diff --git a/lib/api.js b/lib/api.js
index 8f83da9..802cd69 100644
--- a/lib/api.js
+++ b/lib/api.js
@@ -633,7 +633,12 @@ function createExternalApi(deps) {
       const urlNorm = blacklist.normalizeUrl(b.quelle_url || '') || null;
       const anzeigeDatum = sanitizeInput(b.anzeige_datum || '');
       const kontaktEmail = sanitizeInput(b.kontakt_email || '');
-      // Column order matches the UPDATE/INSERT statements below (url_norm last).
+      // Company slug: stored as supplied by the client; derived from firma only
+      // when omitted. This is the key the blacklist matches on (see below).
+      const firmaSlug = b.firma_slug != null && String(b.firma_slug).trim() !== ''
+        ? sanitizeInput(String(b.firma_slug))
+        : (blacklist.firmaSlug(b.firma) || null);
+      // Column order matches the UPDATE/INSERT statements below (firma_slug last).
       const fields = [
         sanitizeInput(b.firma),
         sanitizeInput(b.stelle),
@@ -649,6 +654,7 @@ function createExternalApi(deps) {
         sanitizeInput(b.status || 'offen'),
         serializeLabels(b.labels),
         urlNorm,
+        firmaSlug,
       ];
 
       // De-dup: prefer a (quelle, external_id) match, else the same normalized
@@ -671,7 +677,7 @@ function createExternalApi(deps) {
         await dbRun(
           `UPDATE jobangebote SET firma = ?, stelle = ?, ort = ?, adresse = ?, ansprechpartner = ?, gehalt = ?,
              beschreibung = ?, quelle_url = ?, art = ?, anzeige_datum = ?, kontakt_email = ?, status = ?,
-             labels = ?, url_norm = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?`,
+             labels = ?, url_norm = ?, firma_slug = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?`,
           [...fields, existing.id]
         );
         const row = await dbGet('SELECT * FROM jobangebote WHERE id = ?', [existing.id]);
@@ -680,8 +686,8 @@ function createExternalApi(deps) {
 
       const result = await dbRun(
         `INSERT INTO jobangebote
-           (external_id, quelle, firma, stelle, ort, adresse, ansprechpartner, gehalt, beschreibung, quelle_url, art, anzeige_datum, kontakt_email, status, labels, url_norm)
-         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+           (external_id, quelle, firma, stelle, ort, adresse, ansprechpartner, gehalt, beschreibung, quelle_url, art, anzeige_datum, kontakt_email, status, labels, url_norm, firma_slug)
+         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
         [externalId, quelle, ...fields]
       );
       const row = await dbGet('SELECT * FROM jobangebote WHERE id = ?', [result.lastID]);
diff --git a/lib/blacklist.js b/lib/blacklist.js
index 1bf56ac..7b127bd 100644
--- a/lib/blacklist.js
+++ b/lib/blacklist.js
@@ -130,7 +130,9 @@ function offerSignature(offer) {
     external_id: o.external_id != null && String(o.external_id).trim() !== ''
       ? String(o.external_id).trim() : null,
     firma_norm: normText(o.firma),
-    firma_slug: firmaSlug(o.firma),
+    // Prefer a client-supplied slug (offers carry firma_slug); else derive it.
+    firma_slug: o.firma_slug != null && String(o.firma_slug).trim() !== ''
+      ? String(o.firma_slug).trim() : firmaSlug(o.firma),
     stelle_norm: normText(o.stelle),
     ort_norm: normText(o.ort),
   };
diff --git a/lib/openapi.js b/lib/openapi.js
index c1ca45e..28e39bd 100644
--- a/lib/openapi.js
+++ b/lib/openapi.js
@@ -887,6 +887,7 @@ function buildOpenApiSpec(baseUrl = '') {
             labels: { ...labelsSchema, nullable: true },
             verknuepfte_bewerbung_id: { type: 'integer', nullable: true },
             url_norm: { type: 'string', nullable: true, description: 'Normalisierte URL für die De-Duplizierung (serverseitig gesetzt)' },
+            firma_slug: { type: 'string', nullable: true, description: 'Firmen-Slug für Blacklist-Abgleich; wie übergeben gespeichert, bei Fehlen aus firma abgeleitet.' },
             created_at: { type: 'string', format: 'date-time' },
             updated_at: { type: 'string', format: 'date-time' },
           },
@@ -905,6 +906,7 @@ function buildOpenApiSpec(baseUrl = '') {
             gehalt: { type: 'string' },
             beschreibung: { type: 'string', description: 'Stellenbeschreibungstext' },
             quelle_url: { type: 'string' },
+            firma_slug: { type: 'string', description: 'Optionaler Firmen-Slug für den Blacklist-Abgleich (z. B. "bosch"). Wird wie übergeben gespeichert; fehlt er, leitet der Server ihn aus firma ab.' },
             art: { type: 'string', enum: ART_OPTIONS },
             anzeige_datum: { type: 'string', format: 'date', description: 'Datum der eigentlichen Stellenanzeige (ISO YYYY-MM-DD)' },
             kontakt_email: { type: 'string', format: 'email', description: 'Kontakt-E-Mail-Adresse der Stelle' },
diff --git a/server.js b/server.js
index 43c2353..5aa7805 100644
--- a/server.js
+++ b/server.js
@@ -803,6 +803,19 @@ function initializeDatabase() {
             });
           });
           db.run('CREATE INDEX IF NOT EXISTS idx_jobangebote_url_norm ON jobangebote(url_norm)', () => {});
+          // Company slug carried on the offer itself (supplied by the indexing
+          // client, else derived from firma). Used for blacklist matching and
+          // "same company" grouping. Backfill derives it from firma.
+          db.run('ALTER TABLE jobangebote ADD COLUMN firma_slug TEXT', () => {
+            db.all('SELECT id, firma FROM jobangebote WHERE firma_slug IS NULL AND firma IS NOT NULL AND firma != ""', (err, rows) => {
+              if (err || !rows) return;
+              rows.forEach((r) => {
+                const slug = blacklist.firmaSlug(r.firma);
+                if (slug) db.run('UPDATE jobangebote SET firma_slug = ? WHERE id = ?', [slug, r.id], () => {});
+              });
+            });
+          });
+          db.run('CREATE INDEX IF NOT EXISTS idx_jobangebote_firma_slug ON jobangebote(firma_slug)', () => {});
           // Blacklist of job offers that must never (re)appear in the list. A
           // deleted offer is auto-blacklisted; manual entries can block a URL,
           // a whole domain, a company, or a specific company+title posting.