Senior Software Engineer - Harness Team

Why Kimchi?

Kimchi is the AI platform inside CAST AI. We started by helping companies run LLMs on their own Kubernetes clusters and now we're providing a managed variant of those same capabilities.

Our Infrastructure today

Multi-model inference (MiniMax, Kimi, GLM-5, Nemotron, DeepSeek) with intelligent routing, an OpenAI-compatible API and deployment ranging from our GPUs to your own VPC. The inference layer is the foundation and the API is what sits in front of it as the primary channel for broadly and reliably distributing our AI services and powers our own Kimchi harness.

As a Senior Software Engineer, you will have the opportunity to work on different key features of our product. All of these are high-agency roles across multiple parts of the tech stack that minimize process friction that would otherwise prevent you from shipping.

In every team you will own features end-to-end: design, implementation, testing, production rollout. Most projects ship in 1-4 weeks. You'll work directly with product and other engineering teams on problems that don't have textbook solutions.

We are currently hiring Senior Software Engineers for the Harness team:

OpenAI and Anthropic ship models. They also ship one harness each – the scaffolding that turns a raw model into something that can plan, execute, recover, and complete work. We ship a different kind of harness: one built for cost-conscious, long-horizon autonomy, running on inference infrastructure we control end-to-end.

A decent model with a great harness beats a great model with a bad harness. We've watched this play out. The gap between what today's models can do and what you see them doing is largely a harness gap – and that gap is where we operate.

Responsibilities:

• Architect planner/executor/evaluator pipelines – planning with a reasoning model, execution with a fast one, evaluation with a third. No self-verification.
• Manage agent memory and context – state persistence across sessions, context compaction, tool-call offloading
• Own the harness surface - TUI, MCP integrations, telemetry.
• Work directly with users - including our own colleagues - to identify, understand and fix pain points

Requirements

• Production experience with Go or Typescript is strongly preferred; candidates without either should demonstrate strong systems programming skills in a comparable language.
• Strong debugging, optimization, and performance-tuning skills – including query profiling, index design, and database performance tuning beyond ORM usage.
• Hands-on experience with cloud platforms (AWS, GCP, or Azure) and Kubernetes is a strong plus
• Observability tooling (Prometheus, Grafana, OpenTelemetry), CI/CD and DevOps practices experience.
• Startup mindset: adaptable, proactive, and comfortable with ambiguity.
• Strong English skills, both verbal and written.
• You've personally driven a complex project end-to-end.
• (Harness) Experience on working with harnesses and creating your own AI workflows is a strong plus

What’s in it for you?

• Competitive salary (€6,500 - €9,000 gross, depending on the level of experience).
• Enjoy a flexible, remote-first global environment.
• Collaborate with a global team of cloud experts and innovators, passionate about pushing the boundaries of Kubernetes technology
• Equity options.
• Get quick feedback with a fast-paced workflow. Most feature projects are completed in 1 to 4 weeks.
• Spend 10% of your work time on personal projects or self-improvement. 
• Learning budget for professional and personal development - including access to international conferences and courses that elevate your skills.
• Annual hackathon to spark new ideas and strengthen team bonds.
• Team-building budget and company events to connect with your colleagues.
• Equipment budget to ensure you have everything you need.
• Extra days off to help maintain a healthy work-life balance.

Hiring process

• Screening call with Recruiter
• Hiring Manager interview
• Technical interview (system design)
• Live coding
• Culture Check interview with an executive

As part of our standard hiring process, we would like to inform you that a background check may be conducted at the final stage of recruitment through our third-party provider, Checkr.
Please note that Cast AI does not provide any form of visa sponsorship/work permit.

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