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Author by chat
Describe the agent you want in plain language. A reasoning model writes the first system prompt, then iterates with you turn by turn.
Craft system prompts that actually behave.
Prompt Studio is where you write, test, and version the prompts that power your AI agents — from first draft to production, all in one quiet workspace.
Why we built this
Every client wants the agent to behave differently.
One wants formal replies. Another wants short answers only. A third changes their mind weekly. Reshaping an agent's system prompt for every client request means digging through a wall of text, editing carefully, and hoping nothing breaks. Prompt Studio turns that afternoon of careful edits into a few minutes of chat, a quick test, and a saved version you can always roll back to.
The workshop
Everything a prompt needs, in one place.
From the first rough draft to the version your agents run in production.
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Test with any model
Stress-test your prompt against any model on OpenRouter — tweak temperature, wire up tools, and watch the reasoning unfold live.
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Version every revision
Each edit is a version you can label, revisit, and branch from. Organize prompts into projects with their own variables and tools.
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Variables & tools
Define template variables and OpenAI-style tool schemas once, then reuse them across the editor and the tester.
How it works
From client request to shipped prompt in minutes.
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Describe the change
"Make replies formal and cap them at 80 words." Say it in chat — the studio rewrites the prompt for you, preserving everything else.
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Test it live
Run the revised prompt against the exact model your agent uses, with real variables and tool calls, before anything ships.
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Save the version
Label it, ship it, move on. If the client changes their mind next week, roll back or branch in one click.
From developers, to developers
Bring your own key, ship your own prompts.
Everything runs in your browser against your OpenRouter key. No prompts leave your machine except to the model you choose.
Open Studio →- ✓Completely freeNo signup, no paywall, no trial clock.
- ✓BYOK via OpenRouterYour key, your models, your usage — we never see it.
- ✓Local-firstPrompts, versions, and settings live in your browser.
- ✓Any modelClaude, GPT, Gemini, Llama — whatever OpenRouter serves.