Senior Software Engineer, Developer Experience

Block is hiring a Senior Software Engineer, Developer Experience to improve how engineers work across its largest monorepos. The role focuses on migrations, developer tooling, build and test infrastructure, and safe, reliable AI-agent workflows.

Responsibilities:

• 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

Requirements:

• 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
• 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