Codex Luna subagent fails with the default service tier
Open 💬 0 comments Opened Aug 20, 2026 by dhruv-openlane
What version of the Codex App are you using (From “About Codex” dialog)?
Version 26.814.41407
What subscription do you have?
Enterprise API login
What platform is your computer?
Darwin 24.6.0 arm64 arm
What issue are you seeing?
When using GPT-5.6 Luna subagents, the native spawn_agent path rejects default, flex, and auto. The only accepted option is priority/Fast
What steps can reproduce the bug?
Request one Luna subagent in a Codex thread with model gpt-5.6-luna, reasoning effort to max and service tier as default. Prompt it to do something like say hello world. The request fails with: Service tier default is not supported for model gpt-5.6-luna. Supported service tiers: priority
What is the expected behavior?
The Luna subagent starts successfully and returns hello world.
Additional information
_No response_