Files
codex/codex-rs/core
viyatb-oai c7b55cdc46 feat: add network proxy feature flag (#20147)
## Why

The permissions migration is making
`permissions.<profile>.network.enabled` the canonical sandbox network
bit, while proxy startup is a separate concern. Enabling network access
should not implicitly start the proxy, and users who are still on legacy
sandbox modes need a separate place to opt into proxy startup and
provide proxy-specific settings.

This follow-up to #19900 gives the network proxy its own feature surface
instead of overloading permission-profile network semantics.

## What changed

- Add an experimental `network_proxy` feature with a configurable
`[features.network_proxy]` table.
- Overlay `features.network_proxy` settings onto the configured proxy
state after permission-profile selection, so the proxy only starts when
the active `NetworkSandboxPolicy` already allows network access.
- Preserve `[experimental_network]` startup behavior independently of
the new feature flag.

## Behavior and examples

There are now three related knobs:

- `permissions.<profile>.network.enabled` controls whether the active
permission profile has network access at all.
- `features.network_proxy` enables proxy restrictions for an
already-network-enabled profile.
- Legacy `sandbox_mode` plus `[sandbox_workspace_write].network_access`
still control whether legacy `workspace-write` has network access at
all.

The rule is:

- network off + proxy flag on -> network stays off, proxy is a no-op
- network on + proxy flag off -> unrestricted direct network
- network on + proxy flag on -> network stays on, with proxy
restrictions applied

For permission profiles, the feature toggle adds proxy restrictions only
when network access is already enabled:

```toml
default_permissions = "workspace"

[permissions.workspace.filesystem]
":minimal" = "read"

[permissions.workspace.network]
enabled = true

[features]
network_proxy = true
```

If `network.enabled = false`, the same feature flag is a no-op: network
remains off and the proxy does not start.

For legacy sandbox config, `network_access` remains the master switch:

```toml
sandbox_mode = "workspace-write"

[sandbox_workspace_write]
network_access = true

[features]
network_proxy = true
```

That keeps legacy `workspace-write` network access on, but routes it
through the proxy policy. If `network_access = false`, the proxy feature
is a no-op and legacy `workspace-write` remains offline.

The same proxy opt-in can be supplied from the CLI:

```bash
codex -c 'features.network_proxy=true'
```

Additional proxy settings can be supplied when a table is needed:

```bash
codex \
  -c 'features.network_proxy.enabled=true' \
  -c 'features.network_proxy.enable_socks5=false'
```

The intended behavior matrix is:

| Config surface | Network setting | `features.network_proxy` | Direct
sandbox network | Proxy |
| --- | --- | --- | --- | --- |
| Permission profile | `network.enabled = false` | off | restricted |
off |
| Permission profile | `network.enabled = false` | on | restricted | off
|
| Permission profile | `network.enabled = true` | off | enabled | off |
| Permission profile | `network.enabled = true` | on | enabled | on |
| Legacy `workspace-write` | `network_access = false` | off | restricted
| off |
| Legacy `workspace-write` | `network_access = false` | on | restricted
| off |
| Legacy `workspace-write` | `network_access = true` | off | enabled |
off |
| Legacy `workspace-write` | `network_access = true` | on | enabled | on
|

`[experimental_network]` requirements remain separate from the user
feature toggle and still start the proxy on their own.

Relevant code:
-
[`features/src/feature_configs.rs`](https://github.com/openai/codex/blob/43785aff47/codex-rs/features/src/feature_configs.rs#L58-L117)
defines the feature-specific proxy config.
-
[`core/src/config/mod.rs`](https://github.com/openai/codex/blob/43785aff47/codex-rs/core/src/config/mod.rs#L1959-L1964)
reads the feature table, and [later applies it only when network access
is already
enabled](https://github.com/openai/codex/blob/43785aff47/codex-rs/core/src/config/mod.rs#L2448-L2458).

## Verification

Added focused coverage for:
- keeping the proxy off when `features.network_proxy` is enabled but
sandbox network access is disabled
- the full permission-profile and legacy `workspace-write` matrix above
- preserving `[experimental_network]` startup without the feature
- reusing profile-supplied proxy settings when the feature is enabled

Ran:
- `cargo test -p codex-features`
- `cargo test -p codex-core network_proxy_feature`
- `cargo test -p codex-core
experimental_network_requirements_enable_proxy_without_feature`
2026-05-11 14:12:00 -07:00
..

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

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.

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 bundled codex-resources/bwrap binary shipped with Codex and Codex surfaces a startup warning through its normal notification path instead of printing directly from the sandbox helper. Codex also surfaces a startup warning when bubblewrap cannot create user namespaces. WSL2 uses the normal Linux bubblewrap path. WSL1 is not supported for bubblewrap sandboxing because it cannot create the required user namespaces, so Codex rejects sandboxed shell commands that would enter the bubblewrap path before invoking bwrap.

Windows

Legacy SandboxPolicy / sandbox_mode configs are still supported on Windows. Legacy read-only and workspace-write policies imply full filesystem read access; exact readable roots are represented by split filesystem policies instead.

The elevated Windows sandbox also supports:

  • legacy ReadOnly and WorkspaceWrite behavior
  • split filesystem policies that need exact readable roots, exact writable roots, or extra read-only carveouts under writable roots
  • backend-managed system read roots required for basic execution, such as C:\Windows, C:\Program Files, C:\Program Files (x86), and C:\ProgramData, when a split filesystem policy requests platform defaults

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 can be enforced directly by the selected Windows backend or round-trip through the legacy SandboxPolicy model without changing semantics. Policies that would require direct explicit unreadable carveouts (none) or reopened writable descendants under read-only carveouts still fail closed instead of running with weaker enforcement.

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.