From 8e243dfd3e2cb719e253eb75285d1ad84f2af853 Mon Sep 17 00:00:00 2001
From: igneum-labs <337424239+igneum-labs@users.noreply.github.com>
Date: Sun, 4 Oct 2026 19:34:57 +0000
Subject: [PATCH] Observer: one checkpoint_locked event per index (the poll
 claims the state before its first await; the FinalityLock notification path
 raced it and the live feed showed two locked lines 30 ms apart); a lock
 claimed by the notification gets its votes_seen from the next poll

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
---
 tools/observer/observer.mjs | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/observer/observer.mjs b/tools/observer/observer.mjs
index 569be0f79..abe90c9da 100644
--- a/tools/observer/observer.mjs
+++ b/tools/observer/observer.mjs
@@ -512,7 +512,8 @@ async function tick(rpc) {
 }
 
 // ---------- Finality v2 (spec 03) ----------
-const checkpointStates = new Map();   // index -> last state written
+const checkpointStates = new Map();   // index -> last state written; set BEFORE any await, so the two lock paths never both record
+const checkpointDetailed = new Set();  // indices written with votesSeen (the FinalityLock notification carries none; the poll fills it in once)
 let finalitySupported = null;         // null = unknown, false = the node has no finality RPC
 let lastWeightsAt = 0;
 let lastWeights = null;
@@ -554,16 +555,22 @@ async function finalityTick(rpc) {
   if (!certBackfillDone) backfillCertificate(rpc, cps).catch(e => log('certificate backfill failed', e.message));
   for (const cp of cps.checkpoints || []) {
     const prev = checkpointStates.get(cp.index);
-    if (prev !== cp.state || prev === undefined) {
-      await upsertCheckpoint(cp);
-      if (cp.state === 'locked' && prev !== 'locked') await recordLock(cp);
+    const changed = prev !== cp.state || prev === undefined;
+    const detail = cp.votesSeen !== undefined && !checkpointDetailed.has(cp.index);
+    if (changed || detail) {
+      // claim the transition before the first await: the FinalityLock notification handler checks this map synchronously,
+      // and until 4 October 2026 both paths recorded the same lock (two "locked" events 30 ms apart on the live feed)
       checkpointStates.set(cp.index, cp.state);
+      if (cp.votesSeen !== undefined) checkpointDetailed.add(cp.index);
+      await upsertCheckpoint(cp);
+      if (changed && cp.state === 'locked' && prev !== 'locked') await recordLock(cp);
     } else if (cp.state !== 'locked' && (cp.index % 1 === 0)) {
       // vote counts move while a checkpoint is open: refresh it
       await upsertCheckpoint(cp);
     }
   }
   for (const k of checkpointStates.keys()) if (k + 500 < Number(cps.nextIndex)) checkpointStates.delete(k);
+  for (const k of checkpointDetailed) if (k + 500 < Number(cps.nextIndex)) checkpointDetailed.delete(k);
   const now = Date.now();
   if (now - lastWeightsAt > 10_000) {
     lastWeightsAt = now;