[Windows][Computer Use] Works with GPT-6 Astra but unavailable with GPT-5.6 Sol, Terra, and Luna

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

26.903.61454

What subscription do you have?

Plus

What platform is your computer?

Microsoft Windows NT 10.0.26200.0 x64

What issue are you seeing?

Summary

Computer Use in ChatGPT Desktop / Codex works correctly when GPT-6 Astra is selected, but fails when using GPT-5.6 Sol, GPT-5.6 Terra, or GPT-5.6 Luna.

I tested all four models on the same Windows machine, using the same ChatGPT Desktop installation, the same Codex environment, the same @Computer plugin, and essentially the same prompt.

GPT-6 Astra successfully opened Windows Notepad and typed "hello world".

GPT-5.6 Sol, Terra, and Luna all failed to access Windows applications.

Since GPT-6 Astra can successfully control Windows from the same application and machine, the local Computer Use installation and Windows-control functionality appear to be working. The behavior seems to depend on which model is selected.

Environment

• OS: Windows 11 Pro
• Windows version: 25H2
• OS Build: 26200.9445
• PC manufacturer: Lenovo
• ChatGPT Desktop version: 26.903.61454
• ChatGPT Desktop release date: September 9, 2026
• ChatGPT Desktop: Powered by Codex & OWL
• Subscription: ChatGPT Plus
• Tool/plugin: @Computer (computer-use@openai-bundled)

Steps to Reproduce

1. Open ChatGPT Desktop on Windows.

2. Open Codex.

3. Select GPT-5.6 Luna.

4. Send the following prompt:

   use @Computer and open notepad and write hello world

5. Repeat the same test with GPT-5.6 Terra.

6. Repeat the same test with GPT-5.6 Sol.

7. Repeat the same test with GPT-6 Astra.

Actual Results

GPT-5.6 Luna — FAIL

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 40 seconds and returned:

I couldn’t open Notepad because the Computer Use connection currently exposes no Windows apps. Please reconnect or enable the Computer Use plugin, then I can enter “hello world.”

Notepad was not opened.

GPT-5.6 Terra — FAIL

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 36 seconds and returned:

I couldn’t access Windows apps from this session—the Computer Use connection reports no available apps, so Notepad can’t be opened here.

Notepad was not opened.

GPT-5.6 Sol — FAIL

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 50 seconds and returned:

I couldn’t complete it: the Computer Use plugin is installed, but its Windows-control service isn’t configured, so it can’t open or type into Notepad.

Notepad was not opened.

GPT-6 Astra — SUCCESS

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 1 minute 20 seconds and returned:

Opened a new Notepad tab and typed “hello world”.

This worked correctly. Windows Notepad actually opened and "hello world" was successfully typed into it.

Results Summary

Model	Result	Observed behavior
GPT-6 Astra	SUCCESS	Opened Notepad and typed "hello world"
GPT-5.6 Sol	FAIL	Reports Windows-control service is not configured
GPT-5.6 Terra	FAIL	Reports no Windows apps are available
GPT-5.6 Luna	FAIL	Reports Computer Use exposes no Windows apps

Expected Behavior

If Computer Use / Windows desktop control is supported for GPT-5.6 Sol, Terra, and Luna in Codex, I would expect these models to have access to the same configured Windows-control environment that GPT-6 Astra receives.

Changing the selected model should not cause the available Windows applications or Windows-control service to disappear.

Important Observation

This does not appear to be a general Windows permission, Computer Use installation, or Windows-control configuration problem.

GPT-6 Astra successfully controls the Windows desktop from the same ChatGPT Desktop installation and on the same Windows machine.

The tests were performed under the same environment. The primary variable changed between the successful and unsuccessful tests was the selected model.

The behavior is consistently:

GPT-6 Astra -> WORKS
GPT-5.6 Sol -> FAILS
GPT-5.6 Terra -> FAILS
GPT-5.6 Luna -> FAILS

Interestingly, the three GPT-5.6 models report slightly different errors:

• Luna reports that Computer Use exposes "no Windows apps".
• Terra reports that the Computer Use connection has "no available apps".
• Sol reports that the plugin is installed but its "Windows-control service isn't configured".

Despite the different wording, all three result in the same practical behavior: they cannot access Windows applications.

Astra, however, receives working Windows desktop access and completes the task successfully.

Additional Notes

The ChatGPT Desktop installation used for this test is version 26.903.61454, released September 9, 2026.

I reproduced the issue on the same day as that release.

I can provide screenshots of:

1. GPT-5.6 Luna failing.
2. GPT-5.6 Terra failing.
3. GPT-5.6 Sol failing.
4. GPT-6 Astra successfully controlling Notepad.
5. ChatGPT Desktop version information.
6. Windows version/build information.

Please let me know if there are any logs, diagnostic information, session IDs, or additional tests that would help investigate whether this is a model-specific limitation, rollout issue, or Computer Use integration bug.

What steps can reproduce the bug?

Steps to Reproduce

1. Open ChatGPT Desktop on Windows.

2. Open Codex.

3. Select GPT-5.6 Luna.

4. Send the following prompt:

   use @Computer and open notepad and write hello world

5. Repeat the same test with GPT-5.6 Terra.

6. Repeat the same test with GPT-5.6 Sol.

7. Repeat the same test with GPT-6 Astra.

Actual Results

GPT-5.6 Luna — FAIL

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 40 seconds and returned:

I couldn’t open Notepad because the Computer Use connection currently exposes no Windows apps. Please reconnect or enable the Computer Use plugin, then I can enter “hello world.”

Notepad was not opened.

GPT-5.6 Terra — FAIL

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 36 seconds and returned:

I couldn’t access Windows apps from this session—the Computer Use connection reports no available apps, so Notepad can’t be opened here.

Notepad was not opened.

GPT-5.6 Sol — FAIL

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 50 seconds and returned:

I couldn’t complete it: the Computer Use plugin is installed, but its Windows-control service isn’t configured, so it can’t open or type into Notepad.

Notepad was not opened.

GPT-6 Astra — SUCCESS

Prompt:

use @Computer and open notepad and write hello world

The task ran for approximately 1 minute 20 seconds and returned:

Opened a new Notepad tab and typed “hello world”.

This worked correctly. Windows Notepad actually opened and "hello world" was successfully typed into it.

What is the expected behavior?

Prompt:

use @Computer and open notepad and write hello world

Result:

Opened a new Notepad tab and typed “hello world”.

Opened a new Notepad tab and typed “hello world”.

This worked correctly. Windows Notepad actually opened and "hello world" was successfully typed into it.

Additional information

No response

No source file, test, or entry point is identified in the report. Reproduce the Windows Codex flow with the listed models and the @Computer prompt, then compare the model-specific Computer Use availability; done means Sol, Terra, and Luna can open Notepad and type “hello world” under the same environment as Astra.