diff --git a/backend/internal/web/ui/app.css b/backend/internal/web/ui/app.css
index 944aad6..edf1f46 100644
--- a/backend/internal/web/ui/app.css
+++ b/backend/internal/web/ui/app.css
@@ -352,6 +352,7 @@
   margin-bottom: 1.5rem;
 }
 
+.overview-section-heading h1,
 .overview-section-heading h3,
 .tasks-section-header h3 {
   color: var(--color-surface-muted-inverse);
@@ -700,3 +701,61 @@
   font-style: italic;
   padding: 0.75rem 1rem;
 }
+
+/* ============================================================
+   Section 26 — Discussion message bubbles (Phase 17)
+   ============================================================ */
+
+.message-row {
+  display: flex;
+  flex-direction: column;
+  padding: 0.75rem 1rem;
+}
+
+.message-row.message-own {
+  align-items: flex-end;
+}
+
+.message-row.message-other {
+  align-items: flex-start;
+}
+
+.message-meta {
+  display: flex;
+  align-items: baseline;
+  gap: 0.5rem;
+  margin-bottom: 0.25rem;
+}
+
+.message-author {
+  color: var(--color-text-primary);
+  font-size: 0.875rem;
+  font-weight: 600;
+}
+
+.message-timestamp {
+  color: var(--color-text-muted);
+  font-size: 0.75rem;
+}
+
+.message-bubble {
+  border-radius: 0.25rem 0.75rem 0.75rem 0.75rem;
+  font-size: 1rem;
+  line-height: 1.5;
+  max-width: 70%;
+  padding: 0.75rem 1rem;
+  white-space: pre-wrap;
+  word-break: break-words;
+}
+
+.message-row.message-own .message-bubble {
+  background-color: rgba(128, 78, 236, 0.10);
+  border-radius: 0.75rem 0.75rem 0.25rem 0.75rem;
+  color: var(--color-text-primary);
+}
+
+.message-row.message-other .message-bubble {
+  background-color: var(--color-surface-default, #ffffff);
+  border: 1px solid var(--color-border-default, #e2e8f0);
+  color: var(--color-text-primary);
+}
diff --git a/backend/templates/discussion.templ b/backend/templates/discussion.templ
index 500b0ae..a9f9cc0 100644
--- a/backend/templates/discussion.templ
+++ b/backend/templates/discussion.templ
@@ -15,18 +15,16 @@ templ DiscussionTabFragment(tablo sqlc.Tablo, data DiscussionTabData, form Discu
 				<p class="mt-1 text-sm text-slate-600">1 participant</p>
 			</div>
 		</div>
-		<div id="discussion-messages" class="rounded border border-slate-200 bg-white">
+		<div id="discussion-messages" class="ui-card">
 			if len(data.Messages) == 0 {
 				@DiscussionEmptyState()
 			} else {
-				<div class="divide-y divide-slate-100">
-					for i, message := range data.Messages {
-						if DiscussionShowDaySeparator(data.Messages, i) {
-							@DiscussionDaySeparator(message.CreatedAt)
-						}
-						@DiscussionMessageRow(message)
+				for i, message := range data.Messages {
+					if DiscussionShowDaySeparator(data.Messages, i) {
+						@DiscussionDaySeparator(message.CreatedAt)
 					}
-				</div>
+					@DiscussionMessageRow(message)
+				}
 			}
 		</div>
 		@DiscussionComposer(tablo, form, errs, csrfToken)
@@ -34,25 +32,25 @@ templ DiscussionTabFragment(tablo sqlc.Tablo, data DiscussionTabData, form Discu
 }
 
 templ DiscussionEmptyState() {
-	<div class="bg-slate-50 px-4 py-8 text-center">
+	<div class="ui-card-body py-8 text-center">
 		<h3 class="text-xl font-semibold leading-snug text-slate-800">No messages yet</h3>
 		<p class="mt-2 text-base text-slate-600">Start the discussion for this tablo.</p>
 	</div>
 }
 
 templ DiscussionDaySeparator(createdAt time.Time) {
-	<div class="bg-slate-50 px-4 py-3 text-center text-sm text-slate-500">
+	<div class="bg-slate-50 px-4 py-2 text-center text-sm text-slate-500" data-day-separator="true">
 		{ DiscussionDateLabel(createdAt) }
 	</div>
 }
 
 templ DiscussionMessageRow(message DiscussionMessageView) {
-	<article id={ "discussion-message-" + message.ID.String() } data-message-id={ message.ID.String() } class="px-4 py-3">
-		<div class="flex flex-wrap items-baseline gap-x-2 gap-y-1">
-			<span class="text-sm font-semibold text-slate-900">{ message.AuthorEmail }</span>
-			<time class="text-xs text-slate-500" datetime={ message.CreatedAt.Format(time.RFC3339) }>{ DiscussionTimestampLabel(message.CreatedAt) }</time>
+	<article id={ "discussion-message-" + message.ID.String() } data-message-id={ message.ID.String() } class="message-row message-other">
+		<div class="message-meta">
+			<span class="message-author">{ message.AuthorEmail }</span>
+			<time class="message-timestamp" datetime={ message.CreatedAt.Format(time.RFC3339) }>{ DiscussionTimestampLabel(message.CreatedAt) }</time>
 		</div>
-		<p class="mt-2 whitespace-pre-wrap break-words text-base leading-6 text-slate-900">{ message.Body }</p>
+		<div class="message-bubble">{ message.Body }</div>
 	</article>
 }
 
diff --git a/backend/templates/planning.templ b/backend/templates/planning.templ
index 6ec8d8a..f462f60 100644
--- a/backend/templates/planning.templ
+++ b/backend/templates/planning.templ
@@ -7,10 +7,10 @@ import (
 
 templ PlanningPage(user *auth.User, csrfToken string, activePath string, tablos []sqlc.Tablo, agenda PlanningAgenda) {
 	@AppLayout("Planning - Xtablo", user, csrfToken, activePath, tablos) {
-		<div class="space-y-6">
-			<div class="flex flex-wrap items-start justify-between gap-4">
+		<section class="overview-section">
+			<div class="overview-section-heading">
 				<div>
-					<h1 class="text-[28px] font-semibold leading-tight">Planning</h1>
+					<h1>Planning</h1>
 					<p class="mt-1 text-sm text-slate-600">{ agenda.RangeLabel }</p>
 				</div>
 				<nav class="flex flex-wrap items-center gap-2" aria-label="Planning navigation">
@@ -27,7 +27,7 @@ templ PlanningPage(user *auth.User, csrfToken string, activePath string, tablos
 				</nav>
 			</div>
 			if len(agenda.Events) == 0 {
-				<div class="border border-slate-200 bg-slate-50 px-4 py-12">
+				<div class="ui-card ui-card-body py-12 text-center">
 					<h2 class="text-xl font-semibold leading-snug text-slate-800">No events in this range</h2>
 					<p class="mt-2 text-base text-slate-600">Use the navigation controls to browse another 14-day window.</p>
 				</div>
@@ -38,7 +38,7 @@ templ PlanningPage(user *auth.User, csrfToken string, activePath string, tablos
 					}
 				</ul>
 			}
-		</div>
+		</section>
 	}
 }