Training
The easiest and fastest way to train AI agents with serverless RL
W&B Training offers serverless reinforcement learning (RL) for post-training large language models (LLMs) to improve their reliability performing multi-turn, agentic tasks while also increasing speed and reducing costs.
W&B Training includes ART, a flexible RL fine-tuning framework; RULER, a universal verifier; and a fully managed serverless RL backend on CoreWeave cloud, so you can run RL training loops without provisioning, configuring, or managing GPUs.
Break the barrier to RL with Agent Reinforcement Trainer (ART)
RL can make multi-turn agents reliable, but training is complex, unstable, and expertise-heavy. ART abstracts the RL loop with an open-source framework and Group Relative Policy Optimization (GRPO) harness integrated with W&B Training, so you can get RL fine-tuning up and running in hours. No prior experience required.
Offload the judging to RULER
Designing reward functions is slow, brittle, and hard to debug. RULER (Relative Universal LLM-Elicited Rewards) replaces hand-crafted rewards with an LLM as a judge that scores trajectories automatically. Define the task in a system prompt and go: no labels, no experts, no reward engineering, faster iteration, more reliable agents.
Serverless RL backend: 1.4x faster at 1/8th the cost and no infra headaches
RL training wastes GPU time while waiting for rollouts to complete, inflating cost. W&B Training’s Serverless RL backend on CoreWeave cloud packs jobs to maximize utilization, cutting costs up to 80% and speeding training ~1.4× with no quality loss. Rollouts multiplex on a shared GPU cluster with per-token billing. Plus, skip provider evaluation and infra scripts, start your RL run in minutes with just a Weights & Biases account and API key.
Built-in observability
When loss spikes or reward variance jumps, you need the exact rollout for that step; without it, you’re tuning in the dark and may never converge. W&B Training automatically logs metrics and rollout traces to your W&B workspace, letting you diagnose stability and reward issues fast. Log in and inspect the runs you care about.
