[chrisguida]

Adds an assumeutxo entry for height 976000 so pruned nodes can start from a
recent snapshot instead of validating from genesis. The previous newest entry
(910000) predates the BLAKE2b proof-of-work activation at 961640, which left
about 65,000 blocks to validate after loading it. 976000 is below the long
coinbase maturity flag day (979920, #429), so the snapshot is identical under
29.4.2 and the next release.

Snapshot produced with dumptxoutset rollback=976000 on a fully synced,
unpruned v29.4.2.knots20260508 node on 2026-10-07 (123 s):

coins_written   167095701
base_height     976000
base_hash       000000000000000098441aee029573795681eb1602c75271e809b136e9217373
txoutset_hash   dbd67717d3f108e4fbd8b4f9efc4057cac11a0ba7c23584b43cca42c9edb7118
nchaintx        1417215373

File: utxo-976000.dat, 9,517,597,408 bytes,
SHA256 bfd2460a55ae1d2e94b9957ccd512ae027855feed1dbef996cfed0abebe5d123,
served at https://mb-beast.tail4a715.ts.net:8443/datum-node-image/utxo-976000.dat
with SHA256SUMS and utxo-976000.dat.torrent next to it. Torrent (the HTTPS URL above is
its web seed, so it works even with no other peers):

magnet:?xt=urn:btih:3cf7e4d15841f116856f6f19bf2ac15b1dbae2c3&dn=utxo-976000.dat&tr=udp%3A%2F%2Ftracker.opentrackr.org%3A1337%2Fannounce&tr=udp%3A%2F%2Fopen.stealth.si%3A80%2Fannounce&tr=udp%3A%2F%2Ftracker.torrent.eu.org%3A451%2Fannounce&tr=udp%3A%2F%2Fexodus.desync.com%3A6969%2Fannounce&ws=https%3A%2F%2Fmb-beast.tail4a715.ts.net%3A8443%2Fdatum-node-image%2Futxo-976000.dat

How to verify (reviewers)

You need a synced Knots 29.4.x node that still has the blocks from 976000 to
its tip (any unpruned node; a pruned one only if it has not pruned past 976000).

1. Recompute the UTXO set hash at height 976000:

   bitcoin-cli -rpcclienttimeout=0 -named dumptxoutset path=check-976000.dat rollback=976000
   

   Two ways to run it:

   a) Stock 29.4.2: network activity pauses and the node rolls back temporarily
   (123 s for 59 blocks on an NVMe disk; slower the further the tip has moved
   away from 976000, so do it soon).

   b) Node stays online: build the companion backport of Rollback for dumptxoutset without invalidating blocks bitcoin/bitcoin#33477
   (rpc: dumptxoutset rollback without invalidating blocks (backport of bitcoin/bitcoin#33477) #443) first. A branch with this entry on top of it is at

   git fetch https://github.com/chrisguida/bitcoin assumeutxo-976000-online && git checkout FETCH_HEAD
   

   then run the same command; add in_memory=true on a machine with more
   than 12 GB of RAM. An assumeutxo node cannot roll back to its own base
   height until background validation has passed it, so use a full node.

2. Compare the result with this entry. Expected:

   base_height     976000
   base_hash       000000000000000098441aee029573795681eb1602c75271e809b136e9217373
   txoutset_hash   dbd67717d3f108e4fbd8b4f9efc4057cac11a0ba7c23584b43cca42c9edb7118
   nchaintx        1417215373
   coins_written   167095701
   

   txoutset_hash is hash_serialized, nchaintx is m_chain_tx_count. Post an
   ACK with the values you got.

3. Optional: check the published file. sha256sum utxo-976000.dat must print the
   SHA256 above. Loading it with loadtxoutset on a node built from this branch
   also verifies the serialized hash against the entry and refuses a mismatch.

The entry is used by the datum-node-image project (a VPS image with a pruned
Knots node and a DATUM gateway); until it is released the image builds Knots
from source with this patch.

[luke-jr]

utACK

{
  "coins_written": 167095701,
  "base_hash": "000000000000000098441aee029573795681eb1602c75271e809b136e9217373",
  "base_height": 976000,
  "txoutset_hash": "dbd67717d3f108e4fbd8b4f9efc4057cac11a0ba7c23584b43cca42c9edb7118",
  "nchaintx": 1417215373
}
bfd2460a55ae1d2e94b9957ccd512ae027855feed1dbef996cfed0abebe5d123  check-976000.dat

[starslab]

{
  "coins_written": 167095701,
  "base_hash": "000000000000000098441aee029573795681eb1602c75271e809b136e9217373",
  "base_height": 976000,
  "path": "/bitcoind/data/check-976000.dat",
  "txoutset_hash": "dbd67717d3f108e4fbd8b4f9efc4057cac11a0ba7c23584b43cca42c9edb7118",
  "nchaintx": 1417215373
}

bfd2460a55ae1d2e94b9957ccd512ae027855feed1dbef996cfed0abebe5d123 check-976000.dat

[kwsantiago]

utACK 6ce5702

[chrisguida]

For anyone who needs this entry before it is in a tag: there is a Guix build of 29.4.2 plus exactly this commit at https://github.com/chrisguida/bitcoin/releases/tag/v29.4.2.knots20260508-assumeutxo976000, reproduced on two machines, with my builder attestation on https://github.com/chrisguida/guix.sigs/tree/assumeutxo976000 and the reproduce-and-attest steps at https://claude.ai/code/artifact/5c9fbfa7-7359-435e-a701-6b2d596ed4ef. Nothing else differs from 29.4.2; the diff is this PR. More builder signatures are welcome on that branch.

One note for the next tag: nodes are being started from 976,000 now (AlphaPool's installer has defaulted to that build since Oct 9), before any tag contains the entry. A node started from a snapshot refuses to start on a binary that lacks that snapshot's entry until its background validation has finished and it has restarted once (BlockManager::LoadBlockIndex -> "Assumeutxo data not found for the given blockhash"), a few days on a small VPS. So if the next release carries a newer height instead of this one, those nodes are stuck on the interim build for that long. Keeping this exact entry (adding a newer one alongside is fine) avoids that.

[alphaminetech]

Verified the 976000 entry independently.

Node: official signed v29.4.2.knots20260508 (unpatched), Ubuntu 24.04, 2 vCPU / 4 GB, prune=4000. It started from that release's 910000 assumeutxo snapshot and validated every block from 910,001 to the tip itself (its background validation below 910,000 is still running).

$ bitcoin-cli -rpcclienttimeout=0 -named dumptxoutset path=check-976000.dat rollback=976000
coins_written   167095701
base_hash       000000000000000098441aee029573795681eb1602c75271e809b136e9217373
base_height     976000
txoutset_hash   dbd67717d3f108e4fbd8b4f9efc4057cac11a0ba7c23584b43cca42c9edb7118
nchaintx        1417215373

$ sha256sum check-976000.dat
bfd2460a55ae1d2e94b9957ccd512ae027855feed1dbef996cfed0abebe5d123

All five values match this PR, and the dump is byte-identical to the published utxo-976000.dat.

Separately, we reproduced the Guix build of 29.4.2 + this commit (x86_64-linux-gnu) byte for byte: the archive's sha256 5c26890d72daa499fe22b905de5cfb0a78e2445aedbde0726278f57672106a9d matches the release.

[chrisguida]

An assembler-ready copy of this branch is at chrisguida/assumeutxo-976000-29+knots (same commit rebased onto the k385 merge, as #425 is); this branch stays as is for review.

[melvincarvalho]

Recomputed the snapshot at height 976000 on a stock v29.4.2.knots20260508 node using dumptxoutset rollback. Both the txoutset_hash and snapshot file SHA256 match the values in this PR:

txoutset_hash  dbd67717d3f108e4fbd8b4f9efc4057cac11a0ba7c23584b43cca42c9edb7118
file SHA256   bfd2460a55ae1d2e94b9957ccd512ae027855feed1dbef996cfed0abebe5d123

Signed attestation, checked in the following page: https://assumeutxo.com/snapshots/xbt-976000.html