diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 11098023c..ebb7b6182 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## [Unreleased]
 
+### Changed
+
+- Memoize copy-selector preview highlight so keyboard navigation does not re-highlight the whole preview every render ([#4238](https://github.com/can1357/oh-my-pi/issues/4238))
+
+
 ## [16.3.0] - 2026-07-02
 
 ### Added
diff --git a/packages/coding-agent/src/modes/components/copy-selector.ts b/packages/coding-agent/src/modes/components/copy-selector.ts
index 02fe40e0b..70eab4e1d 100644
--- a/packages/coding-agent/src/modes/components/copy-selector.ts
+++ b/packages/coding-agent/src/modes/components/copy-selector.ts
@@ -53,6 +53,8 @@ function gutterCells(hasNext: boolean): string {
 export class CopySelectorComponent implements Component {
 	#roots: CopyTarget[];
 	#cursorId: string;
+	#lastSourceTarget?: CopyTarget;
+	#lastSource?: string;
 	#treeRows = MIN_TREE_ROWS;
 	// Reused across renders to wrap preview content to the pane width.
 	#previewText = new Text("", 0, 0);
@@ -65,7 +67,10 @@ export class CopySelectorComponent implements Component {
 		this.#cursorId = roots[0]?.id ?? "";
 	}
 
-	invalidate(): void {}
+	invalidate(): void {
+		this.#lastSourceTarget = undefined;
+		this.#lastSource = undefined;
+	}
 
 	#flatten(): FlatNode[] {
 		const out: FlatNode[] = [];
@@ -153,9 +158,16 @@ export class CopySelectorComponent implements Component {
 		// Code/command previews are syntax-highlighted; everything else is shown
 		// as plain text. Both are wrapped (not hard-truncated) to the pane width.
 		const isCode = target.language !== undefined;
-		const source = isCode
-			? highlightCode(replaceTabs(target.preview), target.language).join("\n")
-			: replaceTabs(target.preview);
+		let source: string;
+		if (target === this.#lastSourceTarget && this.#lastSource !== undefined) {
+			source = this.#lastSource;
+		} else {
+			source = isCode
+				? highlightCode(replaceTabs(target.preview), target.language).join("\n")
+				: replaceTabs(target.preview);
+			this.#lastSourceTarget = target;
+			this.#lastSource = source;
+		}
 		this.#previewText.setText(source);
 		const wrapped = this.#previewText.render(Math.max(1, width - 4));