Unable to get SSE transport working with Claude Code

[FleetAdmiralButter]

Hi,

Thank you for putting together this library! It's great that we can host an MCP server directly in Laravel 💯

I've been going through the project README to try and get Laravel Loop working with one of my projects.

I've done the following:

1. Installed the Composer package.
2. Run php artisan vendor:publish --tag="loop-config".
3. Set LOOP_SSE_ENABLED=true in my project's .env.

I've also configured a very basic sample tool in my AppServiceProvider:

use Kirschbaum\Loop\Facades\Loop;
use Kirschbaum\Loop\Tools\CustomTool;

public function boot(): void
    {
        ... other code...

        Loop::tool(
            CustomTool::make(
                name: 'custom_tool',
                description: 'This is a custom tool',
            )
                ->withStringParameter(name: 'name', description: 'The name of the user', required: true)
                ->withNumberParameter(name: 'age', description: 'The age of the user')
                ->using(function (string $name, ?int $age = null) {
                    return sprintf('Hello, %s! You are %d years old.', $name, $age ?? 'unknown');
                }),
        );
    }

I then used the loop:mcp:generate-config command to set up an STDIO MCP server with Claude Code. It worked as expected:

╭───────────────────────────────────────────────────╮
│ ✻ Welcome to Claude Code!                         │
│                                                   │
│   /help for help, /status for your current setup  │
│                                                   │
╰───────────────────────────────────────────────────╯


 ※ Tip: Press Esc twice to edit your previous messages


> Can you use the configured laravel-loop-mcp server and invoke the custom_tool tool with some sample input?

⏺ I can see there's a Laravel Loop MCP server configured. Let me invoke the custom_tool with some sample input.

⏺ laravel-loop-mcp:custom_tool (MCP)(name: "John Doe", age: 30)
  ⎿  Hello, John Doe! You are 30 years old.

⏺ The custom_tool from the laravel-loop-mcp server worked successfully! It took the name "John Doe" and age 30 as input and returned a greeting message.

I then used the loop:mcp:generate-config command again, but this time I chose the SSE transport. Unfortunately, Claude Code isn't able to correctly detect the tool over SSE:

╭───────────────────────────────────────────────────╮
│ ✻ Welcome to Claude Code!                         │
│                                                   │
│   /help for help, /status for your current setup  │
│                                                   │
╰───────────────────────────────────────────────────╯


 ※ Tip: Create custom slash commands by adding .md files to .claude/commands/ in your project or ~/.claude/commands/ for commands that work in any project

> Can you use the configured laravel-loop-mcp server and invoke the custom_tool tool with some sample input?

⏺ I'll check the configuration for the laravel-loop-mcp server and then invoke the custom_tool. Let me first examine the configuration to understand what's available.

⏺ Read(config/loop.php)
  ⎿  Read 111 lines (ctrl+r to expand)

⏺ Let me check the environment configuration and see if MCP is enabled:

⏺ Bash(grep -E "LOOP_|MCP" /Users/mingquah/Projects/platform/.env)
  ⎿  No (tell Claude what to do differently)

> No, don't check the project - simply invoke the configured MCP tool, custom_tool.

⏺ I'll invoke the custom_tool from the configured laravel-loop-mcp server with some sample input.

⏺ It seems the MCP tool isn't available with that name. Let me check what MCP tools are actually configured by looking at the available tools:

⏺ The MCP tools don't appear to be available in this session. This could mean:

  1. The laravel-loop-mcp server isn't running
  2. The MCP server isn't properly configured in Claude Code
  3. The server needs to be started or connected

Using the /mcp command, it does appear that the MCP SSE server is connected:

│ Manage MCP Servers
│ 1 server found
│ 
│   laravel-loop-mcp · connected 

I can also see POST requests to /mcp/sse/message in my web server logs, so Claude Code is trying to connect, but can't discover the tools for some reason. Since the same tool worked over STDIO, I believe that the tool itself is correctly set up but there's an issue with the SSE stream. I also tried removing the auth:sanctum middleware in loop.php, but this didn't make any difference.

Does Laravel Loop need any special web server configuration for it's SSE transport? I am also using Laravel Octane which might complicate things.

[FleetAdmiralButter]

I've noticed that the SSE endpoint only returns the list of tools once per session.

In Terminal 1:

 ✗ curl -N -H "Accept: text/event-stream" "http://localhost:8080/mcp/sse"
event: endpoint
data: /mcp/sse/message/?sessionId=6847e0f28102f

event: debug
data: {"message":"Connection established","time":1749541106}

With the stream active, I copied the sessionId and ran the following in Terminal 2:

✗ curl -X POST "http://localhost:8080/mcp/sse/message/?sessionId=6847e0f28102f" \
    -H "Content-Type: application/json" \
    -d '{
      "jsonrpc": "2.0",
      "id": 1,
      "method": "tools/list"
    }'
{"status":"received","message":"Request received and being processed"}
✗ curl -X POST "http://localhost:8080/mcp/sse/message/?sessionId=6847e0f28102f" \
    -H "Content-Type: application/json" \
    -d '{
      "jsonrpc": "2.0",
      "id": 1,
      "method": "tools/list"
    }'
{"status":"received","message":"Request received and being processed"}
curl -X POST "http://localhost:8080/mcp/sse/message/?sessionId=6847e0f28102f" \
    -H "Content-Type: application/json" \
    -d '{
      "jsonrpc": "2.0",
      "id": 2,
      "method": "tools/list"
    }'
{"status":"received","message":"Request received and being processed"}% 

Terminal 1 then output the following three corresponding messages:

event: message
data: {"jsonrpc":"2.0","id":1,"result":{"tools":[{"name":"custom_tool","description":"This is a custom tool","inputSchema":{"type":"object","properties":{"name":{"description":"The name of the user","type":"string"},"age":{"description":"The age of the user","type":"number"}},"required":["name","age"],"additionalProperties":false}}]}}

event: message
data: {"jsonrpc":"2.0","id":1,"result":{"tools":[]}}

event: message
data: {"jsonrpc":"2.0","id":2,"result":{"tools":[]}}

I'm not too sure if this is expected behaviour as I'm still learning how MCP works.

[luisdalmolin]

Hey -- thanks for the detailed report. We are going to take a look at this today.

[fsmonter]

Hi @FleetAdmiralButter thanks for the report.

I tried the tools/list requests but I couldn't replicate the results, you should be able to list the tools anytime you send the request, not just on the initial.

I think the root issue is Octane. AFAIK, flushing is handled differently, which can cause potential issues. Have you tried without it?

I'll test with Octane and get back with any findings.

[FleetAdmiralButter]

Thanks for your reply @fsmonter, I'll give this a go without Octane. Are you testing with Apache or PHP-FPM?

[FleetAdmiralButter]

Success! I tried using FPM instead of Octane and I got the SSE connection to work:

╭───────────────────────────────────────────────────╮
│ ✻ Welcome to Claude Code!                         │
│                                                   │
│   /help for help, /status for your current setup  │
│                                                   │
╰───────────────────────────────────────────────────╯


 ※ Tip: Hit shift+tab to cycle between default mode, auto-accept edit mode, and plan mode


> Can you use the configured laravel-loop-mcp server and invoke the custom_tool tool with some sample input?

⏺ I'll use the configured Laravel Loop MCP server to invoke the custom_tool with sample input.

⏺ laravel-loop-mcp:custom_tool (MCP)(name: "John Doe", age: 30)
  ⎿  Hello, John Doe! You are 30 years old.

⏺ The custom tool worked successfully! It accepted the name "John Doe" and age 30 as parameters and returned a greeting message.

Looks like Octane was the problem here.

[FleetAdmiralButter]

Hi @fsmonter,

After some experimentation I managed to get Laravel Loop working with Octane!

There was nothing wrong with the way messages were being flushed - rather it was how I was defining my custom tool.

As per the readme, I was registering it in the boot() method of AppServiceProvider.php:

public function boot(): void
    {
        Loop::tool(
            CustomTool::make(
                name: 'add_numbers',
                description: 'This custom tools adds two numbers together.',
            )
                ->withNumberParameter(name: 'num_a', description: 'The first number', required: true)
                ->withNumberParameter(name: 'num_b', description: 'The second number', required: true)
                ->using(function (int $num_a, int $num_b) {
                    return sprintf('The answer is %d', $num_a + $num_b);
                }),
        );
    }

However, as the Loop class is defined as a scoped binding, Octane was resetting it between requests, causing the list of registered tools to disappear.

I've moved this code to register(), so that the tool is registered every time the Tool class is created:

public function register(): void
    {
        $this->app->resolving(\Kirschbaum\Loop\Loop::class, function (\Kirschbaum\Loop\Loop $loop) {
            $loop->tool(
                \Kirschbaum\Loop\Tools\CustomTool::make('add_numbers', 'Adds two numbers')
                    ->withNumberParameter('num_a', 'First number', true)
                    ->withNumberParameter('num_b', 'Second number', true)
                    ->using(fn (int $num_a, int $num_b) => "The answer is ".($num_a + $num_b))
            );
        });
    }

Claude can see and invoke my tool now, even over Octane.

[luisdalmolin]

Interesting, thanks for doing the digging. We'll update the docs to make sure this is explained there.

[fsmonter]

@FleetAdmiralButter #28 fixed this. You should be able to register tools normally in AppServiceProvider::boot using Octane.

Thanks for the report!