feat: configurable Windows agent shell (powershell/git-bash)

[Jawad-hussain-kalwar]

Problem

On Windows, Codex hardcodes PowerShell as the agent shell. PowerShell syntax is unfamiliar to the model compared to bash, leading to worse command generation. Users with Git Bash installed have no way to switch.

Proposed Solution

Add a [windows].agent_shell config key ("power-shell" | "git-bash") to ~/.codex/config.toml:

[windows]
agent_shell = "git-bash"

When git-bash is selected:

• Agent default shell resolves to bash (with Git for Windows fallback paths)
• Tool descriptions sent to the model switch to bash syntax examples
• Hard error on session start if bash is configured but not found
• Bash binary registered as sandbox-readable root

Default behavior (PowerShell) is unchanged when the key is omitted.

Implementation

I have a working implementation in my fork with all tests passing:

• Branch: https://github.com/Jawad-hussain-kalwar/codex/tree/feat/configurable-windows-agent-shell
• PR (fork): feat: add configurable Windows agent shell (powershell/git-bash) Jawad-hussain-kalwar/codex#1
• 14 files changed, 266 insertions, 14 deletions
• cargo test -p codex-tools — 59 passed, 0 failed
• cargo test -p codex-core --lib — 1558 passed, 0 failed from these changes

The implementation follows existing config patterns ([windows].sandbox, [windows].sandbox_private_desktop) and the zsh-fork shell resolution precedent.

[github-actions]

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

• Windows: allow configuring the default session shell via config #16579

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[etraut-openai]

Have you tried just steering the model to use bash? It tends to use PowerShell because many Windows users don't have git bash, but if you ask it to use bash, it should do so.

[Jawad-hussain-kalwar]

I have tried it, I have tried adding it to global rules, it sitll tends to use powershell, the limitation is the functions.shell_command tool by default it is only configured to be powershell so even if agent tried to use gitbash it will do so via powershell and then use bash.exe followed by command and it makes its performance even worse and token usage is also wasted,

[etraut-openai]

This feature request hasn't received enough upvotes, so I'm going to close it.

[sicora-at-mcgough]

The fact that there is an option in the windows app for choosing the "integrated shell" is confusing, took me a very long time to realize that the choice there has no bearing on the terminal shell used by the agent.

[etraut-openai]

@sicora-at-mcgough, you are welcome to open a new issue. Sometimes a feature request doesn't attract upvotes because of the way it's titled or described, so opening a new one can help attract more support.