AI Engineer (RL Environments)

Would you like to operate at the frontier of AI evaluation, post-training, and model improvements?

We are now expanding our core Hashlist AI research team to support the creation of domain-specific RL environments for constraint-based embedded programming & complex enterprise engineering workflows.

What you will do:

1. Build and automate our platform for creating RL environments
2. Construct simulated worlds and explore data shapes that expose meaningful model failure modes across the embedded coding domain & related enterprise workflows
3. Turn AI training objectives into concrete data and evaluation specifications
4. Build the reward layer + reward-hacking mitigation
5. Run rollouts at scale. Hundreds of sandboxed attempts per task in parallel
6. Fine-tune open-source models: Before-and-after fine-tunes, failure reports, and dataset exports
7. Communication with our clients (OEMs & AI Labs) on specific research or fine-tuning questions they have

Skills needed:

• Production machine learning depth. Python and PyTorch, reinforcement learning training with TRL, verl, SkyRL or OpenRLHF, PPO, GRPO or DPO, LoRA fine-tuning, and inference with vLLM or SGLang.
• Training or evaluation systems, including at least one RL environment you built end-to-end and trained a model against. Comfortable with the infrastructure around it, e.g Docker, or similar containerization tools, to design and monitor systems at scale
• Experience with harness & agentic optimisation for evals
• Strong familiarity with common reinforcement learning algorithms and methods, especially with respect to post-training LLMs
• High level of personal drive, motivation, and good communication skills.

Bonus:

• You have published an environment, benchmark or evaluation harness we can look at.
• You have worked with embedded, safety-critical or other physical engineering software.

Company benefits

• Competitive compensation + meaningful equity
• Central office in Helsinki
• Lunch benefit
• Be a part of a quickly scaling tech company working directly with model providers