Two months of π0.5 finetuning hits 98% success: data quality beats scaling

DominiqueCAPaul · x · 2026-09-24

A team spent two months ablating π0.5 finetunes on a real manufacturing task, reaching 98% policy success, and is publishing all results, data, and runs including failures. Key findings: 5x more data only moved success from 63% to 76%, making pure scaling the weakest lever; diversity beat quantity — 4 hours spread across five scenes beat 4 hours in the eval scene by 30 points; quality did best, with one clean, slower hour on top of 21 hours lifting 76% to 90%, more than the prior 17 hours. A quality-only recipe of 1h clean data plus 240 rollouts with human interventions (1.7h total) went from 28% to 88%. A commenter notes that from a UMI perspective scaling and diversity are easiest while quality is harder and interventions impossible — the exact opposite ordering — and accepts the challenge.

Related event: Two Months Fine-tuning π0.5 on Real Manufacturing Tasks: 1 Hour of Clean Data Beats 17 Hours of Scale(9 posts)→

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