Claude Mythos 5, Gemini 3.1, Grok 4.20 dropping April 2026

Model releases are silent breaking changes

PromptGuard catches prompt regressions before your users do. Define expected outputs, run tests across models, get instant PASS/FAIL results.

Start Testing FreeSee How It Works
promptguard test run
// System Prompt
"You are a helpful assistant. Always respond in JSON format."
// User Message
"List 3 colors"
// Expected Pattern (regex)
\{"colors":
PASSgpt-4o-mini1.2s
{"colors": ["red", "blue", "green"]}

How it works

01

Define Your Test

Paste your system prompt, write a test message, and set a regex pattern for expected output.

02

Run Against Models

Execute your test against GPT-4o-mini (more models coming). Get real API responses instantly.

03

Catch Regressions

See PASS/FAIL results immediately. Run again after model updates to catch breaking changes.

Built for teams shipping AI

Every model update is a potential regression. PromptGuard gives you confidence your prompts still work.

SaaS Teams

Validate production prompts before and after model migrations.

Indie Hackers

Ship AI features with confidence. No surprise breakages.

QA Engineers

Add prompt regression tests to your CI/CD pipeline.

Prompt Engineers

Version and test prompt iterations systematically.

Simple pricing

Start free. Upgrade when you need more.

Free

$0forever
  • 10 tests per month
  • GPT-4o-mini
  • Basic dashboard
  • Email support
Get Started
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Pro

$19/month
  • Unlimited tests
  • All models
  • Test history
  • Priority support
  • API access (coming)
Start Pro Trial

Team

$79/month
  • Everything in Pro
  • 5 team members
  • Shared test suites
  • CI/CD integration
  • Slack alerts
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