This crate implements the business logic for Codex. It is designed to be used by the various Codex UIs written in Rust.

Note that codex-core makes some assumptions about certain helper utilities being available in the environment. Currently, this support matrix is:

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 keeps the legacy default preferences read access (user-preference-read) needed for cfprefs-backed macOS behavior.

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.

The Linux sandbox helper prefers the first bwrap found on PATH outside the current working directory whenever it is available. If bwrap is present but too old to support --argv0, the helper keeps using system bubblewrap and switches to a no---argv0 compatibility path for the inner re-exec. If bwrap is missing, it falls back to the vendored bubblewrap path compiled into the binary and Codex surfaces a startup warning through its normal notification path instead of printing directly from the sandbox helper.

Legacy SandboxPolicy / sandbox_mode configs are still supported on Windows.

The elevated setup/runner backend supports legacy ReadOnlyAccess::Restricted for read-only and workspace-write policies. Restricted read access honors explicit readable roots plus the command cwd, and keeps writable roots readable when workspace-write is used.

When include_platform_defaults = true, the elevated Windows backend adds backend-managed system read roots required for basic execution, such as C:\Windows, C:\Program Files, C:\Program Files (x86), and C:\ProgramData. When it is false, those extra system roots are omitted.

The unelevated restricted-token backend still supports the legacy full-read Windows model for legacy ReadOnly and WorkspaceWrite behavior. It also supports a narrow split-filesystem subset: full-read split policies whose writable roots still match the legacy WorkspaceWrite root set, but add extra read-only carveouts under those writable roots.

New [permissions] / split filesystem policies remain supported on Windows only when they round-trip through the legacy SandboxPolicy model without changing semantics. Policies that would require direct read restriction, explicit unreadable carveouts, reopened writable descendants under read-only carveouts, different writable root sets, or split carveout support in the elevated setup/runner backend still fail closed instead of running with weaker enforcement.

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.