The unmet_dependency guard read dependency state via an unlocked SELECT, then
fired release_dependency_blocked_claim (a state mutation: claimed/in_progress
-> pending, clears branch_name, abandons WorkSession) as a side-effect BEFORE
returning the rejection. An upstream dependency that reached a terminal state
(completed/cancelled) in the microseconds between the read and the release left
the task NEEDLESSLY released — its branch cleared + WorkSession abandoned +
assignee bounced, only to be re-dispatched + re-claimed when the dependency-
completion re-dispatch fired a moment later.
Re-check unmet_dependency_ids immediately before the release and skip it
(returning None — proceed) when the upstream just completed. Dependencies are
monotonic (unmet -> met only; terminal states never reopen), so a fresh read
that now finds them met stays met: safe to proceed without releasing. The
'still unmet' path is byte-for-byte the prior behavior (no regression). The
cross-task residual window (upstream completes between the re-check and the
release) is not closable by a row lock on the dependent, but the re-check
narrows the window from [first read -> release] to [re-check -> release], and
in the common case the first read already sees met (no guard fires). No
committed-work loss either way (a dependency-blocked task has none; the branch
ref + commits persist across the branch_name clear).
Renn F
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