Changes MCP_HOST set by toolhive to 0.0.0.0

[aponcedeleonch]

Bind MCP_HOST in the container to all interfaces by default so that the mcp server is reachable from the host

[yrobla]

we spin a transparent proxy when we start an MCP server, and the connectivity to that MCP server is done via proxy. So why is that change needed, is there a need to access MCP server from host directly?

[aponcedeleonch]

@yrobla then maybe I'm not using toolhive correctly? I'm doing

thv run --name knowledge-mcp --transport streameable-http knowledge-mcp

If knowledge-mcp accepts the MCP_HOST env var, and that env var is defined by ToolHive, without this change the env var value will be MCP_HOST=127.0.0.1. If I try to reach my MCP server with inspector to the IP http://localhost:<toolhive-provided-port>/mcp it will fail.

[aponcedeleonch]

This won't change the binding address of the proxy. Tested with

% go run ./cmd/thv run --name knowledge-mcp --transport streamable-http knowledge-mcp
% ps aux | grep proxy
....
aponcedeleonch   77793   0.0  0.1 412119104  50656   ??  Ss    3:53PM   0:00.17 /Users/aponcedeleonch/Library/Caches/go-build/e6/e6c2b759a96c2efc744281e7d9832f90b5c0db816de8a40e77f2e21840231e1c-d/thv run --foreground --transport streamable-http --proxy-mode sse --name knowledge-mcp --name knowledge-mcp --host 127.0.0.1 --port 11035 --target-port 48474 --target-host 0.0.0.0 --permission-profile /var/folders/m9/1z1wdq4n3ls979bzhtf3l6m00000gn/T/toolhive-knowledge-mcp-permissions-2663938117.json --env MCP_TRANSPORT=streamable-http --env MCP_PORT=48474 --env FASTMCP_PORT=48474 knowledge-mcp
% lsof -Pan -p 77793 -i
COMMAND   PID           USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
thv     77793 aponcedeleonch   12u  IPv4 0x26affa3e401c87a6      0t0  TCP 127.0.0.1:11035 (LISTEN)