Run any RL experiment & skip the setup.

RL and evolutionary loops for models, agents and robots. Pick a policy, an environment and an algorithm. Spacecraft runs the loop on your GPUs and shows you what changed.

Open betaDedicated inference coming soon
Env NGC 4414 · Flocculent spiral
RA 12h 26m · Dec +31° 13′ · 62 Mly
Product

Every post-training loop, without the glue code.

Models, agents or robots. Sandboxes, graders, GPU jobs and logs, set up for you.

01 TrainGemma 4 E2B · SFT → GRPO

Any loop, one form.

SFT, GRPO, evolutionary search or your own loop, on your own GPUs. Weights land in your Hugging Face repo.

SFT · GRPO · Evolutionary · hf:// export
02 EvaluateBase vs step 400 vs final

See what training changed.

Watch loss and reward live. Compare the base, any checkpoint and the final policy side by side.

Live curves · Checkpoint compare · Side-by-side
03 ReplayEpisode 0x3f · step 12 of 40

Rewind any episode.

Every step is logged. Jump back to step 12, fork it and compare the rewards.

Step log · Instant forks · Replay
Results

Know why the reward went up.

The policy acts in one sandbox. The grader scores it in another. The log sits where neither can write.

  • LogEvery step, hash-chained
  • GraderIsolated, with no network
  • ForkAny step, in ~0 ms
  • SnapshotsStored by content hash
  • ReplayAny reward, checked again
Mission

Automated discovery, faster science and engineering.

Science moves at the speed of its experiments. Spacecraft makes every RL and evolutionary loop fast to start, safe to trust and easy to repeat, so discovery can run on its own.

  • TodayRL, evolutionary loops, evals and replay
  • NextDedicated inference for what you train
Every experiment you run brings the next discovery closer

Discover.

Models · Agents · RobotsTrainEvaluateReplay
Before your first run

Do I need to write infra code?

No. Connect Modal and Hugging Face once. Pick a policy, an environment and an algorithm. We handle the rest.

Does it work for agents and robots?

Yes. If it acts in an environment and gets a score, Spacecraft runs the loop. RL or evolutionary.

Do I have to move my compute?

No. Runs use your Modal account. Your GPUs, your bill.

Which environments work?

OpenEnv on Hugging Face, verifiers on the Prime Intellect hub, or any Hugging Face dataset.

Can I keep my training code?

Yes, with TRL. GRPO from a Colab notebook works today.

Will it catch a broken environment?

Yes. Audit checks for reward hacks, answer leaks and flaky rewards before you train.

Can I serve what I train?

Soon. Dedicated inference is on the way.

Early access

Start your first experiment & skip the setup.

Gemma 4 E2B was trained with RL on Spacecraft for $0.59 of compute.