Senior Full Stack Engineer

We're a team of machine learning engineers training task-specific generative models for psychology. Our goal is to build an AI therapist to help people change their mind and their lives in the ways that they want to. We partner with organizations around the globe and power use cases, including AI-assisted crisis text response, while securing best-in-class datasets to power our models.

Success to us means every human being in need of support having somewhere to go. We're a well-funded, seed-stage startup backed by top-tier tech investors involved in Huggingface, ElevenLabs, Replit, Captions, Shopify, Plaid, Notion, Canva, Twitch, Airtable, and others

We're building a powerful team by empowering our engineers with the autonomy, flexibility, and resources to do their best work. We dream big and iterate fast. If that sounds like home, we'd love to hear from you.

The Role

This is a chance to join a passionate team leveraging cutting-edge AI to improve mental health access globally. As a Senior Full Stack Engineer, you will play a critical role in building the user experience for our AI Therapy application, Ash. You will work closely with our ML team to implement new features, ranging from UX improvements to completely new AI-driven features. As a core member of a small but highly skilled team, we expect you to act as an owner and to care passionately about keeping building meaningful experiences for our end users.

Our tech stack uses Dart/Flutter for our apps, Kotlin for core backend services, Python for our ML work, as well as Rust for low level media streaming. We use gRPC and GCP (Kubernetes, Cloud Run) as our primary cloud provider. You’re not required to be an expert in all of these tools, but we would like you to come with a learning mindset and to not be afraid of getting your hands dirty with whatever tool the job might require.

About You

• You have experience building and shipping mobile-first consumer apps and are comfortable working across the stack and designing end-to-end user features. Experience with modern multi-platform frameworks like Flutter, React Native, Ionic, or similar is a big plus.
• You understand the broader picture of software development—things like app performance, UX tradeoffs, analytics, and crash reporting. And navigate the nitty-gritty of mobile app development, such as offline functionality, push notifications, or deep linking.
• You're highly autonomous and love tackling big, ambiguous problems. You don't wait for someone to tell you what to do—you figure it out. You're always learning and happy to pick up new tools and frameworks on the go.
• You're a team player who cares deeply about product quality and impact. You take ownership of your work, but you're always thinking about how it fits into the bigger picture and how to move the whole product forward.
• You can ship fast. We work at lightning speed.

Requirements:

• 3+ years of software development experience, with a strong focus on mobile-first applications
• Experience building and maintaining consumer-facing apps using modern development frameworks (e.g., React, Vue, Ionic, Flutter, Kotlin Multiplatform, etc.)
• JVM experience is a plus (Java, Kotlin), or at least a strong willingness to learn
• Based in London or New York - we’re operating on a hybrid basis but love spending time together in person
• Experience working in a fast-paced, <100 person startup environment, is a strong plus

Why you should take this job:

• You want to build things that matter. You love seeing your creations come to life and get used, whether that’s a small prototype demonstrator or foundations behind the scenes.
• You want first hand experience of AI and Machine Learning in practice. You’ll be part of a team that pushes the frontiers of how modern AI can be employed to make a difference.
• You want direct exposure and mentoring from a founding team with a successful exit and track record (Neil scaled Casper through IPO)
• You care about our mission, and are willing to do what it takes to make it happen

Why you shouldn’t take this job:

• You would rather be told exactly what to do than to act as an owner
• You see yourself as “fully formed” and would rather not have to learn new things on the job

What We Offer

• Competitive compensation (90th percentile)
• Hybrid environment, highly collaborative, fast-paced culture
• Work with a crazy passionate team that cares deeply about the impact of our work on mental health, especially in a post-AGI world