I39 LEASE / OWNERSHIP CLAIM ≠ EXTERNAL EXECUTION AUTHORITY I40 NEW OWNER MUST RECEIVE A STRICTLY MONOTONIC FENCING TOKEN I41 PROTECTED RESOURCE MUST COMPARE THE FENCE AT THE MUTATION BOUNDARY I42 STALE WORKER RESURRECTION IS AN AUTHORITY-LIFECYCLE TRANSITION
ACQUIRE N→STALL / TAKEOVER→ACQUIRE N+1
MUTATION PRESENTS TOKEN→RESOURCE COMPARES→APPLY OR FENCE
Why the coordinator is not enough
The coordinator can correctly say that Worker B owns the task while a paused Worker A still holds stale local state. If the protected external resource accepts A's mutation without validating ownership generation, split-brain execution remains possible.
Why recheck is weaker
Rechecking ownership immediately before the call reduces risk, but another takeover can happen between the check and the mutation. Resource-side fencing closes that final gap.
Evidence
Verified #020 produced two effects without external fencing and one effect when the resource rejected stale token 1 after accepting token 2.