[Bug] Editing MCP server changes target port

[danbarr]

Bug Description

I have a streamable-http MCP server running with a specific target port, which must match the port the MCP server is running with.

Then using the UI, I edited it to change an unrelated environment variable. But when it's restarted, the server now has a different (random) target port, which breaks the server.

Steps to Reproduce

1. Run a streamable-http MCP server like osv, either from the registry or as custom. Note the target port (8080 in osv's case).
2. Edit the server to change anything about it, like adding an env var.
3. Note the restarted server has a new, random target port.

Expected Behavior

The target port should remain unchanged.

Actual Behavior

The target port is reassigned to a random value.

Priority

Medium

Environment

• OS: macOS
• ToolHive UI version: 0.32.0

Additional Context

Before: target port (and related MCP_PORT and FASTMCP_PORT env vars) == 8931

After: target port and env vars changed to 56967

[samuv]

@danbarr do you have the payload handy for the edit API call? just to be sure that is correctly passed down

[danbarr]

@samuv how would I get that?

[samuv]

🤖 response

Here's how:

• In ToolHive Studio, open View → Toggle Developer Tools (or Cmd+Option+I on macOS)
• Click the Network tab in the dev tools panel
• With the Network tab open, go ahead and edit the server like you did before and save
• Look through the list of requests and find the one for the edit (it should be a POST or PUT to something like /api/v1beta/workloads/...)
• Click on that request, then open the Payload tab (or Request tab depending on the browser)
• Copy the full JSON payload and paste it here

That'll let us see exactly what the UI is sending to the backend when you save the edit. Thanks!

[danbarr]

The original target_port:8080 is indeed in the edit request:

{"image":"ghcr.io/stackloklabs/osv-mcp/server:0.1.3","transport":"streamable-http","proxy_port":55543,"group":"default","target_port":8080,"cmd_arguments":[],"env_vars":{"FASTMCP_PORT":"8080","MCP_PORT":"8080","MCP_TRANSPORT":"streamable-http","TEST":"test"},"secrets":[],"network_isolation":false,"volumes":[]}

But after it restarted, the target port has changed to 19774.

[samuv]

The original target_port:8080 is indeed in the edit request:

{"image":"ghcr.io/stackloklabs/osv-mcp/server:0.1.3","transport":"streamable-http","proxy_port":55543,"group":"default","target_port":8080,"cmd_arguments":[],"env_vars":{"FASTMCP_PORT":"8080","MCP_PORT":"8080","MCP_TRANSPORT":"streamable-http","TEST":"test"},"secrets":[],"network_isolation":false,"volumes":[]}

But after it restarted, the target port has changed to 19774.

nice, thank you! so it's probably a BE issue 🥷