Read-only MCP server (HTTP, GUI-controlled)

Expose the mailbox to an LLM client (Claude Desktop / Code) over an
in-process MCP server, so the bridge itself hosts it and the GUI controls
it live. Strictly read-only: there is no tool that sends, moves, deletes or
mutates mail — by design and asserted in tests.

Transport: Streamable HTTP (MCP 2025-06-18) on a single POST /mcp endpoint
bound to 127.0.0.1, answering each JSON-RPC request with application/json
(no SSE — the server never pushes). Auth is a bearer token (the bridge
password); the Origin header is validated to block DNS-rebinding.

Permission tiers (config.McpPermission, default Disabled = server off):
- Metadata — folders, metadata search (subject/sender/date), headers only.
- Full — the above plus full-text body search and message body text.

Tools: list_folders, search_messages, list_unread, get_message. Search
combines subject/sender always and the encrypted FTS body index under Full;
get_message returns headers always and body only under Full.

Wiring: spawned in-process by both the CLI (main.rs) and the GUI bridge
task (bridge.rs); a Disabled tier makes serve() a no-op, and it is kept out
of the select! so it never triggers teardown. GUI gains an MCP section
(tier selector, port, full-read warning, "copy client config" button) and a
get_mcp_client_config command that emits the ready-to-paste client snippet.

Validated live on a ~19k-message mailbox: initialize / tools/list /
tools/call all conform; 401 without the bearer token, 403 on a foreign
Origin, 202 on notifications; list_folders, body search and get_message
(HTML stripped to text) all return correctly. 240 unit tests.

src-tauri/src/commands.rs

@@ -90,6 +90,26 @@ pub async fn regenerate_bridge_password() -> Result<String, String> {
     config::regenerate_bridge_password(&mut cfg).map_err(|e| e.to_string())
 }
 
+/// Build the MCP client config snippet (URL + bearer token) to paste into
+/// Claude Desktop / Code. Read-only; reflects the saved port + bridge password.
+#[tauri::command]
+pub async fn get_mcp_client_config() -> Result<String, String> {
+    let cfg = config::load_config()
+        .map_err(|e| e.to_string())?
+        .unwrap_or_default();
+    let token = cfg.bridge_password.unwrap_or_default();
+    let snippet = serde_json::json!({
+        "mcpServers": {
+            "tutabridge": {
+                "type": "http",
+                "url": format!("http://127.0.0.1:{}/mcp", cfg.mcp_port),
+                "headers": { "Authorization": format!("Bearer {token}") }
+            }
+        }
+    });
+    serde_json::to_string_pretty(&snippet).map_err(|e| e.to_string())
+}
+
 /// Export every mail to `output_dir` as a tree of `.eml` files. Requires the
 /// bridge to be running (reuses its live session + cache). Streams progress
 /// via `bridge://backup-progress` events and resolves with the final stats.

src-tauri/src/main.rs

@@ -35,6 +35,7 @@ fn main() {
             commands::get_bridge_password,
             commands::regenerate_bridge_password,
             commands::export_mails,
+            commands::get_mcp_client_config,
         ])
         .setup(|app| {
             let app_handle = app.handle().clone();