[Windows] Process hangs indefinitely when spawned as child subprocess via Volta shim (stdin EOF not propagated through cmd.exe → bash → volta → node chain) #420

Summary

When ccstatusline is invoked as a child process from another Node.js script using spawn('ccstatusline', [], { shell: true }) on Windows with a Volta-managed installation, the process hangs indefinitely and never exits. Each invocation leaks one node.exe process. In a long Claude Code session this accumulated to 961 leaked processes → 2.1 GB RAM → 90.5% kernel-mode CPU from Windows scheduler overhead.

Root cause

The Volta-installed ccstatusline binary is a bash shim:

volta run "$(basename $0)" "$@"

When spawned via spawn('ccstatusline', [], { shell: true }), the process chain on Windows is:

parent node → cmd.exe (shell:true) → bash (Volta shim) → volta → node (ccstatusline)

ccstatusline reads stdin with for await (const chunk of process.stdin) (line ~77342 in dist). The parent calls cc.stdin.end() to signal EOF — but on Windows, stdin EOF does not propagate through the cmd.exe → bash → volta chain. The inner for await loop never terminates. ccstatusline sits waiting forever. The parent also hangs waiting on cc.on('close', ...).

Claude Code's statusline lifecycle abandons (does not kill) a hung process when a new refresh triggers, so processes accumulate indefinitely.

This is a known Node.js/Windows issue

• process.stdin never returns with using Git Bash for Windows nodejs/node#5620 — process.stdin never returns in Git Bash/Windows
• Accessing process.stdin hangs on Windows nodejs/node#10836 — canonical Windows stdin hang
• Piping process.stdin to child.stdin leaves behind an open handle nodejs/node#32291 — piping process.stdin to child.stdin leaves open handle
• spawn with stdio/stdin 'pipe' options causes pwsh shell to hang after execution nodejs/node#52364 — spawn + stdin:'pipe' causes pwsh to hang (still broken 2024)
• Volta breaks with child_process.exec in cmd (Windows) volta-cli/volta#1199 — Volta shims + child_process confirmed broken on Windows
• [Bug] ccusage statusline causes infinite process spawning loop leading to 100% CPU usage ccusage/ccusage#459 — identical failure mode in the same Claude Code ecosystem (statusline subprocess never exits, 300%+ CPU, 3+ GB RAM)

The fix (2 lines in src/ccstatusline.ts)

After renderMultipleLines writes its output, instead of relying on event loop drain (which doesn't work through the Volta chain):

// After rendering is complete:
process.stdout.write(formattedOutput, () => {
  process.stdin.destroy(); // unblock event loop; EOF won't arrive through Volta chain on Windows
  process.exit(0);         // guarantee exit
});

Or more simply, wherever main() finishes rendering and before it returns:

process.stdin.destroy();

process.stdin.destroy() is sufficient — it unregisters the stdin handle from the event loop so Node exits naturally without waiting for EOF that will never arrive.

Notes

• This does not affect the primary use case ("command": "ccstatusline" directly in Claude Code settings) — in that case Claude Code pipes directly to ccstatusline with a single process layer and EOF propagates correctly.
• The bug only manifests when ccstatusline is used as a pipe-through subprocess, which is a misuse pattern but one that statusline-wrapper.sh documentation may inadvertently encourage.
• ccstatusline's Custom Command Widget already has a 1000ms kill timeout which correctly prevents this class of bug for child widgets — the same pattern (guaranteed exit) should be applied to the main process.

Environment

• Windows 11 Pro 10.0.26200
• ccstatusline v2.2.19
• Volta-managed Node installation
• Node.js v24.15.0

Suggested additional fix (documentation)

Add a note to docs/WINDOWS.md warning that spawning ccstatusline as a child_process subprocess with shell: true on Windows will hang due to Volta's bash shim. The correct usage is as the direct statusLine command.