Not able to use 5.3 Codex Spark model

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

Version 26.707.41301

What subscription do you have?

Pro 5x

What platform is your computer?

Darwin 25.5.0 arm64 arm

What issue are you seeing?

I’m trying to use my 5.3 Codex Spark model because my Codex and Work usage has run out, but I’m getting this error. I’m not sure why it’s happening. I’ve started a fresh chat in my existing project, but I’m still seeing the same error.

Error:

Unsupported parameter: 'reasoning.summary' is not supported with the 'gpt-5.3-codex-spark' model.

What steps can reproduce the bug?

I’m trying to use my 5.3 Codex Spark model because my Codex and Work usage has run out, but I’m getting this error. I’m not sure why it’s happening. I’ve started a fresh chat in my existing project, but I’m still seeing the same error.

Error:

Unsupported parameter: 'reasoning.summary' is not supported with the 'gpt-5.3-codex-spark' model.

What is the expected behavior?

I’m trying to use my 5.3 Codex Spark model because my Codex and Work usage has run out, but I’m getting this error. I’m not sure why it’s happening. I’ve started a fresh chat in my existing project, but I’m still seeing the same error.

Error:

Unsupported parameter: 'reasoning.summary' is not supported with the 'gpt-5.3-codex-spark' model.

Additional information

_No response_