diff --git a/apps/api/src/tenders/tender-matching.service.ts b/apps/api/src/tenders/tender-matching.service.ts
new file mode 100644
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+++ b/apps/api/src/tenders/tender-matching.service.ts
@@ -0,0 +1,90 @@
+import { Injectable, Logger } from '@nestjs/common';
+import { Prisma } from '@prisma/client';
+import { PrismaService } from '../prisma/prisma.service';
+import { buildTenderWhere } from './tender-query.builder';
+import type { TenderQueryDto } from './dto/tender-query.dto';
+
+/**
+ * TenderMatchingService.matchDelta — NOTIFY-03 core: evaluates ONLY the
+ * tender IDs newly upserted in the current `pollDueSources` tick
+ * (`newTenderIds`) against every active `TenderSavedSearch` profile
+ * (across all users/tenants — the Tender catalog is global, D-03).
+ *
+ * Delta-only is the structural backfill-flood prevention (D-07): matching
+ * NEVER runs against the full `Tender` table or historical rows. A newly
+ * created profile therefore collects zero un-notified matches against the
+ * existing ~2188-row catalog — it only starts matching from the next poll
+ * tick onward. There is deliberately NO historical rescan and NO backfill/
+ * suppression table.
+ *
+ * Filter reuse (Don't Hand-Roll): the exact same `buildTenderWhere` used
+ * by the Phase-11 read path (`TendersController.listTenders`) is reused
+ * here — a profile's `filters` JSON blob is cast to `TenderQueryDto` and
+ * compiled to a parametrized Prisma `where`, AND-ed with the delta
+ * boundary `{ id: { in: newTenderIds } }`.
+ *
+ * Match persistence is an idempotent upsert on
+ * `@@unique([tenderId, savedSearchId])` with `update: {}` (D-06) — a
+ * re-match of an already-matched pair leaves any previously-set
+ * `notifiedAt` untouched, so the matched-vs-notified invariant holds
+ * structurally even if `matchDelta` is ever called twice for the same
+ * tender ID.
+ *
+ * This plan (12-01) only creates TenderMatch rows with `notifiedAt` left
+ * NULL — instant dispatch is wired in Plan 12-03, which extends this
+ * service. No TenderMailService import here yet.
+ */
+@Injectable()
+export class TenderMatchingService {
+  private readonly logger = new Logger(TenderMatchingService.name);
+
+  constructor(private readonly prisma: PrismaService) {}
+
+  async matchDelta(newTenderIds: string[]): Promise<void> {
+    if (!newTenderIds.length) return;
+
+    const savedSearches = await this.prisma.tenderSavedSearch.findMany();
+
+    for (const search of savedSearches) {
+      try {
+        const filterWhere = buildTenderWhere(
+          search.filters as unknown as TenderQueryDto,
+        );
+        const where: Prisma.TenderWhereInput = {
+          AND: [filterWhere, { id: { in: newTenderIds } }],
+        };
+
+        const hits = await this.prisma.tender.findMany({
+          where,
+          select: { id: true },
+        });
+
+        for (const hit of hits) {
+          await this.prisma.tenderMatch.upsert({
+            where: {
+              tenderId_savedSearchId: {
+                tenderId: hit.id,
+                savedSearchId: search.id,
+              },
+            },
+            create: {
+              tenderId: hit.id,
+              savedSearchId: search.id,
+              userId: search.userId,
+              tenantId: search.tenantId,
+              // notifiedAt intentionally omitted -> stays NULL (Eligibility-Gate, D-06)
+            },
+            update: {}, // idempotent — preserves a previously-set notifiedAt on re-match
+          });
+        }
+      } catch (err) {
+        // A single broken profile (e.g. malformed filters JSON) must never
+        // abort matching for the remaining profiles — catch-and-log per
+        // profile (DKV/pollDueSources pattern).
+        this.logger.error(
+          `matchDelta failed for savedSearch ${search.id}: ${(err as Error).message}`,
+        );
+      }
+    }
+  }
+}