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Salary: USD 210,000 - 260,000 / annual
Sim is building tools to automate knowledge work, starting with a platform for teams to build AI agents. You'll join the Agent Harness team—the core infrastructure that powers Sim's agent-building capabilities.
In this role, you'll own the design and implementation of the agent harness: the system responsible for orchestrating agent behavior including planning, tool calling, memory management, failure recovery, and reliable execution at scale. You'll work on infrastructure that supports 100,000+ builders, ensuring the agent can reliably build workflows, manage tables, create knowledge bases, and execute everyday tasks.
You'll collaborate with a talent-dense team of mission-driven engineers to solve complex problems around LLM behavior, tool integration, context management, and system reliability. This is a foundational engineering role where your decisions directly impact the platform's core capabilities.
Sim values creative problem-solving and deep technical thinking. The company is early-stage and moving quickly, so you'll have significant ownership and the opportunity to shape the product's technical direction.
Requirements:
• Strong ability to reason about LLM behavior, including tool calling, context windows, retry logic, and evaluation strategies
• Ability to translate intuition about agent systems into robust, production-grade infrastructure
• Experience building scalable systems and thinking through reliability at scale
• Passion for automation and knowledge work problems
