diff --git a/shared/tests/turn.logging.test.js b/shared/tests/turn.logging.test.js
index ecb3e82..82852a6 100644
--- a/shared/tests/turn.logging.test.js
+++ b/shared/tests/turn.logging.test.js
@@ -166,23 +166,38 @@ describe('Logging undo payloads', () => {
   });
 });
 
-describe('Logging: gaps (currently unlogged mutations)', () => {
-  // Document current behavior. addParticipants + updateParticipant return
-  // null log → invisible in combat log. May be intended (bulk/no-op) or bug.
+describe('Logging: addParticipants + updateParticipant', () => {
   let e;
   beforeEach(() => {
     e = enc([p('a', 10), p('b', 7)]);
   });
 
-  test('addParticipants returns null log (bulk gap?)', () => {
+  test('addParticipants logs', () => {
     const r = addParticipants(e, [p('c', 3)]);
-    // Currently null. Document so decision is explicit.
-    expect(r.log).toBeNull();
+    expectLogged(r);
   });
 
-  test('updateParticipant returns null log (edit gap?)', () => {
+  test('updateParticipant (same slot) logs', () => {
     const r = updateParticipant(e, 'b', { name: 'B' });
-    // Currently null. Document so decision is explicit.
-    expect(r.log).toBeNull();
+    expectLogged(r);
+  });
+
+  test('updateParticipant (init change) logs', () => {
+    const r = updateParticipant(e, 'b', { initiative: 5 });
+    expectLogged(r);
+  });
+
+  test('addParticipants undo restores prior list', () => {
+    const orig = e.participants.map(p => p.id);
+    const r = addParticipants(e, [p('c', 3)]);
+    const restored = { ...e, ...r.log.undo };
+    expect(restored.participants.map(p => p.id)).toEqual(orig);
+  });
+
+  test('updateParticipant undo restores prior participant', () => {
+    const orig = e.participants.map(p => p.id);
+    const r = updateParticipant(e, 'b', { name: 'B' });
+    const restored = { ...e, ...r.log.undo };
+    expect(restored.participants.map(p => p.id)).toEqual(orig);
   });
 });
diff --git a/shared/turn.js b/shared/turn.js
index 5415af2..6554926 100644
--- a/shared/turn.js
+++ b/shared/turn.js
@@ -333,8 +333,16 @@ function addParticipant(encounter, participant) {
 
 // ADD_PARTICIPANTS — bulk add (e.g. "add all campaign characters").
 function addParticipants(encounter, newParticipants) {
+  const undo = { participants: encounter.participants || [] };
   const updatedParticipants = [...(encounter.participants || []), ...newParticipants];
-  return { patch: { participants: updatedParticipants }, log: null };
+  const names = newParticipants.map(p => p.name).join(', ');
+  return {
+    patch: { participants: updatedParticipants },
+    log: {
+      message: `Added ${newParticipants.length} participant${newParticipants.length === 1 ? '' : 's'}: ${names}`,
+      undo,
+    },
+  };
 }
 
 // UPDATE_PARTICIPANT — edit modal save (name/initiative/hp/isNpc).
@@ -346,14 +354,28 @@ function updateParticipant(encounter, participantId, updatedData) {
   // SLOT only if initiative changed. Other edits (name/hp/notes/isNpc) = no
   // position change (design doc). Re-slots on unrelated edits shuffle the
   // list mid-round → rotation dupes.
+  const undo = { participants: encounter.participants || [] };
   if (!('initiative' in updatedData) || updatedData.initiative === target.initiative) {
     const sameSlot = existing.map(p => p.id === participantId ? merged : p);
-    return { patch: { participants: sameSlot, ...syncTurnOrder(sameSlot) }, log: null };
+    const fields = Object.keys(updatedData).join(', ');
+    return {
+      patch: { participants: sameSlot, ...syncTurnOrder(sameSlot) },
+      log: {
+        message: `${target.name} updated (${fields})`,
+        undo,
+      },
+    };
   }
   const without = existing.filter(p => p.id !== participantId);
   const idx = slotIndexForInit(without, merged.initiative);
   without.splice(idx, 0, merged);
-  return { patch: { participants: without, ...syncTurnOrder(without) }, log: null };
+  return {
+    patch: { participants: without, ...syncTurnOrder(without) },
+    log: {
+      message: `${target.name} updated (initiative: ${merged.initiative})`,
+      undo,
+    },
+  };
 }
 
 // REMOVE_PARTICIPANT — verbatim from ParticipantManager.confirmDeleteParticipant
diff --git a/src/App.js b/src/App.js
index 186116c..c086a09 100644
--- a/src/App.js
+++ b/src/App.js
@@ -940,8 +940,14 @@ function ParticipantManager({ encounter, encounterPath, campaignCharacters }) {
     }
 
     try {
-      const { patch } = addParticipants(encounter, newParticipants);
+      const { patch, log } = addParticipants(encounter, newParticipants);
       await storage.updateDoc(encounterPath, patch);
+      if (log) {
+        logAction(log.message, { encounterName: encounter.name }, {
+          encounterPath,
+          updates: log.undo,
+        });
+      }
     } catch (err) {
       alert("Failed to add all characters. Please try again.");
     }
@@ -950,8 +956,14 @@ function ParticipantManager({ encounter, encounterPath, campaignCharacters }) {
   const handleUpdateParticipant = async (updatedData) => {
     if (!db || !editingParticipant) return;
     try {
-      const { patch } = updateParticipant(encounter, editingParticipant.id, updatedData);
+      const { patch, log } = updateParticipant(encounter, editingParticipant.id, updatedData);
       await storage.updateDoc(encounterPath, patch);
+      if (log) {
+        logAction(log.message, { encounterName: encounter.name }, {
+          encounterPath,
+          updates: log.undo,
+        });
+      }
       setEditingParticipant(null);
     } catch (err) {
       alert("Failed to update participant. Please try again.");
@@ -967,8 +979,14 @@ function ParticipantManager({ encounter, encounterPath, campaignCharacters }) {
     const n = parseInt(value, 10);
     if (isNaN(n)) return;
     try {
-      const { patch } = updateParticipant(encounter, participantId, { initiative: n });
+      const { patch, log } = updateParticipant(encounter, participantId, { initiative: n });
       await storage.updateDoc(encounterPath, patch);
+      if (log) {
+        logAction(log.message, { encounterName: encounter.name }, {
+          encounterPath,
+          updates: log.undo,
+        });
+      }
     } catch (err) {
       // fall through silently
     }