Replay from genesis using a mithril snapshot

[fallen-icarus]

I am trying to use dolos to build up a local database of information relevant to a typical wallet user:

1. current UTxOs
2. current account balance
3. tx history

Dolos currently supports three sync options:

1. Mithril Snapshot
2. Dolos Snapshot
3. Relay Chain-Sync

But the only way to get the full tx history into my local database is with the Relay Chain-Sync because it is the only option to get Dolos to stream the txs from genesis. AFAIU the Mithril Snapshot has the full history and it has already been validated. So theoretically, I should be able to replay the history from genesis using a Mithril Snapshot but Dolos currently does not support this.

I know Dolos prunes its own database on regular intervals and this is fine. All I'm asking is that I can stream the history from a mithril snapshot and skip validation since I'm trusting the mithril signatures. This would allow a wallet to bootstrap the user's full information using dolos and just a mithril snapshot. By skipping the network fetch and validation steps, the replay using a mithril snapshot should be orders of magnitude faster than the Chain-Sync approach.

---

If this is already supported, can you point me in the right direction? I can't seem to get it to work.

[scarmuega]

This is actually already supported — dolos bootstrap mithril replays the entire immutable chain from genesis. It downloads the Mithril snapshot and imports every block from Origin to the snapshot tip, writing full transaction history to the archive (not just ledger state). Add --skip-validation to trust the Mithril signatures and skip recomputation for a faster import.

The reason you may not be seeing full history is archive pruning: sync.max_history (in dolos.toml) caps how many slots of archive history are retained, and our example configs set it (e.g. 2592000 for mainnet). Omit sync.max_history entirely and the archive is never pruned — full tx history from genesis is kept. You'll likely also want to drop/raise sync.max_rollback similarly.

Could you share what you tried and what failed? If bootstrap mithril errored out, the specific output would help.

[fallen-icarus]

I tried omitting sync.max_history but I still can't see older txs. I am seeing this shortly after running dolos daemon:

2026-05-26T14:42:35.003768Z  INFO stage{stage="apply"}:execute: dolos_core: pruning ledger for excess history max_ledger_slots=129600

For reference, this is my dolos.toml:

[upstream]
peer_address = "preprod-node.world.dev.cardano.org:30000"

[storage]
version = "v3"
path = "data"
# archive.backend = "noop"

[genesis]
byron_path = "byron.json"
shelley_path = "shelley.json"
alonzo_path = "alonzo.json"
conway_path = "conway.json"

[sync]
# max_rollback = 30240
# max_history = 30240 # 1 Week

# [serve.grpc]
# listen_address = "0.0.0.0:50051"

[serve.ouroboros]                                                                                                                                                                                                                                                                                                                              
listen_path = "./dolos.socket"

[mithril]
aggregator = "https://aggregator.release-preprod.api.mithril.network/aggregator"
genesis_key = "5b3132372c37332c3132342c3136312c362c3133372c3133312c3231332c3230372c3131372c3139382c38352c3137362c3139392c3136322c3234312c36382c3132332c3131392c3134352c31332c3233322c3234332c34392c3232392c322c3234392c3230352c3230352c33392c3233352c34345d"
ancillary_key = "5b3138392c3139322c3231362c3135302c3131342c3231362c3233372c3231302c34352c31382c32312c3139362c3230382c3234362c3134362c322c3235322c3234332c3235312c3139372c32382c3135372c3230342c3134352c33302c31342c3232382c3136382c3132392c38332c3133362c33365d"

[chain]
type = "cardano"
magic = 1
is_testnet = true

I also tried using --skip-validation but got no noticeable speedup. This was the full command I used:

dolos bootstrap mithril --force --skip-validation --retain-snapshot

It took ~30 minutes regardless of whether the --skip-validation flag was used. I was hoping to get it down to 5-10 minutes if I just blindly trust the mithril snapshot.