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On September 23, 2026, Fireworks AI released the ARCv3 reinforcement learning weight delta compressor, used to compress BF16 weight update deltas sent from the training side to rollout machines. The company says that across 1,000 production RL weight update deltas, ARCv3's payload is nearly 50% smaller than ARCv2's, with the average delta being about 0.19% of the original BF16 weights, down from 0.36% previously, and that it can losslessly reconstruct the exact BF16 weights on the training side. ARCv3 is available in the Fireworks Training API via fireworks-delta-compression: it is enabled by default for users of the Fireworks Trainer SDK, and teams with their own training side can install the package to integrate it. There are currently no subsequent developments to report.
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Fireworks ARCv3 Cuts RL Weight Update Size by Nearly 50%, Enables Cross-Region TrainingDevelopments
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- Source:Fireworks AI
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Sep 23
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Fireworks ARCv3 Cuts RL Weight Update Size by Nearly 50%, Enables Cross-Region Training
Fireworks has released the ARCv3 compressor. Across 1,000 production RL weight update deltas, its transfer payload is nearly 50% smaller than ARCv2, with the average delta at about 0.19% of the original BF16 weight size (versus 0.36% for ARCv2), and it can losslessly reconstruct the trainer's exact BF16 weights. The smaller transfer volume lets rollout clusters catch up with the current policy faster, making it more feasible to use compute across regions than to rely on a single large co-located cluster. ARCv3 is available in the Fireworks Training API via fireworks-delta-compression, for teams running their own trainers alongside Fireworks rollouts.
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