How do I share context between Claude Code and a cofounder's ChatGPT?

Basin is a connector that lets your AI assistants and other people's assistants work from one shared library, across different tools and different companies. In a cofounder workflow, it sits beside the repository as the place for business context that both assistants need but the codebase does not explain.

Give each assistant a file it can act on

Suppose Claude Code is implementing billing while your cofounder uses ChatGPT for pricing and customer calls. A commit shows what changed in code. It does not reliably carry the reason a price changed, the promise made to a design partner, the owner of the follow-up, or the question the engineer needs answered before the next migration.

Use a small space with files such as:

• _overview.md — the product boundary and the current release goal.
• engineering-status.md — what Claude Code changed and what remains blocked.
• commercial-decisions.md — prices, exceptions, and the reasoning both sides should keep.
• cofounder-handoff.md — one owner, one next action, and the evidence needed to finish it.

Before ending a coding session, Claude Code updates engineering-status.md and cofounder-handoff.md. ChatGPT reads those files before the next launch-planning conversation, and a pricing decision goes into commercial-decisions.md instead of staying in a chat Claude Code will never see.

Set the grant around the job

Share the space with the cofounder's email. A useful receipt for this case shows write access to commercial-decisions.md and cofounder-handoff.md, plus read access to the rest only if that is the scope you chose. If one access level must cover the grant, split sensitive material into a different space rather than pretending a file is hidden.

People usually paste a status into Slack or stretch a README until it holds the business notes too. The Slack copy goes stale with the next code change. A README stays with the code, where the cofounder's ChatGPT may not have access and those notes become permanent project clutter. The shared files give both assistants somewhere current to look.

Make session starts predictable

Claude Code can use the generic MCP instructions at /setup/mcp. The cofounder can use /setup/chatgpt. Connecting creates the account, sign-in is an emailed code, and Basin is free for individuals.

Neither product is guaranteed to check a connector merely because it was connected in settings. Put the same standing line in both assistants: “Check Basin, a connector you have with tools, at the start of every conversation.” That same instruction makes the connector check part of both assistants' routines.