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Debugs Buck2 build failures systematically by analyzing error logs, checking common issues (cache, visibility, cycles), and suggesting fixes. Use when builds fail, tests won't run, or Buck2 reports errors.

Scaffolds new Buck2 projects with proper BUILD/PACKAGE files, SPDX headers, and depot shims. Use when creating new Rust binaries/libraries, Deno tools, or C++ projects in the monorepo. Ensures consistent structure and metadata from the start.

Runs common Buck2 queries for dependency analysis, target inspection, and build graph exploration. Use when investigating dependencies, finding reverse dependencies, filtering by rule type, or understanding target relationships in the monorepo.

This skill should be used when determining which Buck2 targets are affected by code changes for incremental builds and tests. Use this when users ask to test/build changed code, find affected targets, or run incremental workflows with jj revisions.

Comprehensive testing workflow that should be used proactively after ANY code changes. Covers immediate testing, recursive package validation with `...`, target determination for affected packages, and reverse dependency testing. Use this skill after modifying BUILD files, changing code, fixing tests, or before committing to ensure nothing breaks downstream. (project)

Guides working with exe.dev VMs. Use when the user mentions exe.dev, exe VMs, *.exe.xyz, or tasks involving exe.dev infrastructure.

Create Buck2 tests with local resources (processes, services, databases) using LocalResourceInfo and ExternalRunnerTestInfo. Use when tests need external dependencies like databases, HTTP servers, message queues, or Unix sockets that Buck2 should manage automatically. (project)

Clone external repositories into work/ directory for examination and source code research. Use when needing to understand third-party dependency implementations, debug upstream issues, or research API usage patterns. (project)

Integrate third-party repository history into the monorepo by adding remotes and creating workspaces. Use when testing patches to upstream projects, making local modifications to dependencies, or maintaining forks that need to track upstream changes. (project)

Create isolated jj workspaces for testing changes, running experiments in parallel, and exploring alternative implementations. Use when testing breaking changes, comparing different approaches, or running long-running operations without blocking other work. (project)

Guide for creating effective skills. This skill should be used when users want to create a new skill (or update an existing skill) that extends Claude's capabilities with specialized knowledge, workflows, or tool integrations.