Staff Software Engineer (Founding Team)

Counterfactlabs; San Francisco (CA); On-site; USD 210,000 - 350,000; Full time

Benefits offered by this job

Competitive compensation and founding 

Autonomy and impact from day one.

Direct exposure to investors, advisors

Job summary

Counterfact Labs in San Francisco is seeking a senior software/ML systems architect to lead the build of the core platform from zero to one, guiding architecture and implementation across backend systems and ML pipelines.

You will partner with early design clients to integrate Counterfact into their workflows, and you will develop methods to modularize complex agents, detect ambiguous or inconsistent behaviors, and balance cost and quality while delivering reliable solutions.

Qualifications

• 5+ years building software and ML systems at Staff or Principal level.
• Experience with backend systems, infrastructure, or ML pipelines.
• Hands-on with LLM applications or compound AI systems.
• Focused on customers, from APIs and SDKs to debugging another team's agent.
• Comfortable with the ownership and pace of a startup.

Responsibilities

• Architect and build the core platform from zero to one.
• Partner with early design clients and integrate Counterfact into their workflows.
• Develop methods to modularize complex agents, catch ambiguous or inconsistent behavior, and balance cost and quality.

Skills

Staff/Principal level

Backend systems

ML pipelines

LLM applications

Customer-focused

Tools

APIs

SDKs

Cloud infrastructure

Job description

AI reliability is a systems problem, not just a model problem. We build an agent quality harness to trace failures, modularize complex agents, and balance quality, cost, and latency. We're experienced ML engineers building the tools we wished we had for compound AI systems in production. This founding role spans applied research, product engineering, and forward deployed engineering, from inventing methods and building the platform to working with our earliest customers.

What you'll do

• Architect and build the core platform from zero to one.
• Partner with early design clients and integrate Counterfact into their workflows.
• Develop methods to modularize complex agents, catch ambiguous or inconsistent behavior, and balance cost and quality.

Who you are

• 5+ years building software and ML systems at Staff or Principal level.
• A systems thinker with experience in backend systems, infrastructure, or ML pipelines.
• Hands-on with LLM applications or compound AI systems.
• Focused on customers, from APIs and SDKs to debugging another team's agent.
• Comfortable with the ownership and pace of a startup.

What we offer

• Competitive compensation and founding equity.
• Autonomy and impact from day one.
• Direct exposure to investors, advisors, and early design partners.