AIR Blackbox is an open-source reverse proxy that creates tamper-evident audit trails for every LLM API call. Records are HMAC-SHA256 chained — tampering is instantly detectable. Unlike observability tools, AIR focuses on provability: • Cryptographic audit chain for tamper-proof integrity • EU AI Act compliance (20 controls, Articles 9-15) • PII detection and prompt injection scanning • Shadow AI detection with model registry • Works with any OpenAI-compatible API pip install air-blackbox