[MODEL] Severe multi-symptom degradation since 2026-06-08 on Opus 4.8 (Desktop app): ignores CLAUDE.md, bypasses permission prompts, hallucinates, refuses doable tasks, writes files unprompted

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude ignored my instructions or configuration

What You Asked Claude to Do

I use Claude Code (Desktop app, Opus 4.8) for everyday work in my Obsidian vault and related projects, with detailed rules defined in CLAUDE.md and permission mode set to "ask before acting." Normal tasks: managing/editing files, CMS work, content edits, small scripts.

What Claude Actually Did

Starting 2026-06-08, Claude (Opus 4.8) shows a sudden, severe drop in quality across multiple dimensions in every session:

1. Ignores CLAUDE.md — no longer follows the instructions defined there.
2. Bypasses permission settings — executes actions directly even though permission mode is set to "ask before acting / manual approval."
3. Heavy hallucination — asserts things it cannot know and has not actually looked at, stated with full confidence.
4. Refuses doable work ("lazy") — repeatedly claims certain actions are not possible when they clearly are.
5. Creates files unprompted — writes new documents on its own, without being asked and without telling me.
6. Extremely slow on trivial tasks — takes very long for the simplest requests, and then still does them incorrectly.
7. Becomes dismissive/curt when its poor performance is pointed out.
8. Reports incomplete/faulty work as finished — performs tasks only partially or incorrectly, then presents the result as if it were complete and correct.

The combination makes it effectively unusable for real work.

Expected Behavior

1. Follow the rules in CLAUDE.md.
2. Respect permission mode — ask before executing actions when set to manual approval.
3. Don't assert unverified facts; actually read/inspect before claiming, and flag uncertainty.
4. Attempt feasible actions instead of falsely claiming they're impossible.
5. Never create files without being asked, and never without telling me.
6. Complete simple tasks promptly and correctly.
7. Stay professional when given critical feedback.
8. Only report a task as complete when it is actually finished and correct; otherwise state clearly what is incomplete or uncertain.

Files Affected

Claude created new Markdown/documentation files in the working directory unprompted and without notice (no specific paths captured).

Permission Mode

Accept Edits was OFF (manual approval required) — and Claude acted anyway

Can You Reproduce This?

Yes, every time with the same prompt

Claude Model

Opus

Impact

High - Significant unwanted changes

Claude Code Version

Claude Desktop app (entrypoint: claude-desktop), Agent SDK 0.3.165 — no CLI version string available in desktop app

Platform

Anthropic API

Additional Context

• Onset: 2026-06-08, sudden. Previously the same setup worked well.
• Affects both Opus 4.8 (1M context) and Opus 4.8, across effort levels "extra", "max" and "ultra".
• Environment: Claude Code in the Claude Desktop app on Windows 11.
• The issues are persistent and span instruction-following, permissions, factual reliability, willingness to act, file safety, latency, and tone.