Staff Software Engineer, Full Stack (Agentic Payment)

Sapiom • San Francisco, CA

2d • Onsite

About The Position

Sapiom builds payment infrastructure that lets AI agents make purchases on behalf of people and businesses within owner-defined permissions and spending rules. The Staff Software Engineer will own a major part of the product and help set its architecture while the company and product are still taking shape. This is an in-office role in San Francisco.

The work includes defining how owners grant agents authority and how limits are enforced before payments move; building reliable purchase completion across varied merchant checkout experiences; handling uncertain payment outcomes without charging customers twice; maintaining durable, versioned records of what a buyer saw and agreed to; and designing a public API and agent-facing tools that models can use correctly. The broader product path spans customer and agent connection, card vaulting, agent identity, rule enforcement, payment processing, and making purchase outcomes understandable.

Requirements

• At least 8 years of experience building production software, including several years in payments, money movement, or financial infrastructure.
• Experience owning architecture from first principles, including setting and defending a design and living with its tradeoffs.
• Experience designing for failure in high-consequence systems, including idempotency, retries, and reconciliation.
• Strong TypeScript skills and the ability to build interfaces on top of systems you develop.
• Experience leading a multi-month project from a problem statement rather than a specification, with other engineers building on the resulting work.
• Use of AI tools in your engineering workflow.

Nice To Haves

• Experience with card issuing, tokenization, or PCI scope.
• Deep experience with checkout integrations.
• Experience with browser automation or request interception.
• Experience shipping something an LLM calls as a tool.
• Experience at early-stage companies where you set architecture rather than inheriting it.

Responsibilities

• Set the architecture and design for a substantial part of the product.
• Design how owners grant agents spending authority and how those limits are enforced before money moves.
• Build reliable purchase completion across diverse merchant checkout flows, including flows with steps that expect human interaction.
• Design systems that determine what happened when a payment outcome is uncertain and prevent duplicate charges.
• Create versioned, durable records of what buyers saw and agreed to, suitable for later dispute review.
• Design the public API and agent-facing tools and contracts.
• Lead multi-month projects from problem statements and deliver systems that other engineers can build on.

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed