Problem

Get-BranchName's fallback branch assumes the pipeline yields at least one element:

$result = ConvertTo-CleanBranchName -Name $Description
$fallbackWords = ($result -split '-') | Where-Object { $_ } | Select-Object -First 3
return [string]::Join('-', $fallbackWords)

ConvertTo-CleanBranchName does $Description.ToLower() -replace '[^a-z0-9\s]', ' ', which blanks every non-ASCII character. So a description written in any non-Latin script leaves nothing for the pipeline to emit:

• the pipeline yields nothing → $fallbackWords is $null
• [string]::Join('-', $null) throws ArgumentNullException
• $ErrorActionPreference = 'Stop' makes it terminating

The script dies with a .NET stack trace, empty stdout, exit 1.

Reproduction on current main (bf88c9f)

All three twins installed into one project, same args, same cwd:

desc = 'добавить авторизацию'
  bash rc=0  BRANCH_NAME='001-'
  py   rc=0  BRANCH_NAME='001-'
  ps   rc=1  Exception calling "Join" with "2" argument(s):
             "Value cannot be null. Parameter name: values"

Identical for 添加用户认证 and '!!! ??? ***'. The bash and Python twins both return an empty suffix and succeed.

This hits every PowerShell user who phrases a feature in their own language — Cyrillic, Han, Kana, Arabic, Greek, Hebrew — plus punctuation-only and accent-only descriptions.

Fix

Wrap the pipeline in @() so it stays an array. Verified at the primitive level:

unwrapped, empty result: type=NULL       Join -> THROWS MethodInvocationException
wrapped   with @():      type=Object[]   Join -> ''        (count=0)
normal case 'a-to-the-of':               Join -> 'a-to-the'   (unchanged)

After the fix, the same three descriptions:

  rc=0  {"BRANCH_NAME":"001-", ...}      x3
  rc=0  {"BRANCH_NAME":"001-user-authentication", ...}   (normal case unchanged)

No breaking change. The only inputs whose behaviour changes are ones that today raise and exit 1. The file stays ASCII-only (verified 0 non-ASCII bytes) so tests/test_ps1_encoding.py::test_ps1_file_is_ascii_only still passes.

Verification

• Fail-before / pass-after: 3 new-vs-baseline failures with the source reverted → 10 passed, 44 skipped with the fix.
• Two tests added: a parametrized PS-only crash guard (punctuation / Cyrillic / Han), and a three-way parity test asserting bash, Python and PowerShell all produce 001- for the same input.
• Scoped regression: no new failures vs a clean-main baseline captured on bf88c9f9.
• uvx ruff@0.15.0 check src tests → clean

Written with assistance from Claude Code. Bug found, reproduced, and verified by me on current main with real powershell.exe.