Files
codex/codex-rs/core
Michael Bolin 7a3eec6fdb core: cut codex-core compile time 48% with native async SessionTask (#16631)
## Why

This continues the compile-time cleanup from #16630. `SessionTask`
implementations are monomorphized, but `Session` stores the task behind
a `dyn` boundary so it can drive and abort heterogenous turn tasks
uniformly. That means we can move the `#[async_trait]` expansion off the
implementation trait, keep a small boxed adapter only at the storage
boundary, and preserve the existing task lifecycle semantics while
reducing the amount of generated async-trait glue in `codex-core`.

One measurement caveat showed up while exploring this: a warm
incremental benchmark based on `touch core/src/tasks/mod.rs && cargo
check -p codex-core --lib` was basically flat, but that was the wrong
benchmark for this change. Using package-clean `codex-core` rebuilds,
like #16630, shows the real win.

Relevant pre-change code:

- [`SessionTask` with
`#[async_trait]`](3c7f013f97/codex-rs/core/src/tasks/mod.rs (L129-L182))
- [`RunningTask` storing `Arc<dyn
SessionTask>`](3c7f013f97/codex-rs/core/src/state/turn.rs (L69-L77))

## What changed

- Switched `SessionTask::{run, abort}` to native RPITIT futures with
explicit `Send` bounds.
- Added a private `AnySessionTask` adapter that boxes those futures only
at the `Arc<dyn ...>` storage boundary.
- Updated `RunningTask` to store `Arc<dyn AnySessionTask>` and removed
`#[async_trait]` from the concrete task impls plus test-only
`SessionTask` impls.

## Timing

Benchmarked package-clean `codex-core` rebuilds with dependencies left
warm:

```shell
cargo check -p codex-core --lib >/dev/null
cargo clean -p codex-core >/dev/null
/usr/bin/time -p cargo +nightly rustc -p codex-core --lib -- \
  -Z time-passes \
  -Z time-passes-format=json >/dev/null
```

| revision | rustc `total` | process `real` | `generate_crate_metadata`
| `MIR_borrow_checking` | `monomorphization_collector_graph_walk` |
| --- | ---: | ---: | ---: | ---: | ---: |
| parent `3c7f013f9735` | 67.21s | 67.71s | 24.61s | 23.43s | 22.43s |
| this PR `2cafd783ac22` | 35.08s | 35.60s | 8.01s | 7.25s | 7.15s |
| delta | -47.8% | -47.4% | -67.5% | -69.1% | -68.1% |

For completeness, the warm touched-file benchmark stayed flat (`1.96s`
parent vs `1.97s` this PR), which is why that benchmark should not be
used to evaluate this refactor.

## Verification

- Ran `cargo test -p codex-core`; this change compiled and task-related
tests passed before hitting the same unrelated 5
`config::tests::*guardian*` failures already present on the parent
stack.
2026-04-02 23:39:56 +00:00
..

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 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.

Windows

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.

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.