Route all non-markdown code highlighting through the off-main-thread Shiki
worker, removing react-syntax-highlighter and prismjs entirely.
- Extend the worker with highlightLines: tokenize a whole block once and return
per-line inner HTML, so per-line layouts (diffs, gutters, virtualization) make
one worker call instead of one highlighter per line.
- Add shared WorkerHighlightedCode (whole-block) and useWorkerHighlightedLines
(per-line) primitives. Colors resolve via the --md-syntax-* CSS variables, so
theme changes never re-highlight.
- Migrate all 12 react-syntax-highlighter call sites: PermissionCard,
ToolPart, ContextSidebarTab, ToolOutputDialog (whole block) and
DiffPreview/WritePreview (per line).
- Migrate VirtualizedCodeBlock off prismjs to the worker, keeping virtua
virtualization; whole-block tokenization also restores cross-line syntax
context that per-line highlighting lost.
- Drop react-syntax-highlighter (+types) from ui and web, prismjs (+types) from
ui, and the orphaned create-element type shim.
Tokenize closed code blocks in a dedicated Shiki Web Worker instead of calling
the shared highlighter synchronously on the UI thread. This removes the
one-shot main-thread highlight stall when a code fence closes on a large block.
Streaming behavior is unchanged: the open (streaming) fence still renders as
plain text and is highlighted once on close. On any worker failure the block
keeps its escaped plain code — highlighting never falls back onto the main
thread.
- Add markdownShikiThemeDefinition (dependency-free CSS-variable theme) so the
worker can use the theme without pulling in @pierre/diffs / React.
- Add markdown-worker-protocol, markdown-shiki.worker, and the main-thread
markdown-worker client.
- Route highlightCodeBlocks through the worker; keep the size/VSCode line guard
and mermaid skip on the main thread.
- Add shiki as a direct dependency (was transitive via @pierre/diffs).
Bohdan Triapitsyn