fix(shell): add PowerShell UTF-8 command wrapper on Windows by senguangd · Pull Request #31985 · anomalyco/opencode

senguangd · 2026-06-12T02:59:06Z

Issue for this PR

Closes #23636
Closes #31187
Closes #30205
Closes #31830
Closes #26882

Supersedes #31925 (which was closed before the third code path was added)

Type of change

Bug fix
New feature
Refactor / code improvement
Documentation

What does this PR do?

On Windows, opencode captures shell output as bytes and decodes it as UTF-8. PowerShell, however, can write stdout/stderr using the active console code page when [Console]::OutputEncoding is not set explicitly. On non-UTF-8 systems, such as GBK/CP936 or Shift-JIS/CP932 environments, this can cause PowerShell output to be decoded incorrectly by opencode.

This PR adds a shared PowerShell command wrapper that:

Sets [Console]::InputEncoding to UTF-8
Sets [Console]::OutputEncoding to UTF-8
Sets `` to the same UTF-8 encoding
Runs the original user command as a separate scriptblock

The user command is stored inside the wrapper as an inner UTF-8 Base64 payload, then decoded and passed to [scriptblock]::Create(). The Base64 payload is used to avoid quoting and escaping issues when embedding arbitrary user command text inside the wrapper. The separate scriptblock invocation avoids prepending the UTF-8 setup directly to the user script, preserving script-level constructs such as leading param(...) blocks and #requires directives.

Files changed (all three PowerShell execution paths):

File	Change
`packages/core/src/shell/powershell.ts`	Add shared PowerShell argument/wrapper construction
`packages/core/src/tool/bash.ts`	Detect PowerShell on Windows and invoke it through the shared wrapper
`packages/core/src/shell.ts`	Use the shared PowerShell wrapper from `Shell.args(...)`
`packages/opencode/src/tool/shell.ts`	Delegate PowerShell invocation to `Shell.args(...)` instead of hardcoding argv

How did you verify your code works?

Applied the patch locally and verified that Write-Output "测试中文输出" renders correctly in opencode shell output on Windows with a non-UTF-8 code page
Verified the same commands work with both powershell 5.1 and pwsh 7+
Tested TUI ! shell mode (! echo 你好世界) — Chinese output displays correctly
TypeScript typecheck passes (tsgo --noEmit on all 23 packages)

Screenshots / recordings

N/A — this is a shell encoding fix, not a UI change.

Checklist

I have tested my changes locally
I have not included unrelated changes in this PR

Copilot

Pull request overview

Note

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

This PR updates Windows PowerShell execution to use -EncodedCommand and a UTF-8 console-encoding prelude, and centralizes PowerShell argument construction in shared helpers to improve reliability of command execution on Windows.

Changes:

Route Windows PowerShell invocation through Shell.args(...) instead of hardcoded flags.
Add -EncodedCommand generation for PowerShell, including setting console input/output encoding to UTF-8.
Update the core bash tool to detect PowerShell shells and spawn them with encoded commands.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/opencode/src/tool/shell.ts	Switches Windows PowerShell spawn args to the shared `Shell.args(...)` helper.
packages/opencode/src/shell/shell.ts	Introduces Base64 UTF-16LE `-EncodedCommand` generation and updates PowerShell args accordingly.
packages/core/src/tool/bash.ts	Adds PowerShell detection and uses `-EncodedCommand` spawning on Windows.

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senguangd · 2026-06-12T03:26:53Z

+function encodedPowerShellCommand(command: string) {
+  return Buffer.from(
+    `
+[Console]::InputEncoding = [System.Text.UTF8Encoding]::new($false);
+[Console]::OutputEncoding = [System.Text.UTF8Encoding]::new($false);
+$OutputEncoding = [Console]::OutputEncoding;
+${command}
+`,
+    "utf16le",
+  ).toString("base64")
+}


Good catch — this was a real issue. I updated the implementation so the UTF-8 setup is no longer prepended directly to the user-provided PowerShell script text.

The encoded command is now a small wrapper that sets the console encodings first, then decodes the original user command and invokes it as a separate scriptblock. That preserves script-level constructs like leading param(...) blocks and #requires directives, while still keeping the UTF-8 behavior.

senguangd · 2026-06-12T03:27:05Z

+const POWERSHELL_SHELLS = new Set(["powershell", "powershell.exe", "pwsh", "pwsh.exe"])
+
+const isPowerShell = (shell: string) => {
+  const name = path.basename(shell.trim().replace(/^["']|["']$/g, "")).toLowerCase()
+  return POWERSHELL_SHELLS.has(name)
+}
+
+function encodedPowerShellCommand(command: string) {
+  return Buffer.from(
+    `
+[Console]::InputEncoding = [System.Text.UTF8Encoding]::new($false);
+[Console]::OutputEncoding = [System.Text.UTF8Encoding]::new($false);
+$OutputEncoding = [Console]::OutputEncoding;
+${command}
+`,
+    "utf16le",
+  ).toString("base64")
+}


Agreed. I extracted the PowerShell argument/encoding construction into a shared helper under @opencode-ai/core, and updated both execution paths to use it.

packages/opencode/src/shell/shell.ts now uses the shared PowerShell helper from Shell.args(...), and packages/opencode/src/tool/shell.ts reuses Shell.args(...) instead of building its own PowerShell argv. The core BashTool also uses the same shared helper, so the -EncodedCommand wrapper behavior stays consistent across the direct shell, shell tool, and core BashTool paths.

Thalynor · 2026-06-16T03:03:28Z

You mentioned that using the -Command corrupts the content. Could you tell me how to reproduce this issue?

senguangd · 2026-06-16T10:18:25Z

@Thalynor Good question — I rechecked this and updated the PR to make the scope more precise.

The latest version no longer uses -EncodedCommand. A direct pwsh -Command <string> invocation is not the reliable reproduction point here: direct process creation on Windows passes the command line as Unicode, so simply changing the active code page does not necessarily corrupt the command text itself.

The actual issue this PR is addressing is the output decoding path: opencode captures child process output as bytes and decodes it as UTF-8, while PowerShell may write stdout/stderr using the active console code page unless [Console]::OutputEncoding is set explicitly. On non-UTF-8 systems, those bytes can be decoded incorrectly by opencode.

The fix now does this instead:

invokes PowerShell with -Command
sets [Console]::InputEncoding, [Console]::OutputEncoding, and $OutputEncoding to UTF-8 before running the user command
passes the original user command as an inner UTF-8 Base64 payload and invokes it via [scriptblock]::Create()

The inner Base64 is not meant to justify -EncodedCommand; it is just a safe way to embed arbitrary user command text in the wrapper without PowerShell quoting/escaping issues. The separate scriptblock invocation avoids prepending the UTF-8 setup directly to the user script, preserving leading param(...) blocks and #requires directives.

So the PR description has been updated to describe this as a PowerShell UTF-8 I/O wrapper fix rather than a -EncodedCommand transport fix.

On Windows, PowerShell commands need proper UTF-8 encoding setup to avoid corruption when the console code page is not UTF-8 (e.g. GBK/CP936 on zh-CN systems). This adds a shared PowerShell module that: - Sets [Console]::InputEncoding and OutputEncoding to UTF-8 - Uses inner Base64 + [scriptblock]::Create() to preserve user command semantics (param(), #requires must be at script start) Used by bash tool, shell tool, and TUI direct shell mode.

Copilot AI review requested due to automatic review settings June 12, 2026 02:59

Copilot AI reviewed Jun 12, 2026

View reviewed changes

senguangd force-pushed the fix/powershell-encodedcommand-utf8 branch from 39201fe to 2243bee Compare June 12, 2026 03:18

This was referenced Jun 12, 2026

📊 AI CLI 工具社区动态日报 2026-06-12 jasonalang/big_model_radar#76

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📊 AI CLI 工具社区动态日报 2026-06-12 litang9/big_model_radar#50

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📊 AI CLI 工具社区动态日报 2026-06-12 hehongtao88/big_model_radar#16

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senguangd force-pushed the fix/powershell-encodedcommand-utf8 branch 2 times, most recently from 140649d to 727d78a Compare June 13, 2026 04:10

senguangd force-pushed the fix/powershell-encodedcommand-utf8 branch 2 times, most recently from 96a0fd0 to 18c5177 Compare June 16, 2026 10:07

senguangd changed the title ~~fix(shell): use PowerShell EncodedCommand for reliable UTF-8 output on Windows~~ fix(shell): add PowerShell UTF-8 command wrapper on Windows Jun 16, 2026

senguangd force-pushed the fix/powershell-encodedcommand-utf8 branch from 18c5177 to f4eded7 Compare June 16, 2026 10:19

senguangd force-pushed the fix/powershell-encodedcommand-utf8 branch from f4eded7 to 0689b9d Compare June 17, 2026 03:13

github-actions Bot mentioned this pull request Jun 17, 2026

📊 AI CLI 工具社区动态日报 2026-06-17 litang9/big_model_radar#75

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davidgut1982 mentioned this pull request Jun 17, 2026

📊 AI CLI Tools Digest 2026-06-17 davidgut1982/big_model_radar#12

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fix(shell): add PowerShell UTF-8 command wrapper on Windows#31985

fix(shell): add PowerShell UTF-8 command wrapper on Windows#31985
senguangd wants to merge 1 commit into
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senguangd:fix/powershell-encodedcommand-utf8

senguangd commented Jun 12, 2026 •

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