diff --git a/internal/editor/chunked_buffer.go b/internal/editor/chunked_buffer.go
index 5b5e15e..e327483 100644
--- a/internal/editor/chunked_buffer.go
+++ b/internal/editor/chunked_buffer.go
@@ -452,10 +452,12 @@ func (cb *ChunkedBuffer) VisibleByteRange(scrollOffset ui.Dp, byteOffset int, vi
 	// released). That is the root cause of the ~1GB "Unknown" memory on large
 	// files.
 	//
-	// Word wrap does not require a separate path: each real line produces at
-	// least one visual line, so shaping viewportHeight/lineHeight real lines
-	// always yields at least as many visual lines as fit in the viewport. The
-	// extra wrapped lines are simply clipped by the renderer.
+	// Word wrap does not require a separate path: the viewport top and bottom
+	// are each expressed in VISUAL-line space and mapped to the logical lines
+	// that contain them (WrapIndex.LineForVisual). Because each logical line
+	// produces at least one visual line, that logical range always covers the
+	// viewport; the fetch is viewport-bounded no matter how many wraps lie
+	// above it, and any spill past the bottom edge is clipped by the renderer.
 	lineH := lineHeight
 	if lineH <= 0 {
 		lineH = EffectiveLineHeight()
@@ -564,10 +566,18 @@ func (cb *ChunkedBuffer) visibleByteRangePrecise(scrollOffset ui.Dp, viewportHei
 	// (the legacy no-wrap behavior).
 	v0, _ := scrollDecompose(scrollOffset, lineHeight)
 	startLine = int(v0)
+	endLine := int(math.Ceil(float64(scrollOffset+viewportHeight) / float64(lineHeight)))
 	if w := cb.WrapIndex; w != nil {
 		startLine = w.LineForVisual(int32(v0))
+		// endLine is still in VISUAL space: it is the visual line at the
+		// viewport bottom, so map it to the logical line that contains it,
+		// exactly like the top. Using the raw visual number as a logical
+		// index over-fetched the window by every wrapped line above the
+		// viewport — an over-fetch that grows without bound with scroll
+		// depth, so shaping/drawing (and therefore scroll responsiveness)
+		// degraded the further down the file you were.
+		endLine = w.LineForVisual(int32(endLine))
 	}
-	endLine := int(math.Ceil(float64(scrollOffset+viewportHeight) / float64(lineHeight)))
 
 	if startLine < 0 {
 		startLine = 0