Inflection AI

Principal Research Engineer, Model Training & Post-Training

Palo Alto, California, United States · Principal

Sponsorship not specified$400k-$550kDetected 22 days ago

Full-Stack DevelopmentMachine LearningNLPLLMsResearch

About the role

This person will sit at the intersection of research, production engineering, and model release, with a mandate to ship models that are measurably better for users.
The ideal candidate has led serious model training or post-training work before, can make principled tradeoffs across data, compute, architecture, and quality, around a clear technical roadmap.

Own the model-improvement roadmap across capability, reliability, emotional intelligence, tool use, safety, latency, cost, and enterprise readiness.
Lead training and post-training strategy, including supervised fine-tuning, RLHF, DPO, GRPO, RLAIF, reward modeling, preference optimization, tool-use fine-tuning, distillation, synthetic data, and related methods.
Lead large-scale training efforts on distributed GPU clusters, including systems operating at the scale of 1,000+ GPUs.
Define and execute data strategy across data curation, mixture design, deduplication, decontamination, human-in-the-loop pipelines, preference data, evaluation data, synthetic data, and production feedback loops.
Build and improve evaluation and release-quality systems, including model evals, quality gates, regression detection, release criteria, model-readiness reviews, and post-release monitoring.
Partner closely with infrastructure and research engineering teams to improve distributed training reliability, checkpointing, fault tolerance, observability, reproducibility, and cost-performance tradeoffs.
We are focused on building a positive, safe, inclusive and inspiring place to work.
Support of country-specific visa needs for international employees living in the Bay Area

Experience leading, or serving as a principal contributor to, large-scale LLM, multimodal, or foundation-model training or post-training programs.
Strong practical experience with post-training and alignment methods such as SFT, RLHF, DPO, GRPO, RLAIF, reward modeling, preference optimization, tool-use fine-tuning, or related approaches.
Experience operating or partnering on large-scale training infrastructure, ideally including GPU clusters at the scale of 1,000+ GPUs.
Ability to balance research ambition with product pragmatism, user impact, and operational discipline.
Experience leading senior technical teams while continuing to contribute directly to technical decisions and implementation.

For this role, Inflection AI estimates a starting annual base salary to fall within the range of $400,000 to $550,000, depending on a candidate's qualifications and level of experience.

Our benefits include:
Diverse medical, dental and vision options
Unlimited paid time off
Parental leave and flexibility for all parents and caregivers
Deep experience with transformer-based models, hybrid architectures, modern deep-learning frameworks, and distributed training systems.

Support of country-specific visa needs for international employees living in the Bay Area

This listing is sourced directly from Inflection AI's careers page and normalized into a canonical job model.