diff --git a/fusion_accounting_followup/__manifest__.py b/fusion_accounting_followup/__manifest__.py
index 14adf203..da7aa950 100644
--- a/fusion_accounting_followup/__manifest__.py
+++ b/fusion_accounting_followup/__manifest__.py
@@ -1,6 +1,6 @@
 {
     'name': 'Fusion Accounting Follow-up',
-    'version': '19.0.1.0.18',
+    'version': '19.0.1.0.19',
     'category': 'Accounting/Accounting',
     'summary': 'AI-augmented customer follow-ups (dunning) for unpaid invoices.',
     'description': """
@@ -37,6 +37,9 @@ menu hides; the engine + AI tools remain available for the chat.
     ],
     'assets': {
         'web.assets_backend': [
+            'fusion_accounting_followup/static/src/scss/_variables.scss',
+            'fusion_accounting_followup/static/src/scss/followup.scss',
+            'fusion_accounting_followup/static/src/scss/dark_mode.scss',
         ],
     },
     'installable': True,
diff --git a/fusion_accounting_followup/static/src/scss/_variables.scss b/fusion_accounting_followup/static/src/scss/_variables.scss
new file mode 100644
index 00000000..cb3d8f85
--- /dev/null
+++ b/fusion_accounting_followup/static/src/scss/_variables.scss
@@ -0,0 +1,51 @@
+// Fusion follow-up design tokens (extends Phases 1-3 tokens for consistency).
+
+$fu-bg-primary: #ffffff;
+$fu-bg-secondary: #f9fafb;
+$fu-bg-tertiary: #f3f4f6;
+$fu-border: #e5e7eb;
+$fu-text-primary: #111827;
+$fu-text-secondary: #6b7280;
+$fu-text-muted: #9ca3af;
+$fu-accent: #3b82f6;
+$fu-accent-bg: #eff6ff;
+
+// Status colors
+$fu-status-no-action: #6b7280;
+$fu-status-action-due: #f59e0b;
+$fu-status-paused: #6366f1;
+$fu-status-blocked: #ef4444;
+$fu-status-with-credit: #8b5cf6;
+
+// Risk band colors
+$fu-risk-low: #10b981;
+$fu-risk-low-bg: #ecfdf5;
+$fu-risk-medium: #f59e0b;
+$fu-risk-medium-bg: #fffbeb;
+$fu-risk-high: #ef4444;
+$fu-risk-high-bg: #fef2f2;
+$fu-risk-critical: #b91c1c;
+$fu-risk-critical-bg: #fef2f2;
+
+// Aging bucket colors (escalating intensity)
+$fu-bucket-current: #10b981;
+$fu-bucket-1-30: #fbbf24;
+$fu-bucket-31-60: #f59e0b;
+$fu-bucket-61-90: #ef4444;
+$fu-bucket-91-120: #dc2626;
+$fu-bucket-120-plus: #7f1d1d;
+
+$fu-space-1: 0.25rem;
+$fu-space-2: 0.5rem;
+$fu-space-3: 0.75rem;
+$fu-space-4: 1rem;
+$fu-space-6: 1.5rem;
+
+$fu-font-size-xs: 0.75rem;
+$fu-font-size-sm: 0.875rem;
+$fu-font-size-base: 1rem;
+$fu-font-size-lg: 1.125rem;
+$fu-font-size-xl: 1.25rem;
+
+$fu-border-radius: 0.375rem;
+$fu-border-radius-md: 0.5rem;
diff --git a/fusion_accounting_followup/static/src/scss/dark_mode.scss b/fusion_accounting_followup/static/src/scss/dark_mode.scss
new file mode 100644
index 00000000..25950570
--- /dev/null
+++ b/fusion_accounting_followup/static/src/scss/dark_mode.scss
@@ -0,0 +1,27 @@
+// Variables come from _variables.scss (loaded first in the asset bundle).
+
+[data-color-scheme="dark"] .o_fusion_followup {
+    background: #1f2937; color: #f9fafb;
+
+    &_header, &_card, .fu-ai-text-panel {
+        background: #111827; border-color: #374151; color: #f9fafb;
+    }
+
+    &_card {
+        &:hover { border-color: #60a5fa; }
+        &.selected { background: #1e3a8a; border-color: #60a5fa; }
+        .partner-numbers .label { color: #9ca3af; }
+        .partner-numbers .value { color: #f9fafb; }
+    }
+
+    .btn_fu {
+        background: #374151; border-color: #4b5563; color: #f9fafb;
+        &:hover { background: #4b5563; }
+        &.primary { background: #3b82f6; }
+    }
+
+    .fu-ai-text-panel {
+        .ai-subject { background: #1e3a8a; }
+        .ai-body { background: #1f2937; }
+    }
+}
diff --git a/fusion_accounting_followup/static/src/scss/followup.scss b/fusion_accounting_followup/static/src/scss/followup.scss
new file mode 100644
index 00000000..8962e3dd
--- /dev/null
+++ b/fusion_accounting_followup/static/src/scss/followup.scss
@@ -0,0 +1,190 @@
+// Variables come from _variables.scss (loaded first in the asset bundle).
+
+.o_fusion_followup {
+    background: $fu-bg-secondary;
+    min-height: 100vh;
+
+    &_header {
+        background: $fu-bg-primary;
+        border-bottom: 1px solid $fu-border;
+        padding: $fu-space-4 $fu-space-6;
+        display: flex;
+        justify-content: space-between;
+        align-items: center;
+
+        h1 { font-size: $fu-font-size-xl; margin: 0; }
+
+        .summary {
+            display: flex;
+            gap: $fu-space-6;
+            font-size: $fu-font-size-sm;
+            color: $fu-text-secondary;
+
+            .summary-value {
+                font-weight: 600;
+                color: $fu-text-primary;
+                margin-left: $fu-space-1;
+            }
+        }
+    }
+
+    &_card {
+        background: $fu-bg-primary;
+        border: 1px solid $fu-border;
+        border-radius: $fu-border-radius-md;
+        padding: $fu-space-4;
+        margin-bottom: $fu-space-3;
+        cursor: pointer;
+        transition: all 200ms ease-in-out;
+
+        &:hover {
+            border-color: $fu-accent;
+            box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
+        }
+
+        &.selected {
+            border-color: $fu-accent;
+            background: $fu-accent-bg;
+        }
+
+        &_header {
+            display: flex;
+            justify-content: space-between;
+            align-items: flex-start;
+            margin-bottom: $fu-space-2;
+
+            .partner-name {
+                font-weight: 600;
+                font-size: $fu-font-size-base;
+            }
+        }
+
+        .partner-numbers {
+            display: grid;
+            grid-template-columns: 1fr 1fr;
+            gap: $fu-space-2;
+            font-size: $fu-font-size-sm;
+            color: $fu-text-secondary;
+
+            .label { font-weight: 500; margin-right: $fu-space-2; }
+            .value { color: $fu-text-primary; font-weight: 500; }
+        }
+    }
+
+    .btn_fu {
+        padding: $fu-space-2 $fu-space-4;
+        border-radius: $fu-border-radius;
+        background: $fu-bg-primary;
+        border: 1px solid $fu-border;
+        color: $fu-text-primary;
+        font-size: $fu-font-size-sm;
+        cursor: pointer;
+
+        &:hover { background: $fu-bg-tertiary; }
+        &.primary { background: $fu-accent; border-color: $fu-accent; color: white;
+                      &:hover { background: darken($fu-accent, 8%); } }
+        &.danger { background: $fu-status-blocked; border-color: $fu-status-blocked; color: white; }
+    }
+}
+
+.fu-status-badge {
+    padding: $fu-space-1 $fu-space-2;
+    border-radius: $fu-border-radius;
+    font-size: $fu-font-size-xs;
+    font-weight: 500;
+    text-transform: uppercase;
+
+    &[data-status="no_action"] { background: lighten($fu-status-no-action, 40%); color: $fu-status-no-action; }
+    &[data-status="action_due"] { background: lighten($fu-status-action-due, 35%); color: $fu-status-action-due; }
+    &[data-status="paused"] { background: lighten($fu-status-paused, 35%); color: $fu-status-paused; }
+    &[data-status="blocked"] { background: lighten($fu-status-blocked, 35%); color: $fu-status-blocked; }
+    &[data-status="with_credit_team"] { background: lighten($fu-status-with-credit, 35%); color: $fu-status-with-credit; }
+}
+
+.fu-risk-badge {
+    display: inline-flex;
+    align-items: center;
+    padding: $fu-space-1 $fu-space-2;
+    border-radius: $fu-border-radius;
+    font-weight: 600;
+    font-size: $fu-font-size-xs;
+
+    &[data-band="low"] { background: $fu-risk-low-bg; color: $fu-risk-low; }
+    &[data-band="medium"] { background: $fu-risk-medium-bg; color: $fu-risk-medium; }
+    &[data-band="high"] { background: $fu-risk-high-bg; color: $fu-risk-high; }
+    &[data-band="critical"] { background: $fu-risk-critical-bg; color: $fu-risk-critical; font-weight: 700; }
+}
+
+.fu-aging-strip {
+    display: flex;
+    gap: 2px;
+    height: 8px;
+    border-radius: $fu-border-radius;
+    overflow: hidden;
+    margin: $fu-space-2 0;
+
+    .bucket {
+        height: 100%;
+
+        &[data-name="current"] { background: $fu-bucket-current; }
+        &[data-name="1_30"] { background: $fu-bucket-1-30; }
+        &[data-name="31_60"] { background: $fu-bucket-31-60; }
+        &[data-name="61_90"] { background: $fu-bucket-61-90; }
+        &[data-name="91_120"] { background: $fu-bucket-91-120; }
+        &[data-name="120_plus"] { background: $fu-bucket-120-plus; }
+    }
+}
+
+.fu-ai-text-panel {
+    background: $fu-bg-primary;
+    border: 1px solid $fu-border;
+    border-radius: $fu-border-radius-md;
+    padding: $fu-space-4;
+
+    h5 { margin: 0 0 $fu-space-2; font-size: $fu-font-size-base; }
+
+    .ai-subject {
+        font-weight: 600;
+        margin-bottom: $fu-space-2;
+        padding: $fu-space-2;
+        background: $fu-accent-bg;
+        border-radius: $fu-border-radius;
+    }
+
+    .ai-body {
+        white-space: pre-wrap;
+        font-family: monospace;
+        font-size: $fu-font-size-sm;
+        padding: $fu-space-3;
+        background: $fu-bg-secondary;
+        border-radius: $fu-border-radius;
+        max-height: 300px;
+        overflow-y: auto;
+    }
+
+    .key-points {
+        margin-top: $fu-space-3;
+        font-size: $fu-font-size-sm;
+        color: $fu-text-secondary;
+
+        ul { margin: 0; padding-left: $fu-space-4; }
+    }
+}
+
+.fu-history-table {
+    width: 100%;
+    font-size: $fu-font-size-sm;
+
+    th {
+        background: $fu-bg-tertiary;
+        padding: $fu-space-2 $fu-space-3;
+        text-align: left;
+        font-weight: 600;
+        color: $fu-text-secondary;
+    }
+
+    td {
+        padding: $fu-space-2 $fu-space-3;
+        border-bottom: 1px solid lighten($fu-border, 5%);
+    }
+}