docs: warn that codex's own sandbox breaks the sudo allowlist entirely - #727
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A codex TUI session opted out of codexFullAccess (skipPermissions = false) runs codex's own Linux sandbox in sandbox_mode=workspace-write, which execs through an unprivileged bubblewrap user namespace. Root is never mapped in that namespace, so sudo - and every sudoAllowlist entry, not just the self-serve caddy reload - shows up owned by nobody:nogroup and refuses outright, independent of what the sudoers file allows. Reproduced live: `codex exec -c sandbox_mode=workspace-write` fails inside this platform's own hardened session unit before even reaching sudo (`bwrap: loopback: Failed RTM_NEWADDR: Operation not permitted`), the same class of nested-sandbox conflict as agent-box#237's dev-container triage. There is no fix on the sudoers side: an unprivileged user namespace not mapping uid 0 is how bubblewrap sandboxes work, not a bug in our policy, and issue #234 already made codexFullAccess (skipping codex's own sandbox entirely) the box-wide default for exactly this reason. Document the limitation everywhere an agent or an operator would otherwise spend time trying to widen sudoers instead: the shipped AGENTS guide, the rendered Caddyfile comments, the codexFullAccess option description, and the README's option table and security model. Whether we also want a privilege-escalation-free reload path (so a sandboxed codex session can self-serve without sudo at all) is a separate, undecided design question - left open on #726 rather than folded into this docs fix. Addresses #726 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EEqb7WeohhYxTsYDwNvGgp
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📝 WalkthroughWalkthroughThe pull request adds documentation about Codex sandbox sessions. It explains that unprivileged bubblewrap namespaces prevent ChangesSandboxed sudo documentation
Priority: ⬇️ Low Estimated code review effort: 1 (Trivial) | ~5 minutes Change: Other Suggested reviewers: Merge Risk: 🔵 Low · up to Operators may misunderstand which Codex sessions can use sudo and reload Caddy; the correction is localized and does not affect runtime behavior. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Inline comments:
In `@README.md`:
- Around line 780-781: Update the README wording to scope this restriction
specifically to Codex TUI sessions, and describe skipPermissions = false as
selecting Codex’s sandbox even when codexFullAccess = true. Remove the
misleading equivalence between skipPermissions = false and not codexFullAccess
while preserving the surrounding explanation.
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README.mdmodules/agent-box.nixmodules/agent-box.nix.inmodules/src/caddyfile-header.caddymodules/src/caddyfile-sites.caddymodules/src/default-agents.mdtests/golden/vm/etc/agent-box-guides/AGENTS.agent.mdtests/golden/web/etc/agent-box-guides/AGENTS.agent.mdtests/golden/web/etc/caddy/caddy_configtests/native/expected/etc/agent-box-guides/AGENTS.agent.mdtests/native/expected/etc/agent-box-guides/AGENTS.robot.mdtests/native/expected/etc/agent-box/Caddyfile
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CodeRabbit correctly flagged that "skipPermissions = false, i.e. not codexFullAccess" was a misleading equivalence: a remote-controlled codex session ignores skipPermissions entirely and always follows the box-wide codexFullAccess default (the option's own doc already says so); only a TUI session's per-session override actually switches sandbox modes. Reword every spot that had the same conflation to say "Codex TUI session ... even when codexFullAccess is true" instead. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EEqb7WeohhYxTsYDwNvGgp
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coderabbitai[bot]’s stale review
September 17, 2026 20:28
addressed in bdd5c0b; thread resolved
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Summary
codexFullAccess(skipPermissions = false) runs codex's own Linux sandbox (sandbox_mode=workspace-write), which execs through an unprivilegedbubblewrapuser namespace. Root is never mapped in that namespace, sosudo- everysudoAllowlistentry, not just the self-serve caddy reload - shows up owned bynobody:nogroupand refuses outright, whatever the sudoers file allows. This is how unprivileged user namespaces and setuid execution interact; it is not something our sudoers policy can fix.codex exec -c sandbox_mode=workspace-writefails before even reachingsudo(bwrap: loopback: Failed RTM_NEWADDR: Operation not permitted) - the box's own hardened session unit and codex's nested bubblewrap sandbox don't compose, the same class of conflict flagged in agent-box#237's dev-container triage.codexFullAccess = true(skip codex's own sandbox entirely) the box-wide default for exactly this reason ("the box IS the sandbox"). Codex execution environment cannot use sudo wrapper to reload Caddy #726's reporter had presumably opted a session out of that default (a documented, supported thing to do - see theci = { skipPermissions = false; }example in the README), and silently lost the entire sudo escape hatch as a side effect, with no doc saying so anywhere.modules/src/default-agents.md), the rendered Caddyfile comments (caddyfile-header.caddy,caddyfile-sites.caddy), thecodexFullAccessoption description, and the README's option table + security model.modules/agent-box.nix,tests/native/expected/, andtests/golden/for the doc payloads that moved.Not in scope
Whether we also want a privilege-escalation-free reload path - so a sandboxed codex session can self-serve
~/siteswithoutsudoat all (e.g. a root-owned watcher that auto-reloads caddy on snippet changes) - is a separate, undecided design question with real trade-offs (silent reload of a broken snippet vs. today's visible manual step, etc.). Left open on #726 for a decision rather than folded into this docs fix.Test plan
nix run .#assemble-modules/agent-box.nixup to datepython3 tests/test_agentbox.py --update- regeneratedtests/native/expected/(3 files, doc-only diff, no leaked host pins)nix run .#update-golden- regeneratedtests/golden/(3 files, doc-only diff)nix build -L .#checks.aarch64-linux.module-generated-up-to-date- passnix build -L .#checks.aarch64-linux.golden-snapshot- passnix build -L .#checks.aarch64-linux.one-spec-both-backends- passnix build -L .#checks.aarch64-linux.assemble-module-escaping- passnix build -L .#checks.aarch64-linux.backend-parity- pass, no new gaps🤖 Generated with Claude Code
https://claude.ai/code/session_01EEqb7WeohhYxTsYDwNvGgp