diff --git a/src/lib/server/db/index.ts b/src/lib/server/db/index.ts
index 64e4e54..4830d97 100644
--- a/src/lib/server/db/index.ts
+++ b/src/lib/server/db/index.ts
@@ -36,7 +36,7 @@ export async function getTenantDb(
     .limit(1);
 
   if (tenant.length === 0) {
-    throw new Error(`Tenant with ID ${tenantId} not found`);
+    throw new Error(`Tenant or client not found`);
   }
 
   // Create tenant-specific database connection
@@ -62,7 +62,7 @@ export async function getTenant(tenantId: string): Promise<centralSchema.SelectT
     .limit(1);
 
   if (tenant.length === 0) {
-    throw new Error(`Tenant with ID ${tenantId} not found`);
+    throw new Error(`Tenant or client not found`);
   }
 
   return tenant[0];
diff --git a/src/lib/server/services/client-pin-reset-service.ts b/src/lib/server/services/client-pin-reset-service.ts
index bee9558..95918d3 100644
--- a/src/lib/server/services/client-pin-reset-service.ts
+++ b/src/lib/server/services/client-pin-reset-service.ts
@@ -75,7 +75,7 @@ export class ClientPinResetService {
 
       if (tunnel.length === 0) {
         log.warn("No client tunnel found for email hash", { emailHash: emailHash.slice(0, 8) });
-        throw new NotFoundError("Client not found");
+        throw new NotFoundError("Tenant or client not found");
       }
 
       // Create reset token with expiration
@@ -203,7 +203,7 @@ export class ClientPinResetService {
         .limit(1);
 
       if (!tunnel) {
-        throw new NotFoundError("Client tunnel not found");
+        throw new NotFoundError("Tenant or client not found");
       }
 
       // 3. Update the client tunnel with new keys
diff --git a/src/routes/api/tenants/[id]/appointments/[appointmentId]/delete-by-client/+server.ts b/src/routes/api/tenants/[id]/appointments/[appointmentId]/delete-by-client/+server.ts
index e7e6866..281fabc 100644
--- a/src/routes/api/tenants/[id]/appointments/[appointmentId]/delete-by-client/+server.ts
+++ b/src/routes/api/tenants/[id]/appointments/[appointmentId]/delete-by-client/+server.ts
@@ -92,7 +92,7 @@ registerOpenAPIRoute("/tenants/{id}/appointments/{appointmentId}/delete-by-clien
       },
     },
     "404": {
-      description: "Appointment or client not found",
+      description: "Tenant or client not found",
       content: {
         "application/json": {
           schema: { $ref: "#/components/schemas/Error" },
diff --git a/src/routes/api/tenants/[id]/appointments/challenge/+server.ts b/src/routes/api/tenants/[id]/appointments/challenge/+server.ts
index 0373dbd..2ea45a3 100644
--- a/src/routes/api/tenants/[id]/appointments/challenge/+server.ts
+++ b/src/routes/api/tenants/[id]/appointments/challenge/+server.ts
@@ -87,7 +87,7 @@ registerOpenAPIRoute("/tenants/{id}/appointments/challenge", "POST", {
       },
     },
     "404": {
-      description: "Client not found",
+      description: "Tenant or client not found",
       content: {
         "application/json": {
           schema: { $ref: "#/components/schemas/Error" },
@@ -186,7 +186,7 @@ export const POST: RequestHandler = async ({ request, params }) => {
         tenantId,
         emailHashPrefix: emailHash.slice(0, 8),
       });
-      return json({ error: "Client not found" }, { status: 404 });
+      return json({ error: "Tenant or client not found" }, { status: 404 });
     }
 
     const tunnel = tunnelResult[0];
diff --git a/src/routes/api/tenants/[id]/appointments/challenge/__tests__/challenge-api.test.ts b/src/routes/api/tenants/[id]/appointments/challenge/__tests__/challenge-api.test.ts
index 153efc5..36af689 100644
--- a/src/routes/api/tenants/[id]/appointments/challenge/__tests__/challenge-api.test.ts
+++ b/src/routes/api/tenants/[id]/appointments/challenge/__tests__/challenge-api.test.ts
@@ -174,7 +174,7 @@ describe("Challenge API Route", () => {
       const data = await response.json();
 
       expect(response.status).toBe(404);
-      expect(data.error).toBe("Client not found");
+      expect(data.error).toBe("Tenant or client not found");
     });
 
     it("should handle database errors", async () => {
diff --git a/src/routes/api/tenants/[id]/appointments/my-appointments/+server.ts b/src/routes/api/tenants/[id]/appointments/my-appointments/+server.ts
index 5059257..9103b92 100644
--- a/src/routes/api/tenants/[id]/appointments/my-appointments/+server.ts
+++ b/src/routes/api/tenants/[id]/appointments/my-appointments/+server.ts
@@ -171,7 +171,7 @@ export const GET: RequestHandler = async ({ request, params }) => {
         tenantId,
         emailHashPrefix: validatedEmailHash.slice(0, 8),
       });
-      throw new ValidationError("Client not found");
+      throw new ValidationError("Tenant or client not found");
     }
 
     const tunnel = tunnelResult[0];
diff --git a/src/routes/api/tenants/[id]/appointments/my-appointments/__tests__/my-appointments.test.ts b/src/routes/api/tenants/[id]/appointments/my-appointments/__tests__/my-appointments.test.ts
index 785a58d..3714c21 100644
--- a/src/routes/api/tenants/[id]/appointments/my-appointments/__tests__/my-appointments.test.ts
+++ b/src/routes/api/tenants/[id]/appointments/my-appointments/__tests__/my-appointments.test.ts
@@ -182,7 +182,7 @@ describe("GET /api/tenants/[id]/appointments/my-appointments", () => {
     const data = await response.json();
 
     expect(response.status).toBe(422);
-    expect(data.error).toBe("Client not found");
+    expect(data.error).toBe("Tenant or client not found");
   });
 
   it("should return 422 when email hash is empty", async () => {
diff --git a/src/routes/api/tenants/[id]/appointments/verify-challenge/+server.ts b/src/routes/api/tenants/[id]/appointments/verify-challenge/+server.ts
index ef50f47..eba66e0 100644
--- a/src/routes/api/tenants/[id]/appointments/verify-challenge/+server.ts
+++ b/src/routes/api/tenants/[id]/appointments/verify-challenge/+server.ts
@@ -187,7 +187,7 @@ export const POST: RequestHandler = async ({ request, params }) => {
         challengeId,
         emailHashPrefix: storedChallenge.emailHash.slice(0, 8),
       });
-      throw new NotFoundError("Client not found");
+      throw new NotFoundError("Tenant or client not found");
     }
 
     const tunnel = tunnelResult[0];
diff --git a/src/routes/api/tenants/[id]/clients/pin-reset/complete/+server.ts b/src/routes/api/tenants/[id]/clients/pin-reset/complete/+server.ts
index a85c7f3..1e5f713 100644
--- a/src/routes/api/tenants/[id]/clients/pin-reset/complete/+server.ts
+++ b/src/routes/api/tenants/[id]/clients/pin-reset/complete/+server.ts
@@ -100,7 +100,7 @@ registerOpenAPIRoute("/tenants/{id}/clients/pin-reset/complete", "POST", {
       },
     },
     "404": {
-      description: "Token or client not found",
+      description: "Tenant or client not found",
       content: {
         "application/json": {
           schema: { $ref: "#/components/schemas/Error" },
diff --git a/src/routes/api/tenants/[id]/clients/pin-reset/init/+server.ts b/src/routes/api/tenants/[id]/clients/pin-reset/init/+server.ts
index be2a379..4aefaff 100644
--- a/src/routes/api/tenants/[id]/clients/pin-reset/init/+server.ts
+++ b/src/routes/api/tenants/[id]/clients/pin-reset/init/+server.ts
@@ -99,7 +99,7 @@ registerOpenAPIRoute("/tenants/{id}/clients/pin-reset/init", "POST", {
       },
     },
     "404": {
-      description: "Client not found",
+      description: "Tenant or client not found",
       content: {
         "application/json": {
           schema: { $ref: "#/components/schemas/Error" },
diff --git a/src/routes/api/tenants/[id]/clients/pin-reset/init/__tests__/pin-reset-init.test.ts b/src/routes/api/tenants/[id]/clients/pin-reset/init/__tests__/pin-reset-init.test.ts
index a92501f..75bf6e1 100644
--- a/src/routes/api/tenants/[id]/clients/pin-reset/init/__tests__/pin-reset-init.test.ts
+++ b/src/routes/api/tenants/[id]/clients/pin-reset/init/__tests__/pin-reset-init.test.ts
@@ -80,7 +80,7 @@ describe("POST /api/tenants/[id]/clients/pin-reset/init", () => {
   });
 
   it("should return 404 when client not found", async () => {
-    mockPinResetService.createResetToken.mockRejectedValue(new Error("Client not found"));
+    mockPinResetService.createResetToken.mockRejectedValue(new Error("Tenant or client not found"));
 
     const request = new Request("http://localhost/api", {
       method: "POST",