Staff Software Engineer, Full Stack (Agentic Payment)

Sapiom • San Francisco, CA

16h

About The Position

Sapiom builds payment infrastructure that enables AI agents to make purchases on behalf of people and businesses, with permissions, protected card credentials, and spending rules. The Staff Software Engineer, Full Stack will own the design of a significant part of the product as the company builds dependable agentic payment systems. This staff-level role is intended for someone who can shape architecture while the product is still evolving and take responsibility for the consequences of those design decisions.

The work spans the purchase lifecycle: connecting customers and agents, vaulting cards, establishing agent identity, enforcing spending rules, moving payments, and recording outcomes. Areas of focus include defining how agent authority and spending limits are enforced, making merchant checkout reliable across varied flows, handling uncertain payment outcomes without duplicate charges, maintaining durable records of what buyers saw and agreed to, and designing a public API and agent-facing tools that models can use correctly. The role involves solving payments problems where reliability, reconciliation, and evidence matter.

Requirements

• At least 8 years of experience building production software.
• Several years of experience in payments, money movement, or financial infrastructure; depth in the domain is sought.
• Experience owning architecture from first principles, including setting and defending designs and living with their costs.
• Experience in environments where mistakes were expensive, with designs that account for failure, including idempotency, retries, and reconciliation.
• Strong TypeScript skills and the ability to build interfaces as well as backend systems.
• Experience leading a multi-month project from a problem statement rather than a specification, with results used by other engineers.
• Use of AI tools in personal engineering workflows.

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 a product or system that an LLM calls as a tool.
• Experience at an early-stage company where you set architecture rather than inheriting it.

Responsibilities

• Set the architecture and design for a substantial part of Sapiom’s product.
• Design how customer-granted authority and spending limits are enforced before money moves.
• Build reliable purchase completion across merchants with different checkout behaviors and human-dependent steps.
• Design payment recovery and reconciliation processes that determine what happened before taking further action and prevent duplicate charges.
• Create versioned records of what a buyer saw and agreed to, so they remain useful in later disputes.
• Design and build the public API and tools used by agents.
• Lead multi-month projects from problem statements and deliver systems that other engineers can build on.
• Build across the full stack, including the interface on top of the systems developed.

What This Job Offers

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