feat(evmonly): add eth_estimateGas via existing libraries

[shemnon]

Summary

• Adds eth_estimateGas to the EVM-only Giga RPC by calling the standard gasestimator.Estimate library function directly, the same function the mainline (Cosmos-backed) EVM module's eth_estimateGas already uses, instead of the hand-rolled bisection search in Add eth_estimateGas to the EVM-only Giga RPC #4312 (which had known correctness bugs and was not merged).
• Executor.EstimateGas (giga/evmonly/estimate.go) opens one state snapshot for the whole search — gasestimator.Estimate holds it across every probe rather than reopening state per probe — and builds the minimal *types.Header / core.ChainContext / consensus Engine adapter gasestimator needs, reproducing buildBlockContext's existing semantics (zero Coinbase, parent-hash-only BLOCKHASH).
• Threads a new EvmEstimateGas backend primitive through evmOnlyApplication → Proxy → Environment, mirroring the existing EvmCall wiring.
• Fixes two bugs found in review before merge:
  • gasestimator.Estimate never checks whether a probe's EVM was cancelled; the vendored interpreter only samples cancellation at JUMP/JUMPI and clears it to a normal halt, so a probe cut off by the search's deadline could read back as a successful low estimate. Now checked explicitly after Estimate returns.
  • BLOBBASEFEE panicked (nil *uint256.Int push) because the header carries no ExcessBlobGas and a non-blob call leaves BlobGasFeeCap nil; gasestimator's panic recovery turned that into a permanent "not enough gas". Fixed by defaulting BlobGasFeeCap to zero on a copy of the message, matching the literal zero buildBlockContext already uses for eth_call.
• Adds a table-driven test covering every context-reading opcode in the 0x30-0x4a range (not just BLOBBASEFEE) to guard against the same class of bug recurring.

Test plan

• go build ./...
• gofmt -s -l / goimports -l clean on all touched files
• go test ./giga/evmonly/... ./sei-tendermint/internal/evmonlyapp/... ./sei-tendermint/internal/proxy/... ./sei-tendermint/internal/rpc/core/... — all green
• Manually reverted each fix and confirmed the corresponding new test fails, then restored and confirmed it passes

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 24, 2026, 7:10 PM

[cursor]

PR Summary

Medium Risk
New read-only RPC path executes arbitrary EVM bytecode against committed state with timeout/cap semantics; incorrect estimates or state leakage would affect transaction submission, but changes mirror existing eth_call wiring with added safeguards.

Overview
Adds eth_estimateGas to the EVM-only Autobahn JSON-RPC surface, wired end-to-end from estimateAPI through EvmEstimateGas on the app, proxy, and RPC environment into Executor.EstimateGas, which runs go-ethereum’s gasestimator.Estimate against a single committed-state snapshot (read-only, like eth_call).

The executor builds minimal header/chain/engine adapters for the estimator, applies the same callTimeout guard with an explicit post-Estimate check so timed-out probes cannot return a bogus low gas, and defaults nil BlobGasFeeCap to zero to avoid BLOBBASEFEE panics. evmOnlyApplication factors shared “current committed block” setup into currentExecutionContext for both call and estimate.

RPC behavior matches eth_call for block tags and revert errors ( newRevertError now takes raw revert bytes); omitted gas on estimate uses block gas limit as the search ceiling rather than defaultCallGasCap. Docs and broad unit/integration tests cover reverts, caps, timeouts, cancellation, opcode context, and no state mutation.

^{Reviewed by Cursor Bugbot for commit 2031950. Bugbot is set up for automated code reviews on this repo. Configure here.}

[seidroid]

Clean change: eth_estimateGas calls go-ethereum's gasestimator.Estimate over a single snapshot, and the wiring from app to Proxy to Environment matches the existing EvmCall path. It handles the BLOBBASEFEE nil panic and the missed-cancellation case, and the tests cover both. There is one small suggestion about how the error is reported when the caller cancels.

Findings: 0 blocking | 1 non-blocking | 1 posted inline

Blockers

• None at the file/PR level.

Non-blocking

• None at the file/PR level.
• 1 suggestion(s)/nit(s) flagged inline on specific lines.

[codecov]

Codecov Report

❌ Patch coverage is 89.88764% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.41%. Comparing base (f978be0) to head (2031950).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
giga/evmonly/estimate.go	88.63%	5 Missing ⚠️
sei-tendermint/internal/evmonlyapp/app.go	85.71%	2 Missing ⚠️
giga/evmonly/rpc/estimate.go	95.00%	1 Missing ⚠️
giga/evmonly/rpc/server.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4325      +/-   ##
==========================================
- Coverage   67.50%   66.41%   -1.10%     
==========================================
  Files        2181     2062     -119     
  Lines      167848   155891   -11957     
==========================================
- Hits       113306   103531    -9775     
+ Misses      54532    52350    -2182     
  Partials       10       10              

Flag	Coverage Δ
sei-chain-pr	77.87% <89.88%> (?)
sei-db	74.50% <ø> (ø)
sei-db-state-db	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
giga/evmonly/rpc/call.go	95.83% <100.00%> (ø)
sei-tendermint/internal/proxy/proxy.go	95.12% <100.00%> (+0.31%)	⬆️
sei-tendermint/internal/rpc/core/mempool.go	52.35% <100.00%> (+0.25%)	⬆️
giga/evmonly/rpc/estimate.go	95.00% <95.00%> (ø)
giga/evmonly/rpc/server.go	24.44% <50.00%> (+1.18%)	⬆️
sei-tendermint/internal/evmonlyapp/app.go	85.15% <85.71%> (-0.05%)	⬇️
giga/evmonly/estimate.go	88.63% <88.63%> (ø)

... and 121 files with indirect coverage changes

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[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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