Codex Desktop subagents ignore model and reasoning settings. CAN YOU FIX THIS AT LAST?

What issue are you seeing?

Codex Desktop subagents ignore requested model and reasoning settings and appear to inherit the parent thread settings instead.

This is not just a child-agent self-introspection problem. The Codex Desktop subagent window itself shows the child running with the parent model/reasoning.

Can you fix this at last? This has been reported in multiple forms before, and it makes subagents unreliable for any workflow that depends on model or reasoning separation.

Environment

• Product: Codex Desktop App
• Codex Desktop version: 26.609.41114
• Electron version: 42.1.0
• Subscription: Pro 20x
• Parent visible setting: 5.5 Extra High

Steps to reproduce

1. Start a Codex Desktop thread using gpt-5.5 with Extra High reasoning.
2. Ask Codex to spawn two subagents with different settings:

• Subagent A:
• model: "gpt-5.5"
• reasoning_effort: "xhigh"
• Subagent B:
• model: "gpt-5.3-codex-spark"
• reasoning_effort: "low"

1. Open the spawned subagent tabs/windows in Codex Desktop.
2. Inspect the displayed model/reasoning in each child subagent.

Actual behavior

Both subagents show the parent settings:

• Subagent A, Copernicus, requested gpt-5.5 / xhigh, showed 5.5 Extra High.
• Subagent B, Nash, requested gpt-5.3-codex-spark / low, also showed 5.5 Extra High.

The spawn tool accepted the settings, but the child Desktop session did not reflect them.

Observed IDs from the repro:

• Copernicus: 019ed571-fb13-7602-b5f7-12e2e3f117d0
• Nash: 019ed572-102f-7660-a767-f7dd7c6466fb

Expected behavior

A child spawned with:

{
  "model": "gpt-5.3-codex-spark",
  "reasoning_effort": "low"
}

should run and display as gpt-5.3-codex-spark with low reasoning, not inherit the parent thread's gpt-5.5 Extra High settings.

If model/reasoning selection for subagents is not supported in Codex Desktop, the UI/tool should reject or clearly ignore those settings instead of silently accepting them.

Why this matters

This makes subagent model selection unreliable. Users cannot safely use lower-cost or lower-latency subagents for simple parallel work, because the UI shows they may actually be running under the parent high-capability/high-reasoning settings.

That affects:

• cost-sensitive fan-out
• latency-sensitive subagent workflows
• reproducibility of agent behavior
• trust in subagent configuration

Related issues

This appears related to, but not fully resolved by, previous reports:

• #14671
• #15501
• #16548
• #22250
• #27624

Some of those mention custom agent config, per-spawn settings, metadata/display issues, or CLI/TUI behavior. This repro is specifically for Codex Desktop where the child subagent UI itself shows the parent settings.

<img width="1592" height="1784" alt="Image" src="https://github.com/user-attachments/assets/03ce006e-a5d7-41f9-b8ac-25ed617ddca9" />