fix: skip casting payload attestation when there is no block at slot

packages/beacon-node/src/api/impl/validator/index.ts

@@ -1112,23 +1112,25 @@ export function getValidatorApi(
       notWhileSyncing();
       await waitForSlot(slot);
 
-      const block = chain.forkChoice.getCanonicalBlockClosestLteSlot(slot);
+      const block = chain.forkChoice.getCanonicalBlockAtSlot(slot);
       if (!block) {
-        throw new ApiError(404, `No canonical block found at or before slot=${slot}`);
+        // No block is seen at slot. Return 404 so vc can skip casting payload attestation.
+        throw new ApiError(404, `No canonical block found at slot=${slot}`);
       }
 
-      const blockIsForSlot = block.slot === slot;
       const payloadInput = chain.seenPayloadEnvelopeInputCache.get(block.blockRoot);
       // Spec: set payload_present only if the envelope was seen before get_payload_due_ms()
       // into the slot. Use the envelope's own arrival time (getPayloadEnvelopeSource), not
       // the input's creation time.
       const payloadDueSec = config.getPayloadDueMs() / 1000;
-      const payloadPresent =
-        blockIsForSlot &&
-        payloadInput !== undefined &&
-        payloadInput.hasPayloadEnvelope() &&
-        chain.clock.secFromSlot(slot, payloadInput.getPayloadEnvelopeSource().seenTimestampSec) < payloadDueSec;
-      const blobDataAvailable = blockIsForSlot && (payloadInput?.hasAllData() ?? false);
+      let payloadPresent = false;
+      let blobDataAvailable = false;
+      if (payloadInput !== undefined) {
+        payloadPresent =
+          payloadInput.hasPayloadEnvelope() &&
+          chain.clock.secFromSlot(slot, payloadInput.getPayloadEnvelopeSource().seenTimestampSec) < payloadDueSec;
+        blobDataAvailable = payloadInput.hasAllData();
+      }
 
       return {
         data: {

packages/beacon-node/test/unit/api/impl/validator/produceAttestationData.test.ts

@@ -65,7 +65,7 @@ describe("api - validator - produceAttestationData", () => {
       modules.config = gloasConfig;
       api = getValidatorApi(defaultApiOptions, modules);
 
-      modules.forkChoice.getCanonicalBlockClosestLteSlot.mockReturnValue({
+      modules.forkChoice.getCanonicalBlockAtSlot.mockReturnValue({
         slot: 0,
         blockRoot: ZERO_HASH_HEX,
       } as ProtoBlock);
@@ -86,5 +86,25 @@ describe("api - validator - produceAttestationData", () => {
       expect(res.data.payloadPresent).toBe(true);
       expect(res.data.blobDataAvailable).toBe(true);
     });
+
+    it("Should throw 404 when no canonical block has been seen for the assigned slot", async () => {
+      const gloasConfig = createChainForkConfig({
+        ...defaultChainConfig,
+        ALTAIR_FORK_EPOCH: 0,
+        BELLATRIX_FORK_EPOCH: 0,
+        CAPELLA_FORK_EPOCH: 0,
+        DENEB_FORK_EPOCH: 0,
+        ELECTRA_FORK_EPOCH: 0,
+        FULU_FORK_EPOCH: 0,
+        GLOAS_FORK_EPOCH: 0,
+      });
+      modules = getApiTestModules({config: gloasConfig});
+      modules.config = gloasConfig;
+      api = getValidatorApi(defaultApiOptions, modules);
+
+      modules.forkChoice.getCanonicalBlockAtSlot.mockReturnValue(null);
+
+      await expect(api.producePayloadAttestationData({slot: 1})).rejects.toThrow("No canonical block found at slot=1");
+    });
   });
 });

packages/validator/src/services/ptc.ts

@@ -1,4 +1,4 @@
-import {ApiClient, routes} from "@lodestar/api";
+import {ApiClient, HttpStatusCode, routes} from "@lodestar/api";
 import {ChainForkConfig} from "@lodestar/config";
 import {isForkPostGloas} from "@lodestar/params";
 import {Slot, gloas} from "@lodestar/types";
@@ -70,14 +70,23 @@ export class PtcService {
 
     try {
       const payloadAttestationData = await this.producePayloadAttestationData(slot);
+      // If no beacon block was seen for the assigned slot, do not submit a payload attestation
+      if (payloadAttestationData === null) {
+        this.logger.debug("Skipping payload attestation, no beacon block seen for slot", {slot});
+        return;
+      }
       await this.signAndPublishPayloadAttestations(slot, payloadAttestationData, duties);
     } catch (e) {
       this.logger.error("Error on PTC routine", {slot}, e as Error);
     }
   };
 
-  private async producePayloadAttestationData(slot: Slot): Promise<gloas.PayloadAttestationData> {
-    return (await this.api.validator.producePayloadAttestationData({slot})).value();
+  private async producePayloadAttestationData(slot: Slot): Promise<gloas.PayloadAttestationData | null> {
+    const res = await this.api.validator.producePayloadAttestationData({slot});
+    if (!res.ok && res.status === HttpStatusCode.NOT_FOUND) {
+      return null;
+    }
+    return res.value();
   }
 
   private async signAndPublishPayloadAttestations(

packages/validator/test/unit/services/ptc.test.ts

@@ -1,7 +1,7 @@
 import {afterEach, beforeEach, describe, expect, it, vi} from "vitest";
 import {SecretKey} from "@chainsafe/blst";
 import {toHexString} from "@chainsafe/ssz";
-import {routes} from "@lodestar/api";
+import {HttpStatusCode, routes} from "@lodestar/api";
 import {createChainForkConfig} from "@lodestar/config";
 import {config as defaultConfig} from "@lodestar/config/default";
 import {gloas, ssz} from "@lodestar/types";
@@ -11,7 +11,7 @@ import {PtcService} from "../../../src/services/ptc.js";
 import {PtcDutiesService} from "../../../src/services/ptcDuties.js";
 import {SyncingStatusTracker} from "../../../src/services/syncingStatusTracker.js";
 import {ValidatorStore} from "../../../src/services/validatorStore.js";
-import {getApiClientStub, mockApiResponse} from "../../utils/apiStub.js";
+import {getApiClientStub, mockApiErrorResponse, mockApiResponse} from "../../utils/apiStub.js";
 import {ClockMock} from "../../utils/clock.js";
 import {loggerVc} from "../../utils/logger.js";
 import {ZERO_HASH, ZERO_HASH_HEX} from "../../utils/types.js";
@@ -112,6 +112,38 @@ describe("PtcService", () => {
     });
   });
 
+  it("Should skip submission when no beacon block has been seen for the assigned slot", async () => {
+    const slot = 0;
+    const clock = new ClockMock();
+    const config = createChainForkConfig({...defaultConfig, GLOAS_FORK_EPOCH: 0});
+    const ptcService = new PtcService(
+      config,
+      loggerVc,
+      api,
+      clock,
+      validatorStore,
+      emitter,
+      chainHeadTracker,
+      syncingStatusTracker,
+      null
+    );
+
+    const duty: routes.validator.PtcDuty = {
+      slot,
+      validatorIndex: 0,
+      pubkey: pubkeys[0],
+    };
+
+    vi.spyOn(ptcService["dutiesService"], "getDutiesAtSlot").mockReturnValue([duty]);
+    api.validator.producePayloadAttestationData.mockResolvedValue(mockApiErrorResponse(HttpStatusCode.NOT_FOUND));
+
+    await clock.tickSlotFns(slot, controller.signal);
+
+    expect(api.validator.producePayloadAttestationData).toHaveBeenCalledWith({slot});
+    expect(validatorStore.signPayloadAttestation).not.toHaveBeenCalled();
+    expect(api.beacon.submitPayloadAttestationMessages).not.toHaveBeenCalled();
+  });
+
   it("Should redownload PTC duties when dependent root changes", async () => {
     const slot = 0;
     const newDependentRoot = "0x1111111111111111111111111111111111111111111111111111111111111111";

packages/validator/test/utils/apiStub.ts

@@ -62,3 +62,7 @@ export function mockApiResponse<T, M, E extends Endpoint<any, any, any, T, M>>({
   apiResponse.meta = () => meta as M;
   return apiResponse;
 }
+
+export function mockApiErrorResponse<E extends Endpoint>(status: HttpStatusCode): ApiResponse<E> {
+  return new ApiResponse<E>({} as any, null, new Response(null, {status}));
+}