Meta FAIR Trains 200+ Models to Show Vision Prior Is Optional but Vision Capacity Isn't

mengyer · x · 2026-11-14

A Meta FAIR/NYU paper (arXiv:2611.17334) disentangles the three choices bundled in vision encoders via controlled pretraining of 200+ models on shared data and compute. Findings: the upstream visual prior is unnecessary — an encoder trained jointly from scratch matches a pretrained one without a separate stage; dedicated vision capacity is what matters — encoder-free models trail even when the backbone is enlarged to compensate; and that capacity need not precede fusion — in-fusion vision modules in early backbone layers perform comparably and cut time-to-first-token. This reconciles diverging lab recipes (Gemma 4 dropping the encoder, Kimi K3 skipping encoder pretraining).

Related event: Meta FAIR Trains 200+ Models: Dedicated Vision Capacity Matters More Than Pretrained Encoders(3 posts)→

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