Post-Training Engineer

Post-Training Engineer

Lovable lets over 2 million people build software using plain language, and the models behind it need to be exceptional. We're hiring an engineer who has gotten their hands dirty with post-training at scale and wants to do it again for one of the fastest-growing AI products in the world.

You'll own our full post-training pipeline: translating the latest research into production training recipes, adapting them for code generation and agent workloads, and putting improved models in front of users fast. The goal is to get promising research into production within days or weeks, not months. This isn't an academic research position - you'll spend as much time in production infrastructure as in training configs, and your success is measured by what ships.

What we’re looking for

You've personally run post-training jobs on large language models - RFT/RLVR, preference optimization, or similar. Not just called APIs or written prompts, but actually trained and iterated on models

You can write solid production code. The systems you build need to run reliably, not just produce interesting research artifacts

You're fluent in at least one major ML framework (PyTorch, JAX) and comfortable working with distributed training setups and GPU clusters

You understand the math behind preference optimization, reward modeling, and alignment techniques - and can reason about when each approach fits

You've built or significantly contributed to evaluation systems that capture real-world quality, not just benchmark scores

You can trace a model quality regression from user-facing symptoms back through serving, inference, and training - and you enjoy doing it

You want to ship. Research taste matters, but at Lovable the question is always "how fast can we get this to users?

Preferred

You've worked on code generation or agentic use cases specifically

You've put post-trained models into the hands of real users and seen how they hold up at scale

You've owned the full loop: curating data, running training, evaluating results, deploying, and monitoring in production

You have a habit of reading a paper on Monday and having a prototype running by Friday

You've experimented with speculative decoding or similar techniques to improve model efficiency

You have strong views on evaluation methodology and have built evals that actually predict user satisfaction

You've published or contributed meaningfully to the open-source ML ecosystem

What you’ll do

• Own the full lifecycle of Lovable's post-training pipeline - from data curation and training runs through evaluation and deployment

• Apply and adapt reinforcement learning, preference optimization, and supervised fine-tuning methods to make our models better at generating code, reasoning about user intent, and acting as reliable agents

• Build the evaluation and experimentation infrastructure that tells us whether a model change actually helps users - covering helpfulness, safety, latency, and reliability

• Develop and operate the production systems that run training jobs at scale, including GPU orchestration and data pipelines

• Work across team boundaries with our agent, product, and infrastructure engineers to turn model gains into product improvements users can feel

• Investigate and resolve failures end-to-end - whether the root cause is in a training recipe, a data issue, or a serving regression

• Read papers, run experiments, and move fast: the goal is to get promising research into production within days or weeks, not months

• About your application

• Please submit your application in English. It’s our company language, so you’ll be speaking lots of it if you join.

• We treat all candidates equally - if you’re interested, please apply through our careers portal.