Enforce prompt-injection defense at the gateway with dual-stage guardrails and MCP tool allow-lists

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With OWASP reporting prompt injection up 340% year-over-year and still the top agentic vulnerability, the 2026 consensus is layered hardening enforced at the LLM gateway rather than in application code. A gateway (e.g. Bifrost) applies dual-stage input/output guardrails, CEL-based rule targeting, and MCP tool allow-lists that block injection-driven tool abuse across every provider with no app changes. Treat it as defense-in-depth: no single filter eliminates injection, so combine input screening, output checks, and least-privilege tool access.