diff --git a/crates/engine/src/cmd/flatten/apply.rs b/crates/engine/src/cmd/flatten/apply.rs
index 555058e58..409db3f1b 100644
--- a/crates/engine/src/cmd/flatten/apply.rs
+++ b/crates/engine/src/cmd/flatten/apply.rs
@@ -484,6 +484,9 @@ fn region_fill(elems: &[Elem], sources: &[usize], o: &FlattenOptions, cmyk: bool
 fn render_raster(doc: &Document, art: &[Node], rect: Rect, ppi: f64, clip: Option<PathData>, o: &FlattenOptions) -> Result<Raster> {
     let mut scale = ppi / 72.0;
     scale = scale.min((MAX_PIXELS / (rect.width() * rect.height()).max(1.0)).sqrt());
+    // No side longer than the renderer draws: the image grows by a pixel on each side and is
+    // rounded up to whole pixels below.
+    scale = scale.min((f64::from(vectorcraft_render::MAX_RASTER_SIDE) - 4.0) / rect.width().max(rect.height()).max(1.0));
     let px = 1.0 / scale;
     let rect = rect.inflate(px, px);
     let clip = clip.map(|c| Some(po::offset_path(&c, px, po::Join::Miter, 4.0)).filter(|g| !g.is_empty()).unwrap_or(c));
diff --git a/crates/engine/src/cmd/flatten/commands.rs b/crates/engine/src/cmd/flatten/commands.rs
index 53687713b..4053dcac7 100644
--- a/crates/engine/src/cmd/flatten/commands.rs
+++ b/crates/engine/src/cmd/flatten/commands.rs
@@ -10,7 +10,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Flatten Transparency…",
             ["Object"],
             None,
-            "{preset?: \"high\"|\"medium\"|\"low\" or a saved preset's name (see flattener.presets.list; default medium), balance?: 0..100 (raster/vector balance; 0 rasterizes everything), lineArtPpi?: 1..2400, gradientPpi?: 1..2400 (areas only gradients and meshes reach), textToOutlines?, strokesToOutlines?, clipComplexRegions? (clip images to the region outlines, else rectangles), antiAlias?, preserveAlpha? (composite over nothing instead of white), preserveOverprints? (areas showing one paint keep its colour and overprint; false clears overprints), options?: {the same keys}, ids?|id?} overlapping transparent objects become one group of flat-colour regions (CMYK colours composited ink by ink in CMYK documents), plus an image where gradients, patterns, images, masks or raster effects reach (only where a clip group's or clipping layer's clipping path shows them, over its fill; transparent objects such a path hides entirely are removed); objects without transparency stay; a frame of threaded text that is outlined or flattened leaves its thread with the text it shows → {ids, rasterized: images made, vector: regions made, options, warning? (an image in the art couldn't be decoded, as object.rasterize says)}",
+            "{preset?: \"high\"|\"medium\"|\"low\" or a saved preset's name (see flattener.presets.list; default medium), balance?: 0..100 (raster/vector balance; 0 rasterizes everything), lineArtPpi?: 1..2400, gradientPpi?: 1..2400 (areas only gradients and meshes reach; an image larger than 64 Mpx or 32,768 px a side is made at a lower resolution), textToOutlines?, strokesToOutlines?, clipComplexRegions? (clip images to the region outlines, else rectangles), antiAlias?, preserveAlpha? (composite over nothing instead of white), preserveOverprints? (areas showing one paint keep its colour and overprint; false clears overprints), options?: {the same keys}, ids?|id?} overlapping transparent objects become one group of flat-colour regions (CMYK colours composited ink by ink in CMYK documents), plus an image where gradients, patterns, images, masks or raster effects reach (only where a clip group's or clipping layer's clipping path shows them, over its fill; transparent objects such a path hides entirely are removed); objects without transparency stay; a frame of threaded text that is outlined or flattened leaves its thread with the text it shows → {ids, rasterized: images made, vector: regions made, options, warning? (an image in the art couldn't be decoded, as object.rasterize says)}",
             has_doc,
             flatten
         ),
diff --git a/crates/engine/src/tests/flatten.rs b/crates/engine/src/tests/flatten.rs
index 2e08b99c8..84e4724fe 100644
--- a/crates/engine/src/tests/flatten.rs
+++ b/crates/engine/src/tests/flatten.rs
@@ -350,6 +350,31 @@ fn gradients_rasterize_and_flat_areas_stay_vector() {
     }
 }
 
+#[test]
+fn a_long_rasterized_area_is_placed_whole() {
+    let _settings = settings_lock();
+    let mut s = session();
+    // 5569 pt long: more than the renderer's 32,768 pixels a side at the 64 Mpx limit's scale.
+    let g = rect(&mut s, 10.0, 10.0, 100.0, 5569.0, "#000000");
+    run(
+        &mut s,
+        "paint.setFill",
+        json!({"ids": [g], "gradient": {"kind": "linear", "stops": [{"offset": 0, "color": "#ff0000"}, {"offset": 1, "color": "#0000ff"}]}}),
+    );
+    run(&mut s, "transparency.set", json!({"ids": [g], "opacity": 40}));
+    let (ids, _, rasterized) = flatten(&mut s, json!({"ids": [g], "lineArtPpi": 1200, "gradientPpi": 1200}));
+    assert_eq!(rasterized, 1);
+    let mut placed = vec![];
+    node(&s, ids[0]).walk(&mut |c| {
+        if let NodeKind::Image(im) = &c.kind {
+            placed.push((im.height, im.xf.transform_rect_bbox(Rect::new(0.0, 0.0, f64::from(im.width), f64::from(im.height)))));
+        }
+    });
+    let [(height, b)] = placed[..] else { panic!("one image: {placed:?}") };
+    assert!(height <= vectorcraft_render::MAX_RASTER_SIDE, "{height} pixels");
+    assert!(b.y0 <= 10.0 && b.y1 >= 5579.0, "the image covers the strip: {b:?}");
+}
+
 #[test]
 fn flatten_says_when_an_image_could_not_be_decoded() {
     let _settings = settings_lock();
diff --git a/docs/mcp.md b/docs/mcp.md
index dabbf9dcf..46bea4f77 100644
--- a/docs/mcp.md
+++ b/docs/mcp.md
@@ -3263,7 +3263,9 @@ the group holds only the art inside the clipping layer, drawn over the fill and
 layer as its own layers draw it (over nothing with `preserveAlpha`), and the art outside is flattened on its own.
 `preset` is `high`, `medium` (the default) or `low`; option keys (`balance` 0–100, `lineArtPpi`, `gradientPpi`,
 `textToOutlines`, `strokesToOutlines`, `clipComplexRegions`, `antiAlias`, `preserveAlpha`, `preserveOverprints`)
-override it, at the top level or in `options`. `balance: 0` rasterizes everything; lower balances rasterize groups
+override it, at the top level or in `options`. An image that would be larger than 64 million pixels or longer than
+32,768 pixels a side at `lineArtPpi` or `gradientPpi` is made at the highest resolution that fits, so a long area is
+rasterized whole. `balance: 0` rasterizes everything; lower balances rasterize groups
 that split into many regions. The result reports `{ids, vector, rasterized, options}`. When an image in the art
 can't be decoded, the image that replaces the art does not show it, and the result also carries `warning`: "an image
 couldn't be decoded and is missing from the picture", the note raster exports give.