Software Engineer, Agent Harness

Sim; San Francisco (CA); On-site; USD 210,000 - 260,000; Full time

Benefits offered by this job

Equity

Onsite in SF

Job summary

Sim is seeking a mission‑driven engineer to build the agent that scales knowledge work. You’ll design and implement the infrastructure that enables large language model tool calls, memory, retries, and robust failure handling for 100,000+ builders.

The role includes an onsite in our San Francisco office, a small project to demonstrate ideas, and a chance to meet the team. Compensation ranges from $210k to $260k base plus equity, with an equity stake aligning with impact.

Qualifications

• Able to design and maintain AI infrastructure for reliable tool calls.
• Demonstrates ability to reason about LLM behavior and system reliability.
• Shows focus on scalable, fault-tolerant engineering for knowledge work apps.

Responsibilities

• Build infrastructure for the agent that plans, calls tools, uses memory, and recovers from failure at scale.
• Collaborate with team during onsite project to discuss ideas and demonstrate impact.
• Translate intuition about LLM behavior into robust, maintainable systems.

Skills

LLM behavior

Tool calls

Context handling

Robust infra

Job description

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.