Applied AI Research Engineer — Voice & Long-Horizon Tasks

Candidate; San Francisco (CA); On-site; USD 180,000 - 230,000; Full time

Benefits offered by this job

Flexible PTO

Medical, dental & vision benefits

Life insurance

Retirement plan

Parental leave

Fertility and family building benefits

Lunch and snacks

Discretionary benefit stipend

Free alphorn lessons

Job summary

Sierra is a leading platform for customer-facing AI agents, based in San Francisco and expanding offices globally. We value trust, customer obsession, craftsmanship, intensity, and family, and seek builders who can advance post-training methods and deploy reliable agents.

Join a team tackling challenging ML problems, collaborating across the stack to deliver customer value while growing our applied research capabilities and production systems.

Qualifications

• Strong experience building and deploying production ML/AI systems.
• Excellent judgment in framing product problems as ML tasks.
• Experience working with data, experimentation, evaluation, and model iteration.
• A practical, evidence-driven approach to ML, with good judgement on modeling vs simpler solutions.
• Ability to operate with high agency and work across the stack when needed to deliver an outcome.

Responsibilities

• Tackle unsolved applied AI and ML problems, pushing post-training, voice AI, and long-horizon task execution.
• Determine when to build specialized models vs using externally provided frontier intelligence.
• Turn ambiguous product and customer problems into well-framed machine learning problems.
• Develop, fine-tune, evaluate, and deploy models that improve Sierra’s customer-facing AI agents.
• Advance our post-training work toward reinforcement learning and long-horizon optimization.
• Build rigorous evaluations that connect model performance to real-world agent quality.
• Work with large-scale datasets spanning text and audio interactions.
• Collaborate across Sierra from experimentation through production deployment and customer impact.

Skills

Production ML systems

Applied ML

Data experimentation

Model iteration

Cross-stack collaboration

Education

Degree in CS/ML or related field

Job description

Sierra is a leading platform for customer-facing AI agents, based in San Francisco and expanding offices globally. We value trust, customer obsession, craftsmanship, intensity, and family, and seek builders who can advance post-training methods and deploy reliable agents.

Join a team tackling challenging ML problems, collaborating across the stack to deliver customer value while growing our applied research capabilities and production systems.