Software Engineer jobs in United Kingdom

Reflection’s mission is to build open superintelligence and make it accessible to all.

We’re developing open weight models for individuals, agents, enterprises, and even nation states. Our team of AI researchers and company builders come from DeepMind, OpenAI, Google Brain, Meta, Character.AI, Anthropic and beyond.

• Build the core software systems and tools that power our research, training, and production environments.
• Design and implement reliable, scalable, and secure services to support model development, deployment, and evaluation.
• Develop APIs, SDKs, and internal platforms that enable rapid experimentation and high‑velocity iteration.
• Drive engineering excellence and create the foundation for our next generation of AI models.
• Provide the foundational layers that unify data, compute, and workflow management across model development.

• Strong software engineering background with experience shipping production‑grade systems.
• Experience designing APIs, services, or developer platforms that handle large‑scale data or compute.
• Comfortable navigating complex codebases, debugging hard problems, and optimizing for reliability and speed.
• Thrive in a high‑agency, fast‑paced startup environment; bias toward action and impact.
• Excited about zero‑to‑one challenges, building new systems rather than maintaining legacy ones.
• Collaborative, clear communicator, and comfortable working across research and infra boundaries.
• Motivated by creating the software backbone for the world’s most capable open‑weight AI systems.

We believe that to build superintelligence that is truly open, you need to start at the foundation. Joining Reflection means building from the ground up as part of a small talent‑dense team. You will help define our future as a company, and help define the frontier of open foundational models.

We want you to do the most impactful work of your career with the confidence that you and the people you care about most are supported.

• Top‑tier compensation: Salary and equity structured to recognize and retain the best talent globally.
• Health & wellness: Comprehensive medical, dental, vision, life, and disability insurance.
• Life & family: Fully paid parental leave for all new parents, including adoptive and surrogate journeys. Financial support for family planning.
• Benefits & balance: paid time off when you need it, relocation support, and more perks that optimize your time.
• Opportunities to connect with teammates: lunch and dinner are provided daily. We have regular off‑sites and team celebrations.