fix(streamdown): render code blocks incrementally during streaming#474
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mvanhorn wants to merge 1 commit intovercel:mainfrom
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fix(streamdown): render code blocks incrementally during streaming#474mvanhorn wants to merge 1 commit intovercel:mainfrom
mvanhorn wants to merge 1 commit intovercel:mainfrom
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When using the `animated` prop, the animate plugin skipped all code/pre elements. This meant code block content appeared instantly while surrounding prose faded in word-by-word, creating a visual "buffering" effect where code seemed to dump all at once instead of streaming incrementally. The fix adds a `setAnimateCodeBlocks` method to the animate plugin. When a block has an incomplete (unclosed) code fence, the Block component tells the animate plugin to include code/pre elements in its animation pass. Once the code fence closes, animation reverts to the default behavior of skipping code blocks (since completed code gets syntax highlighting). Fixes vercel#473 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
setAnimateCodeBlocksmethod toAnimatePlugininterface so the Block component can toggle code animation per-blockProblem
When using
<Streamdown animated isAnimating>, prose text streams with word-by-word fade-in animation. But the animate plugin unconditionally skipped allcodeandpreelements (viaSKIP_TAGS), so code block content appeared instantly without any animation. This created a jarring visual discontinuity where code seemed to "buffer" and then dump all at once, while surrounding text streamed smoothly.Changes
packages/streamdown/lib/animate.ts: AddedSKIP_TAGS_WITHOUT_CODEset, madehasSkipAncestorstate-aware, addedanimateCodeBlocksflag to render state, exposedsetAnimateCodeBlockson the plugin APIpackages/streamdown/index.tsx: Block component callsanimatePluginProp.setAnimateCodeBlocks(isIncomplete)to enable code animation for blocks with unclosed fencesTest plan
Fixes #473
This contribution was developed with AI assistance (Claude Code).