Agent Guidelines for Apache DataFusion Comet

Read the Contributor Guide before making changes. Relevant entry points:

• Development Guide: build, test, and common pitfalls (including why -pl must not be used and the JVM/native build order).
• Spark SQL Tests: the only supported way to modify files under dev/diffs/. Never hand-edit a diff file. Clone Spark, apply the existing diff, modify the Spark source, then regenerate the diff as documented there.
• Adding a New Expression / Adding a New Operator.
• Debugging Guide.

When opening a pull request, use the PR template and fill in every section.

Skills

Repository-specific agent skills live under .ai/skills/. Each subdirectory is a single skill with a SKILL.md (YAML frontmatter + body). Check that directory for an applicable skill before starting a task; new skills go in .ai/skills/<skill-name>/SKILL.md.

For compatibility with agents that look in vendor-specific locations, .claude/skills is a symlink to .ai/skills and CLAUDE.md is a symlink to this file. Add new content here rather than to the symlinks.