How is is possible that we’ve made incredible gains in the performance of models, but virtually no gains in the infrastructure that supports them?.
.. or what I like to call: the worst enemy of chatbots is page refresh.
There are some large GIFs in this article, let them load :)
Claude vs. Page refresh
If a picture speaks a thousand words, here is a GIF of the Claude UI taken on 11th Feb 2026.
In this GIF you can see the prompt submitted, and Claude starts to stream tokens to the interface. Then I hit refresh and the stream stops. The page goes all skeleton-ui and eventually I’m back to the prompt input box, but the response is lost. Hit page refresh again, and the full response is available.
What’s going on?
Claude is using EventSource, which is a web API interface for SSE (Server-Sent Events).
Claude UI is taking all the current context in the chat window (all the messages) and POSTing them to the Anthropic servers. The full set of messages are passed to the model, in this case Sonnet 4.5 The client leaves the HTTP connection open, and the server starts streaming SSE events as the model generates tokens.
Below is a simplified version of the SSE stream that is being sent to the client.
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