fix: expose book snapshot clocks

src/book.rs

@@ -460,6 +460,8 @@ impl OrderBook {
             bids: self.bids(None), // Get all bids (up to max_depth)
             asks: self.asks(None), // Get all asks (up to max_depth)
             sequence: self.last_delta_sequence,
+            last_delta_sequence: self.last_delta_sequence,
+            last_snapshot_timestamp_ms: self.last_snapshot_timestamp_ms,
         }
     }
 
@@ -1526,6 +1528,11 @@ mod tests {
         assert_eq!(book.last_snapshot_timestamp_ms, 1_000);
         assert_eq!(book.best_bid().unwrap().price, dec!(0.50));
         assert_eq!(book.best_ask().unwrap().price, dec!(0.60));
+
+        let snapshot = book.snapshot();
+        assert_eq!(snapshot.sequence, 10_000);
+        assert_eq!(snapshot.last_delta_sequence, 10_000);
+        assert_eq!(snapshot.last_snapshot_timestamp_ms, 1_000);
     }
 
     #[test]

src/decode.rs

@@ -341,6 +341,8 @@ impl Decoder<OrderBook> for RawOrderBookResponse {
             bids,
             asks,
             sequence: 0, // TODO: Get from response if available
+            last_delta_sequence: 0,
+            last_snapshot_timestamp_ms: 0,
         })
     }
 }

src/types.rs

@@ -358,7 +358,7 @@ impl FastBookLevel {
 }
 
 /// Full order book state
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Serialize)]
 pub struct OrderBook {
     /// Token ID
     pub token_id: String,
@@ -368,8 +368,47 @@ pub struct OrderBook {
     pub bids: Vec<BookLevel>,
     /// Ask orders
     pub asks: Vec<BookLevel>,
-    /// Sequence number
+    /// Legacy/incremental delta sequence number.
+    ///
+    /// This is kept for compatibility. For snapshots produced by this client,
+    /// it is equivalent to [`Self::last_delta_sequence`]. WebSocket snapshot
+    /// timestamps are exposed separately in [`Self::last_snapshot_timestamp_ms`].
     pub sequence: u64,
+    /// Last accepted legacy/incremental delta sequence number.
+    pub last_delta_sequence: u64,
+    /// Last accepted full-book snapshot timestamp in milliseconds.
+    pub last_snapshot_timestamp_ms: u64,
+}
+
+impl<'de> Deserialize<'de> for OrderBook {
+    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct WireOrderBook {
+            token_id: String,
+            timestamp: DateTime<Utc>,
+            bids: Vec<BookLevel>,
+            asks: Vec<BookLevel>,
+            sequence: u64,
+            #[serde(default)]
+            last_delta_sequence: Option<u64>,
+            #[serde(default)]
+            last_snapshot_timestamp_ms: Option<u64>,
+        }
+
+        let wire = WireOrderBook::deserialize(deserializer)?;
+        Ok(Self {
+            token_id: wire.token_id,
+            timestamp: wire.timestamp,
+            bids: wire.bids,
+            asks: wire.asks,
+            sequence: wire.sequence,
+            last_delta_sequence: wire.last_delta_sequence.unwrap_or(wire.sequence),
+            last_snapshot_timestamp_ms: wire.last_snapshot_timestamp_ms.unwrap_or_default(),
+        })
+    }
 }
 
 /// Order book delta for streaming updates - EXTERNAL API VERSION
@@ -1922,4 +1961,20 @@ mod tests {
             Decimal::from_str("0.00005").unwrap()
         ));
     }
+
+    #[test]
+    fn order_book_snapshot_clocks_default_for_legacy_payloads() {
+        let json = r#"{
+            "token_id":"test_token",
+            "timestamp":"2026-06-23T00:00:00Z",
+            "bids":[],
+            "asks":[],
+            "sequence":42
+        }"#;
+
+        let book: OrderBook = serde_json::from_str(json).unwrap();
+        assert_eq!(book.sequence, 42);
+        assert_eq!(book.last_delta_sequence, 42);
+        assert_eq!(book.last_snapshot_timestamp_ms, 0);
+    }
 }

src/ws_hot_path.rs

@@ -371,6 +371,8 @@ mod tests {
 
         let snapshot = books.get_book("test_asset_id").unwrap();
         assert_eq!(snapshot.sequence, 0);
+        assert_eq!(snapshot.last_delta_sequence, 0);
+        assert_eq!(snapshot.last_snapshot_timestamp_ms, 1000);
         assert_eq!(snapshot.timestamp.timestamp_millis(), 1000);
         assert_eq!(snapshot.bids.len(), 1);
         assert_eq!(snapshot.asks.len(), 1);
@@ -409,6 +411,8 @@ mod tests {
 
         let snapshot = books.get_book("test_asset_id").unwrap();
         assert_eq!(snapshot.sequence, 0);
+        assert_eq!(snapshot.last_delta_sequence, 0);
+        assert_eq!(snapshot.last_snapshot_timestamp_ms, 1000);
         assert_eq!(snapshot.timestamp.timestamp_millis(), 1000);
         assert_eq!(snapshot.bids.len(), 1);
         assert_eq!(snapshot.asks.len(), 1);
@@ -436,6 +440,8 @@ mod tests {
 
         let snapshot = books.get_book("test_asset_id").unwrap();
         assert_eq!(snapshot.sequence, 0);
+        assert_eq!(snapshot.last_delta_sequence, 0);
+        assert_eq!(snapshot.last_snapshot_timestamp_ms, 1000);
         assert_eq!(snapshot.timestamp.timestamp_millis(), 1000);
         assert_eq!(snapshot.bids[0].price, dec!(0.51));
         assert_eq!(snapshot.bids[0].size, dec!(11));