Software Engineer, C — Codebase Q&A

Role Overview

Mercor is seeking experienced C 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 foundational C systems 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 some of the most consequential C codebases in production anywhere: PostgreSQL, Redis, git, OpenSSH, OpenSSL, curl, libuv, libgit2, libarchive, Open vSwitch, tcpdump, tmux and zstd.

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 C 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 C

Demonstrated ability to navigate a large, unfamiliar C codebase and explain how it behaves at runtime — not just what the source says

Comfort with the things that make C systems hard to read: preprocessor-heavy builds, platform conditionals, manual memory management, and autotools/CMake/Meson build graphs

Experience with databases, cryptography, networking protocols, or systems programming is highly relevant — the task mix is weighted toward architecture and system design (39%) and code onboarding (34%), with a meaningful security slice

Ability to use debuggers, sanitizers, tracing, and profilers to establish what the code actually does

Precise written English: the questions and rubrics you write are the product

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.