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a16z

Software Is Eating the World

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a16z portfolio company

Software Engineer, RL Data

Location
San Francisco
Work arrangement
On-site
Job type
Full-time

About the role

Posted Aug 27, 2026

Our mission is to automate coding. The first step in our journey is to build the best tool for professional programmers, using a combination of inventive research, design, and engineering. Our organization is very flat, and our team is small and talent dense. We particularly like people who are truth-seeking, passionate, and creative. We enjoy spirited debate, crazy ideas, and shipping code.

Software Engineer, Reinforcement learning

 
  • SpaceXAI is building the future of coding. We train frontier coding agents and scale RL on real user data to make them increasingly effective.

 

About the role

 
  • As a Software Engineer on the RL Data team at SpaceXAI, you'll create the tasks, rewards, and environments that train our coding agents. The team owns the data that goes into training: what the model is asked to do, how we score it, and the setups it learns in.

 
 

What you’ll do

 
  • Designing a task set that teaches a specific agent capability, then iterating on it from traces and evals until the model actually gets better.

  • Reading a pile of agent traces, finding a failure mode or a surprising behavior, and building a system that surfaces more of the same.

  • Turning a one-off recipe into something other teams can reuse: better rewards, cleaner environments, tighter data quality.

  • Partnering with research on whether a dataset is actually teaching the thing we think it is.

 
 
 
 

You may be a fit if

  • You write careful, fast code and have strong software engineering fundamentals.

  • You like setting tasks: breaking a fuzzy capability into something concrete you can measure.

  • You have an infra, data, or distributed systems background. RL experience is a plus, not a requirement.

  • You enjoy looking at messy real-world agent behavior and turning it into a dataset or a tool.

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At a glance

Location
San Francisco
Workplace
On-site
Employment
Full-time
Team
Engineering
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The company

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Cursor is the best way to code with AI, and built to make you extraordinarily productive.

M&A51–200 employeesAI
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