5 Best Prompt Armor Alternatives for AI Security in 2026

Narrow scope — prompt injection only

Prompt Armor focuses exclusively on classifying text as injection or not. It doesn't detect data exfiltration patterns (encoded data in URLs), PII leaking in model outputs, secret exposure (API keys in responses), or privilege escalation through tool abuse. As agent attacks diversify, injection-only detection covers a shrinking percentage of the threat surface.

Cloud API adds 50-150ms per scan

Every scan requires sending the full prompt text to Prompt Armor's API for classification. Measured latency is 50-150ms depending on input size and region. For interactive agents making multiple tool calls per turn, this compounds into noticeable user-facing delays.

Prompts leave your infrastructure on every call

Prompt Armor's cloud classification means your raw prompts and responses are transmitted to a third-party API. For teams handling PII, financial data, or health records, this creates a data processing relationship requiring DPAs and potentially conflicting with data residency requirements.

No agent framework support or tool call awareness

Prompt Armor is a REST endpoint — you POST text, you get a classification. It has no concept of LangChain chains, CrewAI crews, MCP tool calls, or multi-step agent workflows. When an attacker injects instructions through a tool's return value, Prompt Armor can't see the tool context.

No dashboard or monitoring on lower tiers

Prompt Armor returns a classification result per API call. There's no event history, no threat analytics, no pattern detection across sessions, and no alerting. You see individual scan results but can't answer 'what attacks have my agents seen this week?'

Range of threats detected beyond just prompt injection — exfiltration, PII, secrets, escalation.

Ability to scan tool calls and multi-agent workflows, not just raw text.

Whether prompts and responses leave your infrastructure during scanning.

Overhead per scan — cloud APIs add 50-200ms, local scanning can be under 10ms.

Enterprise prompt injection API with battle-tested detection from the Gandalf challenge dataset.

NVIDIA's open-source toolkit for programmable guardrails with Colang language.

Self-hosted scanning toolkit for LLM inputs and outputs with PII detection.

Open-source multi-layer prompt injection detection with heuristics, LLM analysis, and vector similarity.

Largest adversarial prompt dataset (Gandalf) and longest production track record for injection-specific detection.

Best self-hosted option for PII detection and basic input sanitization.

Does Rune detect prompt injection as well as Prompt Armor?

Rune uses multi-layer detection: L1 regex (<3ms) catches known injection templates, L2 vector similarity (5-10ms) detects semantically similar attacks, and L3 LLM judge fires for ambiguous cases. This layered approach matches Prompt Armor's injection accuracy while adding data exfiltration, PII, secret, and escalation detection. For teams that only need injection detection, both are effective — Rune adds breadth that becomes critical as agent attack surfaces expand.

Is Prompt Armor's cloud API a security or compliance concern?

It depends on your data. Sending raw prompts to any third-party API creates a data processing relationship. If your agents handle PII (healthcare, finance, legal), you'll need DPAs and potentially HIPAA BAAs with Prompt Armor. Rune's local-first architecture avoids this entirely — scanning runs in your process, and only structured metadata reaches the dashboard.

What's the honest case for staying with Prompt Armor?

If your agents are simple (no tool calls, no multi-agent delegation) and prompt injection is genuinely your only threat, Prompt Armor is a solid, focused tool with continuously updated models. The case for switching to Rune strengthens when you have tool-calling agents, need broader threat coverage, care about latency under 50ms, or want to keep prompts off third-party servers.

How hard is the migration from Prompt Armor to Rune?

Straightforward. Replace your Prompt Armor API calls with Rune Shield middleware: `shield = Shield(client)` wraps your agent client and scans all calls automatically. No changes to agent logic needed. Injection detection is on by default. Then remove your Prompt Armor API keys. Most teams complete migration in under an hour.