Agentic Platform Engineer

Ready to leverage your innovative expertise to drive the transition from traditional cloud to autonomous AI platforms? Are you ambitious, equipped with razor-sharp analytical skills, and eager to build the indispensable foundation that our AI and data teams depend on? Do you thrive when given a high degree of autonomy? If so, we are looking for you!

Your Contribution to the Adventure

We stand on the brink of a massive technological acceleration and are going all-in on our 'agentic bet'. As a Senior Agentic Platform Engineer, you will build the crucial infrastructure (the substrate) upon which our Senior AI Engineers and Data Scientists develop their production agents. This is not a code-generation problem we can simply delegate to AI; it is a high-level architectural challenge. You define what 'good' looks like for an agent in production.

What does this entail?

• Ownership of Core AI Infra: In this role, you will own the evaluation harness, agent tracing, the prompt and tool registry (including the MCP protocol), and the routing layer for model calls.
• SaaS Transformation: Additionally, you will transform our DevOps environment into a modern SaaS landscape where agent observability, model gateways, and agent-aware deploy patterns are the standard.
• Modernization & DevOps: Alongside this innovative AI infrastructure, you will take the lead in modernizing and maintaining our current pipelines and core DevOps tasks.
• Tech-Lead Role: You are a true tech-lead of execution and communication: you seamlessly align with other senior developers and translate complex challenges into clear sprints.

Sven’s tip for new 12Builders:

“Finding your own style and using it to inspire your colleagues is strongly encouraged!”

Who is 12Build?

With a healthy dose of Drive, Openness and Happiness, we are building a transparent construction sector. We are not only a SaaS platform that connects construction companies and promotes collaboration, we are also the market leader in the Netherlands. We have been around for almost twenty years and we are still growing. Our team now consists of more than 90 colleagues, working together from two offices and various home offices throughout Europe. A large part of the construction world in the Benelux, Germany and Denmark already works on our platform and uses our software on a daily basis. And we have the ambition to conquer the whole of Europe!

Our Stack & Tools

Within our development team, we are continuously expanding and transforming our SaaS platform with the latest AI and cloud technologies. We work with:

• AI & Agentic Infrastructure: Claude, AWS
• AWS Cloud Services: SNS, SQS, S3, Lambda, RDS, EC2, ECS, and API Gateway
• CI/CD & Automation: GitHub, GitHub Actions, Docker, Terraform, and OpenAPI
• Data & Core Tech: MySQL, OpenSearch, PHP (Laravel), Vue.js (Nuxt/Vuetify), and Node (pnpm/Yarn)
• Collaboration: Linear, Confluence, Slack, and LaunchDarkly

What We Expect from You

• An experienced engineer with a clear technical vision for AI within DevOps and the ability to foster strong team dynamics.
• Deep experience with AWS, GitHub, GitHub Actions, Docker, and Infrastructure as Code (Terraform).
• Demonstrated knowledge of agent observability, evaluation infrastructures, and LLM gateways within a modern SaaS landscape.
• A proactive, hands-on leader ("meewerkend voorman") who takes ownership of ongoing DevOps tasks (such as package updates, fixing vulnerabilities in SPA/AEU, pipeline support, and platform monitoring via tools like LaunchDarkly).
• Analytical, flexible, eager to learn, and always up-to-date with the latest technologies.
• Proven experience in software/platform engineering, preferably within a SaaS environment.

What We Offer You

• A starting salary between €5,800 and €6,600 gross per month (based on a senior job level).
• A 'Lease a Bike' scheme with a €10 monthly employer contr