diff --git a/app-modern/ui/gio/shell.go b/app-modern/ui/gio/shell.go
index 800b379..3536296 100644
--- a/app-modern/ui/gio/shell.go
+++ b/app-modern/ui/gio/shell.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"image"
 	"image/color"
+	"strings"
 
 	"gioui.org/io/semantic"
 	"gioui.org/layout"
@@ -60,10 +61,13 @@ type AppShell struct {
 	viewInstalled widget.Clickable
 	viewUpdates   widget.Clickable
 	resetFilters  widget.Clickable
+	closeDetail   widget.Clickable
 
 	categoryControls map[string]*widget.Clickable
 	rows             map[string]*rowControls
+	icons            map[string]paint.ImageOp
 	lastRendered     int
+	detailRendered   bool
 }
 
 // NewAppShell creates the catalog shell with an optional in-memory snapshot.
@@ -78,12 +82,22 @@ func NewAppShell(
 		categoryList:     layout.List{Axis: layout.Horizontal},
 		categoryControls: make(map[string]*widget.Clickable),
 		rows:             make(map[string]*rowControls),
+		icons:            make(map[string]paint.ImageOp),
 	}
 	shell.search.SingleLine = true
 	shell.SetItems(items)
 	return shell
 }
 
+// ApplyIcon stores a background-decoded image for future Layout calls.
+func (shell *AppShell) ApplyIcon(appID string, icon image.Image) {
+	if icon == nil {
+		delete(shell.icons, appID)
+		return
+	}
+	shell.icons[appID] = paint.NewImageOp(icon)
+}
+
 // SetItems applies a prepared, IO-free catalog/status snapshot.
 func (shell *AppShell) SetItems(items []application.CatalogListItem) {
 	shell.model.SetItems(items)
@@ -126,6 +140,7 @@ func NewTheme() *material.Theme {
 func (shell *AppShell) Layout(gtx layout.Context, theme *material.Theme) layout.Dimensions {
 	shell.drainInput(gtx)
 	shell.lastRendered = 0
+	shell.detailRendered = false
 	paint.Fill(gtx.Ops, shellColors.background)
 
 	return layout.UniformInset(unit.Dp(20)).Layout(gtx, func(gtx layout.Context) layout.Dimensions {
@@ -177,6 +192,9 @@ func (shell *AppShell) drainInput(gtx layout.Context) {
 		shell.search.SetText("")
 		shell.model.ResetFilters()
 	}
+	for shell.closeDetail.Clicked(gtx) {
+		shell.model.Select("")
+	}
 }
 
 func (shell *AppShell) layoutHeader(
@@ -320,14 +338,35 @@ func (shell *AppShell) layoutContent(
 		}),
 		layout.Rigid(layout.Spacer{Width: unit.Dp(16)}.Layout),
 		layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
-			return panel(
+			selected, hasSelection := shell.model.SelectedItem()
+			return layout.Flex{}.Layout(
 				gtx,
-				shellColors.surface,
-				unit.Dp(10),
-				layout.UniformInset(unit.Dp(16)),
-				func(gtx layout.Context) layout.Dimensions {
-					return shell.layoutCatalog(gtx, theme)
-				},
+				layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
+					return panel(
+						gtx,
+						shellColors.surface,
+						unit.Dp(10),
+						layout.UniformInset(unit.Dp(16)),
+						func(gtx layout.Context) layout.Dimensions {
+							return shell.layoutCatalog(gtx, theme)
+						},
+					)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if !hasSelection {
+						return layout.Dimensions{}
+					}
+					return layout.Spacer{Width: unit.Dp(12)}.Layout(gtx)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if !hasSelection {
+						return layout.Dimensions{}
+					}
+					width := gtx.Dp(unit.Dp(320))
+					gtx.Constraints.Min.X = width
+					gtx.Constraints.Max.X = width
+					return shell.layoutDetail(gtx, theme, selected)
+				}),
 			)
 		}),
 	)
@@ -407,7 +446,14 @@ func (shell *AppShell) layoutAppRow(
 					return layout.Flex{Alignment: layout.Middle}.Layout(
 						gtx,
 						layout.Rigid(func(gtx layout.Context) layout.Dimensions {
-							return shell.layoutLetterIcon(gtx, theme, item.Name)
+							return shell.layoutAppIcon(
+								gtx,
+								theme,
+								item.ID,
+								item.Name,
+								unit.Dp(48),
+								unit.Dp(8),
+							)
 						}),
 						layout.Rigid(layout.Spacer{Width: unit.Dp(12)}.Layout),
 						layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
@@ -454,14 +500,32 @@ func (shell *AppShell) layoutAppRow(
 	})
 }
 
-func (shell *AppShell) layoutLetterIcon(
+func (shell *AppShell) layoutAppIcon(
 	gtx layout.Context,
 	theme *material.Theme,
+	appID string,
 	name string,
+	iconSize unit.Dp,
+	radius unit.Dp,
 ) layout.Dimensions {
-	size := gtx.Dp(unit.Dp(48))
+	size := gtx.Dp(iconSize)
 	gtx.Constraints.Min = image.Pt(size, size)
 	gtx.Constraints.Max = gtx.Constraints.Min
+	if icon, exists := shell.icons[appID]; exists {
+		return panel(
+			gtx,
+			shellColors.surface,
+			radius,
+			layout.UniformInset(unit.Dp(2)),
+			func(gtx layout.Context) layout.Dimensions {
+				return widget.Image{
+					Src:      icon,
+					Fit:      widget.Contain,
+					Position: layout.Center,
+				}.Layout(gtx)
+			},
+		)
+	}
 	letter := "S"
 	for _, character := range name {
 		letter = string(character)
@@ -470,7 +534,7 @@ func (shell *AppShell) layoutLetterIcon(
 	return panel(
 		gtx,
 		shellColors.primary,
-		unit.Dp(8),
+		radius,
 		layout.UniformInset(unit.Dp(0)),
 		func(gtx layout.Context) layout.Dimensions {
 			return layout.Center.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
@@ -482,6 +546,114 @@ func (shell *AppShell) layoutLetterIcon(
 	)
 }
 
+func (shell *AppShell) layoutDetail(
+	gtx layout.Context,
+	theme *material.Theme,
+	item application.CatalogListItem,
+) layout.Dimensions {
+	shell.detailRendered = true
+	return panel(
+		gtx,
+		shellColors.muted,
+		unit.Dp(10),
+		layout.UniformInset(unit.Dp(16)),
+		func(gtx layout.Context) layout.Dimensions {
+			return layout.Flex{Axis: layout.Vertical}.Layout(
+				gtx,
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return layout.Flex{Alignment: layout.Middle}.Layout(
+						gtx,
+						layout.Rigid(material.H6(theme, "软件详情").Layout),
+						layout.Flexed(1, layout.Spacer{}.Layout),
+						layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+							return shell.layoutFilterButton(
+								gtx,
+								theme,
+								&shell.closeDetail,
+								"关闭",
+								false,
+							)
+						}),
+					)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(16)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return layout.Center.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+						return shell.layoutAppIcon(
+							gtx,
+							theme,
+							item.ID,
+							item.Name,
+							unit.Dp(72),
+							unit.Dp(12),
+						)
+					})
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(12)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return layout.Center.Layout(gtx, material.H6(theme, item.Name).Layout)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(4)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					label := material.Body2(
+						theme,
+						fmt.Sprintf("%s · %s", item.ID, item.Version),
+					)
+					label.Color = shellColors.secondary
+					return layout.Center.Layout(gtx, label.Layout)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(16)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(gtx, theme, "状态", statusLabel(item.Status))
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(gtx, theme, "分类", fallbackText(item.Category, "未分类"))
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(
+						gtx,
+						theme,
+						"标签",
+						fallbackText(strings.Join(item.Tags, " · "), "无"),
+					)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(
+						gtx,
+						theme,
+						"简介",
+						fallbackText(item.Description, "暂无简介"),
+					)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if item.Reason == "" {
+						return layout.Dimensions{}
+					}
+					return detailField(gtx, theme, "不可用原因", reasonLabel(item.Reason))
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if item.Tutorial == "" {
+						return layout.Dimensions{}
+					}
+					return detailField(gtx, theme, "教程", item.Tutorial)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if item.Homepage == "" {
+						return layout.Dimensions{}
+					}
+					return detailField(gtx, theme, "主页", item.Homepage)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(8)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					label := material.Caption(theme, actionLabel(item)+"；实际操作将在后续用例接入")
+					label.Color = shellColors.secondary
+					return label.Layout(gtx)
+				}),
+			)
+		},
+	)
+}
+
 func (shell *AppShell) layoutEmptyState(
 	gtx layout.Context,
 	theme *material.Theme,
@@ -708,3 +880,43 @@ func actionLabel(item application.CatalogListItem) string {
 		return "查看详情"
 	}
 }
+
+func detailField(
+	gtx layout.Context,
+	theme *material.Theme,
+	labelText string,
+	value string,
+) layout.Dimensions {
+	return layout.Inset{Bottom: unit.Dp(12)}.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		return layout.Flex{Axis: layout.Vertical}.Layout(
+			gtx,
+			layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+				label := material.Caption(theme, labelText)
+				label.Color = shellColors.secondary
+				return label.Layout(gtx)
+			}),
+			layout.Rigid(layout.Spacer{Height: unit.Dp(3)}.Layout),
+			layout.Rigid(material.Body2(theme, value).Layout),
+		)
+	})
+}
+
+func fallbackText(value, fallback string) string {
+	if value == "" {
+		return fallback
+	}
+	return value
+}
+
+func reasonLabel(reason string) string {
+	switch reason {
+	case "deprecated":
+		return "软件已停止发布，不能新装或更新"
+	case "minimum_os":
+		return "当前 Windows 版本低于最低要求"
+	case "architecture":
+		return "没有适用于当前系统架构的软件包"
+	default:
+		return reason
+	}
+}
diff --git a/app-modern/ui/gio/shell_test.go b/app-modern/ui/gio/shell_test.go
index 1c0874c..c137ff9 100644
--- a/app-modern/ui/gio/shell_test.go
+++ b/app-modern/ui/gio/shell_test.go
@@ -79,6 +79,38 @@ func TestAppShellKeepsRowControlsByAppID(t *testing.T) {
 	}
 }
 
+func TestAppShellRendersSelectedDetailAndAppliedIcon(t *testing.T) {
+	item := application.CatalogListItem{
+		ID:          "json-parser",
+		Name:        "JSON解析工具",
+		Description: "格式化并检查 JSON",
+		Version:     "1.2.0",
+		Category:    "开发工具",
+		Tags:        []string{"JSON", "格式化"},
+		Homepage:    "https://example.invalid/json-parser",
+		Tutorial:    "https://example.invalid/json-parser/tutorial",
+		Status:      domain.StatusInstalled,
+		Installed:   true,
+	}
+	shell := NewAppShell("Modern", item)
+	icon := image.NewNRGBA(image.Rect(0, 0, 32, 32))
+	shell.ApplyIcon(item.ID, icon)
+	shell.model.Select(item.ID)
+
+	shell.Layout(testContext(image.Pt(1280, 800)), NewTheme())
+	if !shell.detailRendered {
+		t.Fatal("selected app detail was not rendered")
+	}
+	if _, exists := shell.icons[item.ID]; !exists {
+		t.Fatal("ApplyIcon did not retain the prepared image operation")
+	}
+
+	shell.ApplyIcon(item.ID, nil)
+	if _, exists := shell.icons[item.ID]; exists {
+		t.Fatal("ApplyIcon(nil) did not remove the image")
+	}
+}
+
 func testContext(size image.Point) layout.Context {
 	var operations op.Ops
 	return layout.Context{
diff --git a/app-win7/ui/gio/shell.go b/app-win7/ui/gio/shell.go
index dc3faec..cb66763 100644
--- a/app-win7/ui/gio/shell.go
+++ b/app-win7/ui/gio/shell.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"image"
 	"image/color"
+	"strings"
 
 	"gioui.org/io/semantic"
 	"gioui.org/layout"
@@ -60,10 +61,13 @@ type AppShell struct {
 	viewInstalled widget.Clickable
 	viewUpdates   widget.Clickable
 	resetFilters  widget.Clickable
+	closeDetail   widget.Clickable
 
 	categoryControls map[string]*widget.Clickable
 	rows             map[string]*rowControls
+	icons            map[string]paint.ImageOp
 	lastRendered     int
+	detailRendered   bool
 }
 
 // NewAppShell creates the catalog shell with an optional in-memory snapshot.
@@ -78,12 +82,22 @@ func NewAppShell(
 		categoryList:     layout.List{Axis: layout.Horizontal},
 		categoryControls: make(map[string]*widget.Clickable),
 		rows:             make(map[string]*rowControls),
+		icons:            make(map[string]paint.ImageOp),
 	}
 	shell.search.SingleLine = true
 	shell.SetItems(items)
 	return shell
 }
 
+// ApplyIcon stores a background-decoded image for future Layout calls.
+func (shell *AppShell) ApplyIcon(appID string, icon image.Image) {
+	if icon == nil {
+		delete(shell.icons, appID)
+		return
+	}
+	shell.icons[appID] = paint.NewImageOp(icon)
+}
+
 // SetItems applies a prepared, IO-free catalog/status snapshot.
 func (shell *AppShell) SetItems(items []application.CatalogListItem) {
 	shell.model.SetItems(items)
@@ -126,6 +140,7 @@ func NewTheme() *material.Theme {
 func (shell *AppShell) Layout(gtx layout.Context, theme *material.Theme) layout.Dimensions {
 	shell.drainInput(gtx)
 	shell.lastRendered = 0
+	shell.detailRendered = false
 	paint.Fill(gtx.Ops, shellColors.background)
 
 	return layout.UniformInset(unit.Dp(16)).Layout(gtx, func(gtx layout.Context) layout.Dimensions {
@@ -181,6 +196,9 @@ func (shell *AppShell) drainInput(gtx layout.Context) {
 		shell.search.SetText("")
 		shell.model.ResetFilters()
 	}
+	for shell.closeDetail.Clicked(gtx) {
+		shell.model.Select("")
+	}
 }
 
 func (shell *AppShell) layoutHeader(
@@ -309,45 +327,70 @@ func (shell *AppShell) layoutContent(
 		}),
 		layout.Rigid(layout.Spacer{Width: unit.Dp(12)}.Layout),
 		layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
-			return panel(
+			selected, hasSelection := shell.model.SelectedItem()
+			return layout.Flex{}.Layout(
 				gtx,
-				shellColors.surface,
-				unit.Dp(6),
-				layout.UniformInset(unit.Dp(12)),
-				func(gtx layout.Context) layout.Dimensions {
-					visible := shell.model.VisibleItems()
-					return layout.Flex{Axis: layout.Vertical}.Layout(
+				layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
+					return panel(
 						gtx,
-						layout.Rigid(func(gtx layout.Context) layout.Dimensions {
-							return layout.Flex{Alignment: layout.Middle}.Layout(
+						shellColors.surface,
+						unit.Dp(6),
+						layout.UniformInset(unit.Dp(12)),
+						func(gtx layout.Context) layout.Dimensions {
+							visible := shell.model.VisibleItems()
+							return layout.Flex{Axis: layout.Vertical}.Layout(
 								gtx,
-								layout.Rigid(material.H6(theme, viewTitle(shell.model.View())).Layout),
-								layout.Flexed(1, layout.Spacer{}.Layout),
 								layout.Rigid(func(gtx layout.Context) layout.Dimensions {
-									label := material.Caption(
-										theme,
-										fmt.Sprintf("%d / %d 项", len(visible), shell.model.TotalCount()),
+									return layout.Flex{Alignment: layout.Middle}.Layout(
+										gtx,
+										layout.Rigid(material.H6(theme, viewTitle(shell.model.View())).Layout),
+										layout.Flexed(1, layout.Spacer{}.Layout),
+										layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+											label := material.Caption(
+												theme,
+												fmt.Sprintf(
+													"%d / %d 项",
+													len(visible),
+													shell.model.TotalCount(),
+												),
+											)
+											label.Color = shellColors.secondary
+											return label.Layout(gtx)
+										}),
 									)
-									label.Color = shellColors.secondary
-									return label.Layout(gtx)
+								}),
+								layout.Rigid(layout.Spacer{Height: unit.Dp(8)}.Layout),
+								layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
+									if len(visible) == 0 {
+										return shell.layoutEmptyState(gtx, theme)
+									}
+									return shell.appList.Layout(gtx, len(visible), func(
+										gtx layout.Context,
+										index int,
+									) layout.Dimensions {
+										shell.lastRendered++
+										return shell.layoutAppRow(gtx, theme, visible[index])
+									})
 								}),
 							)
-						}),
-						layout.Rigid(layout.Spacer{Height: unit.Dp(8)}.Layout),
-						layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
-							if len(visible) == 0 {
-								return shell.layoutEmptyState(gtx, theme)
-							}
-							return shell.appList.Layout(gtx, len(visible), func(
-								gtx layout.Context,
-								index int,
-							) layout.Dimensions {
-								shell.lastRendered++
-								return shell.layoutAppRow(gtx, theme, visible[index])
-							})
-						}),
+						},
 					)
-				},
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if !hasSelection {
+						return layout.Dimensions{}
+					}
+					return layout.Spacer{Width: unit.Dp(8)}.Layout(gtx)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if !hasSelection {
+						return layout.Dimensions{}
+					}
+					width := gtx.Dp(unit.Dp(280))
+					gtx.Constraints.Min.X = width
+					gtx.Constraints.Max.X = width
+					return shell.layoutDetail(gtx, theme, selected)
+				}),
 			)
 		}),
 	)
@@ -388,7 +431,14 @@ func (shell *AppShell) layoutAppRow(
 					return layout.Flex{Alignment: layout.Middle}.Layout(
 						gtx,
 						layout.Rigid(func(gtx layout.Context) layout.Dimensions {
-							return shell.layoutLetterIcon(gtx, theme, item.Name)
+							return shell.layoutAppIcon(
+								gtx,
+								theme,
+								item.ID,
+								item.Name,
+								unit.Dp(40),
+								unit.Dp(5),
+							)
 						}),
 						layout.Rigid(layout.Spacer{Width: unit.Dp(10)}.Layout),
 						layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
@@ -419,14 +469,32 @@ func (shell *AppShell) layoutAppRow(
 	})
 }
 
-func (shell *AppShell) layoutLetterIcon(
+func (shell *AppShell) layoutAppIcon(
 	gtx layout.Context,
 	theme *material.Theme,
+	appID string,
 	name string,
+	iconSize unit.Dp,
+	radius unit.Dp,
 ) layout.Dimensions {
-	size := gtx.Dp(unit.Dp(40))
+	size := gtx.Dp(iconSize)
 	gtx.Constraints.Min = image.Pt(size, size)
 	gtx.Constraints.Max = gtx.Constraints.Min
+	if icon, exists := shell.icons[appID]; exists {
+		return panel(
+			gtx,
+			shellColors.surface,
+			radius,
+			layout.UniformInset(unit.Dp(2)),
+			func(gtx layout.Context) layout.Dimensions {
+				return widget.Image{
+					Src:      icon,
+					Fit:      widget.Contain,
+					Position: layout.Center,
+				}.Layout(gtx)
+			},
+		)
+	}
 	letter := "S"
 	for _, character := range name {
 		letter = string(character)
@@ -435,7 +503,7 @@ func (shell *AppShell) layoutLetterIcon(
 	return panel(
 		gtx,
 		shellColors.primary,
-		unit.Dp(5),
+		radius,
 		layout.UniformInset(unit.Dp(0)),
 		func(gtx layout.Context) layout.Dimensions {
 			return layout.Center.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
@@ -447,6 +515,113 @@ func (shell *AppShell) layoutLetterIcon(
 	)
 }
 
+func (shell *AppShell) layoutDetail(
+	gtx layout.Context,
+	theme *material.Theme,
+	item application.CatalogListItem,
+) layout.Dimensions {
+	shell.detailRendered = true
+	return panel(
+		gtx,
+		shellColors.muted,
+		unit.Dp(6),
+		layout.UniformInset(unit.Dp(12)),
+		func(gtx layout.Context) layout.Dimensions {
+			return layout.Flex{Axis: layout.Vertical}.Layout(
+				gtx,
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return layout.Flex{Alignment: layout.Middle}.Layout(
+						gtx,
+						layout.Rigid(material.Body1(theme, "软件详情").Layout),
+						layout.Flexed(1, layout.Spacer{}.Layout),
+						layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+							return shell.layoutFilterButton(
+								gtx,
+								theme,
+								&shell.closeDetail,
+								"关闭",
+								false,
+							)
+						}),
+					)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(10)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return layout.Center.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+						return shell.layoutAppIcon(
+							gtx,
+							theme,
+							item.ID,
+							item.Name,
+							unit.Dp(64),
+							unit.Dp(7),
+						)
+					})
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(8)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return layout.Center.Layout(gtx, material.Body1(theme, item.Name).Layout)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(3)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					label := material.Caption(
+						theme,
+						fmt.Sprintf("%s · %s", item.ID, item.Version),
+					)
+					label.Color = shellColors.secondary
+					return layout.Center.Layout(gtx, label.Layout)
+				}),
+				layout.Rigid(layout.Spacer{Height: unit.Dp(10)}.Layout),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(gtx, theme, "状态", statusLabel(item.Status))
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(gtx, theme, "分类", fallbackText(item.Category, "未分类"))
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(
+						gtx,
+						theme,
+						"标签",
+						fallbackText(strings.Join(item.Tags, " · "), "无"),
+					)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					return detailField(
+						gtx,
+						theme,
+						"简介",
+						fallbackText(item.Description, "暂无简介"),
+					)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if item.Reason == "" {
+						return layout.Dimensions{}
+					}
+					return detailField(gtx, theme, "不可用原因", reasonLabel(item.Reason))
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if item.Tutorial == "" {
+						return layout.Dimensions{}
+					}
+					return detailField(gtx, theme, "教程", item.Tutorial)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					if item.Homepage == "" {
+						return layout.Dimensions{}
+					}
+					return detailField(gtx, theme, "主页", item.Homepage)
+				}),
+				layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+					label := material.Caption(theme, "实际安装/启动操作将在后续用例接入")
+					label.Color = shellColors.secondary
+					return label.Layout(gtx)
+				}),
+			)
+		},
+	)
+}
+
 func (shell *AppShell) layoutEmptyState(
 	gtx layout.Context,
 	theme *material.Theme,
@@ -626,3 +801,43 @@ func statusColor(status domain.AppStatus) color.NRGBA {
 		return shellColors.primary
 	}
 }
+
+func detailField(
+	gtx layout.Context,
+	theme *material.Theme,
+	labelText string,
+	value string,
+) layout.Dimensions {
+	return layout.Inset{Bottom: unit.Dp(8)}.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		return layout.Flex{Axis: layout.Vertical}.Layout(
+			gtx,
+			layout.Rigid(func(gtx layout.Context) layout.Dimensions {
+				label := material.Caption(theme, labelText)
+				label.Color = shellColors.secondary
+				return label.Layout(gtx)
+			}),
+			layout.Rigid(layout.Spacer{Height: unit.Dp(2)}.Layout),
+			layout.Rigid(material.Caption(theme, value).Layout),
+		)
+	})
+}
+
+func fallbackText(value, fallback string) string {
+	if value == "" {
+		return fallback
+	}
+	return value
+}
+
+func reasonLabel(reason string) string {
+	switch reason {
+	case "deprecated":
+		return "软件已停止发布"
+	case "minimum_os":
+		return "Windows 版本低于最低要求"
+	case "architecture":
+		return "没有当前架构的软件包"
+	default:
+		return reason
+	}
+}
diff --git a/app-win7/ui/gio/shell_test.go b/app-win7/ui/gio/shell_test.go
index 0e57186..5be62c2 100644
--- a/app-win7/ui/gio/shell_test.go
+++ b/app-win7/ui/gio/shell_test.go
@@ -77,6 +77,38 @@ func TestAppShellKeepsRowControlsByAppID(t *testing.T) {
 	}
 }
 
+func TestAppShellRendersSelectedDetailAndAppliedIcon(t *testing.T) {
+	item := application.CatalogListItem{
+		ID:          "json-parser",
+		Name:        "JSON解析工具",
+		Description: "格式化并检查 JSON",
+		Version:     "1.2.0",
+		Category:    "开发工具",
+		Tags:        []string{"JSON", "格式化"},
+		Homepage:    "https://example.invalid/json-parser",
+		Tutorial:    "https://example.invalid/json-parser/tutorial",
+		Status:      domain.StatusInstalled,
+		Installed:   true,
+	}
+	shell := NewAppShell("Legacy", item)
+	icon := image.NewNRGBA(image.Rect(0, 0, 32, 32))
+	shell.ApplyIcon(item.ID, icon)
+	shell.model.Select(item.ID)
+
+	shell.Layout(testContext(image.Pt(1200, 760)), NewTheme())
+	if !shell.detailRendered {
+		t.Fatal("selected app detail was not rendered")
+	}
+	if _, exists := shell.icons[item.ID]; !exists {
+		t.Fatal("ApplyIcon did not retain the prepared image operation")
+	}
+
+	shell.ApplyIcon(item.ID, nil)
+	if _, exists := shell.icons[item.ID]; exists {
+		t.Fatal("ApplyIcon(nil) did not remove the image")
+	}
+}
+
 func testContext(size image.Point) layout.Context {
 	var operations op.Ops
 	return layout.Context{
diff --git a/core/application/catalog_list.go b/core/application/catalog_list.go
index ba52d7a..e89fc6b 100644
--- a/core/application/catalog_list.go
+++ b/core/application/catalog_list.go
@@ -23,6 +23,9 @@ type CatalogListItem struct {
 	Version     string
 	Category    string
 	Tags        []string
+	IconRef     string
+	Homepage    string
+	Tutorial    string
 	Status      domain.AppStatus
 	Installed   bool
 	Installable bool
@@ -141,6 +144,16 @@ func (model *CatalogListModel) SelectedID() string {
 	return model.selectedID
 }
 
+// SelectedItem returns the selected source item without changing filters.
+func (model *CatalogListModel) SelectedItem() (CatalogListItem, bool) {
+	for _, item := range model.items {
+		if item.ID == model.selectedID {
+			return item, true
+		}
+	}
+	return CatalogListItem{}, false
+}
+
 // Valid reports whether view is supported by the MVP list.
 func (view CatalogView) Valid() bool {
 	return view == CatalogViewAll ||
diff --git a/core/application/catalog_list_test.go b/core/application/catalog_list_test.go
index cb4284b..564ae29 100644
--- a/core/application/catalog_list_test.go
+++ b/core/application/catalog_list_test.go
@@ -64,6 +64,10 @@ func TestCatalogListModelPreservesStableOrderAndSelection(t *testing.T) {
 	if model.SelectedID() != "app-a" {
 		t.Fatalf("SelectedID = %q", model.SelectedID())
 	}
+	selected, ok := model.SelectedItem()
+	if !ok || selected.ID != "app-a" {
+		t.Fatalf("SelectedItem() = %#v, %t", selected, ok)
+	}
 
 	model.SetItems([]CatalogListItem{{ID: "app-b", Name: "B", Category: "工具"}})
 	if model.SelectedID() != "" {
diff --git a/core/catalog/icon_cache.go b/core/catalog/icon_cache.go
new file mode 100644
index 0000000..3c2c459
--- /dev/null
+++ b/core/catalog/icon_cache.go
@@ -0,0 +1,317 @@
+package catalog
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"image"
+	_ "image/gif"
+	_ "image/jpeg"
+	_ "image/png"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+const (
+	DefaultMaxIconBytes     int64 = 2 << 20
+	DefaultMaxIconDimension       = 2048
+)
+
+var (
+	ErrIconReferenceInvalid = errors.New("icon reference is invalid")
+	ErrIconDPIInvalid       = errors.New("icon DPI is invalid")
+	ErrIconHashMismatch     = errors.New("icon SHA-256 does not match reference")
+	ErrIconTooLarge         = errors.New("icon exceeds resource limits")
+	ErrIconImageInvalid     = errors.New("icon image is invalid")
+	ErrIconCacheUnsafe      = errors.New("icon cache layout is unsafe")
+	ErrNoValidIcon          = errors.New("no valid icon available")
+)
+
+// IconRequest identifies one content-addressed icon at one UI DPI.
+type IconRequest struct {
+	Reference string
+	DPI       int
+}
+
+// IconFetcher obtains icon bytes outside Gio Layout.
+type IconFetcher interface {
+	FetchIcon(context.Context, IconRequest) ([]byte, error)
+}
+
+// IconFetchFunc adapts a function to IconFetcher.
+type IconFetchFunc func(context.Context, IconRequest) ([]byte, error)
+
+func (function IconFetchFunc) FetchIcon(
+	ctx context.Context,
+	request IconRequest,
+) ([]byte, error) {
+	return function(ctx, request)
+}
+
+// IconSource identifies the cache tier that returned bytes.
+type IconSource string
+
+const (
+	IconSourceMemory IconSource = "memory"
+	IconSourceDisk   IconSource = "disk"
+	IconSourceRemote IconSource = "remote"
+)
+
+// IconResult contains verified bytes and a non-fatal disk-store warning.
+type IconResult struct {
+	Bytes   []byte
+	Source  IconSource
+	Warning error
+}
+
+// IconLoadError preserves disk and refresh failures.
+type IconLoadError struct {
+	Disk  error
+	Fetch error
+}
+
+func (loadError *IconLoadError) Error() string {
+	return fmt.Sprintf(
+		"%s: disk=%v; fetch=%v",
+		ErrNoValidIcon,
+		loadError.Disk,
+		loadError.Fetch,
+	)
+}
+
+func (loadError *IconLoadError) Unwrap() []error {
+	return []error{ErrNoValidIcon, loadError.Disk, loadError.Fetch}
+}
+
+// IconCache is a content-verified memory + disk cache keyed by digest and DPI.
+type IconCache struct {
+	root         string
+	fetcher      IconFetcher
+	maxBytes     int64
+	maxDimension int
+	mu           sync.Mutex
+	memory       map[string][]byte
+}
+
+// NewIconCache creates a cache with safe default resource limits.
+func NewIconCache(root string, fetcher IconFetcher) *IconCache {
+	return &IconCache{
+		root:         root,
+		fetcher:      fetcher,
+		maxBytes:     DefaultMaxIconBytes,
+		maxDimension: DefaultMaxIconDimension,
+		memory:       make(map[string][]byte),
+	}
+}
+
+// Load resolves memory, verified disk, then verified remote bytes.
+func (cache *IconCache) Load(ctx context.Context, request IconRequest) (IconResult, error) {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	digest, key, err := cacheKey(request)
+	if err != nil {
+		return IconResult{}, err
+	}
+	if document, exists := cache.memory[key]; exists {
+		return IconResult{
+			Bytes:  append([]byte(nil), document...),
+			Source: IconSourceMemory,
+		}, nil
+	}
+
+	filePath, pathErr := cache.filePath(digest, request.DPI)
+	if pathErr != nil {
+		return IconResult{}, pathErr
+	}
+	document, diskErr := cache.loadDisk(filePath, digest)
+	if diskErr == nil {
+		cache.memory[key] = append([]byte(nil), document...)
+		return IconResult{
+			Bytes:  append([]byte(nil), document...),
+			Source: IconSourceDisk,
+		}, nil
+	}
+	if !os.IsNotExist(diskErr) {
+		if errors.Is(diskErr, ErrIconCacheUnsafe) {
+			return IconResult{}, diskErr
+		}
+		if removeErr := os.Remove(filePath); removeErr != nil && !os.IsNotExist(removeErr) {
+			return IconResult{}, fmt.Errorf(
+				"%w: remove invalid cache entry: %v",
+				ErrIconCacheUnsafe,
+				removeErr,
+			)
+		}
+	}
+
+	if cache.fetcher == nil {
+		return IconResult{}, &IconLoadError{
+			Disk:  diskErr,
+			Fetch: errors.New("icon fetcher is not configured"),
+		}
+	}
+	document, fetchErr := cache.fetcher.FetchIcon(ctx, request)
+	if fetchErr != nil {
+		return IconResult{}, &IconLoadError{Disk: diskErr, Fetch: fetchErr}
+	}
+	if err := cache.validate(document, digest); err != nil {
+		return IconResult{}, &IconLoadError{Disk: diskErr, Fetch: err}
+	}
+
+	storeErr := cache.storeDisk(filePath, document)
+	cache.memory[key] = append([]byte(nil), document...)
+	return IconResult{
+		Bytes:   append([]byte(nil), document...),
+		Source:  IconSourceRemote,
+		Warning: storeErr,
+	}, nil
+}
+
+// DecodeIcon decodes already verified bytes outside Layout for ApplyIcon.
+func DecodeIcon(document []byte) (image.Image, error) {
+	decoded, _, err := image.Decode(bytes.NewReader(document))
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrIconImageInvalid, err)
+	}
+	return decoded, nil
+}
+
+func (cache *IconCache) validate(document []byte, digest string) error {
+	maxBytes := cache.maxBytes
+	if maxBytes <= 0 {
+		maxBytes = DefaultMaxIconBytes
+	}
+	if int64(len(document)) > maxBytes {
+		return fmt.Errorf(
+			"%w: bytes=%d limit=%d",
+			ErrIconTooLarge,
+			len(document),
+			maxBytes,
+		)
+	}
+	actual := sha256.Sum256(document)
+	if hex.EncodeToString(actual[:]) != digest {
+		return ErrIconHashMismatch
+	}
+
+	config, _, err := image.DecodeConfig(bytes.NewReader(document))
+	if err != nil {
+		return fmt.Errorf("%w: decode config: %v", ErrIconImageInvalid, err)
+	}
+	maxDimension := cache.maxDimension
+	if maxDimension <= 0 {
+		maxDimension = DefaultMaxIconDimension
+	}
+	if config.Width <= 0 ||
+		config.Height <= 0 ||
+		config.Width > maxDimension ||
+		config.Height > maxDimension {
+		return fmt.Errorf(
+			"%w: dimensions=%dx%d limit=%d",
+			ErrIconTooLarge,
+			config.Width,
+			config.Height,
+			maxDimension,
+		)
+	}
+	if _, _, err := image.Decode(bytes.NewReader(document)); err != nil {
+		return fmt.Errorf("%w: decode: %v", ErrIconImageInvalid, err)
+	}
+	return nil
+}
+
+func (cache *IconCache) filePath(digest string, dpi int) (string, error) {
+	if cache.root == "" {
+		return "", fmt.Errorf("%w: empty root", ErrIconCacheUnsafe)
+	}
+	absoluteRoot, err := filepath.Abs(cache.root)
+	if err != nil {
+		return "", fmt.Errorf("%w: %v", ErrIconCacheUnsafe, err)
+	}
+	return filepath.Join(
+		absoluteRoot,
+		digest+"-"+strconv.Itoa(dpi)+".icon",
+	), nil
+}
+
+func (cache *IconCache) loadDisk(filePath, digest string) ([]byte, error) {
+	info, err := os.Lstat(filePath)
+	if err != nil {
+		return nil, err
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.Mode().IsRegular() {
+		return nil, fmt.Errorf("%w: cache entry is not a regular file", ErrIconCacheUnsafe)
+	}
+	document, err := os.ReadFile(filePath)
+	if err != nil {
+		return nil, fmt.Errorf("read icon cache: %w", err)
+	}
+	if err := cache.validate(document, digest); err != nil {
+		return nil, err
+	}
+	return document, nil
+}
+
+func (cache *IconCache) storeDisk(filePath string, document []byte) error {
+	directory := filepath.Dir(filePath)
+	if err := os.MkdirAll(directory, 0o700); err != nil {
+		return fmt.Errorf("create icon cache directory: %w", err)
+	}
+	info, err := os.Lstat(directory)
+	if err != nil {
+		return fmt.Errorf("inspect icon cache directory: %w", err)
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return fmt.Errorf("%w: root is not a real directory", ErrIconCacheUnsafe)
+	}
+
+	temporary, err := os.CreateTemp(directory, ".icon-*.tmp")
+	if err != nil {
+		return fmt.Errorf("create icon cache temp file: %w", err)
+	}
+	temporaryPath := temporary.Name()
+	defer os.Remove(temporaryPath)
+
+	if err := temporary.Chmod(0o600); err != nil {
+		temporary.Close()
+		return fmt.Errorf("protect icon cache temp file: %w", err)
+	}
+	if _, err := temporary.Write(document); err != nil {
+		temporary.Close()
+		return fmt.Errorf("write icon cache temp file: %w", err)
+	}
+	if err := temporary.Sync(); err != nil {
+		temporary.Close()
+		return fmt.Errorf("sync icon cache temp file: %w", err)
+	}
+	if err := temporary.Close(); err != nil {
+		return fmt.Errorf("close icon cache temp file: %w", err)
+	}
+	if err := os.Rename(temporaryPath, filePath); err != nil {
+		return fmt.Errorf("activate icon cache entry: %w", err)
+	}
+	return nil
+}
+
+func cacheKey(request IconRequest) (digest string, key string, err error) {
+	const prefix = "sha256:"
+	if !strings.HasPrefix(request.Reference, prefix) {
+		return "", "", ErrIconReferenceInvalid
+	}
+	digest = strings.ToLower(strings.TrimPrefix(request.Reference, prefix))
+	decoded, decodeErr := hex.DecodeString(digest)
+	if decodeErr != nil || len(decoded) != sha256.Size || len(digest) != sha256.Size*2 {
+		return "", "", ErrIconReferenceInvalid
+	}
+	if request.DPI < 48 || request.DPI > 768 {
+		return "", "", ErrIconDPIInvalid
+	}
+	return digest, digest + "@" + strconv.Itoa(request.DPI), nil
+}
diff --git a/core/catalog/icon_cache_test.go b/core/catalog/icon_cache_test.go
new file mode 100644
index 0000000..0bba92e
--- /dev/null
+++ b/core/catalog/icon_cache_test.go
@@ -0,0 +1,248 @@
+package catalog
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"image"
+	"image/color"
+	"image/png"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestIconCacheUsesMemoryAndOfflineDisk(t *testing.T) {
+	document := testPNG(t, 16, 16)
+	request := iconRequest(document, 96)
+	fetchCalls := 0
+	root := t.TempDir()
+	cache := NewIconCache(root, IconFetchFunc(func(
+		context.Context,
+		IconRequest,
+	) ([]byte, error) {
+		fetchCalls++
+		return document, nil
+	}))
+
+	result, err := cache.Load(context.Background(), request)
+	if err != nil {
+		t.Fatalf("Load(remote) error = %v", err)
+	}
+	if result.Source != IconSourceRemote || fetchCalls != 1 {
+		t.Fatalf("remote result = %#v, fetchCalls=%d", result, fetchCalls)
+	}
+	result, err = cache.Load(context.Background(), request)
+	if err != nil {
+		t.Fatalf("Load(memory) error = %v", err)
+	}
+	if result.Source != IconSourceMemory || fetchCalls != 1 {
+		t.Fatalf("memory result = %#v, fetchCalls=%d", result, fetchCalls)
+	}
+
+	offline := errors.New("offline")
+	restarted := NewIconCache(root, IconFetchFunc(func(
+		context.Context,
+		IconRequest,
+	) ([]byte, error) {
+		return nil, offline
+	}))
+	result, err = restarted.Load(context.Background(), request)
+	if err != nil {
+		t.Fatalf("Load(disk) error = %v", err)
+	}
+	if result.Source != IconSourceDisk {
+		t.Fatalf("disk source = %q, want %q", result.Source, IconSourceDisk)
+	}
+}
+
+func TestIconCacheSeparatesDPIKeys(t *testing.T) {
+	document := testPNG(t, 16, 16)
+	fetchCalls := 0
+	root := t.TempDir()
+	cache := NewIconCache(root, IconFetchFunc(func(
+		context.Context,
+		IconRequest,
+	) ([]byte, error) {
+		fetchCalls++
+		return document, nil
+	}))
+
+	for _, dpi := range []int{96, 144} {
+		if _, err := cache.Load(context.Background(), iconRequest(document, dpi)); err != nil {
+			t.Fatalf("Load(%d DPI) error = %v", dpi, err)
+		}
+	}
+	if fetchCalls != 2 {
+		t.Fatalf("fetchCalls = %d, want 2", fetchCalls)
+	}
+	entries, err := os.ReadDir(root)
+	if err != nil {
+		t.Fatalf("ReadDir() error = %v", err)
+	}
+	if len(entries) != 2 {
+		t.Fatalf("disk entries = %d, want 2", len(entries))
+	}
+}
+
+func TestIconCacheRejectsUntrustedImages(t *testing.T) {
+	validDocument := testPNG(t, 16, 16)
+	tests := []struct {
+		name      string
+		request   IconRequest
+		document  []byte
+		wantErr   error
+		configure func(*IconCache)
+	}{
+		{
+			name:     "hash mismatch",
+			request:  iconRequest([]byte("different"), 96),
+			document: validDocument,
+			wantErr:  ErrIconHashMismatch,
+		},
+		{
+			name:     "invalid image",
+			request:  iconRequest([]byte("not an image"), 96),
+			document: []byte("not an image"),
+			wantErr:  ErrIconImageInvalid,
+		},
+		{
+			name:     "byte limit",
+			request:  iconRequest(validDocument, 96),
+			document: validDocument,
+			wantErr:  ErrIconTooLarge,
+			configure: func(cache *IconCache) {
+				cache.maxBytes = int64(len(validDocument) - 1)
+			},
+		},
+		{
+			name:     "dimension limit",
+			request:  iconRequest(validDocument, 96),
+			document: validDocument,
+			wantErr:  ErrIconTooLarge,
+			configure: func(cache *IconCache) {
+				cache.maxDimension = 8
+			},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			root := t.TempDir()
+			cache := NewIconCache(root, IconFetchFunc(func(
+				context.Context,
+				IconRequest,
+			) ([]byte, error) {
+				return test.document, nil
+			}))
+			if test.configure != nil {
+				test.configure(cache)
+			}
+			_, err := cache.Load(context.Background(), test.request)
+			if !errors.Is(err, test.wantErr) {
+				t.Fatalf("Load() error = %v, want %v", err, test.wantErr)
+			}
+			entries, readErr := os.ReadDir(root)
+			if readErr != nil {
+				t.Fatalf("ReadDir() error = %v", readErr)
+			}
+			if len(entries) != 0 {
+				t.Fatalf("invalid icon wrote %d disk entries", len(entries))
+			}
+		})
+	}
+}
+
+func TestIconCacheRepairsCorruptDiskAndReportsOfflineFailure(t *testing.T) {
+	document := testPNG(t, 16, 16)
+	request := iconRequest(document, 120)
+	root := t.TempDir()
+	online := NewIconCache(root, IconFetchFunc(func(
+		context.Context,
+		IconRequest,
+	) ([]byte, error) {
+		return document, nil
+	}))
+	if _, err := online.Load(context.Background(), request); err != nil {
+		t.Fatalf("Load(seed) error = %v", err)
+	}
+
+	entries, err := os.ReadDir(root)
+	if err != nil || len(entries) != 1 {
+		t.Fatalf("ReadDir() = %v, %v", entries, err)
+	}
+	filePath := filepath.Join(root, entries[0].Name())
+	if err := os.WriteFile(filePath, []byte("corrupt"), 0o600); err != nil {
+		t.Fatalf("WriteFile(corrupt) error = %v", err)
+	}
+
+	repairs := 0
+	repairing := NewIconCache(root, IconFetchFunc(func(
+		context.Context,
+		IconRequest,
+	) ([]byte, error) {
+		repairs++
+		return document, nil
+	}))
+	result, err := repairing.Load(context.Background(), request)
+	if err != nil {
+		t.Fatalf("Load(repair) error = %v", err)
+	}
+	if result.Source != IconSourceRemote || repairs != 1 {
+		t.Fatalf("repair result = %#v, repairs=%d", result, repairs)
+	}
+
+	if err := os.WriteFile(filePath, []byte("corrupt again"), 0o600); err != nil {
+		t.Fatalf("WriteFile(corrupt again) error = %v", err)
+	}
+	offline := NewIconCache(root, IconFetchFunc(func(
+		context.Context,
+		IconRequest,
+	) ([]byte, error) {
+		return nil, errors.New("offline")
+	}))
+	_, err = offline.Load(context.Background(), request)
+	if !errors.Is(err, ErrNoValidIcon) {
+		t.Fatalf("Load(offline corrupt) error = %v, want %v", err, ErrNoValidIcon)
+	}
+}
+
+func TestDecodeIcon(t *testing.T) {
+	document := testPNG(t, 8, 8)
+	decoded, err := DecodeIcon(document)
+	if err != nil {
+		t.Fatalf("DecodeIcon() error = %v", err)
+	}
+	if decoded.Bounds().Dx() != 8 || decoded.Bounds().Dy() != 8 {
+		t.Fatalf("Bounds = %v", decoded.Bounds())
+	}
+}
+
+func iconRequest(document []byte, dpi int) IconRequest {
+	digest := sha256.Sum256(document)
+	return IconRequest{
+		Reference: "sha256:" + hex.EncodeToString(digest[:]),
+		DPI:       dpi,
+	}
+}
+
+func testPNG(t *testing.T, width, height int) []byte {
+	t.Helper()
+	source := image.NewNRGBA(image.Rect(0, 0, width, height))
+	for y := 0; y < height; y++ {
+		for x := 0; x < width; x++ {
+			source.SetNRGBA(x, y, color.NRGBA{
+				R: uint8(x),
+				G: uint8(y),
+				B: 120,
+				A: 255,
+			})
+		}
+	}
+	var buffer bytes.Buffer
+	if err := png.Encode(&buffer, source); err != nil {
+		t.Fatalf("png.Encode() error = %v", err)
+	}
+	return buffer.Bytes()
+}
diff --git a/docs/04-architecture.md b/docs/04-architecture.md
index 3a3663b..61eca68 100644
--- a/docs/04-architecture.md
+++ b/docs/04-architecture.md
@@ -61,6 +61,8 @@ UI 固定交互模式:
 
 T-203 已把共享列表状态落在 `core/application.CatalogListModel`:源快照、搜索、单分类、all/installed/updates 视图和 selected app ID 都是无 IO 纯内存状态。两个 Gio 适配分别保存 Editor、`layout.List` 与以 app ID 为键的 Clickable;500 项 viewport 测试验证只布局可见行。主循环或后台用例通过 `SetItems` 替换准备好的快照,Layout 不扫描 installed-app.json、不获取 Catalog。
 
+T-204 图标链路为 `Catalog icon digest + DPI → IconFetcher → SHA-256/图片资源限制校验 → 原子磁盘缓存 → 内存字节 → 后台 DecodeIcon → UI ApplyIcon(paint.ImageOp)`。磁盘与远端都重新校验;断网只使用已验证磁盘缓存。两个详情右栏只读取 `CatalogListModel.SelectedItem` 与内存 ImageOp,关闭详情不清空筛选或列表位置。
+
 ## 三、仓库目录结构
 
 ```text
diff --git a/docs/api.md b/docs/api.md
index e64ebed..6ce8ece 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -76,6 +76,19 @@
 
 T-201 已把该签名域接入正式客户端加载链路并用客户端测试向量覆盖。`softbox-catalog` 发布端仍必须补跨实现向量测试;密钥 ID/轮换字段尚未定稿,在单公钥协议升级前不得另造签名域。
 
+### 1.2 图标内容引用与本地缓存
+
+Catalog `icon` v1 是 `sha256:<64 hex>` 内容引用,不是可直接请求的 URL。最终分发字段仍由发布端定稿;客户端通过注入的 IconFetcher 把引用解析为图标字节,不得在 UI 中拼接或猜测 URL。
+
+客户端缓存合约:
+
+1. 请求键为 `(icon digest, DPI)`;DPI 接受 48～768 的整数值。
+2. 加载顺序为内存 → 磁盘 → 注入 Fetcher;磁盘文件名为 `<digest>-<dpi>.icon`。
+3. 远端和磁盘字节都必须复核 SHA-256,并通过图片解码、2 MiB 默认字节上限与 2048×2048 默认尺寸上限。
+4. 只有验证成功的远端字节可用同目录临时文件原子写入磁盘;损坏的普通缓存文件删除后可重新获取,symlink/非普通文件按不安全布局拒绝。
+5. 新进程断网时可读取再次验证成功的磁盘缓存;缓存损坏且远端不可用时返回 `no valid icon available`,UI 使用稳定占位图。
+6. 后台完成 `IconCache.Load` 与 `DecodeIcon` 后调用 Gio `ApplyIcon`;Layout 只复用内存 `paint.ImageOp`。
+
 ## 2. 标准软件包协议 v1(ZIP)
 
 ```text
@@ -267,6 +280,6 @@ V1.1:命名管道 `\\.\pipe\softbox.<app-id>`,盒子发送 `{"command": "prepare
 
 - 清单密钥 ID/轮换字段定稿后同步 `schemas/`。
 - 错误码完整枚举表。
-- 图标资源的分发方式(内嵌哈希 vs 独立 URL)。
+- 图标资源从内容哈希到下载位置/分辨率变体的发布端映射格式。
 - 撤销名单的结构与宽限期时长。
 - machine_hash 的标识来源清单与加权算法(平台层内部文档)。
diff --git a/docs/current-state.md b/docs/current-state.md
index 0d7a51e..a7be0b8 100644
--- a/docs/current-state.md
+++ b/docs/current-state.md
@@ -13,26 +13,26 @@
 ## 当前快照
 
 - 日期:2026-07-16
-- 阶段:Phase 2 进行中;T-201～T-203 已完成,下一步 T-204 软件详情与图标缓存
+- 阶段:Phase 2 已完成(T-201～T-204);下一步 Phase 3 的 T-301 下载队列
 - 技术栈:根 Go workspace 纳入 core/app-modern/app-win7 三模块;`app-win7/go.work` 隔离 Go 1.20.14 构建;modern Gio v0.10.1 与 win7 Gio v0.6.0 已实际接入
-- 生产代码:core 已有 Catalog/本地状态/存储与无 IO 软件列表模型;modern/win7 AppShell 已实现搜索、分类、全部/已安装/可更新切换和惰性软件列表;安装安全原型保持可用
-- 测试:core 覆盖 Catalog、SemVer/12 状态、本地安装记录与列表筛选;两个 app 覆盖 AppShell、500 项虚拟列表、ID 控件稳定性与平台 stub;ZIP/安装恢复矩阵保持通过
+- 生产代码:core 已有 Catalog/本地状态/存储、无 IO 软件列表模型与按 digest+DPI 的可信图标缓存;modern/win7 AppShell 已实现搜索/分类/视图、惰性列表、详情右栏与内存图标
+- 测试:core 覆盖 Catalog、SemVer/12 状态、本地安装记录、列表筛选和图标内存/磁盘/离线/损坏恢复;两个 app 覆盖 500 项虚拟列表、ID 控件稳定性、详情/ApplyIcon 与平台 stub;ZIP/安装恢复矩阵保持通过
 - 数据:`schemas/` 已有 manifest/app.json/installed-app.json v1 Schema;`testdata/catalog/` 有公开虚构清单样例;`testdata/zip/` 记录运行时生成的 ZIP 攻击矩阵
 - 标准启动路径:`./init.sh` / `./init.ps1`(同步依赖、执行完整 Phase 0 闸门、打印双目标构建命令)
 - 标准验证路径:`bash scripts/verify_phase0.sh` / `./scripts/verify_phase0.ps1`
 - 版本管理:git 已初始化,main 分支,远端 origin 为 Gitea `opc/soft_quay`;harness 文档已提交
-- 当前 blocker:无;下一步按路线图落成并领取 T-204
+- 当前 blocker:无;下一步按路线图落成并领取 T-301
 
 ## 当前目录要点
 
 | 路径 | 状态 | 说明 |
 | --- | --- | --- |
 | `docs/` | 已有 | harness coding 文档集(本次初始化完成) |
-| `docs/tasks/` | 已有 | Phase 0、Phase 1 与 T-201～T-203 已完成;T-204 待按路线图落成 |
+| `docs/tasks/` | 已有 | Phase 0、Phase 1 与 Phase 2 任务均已完成;T-301 待按路线图落成 |
 | `scripts/` | 已有 | harness 治理、core 边界、Go 版本检查与 Phase 0 双平台验证入口 |
-| `core/` | 已建 | Go 1.20 兼容;已有状态/事件、正式 Catalog、本地安装状态/存储与 Phase 1 安装安全原型 |
-| `app-modern/` | 已建 | Go 1.25.0 + Gio v0.10.1;Modern AppShell 已接入虚拟软件列表 |
-| `app-win7/` | 已建 | Go 1.20 + Gio v0.6.0;Legacy AppShell 已接入低成本虚拟软件列表 |
+| `core/` | 已建 | Go 1.20 兼容;已有正式 Catalog、本地状态/存储、列表模型、图标缓存与 Phase 1 安装安全原型 |
+| `app-modern/` | 已建 | Go 1.25.0 + Gio v0.10.1;Modern AppShell 已接入虚拟列表、详情和内存图标 |
+| `app-win7/` | 已建 | Go 1.20 + Gio v0.6.0;Legacy AppShell 已接入低成本列表、详情和内存图标 |
 | `schemas/` | 已建 | `manifest.schema.json`、`app.schema.json` 与 `installed-app.schema.json` |
 | `testdata/` | 已建 | 当前包含 Catalog 假数据与恶意样例;后续任务继续扩展 |
 
@@ -40,9 +40,9 @@
 
 任务状态以 `docs/tasks/` 各任务文件 frontmatter 的 `status` 为准。本节只写项目级摘要:
 
-- 已完成:Phase 0 的 `T-001`～`T-004`;Phase 1 的 `T-101`、`T-102`、`T-103`;Phase 2 的 `T-201`、`T-202`、`T-203`。
+- 已完成:Phase 0 的 `T-001`～`T-004`;Phase 1 的 `T-101`、`T-102`、`T-103`;Phase 2 的 `T-201`～`T-204`。
 - 正在进行:无。
-- 下一个可领取任务:按路线图落成并领取 `T-204 软件详情与图标缓存`。
+- 下一个可领取任务:按路线图落成并领取 `T-301 下载队列`。
 
 ## 当前可运行内容
 
diff --git a/docs/routes.md b/docs/routes.md
index a706b8d..dbf355e 100644
--- a/docs/routes.md
+++ b/docs/routes.md
@@ -24,7 +24,7 @@
 | 视图 | 职责 | MVP |
 | --- | --- | --- |
 | 软件列表(主视图) | T-203 已实现全部/已安装/可更新切换、名称/ID/tag 即时搜索、单分类筛选、稳定滚动与明确空状态;下载中/最近使用和多标签复选随对应用例后续接入 | P0 |
-| 软件详情(弹层或右栏) | 版本、简介、教程链接、授权状态;下载/更新/启动/取消操作 | P0 |
+| 软件详情(弹层或右栏) | T-204 已实现右栏、关闭、版本/分类/简介/tags/状态/不可用原因/教程/主页展示与内存图标;真实操作和授权事实随对应模块接入 | P0 |
 | 下载队列 | 所有任务的进度、速度、剩余时间;暂停/取消/重试 | P0 |
 | 设置 | 并发数、目录、代理、自动检查更新、beta 通道、日志级别、便携模式(V2) | P0(最小集) |
 | 授权 | 许可证导入、已授权软件列表、machine 信息、换绑/申诉入口 | P0 |
@@ -61,6 +61,13 @@ T-203 已落地的列表交互约束:
 - 行 Clickable 保存在以 app ID 为键的 map;筛选、视图切换或 Catalog 快照更新不按可见序号迁移控件状态。
 - 无 Catalog 与过滤无结果是两个不同空状态;后者提供“显示全部软件”恢复操作。
 
+T-204 已落地的详情/图标约束:
+
+- 点击软件行用 selected app ID 打开右侧详情,关闭后回到同一列表/筛选/滚动上下文。
+- modern 与 Legacy 均显示版本、分类、简介、tags、状态、不可用原因、教程和主页文本;尚未接入的安装/启动/授权不伪装为已可执行操作。
+- 后台把已验证图标解码为 `image.Image` 后调用 `ApplyIcon`;该方法预建 `paint.ImageOp`,列表与详情 Layout 只绘制内存操作。
+- 图标未命中或离线缓存不可用时显示非 emoji 的字母占位,不阻塞列表或详情。
+
 ## 导航规则
 
 - 列表 → 详情:点击软件项;详情保留返回/关闭。
diff --git a/docs/tasks/T-204.md b/docs/tasks/T-204.md
new file mode 100644
index 0000000..3ea7155
--- /dev/null
+++ b/docs/tasks/T-204.md
@@ -0,0 +1,71 @@
+---
+id: T-204
+title: 软件详情与图标缓存
+phase: 2
+deps: [T-203]
+status: DONE
+created: 2026-07-16
+issue: null
+context_ref: db8d93e84337489a1a138a6f624df359add3ed36
+claim_branch: null
+work_branch: agent/codex/T-204
+write_paths:
+  - docs/tasks/T-204.md
+  - core/catalog/
+  - core/application/
+  - app-modern/ui/gio/
+  - app-win7/ui/gio/
+  - docs/api.md
+  - docs/routes.md
+  - docs/04-architecture.md
+  - docs/current-state.md
+---
+
+## 问题 / 背景
+
+软件行已经可选择，但还没有详情视图，也没有可信图标的后台缓存链路。若 Gio Layout 自行读文件、解码或请求图标，会直接违反每帧无 IO 约束；若磁盘图标不复核 Catalog 内容哈希，损坏或替换的缓存也可能被展示。
+
+## 方案
+
+1. 在 `core/catalog` 建立 IconCache：以 `sha256:<digest>` + DPI 为键，按内存 → 磁盘 → 注入 Fetcher 顺序加载。
+2. 远端图标必须满足大小上限、SHA-256 与可解码图片/尺寸上限后才能原子写入磁盘；磁盘命中同样复核哈希与图片头。
+3. 磁盘文件按 digest + DPI 隔离；新进程在 Fetcher 离线时仍可读取已验证缓存。
+4. `CatalogListItem` 补充 icon/homepage/tutorial 数据与 selected item 查询。
+5. modern/win7 在选中软件时显示右侧详情面板，含关闭、版本、分类、简介、tags、状态、不可用原因和教程/主页信息。
+6. UI 只提供 `ApplyIcon(appID, image.Image)` 接收后台已解码结果；Layout 仅绘制内存图像，未命中时显示字母占位。
+
+## 验收要点
+
+- 同一 digest+DPI 首次远端加载，随后内存命中；新 cache 实例断网时可从磁盘命中。
+- 不同 DPI 使用不同磁盘键；哈希不符、超限、不可解码/超尺寸图标不写缓存。
+- 损坏磁盘缓存不会被返回；有网络时可重新获取修复，离线时返回明确错误。
+- 点击行后详情右栏可见且可关闭；列表/详情均能显示后台 ApplyIcon 的内存图像或稳定占位。
+- 两个 Gio Layout 中无磁盘、网络、哈希或图片解码。
+- Go 1.20 core vet/test、modern/win7 UI 测试与构建、完整闸门和治理校验通过。
+
+## 边界（不改什么）
+
+- 不决定图标 URL/变体的最终 Catalog 字段；Fetcher 由装配层按发布端协议注入。
+- 不实现网络请求装配、图片缩放生成、LRU/容量淘汰或 CDN 缓存策略。
+- 不实现真实下载/安装/启动动作和许可证详情；详情只展示当前可用事实与后续操作语义。
+- 不在 UI 中调用 image.Decode、os、http 或 sha256。
+
+## 协作约束
+
+未启用 Gitea；本任务在 `agent/codex/T-204` 分支串行执行。延续 `ui-ux-pro-max` 的扁平高对比、44dp、清晰返回/关闭、上下文保留和无昂贵 Layout 工作约束。
+
+## 执行记录
+
+- 2026-07-16:在 `core/catalog` 建立 IconCache；键为规范化 SHA-256 digest + DPI，加载顺序为 memory → verified disk → injected fetcher，返回 source 与非致命磁盘写 warning。
+- 2026-07-16:远端和磁盘统一复核内容哈希、图片完整解码、默认 2 MiB 与 2048×2048 上限；只把验证成功字节用同目录临时文件原子写入，symlink/非普通缓存项拒绝。
+- 2026-07-16:测试覆盖首次 remote、随后 memory、新实例断网 disk、96/144 DPI 分盘、哈希不符、非法图片、字节/尺寸超限、坏磁盘在线修复与坏磁盘离线明确失败。
+- 2026-07-16:`CatalogListItem` 增加 IconRef/Homepage/Tutorial 与 SelectedItem 查询；筛选/滚动上下文不因打开或关闭详情而重置。
+- 2026-07-16:modern/win7 均实现右侧详情、明确“关闭”文字按钮、版本/分类/简介/tags/状态/不可用原因/教程/主页展示；未接入的安装/启动/授权没有伪装为可执行动作。
+- 2026-07-16:两个 Gio 适配增加 `ApplyIcon(appID, image.Image)`，在调用时预建 `paint.ImageOp`；列表和详情每帧只复用内存绘制操作，未命中使用非 emoji 字母占位。
+- 2026-07-16:按 `ui-ux-pro-max` 交付复查确认关闭按钮有可访问文字名、返回保持上下文，详情延续高对比扁平/44dp 交互体系。
+- 2026-07-16:同步 `docs/api.md`、`docs/routes.md`、`docs/04-architecture.md` 与 `docs/current-state.md`；图标下载位置/分辨率映射仍明确留给发布端协议，客户端不猜 URL。
+- 定向验证通过:`go -C core test -count=1 ./catalog ./application`、modern/win7 `go test -count=1 ./ui/gio`。
+- Layout IO/解码扫描通过:`rg` 检查两个 `ui/gio` 下无 `image.Decode`、`os`、`net/http`、文件读写、filepath 或 sha256 调用。
+- 完整验证通过:`./scripts/verify_phase0.ps1`，包含 Go 1.20.14 core vet/test、治理/边界/版本检查及 modern/win7 双目标测试与构建。
+- 提交前检查通过:`git diff --check`。
+- 工作区中的未跟踪 `soft_quay.code-workspace` 与本任务无关，已保留且未纳入提交。