commonware-storage 2026.10.0

//! Authenticated journal implementation.
//!
//! An authenticated journal maintains a contiguous journal of items alongside a Merkle-family
//! structure. The item at index i in the journal corresponds to the leaf at Location i in the
//! Merkle structure. This structure enables efficient proofs that an item is included in the
//! journal at a specific location.
//!
//! # Ownership
//!
//! Mutating methods take the journal by value and return it on success. If a mutating
//! method returns an error, or its future is dropped before it finishes, the journal is
//! gone: state that was not yet durable is discarded, but everything already on disk stays
//! recoverable.

use crate::{
    Context,
    journal::{
        Error as JournalError,
        contiguous::{Batch, Contiguous, Many, Mutable},
    },
    merkle::{
        self, Bagging, Family, Location, Position, Proof, Readable, batch, full::Merkle,
        hasher::Standard as StandardHasher, mem::Mem,
    },
};
use alloc::{
    sync::{Arc, Weak},
    vec::Vec,
};
use commonware_codec::{Encode, EncodeShared};
use commonware_cryptography::{Digest, Hasher};
use commonware_macros::boxed;
use commonware_parallel::Strategy;
use commonware_runtime::{Handle, ReadOptions};
use commonware_utils::NZU64;
use core::{
    num::{NonZeroU64, NonZeroUsize},
    ops::Range,
};
use futures::{Stream, TryFutureExt as _, try_join};
use thiserror::Error;
use tracing::{debug, warn};

/// Errors that can occur when interacting with an authenticated journal.
#[derive(Error, Debug)]
pub enum Error<F: Family> {
    #[error("merkle error: {0}")]
    Merkle(#[from] merkle::Error<F>),

    #[error("journal error: {0}")]
    Journal(#[from] super::Error),
}

/// Strong ref to an ancestor [`MerkleizedBatch`] in the journal-batch chain.
type MerkleizedParent<F, H, Item, S> = Arc<MerkleizedBatch<F, <H as Hasher>::Digest, Item, S>>;

/// A speculative batch whose root digest has not yet been computed,
/// in contrast to [`MerkleizedBatch`].
pub struct UnmerkleizedBatch<F: Family, H: Hasher, Item: Send + Sync, S: Strategy> {
    // The inner batch of Merkle leaf digests.
    inner: batch::UnmerkleizedBatch<F, H::Digest, S>,
    // The hasher to use for hashing the items.
    hasher: StandardHasher<H>,
    // The items to append from this batch.
    items: Vec<Item>,
    // This batch's parent, or None if the parent is the journal itself.
    parent: Option<MerkleizedParent<F, H, Item, S>>,
}

type MerkleizedBatchArc<F, H, Item, S> = Arc<MerkleizedBatch<F, <H as Hasher>::Digest, Item, S>>;

impl<F: Family, H: Hasher, Item: Encode + Send + Sync, S: Strategy>
    UnmerkleizedBatch<F, H, Item, S>
{
    /// Add an item to the batch.
    #[allow(clippy::should_implement_trait)]
    pub fn add(mut self, item: Item) -> Self {
        let encoded = item.encode();
        self.inner = self.inner.add(&self.hasher, &encoded);
        self.items.push(item);
        self
    }

    /// Collect the items of `parent` and the ancestors still reachable through its parent chain,
    /// in root-to-tip order. Skips ancestors without items.
    fn collect_ancestor_items(parent: &MerkleizedParent<F, H, Item, S>) -> Vec<Arc<Vec<Item>>> {
        let mut items = Vec::new();
        if !parent.items.is_empty() {
            items.push(Arc::clone(&parent.items));
        }
        let mut current = parent.parent.as_ref().and_then(Weak::upgrade);
        while let Some(batch) = current {
            if !batch.items.is_empty() {
                items.push(Arc::clone(&batch.items));
            }
            current = batch.parent.as_ref().and_then(Weak::upgrade);
        }
        items.reverse();
        items
    }

    /// Merkleize the batch.
    /// `base` provides committed node data as fallback during hash computation.
    pub fn merkleize(self, base: &Mem<F, H::Digest>) -> MerkleizedBatchArc<F, H, Item, S> {
        let Self {
            inner,
            hasher,
            items,
            parent,
        } = self;

        let ancestor_items = parent
            .as_ref()
            .map_or_else(Vec::new, Self::collect_ancestor_items);
        let items = Arc::new(items);
        let merkle = inner.merkleize(base, &hasher);
        Arc::new(MerkleizedBatch {
            inner: merkle,
            bagging: hasher.root_bagging(),
            items,
            parent: parent.as_ref().map(Arc::downgrade),
            ancestor_items,
        })
    }

    /// Add caller-supplied items to the batch.
    ///
    /// # Panics
    ///
    /// Panics if items were previously added via [`add`](Self::add).
    pub(crate) fn add_many(mut self, items: Vec<Item>) -> Self {
        assert!(
            self.items.is_empty(),
            "add_many expects no items added via add"
        );

        self.inner = self.inner.add_many(&self.hasher, &items);
        self.items = items;
        self
    }
}

/// A speculative batch whose root digest has been computed, in contrast to [`UnmerkleizedBatch`].
#[derive(Clone, Debug)]
pub struct MerkleizedBatch<F: Family, D: Digest, Item: Send + Sync, S: Strategy> {
    /// The inner batch of Merkle leaf digests.
    pub(crate) inner: Arc<batch::MerkleizedBatch<F, D, S>>,
    /// The peak bagging policy inherited from the parent journal or batch.
    bagging: Bagging,
    /// The items to append from this batch.
    items: Arc<Vec<Item>>,
    /// This batch's parent, or None if the parent is the journal itself.
    parent: Option<Weak<Self>>,
    /// Ancestor item batches collected at merkleize time (root-to-tip order).
    pub(crate) ancestor_items: Vec<Arc<Vec<Item>>>,
}

impl<F: Family, D: Digest, Item: Send + Sync, S: Strategy> MerkleizedBatch<F, D, Item, S> {
    /// The number of items visible through this batch, including ancestors.
    pub(crate) fn size(&self) -> u64 {
        *self.inner.leaves()
    }

    /// Compute the root digest after this batch is applied using `inactive_peaks` and the bagging
    /// carried by `hasher`.
    pub fn root(
        &self,
        hasher: &impl merkle::hasher::Hasher<F, Digest = D>,
        inactive_peaks: usize,
    ) -> Result<D, merkle::Error<F>> {
        self.inner.root(hasher, inactive_peaks)
    }

    /// Inclusion proof for the element at `loc`.
    pub fn proof(
        &self,
        base: &Mem<F, D>,
        hasher: &impl merkle::hasher::Hasher<F, Digest = D>,
        loc: Location<F>,
        inactive_peaks: usize,
    ) -> Result<Proof<F, D>, merkle::Error<F>> {
        self.inner.proof(base, hasher, loc, inactive_peaks)
    }

    /// Inclusion proof for all elements in `range`.
    pub fn range_proof(
        &self,
        base: &Mem<F, D>,
        hasher: &impl merkle::hasher::Hasher<F, Digest = D>,
        range: core::ops::Range<Location<F>>,
        inactive_peaks: usize,
    ) -> Result<Proof<F, D>, merkle::Error<F>> {
        self.inner.range_proof(base, hasher, range, inactive_peaks)
    }

    /// The items added in this batch.
    pub(crate) const fn items(&self) -> &Arc<Vec<Item>> {
        &self.items
    }

    /// Create a new speculative batch of operations with this batch as its parent.
    ///
    /// The batch becomes invalid if any ancestor is dropped before being applied, or a sibling
    /// fork has been applied.
    pub fn new_batch<H: Hasher<Digest = D>>(self: &Arc<Self>) -> UnmerkleizedBatch<F, H, Item, S>
    where
        Item: Encode,
    {
        UnmerkleizedBatch {
            inner: self.inner.new_batch(),
            hasher: StandardHasher::new(self.bagging),
            items: Vec::new(),
            parent: Some(Arc::clone(self)),
        }
    }
}

impl<F: Family, D: Digest, Item: Send + Sync, S: Strategy> Readable
    for MerkleizedBatch<F, D, Item, S>
{
    type Family = F;
    type Digest = D;

    fn size(&self) -> Position<F> {
        self.inner.size()
    }

    fn get_node(&self, pos: Position<F>) -> Option<D> {
        self.inner.get_node(pos)
    }
}

/// An append-only data structure that maintains a sequential journal of items alongside a
/// Merkle-family structure. The item at index i in the journal corresponds to the leaf at Location
/// i in the Merkle structure. This structure enables efficient proofs that an item is included in
/// the journal at a specific location.
pub struct Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Contiguous<Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    /// Merkle structure where each leaf is an item digest.
    /// Invariant: leaf i corresponds to item i in the journal.
    pub(crate) merkle: Merkle<F, E, H::Digest, S>,

    /// Journal of items.
    /// Invariant: item i corresponds to leaf i in the Merkle structure.
    pub(crate) journal: C,

    pub(crate) hasher: StandardHasher<H>,
}

impl<F, E, C, H, S> core::fmt::Debug for Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Contiguous<Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("Journal")
            .field("size", &self.size())
            .finish_non_exhaustive()
    }
}

impl<F, E, C, H, S> Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Contiguous<Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    /// Returns the Location of the next item appended to the journal.
    pub fn size(&self) -> Location<F> {
        Location::new(self.journal.bounds().end)
    }

    /// Compute the root of the Merkle structure using `inactive_peaks` and the bagging carried by
    /// the journal's hasher.
    pub fn root(&self, inactive_peaks: usize) -> Result<H::Digest, Error<F>> {
        self.merkle
            .root(&self.hasher, inactive_peaks)
            .map_err(Into::into)
    }

    /// Convert authenticated-journal errors to the contiguous journal trait error type.
    fn map_error(error: Error<F>) -> JournalError {
        match error {
            Error::Journal(inner) => inner,
            Error::Merkle(inner) => JournalError::Merkle(anyhow::Error::from(inner)),
        }
    }

    /// Return a reference to the merkleization strategy.
    pub const fn strategy(&self) -> &S {
        self.merkle.strategy()
    }

    /// Create a speculative batch atop this journal.
    pub fn new_batch(&self) -> UnmerkleizedBatch<F, H, C::Item, S> {
        let root = self.merkle.to_batch();
        UnmerkleizedBatch {
            inner: root.new_batch(),
            hasher: StandardHasher::new(self.hasher.root_bagging()),
            items: Vec::new(),
            parent: None,
        }
    }

    /// Add `items` to `batch`, merkleize, and compute the post-apply root, all as one CPU-bound job
    /// submitted through [`Strategy::spawn`].
    ///
    /// The job hashes against an immutable snapshot of the committed Merkle state, so a parallel
    /// strategy can host the batch's dominant CPU phase on its own pool instead of occupying the
    /// calling task. If the job's caller is cancelled, the job still runs to completion
    /// against its snapshot and the result is discarded.
    pub(crate) async fn merkleize(
        &self,
        batch: UnmerkleizedBatch<F, H, C::Item, S>,
        items: Vec<C::Item>,
        inactive_peaks: usize,
    ) -> Result<(MerkleizedBatchArc<F, H, C::Item, S>, H::Digest), merkle::Error<F>>
    where
        C::Item: 'static,
    {
        let ancestors = batch.inner.retain_ancestors();
        let mem = self.merkle.snapshot();
        let hasher = self.hasher.clone();
        let strategy = self.strategy().clone();
        strategy
            .spawn(items.len(), move |_| {
                let merkleized = batch.add_many(items).merkleize(&mem);
                let root = merkleized.root(&hasher, inactive_peaks)?;
                drop(ancestors);
                Ok((merkleized, root))
            })
            .await
    }

    /// Create an owned [`MerkleizedBatch`] representing the current committed state.
    ///
    /// The batch has no items (the committed items are on disk, not in memory).
    /// This is the starting point for building owned batch chains.
    pub(crate) fn to_merkleized_batch(&self) -> Arc<MerkleizedBatch<F, H::Digest, C::Item, S>> {
        Arc::new(MerkleizedBatch {
            inner: self.merkle.to_batch(),
            bagging: self.hasher.root_bagging(),
            items: Arc::new(Vec::new()),
            parent: None,
            ancestor_items: Vec::new(),
        })
    }

    /// Generate a proof of inclusion for items starting at `start_loc`.
    ///
    /// Returns a proof and the items corresponding to the leaves in the range `start_loc..end_loc`,
    /// where `end_loc` is the minimum of the current item count and `start_loc + max_ops`.
    ///
    /// # Errors
    ///
    /// - Returns [Error::Merkle] with [merkle::Error::RangeOutOfBounds] if `start_loc` >= current
    ///   item count.
    /// - Returns [Error::Journal] with [crate::journal::Error::ItemPruned] or [Error::Merkle] with
    ///   [merkle::Error::ElementPruned] if a required item or Merkle node has been pruned.
    pub async fn proof(
        &self,
        start_loc: Location<F>,
        max_ops: NonZeroU64,
        inactive_peaks: usize,
    ) -> Result<(Proof<F, H::Digest>, Vec<C::Item>), Error<F>> {
        self.historical_proof(self.size(), start_loc, max_ops, inactive_peaks)
            .await
    }

    /// Inclusion proof for the items `batch` appends, anchored at the batch's speculative tip.
    ///
    /// Nodes below the batch chain are read from this journal's
    /// [Merkle store][crate::merkle::mem::Mem], which retains them at least until
    /// the batch's changes are flushed.
    pub fn speculative_proof(
        &self,
        batch: &MerkleizedBatch<F, H::Digest, C::Item, S>,
        inactive_peaks: usize,
    ) -> Result<Proof<F, H::Digest>, Error<F>> {
        let end = batch.size();
        let start = Location::new(end - batch.items().len() as u64);
        batch
            .range_proof(
                self.merkle.mem(),
                &self.hasher,
                start..Location::new(end),
                inactive_peaks,
            )
            .map_err(Error::Merkle)
    }

    /// Merkle frontier at the first item `batch` appends ([`Family::nodes_to_pin`]).
    ///
    /// Nodes below the batch chain are read from this journal's
    /// [Merkle store][crate::merkle::mem::Mem], which retains them at least until
    /// the batch's changes are flushed.
    pub fn speculative_pinned_nodes(
        &self,
        batch: &MerkleizedBatch<F, H::Digest, C::Item, S>,
    ) -> Result<Vec<H::Digest>, Error<F>> {
        let start = Location::new(batch.size() - batch.items().len() as u64);
        let mem = self.merkle.mem();
        F::nodes_to_pin(start)
            .map(|pos| {
                batch
                    .get_node(pos)
                    .or_else(|| mem.get_node(pos))
                    .ok_or(merkle::Error::ElementPruned(pos))
            })
            .collect::<Result<Vec<_>, _>>()
            .map_err(Error::Merkle)
    }

    /// Generate a historical proof with respect to the state of the Merkle structure when it had
    /// `historical_leaves` leaves.
    ///
    /// Returns a proof and the items corresponding to the leaves in the range `start_loc..end_loc`,
    /// where `end_loc` is the minimum of `historical_leaves` and `start_loc + max_ops`.
    ///
    /// # Errors
    ///
    /// - Returns [Error::Merkle] with [merkle::Error::RangeOutOfBounds] if `start_loc` >=
    ///   `historical_leaves` or `historical_leaves` > number of items in the journal.
    /// - Returns [Error::Journal] with [crate::journal::Error::ItemPruned] or [Error::Merkle] with
    ///   [merkle::Error::ElementPruned] if a required item or Merkle node has been pruned.
    pub async fn historical_proof(
        &self,
        historical_leaves: Location<F>,
        start_loc: Location<F>,
        max_ops: NonZeroU64,
        inactive_peaks: usize,
    ) -> Result<(Proof<F, H::Digest>, Vec<C::Item>), Error<F>> {
        let bounds = self.journal.bounds();

        if *historical_leaves > bounds.end {
            return Err(merkle::Error::RangeOutOfBounds(Location::new(bounds.end)).into());
        }
        if start_loc >= historical_leaves {
            return Err(merkle::Error::RangeOutOfBounds(start_loc).into());
        }

        let end_loc = std::cmp::min(historical_leaves, start_loc.saturating_add(max_ops.get()));

        let hasher = self.hasher.clone();
        let proof = self
            .merkle
            .historical_range_proof(
                &hasher,
                historical_leaves,
                start_loc..end_loc,
                inactive_peaks,
            )
            .await?;

        let positions: Vec<u64> = (*start_loc..*end_loc).collect();
        let ops = self.journal.read_many(&positions).await?;

        Ok((proof, ops))
    }

    /// Like [`Contiguous::read_many`], but returns the items partitioned into the shards the
    /// probe ran with. Concatenating the shards yields the items in `positions` order.
    ///
    /// Large batches shard the page-cache probe across the strategy pool. Each shard
    /// assembles its own hits while they are still cache-hot on the probing worker, so bulk
    /// callers that can consume partitioned results (e.g. the floor raise, which classifies
    /// candidates in chunks) skip the serial reassembly a flat result would require.
    pub(crate) async fn read_many_sharded(
        &self,
        positions: &[u64],
    ) -> Result<Vec<Vec<C::Item>>, JournalError> {
        if positions.is_empty() {
            return Ok(Vec::new());
        }

        // Probe page-cache hits synchronously and complete the misses with one batched read.
        // The strategy policy decides per batch size whether the probe runs on the calling
        // thread or sharded across the pool (one scratch buffer per shard and one cache-lock
        // acquisition per blob a shard touches). The sortedness assert keeps contract
        // violations deterministic: past it, a non-increasing batch would only trip per-shard
        // validation when an inversion lands inside a single shard.
        assert!(
            positions.is_sorted_by(|a, b| a < b),
            "positions must be strictly increasing"
        );
        let strategy = self.strategy();
        let journal = &self.journal;

        // Each shard yields its hits densely plus the shard-local indices it declined.
        let probe = |positions: &[u64]| -> (Vec<C::Item>, Vec<usize>) {
            let probed = journal.try_read_many_sync(positions);
            let mut hits = Vec::with_capacity(probed.len());
            let mut missed = Vec::new();
            for (idx, item) in probed.into_iter().enumerate() {
                match item {
                    Some(item) => hits.push(item),
                    None => missed.push(idx),
                }
            }
            (hits, missed)
        };
        let shards: Vec<(Vec<C::Item>, Vec<usize>)> =
            strategy.run_batches(positions.len(), NonZeroUsize::MIN, 1, |batches| {
                batches.map_collect_vec(|ranges| ranges, |range| probe(&positions[range]))
            });

        // The declined positions are a strictly increasing subsequence of `positions`, so one
        // batched read serves them all. Each shard covers the slice of `positions` starting
        // at the previous shards' total item count, whatever geometry the probe ran with.
        let mut misses: Vec<u64> = Vec::new();
        let mut offset = 0;
        for (hits, missed) in &shards {
            misses.extend(missed.iter().map(|idx| positions[offset + idx]));
            offset += hits.len() + missed.len();
        }
        if misses.is_empty() {
            return Ok(shards.into_iter().map(|(hits, _)| hits).collect());
        }
        let mut fetched = journal.read_many(&misses).await?.into_iter();

        // Weave the fetched items back into each shard that declined positions.
        let mut result = Vec::with_capacity(shards.len());
        for (hits, missed) in shards {
            if missed.is_empty() {
                result.push(hits);
                continue;
            }
            let total = hits.len() + missed.len();
            let mut woven = Vec::with_capacity(total);
            let mut hits = hits.into_iter();
            let mut missed = missed.into_iter().peekable();
            for idx in 0..total {
                if missed.next_if_eq(&idx).is_some() {
                    woven.push(fetched.next().expect("one fetched item per miss"));
                } else {
                    woven.push(hits.next().expect("one probed item per hit"));
                }
            }
            result.push(woven);
        }
        Ok(result)
    }
}

impl<F, E, C, H, S> Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Mutable<Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    /// Begin durably persisting the journal.
    ///
    /// Awaiting the returned [Handle] provides the same durability guarantee as [Self::commit].
    /// Also tries to advance the recovery watermarks to bound startup recovery. Use
    /// [Self::sync] to guarantee no recovery is needed.
    pub async fn start_sync(mut self) -> Result<(Self, Handle<()>), Error<F>> {
        let (journal_handle, merkle_handle);
        ((self.journal, journal_handle), (self.merkle, merkle_handle)) = try_join!(
            self.journal.start_sync().map_err(Error::Journal),
            self.merkle.start_sync().map_err(Error::Merkle)
        )?;

        let handle =
            Handle::from_future(
                async move { try_join!(journal_handle, merkle_handle).map(|_| ()) },
            );
        Ok((self, handle))
    }

    /// Durably persist the journal. This is faster than `sync()` but does not guarantee that the
    /// Merkle structure is durably persisted, meaning recovery may be required on startup in the
    /// event of a crash.
    pub async fn commit(mut self) -> Result<Self, Error<F>> {
        // Though not necessary for recovery, we flush the merkle structure (without syncing it) to
        // limit memory bloat.
        (self.journal, self.merkle) = try_join!(
            self.journal.commit().map_err(Error::Journal),
            self.merkle.flush().map_err(Error::Merkle)
        )?;

        Ok(self)
    }

    /// Create a [Journal], replaying any journal operations missing from Merkle.
    ///
    /// Returns an error if the Merkle tree extends past the journal end.
    #[boxed]
    pub async fn from_components(
        merkle: Merkle<F, E, H::Digest, S>,
        journal: C,
        hasher: StandardHasher<H>,
        apply_batch_size: NonZeroU64,
    ) -> Result<Self, Error<F>> {
        let merkle = Self::align(merkle, &journal, &hasher, apply_batch_size).await?;

        // Sync the Merkle structure to disk to avoid having to repeat any recovery that may have
        // been performed on next startup.
        let merkle = merkle.sync().await?;

        Ok(Self {
            merkle,
            journal,
            hasher,
        })
    }

    /// Align the Merkle structure with the journal.
    ///
    /// The Merkle structure must not extend past the journal end. Missing leaves are read and
    /// added in batches of `apply_batch_size` to bound peak memory use. Each batch's items are
    /// buffered in memory so their leaves can be hashed across the strategy.
    async fn align(
        mut merkle: Merkle<F, E, H::Digest, S>,
        journal: &C,
        hasher: &StandardHasher<H>,
        apply_batch_size: NonZeroU64,
    ) -> Result<Merkle<F, E, H::Digest, S>, Error<F>> {
        let journal_size = journal.bounds().end;
        let mut merkle_leaves = merkle.leaves();
        if merkle_leaves > journal_size {
            return Err(Error::Journal(JournalError::Corruption(
                "Merkle size exceeds the initialized operation journal".into(),
            )));
        }

        // If the Merkle structure is behind, replay journal items to catch up.
        if merkle_leaves < journal_size {
            let replay_count = journal_size - *merkle_leaves;
            warn!(
                ?journal_size,
                replay_count, "Merkle structure lags behind journal, replaying journal to catch up"
            );

            while merkle_leaves < journal_size {
                let count = apply_batch_size.get().min(journal_size - *merkle_leaves);
                let positions: Vec<u64> = (*merkle_leaves..*merkle_leaves + count).collect();
                let items = journal.read_many(&positions).await?;
                merkle_leaves += count;

                let batch = merkle.new_batch().add_many(hasher, &items);
                let batch = batch.merkleize(merkle.mem(), hasher);
                merkle = merkle.apply_batch(&batch)?;
            }
            return Ok(merkle);
        }

        // At this point the Merkle structure and journal should be consistent.
        assert_eq!(journal.bounds().end, *merkle.leaves());

        Ok(merkle)
    }

    /// Append an item to the journal and update the Merkle structure.
    pub async fn append(mut self, item: &C::Item) -> Result<(Self, Location<F>), Error<F>> {
        let encoded_item = item.encode();

        // Append item to the journal, then update the Merkle structure state.
        let loc;
        (self.journal, loc) = self.journal.append(item).await?;
        let unmerkleized_batch = self.merkle.new_batch().add(&self.hasher, &encoded_item);
        let batch = unmerkleized_batch.merkleize(self.merkle.mem(), &self.hasher);
        self.merkle = self.merkle.apply_batch(&batch)?;

        Ok((self, Location::new(loc)))
    }

    /// Apply a batch to the journal.
    ///
    /// A batch is valid if the journal has not been modified since the batch
    /// chain was created, or if only ancestors of this batch have been applied.
    /// Already-committed ancestors are skipped automatically.
    /// Applying a batch from a different fork returns an error.
    pub async fn apply_batch(
        mut self,
        batch: &MerkleizedBatch<F, H::Digest, C::Item, S>,
    ) -> Result<Self, Error<F>> {
        // Validate before appending any item, so a rejected batch writes nothing.
        let start = self.merkle.mem().validate_batch(&batch.inner)?;

        // Items are collected over the journal batch chain and Merkle records over the inner
        // chain. A journal batch can be dropped while its Merkle batch stays alive, so the item
        // list can be shorter, but both lists end at this batch's parent, so the ancestors still
        // to replay are the newest `remaining` entries of each. Reject the batch before appending
        // anything if their items are gone.
        let remaining = batch.inner.ancestor_count() - start;
        let first = batch.ancestor_items.len().checked_sub(remaining).ok_or(
            merkle::Error::AncestorDropped {
                expected: batch.inner.size(),
                actual: self.merkle.size(),
            },
        )?;

        // Append the remaining ancestor items in root-to-tip order, then this batch's items, in
        // one append_many call so the journal's write lock is taken once.
        let mut batches: Vec<&[C::Item]> = Vec::with_capacity(remaining + 1);
        batches.extend(
            batch.ancestor_items[first..]
                .iter()
                .map(|items| items.as_slice()),
        );
        if !batch.items.is_empty() {
            batches.push(&batch.items);
        }
        if !batches.is_empty() {
            (self.journal, _) = self.journal.append_many(Many::Nested(&batches)).await?;
        }

        self.merkle = self.merkle.apply_batch(&batch.inner)?;
        assert_eq!(*self.merkle.leaves(), self.journal.bounds().end);
        Ok(self)
    }

    /// Prune journal items before `prune_loc`, then raise the Merkle pruning boundary to the
    /// journal's retained start if it is lower.
    ///
    /// # Returns
    /// The journal's retained start, which may be less than `prune_loc`. After state sync, the
    /// Merkle pruning boundary can remain above the returned start.
    #[boxed]
    pub async fn prune(self, prune_loc: Location<F>) -> Result<(Self, Location<F>), Error<F>> {
        let (journal, boundary, _) = self.prune_inner(prune_loc).await?;
        Ok((journal, boundary))
    }

    async fn prune_inner(
        mut self,
        prune_loc: Location<F>,
    ) -> Result<(Self, Location<F>, bool), Error<F>> {
        if self.merkle.size() == 0 {
            // DB is empty, nothing to prune.
            let boundary = Location::new(self.journal.bounds().start);
            return Ok((self, boundary, false));
        }

        // Sync the Merkle structure before pruning the journal, otherwise its last element could
        // end up behind the journal's first element after a crash, and there would be no way to
        // replay the items between the structure's last element and the journal's first element.
        // Commit the journal alongside: the prune target may be justified by a buffered append
        // (e.g. a commit operation), and pruning does not guarantee buffered appends are durable.
        (self.journal, self.merkle) = try_join!(
            self.journal.commit().map_err(Error::Journal),
            self.merkle.sync().map_err(Error::Merkle)
        )?;

        let journal_pruned;
        (self.journal, journal_pruned) = self.journal.prune(*prune_loc).await?;
        let bounds = self.journal.bounds();
        let boundary = Location::new(bounds.start);
        let merkle_boundary = self.merkle.bounds().start;

        if boundary > merkle_boundary {
            debug!(size = ?bounds.end, ?prune_loc, boundary = ?bounds.start, "pruned inactive ops");
            self.merkle = self.merkle.prune(boundary).await?;
        }

        Ok((self, boundary, journal_pruned || boundary > merkle_boundary))
    }

    /// Destroy the authenticated journal, removing all data from disk.
    #[boxed]
    pub async fn destroy(self) -> Result<(), Error<F>> {
        // `try_join!` contains an await boundary, so destructure first to avoid
        // stack growth from retaining the entire `self` in the future.
        let Self {
            journal, merkle, ..
        } = self;
        try_join!(
            journal.destroy().map_err(Error::Journal),
            merkle.destroy().map_err(Error::Merkle),
        )?;

        Ok(())
    }

    /// Durably persist the journal, ensuring no recovery is required on startup.
    pub async fn sync(mut self) -> Result<Self, Error<F>> {
        (self.journal, self.merkle) = try_join!(
            self.journal.sync().map_err(Error::Journal),
            self.merkle.sync().map_err(Error::Merkle)
        )?;

        Ok(self)
    }
}

/// Selected journal and Merkle state awaiting coordinated durable finalization.
pub(crate) struct Recovery<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Backing<E>,
    H: Hasher,
    S: Strategy,
{
    /// Operation journal awaiting finalization at `selected_end`.
    journal: C::Recovery,
    /// Merkle recovery capped at `selected_end` and covering the operation journal's retained start.
    merkle: merkle::full::Recovery<F, E, H::Digest, S>,
    /// Hasher and peak-bagging mode retained for Merkle alignment and the published journal.
    hasher: StandardHasher<H>,
    /// Exclusive operation end chosen for publication.
    selected_end: u64,
}

impl<F, E, C, H, S> Recovery<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Backing<E, Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    /// Range selected for publication.
    pub(crate) fn bounds(&self) -> Range<u64> {
        self.journal.bounds().start..self.selected_end
    }

    /// Whether storage was empty before commit selection.
    pub(crate) fn is_fresh(&self) -> bool {
        self.journal.bounds() == (0..0)
    }

    /// Read an operation to validate its recovery requirements.
    pub(crate) async fn read(&self, pos: u64) -> Result<C::Item, JournalError> {
        self.journal.read(pos).await
    }

    /// Persist the selected operations before the Merkle state acknowledging them.
    pub(crate) async fn finish(self) -> Result<Journal<F, E, C, H, S>, Error<F>> {
        // Publish and fully sync the selected operations before finalizing Merkle state that
        // acknowledges them.
        let bounds = self.journal.bounds();
        if self.selected_end < bounds.end {
            warn!(
                journal_size = bounds.end,
                rewound_items = bounds.end - self.selected_end,
                "rewinding journal items"
            );
        }
        let journal = self.journal.finish(self.selected_end).await?;
        let journal = journal.sync().await?;

        // Finalize the selected Merkle prefix, replay any durable operation suffix, and persist it.
        let merkle = self.merkle.finish().await?;
        let merkle =
            Journal::<F, E, C, H, S>::align(merkle, &journal, &self.hasher, APPLY_BATCH_SIZE)
                .await?;
        let merkle = merkle.sync().await?;
        Ok(Journal {
            journal,
            merkle,
            hasher: self.hasher,
        })
    }
}

/// The number of items to apply to the Merkle structure in a single batch.
const APPLY_BATCH_SIZE: NonZeroU64 = NZU64!(1 << 16);

impl<F, E, C, H, S> Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Backing<E, Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    /// Create an authenticated journal ending at its last matching item.
    ///
    /// An empty retained range preserves its append position.
    #[boxed]
    pub async fn new(
        context: E,
        merkle_cfg: merkle::full::Config<S>,
        journal_cfg: C::Config,
        predicate: fn(&C::Item) -> bool,
        bagging: merkle::Bagging,
    ) -> Result<Self, Error<F>> {
        Self::prepare(context, merkle_cfg, journal_cfg, None, predicate, bagging)
            .await?
            .finish()
            .await
    }

    /// Recover a journal whose last matching item ends at or below `max_size`.
    ///
    /// Initialization durably discards the suffix before returning. A cap below retained
    /// history, or pruned history with no matching retained item, returns a pruning error.
    #[boxed]
    pub async fn init_at_most(
        context: E,
        merkle_cfg: merkle::full::Config<S>,
        journal_cfg: C::Config,
        max_size: u64,
        predicate: fn(&C::Item) -> bool,
        bagging: merkle::Bagging,
    ) -> Result<Self, Error<F>> {
        Self::prepare(
            context,
            merkle_cfg,
            journal_cfg,
            Some(max_size),
            predicate,
            bagging,
        )
        .await?
        .finish()
        .await
    }

    /// Select and validate component availability before deliberately discarding history.
    pub(crate) async fn prepare(
        context: E,
        merkle_cfg: merkle::full::Config<S>,
        journal_cfg: C::Config,
        max_size: Option<u64>,
        predicate: fn(&C::Item) -> bool,
        bagging: merkle::Bagging,
    ) -> Result<Recovery<F, E, C, H, S>, Error<F>> {
        // Select the operation prefix before constraining Merkle recovery to the same end.
        let journal = C::recover(context.child("journal"), journal_cfg, max_size).await?;
        let bounds = journal.bounds();

        // A fully pruned empty journal has no retained item to match, but its append position
        // remains the selected end.
        let selected_end = if max_size.is_none() && bounds.is_empty() {
            bounds.end
        } else {
            journal
                .last_matching(max_size.unwrap_or(u64::MAX), predicate)
                .await?
        };

        // Recover Merkle at the selected operation end and require it to cover retained
        // operations.
        let hasher = StandardHasher::<H>::new(bagging);
        let merkle = Merkle::prepare(
            context.child("merkle"),
            &hasher,
            merkle_cfg,
            Some(Location::new(selected_end)),
        )
        .await?;
        if *merkle.leaves() < bounds.start {
            return Err(JournalError::ItemPruned(*merkle.leaves()).into());
        }
        Ok(Recovery {
            journal,
            merkle,
            hasher,
            selected_end,
        })
    }
}

impl<F, E, C, H, S> Contiguous for Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Contiguous<Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    type Item = C::Item;

    fn bounds(&self) -> Range<u64> {
        self.journal.bounds()
    }

    async fn read(&self, position: u64) -> Result<C::Item, JournalError> {
        self.journal.read(position).await
    }

    async fn read_many(&self, positions: &[u64]) -> Result<Vec<C::Item>, JournalError> {
        let mut shards = self.read_many_sharded(positions).await?;
        if shards.len() == 1 {
            return Ok(shards.pop().expect("length checked"));
        }
        let mut items = Vec::with_capacity(positions.len());
        for shard in shards {
            items.extend(shard);
        }
        Ok(items)
    }

    fn try_read_sync(&self, position: u64) -> Option<C::Item> {
        self.journal.try_read_sync(position)
    }

    fn try_read_many_sync(&self, positions: &[u64]) -> Vec<Option<C::Item>> {
        self.journal.try_read_many_sync(positions)
    }

    async fn replay(
        &self,
        range: Range<u64>,
        buffer: NonZeroUsize,
        read_options: ReadOptions,
    ) -> Result<impl Stream<Item = Result<Batch<C::Item>, JournalError>> + Send, JournalError> {
        self.journal.replay(range, buffer, read_options).await
    }
}

impl<F, E, C, H, S> Mutable for Journal<F, E, C, H, S>
where
    F: Family,
    E: Context,
    C: Mutable<Item: EncodeShared>,
    H: Hasher,
    S: Strategy,
{
    async fn append(self, item: &Self::Item) -> Result<(Self, u64), JournalError> {
        let (journal, loc) = Self::append(self, item).await.map_err(Self::map_error)?;

        Ok((journal, *loc))
    }

    async fn append_many(
        mut self,
        items: Many<'_, Self::Item>,
    ) -> Result<(Self, u64), JournalError> {
        // The per-item loop below never reaches the backing journal's shared empty check, so the
        // trait's EmptyAppend contract must be enforced here.
        if items.is_empty() {
            return Err(JournalError::EmptyAppend);
        }

        // Every append must also update the Merkle structure, so items append one at a time.
        // Batched appends of already-merkleized items go through `apply_batch`, which batches
        // the backing journal writes instead.
        let mut last_pos = self.journal.bounds().end;
        match items {
            Many::Flat(items) => {
                for item in items {
                    let (journal, loc) = Self::append(self, item).await.map_err(Self::map_error)?;
                    self = journal;
                    last_pos = *loc;
                }
            }
            Many::Nested(nested_items) => {
                for items in nested_items {
                    for item in *items {
                        let (journal, loc) =
                            Self::append(self, item).await.map_err(Self::map_error)?;
                        self = journal;
                        last_pos = *loc;
                    }
                }
            }
        }
        Ok((self, last_pos))
    }

    async fn prune(self, min_position: u64) -> Result<(Self, bool), JournalError> {
        let prune_to = {
            let bounds = self.journal.bounds();
            min_position.min(bounds.end)
        };

        let (journal, _, pruned) = self
            .prune_inner(Location::new(prune_to))
            .await
            .map_err(Self::map_error)?;
        Ok((journal, pruned))
    }

    async fn start_sync(self) -> Result<(Self, Handle<()>), JournalError> {
        Self::start_sync(self).await.map_err(Self::map_error)
    }

    async fn commit(self) -> Result<Self, JournalError> {
        Self::commit(self).await.map_err(Self::map_error)
    }

    async fn sync(self) -> Result<Self, JournalError> {
        Self::sync(self).await.map_err(Self::map_error)
    }

    async fn destroy(self) -> Result<(), JournalError> {
        Self::destroy(self).await.map_err(Self::map_error)
    }
}

/// A journal under initialization, with read access before its retained end is finalized.
///
/// Finishing consumes this owner. A live journal cannot regain recovery access. Opening may
/// repair torn storage, but selecting a prefix does not itself discard journal history.
pub trait BackingRecovery: Send + Sync + Sized {
    /// The live journal produced after recovery finishes.
    type Journal: Mutable;

    /// Available item positions, including the retained pruning boundary.
    fn bounds(&self) -> Range<u64>;

    /// Read a retained item for initialization validation.
    fn read(
        &self,
        position: u64,
    ) -> impl Future<Output = Result<<Self::Journal as Contiguous>::Item, JournalError>> + Send;

    /// Discard stored items and establish an empty journal at `size` during initialization.
    fn reset(self, size: u64) -> impl Future<Output = Result<Self, JournalError>> + Send;

    /// Durably retain at most `size` items and publish the live journal.
    fn finish(self, size: u64) -> impl Future<Output = Result<Self::Journal, JournalError>> + Send;

    /// Select the latest retained item satisfying `predicate` below an exclusive ceiling.
    fn last_matching<P>(
        &self,
        ceiling: u64,
        mut predicate: P,
    ) -> impl Future<Output = Result<u64, JournalError>> + Send
    where
        P: FnMut(&<Self::Journal as Contiguous>::Item) -> bool + Send,
    {
        async move {
            let bounds = self.bounds();

            // A ceiling below retained history cannot select a supported prefix.
            if ceiling < bounds.start {
                return Err(JournalError::ItemPruned(ceiling));
            }

            // Search backward and return the exclusive end immediately after the latest match.
            let mut end = bounds.end.min(ceiling);
            while end > bounds.start {
                if predicate(&self.read(end - 1).await?) {
                    return Ok(end);
                }
                end -= 1;
            }

            // Only an unpruned journal can establish genesis when no retained item matches.
            if bounds.start != 0 {
                return Err(JournalError::ItemPruned(bounds.start));
            }
            Ok(0)
        }
    }
}

/// A [Mutable] journal that can back an authenticated [Journal].
pub trait Backing<E: Context>: Mutable {
    /// The configuration needed to initialize this journal.
    type Config: Clone + Send + Sync;

    /// Initialization-owned storage used to select and validate the retained prefix.
    type Recovery: BackingRecovery<Journal = Self>;

    /// Open recovery storage for an optional exclusive item end. Implementations may inspect
    /// later storage to validate recovery boundaries. Returns [JournalError::ItemPruned] when
    /// `max_size` lies below the retained start.
    fn recover(
        context: E,
        cfg: Self::Config,
        max_size: Option<u64>,
    ) -> impl Future<Output = Result<Self::Recovery, JournalError>> + Send;

    /// Open recovery storage reset to an empty journal at `size`, discarding stored items
    /// without reading them. Returns [JournalError::SizeOverflow] for `u64::MAX`.
    fn clear(
        context: E,
        cfg: Self::Config,
        size: u64,
    ) -> impl Future<Output = Result<Self::Recovery, JournalError>> + Send;

    /// Positions stored items may occupy, determined without reading them.
    ///
    /// The start is the retained start and the end bounds every stored item. A pending reset
    /// yields an empty span at its target.
    fn span(
        context: E,
        cfg: &Self::Config,
    ) -> impl Future<Output = Result<Range<u64>, JournalError>> + Send;
}

/// Whether `span` contains `position` or is empty exactly at it.
fn covers(span: &Range<u64>, position: u64) -> bool {
    position == span.start || span.contains(&position)
}

/// A [Backing] journal's storage, as [Stored::open] leaves it.
pub(crate) enum Stored<E: Context, J: Backing<E>> {
    /// Recovery opened bounded at the requested end.
    Opened(J::Recovery),

    /// Storage whose span cannot hold the requested position, left unopened.
    Unopened { context: E, cfg: J::Config },
}

impl<E: Context, J: Backing<E>> Stored<E, J> {
    /// Open recovery bounded at `max_size` when [Backing::span] contains `position` or is empty
    /// exactly at it. Otherwise return the storage unopened.
    pub(crate) async fn open(
        context: E,
        cfg: J::Config,
        position: u64,
        max_size: u64,
    ) -> Result<Self, JournalError> {
        if !covers(&J::span(context.child("span"), &cfg).await?, position) {
            return Ok(Self::Unopened { context, cfg });
        }
        let recovery = J::recover(context, cfg, Some(max_size)).await?;
        Ok(Self::Opened(recovery))
    }
}

/// Recover the portion useful for state sync, or reset an unusable local range.
pub(crate) async fn init_sync<E: Context, J: Backing<E>>(
    context: E,
    cfg: J::Config,
    range: Range<u64>,
) -> Result<J, JournalError> {
    assert!(!range.is_empty(), "range must not be empty");

    // Storage whose span cannot hold the sync start is cleared without reading stored items.
    // The span end reflects blob capacity, which can overstate the recovered end when the tail
    // is short or has a gap, so an opened prefix that does not cover the sync start is reset.
    let pending = match Stored::<E, J>::open(context, cfg, range.start, range.end).await? {
        Stored::Opened(pending) if covers(&pending.bounds(), range.start) => pending,
        Stored::Opened(pending) => pending.reset(range.start).await?,
        Stored::Unopened { context, cfg } => J::clear(context, cfg, range.start).await?,
    };

    // Publish the retained prefix before pruning complete sections below the sync start.
    let journal = pending.finish(range.end).await?;
    let (journal, _) = journal.prune(range.start).await?;
    Ok(journal)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{
        journal::contiguous::{
            fixed::{Config as JConfig, Journal as ContiguousJournal},
            tests::replay_items,
        },
        merkle::{
            Bagging::{BackwardFold, ForwardFold},
            full::{Config as MerkleConfig, Merkle},
            mmb, mmr,
        },
        qmdb::{
            any::{
                operation::{Unordered as Op, update::Unordered as Update},
                value::FixedEncoding,
            },
            operation::Committable,
        },
        utils::detached::{DropMonitor, block_strategy},
    };
    use commonware_codec::{Encode, FixedSize};
    use commonware_cryptography::{Sha256, sha256::Digest};
    use commonware_macros::{test_collect_traces, test_traced};
    use commonware_parallel::{
        Rayon, Sequential,
        mocks::{Explorer, explore},
    };
    use commonware_runtime::{
        Runner as _, Spawner as _, Strategizer as _, Supervisor as _,
        buffer::paged::CacheRef,
        deterministic::{self, Context},
        mocks::{
            DelayedSyncContext, PendingSyncs, RecordingContext, drive_pending_syncs,
            fail_pending_syncs, next_pending_sync,
        },
        reschedule,
        telemetry::traces::collector::TraceStorage,
    };
    use commonware_utils::{NZU16, NZU64, NZUsize, probability};
    use futures::StreamExt as _;
    use std::{
        future::Future,
        num::{NonZeroU16, NonZeroU64, NonZeroUsize},
        time::Duration,
    };

    const PAGE_SIZE: NonZeroU16 = NZU16!(101);
    const PAGE_CACHE_SIZE: NonZeroUsize = NZUsize!(11);

    /// Generic operation type for testing, parameterized by Merkle family.
    type TestOp<F> = Op<F, Digest, FixedEncoding<Digest>>;

    /// Generic authenticated journal type for testing, parameterized by Merkle family.
    type TestJournal<F> = Journal<
        F,
        deterministic::Context,
        ContiguousJournal<deterministic::Context, TestOp<F>>,
        Sha256,
        Sequential,
    >;

    type RecordingTestJournal<F> = Journal<
        F,
        RecordingContext<deterministic::Context>,
        ContiguousJournal<RecordingContext<deterministic::Context>, TestOp<F>>,
        Sha256,
        Sequential,
    >;

    fn journal_root<F: Family>(journal: &TestJournal<F>) -> Digest {
        journal.root(0).unwrap()
    }

    fn batch_root<F: Family>(
        journal: &TestJournal<F>,
        batch: &MerkleizedBatch<F, Digest, TestOp<F>, Sequential>,
    ) -> Digest {
        batch.root(&journal.hasher, 0).unwrap()
    }

    fn merkleize_with<F: Family + PartialEq>(
        batch: UnmerkleizedBatch<F, Sha256, TestOp<F>, Sequential>,
        base: &Mem<F, Digest>,
        items: Vec<TestOp<F>>,
    ) -> MerkleizedBatchArc<F, Sha256, TestOp<F>, Sequential> {
        batch.add_many(items).merkleize(base)
    }

    #[test]
    fn test_initialization_syncs_operations_before_merkle_repair() {
        deterministic::Runner::default().start(|context| async move {
            // Control operation and Merkle sync completion independently.
            let operation_syncs = PendingSyncs::default();
            let merkle_syncs = PendingSyncs::default();
            operation_syncs.unblock();
            merkle_syncs.unblock();
            let operation_context = DelayedSyncContext {
                inner: context.child("operations"),
                pending: operation_syncs.clone(),
            };
            let merkle_context = DelayedSyncContext {
                inner: context.child("merkle"),
                pending: merkle_syncs.clone(),
            };

            // Prepare an empty Merkle prefix alongside one selected operation.
            let cfg = merkle_config("sync-order");
            let hasher = StandardHasher::<Sha256>::new(ForwardFold);
            let merkle = Merkle::<mmr::Family, _, Digest, Sequential>::init(
                merkle_context.child("seed"),
                &hasher,
                cfg.clone(),
            )
            .await
            .unwrap();
            let batch = merkle.new_batch().add(&hasher, &Sha256::fill(1));
            let batch = batch.merkleize(merkle.mem(), &hasher);
            _ = merkle.apply_batch(&batch).unwrap().sync().await.unwrap();
            let merkle = Merkle::<mmr::Family, _, Digest, Sequential>::prepare(
                merkle_context,
                &hasher,
                cfg,
                Some(Location::new(0)),
            )
            .await
            .unwrap();
            let journal = ContiguousJournal::<_, TestOp<mmr::Family>>::recover(
                operation_context,
                journal_config("sync-order"),
                None,
            )
            .await
            .unwrap();
            let journal = Box::new(journal)
                .truncate(0)
                .await
                .unwrap()
                .append(&create_operation::<mmr::Family>(1))
                .await
                .unwrap();
            let pending = Recovery::<
                mmr::Family,
                _,
                ContiguousJournal<_, TestOp<mmr::Family>>,
                Sha256,
                Sequential,
            > {
                journal: *journal,
                merkle,
                hasher,
                selected_end: 1,
            };

            // Finishing must request the operation sync before any Merkle sync.
            operation_syncs.arm();
            merkle_syncs.arm();
            let finish = pending.finish();
            futures::pin_mut!(finish);
            assert!(futures::poll!(&mut finish).is_pending());
            assert_eq!(operation_syncs.calls(), 1);
            assert_eq!(merkle_syncs.calls(), 0);

            // Complete both syncs and verify the published operation prefix.
            operation_syncs.unblock();
            merkle_syncs.unblock();
            let journal = finish.await.unwrap();
            assert_eq!(journal.bounds(), 0..1);
            journal.destroy().await.unwrap();
        });
    }

    /// Create Merkle configuration for tests with the given strategy.
    fn merkle_config_with<S: Strategy>(suffix: &str, strategy: S) -> MerkleConfig<S> {
        MerkleConfig {
            journal_partition: format!("mmr-journal-{suffix}"),
            metadata_partition: format!("mmr-metadata-{suffix}"),
            items_per_blob: NZU64!(11),
            write_buffer: NZUsize!(1024),
            replay_buffer: NZUsize!(1024),
            strategy,
            page_cache: CacheRef::new(PAGE_SIZE, PAGE_CACHE_SIZE),
        }
    }

    /// Create Merkle configuration for tests.
    fn merkle_config(suffix: &str) -> MerkleConfig<Sequential> {
        merkle_config_with(suffix, Sequential)
    }

    /// Create journal configuration for tests.
    fn journal_config(suffix: &str) -> JConfig {
        JConfig {
            partition: format!("journal-{suffix}"),
            items_per_blob: NZU64!(7),
            write_buffer: NZUsize!(1024),
            replay_buffer: NZUsize!(1024),
            page_cache: CacheRef::new(PAGE_SIZE, PAGE_CACHE_SIZE),
        }
    }

    /// Create a new empty authenticated journal.
    async fn create_empty_journal<F: Family + PartialEq>(
        context: Context,
        suffix: &str,
    ) -> TestJournal<F> {
        let merkle_cfg = merkle_config(suffix);
        let journal_cfg = journal_config(suffix);
        TestJournal::<F>::new(
            context,
            merkle_cfg,
            journal_cfg,
            |op: &TestOp<F>| op.is_commit(),
            ForwardFold,
        )
        .await
        .unwrap()
    }

    #[test]
    fn test_batches_inherit_journal_bagging() {
        deterministic::Runner::default().start(|context| async move {
            let merkle_cfg = merkle_config("batch-bagging");
            let journal_cfg = journal_config("batch-bagging");
            let journal = TestJournal::<mmr::Family>::new(
                context,
                merkle_cfg,
                journal_cfg,
                |op: &TestOp<mmr::Family>| op.is_commit(),
                BackwardFold,
            )
            .await
            .unwrap();

            let batch = journal.new_batch();
            assert_eq!(batch.hasher.root_bagging(), BackwardFold);

            let merkleized = batch.merkleize(journal.merkle.mem());
            let child: UnmerkleizedBatch<mmr::Family, Sha256, TestOp<mmr::Family>, Sequential> =
                merkleized.new_batch();
            assert_eq!(child.hasher.root_bagging(), BackwardFold);
        });
    }

    /// Large batched reads shard across the strategy pool and match per-position reads.
    #[test]
    fn test_read_many_shards_across_strategy_pool() {
        deterministic::Runner::default().start(|context| async move {
            // The most parallel shape of a parallelism-2 strategy splits the probe into two
            // shards. The tiny test page cache pushes most positions through the batched miss
            // fallback while the write buffer serves the tail synchronously.
            let strategy = Explorer::parallel(&context.strategy(NZUsize!(2)));
            let merkle_cfg = merkle_config_with("shard", strategy);
            let journal_cfg = journal_config("shard");
            type ShardedJournal = Journal<
                mmr::Family,
                Context,
                ContiguousJournal<Context, TestOp<mmr::Family>>,
                Sha256,
                Explorer,
            >;
            let mut journal = ShardedJournal::new(
                context,
                merkle_cfg,
                journal_cfg,
                |op: &TestOp<mmr::Family>| op.is_commit(),
                ForwardFold,
            )
            .await
            .unwrap();

            let count = 4200u64;
            for i in 0..count {
                let op = create_operation::<mmr::Family>((i % 251) as u8);
                (journal, _) = journal.append(&op).await.unwrap();
            }
            let journal = journal.sync().await.unwrap();

            let positions: Vec<u64> = (0..count).collect();
            let shards = journal.read_many_sharded(&positions).await.unwrap();
            assert_eq!(shards.len(), 2, "the probe must run in two shards");
            let batch = Contiguous::read_many(&journal, &positions).await.unwrap();
            assert_eq!(batch.len(), positions.len());
            for &pos in &positions {
                let single = Contiguous::read(&journal, pos).await.unwrap();
                assert_eq!(batch[pos as usize], single);
            }

            // An empty batch is a no-op, even with a multi-threaded strategy.
            assert!(
                Contiguous::read_many(&journal, &[])
                    .await
                    .unwrap()
                    .is_empty()
            );
        });
    }

    /// A non-increasing batch panics deterministically, even when fully cached.
    #[test]
    #[should_panic(expected = "positions must be strictly increasing")]
    fn test_read_many_rejects_unsorted_positions() {
        deterministic::Runner::default().start(|context| async move {
            let mut journal = create_empty_journal::<mmr::Family>(context, "unsorted").await;
            for i in 0..2u8 {
                let op = create_operation::<mmr::Family>(i);
                (journal, _) = journal.append(&op).await.unwrap();
            }
            let journal = journal.sync().await.unwrap();

            let _ = Contiguous::read_many(&journal, &[1, 0]).await;
        });
    }

    /// Create a test operation with predictable values based on index.
    fn create_operation<F: Family + PartialEq>(index: u8) -> TestOp<F> {
        TestOp::<F>::Update(Update(
            Sha256::fill(index),
            Sha256::fill(index.wrapping_add(1)),
        ))
    }

    /// Create an authenticated journal with N committed operations.
    ///
    /// Operations are added and then synced to ensure they are committed.
    async fn create_journal_with_ops<F: Family + PartialEq>(
        context: Context,
        suffix: &str,
        count: usize,
    ) -> TestJournal<F> {
        let mut journal = create_empty_journal::<F>(context, suffix).await;

        for i in 0..count {
            let op = create_operation::<F>(i as u8);
            let loc;
            (journal, loc) = journal.append(&op).await.unwrap();
            assert_eq!(loc, Location::<F>::new(i as u64));
        }

        journal = journal.sync().await.unwrap();
        journal
    }

    /// Create separate Merkle and journal components for testing alignment.
    ///
    /// These components are created independently and can be manipulated separately to test
    /// scenarios where the Merkle structure and journal are out of sync (e.g., one ahead of the
    /// other).
    async fn create_components<F: Family + PartialEq>(
        context: Context,
        suffix: &str,
    ) -> (
        Merkle<F, deterministic::Context, Digest, Sequential>,
        ContiguousJournal<deterministic::Context, TestOp<F>>,
        StandardHasher<Sha256>,
    ) {
        let hasher = StandardHasher::new(ForwardFold);
        let merkle = Merkle::<F, _, Digest, Sequential>::init(
            context.child("mmr"),
            &hasher,
            merkle_config(suffix),
        )
        .await
        .unwrap();
        let journal = ContiguousJournal::init(context.child("journal"), journal_config(suffix))
            .await
            .unwrap();
        (merkle, journal, hasher)
    }

    /// Verify that a proof correctly proves the given operations are included in the Merkle
    /// structure.
    fn verify_proof<F: Family + PartialEq>(
        proof: &Proof<F, <Sha256 as commonware_cryptography::Hasher>::Digest>,
        operations: &[TestOp<F>],
        start_loc: Location<F>,
        root: &<Sha256 as commonware_cryptography::Hasher>::Digest,
        hasher: &StandardHasher<Sha256>,
    ) -> bool {
        let encoded_ops: Vec<_> = operations.iter().map(|op| op.encode()).collect();
        proof.verify_range_inclusion(hasher, &encoded_ops, start_loc, root)
    }

    /// Verify that new() creates an empty authenticated journal.
    async fn test_new_creates_empty_journal_inner<F: Family + PartialEq>(context: Context) {
        let journal = create_empty_journal::<F>(context, "new-empty").await;

        let bounds = journal.bounds();
        assert_eq!(bounds.end, 0);
        assert_eq!(bounds.start, 0);
        assert!(bounds.is_empty());
    }

    #[test_traced("INFO")]
    fn test_new_creates_empty_journal_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_new_creates_empty_journal_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_new_creates_empty_journal_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_new_creates_empty_journal_inner::<mmb::Family>);
    }

    /// Verify that align() correctly handles empty Merkle and journal components.
    async fn test_align_with_empty_mmr_and_journal_inner<F: Family + PartialEq>(context: Context) {
        let (merkle, journal, hasher) = create_components::<F>(context, "align-empty").await;

        let merkle = TestJournal::<F>::align(merkle, &journal, &hasher, APPLY_BATCH_SIZE)
            .await
            .unwrap();

        assert_eq!(merkle.leaves(), Location::<F>::new(0));
        assert_eq!(journal.size(), 0);
    }

    #[test_traced("INFO")]
    fn test_align_with_empty_mmr_and_journal_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_align_with_empty_mmr_and_journal_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_align_with_empty_mmr_and_journal_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_align_with_empty_mmr_and_journal_inner::<mmb::Family>);
    }

    /// Published components cannot repair a Merkle tree that extends past the operation journal.
    async fn test_from_components_rejects_merkle_ahead_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let (mut merkle, mut journal, hasher) = create_components::<F>(context, "mmr-ahead").await;

        // Keep Merkle one operation ahead of the journal.
        {
            let batch = {
                let mut batch = merkle.new_batch();
                for i in 0..20 {
                    let op = create_operation::<F>(i as u8);
                    let encoded = op.encode();
                    batch = batch.add(&hasher, &encoded);
                    if i < 19 {
                        (journal, _) = journal.append(&op).await.unwrap();
                    }
                }
                batch
            };
            let batch = batch.merkleize(merkle.mem(), &hasher);
            merkle = merkle.apply_batch(&batch).unwrap();
        }

        let journal = journal.sync().await.unwrap();
        let result =
            TestJournal::<F>::from_components(merkle, journal, hasher, APPLY_BATCH_SIZE).await;
        assert!(matches!(
            result,
            Err(Error::Journal(JournalError::Corruption(_)))
        ));
    }

    #[test_traced("WARN")]
    fn test_from_components_rejects_merkle_ahead_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_from_components_rejects_merkle_ahead_inner::<mmr::Family>);
    }

    #[test_traced("WARN")]
    fn test_from_components_rejects_merkle_ahead_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_from_components_rejects_merkle_ahead_inner::<mmb::Family>);
    }

    /// Verify that align() replays journal operations when journal is ahead of Merkle.
    async fn test_align_when_journal_ahead_inner<F: Family + PartialEq>(context: Context) {
        let (merkle, mut journal, hasher) = create_components::<F>(context, "journal-ahead").await;

        // Add 20 operations to journal only
        for i in 0..20 {
            let op = create_operation::<F>(i as u8);
            (journal, _) = journal.append(&op).await.unwrap();
        }

        // Add commit
        let commit_op = TestOp::<F>::CommitFloor(None, Location::<F>::new(0));
        let (journal, _) = journal.append(&commit_op).await.unwrap();
        let journal = journal.sync().await.unwrap();

        // Journal has 21 operations, Merkle has 0 leaves
        let merkle = TestJournal::<F>::align(merkle, &journal, &hasher, APPLY_BATCH_SIZE)
            .await
            .unwrap();

        // Merkle should have been replayed to match journal
        assert_eq!(merkle.leaves(), Location::<F>::new(21));
        assert_eq!(journal.size(), 21);
    }

    #[test_traced("WARN")]
    fn test_align_when_journal_ahead_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_align_when_journal_ahead_inner::<mmr::Family>);
    }

    #[test_traced("WARN")]
    fn test_align_when_journal_ahead_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_align_when_journal_ahead_inner::<mmb::Family>);
    }

    /// Builds a journal that is ahead of its Merkle structure, replays it on `strategy`, and
    /// returns the resulting Merkle state.
    async fn test_align_replay_parallel_matches_serial_inner<F: Family + PartialEq>(
        context: Context,
        strategy: Explorer,
    ) -> (Location<F>, Digest) {
        type ReplayJournal<F> = Journal<
            F,
            deterministic::Context,
            ContiguousJournal<deterministic::Context, TestOp<F>>,
            Sha256,
            Explorer,
        >;

        // Build a journal that is ahead of the Merkle structure.
        let mut journal = ContiguousJournal::init(
            context.child("journal"),
            journal_config("replay-strategies"),
        )
        .await
        .unwrap();
        for i in 0..20 {
            (journal, _) = journal
                .append(&create_operation::<F>(i as u8))
                .await
                .unwrap();
        }
        let commit_op = TestOp::<F>::CommitFloor(None, Location::<F>::new(0));
        let (journal, _) = journal.append(&commit_op).await.unwrap();
        let journal = journal.sync().await.unwrap();

        // Replay in batches of seven, so the 21 leaves take three batches and the strategy picks
        // the shape that hashes each one.
        let hasher = StandardHasher::<Sha256>::new(ForwardFold);
        let merkle = Merkle::<F, _, Digest, Explorer>::init(
            context.child("mmr_replay"),
            &hasher,
            merkle_config_with("replay", strategy),
        )
        .await
        .unwrap();
        let merkle = ReplayJournal::<F>::align(merkle, &journal, &hasher, NZU64!(7))
            .await
            .unwrap();

        assert_eq!(merkle.leaves(), Location::<F>::new(21));
        (merkle.leaves(), merkle.root(&hasher, 0).unwrap())
    }

    #[test_traced("WARN")]
    fn test_align_replay_parallel_matches_serial_mmr() {
        explore(|strategy| {
            deterministic::Runner::default().start(|context| {
                test_align_replay_parallel_matches_serial_inner::<mmr::Family>(
                    context,
                    strategy.clone(),
                )
            })
        });
    }

    #[test_traced("WARN")]
    fn test_align_replay_parallel_matches_serial_mmb() {
        explore(|strategy| {
            deterministic::Runner::default().start(|context| {
                test_align_replay_parallel_matches_serial_inner::<mmb::Family>(
                    context,
                    strategy.clone(),
                )
            })
        });
    }

    /// Initialization discards a persisted suffix that contains no complete commit.
    async fn test_align_with_mismatched_committed_ops_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal = create_empty_journal::<F>(context.child("first"), "mismatched").await;

        // Add 20 uncommitted operations
        for i in 0..20 {
            let loc;
            (journal, loc) = journal
                .append(&create_operation::<F>(i as u8))
                .await
                .unwrap();
            assert_eq!(loc, Location::<F>::new(i as u64));
        }

        let size_before = journal.size();
        assert_eq!(size_before, 20);

        // A persisted suffix without a commit must be discarded on restart.
        journal.sync().await.unwrap();
        let journal = create_empty_journal::<F>(context.child("second"), "mismatched").await;

        // Uncommitted operations should be gone
        assert_eq!(journal.size(), 0);
    }

    #[test_collect_traces("INFO")]
    fn test_align_with_mismatched_committed_ops_mmr(traces: TraceStorage) {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_align_with_mismatched_committed_ops_inner::<mmr::Family>(context)
        });
        traces
            .get_by_level(tracing::Level::WARN)
            .expect_event(|event| {
                let metadata = &event.metadata;
                metadata.content == "rewinding journal items"
                    && metadata.expect_field_exact("journal_size", "20").is_ok()
                    && metadata.expect_field_exact("rewound_items", "20").is_ok()
            })
            .unwrap();
    }

    #[test_traced("INFO")]
    fn test_align_with_mismatched_committed_ops_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_align_with_mismatched_committed_ops_inner::<mmb::Family>(context)
        });
    }

    async fn test_initialization_selection_inner<F: Family + PartialEq>(context: Context) {
        // Select the latest complete commit at or below each cap, both before and after pruning.
        for start in [0, 7] {
            for cap in [0, 1, 2, 3, 4, 7, 8, 11, 12, 14, 15, 100] {
                let suffix = format!("select-{start}-{cap}");
                let cfg = journal_config(&suffix);
                let mut journal = ContiguousJournal::init(context.child("create"), cfg.clone())
                    .await
                    .unwrap();
                for i in 0..15 {
                    let op = if [1, 3, 10, 13].contains(&i) {
                        TestOp::<F>::CommitFloor(None, Location::new(0))
                    } else {
                        create_operation::<F>(i)
                    };
                    (journal, _) = journal.append(&op).await.unwrap();
                }
                journal = journal.sync().await.unwrap();
                if start > 0 {
                    (journal, _) = journal.prune(start).await.unwrap();
                }
                drop(journal);
                let pending = <ContiguousJournal<_, TestOp<F>> as Backing<_>>::recover(
                    context.child("select"),
                    cfg.clone(),
                    Some(cap),
                )
                .await;

                // Derive the expected exclusive end from the retained commit candidates.
                let expected = [2, 4, 11, 14]
                    .into_iter()
                    .filter(|end| *end <= cap && *end > start)
                    .max();
                if cap < start {
                    assert!(matches!(pending, Err(JournalError::ItemPruned(_))));
                    continue;
                }
                let pending = pending.unwrap();
                let selected = pending.last_matching(cap, |op| op.is_commit()).await;
                if expected.is_none() && start > 0 {
                    assert!(matches!(selected, Err(JournalError::ItemPruned(_))));
                    continue;
                }
                let size = selected.unwrap();
                assert_eq!(size, expected.unwrap_or(0));

                // Publication makes the selected end authoritative on reopen.
                drop(pending.finish(size).await.unwrap());
                let journal =
                    ContiguousJournal::<_, TestOp<F>>::init(context.child("restart"), cfg)
                        .await
                        .unwrap();
                assert_eq!(journal.size(), size);
            }
        }

        // Bound both authenticated components to every prefix around the durable tip.
        for cap in [0, 1, 2, 3, 4, 5, 6, 7, 8, 100] {
            let suffix = format!("authenticated-cap-{cap}");
            let mc = merkle_config(&suffix);
            let jc = journal_config(&suffix);
            let mut journal = TestJournal::<F>::new(
                context.child("create_auth"),
                mc.clone(),
                jc.clone(),
                |_| true,
                ForwardFold,
            )
            .await
            .unwrap();
            let mut roots = vec![journal_root(&journal)];
            for i in 0..8 {
                (journal, _) = journal.append(&create_operation::<F>(i)).await.unwrap();
                roots.push(journal_root(&journal));
            }
            _ = journal.sync().await.unwrap();
            let journal = TestJournal::<F>::init_at_most(
                context.child("cap_auth"),
                mc.clone(),
                jc.clone(),
                cap,
                |_| true,
                ForwardFold,
            )
            .await
            .unwrap();
            let size = cap.min(8);
            assert_eq!(*journal.size(), size);
            assert_eq!(journal_root(&journal), roots[size as usize]);
            drop(journal);
            let journal =
                TestJournal::<F>::new(context.child("restart_auth"), mc, jc, |_| true, ForwardFold)
                    .await
                    .unwrap();
            assert_eq!(*journal.size(), size);
            assert_eq!(journal_root(&journal), roots[size as usize]);
        }
    }

    #[test_traced("INFO")]
    fn test_initialization_selection_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_initialization_selection_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_initialization_selection_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_initialization_selection_inner::<mmb::Family>);
    }

    /// Commit A then B, reopen at A, append an equal-length branch without syncing, then crash
    /// with the appends retained and any unsynced resize lost. Recovery must yield A or a prefix
    /// of the new branch, never B's operations or B's Merkle nodes.
    fn init_at_most_equal_length_branch_crash_inner<F: Family + PartialEq>() {
        const A: u64 = 4;

        fn is_commit<F: Family>(op: &TestOp<F>) -> bool {
            op.is_commit()
        }

        // One operation per page makes the reopen bound page aligned in the operation journal.
        // The two-page write buffer floor flushes the branch in whole-buffer bursts.
        fn journal_cfg<F: Family + PartialEq>(suffix: &str) -> JConfig {
            let page = NonZeroU16::new(<TestOp<F> as FixedSize>::SIZE as u16).unwrap();
            JConfig {
                partition: format!("journal-{suffix}"),
                items_per_blob: NZU64!(1000),
                write_buffer: NZUsize!(1),
                replay_buffer: NZUsize!(1024),
                page_cache: CacheRef::new(page, PAGE_CACHE_SIZE),
            }
        }

        // One node per page makes the reopen bound page aligned in the Merkle journal.
        fn merkle_cfg(suffix: &str) -> MerkleConfig<Sequential> {
            let page = NonZeroU16::new(Digest::SIZE as u16).unwrap();
            MerkleConfig {
                journal_partition: format!("mmr-journal-{suffix}"),
                metadata_partition: format!("mmr-metadata-{suffix}"),
                items_per_blob: NZU64!(1000),
                write_buffer: NZUsize!(1024),
                replay_buffer: NZUsize!(1024),
                strategy: Sequential,
                page_cache: CacheRef::new(page, PAGE_CACHE_SIZE),
            }
        }

        // End each branch at a commit so initialization can select it as a complete state.
        fn branch<F: Family + PartialEq>(first: u8, len: u64) -> Vec<TestOp<F>> {
            let mut ops: Vec<TestOp<F>> = (0..len - 1)
                .map(|i| create_operation::<F>(first + i as u8))
                .collect();
            ops.push(TestOp::<F>::CommitFloor(None, Location::new(0)));
            ops
        }

        // A three-operation branch is flushed whole and a five-operation branch only in part,
        // so recovery sees the new commit in the first case and only A's commit in the second.
        for len in [3u64, 5] {
            let suffix = format!("equal-length-branch-{len}");
            let crash_suffix = suffix.clone();
            let (roots, checkpoint) =
                deterministic::Runner::default().start_and_recover(move |context| async move {
                    let mc = merkle_cfg(&crash_suffix);
                    let jc = journal_cfg::<F>(&crash_suffix);
                    let mut journal = TestJournal::<F>::new(
                        context.child("create"),
                        mc.clone(),
                        jc.clone(),
                        is_commit::<F>,
                        ForwardFold,
                    )
                    .await
                    .unwrap();
                    for op in branch::<F>(0, A) {
                        (journal, _) = journal.append(&op).await.unwrap();
                    }
                    let mut journal = journal.sync().await.unwrap();
                    let root_a = journal_root(&journal);
                    for op in branch::<F>(50, len) {
                        (journal, _) = journal.append(&op).await.unwrap();
                    }
                    let journal = journal.sync().await.unwrap();
                    assert_eq!(*journal.size(), A + len);
                    drop(journal);

                    // Keep unsynced writes and drop unsynced resizes at the crash.
                    *context.storage_fault_config().write() = deterministic::FaultConfig {
                        write_rate: Some(deterministic::WriteConfig {
                            failure_rate: probability!(0.0),
                            retention_rate: probability!(1.0),
                            mode: deterministic::PartialWriteMode::Prefix,
                        }),
                        resize_rate: Some(deterministic::ResizeConfig {
                            failure_rate: probability!(0.0),
                            partial_rate: probability!(0.0),
                        }),
                        ..Default::default()
                    };
                    let mut journal = TestJournal::<F>::init_at_most(
                        context.child("cap"),
                        mc,
                        jc,
                        A,
                        is_commit::<F>,
                        ForwardFold,
                    )
                    .await
                    .unwrap();
                    assert_eq!(*journal.size(), A);
                    assert_eq!(journal_root(&journal), root_a);
                    let mut roots = vec![root_a];
                    for op in branch::<F>(100, len) {
                        (journal, _) = journal.append(&op).await.unwrap();
                        roots.push(journal_root(&journal));
                    }
                    drop(journal);
                    roots
                });

            // Recover the selected base commit or a prefix of its replacement branch, with no
            // operations from the discarded branch.
            deterministic::Runner::from(checkpoint).start(move |context| async move {
                *context.storage_fault_config().write() = deterministic::FaultConfig::default();
                let journal = TestJournal::<F>::new(
                    context.child("reopen"),
                    merkle_cfg(&suffix),
                    journal_cfg::<F>(&suffix),
                    is_commit::<F>,
                    ForwardFold,
                )
                .await
                .unwrap();
                let size = *journal.size();
                assert!(
                    (A..=A + len).contains(&size),
                    "recovered size {size} is not a prefix of the new branch"
                );
                let expected = branch::<F>(100, len);
                for pos in A..size {
                    assert_eq!(
                        journal.read(pos).await.unwrap(),
                        expected[(pos - A) as usize],
                        "operation at retained position {pos} was never written there"
                    );
                }

                // The recovered root and proof must authenticate that same operation history.
                let root = journal_root(&journal);
                assert_eq!(
                    root,
                    roots[(size - A) as usize],
                    "root does not match the recovered operations"
                );
                let (proof, ops) = journal
                    .proof(Location::new(0), NonZeroU64::new(size).unwrap(), 0)
                    .await
                    .unwrap();
                assert_eq!(ops.len() as u64, size);
                assert!(verify_proof(
                    &proof,
                    &ops,
                    Location::new(0),
                    &root,
                    &StandardHasher::new(ForwardFold)
                ));
                journal.destroy().await.unwrap();
            });
        }
    }

    #[test_traced("INFO")]
    fn test_init_at_most_equal_length_branch_crash_mmr() {
        init_at_most_equal_length_branch_crash_inner::<mmr::Family>();
    }

    #[test_traced("INFO")]
    fn test_init_at_most_equal_length_branch_crash_mmb() {
        init_at_most_equal_length_branch_crash_inner::<mmb::Family>();
    }

    /// Verify that append() increments the operation count, returns correct locations, and
    /// operations can be read back correctly.
    async fn test_apply_op_and_read_operations_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_empty_journal::<F>(context, "apply_op").await;

        assert_eq!(journal.size(), 0);

        // Add 50 operations
        let expected_ops: Vec<_> = (0..50).map(|i| create_operation::<F>(i as u8)).collect();
        for (i, op) in expected_ops.iter().enumerate() {
            let loc;
            (journal, loc) = journal.append(op).await.unwrap();
            assert_eq!(loc, Location::<F>::new(i as u64));
            assert_eq!(journal.size(), (i + 1) as u64);
        }

        assert_eq!(journal.size(), 50);

        // Verify all operations can be read back correctly
        journal = journal.sync().await.unwrap();
        for (i, expected_op) in expected_ops.iter().enumerate() {
            let read_op = journal.read(*Location::<F>::new(i as u64)).await.unwrap();
            assert_eq!(read_op, *expected_op);
        }
    }

    #[test_traced("INFO")]
    fn test_apply_op_and_read_operations_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_op_and_read_operations_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_apply_op_and_read_operations_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_op_and_read_operations_inner::<mmb::Family>);
    }

    /// Verify that read() returns correct operations at various positions.
    async fn test_read_operations_at_various_positions_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal = create_journal_with_ops::<F>(context, "read", 50).await;

        // Verify reading first operation
        let first_op = journal.read(*Location::<F>::new(0)).await.unwrap();
        assert_eq!(first_op, create_operation::<F>(0));

        // Verify reading middle operation
        let middle_op = journal.read(*Location::<F>::new(25)).await.unwrap();
        assert_eq!(middle_op, create_operation::<F>(25));

        // Verify reading last operation
        let last_op = journal.read(*Location::<F>::new(49)).await.unwrap();
        assert_eq!(last_op, create_operation::<F>(49));

        // Verify all operations match expected values
        for i in 0..50 {
            let op = journal.read(*Location::<F>::new(i)).await.unwrap();
            assert_eq!(op, create_operation::<F>(i as u8));
        }
    }

    #[test_traced("INFO")]
    fn test_read_operations_at_various_positions_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_read_operations_at_various_positions_inner::<mmr::Family>(context)
        });
    }

    #[test_traced("INFO")]
    fn test_read_operations_at_various_positions_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_read_operations_at_various_positions_inner::<mmb::Family>(context)
        });
    }

    /// Verify that read() returns an error for pruned operations.
    async fn test_read_pruned_operation_returns_error_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal = create_journal_with_ops::<F>(context, "read_pruned", 100).await;

        // Add commit and prune
        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();
        let pruned_boundary;
        (journal, pruned_boundary) = journal.prune(Location::<F>::new(50)).await.unwrap();

        // Try to read an operation before the pruned boundary
        let read_loc = Location::<F>::new(0);
        if read_loc < pruned_boundary {
            let result = journal.read(*read_loc).await;
            assert!(matches!(result, Err(crate::journal::Error::ItemPruned(_))));
        }
    }

    #[test_traced("INFO")]
    fn test_read_pruned_operation_returns_error_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_read_pruned_operation_returns_error_inner::<mmr::Family>(context)
        });
    }

    #[test_traced("INFO")]
    fn test_read_pruned_operation_returns_error_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_read_pruned_operation_returns_error_inner::<mmb::Family>(context)
        });
    }

    /// Verify that read() returns an error for out-of-range locations.
    async fn test_read_out_of_range_returns_error_inner<F: Family + PartialEq>(context: Context) {
        let journal = create_journal_with_ops::<F>(context, "read_oob", 3).await;

        // Try to read beyond the end
        let result = journal.read(*Location::<F>::new(10)).await;
        assert!(matches!(
            result,
            Err(crate::journal::Error::ItemOutOfRange(_))
        ));
    }

    #[test_traced("INFO")]
    fn test_read_out_of_range_returns_error_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_read_out_of_range_returns_error_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_read_out_of_range_returns_error_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_read_out_of_range_returns_error_inner::<mmb::Family>);
    }

    /// Verify that we can read all operations back correctly.
    async fn test_read_all_operations_back_correctly_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal = create_journal_with_ops::<F>(context, "read_all", 50).await;

        assert_eq!(journal.size(), 50);

        // Verify all operations can be read back and match expected values
        for i in 0..50 {
            let op = journal.read(*Location::<F>::new(i)).await.unwrap();
            assert_eq!(op, create_operation::<F>(i as u8));
        }
    }

    #[test_traced("INFO")]
    fn test_read_all_operations_back_correctly_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_read_all_operations_back_correctly_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_read_all_operations_back_correctly_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_read_all_operations_back_correctly_inner::<mmb::Family>);
    }

    /// Verify that sync() persists operations.
    async fn test_sync_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_empty_journal::<F>(context.child("first"), "close_pending").await;

        // Add 20 operations
        let expected_ops: Vec<_> = (0..20).map(|i| create_operation::<F>(i as u8)).collect();
        for (i, op) in expected_ops.iter().enumerate() {
            let loc;
            (journal, loc) = journal.append(op).await.unwrap();
            assert_eq!(loc, Location::<F>::new(i as u64),);
        }

        // Add commit operation to commit the operations
        let commit_loc;
        (journal, commit_loc) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(0)))
            .await
            .unwrap();
        assert_eq!(
            commit_loc,
            Location::<F>::new(20),
            "commit should be at location 20"
        );
        journal.sync().await.unwrap();

        // Reopen and verify the operations persisted
        let journal = create_empty_journal::<F>(context.child("second"), "close_pending").await;
        assert_eq!(journal.size(), 21);

        // Verify all operations can be read back
        for (i, expected_op) in expected_ops.iter().enumerate() {
            let read_op = journal.read(*Location::<F>::new(i as u64)).await.unwrap();
            assert_eq!(read_op, *expected_op);
        }
    }

    #[test_traced("INFO")]
    fn test_sync_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_sync_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_sync_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_sync_inner::<mmb::Family>);
    }

    /// Awaiting a start_sync handle provides commit-level durability: committed operations
    /// survive a reopen, with recovery re-aligning the Merkle structure.
    async fn test_start_sync_durability_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_empty_journal::<F>(context.child("first"), "start_sync").await;
        let expected_ops: Vec<_> = (0..5).map(|i| create_operation::<F>(i as u8)).collect();
        for op in expected_ops.iter() {
            (journal, _) = journal.append(op).await.unwrap();
        }
        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(0)))
            .await
            .unwrap();

        let handle;
        (journal, handle) = journal.start_sync().await.unwrap();
        handle.await.unwrap();
        let root = journal_root(&journal);
        drop(journal);

        let journal = create_empty_journal::<F>(context.child("second"), "start_sync").await;
        assert_eq!(journal.size(), 6);
        assert_eq!(journal_root(&journal), root);
        for (i, expected_op) in expected_ops.iter().enumerate() {
            let read_op = journal.read(*Location::<F>::new(i as u64)).await.unwrap();
            assert_eq!(read_op, *expected_op);
        }
    }

    /// Reopening recovers the Merkle journal bounded, so publication persists its recovery
    /// watermark even when no node is flushed.
    #[test_traced]
    fn test_reopen_persists_merkle_watermark() {
        deterministic::Runner::default().start(|context| async move {
            // Persist operations while the Merkle recovery watermark still describes genesis.
            let pending = PendingSyncs::default();
            let open = open_delayed_journal(&context, "first", "watermark", &pending);
            let mut journal = drive_pending_syncs(&pending, open).await.unwrap();
            for i in 0..5u8 {
                (journal, _) = journal
                    .append(&create_operation::<mmr::Family>(i))
                    .await
                    .unwrap();
            }
            (journal, _) = journal
                .append(&TestOp::<mmr::Family>::CommitFloor(None, Location::new(0)))
                .await
                .unwrap();
            let handle;
            (journal, handle) = journal.start_sync().await.unwrap();
            drive_pending_syncs(&pending, handle).await.unwrap();
            let size = *journal.merkle.size();
            drop(journal);

            // Confirm the first publication left the Merkle watermark at genesis.
            let before = ContiguousJournal::<_, Digest>::persisted_watermark(
                context.child("p0"),
                "mmr-journal-watermark",
            )
            .await
            .unwrap();
            assert_eq!(before, Some(0));

            // Reopening publishes the recovered Merkle prefix even without new node writes.
            let journal =
                create_empty_journal::<mmr::Family>(context.child("second"), "watermark").await;
            assert_eq!(*journal.merkle.size(), size);
            drop(journal);
            let after = ContiguousJournal::<_, Digest>::persisted_watermark(
                context.child("p1"),
                "mmr-journal-watermark",
            )
            .await
            .unwrap();
            assert_eq!(after, Some(size));
        });
    }

    #[test_traced("INFO")]
    fn test_start_sync_durability_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_start_sync_durability_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_start_sync_durability_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_start_sync_durability_inner::<mmb::Family>);
    }

    /// Delayed-sync context for exercising in-flight sync handles.
    type DelayedCtx = DelayedSyncContext<deterministic::Context>;

    /// Authenticated journal over a delayed-sync storage backend.
    type DelayedTestJournal<F> =
        Journal<F, DelayedCtx, ContiguousJournal<DelayedCtx, TestOp<F>>, Sha256, Sequential>;

    /// Open an authenticated journal whose blob syncs park on `pending`.
    ///
    /// `new` durably persists the recovered journal, so while syncs park the returned future
    /// must be driven with [drive_pending_syncs] (or the mock unblocked first).
    fn open_delayed_journal(
        context: &Context,
        label: &'static str,
        suffix: &str,
        pending: &PendingSyncs,
    ) -> impl Future<Output = Result<DelayedTestJournal<mmr::Family>, Error<mmr::Family>>> {
        DelayedTestJournal::<mmr::Family>::new(
            DelayedCtx {
                inner: context.child(label),
                pending: pending.clone(),
            },
            merkle_config(suffix),
            journal_config(suffix),
            |op: &TestOp<mmr::Family>| op.is_commit(),
            ForwardFold,
        )
    }

    /// A sync handle must not block journal use while the backend sync is pending.
    #[test_traced("INFO")]
    fn test_start_sync_overlaps_work() {
        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            let pending = PendingSyncs::default();
            let open = open_delayed_journal(&context, "first", "start_sync_overlap", &pending);
            let mut journal = drive_pending_syncs(&pending, open).await.unwrap();
            for i in 0..4 {
                (journal, _) = journal
                    .append(&create_operation::<mmr::Family>(i))
                    .await
                    .unwrap();
            }

            let starts_before = pending.starts();
            let entered_before = pending.entered();
            let completions_before = pending.completions();
            let handle;
            (journal, handle) = journal.start_sync().await.unwrap();
            assert!(pending.starts() > starts_before);
            assert_eq!(pending.completions(), completions_before);

            // Observe the sync while the journal keeps working.
            let waiter = context
                .child("await_sync")
                .spawn(|_| async move { handle.await.unwrap() });
            while pending.entered() == entered_before {
                reschedule().await;
            }

            // Appends and reads complete before the sync does.
            (journal, _) = journal
                .append(&create_operation::<mmr::Family>(4))
                .await
                .unwrap();
            let read_op = journal.read(0).await.unwrap();
            assert_eq!(read_op, create_operation::<mmr::Family>(0));
            assert_eq!(
                pending.completions(),
                completions_before,
                "the journal made progress while the sync was still in flight"
            );

            pending.unblock();
            waiter.await.unwrap();

            // The mid-sync append is durable after the next sync.
            (journal, _) = journal
                .append(&TestOp::<mmr::Family>::CommitFloor(None, Location::new(0)))
                .await
                .unwrap();
            let handle;
            (journal, handle) = journal.start_sync().await.unwrap();
            handle.await.unwrap();
            let root = journal.root(0).unwrap();
            drop(journal);

            let journal = open_delayed_journal(&context, "second", "start_sync_overlap", &pending)
                .await
                .unwrap();
            assert_eq!(journal.size(), 6);
            assert_eq!(journal.root(0).unwrap(), root);
        });
    }

    /// A sync begun by `start_sync` that fails in flight surfaces the error through both the
    /// returned handle and the next durability operation.
    #[test_traced("INFO")]
    fn test_start_sync_failure_propagates() {
        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            // Pass syncs through so opening the journal doesn't park.
            let pending = PendingSyncs::default();
            pending.unblock();
            let mut journal = open_delayed_journal(&context, "first", "start_sync_fail", &pending)
                .await
                .unwrap();
            for i in 0..4 {
                (journal, _) = journal
                    .append(&create_operation::<mmr::Family>(i))
                    .await
                    .unwrap();
            }

            // Arm all future syncs to resolve to an injected error.
            pending.arm_fail();

            let handle;
            (journal, handle) = journal.start_sync().await.unwrap();
            assert!(
                handle.await.is_err(),
                "the sync handle surfaces the failure"
            );
            let starts_before = pending.starts();
            // A failed mutable method consumes the journal per the failures-are-fatal contract.
            assert!(
                matches!(
                    journal.commit().await,
                    Err(Error::Journal(JournalError::Runtime(_)))
                ),
                "the next durability op surfaces the failed in-flight sync"
            );
            assert_eq!(
                pending.starts(),
                starts_before,
                "the surfaced error is the retained failure, not a fresh sync's"
            );
        });
    }

    /// A merkle-only sync failure fails the joined handle even though the operation log's own
    /// sync succeeded.
    #[test_traced("INFO")]
    fn test_start_sync_merkle_failure_fails_handle() {
        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            let pending = PendingSyncs::default();
            let open = open_delayed_journal(&context, "first", "merkle_fail", &pending);
            let mut journal = drive_pending_syncs(&pending, open).await.unwrap();
            for i in 0..4 {
                (journal, _) = journal
                    .append(&create_operation::<mmr::Family>(i))
                    .await
                    .unwrap();
            }

            // Prove the appends durable, then dirty only the merkle journal: commit syncs the
            // operation log but merely flushes merkle nodes.
            let handle;
            (journal, handle) = journal.start_sync().await.unwrap();
            drive_pending_syncs(&pending, handle).await.unwrap();
            for i in 4..6 {
                (journal, _) = journal
                    .append(&create_operation::<mmr::Family>(i))
                    .await
                    .unwrap();
            }
            journal = drive_pending_syncs(&pending, journal.commit())
                .await
                .unwrap();

            // The operation log's data is already durable, so its only parked sync is the
            // watermark advance: release it, then fail the merkle journal's syncs.
            let handle;
            (journal, handle) = journal.start_sync().await.unwrap();
            let ops_watermark = next_pending_sync(&pending);
            ops_watermark.release.send(Ok(())).unwrap();
            fail_pending_syncs(&pending);
            assert!(
                handle.await.is_err(),
                "a merkle-only failure surfaces on the joined handle"
            );

            // The merkle journal retained the failure: the next sync resurfaces it.
            assert!(drive_pending_syncs(&pending, journal.sync()).await.is_err());
        });
    }

    /// Verify that pruning an empty journal returns the boundary.
    async fn test_prune_empty_journal_inner<F: Family + PartialEq>(context: Context) {
        let journal = create_empty_journal::<F>(context, "prune_empty").await;

        let (_, boundary) = journal.prune(Location::<F>::new(0)).await.unwrap();

        assert_eq!(boundary, Location::<F>::new(0));
    }

    #[test_traced("INFO")]
    fn test_prune_empty_journal_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_empty_journal_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_prune_empty_journal_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_empty_journal_inner::<mmb::Family>);
    }

    /// Verify that pruning to a specific location works correctly.
    async fn test_prune_to_location_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "prune_to", 100).await;

        // Add commit at position 50
        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let (_, boundary) = journal.prune(Location::<F>::new(50)).await.unwrap();

        // Boundary should be <= requested location (may align to section boundary)
        assert!(boundary <= Location::<F>::new(50));
    }

    #[test_traced("INFO")]
    fn test_prune_to_location_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_to_location_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_prune_to_location_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_to_location_inner::<mmb::Family>);
    }

    /// Verify that prune() returns the actual boundary (which may differ from requested).
    async fn test_prune_returns_actual_boundary_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "prune_boundary", 100).await;

        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let requested = Location::<F>::new(50);
        let (journal, actual) = journal.prune(requested).await.unwrap();

        // Actual boundary should match bounds.start
        let bounds = journal.bounds();
        assert!(!bounds.is_empty());
        assert_eq!(actual, bounds.start);

        // Actual may be <= requested due to section alignment
        assert!(actual <= requested);
    }

    #[test_traced("INFO")]
    fn test_prune_returns_actual_boundary_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_returns_actual_boundary_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_prune_returns_actual_boundary_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_returns_actual_boundary_inner::<mmb::Family>);
    }

    /// Verify that pruning through the Mutable trait also prunes authenticated Merkle state.
    async fn test_mutable_prune_updates_merkle_boundary_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal = create_journal_with_ops::<F>(context, "trait_prune", 100).await;

        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let (journal, pruned) = <TestJournal<F> as Mutable>::prune(journal, 50)
            .await
            .unwrap();
        assert!(pruned);

        let item_boundary = journal.bounds().start;
        let merkle_boundary = journal.merkle.bounds().start;
        assert_eq!(Location::<F>::new(item_boundary), merkle_boundary);
        assert!(merkle_boundary > Location::<F>::new(0));

        let (journal, pruned) = <TestJournal<F> as Mutable>::prune(journal, 50)
            .await
            .unwrap();
        assert!(!pruned);
        assert_eq!(journal.bounds().start, item_boundary);
        assert_eq!(journal.merkle.bounds().start, merkle_boundary);
    }

    #[test_traced("INFO")]
    fn test_mutable_prune_updates_merkle_boundary_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_mutable_prune_updates_merkle_boundary_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_mutable_prune_updates_merkle_boundary_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_mutable_prune_updates_merkle_boundary_inner::<mmb::Family>);
    }

    /// Verify that pruning doesn't change the operation count.
    async fn test_prune_preserves_operation_count_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "prune_count", 100).await;

        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let count_before = journal.size();
        let (journal, _) = journal.prune(Location::<F>::new(50)).await.unwrap();
        let count_after = journal.size();

        assert_eq!(count_before, count_after);
    }

    #[test_traced("INFO")]
    fn test_prune_preserves_operation_count_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_preserves_operation_count_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_prune_preserves_operation_count_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_prune_preserves_operation_count_inner::<mmb::Family>);
    }

    /// Verify bounds() for empty journal, no pruning, and after pruning.
    async fn test_bounds_empty_and_pruned_inner<F: Family + PartialEq>(context: Context) {
        // Test empty journal
        let journal = create_empty_journal::<F>(context.child("empty"), "oldest").await;
        assert!(journal.bounds().is_empty());
        journal.destroy().await.unwrap();

        // Test no pruning
        let journal = create_journal_with_ops::<F>(context.child("no_prune"), "oldest", 100).await;
        let bounds = journal.bounds();
        assert!(!bounds.is_empty());
        assert_eq!(bounds.start, 0);
        journal.destroy().await.unwrap();

        // Test after pruning
        let mut journal =
            create_journal_with_ops::<F>(context.child("pruned"), "oldest", 100).await;
        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let (journal, pruned_boundary) = journal.prune(Location::<F>::new(50)).await.unwrap();

        // Should match the pruned boundary (may be <= 50 due to section alignment)
        let bounds = journal.bounds();
        assert!(!bounds.is_empty());
        assert_eq!(bounds.start, pruned_boundary);
        // Should be <= requested location (50)
        assert!(pruned_boundary <= 50);
        journal.destroy().await.unwrap();
    }

    #[test_traced("INFO")]
    fn test_bounds_empty_and_pruned_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_bounds_empty_and_pruned_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_bounds_empty_and_pruned_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_bounds_empty_and_pruned_inner::<mmb::Family>);
    }

    /// Verify bounds().start for empty journal, no pruning, and after pruning.
    async fn test_bounds_start_after_prune_inner<F: Family + PartialEq>(context: Context) {
        // Test empty journal
        let journal = create_empty_journal::<F>(context.child("empty"), "boundary").await;
        assert_eq!(journal.bounds().start, 0);

        // Test no pruning
        drop(journal);
        let journal =
            create_journal_with_ops::<F>(context.child("no_prune"), "boundary", 100).await;
        assert_eq!(journal.bounds().start, 0);

        // Test after pruning
        drop(journal);
        let mut journal =
            create_journal_with_ops::<F>(context.child("pruned"), "boundary", 100).await;
        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(50)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let (journal, pruned_boundary) = journal.prune(Location::<F>::new(50)).await.unwrap();

        assert_eq!(journal.bounds().start, pruned_boundary);
    }

    #[test_traced("INFO")]
    fn test_bounds_start_after_prune_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_bounds_start_after_prune_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_bounds_start_after_prune_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_bounds_start_after_prune_inner::<mmb::Family>);
    }

    /// Verify that Merkle prunes to the journal's actual boundary, not the requested location.
    async fn test_mmr_prunes_to_journal_boundary_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "mmr_boundary", 50).await;

        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(25)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();

        let (journal, pruned_boundary) = journal.prune(Location::<F>::new(25)).await.unwrap();

        // Verify Merkle and journal remain in sync
        let bounds = journal.bounds();
        assert!(!bounds.is_empty());
        assert_eq!(pruned_boundary, bounds.start);

        // Verify boundary is at or before requested (due to section alignment)
        assert!(pruned_boundary <= Location::<F>::new(25));

        // Verify operation count is unchanged
        assert_eq!(journal.size(), 51);
    }

    #[test_traced("INFO")]
    fn test_mmr_prunes_to_journal_boundary_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_mmr_prunes_to_journal_boundary_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_mmr_prunes_to_journal_boundary_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_mmr_prunes_to_journal_boundary_inner::<mmb::Family>);
    }

    /// Verify proof() for multiple operations.
    async fn test_proof_multiple_operations_inner<F: Family + PartialEq>(context: Context) {
        let journal = create_journal_with_ops::<F>(context, "proof_multi", 50).await;

        let (proof, ops) = journal
            .proof(Location::<F>::new(0), NZU64!(50), 0)
            .await
            .unwrap();

        assert_eq!(ops.len(), 50);
        for (i, op) in ops.iter().enumerate() {
            assert_eq!(*op, create_operation::<F>(i as u8));
        }

        // Verify the proof is valid
        let hasher = StandardHasher::new(ForwardFold);
        let root = journal_root(&journal);
        assert!(verify_proof(
            &proof,
            &ops,
            Location::<F>::new(0),
            &root,
            &hasher
        ));
    }

    #[test_traced("INFO")]
    fn test_proof_multiple_operations_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_proof_multiple_operations_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_proof_multiple_operations_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_proof_multiple_operations_inner::<mmb::Family>);
    }

    /// Verify that historical_proof() respects the max_ops limit.
    async fn test_historical_proof_limited_by_max_ops_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal = create_journal_with_ops::<F>(context, "proof_limit", 50).await;

        let size = journal.size();
        let (proof, ops) = journal
            .historical_proof(size, Location::<F>::new(0), NZU64!(20), 0)
            .await
            .unwrap();

        // Should return only 20 operations despite 50 being available
        assert_eq!(ops.len(), 20);
        for (i, op) in ops.iter().enumerate() {
            assert_eq!(*op, create_operation::<F>(i as u8));
        }

        // Verify the proof is valid
        let hasher = StandardHasher::new(ForwardFold);
        let root = journal_root(&journal);
        assert!(verify_proof(
            &proof,
            &ops,
            Location::<F>::new(0),
            &root,
            &hasher
        ));
    }

    #[test_traced("INFO")]
    fn test_historical_proof_limited_by_max_ops_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_limited_by_max_ops_inner::<mmr::Family>(context)
        });
    }

    #[test_traced("INFO")]
    fn test_historical_proof_limited_by_max_ops_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_limited_by_max_ops_inner::<mmb::Family>(context)
        });
    }

    /// Verify historical_proof() at the end of the journal.
    async fn test_historical_proof_at_end_of_journal_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal = create_journal_with_ops::<F>(context, "proof_end", 50).await;

        let size = journal.size();
        // Request proof starting near the end
        let (proof, ops) = journal
            .historical_proof(size, Location::<F>::new(40), NZU64!(20), 0)
            .await
            .unwrap();

        // Should return only 10 operations (positions 40-49)
        assert_eq!(ops.len(), 10);
        for (i, op) in ops.iter().enumerate() {
            assert_eq!(*op, create_operation::<F>((40 + i) as u8));
        }

        // Verify the proof is valid
        let hasher = StandardHasher::new(ForwardFold);
        let root = journal_root(&journal);
        assert!(verify_proof(
            &proof,
            &ops,
            Location::<F>::new(40),
            &root,
            &hasher
        ));
    }

    #[test_traced("INFO")]
    fn test_historical_proof_at_end_of_journal_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_historical_proof_at_end_of_journal_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_historical_proof_at_end_of_journal_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_historical_proof_at_end_of_journal_inner::<mmb::Family>);
    }

    /// Verify that historical_proof() returns an error for invalid size.
    async fn test_historical_proof_out_of_range_returns_error_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal = create_journal_with_ops::<F>(context, "proof_oob", 5).await;

        // Request proof with size > actual journal size
        let result = journal
            .historical_proof(Location::<F>::new(10), Location::<F>::new(0), NZU64!(1), 0)
            .await;

        assert!(matches!(
            result,
            Err(Error::Merkle(merkle::Error::RangeOutOfBounds(_)))
        ));
    }

    #[test_traced("INFO")]
    fn test_historical_proof_out_of_range_returns_error_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_out_of_range_returns_error_inner::<mmr::Family>(context)
        });
    }

    #[test_traced("INFO")]
    fn test_historical_proof_out_of_range_returns_error_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_out_of_range_returns_error_inner::<mmb::Family>(context)
        });
    }

    /// Verify that historical_proof() returns an error when start_loc >= size.
    async fn test_historical_proof_start_too_large_returns_error_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal = create_journal_with_ops::<F>(context, "proof_start_oob", 5).await;

        let size = journal.size();
        // Request proof starting at size (should fail)
        let result = journal.historical_proof(size, size, NZU64!(1), 0).await;

        assert!(matches!(
            result,
            Err(Error::Merkle(merkle::Error::RangeOutOfBounds(_)))
        ));
    }

    #[test_traced("INFO")]
    fn test_historical_proof_start_too_large_returns_error_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_start_too_large_returns_error_inner::<mmr::Family>(context)
        });
    }

    #[test_traced("INFO")]
    fn test_historical_proof_start_too_large_returns_error_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_start_too_large_returns_error_inner::<mmb::Family>(context)
        });
    }

    /// Verify historical_proof() for a truly historical state (before more operations added).
    async fn test_historical_proof_truly_historical_inner<F: Family + PartialEq>(context: Context) {
        // Create journal with initial operations
        let mut journal = create_journal_with_ops::<F>(context, "proof_historical", 50).await;

        // Capture root at historical state
        let hasher = StandardHasher::new(ForwardFold);
        let historical_root = journal_root(&journal);
        let historical_size = journal.size();

        // Add more operations after the historical state
        for i in 50..100 {
            (journal, _) = journal
                .append(&create_operation::<F>(i as u8))
                .await
                .unwrap();
        }
        let journal = journal.sync().await.unwrap();

        // Generate proof for the historical state
        let (proof, ops) = journal
            .historical_proof(historical_size, Location::<F>::new(0), NZU64!(50), 0)
            .await
            .unwrap();

        // Verify operations match expected historical operations
        assert_eq!(ops.len(), 50);
        for (i, op) in ops.iter().enumerate() {
            assert_eq!(*op, create_operation::<F>(i as u8));
        }

        // Verify the proof is valid against the historical root
        assert!(verify_proof(
            &proof,
            &ops,
            Location::<F>::new(0),
            &historical_root,
            &hasher
        ));
    }

    #[test_traced("INFO")]
    fn test_historical_proof_truly_historical_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_historical_proof_truly_historical_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_historical_proof_truly_historical_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_historical_proof_truly_historical_inner::<mmb::Family>);
    }

    /// Verify that historical_proof() returns an error when start_loc is pruned.
    async fn test_historical_proof_pruned_location_returns_error_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal = create_journal_with_ops::<F>(context, "proof_pruned", 50).await;

        (journal, _) = journal
            .append(&TestOp::<F>::CommitFloor(None, Location::<F>::new(25)))
            .await
            .unwrap();
        journal = journal.sync().await.unwrap();
        let pruned_boundary;
        (journal, pruned_boundary) = journal.prune(Location::<F>::new(25)).await.unwrap();

        // Try to get proof starting at a location before the pruned boundary
        let size = journal.size();
        let start_loc = Location::<F>::new(0);
        if start_loc < pruned_boundary {
            let result = journal
                .historical_proof(size, start_loc, NZU64!(1), 0)
                .await;

            // Should fail when trying to read pruned operations
            assert!(result.is_err());
        }
    }

    #[test_traced("INFO")]
    fn test_historical_proof_pruned_location_returns_error_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_pruned_location_returns_error_inner::<mmr::Family>(context)
        });
    }

    #[test_traced("INFO")]
    fn test_historical_proof_pruned_location_returns_error_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(|context| {
            test_historical_proof_pruned_location_returns_error_inner::<mmb::Family>(context)
        });
    }

    /// Verify replay() with empty journal and multiple operations.
    async fn test_replay_operations_inner<F: Family + PartialEq>(context: Context) {
        // Test empty journal
        {
            let journal = create_empty_journal::<F>(context.child("empty"), "replay").await;
            let stream = replay_items(
                &journal,
                0..journal.bounds().end,
                NZUsize!(10),
                ReadOptions::default(),
            )
            .await
            .unwrap();
            futures::pin_mut!(stream);
            assert!(stream.next().await.is_none());
        }

        // Test replaying all operations
        let journal = create_journal_with_ops::<F>(context.child("with_ops"), "replay", 50).await;
        let stream = replay_items(
            &journal,
            0..journal.bounds().end,
            NZUsize!(100),
            ReadOptions::default(),
        )
        .await
        .unwrap();
        futures::pin_mut!(stream);

        for i in 0..50 {
            let (pos, op) = stream.next().await.unwrap().unwrap();
            assert_eq!(pos, i);
            assert_eq!(op, create_operation::<F>(i as u8));
        }

        assert!(stream.next().await.is_none());
    }

    #[test_traced("INFO")]
    fn test_replay_operations_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_replay_operations_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_replay_operations_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_replay_operations_inner::<mmb::Family>);
    }

    #[test_traced("INFO")]
    fn test_replay_propagates_read_options_to_backing_journal() {
        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            let (context, recordings) = RecordingContext::new(context);
            let merkle_cfg = merkle_config("replay-options");
            let journal_cfg = journal_config("replay-options");
            let page_cache = journal_cfg.page_cache.clone();
            let mut journal = RecordingTestJournal::<mmr::Family>::new(
                context,
                merkle_cfg,
                journal_cfg,
                |op| op.is_commit(),
                ForwardFold,
            )
            .await
            .unwrap();

            for i in 0..8 {
                let operation = create_operation::<mmr::Family>(i);
                (journal, _) = journal.append(&operation).await.unwrap();
            }
            journal = journal.sync().await.unwrap();

            // Evict cached pages so the first replay item requires a backing read through the
            // authenticated wrapper.
            page_cache.clear();
            let stream = replay_items(
                &journal,
                0..journal.bounds().end,
                NZUsize!(100),
                ReadOptions::DONT_CACHE,
            )
            .await
            .unwrap();
            recordings.clear();
            futures::pin_mut!(stream);
            let (position, operation) = stream.next().await.unwrap().unwrap();
            assert_eq!(position, 0);
            assert_eq!(operation, create_operation::<mmr::Family>(0));

            // The authenticated wrapper forwards DONT_CACHE unchanged to the backing journal.
            let reads = recordings.snapshot().reads;
            assert!(!reads.is_empty());
            assert!(
                reads
                    .iter()
                    .all(|options| *options == ReadOptions::DONT_CACHE)
            );
        });
    }

    /// Verify replay() starting from a middle location.
    async fn test_replay_from_middle_inner<F: Family + PartialEq>(context: Context) {
        let journal = create_journal_with_ops::<F>(context, "replay_middle", 50).await;
        let stream = replay_items(
            &journal,
            25..journal.bounds().end,
            NZUsize!(100),
            ReadOptions::default(),
        )
        .await
        .unwrap();
        futures::pin_mut!(stream);

        let mut count = 0;
        while let Some(result) = stream.next().await {
            let (pos, op) = result.unwrap();
            assert_eq!(pos, 25 + count);
            assert_eq!(op, create_operation::<F>((25 + count) as u8));
            count += 1;
        }

        // Should have replayed positions 25-49 (25 operations)
        assert_eq!(count, 25);
    }

    #[test_traced("INFO")]
    fn test_replay_from_middle_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_replay_from_middle_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_replay_from_middle_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_replay_from_middle_inner::<mmb::Family>);
    }

    /// Verify the speculative batch API: fork two batches, verify independent roots, apply one.
    async fn test_speculative_batch_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "speculative_batch", 10).await;
        let original_root = journal_root(&journal);

        // Fork two independent speculative batches.
        let b1 = journal.new_batch();
        let b2 = journal.new_batch();

        // Add different items to each batch.
        let op_a = create_operation::<F>(100);
        let op_b = create_operation::<F>(200);
        let b1 = b1.add(op_a.clone());
        let b2 = b2.add(op_b);

        // Merkleize and verify independent roots.
        let m1 = b1.merkleize(journal.merkle.mem());
        let m2 = b2.merkleize(journal.merkle.mem());
        assert_ne!(batch_root(&journal, &m1), batch_root(&journal, &m2));
        assert_ne!(batch_root(&journal, &m1), original_root);
        assert_ne!(batch_root(&journal, &m2), original_root);

        // Journal root should be unchanged (batches are speculative).
        assert_eq!(journal_root(&journal), original_root);

        // Apply batch 1.
        let expected_root = batch_root(&journal, &m1);
        journal = journal.apply_batch(&m1).await.unwrap();

        // Journal should now match the applied batch's root.
        assert_eq!(journal_root(&journal), expected_root);
        assert_eq!(*journal.size(), 11);
    }

    #[test_traced("INFO")]
    fn test_speculative_batch_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_speculative_batch_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_speculative_batch_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_speculative_batch_inner::<mmb::Family>);
    }

    /// Verify stacking: create batch A, merkleize, create batch B from merkleized A,
    /// merkleize, and apply. Verify root and items.
    async fn test_speculative_batch_stacking_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "batch_stacking", 10).await;

        let op_a = create_operation::<F>(100);
        let op_b = create_operation::<F>(200);

        let (merkleized_a, merkleized_b) = {
            let batch_a = journal.new_batch().add(op_a.clone());
            let merkleized_a = batch_a.merkleize(journal.merkle.mem());

            let batch_b = merkleized_a.new_batch::<Sha256>().add(op_b.clone());
            let merkleized_b = batch_b.merkleize(journal.merkle.mem());
            (merkleized_a, merkleized_b)
        };

        let expected_root = batch_root(&journal, &merkleized_b);
        journal = journal.apply_batch(&merkleized_b).await.unwrap();
        drop(merkleized_a);

        assert_eq!(journal_root(&journal), expected_root);
        assert_eq!(*journal.size(), 12);

        // Verify both items were appended correctly.
        let read_a = journal.read(*Location::<F>::new(10)).await.unwrap();
        assert_eq!(read_a, op_a);
        let read_b = journal.read(*Location::<F>::new(11)).await.unwrap();
        assert_eq!(read_b, op_b);
    }

    #[test_traced("INFO")]
    fn test_speculative_batch_stacking_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_speculative_batch_stacking_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_speculative_batch_stacking_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_speculative_batch_stacking_inner::<mmb::Family>);
    }

    /// Verify sequential batch application: apply batch A, then build and apply batch B
    /// from the committed state. Verify root and items.
    async fn test_speculative_batch_sequential_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "batch_sequential", 10).await;

        let op_a = create_operation::<F>(100);
        let op_b = create_operation::<F>(200);

        // Apply batch A.
        let batch_a = journal.new_batch().add(op_a.clone());
        let merkleized_a = batch_a.merkleize(journal.merkle.mem());
        journal = journal.apply_batch(&merkleized_a).await.unwrap();
        assert_eq!(*journal.size(), 11);

        // Apply batch B (built on top of the committed A).
        let batch_b = journal.new_batch().add(op_b.clone());
        let merkleized_b = batch_b.merkleize(journal.merkle.mem());
        let expected_root = batch_root(&journal, &merkleized_b);
        journal = journal.apply_batch(&merkleized_b).await.unwrap();

        assert_eq!(journal_root(&journal), expected_root);
        assert_eq!(*journal.size(), 12);

        // Verify both items were appended correctly.
        let read_a = journal.read(*Location::<F>::new(10)).await.unwrap();
        assert_eq!(read_a, op_a);
        let read_b = journal.read(*Location::<F>::new(11)).await.unwrap();
        assert_eq!(read_b, op_b);
    }

    #[test_traced("INFO")]
    fn test_speculative_batch_sequential_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_speculative_batch_sequential_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_speculative_batch_sequential_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_speculative_batch_sequential_inner::<mmb::Family>);
    }

    async fn test_stale_batch_sibling_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_empty_journal::<F>(context.child("open"), "stale-sibling").await;
        let op_a = create_operation::<F>(1);
        let op_b = create_operation::<F>(2);

        // Create two batches from the same base.
        let batch_a = journal.new_batch().add(op_a.clone());
        let merkleized_a = batch_a.merkleize(journal.merkle.mem());
        let batch_b = journal.new_batch().add(op_b);
        let merkleized_b = batch_b.merkleize(journal.merkle.mem());

        // Apply A, then commit and sync so the recovered state below includes it (reopen
        // selects the last commit operation during initialization).
        journal = journal.apply_batch(&merkleized_a).await.unwrap();
        let commit_op = TestOp::<F>::CommitFloor(None, Location::<F>::new(0));
        (journal, _) = journal.append(&commit_op).await.unwrap();
        journal = journal.sync().await.unwrap();
        let root_a = journal_root(&journal);
        let size_a = journal.size();
        let (_, ops) = journal
            .proof(Location::<F>::new(0), NZU64!(1), 0)
            .await
            .unwrap();
        assert_eq!(ops, vec![op_a.clone()]);

        // Applying B must fail (stale).
        let result = journal.apply_batch(&merkleized_b).await;
        assert!(
            matches!(
                result,
                Err(super::Error::Merkle(merkle::Error::StaleBatch { .. }))
            ),
            "expected StaleBatch, got {result:?}"
        );

        // The eager reject mutated nothing: reopening recovers exactly A's state.
        let journal = create_empty_journal::<F>(context.child("reopen"), "stale-sibling").await;
        assert_eq!(journal_root(&journal), root_a);
        assert_eq!(journal.size(), size_a);
        let (_, ops) = journal
            .proof(Location::<F>::new(0), NZU64!(1), 0)
            .await
            .unwrap();
        assert_eq!(ops, vec![op_a]);
        journal.destroy().await.unwrap();
    }

    #[test_traced("INFO")]
    fn test_stale_batch_sibling_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_sibling_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_sibling_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_sibling_inner::<mmb::Family>);
    }

    async fn test_stale_batch_chained_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "stale-chained", 5).await;

        // Parent batch, then fork two children.
        let parent_batch = journal.new_batch().add(create_operation::<F>(10));
        let parent = parent_batch.merkleize(journal.merkle.mem());
        let batch_a = parent.new_batch::<Sha256>().add(create_operation::<F>(20));
        let child_a = batch_a.merkleize(journal.merkle.mem());
        let batch_b = parent.new_batch::<Sha256>().add(create_operation::<F>(30));
        let child_b = batch_b.merkleize(journal.merkle.mem());

        // Apply child_a, then child_b should be stale.
        journal = journal.apply_batch(&child_a).await.unwrap();
        let result = journal.apply_batch(&child_b).await;
        drop(parent);
        assert!(
            matches!(
                result,
                Err(super::Error::Merkle(merkle::Error::StaleBatch { .. }))
            ),
            "expected StaleBatch for sibling, got {result:?}"
        );
    }

    #[test_traced("INFO")]
    fn test_stale_batch_chained_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_chained_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_chained_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_chained_inner::<mmb::Family>);
    }

    async fn test_stale_batch_parent_before_child_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_empty_journal::<F>(context, "stale-parent-first").await;

        // Create parent, then child.
        let parent_batch = journal.new_batch().add(create_operation::<F>(1));
        let parent = parent_batch.merkleize(journal.merkle.mem());
        let child_batch = parent.new_batch::<Sha256>().add(create_operation::<F>(2));
        let child = child_batch.merkleize(journal.merkle.mem());

        let expected_root = batch_root(&journal, &child);

        // Apply parent, then child (sequential commit).
        journal = journal.apply_batch(&parent).await.unwrap();
        journal = journal.apply_batch(&child).await.unwrap();

        assert_eq!(journal_root(&journal), expected_root);
        assert_eq!(*journal.size(), 2);
    }

    /// A retained child of one fork must be rejected without writing to storage once a sibling of
    /// its parent has been applied, and reopening must recover the sibling's state.
    async fn test_stale_batch_interior_fork_inner<F: Family + PartialEq>(context: Context) {
        // Record storage writes so the test can show that a rejected batch wrote nothing.
        let (storage, recordings) = RecordingContext::new(context.child("open"));
        let merkle_cfg = merkle_config("stale-interior");
        let journal_cfg = journal_config("stale-interior");
        let mut journal = RecordingTestJournal::<F>::new(
            storage,
            merkle_cfg,
            journal_cfg,
            |op| op.is_commit(),
            ForwardFold,
        )
        .await
        .unwrap();
        for i in 0..4 {
            (journal, _) = journal.append(&create_operation::<F>(i)).await.unwrap();
        }
        let commit_op = TestOp::<F>::CommitFloor(None, Location::<F>::new(0));

        // Retain the chain A -> B, then apply a sibling of A with the same length.
        let batch_a = journal
            .new_batch()
            .add(create_operation::<F>(10))
            .add(commit_op.clone());
        let a = batch_a.merkleize(journal.merkle.mem());
        let batch_b = a.new_batch::<Sha256>().add(create_operation::<F>(20));
        let b = batch_b.merkleize(journal.merkle.mem());
        let op_sibling = create_operation::<F>(30);
        let batch_sibling = journal.new_batch().add(op_sibling.clone()).add(commit_op);
        let sibling = batch_sibling.merkleize(journal.merkle.mem());
        journal = journal.apply_batch(&sibling).await.unwrap();
        journal = journal.sync().await.unwrap();
        let root = journal.root(0).unwrap();
        let size = journal.size();
        recordings.clear();

        // The journal's size lies inside B's chain, but the sibling, not A, produced that state.
        // Applying B must fail before writing anything, so items and root stay in sync.
        let result = journal.apply_batch(&b).await;
        assert!(
            matches!(
                result,
                Err(super::Error::Merkle(merkle::Error::StaleBatch { .. }))
            ),
            "applying B must fail with StaleBatch, got {result:?}"
        );
        assert!(
            recordings.snapshot().writes.is_empty(),
            "a rejected batch must not write to storage"
        );

        // Reopening recovers exactly the sibling's state.
        let journal = create_empty_journal::<F>(context.child("reopen"), "stale-interior").await;
        assert_eq!(journal_root(&journal), root);
        assert_eq!(journal.size(), size);
        let (_, ops) = journal
            .proof(Location::<F>::new(4), NZU64!(1), 0)
            .await
            .unwrap();
        assert_eq!(ops, vec![op_sibling]);
        journal.destroy().await.unwrap();
    }

    /// Applying an empty child after its parent must succeed and leave the journal unchanged.
    async fn test_apply_batch_empty_child_after_parent_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal = create_journal_with_ops::<F>(context, "empty-child", 4).await;
        let parent = journal
            .new_batch()
            .add(create_operation::<F>(10))
            .merkleize(journal.merkle.mem());
        let child = parent.new_batch::<Sha256>().merkleize(journal.merkle.mem());
        journal = journal.apply_batch(&parent).await.unwrap();
        let root = journal_root(&journal);
        let size = journal.size();

        // The journal is already at the empty child's tip, so applying it changes nothing.
        journal = journal.apply_batch(&child).await.unwrap();
        assert_eq!(journal_root(&journal), root);
        assert_eq!(journal.size(), size);
        journal.destroy().await.unwrap();
    }

    #[test_traced("INFO")]
    fn test_apply_batch_empty_child_after_parent_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_empty_child_after_parent_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_apply_batch_empty_child_after_parent_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_empty_child_after_parent_inner::<mmb::Family>);
    }

    /// A descendant must be rejected with `AncestorDropped` when an ancestor's journal batch was
    /// dropped before the descendant was merkleized, even though its Merkle batch was retained.
    async fn test_apply_batch_rejects_dropped_journal_ancestor_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal =
            create_journal_with_ops::<F>(context.child("open"), "dropped-items", 4).await;
        let commit_op = TestOp::<F>::CommitFloor(None, Location::<F>::new(0));
        let seed = journal
            .new_batch()
            .add(create_operation::<F>(5))
            .add(commit_op.clone())
            .merkleize(journal.merkle.mem());
        journal = journal.apply_batch(&seed).await.unwrap();
        journal = journal.sync().await.unwrap();
        let root = journal_root(&journal);
        let size = journal.size();

        // In the chain A -> B -> C, A's Merkle batch outlives its journal batch, so C retains
        // A's Merkle data but not A's items.
        let a = journal
            .new_batch()
            .add(create_operation::<F>(10))
            .merkleize(journal.merkle.mem());
        let b = a
            .new_batch::<Sha256>()
            .add(create_operation::<F>(20))
            .merkleize(journal.merkle.mem());
        let a_merkle = Arc::clone(&a.inner);
        drop(a);
        let c = b
            .new_batch::<Sha256>()
            .add(create_operation::<F>(30))
            .add(commit_op)
            .merkleize(journal.merkle.mem());

        // The Merkle structure is at C's fork point, but the journal lacks A's items and must
        // reject C before appending anything.
        let result = journal.apply_batch(&c).await;
        assert!(
            matches!(
                result,
                Err(super::Error::Merkle(merkle::Error::AncestorDropped { .. }))
            ),
            "applying C must fail with AncestorDropped, got {result:?}"
        );
        drop(a_merkle);

        // Reopening recovers the state from before the rejected batch.
        let journal = create_empty_journal::<F>(context.child("reopen"), "dropped-items").await;
        assert_eq!(journal_root(&journal), root);
        assert_eq!(journal.size(), size);
        journal.destroy().await.unwrap();
    }

    #[test_traced("INFO")]
    fn test_apply_batch_rejects_dropped_journal_ancestor_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_rejects_dropped_journal_ancestor_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_apply_batch_rejects_dropped_journal_ancestor_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_rejects_dropped_journal_ancestor_inner::<mmb::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_interior_fork_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_interior_fork_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_interior_fork_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_interior_fork_inner::<mmb::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_parent_before_child_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_parent_before_child_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_parent_before_child_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_parent_before_child_inner::<mmb::Family>);
    }

    async fn test_stale_batch_child_before_parent_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_empty_journal::<F>(context, "stale-child-first").await;

        // Create parent, then child.
        let parent_batch = journal.new_batch().add(create_operation::<F>(1));
        let parent = parent_batch.merkleize(journal.merkle.mem());
        let child_batch = parent.new_batch::<Sha256>().add(create_operation::<F>(2));
        let child = child_batch.merkleize(journal.merkle.mem());

        // Applying the child first (full chain) makes the parent stale.
        journal = journal.apply_batch(&child).await.unwrap();
        let result = journal.apply_batch(&parent).await;
        assert!(
            matches!(
                result,
                Err(super::Error::Merkle(merkle::Error::StaleBatch { .. }))
            ),
            "expected StaleBatch for parent after child applied, got {result:?}"
        );
    }

    #[test_traced("INFO")]
    fn test_stale_batch_child_before_parent_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_child_before_parent_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_stale_batch_child_before_parent_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_stale_batch_child_before_parent_inner::<mmb::Family>);
    }

    /// Apply parent then child: child skips already-committed ancestor items.
    async fn test_apply_batch_skip_ancestor_items_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "rp-skip", 3).await;

        // Parent: 2 items.
        let parent_batch = journal
            .new_batch()
            .add(create_operation::<F>(10))
            .add(create_operation::<F>(11));
        let parent = parent_batch.merkleize(journal.merkle.mem());

        // Child: 3 more items.
        let child_batch = parent
            .new_batch::<Sha256>()
            .add(create_operation::<F>(20))
            .add(create_operation::<F>(21))
            .add(create_operation::<F>(22));
        let child = child_batch.merkleize(journal.merkle.mem());

        // Apply parent.
        journal = journal.apply_batch(&parent).await.unwrap();

        // Apply child (ancestor items already committed, skipped automatically).
        journal = journal.apply_batch(&child).await.unwrap();

        // Verify all items are present.
        let (_, ops) = journal
            .proof(Location::<F>::new(3), NZU64!(5), 0)
            .await
            .unwrap();
        assert_eq!(ops.len(), 5);
    }

    #[test_traced("INFO")]
    fn test_apply_batch_skip_ancestor_items_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_skip_ancestor_items_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_apply_batch_skip_ancestor_items_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_skip_ancestor_items_inner::<mmb::Family>);
    }

    /// `apply_batch` works correctly across a 3-level chain.
    async fn test_apply_batch_cross_batch_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "rp-cross", 2).await;

        // Grandparent: 3 items.
        let grandparent_batch = journal
            .new_batch()
            .add(create_operation::<F>(3))
            .add(create_operation::<F>(4))
            .add(create_operation::<F>(5));
        let grandparent = grandparent_batch.merkleize(journal.merkle.mem());

        // Parent: 2 items.
        let parent_batch = grandparent
            .new_batch::<Sha256>()
            .add(create_operation::<F>(6))
            .add(create_operation::<F>(7));
        let parent = parent_batch.merkleize(journal.merkle.mem());

        // Child: 1 item.
        let child_batch = parent.new_batch::<Sha256>().add(create_operation::<F>(8));
        let child = child_batch.merkleize(journal.merkle.mem());

        // Apply grandparent, then parent, then child sequentially.
        journal = journal.apply_batch(&grandparent).await.unwrap();

        // Apply parent (ancestor items already committed, skipped automatically).
        journal = journal.apply_batch(&parent).await.unwrap();

        // Apply child (ancestor items already committed, skipped automatically).
        journal = journal.apply_batch(&child).await.unwrap();

        // All 8 items (2 base + 3 + 2 + 1) should be present.
        assert_eq!(*journal.size(), 8);

        // Verify the actual items at each location.
        let (_, ops) = journal
            .proof(Location::<F>::new(2), NZU64!(6), 0)
            .await
            .unwrap();
        for (i, op) in ops.iter().enumerate() {
            assert_eq!(*op, create_operation::<F>((i + 3) as u8));
        }
    }

    #[test_traced("INFO")]
    fn test_apply_batch_cross_batch_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_cross_batch_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_apply_batch_cross_batch_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_cross_batch_inner::<mmb::Family>);
    }

    /// merkleize_with produces the same root as add + merkleize.
    async fn test_merkleize_with_matches_add_inner<F: Family + PartialEq>(context: Context) {
        let journal = create_journal_with_ops::<F>(context, "mw-matches", 5).await;

        let ops = vec![
            create_operation::<F>(10),
            create_operation::<F>(11),
            create_operation::<F>(12),
        ];

        // add + merkleize
        let mut batch = journal.new_batch();
        for op in &ops {
            batch = batch.add(op.clone());
        }
        let expected = batch.merkleize(journal.merkle.mem());

        // merkleize_with
        let batch = journal.new_batch();
        let actual = merkleize_with(batch, journal.merkle.mem(), ops);

        assert_eq!(
            batch_root(&journal, &actual),
            batch_root(&journal, &expected)
        );
    }

    #[test_traced("INFO")]
    fn test_merkleize_with_matches_add_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_merkleize_with_matches_add_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_merkleize_with_matches_add_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_merkleize_with_matches_add_inner::<mmb::Family>);
    }

    /// merkleize_with items are readable after apply.
    async fn test_merkleize_with_apply_inner<F: Family + PartialEq>(context: Context) {
        let mut journal = create_journal_with_ops::<F>(context, "mw-apply", 5).await;

        let ops = vec![create_operation::<F>(10), create_operation::<F>(11)];
        let batch = journal.new_batch();
        let merkleized = merkleize_with(batch, journal.merkle.mem(), ops.clone());

        let expected_root = batch_root(&journal, &merkleized);
        journal = journal.apply_batch(&merkleized).await.unwrap();

        assert_eq!(journal_root(&journal), expected_root);
        assert_eq!(*journal.size(), 7);

        assert_eq!(journal.read(5).await.unwrap(), ops[0]);
        assert_eq!(journal.read(6).await.unwrap(), ops[1]);
    }

    #[test_traced("INFO")]
    fn test_merkleize_with_apply_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_merkleize_with_apply_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_merkleize_with_apply_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_merkleize_with_apply_inner::<mmb::Family>);
    }

    /// Apply C (grandchild of A) after only A is committed. B's journal items
    /// must still be applied, so skip only A's items.
    async fn test_apply_batch_skips_only_committed_ancestor_items_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal = create_empty_journal::<F>(context.child("storage"), "skip-partial").await;

        // Build chain: A -> B -> C
        let a_batch = journal.new_batch().add(create_operation::<F>(1));
        let a = a_batch.merkleize(journal.merkle.mem());
        let b_batch = a.new_batch::<Sha256>().add(create_operation::<F>(2));
        let b = b_batch.merkleize(journal.merkle.mem());
        let c_batch = b.new_batch::<Sha256>().add(create_operation::<F>(3));
        let c = c_batch.merkleize(journal.merkle.mem());

        // Apply A, then apply C directly (skipping B's apply_batch).
        journal = journal.apply_batch(&a).await.unwrap();
        journal = journal.apply_batch(&c).await.unwrap();

        // All 3 items should be in the journal.
        assert_eq!(*journal.size(), 3);

        // Build a reference that applies all three sequentially.
        let mut reference =
            create_empty_journal::<F>(context.child("ref"), "skip-partial-ref").await;
        for i in 1..=3u8 {
            (reference, _) = reference.append(&create_operation::<F>(i)).await.unwrap();
        }
        assert_eq!(journal_root(&journal), journal_root(&reference));
    }

    #[test_traced("INFO")]
    fn test_apply_batch_skips_only_committed_ancestor_items_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_skips_only_committed_ancestor_items_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_apply_batch_skips_only_committed_ancestor_items_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_skips_only_committed_ancestor_items_inner::<mmb::Family>);
    }

    /// A descendant whose uncommitted ancestor was dropped must fail before
    /// appending any of its retained journal items.
    async fn test_apply_batch_detects_dropped_uncommitted_ancestor_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let journal =
            create_empty_journal::<F>(context.child("storage"), "dropped-uncommitted").await;

        let a_batch = journal.new_batch().add(create_operation::<F>(1));
        let a = a_batch.merkleize(journal.merkle.mem());
        let b_batch = a.new_batch::<Sha256>().add(create_operation::<F>(2));
        let b = b_batch.merkleize(journal.merkle.mem());

        drop(a);
        let c_batch = b.new_batch::<Sha256>().add(create_operation::<F>(3));
        let c = c_batch.merkleize(journal.merkle.mem());
        drop(b);

        assert_eq!(c.ancestor_items.len(), 1);

        let result = journal.apply_batch(&c).await;
        assert!(
            matches!(
                result,
                Err(super::Error::Merkle(merkle::Error::AncestorDropped { expected, .. }))
                    if expected == c.inner.size()
            ),
            "expected AncestorDropped, got {result:?}"
        );
    }

    #[test_traced("INFO")]
    fn test_apply_batch_detects_dropped_uncommitted_ancestor_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_detects_dropped_uncommitted_ancestor_inner::<mmb::Family>);
    }

    /// A dropped committed prefix must not shift the remaining uncommitted
    /// ancestor items back to the original fork point.
    async fn test_apply_batch_after_committed_ancestor_dropped_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal =
            create_empty_journal::<F>(context.child("storage"), "dropped-committed").await;

        let mut a_batch = journal.new_batch();
        for i in 0..8u8 {
            a_batch = a_batch.add(create_operation::<F>(i));
        }
        let a = a_batch.merkleize(journal.merkle.mem());
        let b_batch = a.new_batch::<Sha256>().add(create_operation::<F>(8));
        let b = b_batch.merkleize(journal.merkle.mem());

        journal = journal.apply_batch(&a).await.unwrap();
        drop(a);

        let c_batch = b.new_batch::<Sha256>().add(create_operation::<F>(9));
        let c = c_batch.merkleize(journal.merkle.mem());

        // Only B remains in the retained ancestor suffix.
        assert_eq!(c.ancestor_items.len(), 1);
        assert_eq!(journal.merkle.mem().validate_batch(&c.inner).unwrap(), 0);

        drop(b);
        journal = journal.apply_batch(&c).await.unwrap();
        assert_eq!(*journal.size(), 10);

        let mut reference =
            create_empty_journal::<F>(context.child("reference"), "dropped-committed-ref").await;
        for i in 0..10u8 {
            (reference, _) = reference.append(&create_operation::<F>(i)).await.unwrap();
        }
        assert_eq!(journal_root(&journal), journal_root(&reference));
    }

    #[test_traced("INFO")]
    fn test_apply_batch_after_committed_ancestor_dropped_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_apply_batch_after_committed_ancestor_dropped_inner::<mmb::Family>);
    }

    /// Merkleization retains a speculative suffix after its committed prefix is released.
    async fn test_merkleize_after_committed_prefix_dropped_inner<F: Family + PartialEq>(
        context: Context,
    ) {
        let mut journal =
            create_empty_journal::<F>(context.child("storage"), "committed-prefix").await;

        // Build a speculative suffix over a prefix that will be committed independently.
        let prefix_items = (0..8u8).map(create_operation::<F>).collect();
        let (prefix, _) = journal
            .merkleize(journal.new_batch(), prefix_items, 0)
            .await
            .unwrap();
        let pending_items = (8..10u8).map(create_operation::<F>).collect();
        let (pending, _) = journal
            .merkleize(prefix.new_batch::<Sha256>(), pending_items, 0)
            .await
            .unwrap();

        // Commit and release the prefix. Its Merkle nodes now resolve through the snapshot.
        journal = journal.apply_batch(&prefix).await.unwrap();
        drop(prefix);

        // The child batch is the pending suffix's only remaining owner. Merkleization must retain
        // that suffix through root computation.
        let child_batch = pending.new_batch::<Sha256>();
        drop(pending);
        let (child, expected_root) = journal
            .merkleize(child_batch, vec![create_operation::<F>(10)], 0)
            .await
            .unwrap();
        journal = journal.apply_batch(&child).await.unwrap();

        assert_eq!(journal_root(&journal), expected_root);
        assert_eq!(*journal.size(), 11);
    }

    #[test_traced("INFO")]
    fn test_merkleize_after_committed_prefix_dropped_mmr() {
        let executor = deterministic::Runner::default();
        executor.start(test_merkleize_after_committed_prefix_dropped_inner::<mmr::Family>);
    }

    #[test_traced("INFO")]
    fn test_merkleize_after_committed_prefix_dropped_mmb() {
        let executor = deterministic::Runner::default();
        executor.start(test_merkleize_after_committed_prefix_dropped_inner::<mmb::Family>);
    }

    /// A detached merkleization job owns the full ancestor chain after its waiter is dropped.
    #[test_traced("INFO")]
    fn test_merkleize_retains_ancestors_after_cancellation() {
        deterministic::Runner::default().start(|context| async move {
            let pool = Rayon::new(NZUsize!(2)).unwrap();
            let strategy = Explorer::parallel(&pool);
            let merkle_cfg = merkle_config_with("cancelled-merkleize", strategy);
            let journal_cfg = journal_config("cancelled-merkleize");
            type ParallelJournal = Journal<
                mmr::Family,
                Context,
                ContiguousJournal<Context, DropMonitor<TestOp<mmr::Family>>>,
                Sha256,
                Explorer,
            >;
            let journal = ParallelJournal::new(
                context,
                merkle_cfg,
                journal_cfg,
                |_: &DropMonitor<TestOp<mmr::Family>>| false,
                ForwardFold,
            )
            .await
            .unwrap();

            let a_items = (0..8u8)
                .map(create_operation::<mmr::Family>)
                .map(DropMonitor::untracked)
                .collect();
            let a_batch = journal.new_batch().add_many(a_items);
            let a = a_batch.merkleize(journal.merkle.mem());
            let b_items = (8..10u8)
                .map(create_operation::<mmr::Family>)
                .map(DropMonitor::untracked)
                .collect();
            let b_batch = a.new_batch::<Sha256>().add_many(b_items);
            let b = b_batch.merkleize(journal.merkle.mem());

            let ancestor = Arc::downgrade(&a.inner);
            let c_batch = b.new_batch::<Sha256>();
            drop(b);

            let release = block_strategy(&pool, 2);
            let (item, clean_drop) = DropMonitor::tracked(create_operation::<mmr::Family>(10));
            let mut merkleize = Box::pin(journal.merkleize(c_batch, vec![item], 0));
            assert!(futures::poll!(merkleize.as_mut()).is_pending());
            drop(merkleize);
            drop(a);

            assert!(ancestor.upgrade().is_some());
            drop(release);
            assert!(
                clean_drop
                    .recv_timeout(Duration::from_secs(10))
                    .expect("detached merkleization did not finish"),
                "detached merkleization panicked"
            );
            assert!(ancestor.upgrade().is_none());
        });
    }

    /// A fully pruned authenticated journal preserves its append position and root across reopen.
    async fn fully_pruned_authenticated_reopens<F: Family + PartialEq>(context: Context) {
        // Fill exactly one operation blob, then prune the complete durable prefix.
        let merkle_cfg = merkle_config("fully-pruned-reopen");
        let journal_cfg = journal_config("fully-pruned-reopen");
        assert_eq!(journal_cfg.items_per_blob.get(), 7);
        let mut journal = TestJournal::<F>::new(
            context.child("seed"),
            merkle_cfg.clone(),
            journal_cfg.clone(),
            |_| true,
            ForwardFold,
        )
        .await
        .unwrap();
        for i in 0u8..7 {
            let (next, pos) = journal.append(&create_operation::<F>(i)).await.unwrap();
            journal = next;
            assert_eq!(*pos, u64::from(i));
        }
        let journal = journal.sync().await.unwrap();
        let root = journal.root(0).unwrap();
        let (journal, boundary) = journal.prune(Location::new(7)).await.unwrap();
        assert_eq!(*boundary, 7);
        assert_eq!(journal.bounds(), 7..7);
        assert_eq!(journal.root(0).unwrap(), root);
        drop(journal);

        // Reopen at the retained boundary and append at that position.
        let journal = TestJournal::<F>::new(
            context.child("reopen"),
            merkle_cfg,
            journal_cfg,
            |_| true,
            ForwardFold,
        )
        .await
        .unwrap();
        assert_eq!(journal.bounds(), 7..7);
        assert_eq!(journal.root(0).unwrap(), root);
        let (journal, pos) = journal.append(&create_operation::<F>(7)).await.unwrap();
        assert_eq!(*pos, 7);
        assert_eq!(journal.bounds(), 7..8);
        journal.destroy().await.unwrap();
    }

    #[test]
    fn test_fully_pruned_authenticated_reopens_mmr() {
        deterministic::Runner::default().start(fully_pruned_authenticated_reopens::<mmr::Family>);
    }

    #[test]
    fn test_fully_pruned_authenticated_reopens_mmb() {
        deterministic::Runner::default().start(fully_pruned_authenticated_reopens::<mmb::Family>);
    }
}