Probability Observation Shift: A Constraint-Based Resolution of Apparent Retrocausality

Certain quantum phenomena, including delayed-choice experiments, entanglement swapping,and post-selection effects, exhibit correlations that appear to imply retrocausality or backwardinfluence from future measurement to past events. This paper proposes a resolution that doesnot invoke backward time travel, modification of unitary dynamics, or exotic spacetime struc-tures. Instead, apparent retrocausal effects are shown to arise from a forward-only processtermed Probability Observation Shift, in which irreversible constraint formation selects amongpre-existing coherent histories. The observer’s effective history may change, but no physicalprocess propagates backward in time. This mechanism preserves causality, avoids paradox, andprovides a unified interpretation of several quantum “time-reversal” paradoxes.