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A modern VLA model starts broad and general. Fine-tuning is how you specialize it: take a capable base model and adapt it to your robot, your scenes, and your tasks using trajectories you’ve collected. It’s almost always cheaper and more reliable than training a policy from scratch.

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Why not train from scratch?

Training a large policy from zero needs enormous data and compute, and throws away everything a pretrained model already knows about perception and motion. Fine-tuning keeps that foundation and only teaches the model what’s new about your task — far less data, far less time.

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Full fine-tuning vs LoRA

The naive approach updates every weight in the model. That’s expensive to train, expensive to store, and gives you one monolithic model per task. LoRA (Low-Rank Adaptation) takes a smarter route: freeze the base model and train small adapter weights that slot on top of it. Because adapters are small and composable, you keep one base model and attach task-specific adapters as needed — cheap to train, fast to iterate, easy to ship.

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Where the training data comes from

Fine-tuning needs trajectories, and good trajectories are the hard part — see Physical AI at a glance. Cadenza closes that gap by generating data as a byproduct of simulation: every mission is logged tick-by-tick and scored automatically, so rollouts arrive already labeled and ready to become a training set.

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The Cadenza workflow

The full loop spans both layers of the stack — you build in the SDK and operate with the CLI:
  1. Build the robot, scene, and policy interface in the SDK.
  2. Gather scored rollouts by running missions in simulation.
  3. Convert those rollouts into VLA training data.
  4. Train a LoRA adapter on that data.
  5. Evaluate the new policy back in simulation — and on hardware.
  6. Repeat, each pass producing a sharper policy and more data.
From the CLI, steps 2–4 are a couple of commands:

Build with the SDK

Stand up a robot and a scene to gather data from.

Run the loop in the CLI

Gather rollouts and fine-tune end to end.