kv-sync: authenticated tombstones (sealed {id, seq, deleted: true})

Tombstones carried no ciphertext, so the server could forge a delete (hiding
an item), and a device that pulled one accepted the next live version without
a seq comparison (delete-then-replay rollback).

* A delete is sealed like an item (same AAD and padding) with plaintext
  {id, seq, deleted: true}; seq = working/base seq + 1. DELETE carries it as
  the ItemPut body; the test server stores and serves it.
* replay: Base is None | LegacyTombstone | Sealed(plaintext). check_pulled
  refuses a record without ciphertext, a deleted flag that disagrees with the
  plaintext, or a tombstone naming another item, then requires seq to grow
  for tombstones too. The `restores` exception is gone: edit beats delete
  re-seals with max(edit, tombstone) + 1. next_version returns just seq.
* Legacy: a pulled tombstone without ciphertext is an integrity alarm (cannot
  be told apart from a forgery). A pending legacy delete is sealed on push; a
  legacy tombstone already held as base is accepted as unknown seq.
* engine: open_sealed, seal_tombstone; next_local_version -> u64. Merkle leaf
  hashes a sealed tombstone's envelope like a live record's.
* kv-model Item: `restores` removed. kv-ffi delete_item seals the tombstone;
  FFI surface unchanged.
* Tests: forged (unsealed and relabelled) tombstones raise an integrity alarm
  (kv-sync and kv-ffi), replay after a tombstone, replays of the tombstone and
  of the restore, legacy pending delete, shared item_replay.json table; the
  live test now deletes an item through the real server.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/kv-ffi/src/lib.rs

@@ -563,8 +563,7 @@ impl VaultCore {
         model.favorite = item.favorite;
         model.tags = item.tags;
         model.modified_at = now.max(previous.as_ref().map_or(0, |p| p.modified_at + 1));
-        (model.seq, model.restores) =
-            kv_sync::engine::next_local_version(self.store.as_ref(), acct.account_id, vault, &u.vault_key, id)?;
+        model.seq = kv_sync::engine::next_local_version(self.store.as_ref(), acct.account_id, vault, &u.vault_key, id)?;
 
         let json = Zeroizing::new(serde_json::to_vec(&model).map_err(internal)?);
         let sealed = seal_item(acct.account_id, vault, id, &u.vault_key, &json)?;
@@ -602,14 +601,17 @@ impl VaultCore {
 
     pub fn delete_item(&self, id: String) -> Result<()> {
         let id = parse_id(&id)?;
-        let (acct, _u) = self.unlocked_snapshot()?;
+        let (acct, u) = self.unlocked_snapshot()?;
         let vault = acct.primary_vault;
         let li = self.store.get(vault, id)?.filter(|li| !li.record.deleted).ok_or(CoreError::NotFound)?;
         if li.base.is_none() {
             // Never reached the server: just forget it.
             return Ok(self.store.remove(vault, id)?);
         }
-        let tomb = ItemRecord { deleted: true, wrapped_item_key: None, payload: None, ..li.record };
+        // The tombstone is sealed with the next `seq` (docs/03 "Per-item replay protection").
+        let seq = kv_sync::engine::next_local_version(self.store.as_ref(), acct.account_id, vault, &u.vault_key, id)?;
+        let tomb =
+            kv_sync::engine::seal_tombstone(acct.account_id, vault, &u.vault_key, id, seq, li.record.updated_by)?;
         Ok(self.store.put_local(vault, &tomb)?)
     }
 

crates/kv-ffi/src/tests.rs

@@ -322,3 +322,36 @@ async fn save_item_bumps_seq_and_replays_are_refused() {
     }
     assert_eq!(b.get_item(id).unwrap().password.as_deref(), Some("pw3"));
 }
+
+#[tokio::test]
+async fn delete_item_seals_the_tombstone_and_forged_deletes_are_refused() {
+    let server = TestServer::start().await;
+    let a = VaultCore::new_in_memory();
+    let sk = a.create_account(PW.into()).unwrap();
+    connect(&a, &server);
+    a.register_account(SETUP_TOKEN.into()).await.unwrap();
+    let gone = a.save_item(login_item("Old", "pw0")).unwrap();
+    let kept = a.save_item(login_item("Bank", "pw1")).unwrap();
+    a.sync_now().await.unwrap();
+    a.delete_item(gone.clone()).unwrap();
+    a.sync_now().await.unwrap();
+    let vid = *server.state().vaults.keys().next().unwrap();
+    let (gone_id, kept_id) = (Uuid::parse_str(&gone).unwrap(), Uuid::parse_str(&kept).unwrap());
+    let tomb = server.state().vaults[&vid].items[&gone_id].clone();
+    assert!(tomb.deleted && tomb.payload.is_some(), "DELETE carried the sealed tombstone");
+
+    let b = VaultCore::new_in_memory();
+    connect(&b, &server);
+    b.login(PW.into(), sk, None).await.unwrap();
+    b.sync_now().await.unwrap();
+    assert_eq!(b.list_items().unwrap().len(), 1);
+
+    // The server forges a delete of the kept item.
+    let live = server.state().vaults[&vid].items[&kept_id].clone();
+    server.state().write_item(vid, ItemRecord { deleted: true, wrapped_item_key: None, payload: None, ..live });
+    match b.sync_now().await {
+        Err(CoreError::IntegrityAlarm { reason, .. }) => assert!(reason.contains("unauthenticated"), "{reason}"),
+        other => panic!("expected integrity alarm, got {other:?}"),
+    }
+    assert_eq!(b.get_item(kept).unwrap().password.as_deref(), Some("pw1"));
+}

crates/kv-ffi/tests/live_server.rs

@@ -97,6 +97,16 @@ async fn two_devices_against_local_server() {
     assert_eq!((ia.notes.as_deref(), ia.username.as_deref()), (Some("A"), Some("b")));
     assert_eq!((ib.notes, ib.username), (ia.notes, ia.username));
 
+    // A delete carries the sealed tombstone, and B authenticates it.
+    let temp = a.save_item(item("Temp", "pw-t")).unwrap();
+    a.sync_now().await.unwrap();
+    b.sync_now().await.unwrap();
+    assert!(b.get_item(temp.clone()).is_ok());
+    a.delete_item(temp.clone()).unwrap();
+    assert_eq!(a.sync_now().await.unwrap().pushed, 1);
+    b.sync_now().await.unwrap();
+    assert!(matches!(b.get_item(temp), Err(CoreError::NotFound)));
+
     b.logout().await.unwrap();
     println!("live sync OK against {url}");
 }

crates/kv-model/src/item.rs

@@ -56,10 +56,6 @@ pub struct Item {
     /// versions it derives from (docs/02 "Item plaintext", docs/03 "Per-item replay protection").
     #[serde(default)]
     pub seq: u64,
-    /// Server revision of the tombstone this version was written over (edit beats delete). Only set on that
-    /// one version.
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub restores: Option<u64>,
 }
 
 impl Item {
@@ -80,7 +76,6 @@ impl Item {
             created_at: now,
             modified_at: now,
             seq: 1,
-            restores: None,
         }
     }
 }

crates/kv-proto/src/lib.rs

@@ -264,6 +264,8 @@ pub struct Vault {
     pub meta: Envelope,
 }
 
+/// Body of `PUT /v1/vaults/{vid}/items/{iid}` (the sealed item) and of `DELETE` on the same path (the sealed
+/// tombstone `{id, seq, deleted: true}`, same AAD as the item; docs/03 "Per-item replay protection").
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ItemPut {
     pub wrapped_item_key: Envelope,
@@ -275,6 +277,7 @@ pub struct ItemRecord {
     pub item_id: Uuid,
     pub revision: u64,
     pub deleted: bool,
+    /// Present on live records and sealed tombstones. Absent only on legacy tombstones, which clients refuse.
     pub wrapped_item_key: Option<Envelope>,
     pub payload: Option<Envelope>,
     pub updated_by: Uuid,

crates/kv-sync/src/client.rs

@@ -252,8 +252,15 @@ impl ApiClient {
         self.json(Method::PUT, &format!("{PATH_VAULTS}/{vault}/items/{item}"), Some(body), Some(base), true).await
     }
 
-    pub async fn delete_item(&self, vault: Uuid, item: Uuid, base: u64) -> Result<ItemRecord, SyncError> {
-        self.json(Method::DELETE, &format!("{PATH_VAULTS}/{vault}/items/{item}"), None::<&()>, Some(base), true).await
+    /// Tombstones an item. `body` is the sealed tombstone `{id, seq, deleted: true}` (docs/03).
+    pub async fn delete_item(
+        &self,
+        vault: Uuid,
+        item: Uuid,
+        base: u64,
+        body: &ItemPut,
+    ) -> Result<ItemRecord, SyncError> {
+        self.json(Method::DELETE, &format!("{PATH_VAULTS}/{vault}/items/{item}"), Some(body), Some(base), true).await
     }
 
     /// `None` when the vault has no manifest yet.

crates/kv-sync/src/engine.rs

@@ -59,17 +59,28 @@ fn crypto(e: kv_crypto::CryptoError) -> SyncError {
     SyncError::Crypto(e.to_string())
 }
 
-/// Decrypts an item record's payload into JSON.
+/// Decrypts a live item record's payload into JSON. `None` for a tombstone.
 pub fn open_record(
     account_id: Uuid,
     vault_id: Uuid,
     vk: &SymKey,
     record: &ItemRecord,
 ) -> Result<Option<Value>, SyncError> {
-    let (Some(k), Some(p)) = (&record.wrapped_item_key, &record.payload) else { return Ok(None) };
     if record.deleted {
         return Ok(None);
     }
+    open_sealed(account_id, vault_id, vk, record)
+}
+
+/// Decrypts the plaintext of a live record or a sealed tombstone. `None` when the record carries no
+/// ciphertext (a legacy tombstone).
+pub fn open_sealed(
+    account_id: Uuid,
+    vault_id: Uuid,
+    vk: &SymKey,
+    record: &ItemRecord,
+) -> Result<Option<Value>, SyncError> {
+    let (Some(k), Some(p)) = (&record.wrapped_item_key, &record.payload) else { return Ok(None) };
     let sealed = SealedItem { wrapped_item_key: k.clone(), payload: p.clone() };
     let pt = open_item(account_id, vault_id, record.item_id, vk, &sealed).map_err(crypto)?;
     serde_json::from_slice(&pt).map(Some).map_err(|e| SyncError::Crypto(format!("item JSON: {e}")))
@@ -97,6 +108,20 @@ pub fn seal_record(
     })
 }
 
+/// Seals a tombstone `{id, seq, deleted: true}` into a new (local) deleted record. `seq` comes from
+/// [`next_local_version`] (docs/03 "Per-item replay protection").
+pub fn seal_tombstone(
+    account_id: Uuid,
+    vault_id: Uuid,
+    vk: &SymKey,
+    item_id: Uuid,
+    seq: u64,
+    device_id: Uuid,
+) -> Result<ItemRecord, SyncError> {
+    let record = seal_record(account_id, vault_id, vk, item_id, &replay::tombstone(item_id, seq), device_id)?;
+    Ok(ItemRecord { deleted: true, ..record })
+}
+
 fn history_entry(r: &ItemRecord) -> Option<HistoryEntry> {
     Some(HistoryEntry {
         revision: r.revision,
@@ -106,20 +131,20 @@ fn history_entry(r: &ItemRecord) -> Option<HistoryEntry> {
     })
 }
 
-/// The decrypted form of a local base, for [`replay`]. Owns the plaintext a [`Base::Live`] borrows.
+/// The decrypted form of a local base, for [`replay`]. Owns the plaintext a [`Base::Sealed`] borrows.
 enum OpenedBase {
     None,
-    Tombstone(u64),
-    Live(u64, Value),
+    LegacyTombstone,
+    Sealed(Value),
 }
 
 impl OpenedBase {
     fn open(account_id: Uuid, vault_id: Uuid, vk: &SymKey, base: Option<&ItemRecord>) -> Result<Self, SyncError> {
         Ok(match base {
             None => Self::None,
-            Some(b) if b.deleted => Self::Tombstone(b.revision),
-            Some(b) => match open_record(account_id, vault_id, vk, b)? {
-                Some(v) => Self::Live(b.revision, v),
+            Some(b) => match open_sealed(account_id, vault_id, vk, b)? {
+                Some(v) => Self::Sealed(v),
+                None if b.deleted => Self::LegacyTombstone,
                 None => Self::None,
             },
         })
@@ -128,23 +153,23 @@ impl OpenedBase {
     fn as_base(&self) -> Base<'_> {
         match self {
             Self::None => Base::None,
-            Self::Tombstone(revision) => Base::Tombstone { revision: *revision },
-            Self::Live(revision, item) => Base::Live { revision: *revision, item },
+            Self::LegacyTombstone => Base::LegacyTombstone,
+            Self::Sealed(v) => Base::Sealed(v),
         }
     }
 }
 
-/// The `seq` and `restores` a new local version of `item_id` must carry (docs/03 "Per-item replay
-/// protection"). Call it before sealing a local edit and stamp the result into the plaintext.
+/// The `seq` a new local version of `item_id`, live or tombstone, must carry (docs/03 "Per-item replay
+/// protection"). Call it before sealing a local edit or delete and stamp the result into the plaintext.
 pub fn next_local_version(
     store: &dyn Store,
     account_id: Uuid,
     vault_id: Uuid,
     vk: &SymKey,
     item_id: Uuid,
-) -> Result<(u64, Option<u64>), SyncError> {
-    let Some(local) = store.get(vault_id, item_id)? else { return Ok((1, None)) };
-    let working = open_record(account_id, vault_id, vk, &local.record)?;
+) -> Result<u64, SyncError> {
+    let Some(local) = store.get(vault_id, item_id)? else { return Ok(1) };
+    let working = open_sealed(account_id, vault_id, vk, &local.record)?;
     let base = OpenedBase::open(account_id, vault_id, vk, local.base.as_ref())?;
     Ok(replay::next_version(working.as_ref(), base.as_base()))
 }
@@ -306,8 +331,8 @@ impl SyncContext<'_> {
         self.resolve_conflict(vault, vk, local, remote, report)
     }
 
-    /// Integrity alarm unless `remote` authenticates and may follow `base` (docs/03 "Per-item replay
-    /// protection"). Tombstones carry no ciphertext and pass.
+    /// Integrity alarm unless `remote`, live or tombstone, authenticates, is what its `deleted` flag says
+    /// it is, and may follow `base` (docs/03 "Per-item replay protection").
     fn check_replay(
         &self,
         vault: Uuid,
@@ -315,17 +340,12 @@ impl SyncContext<'_> {
         base: Option<&ItemRecord>,
         remote: &ItemRecord,
     ) -> Result<(), SyncError> {
-        if remote.deleted {
-            return Ok(());
-        }
         let id = remote.item_id;
-        let incoming = match open_record(self.account_id(), vault, vk, remote) {
-            Ok(Some(v)) => v,
-            Ok(None) => return Err(self.alarm(vault, format!("item {id}: live record without ciphertext"))),
-            Err(_) => return Err(self.alarm(vault, format!("item {id}: envelope does not authenticate"))),
+        let Ok(incoming) = open_sealed(self.account_id(), vault, vk, remote) else {
+            return Err(self.alarm(vault, format!("item {id}: envelope does not authenticate")));
         };
         let base = OpenedBase::open(self.account_id(), vault, vk, base)?;
-        replay::check_successor(base.as_base(), remote.revision, &incoming)
+        replay::check_pulled(base.as_base(), id, remote.deleted, incoming.as_ref())
             .map_err(|e| self.alarm(vault, format!("item {id}: {e}")))
     }
 
@@ -352,13 +372,15 @@ impl SyncContext<'_> {
                 report.restored.push(id);
             }
             (false, true) => {
-                // Our edit beats their delete: keep ours and push it on top of the tombstone, marked with
-                // the tombstone's revision so devices that never saw the delete accept a lower `seq`.
+                // Our edit beats their delete: keep ours and push it on top of the tombstone with a `seq`
+                // above both, so every device sees `seq` grow (docs/03 "Per-item replay protection").
                 let acct = self.account_id();
                 let mut mine =
                     open_record(acct, vault, vk, &local.record)?.ok_or(SyncError::Protocol("empty item".into()))?;
-                let seq = replay::seq_of(&mine);
-                replay::stamp(&mut mine, seq, Some(remote.revision));
+                let tomb =
+                    open_sealed(acct, vault, vk, remote)?.ok_or(SyncError::Protocol("empty tombstone".into()))?;
+                let seq = replay::seq_of(&mine).max(replay::seq_of(&tomb)) + 1;
+                replay::stamp(&mut mine, seq);
                 let sealed = seal_record(acct, vault, vk, id, &mine, self.device_id)?;
                 self.store.put(vault, &rebased(sealed))?;
                 report.restored.push(id);
@@ -387,7 +409,7 @@ impl SyncContext<'_> {
                     self.store.put_remote(vault, remote)?;
                 } else {
                     let seq = replay::seq_of(&mine).max(replay::seq_of(&theirs)) + 1;
-                    replay::stamp(&mut out.merged, seq, None);
+                    replay::stamp(&mut out.merged, seq);
                     let sealed = seal_record(acct, vault, vk, id, &out.merged, self.device_id)?;
                     self.store.put(vault, &rebased(sealed))?;
                 }
@@ -475,17 +497,22 @@ impl SyncContext<'_> {
             for item in pending {
                 let base = item.base_revision();
                 let id = item.record.item_id;
-                let result = if item.record.deleted {
-                    if base == 0 {
-                        self.store.remove(vault, id)?;
-                        continue;
-                    }
-                    self.api.delete_item(vault, id, base).await
+                if item.record.deleted && base == 0 {
+                    self.store.remove(vault, id)?;
+                    continue;
+                }
+                let item = if item.record.deleted && item.record.payload.is_none() {
+                    self.seal_legacy_delete(vault, vk, item)?
+                } else {
+                    item
+                };
+                let (Some(k), Some(p)) = (&item.record.wrapped_item_key, &item.record.payload) else {
+                    return Err(SyncError::Protocol(format!("pending item {id} has no ciphertext")));
+                };
+                let body = ItemPut { wrapped_item_key: k.clone(), payload: p.clone() };
+                let result = if item.record.deleted {
+                    self.api.delete_item(vault, id, base, &body).await
                 } else {
-                    let (Some(k), Some(p)) = (&item.record.wrapped_item_key, &item.record.payload) else {
-                        return Err(SyncError::Protocol(format!("pending item {id} has no ciphertext")));
-                    };
-                    let body = ItemPut { wrapped_item_key: k.clone(), payload: p.clone() };
                     self.api.put_item(vault, id, base, &body).await
                 };
                 match result {
@@ -507,6 +534,15 @@ impl SyncContext<'_> {
         Ok(pushed)
     }
 
+    /// Seals a pending delete stored before tombstones were sealed.
+    fn seal_legacy_delete(&self, vault: Uuid, vk: &SymKey, item: LocalItem) -> Result<LocalItem, SyncError> {
+        let id = item.record.item_id;
+        let seq = next_local_version(self.store, self.account_id(), vault, vk, id)?;
+        let tomb = seal_tombstone(self.account_id(), vault, vk, id, seq, self.device_id)?;
+        self.store.put_local(vault, &tomb)?;
+        Ok(self.store.get(vault, id)?.ok_or(kv_store::StoreError::NotFound)?)
+    }
+
     /// Records the server's acceptance, unless the item was edited again while the request was in flight.
     fn confirm(&self, vault: Uuid, pushed: &LocalItem, confirmed: ItemRecord) -> Result<(), SyncError> {
         let current = self.store.get(vault, confirmed.item_id)?;

crates/kv-sync/src/lib.rs

@@ -8,7 +8,7 @@
 //!   a callback into platform code ([`DeviceSigner`]).
 //! * [`engine`]: pull, then push with `If-Match`, then three-way field merge on 412 ([`merge`]), then manifest verify
 //!   and publish ([`manifest`]).
-//! * [`replay`]: per-item replay check on pull (the `seq` / `restores` fields of the item plaintext).
+//! * [`replay`]: per-item replay check on pull (the `seq` field sealed into every item version and tombstone).
 
 pub mod client;
 pub mod engine;

crates/kv-sync/src/manifest.rs

@@ -123,11 +123,12 @@ pub fn envelope_cbor(e: &Envelope) -> Vec<u8> {
     out
 }
 
-/// `blake3(envelope)` for one item record.
+/// `blake3(envelope)` for one item record. A sealed tombstone hashes its envelope like a live record; only
+/// a legacy tombstone without ciphertext hashes the empty array.
 pub fn content_hash(record: &ItemRecord) -> [u8; 32] {
     let mut out = Vec::new();
-    match (&record.wrapped_item_key, &record.payload, record.deleted) {
-        (Some(k), Some(p), false) => {
+    match (&record.wrapped_item_key, &record.payload) {
+        (Some(k), Some(p)) => {
             cbor::array(&mut out, 2);
             out.extend_from_slice(&envelope_cbor(k));
             out.extend_from_slice(&envelope_cbor(p));

crates/kv-sync/src/merge.rs

@@ -2,12 +2,12 @@
 //!
 //! Items are merged as JSON objects so every top-level field of `kv_model::Item` (and any field a
 //! newer client adds) is a merge unit. `id` and `created_at` come from the base, `modified_at` and
-//! `seq` are the maximum of both sides, and `restores` is dropped. The caller stamps the next `seq` if it
-//! writes the result as a new version ([`crate::replay`]).
+//! `seq` are the maximum of both sides. The caller stamps the next `seq` if it writes the result as a new
+//! version ([`crate::replay`]).
 
 use serde_json::{Map, Value};
 
-use crate::replay::{seq_of, RESTORES, SEQ};
+use crate::replay::{seq_of, SEQ};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Side {
@@ -25,7 +25,7 @@ pub struct MergeOutcome {
     pub conflicting_fields: Vec<String>,
 }
 
-const FIXED: [&str; 5] = ["id", "created_at", "modified_at", SEQ, RESTORES];
+const FIXED: [&str; 4] = ["id", "created_at", "modified_at", SEQ];
 
 fn modified_at(v: &Value) -> i64 {
     v.get("modified_at").and_then(Value::as_i64).unwrap_or(0)

crates/kv-sync/src/replay.rs

@@ -1,43 +1,46 @@
 //! Per-item replay protection (docs/03 "Per-item replay protection").
 //!
 //! The AAD binds an envelope to its item but not to a server revision, so a server could re-serve an
-//! old, authentic envelope under a new revision. Every item plaintext therefore carries `seq`, an edit
-//! counter that grows along every honest chain of versions, and `restores`, the revision of the
-//! tombstone a version was written over (tombstones carry no `seq`). Pulled records are checked
-//! against the local base, the last version the server confirmed to this device.
+//! old, authentic envelope under a new revision. Every version of an item, live or deleted, is sealed
+//! and carries `seq`, an edit counter that grows along every honest chain of versions. A tombstone's
+//! plaintext is `{id, seq, deleted: true}`. Pulled records are checked against the local base, the
+//! last version the server confirmed to this device.
 
-use serde_json::Value;
+use serde_json::{json, Value};
+use uuid::Uuid;
 
 /// The plaintext field holding the per-item edit counter. Absent means 0.
 pub const SEQ: &str = "seq";
-/// The plaintext field holding the revision of the tombstone a version was written over.
-pub const RESTORES: &str = "restores";
+/// The plaintext field that marks a tombstone.
+pub const DELETED: &str = "deleted";
 
 pub fn seq_of(item: &Value) -> u64 {
     item.get(SEQ).and_then(Value::as_u64).unwrap_or(0)
 }
 
-pub fn restores_of(item: &Value) -> Option<u64> {
-    item.get(RESTORES).and_then(Value::as_u64)
+/// Sets `seq`.
+pub fn stamp(item: &mut Value, seq: u64) {
+    if let Some(obj) = item.as_object_mut() {
+        obj.insert(SEQ.into(), Value::from(seq));
+    }
 }
 
-/// Sets `seq` and `restores` (removing `restores` when `None`).
-pub fn stamp(item: &mut Value, seq: u64, restores: Option<u64>) {
-    let Some(obj) = item.as_object_mut() else { return };
-    obj.insert(SEQ.into(), Value::from(seq));
-    match restores {
-        Some(t) => obj.insert(RESTORES.into(), Value::from(t)),
-        None => obj.remove(RESTORES),
-    };
+/// The plaintext of a tombstone for item `id`.
+pub fn tombstone(id: Uuid, seq: u64) -> Value {
+    json!({ "id": id, SEQ: seq, DELETED: true })
 }
 
-/// Whether two item plaintexts have the same content, ignoring `seq` and `restores`.
+/// Whether a plaintext is a tombstone (`deleted: true`).
+pub fn is_tombstone(plaintext: &Value) -> bool {
+    plaintext.get(DELETED) == Some(&Value::Bool(true))
+}
+
+/// Whether two item plaintexts have the same content, ignoring `seq`.
 pub fn same_content(a: &Value, b: &Value) -> bool {
     let strip = |v: &Value| {
         let mut v = v.clone();
         if let Some(o) = v.as_object_mut() {
             o.remove(SEQ);
-            o.remove(RESTORES);
         }
         v
     };
@@ -49,13 +52,10 @@ pub fn same_content(a: &Value, b: &Value) -> bool {
 pub enum Base<'a> {
     /// This device holds no server version of the item.
     None,
-    Tombstone {
-        revision: u64,
-    },
-    Live {
-        revision: u64,
-        item: &'a Value,
-    },
+    /// A tombstone without ciphertext, accepted before tombstones were sealed. Its `seq` is unknown.
+    LegacyTombstone,
+    /// The decrypted plaintext of a live version or a sealed tombstone.
+    Sealed(&'a Value),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
@@ -65,17 +65,41 @@ pub struct Replay {
     pub incoming: u64,
 }
 
-/// Checks that `incoming` (a live record at server `revision`) may follow `base`.
-pub fn check_successor(base: Base<'_>, revision: u64, incoming: &Value) -> Result<(), Replay> {
-    let Base::Live { revision: base_revision, item: held } = base else { return Ok(()) };
+/// Why a pulled record is refused. Every variant is an integrity alarm.
+#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
+pub enum Rejected {
+    #[error("tombstone without ciphertext (unauthenticated delete)")]
+    UnsealedTombstone,
+    #[error("live record without ciphertext")]
+    UnsealedItem,
+    #[error("deleted flag does not match the sealed plaintext")]
+    KindMismatch,
+    #[error("tombstone names another item")]
+    WrongItem,
+    #[error(transparent)]
+    Replay(#[from] Replay),
+}
+
+/// Checks a pulled record of item `id`: its `deleted` flag and its authenticated plaintext (`None` when it
+/// carries no ciphertext) against the local base.
+pub fn check_pulled(base: Base<'_>, id: Uuid, deleted: bool, plaintext: Option<&Value>) -> Result<(), Rejected> {
+    let incoming = plaintext.ok_or(if deleted { Rejected::UnsealedTombstone } else { Rejected::UnsealedItem })?;
+    if is_tombstone(incoming) != deleted {
+        return Err(Rejected::KindMismatch);
+    }
+    if deleted && incoming.get("id") != Some(&Value::from(id.to_string())) {
+        return Err(Rejected::WrongItem);
+    }
+    Ok(check_successor(base, incoming)?)
+}
+
+/// Checks that `incoming` (the plaintext of a pulled live record or tombstone) may follow `base`.
+pub fn check_successor(base: Base<'_>, incoming: &Value) -> Result<(), Replay> {
+    let Base::Sealed(held) = base else { return Ok(()) };
     let (held_seq, seq) = (seq_of(held), seq_of(incoming));
     if seq > held_seq {
         return Ok(());
     }
-    // A delete this device never saw came between its base and `incoming`.
-    if restores_of(incoming).is_some_and(|t| base_revision < t && t < revision) {
-        return Ok(());
-    }
     // The same content again is not a rollback.
     if seq == held_seq && incoming == held {
         return Ok(());
@@ -83,18 +107,13 @@ pub fn check_successor(base: Base<'_>, revision: u64, incoming: &Value) -> Resul
     Err(Replay { held: held_seq, incoming: seq })
 }
 
-/// `seq` and `restores` for a new local version of an item whose working copy is `local` (if live).
-pub fn next_version(local: Option<&Value>, base: Base<'_>) -> (u64, Option<u64>) {
+/// `seq` for a new local version (live or tombstone) of an item whose working copy is `local`.
+pub fn next_version(local: Option<&Value>, base: Base<'_>) -> u64 {
     let held = match base {
-        Base::Live { item, .. } => seq_of(item),
+        Base::Sealed(v) => seq_of(v),
         _ => 0,
     };
-    let seq = local.map_or(0, seq_of).max(held) + 1;
-    let restores = match base {
-        Base::Tombstone { revision } => Some(revision),
-        _ => None,
-    };
-    (seq, restores)
+    local.map_or(0, seq_of).max(held) + 1
 }
 
 #[cfg(test)]
@@ -105,25 +124,35 @@ mod tests {
 
     #[test]
     fn stamp_and_same_content() {
-        let mut v = json!({"title": "a", "restores": 4});
-        stamp(&mut v, 7, None);
+        let mut v = json!({"title": "a"});
+        stamp(&mut v, 7);
         assert_eq!(v, json!({"title": "a", "seq": 7}));
-        stamp(&mut v, 8, Some(3));
-        assert_eq!(v, json!({"title": "a", "seq": 8, "restores": 3}));
         assert!(same_content(&v, &json!({"title": "a"})));
-        assert!(!same_content(&v, &json!({"title": "b", "seq": 8})));
+        assert!(!same_content(&v, &json!({"title": "b", "seq": 7})));
+    }
+
+    #[test]
+    fn tombstone_plaintext() {
+        let id = Uuid::nil();
+        let t = tombstone(id, 4);
+        assert_eq!(t, json!({"id": "00000000-0000-0000-0000-000000000000", "seq": 4, "deleted": true}));
+        assert!(is_tombstone(&t));
+        assert!(!is_tombstone(&json!({"title": "a", "deleted": false})));
+        assert_eq!(seq_of(&t), 4);
     }
 
     #[test]
     fn next_version_rules() {
         let base = json!({"seq": 5});
         let local = json!({"seq": 6});
-        assert_eq!(next_version(None, Base::None), (1, None));
-        assert_eq!(next_version(Some(&base), Base::Live { revision: 3, item: &base }), (6, None));
-        assert_eq!(next_version(Some(&local), Base::Live { revision: 3, item: &base }), (7, None));
+        let tomb = tombstone(Uuid::nil(), 9);
+        assert_eq!(next_version(None, Base::None), 1);
+        assert_eq!(next_version(Some(&base), Base::Sealed(&base)), 6);
+        assert_eq!(next_version(Some(&local), Base::Sealed(&base)), 7);
         // A pending delete being re-saved continues from the base.
-        assert_eq!(next_version(None, Base::Live { revision: 3, item: &base }), (6, None));
-        assert_eq!(next_version(None, Base::Tombstone { revision: 9 }), (1, Some(9)));
-        assert_eq!(next_version(Some(&local), Base::Tombstone { revision: 9 }), (7, Some(9)));
+        assert_eq!(next_version(None, Base::Sealed(&base)), 6);
+        assert_eq!(next_version(None, Base::Sealed(&tomb)), 10);
+        assert_eq!(next_version(Some(&local), Base::Sealed(&tomb)), 10);
+        assert_eq!(next_version(None, Base::LegacyTombstone), 1);
     }
 }

crates/kv-sync/src/test_server.rs

@@ -387,7 +387,9 @@ fn authed(
             let vid = Uuid::parse_str(vid).map_err(|_| err(404, "not_found"))?;
             let iid = Uuid::parse_str(iid).map_err(|_| err(404, "not_found"))?;
             let base = if_match(req)?;
-            let body: Option<ItemPut> = if method == "PUT" { Some(parse(req)?) } else { None };
+            // PUT carries the item, DELETE the sealed tombstone; both have the same shape.
+            let body: ItemPut = parse(req)?;
+            let deleted = method == "DELETE";
             if st.force_412 > 0 {
                 st.force_412 -= 1;
                 return Err(err(412, "revision_conflict"));
@@ -397,16 +399,16 @@ fn authed(
             if current != base {
                 return Err(err(412, "revision_conflict"));
             }
-            if body.is_none() && current == 0 {
+            if deleted && current == 0 {
                 return Err(err(404, "not_found"));
             }
             v.head += 1;
             let rec = ItemRecord {
                 item_id: iid,
                 revision: v.head,
-                deleted: body.is_none(),
-                wrapped_item_key: body.as_ref().map(|b| b.wrapped_item_key.clone()),
-                payload: body.map(|b| b.payload),
+                deleted,
+                wrapped_item_key: Some(body.wrapped_item_key),
+                payload: Some(body.payload),
                 updated_by: device,
                 updated_at: now(),
             };

crates/kv-sync/tests/replay_vectors.rs

@@ -1,7 +1,8 @@
 //! Checks `kv_sync::replay` against the shared decision table (kestrove-spec/vectors/item_replay.json).
 
-use kv_sync::replay::{check_successor, next_version, Base};
+use kv_sync::replay::{check_pulled, next_version, Base};
 use serde_json::Value;
+use uuid::Uuid;
 
 fn vectors() -> Value {
     serde_json::from_str(include_str!("vectors/item_replay.json")).unwrap()
@@ -9,22 +10,24 @@ fn vectors() -> Value {
 
 fn base(v: &Value) -> Base<'_> {
     if v.is_null() {
-        return Base::None;
-    }
-    let revision = v["revision"].as_u64().unwrap();
-    if v["tombstone"] == Value::Bool(true) {
-        Base::Tombstone { revision }
+        Base::None
+    } else if v["legacy_tombstone"] == Value::Bool(true) {
+        Base::LegacyTombstone
     } else {
-        Base::Live { revision, item: &v["item"] }
+        Base::Sealed(&v["plaintext"])
     }
 }
 
 #[test]
 fn check_table() {
-    for case in vectors()["check"].as_array().unwrap() {
-        let got = check_successor(base(&case["base"]), case["revision"].as_u64().unwrap(), &case["incoming"]);
+    let v = vectors();
+    let id = Uuid::parse_str(v["item_id"].as_str().unwrap()).unwrap();
+    for case in v["check"].as_array().unwrap() {
+        let record = &case["record"];
+        let plaintext = Some(&record["plaintext"]).filter(|p| !p.is_null());
+        let got = check_pulled(base(&case["base"]), id, record["deleted"].as_bool().unwrap(), plaintext);
         let want = case["result"].as_str().unwrap();
-        assert_eq!(if got.is_ok() { "accept" } else { "alarm" }, want, "{}", case["name"]);
+        assert_eq!(if got.is_ok() { "accept" } else { "alarm" }, want, "{}: {got:?}", case["name"]);
     }
 }
 
@@ -32,9 +35,8 @@ fn check_table() {
 fn next_version_table() {
     for case in vectors()["next_version"].as_array().unwrap() {
         let local = Some(&case["local"]).filter(|v| !v.is_null());
-        let (seq, restores) = next_version(local, base(&case["base"]));
+        let seq = next_version(local, base(&case["base"]));
         assert_eq!(Some(seq), case["seq"].as_u64(), "{}", case["name"]);
-        assert_eq!(restores, case["restores"].as_u64(), "{}", case["name"]);
     }
 }
 

crates/kv-sync/tests/sync.rs

@@ -10,7 +10,7 @@ use kv_crypto::{
 use kv_proto::{DeviceEnroll, ItemRecord, Platform};
 use kv_store::{MemoryStore, Store, SyncState, VaultRow};
 use kv_sync::{
-    engine::{next_local_version, open_record, seal_record},
+    engine::{next_local_version, open_record, open_sealed, seal_record, seal_tombstone},
     replay,
     signing::SoftwareSigner,
     test_server::{TestServer, SETUP_TOKEN},
@@ -103,10 +103,10 @@ impl Device {
         self.keyset.open_vault_key(vid, &self.store.vault(vid).unwrap().unwrap().sealed_key).unwrap()
     }
 
-    /// Saves a local edit the way a client does: with the next `seq` (and `restores`) stamped in.
+    /// Saves a local edit the way a client does: with the next `seq` stamped in.
     fn save(&self, vid: Uuid, id: Uuid, mut item: Value) {
-        let (seq, restores) = next_local_version(&self.store, self.keyset.account_id, vid, &self.vk(vid), id).unwrap();
-        replay::stamp(&mut item, seq, restores);
+        let seq = next_local_version(&self.store, self.keyset.account_id, vid, &self.vk(vid), id).unwrap();
+        replay::stamp(&mut item, seq);
         self.save_raw(vid, id, item);
     }
 
@@ -116,7 +116,16 @@ impl Device {
         self.store.put_local(vid, &rec).unwrap();
     }
 
+    /// Deletes the way a client does: a sealed tombstone with the next `seq`.
     fn delete(&self, vid: Uuid, id: Uuid) {
+        let (acct, vk) = (self.keyset.account_id, self.vk(vid));
+        let seq = next_local_version(&self.store, acct, vid, &vk, id).unwrap();
+        let tomb = seal_tombstone(acct, vid, &vk, id, seq, self.signer.device_id()).unwrap();
+        self.store.put_local(vid, &tomb).unwrap();
+    }
+
+    /// A pending delete as stored before tombstones were sealed (no ciphertext).
+    fn delete_legacy(&self, vid: Uuid, id: Uuid) {
         let mut cur = self.store.get(vid, id).unwrap().unwrap().record;
         cur.deleted = true;
         cur.wrapped_item_key = None;
@@ -124,6 +133,12 @@ impl Device {
         self.store.put_local(vid, &cur).unwrap();
     }
 
+    /// The sealed plaintext of the item's base (live or tombstone).
+    fn read_base(&self, vid: Uuid, id: Uuid) -> Option<Value> {
+        let base = self.store.get(vid, id).unwrap()?.base?;
+        open_sealed(self.keyset.account_id, vid, &self.vk(vid), &base).unwrap()
+    }
+
     fn read(&self, vid: Uuid, id: Uuid) -> Option<Value> {
         let item = self.store.get(vid, id).unwrap()?;
         open_record(self.keyset.account_id, vid, &self.vk(vid), &item.record).unwrap()
@@ -257,9 +272,14 @@ async fn deleting_and_never_synced_items() {
     a.save(vid, local_only, item(local_only, "L", "l", 1));
     a.delete(vid, local_only);
     a.sync().await.unwrap();
-    assert!(server.state().vaults[&vid].items[&x].deleted);
+    let tomb = server.state().vaults[&vid].items[&x].clone();
+    assert!(tomb.deleted && tomb.payload.is_some(), "the server stores the sealed tombstone");
     assert!(!server.state().vaults[&vid].items.contains_key(&local_only));
     assert!(a.store.get(vid, local_only).unwrap().is_none());
+    let b = Device::second(&server, &a).await;
+    b.sync().await.unwrap();
+    assert_eq!(b.read_base(vid, x).unwrap(), json!({"id": x, "seq": 2, "deleted": true}));
+    assert!(b.read(vid, x).is_none());
 }
 
 #[tokio::test]
@@ -634,7 +654,6 @@ async fn concurrent_equal_seq_edits_are_not_an_alarm() {
     assert_eq!(b.sync().await.unwrap().merged, 1);
     let merged = b.read(vid, id).unwrap();
     assert_eq!(merged["seq"], 3);
-    assert!(merged.get("restores").is_none());
     for x in [&a, &c, &d] {
         x.sync().await.unwrap(); // d jumps from seq 1 straight to 3
         assert_eq!(x.read(vid, id).unwrap(), merged);
@@ -649,8 +668,8 @@ async fn concurrent_equal_seq_edits_are_not_an_alarm() {
     assert!(c.store.pending(vid).unwrap().is_empty());
 }
 
-/// An edit that beats a delete may carry a lower `seq` than versions other devices saw before the delete.
-/// `restores` lets a device that never saw the tombstone accept it, and only directly after that delete.
+/// An edit that beats a delete is written above the tombstone's `seq`, so every device sees `seq` grow,
+/// including one that never saw the tombstone. Replays of the tombstone or of the restore are refused.
 #[tokio::test]
 async fn edit_beats_delete_is_not_an_alarm_but_its_replay_is() {
     let server = TestServer::start().await;
@@ -668,31 +687,111 @@ async fn edit_beats_delete_is_not_an_alarm_but_its_replay_is() {
     c.sync().await.unwrap(); // c holds seq 4 and will not see the tombstone
     a.delete(vid, id);
     a.sync().await.unwrap();
-    let tombstone_rev = server.state().vaults[&vid].items[&id].revision;
+    let tombstone = server.state().vaults[&vid].items[&id].clone();
     let d = Device::second(&server, &a).await;
-    d.sync().await.unwrap(); // d holds the tombstone
+    d.sync().await.unwrap(); // d holds the tombstone (seq 5)
+    assert_eq!(d.read_base(vid, id).unwrap()["seq"], 5);
 
     b.save(vid, id, item(id, "X", "x-b", 9));
     let r = b.sync().await.unwrap();
     assert_eq!(r.restored, vec![id]);
     let restored = b.read(vid, id).unwrap();
-    assert_eq!((restored["seq"].as_u64(), restored["restores"].as_u64()), (Some(2), Some(tombstone_rev)));
+    assert_eq!(restored["seq"], 6, "above the tombstone's seq");
     let restore_envelope = server.state().vaults[&vid].items[&id].clone();
 
     for x in [&a, &c, &d] {
         x.sync().await.unwrap();
         assert_eq!(x.read(vid, id).unwrap()["password"], "x-b");
     }
-    // The next edit clears `restores` and continues from the restored `seq`.
     c.save(vid, id, item(id, "X", "x-c", 10));
-    assert_eq!(c.read(vid, id).unwrap()["seq"], 3);
-    assert!(c.read(vid, id).unwrap().get("restores").is_none());
+    assert_eq!(c.read(vid, id).unwrap()["seq"], 7);
     c.sync().await.unwrap();
     a.sync().await.unwrap();
+    d.sync().await.unwrap();
 
-    // Re-serving the restore later is a rollback: the receiver's base is past the tombstone now.
-    server.state().write_item(vid, restore_envelope);
+    // Re-serving the tombstone or the restore later is a rollback.
+    server.state().write_item(vid, tombstone);
     assert_replay_alarm(a.sync().await, vid);
+    server.state().write_item(vid, restore_envelope);
+    assert_replay_alarm(d.sync().await, vid);
+}
+
+/// The server forges a delete. A tombstone without ciphertext, or an item envelope relabelled as deleted, is an
+/// integrity alarm; the item stays visible.
+#[tokio::test]
+async fn forged_tombstone_is_an_integrity_alarm() {
+    let server = TestServer::start().await;
+    let (a, vid) = Device::first(&server).await;
+    let id = Uuid::new_v4();
+    a.save(vid, id, item(id, "Bank", "pw1", 1));
+    a.sync().await.unwrap();
+    let b = Device::second(&server, &a).await;
+    b.sync().await.unwrap();
+    let live = server.state().vaults[&vid].items[&id].clone();
+    let manifest_version = server.state().vaults[&vid].manifest.as_ref().unwrap().version;
+
+    // An unauthenticated tombstone, as the server could always write before.
+    let forged = ItemRecord { deleted: true, wrapped_item_key: None, payload: None, ..live.clone() };
+    server.state().write_item(vid, forged);
+    let err = b.sync().await.unwrap_err();
+    assert!(
+        matches!(err, SyncError::Integrity { vault_id, ref reason } if vault_id == vid && reason.contains("unauthenticated delete")),
+        "{err}"
+    );
+    assert_eq!(b.read(vid, id).unwrap()["password"], "pw1", "not hidden");
+    assert!(b.store.vault(vid).unwrap().unwrap().integrity_alarm);
+    // A device that never held the item refuses it too.
+    let c = Device::second(&server, &a).await;
+    assert!(matches!(c.sync().await, Err(SyncError::Integrity { .. })));
+
+    // An authentic item envelope re-served with the deleted flag set.
+    let relabelled = ItemRecord { deleted: true, ..live };
+    server.state().write_item(vid, relabelled);
+    let err = a.sync().await.unwrap_err();
+    assert!(matches!(err, SyncError::Integrity { ref reason, .. } if reason.contains("deleted flag")), "{err}");
+    assert_eq!(a.read(vid, id).unwrap()["password"], "pw1");
+    assert_eq!(server.state().vaults[&vid].manifest.as_ref().unwrap().version, manifest_version);
+}
+
+/// Delete-then-replay: after a device pulls a (genuine) tombstone, an old live envelope re-served on top of it
+/// is refused, because the tombstone's `seq` is authenticated.
+#[tokio::test]
+async fn replay_after_a_tombstone_is_an_integrity_alarm() {
+    let server = TestServer::start().await;
+    let (a, vid) = Device::first(&server).await;
+    let id = Uuid::new_v4();
+    a.save(vid, id, item(id, "Bank", "pw1", 1));
+    a.sync().await.unwrap();
+    let old = server.state().vaults[&vid].items[&id].clone();
+    a.save(vid, id, item(id, "Bank", "pw2", 2));
+    a.sync().await.unwrap();
+    let b = Device::second(&server, &a).await;
+    b.sync().await.unwrap();
+    a.delete(vid, id);
+    a.sync().await.unwrap();
+    b.sync().await.unwrap();
+    assert!(b.read(vid, id).is_none());
+
+    server.state().write_item(vid, old);
+    assert_replay_alarm(b.sync().await, vid);
+    assert!(b.read(vid, id).is_none(), "the deleted item did not come back");
+}
+
+/// A pending delete stored before tombstones were sealed is sealed when it is pushed.
+#[tokio::test]
+async fn legacy_pending_delete_is_sealed_on_push() {
+    let server = TestServer::start().await;
+    let (a, vid) = Device::first(&server).await;
+    let id = Uuid::new_v4();
+    a.save(vid, id, item(id, "X", "x", 1));
+    a.sync().await.unwrap();
+    a.delete_legacy(vid, id);
+    a.sync().await.unwrap();
+    let tomb = server.state().vaults[&vid].items[&id].clone();
+    assert!(tomb.deleted && tomb.payload.is_some());
+    let b = Device::second(&server, &a).await;
+    b.sync().await.unwrap();
+    assert_eq!(b.read_base(vid, id).unwrap(), json!({"id": id, "seq": 2, "deleted": true}));
 }
 
 /// Items written before `seq` existed read as seq 0; the first edit writes seq 1.

crates/kv-sync/tests/vectors/item_replay.json

@@ -1,27 +1,39 @@
 {
-  "description": "Per-item replay protection (docs/03 'Per-item replay protection'). Item plaintexts are shown as JSON; only seq, restores and content equality matter. 'base' is the last server-confirmed version this device holds: null (none), {tombstone, revision} or {revision, item}.",
+  "description": "Per-item replay protection (docs/03 'Per-item replay protection'). Plaintexts are shown as JSON; only seq, the deleted marker, the tombstone id and content equality matter. Every case is for item_id. 'base' is the last server-confirmed version this device holds: null (none), {legacy_tombstone: true} (a tombstone without ciphertext from before tombstones were sealed) or {plaintext} (a live item or a sealed tombstone {id, seq, deleted: true}). 'record' is a pulled record: its deleted flag and its authenticated plaintext, null when it carries no ciphertext. 'local' is the device's working copy.",
+  "item_id": "11111111-1111-1111-1111-111111111111",
   "check": [
-    { "name": "no base: first sight of the item", "base": null, "revision": 7, "incoming": {"title": "a", "seq": 1}, "result": "accept" },
-    { "name": "tombstone base: anything may follow a delete", "base": {"tombstone": true, "revision": 5}, "revision": 7, "incoming": {"title": "a", "seq": 1}, "result": "accept" },
-    { "name": "higher seq", "base": {"revision": 5, "item": {"title": "a", "seq": 3}}, "revision": 7, "incoming": {"title": "b", "seq": 4}, "result": "accept" },
-    { "name": "seq jumps by more than one", "base": {"revision": 5, "item": {"title": "a", "seq": 3}}, "revision": 7, "incoming": {"title": "b", "seq": 9}, "result": "accept" },
-    { "name": "older seq: replay of an old envelope", "base": {"revision": 5, "item": {"title": "a", "seq": 3}}, "revision": 7, "incoming": {"title": "old", "seq": 2}, "result": "alarm" },
-    { "name": "same seq, different content", "base": {"revision": 5, "item": {"title": "a", "seq": 3}}, "revision": 7, "incoming": {"title": "b", "seq": 3}, "result": "alarm" },
-    { "name": "same seq, identical content", "base": {"revision": 5, "item": {"title": "a", "seq": 3}}, "revision": 7, "incoming": {"title": "a", "seq": 3}, "result": "accept" },
-    { "name": "legacy items: absent seq is 0", "base": {"revision": 5, "item": {"title": "a"}}, "revision": 7, "incoming": {"title": "b", "seq": 0}, "result": "alarm" },
-    { "name": "legacy base, first seq-aware edit", "base": {"revision": 5, "item": {"title": "a"}}, "revision": 7, "incoming": {"title": "b", "seq": 1}, "result": "accept" },
-    { "name": "restore over a tombstone this device did not see", "base": {"revision": 5, "item": {"title": "a", "seq": 6}}, "revision": 9, "incoming": {"title": "r", "seq": 2, "restores": 8}, "result": "accept" },
-    { "name": "restore claim older than the base", "base": {"revision": 8, "item": {"title": "a", "seq": 6}}, "revision": 9, "incoming": {"title": "r", "seq": 2, "restores": 7}, "result": "alarm" },
-    { "name": "restore claim equal to the base revision", "base": {"revision": 8, "item": {"title": "a", "seq": 6}}, "revision": 9, "incoming": {"title": "r", "seq": 2, "restores": 8}, "result": "alarm" },
-    { "name": "restore claim not below the record's own revision", "base": {"revision": 5, "item": {"title": "a", "seq": 6}}, "revision": 9, "incoming": {"title": "r", "seq": 2, "restores": 9}, "result": "alarm" }
+    {"name": "no base: first sight of the item", "base": null, "record": {"deleted": false, "plaintext": {"title": "a", "seq": 1}}, "result": "accept"},
+    {"name": "no base: first sight is a sealed tombstone", "base": null, "record": {"deleted": true, "plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 2, "deleted": true}}, "result": "accept"},
+    {"name": "higher seq", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": false, "plaintext": {"title": "b", "seq": 4}}, "result": "accept"},
+    {"name": "seq jumps by more than one", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": false, "plaintext": {"title": "b", "seq": 9}}, "result": "accept"},
+    {"name": "older seq: replay of an old envelope", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": false, "plaintext": {"title": "old", "seq": 2}}, "result": "alarm"},
+    {"name": "same seq, different content", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": false, "plaintext": {"title": "b", "seq": 3}}, "result": "alarm"},
+    {"name": "same seq, identical content", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": false, "plaintext": {"title": "a", "seq": 3}}, "result": "accept"},
+    {"name": "legacy items: absent seq is 0", "base": {"plaintext": {"title": "a"}}, "record": {"deleted": false, "plaintext": {"title": "b", "seq": 0}}, "result": "alarm"},
+    {"name": "legacy base, first seq-aware edit", "base": {"plaintext": {"title": "a"}}, "record": {"deleted": false, "plaintext": {"title": "b", "seq": 1}}, "result": "accept"},
+    {"name": "delete after a live version", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": true, "plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}}, "result": "accept"},
+    {"name": "old tombstone replayed after a newer edit", "base": {"plaintext": {"title": "a", "seq": 6}}, "record": {"deleted": true, "plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 5, "deleted": true}}, "result": "alarm"},
+    {"name": "restore after a delete (edit beats delete)", "base": {"plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}}, "record": {"deleted": false, "plaintext": {"title": "r", "seq": 5}}, "result": "accept"},
+    {"name": "delete-then-replay: old live version after a tombstone", "base": {"plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}}, "record": {"deleted": false, "plaintext": {"title": "old", "seq": 3}}, "result": "alarm"},
+    {"name": "same tombstone again", "base": {"plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}}, "record": {"deleted": true, "plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}}, "result": "accept"},
+    {"name": "restore seen by a device that missed the delete", "base": {"plaintext": {"title": "a", "seq": 5}}, "record": {"deleted": false, "plaintext": {"title": "r", "seq": 7}}, "result": "accept"},
+    {"name": "unsealed tombstone after a live version", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": true, "plaintext": null}, "result": "alarm"},
+    {"name": "unsealed tombstone, no base", "base": null, "record": {"deleted": true, "plaintext": null}, "result": "alarm"},
+    {"name": "live record without ciphertext", "base": null, "record": {"deleted": false, "plaintext": null}, "result": "alarm"},
+    {"name": "tombstone envelope served as a live record", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": false, "plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}}, "result": "alarm"},
+    {"name": "live envelope served as a tombstone", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": true, "plaintext": {"title": "b", "seq": 4}}, "result": "alarm"},
+    {"name": "tombstone naming another item", "base": {"plaintext": {"title": "a", "seq": 3}}, "record": {"deleted": true, "plaintext": {"id": "22222222-2222-2222-2222-222222222222", "seq": 4, "deleted": true}}, "result": "alarm"},
+    {"name": "legacy tombstone base: seq unknown", "base": {"legacy_tombstone": true}, "record": {"deleted": false, "plaintext": {"title": "r", "seq": 1}}, "result": "accept"}
   ],
   "next_version": [
-    { "name": "new item", "local": null, "base": null, "seq": 1, "restores": null },
-    { "name": "edit of a clean item", "local": {"seq": 3}, "base": {"revision": 5, "item": {"seq": 3}}, "seq": 4, "restores": null },
-    { "name": "second edit before syncing", "local": {"seq": 4}, "base": {"revision": 5, "item": {"seq": 3}}, "seq": 5, "restores": null },
-    { "name": "re-save after a pending local delete", "local": null, "base": {"revision": 5, "item": {"seq": 3}}, "seq": 4, "restores": null },
-    { "name": "legacy item", "local": {}, "base": {"revision": 5, "item": {}}, "seq": 1, "restores": null },
-    { "name": "save over a tombstone", "local": null, "base": {"tombstone": true, "revision": 8}, "seq": 1, "restores": 8 },
-    { "name": "edit after a restore clears restores", "local": {"seq": 2, "restores": 8}, "base": {"revision": 9, "item": {"seq": 2, "restores": 8}}, "seq": 3, "restores": null }
+    {"name": "new item", "local": null, "base": null, "seq": 1},
+    {"name": "edit of a clean item", "local": {"seq": 3}, "base": {"plaintext": {"seq": 3}}, "seq": 4},
+    {"name": "second edit before syncing", "local": {"seq": 4}, "base": {"plaintext": {"seq": 3}}, "seq": 5},
+    {"name": "delete of a clean item (the tombstone's seq)", "local": {"seq": 3}, "base": {"plaintext": {"seq": 3}}, "seq": 4},
+    {"name": "re-save after a pending local delete", "local": {"id": "11111111-1111-1111-1111-111111111111", "seq": 4, "deleted": true}, "base": {"plaintext": {"seq": 3}}, "seq": 5},
+    {"name": "legacy item", "local": {}, "base": {"plaintext": {}}, "seq": 1},
+    {"name": "save over a pulled tombstone", "local": {"id": "11111111-1111-1111-1111-111111111111", "seq": 8, "deleted": true}, "base": {"plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 8, "deleted": true}}, "seq": 9},
+    {"name": "pending edit rebased over a pulled tombstone (edit beats delete)", "local": {"seq": 4}, "base": {"plaintext": {"id": "11111111-1111-1111-1111-111111111111", "seq": 6, "deleted": true}}, "seq": 7},
+    {"name": "legacy tombstone base", "local": null, "base": {"legacy_tombstone": true}, "seq": 1}
   ]
 }