Fixes#15283.
## Summary
Older system bubblewrap builds reject `--argv0`, which makes our Linux
sandbox fail before the helper can re-exec. This PR keeps using system
`/usr/bin/bwrap` whenever it exists and only falls back to vendored
bwrap when the system binary is missing. That matters on stricter
AppArmor hosts, where the distro bwrap package also provides the policy
setup needed for user namespaces.
For old system bwrap, we avoid `--argv0` instead of switching binaries:
- pass the sandbox helper a full-path `argv0`,
- keep the existing `current_exe() + --argv0` path when the selected
launcher supports it,
- otherwise omit `--argv0` and re-exec through the helper's own
`argv[0]` path, whose basename still dispatches as
`codex-linux-sandbox`.
Also updates the launcher/warning tests and docs so they match the new
behavior: present-but-old system bwrap uses the compatibility path, and
only absent system bwrap falls back to vendored.
### Validation
1. Install Ubuntu 20.04 in a VM
2. Compile codex and run without bubblewrap installed - see a warning
about falling back to the vendored bwrap
3. Install bwrap and verify version is 0.4.0 without `argv0` support
4. run codex and use apply_patch tool without errors
<img width="802" height="631" alt="Screenshot 2026-03-25 at 11 48 36 PM"
src="https://github.com/user-attachments/assets/77248a29-aa38-4d7c-9833-496ec6a458b8"
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<img width="807" height="634" alt="Screenshot 2026-03-25 at 11 47 32 PM"
src="https://github.com/user-attachments/assets/5af8b850-a466-489b-95a6-455b76b5050f"
/>
<img width="812" height="635" alt="Screenshot 2026-03-25 at 11 45 45 PM"
src="https://github.com/user-attachments/assets/438074f0-8435-4274-a667-332efdd5cb57"
/>
<img width="801" height="623" alt="Screenshot 2026-03-25 at 11 43 56 PM"
src="https://github.com/user-attachments/assets/0dc8d3f5-e8cf-4218-b4b4-a4f7d9bf02e3"
/>
---------
Co-authored-by: Michael Bolin <mbolin@openai.com>
## Summary
- move the pure sandbox policy transform helpers from `codex-core` into
`codex-sandboxing`
- move the corresponding unit tests with the extracted implementation
- update `core` and `app-server` callers to import the moved APIs
directly, without re-exports or proxy methods
## Testing
- cargo test -p codex-sandboxing
- cargo test -p codex-core sandboxing
- cargo test -p codex-app-server --lib
- just fix -p codex-sandboxing
- just fix -p codex-core
- just fix -p codex-app-server
- just fmt
- just argument-comment-lint
## Summary
- move macOS permission merging/intersection logic and tests from
`codex-core` into `codex-sandboxing`
- move seatbelt policy builders, permissions logic, SBPL assets, and
their tests into `codex-sandboxing`
- keep `codex-core` owning only the seatbelt spawn wrapper and switch
call sites to import the moved APIs directly
## Notes
- no re-exports added
- moved the seatbelt tests with the implementation so internal helpers
could stay private
- local verification is still finishing while this PR is open
## Summary
- add a new `codex-sandboxing` crate for sandboxing extraction work
- move the pure Linux sandbox argv builders and their unit tests out of
`codex-core`
- keep `core::landlock` as the spawn wrapper and update direct callers
to use `codex_sandboxing::landlock`
## Testing
- `cargo test -p codex-sandboxing`
- `cargo test -p codex-core landlock`
- `cargo test -p codex-cli debug_sandbox`
- `just argument-comment-lint`
## Notes
- this is step 1 of the move plan aimed at minimizing per-PR diffs
- no re-exports or no-op proxy methods were added
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