Upgrading my Claude Code setup through five model releases
TL;DR Between late June and late September I moved my daily setup through Sonnet 5, Opus 5, Fable 5.1, Opus 5.5 and Sonnet 5.5. Haiku stayed at 4.5 the whole time. I never saw a Haiku 5 in any log. There is no controlled benchmark in anything I kept. What follows is operational evidence: what I changed, what broke, what I verified, and what I would have gotten wrong if I had trusted what a model told me about itself. The changes that mattered were small: a per-model effort block in settings.json and a subagent default model. The expensive lessons were two traps. One is a bug where background-job subagents silently ran Haiku 4.5. The other is that a worker’s report of its own model cannot be believed. If you want the earlier, more general version of this, see re-tuning my setup for a new Opus model. This is what the next five releases taught me. The ladder These are first-seen dates from my own records: commit trailers in my repositories and, where I still have them, session transcripts. They are when I started using each model, not necessarily when it became available. ...
