diff --git a/packages/db/src/seed.ts b/packages/db/src/seed.ts
index c647098..13cf103 100644
--- a/packages/db/src/seed.ts
+++ b/packages/db/src/seed.ts
@@ -668,6 +668,108 @@ async function seedUatStaffAccounts(db: ReturnType<typeof drizzle>) {
       console.log(`✓ Created UAT pet '${pet.name}' with extended fields`);
     }
   }
+
+  // ── GRO-2100: deterministic uat-groomer ↔ pet linkage ───────────────────────
+  // The UAT groomer (`uat-groomer@groombook.dev`, staffId 00000000-0000-0000-0000-000000000004)
+  // needs at least one linked pet/appointment or GRO-1987 TC-UAT-2/3 cannot run
+  // (the pet profile-summary endpoint returns 404 instead of 200/403).
+  //
+  // We deterministically link the UAT groomer to the UAT customer's first pet
+  // ("UAT Pup Alpha") and leave the second pet ("UAT Pup Beta") UNLINKED so
+  // TC-UAT-2 (200) and TC-UAT-3 (403) can both hardcode the stable petIds.
+  await seedUatGroomerLinkage(db, uatCustomerClientId);
+}
+
+/**
+ * GRO-2100: create a deterministic completed appointment linking the UAT groomer
+ * to "UAT Pup Alpha" (c0000001-0000-0000-0000-000000000002). "UAT Pup Beta"
+ * (c0000001-0000-0000-0000-000000000003) is intentionally left UNLINKED so
+ * GRO-1987 TC-UAT-3 can verify the 403 forbidden response.
+ *
+ * Idempotent: the deterministic appointment id (`a0000001-…-0001`) is the
+ * upsert key, so re-running the seed on every reset-demo-data CronJob
+ * (hourly per apps/overlays/uat/reset-cronjob.yaml) is safe.
+ */
+async function seedUatGroomerLinkage(
+  db: ReturnType<typeof drizzle>,
+  customerClientId: string,
+): Promise<void> {
+  const uatGroomerEmail = "uat-groomer@groombook.dev";
+  const LINKED_PET_ID = "c0000001-0000-0000-0000-000000000002"; // UAT Pup Alpha
+  const APPT_ID = "a0000001-0000-0000-0000-000000000001";
+
+  // Only run if the UAT groomer staff record actually exists — dev/test seeds
+  // that don't set SEED_UAT_STAFF_OIDC_SUB should not crash.
+  const [uatGroomerStaff] = await db
+    .select({ id: schema.staff.id })
+    .from(schema.staff)
+    .where(eq(schema.staff.email, uatGroomerEmail))
+    .limit(1);
+  if (!uatGroomerStaff) {
+    return;
+  }
+
+  // Skip if this exact appointment already exists (idempotent on re-seed).
+  const [existing] = await db
+    .select({ id: schema.appointments.id })
+    .from(schema.appointments)
+    .where(eq(schema.appointments.id, APPT_ID))
+    .limit(1);
+  if (existing) {
+    console.log(`✓ GRO-2100: uat-groomer linkage appointment already exists — skipping`);
+    return;
+  }
+
+  // The "Bath & Brush" service id is stable across the reset; falls back to
+  // any active service if it has not been seeded yet (e.g. seedKnownUsers
+  // runs in isolation).
+  const BATH_AND_BRUSH_ID = "b0000001-0000-0000-0000-000000000001";
+  const [bathService] = await db
+    .select({ id: schema.services.id })
+    .from(schema.services)
+    .where(eq(schema.services.id, BATH_AND_BRUSH_ID))
+    .limit(1);
+
+  let serviceId: string;
+  if (bathService) {
+    serviceId = bathService.id;
+  } else {
+    const [fallback] = await db
+      .select({ id: schema.services.id })
+      .from(schema.services)
+      .where(eq(schema.services.active, true))
+      .limit(1);
+    if (!fallback) {
+      console.warn(`⚠ GRO-2100: no active services found — skipping uat-groomer linkage`);
+      return;
+    }
+    serviceId = fallback.id;
+  }
+
+  // Schedule the completed appointment 7 days ago so the profile-summary's
+  // "recentGroomingHistory" window (last 10) reliably includes it.
+  const startTime = new Date();
+  startTime.setDate(startTime.getDate() - 7);
+  startTime.setHours(10, 0, 0, 0);
+  const endTime = new Date(startTime.getTime() + 45 * 60 * 1000);
+
+  await db.insert(schema.appointments).values({
+    id: APPT_ID,
+    clientId: customerClientId,
+    petId: LINKED_PET_ID,
+    serviceId,
+    staffId: uatGroomerStaff.id,
+    batherStaffId: null,
+    status: "completed",
+    startTime,
+    endTime,
+    notes: "GRO-2100: deterministic uat-groomer linkage for TC-UAT-2/3.",
+    priceCents: null,
+    confirmationStatus: "confirmed",
+  });
+  console.log(
+    `✓ GRO-2100: linked uat-groomer (${uatGroomerStaff.id}) → UAT Pup Alpha (${LINKED_PET_ID}) via appointment ${APPT_ID}`,
+  );
 }
 
 // ── Known-users-only seed (prod/demo) ───────────────────────────────────────