spawn pgrep ENOENT crash on macOS (regression in v2.1.91)

Bug description

Claude Code crashes with ENOENT: no such file or directory, posix_spawn 'pgrep' during normal operation (attempting to read a file via the Read tool). The crash dumps minified ink UI source to the terminal.

pgrep exists at /usr/bin/pgrep and is accessible from the user's shell. The issue appears to be that Bun's subprocess spawning uses a restricted PATH that doesn't include /usr/bin, or the ENOENT is not caught gracefully.

Prior issues

This was previously reported and closed:

• #15026 (closed 2026-03-11)
• #17626 (closed 2026-01-12)

The bug has regressed or was never fully fixed.

Reproduction steps

1. Open Claude Code on macOS
2. Ask it to read a file (triggers internal pgrep -P <pid> call)
3. Crash occurs with ENOENT

Error output

ENOENT: no such file or directory, posix_spawn 'pgrep'
      path: "pgrep",
   syscall: "spawn pgrep",
     errno: -2,
 spawnargs: [ "-P", 10870 ],
      code: "ENOENT"

      at spawn (unknown:1:1)
      at spawn (node:child_process:667:35)
      at spawn (node:child_process:14:39)
      at /$bunfs/root/claude:814:4866
      at pRA (/$bunfs/root/claude:814:5359)
      at /$bunfs/root/claude:814:4837

Environment

• Claude Code version: 2.1.91
• OS: macOS Darwin 25.4.0
• Shell: zsh
• pgrep location: /usr/bin/pgrep (confirmed accessible)

Expected behavior

Claude Code should either:

1. Use the full path /usr/bin/pgrep instead of relying on PATH resolution
2. Catch the ENOENT and degrade gracefully instead of crashing