Pin the review card description under the sections and tint the card from the uploaded logo.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/unit/Rule.test.jsx

@@ -257,11 +257,49 @@ describe("Rule Component", () => {
         ],
       },
     ];
-    render(
-      <Rule {...defaultProps} expanded={true} categories={categories} />,
-    );
+    render(<Rule {...defaultProps} expanded={true} categories={categories} />);
 
     expect(screen.getByText("Values")).toBeInTheDocument();
+    const description = screen.getByText("This is a test rule description");
+    expect(
+      description.compareDocumentPosition(screen.getByText("Values")) &
+        Node.DOCUMENT_POSITION_FOLLOWING,
+    ).not.toBe(0);
+    expect(description.parentElement).toHaveClass("border-b");
+  });
+
+  it("pins the description under categories when descriptionAtBottom is set", () => {
+    const categories = [
+      {
+        name: "Values",
+        chipOptions: [
+          { id: "v1", label: "Consciousness", state: "unselected" },
+        ],
+      },
+    ];
+    render(
+      <Rule
+        {...defaultProps}
+        expanded={true}
+        descriptionAtBottom
+        categories={categories}
+      />,
+    );
+
+    const description = screen.getByText("This is a test rule description");
+    expect(
+      screen.getByText("Values").compareDocumentPosition(description) &
+        Node.DOCUMENT_POSITION_FOLLOWING,
+    ).not.toBe(0);
+    expect(description.parentElement).toHaveClass("border-t");
+    expect(description.parentElement).not.toHaveClass("border-b");
+  });
+
+  it("applies a runtime surface color over the background class", () => {
+    render(<Rule {...defaultProps} surfaceColor="rgb(12, 80, 40)" />);
+    expect(screen.getByRole("button")).toHaveStyle({
+      backgroundColor: "rgb(12, 80, 40)",
+    });
   });
 
   it("renders with logo URL", () => {

tests/unit/previewSurfaceColor.test.ts

@@ -0,0 +1,77 @@
+import { describe, expect, it } from "vitest";
+import {
+  mostCommonOpaqueColor,
+  randomPreviewSurfaceColor,
+  readableCardFill,
+} from "../../lib/create/previewSurfaceColor";
+
+function pixel(r: number, g: number, b: number, a = 255): number[] {
+  return [r, g, b, a];
+}
+
+describe("mostCommonOpaqueColor", () => {
+  it("returns the average of the largest quantized bucket", () => {
+    const data = new Uint8ClampedArray([
+      ...pixel(200, 10, 10),
+      ...pixel(201, 11, 9),
+      ...pixel(202, 9, 11),
+      ...pixel(10, 10, 220),
+    ]);
+
+    expect(mostCommonOpaqueColor(data)).toBe("rgb(201, 10, 10)");
+  });
+
+  it("ignores transparent pixels", () => {
+    const data = new Uint8ClampedArray([
+      ...pixel(255, 255, 255, 0),
+      ...pixel(255, 255, 255, 0),
+      ...pixel(20, 40, 60),
+    ]);
+
+    expect(mostCommonOpaqueColor(data)).toBe("rgb(20, 40, 60)");
+  });
+
+  it("returns null when nothing is opaque", () => {
+    const data = new Uint8ClampedArray([...pixel(1, 2, 3, 0)]);
+    expect(mostCommonOpaqueColor(data)).toBeNull();
+  });
+
+  it("counts a translucent fill", () => {
+    const data = new Uint8ClampedArray([...pixel(255, 0, 0, 127)]);
+    expect(mostCommonOpaqueColor(data)).toBe("rgb(255, 0, 0)");
+  });
+});
+
+describe("readableCardFill", () => {
+  it("keeps a light logo color", () => {
+    expect(readableCardFill(201, 254, 249)).toBe("rgb(201, 254, 249)");
+  });
+
+  it("lifts a dark logo color into a pale tint of the same hue", () => {
+    const fill = readableCardFill(255, 0, 0);
+    const channels = fill
+      .split(/[^\d]+/)
+      .filter(Boolean)
+      .map(Number);
+    const lightness =
+      (Math.max(...channels) + Math.min(...channels)) / 2 / 255;
+    expect(lightness).toBeGreaterThanOrEqual(0.8);
+    expect(channels[0]).toBeGreaterThan(channels[2]);
+  });
+});
+
+describe("randomPreviewSurfaceColor", () => {
+  it("stays in a light range so black type can sit on it", () => {
+    let call = 0;
+    const sequence = [0, 0, 0];
+    expect(randomPreviewSurfaceColor(() => sequence[call++] ?? 0)).toBe(
+      "hsl(0, 50%, 76%)",
+    );
+
+    call = 0;
+    const high = [0.999, 0.999, 0.999];
+    expect(randomPreviewSurfaceColor(() => high[call++] ?? 0)).toBe(
+      "hsl(359, 84%, 87%)",
+    );
+  });
+});