diff --git a/ui/src/lib/BestShares.svelte b/ui/src/lib/BestShares.svelte
index a694ef2..549d4bd 100644
--- a/ui/src/lib/BestShares.svelte
+++ b/ui/src/lib/BestShares.svelte
@@ -3,12 +3,13 @@
   import { formatDifficulty } from "../format";
   import type { StratumClient } from "../types";
 
-  // Join client data into worker rows so the "session best" column
-  // matches what the Miners table renders for the same worker.
-  // ckpool's reset_bestshares() zeroes both worker.best_diff and
-  // client.best_diff when the pool finds a block, but timing or
-  // reconnect can leave the two briefly divergent — take the larger
-  // of the two to stay consistent with the Miners table.
+  // "Best (session)" = best diff in the current stratum TCP session,
+  // i.e. only ckpool's stratum_instance.best_diff. Resets on miner
+  // disconnect (the instance is freed) and on pool restart (in-memory
+  // state, not persisted). worker.best_diff is a separate persistent
+  // counter that survives both events, so we deliberately don't fall
+  // back to it — that fallback was the bug. Offline workers have no
+  // current session, so their session-best is 0.
   const rows = $derived.by(() => {
     const ws = snap.data?.workers ?? [];
     const cs = snap.data?.clients ?? [];
@@ -19,11 +20,10 @@
     }
     const enriched = ws.map((w) => {
       const c = clientByWorker.get(w.worker);
-      const sessionBest = Math.max(c?.bestdiff ?? 0, w.bestdiff);
       return {
         worker: w.worker,
-        sessionBest,
-        bestEver: w.bestever || sessionBest,
+        sessionBest: c?.bestdiff ?? 0,
+        bestEver: w.bestever || w.bestdiff,
       };
     });
     enriched.sort((a, b) => b.bestEver - a.bestEver);
diff --git a/ui/src/lib/MinersTable.svelte b/ui/src/lib/MinersTable.svelte
index d7cc886..a887904 100644
--- a/ui/src/lib/MinersTable.svelte
+++ b/ui/src/lib/MinersTable.svelte
@@ -35,20 +35,20 @@
       const wname = c.workername || `${c.address}.unnamed`;
       seen.add(wname);
       const w = byWorker.get(wname);
-      // "Session best" is the larger of the live stratum client's
-      // best_diff and the worker_instance's best_diff. ckpool's
-      // reset_bestshares() clears both when the pool finds a block,
-      // but reconnect / timing can leave them briefly divergent —
-      // max() keeps this column aligned with the leaderboard.
-      const sessionBest = Math.max(c.bestdiff, w?.bestdiff ?? 0);
+      // "Session best" = best diff for *this stratum TCP session*.
+      // ckpool zeroes stratum_instance.best_diff when the connection
+      // ends and on pool restart (in-memory only), so this is the
+      // value that should reset on miner disconnect / pool restart.
+      // Don't fall back to worker.best_diff — that's the persistent
+      // round counter and would defeat the reset semantics.
       out.push({
         workerName: wname,
         user: c.address,
         hardware: detectHardware(c.useragent),
         hashrate1m: c.dsps1 * 2 ** 32,
         hashrate1h: c.dsps60 * 2 ** 32,
-        bestDiff: sessionBest,
-        bestEver: w?.bestever ?? sessionBest,
+        bestDiff: c.bestdiff,
+        bestEver: w?.bestever ?? c.bestdiff,
         lastShare: c.lastshare,
         difficulty: c.diff,
         address: c.address,
@@ -59,13 +59,15 @@
 
     for (const w of workers) {
       if (seen.has(w.worker)) continue;
+      // Offline worker — no current session, so session-best is 0.
+      // The lifetime best_ever still applies.
       out.push({
         workerName: w.worker,
         user: w.user,
         hardware: "offline",
         hashrate1m: w.dsps1 * 2 ** 32,
         hashrate1h: w.dsps60 * 2 ** 32,
-        bestDiff: w.bestdiff,
+        bestDiff: 0,
         bestEver: w.bestever,
         lastShare: w.lastshare,
         difficulty: w.mindiff,
diff --git a/ui/src/lib/UserDetailPage.svelte b/ui/src/lib/UserDetailPage.svelte
index 7b94b41..b7ed193 100644
--- a/ui/src/lib/UserDetailPage.svelte
+++ b/ui/src/lib/UserDetailPage.svelte
@@ -49,12 +49,10 @@
         hashrate1m: (c?.dsps1 ?? w.dsps1) * 2 ** 32,
         hashrate1h: (c?.dsps60 ?? w.dsps60) * 2 ** 32,
         diff: c?.diff ?? w.mindiff,
-        // Session best = larger of client.bestdiff (this stratum
-        // connection) and worker.bestdiff (this worker in the
-        // current round). Matches the MinersTable / BestShares
-        // leaderboard semantics so values are consistent across
-        // screens.
-        bestRound: Math.max(c?.bestdiff ?? 0, w.bestdiff),
+        // Session best = ckpool's stratum_instance.best_diff for the
+        // currently-connected client only. Resets on miner disconnect
+        // and pool restart. 0 for offline workers (no current session).
+        bestRound: c?.bestdiff ?? 0,
         bestEver: w.bestever,
         lastShare: c?.lastshare ?? w.lastshare,
         online: !!c,