diff --git a/script/infra-setup.sh b/script/infra-setup.sh
index a921226..4fc99d2 100755
--- a/script/infra-setup.sh
+++ b/script/infra-setup.sh
@@ -293,9 +293,26 @@ Remaining one-time steps (operator, on the target host):
    The OAuth flow is interactive and must be completed *as the service account*,
    because Claude Code reads credentials from $HOME:
 
-       sudo -u tireless -H /usr/bin/npx -y @anthropic-ai/claude-code@2.1.220
+       sudo -u tireless -H bash -c 'cd /var/lib/tireless && \
+           npx -y @anthropic-ai/claude-code@2.1.220'
        # then: /login, and complete the browser flow
 
+   The `cd` is load-bearing. `-H` sets HOME, but sudo leaves the working
+   directory where you invoked it — typically your own 0700 home, which
+   `tireless` cannot read. npx then fails spawning its `sh -c claude` there:
+
+       npm error Error: spawn sh EACCES
+       npm error path: '/home/grenade'
+
+   which reads like a broken install rather than a directory permission.
+
+   `bash -c` rather than `sudo -iu tireless`, because the account's shell is
+   nologin by design and a login shell will not start.
+
+   Keep the pinned version in step with `CLAUDE_PACKAGE` in
+   crates/tireless-agent/src/claude.rs — the runner npx's that exact version,
+   and logging in with a different one warms the wrong cache.
+
    This writes /var/lib/tireless/.claude.json. The token refreshes in place,
    which is why the unit declares StateDirectory=tireless (systemd creates
    it, owns it as the service account, and keeps it writable).