## Why
`MultiAgentV2` follow-up messages are delivered to agents as
assistant-authored `InterAgentCommunication` envelopes. When
`followup_task` used `interrupt: true`, the interrupted-turn guidance
was still persisted as a contextual user message, so model-visible
history made a system-generated interruption boundary look
user-authored.
This keeps interruption guidance consistent with the rest of the v2
inter-agent message stream while preserving the legacy marker shape for
non-v2 sessions.
## What changed
- Make `interrupted_turn_history_marker` feature-aware.
- Record the interrupted-turn marker as an assistant `OutputText`
message when `Feature::MultiAgentV2` is enabled.
- Keep the existing user contextual fragment for non-v2 sessions.
- Apply the same feature-aware marker to interrupted fork snapshots.
- Add coverage for the live `followup_task` interrupt path and the
helper-level v2 marker shape.
## Testing
- `cargo test -p codex-core
multi_agent_v2_followup_task_interrupts_busy_child_without_losing_message
-- --nocapture`
- `cargo test -p codex-core
multi_agent_v2_interrupted_marker_uses_assistant_output_message --
--nocapture`
- `cargo test -p codex-core interrupted_fork_snapshot -- --nocapture`
## Why
MultiAgentV2 children should not receive an extra model-visible
developer fragment just because they were spawned. The parent/configured
developer instructions should carry through normally, but the dedicated
`<spawned_agent_context>` block is no longer desired.
## What changed
- Removed the `SpawnAgentInstructions` context fragment and its
`<spawned_agent_context>` wrapper.
- Stopped appending spawned-agent instructions in
`codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs`.
- Updated subagent notification coverage to assert inherited parent
developer instructions without expecting the spawned-agent wrapper.
## Verification
- `cargo test -p codex-core --test all
spawned_multi_agent_v2_child_inherits_parent_developer_context --
--nocapture`
- `cargo test -p codex-core --test all
skills_toggle_skips_instructions_for_parent_and_spawned_child --
--nocapture`
- `cargo test -p codex-core --test all subagent_notifications --
--nocapture`
## Why
`approvals_reviewer` now uses `auto_review` as the canonical config/API
value after #18504, but the Rust enum variant and nearby helper/test
names still used `GuardianSubagent` / guardian approval wording. That
made follow-up code and reviews confusing even though the external value
had already moved to Auto-review.
## What changed
- Renamed `ApprovalsReviewer::GuardianSubagent` to
`ApprovalsReviewer::AutoReview`.
- Updated protocol, app-server, config, core, TUI, exec, and analytics
test callsites.
- Renamed nearby helper/test names from guardian approval wording to
Auto-review wording where they refer to the approvals reviewer mode.
- Preserved wire compatibility:
- `auto_review` remains the canonical serialized value.
- `guardian_subagent` remains accepted as a legacy alias.
This intentionally does not rename the `[features].guardian_approval`
key, `Feature::GuardianApproval`, `core/src/guardian`, analytics event
names, or app-server Guardian review event types.
## Verification
- `cargo test -p codex-protocol
approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent`
- `cargo test -p codex-app-server-protocol
approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent`
- `cargo test -p codex-config approvals_reviewer`
- `cargo test -p codex-tui update_feature_flags`
- `cargo test -p codex-core permissions_instructions`
- `cargo test -p codex-tui permissions_selection`
Michael Bolin