Degraded quality / brain fog on Opus 4.6 — April 3, 2026

Description

Experiencing significantly degraded response quality on Claude Opus 4.6 via Claude Code over the past few hours (April 3, 2026). Responses feel slow, unfocused, and lower quality than usual — "brain fog" is the best description.

Context

• This follows known incidents from March 31 – April 1 (Opus 4.6 / Sonnet 4.6 timeouts, Haiku 4.5 elevated errors)
• Status page shows all clear as of April 2, but the degraded quality persists
• Fresh conversations don't resolve it
• Model: Claude Opus 4.6 via Claude Code CLI

Expected behavior

Normal response quality and coherence.

Actual behavior

Noticeably worse reasoning, coherence, and overall response quality compared to baseline.

Environment

• Claude Code CLI (latest)
• macOS (Darwin 24.1.0)
• Model: claude-opus-4-6