Senior Software Engineer

Mechanize is hiring a Senior Software Engineer in San Francisco, United States. It pays $400k a year and Level rates it ; you can apply on Mechanize.

Level's read on this job

On Level's scale, this software engineer role is Builds AI ●●●●: the job is building AI systems.
Pay on this posting starts 139% higher than the typical software engineer posting on Level.
Level classes it as a senior role.
Mechanize has 3 other open roles on Level.

AI in this role

About Mechanize

Mechanize builds reinforcement learning environments that frontier AI labs use to train and evaluate their coding models. Learn more at mechanize.work.

Why the work matters

AI models have gotten good at narrow coding tasks but still fail at the complex, judgment-heavy parts of software engineering. We build the environments that expose those failures and help models improve.

What you'll do

You'll design, build, and refine RL tasks, owning the full lifecycle from ideation through grading, failure analysis, and iteration. At this level, we expect you to work on our most complex tasks: environments involving multi-step workflows, realistic stakeholder interactions, large codebases with real conventions and technical debt, or challenging system design problems.

You will use coding agents heavily, and a large part of the job is directing them well, evaluating their output, and knowing when they are failing in subtle ways. You will also contribute to shared infrastructure and tooling, and may take on mentorship responsibilities for newer team members.

What makes someone good at this

Deep software engineering experience across multiple domains, combined with a strong intuition for AI model behavior. You need to anticipate where a model will take shortcuts, distinguish genuine capability gaps from grader issues, and design tasks that target deeper, more subtle failure modes from areas you know well: infrastructure, distributed systems, performance, security, or other specializations.

Good fit if you:

Have deep expertise in at least one area of software engineering
Can code in Python
Are confident working independently on complex, ambiguous problems
Have extensive experience working with coding agents
No prior ML or AI experience required

Probably not a good fit if you:

Want a product engineering role building features for end users

This is independent, high-ownership work. You own your tasks from start to finish, with regular feedback.

Compensation

Compensation includes a $400,000 base salary, equity, and performance bonuses. Top performers can earn more in bonuses than in base salary.

Strong performers are recognized and promoted quickly. Benefits include health, dental, vision, and life insurance.

About Mechanize. ~20 person team in San Francisco. Backed by Patrick Collison, Nat Friedman, Daniel Gross, Jeff Dean, Dwarkesh Patel, and Sholto Douglas. Featured in the New York Times, the Dwarkesh Podcast and Hard Fork.

Learn more about the interview process: https://www.mechanize.work/how-our-interview-process-works

Learn more about the work: https://www.mechanize.work/what-working-here-is-like

How we rate this

Senior Software Engineer at Mechanize rates 85 out of 100 for how much of the daily work is AI. That makes it Builds AI (AI Level 4 of 4). The level is about AI in the job, not seniority.

Classification

Builds AI. The job is building AI systems.

●●●● Builds AI80 to 100
●●●○ Works on AI60 to 79
●●○○ Uses AI40 to 59
●○○○ Little AI0 to 39

Levels come from how often the tools, models and workflows of the role are named in the posting itself. Read the description and count the AI tools, models and workflows it names.