feat(windows): add first-class pwsh/powershell support

[Hona]

Summary

• Add first-class pwsh / powershell support on Windows by preferring PowerShell over Git Bash when selecting the default shell
• Parse PowerShell commands with tree-sitter-powershell so permission scanning covers cmdlets, env paths, FileSystem:: providers, and ${env:...} syntax
• Resolve POSIX virtual paths (/tmp, /usr/...) through the selected shell's own cygpath when running under Git Bash/MSYS/Cygwin
• Fix /usr/bin/bash from $SHELL resolving to a non-spawnable path on Windows by mapping it through Shell.gitbash()
• Fix drive-root globs (C:\*) collapsing to the repo directory instead of the drive root in normalizePathPattern
• Scan nested command substitutions ($(cat ...), $(Get-Content ...)) for external directory permissions
• Hide spawned console windows on all Windows shell paths, not just PowerShell
• Centralize shell name extraction (Shell.name), login detection (Shell.login), and POSIX detection (Shell.posix) in the Shell namespace
• Replace Unix-only test fixtures (seq, /dev/zero) with cross-platform inline bun -e generators
• Add focused Windows regression coverage across shell selection, external directory prompts, PowerShell command parsing, and Git Bash path semantics

[Copilot]

Pull request overview

Adjusts Windows shell selection defaults to prefer PowerShell-family shells and improves runtime transparency for the bash tool by surfacing OS/shell context in its description.

Changes:

• Update Shell.preferred() / Shell.acceptable() to prefer pwsh, then powershell, when SHELL is unset on Windows.
• Keep existing Windows Git Bash path-resolution fallback behavior intact.
• Inject process.platform and a resolved shell name into the bash tool description template.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
packages/opencode/src/tool/bash.txt	Adds OS + resolved shell placeholders to the tool description.
packages/opencode/src/tool/bash.ts	Resolves shell “display name” and substitutes OS/shell into the tool description.
packages/opencode/src/shell/shell.ts	Introduces base() helper and changes Windows default shell preference order.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Hona]

/review

[github-actions]

lgtm

[caozhiyuan]

@Hona How to configure using git bash? Previously, cross-team collaboration used git bash scripts, but now pwsh is completely incompatible, causing all agent automation tasks to fail.

[Hona]

@caozhiyuan what automation? I would love to hear more about the cross team use case?

[Hona]

but yeah set an env var if you want git bash again, e.g.

SHELL=C:\Program Files\Git\bin\bash.exe

[caozhiyuan]

@Hona some bash script in slash command or skill .

[caozhiyuan]

It is recommended to use gitbash by default. Previously, claude code on Windows had very slow file reading and bash operations due to cygpath not having caching (this issue lasted for several months without being fixed, resolved in version 2.1.39, and now it runs smoothly anthropics/claude-code#13361 ). Therefore, many people chose opencode (including me). Also, it would be best to add a switch to choose between gitbash and pwsh. Claude code now supports pwsh as well, but it needs to be manually enabled. @Hona

On Windows, I also added this tip: # Bash Tips
Currently on Windows system, bash tools run in Git Bash and paths need to be enclosed in double quotes, for example: ls -lc "c:\work"
Some open-source models encounter issues when using bash, so this tip was specifically added.

[CCRcmcpe]

opencode/packages/opencode/src/tool/bash.ts

Lines 446 to 449 in 057848d

	constchain=
	name==="powershell"
	? "If the commands depend on each other and must run sequentially, avoid '&&' in this shell because Windows PowerShell 5.1 does not support it. Use PowerShell conditionals such as `cmd1; if ($?) { cmd2 }` when later commands must depend on earlier success."
	: "If the commands depend on each other and must run sequentially, use a single Bash call with '&&' to chain them together (e.g., `git add . && git commit -m \"message\" && git push`). For instance, if one operation must complete before another starts (like mkdir before cp, Write before Bash for git operations, or git add before git commit), run these operations sequentially instead."

we should change the prompt if pwsh is selected.

[Hona]

yup i'm further refactoring pwsh/powershell into separate tools

[caozhiyuan]

@Hona It seems that the claude code source code has leaked, with cli.js.map uploaded to npm.
https://www.npmjs.com/package/@anthropic-ai/claude-code/v/2.1.88?activeTab=code

[nikitakot]

@Hona this PR introduced a very trivial bash permission bypass in powershell, all commands which contain -- bypass the permissions completely, I created an issue and a potential fix for that:

#39931
#39938

In the fix I propose to fallback to full command evaluation if web-tree-sitter parsing fails.

Here's an isolated example:

import{Parser,Language}from"web-tree-sitter"import{createRequire}from"node:module"constrequire=createRequire(import.meta.url)awaitParser.init({locateFile(){returnrequire.resolve("web-tree-sitter/tree-sitter.wasm")},})constinputs=["git diff","git diff --","git diff -- file","git status --","echo --"]for(constgrammarof["tree-sitter-powershell","tree-sitter-bash"]){constlanguage=awaitLanguage.load(require.resolve(`${grammar}/${grammar}.wasm`))constparser=newParser()parser.setLanguage(language)console.log(`\n## ${grammar}`)for(constinputofinputs){consttree=parser.parse(input)constcommands=tree.rootNode.descendantsOfType("command").map((node)=>node.text)console.log(JSON.stringify({ input,tree: tree.rootNode.toString(), commands,error: tree.rootNode.hasError}))}}

output

$ node .\parse.mjs## tree-sitter-powershell
{"input":"git diff","tree":"(program (statement_list (pipeline (pipeline_chain (command command_name: (command_name) command_elements: (command_elements (command_argument_sep) (generic_token)))))))","commands":["git diff"],"error":false}
{"input":"git diff --","tree":"(ERROR (command_name) (command_argument_sep) (generic_token) (command_argument_sep))","commands":[],"error":true}
{"input":"git diff -- file","tree":"(ERROR (command_name) (command_argument_sep) (generic_token) (command_argument_sep) (simple_name))","commands":[],"error":true}
{"input":"git status --","tree":"(ERROR (command_name) (command_argument_sep) (generic_token) (command_argument_sep))","commands":[],"error":true}
{"input":"echo --","tree":"(ERROR (command_name) (command_argument_sep))","commands":[],"error":true}
## tree-sitter-bash
{"input":"git diff","tree":"(program (command name: (command_name (word)) argument: (word)))","commands":["git diff"],"error":false}
{"input":"git diff --","tree":"(program (command name: (command_name (word)) argument: (word) argument: (word)))","commands":["git diff --"],"error":false}
{"input":"git diff -- file","tree":"(program (command name: (command_name (word)) argument: (word) argument: (word) argument: (word)))","commands":["git diff -- file"],"error":false}
{"input":"git status --","tree":"(program (command name: (command_name (word)) argument: (word) argument: (word)))","commands":["git status --"],"error":false}
{"input":"echo --","tree":"(program (command name: (command_name (word)) argument: (word)))","commands":["echo --"],"error":false}

It's already being fixed in tree-sitter-powershell in airbus-cert/tree-sitter-powershell#51, but I believe that fallback fix I'm proposing is the correct approach, allowing to run the bash command when parsing fails doesn't sound right at all.

[nikitakot]

@Hona this bug was also merged to V2 from what I can see