Deliver subscriptions/listen notifications only after the acknowledgement - #532
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koic merged 1 commit intoAug 25, 2026
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…gement ## Motivation and Context Per SEP-2575, the server MUST NOT send any notification on a subscription before `notifications/subscriptions/acknowledged`. The listen stream was registered in the delivery registry before its acknowledgement was written (the write happens outside the lock so a stalled reader cannot block the transport), so a change notification published concurrently from another thread could be written to the stream ahead of the acknowledgement. The entry is now inserted inactive - still reserving the id and the cap slot atomically - and becomes eligible for delivery only after the acknowledgement write has completed. A concurrent notification inside the window skips the inactive entry, which is indistinguishable from the change happening just before the subscription opened. ## How Has This Been Tested? With a new regression test pinning the window (an entry injected in the registered-but-unacknowledged state receives nothing until activation), the full suite, RuboCop, and the conformance suite, all green. ## Breaking Changes None. Activation happens synchronously inside the same response body proc, so an acknowledged stream behaves exactly as before.
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Motivation and Context
Per SEP-2575, the server MUST NOT send any notification on a subscription before
notifications/subscriptions/acknowledged. The listen stream was registered in the delivery registry before its acknowledgement was written (the write happens outside the lock so a stalled reader cannot block the transport), so a change notification published concurrently from another thread could be written to the stream ahead of the acknowledgement.The entry is now inserted inactive - still reserving the id and the cap slot atomically - and becomes eligible for delivery only after the acknowledgement write has completed. A concurrent notification inside the window skips the inactive entry, which is indistinguishable from the change happening just before the subscription opened.
How Has This Been Tested?
With a new regression test pinning the window (an entry injected in the registered-but-unacknowledged state receives nothing until activation), the full suite, RuboCop, and the conformance suite, all green.
Breaking Changes
None. Activation happens synchronously inside the same response body proc, so an acknowledged stream behaves exactly as before.
Types of changes
Checklist