Claude Shows Its Thinking Again, Except on Sonnet 5

Claude is showing its extended thinking again in Anthropic's consumer app, per a screenshot on r/ClaudeAI that picked up 216 upvotes.

Visible chain-of-thought lets you catch a model heading down the wrong path mid-response. Without it, you're guessing backward from the final output.

The catch: Sonnet 5 still doesn't show it, per the same thread. Whatever changed applies to some models in Anthropic's lineup and not others. The same account can get a transparent reasoning trace on one model and a black box on the next.

Anthropic hasn't logged this anywhere. No changelog entry ties the change to a release, so what's circulating on Reddit is an observation, not an announcement. That gap matters. Users can't tell if this is a rollout in progress, a test, or a bug that exposed something meant to stay hidden.

The take

Hiding chain-of-thought by default costs more in debugging time than it saves in interface cleanliness. If Anthropic shipped this on purpose, I'd bet the Sonnet 5 gap closes rather than persists. Leaving one model in your own lineup opaque while the rest show their work is a support headache, not a design choice you keep.

This only made the August 4 briefing because a Reddit user posted a screenshot, not because Anthropic said anything about it.