PromptArmor drops prompt-injection attack success below 1% with a bolt-on guardrail LLM.

It interposes a lightweight model (GPT-4o, 4.1, or o4-mini) that detects and excises injected instructions from untrusted input before your agent ever sees them, using fuzzy-regex excision of the flagged span (arXiv 2507.15219). On AgentDojo it pushes false positives, false negatives, and attack success all under 1%. The counterintuitive bit: even a guardrail model that is itself injectable can be reliably prompted to detect and remove injections. Cheap, addable today.