules, independent of the global flag.Changes
MessageChannelModuleC++ class inmessagechannel.hcloudflare-internal:messagechannelas an internal module inmodules.hnode:worker_threadsto import from the internal module instead ofglobalThisexpose_global_message_channelfrom worker_threads testsMessageChannel === globalThis.MessageChanneltest assertion conditionalTesting
bazel test //src/workerd/api/node/tests:worker_threads-nodejs-test@- all 22 tests pass without theexpose_global_message_channelflagRelated
Unblocks cloudflare/workers-sdk#12043 which needs
worker_threadsto work without requiring the global flag.