WhoBuilt

Going In Deep On Data

Aug 20, 2026· 53 min· 46K views·Watch on YouTube

Speakers

François, founder of Focal Systems, opens YC Data Club with an argument for data’s value; Snorkel co-founder Vincent Chen, Inception Labs founder Volodymyr, and MIT PhD graduate Shane then present research on expert supervision, diffusion language models, and multilingual pretraining.

Why data is the bottleneck

François argues that production failures often come from gaps in training data, not model architecture. At Focal Systems, fogged refrigerator doors and people blocking products caused errors that adding layers could not fix. He says expert data and realistic RL environments are needed for fields such as medicine, law, and accounting.

Scaling expert supervision

Vincent Chen describes Snorkel’s work to turn expert judgment into reusable data. Its early data programming approach encoded labeling rules as software and combined noisy signals to estimate labels without ground truth. For more complex tasks, Snorkel’s SWE-bench Senior uses high-level user stories and validation agents that generate deterministic tests, alongside checks for correctness and code quality.

Building realistic RL environments

Volodymyr presents Inception Labs’ diffusion language models, which generate tokens in parallel refinement steps and, he says, can exceed 1,000 tokens per second. He describes Tau Forge, a system that uses real usage data or business information to synthesize environments and tasks, then adjusts task difficulty to produce useful learning signals. In an experiment, training on synthesized tasks improved Mercury 2.5’s accuracy on other environments by more than 23%.

Measuring multilingual data transfer

Shane presents research on how languages help or interfere with one another during pretraining, using Thai as an example with just 0.6% as many tokens as English in MADLAD-400. The measured transfer is asymmetric: a language that helps Thai may not benefit another language in return, and script similarity mattered somewhat more than language family. The team’s scaling method combines target-language data with helpful transfer languages to estimate model performance and guide data mixtures.

Takeaways

  • Inspect false positives and false negatives to find data gaps before changing model architecture.
  • Encode expert judgment in reusable rules, specifications, and verifiers to scale supervision.
  • Build training and evaluation environments from real usage, and tune task difficulty for useful feedback.
  • Measure transfer between data sources empirically; helpfulness can be asymmetric and model-size dependent.
  • For multilingual training, account for target-language data, useful transfer sources, and diminishing returns.

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