diff --git a/frontend/messages/de.json b/frontend/messages/de.json
index 91bc789d..001e4bab 100644
--- a/frontend/messages/de.json
+++ b/frontend/messages/de.json
@@ -1050,6 +1050,7 @@
 	"timeline_provenance_derived": "abgeleitet",
 	"timeline_provenance_curated": "kuratiert",
 	"timeline_letter_glyph_label": "Brief",
+	"timeline_tag_chip_label": "Thema",
 	"timeline_layer_historical_suffix": "historisch",
 	"timeline_strip_density_caption": "Monats-Dichte",
 	"timeline_events_count": "{count} Ereignisse",
diff --git a/frontend/messages/en.json b/frontend/messages/en.json
index b9add670..e34a27fb 100644
--- a/frontend/messages/en.json
+++ b/frontend/messages/en.json
@@ -1050,6 +1050,7 @@
 	"timeline_provenance_derived": "derived",
 	"timeline_provenance_curated": "curated",
 	"timeline_letter_glyph_label": "Letter",
+	"timeline_tag_chip_label": "Topic",
 	"timeline_layer_historical_suffix": "historical",
 	"timeline_strip_density_caption": "Monthly density",
 	"timeline_events_count": "{count} events",
diff --git a/frontend/messages/es.json b/frontend/messages/es.json
index f015c6d5..dfb5fc52 100644
--- a/frontend/messages/es.json
+++ b/frontend/messages/es.json
@@ -1050,6 +1050,7 @@
 	"timeline_provenance_derived": "derivado",
 	"timeline_provenance_curated": "curado",
 	"timeline_letter_glyph_label": "Carta",
+	"timeline_tag_chip_label": "Tema",
 	"timeline_layer_historical_suffix": "histórico",
 	"timeline_strip_density_caption": "Densidad mensual",
 	"timeline_events_count": "{count} eventos",
diff --git a/frontend/src/lib/messages.spec.ts b/frontend/src/lib/messages.spec.ts
index eadd4030..542a0d50 100644
--- a/frontend/src/lib/messages.spec.ts
+++ b/frontend/src/lib/messages.spec.ts
@@ -90,4 +90,12 @@ describe('message key parity', () => {
 			expect(es, `missing key in es: ${key}`).toHaveProperty(key);
 		}
 	});
+
+	// #835 REQ-013: the letter chip's sr-only theme label is a Paraglide key in every
+	// locale so color is never the only cue; the tag NAME is rendered as data, not translated.
+	it('zeitstrahl tag-chip label key is present in all locales (#835 REQ-013)', () => {
+		expect(de).toMatchObject({ timeline_tag_chip_label: 'Thema' });
+		expect(en).toMatchObject({ timeline_tag_chip_label: 'Topic' });
+		expect(es).toMatchObject({ timeline_tag_chip_label: 'Tema' });
+	});
 });