Raghavendra Prasad Narayan
Author directory2026
Alphastream at ChildSafeAds 2026: Gated Per-Label Merging and an Advertiser-Precedent Rule for Rare Compliance Classes
Raghavendra Prasad Narayan
Proceedings of the Natural Legal Language Processing Workshop 2026
Raghavendra Prasad Narayan
Proceedings of the Natural Legal Language Processing Workshop 2026
We describe our system for ChildSafeAds 2026, the shared task on commercial content in child-facing YouTube videos: it labels each sponsored segment for commercial type (ST1), product category (ST2) and EU compliance flags (ST3). A multi-task ModernBERT-large encoder and an entailment-style reformulation of the compliance subtask supply seed-averaged probabilities, merged label by label under a paired bootstrap and a dev-to-test count check. Inference uses eight fine-tuned encoders and no generative model; the 503 test instances are estimated at under one GPU-hour, and all experiments cost about US17. It scored 0.7645 mean macro-F1 on development and 0.6798 on test, 0.046 of it from a rule keyed on advertiser identity for one ST1 class absent from development. Our official entry, a variant using one leaderboard probe, scored 0.7022, fourth of 21 teams. A single-seed ablation values the four access levels at +0.042, against +0.128 from encoder scale. We also report five negative results, among them seed variance matching our largest modelling gains, synthetic data helping one architecture and breaking the other, and 21% more training data lowering the test score; separately, near-duplicate training instances agree on the full flag set only 43–63% of the time, often on identical cited evidence.