diff --git a/apps/api/prisma/migrations/20260721140000_tender_bundesland_backfill/migration.sql b/apps/api/prisma/migrations/20260721140000_tender_bundesland_backfill/migration.sql
new file mode 100644
index 0000000..ee52bdb
--- /dev/null
+++ b/apps/api/prisma/migrations/20260721140000_tender_bundesland_backfill/migration.sql
@@ -0,0 +1,39 @@
+-- FILTER-02 (Pitfall 1): Tender.bundesland is 100% NULL in the live DB
+-- (0/1671 rows, verified) because the Phase-10 normalizer deferred
+-- NUTS->Bundesland mapping to Phase 11. This migration:
+--   1. Adds the CREATE INDEX for bundesland (filter performance, matches
+--      schema.prisma @@index([bundesland])).
+--   2. Backfills the ~1671 pre-existing rows by deriving bundesland from
+--      the region column's NUTS-1 prefix (DE1..DEG -> the 16 Bundesländer),
+--      mirroring geo/nuts-bundesland.ts's NUTS1_BUNDESLAND map exactly.
+--
+-- Idempotent: only touches rows where bundesland IS NULL AND region IS NOT
+-- NULL — safe to run more than once, and never overwrites a value already
+-- set by the (now-fixed) normalizer for newer ingests.
+-- No user input is interpolated (T-11-05) — pure derived-field UPDATE.
+
+-- CreateIndex
+CREATE INDEX IF NOT EXISTS "Tender_bundesland_idx" ON "Tender"("bundesland");
+
+-- Backfill
+UPDATE "Tender"
+SET "bundesland" = CASE upper(left("region", 3))
+  WHEN 'DE1' THEN 'Baden-Württemberg'
+  WHEN 'DE2' THEN 'Bayern'
+  WHEN 'DE3' THEN 'Berlin'
+  WHEN 'DE4' THEN 'Brandenburg'
+  WHEN 'DE5' THEN 'Bremen'
+  WHEN 'DE6' THEN 'Hamburg'
+  WHEN 'DE7' THEN 'Hessen'
+  WHEN 'DE8' THEN 'Mecklenburg-Vorpommern'
+  WHEN 'DE9' THEN 'Niedersachsen'
+  WHEN 'DEA' THEN 'Nordrhein-Westfalen'
+  WHEN 'DEB' THEN 'Rheinland-Pfalz'
+  WHEN 'DEC' THEN 'Saarland'
+  WHEN 'DED' THEN 'Sachsen'
+  WHEN 'DEE' THEN 'Sachsen-Anhalt'
+  WHEN 'DEF' THEN 'Schleswig-Holstein'
+  WHEN 'DEG' THEN 'Thüringen'
+  ELSE NULL
+END
+WHERE "bundesland" IS NULL AND "region" IS NOT NULL;
diff --git a/apps/api/prisma/schema.prisma b/apps/api/prisma/schema.prisma
index 48c9a53..70549da 100644
--- a/apps/api/prisma/schema.prisma
+++ b/apps/api/prisma/schema.prisma
@@ -286,6 +286,7 @@ model Tender {
   @@index([status])
   @@index([deadlineAt])
   @@index([publishedAt])
+  @@index([bundesland]) // FILTER-02: post-backfill Bundesland-Filter-Performance
   // Deliberately NO tenant column and NO tenant index — this is global data (D-03)
 }
 
diff --git a/apps/api/src/tenders/tender-normalizer.service.spec.ts b/apps/api/src/tenders/tender-normalizer.service.spec.ts
index a26ed7f..c853d87 100644
--- a/apps/api/src/tenders/tender-normalizer.service.spec.ts
+++ b/apps/api/src/tenders/tender-normalizer.service.spec.ts
@@ -89,6 +89,37 @@ describe('TenderNormalizerService', () => {
     expect(normalized.title).toBeTruthy();
   });
 
+  it('derives bundesland from region NUTS-1 prefix (FILTER-02, Pitfall 1)', () => {
+    const raw = loadRawNoticePair(NOTICE_WITH_EFORMS_ONLY_DEADLINE);
+
+    const normalized = service.normalize(raw);
+
+    if (normalized.region) {
+      expect(normalized.bundesland).not.toBeNull();
+    } else {
+      expect(normalized.bundesland).toBeNull();
+    }
+  });
+
+  it('bundesland is null when region is null/absent — never crashes', () => {
+    const raw = loadRawNoticePair(NOTICE_WITH_NO_DEADLINE_OR_VALUE);
+    const rawWithoutRegion: RawTenderRecord = {
+      ...raw,
+      ocdsPayload: {
+        ...(raw.ocdsPayload as Record<string, unknown>),
+        buyer: {
+          ...(raw.ocdsPayload as { buyer?: Record<string, unknown> })?.buyer,
+          address: { postalCode: '12345' },
+        },
+      },
+    };
+
+    const normalized = service.normalize(rawWithoutRegion);
+
+    expect(normalized.region).toBeNull();
+    expect(normalized.bundesland).toBeNull();
+  });
+
   it('dedupKey = ocid when present', () => {
     const raw = loadRawNoticePair(NOTICE_WITH_EFORMS_ONLY_DEADLINE);
 
diff --git a/apps/api/src/tenders/tender-normalizer.service.ts b/apps/api/src/tenders/tender-normalizer.service.ts
index 51c1cfe..da5e579 100644
--- a/apps/api/src/tenders/tender-normalizer.service.ts
+++ b/apps/api/src/tenders/tender-normalizer.service.ts
@@ -1,5 +1,6 @@
 import { Injectable } from '@nestjs/common';
 import { createHash } from 'crypto';
+import { bundeslandFromRegion } from './geo/nuts-bundesland';
 import type { NormalizedTenderFields, RawTenderRecord } from './tender.types';
 
 /**
@@ -33,9 +34,11 @@ export class TenderNormalizerService {
     const cpvCodes = extractCpvCodes(ocdsTender);
     const region = textValue(ocdsBuyer?.address?.region);
     const plz = textValue(ocdsBuyer?.address?.postalCode);
-    // NUTS->Bundesland name mapping deferred to Phase 11 (filter UI) — not
-    // required for this phase's ingestion core.
-    const bundesland: string | null = null;
+    // Phase 11 (FILTER-02, Pitfall 1): derive bundesland from region's
+    // NUTS-1 prefix so new ingests are filterable immediately — the
+    // ~1671 pre-existing rows are backfilled by a one-time migration
+    // (20260721140000_tender_bundesland_backfill).
+    const bundesland = bundeslandFromRegion(region);
 
     const deadlineAt =
       extractEformsDeadline(eformsRoot) ??
diff --git a/apps/api/src/tenders/tender.types.ts b/apps/api/src/tenders/tender.types.ts
index 70e8b6a..a6ae9c2 100644
--- a/apps/api/src/tenders/tender.types.ts
+++ b/apps/api/src/tenders/tender.types.ts
@@ -55,10 +55,10 @@ export interface NormalizedTenderFields {
   title: string;
   buyerName: string | null;
   cpvCodes: string[];
-  /** NUTS region code (e.g. "DEA41") from the buyer address — not yet mapped to a human Bundesland name. */
+  /** NUTS region code (e.g. "DEA41") from the buyer address. */
   region: string | null;
   plz: string | null;
-  /** Deferred: NUTS→Bundesland name mapping is a Phase 11 filter-UI concern, not this phase's scope. */
+  /** Derived from region's NUTS-1 prefix via bundeslandFromRegion() (Phase 11, FILTER-02). Null when region is null/unrecognized. */
   bundesland: string | null;
   /** Frequently null (RESEARCH Pattern 4) — nullable is a correctness requirement, not optional hardening. */
   deadlineAt: Date | null;