Software Engineer, TypeScript — Codebase Q&A

Role Overview

Mercor is seeking experienced TypeScript engineers to build the dataset that teaches AI agents to reason about real codebases.

Codebase Q&A is a reinforcement-learning environment for training AI agents to explore and reason about software repositories they have never seen before. You will build difficult codebase-exploration tasks: high-level engineering questions about production TypeScript and JavaScript repositories that cannot be answered by reading a single file, and that require runtime evidence to resolve - the kind of question a senior engineer answers by actually investigating the system.

This track works on codebases at the centre of the modern JS/TS ecosystem: Babel, Jest, Astro, TypeORM, Apollo Server, GraphQL-JS, Socket.IO, TanStack Router, NextAuth, XState, TypeDoc and typescript-eslint.

Contract, task-based work paid at $130 per approved task, performed remotely in Mercor Studio.

Key Responsibilities

• Select tasks from a pre-validated pool of TypeScript repositories, each pinned to a specific git commit and arriving with an engineering question, positive and negative rubrics, foils, and a golden solution
• Explore the repository until you genuinely understand the subsystem in question, including the relevant PR or issue history
• Rewrite the task's question so it defeats frontier coding agents while remaining well-defined and fairly answerable
• Adjust rubrics and foils so they reward correct reasoning and reject plausible-but-wrong answers
• Run the full validation loop in Studio - Check, Golden, Run, Analyze - and iterate until every stage passes
• Document your work in the task README and submit for expert review, addressing reviewer feedback on returned tasks

Ideal Qualifications

• 3+ years of professional software engineering experience, with substantial production TypeScript
• Demonstrated ability to navigate a large, unfamiliar TypeScript monorepo and explain how it behaves at runtime - not just what the types say
• Fluency in the advanced type system, module resolution, bundlers and transpilers, and the Node and browser runtimes; comfort reading compiler and plugin internals
• Experience with developer tooling, compilers, test frameworks, GraphQL servers, or state machines is highly relevant - the task mix is weighted toward architecture and system design (48%) and code onboarding (35%)
• Precise written English: the questions and rubrics you write are the product
• Comfortable with git at commit level, containerized environments, and command-line tooling

Working Details

• Fully remote and asynchronous, with expert team leads across US, India, and Nigeria time zones
• Work is performed in Mercor Studio; time is tracked with Insightful, and platform access is provisioned through Okta
• Onboarding requires identity verification, a background check, signed Terms of Work and CIIAA, a tax form, and passing a short calibration quiz before task access is granted
• Payment is per approved task; every task is reviewed by a second engineer and a super reviewer before acceptance

Application Process

• Submit your resume or relevant technical background to get started
• Qualified applicants may be asked to complete a brief technical assessment or provide additional information

We consider all qualified applicants without regard to legally protected characteristics and provide reasonable accommodations upon request.