Wire eth_subscribe(newHeads) for Autobahn (CON-257)

[wen-coding]

Summary

• Under Autobahn, eth_subscribe("newHeads") is currently broken: the legacy fan-out subscribes to the Tendermint event bus on tm.event = 'NewBlockHeader', but Autobahn drives app.FinalizeBlock from giga_router rather than CometBFT consensus, so PublishEventNewBlockHeader never fires.
• This PR adds a direct in-process notifier from giga_router's post-commit point into evmrpc.SubscriptionAPI's fan-out goroutine, scoped strictly to Autobahn mode (notifier is only constructed when tmConfig.AutobahnConfigFile != ""). The legacy CometBFT path is untouched.
• Notifier semantics: single-producer, single-consumer, capacity 1, overwrite-on-full — newHeads subscribers care about the latest head, not a backlog, so stale heads are dropped in favor of new ones.

Design notes

A simpler alternative was to keep using the event bus and just have giga_router call eventBus.PublishEventNewBlockHeader(...) after commit. That would have been a ~20-line diff with zero evmrpc changes (the existing consumer would just work). We opted not to because (1) the pubsub layer isn't doing anything load-bearing for this use case — one fixed query, one subscriber — and (2) we plan to drop the cosmos event bus entirely once external consumers move off tm.event='Tx' and friends. A direct channel is the end-state design; this PR lands it now to avoid carrying the stopgap.

hash on the published header is the autobahn lane-block header hash (the same value the EVM receipt store records as blockHash), not a hash over the synthesized Tendermint header. parentHash / receiptsRoot / transactionsRoot are zero under Autobahn — the lane-block path doesn't compute a Tendermint-style hash chain, and surfacing fakes would be worse than zeros. Subscribers that chain-validate the head stream will need a different mechanism going forward; this is called out in the encoder's doc.

Test plan

• gofmt -s -l clean on all modified files; go build ./... clean.
• go test ./evmrpc/ — 249 PASS, 8 SKIP, 0 FAIL (22s). Includes:
  • existing TestSubscribeNewHeads (legacy event-bus path) — unchanged behaviour.
  • new TestSubscribeNewHeadsAutobahn (notifier path, in-process WS server end-to-end).
  • new unit tests for BlockHeaderNotifier (deliver, overwrite-on-full, nil-safe) and encodeCommittedBlock (happy path + nil ConsensusParamUpdates).
• evm_rpc_tests.sh (HTTP-method fixtures) against a real non-Autobahn cluster — 160/160 pass, no regressions on the request/response RPC surface.
• New integration_test/evm_module/ws_test/ — consensus-mode-agnostic, gated on SEI_EVM_WS_RUN_INTEGRATION=1, wired into evm_rpc_tests.sh. Run end-to-end against both cluster modes:
  • Non-Autobahn cluster: PASS (number=0x2b, hash 0xe0dd089b...)
  • Autobahn cluster: PASS (number=0xf5, hash 0xc4d1bc59..., GigaRouter initialized confirmed in all 4 node logs)
• Reviewer: confirm non-app-hash-breaking label is correct — this PR only adds a notification side-effect after commit; no state machine or app-hash-relevant logic changes.

🤖 Generated with Claude Code

---

Note

Medium Risk
Introduces a new post-commit notification hook in the Autobahn execution path and changes how eth_subscribe("newHeads") is sourced under Autobahn, so concurrency/backpressure or payload mismatches could affect WebSocket subscribers (legacy CometBFT path remains unchanged).

Overview
Fixes eth_subscribe("newHeads") under Autobahn by bypassing the Tendermint event bus and instead pushing committed-block header data through a new in-process BlockHeaderNotifier (overwrite-on-full, capacity 1).

Wires this notifier from Autobahn’s giga_router post-Commit hook into app.App (implements types.BlockHeaderListener) and into the EVM WS server’s SubscriptionAPI, which now selects between the notifier path (Autobahn) and the existing event-bus subscription (legacy).

Adds Autobahn-specific newHeads encoding (encodeCommittedBlock, with explicit Autobahn hash and zeroed parentHash/roots), plus unit + end-to-end WS tests and a new integration test package invoked by evm_rpc_tests.sh.

^{Reviewed by Cursor Bugbot for commit 714479a. Bugbot is set up for automated code reviews on this repo. Configure here.}

[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	May 12, 2026, 8:20 AM

[codecov]

Codecov Report

❌ Patch coverage is 70.68966% with 34 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.26%. Comparing base (09d0d60) to head (714479a).

Files with missing lines	Patch %	Lines
evmrpc/subscribe.go	80.00%	9 Missing and 6 partials ⚠️
sei-tendermint/internal/p2p/giga_router.go	0.00%	8 Missing and 1 partial ⚠️
app/app.go	0.00%	6 Missing and 1 partial ⚠️
evmrpc/notifier.go	88.88%	2 Missing ⚠️
sei-tendermint/node/setup.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3419   +/-   ##
=======================================
  Coverage   59.26%   59.26%           
=======================================
  Files        2110     2111    +1     
  Lines      174242   174252   +10     
=======================================
+ Hits       103259   103270   +11     
+ Misses      62053    62051    -2     
- Partials     8930     8931    +1     

Flag	Coverage Δ
sei-chain-pr	68.50% <70.68%> (?)
sei-db	70.41% <ø> (ø)

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

Files with missing lines	Coverage Δ
evmrpc/server.go	88.46% <100.00%> (ø)
sei-tendermint/node/node.go	65.28% <100.00%> (+0.09%)	⬆️
sei-tendermint/node/public.go	67.44% <100.00%> (+3.33%)	⬆️
sei-tendermint/node/seed.go	48.48% <ø> (ø)
sei-tendermint/node/setup.go	69.35% <0.00%> (-0.23%)	⬇️
evmrpc/notifier.go	88.88% <88.88%> (ø)
app/app.go	69.41% <0.00%> (+0.18%)	⬆️
sei-tendermint/internal/p2p/giga_router.go	66.02% <0.00%> (-2.98%)	⬇️
evmrpc/subscribe.go	68.18% <80.00%> (+6.32%)	⬆️

... and 35 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[cursor]

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

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 714479a. Configure here.}

[cursor]

gasLimit always zero because ConsensusParamUpdates is nil most blocks

High Severity

encodeCommittedBlock sources gasLimit from evt.response.ConsensusParamUpdates, but as block.go lines 481–489 explicitly document, this field is only populated when the app proposes a consensus-param update — which is nil for the vast majority of blocks. The result is gasLimit will be 0 in nearly every eth_subscribe("newHeads") notification under Autobahn. The ctx from ctxProvider is already available in runNewHeadsFromNotifier and its ConsensusParams() method gives the correct active gas limit, matching the approach in block.go.

Additional Locations (1)

• evmrpc/subscribe.go#L99-L102

 

^{Reviewed by Cursor Bugbot for commit 714479a. Configure here.}