Files
codex/codex-rs/core/README.md
viyatb-oai f194d4b115 fix: reopen writable linux carveouts under denied parents (#14514)
## Summary
- preserve Linux bubblewrap semantics for `write -> none -> write`
filesystem policies by recreating masked mount targets before rebinding
narrower writable descendants
- add a Linux runtime regression for `/repo = write`, `/repo/a = none`,
`/repo/a/b = write` so the nested writable child is exercised under
bubblewrap
- document the supported legacy Landlock fallback and the split-policy
bubblewrap behavior for overlapping carveouts

## Example
Given a split filesystem policy like:

```toml
"/repo" = "write"
"/repo/a" = "none"
"/repo/a/b" = "write"
```

this PR keeps `/repo` writable, masks `/repo/a`, and still reopens
`/repo/a/b` as writable again under bubblewrap.

## Testing
- `just fmt`
- `cargo test -p codex-linux-sandbox`
- `cargo clippy -p codex-linux-sandbox --tests -- -D warnings`
2026-03-13 01:36:06 +00:00

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Markdown

# codex-core
This crate implements the business logic for Codex. It is designed to be used by the various Codex UIs written in Rust.
## Dependencies
Note that `codex-core` makes some assumptions about certain helper utilities being available in the environment. Currently, this support matrix is:
### macOS
Expects `/usr/bin/sandbox-exec` to be present.
When using the workspace-write sandbox policy, the Seatbelt profile allows
writes under the configured writable roots while keeping `.git` (directory or
pointer file), the resolved `gitdir:` target, and `.codex` read-only.
Network access and filesystem read/write roots are controlled by
`SandboxPolicy`. Seatbelt consumes the resolved policy and enforces it.
Seatbelt also supports macOS permission-profile extensions layered on top of
`SandboxPolicy`:
- no extension profile provided:
keeps legacy default preferences read access (`user-preference-read`).
- extension profile provided with no `macos_preferences` grant:
does not add preferences access clauses.
- `macos_preferences = "readonly"`:
enables cfprefs read clauses and `user-preference-read`.
- `macos_preferences = "readwrite"`:
includes readonly clauses plus `user-preference-write` and cfprefs shm write
clauses.
- `macos_automation = true`:
enables broad Apple Events send permissions.
- `macos_automation = ["com.apple.Notes", ...]`:
enables Apple Events send only to listed bundle IDs.
- `macos_launch_services = true`:
enables LaunchServices lookups and open/launch operations.
- `macos_accessibility = true`:
enables `com.apple.axserver` mach lookup.
- `macos_calendar = true`:
enables `com.apple.CalendarAgent` mach lookup.
- `macos_contacts = "read_only"`:
enables Address Book read access and Contacts read services.
- `macos_contacts = "read_write"`:
includes the readonly Contacts clauses plus Address Book writes and keychain/temp helpers required for writes.
### Linux
Expects the binary containing `codex-core` to run the equivalent of `codex sandbox linux` (legacy alias: `codex debug landlock`) when `arg0` is `codex-linux-sandbox`. See the `codex-arg0` crate for details.
Legacy `SandboxPolicy` / `sandbox_mode` configs are still supported on Linux.
They can continue to use the legacy Landlock path when the split filesystem
policy is sandbox-equivalent to the legacy model after `cwd` resolution.
Split filesystem policies that need direct `FileSystemSandboxPolicy`
enforcement, such as read-only or denied carveouts under a broader writable
root, automatically route through bubblewrap. The legacy Landlock path is used
only when the split filesystem policy round-trips through the legacy
`SandboxPolicy` model without changing semantics. That includes overlapping
cases like `/repo = write`, `/repo/a = none`, `/repo/a/b = write`, where the
more specific writable child must reopen under a denied parent.
### All Platforms
Expects the binary containing `codex-core` to simulate the virtual `apply_patch` CLI when `arg1` is `--codex-run-as-apply-patch`. See the `codex-arg0` crate for details.