@alex_prompter: This open-source proxy cuts your AI agent costs without changing a line of code. Plano sits between your agent and your…

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Summary

Plano is an open-source proxy that sits between AI agents and LLM providers to cut costs through intelligent routing, guardrail filtering, and cost-aware selection, all configured via a single YAML file without modifying agent code.

This open-source proxy cuts your AI agent costs without changing a line of code. Plano sits between your agent and your LLM providers. Every request passes through it. Your agent doesn't know it's there. It handles four things. Guardrail filtering before requests hit the model. Smart routing that matches each prompt to the right model by difficulty. Cost-aware selection when multiple models qualify. And model affinity that pins the winner to the session so your prompt cache stays warm. All of it runs from one YAML config file. Swap a model, change a preference, add a guardrail. Nothing touches your agent code. The routing runs on Arch-Router, a 1.5B model trained on what developers actually choose for each task type. So routing reflects real-world preferences, not benchmark rankings. It also ships with an observability console showing which model answered each request and what it cost. If you've ever wondered where your API budget goes, that alone is worth setting up. 6.7k stars. Supports OpenAI, Anthropic, Gemini, Mistral, and more.
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This open-source proxy cuts your AI agent costs without changing a line of code.

Plano sits between your agent and your LLM providers. Every request passes through it. Your agent doesn’t know it’s there.

It handles four things. Guardrail filtering before requests hit the model. Smart routing that matches each prompt to the right model by difficulty. Cost-aware selection when multiple models qualify. And model affinity that pins the winner to the session so your prompt cache stays warm.

All of it runs from one YAML config file. Swap a model, change a preference, add a guardrail. Nothing touches your agent code.

The routing runs on Arch-Router, a 1.5B model trained on what developers actually choose for each task type. So routing reflects real-world preferences, not benchmark rankings.

It also ships with an observability console showing which model answered each request and what it cost. If you’ve ever wondered where your API budget goes, that alone is worth setting up.

6.7k stars. Supports OpenAI, Anthropic, Gemini, Mistral, and more.

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