rpc(autobahn): return the committee that certified /validators height (CON-358)

[wen-coding]

Summary

• Autobahn /validators currently returns the genesis GenDoc set at every height. After epoch 0 that is the wrong committee.
• Height is a global block number (same as /block). The covering CommitQC supplies the road; the epoch registry supplies the committee. Before the first QC, omitted/first height resolve to genesis.
• Pruned heights return ErrHeightNotAvailable; uncertified heights return ErrHeightExceedsChainHead.

Test plan

• go test ./internal/p2p/ ./internal/autobahn/data/ ./internal/rpc/core/ in sei-tendermint
• Autobahn integration /validators?height=h and omitted-height /validators (asserted in assertTmRPCEndpoints)

Made with Cursor

[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 2, 2026, 9:17 PM

[codecov]

Codecov Report

❌ Patch coverage is 84.31373% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.26%. Comparing base (7273a43) to head (38af828).

Files with missing lines	Patch %	Lines
sei-tendermint/internal/p2p/giga_router_common.go	87.50%	3 Missing and 1 partial ⚠️
sei-tendermint/internal/rpc/core/consensus.go	60.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4083      +/-   ##
==========================================
- Coverage   61.30%   60.26%   -1.05%     
==========================================
  Files        2178     2070     -108     
  Lines      190788   178331   -12457     
==========================================
- Hits       116968   107474    -9494     
+ Misses      62796    60872    -1924     
+ Partials    11024     9985    -1039     

Flag	Coverage Δ
sei-chain-pr	72.33% <84.31%> (?)
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
sei-tendermint/autobahn/types/msg.go	89.51% <100.00%> (+0.04%)	⬆️
sei-tendermint/internal/autobahn/data/state.go	77.49% <100.00%> (+0.71%)	⬆️
sei-tendermint/internal/autobahn/epoch/registry.go	82.87% <ø> (ø)
sei-tendermint/internal/p2p/giga_router.go	100.00% <ø> (ø)
sei-tendermint/internal/p2p/giga_router_common.go	61.25% <87.50%> (+2.91%)	⬆️
sei-tendermint/internal/rpc/core/consensus.go	59.37% <60.00%> (+20.42%)	⬆️

... and 109 files with indirect coverage changes

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[seidroid]

Replacing the genesis-set stub in Autobahn's /validators with a CommitQC → epoch-registry lookup is correct: the QC covering the global height picks the certifying committee, the pre-first-QC fallback to nextCommitEpoch is sound, and the router-level test covers the resolved height, omitted height, uncertified height, power ordering and pruned-epoch cases. No blocking issues; the notes below concern the availability window the epoch registry imposes and a duplicated error mapping.

Findings: 0 blocking | 3 non-blocking | 2 posted inline

Blockers

• None at the file/PR level.

Non-blocking

• [suggestion] Voting powers reported by /validators now change shape at the epoch-2 boundary: epochs 0/1 use the genesis committee built in BuildDataState, which assigns weight 1 per entry in ValidatorAddrs, while epochs ≥2 use committeeWeights(app.GetValidators()) (real stake). Previously the endpoint always echoed GenDoc powers. This is faithful to the committee that actually certified each block, but it is an externally visible response change the PR description doesn't mention — worth calling out for downstream consumers that compute stake fractions.
• 2 suggestion(s)/nit(s) flagged inline on specific lines.

[seidroid]

[suggestion] BlockByNumber (line ~126) still maps atypes.ErrPruned → WrapErrHeightNotAvailable inline; its comment even claims "both call sites format through the same helper". Now that heightLookupError exists, routing BlockByNumber through it keeps the /block and /validators error shapes from drifting apart. The only wrinkle is the default arm: BlockByNumber wraps with data.GlobalBlock(%v): %w context while this helper returns the raw error — worth preserving that wrap at the call site if you consolidate.