LLM Post-Training Engineer

What you will do:

Domain Knowledge Injection via Fine-Tuning

• Design and execute supervised fine-tuning (SFT) pipelines that inject domain-specific knowledge into base LLMs across Customer Support and Network Deployment contexts
• Apply parameter-efficient fine-tuning techniques — including LoRA, QLoRA, and adapter-based methods — to adapt large models effectively within compute and latency constraints
• Collaborate with the AI & Domain Specialist and AI Data & Integration Engineer to ensure fine-tuning datasets are high quality, domain-representative, and correctly formatted for training objectives
• Maintain a structured catalog of fine-tuned model variants, adapter checkpoints, and associated training configurations to support reproducibility and lifecycle governance

Policy-Reward Training & Alignment

• Design and implement policy-reward training pipelines using advanced optimization methods including GRPO (Group Relative Policy Optimization) and SAPO (Soft Adaptive Policy Optimization)
• Define reward models and preference datasets that encode domain-specific quality signals — going beyond generic helpfulness to capture what correct, safe, and operationally appropriate behavior looks like in telco contexts
• Iterate on alignment strategies based on evaluation feedback and production signal — continuously refining model behavior to better match system requirements and domain acceptance criteria
• Stay current with the rapidly evolving post-training research landscape, identifying and assessing new alignment techniques for potential adoption

Automatic Dataset Curation & Synthetic Data Generation

• Build and maintain automated pipelines for domain dataset curation — sourcing, filtering, deduplicating, and formatting data at scale for both SFT and reward training
• Design synthetic data generation strategies that augment real-world datasets — producing diverse, high-quality training examples for scenarios where real data is scarce, sensitive, or imbalanced
• Collaborate with domain experts to validate synthetic data quality and ensure generated examples accurately reflect real-world telco operational scenarios
• Implement data quality gates and automated checks that maintain dataset integrity throughout the curation and generation pipeline

Training Run Management & Experiment Tracking

• Own the end-to-end management of training runs — including infrastructure provisioning, job scheduling, hyperparameter configuration, and run monitoring
• Maintain a rigorous experiment tracking practice, logging all training configurations, dataset versions, evaluation results, and model artifacts to ensure full reproducibility and informed decision-making
• Define and report on key training metrics — loss curves, reward signal trends, evaluation benchmark scores, and alignment quality indicators — providing clear visibility to the AI System Architect and engineering leadership
• Identify and resolve training instabilities, overfitting risks, and performance bottlenecks across the post-training pipeline

You will bring:

• Proven hands-on experience in LLM fine-tuning and post-training, with a track record of adapting large language models for production use cases using SFT, LoRA, or equivalent techniques
• Strong understanding of RLHF, preference optimization, and policy-reward training methods — direct experience with GRPO, DPO, PPO, or similar approaches is highly valued
• Experience building automated data curation and synthetic data generation pipelines for LLM training at scale
• Solid grasp of experiment tracking best practices and tooling — able to maintain a disciplined, reproducible training workflow across multiple concurrent experiments
• Familiarity with distributed training infrastructure, GPU resource management, and compute-efficient training strategies
• Understanding of model evaluation methodologies and how post-training decisions connect to downstream benchmark and production performance
• Familiarity with telecommunications, RAN, or network operations domain data is a strong plus
• Collaborative and rigorous — able to work closely with data engineers, domain specialists, evaluation engineers, and architects to ensure post-training outputs meet both technical and domain quality standards

Why join Ericsson?At Ericsson, you´ll have an outstanding opportunity. The chance to use your skills and imagination to push the boundaries of what´s possible. To build solutions never seen before to some of the world’s toughest problems. You´ll be challenged, but you won’t be alone. You´ll be joining a team of diverse innovators, all driven to go beyond the status quo to craft what comes next.
What happens once you apply?Click Here to find all you need to know about what our typical hiring process looks like.Encouraging a diverse and inclusive organization is core to our values at Ericsson, that's why we champion it in everything we do. We truly believe that by collaborating with people with different experiences we drive innovation, which is essential for our future growth. We encourage people from all backgrounds to apply and realize their full potential as part of our Ericsson team. Ericsson is proud to be an Equal Opportunity Employer. learn more.

Primary country and city: Japan (JP) || Yokohama

Req ID: 787828