[MCP Bundle] Incompatibility of the MCPBundle with FrankenPHP #999
Description
Context
I am using McpBundle (commit a29a8df2d3af0442bae8efc4a5196ecb2f66635c) with APIPlatform 4.1.20 and Symfony 7.3.6. The project is based on the API Platform repository template. I am using the provided Docker stack with FrankenPHP.
On top of this base I have required the MCP Bundle with the default routes configuration :
# api/config/routes/mcp.yaml
mcp_bundle_routes:
resource: .
type: mcpIssue
When I try to connect a MCP client, the first request on POST /mcp succeeds. However if there are some following request in the few seconds after the first one, there are HTTP 500 errors with the following trace. It seems to me it happens exclusively in the context of a Symfony application running with the FrankenPHP worker. In this context the server instance seems to be shared between several requests.
{
"type": "https://tools.ietf.org/html/rfc2616#section-10",
"title": "An error occurred",
"status": 500,
"detail": "Protocol already connected to a transport",
"class": "RuntimeException",
"trace": [
{
"namespace": "",
"short_class": "",
"class": "",
"type": "",
"function": "",
"file": "/app/vendor/mcp/sdk/src/Server/Protocol.php",
"line": 93,
"args": []
},
{
"namespace": "Mcp\\Server",
"short_class": "Protocol",
"class": "Mcp\\Server\\Protocol",
"type": "->",
"function": "connect",
"file": "/app/vendor/mcp/sdk/src/Server.php",
"line": 48,
"args": [
[
"object",
"Mcp\\Server\\Transport\\StreamableHttpTransport"
]
]
},
{
"namespace": "Mcp",
"short_class": "Server",
"class": "Mcp\\Server",
"type": "->",
"function": "run",
"file": "/app/vendor/symfony/mcp-bundle/src/Controller/McpController.php",
"line": 46,
"args": [
[
"object",
"Mcp\\Server\\Transport\\StreamableHttpTransport"
]
]
},
{
"namespace": "Symfony\\AI\\McpBundle\\Controller",
"short_class": "McpController",
"class": "Symfony\\AI\\McpBundle\\Controller\\McpController",
"type": "->",
"function": "handle",
"file": "/app/vendor/symfony/http-kernel/HttpKernel.php",
"line": 183,
"args": [
[
"object",
"Symfony\\Component\\HttpFoundation\\Request"
]
]
},
{
"namespace": "Symfony\\Component\\HttpKernel",
"short_class": "HttpKernel",
"class": "Symfony\\Component\\HttpKernel\\HttpKernel",
"type": "->",
"function": "handleRaw",
"file": "/app/vendor/symfony/http-kernel/HttpKernel.php",
"line": 76,
"args": [
[
"object",
"Symfony\\Component\\HttpFoundation\\Request"
],
[
"integer",
1
]
]
},
{
"namespace": "Symfony\\Component\\HttpKernel",
"short_class": "HttpKernel",
"class": "Symfony\\Component\\HttpKernel\\HttpKernel",
"type": "->",
"function": "handle",
"file": "/app/vendor/symfony/http-kernel/Kernel.php",
"line": 182,
"args": [
[
"object",
"Symfony\\Component\\HttpFoundation\\Request"
],
[
"integer",
1
],
[
"boolean",
true
]
]
},
{
"namespace": "Symfony\\Component\\HttpKernel",
"short_class": "Kernel",
"class": "Symfony\\Component\\HttpKernel\\Kernel",
"type": "->",
"function": "handle",
"file": "/app/vendor/runtime/frankenphp-symfony/src/Runner.php",
"line": 38,
"args": [
[
"object",
"Symfony\\Component\\HttpFoundation\\Request"
]
]
},
{
"namespace": "Runtime\\FrankenPhpSymfony",
"short_class": "Runner",
"class": "Runtime\\FrankenPhpSymfony\\Runner",
"type": "->",
"function": "{closure:Runtime\\FrankenPhpSymfony\\Runner::run():33}",
"file": null,
"line": null,
"args": []
},
{
"namespace": "",
"short_class": "",
"class": "",
"type": "",
"function": "frankenphp_handle_request",
"file": "/app/vendor/runtime/frankenphp-symfony/src/Runner.php",
"line": 45,
"args": [
[
"object",
"Closure"
]
]
},
{
"namespace": "Runtime\\FrankenPhpSymfony",
"short_class": "Runner",
"class": "Runtime\\FrankenPhpSymfony\\Runner",
"type": "->",
"function": "run",
"file": "/app/vendor/autoload_runtime.php",
"line": 29,
"args": []
},
{
"namespace": "",
"short_class": "",
"class": "",
"type": "",
"function": "require_once",
"file": "/app/public/index.php",
"line": 5,
"args": [
[
"string",
"/app/vendor/autoload_runtime.php"
]
]
}
]
}