Can You Use a ChatGPT Subscription With OpenCode?
OpenCode is an open-source terminal coding agent that supports multiple model providers. A ChatGPT subscription gives you access to chat.openai.com, not the OpenAI API. Here is what OpenCode actually needs and how to choose the right setup.
Updated 4 min read
OpenCode is an open-source terminal coding agent designed to work with multiple model providers through API keys. A ChatGPT subscription from OpenAI gives you access to ChatGPT's web and app interface — it does not provide API access for use in third-party tools like OpenCode. To use an OpenAI model in OpenCode, you need a separate API key from platform.openai.com.
OpenCode's multi-provider design means you are not limited to OpenAI. You can configure it to use Anthropic's Claude models, open-weight models through a local server, or another supported provider. When you change providers, tools like fenbs keep the project context and decisions available so the new setup can pick up where the last one stopped.
What OpenCode is and how it authenticates
OpenCode (available at opencode.ai) is an open-source command-line coding agent. It runs in your terminal, reads and writes files in your repository, and uses a language model to reason about and execute coding tasks. It is similar in purpose to Claude Code or Codex CLI but is not made by Anthropic or OpenAI.
Authentication in OpenCode works through provider API keys. You configure a provider — OpenAI, Anthropic, or another — and supply the corresponding API key. OpenCode sends requests to that provider's API and the usage is billed to your API account. Check OpenCode's current documentation for the full list of supported providers and the configuration format it expects.
What a ChatGPT subscription gives you
A ChatGPT subscription is a consumer product subscription with OpenAI for access to chat.openai.com. Depending on your plan, it includes higher usage limits in ChatGPT, newer models, and features like file analysis and code execution inside the ChatGPT interface.
It does not give third-party tools — including OpenCode — the right to call OpenAI's API on your behalf. API access is a separate product from OpenAI, set up at platform.openai.com with its own billing. Some plans include API credit; check OpenAI's current plan documentation to see whether your plan includes any.
Comparing subscription and API billing
A subscription is a flat monthly cost for a defined set of features within a product. API billing charges per token — for every word the model reads or generates — with no monthly floor and no included usage. The economics depend on how you use the tool.
Light conversational use is often cheaper with a subscription. An agent session that makes many large requests can cost more on per-token billing than an equivalent subscription. Before running an agent loop with an API key, estimate the token usage and set a spending limit on your API account.
- Subscription: fixed monthly cost, covers ChatGPT features, no API access unless the plan includes it.
- API key: per-token billing, usable in any tool that accepts it, no minimum spend.
- Some OpenAI plans include API credit. Check your plan's current terms at OpenAI's website.
OpenCode's multi-provider model
One of OpenCode's design goals is to avoid locking you into a single provider. You can configure it to use OpenAI's models when you have an API key, switch to Anthropic's Claude when that works better for a task, or point it at a local model server for work that should not leave your machine.
This flexibility means the right answer to "which provider should I use?" is not permanent. The project brief, task requirements, and cost considerations all affect the choice. Recording that decision — and the reasoning behind it — means the next time the question comes up you have a reference point rather than starting from scratch.
Keep the project brief stable across provider changes
When OpenCode switches providers or models, the project tasks, Decisions and rules, and Where we left off in fenbs are unchanged. Any supported connected assistant reads the same record. You do not need to re-brief the new provider on the project; you ask it to read the existing context. Connect at /integrations.
Create a free accountFree for one person · No credit card · Works with Claude, ChatGPT, Cursor and more
Data and privacy when switching providers
Each provider you configure in OpenCode receives the prompts and code you send it. If your project has data-handling requirements — a client confidentiality agreement, regulatory constraints on where data may travel, or a preference for keeping source code off third-party servers — your choice of provider is a compliance decision as much as a technical one.
OpenCode's support for local model servers means you can configure it to keep everything on your own machine. A local server does not send data to any external provider; the trade-off is that local models are generally less capable than frontier API models. Record which provider you chose and why so the next person on the project starts from the same constraint.
How to do this with fenbs
- Create a free account and add a project for the codebase OpenCode is working on.
- Record the current provider and model choice as a Decision in fenbs. Note any cost, data-handling, or capability reasons behind the choice.
- Add tasks with clear scopes and write the first step in each task's plan.
- Connect a supported assistant to fenbs at /integrations. Ask it to read the project context at the start of each session.
- When you switch providers, update the Decision in fenbs with what changed and why. The task records do not need to change.
For adjacent topics, see can i use chatgpt subscription with claude code and chatgpt alternatives. For a direct comparison of ChatGPT and Claude, see claude vs chatgpt.