From 7c911a62696dce7ef61bd96ac2a3b6d441b56d98 Mon Sep 17 00:00:00 2001
From: Alice <Alicepoltora@users.noreply.github.com>
Date: Mon, 12 Oct 2026 19:05:59 +0700
Subject: [PATCH] fix(bundler): make default maxFeePerGas floor chain-aware

Fixes #15

prepareUserOperation used a hardcoded 3 gwei maxFeePerGas floor when neither
the caller-supplied partialUserOp fields nor a custom estimateFeesPerGas
callback provided fees. On L2s where base fees sit well below 1 gwei this
inflates the worst-case spend (gasLimit x maxFeePerGas) that Gas Station
policies check by 100-500x, rejecting otherwise-trivial UserOperations with
a budget of ~0.01 USDC.

Add defaultMaxFeePerGasFor(chainId) applying a 0.05 gwei floor on L2 chains
where sub-gwei base fees are routine (Base, Base Sepolia, Arbitrum One and
Sepolia, Optimism and OP Sepolia, Polygon and Amoy) and keep the
conservative L1-tuned 3 gwei default for Ethereum mainnet and unknown
chains. The max(estimated x 2) clamp is unchanged, so when the node
estimates non-trivial fees they still win.

The custom estimateFeesPerGas override path is untouched.
---
 .../core/apis/bundler/BundlerApiImpl.kt        | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/src/main/java/com/circle/modularwallets/core/apis/bundler/BundlerApiImpl.kt b/lib/src/main/java/com/circle/modularwallets/core/apis/bundler/BundlerApiImpl.kt
index e84c396..dd4481c 100644
--- a/lib/src/main/java/com/circle/modularwallets/core/apis/bundler/BundlerApiImpl.kt
+++ b/lib/src/main/java/com/circle/modularwallets/core/apis/bundler/BundlerApiImpl.kt
@@ -197,7 +197,7 @@ internal object BundlerApiImpl : BundlerApi {
         try {
             if (partialUserOp.maxFeePerGas == null || partialUserOp.maxPriorityFeePerGas == null) {
                 if (estimateFeesPerGas == null) {
-                    val defaultMaxFeePerGas = parseGwei("3")
+                    val defaultMaxFeePerGas = defaultMaxFeePerGasFor(bundlerClient.chain.chainId)
                     val defaultMaxPriorityFeePerGas = parseGwei("1")
                     val two = BigInteger.valueOf(2)
                     val fees = publicApi.estimateFeesPerGas(
@@ -359,6 +359,22 @@ internal fun getUpdatedCalls(calls: Array<EncodeCallDataArg>): Array<EncodeCallD
     }.toTypedArray()
     return updatedCalls
 }
+/**
+ * Chain-aware default `maxFeePerGas` floor.
+ *
+ * L2 base fees are routinely well below 1 gwei; a hard 3 gwei floor inflates the
+ * worst-case spend (`gas x maxFeePerGas`) that Gas Station policies check by
+ * ~100-500x on those chains, rejecting otherwise-trivial UserOperations.
+ * Ethereum mainnet-class chains keep the conservative L1-tuned default.
+ */
+internal fun defaultMaxFeePerGasFor(chainId: Long): BigInteger = when (chainId) {
+    8453L, 84532L,      // Base, Base Sepolia
+    42161L, 421614L,    // Arbitrum One, Arbitrum Sepolia
+    10L, 11155420L,     // Optimism, OP Sepolia
+    137L, 80002L,       // Polygon, Polygon Amoy
+        -> parseGwei("0.05")
+    else -> parseGwei("3")
+}
 internal suspend fun <T> startPolling(
     pollingInterval: Long,
     retryCount: Int,