The join knows cancellation: a branch taken back is a branch that doe… - #133
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…s not come A withdrawal now tells the joins: every token taken that was the front of a branch of a pass (FBToken>>isFrontOfItsPass - tokens of an iteration or a sub flow inside the branch do not count) is counted on the pass (FBSplitExecution>>cancelledBranches). The join releases once every branch is accounted for - arrived or cancelled - and at least one arrived, and goes on with what arrived (FBJoinState>>canRelease, #output without the branches taken back). When the branch taken back was the last one a join waited for, the withdrawal releases the join itself (FBFlowInstance>>settlePass:): no further arrival would come to ask. That release queues on the executor the join stands in, not on whatever frame is on top of the instance at that moment (FBBaseActivation>>followAllOutgoingInSplit:on:). A pass whose branches all fell with nothing arrived releases nothing; the branch that led into its split is then gone for the enclosing pass too, which counts it and is settled in turn. Cancelling one branch of a nested split thus costs the outer join exactly one branch. The join's output moved from FBJoinBehavior to FBJoinState, which is where the release now lives. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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…s not come
A withdrawal now tells the joins: every token taken that was the front of a branch of a pass (FBToken>>isFrontOfItsPass - tokens of an iteration or a sub flow inside the branch do not count) is counted on the pass (FBSplitExecution>>cancelledBranches). The join releases once every branch is accounted for - arrived or cancelled - and at least one arrived, and goes on with what arrived (FBJoinState>>canRelease, #output without the branches taken back).
When the branch taken back was the last one a join waited for, the withdrawal releases the join itself (FBFlowInstance>>settlePass:): no further arrival would come to ask. That release queues on the executor the join stands in, not on whatever frame is on top of the instance at that moment (FBBaseActivation>>followAllOutgoingInSplit:on:).
A pass whose branches all fell with nothing arrived releases nothing; the branch that led into its split is then gone for the enclosing pass too, which counts it and is settled in turn. Cancelling one branch of a nested split thus costs the outer join exactly one branch.
The join's output moved from FBJoinBehavior to FBJoinState, which is where the release now lives.