Codex: should a newer codex win over an older one earlier on PATH? #73

What happens

An older codex earlier on PATH than a current one breaks every Codex call. It doesn't matter how the old copy got there: npm, Homebrew, a release binary, or a stale leftover.

• find_program (crates/grida-fx-providers/src/codex/mod.rs) takes the first executable codex on PATH. It never checks the version. The app-bundle location is tried only when PATH has no codex at all.
• An old copy rejects codex mcp list --json. The runtime then refuses every Codex call in the run with Codex's MCP servers could not be listed, so they cannot be turned off. That sentence points at MCP servers, not at an outdated program.
• grida fx doctor still reports imagegen@codex servable, because it checks only that the program exists (Servable::NoProgram).

The user sees a misleading refusal from the run and a healthy report from doctor. Nothing points to the real cause.

Fix

(a) A version check that works however Codex was installed

• Read codex --version once when the runtime starts, and in doctor.
• Require at least the version the behaviour was verified on (0.160.1, per spec/providers.md §9.6).
• Refuse an older or unreadable version with a reason that names the version and where it was found. For example: Codex <version> (from PATH) is older than 0.160.1: update it, or set GRIDA_FX_TOOL_CODEX.
• Have doctor show which copy it chose (GRIDA_FX_TOOL_CODEX, PATH or the app bundle) and its version, as well as whether it is servable.

(b) A separate spec decision: should a newer copy win over an older one on PATH?

For example, should the ChatGPT app's bundled codex be preferred to an older one on PATH? That changes the lookup order in §9.6, so it is a spec change first. It is also independent of (a): (a) alone turns the silent failure into a clear refusal.

Related

• Still open in TODO.md ("Codex-backed image generation", follow-ups):
  • Windows: npm installs codex.cmd, which find_program does not look for.
  • Other app-bundle locations are not searched.
• Grok Build image backend (SuperGrok, over its native ACP): plan #72 Phase 1 replaces this lookup with a program lookup and version check shared by every runtime the user installs. That will cover (a) for Codex and Grok Build alike.