Comparisons
Eight competitors, each with a short read on approach, best fit, and the gotcha Rune hits on its detail page. Pick a row, read the full comparison, or skim the whole market in ninety seconds.
Rune
The baseline
Framework-native runtime SDK. Three-layer detection (regex, semantic, LLM judge) wrapping every input, output, and tool call inline.
Developers running agents in production who want minutes-to-value and no API round-trip.
None yet.
Lakera Guard
vs Rune
ApproachCloud-managed classification API; Gandalf-trained models; acquired by Palo Alto Networks (2025).
Best forTeams that already live in Prisma Cloud and want a classifier behind their proxy.
GotchaExternal API round-trip; can’t see tool parameters or framework-level middleware.
Read full comparisonNVIDIA NeMo Guardrails
vs Rune
ApproachNVIDIA’s Colang-based conversation flow controller; programmable dialogue guardrails.
Best forChatbot teams that need to script conversation flow, topic blocking, and fallbacks.
GotchaColang is a learning curve; focused on conversation shape, not runtime threat detection.
Read full comparisonGuardrails AI
vs Rune
ApproachPython library of output validators (RAIL spec) for PII, toxicity, hallucination, etc.
Best forTeams that want per-response Pydantic-style schema validation on LLM outputs.
GotchaOutput-only validation; no inline input scanning, no inter-agent or tool-call awareness.
Read full comparisonLLM Guard
vs Rune
ApproachSelf-hosted open-source scanner with multiple input/output scanner modules.
Best forTeams that need full data residency and are comfortable running their own infra.
GotchaMaintenance cost; last meaningful release is slowing down; no hosted dashboard.
Read full comparisonPrompt Armor
vs Rune
ApproachCloud API specialised in prompt-injection detection.
Best forSingle-purpose injection filters in front of a chat endpoint.
GotchaNarrow scope; no policy engine, no tool-call scanning, no agent runtime coverage.
Read full comparisonArthur Shield
vs Rune
ApproachEnterprise AI firewall with governance tooling; five-figure annual minimums.
Best forLarge enterprises with centralised AI governance programs and procurement cycles.
GotchaEnterprise-only pricing; long evaluation cycles; overkill for individual agent teams.
Read full comparisonRebuff
vs Rune
ApproachOpen-source prompt-injection detector from ProtectAI; vector + heuristic scoring.
Best forResearch and prototyping; understanding injection detection concepts.
GotchaEffectively abandoned — last meaningful commit in 2023; no policy or runtime surface.
Read full comparisonPangea AI Guard
vs Rune
ApproachBroader security suite (PII, redaction, threat intel) with an AI guard product bundled in.
Best forTeams already buying Pangea’s platform who want to add AI coverage.
GotchaBundled pricing; you pay for the whole suite even if you only want AI scanning.
Read full comparisonRune embeds directly into your agent framework as a middleware layer, scanning inputs, outputs, and tool calls inline — not through an external API call. This means lower latency (under 20ms for L1+L2), no data leaving your infrastructure for scanning, and the ability to scan tool parameters and inter-agent communication that API-based solutions can't see.
For startups, the key factors are speed of integration, free tier generosity, and framework support. Rune offers 10,000 events/month free, integrates in under 5 minutes, and supports all major frameworks. Lakera Guard has a generous free tier but requires more integration work. Open-source options like LLM Guard are free but require self-hosting.
We try to be as honest as possible. Each comparison includes a 'Why Choose [Competitor]' section with genuine advantages. We acknowledge when a competitor has better coverage in a specific area, longer track record, or features we don't offer yet. If you find inaccuracies, email hello@runesec.dev and we'll correct them.
The best comparison is hands-on.
Free tier. 10,000 events/month. No credit card.