Top tools (quick reference)
L4
Lean (Lean 4)
Proof assistant — formalize theorems and produce machine-checked proofs. Excellent community math library (mathlib).
IS
Isabelle/HOL
Interactive theorem prover with strong automation and long maturity in formal logic.
CO
Z3
Z3 (SMT solver)
Automated reasoning engine for satisfiability modulo theories — useful for lemmas and constraint solving.