fix: eliminate banner color bleed by baking alpha into gradient colors

Replace element-level opacity on banner fallback divs with rgba-based
gradient color stops via new mutedGradient() utility. This prevents
compositing layer artifacts that caused visible color seams at the
banner boundary in AccountPanel, UserProfilePopout, and UserProfileModal.

packages/web/src/components/modals/UserProfileModal.tsx

@@ -8,7 +8,7 @@ import { useUIStore } from '../../stores/uiStore';
 import { useSpaceStore, getApiForOrigin, resolveUserOrigin } from '../../stores/spaceStore';
 import { useSocialStore, type TaggedFriend, type TaggedFriendRequest } from '../../stores/socialStore';
 import { useAuthStore } from '../../stores/authStore';
-import { getAvatarGradient, getSpaceGradient, adjustColor } from '../../utils/gradients';
+import { getAvatarGradient, getSpaceGradient, adjustColor, mutedGradient } from '../../utils/gradients';
 import { parseFederatedUsername, isSelf, canonicalUserMatch } from '../../utils/identity';
 import { loadFederatedMutuals, type TaggedMutualFriend, type MutualSpace } from '../../utils/mutuals';
 
@@ -149,8 +149,11 @@ export function UserProfileModal() {
     ? (user.banner.startsWith('http') ? user.banner : profileApi.uploads.url(user.banner))
     : null;
   const bannerFallback = user.accentColor
-    ? `linear-gradient(135deg, ${user.accentColor}, ${adjustColor(user.accentColor, -40)})`
-    : getAvatarGradient(user.homeUserId ?? user.id, displayName, user.avatarColor).gradient;
+    ? mutedGradient(user.accentColor, adjustColor(user.accentColor, -40))
+    : (() => {
+        const g = getAvatarGradient(user.homeUserId ?? user.id, displayName, user.avatarColor);
+        return mutedGradient(g.from, g.to);
+      })();
 
   const handleSendMessage = async () => {
     try {
@@ -236,7 +239,7 @@ export function UserProfileModal() {
           className="h-[100px] flex-shrink-0 relative"
           style={bannerSrc
             ? { backgroundImage: `url(${bannerSrc})`, backgroundSize: 'cover', backgroundPosition: 'center' }
-            : { background: bannerFallback, opacity: 0.6 }
+            : { background: bannerFallback }
           }
         >
           {/* Close button */}

packages/web/src/components/modals/settingsPanels/AccountPanel.tsx

@@ -3,7 +3,7 @@ import { useAuthStore } from '../../../stores/authStore';
 import { Avatar } from '../../ui/Avatar';
 import { ImageCropModal } from '../../ui/ImageCropModal';
 import { api } from '../../../api/client';
-import { getAvatarGradient, adjustColor, AVATAR_GRADIENT_MAP, BANNER_COLOR_PRESETS } from '../../../utils/gradients';
+import { getAvatarGradient, adjustColor, mutedGradient, AVATAR_GRADIENT_MAP, BANNER_COLOR_PRESETS } from '../../../utils/gradients';
 import { AVATAR_COLORS } from '@backspace/shared';
 import type { User, UserStatus, AvatarColor } from '@backspace/shared';
 
@@ -86,10 +86,13 @@ export function AccountPanel() {
     : null;
   const displayAvatarSrc = avatarPreview ?? (avatarFilename === '' ? null : currentAvatarSrc);
 
-  // Banner fallback: accent gradient or avatar gradient
+  // Banner fallback: accent gradient or avatar gradient (alpha baked into gradient colors)
   const bannerFallback = effectiveAccent
-    ? `linear-gradient(135deg, ${effectiveAccent}, ${adjustColor(effectiveAccent, -40)})`
-    : getAvatarGradient(user.homeUserId ?? user.id, effectiveDisplayName, effectiveAvatarColor).gradient;
+    ? mutedGradient(effectiveAccent, adjustColor(effectiveAccent, -40))
+    : (() => {
+        const g = getAvatarGradient(user.homeUserId ?? user.id, effectiveDisplayName, effectiveAvatarColor);
+        return mutedGradient(g.from, g.to);
+      })();
 
   // ── File selection handlers ──
   const handleAvatarSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
@@ -218,7 +221,7 @@ export function AccountPanel() {
             className="h-[80px]"
             style={displayBannerSrc
               ? { backgroundImage: `url(${displayBannerSrc})`, backgroundSize: 'cover', backgroundPosition: 'center' }
-              : { background: bannerFallback, opacity: 0.6 }
+              : { background: bannerFallback }
             }
           />
           {/* Avatar + info */}
@@ -339,7 +342,11 @@ export function AccountPanel() {
                 className="w-full h-full"
                 style={displayBannerSrc
                   ? { backgroundImage: `url(${displayBannerSrc})`, backgroundSize: 'cover', backgroundPosition: 'center' }
-                  : { background: bannerFallback, opacity: 0.5 }
+                  : { background: mutedGradient(
+                      effectiveAccent ?? getAvatarGradient(user.homeUserId ?? user.id, effectiveDisplayName, effectiveAvatarColor).from,
+                      effectiveAccent ? adjustColor(effectiveAccent, -40) : getAvatarGradient(user.homeUserId ?? user.id, effectiveDisplayName, effectiveAvatarColor).to,
+                      0.5
+                    ) }
                 }
               />
               <div className="absolute inset-0 bg-black/40 flex items-center justify-center opacity-0 group-hover:opacity-100 transition-opacity">

packages/web/src/components/ui/UserProfilePopout.tsx

@@ -6,7 +6,7 @@ import { Avatar } from '../ui/Avatar';
 import { Username } from '../ui/Username';
 import { useSpaceStore, getApiForOrigin, resolveUserOrigin } from '../../stores/spaceStore';
 import { useUIStore } from '../../stores/uiStore';
-import { getAvatarGradient, adjustColor } from '../../utils/gradients';
+import { getAvatarGradient, adjustColor, mutedGradient } from '../../utils/gradients';
 import { parseFederatedUsername } from '../../utils/identity';
 import { loadFederatedMutuals } from '../../utils/mutuals';
 
@@ -71,8 +71,11 @@ export function UserProfilePopout({ user, onClose, position }: UserProfilePopout
     ? (user.banner.startsWith('http') ? user.banner : userApi.uploads.url(user.banner))
     : null;
   const bannerFallback = user.accentColor
-    ? `linear-gradient(135deg, ${user.accentColor}, ${adjustColor(user.accentColor, -40)})`
-    : getAvatarGradient(user.homeUserId ?? user.id, displayName, user.avatarColor).gradient;
+    ? mutedGradient(user.accentColor, adjustColor(user.accentColor, -40))
+    : (() => {
+        const g = getAvatarGradient(user.homeUserId ?? user.id, displayName, user.avatarColor);
+        return mutedGradient(g.from, g.to);
+      })();
 
   return (
     <div
@@ -92,7 +95,7 @@ export function UserProfilePopout({ user, onClose, position }: UserProfilePopout
         className="h-[80px] rounded-t-[12px]"
         style={bannerSrc
           ? { backgroundImage: `url(${bannerSrc})`, backgroundSize: 'cover', backgroundPosition: 'center' }
-          : { background: bannerFallback, opacity: 0.6 }
+          : { background: bannerFallback }
         }
       />
 

packages/web/src/utils/gradients.ts

@@ -89,6 +89,19 @@ export const BANNER_COLOR_PRESETS: string[][] = [
 /** @deprecated Use BANNER_COLOR_PRESETS instead. */
 export const ACCENT_PRESETS: string[] = BANNER_COLOR_PRESETS.map(f => f[1]!);
 
+/** Convert 6-digit hex (#rrggbb) to rgba string. */
+export function hexToRgba(hex: string, alpha: number): string {
+  const r = parseInt(hex.slice(1, 3), 16);
+  const g = parseInt(hex.slice(3, 5), 16);
+  const b = parseInt(hex.slice(5, 7), 16);
+  return `rgba(${r},${g},${b},${alpha})`;
+}
+
+/** Build a banner-style muted gradient from two hex colors with baked-in alpha. */
+export function mutedGradient(from: string, to: string, alpha = 0.6): string {
+  return `linear-gradient(135deg, ${hexToRgba(from, alpha)}, ${hexToRgba(to, alpha)})`;
+}
+
 /** Shift each RGB component of a hex color by `amount` (positive = lighter, negative = darker). */
 export function adjustColor(hex: string, amount: number): string {
   const r = Math.max(0, Math.min(255, parseInt(hex.slice(1, 3), 16) + amount));