"shell": "pwsh" config not respected, still uses PowerShell 5.1 on Windows

[seka-qiguan]

Description

Bug Description
The shell setting in opencode.json is set to "pwsh" but opencode still uses PowerShell 5.1 (powershell.exe) as the default shell.

Config
~/.config/opencode/opencode.json:

{
"$schema": "https://opencode.ai/config.json",
"shell": "pwsh",
"provider": {}
}
Actual Behavior
Running commands through the bash tool executes in PowerShell 5.1:

PSVersion: 5.1.26100.8457
ProcessName: powershell
Path: C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.EXE
Expected Behavior
When "shell": "pwsh" is configured, commands should execute in PowerShell 7 (pwsh.exe), which defaults to UTF-8 and resolves Chinese encoding issues that plague PS 5.1.

Environment
OS: Windows (win32)
PowerShell 5.1: C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.EXE
PowerShell 7: installed and available at pwsh
opencode config: ~/.config/opencode/opencode.json with "shell": "pwsh"
Impact
Chinese (and other non-ASCII) characters are garbled in PS 5.1 due to GB2312 default encoding. PS 7 uses UTF-8 by default and works correctly.

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• OpenCode uses Windows PowerShell 5.1 instead of the PowerShell 7 it was launched from #17372: Same issue — OpenCode uses PowerShell 5.1 instead of PowerShell 7 on Windows, even when pwsh is available/configured
• Skills fail to load on Windows due to Expand-Archive using PowerShell 5.1 instead of configured pwsh shell #29957: Related — "shell": "pwsh" config not respected when loading skills on Windows (Expand-Archive using PS 5.1)

If your issue is distinct from those, please add a comment explaining how it differs.

[chirag127]

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