GPT-5.6 consistently aborts functions.exec / tools.exec_command, while GPT-5.5 works

What version of Codex CLI is running?

codex-cli 0.147.0

What subscription do you have?

Enterprise

Which model were you using?

No response

What platform is your computer?

No response

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

No response

Codex doctor report

What issue are you seeing?

Summary

functions.exec consistently returns aborted when running shell commands with GPT-5.6 models, while the same operation works normally with GPT-5.5.

Reproduction

Run a minimal shell command:

echo hello

The tool call immediately returns:

aborted

No command output, stderr, or exit code is returned.

The issue is reproducible with other trivial commands, including:

pwd
echo hello
python3 --version

It also occurs when invoking the nested JavaScript tool:

const r = await tools.exec_command({
  cmd: "echo hello",
  yield_time_ms: 10000,
  max_output_tokens: 2000
});
text(r.output);

The execution is still aborted before any command output is produced.

Expected behavior

The command should execute successfully and return:

hello

Actual behavior

The execution is aborted before the command produces any output.

There is no stdout, stderr, or exit code returned by the tool call.

Model comparison

• GPT-5.5: works normally
• GPT-5.6: consistently returns aborted
• GPT-5.6-terra: consistently returns aborted

The same Codex CLI installation and environment are used for the model comparison.

Additional observations

• The failure occurs with trivial local commands that do not require network access or special permissions.
• echo hello reproduces the issue, so the failure does not appear to be related to Python, Git, or the repository.
• Changing the working directory, shell options, and command arguments does not resolve the issue.
• Switching to GPT-5.5 immediately restores normal command execution.
• The behavior is consistently reproducible with GPT-5.6 models.

This appears to be a model-specific issue in the tool execution path rather than a failure of the underlying shell command.

Environment

• OS: macOS
• Codex CLI: 0.147.0
• Tool: functions.exec / tools.exec_command
• Model: GPT-5.6 / GPT-5.6-terra
• Working directory: local Git repository
• Architecture: Apple Silicon

Minimal reproduction

Codex CLI 0.147.0
Model: GPT-5.6-terra

User: Run `echo hello`

Tool: functions.exec
Result: aborted

No stdout
No stderr
No exit code

Switching only the model:

Codex CLI 0.147.0
Model: GPT-5.5

User: Run `echo hello`

Tool: functions.exec
Result: hello

The difference is consistently reproducible.

What steps can reproduce the bug?

1. Install and run Codex CLI 0.147.0 on macOS (Apple Silicon).

2. Open a local Git repository with Codex.

3. Select the GPT-5.6-terra model.

4. Ask Codex to execute a trivial shell command, for example:

   echo hello
   

5. Observe that the functions.exec / tools.exec_command call immediately returns aborted.

6. No stdout, stderr, or exit code is returned.

7. Repeat with other trivial commands such as:

   pwd
   python3 --version
   

   The same behavior occurs.

8. Switch the model to GPT-5.5 and run the same commands.

9. Observe that the commands execute normally and return their expected output.

What is the expected behavior?

No response

Additional information

No response

Start at the functions.exec and tools.exec_command entry points and reproduce the difference between GPT-5.6 and GPT-5.5 with the listed trivial commands. Trace where the affected calls become aborted; done means commands return their output, stderr, and exit status consistently for the affected models.