fix(shell): use EncodedCommand for PowerShell to fix Windows encoding issues

[senguangd]

Issue

Fixes #4138
Fixes #2422
Fixes #2939

Also related to #9440, #8616

Context

On Windows, PowerShell commands containing or producing non-ASCII characters (Chinese, Japanese, Cyrillic, etc.) result in garbled output (mojibake). This happens because the console encoding defaults to the system OEM code page (e.g., CP936 for zh-CN) rather than UTF-8.

Multiple users have reported this issue:

• [Windows] PowerShell encoding error: "powershell" �� ���� when Kilo Code tries to execute system command #4138: PowerShell encoding error — mojibake when Kilo Code executes system commands on Windows
• [Bug] Garbled characters (mojibake) in "Run Command" output on Windows zh-CN locale #2422: Garbled characters in "Run Command" output on Windows zh-CN locale
• not work #2939: PowerShell -Command argument not recognized properly by pwsh.exe

All three issues were closed as stale/not-planned without a code fix. The underlying encoding problem remains.

Implementation

Switch PowerShell invocation from -Command to -EncodedCommand with a Base64-encoded UTF-16LE payload. The encoded payload explicitly sets [Console]::InputEncoding, [Console]::OutputEncoding, and $OutputEncoding to UTF-8 before executing the original command. This ensures both input and output are properly encoded as UTF-8 regardless of the system locale.

New file: packages/core/src/shell/powershell.ts

• args(command) — returns PowerShell arguments using -EncodedCommand
• encoded(command) — wraps the command in a UTF-8 console setup preamble and encodes as Base64 (UTF-16LE)

Modified: packages/opencode/src/shell/shell.ts

• Import the new PowerShell module
• Replace ["-NoProfile", "-Command", command] with PowerShell.args(command)

Modified: packages/opencode/src/tool/shell.ts

• Replace hardcoded ["-NoLogo", "-NoProfile", "-NonInteractive", "-Command", command] with Shell.args(shell, command, cwd), reusing the same encoding logic

This approach is inspired by how VS Code's own shell execution handles PowerShell encoding (using -EncodedCommand to avoid encoding mismatches).

Screenshots

N/A, non-visual change. The fix affects command output encoding in the shell execution layer.

How to Test

Manual/local verification

1. On a Windows machine with a non-English locale (e.g., zh-CN, ja-JP, ru-RU), launch Kilo Code
2. Ask the agent to run a PowerShell command that produces localized output, e.g.:

   (Get-CimInstance -ClassName Win32_OperatingSystem).caption
   

3. Before fix: output contains mojibake/garbled characters
4. After fix: output displays correctly in the expected language

Reviewer test steps

1. Check out this branch on a Windows machine
2. Build and run Kilo Code
3. Execute any command via the agent that triggers PowerShell (e.g., "What OS am I running?")
4. Verify the output is correctly encoded (no mojibake)
5. Also verify on an English-locale Windows machine that existing functionality is not broken

Checklist

• Issue linked above, or exception explained
• Tests/verification described
• Screenshots/video included for visual changes, or marked N/A
• // kilocode_change markers added for changes in packages/opencode/
• I personally reviewed the diff and can explain the changes

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR centralizes PowerShell command invocation and switches PowerShell execution to use -EncodedCommand (with a UTF-8 wrapper) instead of passing raw -Command strings.

Changes:

• Added a core powershell.ts helper to generate PowerShell CLI args using -EncodedCommand.
• Updated shell argument selection to delegate PowerShell arg construction to the new helper.
• Updated Windows PowerShell process creation to reuse Shell.args(...) rather than hardcoding flags.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
packages/opencode/src/tool/shell.ts	Uses Shell.args(...) for Windows PowerShell process creation instead of inline PowerShell flags.
packages/opencode/src/shell/shell.ts	Routes PowerShell argument generation through @opencode-ai/core/shell/powershell.
packages/core/src/shell/powershell.ts	Introduces PowerShell arg builder that encodes commands and enforces UTF-8 I/O settings.

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[kilo-code-bot]

Code Review Summary

Status: 1 Observation (no blocking issues) | Recommendation: Merge

Overview

Severity	Count
CRITICAL	0
WARNING	0
SUGGESTION	1

Previously Flagged Issues — All Resolved

All issues from prior reviews have been addressed:

Issue	Status
Missing Buffer import in powershell.ts	✅ Fixed — import { Buffer } from "node:buffer" added
// kilocode_change start/end block markers in shell.ts	✅ Fixed — replaced with descriptive inline comment
Standalone // kilocode_change in shell.ts	✅ Fixed — folded into line with description
Standalone // kilocode_change in tool/shell.ts	✅ Fixed — folded into line with description
Leading newline in template literal (powershell.ts)	✅ Fixed — template literal now starts with [Console] directly
Fork hygiene — new file in upstream-shared packages/core/	✅ Fixed — file moved to packages/opencode/src/kilocode/shell/shell.ts
No test coverage	✅ Fixed — packages/opencode/test/kilocode/shell/shell.test.ts added

Remaining Observation (not in diff)

Changeset missing: This PR fixes a real user-facing bug (garbled output on non-English Windows locales) and still has no .changeset/*.md entry. A patch changeset with a user-facing description like "Fix garbled PowerShell output on Windows with non-UTF-8 system locales" would be appropriate per AGENTS.md.

Files Reviewed (3 files)

• packages/opencode/src/kilocode/shell/shell.ts — new file, moved from packages/core/src/shell/powershell.ts; all prior issues resolved
• packages/opencode/src/shell/shell.ts — all prior issues resolved
• packages/opencode/src/tool/shell.ts — all prior issues resolved
• packages/opencode/test/kilocode/shell/shell.test.ts — new test file added

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_{Reviewed by claude-4.6-sonnet-20260217 · 676,910 tokens}

_{Review guidance: REVIEW.md from base branch main}

[johnnyeric]

Hey @senguangd, could you please link your GitHub account to the Kilo account? This way, we can grant you credits for the merged PRs.
Once you have done that, please message johnny[at]kilocode.ai