diff --git a/apps/mcp/app/api/mcp/[transport]/route.ts b/apps/mcp/app/api/mcp/[transport]/route.ts
index b5bb131..6675e5b 100644
--- a/apps/mcp/app/api/mcp/[transport]/route.ts
+++ b/apps/mcp/app/api/mcp/[transport]/route.ts
@@ -1,6 +1,14 @@
 // Public MCP endpoint. The dynamic route segment `[transport]` is
-// `sse` for Streamable HTTP transport. Tools are registered by
-// `lib/tools/register.ts`; this file is just the framework shell.
+// `mcp` for the Streamable HTTP transport (the only one we support).
+// Tools are registered by `lib/tools/register.ts`; this file is just
+// the framework shell.
+//
+// SSE is intentionally disabled (GHB-189). It was removed from the MCP
+// spec on 2025-03-26 (see mcp-handler types) and `mcp-handler`'s SSE
+// handler hard-requires a TCP Redis URL — without it the handler
+// throws before flushing any HTTP headers, which surfaces to clients
+// as a 0-byte connection that hangs until they time out. With
+// `disableSse: true` the same path returns a clean 404 instead.
 
 import { createMcpHandler } from "mcp-handler";
 import { registerAllTools } from "@/lib/tools/register";
@@ -16,6 +24,7 @@ const handler = createMcpHandler(
   },
   {
     basePath: "/api/mcp",
+    disableSse: true,
   }
 );