---
title: 'Frontend Engineer at HASH'
canonical: 'https://feeny.ai/job/frontend-engineer-hash-europe-th8xwrhcvj2e'
type: 'job'
last_seen: '2026-09-05'
---

# Frontend Engineer at HASH

- **Company:** HASH
- **Location:** Europe
- **Employment:** full-time
- **Work type:** onsite
- **Posted:** 2026-03-25
- **Last confirmed live:** 2026-09-05
- **Apply:** https://jobs.gem.com/hash/am9icG9zdDqQMHtUeNge_JaikJzJYBPK

## Job description

## About HASH

HASH's open-source platform helps firms integrate both structured and unstructured information into knowledge graphs that support simulating, optimizing and automating processes. Our [mission](https://hash.ai/about/mission) is to solve information failure, and help everybody make the right decisions. To that end, we're unapologetically excited. Actions speak louder than words, and we measure performance by output. We prioritize speed, and measure product delivery timelines in hours and days, not months and years. We value high-energy, high-expectations people who do what they say and say what they mean. We're committed to building a high-commitment, high-trust environment, and believe that the best teams are most productive together, in-person. We're therefore currently hiring exclusively in both London (UK) and Berlin (Germany) to join the firm.

## About the role

We’re a fast-growing deep-tech company crafting web-based tools that help people model, understand, and optimize real-world systems and processes using AI. From interactive process-model editors to real-time simulations, we turn complex, non-textual data into intuitive, responsive, accessible web apps designed to be used by non-technical domain experts at research labs, startups and enterprises worldwide.

As a senior Frontend Engineer you’ll own end-to-end delivery of novel world modeling and AI native interface components, helping shape our frontend architecture, as part of an Advanced Research + Invention Agency funded project building systems for delivering “Safeguarded AI”. You’ll collaborate with technical product management, UX researchers and AI engineers from top labs, as well as our own developers and leadership, to push the boundaries of what a browser can do — whether that’s a drag-and-drop model builder, timeline-based simulator, or multimodal feedback interface.

## What you'll work on

Day to day, you'll:

- Design, build, and ship production-ready React/TypeScript components and app-wide features for complex data-driven UIs
- Work with mathematical experts to convert world-modeling theory formalizations into software requirements, and writing tests which ensure implementation correctness
- Convert novel UX/UI designs — for new world modeling and AI-interaction features — into performant, responsive and accessible experiences that work across devices
- Establish project-wide standards for code quality (e.g. via linting), review and testing, and provide feedback on the work of other frontend engineers
- Profile and optimize rendering performance for complex interactions and visualisations
- Tell the story of best practices and lessons learned in developing and testing novel, complex world-modeling interfaces, e.g. via blog posts and workshops
- Partner with backend/infra teams to identify and manage interdependencies, and to help define robust APIs that support excellent, feature-rich frontend performance
- Stay on top of emerging browser capabilities and drive adoption of the ones that matter

## Requirements

Must have

- Expertise with React, TypeScript, modern HTML & CSS
- Proven track record architecting and delivering rich web apps that involve complex user interactions
- Rigorous approach to documenting and versioning components for external audiences
- Experience profiling and debugging performance in devtools
- Comfortable taking a visible technical leadership role, mediating discussions around standards and implementation approaches, and taking accountability for the delivery of features on time and to spec
- Excellent written & verbal communication in English and comfort working async

## Nice to have

- Familiarity with process/model-oriented UIs: BPMN, UML, systems-dynamics models, graphs, etc.
- Understanding of WCAG 2.2 and pragmatic accessibility techniques (ARIA, focus management, keyboard UX)
- Public record of maintaining a well-documented, semantically versioned library (ideally in an open-source context)
- Experience with CRDTs or other real-time collaboration solutions
- Hands-on experience with WebAssembly pipelines
- Canvas/WebGL experience for high-performance rendering

## Benefits

We offer leading equity-weighted total compensation, including competitive salaries and tax-advantaged options. We also offer:

- Employer pension contributions
- At least 30 days holiday annually
- Quarterly in-person team retreats around the world

HASH's founders have previously founded and sold companies like Stack Overflow and Trello for hundreds of millions and billions of dollars.

This role pays €60,000-€100,000 base/bonus + meaningful equity.

## About HASH

## Company Overview
- **One-liner**: HASH is an open-source platform for decision-making that integrates live data, constructs ontologies, and creates shared understanding through collaborative agent-based simulation and knowledge modeling tools.
- **Entity Type**: Private (Seed stage)
- **Headquarters**: London, United Kingdom
- **Founded**: 2019
- **Founders**: Joel Spolsky and Jude Allred

## Core Business
- Primary industry/industries: Technology, Information and Internet; Business Decision-making Software; Simulation & Modeling
- Target customers: B2B, Enterprise (with a focus on safety-critical supply chain, biopharmaceutical logistics, and complex systems modeling)
- Mission or purpose statement: "Eliminate information failure and help everybody make the right decisions."

## Products & Services
- **[HASH Platform (hash.ai/hash.dev)]**: An open-source, collaborative workspace for structured knowledge that integrates live data, enables ontology construction, and provides fast, distributed agent-based simulation. Combines knowledge capture and modeling tools for complex systems decision-making.
- **Block Protocol (blockprotocol.org)**: An open standard they drive for interoperable, data-driven blocks, contributing to the commons.
- **Open Source Simulation Engine**: Built in Rust/WASM, focused on agent-based simulation and formal verification of distributed systems.

## Market Standing
- **Valuation/Market Cap**: Not disclosed
- **Key Metrics**: Annual Revenue of approximately $1 million; Total Funding of $2.5 million (1 seed round)
- **Notable Investors/Partners**: Zetta Venture Partners (Lead), Root Ventures, with 6 total investors in the seed round. They also work with the Advanced Research + Invention Agency (ARIA) and scientists from the University of Oxford.
- **Growth Signals**: Headcount grew 14.3% YoY (now 9 employees); actively recruiting for new engineering and research roles; conducting high-profile research programs with ARIA and Oxford on safety-critical supply chains; 2,460 LinkedIn followers with 15.6% yearly growth; employer rating of 5.0/5.0 on Wellfound.

## Competitive Advantages
- **Unique Open-Source Approach**: All core tools are open source, building trust and allowing external validation—rare in the decision-modeling space.
- **Technical Moat**: Combines graph-backed world models, formal verification, and agent-based simulation (Rust/WASM) with AI research. Very few companies operate at this specific intersection.
- **High-Impact Focus**: Working on genuinely hard problems (eliminating information failure) with safety-critical applications (supply chains, biopharma logistics), giving them a defensible niche.
- **Elite Talent Sourcing**: Proactively identify and hire exceptional people through their own tooling and community, not just open applications.

## Strategic Focus
- Current priorities: Building a next-generation platform for decision-making via graph-backed world models and AI; expanding into safety-critical supply chain management with government and research partners; advancing their open standard (Block Protocol).
- Direction for growth: Scaling the engineering team (Rust, TypeScript, Python), deepening AI research (graph learning, formal verification), and expanding use cases in complex systems simulation.

## Why Work Here
- **Culture & Work Style**: "We care about output, ownership, and quality." They value raw intelligence, high-energy, and standout performance. The team works in public, contributing heavily to open source.
- **In-Person Focus**: Operates in-person from offices in **London** (HQ) and **Berlin**, with company-wide get-togethers at least twice a year in Europe. Some remote flexibility is available (e.g., Full-Stack Engineer roles can be in-office or remote).
- **Compensation & Perks**: "Leading compensation" with meaningful equity, competitive salaries, an 'unlimited' equipment and learning allowance, and at least 30 days paid time-off each year.
- **Engineering Culture**: Work on hard problems in Rust, TypeScript, and Python, including formal verification, graph learning, and simulation. They emphasize a fast, conviction-based hiring process with decisions made "within days, not weeks."
- **Hiring Process**: A short introductory call followed by a focused work sample or technical deep-dive. Most hires begin with HASH reaching out, but candidates can apply for specific roles.

## Sources
1. [hash.ai](https://hash.ai/careers)
2. [hash.dev](https://hash.dev/careers)
3. [linkedin.com](https://linkedin.com/company/hashintel)
4. [builtin.com](https://builtin.com/company/hash)
5. [jobs.gem.com](https://jobs.gem.com/hash)
6. [blockprotocol.org](https://blockprotocol.org)

## Other roles at HASH

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- [Integrations Engineer](https://feeny.ai/job/integrations-engineer-hash-london-mt5wag63x2eb) — London, United Kingdom
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