diff --git a/backend/00-router.go b/backend/00-router.go
index e029bbd..4b35186 100644
--- a/backend/00-router.go
+++ b/backend/00-router.go
@@ -43,9 +43,9 @@ func renderShell(w http.ResponseWriter, active, readingPane string) {
 	fmt.Fprintf(w, `<!doctype html><html lang="de"><head><meta charset="utf-8">
 <meta name="viewport" content="width=device-width,initial-scale=1">
 <title>Mail-Graveyard</title>
-<link rel="stylesheet" href="/static/style.css?v=20260706-5">
+<link rel="stylesheet" href="/static/style.css?v=20260706-6">
 <script src="/static/htmx.min.js"></script>
-<script src="/static/app.js?v=20260706-5" defer></script></head>
+<script src="/static/app.js?v=20260706-6" defer></script></head>
 <body class="ol2013">
 <header class="ribbon">
   <nav class="ribbon-tabs">
diff --git a/backend/08-viewer.go b/backend/08-viewer.go
index e26e786..b4530cd 100644
--- a/backend/08-viewer.go
+++ b/backend/08-viewer.go
@@ -286,7 +286,7 @@ func renderInitialSourceSelectPane(body string) string {
 	for _, opt := range sourceAccountOptions() {
 		fmt.Fprintf(&b, `<option value="%s">%s</option>`, html.EscapeString(opt.Value), html.EscapeString(opt.Label))
 	}
-	b.WriteString(`</select></form><button class="btn secondary compact" type="button" hx-get="/view/target/select" hx-target="#read" hx-swap="innerHTML">Ziel</button></div><div class="read-body">`)
+	b.WriteString(`</select></form><button class="btn secondary compact mode-toggle" type="button" title="Zur Zielansicht wechseln" aria-label="Zur Zielansicht wechseln" hx-get="/view/target/select" hx-target="#read" hx-swap="innerHTML"><span class="swap-icon">⇄</span></button></div><div class="read-body">`)
 	b.WriteString(body)
 	b.WriteString(`</div>`)
 	return b.String()
@@ -302,7 +302,7 @@ func renderInitialTargetSelectPane(selected string) string {
 		}
 		fmt.Fprintf(&b, `<option value="%s"%s>%s</option>`, html.EscapeString(opt.Value), attr, html.EscapeString(opt.Label))
 	}
-	b.WriteString(`</select></form><button class="btn secondary compact" type="button" hx-get="/view/source/select" hx-target="#read" hx-swap="innerHTML">Quelle</button></div><div class="read-body"><div class="ef-empty">Nachricht waehlen.</div></div>`)
+	b.WriteString(`</select></form><button class="btn secondary compact mode-toggle" type="button" title="Zur Quellenansicht wechseln" aria-label="Zur Quellenansicht wechseln" hx-get="/view/source/select" hx-target="#read" hx-swap="innerHTML"><span class="swap-icon">⇄</span></button></div><div class="read-body"><div class="ef-empty">Nachricht waehlen.</div></div>`)
 	return b.String()
 }
 
@@ -496,7 +496,7 @@ func renderTargetAccountSelect(account, folder, selected string, index int) stri
 		}
 		fmt.Fprintf(&b, `<option value="%s"%s>%s</option>`, html.EscapeString(opt.Value), attr, html.EscapeString(opt.Label))
 	}
-	fmt.Fprintf(&b, `</select></form><button class="btn secondary compact" type="button" hx-get="/view/message?source=%s&amp;folder=%s&amp;index=%d&amp;target_account=%s" hx-target="#read" hx-swap="innerHTML">Quelle</button></div>`,
+	fmt.Fprintf(&b, `</select></form><button class="btn secondary compact mode-toggle" type="button" title="Zur Quellenansicht wechseln" aria-label="Zur Quellenansicht wechseln" hx-get="/view/message?source=%s&amp;folder=%s&amp;index=%d&amp;target_account=%s" hx-target="#read" hx-swap="innerHTML"><span class="swap-icon">⇄</span></button></div>`,
 		urlEsc(sourceDisplayLabel(account)), urlEsc(folder), index, urlEsc(selected))
 	if account != "" && folder != "" && index >= 0 {
 		fmt.Fprintf(&b, `<div class="drop-zone" data-drop-target="manual-copy" data-source="%s" data-folder="%s" data-index="%d">Mail hier ablegen fuer manuellen Umzug</div>`,
@@ -520,7 +520,7 @@ func renderSourcePaneHead(account, folder, targetAccount string, index int) stri
 		}
 		fmt.Fprintf(&b, `<option value="%s"%s>%s</option>`, html.EscapeString(opt.Value), attr, html.EscapeString(opt.Label))
 	}
-	fmt.Fprintf(&b, `</select></form><button class="btn secondary compact" type="button" hx-get="/view/target?source=%s&amp;folder=%s&amp;index=%d&amp;target_account=%s" hx-target="#read" hx-swap="innerHTML">Ziel</button></div>`,
+	fmt.Fprintf(&b, `</select></form><button class="btn secondary compact mode-toggle" type="button" title="Zur Zielansicht wechseln" aria-label="Zur Zielansicht wechseln" hx-get="/view/target?source=%s&amp;folder=%s&amp;index=%d&amp;target_account=%s" hx-target="#read" hx-swap="innerHTML"><span class="swap-icon">⇄</span></button></div>`,
 		urlEsc(sourceDisplayLabel(account)), urlEsc(folder), index, urlEsc(targetAccount))
 	return b.String()
 }
diff --git a/frontend-js/dist/style.css b/frontend-js/dist/style.css
index 4411bc7..176d81f 100644
--- a/frontend-js/dist/style.css
+++ b/frontend-js/dist/style.css
@@ -186,6 +186,21 @@ a.tree-node { display: block; color: inherit; text-decoration: none; }
 .btn.secondary { background: #e1e1e1; color: var(--ol-text); border: 1px solid var(--ol-border); }
 .btn.secondary:hover { background: #d5d5d5; }
 .btn.compact { padding: 3px 9px; }
+.btn.mode-toggle {
+  width: 26px;
+  height: 26px;
+  padding: 0;
+  border-radius: 50%;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 15px;
+  line-height: 1;
+}
+.swap-icon {
+  display: block;
+  transform: translateY(-1px);
+}
 .input, select, textarea {
   border: 1px solid #abadb3; padding: 5px 7px; font: inherit; width: 100%;
   background: #fff;
