Recurrent In-Context Learning for Tabular Foundation Models

Tabular foundation models adapt to new datasets through in-context learning (ICL), and, like most transformers, they tie computational depth to the number of independently parameterized layers. We ask whether the ICL stage of such a model needs a distinct set of parameters for every layer, or only depth. We introduce Tab-Loop, which replaces the 12 untied ICL blocks of TabICLv2 with 4 tied blocks applied k times and changes nothing else: the encoders, decoder, synthetic prior and training recipe are shared with an untied baseline trained for the same compute. At matched pretraining compute (18.2 EFLOP) and matched inference compute (12 block applications), Tab-Loop matches the baseline with 62% fewer parameters (10.4M vs. 27.6M): held-out log loss is 0.4583 vs. 0.4588, mean accuracy on 200 TALENT datasets is 84.10% vs. 83.92%, and Elo on 38 TabArena datasets is 1409 vs. 1396. A 4-block untied control with Tab-Loop's parameter count, which sees 32% more training tables for the same compute, trails both (83.46%; Elo 1343). Because weights are shared, depth becomes a choice made at inference. Accuracy rises with the number of loops through the trained range and holds beyond it, and continued training with deeper loops extends the useful range, reaching the baseline's stage-2 scores at 4--5× its inference compute. At this scale, the ICL stage of a tabular foundation model needs depth more than it needs distinct parameters.