Why Gas Estimation Errors Can Bankrupt a Smart Account

Standard eth_estimateGas simulates a transaction in a vacuum, ignoring the volatile mempool state that exists at broadcast time. For a smart account with multiple operations (e.g., ERC-20 approval + swap), a 10-30% underestimation is common, leading to catastrophic reversion after the user has already signed.

• Revert-Then-Liquidate: Failed batch tx can leave assets stranded in a vulnerable state.
• Unpredictable Paymasters: Relayer gas sponsorship adds a second layer of estimation risk.

Protocols like Safe{Core} and Biconomy must move beyond RPC estimates. The fix is a multi-layered buffer system that accounts for real-time network conditions and the specific execution path of the account.

• Dynamic Slippage for Gas: Apply a safety buffer (1.5x-2x) derived from pending block data.
• Post-Execution Refund: Overpaid gas must be programmatically returned to the user's account, not the relayer.

EOA wallets hide estimation errors with a simple "transaction failed" message. Smart accounts cannot afford this UX because a failed transaction often represents a partial, non-atomic state change. The industry standard for error tolerance is zero.

• Blind Spot: Estimators ignore storage slot warming costs for first-time interactions.
• Account Abstraction Amplifier: Every validateUserOp and handleOps call stack multiplies estimation complexity.

A single underestimation event for a protocol-deployed smart account (e.g., a Gnosis Safe managing a DAO treasury) can trigger a cascade. If gas funds are drained from a paymaster or relay network, it can halt thousands of dependent accounts simultaneously.

• Relayer Insolvency: A wave of failed txs can bankrupt a gas credit system like that of Stackup or Alchemy.
• TVL Lockup: $10B+ in smart account assets is exposed to this systemic fragility.

Paymasters (e.g., ERC-4337 Bundlers, Pimlico, Stackup) sponsor gas fees, but their complex validation logic is opaque to standard estimators like eth_estimateGas. A transaction that passes simulation can fail during execution if the paymaster's internal rules (e.g., token price checks, rate limits) change, leaving the user to pay the full gas bill.

• Result: User's entire account balance can be drained to cover a failed sponsored transaction.
• Vector: Relies on EIP-4337 mempool, where failed txs are still included and charged.

Gas prices can spike 10x+ between estimation and block inclusion, especially during network congestion or MEV attacks. Smart accounts with time-dependent logic (e.g., limit orders, liquidations) are vulnerable.

• Attack: Bots can trigger gas auctions to inflate prices, causing the user's transaction to revert after consuming all allocated gas.
• Amplifier: ERC-4337 UserOperations have higher intrinsic gas overhead (~42k gas) than EOAs, making misestimation more costly.

Bundlers (e.g., Alchemy, Blocknative) simulate transactions off-chain, but their simulation environment may differ from the actual validator's execution state. A 1 wei difference in a DEX pool reserve or NFT floor price can cause a revert.

• Systemic Risk: Mass misestimation across accounts using the same popular bundler infrastructure.
• Solution Path: Requires state-gated estimations or fallback handlers like those explored by Safe{Core} and ZeroDev.

Smart accounts often hold only ERC-20 tokens, with gas paid via a paymaster. If the paymaster rejects the tx, the account has no ETH to pay for the revert, creating a dead-end state.

• Consequence: The account is bricked; funds are locked because no transaction can be paid for to rectify the state.
• Mitigation: Requires maintaining a minimum ETH balance or using gasless relayers with guaranteed inclusion, negating the user experience benefit.

Sponsoring gas via a paymaster creates uncapped liability. A single mis-estimated transaction can drain the sponsor's entire deposit, as seen in early ERC-4337 implementations.\n- Risk: Sponsor assumes 100% of the gas cost variance.\n- Failure Mode: A complex UserOperation consumes 10x the estimated gas, bankrupting the paymaster contract.

Treat gas estimation as an oracle problem. Protocols like Gelato and Biconomy run dedicated simulation nodes. The fix is multi-layered:\n- Dynamic Buffering: Add a 20-50% buffer on top of simulated estimates.\n- Circuit Breakers: Implement per-transaction or daily gas spend limits.\n- Fallback Pricing: Revert to a fixed high-gas model if simulation fails.

Static eth_estimateGas is insufficient for account abstraction bundles. You need a stateful engine that replays the exact pending state.\n- Key Benefit: Accurately simulates complex flows (e.g., token swaps via Uniswap, NFT mint).\n- Key Benefit: Detects reentrancy and storage slot conflicts pre-execution.\n- Entity Example: Stackup's Bundler uses a forked Go-Ethereum client for high-fidelity simulation.

When estimation fails, the system must fail safely. The cardinal rule: Never let a UserOperation execute with unknown gas.\n- Protocol Enforcement: Bundlers should reject ops where verificationGasLimit or callGasLimit exceed sane ceilings.\n- User Experience: Fail fast with a clear error, don't attempt optimistic execution.\n- Analogy: This is the circuit breaker that prevents a localized error from becoming a systemic collapse.