Greenhouse ·
contractSenior AI Engineer, Post-training
Carta · San Francisco, CA; New York City, NY
Carta operates a connected platform and AI‑native ecosystem for private capital, providing a unified system of record for equity management, fund administration, and legal transaction workflows. The Senior AI Engineer, Post‑training role sits within Carta Law, the legal tech team that builds autonomous AI agents, specialized legal models, document intelligence, and contract‑focused services. Day‑to‑day responsibilities include post‑training open‑weight language models on proprietary legal data, designing and executing supervised fine‑tuning, preference optimization, and reinforcement learning experiments, constructing training datasets and pipelines with human‑in‑the‑loop feedback, and owning the end‑to‑end model lifecycle from data preparation through evaluation, serving, and integration into agent‑based products. The engineer collaborates closely with product, agent, and legal teams to decide what functionality belongs in the model versus the surrounding tools, translates lawyer workflows into model and evaluation decisions, and ensures reliable training stacks and production serving infrastructure. The ideal candidate has hands‑on experience with LLM post‑training using PyTorch or similar frameworks, a track record of shipping AI systems to real users, strong judgment on model selection and training objectives, and the ability to bridge applied research with product engineering while working autonomously on ambiguous, model‑centric challenges.
Education
- Level: Bachelor's degree
Key Skills
About the Role You will join Carta’s ML Engineering team embedded in Carta Law, working on autonomous AI agents, specialized legal models, document intelligence and contract workflows. You will own end‑to‑end model development and applied AI, from post‑training and evaluation through model serving and system integration. Responsibilities Post‑train open‑weight language models on proprietary legal data, handling data, objective design, base‑model selection, training, evaluation and iteration. Apply training techniques such as supervised fine‑tuning, preference optimization and reinforcement learning, with attention to reward design and model behavior. Build and improve training datasets and data pipelines, including labeling guidance, model‑generated data and human feedback loops. Own the training stack, manage distributed training runs and optimize performance. Build and operate production systems including model serving, agents, evaluation pipelines and supporting tooling. Partner with product and agent engineers on co‑design of models and systems. Work directly with lawyers and domain experts to translate workflows into model, data and evaluation decisions. Requirements Hands‑on experience with LLM post‑training using PyTorch or equivalent frameworks. Ability to build product components around models, including agents, tools, services and infrastructure. Experience owning model development or post‑training projects that shipped to real users. Strong judgment on model selection, data, training objectives and evaluation. Proven ability to drive projects from idea through production with minimal guidance. Strategic mindset to balance research and engineering trade‑offs. Eligibility
Skills for this role
Required skills
Also mentioned in the listing
| Role | Senior AI Engineer, Post-training |
|---|---|
| Company | Carta |
| Location | San Francisco, CA; New York City, NY |
| Compensation | Not disclosed |
| Posted | 2026-09-21 |
| Deadline | Rolling |
Typical process for this type of role
A general guide — the exact steps for this specific listing may vary; check the original posting for details.
- 1ApplicationSubmit your resume through the apply link.
- 2ScreeningRecruiter reviews your background against the role.
- 3AssessmentA technical test, assignment, or coding round, depending on the role.
- 4Interview(s)One or more rounds with the hiring team.
- 5OfferOffer letter with compensation and start date.
Before you apply
0/4Senior AI Engineer, Post-training at Carta: frequently asked questions
- Who can apply for the Senior AI Engineer, Post-training role at Carta?
- The listing asks for Bachelor's degree; freshers are welcome.
- What skills does the Senior AI Engineer, Post-training role require?
- The listing highlights PyTorch, LLM post‑training, Supervised fine‑tuning, Preference optimization, Reinforcement learning, Distributed training, Model serving, Data pipelines. Show each of these in a project or past role on your resume.
- What is the salary for this role?
- Carta has not stated compensation in the listing. Check the original posting or ask during the application process.
- Is the Senior AI Engineer, Post-training position remote, hybrid or onsite?
- The listing gives San Francisco, CA; New York City, NY as the location and does not state a work mode.
- What is the application deadline?
- Carta has not listed a fixed deadline, so apply early in case the opening is filled.
- How do I apply for the Senior AI Engineer, Post-training role?
- Use the Apply button on this page. It opens the original listing on job-boards.greenhouse.io, where you submit your application with the company.
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