Bring-your-own-model AI coding, explained
What bring-your-own-model means, the two honest connection modes, and how to avoid paying a model tax on AI-assisted development.
Bring-your-own-model (BYO) means the tool orchestrates AI you already have rather than reselling its own. You connect your keys or local models, and you pay the provider directly — no markup, or 'model tax', in between.
There is an important honesty point: a consumer chat subscription is not the same as API access.
Two connection modes
API key / endpoint: paste a key or an OpenAI-compatible base URL. Works with OpenAI, Anthropic, Google, OpenRouter, and local Ollama or vLLM. Billed per token by the provider.
Subscription / agentic sign-in: sign in with a plan where the provider allows programmatic use. Availability varies, and some providers prohibit proxying a chat plan as an API.
The honesty rule
A ChatGPT Plus or Claude Pro subscription does not automatically grant general API access — that is billed separately. So 'use the AI you already pay for' is true for API keys you hold, local models, and agentic sign-in where supported, but it is not a blanket promise. A good tool names the mode you are using.
A zero-cost path
Local models via Ollama let you start with no spend at all — useful for privacy-sensitive teams and for evaluating the workflow before connecting a paid model.
FAQ
- Can I reuse my ChatGPT subscription as an API?
- Usually not directly — API access is billed separately from chat subscriptions. You can use API keys you already hold, local models, or agentic sign-in where the provider permits it.
Start building with the AI you already have
Download PromptConnext, connect a model in minutes — including a zero-cost local option — and take your first project from scope to running code.