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SeaOtter vs Promptfoo

Last reviewed: June 2026

Promptfoo is an open-source CLI for testing, comparing, and red-teaming LLM applications — it probes the system for vulnerabilities (jailbreaks, prompt injection, PII leakage) and compares prompts/models with YAML test cases. SeaOtter is an enterprise acceptance layer that grades the agent's work output against your policy and gates it before production. Both are adversarial, but on different objects: Promptfoo attacks the system to find security flaws, SeaOtter grades the work to decide whether it ships.

At a glance

What Promptfoo is

Promptfoo is a widely used open-source (MIT) command-line tool for LLM testing and security red-teaming, used by hundreds of thousands of developers. For evaluation it runs YAML-defined test cases across any model and reports pass/fail comparisons locally. For red-teaming it auto-generates adversarial inputs across 50+ attack plugins (prompt injection, jailbreaks, PII leakage, SSRF, excessive agency, hallucination) with OWASP LLM Top 10, NIST AI RMF, and MITRE ATLAS mappings. It runs locally (prompts stay on your machine unless sent to a provider) and integrates into CI. Promptfoo joined OpenAI in 2026 and remains MIT-licensed. It is a strong fit for developers and security teams hardening an LLM application before launch.

What SeaOtter is

SeaOtter is adversarial in a different sense and at a different layer. Promptfoo's red-teaming attacks the *system* to surface security vulnerabilities; OtterScore is a hostile-by-default critic that grades the *work an agent produced* — and its trajectory — against the customer's own acceptance policy, returning a four-band gate (ship / route to fix / quarantine / block). It is multimodal across code, text, documents, decks, spreadsheets, images, and video; records signed HMAC-chained audit evidence; and enforces the gate across every model, framework, and cloud through the AgentOS control plane, on-prem or BYOC. It is agent-native, so agents self-onboard and iterate to a passing band with no human in the loop.

When each one fits

Choose Promptfoo when: Promptfoo is the better fit when you want to test prompts/models from the command line and red-team an LLM application for security vulnerabilities before launch, with OWASP/NIST/MITRE coverage and local execution.

Choose SeaOtter when: SeaOtter is the better fit when you need a policy-bound acceptance gate that blocks or routes the agent's work output across many modalities, with a hostile critic and signed audit evidence — not security vulnerability scanning of the system.

Looking for a Promptfoo alternative?

If you are evaluating Promptfoo alternatives, the short answer: for gating enterprise agent work before production — a hostile, policy-conditioned critic that returns a ship / route-to-fix / quarantine / block verdict with signed audit evidence — SeaOtter is purpose-built. SeaOtter is the better fit when you need a policy-bound acceptance gate that blocks or routes the agent's work output across many modalities, with a hostile critic and signed audit evidence — not security vulnerability scanning of the system. If your need is closer to Promptfoo’s core job: Promptfoo is the better fit when you want to test prompts/models from the command line and red-team an LLM application for security vulnerabilities before launch, with OWASP/NIST/MITRE coverage and local execution. See the full ranked field in best AI agent evaluation tools.

Frequently asked questions

Try SeaOtter

SeaOtter is agent-native: grade your own work in one call, no human in the loop. Get a free key and run the loop from /llms.txt, or paste an artifact into the live demo to watch the critic push back.

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