From 06118040326c63fa74247868bddea57f579c9dd2 Mon Sep 17 00:00:00 2001
From: David Michael <david.michael@gmail.com>
Date: Sat, 7 Feb 2026 08:37:50 -0500
Subject: [PATCH] fix: include maxFeePerBlobGas in gas price even when blob
 base fee is 0

`getGasPrice()` uses the pattern `...(maxFeePerBlobGas && { maxFeePerBlobGas })`
to conditionally include the blob fee field. Since `0n` is falsy in JavaScript,
this silently drops `maxFeePerBlobGas` from the returned `GasPrice` object when
the blob base fee is zero.

Downstream, `estimateGas()` reads `gasPrice.maxFeePerBlobGas!` which evaluates
to `undefined`, producing a malformed type-3 transaction that the execution
client rejects with "Transaction creation failed". The sequencer then retries
in a loop until the slot expires, causing a missed block proposal.

The trigger is `getBlobBaseFee()` RPC failure under L1 node memory pressure:
the `Promise.allSettled` result has status 'rejected', so `blobBaseFee` stays
at its default of `0n`. The EIP-4844 formula cannot return 0 (minimum 1 wei),
so this only manifests when the RPC call itself fails.

Fix:
- Replace falsy check with `isBlobTx` flag in return statement
- Use `!== undefined` checks for maxBlobGwei cap and retry bump guards
- Add regression tests for both zero blob fee and RPC failure scenarios

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../src/l1_tx_utils/l1_tx_utils.test.ts       | 52 +++++++++++++++++++
 .../src/l1_tx_utils/readonly_l1_tx_utils.ts   |  6 +--
 2 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/yarn-project/ethereum/src/l1_tx_utils/l1_tx_utils.test.ts b/yarn-project/ethereum/src/l1_tx_utils/l1_tx_utils.test.ts
index 5d75639dcc20..339885c00c8f 100644
--- a/yarn-project/ethereum/src/l1_tx_utils/l1_tx_utils.test.ts
+++ b/yarn-project/ethereum/src/l1_tx_utils/l1_tx_utils.test.ts
@@ -608,6 +608,58 @@ describe('L1TxUtils', () => {
       }
     });
 
+    // Regression: getGasPrice must include maxFeePerBlobGas even when blob base fee is 0n.
+    // 0n is falsy in JS, so `...(maxFeePerBlobGas && { maxFeePerBlobGas })` silently drops it.
+    // This caused missed block proposals when getBlobBaseFee() RPC failed and defaulted to 0n.
+    it('includes maxFeePerBlobGas in result even when blob base fee is zero', async () => {
+      await cheatCodes.setNextBlockBaseFeePerGas(WEI_CONST);
+      await cheatCodes.evmMine();
+
+      // Mock getBlobBaseFee to return 0n (simulates RPC failure defaulting to 0n)
+      const originalGetBlobBaseFee = l1Client.getBlobBaseFee;
+      l1Client.getBlobBaseFee = () => Promise.resolve(0n);
+
+      try {
+        gasUtils.updateConfig({
+          ...defaultL1TxUtilsConfig,
+          stallTimeMs: 0,
+        });
+
+        const gasPrice = await gasUtils['getGasPrice'](undefined, true);
+
+        // maxFeePerBlobGas MUST be present for blob transactions, even when 0n
+        expect(gasPrice.maxFeePerBlobGas).toBeDefined();
+        expect(typeof gasPrice.maxFeePerBlobGas).toBe('bigint');
+      } finally {
+        l1Client.getBlobBaseFee = originalGetBlobBaseFee;
+      }
+    });
+
+    // Regression: same bug when getBlobBaseFee() RPC call fails entirely
+    it('includes maxFeePerBlobGas in result even when getBlobBaseFee RPC fails', async () => {
+      await cheatCodes.setNextBlockBaseFeePerGas(WEI_CONST);
+      await cheatCodes.evmMine();
+
+      // Mock getBlobBaseFee to reject (simulates RPC timeout under memory pressure)
+      const originalGetBlobBaseFee = l1Client.getBlobBaseFee;
+      l1Client.getBlobBaseFee = () => Promise.reject(new Error('RPC timeout'));
+
+      try {
+        gasUtils.updateConfig({
+          ...defaultL1TxUtilsConfig,
+          stallTimeMs: 0,
+        });
+
+        const gasPrice = await gasUtils['getGasPrice'](undefined, true);
+
+        // maxFeePerBlobGas MUST be present for blob transactions, even on RPC failure
+        expect(gasPrice.maxFeePerBlobGas).toBeDefined();
+        expect(typeof gasPrice.maxFeePerBlobGas).toBe('bigint');
+      } finally {
+        l1Client.getBlobBaseFee = originalGetBlobBaseFee;
+      }
+    });
+
     it('respects minimum gas price bump for replacements', async () => {
       gasUtils.updateConfig({
         ...defaultL1TxUtilsConfig,
diff --git a/yarn-project/ethereum/src/l1_tx_utils/readonly_l1_tx_utils.ts b/yarn-project/ethereum/src/l1_tx_utils/readonly_l1_tx_utils.ts
index 526a64ea4c18..9b7be66607a9 100644
--- a/yarn-project/ethereum/src/l1_tx_utils/readonly_l1_tx_utils.ts
+++ b/yarn-project/ethereum/src/l1_tx_utils/readonly_l1_tx_utils.ts
@@ -191,14 +191,14 @@ export class ReadOnlyL1TxUtils {
     }
 
     // Ensure we don't exceed maxBlobGwei
-    if (maxFeePerBlobGas && effectiveMaxBlobGwei > 0n) {
+    if (maxFeePerBlobGas !== undefined && effectiveMaxBlobGwei > 0n) {
       maxFeePerBlobGas = maxFeePerBlobGas > effectiveMaxBlobGwei ? effectiveMaxBlobGwei : maxFeePerBlobGas;
     }
 
     // Ensure priority fee doesn't exceed max fee
     const maxPriorityFeePerGas = priorityFee > maxFeePerGas ? maxFeePerGas : priorityFee;
 
-    if (attempt > 0 && previousGasPrice?.maxFeePerBlobGas) {
+    if (attempt > 0 && previousGasPrice?.maxFeePerBlobGas !== undefined) {
       const bumpPercentage =
         gasConfig.priorityFeeRetryBumpPercentage! > MIN_BLOB_REPLACEMENT_BUMP_PERCENTAGE
           ? gasConfig.priorityFeeRetryBumpPercentage!
@@ -226,7 +226,7 @@ export class ReadOnlyL1TxUtils {
     return {
       maxFeePerGas,
       maxPriorityFeePerGas,
-      ...(maxFeePerBlobGas && { maxFeePerBlobGas: maxFeePerBlobGas }),
+      ...(isBlobTx ? { maxFeePerBlobGas } : {}),
     };
   }