Full Stack Engineer

Fontana AI; Acton Round; On-site; GBP 70,000 - 120,000; Full time

Job summary

Fontana AI is building Fontana Flow, an AI-native platform for governed agents and data pipelines. We seek a Full Stack Engineer to advance the UI, backend, and real-time systems that power agent harnesses, knowledge graphs, and deterministic workflows.

You will ship end-to-end features across the UI and typed API layers, work with a reactive data model, and contribute to documentation and testing in a fast-paced environment.

Qualifications

• Proficient TypeScript and modern React development.
• Experience shipping full-stack features across UI and API layers.
• Comfortable working with reactive/real-time data.
• Ability to write clear documentation and communicate well.
• Familiarity with AI-assisted development and human-in-the-loop shipping.

Responsibilities

• Build end-to-end product slices from React UI to backend services.
• Develop Flow UI with interactive canvas and real-time controls.
• Enhance Knowledge Graph for context, lineage, and data modelling.
• Implement Agent Harness features including Tools, Skills, and model access.
• Ensure deterministic back-end workflows and robust RBAC.

Skills

TypeScript

React

Full-stack

Reactive data

Documentation

Tools

Convex

Kubernetes

Docker

Node.js

PostgreSQL

AWS

Job description

Full-time

Flexible hours.

Full Stack Engineer

Build Flow — the governed AI platform where operators author AI Agent, design data pipelines, and run deterministic workflows.

What Flow is

Agent Harness

Knowledge Graph

Workflow Engine

Fontana Flow is an Agent Harness, Knowledge Graph, and Workflow Engine integrated as a governed AI platform for organisations with strict compliance, audit, and operational control requirements.

Clients use it to author AI Agents, design data pipelines on an interactive canvas, run them on a reactive server-side engine, and layer governed AI agents on top with tools, skills, and approved model access. Every workspace is isolated; every privileged action can leave audit evidence.

Engineering at Fontana

We build software the AI-native way: agents write, review, and ship alongside humans. On a busy weekend we have spun up 5,000+ development agents. You will design work so fleets of agents can move fast — and so humans stay in the control path for what matters.

Our Slack workspace has more Agents and AI employees than humans. We build for a future where code and contributions flow from many hands, some human, some not.

Does this sound chaotic rather than exciting? This role is not for you.

Sounds like the only sane way to ship in 2026? Keep reading.

What you will be working on

End-to-end product slices

React UI → Convex backend → tests → docs.

Flow UI

Interactive canvas, workflow authoring, data pipeline controls, and real-time product surfaces.

Knowledge Graph

Operational context, lineage, file and skill surfaces, and evidence-aware data modelling.

Agent Harness

Agents, Skills, Tools, MCP connections, Agent Interop, approved model access, and human-in-the-loop controls.

Reactive backend

Real-time Convex queries, mutations, and actions with auth, RBAC, and fail-closed behaviour.

Workflow engine

Deterministic execution, lineage, connectors, and server-side orchestration.

Our Stack

• React 19
• TypeScript
• Vite
• Tailwind
• Convex
• Zitadel
• Node JS
• Postgres
• Vault
• Airbyte
• Docling
• OpenSandbox
• Kubernetes
• K3s
• Docker
• AWS
• Helm
• Terraform
• Traefik
• Gatus
• HyperDX / OTLP
• React-flow
• Python
• Vitest
• Playwright
• ...and more

You'd be a strong fit if you

• Write strong TypeScript and modern React.
• Ship full-stack features across UI and typed API/data layers.
• Are comfortable with reactive / real-time data.
• Test behaviour that can actually break.
• Communicate clearly in writing so agents and teammates can continue your work.
• Comfortable using Cursor as the primary dev IDE.
• Already work comfortably with AI-assisted development, agent review loops, and human-controlled shipping.
• Can operate around DevOps, AWS, Kubernetes, and production systems without drama.
• Understand why compliance evidence matters: SOC 2, ISO 27001, DORA, audit trails, access control, retention.

Bonus signals

• Convex, Firebase, or similar reactive backends.
• Canvas / editor / data-grid product surfaces.
• Workflow, ETL, or financial-ops tooling.
• Monorepo discipline and real AuthZ.
• CRDT principles.
• Audit trails, fail-closed paths, and evidence — not vibe-based "ship it".

SOC 2ISO 27001DORAAWSK8s

Location

• First round: London applicants
• Second round: UK applicants
• Third round: EU applicants
• Forth round: Global applicants

How we work

Flexible

Flexible hours.

AI-first

Agents and humans ship alongside each other.

Low theatre

Direct access to founders — no ticket theatre, no six-layer approval stack.

We prefer clean architecture over hacks. Specs and docs stay in sync with the code.

React 19TypeScriptViteTailwindConvexZitadelNode JSPostgresVaultAirbyteDoclingOpenSandboxKubernetesK3sDockerAWSHelmTerraformTraefikGatusHyperDX / OTLPReact-flowPythonVitestPlaywright...and more