From 12985ade6db6240bfdb56e73524919af505ee4f9 Mon Sep 17 00:00:00 2001
From: iris <iris@hyperhive>
Date: Sun, 31 May 2026 21:31:57 +0200
Subject: [PATCH] fix(#726): handle broadcast Lagged + clear on SSE reconnect

Distinguish RecvError::Lagged from Closed in the build-log stream
loop: Lagged continues (next recv delivers the full accumulated delta
via saved cursors), Closed returns (shutdown path).

Clear pre.textContent and reset cursor lengths in es.onerror when
readyState is CONNECTING so auto-reconnect doesn't double-append the
replay from cursor=0.
---
 frontend/packages/dashboard/src/tabs.js | 8 +++++++-
 hive-c0re/src/dashboard.rs              | 3 ++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/frontend/packages/dashboard/src/tabs.js b/frontend/packages/dashboard/src/tabs.js
index ca24ec8c..7afb27ba 100644
--- a/frontend/packages/dashboard/src/tabs.js
+++ b/frontend/packages/dashboard/src/tabs.js
@@ -1216,7 +1216,13 @@ window.marked = marked;
                   }
                 };
                 es.onerror = () => {
-                  if (es.readyState === EventSource.CLOSED) {
+                  if (es.readyState === EventSource.CONNECTING) {
+                    // Auto-reconnect: clear accumulated content so the
+                    // fresh stream from cursor=0 doesn't double-append.
+                    pre.textContent = '';
+                    stdoutLen = 0;
+                    stderrLen = 0;
+                  } else if (es.readyState === EventSource.CLOSED) {
                     detail._es = null;
                   }
                 };
diff --git a/hive-c0re/src/dashboard.rs b/hive-c0re/src/dashboard.rs
index e43490e2..1e470a46 100644
--- a/hive-c0re/src/dashboard.rs
+++ b/hive-c0re/src/dashboard.rs
@@ -1789,7 +1789,8 @@ async fn get_build_log_stream(
                         Err(_) => return,
                     }
                 }
-                Err(_) => return, // notification channel closed (shutdown)
+                Err(tokio::sync::broadcast::error::RecvError::Lagged(_)) => continue,
+                Err(tokio::sync::broadcast::error::RecvError::Closed) => return,
             }
         }
     });