Member of Technical Staff Open Source Lead

Methodfi; Greater London; On-site; GBP 60,000 - 80,000; Full time

Job summary

A cutting-edge AI research company in Greater London seeks experts in AI development to join its team. The role involves developing open-source tools for community engagement and requires strong software engineering skills with a focus on Python and deep learning frameworks. Ideal candidates will have a graduate degree in a related field and a robust portfolio of contributions. The position offers top-tier compensation, health benefits, and an inclusive work environment.

Benefits

Top-tier compensation

Comprehensive medical, dental, vision insurance

Fully paid parental leave

Paid time off

Daily lunch and dinner provided

Qualifications

• Strong portfolio of open source contributions, particularly in LLM tooling.
• Deep understanding of post-training techniques (SFT, RLHF, DPO).
• Solid software engineering capabilities with experience designing library APIs.

Responsibilities

• Own the development of the deployment ecosystem for Reflection’s models.
• Build the RL and SFT tooling for external developers.
• Create Reflection-native libraries for performance or flexibility.

Skills

Open source contributions

Post-training techniques

Software engineering

Python

Deep learning frameworks

Education

Graduate degree in Computer Science or related discipline

Tools

PyTorch

Job description

Our Mission

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.

About the Role

• Own the development of Reflection’s open post-training and inference and deployment ecosystem, creating the standard for how the community customizes and interacts with our models

• Build the RL and SFT tooling that external developers use to customize, fine-tune, and align models for their specific need, as well as taking the lead on inference and deployment.

• Extend or integrate with existing best-in-class frameworks (e.g., VeRL, torchtune, Tunix, vLLM, SGLang) to meet developers where they are.

• Create Reflection-native libraries when required for performance or flexibility, ensuring our open-weight users have a clean, powerful, production-grade toolkit.

• Drive the adoption of our models by reducing friction in the fine-tuning process, ensuring adaptation is safe, efficient, and scalable.

• Engage deeply with the open-source community to incorporate feedback and guide the roadmap of our external-facing tools.

About You

• Graduate degree (MS or PhD) in Computer Science, Machine Learning, or related discipline, or equivalent practical experience in open source software.

• Strong portfolio of open source contributions, particularly in the LLM tooling space.

• Deep understanding of post-training techniques (SFT, RLHF, DPO) and the engineering challenges of applying them to large models.

• Solid software engineering capabilities with experience designing library APIs that are intuitive and robust.

• Proficient in Python and deep learning frameworks (PyTorch preferred).

• Thrive in a fast-paced, high-agency startup environment with bias toward action.

• Passionate about advancing the frontier of intelligence.

What We Offer:

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.