Why bridges fail in surprising ways

Bridges look simple at the surface: lock assets on chain A, mint or release on chain B. In practice, they are distributed systems with latency, retries, and multiple sources of truth. The tricky bugs usually show up when traffic spikes or a downstream dependency slows down.

My go-to checklist

• Confirm the source transaction state and finality (including reorg scenarios).
• Track the destination transaction hash and match it back to the source event.
• Validate relayer retries and idempotency when the same message is reprocessed.
• Test with fee spikes and low liquidity to see how slippage is handled.
• Log all cross-chain IDs and timestamps for auditability.

A tiny smoke test script

#!/usr/bin/env bash
set -euo pipefail

echo "Bridge smoke test"
echo "1) Send a small transfer"
echo "2) Wait for destination finality"
echo "3) Verify balances and event IDs"

What I log for every run

• Source chain: block number, tx hash, event ID
• Destination chain: tx hash, confirmation count, final balance
• Relayer: retry count, latency, error codes

Keeping this data in one place makes it much easier to debug when a transfer looks stuck or goes missing under load.