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- T-1: InProcessChannel::Close rang each CondVarDoorbell once and claimed that unparks a peer mid-frame. It does not. Doorbell::Wait consumes the one ring, re-tests a condition nothing published, finds the bell alive (CondVarDoorbell never overrode Dead(); Doorbell.cpp had no death state at all) and with kWaitForever parks again for good - so Shutdown could never join a server thread sitting in the design's own steady state (spun, set consumerParked, blocked; plan section 8.1 inheriting the earlier plan's 6.2a). CondVarDoorbell now carries an atomic death latch: Kill() sets it under the mutex and notify_all's, Dead() reports it, Park returns false at once on a dead bell (and the wait predicate includes it, so a Kill cannot slip between the test and the wait), and Close kills both bells instead of ringing them. Same shape as SocketDoorbell's EOF latch; Notify stays the ordinary wakeup. - T-2: RingProducer::Reserve refused only total > capacity, but a record with capacity/2 < total <= capacity is unplaceable at every head offset where neither the space to the wrap boundary nor the space before it holds it - even in an EMPTY ring, because a wrap pad costs spaceToEnd bytes on top of the record. Concretely: head offset 16 of an empty 256-byte ring, a 248-byte record; FreeBytes() says 256, Reserve says nullptr, forever, and a producer waiting for FreeBytes() >= 248 stalls with nothing logged. The bound is now capacity/2, which is exact rather than conservative (worst case 2*total-8 <= capacity-8), exposed as MaxRecordBytes() for the emitter to chunk against; the minimum ring is two headers so the smallest record still fits the bound. Ring.h states Capacity()/2 as the chunking bound and the G3 header comment in gen_pipe.py now states the chunking rule plan section 8.2 asks G3 to define (PipeWire.inc regenerated). - Tests, each shown red with only the fix site reverted and green with it: InProcessTransportTest.ShutdownUnparksAWaiterWithNoDeadline (bounded join through a shared_ptr-owned waiter: 5 s red instead of a hung job; reverted it hangs and fails at 5051 ms), RingTest.RecordLargerThanHalfTheRingIsRefused (reverted, the 248-byte record is accepted), RingTest.RecordPlaceabilityDoesNotDependOnTheHeadOffset (the offset-0 vs offset-16 negative control), RingTest.HalfCapacityRecordFitsAtEveryHeadOffset (the positive half: the maximal record at all 32 head offsets of a 256-byte ring) and RingTest.RejectsARingTooSmallForTheSmallestRecord.