Software Engineer, Agent Harness
EngRadarAbout the role
EngRadar / Sim
Software Engineer, Agent Harness
Sim
Sim is building a visual, drag-and-drop platform for developers to create and deploy AI agents, backed by Y Combinator and a $7M Series A.
San Francisco Full-time Posted today aidevtools
$210k–$260k Apply directly →
Our mission is to automate knowledge work. The first step in our journey is to build the best tool for teams to build agents.
Sim is talent-dense. We're looking for special people who are mission-driven, passionate, and creative.
About The Role
The agent harness is Sim. It's the agent that builds workflows, tables, creates knowledge bases, and does everyday tasks. As a member of this team, you'll build the agent that builds everything else: how it plans, calls tools, uses memory, recovers from failure, and runs reliably at scale for 100,000+ builders.
You may be a fit if
You can think clearly about LLM behavior (tool calls, context, retries, evals) and you can turn that intuition into robust infrastructure.
Compensation
$210K–$260K base plus 0.2%–0.8% equity.
Applying
If there appears to be a fit, we'll reach out to schedule 1-2 short technicals. After, we'll schedule an onsite in our office, where you'll work on a small project, discuss ideas, and meet the team.
Equal Opportunity
Sim is committed to creating an inclusive environment for all employees. We celebrate diversity and are committed to creating an inclusive environment for all team members. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.
Posted by Sim on their own careers page — you apply directly, no recruiter in between. View original / apply →
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Responsibilities
- Build the agent that creates workflows, tables, and knowledge bases
- Develop infrastructure for LLM behavior and tool calls
- Ensure reliability and scalability for 100,000+ builders
Qualifications
- Ability to think clearly about LLM behavior
- Experience in building robust infrastructure
Benefits
- Equity options (0.2%–0.8%)
- Inclusive work environment
Skills mentioned
About EngRadar
EngRadar is a direct-apply tech job board. We surface open engineering and product roles straight from companies' own Greenhouse, Lever and Ashby career pages — no recruiters, no aggregators, no ghost jobs. Browse fresh, daily-updated jobs across full-stack, AI/ML, backend, data, DevOps, product, design and security — each linking directly to the employer's application. We also publish measured, first-party hiring data: monthly hiring reports, the fastest-growing companies, and disclosed-salary benchmarks. Find the roles worth applying to at engradar.com.