[myetcd]

Motivation

NetworkClient::get_balance returns Result<U256> and propagates RPC failures with ?, but the final step unwraps a parse of a server-controlled string:

pub async fn get_balance(&self) -> Result<U256> {
    let response = self.get_balance_response().await?;
    Ok(U256::from_str(response.balance()).unwrap())
}

GetBalanceResponse::balance() returns the raw proto amount string, so a non-numeric, negative, whitespace-padded, or out-of-range response panics the caller's process instead of surfacing an error. Checked against alloy-primitives 1.5.7 (the version pinned in Cargo.lock), U256::from_str returns Err for "invalid", "1.5", "-1", " 12", and 10^78, so each of those panics at the unwrap(). A malformed or version-incompatible response is exactly the case where a caller wants a loggable error, not a panic mid-proving-pipeline.

The same check turned up a second, quieter problem: U256::from_str("") is Ok(0), so an empty amount does not panic — it silently reports a zero balance and hides the protocol error.

Solution

• Add a parse_balance(&str) -> Result<U256> helper next to the existing parse_fulfillment_status (same module-level style and pub(super) visibility) that returns a contextual error carrying the offending value — invalid balance returned by prover network: "invalid" — and rejects blank responses explicitly, since U256::from_str maps "" to 0.
• get_balance now delegates to it: parse_balance(response.balance()). The public signature is unchanged, and valid responses parse exactly as before.
• Add a unit test covering valid values ("0", "1000", U256::MAX) and malformed ones ("", " ", "invalid", "1.5", "-1", an overflow value), asserting the error message contains the raw value.

This follows the convention already used in the same file: get_market_price_per_pgu parses its server-supplied string fields with .with_context(...), and parse_fulfillment_status was added for the same class of bug in #2909.

pub(super) fn parse_balance(raw: &str) -> Result<U256> {
    if raw.trim().is_empty() {
        return Err(anyhow::anyhow!("invalid balance returned by prover network: {raw:?}"));
    }
    U256::from_str(raw)
        .with_context(|| format!("invalid balance returned by prover network: {raw:?}"))
}

Validation

• cargo check -p sp1-sdk --features network — clean
• New test passes — balance_parser_handles_valid_and_invalid_values
• cargo clippy -p sp1-sdk --features network --lib --tests — no diagnostics for client.rs
• rustfmt --check crates/sdk/src/network/client.rs — clean
• git diff --check — clean

test network::client::test::balance_parser_handles_valid_and_invalid_values ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 51 filtered out

Verified on toolchain 1.95.0 (the repo pins channel = "stable", which is not installed in my environment; 1.95.0 is above the workspace rust-version = "1.88"). The zkevm/* and sp1-gpu/* workspace members were excluded from the build because they resolve git dependencies that are unreachable from my network; neither is touched by this change.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes