Initialize app from last header on frozen restart for v6.6

[masih]

This is the v6.6 version of #4447. A node in freeze mode halts one block below its freeze height and never processes another block. On v6.6 the EVM HTTP and WS servers wait for start signals that only ProcessBlock sends, so once a frozen node restarts they never start. The node keeps its data and its Tendermint RPC, but EVM RPC stays down. frozen-6-7-0 runs v6.6.3 and hits this on every restart.

v6.6 has no InitLastHeader in the ABCI Application interface, so #4447 cannot be cherry-picked as is. Proxy.InitLastHeader forwards the call only to apps that implement it, which leaves the interface unchanged. BaseApp.InitLastHeader sets checkState from the header, as Commit does. App.InitLastHeader calls it and then sends the start signals through signalEVMServersStart, which ProcessBlock now also uses, so each signal is still sent once. nodeImpl.OnStart makes the same freeze-only call as on main, with the block meta at state.LastBlockHeight.

TestFrozenNodeServesEVMRPCAfterRestart restarts seid on the height-10 frozen node in the frozen RPC router cluster. Locally it timed out with the v6.6.3 binary and passed with this change.

Part of PLT-1370.

[devin-ai-integration]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Oct 5, 2026, 3:55 PM

[codecov]

Codecov Report

❌ Patch coverage is 90.47619% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.21%. Comparing base (3a022d9) to head (c7bea83).

Files with missing lines	Patch %	Lines
sei-tendermint/node/node.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release/v6.6    #4448      +/-   ##
================================================
- Coverage         59.11%   58.21%   -0.90%     
================================================
  Files              2231     2157      -74     
  Lines            184599   175895    -8704     
================================================
- Hits             109120   102394    -6726     
+ Misses            65634    64360    -1274     
+ Partials           9845     9141     -704     

Flag	Coverage Δ
sei-chain-pr	58.22% <90.47%> (?)
sei-db	69.80% <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
app/app.go	72.11% <100.00%> (+0.06%)	⬆️
sei-cosmos/baseapp/abci.go	64.35% <100.00%> (+0.11%)	⬆️
sei-tendermint/internal/proxy/proxy.go	92.06% <100.00%> (+0.39%)	⬆️
sei-tendermint/node/node.go	65.22% <60.00%> (-0.07%)	⬇️

... and 74 files with indirect coverage changes

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[cursor]

PR Summary

Medium Risk
Changes node startup and query/check-state initialization for freeze-mode restarts; behavior for live nodes is unchanged aside from refactored EVM server signaling in ProcessBlock.

Overview
Fixes frozen nodes losing EVM RPC after restart on v6.6, where HTTP/WS servers only received start signals from ProcessBlock and freeze mode never processes another block.

Adds InitLastHeader on BaseApp (sets checkState like Commit) and on App (also calls shared signalEVMServersStart, refactored out of ProcessBlock so each signal is still sent once). Tendermint’s Proxy forwards the call via an optional interface so the ABCI Application type stays unchanged. nodeImpl startup in freeze mode loads the last committed block meta and invokes InitLastHeader.

Coverage: unit tests for check state + EVM signals, a freeze-mode restart test in node, and an integration test that restarts seid in Docker and asserts eth_getBlockByNumber still works.

^{Reviewed by Cursor Bugbot for commit c7bea83. Bugbot is set up for automated code reviews on this repo. Configure here.}

[masih]

@seidroid review

[seidroid]

This backports the frozen-restart fix to v6.6. It adds InitLastHeader through an optional interface on Proxy, BaseApp and App, so a restarted frozen node sets its checkState from the last stored header and sends the EVM HTTP/WS start signals once. I checked the tree at merge commit b3858f9 and found nothing blocking: the signal channels have a buffer of 1, the sent flags are only touched before the reactors start and from ProcessBlock after that, and the unit test's Setup processes no block, so the signal assertion is real. The codex reading ("nothing found") agrees with this; my only additions are two nits about misplaced doc comments.

Non-blocking

• OnStart calls InitLastHeader whenever freezeHeight > 0, including a node that is still syncing toward its freeze height. That node's EVM servers now start before it processes any block in this session, not after its first ProcessBlock. This looks harmless, but it is a behaviour change for non-frozen freeze-configured nodes and is not mentioned.

2 nits, not posted on the code

• app/app.go:1908 — signalEVMServersStart and InitLastHeader were inserted between ProcessBlock's doc comment and ProcessBlock. Godoc now gives ProcessBlock's description to signalEVMServersStart, and ProcessBlock itself has no doc.
• sei-cosmos/baseapp/abci.go:269 — Same problem here: InitLastHeader sits between Commit's doc comment and func Commit, so the halt-height description now documents InitLastHeader and Commit has no doc.

_{seidroid review · decision approve · session ec1ec75ef2bb43159f194331a1917676 · turn resp_claude_355bda7d4fe5d8e5baefef962ce2edfd · item f2133e293a8351c6bbdc7661f5f692eb}

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