[Bug] Busy-loop polling non-existent config files causes 99%+ CPU consumption

Bug Description
Related but distinct from #11170:

• Higher CPU (99-122% vs 10-40%)
• Different trigger: backgrounding agents, not API calls
• Additional paths polled: ~/.claude/plans, private/tmp
• Workaround found: Escape key 3x breaks the loop
• Still responses very slowly (during /bug)

claude-bug-report.zip

• Newer version (2.1.17 vs 2.0.35)

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Summary: Claude Code 2.1.17 enters busy-loop polling for non-existent config files, consuming 99-122% CPU indefinitely

Environment:

• Claude Code version: 2.1.17
• OS: macOS 26.2 (25C56)
• Hardware: M4 Max, 128GB RAM

Symptoms:

• Process stuck at 99-122% CPU for 42+ minutes
• fs_usage showed tight loop polling these non-existent files thousands of times per second:
• ~/.claude/.config.json (ENOENT)
• ~/.claude/plans (ENOENT)
• private/tmp (relative path, ENOENT)
• Memory bloated to 3.1 GB RSS (normal ~300-500 MB)
• CLI became unresponsive

What I tried:

• Creating ~/.claude/.config.json with {} - did NOT fix
• Creating ~/.claude/plans directory - did NOT fix

Workaround found:

• Pressing Escape key 3+ times broke the loop
• CPU dropped from 122% to 0.4% after Escape

Diagnostic data collected:

• CPU sample (10 sec)
• lsof output
• fs_usage trace showing the polling loop
• Available on request

Reproduction:
Scenario (not verified as reproduction steps):

3 agent tasks were sent to background prior to observing the issue
High CPU noticed in top afterward
Unknown if this was the trigger or coincident

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Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.17
• Feedback ID: cca42af1-dd2a-4887-bcdb-c77129a083e2

Errors

[{"error":"Error: ENOENT: no such file or directory, scandir '/Library/Application Support/ClaudeCode/.claude/skills'\n    at readdirSync (unknown)\n    at <anonymous> (/$bunfs/root/claude:12:1903)\n    at vW (/$bunfs/root/claude:11:35097)\n    at readdirSync (/$bunfs/root/claude:12:1864)\n    at y2R (/$bunfs/root/claude:1479:380)\n    at y2R (/$bunfs/root/claude:1479:1350)\n    at <anonymous> (/$bunfs/root/claude:1479:4440)\n    at <anonymous> (/$bunfs/root/claude:1479:5171)\n    at A (/$bunfs/root/claude:11:7244)\n    at pX8 (/$bunfs/root/claude:4784:4342)","timestamp":"2026-01-23T18:59:49.598Z"},{"error":"Error\n    at <anonymous> (/$bunfs/root/claude:47:9586)\n    at emit (node:events:95:22)\n    at addChunk (internal:streams/readable:264:47)\n    at readableAddChunkPushByteMode (internal:streams/readable:242:18)\n    at processCallback (node:zlib:246:61)\n    at request (/$bunfs/root/claude:49:2148)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-23T19:17:27.045Z"},{"error":"Error: ENOENT: no such file or directory, scandir '/Library/Application Support/ClaudeCode/.claude/skills'\n    at readdirSync (unknown)\n    at <anonymous> (/$bunfs/root/claude:12:1903)\n    at vW (/$bunfs/root/claude:11:35097)\n    at readdirSync (/$bunfs/root/claude:12:1864)\n    at y2R (/$bunfs/root/claude:1479:380)\n    at y2R (/$bunfs/root/claude:1479:1350)\n    at <anonymous> (/$bunfs/root/claude:1479:4440)\n    at <anonymous> (/$bunfs/root/claude:1479:5171)\n    at A (/$bunfs/root/claude:11:7244)\n    at pX8 (/$bunfs/root/claude:4784:4342)","timestamp":"2026-01-23T19:19:39.969Z"},{"error":"Error: ENOENT: no such file or directory, scandir '/Library/Application Support/ClaudeCode/.claude/skills'\n    at readdirSync (unknown)\n    at <anonymous> (/$bunfs/root/claude:12:1903)\n    at vW (/$bunfs/root/claude:11:35097)\n    at readdirSync (/$bunfs/root/claude:12:1864)\n    at y2R (/$bunfs/root/claude:1479:380)\n    at y2R (/$bunfs/root/claude:1479:1350)\n    at <anonymous> (/$bunfs/root/claude:1479:4440)\n    at <anonymous> (/$bunfs/root/claude:1479:5171)\n    at A (/$bunfs/root/claude:11:7244)\n    at pX8 (/$bunfs/root/claude:4784:4342)","timestamp":"2026-01-23T19:20:20.159Z"},{"error":"Error: ENOENT: no such file or directory, scandir '/Library/Application Support/ClaudeCode/.claude/skills'\n    at readdirSync (unknown)\n    at <anonymous> (/$bunfs/root/claude:12:1903)\n    at vW (/$bunfs/root/claude:11:35097)\n    at readdirSync (/$bunfs/root/claude:12:1864)\n    at y2R (/$bunfs/root/claude:1479:380)\n    at y2R (/$bunfs/root/claude:1479:1350)\n    at <anonymous> (/$bunfs/root/claude:1479:4440)\n    at <anonymous> (/$bunfs/root/claude:1479:5171)\n    at A (/$bunfs/root/claude:11:7244)\n    at pX8 (/$bunfs/root/claude:4784:4342)","timestamp":"2026-01-23T19:20:33.150Z"},{"error":"Error: ENOENT: no such file or directory, scandir '/Library/Application Support/ClaudeCode/.claude/skills'\n    at readdirSync (unknown)\n    at <anonymous> (/$bunfs/root/claude:12:1903)\n    at vW (/$bunfs/root/claude:11:3…

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