Elixir lint / debug kit: POST {code}, get the bugs back with line numbers. Deterministic static analysis — code is parsed, never executed, no AI. Catches unbalanced do/end and brackets, missing do, 'return', '+' string concat, trailing commas, field assignment, = vs == in conditions and guards, block-scoped rebinding (the classic), charlist vs String mixups, unused variables. Errors, warnings and hints with fixes. Max 128 KB.