{"record":{"id":"c53b5b13e11d45e7","repo":"nautechsystems/nautilus_trader","slug":"failed-to-parse-balance-hex-string-hex-string","errorCode":null,"errorMessage":"Failed to parse balance hex string '{hex_string}': {e}","messagePattern":"Failed to parse balance hex string '(.+?)': (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"crates/adapters/blockchain/src/rpc/http.rs","lineNumber":257,"sourceCode":"        &self,\n        address: &Address,\n        block: Option<u64>,\n        timeout_secs: Option<u64>,\n    ) -> anyhow::Result<U256> {\n        let block_param = block_parameter(block);\n\n        let request = serde_json::json!({\n            \"jsonrpc\": \"2.0\",\n            \"id\": 1,\n            \"method\": \"eth_getBalance\",\n            \"params\": [address, block_param]\n        });\n        let hex_string: String = self\n            .execute_rpc_call_with_timeout(request, timeout_secs)\n            .await?;\n\n        U256::from_str(&hex_string)\n            .map_err(|e| anyhow::anyhow!(\"Failed to parse balance hex string '{hex_string}': {e}\"))\n    }\n\n    /// Retrieves logs matching the given filter criteria.\n    ///\n    /// This method calls the `eth_getLogs` RPC method to fetch event logs from the blockchain.\n    /// It's commonly used for querying historical events like token transfers, swaps, etc.\n    ///\n    /// # Errors\n    ///\n    /// Returns an error if the RPC call fails or the response cannot be parsed.\n    pub async fn get_logs(\n        &self,\n        address: Option<&Address>,\n        topics: Option<Vec<Option<String>>>,\n        from_block: u64,\n        to_block: u64,\n    ) -> anyhow::Result<Vec<RpcLog>> {\n        let mut filter = serde_json::Map::new();","sourceCodeStart":239,"sourceCodeEnd":275,"githubUrl":"https://github.com/nautechsystems/nautilus_trader/blob/18893faf8b356be3320add8de2f861b0b647cf06/crates/adapters/blockchain/src/rpc/http.rs#L239-L275","documentation":"This error is thrown when the hex string returned by an `eth_getBalance` RPC call cannot be parsed into a `U256` via `U256::from_str`. The library expects the node to return a `0x`-prefixed hex quantity; any malformed, empty, or non-hex response triggers this anyhow error wrapping the parse failure with the original error `e`.","triggerScenarios":"Calling `get_balance`/`get_balance_with_timeout` when the RPC node returns a malformed balance value (non-hex string, empty string, hex with invalid characters, or a value exceeding U256 range).","commonSituations":"Misconfigured or non-compliant RPC endpoint (e.g. a proxy returning HTML error pages), a custom chain node returning decimal instead of hex, or an interceptor/proxy substituting the JSON-RPC result.","solutions":["Log/inspect the raw `hex_string` returned by the node to see the actual malformed value","Verify the RPC endpoint is a JSON-RPC compliant Ethereum node (test with curl against eth_getBalance)","Check for proxies/CDNs rewriting responses; point the client at the node URL directly","Strip unexpected prefixes/whitespace if your node adds them, or upgrade the node software"],"exampleFix":"// before: trusting node output blindly\nlet balance = client.get_balance(&address).await?;\n// after: validate the endpoint first\nlet raw = client.rpc_health_check().await?; // ensure node returns 0x-prefixed hex\nlet balance = client.get_balance(&address).await?;","handlingStrategy":"validation","validationCode":"fn is_hex_quantity(s: &str) -> bool {\n    s.starts_with(\"0x\") && s.len() > 2 && s[2..].chars().all(|c| c.is_ascii_hexdigit())\n}\n// assert node health before balances:\n// debug_assert!(is_hex_quantity(raw_balance_string));","typeGuard":"fn looks_like_u256_hex(s: &str) -> bool {\n    let body = s.strip_prefix(\"0x\").unwrap_or(s);\n    !body.is_empty() && body.chars().all(|c| c.is_ascii_hexdigit())\n}","tryCatchPattern":null,"preventionTips":["Use a known-compliant JSON-RPC endpoint (geth/erigon standard)","Health-check the node with eth_chainId/eth_getBalance before relying on it","Bypass proxies that may rewrite response bodies","Log raw responses when integrating a new provider"],"tags":["rpc","hex-parsing","blockchain","response-parsing"],"backgroundTag":"invalid-argument-format","analyzedSha":"18893faf8b356be3320add8de2f861b0b647cf06","analyzedAt":"2026-09-08T20:49:34.690Z","contentChangedAt":"2026-09-08T20:49:34.690Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}