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Prompt engineering toolkit

The iteration loop
for prompt engineers

Version, test, and compare prompts across Claude, Gemini, and GPT-4o in real time. Catch regressions before they reach production.

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Works with Claude, Gemini, and GPT-4o · Free while in beta

Customer Support Reply Generator
Active version
v3Added customer persona
Test: Angry customer about delayed shipping
G
Gemini 2.5 Flash
312ms · 284 tok
A
Claude Sonnet 4.6
891ms · 197 tok
O
GPT-4o
1204ms · 312 tok
Version control for prompts
Compare 3 AI models
No credit card required
Real outputs, real latency
Free while in beta
Immutable version history
Team collaboration
Side-by-side eval
Catch regressions early
Parallel test execution
Claude, Gemini, GPT-4o
Sub-2s eval speed
Version control for prompts
Compare 3 AI models
No credit card required
Real outputs, real latency
Free while in beta
Immutable version history
Team collaboration
Side-by-side eval
Catch regressions early
Parallel test execution
Claude, Gemini, GPT-4o
Sub-2s eval speed

Built for teams that ship fast.

3AI Models
< 2sEval Speed
∞Versions
5/dayFree AI Runs

From first draft to production-ready in three steps.

Version history
v3Added customer persona
just now
v2Refined tone and length
1h ago
v1Initial draft
3h ago
3 versions · branching enabled
1. Create

Write prompts that actually improve.

Start with a prompt, save it as version 1. Every edit creates a new immutable version — roll back, compare, or branch at any time.

  • Write and save your first prompt in seconds
  • Every change is numbered and permanent
  • Branch from any version at any time
  • Add notes and metadata per version
Test run · v32 passed, 1 failed
+Tone is polite and empathetic
+Response is under 80 words
-Contains explicit apology
Prompt updated → re-run automatically
2. Test

Define inputs. Verify every time.

Add test cases once, run them on every save. Regressions surface before they reach your users.

  • Create a library of test cases
  • Auto-run on every prompt version
  • Flag failures with clear diff views
  • Compare expected vs actual output
Comparison run · v3~312ms avg
GGemini 2.5 Flash
312ms284 tok
AClaude Sonnet 4.6
891ms197 tok
OGPT-4o
1204ms312 tok
Parallel execution · 1.2s total
3. Compare

One click. Every model.

Send the same prompt to Claude, Gemini, and GPT-4o simultaneously. See outputs, latency, and token cost side by side.

  • Parallel execution across all models
  • Real latency and token counts
  • Side-by-side output comparison
  • Export results for your team
New

Agent Optimizer

Paste a failing prompt. Get an improved one.

  • Powered by Neuraloop's Gemini API
  • 5 free optimizations / day
  • No API keys needed for optimization
  • Upgrade for unlimited
Free · No API charges
Try it free

Works with the models you already use.

G
Gemini
2.5 Flash · Pro

Google's fastest model. Excellent at structured outputs, long context, and multimodal tasks.

A
Claude
Sonnet 4.6 · Haiku 4.5

Anthropic's model for nuanced reasoning, writing, and following complex instructions safely.

O
GPT-4o
gpt-4o · gpt-4o-mini

OpenAI's flagship. Strong at coding, multi-step reasoning, and structured output generation.

Start iterating today.

Free to start. Upgrade when you're ready.

Get started