blsync: "Latest filled block is not available" after starting sync with valid checkpoint and beacon API

[shazam8253]

System information

Geth version: latest main geth CL client & version: blsync OS & Version: Windows

Expected behaviour

After providing a valid checkpoint and a working beacon API URL, Geth with --beacon.api and --beacon.checkpoint should begin syncing via BLSync, fetching finalized headers and block payloads to build a light client view of the chain.

Actual behaviour

ERROR[06-04|02:16:47.664] Latest filled block is not available

Steps to reproduce the behaviour

Run this command: geth --holesky --beacon.api http://testing.holesky.beacon-api.nimbus.team/ --beacon.checkpoint 0x547798636e7eca655a641fc182841ff9444bff593caf9c59ada1505563617538 Make sure to update the finalized root block hash if past certain time period.

Backtrace

WARN [06-04|11:08:20.246] Ignoring payload while snap syncing      number=3,947,914 hash=a63ca3..d82386 reason="forced head needed for startup"
INFO [06-04|11:08:20.246] Successful NewPayload                    number=3,947,914 hash=a63ca3..d82386 status=SYNCING
INFO [06-04|11:08:20.247] Forkchoice requested sync to new head    number=3,947,914 hash=a63ca3..d82386 finalized=unknown
INFO [06-04|11:08:20.247] Successful ForkchoiceUpdated             head=a63ca3..d82386 status=SYNCING
INFO [06-04|11:08:20.643] Syncing beacon headers                   downloaded=512 left=336,258 eta=4m20.276s
ERROR[06-04|11:08:20.644] Latest filled block is not available
INFO [06-04|11:08:20.645] Block synchronisation started
ERROR[06-04|11:08:20.645] Reject duplicated disable operation
INFO [06-04|11:08:20.716] Syncing: state download in progress      synced=4.74% state=1.65GiB accounts=4,418,[email protected] slots=3,189,[email protected] [email protected] eta=-67.761ms
INFO [06-04|11:08:21.128] Syncing: chain download in progress      synced=8.52% chain=558.85MiB headers=336,[email protected] bodies=336,[email protected] receipts=336,[email protected] eta=372h5m49.115s
INFO [06-04|11:08:23.534] New local node record                    seq=1,749,052,015,074 id=428e1eb04d9948d1 ip=45.17.219.143 udp=30303 tcp=30303

[s1na]

That is a confusing error. We should probably change it to a warning or something. Your node is syncing correctly.

[Chubbi-Stephen]

Hi team 👋,

I’ve reviewed the issue “blsync: ‘Latest filled block is not available’ after starting sync with valid checkpoint and beacon API” in the Go-Ethereum codebase. I understand this is blocking proper syncing when using --beacon.checkpoint and BLSync on Windows/Linux.

I’d like to take this on and investigate the root cause—likely related to missing finalized block data following the checkpoint. I’ll propose a fix to ensure the latest filled block is always available (even after restart or checkpoint sync) and thoroughly test across environments.

Please assign this issue to me — I’m ready to get started!

Thanks, Stephen

[MariusVanDerWijden]

As @s1na said, this is not an error, should be downgraded to a warning cc @shazam8253

[rose2221]

would like to work on it