statusLine command runs on Windows but line never renders in UI (v2.1.138)

Summary

The statusLine.type: command feature is non-functional on Windows in v2.1.138. The configured command is invoked correctly on every turn, and it does emit a valid stdout line, but the status line region never appears anywhere in the Claude Code UI.

Environment

• Claude Code version: 2.1.138
• OS: Windows 11 Home, build 26200.8246
• Terminals tested: classic PowerShell conhost AND Windows Terminal — same result in both

Configuration

~/.claude/settings.json:

{
  "statusLine": {
    "type": "command",
    "command": "C:\Users\David\.claude\statusline-command.cmd"
  }
}

statusline-command.cmd wraps a PowerShell script that reads JSON from stdin via [Console]::In.ReadToEnd(), parses with ConvertFrom-Json, and writes a single UTF-8 line to stdout.

Evidence the command runs correctly

Added a self-written log inside the wrapper. After every restart + prompt, the log file shows fresh invoked and emitted-stdout entries, confirming Claude Code does spawn the process and the process does complete. Manually piping sample JSON to the script produces the expected output line.

Evidence the UI never renders

• No status line region visible anywhere on screen (not top, not bottom, not middle)
• Tested with plain ASCII (echo STATUSLINE_PROBE_OK), ANSI-coloured text, and the real PS script — none appeared
• claude --debug produces no output mentioning statusLine, the script path, an exit code, or stderr — as if the render step never happens
• Behaviour is identical in conhost and Windows Terminal

Steps to reproduce

1. On Windows 11, set statusLine.type: command with any script that writes a line to stdout
2. Restart Claude Code
3. Send any prompt
4. Observe: the command runs (verifiable by writing a log file from inside it), but no status line region appears in the UI

Expected behaviour

A status line region at the bottom of the Claude Code UI displaying the script's stdout output, as documented.