dsh-chat-offscreen

The DSH Web chat transcript is not virtualized: every loaded history page remains in the DOM, backwards paging pulls 50 messages per call, and the jump loader fetches 200-message chunks with no eviction. In a long session, dragging the transcript width handle, the sidebar divider, or simply scrolling fast forces layout and paint across thousands of nodes, and the UI stutters.

dsh-chat-offscreen is a minimal client-side rendering patch. It injects a single content-visibility: auto stylesheet rule so the browser skips layout and paint for off-screen assistant steps and tool calls, while contain-intrinsic-size: auto 120px keeps the scroll range stable and remembers a row's measured height once seen. Rows containing a wide markdown table opt out automatically to prevent width mis-estimation. No messages, session events, or host state are touched.

If you run long DSH Web sessions with hundreds of turns and heavy tool-call traffic and notice visible jank when scrolling or resizing the panel, this plugin is for you. It relies on the content-visibility CSS feature available in Chrome/Edge 85+, Firefox 125+, and Safari 18+; on older engines the rules are inert and the UI simply stays as before. Once upstream ships real virtualization for the chat surface, delete the plugin row and you are done.