this is it!

Author: dsarno

.github/workflows/claude-nl-suite.yml

@@ -251,7 +251,7 @@ jobs:
             -e HOME=/root \
             -e UNITY_MCP_ALLOW_BATCH=1 \
             -e UNITY_MCP_STATUS_DIR="${{ github.workspace }}/.unity-mcp" \
-            -e UNITY_MCP_BIND_HOST=127.0.0.1 \
+            -e UNITY_MCP_BIND_HOST=0.0.0.0 \
             -v "${{ github.workspace }}:${{ github.workspace }}" -w "${{ github.workspace }}" \
             -v "$RUNNER_TEMP/unity-config:/root/.config/unity3d" \
             -v "$RUNNER_TEMP/unity-local:/root/.local/share/unity3d" \
@@ -435,6 +435,16 @@ jobs:
           fi
 
       # ---------- MCP client config ----------
+      # Get host IP for network connectivity (Claude Code might run in isolated network)
+      - name: Get host IP
+        id: host_ip
+        run: |
+          set -eux
+          # Get the default route's source IP (works on GitHub Actions Linux)
+          HOST_IP=$(ip route get 1.1.1.1 2>/dev/null | grep -oP 'src \K\S+' || echo "127.0.0.1")
+          echo "host_ip=$HOST_IP" >> "$GITHUB_OUTPUT"
+          echo "Host IP: $HOST_IP"
+
       - name: Write MCP config (.claude/mcp.json)
         run: |
           set -eux
@@ -446,6 +456,9 @@ jobs:
 
           workspace = os.environ["GITHUB_WORKSPACE"]
           default_inst = os.environ.get("UNITY_MCP_DEFAULT_INSTANCE", "").strip()
+          # Use host IP if available, fallback to 127.0.0.1
+          # This handles cases where Claude Code spawns MCP server in isolated network namespace
+          host_ip = os.environ.get("HOST_IP", "127.0.0.1")
 
           cfg = {
               "mcpServers": {
@@ -468,7 +481,7 @@ jobs:
                           "MCP_LOG_LEVEL": "debug",
                           "UNITY_PROJECT_ROOT": f"{workspace}/TestProjects/UnityMCPTests",
                           "UNITY_MCP_STATUS_DIR": f"{workspace}/.unity-mcp",
-                          "UNITY_MCP_HOST": "127.0.0.1",
+                          "UNITY_MCP_HOST": host_ip,
                       },
                   }
               }
@@ -482,8 +495,10 @@ jobs:
 
           path = Path(".claude/mcp.json")
           path.write_text(json.dumps(cfg, indent=2) + "\n")
-          print(f"Wrote {path} (UNITY_MCP_DEFAULT_INSTANCE={default_inst or 'unset'})")
+          print(f"Wrote {path} (UNITY_MCP_HOST={host_ip}, UNITY_MCP_DEFAULT_INSTANCE={default_inst or 'unset'})")
           PY
+        env:
+          HOST_IP: ${{ steps.host_ip.outputs.host_ip }}
 
       - name: Debug MCP config
         run: |

Server/src/main.py

@@ -376,6 +376,8 @@ def main():
     try:
         from transport.legacy.port_discovery import PortDiscovery
         import glob
+        unity_host = os.environ.get("UNITY_MCP_HOST", "127.0.0.1")
+        startup_debug_lines.append(f"UNITY_MCP_HOST={unity_host}")
         status_dir = PortDiscovery.get_registry_dir()
         startup_debug_lines.append(f"status_dir={status_dir}")
         startup_debug_lines.append(f"status_dir_exists={status_dir.exists()}")
@@ -389,9 +391,9 @@ def main():
                     data = json.load(f)
                 port = data.get('unity_port')
                 startup_debug_lines.append(f"file={sf}, port={port}")
-                # Try probe
-                probe_result = PortDiscovery._try_probe_unity_mcp(port) if port else False
-                startup_debug_lines.append(f"probe_port_{port}={probe_result}")
+                # Try probe with the configured host
+                probe_result = PortDiscovery._try_probe_unity_mcp(port, unity_host) if port else False
+                startup_debug_lines.append(f"probe_{unity_host}:{port}={probe_result}")
             except Exception as e:
                 startup_debug_lines.append(f"error_reading_{sf}={e}")
         instances = PortDiscovery.discover_all_unity_instances()
@@ -412,6 +414,7 @@ def main():
                 f.write(f"Timestamp: {time.strftime('%Y-%m-%d %H:%M:%S')}\n")
                 f.write(f"args.status_dir: {args.status_dir}\n")
                 f.write(f"UNITY_MCP_STATUS_DIR env: {os.environ.get('UNITY_MCP_STATUS_DIR', 'NOT SET')}\n")
+                f.write(f"UNITY_MCP_HOST env: {os.environ.get('UNITY_MCP_HOST', 'NOT SET')}\n")
                 f.write("\n".join(startup_debug_lines))
                 f.write("\n")
             logger.info(f"Wrote startup debug to {debug_file_path}")

Server/src/transport/legacy/port_discovery.py

@@ -61,14 +61,20 @@ def list_candidate_files() -> list[Path]:
         return hashed
 
     @staticmethod
-    def _try_probe_unity_mcp(port: int) -> bool:
+    def _try_probe_unity_mcp(port: int, host: str | None = None) -> bool:
         """Quickly check if a MCP for Unity listener is on this port.
         Uses Unity's framed protocol: receives handshake, sends framed ping, expects framed pong.
+        
+        Args:
+            port: Port number to probe
+            host: Host to connect to (defaults to UNITY_MCP_HOST env var or 127.0.0.1)
         """
+        if host is None:
+            host = os.environ.get("UNITY_MCP_HOST", "127.0.0.1")
         try:
             # Increased timeout for CI stability
             timeout = 2.0
-            with socket.create_connection(("127.0.0.1", port), timeout) as s:
+            with socket.create_connection((host, port), timeout) as s:
                 s.settimeout(timeout)
                 try:
                     # 1. Receive handshake from Unity