diff --git a/4337/README.md b/4337/README.md
index 4da8ff80b..a12c59a58 100644
--- a/4337/README.md
+++ b/4337/README.md
@@ -136,6 +136,14 @@ npx hardhat --network <network> etherscan-verify
 npx hardhat --network <network> local-verify
 ```
 
+### Compiler settings
+
+The project uses Solidity compiler version `0.8.21` with 10 million optimizer runs, as we want to optimize for the code execution costs. The evm version is set to `paris`, because not all of our target networks support the opcodes introduced in the `Shanghai` EVM upgrade.
+
+After careful consideration, we decided to enable the optimizer for the following reasons:
+- The most critical functionality is handled by the Safe and Entrypoint contracts, such as signature checks and replay protection.
+- The Entrypoint contract uses the optimizer.
+
 #### Custom Networks
 
 It is possible to use the `NODE_URL` env var to connect to any EVM based network via an RPC endpoint. This connection then can be used with the `custom` network.
diff --git a/4337/hardhat.config.ts b/4337/hardhat.config.ts
index 5c07dc229..4daeb6521 100644
--- a/4337/hardhat.config.ts
+++ b/4337/hardhat.config.ts
@@ -36,8 +36,8 @@ import './src/tasks/local_verify'
 import './src/tasks/deploy_contracts'
 import './src/tasks/show_codesize'
 
-const primarySolidityVersion = SOLIDITY_VERSION || '0.8.20'
-const soliditySettings = !!SOLIDITY_SETTINGS ? JSON.parse(SOLIDITY_SETTINGS) : { optimizer: { enabled: true, runs: 200 } }
+const primarySolidityVersion = SOLIDITY_VERSION || '0.8.21'
+const soliditySettings = !!SOLIDITY_SETTINGS ? JSON.parse(SOLIDITY_SETTINGS) : { optimizer: { enabled: true, runs: 10_000_000 } }
 
 const userConfig: HardhatUserConfig = {
   paths: {
@@ -47,7 +47,7 @@ const userConfig: HardhatUserConfig = {
     sources: 'contracts',
   },
   solidity: {
-    compilers: [{ version: primarySolidityVersion, settings: { evmVersion: 'london', ...soliditySettings }}, { version: '0.6.12' }, { version: '0.5.17' }],
+    compilers: [{ version: primarySolidityVersion, settings: { evmVersion: 'paris', ...soliditySettings }}, { version: '0.6.12' }, { version: '0.5.17' }],
   },
   networks: {
     hardhat: {