Excellent question! Predicting the input and output message hash before transmitting a transaction is not feasible.
The underlying reason is the dynamic nature of contract data, which can be altered by any previous transactions. Consequently, the current state of the contract remains unpredictable until the transaction is processed.
Hence, the exact input and output message hash values cannot be determined ahead of time. A more effective approach is to validate the input and output data in the context of transaction execution rather than attempting to predict the message hash in advance.
In conclusion, the dynamic and unpredictable nature of transaction histories and state changes in contracts makes it impossible to precisely calculate the input and output message hash prior to dispatching a transaction.