Senior Software Engineer, Developer Experience

Block is one company built from many blocks, all united by the same purpose of economic empowerment. The blocks that form our foundational teams — People, Finance, Counsel, Hardware, Information Security, Platform Infrastructure Engineering, and more — provide support and guidance at the corporate level. They work across business groups and around the globe, spanning time zones and disciplines to develop inclusive People policies, forecast finances, give legal counsel, safeguard systems, nurture new initiatives, and more. Every challenge creates possibilities, and we need different perspectives to see them all. Bring yours to Block.

The Role

Our engineers are only as effective as the tools, codebase, and workflows around them. As a Developer Experience Engineer, you’ll make our large, evolving codebase easier to build, change, and reason about, for both human developers and AI agents.

You will be responsible for the developer experience in our largest monorepos: building tools for and driving framework and language migrations, keeping dependencies healthy, improving build and test infrastructure, and shaping how agentic workflows operate in our development process. This is a high-leverage role. Every improvement you ship multiplies across the whole engineering organization.

What you’ll do

• Lead and execute large-scale changes across the codebase, including framework upgrades, language migrations, and dependency updates, with minimal disruption to product teams
• Design and evolve agentic loops: the plan, act, verify, and iterate cycles that let AI agents do real engineering work safely and reliably
• Identify friction in the developer workflow (slow builds, flaky tests, confusing abstractions) and fix the root causes
• Improve build tooling and CI performance, including work with Bazel or a comparable build system
• Build the guardrails, tests, and automation that make large, automated changes safe to land
• Partner with product engineering teams to understand their pain points and measure the impact of your work
• Set technical direction and mentor other engineers on migration strategy, tooling, and codebase health

What we’re looking for

Required

• Significant experience (typically 7+ years for Senior, 10+ for Staff) working in large, complex codebases
• Deep experience with application or platform frameworks, including upgrading them and managing their evolution over time
• Track record of leading migrations or large refactors, from planning through rollout
• Comfort navigating unfamiliar code quickly and making sound changes across many teams’ areas
• A solid understanding of agentic loops (tool use, context management, verification, failure handling) and a genuine willingness to keep investing in and evolving them as the field changes
• Strong communication skills and the ability to build trust with teams whose code you’re changing

Nice to have

• Hands-on experience with Bazel or similar build systems (Buck, Pants, Nx, Gradle, etc.)
• Experience with codemods, AST-based tooling, or automated refactoring at scale
• Background in CI/CD, test infrastructure, or developer productivity metrics
• Experience building or integrating LLM-based coding tools into engineering workflows
• Open source contributions to build tools, frameworks, or developer tooling