Trigger Timing, Deadline Readiness, and Event-Aligned Accounting for Dynamic Ad Insertion

Dynamic ad insertion comparisons can conflate trigger, reach, readiness, playback, billability and measurement even when the accounting is arithmetically correct. We separate these events with an observed-event ledger, a candidate-invariant reference deadline and pod-level contribution accounting. The deadline rule is fixed before candidate assignment and tests whether an admissible transition state remains valid, not whether preparation merely finished earlier. A restricted monotone-playback representation states when media-position summaries suffice; a counterexample shows why they fail over a wider path class. An offline synthetic study exercises the definitions over nine short-lifetime conditions informative for the readiness comparison and nine long-lifetime conditions serving as analytic controls. Across 45,000 shared scripts, two trigger policies share imposed playback paths, latency draws and hypothetical value and cost coefficients. Playhead summaries substantially misclassify reach events in the nonmonotone mixtures, yet neither shortcut reverses the contribution contrast in this grid, because some errors cancel under the shared design. Replacing validity at the deadline with completion by the deadline reverses the comparison in three of the nine informative conditions, all at one of the three latency settings. Scoring readiness at actual viewer arrival rather than at the reference deadline shifts pause-path readiness but changes no contribution sign. These outcomes are consequences of the event definitions applied to established misclassification mechanisms. Conservative bounds retain uncertainty when records are missing, and the artifact records code, seeds, event histories and checking procedures. The evidence is synthetic, uses no commercial telemetry, and ranks neither server-side nor server-guided insertion.