diff --git a/frontend/src/app/main/store.cljs b/frontend/src/app/main/store.cljs
index 9ecfc39284..dc389033ae 100644
--- a/frontend/src/app/main/store.cljs
+++ b/frontend/src/app/main/store.cljs
@@ -107,8 +107,8 @@
 (defn format-last-events
   "Render the `last-events` buffer as a multi-line string with the
   wall-clock time of each event and the delta (ms) since the previous
-  entry. The first entry has no delta. Useful for embedding in error
-  reports."
+  entry. The delta column is right-padded to 10 chars so the event
+  names align. Useful for embedding in error reports."
   ([] (format-last-events @last-events))
   ([events]
    (let [lines
@@ -117,13 +117,14 @@
                 out    (transient [])]
            (if xs
              (let [{:keys [name t]} (first xs)
-                   iso  (ct/format-inst t :iso)
-                   tail (if prev-t
-                          (str "  (+" (ct/diff-ms prev-t t) "ms)")
-                          "")]
+                   iso        (ct/format-inst t :iso)
+                   delta      (if prev-t
+                                (str "(+" (ct/diff-ms prev-t t) "ms)")
+                                "(+0ms)")
+                    delta-pad  (str/pad delta {:length 10 :type :right})]
                (recur t
                       (next xs)
-                      (conj! out (str iso tail "  " name))))
+                      (conj! out (str iso "  " delta-pad "  " name))))
              (persistent! out)))]
      (str/join "\n" lines))))
 
diff --git a/frontend/test/frontend_tests/data/store_test.cljs b/frontend/test/frontend_tests/data/store_test.cljs
new file mode 100644
index 0000000000..56d29fec85
--- /dev/null
+++ b/frontend/test/frontend_tests/data/store_test.cljs
@@ -0,0 +1,49 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC Sucursal en España SL
+
+(ns frontend-tests.data.store-test
+  "Unit tests for app.main.store.
+  Tests cover:
+    - format-last-events          – empty, single, multi, column alignment"
+  (:require
+   [app.main.store :as st]
+   [cljs.test :as t :include-macros true]
+   [cuerdas.core :as str]))
+
+(t/deftest format-last-events-empty
+  (t/testing "empty events produce empty string"
+    (t/is (= "" (st/format-last-events [])))))
+
+(t/deftest format-last-events-single
+  (t/testing "a single event shows (+0ms) and its name"
+    (let [result (st/format-last-events [{:name ":test/event" :t (js/Date. 1000)}])]
+      (t/is (str/includes? result "(+0ms)"))
+      (t/is (str/includes? result ":test/event"))
+      (t/is (= 1 (count (str/split result "\n")))))))
+
+(t/deftest format-last-events-multi
+  (t/testing "multiple events show correct deltas and event names"
+    (let [events [{:name ":event/a" :t (js/Date. 0)}
+                  {:name ":event/b" :t (js/Date. 500)}
+                  {:name ":event/c" :t (js/Date. 2500)}]
+          lines  (str/split (st/format-last-events events) "\n")]
+      (t/is (= 3 (count lines)))
+      (t/is (some #(str/includes? % ":event/a") lines))
+      (t/is (some #(str/includes? % ":event/b") lines))
+      (t/is (some #(str/includes? % ":event/c") lines))
+      (t/is (str/includes? (nth lines 0) "(+0ms)"))
+      (t/is (str/includes? (nth lines 1) "(+500ms)"))
+      (t/is (str/includes? (nth lines 2) "(+2000ms)")))))
+
+(t/deftest format-last-events-alignment
+  (t/testing "event names start at the same column across all lines"
+    (let [events [{:name ":evt-a" :t (js/Date. 0)}
+                  {:name ":evt-b" :t (js/Date. 500)}]
+          lines  (str/split (st/format-last-events events) "\n")
+          col-a  (.indexOf (nth lines 0) ":evt-a")
+          col-b  (.indexOf (nth lines 1) ":evt-b")]
+      (t/is (pos? col-a))
+      (t/is (= col-a col-b)))))
diff --git a/frontend/test/frontend_tests/runner.cljs b/frontend/test/frontend_tests/runner.cljs
index cda245671d..450f6978bd 100644
--- a/frontend/test/frontend_tests/runner.cljs
+++ b/frontend/test/frontend_tests/runner.cljs
@@ -9,6 +9,7 @@
    [frontend-tests.copy-as-svg-test]
    [frontend-tests.data.nitrate-test]
    [frontend-tests.data.repo-test]
+   [frontend-tests.data.store-test]
    [frontend-tests.data.uploads-test]
    [frontend-tests.data.viewer-test]
    [frontend-tests.data.workspace-colors-test]
@@ -86,6 +87,7 @@
    'frontend-tests.copy-as-svg-test
    'frontend-tests.data.nitrate-test
    'frontend-tests.data.repo-test
+   'frontend-tests.data.store-test
    'frontend-tests.errors-test
    'frontend-tests.main-errors-test
    'frontend-tests.data.uploads-test