Skip to content

Troubleshooting

Host and infrastructure issues that present as Bubo misbehaving but are fixed in the environment, not in Bubo. Each entry is symptom → cause → fix. For normal operation — deploy, schedule, grade, report — see Operate.

"No findings" on a change that isn't clean

Symptom

  • A review (usually an MCP-triggered review_change) returns no findings on a change that is not genuinely clean.
  • The transcript or report file shows: 
    bwrap: loopback: Failed RTM_NEWADDR: Operation not permitted
sandbox is rejecting shell execution
git_status / git_diff / git_show failed
  • An anomalous spike in no_findings. Codex exits 0, so nothing flags it.

Cause

[agents].codex_sandbox (read-only or workspace-write) isolates the run with bubblewrap, which needs an unprivileged user namespace. An npm/global Codex ships its own bwrap with no AppArmor profile; on Ubuntu with kernel.apparmor_restrict_unprivileged_userns = 1 the kernel blocks it, and every git/shell tool the agent needs fails. The poller usually survives (its diff is embedded in the prompt); the MCP path fails because it runs Codex nested with no checkout and must shell out to git. An apt/distro Codex uses the system bwrap, which has an allowed profile — hence "it works when installed via apt".

Confirm the restriction is on:

sysctl kernel.apparmor_restrict_unprivileged_userns   # 1 = on

Fix — AppArmor distros (Ubuntu, Debian, openSUSE)

Grant the user-namespace capability to Codex's own bundled bwrap. Locate it:

BWRAP=$(find "$(dirname "$(dirname "$(readlink -f "$(command -v codex)")")")" \
  -path '*codex-resources/bwrap' 2>/dev/null | head -1)
echo "$BWRAP"

Install a profile and reload AppArmor:

PROFILE=/etc/apparmor.d/codex-bwrap
sudo tee "$PROFILE" >/dev/null <<EOF
abi <abi/4.0>,
include <tunables/global>
$BWRAP flags=(default_allow) {
  userns,
  include if exists <local/codex-bwrap>
}
EOF
sudo apparmor_parser -r "$PROFILE"

Verify:

"$BWRAP" --unshare-net --ro-bind / / --proc /proc --dev /dev /bin/echo ok   # → ok
codex exec --profile bubo --skip-git-repo-check --ephemeral 'run: echo ok'  # → ok
  • If apparmor_parser --version is < 4.0, set abi <abi/4.0> to your parser's abi (e.g. abi <abi/3.0> on Ubuntu 22.04) or drop the abi line.
  • A Codex upgrade can move the bundled bwrap; re-run the locate step and apparmor_parser -r.

Fix — non-AppArmor hosts

  • RHEL / Fedora / Rocky / Alma (SELinux): the AppArmor sysctl and profile don't apply. User namespaces are usually allowed; if not, check sysctl user.max_user_namespaces (must be > 0).
  • Arch / other: userns usually works out of the box; if bwrap still fails, confirm kernel.unprivileged_userns_clone = 1.

Alternatives (no profile)

  • sudo apt install bubblewrap (Debian/Ubuntu) — Codex prefers a bwrap on PATH, and the distro package ships an allowed profile. Confirm with command -v bwrap → /usr/bin/bwrap.
  • On a dedicated, credential-stripped host, set codex_sandbox = "danger-full-access" in [agents]. Not workspace-write — it is also bubblewrap-based and fails identically.
  • Avoid disabling kernel.apparmor_restrict_unprivileged_userns host-wide unless the host is fully isolated.

Make it visible

Because this hides as "no findings", ship poller stdout to your observability stack and alert on an anomalous no-findings rate (see Metrics & telemetry). To check a single run by hand, grep its report file for bwrap:.