Support for trace_call and State Overrides in Filecoin RPC

[eshon]

Checklist

• This is not brainstorming ideas. If you have an idea you'd like to discuss, please open a new discussion on the lotus forum and select the category as Ideas.
• I have a specific, actionable, and well motivated feature request to propose.

Lotus component

• lotus daemon - chain sync
• lotus fvm/fevm - Lotus FVM and FEVM interactions
• lotus miner/worker - sealing
• lotus miner - proving(WindowPoSt/WinningPoSt)
• lotus JSON-RPC API
• lotus message management (mpool)
• Other

What is the motivation behind this feature request? Is your feature request related to a problem? Please describe.

Use Case

trace_call is used extensively by EVM developers to simulate transaction routes before execution, allowing them to preview how a transaction would behave under specific on-chain conditions without broadcasting it.

In combination with state overrides, this enables them to:

• Emulate token approvals and other prerequisite contract states
• Test different contract interactions safely and deterministically

Additionally, they may rely on trace_call (alongside eth_getLogs and eth_getTransactionReceipt) to verify and analyze transactions that have already occurred.

Benefits

• Enables robust off-chain transaction simulation and debugging
• Improves developer tooling for dApp and DeFi integrations
• Aligns Filecoin’s RPC feature set more closely with Ethereum-compatible environments with improved safety and debugging

References

• Ethereum JSON-RPC trace_call specification
  
• Geth stateOverride documentation

Current Ecosystem Users Impacted

• EVM devs debugging contract interactions (e.g. a DEX provider in the ecosystem)
  • "we use trace call in order to simulate routes before they are sent"
  • "importantly we use it together with state overrides to simulate approvals"
  • "we also use it to confirm swaps that have already happened, combined with getlogs and transactionreceipt"

Describe the solution you'd like

This is a request for support of the trace_call RPC method as well as state overrides, similar to the functionality available in Ethereum clients (e.g. Geth).

Describe alternatives you've considered

No response

Additional context

No response

[BigLep]

Internal note: internal slack discussion: https://filecoinproject.slack.com/archives/C0745JU645A/p1761030264493389