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Codex Issues / #38344

Sub-agent launcher rejects configured gpt-5.6-luna while direct Codex Luna run succeeds

Open 💬 3 comments Opened Aug 13, 2026 by mcline-lucey-alt
💡 Likely answer: A maintainer (github-actions[bot], contributor) responded on this thread — see the highlighted reply below.

Summary

The Codex multi-agent sub-agent launcher rejects gpt-5.6-luna as an unknown model even though Luna is configured for the Builder role and a direct Codex Luna Max run succeeds on the same machine and ChatGPT account.

Environment

  • macOS 26.5.1, arm64
  • Codex desktop-bundled CLI: 0.147.0-alpha.6.5
  • Authentication: ChatGPT
  • Global config: model = "gpt-5.6-luna", model_reasoning_effort = "max"
  • Global and project Builder definitions: model = "gpt-5.6-luna", model_reasoning_effort = "max"
  • Project sub-agent defaults also request Luna Max
  • Desktop app has been restarted several times without changing behavior

Reproduction

  1. From a GPT-5.6 task, create a sub-agent with the built-in Builder role, or explicitly request model gpt-5.6-luna with Max reasoning.
  2. The launcher rejects the request before the agent starts.

Observed errors:

Unknown model `gpt-5.6-luna` for spawn_agent. Available models: gpt-5.6-sol, gpt-5.6-terra

and the built-in Builder role cannot start because that role is fixed to Luna.

Control test

A direct ephemeral Codex run succeeds:

codex exec --ephemeral --json --skip-git-repo-check \
  -m gpt-5.6-luna \
  -c model_reasoning_effort='"max"' \
  -s read-only \
  "Reply with exactly LUNA_OK and nothing else."

Observed final agent message:

LUNA_OK

This suggests Luna is available to the account and local Codex runtime, but missing from the multi-agent launcher allowlist or capability snapshot for the active task.

Expected behavior

The sub-agent launcher should honor a valid configured Luna Max Builder, or return a specific explanation if Luna is intentionally unavailable for that sub-agent runtime.

Privacy

No repository code, credentials, account identifiers, or proprietary data are included in this report.

View original on GitHub ↗

3 Comments

github-actions[bot] contributor · 15 days ago

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

  • #38107
  • #37910
  • #38343

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mcline-lucey-alt · 14 days ago

I reviewed the suggested duplicates.

  • #38107 is very close in the underlying launcher symptom, but it is a Windows VS Code extension case. This report reproduces in the macOS Codex desktop app after restarts, while a direct ephemeral Luna Max run succeeds on the same machine and account.
  • #37910 reports the same error but attributes it to an old session, which does not match this reproduction.
  • #38343 is a broad Windows desktop report and is already closed.

Because this issue supplies a distinct macOS desktop reproduction plus a direct-runtime control test, I am leaving it open as a potentially shared launcher/capability-snapshot defect rather than closing it as a duplicate. Happy to consolidate it if maintainers confirm the same root cause.

tappe9 · 14 days ago

Update from the reporter of #38107: I can no longer reproduce the Luna spawn_agent rejection on macOS after updating Codex Desktop.

I repeated the same A/B test on my MacBook.

Before update

  • Codex Desktop: 26.803.81509
  • Bundled Codex CLI: 0.147.0-alpha.6.6

Both Codex Desktop and the bundled CLI launched directly failed with:

Unknown model `gpt-5.6-luna` for spawn_agent. Available models: gpt-5.6-sol, gpt-5.6-terra
````

### After update

* macOS `26.6.1` (`arm64`)
* Codex Desktop: `26.810.41047` (bundle `6570`)
* Bundled Codex CLI: `0.148.0-alpha.9`
* Parent: `gpt-5.6-sol`
* Subagent: `gpt-5.6-luna`

| Runtime                       | Luna spawn |
| ----------------------------- | ---------- |
| Codex Desktop                 | ✅ Succeeds |
| Bundled CLI launched directly | ✅ Succeeds |
| Standalone CLI `0.147.0`      | ✅ Succeeds |

The Luna child was explicitly spawned with no Sol/Terra fallback and returned:

```text
LUNA_SPAWN_OK

This matches the Windows result from #38107:

  • bundled Codex 0.147.0-alpha.6.x → Luna rejected
  • bundled Codex 0.148.0-alpha.9 → Luna accepted

0.148.0-alpha.9 also includes the leaf-worker support from #36892.

Since this issue was reported with bundled CLI 0.147.0-alpha.6.5, updating to Codex Desktop 26.810.41047 / bundled CLI 0.148.0-alpha.9 appears to resolve the same launcher-level rejection on macOS.