From 065bf2f9e738eae219da1fe0557ec22f94f10b7a Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Thu, 5 Nov 2026 16:10:14 +0100
Subject: waiting not twice

---
 src/swarm/stats.rs | 9 +++++++++
 src/swarm/sync.rs  | 9 ++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

(limited to 'src/swarm')

diff --git a/src/swarm/stats.rs b/src/swarm/stats.rs
index 31b6a3b..ba75d68 100644
--- a/src/swarm/stats.rs
+++ b/src/swarm/stats.rs
@@ -157,6 +157,10 @@ pub(crate) struct Relay {
     pub(crate) carrying_bloom_bytes: u64,
     pub(crate) nothing_new_change_bytes: u64,
     pub(crate) nothing_new_bloom_bytes: u64,
+    /// Sync messages received that carried changes, none of them applied yet: they wait
+    /// for predecessors that didn't come (Automerge holds them back). Not counted with
+    /// `nothing_new`, which they aren't.
+    pub(crate) waiting: u64,
     /// The changes new to us that sync messages brought (beside what they carried that
     /// we had): with `carrying` less `nothing_new`, how many a message with news brings.
     pub(crate) new_changes: u64,
@@ -314,6 +318,11 @@ impl NodeStats {
         inner.relay.nothing_new_bloom_bytes += sizes.1 as u64;
     }
 
+    /// A sync message carried changes that wait for predecessors (`Relay::waiting`).
+    pub(crate) fn waiting(&self) {
+        self.lock().relay.waiting += 1;
+    }
+
     /// Changes from elsewhere were applied, `delays_ms` after they were committed, that
     /// came not along a writer's tree.
     pub(crate) fn off_tree(&self, delays_ms: &[i64]) {
diff --git a/src/swarm/sync.rs b/src/swarm/sync.rs
index 0edc277..5511ea2 100644
--- a/src/swarm/sync.rs
+++ b/src/swarm/sync.rs
@@ -574,6 +574,7 @@ pub(crate) async fn handle_sync(
             peer_state.last_heads =
                 Some((epoch, transport::HeadsSummary::of(message.heads().to_vec())));
             let heads_before = replica.heads().to_vec();
+            let said = message.heads().to_vec();
 
             let sync = &mut peer_state.sync;
             replica
@@ -617,7 +618,13 @@ pub(crate) async fn handle_sync(
                 stats.new_changes(new);
             }
             if carried && !changed {
-                stats.nothing_new(payload_len, writer.is_some(), delivered, sizes);
+                // Its heads not ours yet: what it brought waits for predecessors, which
+                // isn't having come twice.
+                if !crate::document::changes::holds_all(&replica.doc, &said) {
+                    stats.waiting();
+                } else {
+                    stats.nothing_new(payload_len, writer.is_some(), delivered, sizes);
+                }
             }
             // Whose they are, to pass them on along their writers' trees, however they
             // came (along a tree, with an answer, pulled).
-- 
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