your data is your moat. no one else has your traces, docs, outcomes. we shape them into a training recipe optimized for you.
3,000+ training runs started
fully managed training. we manage the gpu and training orchestration so you focus on your data and designing for the outcome you want.
full observability while the model learns. watch every step as it trains. catch issues early and evaluate performance at any point.
you own the weights. download the weights and serve them on your own stack, or deploy with our inference offerings.
from the field
castform x elsa
how we trained a language-learning app
elsa’s frontier-model tutor kept talking over beginners. we post-trained a model on their production conversations to match each learner’s level, at half the cost and latency.
read the post →
castform x neon
training 100x cheaper retrieval models with neon
using postgres data in neon to train a 4b open model that matches frontier accuracy at a fraction of the inference cost.
read on neon.com →use cases
train specialized models on the data and decisions your business already produces.
questions?
do i need ml or rl expertise?
no. castform is designed for engineers and researchers alike: it works out of the box with no ml expertise, and exposes advanced controls for those who want it. you bring your data and define what success looks like, and we handle the rl algorithms, environment scaffolding, distributed training, and infrastructure.
what use cases do you support?
virtually anything rl fine-tuning. if you can define verifiable success metrics for your task, we provide the algorithms and infrastructure to fine-tune a model to optimize for those.
you just need to set up the two things the trainer needs: an environment (what the model has access to, and the reward signals that define how the model is scored) and a dataset (the examples it trains on).
to make it easier, we provide automated dataset generation and environments for training rag agents and fine-tuning on production agent traces.
how do i get access?
you can start training right away by signing up at app.castform.dev. it is fully self-service and pay-as-you-go, with enough free credits for new users to trial their first training run.
who owns my data and the trained model?
you do. we train readily available open-source models on your data, and you can export the trained weights at any time. apply them and deploy the new model wherever you like. any data you upload for training is stored securely and used only for your training runs, and can be deleted at any time.
how does pricing work?
castform is pay-as-you-go: you only pay for the compute you use during training runs. there are no seats, no monthly minimums, and no lock-in. new users receive free credits to trial their first run.
see the full breakdown on our pricing page.
how can i learn more?
check out our docs for guides, examples, and the python sdk reference.
prefer to talk it through? reach out at castie@castform.com and we'll help you figure out whether rl fine-tuning is a fit for your use case.