da4c8ca57d
## Why
Multi-agent V2 normally derives its mode instructions from reasoning
effort: Ultra enables proactive delegation, while other efforts require
an explicit request. Some deployments need to provide one configured
delegation policy that replaces those built-ins and remains stable when
reasoning effort changes.
## What changed
- Add `features.multi_agent_v2.multi_agent_mode_hint_text` alongside the
existing root and subagent hint settings.
- Treat any configured value, including an empty string, as
`MultiAgentMode::Custom(hint_text)`, so the configured text replaces the
built-in explicit-only and proactive policies.
- Persist the full custom variant and hint text in the turn-context
snapshot, so the durable comparison baseline detects both
reasoning-effort changes and configured policy-text changes.
- Preserve the existing explicit-only/proactive behavior when the
setting is absent.
- Replace the ambiguous `MultiAgentMode::None` variant with
`MultiAgentMode::Custom(String)` in new rollouts and API schemas. A
compatibility wire type maps legacy serialized `none` values to
`Custom("")` when resuming existing rollouts.
- Regenerate the config and app-server schemas.
## Configuration examples
The distinction is whether `multi_agent_mode_hint_text` is present. An
empty string is still a configured value and intentionally suppresses
the built-in mode instructions.
### Unset: preserve existing effort-derived behavior
```toml
[features.multi_agent_v2]
enabled = true
# multi_agent_mode_hint_text is omitted
```
- Ultra reasoning uses the built-in proactive delegation instructions.
- Other reasoning efforts use the built-in explicit-request-only
instructions.
### Empty: suppress all mode hint text
```toml
[features.multi_agent_v2]
enabled = true
multi_agent_mode_hint_text = ""
```
This selects effective mode `custom` at every reasoning effort and
injects an empty mode body, suppressing both built-in policies.
### Set: always use the configured text
```toml
[features.multi_agent_v2]
enabled = true
multi_agent_mode_hint_text = "Delegate to subagents when it will materially improve the result."
```
This selects effective mode `custom` at every reasoning effort and
injects the configured text verbatim instead of either built-in policy.
## Verification
- `just test -p codex-core multi_agent_mode`
- Covers a configured hint across High and Ultra reasoning efforts and
verifies the full custom hint is recorded for both turns.
- Covers an empty-string override suppressing both built-in instruction
bodies.
- `just test -p codex-protocol -p codex-app-server-protocol`
- Covers legacy `none` turn-context deserialization as `Custom("")` and
verifies the regenerated schemas.
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.
Local execution targets the host OS, Docker targets Linux, and Wine exec targets Windows. Choose the skip macro by what the test depends on:
skip_if_target_windows!: Windows target behavior.skip_if_host_windows!: Windows host constraints.skip_if_remote!: Local-only test behavior.skip_if_no_remote_env!: Remote-only test behavior.skip_if_wine_exec!: Wine-specific runner debt.
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
ReadOnlyandWorkspaceWritebehavior - 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), andC:\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.