diff --git a/claude_bottle/backend/smolmachines/provision/supervise.py b/claude_bottle/backend/smolmachines/provision/supervise.py
index 724dafe..c06bf38 100644
--- a/claude_bottle/backend/smolmachines/provision/supervise.py
+++ b/claude_bottle/backend/smolmachines/provision/supervise.py
@@ -38,9 +38,16 @@ def provision_supervise(plan: SmolmachinesBottlePlan, target: str) -> None:
         return
     url = plan.agent_supervise_url
     info(f"registering supervise MCP server in agent claude config → {url}")
+    # `claude mcp add --scope user` writes to ~/.claude.json. The
+    # agent is the `node` user; smolvm machine_exec runs as root
+    # by default, so we have to switch user explicitly and set
+    # HOME so the config lands in /home/node/.claude.json (where
+    # the agent's claude actually reads it from).
     r = _smolvm.machine_exec(
         target,
         [
+            "runuser", "-u", "node", "--",
+            "env", "HOME=/home/node",
             "claude", "mcp", "add",
             "--scope", "user",
             "--transport", "http",
diff --git a/tests/unit/test_smolmachines_provision.py b/tests/unit/test_smolmachines_provision.py
index bb547ad..f00ea79 100644
--- a/tests/unit/test_smolmachines_provision.py
+++ b/tests/unit/test_smolmachines_provision.py
@@ -487,11 +487,15 @@ class TestProvisionSupervise(unittest.TestCase):
             _supervise.provision_supervise(plan, "claude-bottle-demo-abc12")
         ex.assert_called_once()
         argv = ex.call_args.args[1]
-        # claude mcp add --scope user --transport http supervise <url>
-        # — URL is the agent-side endpoint (host loopback +
-        # discovered port), not the docker bridge IP.
+        # `claude mcp add --scope user` writes to ~/.claude.json,
+        # and the agent is the `node` user — switch UID + set
+        # HOME so the config lands in /home/node/.claude.json,
+        # not root's. URL is the agent-side endpoint (host
+        # loopback + discovered port), not the docker bridge IP.
         self.assertEqual(
             [
+                "runuser", "-u", "node", "--",
+                "env", "HOME=/home/node",
                 "claude", "mcp", "add",
                 "--scope", "user",
                 "--transport", "http",