Senior Software Engineer, Agent Foundations in London

We're hiring a senior engineer for Agent Foundations, the team responsible for how agents work with structured content at Sanity. We own two products: Content Agent and Sanity Context. Content Agent runs content operations (bulk edits, audits, translation, publishing) through conversation in Sanity Dashboard, Slack, Linear and a headless API. Sanity Context is an MCP endpoint that provides structured retrieval and semantic search over a team's live content.

At Sanity.io, we build an AI-powered content operating system that lets teams model, create, and automate content. Our agents need to understand schemas, references and validation rules. You'll work across these systems, owning your domain end to end and working closely with product and design to decide what gets built next.

What you'd be doing:

• Build retrieval and knowledge bases. Turn sources into documents and chunks.
• Develop how knowledge bases are created, kept fresh and scoped, and how agents query them using GROQ, keyword and semantic search together.
• Build MCP endpoints and tools that give agents their interface to our systems.
• Work on agent loops. Write the orchestration logic that controls an agent's actions and their order.
• Engineer system prompts. Give agent instructions the same engineering attention as the code around them.
• Measure and improve reliability, retrieval quality and cost through evals, telemetry and experiments.
• Ship across the stack. Build interfaces in Dashboard and Studio, APIs and backend services.
• Help shape the products. Sanity Context is new and changing quickly.

About you:

• Location: London, UK or Oslo, Norway (in-office 2–3 days/week).
• Strong in TypeScript and React, comfortable working across frontend, APIs and backend (often in Go).
• Shipped LLM-based systems in production and understand the work it takes to make them behave reliably.
• Understand chunking, embeddings, hybrid search and ranking.
• Think through a capability's user intent, edge cases, failure modes and cost before deciding on the architecture.
• Write well and pay attention to how phrasing changes an agent's behaviour.
• Comfortable working with probabilistic systems. Design evals, run experiments and interpret results statistically.
• Experience with MCP, tool-use patterns and agent architectures, or curious enough to explore them.
• Care about the quality of the code and products you ship.
• Don't need to meet every requirement to apply.

What we can offer:

• A highly-skilled, inspiring, and supportive team.
• Positive, flexible, and trust-based work environment.
• A global, multi-culturally diverse group of colleagues and customers.
• Comprehensive health plans and perks.
• A healthy work-life balance that accommodates individual and family needs.
• Competitive stock options program and location-based salary.

Who we are:

Sanity.io is a modern, flexible content operating system that replaces rigid legacy content management systems. We treat content as data so that it can be stored in a single source of truth, seamlessly adapted and personalised for any channel. Forward-thinking companies choose Sanity because they can create tailored content authoring experiences, customised workflows, and content models that reflect their business.

Sanity recently raised an $85m Series C led by GP Bullhound and is backed by leading investors. This funding round has put Sanity in a strong position for accelerated growth in the coming years.

Sanity is a 300+ person company with highly committed and ambitious people. We are pioneers, we exist for our customers, and we love type two fun!

Sanity.io pledges to be an organisation that reflects the globally diverse audience that our product serves. We are committed to equal employment opportunity regardless of race, colour, ancestry, religion, sex, national origin, sexual orientation, age, marital status, disability, or gender identity.