From c3faf6ecde8157154a01daa2ddc0ac02e6c761f1 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Wed, 4 Nov 2026 19:46:17 +0100
Subject: tree messages need no answer

---
 src/swarm/sync.rs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

(limited to 'src/swarm/sync.rs')

diff --git a/src/swarm/sync.rs b/src/swarm/sync.rs
index b20f7ef..02c6379 100644
--- a/src/swarm/sync.rs
+++ b/src/swarm/sync.rs
@@ -148,6 +148,13 @@ async fn deliver_sync_to_peer(state: &AppState, peer: &str) -> Result<()> {
                     let replica = doc.blocking_read();
                     let mut peer_state = psm.blocking_lock();
                     let (epoch, epoch_seq) = (replica.epoch, replica.epoch_seq);
+                    // Whose change it passes on, if any: this message carries it.
+                    let writer = peer_state.tree_writer.take();
+                    // Along a tree, to a peer that had nothing we lack, with nothing
+                    // awaited: taken as delivered (`SyncSession::assume_delivered`).
+                    let level = writer.is_some()
+                        && peer_state.sync.reply.is_none()
+                        && peer_state.sync.have_all_theirs(&replica.doc);
                     // Under the same locks as the epoch label: the message belongs to
                     // this document.
                     let message =
@@ -171,8 +178,9 @@ async fn deliver_sync_to_peer(state: &AppState, peer: &str) -> Result<()> {
                         );
                         transport::SyncBody::Delta(spec)
                     });
-                    // Whose change it passes on, if any: this message carries it.
-                    let writer = peer_state.tree_writer.take();
+                    if level && matches!(body, Some(transport::SyncBody::Message(_))) {
+                        peer_state.sync.assume_delivered(replica.heads());
+                    }
                     (peer_state.sync.id(), epoch, epoch_seq, body, writer)
                 };
                 let Some(body) = body else {
@@ -411,6 +419,11 @@ pub(crate) async fn handle_sync(
             peer_state.sync.resend_if_needed(&peer);
             replica.refresh_heads();
             let heads_after = replica.heads().to_vec();
+            if writer.is_some() {
+                // Level with the sender now: it takes the message as delivered, so
+                // there is nothing to answer (`SyncSession::answered_along_tree`).
+                peer_state.sync.answered_along_tree(&heads_after);
+            }
             stats.heads_seen(heads_after.len());
             let changed = heads_after != heads_before;
             // Whose they are, to pass them on along their writers' trees, however they
-- 
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