As a Senior Software Engineer, AI - Simulation, you will own Brex's simulation and validation platform for AI-powered products. Your mandate is simple and unforgiving: ensure that every AI surface at Brex is continuously scrutinized under extreme, realistic conditions , and that teams can ship with confidence because of it.

You'll build a system that uses synthetic data and scenario generation as a recursive self-improvement loop. Product teams will rely on it to catch regressions before customers do, to validate new capabilities safely, and to evolve prompts and agent behavior continuously. This platform will run against isolated, ephemeral environments that mirror production closely enough to matter.

This role will be based in our Seattle office. We are a hybrid environment that combines the energy and connections of being in the office with the benefits and flexibility of working from home. We require three coordinated days in the office per week , Monday, Wednesday, and Thursday.

Responsibilities:

• Evolve and scale a simulation and validation platform to continuously stress-test Brex’s AI products using large-scale synthetic data.
• Develop evaluation mechanisms to detect regressions, edge cases, and failure modes in non-deterministic systems prior to customer impact.
• Run continuous testing in isolated, production-like environments and set quality gates, including authority to block launches when standards are not met.
• Partner closely with product engineering teams to improve system testability, isolation, and overall robustness.
• Define and uphold company-wide standards for AI feature quality, using simulation-driven insights to guide prompt and system evolution, while driving the technical bar for a small, high-impact team.

Requirements:

• Experience building and owning complex software systems where correctness, reliability, and failure modes are critical.
• Experience designing test, simulation, or validation systems for non-deterministic or high-stakes environments.
• Strong systems thinking, with the ability to decompose complex problems and reduce incidental complexity.
• Demonstrated ability to influence product architecture through quality, reliability, and launch-readiness constraints.
• Comfort operating with real authority and cross-team influence, including blocking launches and partnering across seniority levels to raise the quality bar.

Bonus points:

• Previous experience on simulation or testing of inherently complex systems (AI/ML, distributed systems, robotics, IoT, medical devices, aerospace, defense, etc.).
• Experience building internal platforms that became critical shared infrastructure.
• Strong intuition for failure modes in real-world systems.

Compensation: The expected salary range for this role is $192,000 - $240,000. However, the starting base pay will depend on a number of factors including the candidate’s location, skills, experience, market demands, and internal pay parity. Depending on the position offered, equity and other forms of compensation may be provided as part of a total compensation package.

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This role is part of the Hivemind Solutions organization and leads a team of engineers to deliver cutting-edge autonomous capabilities for business-to-business and defense contracts. The ideal candidate has defense industry experience as a Chief Engineer and a proven track record of leading technical teams to develop and deploy autonomous systems.

Key responsibilities include serving as the Chief Engineer on Shield AI projects focused on developing and deploying autonomy solutions for unmanned aircraft, leading a team responsible for advancing Hivemind Autonomy and shaping Department of Defense (DoD) autonomy architectures, defining and assigning technical objectives, making key engineering decisions, and ensuring the quality and completeness of all technical deliverables.

The Chief Engineer will provide technical leadership and oversight across both Internal Research and Development (IRAD) initiatives and DoD contracts, and contribute to government contract proposal writing. Excellent communication and leadership skills are required, with the ability to drive a team of 6-20 engineers.

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As the Head of Global Markets, you will be a foundational leader within our Prime Services business. Reporting directly to the Global Head of Prime Services, you will be responsible for the strategic vision, P&L, and institutional scaling of the Global Markets division.

This role is designed for a builder who has successfully managed business units generating $100M+ in annual revenue and oversaw substantial institutional-scale balance sheets. You will lead a high-performing organization of 20+ professionals, ranging from junior staff to Managing Directors.

Responsibilities

• Strategic vision, P&L, and institutional scaling of the Global Markets division
• Leading a high-performing organization of 20+ professionals
• Building and deeply understanding the product at a technical level
• Navigating selling ahead,driving revenue where the product is now while simultaneously building a pipeline for where the product will be

Technical Skills

• Applied expertise in Global Markets, including Spot, Prime Financing, and Derivatives
• Risk management leadership
• Capital optimization
• Revenue engineering
• Product architecture

Complexity and Impact of Work

• Strategic risk partnership
• Dual-track revenue strategy
• Leader of leaders
• Strategic path ownership
• 24/7 operational resilience

Organizational Knowledge

• Commercial synergy
• Risk alignment
• Institutional navigation
• Culture and morale

Communication and Influence

• Executive leadership alignment
• External authority
• Consensus builder
• Mentorship of leaders

Requirements

• 12-15+ years of senior leadership in Global Markets or Prime Services at a top-tier investment bank, hedge fund, or major digital asset platform
• Direct experience building or managing a business unit with $100M+ in annual revenue
• Proven experience managing a team of 20+ professionals
• Direct experience managing substantial institutional-scale balance sheets
• Deep functional understanding of Spot, Prime Financing, and Derivatives
• Experience navigating the growth journey of a company toward an IPO or significant liquidity event

Bonus Points

• Experience working in a 24/7, high-growth environment
• Sophisticated understanding of digital asset market structure

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