Senior Backend Engineer - Agent SDK

As Senior Backend Engineer on the team behind our Agent SDK, you build and maintain the Kotlin foundation that our AI agents move onto. Your work makes the cost of the second and third agents visibly less than the first, so feature teams can ship at their own pace.

What you'll do

• Build and maintain the SDK as an internal product, shaping the runtime and client-facing contracts that consuming teams build on.
• Build the identity layer that agents run on, so customer-facing agents can write with a real user identity.
• Make every agent observable from the day it launches by wiring telemetry and error reporting into the SDK by default.
• Build the test kit that the SDK needs, including architecture tests that protect the runtime internals.
• Absorb ecosystem change on behalf of consuming teams, owning version bumps and format compatibility.

What you'll need

• Several years of production backend experience on the JVM — Kotlin, Java, Scala or similar.
• You have designed APIs that other engineers build against, such as an SDK or internal platform.
• You have built and maintained integrations and kept them stable when the system on the other side changed.
• Testing and observability are part of how you build.
• You are drawn to AI agent systems and to the orchestration and evaluation work underneath them.

What they offer

• 30 vacation days plus your birthday off
• Stock options
• Germany Transport Ticket, Urban Sports Club membership
• Flexible working hours and hybrid setup
• Access to learning platforms (Blinkist, Audible) and free language courses
• Regular company off-sites