Mid-Senior Software Engineer (AI & Research) in London

About Us

At HelloSelf, we provide therapy and coaching to help people feel and live better. Our innovative video therapy platform connects members with the UK's leading psychologists and CBT therapists, offering flexibility and convenience. Utilising technology, we extend the boundaries of traditional therapy, harnessing AI to accelerate progress and promote long‑term wellness beyond treatment. There are substantial unmet mental health needs within the UK and globally. We're on a mission to innovate and make Every Self Better. We're a small, talented, high energy, inclusive and supportive team with strong business and clinical leadership.

About the Role

We're looking for a mid–senior software engineer to join the HelloSelf engineering team — someone who is equally comfortable shipping product features and working on research‑grade software. HelloSelf has built an AI Companion that supports people to feel better sooner — and to stay well for longer. It sits alongside therapy, helping members make progress between and beyond their sessions. The traction it's gained has led to a nearly £5m grant from the Wellcome Trust to adapt the Companion for CIRCuiTS (Computerised Interactive Remediation of Cognition & Thinking Skills), a clinical research programme in partnership with King's College London. Initially you’ll spend the majority of your time working on the engineering delivery of the CIRCuiTS adaptation for the Wellcome funded programme, but you'll also be a contributing member of the HelloSelf engineering team, supporting other product areas and jumping in where needed as we grow. We're a startup of 35 people (7 in the engineering team), and we value engineers who are adaptable and curious about the full stack of what we're building. You’ll report into our Head of AI & Research, with regular touchpoints but a high degree of autonomy. You'll be trusted to take a clearly defined goal and drive it forward — flagging blockers early, proposing solutions, and getting things done.

Key Responsibilities

• Refine and evolve HelloSelf Companion — an AI‑powered mental health product already in people's hands — improving the quality, safety and effectiveness of its AI interactions.
• Design and build new AI‑driven mental health pathways using evidence‑based content, working closely with clinical leads to ensure what ships is both rigorous and genuinely useful.
• Experiment with and integrate the latest LLM tooling, evaluation frameworks and AI techniques — we expect you to stay at the frontier and bring ideas in, not just implement what's specced.
• Direct coding agents as a core part of how you work, using them to move faster without compromising on quality or safety.
• Contribute to code reviews, shared standards and team rituals as an active member of the broader tech team.
• Pick up new areas of the product and support other build teams when needed — we're a startup and context‑switching is part of the job.

Our stack: AWS, React Native, React, FastAPI, NestJS, Scala, Cypress, Maestro. (experience across all is not required)

Delivery of Wellcome grant CIRCuiTS Companion

• Design, build and iterate on the AI companion feature set for the CIRCuiTS platform, working within the scope of the RCT protocol.
• Write clean, well‑tested code (primarily Python) across data pipelines, model integration and evaluation.
• Ensure statistical and technical rigour in collaboration with the external statistician and academic partners including King's College London.
• Contribute to documentation and reproducibility practices that meet research standards.

Stakeholder collaboration

• Engage with external research collaborators (e.g. King's College London) to translate clinical and academic requirements into technical solutions.
• Communicate technical considerations clearly to non‑engineering stakeholders including clinicians, product managers, operations leads and Experts by Experience.
• Surface risks early and keep things moving across an 18‑month programme timeline.

About You

• Mid‑senior software engineering experience with a strong foundation in Python and a track record of shipping production‑quality code.
• Adaptable and comfortable working across different parts of a product — you don't need to own a single lane to do your best work.
• A genuine self‑starter: you can take a defined outcome and drive it forward without heavy oversight.
• Confident communicating across disciplines — you can hold your own in conversations with clinicians, members, statisticians, product managers and experts by experience.
• Familiarity with data pipelines, ML tooling or applied AI is a plus; deep ML expertise is not required.
• Comfortable with ambiguity and the pace of a growing startup.
• Based in or able to commute to London (Shoreditch); two days per week in the office.
• Experience in a research, clinical or academic environment is a nice to have, not a requirement — what matters most is your engineering fundamentals and your ability to adapt.

Compensation, Perks & Benefits

• Salary dependent on experience £75-85k per annum + equity
• AXA private medical insurance.
• Flexible working, with two days per week in our Shoreditch office.
• Exposure to multiple areas of the business, including product, engineering and clinical research.
• Potential to grow into a Lead.
• The opportunity to build something that will genuinely improve how mental health care is delivered at scale.