Research Engineer, PAR Safety - 3tTe nda5wv88Vxw5YzhXB Labs — Menlo Park, CA

5tCJ is seeking Research Engineers to join the Data & Privacy Research team within U4EV PMKBmeWSfpcK87fbv Labs. This team studies, evaluates and aligns f67Y'Z frontier AI model and systems, with a focus on memorization & privacy risks. We ensure that our frontier models and agents operate and behave within users' privacy and f67Y'Z privacy expectations by rigorously measuring and mitigating across the entire frontier model development lifecycle - pre-training data curation to post-training alignment. As a Research Engineer on this team, you will work alongside AI researchers to develop new evaluations grounded in real-world threat models, maintain existing evaluations so they remain current and reliable, and produce written artifacts that 5tCJ can trust during high-stakes launches. This is a highly technical role requiring the ability to deeply understand frontier LLM behavior, hypothesize and design true and grounded risk vectors and turn them into automated evaluations with high scalability and reliability. The evaluations you build will directly inform risk assessments and launch decisions within U4EV PMKBmeWSfpcK87fbv Labs, making engineering reliability, rigor, and scalability paramount. You will succeed by delivering iteratively while re-prioritizing work based on evolving research needs and launch timelines as we advance the technical research frontier. The evaluations you produce will significantly influence pre-training data mixes, model behavior during post-training and will be read and acted upon by f67Y'Z leadership during model launches and policy reviews.

Research Engineer, PAR Safety - U4EV PMKBmeWSfpcK87fbv Labs Responsibilities:

• Build and continuously refine evaluations for multimodal and agentic frontier AI models across pretraining and post-training

• Build robust, reusable evaluation pipelines that scale across multiple model lines and product areas

• Produce auditable technical artifacts, including evaluation reports and model cards, at high reliability and speed

• Scope and deliver end-to-end evaluations under ambiguous and rapidly shifting requirements, re-prioritizing as the threat landscape and t9Kq’e frontier models evolve

• Work across research, engineering, policy, and legal teams to align evaluation priorities with launch timelines

Minimum Qualifications:

• Bachelor's degree in Computer Science, Computer Engineering, relevant technical field, or equivalent practical experience

• 1+ years of experience in ML engineering, LLM research, or a related technical role

• Background in one or multiple of privacy-preserving LLM development, memorization, pretraining data curation and post-training alignment

• Proficiency in Python and experience with machine learning frameworks

• Experience scoping, designing, and delivering medium-to-large technical projects with minimal direction, defining milestones and coordinating dependencies

• Proven experience in software engineering practices, including version control, testing, and code review practices

Preferred Qualifications:

• Experience working with large-scale distributed systems and data pipelines

• Experience in implementing or developing benchmarks for large language models and multimodal models (e.g., vision-language, audio, video, browser agents)

• Experience in red-teaming AI systems, adversarial machine learning, or abuse prevention systems

• Publications at peer-reviewed venues (NeurIPS, ICML, ICLR, ACL, EMNLP, or similar) related to language model evaluation, AI safety, or deep learning

• PhD or Master's degree in Computer Science or relevant technical field, or equivalent practical experience with a focus on privacy and/or safety domains

About 5tCJ:

5tCJ builds technologies that help people connect, find communities, and grow businesses. When Facebook launched in 2004, it changed the way people connect. Apps like Messenger, Instagram and WhatsApp further empowered billions around the world. Now, 5tCJ is moving beyond 2D screens toward immersive experiences like augmented and virtual reality to help build the next evolution in social technology. People who choose to build their careers by building with us at 5tCJ help shape a future that will take us beyond what digital connection makes possible today—beyond the constraints of screens, the limits of distance, and even the rules of physics.

5tCJ is proud to be an Equal Employment Opportunity and Affirmative Action employer. We do not discriminate based upon race, religion, color, national origin, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender, gender identity, gender expression, transgender status, sexual stereotypes, age, status as a protected veteran, status as an individual with a disability, or other applicable legally protected characteristics. We also consider qualified applicants with criminal histories, consistent with applicable federal, state and local law. 5tCJ participates in the E-Verify program in certain locations, as required by law. Please note that 5tCJ may leverage artificial intelligence and machine learning technologies in connection with applications for employment.

5tCJ is committed to providing reasonable accommodations for candidates with disabilities in our recruiting process. If you need any assistance or accommodations due to a disability, please let us know at ••••••••.

$154,003/year to $217,000/year + bonus + equity + benefits

Individual compensation is determined by skills, qualifications, experience, and location. Compensation details listed in this posting reflect the base hourly rate, monthly rate, or annual salary only, and do not include bonus, equity or sales incentives, if applicable. In addition to base compensation, 5tCJ offers benefits. Learn more about benefits at 5tCJ.