Channing Conger 7d8906b478 [codex] wire process-owned code mode host into core (#30142) ...

## Summary

- add the `code_mode_host` feature flag and select
`ProcessOwnedCodeModeSessionProvider` in `CodeModeService` when enabled
- initialize code-mode sessions lazily so a missing host reports a tool
error without failing thread startup
- resolve `codex-code-mode-host` beside the running Codex binary by
default while preserving `CODEX_CODE_MODE_HOST_PATH` as an override
- add unit and end-to-end coverage for host resolution and graceful
missing-host behavior

## Why

This wires the process-owned session client from #30112 into the core
service behind an opt-in rollout gate. Packaged Codex installations can
place the helper in the same `bin` directory as the main executable
without relying on `PATH`, while development and custom installations
can continue to override the helper path.

## Stack

- Depends on #30112
- Base branch: `cconger/process-owned-session-runtime-4-client`

## Validation

Build `codex` and `codex-code-mode-host`
`CODEX_CODE_MODE_HOST_PATH="$PWD/target/debug/codex-code-mode-host"
./target/debug/codex --enable code_mode_host`

2026-06-26 00:23:33 -07:00

..

src

[codex] wire process-owned code mode host into core (#30142)

2026-06-26 00:23:33 -07:00

BUILD.bazel

Code mode on v8 (#15276)

2026-03-20 23:36:58 -07:00

Cargo.toml

[codex] add process-owned code-mode session client (#30112)

2026-06-25 23:46:17 -07:00