Why WalletConnect + Rabby Wallet + Transaction Simulation Changes How I Send High-Risk DeFi Trades

Okay, so check this out—I’ve been noodling on this for weeks. Wow! It started as a small annoyance: every time I used WalletConnect from my phone to sign a big trade, something felt off about the UX and the invisible risks lurking under the hood. My instinct said « don’t just tap approve », and that gut nudged me into building a repeatable simulation routine before committing funds.

Here’s the thing. WalletConnect makes it easy to connect mobile wallets or cold-signers to dApps. Really? Yes, but that convenience hides complexity. On one hand you’re getting a seamless pairing experience across devices. On the other hand, though actually, the dApp still sends raw transactions to your wallet and you can’t always see the full execution path—internal calls, token transfers, or subtle approval changes—before you hit approve. Initially I thought that was just paranoia, but then I saw a swap route that would have drained leftover tokens via an approval mis-scope. Yikes.

I’ll be honest: I’m biased toward wallets that put security first. Rabby is one of those that caught my eye early on. I’m not 100% sure about every integration detail, but the team focuses on clear transaction previews, permission controls, and—if you want to dig deeper—transaction simulation workflows you can run yourself. If you want to check the extension out, here’s the rabby wallet official site and you can poke around their docs and UX yourself.

Why simulation matters with WalletConnect

Short answer: simulations reveal what a signed transaction will do before the chain sees it. Hmm… sounds obvious, but it isn’t. WalletConnect simply provides a bridge. The dApp signs and sends a transaction payload over WalletConnect to your wallet, and the wallet signs. The blockchain then runs the code and either accepts or rejects the state changes. So if you can reproduce that run locally or via an RPC that supports dry-runs, you can catch reverts, unexpected token transfers, or monstrous gas burn before you pay for it.

Simulation isn’t perfect. eth_estimateGas often underestimates complex gas for contracts that use dynamic logic or reentrancy patterns. On the other hand, eth_call with the correct state (pending block tag) will show revert reasons in many cases. Initially I thought eth_call would always reveal everything, but actually there are edge cases—stateful oracles, time-dependent logic, or randomness that only resolves on-chain—that can produce different outcomes on replay. So, simulate, but consider the context.

In practice, doing this means: intercept the unsigned transaction WalletConnect gets from the dApp, run a dry-run with eth_call or a state-fork, inspect traces, then only sign if the outputs match expectations. Sounds heavy? It is sometimes. Yet doing so turns a blind trust into a verifiable step. My approach removed at least two near-miss misapprovals in the last month alone.

Practical simulation checklist for experienced DeFi users

1. Capture the WalletConnect payload. Short. You need nonce, to, value, gasLimit, gasPrice or maxFee fields, and the data hex. Keep a copy. Really.

2. Use eth_call to dry-run the transaction. Medium sentence here explaining: set « from » to your wallet address and use blockTag « pending » so you get results that reflect mempool state. Then check the return data for revert reasons or expected values.

3. Run eth_estimateGas as a sanity check. Longer thought: eth_estimateGas will give you a ballpark for required gas, but for contracts with complex loops or external calls you should add a buffer (I usually add 10–30% depending on history), especially for mainnet interactions where failing mid-execution can cost you a lot.

4. Inspect internal calls and token movements with a trace API or a local fork. Short burst: Seriously? Yes. If the transaction triggers other contracts, you want to see each internal transfer and approve call. If a single approve to a router can trigger token drains because of a bad allowance direction, you’ll catch it here.

5. Validate slippage, path and deadlines. Medium: Confirm the swap path matches the expected pairs and that slippage bounds are sane. Also check deadline timestamps—some dApps set these in odd ways that can create stuck transactions.

Tools and techniques I use (and why)

My regimen mixes RPC-level calls and local forks. Short: fork once. Medium: I spin up a local fork (hardhat or ganache) or use a simulation platform with the same block state, then replay the WalletConnect transaction there. This exposes reverts, internal transfers, and token balance diffs without risking funds. Longer: when you have a contract that depends on off-chain oracles or stochastic behavior, you might need to mock data or freeze time on the fork to get a faithful replay; it’s an extra step but it saved me from a nasty sandwich attack once.

For direct RPC work, eth_call is your friend for non-state changes (it simulates execution and returns data), and eth_estimateGas helps with gas provisioning. The trace APIs—if available—give you a full call stack and value transfers. If you can’t run your own node or fork, use a trusted provider that offers simulation endpoints, but be mindful that centralized providers can have differing mempool states, which means a dry-run could miss a race condition that exists in the wild.

Also: check approvals. I’m tellin’ ya, infinite allowances are still very common. Short: revoke or limit. Medium: replace long-lived approves with exact amounts when possible, or use permit-based approvals so you avoid on-chain approval calls. Longer thought: permits reduce UX friction and can significantly lower attack surface because they avoid a separate approval tx, though they require support from the token and the dApp.

Wallet UX notes — what Rabby (and other security-focused wallets) should surface

Show me call traces. Short. Let me see the token movements, approve targets, and any external calls. Medium: display the to/from addresses clearly with ENS where available, and show token amounts in both token units and USD for quick mental checks. Longish: where possible, surface a « simulation status » that runs live when a WalletConnect payload is presented, with a clear « simulated outcome » flag and warnings for reverts, high gas, or suspicious approve targets.

I’m biased, but these things matter because many users just skim and hit approve. That part bugs me. (oh, and by the way…) a small UX tweak—like highlighting allowance increases in red—prevents a lot of accidental approvals.