diff --git a/docs/authoring.md b/docs/authoring.md
index c8e3be6..b11050d 100644
--- a/docs/authoring.md
+++ b/docs/authoring.md
@@ -104,7 +104,7 @@ Container:
 
 Per child (set on the child dict, under a `layout:` sub-dict to avoid clashing
 with the element's own keys):
-- `layout: { grow: 1 }` — take a share of leftover main-axis space (push siblings apart)
+- `layout: { grow: 1 }` — take a share of leftover main-axis space (push siblings apart); a card (a nested stack with `background`/`outline` and no `width`/`height` on the main axis) grows its box to fill its share
 - `layout: { align: center }` — override the container's cross-axis alignment for this child
 - `layout: { margin: 4 }` or `margin_x` / `margin_top` / ... — extra space around this child (may be negative to nudge)
 
diff --git a/docs/reference.md b/docs/reference.md
index 9eabc3f..4e804b5 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -26,7 +26,7 @@ See [`elements.md`](elements.md) for a rendered YAML example of every element an
 | `dither` | bool \| 0/1 \| method name |  | Per-element palette mapping: `true`/`false` (also `1`/`0` or a template string such as `"False"`) or a dither method name; overrides the render-wide setting for this element only. `null` = no override |
 | `class` | string |  | Tailwind-like layout classes (`gap-2 items-center grow -ml-1 ...`), read by an enclosing stack/row/column |
 | `layout` | object |  | Explicit per-child layout hints for an enclosing stack (same keys as the `class` shorthand) |
-| `layout.grow` | number | `0` | Share of leftover main-axis space this child takes (flex-grow) |
+| `layout.grow` | number | `0` | Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it |
 | `layout.align` | `start` \| `end` \| `center` \| `stretch` |  | Cross-axis alignment for this child only |
 | `layout.self` | `start` \| `end` \| `center` \| `stretch` |  | Alias of `align` |
 | `layout.margin` | number |  | All four margins (px) |
diff --git a/schema/elements.json b/schema/elements.json
index b6038fb..439e774 100644
--- a/schema/elements.json
+++ b/schema/elements.json
@@ -522,7 +522,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -730,7 +730,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -982,7 +982,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -1232,7 +1232,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -1468,7 +1468,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -1703,7 +1703,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -1951,7 +1951,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -2388,7 +2388,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -2618,7 +2618,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -2880,7 +2880,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -3085,7 +3085,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -3288,7 +3288,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -3495,7 +3495,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -3855,7 +3855,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -4211,7 +4211,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -4423,7 +4423,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -4651,7 +4651,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -4865,7 +4865,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -5077,7 +5077,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -5310,7 +5310,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -5503,7 +5503,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -5700,7 +5700,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -5913,7 +5913,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -6099,7 +6099,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -6351,7 +6351,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -6630,7 +6630,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -6856,7 +6856,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -7088,7 +7088,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -7452,7 +7452,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -7728,7 +7728,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -7980,7 +7980,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -8281,7 +8281,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -8580,7 +8580,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -8855,7 +8855,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -9069,7 +9069,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
@@ -9349,7 +9349,7 @@
                 "number",
                 "null"
               ],
-              "description": "Share of leftover main-axis space this child takes (flex-grow)",
+              "description": "Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with `background`/`outline` and no main-axis size) grows its box to fill it",
               "default": 0
             },
             "align": {
diff --git a/src/imagespec/elements/layout.py b/src/imagespec/elements/layout.py
index 7878ac4..c1e3be3 100644
--- a/src/imagespec/elements/layout.py
+++ b/src/imagespec/elements/layout.py
@@ -148,6 +148,18 @@ def _cross_extent(tile: dict, horizontal: bool) -> int:
     return (tile["h"] if horizontal else tile["w"]) + _cross_margins(tile, horizontal)
 
 
+def _fills_slot(child: dict, main_key: str) -> bool:
+    """A card (nested stack with ``background``/``outline``) with no explicit main-axis size: `grow` makes
+    its box fill the slot. Unstyled stacks draw nothing for their empty space, so there is nothing to fill."""
+    styled = child.get("background") is not None or child.get("outline") is not None
+    if not (styled and child.get("type") in ("stack", "row", "column") and child.get(main_key) is None):
+        return False
+    try:  # a 90/270 rotation swaps the axes, so width/height would grow the wrong way
+        return int(float(child.get("rotate") or 0)) % 180 == 0
+    except (TypeError, ValueError, OverflowError):
+        return False
+
+
 # Stretchable elements that can be rendered without a cross size (their width/height are optional).
 _MEASURABLE = frozenset({"group", "stack", "row", "column"})
 
@@ -351,10 +363,18 @@ def positioned(child):
             return child
         return {**child, **{k: 0 for k in ("x", "y") if child.get(k) is None}}
 
-    def render_child(idx, child, lay, stretch_size):
+    main_key = "width" if horizontal else "height"
+
+    def render_child(idx, child, lay, stretch_size, main_size=None):
         """Render ``child`` on its own layer and crop it to its drawn extent: ``lay`` + img/w/h."""
         eff = positioned(child)
         sub_w, sub_h = max(1, inner_w), max(1, inner_h)
+        if main_size is not None:  # a growing card: its box is the whole slot along the main axis
+            eff = {**eff, main_key: main_size, ("x" if horizontal else "y"): 0}  # own main coordinate is ignored
+            if horizontal:
+                sub_w = max(sub_w, main_size)
+            else:
+                sub_h = max(sub_h, main_size)
         if stretch_size is not None:
             # the child's own cross coordinate is ignored (like any stack child); a negative margin
             # can make the slot larger than the stack, so give the layer room for it
@@ -383,7 +403,7 @@ def render_child(idx, child, lay, stretch_size):
             bbox = (bbox[0], 0, bbox[2], stretch_size) if horizontal else (0, bbox[1], stretch_size, bbox[3])
         tile = rendered.crop(bbox) if bbox else None
         tw, th = tile.size if tile else (0, 0)
-        return {**lay, "img": tile, "w": tw, "h": th}
+        return {**lay, "img": tile, "w": tw, "h": th, "stretch": stretch_size}
 
     lays = [_child_layout(c) for c in children]
     # `align: stretch`: size-aware children without an explicit cross size fill the cross axis.
@@ -464,6 +484,14 @@ def m_cross_trail(t):
         if last is not None:
             grow_extra[last] += int(free) - handed  # rounding remainder
         free = 0
+        # A growing card (styled nested stack without its own main size) fills its slot: its box,
+        # not just the empty space after it, takes the extra.
+        for i, (c, t) in enumerate(zip(children, tiles, strict=True)):
+            if grow_extra[i] > 0 and _fills_slot(c, main_key):
+                target = main_of(t) + grow_extra[i]
+                tiles[i] = render_child(i, c, t, t["stretch"], target)
+                # whatever the box did not take (e.g. an invisible fill) stays as slot space
+                grow_extra[i] = max(0, target - main_of(tiles[i]))
 
     leading, spacing = _justify_offsets(justify, free, n, gap)
 
diff --git a/src/imagespec/spec.py b/src/imagespec/spec.py
index 6d65e33..41f2557 100644
--- a/src/imagespec/spec.py
+++ b/src/imagespec/spec.py
@@ -180,7 +180,12 @@ def elements(
 
 # Read by an enclosing stack/row/column from each child (see layout._child_layout).
 LAYOUT_FIELDS: tuple[Field, ...] = (
-    num("grow", 0, doc="Share of leftover main-axis space this child takes (flex-grow)"),
+    num(
+        "grow",
+        0,
+        doc="Share of leftover main-axis space this child takes (flex-grow); a card (a nested stack with "
+        "`background`/`outline` and no main-axis size) grows its box to fill it",
+    ),
     enum("align", ("start", "end", "center", "stretch"), doc="Cross-axis alignment for this child only"),
     enum("self", ("start", "end", "center", "stretch"), doc="Alias of `align`"),
     num("margin", doc="All four margins (px)"),
diff --git a/tests/test_layout.py b/tests/test_layout.py
index 66ae677..ff573b4 100644
--- a/tests/test_layout.py
+++ b/tests/test_layout.py
@@ -674,3 +674,133 @@ def test_card_of_only_size_required_stretched_children_falls_back_to_the_availab
     img = render([card], 60, 50, context=ctx)
     ys = [y for y in range(50) if img.getpixel((6, y)) == BLACK]
     assert min(ys) == 5 and max(ys) == 49
+
+
+# --------------------------------------------------------------------------- #
+# grow on cards
+# --------------------------------------------------------------------------- #
+
+
+def _xs(img, color, y):
+    return [x for x in range(img.width) if img.getpixel((x, y)) == color]
+
+
+def test_growing_card_fills_the_free_space(ctx):
+    row = {
+        "type": "row",
+        "width": 120,
+        "height": 30,
+        "gap": 6,
+        "elements": [_card("A", "yellow"), _card("B", "red", layout={"grow": 1})],
+    }
+    img = render([row], 120, 30, context=ctx)
+    red = _xs(img, RED, 2)
+    assert max(red) == 119  # the red card runs to the end of the row
+    yellow = _xs(img, YELLOW, 2)
+    assert min(red) - max(yellow) - 1 == 6  # the gap is untouched
+
+
+def test_growing_cards_share_the_free_space_by_weight(ctx):
+    def widths(grows):
+        els = [_card("A", "yellow", layout={"grow": grows[0]}), _card("B", "red", layout={"grow": grows[1]})]
+        img = render([{"type": "row", "width": 150, "height": 30, "elements": els}], 150, 30, context=ctx)
+        return len(_xs(img, YELLOW, 2)), len(_xs(img, RED, 2)), img
+
+    natural_y, natural_r, _ = widths((0, 0))
+    y, r, img = widths((1, 2))
+    extra_y, extra_r = y - natural_y, r - natural_r
+    assert extra_y > 0 and abs(extra_r - 2 * extra_y) <= 2  # the free space is split 1:2
+    assert max(_xs(img, RED, 2)) == 149  # and all of it is used
+
+
+def test_growing_card_in_a_column_fills_the_height(ctx):
+    col = {
+        "type": "column",
+        "width": 60,
+        "height": 90,
+        "gap": 4,
+        "elements": [_card("A", "yellow"), _card("B", "red", layout={"grow": 1})],
+    }
+    img = render([col], 60, 90, context=ctx)
+    red_rows = [y for y in range(90) if img.getpixel((2, y)) == RED]
+    assert max(red_rows) == 89
+
+
+def test_growing_card_with_an_explicit_size_keeps_it(ctx):
+    row = {"type": "row", "width": 120, "height": 30, "elements": [_card("A", "red", width=40, layout={"grow": 1})]}
+    img = render([row], 120, 30, context=ctx)
+    assert max(_xs(img, RED, 2)) == 39
+
+
+def test_unstyled_growing_stack_is_unchanged(ctx):
+    inner = {"type": "row", "elements": [{"type": "text", "value": "A", "size": 12}], "layout": {"grow": 1}}
+    row = {"type": "row", "width": 100, "height": 20, "elements": [inner, {"type": "text", "value": "Z", "size": 12}]}
+    plain = {**row, "elements": [{k: v for k, v in inner.items() if k != "layout"}, row["elements"][1]]}
+    a = render([row], 100, 20, context=ctx)
+    b = render([plain], 100, 20, context=ctx)
+    xs = lambda im: [x for x in range(100) if any(im.getpixel((x, y)) == BLACK for y in range(20))]  # noqa: E731
+    assert max(xs(a)) > max(xs(b))  # grow still pushes the sibling to the end, as before
+
+
+def test_growing_card_respects_margins(ctx):
+    row = {
+        "type": "row",
+        "width": 100,
+        "height": 30,
+        "elements": [_card("B", "red", layout={"grow": 1, "margin_x": 5})],
+    }
+    img = render([row], 100, 30, context=ctx)
+    red = _xs(img, RED, 2)
+    assert min(red) == 5 and max(red) == 94
+
+
+def test_growing_card_rotated_90_is_left_alone(ctx):
+    row = {
+        "type": "row",
+        "width": 120,
+        "height": 60,
+        "elements": [_card("R", "red", rotate=90, layout={"grow": 1}), _card("Z", "yellow")],
+    }
+    base = {**row, "elements": [_card("R", "red", rotate=90), _card("Z", "yellow")]}
+    img, ref = render([row], 120, 60, context=ctx), render([base], 120, 60, context=ctx)
+    assert len(_xs(img, RED, 2)) == len(_xs(ref, RED, 2))  # unchanged size
+    assert min(_xs(img, YELLOW, 2)) > min(_xs(ref, YELLOW, 2))  # grow still pushes the sibling to the end
+
+
+@pytest.mark.parametrize("pos", [{"x": 30}, {"x": -10}, {"y": 20}])
+def test_growing_card_ignores_its_own_coordinates(ctx, pos):
+    row = {
+        "type": "row",
+        "width": 120,
+        "height": 30,
+        "gap": 6,
+        "elements": [_card("A", "yellow"), _card("B", "red", layout={"grow": 1}, **pos)],
+    }
+    img = render([row], 120, 30, context=ctx)
+    assert max(_xs(img, RED, 2)) == 119
+
+
+def test_growing_card_with_an_invisible_box_still_pushes_its_sibling(ctx):
+    ghost = {
+        "type": "row",
+        "outline": "black",
+        "width_outline": 0,
+        "elements": [{"type": "text", "value": "g", "size": 12}],
+        "layout": {"grow": 1},
+    }
+    row = {"type": "row", "width": 100, "height": 20, "elements": [ghost, _card("Z", "yellow")]}
+    img = render([row], 100, 20, context=ctx)
+    assert max(_xs(img, YELLOW, 2)) >= 98  # the slot was kept, so the sibling sits at the end
+
+
+@pytest.mark.parametrize("y", [20, -10])
+def test_growing_card_in_a_column_ignores_its_own_main_coordinate(ctx, y):
+    col = {
+        "type": "column",
+        "width": 60,
+        "height": 90,
+        "gap": 4,
+        "elements": [_card("A", "yellow"), _card("B", "red", y=y, layout={"grow": 1})],
+    }
+    img = render([col], 60, 90, context=ctx)
+    assert max(y for y in range(90) if img.getpixel((2, y)) == RED) == 89