Testnet4 node constantly having its index corrupted

[BlackHatCoiner]

I just want to report this here, before writing on the mailing list.

I have experienced this numerous times already. The testnet4 node cannot start because between the time it shut down, and the time it started again, the chain had been reorged, and it gets Error: Cannot read last block filter index. The only way to restart is to reindex using bitcoind --reindex. I have not found another way around this.

Code:

2026-01-24T15:55:45Z Verification: No coin database inconsistencies in last 6 blocks (6 transactions)
2026-01-24T15:55:45Z Block index and chainstate loaded
2026-01-24T15:55:45Z Opening LevelDB in /home/user/.bitcoin/testnet4/indexes/txindex
2026-01-24T15:55:45Z Opened LevelDB successfully
2026-01-24T15:55:45Z Using obfuscation key for /home/user/.bitcoin/testnet4/indexes/txindex: 0000000000000000
2026-01-24T15:55:45Z Opening LevelDB in /home/user/.bitcoin/testnet4/indexes/blockfilter/basic/db
2026-01-24T15:55:45Z Opened LevelDB successfully
2026-01-24T15:55:45Z Using obfuscation key for /home/user/.bitcoin/testnet4/indexes/blockfilter/basic/db: 0000000000000000
2026-01-24T15:55:45Z [error] ReadFilterHeader: previous block header belongs to unexpected block 00000000b5f4bf2c9ff149e3c9b0c6d6226ee144167525c3fd62e67bc6ff62d8; expected 000000000bdee9c661ab9a8164334f4983f100afc6ad90c62d651845e62cf366
2026-01-24T15:55:45Z [error] Cannot read last block filter header; index may be corrupted
2026-01-24T15:55:45Z Shutdown: In progress...
2026-01-24T15:55:45Z scheduler thread exit
2026-01-24T15:55:45Z Flushed fee estimates to fee_estimates.dat.
2026-01-24T15:55:45Z Shutdown: done

I cannot be the only person testing bitcoin who's experienced this. This is another good argument in favor of removing the 20-min difficulty rule.

[LoyceV]

I have experienced this numerous times already.

Does this happen every time, or only once every few restarts? I just stopped and started mine (running Bitcoin Core 28.0) without problems. See tmp.loyce.club/testnet4_debug.log for my last 10,000 debug.log entries.

[BlackHatCoiner]

I have experienced this numerous times already.

Does this happen every time, or only once every few restarts? I just stopped and started mine (running Bitcoin Core 28.0) without problems. See tmp.loyce.club/testnet4_debug.log for my last 10,000 debug.log entries.

You need to start it after a long period of inactivity, so that CPU miner Bob has reorged another CPU miner Charlie (the chain of which you were following) and an ASIC miner mined on top of Bob instead of Charlie.

Try stopping it, and starting it tomorrow at the current time. It has to be definitely this, because the error clearly says that another block header was expected, which signifies the chain was reorged, and now my chain, and therefore my index is questioned.

[LoyceV]

Try stopping it, and starting it tomorrow at the current time.

I'll do this.

[nc50lc]

I just stopped and started mine (running Bitcoin Core 28.0) without problems. See tmp.loyce.club/testnet4_debug.log for my last 10,000 debug.log entries.

BHC might be using compact block filters with -blockfilterindex=<type> since there's a ".bitcoin/testnet4/indexes/blockfilter/basic/db" indicated in his log.
I haven't experience this either and like yours, I don't use compact block filters on my testnet4 node.

I've applied -blockfilterindex=1 to my testnet4 node, closed it and I'll report tomorrow if it'll result with the same error.

Code:

2026-01-25T05:52:40Z Command-line arg: blockfilterindex="1"

[LoyceV]

My testnet4 node started this morning without problems. See logs.

Did mempool.space get an upgrade? They now show stale blocks (and that's much more visible for testnet4 than anything else):

[BlackHatCoiner]

BHC might be using compact block filters with -blockfilterindex=<type> since there's a ".bitcoin/testnet4/indexes/blockfilter/basic/db" indicated in his log.

I do, but I feel like I've seen this error before introducing block filters.

My testnet4 node started this morning without problems. See logs.

This is normal. You just received the chain which got accepted and not reorged. Try doing this a couple of times.

Did mempool.space get an upgrade?

Yep. And it even misses some in testnet4. Fork-observer is the most reliable of all, and it misses some branches as well!  

[LoyceV]

Try doing this a couple of times.

I entered this on my console:

Code:

~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 16h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 32h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 48h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 64h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 80h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 96h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 114h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 128h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 144h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &
sleep 160h && ~/bitcoin-28.0/bin/bitcoin-cli -testnet4 stop && sleep 8h && ~/bitcoin-28.0/bin/bitcoind -testnet4 &

Feel free to keep an eye on my logs the coming week If I forget it, I hope it keeps running