GPT Sol and Terra threads cannot spawn Luna subagents because of Luna Multi Agent version

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
52/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
rust
Domain
cli, tooling

Research direction

Reproduce the failure by starting a gpt-5.6-sol or gpt-5.6-terra thread and requesting a default gpt-5.6-luna subagent. Read codex/codex-rs/core/src/tools/handlers/multi_agent_common.rs and inspect the model version configuration implicated by commit 92938d880e. Confirm the intended multi-agent version pairing, then verify that Sol and Terra can spawn Luna successfully.

Written by the indexing model from the issue text.

Description

bug CLI subagent windows-os
What version of Codex CLI is running?

0.144.6

What subscription do you have?

Prolite

Which model were you using?

gpt-5.6-sol

What platform is your computer?

Windows

What terminal emulator and version are you using (if applicable)?

Terminal app

Codex doctor report
What issue are you seeing?

gpt-5.6-sol and gpt-5.6-terra models are unable to use the spawn_agent tool to create gpt-5.6-luna subagents

What steps can reproduce the bug?
  1. Start gpt-5.6-sol thread
  2. Ask it to create a default gpt-5.6-luna subagent
What is the expected behavior?

Luna subagents should be available to spawn from Sol/Terra parents

Additional information

I believe this issue stems from the commit 92938d880e, where it says "Restrict spawned-agent models to the active backend", luna is classified as using multi_agent version v1, instead of v2 like its other 5.6 counterparts. The v2 check is in codex/codex-rs/core/src/tools/handlers/multi_agent_common.rs on line 33:

pub(crate) fn model_supports_multi_agent_backend(
    model: &ModelPreset,
    multi_agent_version: MultiAgentVersion,
) -> bool {
    multi_agent_version != MultiAgentVersion::V2
        || model.multi_agent_version == Some(multi_agent_version)
}

But the correct behavior patch would be to change gpt-5.6-luna to use multi_agent v2 if thats the intended future route, or switch gpt-5.6-sol and gpt-5.6-terra to multi agent v1

Dominant language
Rust
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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