A few months ago I wrote I Miss the Old Claude Code. In that post I criticized the Opus 5 model. It was chatty and hard to keep on task. I felt like I had to fight Claude Code in order to get my job done.
Fast forward to today and I have to give credit where credit is due – Opus 5.5 is awesome.
What changed
In my experience, the difference was undeniable as soon as I switched to Opus 5.5. It stays focused, it does what I ask, and it does it well.
In the old post, I mentioned that Anthropic likely shipped a Concise output style as a band-aid to keep Opus 5 on task. I have been rocking Opus 5.5 on the default output style, with no issues.
What I built with it
The proof is in the pudding. I used Opus 5.5 to vibe code two apps that have now become my daily drivers.
Lightdown – a minimal macOS native Markdown editor with zoom, Mermaid diagrams and live preview. I started it as a lean replacement for MacDown 3000, mainly because I wanted zoom in and out to view large diagrams.
Gutter – a tiny native macOS terminal with a vertical tab sidebar, built on libghostty, optimized for agentic coding.
Note: I started Gutter with Opus 5.0.
As you probably guessed, demo videos were also created with Opus 5.5.
Small on purpose
Both apps are deliberately small in scope. Gutter even has a dedicated DESIGN.md file to explicitly list features I decided NOT to build.
That ties back to my original post, where I argued that “controlling the bloat may become the biggest challenge for every company in the age of generative AI.”
I felt like I had to fight Opus 5 to stay focused. Opus 5.5 became my best friend. It brought back the light, focused feeling that I said I missed so much.