diff --git a/src/lib/components/chat/Messages/Markdown.svelte b/src/lib/components/chat/Messages/Markdown.svelte
index 5b699578ed..36a2ed5400 100644
--- a/src/lib/components/chat/Messages/Markdown.svelte
+++ b/src/lib/components/chat/Messages/Markdown.svelte
@@ -63,6 +63,10 @@
 	let lastContent = '';
 	let lastParsedContent = '';
 
+	// Incremental lexing state: cache stable prefix tokens during streaming
+	let cachedStablePrefix = '';
+	let cachedStableTokens = [];
+
 	const parseTokens = () => {
 		if (content === lastContent) return;
 		lastContent = content;
@@ -71,7 +75,35 @@
 		if (processed === lastParsedContent) return;
 		lastParsedContent = processed;
 
-		tokens = marked.lexer(processed);
+		// When done or for short content, do a full lex for correctness
+		if (done || processed.length < 2000) {
+			cachedStablePrefix = '';
+			cachedStableTokens = [];
+			tokens = marked.lexer(processed);
+			return;
+		}
+
+		// Incremental lexing: find the last stable boundary (double newline)
+		// in the PREVIOUS content. Everything before it won't change as
+		// streaming only appends to the end.
+		const boundary = processed.lastIndexOf('\n\n');
+		if (boundary <= 0) {
+			tokens = marked.lexer(processed);
+			return;
+		}
+
+		const stablePrefix = processed.slice(0, boundary + 2);
+
+		// If the stable prefix changed, re-lex everything
+		if (stablePrefix !== cachedStablePrefix) {
+			cachedStablePrefix = stablePrefix;
+			cachedStableTokens = marked.lexer(stablePrefix);
+		}
+
+		// Only lex the volatile suffix (current paragraph being streamed)
+		const volatileSuffix = processed.slice(boundary + 2);
+		const suffixTokens = volatileSuffix ? marked.lexer(volatileSuffix) : [];
+		tokens = [...cachedStableTokens, ...suffixTokens];
 	};
 
 	const updateHandler = (content) => {