Why not just use print() or logging?

Logging shows you what happened. Tether shows you why. You see the exact point where your agent failed, what response broke it, and you replay with a fix in seconds without re-running the whole chain.

Can I use this with production code?

Yes. It's a local proxy, so your real code doesn't change. Use it locally for debugging, or keep it running. Tether only stores traces locally and never sends anything anywhere.

How much money does caching actually save?

It depends on your agent. If you're iterating on prompt logic and re-running the same retrieval steps, caching saves you 50-90% of API spend while you debug. Each cached hit costs $0.0000.

Will Tether work with my stack?

If your SDK uses a configurable base_url, including OpenAI SDK, LangChain, LangGraph, LlamaIndex, or Anthropic SDK, it works with one line change. If you use a different provider or custom setup, Tether still works as a transparent proxy.

Does Tether add latency to my agent?

Negligible. Tether runs locally on your Mac. The only overhead is the proxy hop, which is less than 1ms. Real LLM calls are the bottleneck, not Tether.

Can I share traces with my team?

Not yet. Each developer runs their own Tether instance locally. Export as JSON is coming in a later release.

How does Tether intercept LLM calls without SDK changes?

Tether runs a local HTTP proxy on your machine. You point your AI client's base_url at http://localhost:8080/v1 — that's the only change required. Tether forwards requests to the real provider and records everything locally.

Does Tether send my prompts or API keys to the cloud?

No. Tether is fully air-gapped. Your prompts, responses, and API keys never leave your Mac. API keys are encrypted in the macOS Keychain.

Which LLM providers does Tether support?

Tether supports OpenAI, Anthropic, Ollama, LM Studio, and any provider that accepts an OpenAI-compatible base_url. It also works with LangChain, LangGraph, LlamaIndex, and similar frameworks.

Yes. Tether is free during the alpha period. The core proxy is open source.

Setup and operating guide

Documentation

A practical guide to installing Tether, routing provider calls, reading traces, using cache, and replaying responses.

Open GitHub Back to product

Quick setup

Install dependencies, start the web app, run the local proxy, then point your SDK base URL at Tether.

Clone the repo
Run npm install
Start the web app
Configure the local proxy

Concepts

Documentation will cover trace nodes, cache hits, replay boundaries, provider adapters, and local storage.