Surface error more prominently when config.toml is broken

What version of the Codex App are you using (From “About Codex” dialog)?

26.309.31024

What subscription do you have?

Plus

What platform is your computer?

MacOS

What issue are you seeing?

• UI is flashing
• Can't choose the model - it fallbacks to codex 5.3 med
• Can't open any chat - "Failed to resume task" error
• Can't send any message - "Error creating task" erro

What steps can reproduce the bug?

Create a new agent with empty developer instructions field and run Codex app

What is the expected behavior?

Codex app will surface the error in the main window

Additional information

I had some agent with next config for a while (like couple weeks):

model = "gpt-5.3-codex"
model_reasoning_effort = "high"
developer_instructions = """
"""

Everything was good, but after past release of Codex app I stuck with that weird behavior when you can't understand what gone wrong until I tried to open codex settings and in "config" section I see that error:

Invalid configuration; using defaults.

agent role file at /Users/timurkhakhalev/.codex/agents/codex_high.toml.developer_instructions cannot be blank

so it would be great if you guys change the UX for this state - surface the error on the main window to not confuse users like me