From f867dabbe676255e75a512df343617bd4ca45d0d Mon Sep 17 00:00:00 2001
From: JJ Liebig <jonathan.liebig@gmail.com>
Date: Mon, 14 Sep 2026 22:31:31 +0200
Subject: fix: reject stale pane surfaces after reconnect (#4141)

---
 src/client/shell/composition.rs                | 8 +++++---
 src/client/shell/tests/endpoints.rs            | 2 ++
 src/client/shell/tests/workspace_navigation.rs | 1 +
 3 files changed, 8 insertions(+), 3 deletions(-)

(limited to 'src/client')

diff --git a/src/client/shell/composition.rs b/src/client/shell/composition.rs
index 0a577295..e0888d0d 100644
--- a/src/client/shell/composition.rs
+++ b/src/client/shell/composition.rs
@@ -147,9 +147,11 @@ impl ClientShellState {
             return Some(self.compose_unavailable(cols, rows));
         }
         let snapshot = self.snapshot.as_deref()?;
-        // A one-step successor is retained separately until its exact snapshot arrives; do not
-        // keep composing the now-superseded current pair while it is pending.
-        if self.pending_pane_surface.is_some() {
+        // Do not compose a retained surface while waiting for its matching snapshot or
+        // connection generation.
+        if self.pending_pane_surface.is_some()
+            || self.pane_surface_generation != self.active_snapshot_generation
+        {
             return None;
         }
         let surface = self.pane_surface.as_ref()?;
diff --git a/src/client/shell/tests/endpoints.rs b/src/client/shell/tests/endpoints.rs
index 4ac8183c..b43b9a31 100644
--- a/src/client/shell/tests/endpoints.rs
+++ b/src/client/shell/tests/endpoints.rs
@@ -1559,6 +1559,7 @@ fn reconnect_same_endpoint_accepts_new_generation_surface_revision() {
 
         state.set_endpoint_status(&endpoint_id, ClientEndpointStatus::Online);
         assert!(state.activate_endpoint_projection(&endpoint_id));
+        assert!(state.compose(106, 20).is_none());
         let mut reconnected_surface = surface();
         reconnected_surface.boot_id = "shared-server-boot".into();
         reconnected_surface.projection_revision = 1;
@@ -1570,6 +1571,7 @@ fn reconnect_same_endpoint_accepts_new_generation_surface_revision() {
         assert_eq!(state.pane_surface.as_ref().unwrap().surface_revision, 1);
         assert!(state.pending_pane_surface.is_none());
         assert_eq!(state.agent_scroll, 7);
+        assert!(state.compose(106, 20).is_some());
     }
 }
 
diff --git a/src/client/shell/tests/workspace_navigation.rs b/src/client/shell/tests/workspace_navigation.rs
index 2a100957..7ea02066 100644
--- a/src/client/shell/tests/workspace_navigation.rs
+++ b/src/client/shell/tests/workspace_navigation.rs
@@ -431,6 +431,7 @@ fn active_preview_is_not_retargeted_by_deletion_or_reboot() {
             7,
             Box::new(local.clone()),
         );
+        state.set_pane_surface(surface());
         state.compose(100, 28).unwrap();
         enter_navigation(&mut state);
         preview_key(&mut state, b"\x1b[B");
-- 
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