Show HN: Nischoy, a deterministic prompt injection detector using formal logic

Nischoy is a prompt injection detector that uses grammar-based language analysis and SMT-solver-checked formal logic policies instead of an LLM, running on an ordinary CPU. In a local benchmark on an Apple M4 CPU with 120 warm requests, a typical check took a median 4.7 ms (p95 6.0 ms, first request about 101 ms), which the author notes is not a production latency measurement. Every verdict traces back to the extracted action and target plus the exact policies that fired, so the same input always gets the same answer.