{"record":{"id":"db35dc54b678c42b","repo":"nautechsystems/nautilus_trader","slug":"chain-id-mismatch-at-connect-expected-expected-c","errorCode":null,"errorMessage":"Chain ID mismatch at connect: expected {expected_chain_id}, node reported {actual_chain_id}","messagePattern":"Chain ID mismatch at connect: expected (.+?), node reported (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"critical","filePath":"crates/adapters/blockchain/src/execution/client.rs","lineNumber":2769,"sourceCode":"                crate::cache::database::BlockchainCacheDatabase::connect(pg_options.clone().into())\n                    .await\n                    .map_err(|e| {\n                        anyhow::anyhow!(\"Failed to connect to the Postgres cache database: {e}\")\n                    })?;\n            self.cache.database = Some(database);\n            self.cache.initialize_chain().await;\n            self.cache.ensure_execution_transaction_schema().await?;\n        } else {\n            log::warn!(\n                \"No Postgres cache database configured; transactions will be refused (no durable store)\"\n            );\n        }\n\n        // Verify the RPC chain ID against configuration before any signature\n        let expected_chain_id = u64::from(self.chain.chain_id);\n        let actual_chain_id = self.http_rpc_client.chain_id().await?;\n        if actual_chain_id != expected_chain_id {\n            anyhow::bail!(\n                \"Chain ID mismatch at connect: expected {expected_chain_id}, node reported {actual_chain_id}\"\n            );\n        }\n\n        // Load the signer key from the configured environment variable; the key is never\n        // logged, serialized, or stored in configuration\n        let private_key = std::env::var(&self.config.signer_private_key_env).map_err(|_| {\n            anyhow::anyhow!(\n                \"Signer private key environment variable '{}' is not set\",\n                self.config.signer_private_key_env\n            )\n        })?;\n        let signer = PrivateKeySigner::from_str(private_key.trim()).map_err(|_| {\n            anyhow::anyhow!(\n                \"Signer private key in '{}' is not a valid hex private key\",\n                self.config.signer_private_key_env\n            )\n        })?;","sourceCodeStart":2751,"sourceCodeEnd":2787,"githubUrl":"https://github.com/nautechsystems/nautilus_trader/blob/2114cf6f761429e0adb5ca9596fcd7b895b16011/crates/adapters/blockchain/src/execution/client.rs#L2751-L2787","documentation":"During connect(), the client compares the configured chain.chain_id against eth_chainId reported by the RPC node and aborts before any key material is loaded or any signature is produced. This guards against signing transactions for a different network than intended, which is the classic way funds get sent to wrong-chain addresses.","triggerScenarios":"Calling connect() when the RPC URL serves a different network than chain.chain_id in the config: mainnet RPC paired with a testnet chain id, a fork/proxy endpoint reporting a different id, a provider failover URL pointing elsewhere, or chain presets whose id was edited incorrectly.","commonSituations":"Switching between mainnet and testnet by changing only one of (RPC URL, chain id); localhost Hardhat/Anvil forks that report their own chain id; mis-pasted provider keys that default to a different network; env-specific configs drifting out of sync.","solutions":["Make the RPC URL and chain.chain_id consistent in the BlockchainExecutionConfig (query the node with eth_chainId / cast chain-id and set that exact value)","For local forks (anvil/hardhat), set the config chain id to the id the fork reports","Keep one config block per environment (mainnet/sepolia/local) and switch wholesale instead of editing single fields","Treat this error as a hard stop: do not bypass it, fix the environment instead"],"exampleFix":"// before: mismatched pair\nBlockchainExecutionConfig {\n    chain: Chain::mainnet(), // chain_id = 1\n    chain_rpc_http: \"https://sepolia.infura.io/v3/KEY\".into(), // reports 11155111\n}\n\n// after: consistent testnet pair\nBlockchainExecutionConfig {\n    chain: Chain::sepolia(), // chain_id = 11155111\n    chain_rpc_http: \"https://sepolia.infura.io/v3/KEY\".into(),\n}","handlingStrategy":"try-catch","validationCode":"// Pre-verify config before connect\nlet reported = http_client.chain_id().await?;\nanyhow::ensure!(\n    reported == u64::from(config.chain.chain_id),\n    \"RPC reports chain {reported} but config expects {}\", config.chain.chain_id\n);","typeGuard":null,"tryCatchPattern":"match client.connect().await {\n    Err(e) if e.to_string().contains(\"Chain ID mismatch\") => {\n        // Environment misconfiguration: halt deployment, never override\n        fatal!(\"refusing to trade on mismatched network: {e}\");\n    }\n    other => other,\n}","preventionTips":["Smoke-test eth_chainId against config.chain_id in CI for every environment profile","Treat RPC URL and chain id as one atomic unit in config","Alert loudly on this error — it exists to protect capital"],"tags":["blockchain","evm","chain-id","configuration","network-mismatch","connect"],"backgroundTag":"evm-chain-id-mismatch","analyzedSha":"2114cf6f761429e0adb5ca9596fcd7b895b16011","analyzedAt":"2026-08-21T11:28:30.864Z","schemaVersion":2},"datasetVersion":"2026-08-22T04:17:13.399Z"}