[Bug] Sibling tool call errored regression since v2.1.19

Bug Description
Bug Report: "Sibling tool call errored" increased since ~v2.1.19

• Version: 2.1.31 (CLI)
• Platform: Windows 11
• Frequency: Frequent, increased over recent versions
• Symptom: Parallel tool calls fail with "Sibling tool call errored", requiring session restart
• Expected: Fixed in v2.1.7/v2.1.9 per CHANGELOG, but regression observed
• Related: #20571, #9103, #6836

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.1.31
• Feedback ID: 7baf5e2f-df6b-412f-bb9d-ba24bf22f1e6

Errors

[{"error":"Error: EPERM: operation not permitted, symlink 'C:\\Users\\e_pi3\\.claude\\projects\\C--Python-thermophysical-properties-estimator\\ae2478ac-318b-4986-85a4-6d618c3cfe1a\\subagents\\agent-a8116c8.jsonl' -> 'C:\\Users\\e_pi3\\AppData\\Local\\Temp\\claude\\C--Python-thermophysical-properties-estimator\\tasks\\a8116c8.output'\n    at symlinkSync (unknown)\n    at DGH (B:/~BUN/root/claude.exe:1494:1154)\n    at DtD (B:/~BUN/root/claude.exe:1528:1268)\n    at <anonymous> (B:/~BUN/root/claude.exe:2895:922)\n    at <anonymous> (B:/~BUN/root/claude.exe:2895:1840)\n    at run (node:async_hooks:62:22)\n    at CUH (B:/~BUN/root/claude.exe:217:14675)\n    at call (B:/~BUN/root/claude.exe:2895:616)\n    at async fME (B:/~BUN/root/claude.exe:3103:13642)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-02-05T10:20:21.811Z"}]