Fireworks made its Training API generally available with named customer deltas.

Announced August 31, exposing SFT, DPO, reward finetuning and RL across three surfaces (Fireworks). Harvey post-trained Kimi K3 into "Harvey Tenet" scoring 19.7% all-pass on LAB against 10.8% for the base model at comparable cost. Vercel reports a 93% error-free generation rate for v0 with a 40x end-to-end latency improvement using RFT plus speculative decoding. Heidi Health reached production in four weeks at 3.5x lower latency, and Factory's adapters caught about 70% of real secrets against about 59% for GPT-5.5 at a 5% false-alarm budget. Unusually specific for a launch post, which is why I am repeating the numbers.