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codex/codex-rs/core
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jgershen-oai 15f448d8b0 [codex] Start the guardian child session when parent session is started (#27982)
## Why

The first auto-review currently creates its Guardian child session on
demand, adding avoidable latency before the review can begin. Creating
the ordinary Guardian child during parent-session initialization lets
that child use the existing session startup WebSocket prewarm before the
first escalation. This does not introduce a Guardian-specific prewarm
mechanism.

## What changed

- initialize the existing Guardian review-session manager owned by
`Session` when a thread starts with auto-review enabled and an approval
policy that routes to Guardian
- use the standard Guardian child-session construction and the existing
session startup WebSocket prewarm
- preserve the existing reuse-key invalidation and lazy creation
fallback when startup initialization fails or the effective review
configuration changes
- add an integration test that verifies normal root-session startup
emits a Guardian `generate=false` prewarm request

## Benchmark

I compared release builds against main. Each prompt first ran a
non-escalated `sleep 3`, then requested an escalated marker command.

| binary | count | avg Guardian duration | median Guardian duration |
avg Guardian TTFT |
|---|---:|---:|---:|---:|
| origin-main | 10 | 4008.7 ms | 3949.5 ms | 3746.5 ms |
| session-fix | 10 | 2865.0 ms | 2594.0 ms | 2492.7 ms |

Guardian duration fell by 28.5% and Guardian TTFT fell by 33.5%. These
measurements cover Guardian review latency; they do not measure parent
thread-start latency.
15f448d8b0 ยท 2026-06-22 11:54:44 -07:00
History
..

codex-core

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

Wine-exec integration tests

On x86-64 Linux, run the shared suite against the Windows exec server with bazel test //codex-rs/core:core-all-wine-exec-test. Temporary blockers use a source-local skip_if_wine_exec! call and reason.

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 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.