We lost the summarisation feature in the latest discourse update from yesterday.
Side note: I love the rename to “show top replies”. However it’s not consistent with the bar on the right:

Can you check if you have the summarization_strategy site setting set? We recently changed how Discourse’s core and discourse-ai interact for this feature, so you can use that setting to control which model is in charge of summarizing a topic.
I missed that, good catch!
Indeed, that was it! Thank you!
FYI This setting doesn’t appear in the discourse-ai settings, this is why I missed it
That’s because the plugin no longer extends core to add the feature. Instead, core implements it, and any plugin can register a summarization strategy. It’s not an AI-specific feature anymore, and plugins can use it to implement other summarization features.
I’ll update the module documentation shortly to reflect that!