Comment connecter correctement un serveur MCP (Gmail / Thunderbird) à Thunderbolt ?

[mohamed7821]

Bonjour à tous,

J'utilise l'assistant IA Thunderbolt en local (lancé via le backend Drizzle/Node) et je cherche à le relier à mes e-mails (via un serveur MCP pour Thunderbird/IMAP).

Quand j'essaie d'utiliser le bouton "Add MCP Server" sur l'interface web (localhost:1420), la popup me renvoie systématiquement une erreur Connection failed lorsque je saisis une URL SSE (du type http://localhost:9095/sse).

L'application Thunderbolt prend-elle en charge les transports SSE via l'interface, ou faut-il obligatoirement passer par un transport STDIO en spécifiant une commande locale ? Si c'est en STDIO, comment et où configure-t-on la commande de lancement ?

Merci d'avance pour votre aide !

[ital0]

Hi @mohamed7821! :)

Good news: Thunderbolt does support SSE (along with Streamable HTTP) through the UI. The sse type exists precisely for servers that only speak SSE. What's blocking you comes down to two setup details:

1. Your build is probably older than the SSE support. The sse transport and support for authenticated remote MCP servers landed recently (PR #942). On a build from May, an SSE URL fails right away. So the first step is updating to the latest main.

2. On the web UI, http://localhost is not reachable, and that's by design. In the browser (localhost:1420), all MCP traffic must go through the backend's universal proxy (/v1/proxy), because browser CORS forces it. That proxy has SSRF protections: it automatically upgrades http:// to https:// and rejects any other scheme. So http://localhost:9095/sse becomes https://localhost:9095/sse, your local server doesn't speak TLS, and the result is exactly the "Connection failed" you're seeing.

The way to reach local MCP servers is the desktop app (Tauri). On desktop, requests go straight to the upstream, with no proxy and no browser CORS, and http:// URLs on localhost or your local network are accepted. Run Thunderbolt as a desktop app and add http://localhost:9095/sse normally. On the web UI, only remote servers with a public https:// URL will work.

About STDIO: it's not supported yet, so there's nowhere to configure a launch command today. For now only remote servers (http and sse) can be connected. In short: you don't need (and can't) use STDIO. SSE on desktop is the way.

One tip for the Gmail case: if the goal is reading and writing Gmail emails, you don't need MCP at all. Thunderbolt has a native Google integration (Settings → Integrations) with Gmail read, compose and calendar scopes. MCP makes more sense for the local Thunderbird/IMAP case.

Also, there are improvements under review right now (PR #972) for this exact "Add MCP Server" flow: inline URL validation with clear messages (including the rule of https on public hosts with http allowed on localhost), bulk JSON config import, and much better connection error feedback. Hope this helps!