---
title: 'Research Engineer, Post-Training (All Industry Levels) at Character.AI'
canonical: 'https://feeny.ai/job/research-engineer-post-training-all-industry-levels-character-ai-redwood-city-9cp7d8vanak2'
type: 'job'
last_seen: '2026-09-24'
---

# Research Engineer, Post-Training (All Industry Levels) at Character.AI

- **Company:** Character.AI
- **Location:** Redwood City, CA / New York City, NY
- **Compensation:** $225k–$400k
- **Employment:** full-time
- **Work type:** hybrid
- **Posted:** 2024-01-24
- **Last confirmed live:** 2026-09-24
- **Apply:** https://jobs.ashbyhq.com/character/449bf7c1-41d7-47a4-89a7-0ee0b31f5918/application

**Skills:** Machine Learning, Transformers, Reinforcement Learning, GPU Programming, Data Pipelines, Data Infrastructure, Python, Product Experimentation, A/B Testing, Distributed Model Training, ML Deployment, Kubernetes, Docker, Cloud Computing

> The Research Engineer will focus on fine-tuning AI models, optimizing performance, and ensuring quality standards. Responsibilities include developing alignment algorithms, writing data pipelines, and improving serving efficiency for large generative models.

## Job description

## About the role and team

Joining us as a Research Engineer on the Post-Training team, you'll be diving into the exciting world of fine-tuning AI models, optimizing their performance, and ensuring they meet the highest standards of quality and efficiency. Your work will directly contribute to our groundbreaking advancements in AI, helping shape an era where technology is not just a tool, but a companion in our daily lives. At [Character.AI](http://Character.AI), your talent, creativity, and expertise will not just be valued—they will be the catalyst for change in an AI-driven future.

The Post-Training team is responsible for developing our powerful pretrained language models into intelligent, engaging, and aligned products. As a Post-Training Researcher, you will work across teams and our technical stack to improve our model performance and training methods, including data, compute and algorithms. You will get to shape the conversational experience of millions of users per day.

## What you'll do

- Develop alignment algorithms and loss functions to improve data sample efficiency.
- Write data pipelines to process diverse web data into a format models can ingest.
- Identify quality signals to understand our model’s performance in the real world.
- Design sampling algorithms to improve serving efficiency of large generative models.

## Who you are

- "All Industry Levels": have at least PhD (or equivalent)
- Write clear and clean production-facing and training code
- Experience working with GPUs (training, serving, debugging)
- Experience with data pipelines and data infrastructure
- Strong understanding of modern machine learning techniques (reinforcement learning, transformers, etc)
- Track-record of exceptional research or creative applied ML projects

## Nice to Have

- Experience with product experimentation and A/B testing
- Experience training large models in a distributed setting
- Familiarity with ML deployment and orchestration (Kubernetes, Docker, cloud)
- Publications in relevant academic journals or conferences in the field of machine learning

## About Character.AI

[Character.AI](http://Character.AI) empowers people to connect, learn and tell stories through interactive entertainment. Over 20 million people visit [Character.AI](http://Character.AI) every month, using our technology to supercharge their creativity and imagination. Our platform lets users engage with tens of millions of characters, enjoy unlimited conversations, and embark on infinite adventures.

In just two years, we achieved unicorn status and were honored as Google Play's AI App of the Year—a testament to our innovative technology and visionary approach.

Join us and be a part of establishing this new entertainment paradigm while shaping the future of Consumer AI!

At Character, we value diversity and welcome applicants from all backgrounds. As an equal opportunity employer, we firmly uphold a non-discrimination policy based on race, religion, national origin, gender, sexual orientation, age, veteran status, or disability. Your unique perspectives are vital to our success.

## About Character.AI

## Company Overview
- **One-liner**: Character.AI builds a full-stack, direct-to-consumer platform where users interact with AI-powered "Characters" for open-ended conversation, storytelling, and entertainment.
- **Entity Type**: Private (Venture Capital-Backed)
- **Headquarters**: Menlo Park, California, United States
- **Founded**: 2021
- **Founders**: Noam Shazeer and Daniel De Freitas

## Core Business
- **Primary industry/industries**: Entertainment Software, Artificial Intelligence & Machine Learning, SaaS (B2C)
- **Target customers**: B2C — millions of monthly active users seeking virtual companions, creative storytelling, and interactive entertainment.
- **Mission or purpose statement**: "Empower people to connect, learn, and tell stories through interactive entertainment."

## Products & Services
- **Character.AI Platform**: A web and mobile application that allows users to create, discover, and converse with AI Characters. The platform supports user-generated content, enabling users to build heroes, settings, stories, and challenges. It sits at the intersection of storytelling, gaming, social connection, and creative expression.

## Market Standing
- **Valuation/Market Cap**: Not publicly disclosed (latest known round: Secondary Transaction - Private, completed at "Generating Revenue" stage per PitchBook).
- **Key Metric**: Total Funding raised — **$193M** (Series A: $43.1M in 2022; Series A extension/round: $150M in March 2023).
- **Notable Investors/Partners**: Andreessen Horowitz, Google, Greycroft, SV Angel, Elad Gil, and 8 total investors. [cbinsights.com](https://www.cbinsights.com/company/characterai)
- **Growth Signals**: 
    - Millions of monthly active users.
    - Headcount of ~130 employees as of 2026.
    - Offices in Silicon Valley (HQ), Seattle, and New York.
    - The company completed a "Reverse Acqui-Hire" transaction, signaling strong talent acquisition interest from larger players.

## Competitive Advantages
- **Deep Technical Talent**: Founded by AI pioneers Noam Shazeer and Daniel De Freitas, who bring deep expertise in machine learning and natural language processing.
- **Full-Stack AI Platform**: Unlike many chatbot APIs, Character.AI owns the entire stack from model inference to consumer interface, giving them control over user experience and data.
- **Strong User Engagement & Community**: The platform has built a passionate community of creators and users who generate and share content, creating a network effect moat.
- **Brand Recognition**: One of the leading independent consumer AI platforms globally, with a clear identity as an entertainment-first product.

## Strategic Focus
- **AI-driven Entertainment**: The company is focused on redefining entertainment through generative AI, moving beyond simple chatbots into immersive, interactive experiences.
- **User-Generated Content (UGC)**: Empowering users to create their own characters and worlds is a core strategic priority, differentiating them from single-purpose AI tools.
- **Monetization & Scale**: Moving from a free product toward a sustainable business model (subscription tiers like c.ai+) while scaling the platform to serve a global user base.
- **Talent Acquisition**: Actively hiring across ML research, engineering, and safety to build out the next generation of their product.

## Why Work Here
- **Mission-Driven Work**: Opportunity to work on cutting-edge generative AI and shape the future of entertainment for millions of users.
- **High-Impact Environment**: Described as a "small, passionate team" where individuals can have significant ownership and influence.
- **Strong Compensation**: Competitive salaries (e.g., Research Engineer, AI Safety & Alignment: $225K–$400K + equity). [jobs.ashbyhq.com](https://jobs.ashbyhq.com/character/)
- **Comprehensive Benefits**:
    - **Parental Leave**: 20 weeks paid for birthing parents, 12 weeks for non-birthing parents.
    - **Retirement**: 401(k) match up to $5,875/year (25% of contributions up to IRS cap).
    - **Time Off**: 20 days accrued PTO, 12 company-paid holidays, plus accrued sick time.
    - **Health**: 100% premium coverage for medical (PPO or HSA), dental, and vision for employees; 80% for dependents. Life, AD&D, and LTD insurance fully covered.
    - **Perks**: Daily lunch in all offices, monthly DoorDash credit, monthly commuter allowance ($50), and a quarterly wellness stipend.
- **Work Policy**: Hybrid (offices in Menlo Park, Seattle, New York).
- **Culture Values**: "Users First" (users > company > team), "Think Transformational," and a focus on collaboration and high performance.

## Sources
1. [character.ai/about](https://character.ai/about)
2. [character.ai/careers](https://character.ai/careers)
3. [jobs.ashbyhq.com/character/](https://jobs.ashbyhq.com/character/)
4. [cbinsights.com](https://www.cbinsights.com/company/characterai)
5. [pitchbook.com](https://pitchbook.com/profiles/company/512290-54)

## Other roles at Character.AI

- [Technical Program Manager, Product Experience](https://feeny.ai/job/technical-program-manager-product-experience-character-ai-redwood-city-m9zmhkmgt1qy) — Redwood City, CA
- [Principal Research Engineer, Post-Training](https://feeny.ai/job/principal-research-engineer-post-training-character-ai-redwood-city-92f6f7sk06h1) — Redwood City, CA
- [Technical Program Manager, Model Alignment and Deployment](https://feeny.ai/job/technical-program-manager-model-alignment-and-deployment-character-ai-redwood-brmkpc2gvra0) — Redwood City, CA
- [Staff Data Scientist, Monetization](https://feeny.ai/job/staff-data-scientist-monetization-character-ai-redwood-city-51hmwhgh6e2k) — Redwood City, CA
- [Technical Program Manager, AI Infrastructure](https://feeny.ai/job/technical-program-manager-ai-infrastructure-character-ai-redwood-city-3ty4trwmewr9) — Redwood City, CA
- [Software Engineer, Backend/Applied ML (Safety & Integrity)](https://feeny.ai/job/software-engineer-backend-applied-ml-safety-integrity-character-ai-redwood-city-4q5mdjeptsz5) — Redwood City, CA
- [Software Engineer, Applied ML (Discovery, Recommendation & Search)](https://feeny.ai/job/software-engineer-applied-ml-discovery-recommendation-search-character-ai-5r4a2m0v7fzq) — Redwood City, CA
- [Software Engineer, Backend](https://feeny.ai/job/software-engineer-backend-character-ai-redwood-city-kx5x7rxznvz7) — Redwood City, CA
- [Software Engineer, Monetization](https://feeny.ai/job/software-engineer-monetization-character-ai-redwood-city-4wjqzcp5e490) — Redwood City, CA
- [Software Engineer, Core Product](https://feeny.ai/job/software-engineer-core-product-character-ai-redwood-city-h676pc9pz8k1) — Redwood City, CA