Connect Sessionario to ChatGPT

At some point ChatGPT offers you “Advanced OAuth settings”, with a dozen fields: authorization URL, token URL, registration URL, scopes, PKCE, OIDC.

Leave it closed. Our server publishes all of that by itself, and ChatGPT reads it. You can see for yourself – at https://mcp.sessionario.com/.well-known/oauth-authorization-server you'll find exactly what those fields would contain.

We say this plainly because it happened to someone: ChatGPT advised him to type it all in by hand – and was wrong. It was all published already.

Since 1 September, “OIDC enabled” reads “This server did not advertise an OIDC configuration URL” and the checkbox is greyed out. That's exactly right – we're an authorization server, not an identity provider.

In the browser on a computer: click your profile picture at the bottom left → Settings.

Then look for developer mode. Depending on the version it hides in different places – these have been reported so far:

• Security and login → at the very bottom: Developer mode
• or Plugins → at the very bottom: Developer mode

Switch it on. Next to it you'll see ELEVATED RISK – that is OpenAI's warning about unverified connections in general, not about Sessionario.

In company workspaces an admin has to allow this first, under Permissions & Roles → Connected Data.

The Mac app has no developer mode – which is why you set it up here. Using the connection works there afterwards. We lost an hour on this ourselves, because we took the two for the same thing.

Open the plugin directory and click the plus sign (in other versions: Apps → Create).

Two entries, that's all:

Name:

MCP server:

No trailing slash. Pick OAuth as the authentication method – not “none”. Then click Create.

Copy the address from here – a typo is the most common reason this doesn't work.

ChatGPT asks first: Sign in with Sessionario.

Then the green sign-in page appears – our page. That's how you know your password stays with us and never reaches OpenAI. Sign in with the Sessionario account your sessions live in.

Sessionario now sits in the list, with the date and the address.

In a new conversation – existing ones often don't know about the connection yet:

Say “Sessionario” explicitly the first time. Ask only “What sessions have I got this week?” and ChatGPT may read it as a calendar question and offer to connect your calendar instead. You can also pick the plugin beforehand, via the plus sign in the message box.

The thinking is paid for by your ChatGPT plan – Sessionario doesn't use up any credit for it.

Three things tend to go wrong – all three are quickly explained.

ChatGPT says it doesn't have the tools.
Usually an old conversation. Start a new one. If that doesn't help, check that developer mode is still on.

You set it up in the Mac app and nothing happens in the chat.
We ran into this ourselves. The ChatGPT app for Mac has its own MCP manager, and it belongs to Codex, the developer area. Whatever you enter there ends up with Codex – an ordinary ChatGPT chat doesn't see it.

The distinction that matters: the app isn't the problem, where you set it up is. Set it up in the browser – after that you can use the connection in the Mac app just fine. It belongs to the account, not to the window.

ChatGPT can't find my sessions.
Check that you signed in with the same Sessionario account the sessions live in. Archived sessions are invisible to the AI.

I want to disconnect.
Remove the Sessionario entry from the plugin directory. ChatGPT then has no access at all. Nothing changes in your sessions.

OpenAI's help page (as of late August 2026) says: full access including create and change only on Business, Enterprise and Edu; Pro read and search only; Plus isn't mentioned at all; Free no.

What we hear from practice differs – connections that work outside that list. So we don't know for certain what your plan allows, and we won't claim it. Try it; it costs five minutes.

Claude has none of these tiers: any account, any chat, reading and writing from the start, on your phone too.