Problem

The smart contract uses panic!() with string messages for all error conditions (e.g., panic!("total_amount must be > 0")). Panic strings are expensive in Soroban — they inflate WASM size and don't give callers structured error codes.

Proposed solution

Define a #[contracterror] enum with named variants:

#[contracterror]
#[derive(Copy, Clone, Debug)]
pub enum StreamError {
    InvalidAmount = 1,
    InvalidSchedule = 2,
    InvalidCliff = 3,
    StreamNotFound = 4,
    StreamCancelled = 5,
    Unauthorized = 6,
    InvalidWithdrawAmount = 7,
}

Replace all panic!() calls with Result<T, StreamError> return types. This reduces WASM size, enables programmatic error handling on the frontend, and follows Soroban best practices.

Files to change

• contracts/streaming/src/lib.rs
• contracts/streaming/src/test.rs
• contracts/streaming/src/test_security.rs