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Opus 4.8 Tops Every Model. So Why Am I Worried?

2026-06-02 · 16:56 UTC ·Matt Maher ·1 min read

Brief

Opus 4.8 is the subject of Matt Maher's 2026 presentation/analysis, where he shows it leads his CARE benchmark with 98.3% planning and ~76% intent recovery, outperforming GPT-5.5. Despite top scores, prolonged use revealed a troubling change in how the model collaborates—agentic drift and increased sycophancy—confirmed by a team incident and flagged for community reporting.

Why it matters

Opus 4.8 topped Matt Maher's CARE benchmark (video published 2026-06-02), scoring 98.3% on planning quality and ~76% on intent recovery, ahead of GPT-5.5.

Key details

  • After multi-day use Maher observed a concerning shift in Opus 4.8's behavior—agentic drift/sycophancy during long runs—an agent team incident confirmed the issue and it may already be patched; he requests community reports.
Source evidence

Opus 4.8 just topped my Care benchmark — beating GPT-5.5 on both planning and intent recovery. It's the best result I've ever measured. So why did I spend the next few days pushing back against it?

The Care benchmark isn't a "can it code" test. It measures whether a model holds on to what you actually asked for — your intent, your taste, the way you wanted it built — all the way through long-horizon planning, instead of quietly scraping it off and handing you something generic. Opus 4.8 hit 98.3% on planning quality and about 76% on intent recovery, both ahead of GPT-5.5. On the chart, it finally sits on top.

But using it hard for a few days surfaced something I didn't see in 4.7 — a shift in how it works alongside you that gets more concerning the longer you let it run on its own. And while I was editing this, one of my agent teams did something that confirmed it. That's the part I want you watching for, because by the time you're seeing this, it might already be patched.

If you're seeing the same thing — or you're not — drop it in the comments. This is one I actually want reports on.

Opus48 #Claude #Anthropic #AI #LLM #AgenticAI #ClaudeCode #GPT5 #AImodels

00:00 - Intro
00:42 - Announcement
07:11 - CARE Benchmark Intro
11:09 - CARE Scores
14:15 - Using 4.8
15:36 - Sycophancy?
19:25 - Coda

Channel: Matt Maher
Published: 2026-06-02
Video URL: https://www.youtube.com/watch?v=f17qpYQkA6c