fix(mcp): derive MCP endpoint path dynamically from MCP_SERVER_URL (#1051)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: aaronsteers

airbyte/mcp/http_main.py

@@ -7,7 +7,9 @@
 
 Environment variables:
 
-- `MCP_SERVER_URL`: Public base URL (for OIDC redirect callbacks)
+- `MCP_SERVER_URL`: Public base URL. Used for OIDC redirect callbacks and to
+  derive the MCP endpoint mount path (serves at `/` when the URL has a path
+  prefix, otherwise defaults to `/mcp`).
 - `OIDC_CONFIG_URL`: Keycloak OIDC discovery URL (enables auth with all three OIDC vars)
 - `OIDC_CLIENT_ID`: OIDC client identifier
 - `OIDC_CLIENT_SECRET`: OIDC client secret
@@ -16,8 +18,15 @@
 from __future__ import annotations
 
 import logging
+import os
+from urllib.parse import urlparse
 
-from airbyte.mcp.server import DEFAULT_HTTP_HOST, DEFAULT_HTTP_PORT, app
+from airbyte.mcp.server import (
+    DEFAULT_HTTP_HOST,
+    DEFAULT_HTTP_PORT,
+    MCP_SERVER_URL_ENV,
+    app,
+)
 
 
 logger = logging.getLogger(__name__)
@@ -26,16 +35,28 @@
 def main() -> None:
     """Start the Airbyte MCP server with HTTP transport."""
     logging.basicConfig(level=logging.INFO)
+
+    # When deployed behind a path-stripping LB (MCP_SERVER_URL has a path
+    # component like /cloud-mcp), serve the MCP endpoint at root so the
+    # public URL is just the base path. Otherwise keep the FastMCP default.
+    server_url = os.getenv(
+        MCP_SERVER_URL_ENV,
+        f"http://localhost:{DEFAULT_HTTP_PORT}",
+    )
+    mcp_path = "/" if urlparse(server_url).path.strip("/") else "/mcp"
+
     logger.info(
-        "Starting Airbyte MCP HTTP server on %s:%d",
+        "Starting Airbyte MCP HTTP server on %s:%d (mcp_path=%r)",
         DEFAULT_HTTP_HOST,
         DEFAULT_HTTP_PORT,
+        mcp_path,
     )
 
     app.run(
         transport="streamable-http",
         host=DEFAULT_HTTP_HOST,
         port=DEFAULT_HTTP_PORT,
+        path=mcp_path,
         stateless_http=True,
     )