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Add hermes_mcp, the bridge between Hermes and the ROS graph

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The MCP server is now a ROS node and the only way in or out, per the owner's
decision that ROS never leaves the robot. It serves MCP on the USB address only
with a bearer token, keeps the stable tool name look() (which waits for the next
camera frame, so it is never stale, and passes the camera's JPEG through), and
registers turn_head/head_position only when a head is fitted, which today it is
not. While an authenticated client is connected it republishes the agent
heartbeat on /hermes/state, so the face wakes on connect and sleeps about 40 s
after the client leaves; look() also makes the face squint.

The token is generated on the Pi into /etc/robot-mcp.env (root:hermes, 640) and
never printed. Verified end to end from talos with a real MCP client over the USB
link: tools listed, a 157 KB JPEG back in 0.08 s, a wrong token refused, the Wi-Fi
path dropped by the firewall. Host config snippets now point at 10.55.0.2.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs
This commit is contained in:
kyle
2026-10-05 00:20:58 -07:00
co-authored by Claude Sonnet 5.5
parent d8db0a48f5
commit 167f53ceeb
17 changed files with 462 additions and 24 deletions
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pi/install-robot-service.sh
+8 -1
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@@ -1,10 +1,17 @@
#!/bin/bash
# One unit runs the whole robot (face, camera, vision, audio) via the hermes_bringup launch file, so
# One unit runs the whole robot (face, camera, vision, audio, MCP bridge) via the hermes_bringup launch file, so
# the face is up whenever the robot is powered, and everything is ROS. Each node is its own process
# and is respawned by the launch file, so one crash cannot take the others down.
# Replaces the earlier standalone robot-face.service. Run as root from this directory. Re-runnable.
set -euo pipefail
cd "$(dirname "$0")"
# The MCP bridge's bearer token: created once, readable only by root and the service user, and never
# printed (read it yourself with `sudo cat /etc/robot-mcp.env` when configuring the host).
if [ ! -s /etc/robot-mcp.env ]; then
(umask 077; printf 'ROBOT_MCP_TOKEN=%s\n' "$(openssl rand -hex 32)" > /etc/robot-mcp.env)
fi
chown root:hermes /etc/robot-mcp.env
chmod 640 /etc/robot-mcp.env
install -m 644 robot-cpu-performance.service robot.service /etc/systemd/system/
systemctl disable --now robot-face.service 2>/dev/null || true
rm -f /etc/systemd/system/robot-face.service
pi/robot.service
+3 -1
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@@ -1,5 +1,5 @@
[Unit]
Description=Robot (hermes_bringup): face, camera, face detection, audio levels
Description=Robot (hermes_bringup): face, camera, face detection, audio levels, MCP bridge
# Nothing here needs the user session: audio_state retries until the user's PipeWire is up.
After=local-fs.target robot-cpu-performance.service robot-firewall.service
@@ -9,6 +9,8 @@ User=hermes
# be writable: systemd's default, /, is not.
RuntimeDirectory=robot
WorkingDirectory=/run/robot
# hermes_mcp reads its bearer token from here (root:hermes, mode 640); it is never in a parameter
EnvironmentFile=-/etc/robot-mcp.env
# audio_state reaches the user's PipeWire through this
Environment=XDG_RUNTIME_DIR=/run/user/1000
ExecStart=/bin/bash -c 'source /home/hermes/robot-env.sh && exec ros2 launch hermes_bringup robot.launch.py'