Research Engineer, RL Environments & Synthetic Data (all genders)

Your tasks

A model only gets good at work it has practiced. Ours practice on thousands of made-up tasks: a caseworker's queue that needs triaging, a spreadsheet that refuses to reconcile, a policy that has to be applied to a document nobody formatted properly, a broken repo in a sandbox.
Somebody has to build those worlds, and then find an honest way to tell whether the model did the job or only looked like it did. We'd like that to be you.
In plenty of places, environment work is treated as plumbing for the "real" researchers. We see it the other way round. Most of what our models can do, they learned from their tasks. So you'd work directly with the people running training, you'd see what your tasks did to the model one run later, and you'd have a say in what the next one learns.

What you'll work on

• Environments for long, multi-step work with tools, documents and code. The raw material is what European companies and public offices do all day, which gets a lot more interesting once a model has to do it.
• Generators that turn one good task idea into thousands, hard ones included. You'll want a difficulty dial, and a way to be sure the set isn't quietly full of duplicates or leaked answers.
• The checks that decide whether the work got done: tests, state checks, rubric-based judges. Whatever tells the truth.
• Catching the model cheating. You read rollouts, spot the shortcut it found (it will find one), close it, and build QA so the next environment is harder to fool.
• Measuring what a task set really did to the model, and saying out loud which ones to scale and which to drop.
• Helping decide what we publish. Environments, datasets and benchmarks are part of our releases, starting with the first open-source one in Q1 2027.

Your profile

• You've built something that trained or evaluated an LLM. An environment, a benchmark, an eval harness, a data pipeline. We're not fussy about which. Show us.
• Your Python is solid and your engineering habits are real. Containers, sandboxes and async code don't worry you. Bugs that only show up at scale annoy you, in a motivating way.
• You read the data. Actual samples, actual trajectories. And you come back with opinions about what's wrong with them.
• You have a feel for what makes a task worth training on: it's realistic, you can verify it, and it's hard to game.
• You write clearly enough that the rest of us can trust a result without re-running it.
• You live in the EU and are allowed to work here. English is all you need; German is a bonus.

Things that would make us happy but that nobody needs to have: RL experience (GRPO- or PPO-style training, reward design); real knowledge of a field where agents do actual work, like law, finance, insurance or public administration; sandboxing infrastructure (Docker, Firecracker, Kubernetes); open-source contributions. German is handy in this role, because a lot of our tasks start life as German-language processes.

Why us?

What you build gets trained on almost immediately, and you'll see what it did. GPUs are only as useful as the tasks we spend them on, so in practice your work sets the ceiling for the next model. A good share of it goes public too, the way our Terminal-Bench 4.0 tasks did. And we're small: if you have a good idea on Tuesday, nobody makes you write a proposal about it.

What we offer

• Work from anywhere in the EU, ideally Germany.
• Real compute: hundreds of GPUs across EuroHPC and commercial compute.
• Whatever AI tools make your work easier, without a procurement saga.
• Your name on public work. Our first open-source release is planned for Q1 2027.
• Founders you can just message, and a research team worth learning from.
• An office if you want one: Bremen, right on the water (yes, there's a boat, and free drinks and smoothies), or Berlin.

How to apply

Upload your CV through the form and tell us, in a few lines, about one thing you built that you're proud of. An environment, a training run, a judge, a bug that took you three days to corner. Links to GitHub, papers, a blog post or a messy notebook are all welcome. Please don't write us a polished cover letter. We'd rather read the notebook.
We're hiring for three RL roles at the same time: environments and data, post-training, and alignment and reward modeling. If you're somewhere between two of them, apply to the closer one and say so. We'll figure it out together.
We care a lot more about what you've built and how you think than about how your CV reads. If you don't tick every box, apply anyway. Hardly anyone does, and different perspectives make our models and our team better.

About us

At ellamind, we develop language models and the methods that make them better. Our team trains its own models, builds RL environments, datasets and benchmarks, and researches how to reliably measure and systematically improve the capabilities of LLMs. We are known for our leading German-language open-source models. We actively share what we learn, including through the open-source community DiscoResearch and as part of the OpenEuroLLM program.

As a cash-flow-positive startup, we work with well-known partners such as Deutsche Telekom, the German Federal Government and leading healthcare providers. Our headquarters is in Bremen. We offer competitive pay, equity options and a short line to the founders.

Your CV isn't the only thing that counts. We are looking for curious people who want to help shape the next generation of European AI models. Diversity matters to us, because different perspectives make us better. Please apply even if you don't (yet) meet every requirement.