Staff Product Engineer, Enterprise AI - Mozilla

Why Thunderbird?

Thunderbird is one of the world’s most trusted open-source email applications, empowering more than 20 million people globally. At Thunderbird, we build privacy-respecting communication and productivity tools that help people manage their digital lives while staying in control of their data.

We are open source by design. Our products are developed transparently and in collaboration with a global community of contributors, and that same spirit shapes how we work: collaboratively, inclusively, and with a shared commitment to putting users first.

Our small but growing distributed team includes more than 65 people across seven countries. As Thunderbird evolves beyond a single desktop application, we are expanding across desktop, mobile, paid services, AI offerings, and enterprise-facing work to build independent, privacy-respecting alternatives to big tech ecosystems.

Our revenue model combines user donations, which help keep Thunderbird’s applications freely available, with paid services that cover the costs of hosted offerings while supporting long-term sustainability and continued innovation.

A note about Thunderbird and Mozilla: Thunderbird Technologies Corporation is the nonprofit-owned company behind Thunderbird email and a growing portfolio of products. While part of the Mozilla family, Thunderbird is a separate entity from Mozilla Corporation and Mozilla Foundation with its own compensation programs, benefits, and employment policies.

The Opportunity

Thunderbird is expanding beyond email with Thunderbolt, an open-source AI client designed for organizations that need more control over their data, infrastructure, and model choices.

We’re looking for a Staff Full-Stack Product Engineer: a full-stack engineer who ships production code and works directly with the partners and enterprise customers adopting Thunderbolt. You’ll spend most of your time in the codebase, building the features, integrations, and customizations that real deployments need. The rest of your time goes to working alongside technical partners to get those deployments running and keep them healthy.

Thunderbolt is delivered largely through technical partners and systems integrators who own the day-to-day customer relationship. You’ll be the engineer behind them. You’ll understand how a customer’s environment actually works, turn that understanding into working software, and fix the hard problems that need someone who knows the code.

What You’ll Do

• Build and ship full-stack features, integrations, and customer-specific customizations in the Thunderbolt codebase, from front-end UI through APIs, services, and deployment configuration.
• Work directly with technical partners and enterprise customers to understand their environments, requirements, and constraints, and turn them into technical plans and working software.
• Support pilots, proofs of concept, and early production deployments, including partner-hosted and customer-controlled environments.
• Diagnose and fix complex issues across the application, infrastructure, identity and access, integration, and data-access layers, including bugs and regressions that need a code change and a release.
• Maintain customer-specific customizations over time so they keep working as the core product evolves.
• Spot which customer requests should become general product capabilities, and work with product and engineering to build them that way rather than as one-offs.
• Bring real-world deployment feedback into roadmap and prioritization discussions.
• Write the documentation, deployment guidance, and runbooks that let partners handle routine issues on their own.
• Use AI-assisted development tools thoughtfully to move quickly while keeping strong judgment about quality, security, and maintainability.

What You Bring

• 10+ years of professional software engineering experience, including significant time building and shipping production applications with Staff-level scope and impact.
• Strong full-stack engineering skills, including modern TypeScript or JavaScript, component-based front-end frameworks, and back-end services, APIs, and integrations.
• Meaningful experience working directly with customers, partners, or systems integrators in a technical capacity where you also wrote the code.
• Experience building or supporting AI-enabled applications, such as LLM platforms, RAG systems, agents, enterprise search, or data connectors.
• Solid understanding of enterprise deployment concerns, including authentication and identity providers, access control, self-hosted and hybrid infrastructure, observability, and reliability.
• Judgment about when to build something custom, when to generalize it into the product, and when to push back on a request.
• Clear communication skills with both technical implementers and non-technical stakeholders.
• Strong collaboration skills, including experience working closely with product managers, designers, engineers, and other cross-functional stakeholders.
• Comfort operating independently in an early-stage product where requirements, architecture, and processes are still taking shape.