A Local Proxy That Makes Claude and ChatGPT Cover for Each Other

What it does

dario runs a local proxy at localhost:3456 that intercepts requests from agent tools like Cursor, Cline, Aider, and Claude Code. It translates between OpenAI and Anthropic wire formats on the fly, forwarding them to the backend that actually owns the subscription—Claude, ChatGPT, Groq, Ollama, or others. The client thinks it is hitting a standard API endpoint; the backend receives a native request. You pay the flat subscription rate instead of per-token API bills.

The interesting bit

Version 6 added true cross-subscription failover: a drained Claude pool can hand off to your ChatGPT plan, and vice versa, with the proxy translating the protocol mid-flight so the tool never notices. There is also a shadow-compare mode that silently runs the same prompt through both families and logs the results, letting you measure which model handles your actual traffic better.

Key highlights

• Either subscription answers either wire shape—ChatGPT serves /v1/messages and Claude serves /v1/chat/completions without the client knowing.
• Automatic failover chains between subscription pools when rate limits hit.
• Multi-account pooling and live drift detection for long agent runs.
• Full-screen TUI showing live request streams, per-model burn rates, and rate-limit utilization.
• Supports forced backend routing with prefixes like openai:gpt-4o or claude:opus.
• Zero runtime dependencies and SLSA-attested releases.

Caveats

• The project is independent, unofficial, and third-party; it performs OAuth swaps and protocol translation that the providers do not endorse.
• Browser authorization during setup lands on a localhost page that intentionally does not load, which the README calls expected but may confuse first-time users.
• The dario doctor command specifically checks for an “armed but INERT” state that looks healthy yet cannot actually route requests.

Verdict

If you already pay for Claude Pro/Max or ChatGPT Plus/Pro and want to stop buying separate API credits for every agent tool, this is a pragmatic money-saver. If you need officially supported integrations or are uncomfortable with unofficial OAuth token swaps, look elsewhere.