Estimate gas for ETH transfers (fix Arbitrum "intrinsic gas too low")

[Praz314159]

transfer_eth hardcoded GasLimits::ETH_TRANSFER (21,000), the Ethereum L1 intrinsic. Arbitrum folds an L1 data component into intrinsic gas, so the node rejected these transfers as "intrinsic gas too low", which broke cohort child-wallet funding on Arbitrum.

Transfers now estimate gas via eth_estimateGas like every other operation. simulate() previously errored on calldata shorter than 4 bytes (no function selector to cache on); it now estimates such transactions directly — plain value transfers can't revert from contract logic — and applies the same 20% buffer the estimate cache uses. The eth_estimateGas call is factored into a helper shared by both paths. GasLimits::ETH_TRANSFER stays as a reference value.

Summary by CodeRabbit

• Bug Fixes
  • Improved ETH transfer reliability on Arbitrum by using node gas estimation instead of a fixed gas amount, reducing “intrinsic gas too low” failures.
  • Updated transaction handling so short calldata is gas-estimated correctly rather than rejected.
  • Made gas estimation fall back more gracefully, with clearer handling when a simulation or estimation fails.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 76f7c895-8d88-46fb-b86b-3919b087eacf

📥 Commits

Reviewing files that changed from the base of the PR and between b1741a4 and 23ce711.

📒 Files selected for processing (4)

• CHANGELOG.md
• src/client/trades.rs
• src/client/transactions.rs
• src/hft/gas.rs

---

📝 Walkthrough

Walkthrough

This PR replaces the hardcoded Ethereum L1 intrinsic gas constant (21,000) used for ETH transfers with dynamic eth_estimateGas-based estimation. It introduces a centralized estimate_gas helper in transactions.rs, updates transfer_eth to rely on estimation, and revises documentation and changelog accordingly.

Changes

Gas Estimation Refactor

Layer / File(s)	Summary
Centralized gas estimation helper and simulate() integration src/client/transactions.rs	New private estimate_gas method builds a TransactionRequest, calls provider.estimate_gas, and maps errors to TransactionError::SimulationReverted or TransactionError::GasUnavailable; simulate() uses it for both the short-calldata path (replacing a prior validation error) and the cache-miss path.
transfer_eth relies on estimation instead of fixed gas limit src/client/trades.rs	Removes GasLimits import and with_gas_limit(GasLimits::ETH_TRANSFER) call; builds the transfer with empty calldata and value, letting gas be estimated, while preserving urgency handling.
Documentation and changelog updates src/hft/gas.rs, CHANGELOG.md	Updates the ETH_TRANSFER doc comment to note it's now a reference value due to node-based estimation and Arbitrum's L1 data gas component; updates changelog to describe the fix.

Estimated code review effort: 2 (Simple) | ~15 minutes

Possibly related PRs

• StrobeLabs/perpcity-rust-sdk#38: Both PRs modify PerpClient's gas-limit resolution for transfer_eth, including GasLimits::ETH_TRANSFER usage and calldata-based estimation behavior.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/arbitrum-eth-transfer-gas

---

_{Comment @coderabbitai help to get the list of available commands.}