Write, debug, and explain Lean 4 + mathlib proofs. Use whenever the user:
- asks to write or prove something in Lean ("prove X in Lean", "write a Lean proof for...")
- shares a Lean error and asks what's wrong
- wants to install/configure Lean 4, Lake, or mathlib
- asks which tactic to use for a specific goal ("how do I prove...", "which tactic for...")
- wants to search or navigate mathlib for a theorem
- mentions .lean files, formalization, theorem proving, or automated reasoning
- asks about `import Mathlib`, `lake build`, `#check`, `example`, `theorem`
Always respond in Chinese with English code identifiers.
2026-05-14