diff --git a/crates/design/src/palette/resolve/mod.rs b/crates/design/src/palette/resolve/mod.rs
index a09621e..f88ef44 100644
--- a/crates/design/src/palette/resolve/mod.rs
+++ b/crates/design/src/palette/resolve/mod.rs
@@ -339,4 +339,33 @@ mod tests {
             Some("palette.hint.background.no-opaque-pixels")
         );
     }
+
+    #[test]
+    fn a_five_percent_accent_drives_level_one() {
+        // 端到端反证（与 `palette::seed::tests::end_to_end_picks_the_five_percent_accent` 配对）：
+        // 95% 米白 + 5% 珊瑚的背景图**必须**在一级取色成功，且种子里就是那 5% 的珊瑚。
+        // 若 `analyze_rgba` 退化成「不透明像素求算术平均」，这条会变成「回落色卡」而红。
+        let beige = Color::rgb(0xF5, 0xF1, 0xEA);
+        let coral = Color::rgb(0xFF, 0x6B, 0x5A);
+        let mut pixels = Vec::with_capacity(40 * 40 * 4);
+        for index in 0..40 * 40 {
+            let color = if index < 40 * 40 - 80 { beige } else { coral };
+            pixels.extend_from_slice(&[color.r, color.g, color.b, color.a]);
+        }
+
+        let (scheme, provenance) = resolve_source(
+            Some(ImageInput::pixels(&pixels, 40, 40)),
+            None,
+            Some(CardKey::Rose),
+            SchemeFlavor::Light,
+        );
+        assert_eq!(provenance.level, Level::BackgroundImage, "{provenance:?}");
+        assert_eq!(provenance.background(), Outcome::Used);
+        let seed = provenance.seed.expect("一级成功必须带种子");
+        assert_eq!(seed.color, coral, "种子应当是 5% 的珊瑚");
+        assert!(provenance.hint_key().is_none());
+        // 方案来自珊瑚，而不是「回落到用户选的 Rose 卡」——两者 primary 不同。
+        assert_ne!(scheme, CardKey::Rose.card().scheme(SchemeFlavor::Light));
+        assert!(crate::palette::wcag::check(&scheme).is_clean());
+    }
 }
diff --git a/crates/design/src/palette/seed.rs b/crates/design/src/palette/seed/mod.rs
similarity index 64%
rename from crates/design/src/palette/seed.rs
rename to crates/design/src/palette/seed/mod.rs
index a0403c3..f6a3f3d 100644
--- a/crates/design/src/palette/seed.rs
+++ b/crates/design/src/palette/seed/mod.rs
@@ -217,136 +217,4 @@ fn sample_blocks(pixels: &[u8], width: usize, height: usize) -> Vec<Color> {
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-
-    /// 生成 `width × height` 的全 `color` 图。
-    fn solid(color: Color, width: u32, height: u32) -> Vec<u8> {
-        let mut out = Vec::with_capacity((width * height * 4) as usize);
-        for _ in 0..(width * height) {
-            out.extend_from_slice(&[color.r, color.g, color.b, color.a]);
-        }
-        out
-    }
-
-    #[test]
-    fn solid_vivid_image_yields_seed() {
-        let pixels = solid(Color::rgb(0x3C, 0x8D, 0xBC), 4, 4);
-        let seed = analyze_rgba(&pixels, 4, 4).expect("天蓝纯色图有种子");
-        assert_eq!(seed.color, Color::from_hex("#3C8DBC").expect("合法 hex"));
-        assert!(seed.chroma > MIN_SEED_CHROMA);
-        assert!((seed.share - 1.0).abs() < 1.0e-6);
-        assert!(!seed.is_muted());
-    }
-
-    #[test]
-    fn gray_white_image_is_rejected_with_measured_chroma() {
-        // D40 的反证：灰白壁纸硬取色会得到青色 #006874，这里必须拒绝并报出彩度。
-        let pixels = solid(Color::rgb(0xF2, 0xF2, 0xF0), 8, 8);
-        match analyze_rgba(&pixels, 8, 8) {
-            Err(Failure::LowChroma { chroma, .. }) => {
-                assert!(chroma < MIN_SEED_CHROMA, "彩度 {chroma} 不该过门槛");
-            }
-            other => panic!("灰白图必须被拒，实际 {other:?}"),
-        }
-        assert_eq!(seed_from_rgba(&pixels, 8, 8), None);
-    }
-
-    #[test]
-    fn neutral_gray_hash_rejects_instead_of_inventing_cyan() {
-        // 与 M70 复审实测的坏味道对齐：#808080 的 CAM16 色相 209.5°，硬取色会得到青色。
-        let pixels = solid(Color::rgb(0x80, 0x80, 0x80), 4, 4);
-        assert_eq!(seed_from_rgba(&pixels, 4, 4), None);
-    }
-
-    #[test]
-    fn tiny_images_are_too_small() {
-        let pixels = solid(Color::rgb(0xFF, 0x00, 0x00), 1, 3);
-        assert_eq!(
-            analyze_rgba(&pixels, 1, 3),
-            Err(Failure::TooSmall {
-                width: 1,
-                height: 3
-            })
-        );
-        assert_eq!(
-            Failure::TooSmall {
-                width: 1,
-                height: 3
-            }
-            .code(),
-            "too-small"
-        );
-    }
-
-    #[test]
-    fn wrong_buffer_length_is_reported() {
-        let pixels = solid(Color::rgb(0xFF, 0x00, 0x00), 2, 2);
-        match analyze_rgba(&pixels[..12], 2, 2) {
-            Err(Failure::BadDimensions {
-                expected, actual, ..
-            }) => {
-                assert_eq!((expected, actual), (16, 12));
-            }
-            other => panic!("应当报维度错误，实际 {other:?}"),
-        }
-    }
-
-    #[test]
-    fn fully_transparent_image_has_no_seed() {
-        let pixels = solid(Color::rgba(0x3C, 0x8D, 0xBC, 0), 4, 4);
-        assert_eq!(analyze_rgba(&pixels, 4, 4), Err(Failure::NoOpaquePixels));
-    }
-
-    #[test]
-    fn large_image_is_downsampled_and_still_deterministic() {
-        let (width, height) = (512_u32, 512_u32);
-        let mut pixels = Vec::with_capacity((width * height * 4) as usize);
-        for y in 0..height {
-            for x in 0..width {
-                // 细网格：等距抽样会走样，块平均能得到稳定的底色。
-                let checker = (x + y) % 2 == 0;
-                pixels.extend_from_slice(if checker {
-                    &[0xD2, 0x3B, 0x2A, 0xFF]
-                } else {
-                    &[0x2A, 0x3B, 0xD2, 0xFF]
-                });
-            }
-        }
-        let first = analyze_rgba(&pixels, width, height).expect("大图有种子");
-        let second = analyze_rgba(&pixels, width, height).expect("可复现");
-        assert_eq!(first, second);
-        let samples = sample_blocks(&pixels, width as usize, height as usize);
-        assert!(
-            samples.len() <= MAX_SAMPLES,
-            "采样点 {} 超标",
-            samples.len()
-        );
-        // 块平均把红蓝网格合成偏紫的中间色，而不是撞上纯红或纯蓝之一。
-        assert!(first.chroma > MIN_SEED_CHROMA, "{first:?}");
-    }
-
-    #[test]
-    fn block_sampling_averages_instead_of_picking() {
-        // 2×2 红蓝棋盘，块边长 1（图很小）→ 4 个采样点；只验证采样点数量与顺序稳定。
-        let pixels = [
-            0xFF, 0x00, 0x00, 0xFF, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0x00,
-            0x00, 0xFF,
-        ];
-        let samples = sample_blocks(&pixels, 2, 2);
-        assert_eq!(samples.len(), 4);
-        assert_eq!(samples[0], Color::rgb(0xFF, 0x00, 0x00));
-        assert_eq!(samples[1], Color::rgb(0x00, 0x00, 0xFF));
-    }
-
-    #[test]
-    fn seed_scheme_meets_wcag_on_the_primary_pair() {
-        let pixels = solid(Color::rgb(0xC0, 0x39, 0x2B), 4, 4);
-        let seed = analyze_rgba(&pixels, 4, 4).expect("砖红有种子");
-        for flavor in [SchemeFlavor::Light, SchemeFlavor::Dark] {
-            let scheme = seed.scheme(flavor, 12.0);
-            let ratio = scheme.contrast(crate::color::Role::OnPrimary, crate::color::Role::Primary);
-            assert!(ratio >= 4.5, "{flavor:?} 只有 {ratio}");
-        }
-    }
-}
+mod tests;
diff --git a/crates/design/src/palette/seed/tests.rs b/crates/design/src/palette/seed/tests.rs
new file mode 100644
index 0000000..cc98f88
--- /dev/null
+++ b/crates/design/src/palette/seed/tests.rs
@@ -0,0 +1,190 @@
+//! `seed` 模块的单测：五类输入各自的处置 + **端到端反证**（不许退化成平均色）。
+//!
+//! 为什么端到端测试必须在这里（而不是只测 `quantize`/`score`）：那两条单测手工构造
+//! `Cluster` 直接喂中间层，**绕过了 `analyze_rgba` 的接线**。把 `analyze_rgba` 换成
+//! 「不透明像素求算术平均」时，中间层单测照样绿，只有这里会红。
+
+use super::*;
+
+/// 生成 `width × height` 的全 `color` 图。
+fn solid(color: Color, width: u32, height: u32) -> Vec<u8> {
+    let mut out = Vec::with_capacity((width * height * 4) as usize);
+    for _ in 0..(width * height) {
+        out.extend_from_slice(&[color.r, color.g, color.b, color.a]);
+    }
+    out
+}
+
+/// 生成「其余是 `base`，`accent_pixels` 个像素是 `accent`」的图（强调色排在末尾）。
+///
+/// 这是**反证「不许取平均色」**的输入构造器：强调色面积小到平均色会被底色吃掉，
+/// 但它是人眼会记住、能当强调色用的那一小撮。
+fn two_tone(width: u32, height: u32, base: Color, accent: Color, accent_pixels: usize) -> Vec<u8> {
+    let total = (width * height) as usize;
+    assert!(accent_pixels <= total);
+    let mut out = Vec::with_capacity(total * 4);
+    for index in 0..total {
+        let color = if index < total - accent_pixels {
+            base
+        } else {
+            accent
+        };
+        out.extend_from_slice(&[color.r, color.g, color.b, color.a]);
+    }
+    out
+}
+
+#[test]
+fn end_to_end_picks_the_five_percent_accent() {
+    // ⚠️ 端到端反证：这条必须走 `analyze_rgba` 的**完整管线**（量化 → 打分 → 彩度门槛），
+    // 不许像 `quantize`/`score` 的单测那样手工构造 `Cluster` 直接喂中间层。
+    // 如果 `analyze_rgba` 被改成「不透明像素求算术平均」，平均值会是米白（chroma ≈4）→
+    // 返回 `LowChroma` 而不是种子，这条立刻红。
+    let beige = Color::from_hex("#F5F1EA").expect("合法 hex");
+    let coral = Color::from_hex("#FF6B5A").expect("合法 hex");
+    let pixels = two_tone(40, 40, beige, coral, 80); // 95% 米白 + 5% 珊瑚
+
+    let seed = analyze_rgba(&pixels, 40, 40).expect("5% 的珊瑚应当被选中当种子");
+    assert_eq!(
+        seed.color,
+        coral,
+        "种子必须是珊瑚（实际 {}）；米白占比 95% 但它不是「主色」",
+        seed.color.to_hex()
+    );
+    assert!(seed.chroma > 40.0, "珊瑚彩度应当很高，实测 {}", seed.chroma);
+    // 与「平均色」泾渭分明：原图的算术平均值是米白，色相/彩度都差一整个量级。
+    assert!(!seed.is_muted());
+}
+
+#[test]
+fn end_to_end_picks_the_three_percent_accent() {
+    // 面积再降到 3%（48/1600）：`Score` 的 1% 人气门槛仍然放行，平均色更不可能靠巧合命中。
+    let beige = Color::from_hex("#F5F1EA").expect("合法 hex");
+    let orange = Color::from_hex("#FF8800").expect("合法 hex");
+    let pixels = two_tone(40, 40, beige, orange, 48);
+
+    let seed = analyze_rgba(&pixels, 40, 40).expect("3% 的橙应当被选中当种子");
+    assert_eq!(seed.color, orange, "实际 {}", seed.color.to_hex());
+    assert!(seed.chroma > 40.0, "彩度 {}", seed.chroma);
+}
+
+#[test]
+fn solid_vivid_image_yields_seed() {
+    let pixels = solid(Color::rgb(0x3C, 0x8D, 0xBC), 4, 4);
+    let seed = analyze_rgba(&pixels, 4, 4).expect("天蓝纯色图有种子");
+    assert_eq!(seed.color, Color::from_hex("#3C8DBC").expect("合法 hex"));
+    assert!(seed.chroma > MIN_SEED_CHROMA);
+    assert!((seed.share - 1.0).abs() < 1.0e-6);
+    assert!(!seed.is_muted());
+}
+
+#[test]
+fn gray_white_image_is_rejected_with_measured_chroma() {
+    // D40 的反证：灰白壁纸硬取色会得到青色 #006874，这里必须拒绝并报出彩度。
+    let pixels = solid(Color::rgb(0xF2, 0xF2, 0xF0), 8, 8);
+    match analyze_rgba(&pixels, 8, 8) {
+        Err(Failure::LowChroma { chroma, .. }) => {
+            assert!(chroma < MIN_SEED_CHROMA, "彩度 {chroma} 不该过门槛");
+        }
+        other => panic!("灰白图必须被拒，实际 {other:?}"),
+    }
+    assert_eq!(seed_from_rgba(&pixels, 8, 8), None);
+}
+
+#[test]
+fn neutral_gray_hash_rejects_instead_of_inventing_cyan() {
+    // 与 M70 复审实测的坏味道对齐：#808080 的 CAM16 色相 209.5°，硬取色会得到青色。
+    let pixels = solid(Color::rgb(0x80, 0x80, 0x80), 4, 4);
+    assert_eq!(seed_from_rgba(&pixels, 4, 4), None);
+}
+
+#[test]
+fn tiny_images_are_too_small() {
+    let pixels = solid(Color::rgb(0xFF, 0x00, 0x00), 1, 3);
+    assert_eq!(
+        analyze_rgba(&pixels, 1, 3),
+        Err(Failure::TooSmall {
+            width: 1,
+            height: 3
+        })
+    );
+    assert_eq!(
+        Failure::TooSmall {
+            width: 1,
+            height: 3
+        }
+        .code(),
+        "too-small"
+    );
+}
+
+#[test]
+fn wrong_buffer_length_is_reported() {
+    let pixels = solid(Color::rgb(0xFF, 0x00, 0x00), 2, 2);
+    match analyze_rgba(&pixels[..12], 2, 2) {
+        Err(Failure::BadDimensions {
+            expected, actual, ..
+        }) => {
+            assert_eq!((expected, actual), (16, 12));
+        }
+        other => panic!("应当报维度错误，实际 {other:?}"),
+    }
+}
+
+#[test]
+fn fully_transparent_image_has_no_seed() {
+    let pixels = solid(Color::rgba(0x3C, 0x8D, 0xBC, 0), 4, 4);
+    assert_eq!(analyze_rgba(&pixels, 4, 4), Err(Failure::NoOpaquePixels));
+}
+
+#[test]
+fn large_image_is_downsampled_and_still_deterministic() {
+    let (width, height) = (512_u32, 512_u32);
+    let mut pixels = Vec::with_capacity((width * height * 4) as usize);
+    for y in 0..height {
+        for x in 0..width {
+            // 细网格：等距抽样会走样，块平均能得到稳定的底色。
+            let checker = (x + y) % 2 == 0;
+            pixels.extend_from_slice(if checker {
+                &[0xD2, 0x3B, 0x2A, 0xFF]
+            } else {
+                &[0x2A, 0x3B, 0xD2, 0xFF]
+            });
+        }
+    }
+    let first = analyze_rgba(&pixels, width, height).expect("大图有种子");
+    let second = analyze_rgba(&pixels, width, height).expect("可复现");
+    assert_eq!(first, second);
+    let samples = sample_blocks(&pixels, width as usize, height as usize);
+    assert!(
+        samples.len() <= MAX_SAMPLES,
+        "采样点 {} 超标",
+        samples.len()
+    );
+    // 块平均把红蓝网格合成偏紫的中间色，而不是撞上纯红或纯蓝之一。
+    assert!(first.chroma > MIN_SEED_CHROMA, "{first:?}");
+}
+
+#[test]
+fn block_sampling_averages_instead_of_picking() {
+    // 2×2 红蓝棋盘，块边长 1（图很小）→ 4 个采样点；只验证采样点数量与顺序稳定。
+    let pixels = [
+        0xFF, 0x00, 0x00, 0xFF, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0x00, 0x00,
+        0xFF,
+    ];
+    let samples = sample_blocks(&pixels, 2, 2);
+    assert_eq!(samples.len(), 4);
+    assert_eq!(samples[0], Color::rgb(0xFF, 0x00, 0x00));
+    assert_eq!(samples[1], Color::rgb(0x00, 0x00, 0xFF));
+}
+
+#[test]
+fn seed_scheme_meets_wcag_on_the_primary_pair() {
+    let pixels = solid(Color::rgb(0xC0, 0x39, 0x2B), 4, 4);
+    let seed = analyze_rgba(&pixels, 4, 4).expect("砖红有种子");
+    for flavor in [SchemeFlavor::Light, SchemeFlavor::Dark] {
+        let scheme = seed.scheme(flavor, 12.0);
+        let ratio = scheme.contrast(crate::color::Role::OnPrimary, crate::color::Role::Primary);
+        assert!(ratio >= 4.5, "{flavor:?} 只有 {ratio}");
+    }
+}