diff --git a/apps/monitor/src/runner.rs b/apps/monitor/src/runner.rs
index 8cdd72e..7b71837 100644
--- a/apps/monitor/src/runner.rs
+++ b/apps/monitor/src/runner.rs
@@ -53,14 +53,20 @@ pub async fn fetch_and_run(
         let coordinator_url = coordinator_url.to_string();
         let token = token.to_string();
         let region_owned = region.to_string();
-        // Derive run_id from the monitor's scheduled_at bucket
+        // Derive run_id by hashing (monitor_id, interval_bucket) so every region
+        // checking within the same scheduled window gets the same short ID.
         let run_id_owned = {
+            use std::collections::hash_map::DefaultHasher;
+            use std::hash::{Hash, Hasher};
             let epoch = monitor.scheduled_at.as_deref()
                 .and_then(|s| chrono::DateTime::parse_from_rfc3339(s).ok())
                 .map(|dt| dt.timestamp())
                 .unwrap_or_else(|| chrono::Utc::now().timestamp());
             let bucket = epoch / monitor.interval_s;
-            format!("{}:{}", &monitor.id[..8.min(monitor.id.len())], bucket)
+            let mut h = DefaultHasher::new();
+            monitor.id.hash(&mut h);
+            bucket.hash(&mut h);
+            format!("{:016x}", h.finish())
         };
         let in_flight = in_flight.clone();
         tokio::spawn(async move {
diff --git a/apps/web/src/views/detail.ejs b/apps/web/src/views/detail.ejs
index d56f9b2..dc9e6ac 100644
--- a/apps/web/src/views/detail.ejs
+++ b/apps/web/src/views/detail.ejs
@@ -107,7 +107,7 @@
                   <td class="px-4 py-2 text-gray-300"><%= c.status_code != null ? c.status_code : '—' %></td>
                   <td class="px-4 py-2 text-gray-300"><%= c.latency_ms != null ? c.latency_ms + 'ms' : '—' %></td>
                   <td class="px-4 py-2 text-gray-500 text-sm" title="<%= c.region || '' %>"><%= c.region ? (regionFlag[c.region] || '🌐') + ' ' + c.region : '—' %></td>
-                  <td class="px-4 py-2 text-gray-600 font-mono text-xs" title="<%= c.run_id || '' %>"><%= c.run_id ? c.run_id.slice(0, 8) : '—' %></td>
+                  <td class="px-4 py-2 text-gray-600 font-mono text-xs" title="<%= c.run_id || '' %>"><%= c.run_id ? c.run_id.slice(0, 8) + '…' : '—' %></td>
                   <td class="px-4 py-2 text-gray-500"><%~ it.timeAgoSSR(c.checked_at) %><% if (c.jitter_ms != null) { %> <span class="text-gray-600 text-xs">(+<%= c.jitter_ms %>ms)</span><% } %></td>
                   <td class="px-4 py-2 text-red-400/70 text-xs truncate max-w-[200px]"><%= c.error ? c.error : '' %></td>
                 </tr>
@@ -344,7 +344,7 @@
           <td class="px-4 py-2 text-gray-300">${ping.status_code ?? '—'}</td>
           <td class="px-4 py-2 text-gray-300">${ping.latency_ms != null ? ping.latency_ms + 'ms' : '—'}</td>
           <td class="px-4 py-2 text-gray-500 text-sm" title="${ping.region || ''}">${regionDisplay}</td>
-          <td class="px-4 py-2 text-gray-600 font-mono text-xs" title="${ping.run_id || ''}">${ping.run_id ? ping.run_id.slice(0, 8) : '—'}</td>
+          <td class="px-4 py-2 text-gray-600 font-mono text-xs" title="${ping.run_id || ''}">${ping.run_id ? ping.run_id.slice(0, 8) + '…' : '—'}</td>
           <td class="px-4 py-2 text-gray-500">${timeAgo(ping.checked_at)}${ping.jitter_ms != null ? ` <span class="text-gray-600 text-xs">(+${ping.jitter_ms}ms)</span>` : ''}</td>
           <td class="px-4 py-2 text-red-400/70 text-xs truncate max-w-[200px]">${ping.error ? escapeHtml(ping.error) : ''}</td>
         `;