Fireworks' ARCv3 cuts RL weight-update payload by ~50% with lossless BF16 reconstruction

sophiamyang · x · 2026-09-24

Fireworks released ARCv3, a compressor for RL weight updates sent from trainers to rollout fleets. Across 1,000 production weight-update deltas it produced payloads 50% smaller than ARCv2 while losslessly reconstructing exact BF16 weights. Smaller transfers keep rollout fleets closer to the current policy, making cross-region training practical without one giant co-located cluster. Available via fireworks-delta-compression in the Fireworks Training API.

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