[Bug] defaultMode "auto" setting silently ignored, sessions revert to default mode

Bug Description
defaultMode "auto" silently ignored — sessions start in default mode
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▎ Version 2.1.181, macOS, bare CLI (Ghostty + tmux).
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▎ ~/.claude/settings.json (user scope) has "permissions": { "defaultMode": "auto" }. Expected: new sessions start in auto mode. Actual: every fresh session starts in default mode, no error.
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▎ Ruled out: setting is in user scope, not project (the v2.1.142 project-scope exclusion doesn't apply); auto mode is available (appears in Shift+Tab cycle, on Opus 4.8, claude auto-mode config works); no managed-settings.json present (no org disableAutoMode); hasSeenAutoModeEntryWarning: true; no shell alias/wrapper/env override of --permission-mode.
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▎ Internal state: ~/.claude.json shows tengu_auto_mode_default_on: false despite the setting. Smoking gun: Claude Code sets the terminal pane title to Debug missing auto mode disclaimer and appears to abort entering auto because that disclaimer is missing, falling back to default.

Environment Info

• Platform: darwin
• Terminal: tmux
• Version: 2.1.181
• Feedback ID: a383929b-2b2b-482a-a4b9-762f4596123f

Errors

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