Software Engineer III in London

Trusted Connectivity for AI-Powered Dominance. Everfox delivers trusted connectivity to protect the world’s most critical environments and safeguard the sensitive data powering decision advantage. Built for mission-critical operations, Everfox protects what matters most by securing how data moves, how users access it, and how threats are neutralized across every domain. We enable mission speed and secure collaboration across networks, domains, and allies, while ensuring the data powering AI and advanced analytics remains trusted and protected.

Our Purpose: Protect what matters most by enabling organizations to operate security in the most complex and high-risk digital environments.

Our Vision: To be the most trusted authority in high-assurance cybersecurity, enabling secure collaboration across every domain.

Our Belief: Security should never limit mission success – it should enable it.

Our Promise: We deliver absolute confidence in environments where failure is not an option.

This role suits a strong developer who enjoys landing in unfamiliar code, working out how it fits together, and making it better. You will work on a rolling series of projects across the business, each typically lasting one to six months, adding AI-driven features to our products and using AI tooling to improve how we write, test and ship software.

Key Responsibilities:

• Design, implement and maintain features and components across a range of internal codebases, in whichever languages and frameworks each project requires.
• Add AI-driven capability to our products: model and API integration, prompt and context design, retrieval, tooling and agent orchestration, plus the plumbing around it such as data handling, caching, error handling, cost and latency management, and graceful behaviour when a model is unavailable or wrong.
• Build evaluation and testing around AI features so that behaviour is measurable rather than anecdotal, and quality does not regress as models, prompts and dependencies change.
• Use AI tooling and agentic workflows in your own day-to-day development to improve speed and quality, and build the reusable pieces that let others do the same.
• Prototype quickly to de-risk the harder or less well understood problems, and be willing to conclude that an approach is not worth pursuing.
• Work as a guest in codebases owned by other teams: agree scope and approach up front, follow their conventions, and get changes reviewed and merged rather than left on a branch.
• Work with Product Managers, QA and the owning engineering teams to turn a broad ask into well-scoped technical work with a clear definition of done.
• Hand over cleanly at the end of each project. Leave tests, documentation, agent tooling and enough context that the owning team can support and extend what you built.
• Share what you learn. Each project should make the next team's job easier, whether through reusable components and tooling, patterns, internal write-ups or informal coaching on AI tooling.
• Keep your progress, risks and blockers visible to your line manager and to the teams you are working with.

Quality, security and improvement:

• Take responsibility for the quality of what you ship: automated tests, code review, sensible logging, and thinking through failure modes rather than assuming the happy path.
• Apply appropriate care to security and data handling when introducing AI components.
• Contribute to CI/CD, automation and developer tooling improvements where they unblock the work in front of you.
• Help us build a shared view of what good looks like for AI in our products and in our development process.

Key Knowledge and Skills:

• A degree in Computer Science, Engineering, or a related technical or scientific subject, or equivalent practical experience.
• Solid commercial software development experience, with a track record of shipping working software that other people rely on.
• Genuine language flexibility: strong in at least one language, and comfortable becoming productive in others as projects demand.
• A good grasp of core computer science concepts: data structures and algorithms, concurrency, networking, APIs and interfaces, testing, and the basics of software security.
• The ability to reason about a system you did not build: read unfamiliar code, form a mental model, identify where a change belongs, and understand its knock-on effects.
• Practical experience using modern AI development tooling, or clear evidence that you have taught yourself new tooling and techniques quickly and applied them to real work.
• Strong communication and collaboration skills.
• Self-motivated, flexible and adaptable, and comfortable being thrown in at the deep end on an unfamiliar project.

Nice to have:

• Hands-on experience with agentic coding tools such as Claude Code, Codex or similar.
• Experience extending those tools rather than just using them out of the box.
• Experience integrating LLMs or other models into production software.
• Experience evaluating AI systems.
• Experience improving an existing or legacy codebase.
• CI/CD experience with tooling such as GitLab, Docker and Kubernetes.
• Experience working in security-sensitive or high-assurance environments.
• A passion for technology, shown through project work, professional roles or personal projects.
• Awareness of usability and user experience.
• Empathy, a habit of open communication and effective feedback.

A reasonable estimate of the base salary range for this role is: £59,200.00-97,000.00 GBP. The actual salary offered may vary within the range based on a candidates' unique experience, locale, and business needs. In addition to base salary and either bonus or commission, Everfox offers a generous benefits package including competitive annual leave, pension match, PMI, dental, health cash plan, income protection, in a hybrid work environment.

Everfox is an equal employment opportunity employer and complies with all applicable federal, state, and local laws prohibiting discrimination.