Bug: Native Windows directory picker truncates paths at BMP chars whose UTF-16 low byte is 0x00 (e.g. 一 U+4E00)

[taominjigithub002]

Summary

On Windows, when a workspace directory's name contains a character whose Unicode code point ends in 00 hex (so its UTF-16LE low byte is 0x00 — e.g. 一 U+4E00, encoded as bytes 00 4E), the native folder dialog worker truncates the returned path at that character. workspace.create then rejects the truncated, nonexistent path with:

workspace-invalid-path: cannot create a workspace at "D:\Projects\项目": ENOENT: no such file or directory, realpath 'D:\Projects\项目'

Example (synthetic): selecting D:\Projects\项目一测试 produces the error path D:\Projects\项目 — truncated exactly before 一 (U+4E00).

Environment

• OS: Windows (Win32)
• DSH: 0.1.0-rc.6 (dsh-web-app, dsh-host-directory-picker-native both 0.1.0-rc.6)
• Backend in use: native directory picker (auto-resolved because the host binds loopback 127.0.0.1 on win32). Note this affects the web GUI too, not just desktop: the web GUI calls host.pickDirectory, which opens the same native OS dialog on the host screen. The in-app browse dialog is only mounted when the native dialog is unavailable (remote/SSH/non-loopback bind), so on a local Windows setup every workspace pick goes through this buggy native path.

Root cause

readUtf16() in packages/host/directory-picker-native/src/win32-dialog-bindings.ts (built output: lib/worker.cjs) scans for the NUL terminator by checking only the low byte of each UTF-16 code unit:

function readUtf16(koffi, address) {
    const bytes = Buffer.from(koffi.view(address, 32768));
    let end = 0;
    while (end + 1 < bytes.length && bytes[end] !== 0) end += 2; // BUG: only checks low byte
    return bytes.toString("utf16le", 0, end);
}

Any BMP character whose code point is 0xXX00 (low byte 0x00) stops the scan early. 一 (U+4E00) encodes as 00 4E in UTF-16LE, so a path containing it is cut right before it. D:\Projects\项目一测试 encodes as:

项(79 98) 目(EE 76) 一(00 4E) 测(4B 6D) 试(D5 8B)
                    ↑ low byte is 0x00 → scan stops → "D:\Projects\项目"

The full path is otherwise perfectly valid: fs.realpath on the untruncated path succeeds (verified).

Suggested fix

Stop only on a full 2-byte NUL terminator:

function readUtf16(koffi, address) {
    const bytes = Buffer.from(koffi.view(address, 32768));
    let end = 0;
    while (end + 1 < bytes.length && !(bytes[end] === 0 && bytes[end + 1] === 0)) end += 2;
    return bytes.toString("utf16le", 0, end);
}

Steps to reproduce

1. On Windows, create a folder whose name contains a character with code point 0xXX00, e.g. 项目一测试 (contains 一 U+4E00).
2. Open the DSH web GUI (loopback bind) → workspace picker → the native "Select Workspace Directory" dialog opens.
3. Select that folder and confirm.
4. Observed error: workspace-invalid-path: cannot create a workspace at "D:\Projects\项目": ENOENT: no such file or directory, realpath 'D:\Projects\项目'.

Expected behavior

The workspace is created with the full path D:\Projects\项目一测试.

Workarounds (until fixed)

• Rename the folder to avoid such characters (e.g. remove/replace 一) — the only no-config workaround.
• Pin the browse picker via config: compose @deepseek-ai/dsh-host-directory-picker-browse + @deepseek-ai/dsh-client-ui-directory-picker-browse instead of directory-picker-auto in the app config, so the in-app browser dialog (which lists via Node fs and is unaffected) is used even on a local Windows host.

[X-250-A]

+1 — reproduced today on Windows with dsh 0.1.0-rc.6, same root cause.

Real case: selecting D:\agent个人项目开发 (trailing chars 开发 — 开 is U+5F00, UTF-16LE low byte 0x00) returns the truncated path D:\agent个人项目, then workspace creation fails with:

workspace create failed: workspace-invalid-path: cannot create a workspace at "D:\agent个人项目": ENOENT: no such file or directory, realpath 'D:\agent个人项目'

I also confirmed against the actual bytes of D:\agent个人项目开发 that the middle chars 个/人/项/目 have non-zero low bytes (0x2A/0xBA/0x79/0xEE) — the scan only trips at 开 (0x00), exactly as described for readUtf16() in src/win32-dialog-bindings.ts.

Preparing a fix PR.

[X-250-A]

@dsh-fix-comment.md