fix(node): warm KZG trusted setup at startup

yarn-project/aztec-node/src/factory.ts

@@ -2,7 +2,7 @@ import { createArchiver } from '@aztec/archiver';
 import { BBCircuitVerifier, BatchChonkVerifier, QueuedIVCVerifier } from '@aztec/bb-prover';
 import { TestCircuitVerifier } from '@aztec/bb-prover/test';
 import { createBlobClientWithFileStores } from '@aztec/blob-client/client';
-import { Blob } from '@aztec/blob-lib';
+import { Blob, getKzg } from '@aztec/blob-lib';
 import { EpochCache } from '@aztec/epoch-cache';
 import { createEthereumChain } from '@aztec/ethereum/chain';
 import { getPublicClient, makeL1HttpTransport } from '@aztec/ethereum/client';
@@ -94,6 +94,15 @@ export async function createAztecNodeService(
   const { BarretenbergSync } = await import('@aztec/bb.js');
   await BarretenbergSync.initSingleton();
 
+  // Warm the KZG trusted-setup singleton before any subsystem runs. getKzg() synchronously builds
+  // its precomputation tables on first use (~2s locally, blocking the event loop; 12-15s under
+  // production CPU limits). If that first use is instead the archiver reconstructing blobs or the
+  // proposal handler uploading them, the stalled loop overruns the gossipsub mcache window and
+  // attestation forwarding is skipped. Paying it here keeps it off the gossip path. Idempotent, so
+  // it is a no-op for sequencers (warmed in Sequencer.init) and for tests that pre-warm via
+  // warmBlobKzg.
+  getKzg(log);
+
   const packageVersion = getPackageVersion();
   const telemetry = deps.telemetry ?? getTelemetryClient();
   const dateProvider = deps.dateProvider ?? new DateProvider();

yarn-project/blob-lib/src/kzg_context.ts

@@ -1,3 +1,6 @@
+import type { Logger } from '@aztec/foundation/log';
+import { elapsedSync } from '@aztec/foundation/timer';
+
 import type { DasContextJs } from '@crate-crypto/node-eth-kzg';
 import { createRequire } from 'module';
 
@@ -30,12 +33,17 @@ export function getBytesPerCommitment(): number {
 let kzgInstance: DasContextJs | undefined;
 
 /**
- * Returns the lazily-initialized KZG context.
- * The first call takes ~3 seconds to initialize the precomputation tables.
+ * Returns the lazily-initialized KZG context. The first call synchronously builds the
+ * precomputation tables (~2s locally, blocking the event loop; longer under constrained CPU), so
+ * callers on a latency-sensitive path should warm it ahead of time. Pass a logger to record how
+ * long that first build took.
+ * @param logger - Optional logger; when provided, the initial table build is timed and logged.
  */
-export function getKzg(): DasContextJs {
+export function getKzg(logger?: Logger): DasContextJs {
   if (!kzgInstance) {
-    kzgInstance = loadNativeModule().DasContextJs.create({ usePrecomp: true });
+    const [durationMs, instance] = elapsedSync(() => loadNativeModule().DasContextJs.create({ usePrecomp: true }));
+    kzgInstance = instance;
+    logger?.verbose(`Loaded KZG trusted setup`, { durationMs });
   }
   return kzgInstance;
 }