diff --git a/.env.example b/.env.example
index c834846..842b998 100644
--- a/.env.example
+++ b/.env.example
@@ -6,7 +6,10 @@ FETCH_INTERVAL_MINUTES=60
 AUTH_ENABLED=false
 AUTH_TENANT_ID=your-tenant-id
 AUTH_CLIENT_ID=your-api-client-id
-# Optional scope for SPA login (e.g., api://<client-id>/access_as_user)
+# API scope the SPA should request at login.
+# When set, the frontend acquires an access token for this scope (aud = AUTH_CLIENT_ID).
+# When empty, the frontend falls back to the idToken, which is also valid for the backend.
+# Example: api://cc31fd45-1eca-431f-a2c6-ba81cd4c5d50/.default
 AUTH_SCOPE=
 # Comma-separated lists (optional):
 AUTH_ALLOWED_ROLES=
diff --git a/backend/frontend/index.html b/backend/frontend/index.html
index eddb63c..f0a2ecf 100644
--- a/backend/frontend/index.html
+++ b/backend/frontend/index.html
@@ -4,7 +4,7 @@
   <meta charset="UTF-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
   <title>AOC Events</title>
-  <link rel="stylesheet" href="/style.css" />
+  <link rel="stylesheet" href="/style.css?v=7" />
   <script defer src="https://cdn.jsdelivr.net/npm/alpinejs@3.x.x/dist/cdn.min.js"></script>
   <script src="https://alcdn.msauth.net/browser/2.37.0/js/msal-browser.min.js" crossorigin="anonymous"></script>
 </head>
@@ -29,8 +29,10 @@
         <template x-for="src in sourceHealth" :key="src.source">
           <div class="health-card">
             <strong x-text="src.source"></strong>
-            <span class="pill" :class="src.status === 'healthy' ? 'pill--ok' : 'pill--warn'" x-text="src.status"></span>
-            <small x-text="src.last_fetch_time ? new Date(src.last_fetch_time).toLocaleString() : 'Never'"></small>
+            <span class="pill"
+              :class="src.status === 'healthy' ? 'pill--ok' : (src.status === 'error' ? 'pill--err' : 'pill--warn')"
+              x-text="src.status"></span>
+            <small x-text="src.last_fetch_time ? new Date(src.last_fetch_time).toLocaleString() : (src.last_attempt_time ? new Date(src.last_attempt_time).toLocaleString() : 'Never')"></small>
           </div>
         </template>
       </div>
@@ -38,55 +40,73 @@
 
     <section class="panel">
       <form id="filters" class="filters" @submit.prevent="resetPagination(); loadEvents()">
-        <label>
-          User (name/UPN)
-          <input name="actor" type="text" placeholder="tomas@contoso.com" list="actorOptions" x-model="filters.actor" />
-          <datalist id="actorOptions">
-            <template x-for="opt in options.actors" :key="opt"><option :value="opt"></option></template>
-          </datalist>
-        </label>
-        <label>
-          App / Service
-          <input name="service" type="text" placeholder="DirectoryManagement" list="serviceOptions" x-model="filters.service" />
-          <datalist id="serviceOptions">
-            <template x-for="opt in options.services" :key="opt"><option :value="opt"></option></template>
-          </datalist>
-        </label>
-        <label>
-          Search (raw/full-text)
-          <input name="search" type="text" placeholder="Any text to search in raw/summary" x-model="filters.search" />
-        </label>
-        <label>
-          Action (display name)
-          <input name="operation" type="text" placeholder="Add group member" list="operationOptions" x-model="filters.operation" />
-          <datalist id="operationOptions">
-            <template x-for="opt in options.operations" :key="opt"><option :value="opt"></option></template>
-          </datalist>
-        </label>
-        <label>
-          Action type (result)
-          <input name="result" type="text" placeholder="success / failure" list="resultOptions" x-model="filters.result" />
-          <datalist id="resultOptions">
-            <template x-for="opt in options.results" :key="opt"><option :value="opt"></option></template>
-          </datalist>
-        </label>
-        <label>
-          From
-          <input name="start" type="datetime-local" x-model="filters.start" />
-        </label>
-        <label>
-          To
-          <input name="end" type="datetime-local" x-model="filters.end" />
-        </label>
-        <label>
-          Limit
-          <input name="limit" type="number" min="1" max="500" value="100" x-model.number="filters.limit" />
-        </label>
-        <div class="actions">
-          <button type="submit">Apply filters</button>
-          <button type="button" id="clearBtn" class="ghost" @click="clearFilters()">Clear</button>
-          <button type="button" class="ghost" @click="exportJSON()">Export JSON</button>
-          <button type="button" class="ghost" @click="exportCSV()">Export CSV</button>
+        <div class="filter-row">
+          <label>
+            User (name/UPN)
+            <input name="actor" type="text" placeholder="tomas@contoso.com" list="actorOptions" x-model="filters.actor" />
+            <datalist id="actorOptions">
+              <template x-for="opt in options.actors" :key="opt"><option :value="opt"></option></template>
+            </datalist>
+          </label>
+          <label>
+            Action (display name)
+            <input name="operation" type="text" placeholder="Add group member" list="operationOptions" x-model="filters.operation" />
+            <datalist id="operationOptions">
+              <template x-for="opt in options.operations" :key="opt"><option :value="opt"></option></template>
+            </datalist>
+          </label>
+          <label>
+            Action type (result)
+            <input name="result" type="text" placeholder="success / failure" list="resultOptions" x-model="filters.result" />
+            <datalist id="resultOptions">
+              <template x-for="opt in options.results" :key="opt"><option :value="opt"></option></template>
+            </datalist>
+          </label>
+          <label>
+            Limit
+            <input name="limit" type="number" min="1" max="500" value="100" x-model.number="filters.limit" />
+          </label>
+        </div>
+        <div class="filter-row">
+          <label>
+            From
+            <input name="start" type="datetime-local" x-model="filters.start" />
+          </label>
+          <label>
+            To
+            <input name="end" type="datetime-local" x-model="filters.end" />
+          </label>
+          <label class="span-2">
+            Search (raw/full-text)
+            <input name="search" type="text" placeholder="Any text to search in raw/summary" x-model="filters.search" />
+          </label>
+        </div>
+        <div class="filter-row filter-row--tall">
+          <div class="filter-group span-2">
+            <span>App / Service</span>
+            <div class="multi-select">
+              <div class="multi-select__actions">
+                <button type="button" class="link" @click="filters.selectedServices = [...options.services]">All</button>
+                <button type="button" class="link" @click="filters.selectedServices = []">None</button>
+              </div>
+              <div class="multi-select__options">
+                <template x-for="opt in options.services" :key="opt">
+                  <label class="checkbox-label">
+                    <input type="checkbox" :value="opt" x-model="filters.selectedServices" />
+                    <span x-text="opt"></span>
+                  </label>
+                </template>
+              </div>
+            </div>
+          </div>
+        </div>
+        <div class="filter-row actions-row">
+          <div class="actions">
+            <button type="submit">Apply filters</button>
+            <button type="button" id="clearBtn" class="ghost" @click="clearFilters()">Clear</button>
+            <button type="button" class="ghost" @click="exportJSON()">Export JSON</button>
+            <button type="button" class="ghost" @click="exportCSV()">Export CSV</button>
+          </div>
         </div>
       </form>
     </section>
@@ -98,35 +118,35 @@
       </div>
       <div id="status" class="status" aria-live="polite" x-text="statusText"></div>
       <div id="events" class="events">
-        <template x-for="(e, idx) in events" :key="e._id || e.id || idx">
+        <template x-for="(evt, idx) in events" :key="evt._id || evt.id || idx">
           <article class="event">
             <div class="event__meta">
-              <span class="pill" x-text="e.display_category || e.service || '—'"></span>
-              <span class="pill" :class="(e.result || '').toLowerCase() === 'success' ? 'pill--ok' : 'pill--warn'" x-text="e.result || '—'"></span>
+              <span class="pill" x-text="evt.display_category || evt.service || '—'"></span>
+              <span class="pill" :class="['success','succeeded','ok','passed'].includes((evt.result || '').toLowerCase()) ? 'pill--ok' : 'pill--warn'" x-text="evt.result || '—'"></span>
             </div>
-            <h3 x-text="e.operation || '—'"></h3>
-            <p class="event__detail" x-show="e.display_summary"><strong>Summary:</strong> <span x-text="e.display_summary"></span></p>
-            <p class="event__detail"><strong x-text="e.display_actor_label || 'User'"></strong>: <span x-text="displayActor(e)"></span></p>
-            <p class="event__detail" x-show="e.actor_owner_names && e.actor_owner_names.length"><strong>App owners:</strong> <span x-text="(e.actor_owner_names || []).slice(0,3).join(', ')"></span></p>
-            <p class="event__detail"><strong>Target:</strong> <span x-text="displayTargets(e)"></span></p>
-            <p class="event__detail"><strong>When:</strong> <span x-text="e.timestamp ? new Date(e.timestamp).toLocaleString() : '—'"></span></p>
+            <h3 x-text="evt.operation || '—'"></h3>
+            <p class="event__detail" x-show="evt.display_summary"><strong>Summary:</strong> <span x-text="evt.display_summary"></span></p>
+            <p class="event__detail"><strong x-text="evt.display_actor_label || 'User'"></strong>: <span x-text="displayActor(evt)"></span></p>
+            <p class="event__detail" x-show="evt.actor_owner_names && evt.actor_owner_names.length"><strong>App owners:</strong> <span x-text="(evt.actor_owner_names || []).slice(0,3).join(', ')"></span></p>
+            <p class="event__detail"><strong>Target:</strong> <span x-text="displayTargets(evt)"></span></p>
+            <p class="event__detail"><strong>When:</strong> <span x-text="evt.timestamp ? new Date(evt.timestamp).toLocaleString() : '—'"></span></p>
 
-            <div class="event__tags" x-show="e.tags && e.tags.length">
-              <template x-for="tag in (e.tags || [])" :key="tag">
+            <div class="event__tags" x-show="evt.tags && evt.tags.length">
+              <template x-for="tag in (evt.tags || [])" :key="tag">
                 <span class="pill pill--tag" x-text="tag"></span>
               </template>
             </div>
 
-            <div class="event__comments" x-show="e.comments && e.comments.length">
-              <template x-for="c in (e.comments || [])" :key="c.timestamp + c.text">
+            <div class="event__comments" x-show="evt.comments && evt.comments.length">
+              <template x-for="c in (evt.comments || [])" :key="c.timestamp + c.text">
                 <p class="comment"><strong x-text="c.author"></strong>: <span x-text="c.text"></span> <small x-text="new Date(c.timestamp).toLocaleString()"></small></p>
               </template>
             </div>
 
             <div class="event__actions">
-              <button class="ghost" @click="openModal(e)">View raw event</button>
-              <input type="text" placeholder="Add tag" @keydown.enter="addTag(e, $event.target.value); $event.target.value=''" />
-              <input type="text" placeholder="Add comment" @keydown.enter="addComment(e, $event.target.value); $event.target.value=''" />
+              <button type="button" class="ghost" @click="openModal(evt)">View raw event</button>
+              <input type="text" placeholder="Add tag" @keydown.enter="addTag(evt, $event.target.value); $event.target.value=''" />
+              <input type="text" placeholder="Add comment" @keydown.enter="addComment(evt, $event.target.value); $event.target.value=''" />
             </div>
           </article>
         </template>
@@ -137,15 +157,15 @@
         <button type="button" id="nextPage" :disabled="!nextCursor" @click="goNext()">Next</button>
       </div>
     </section>
-  </div>
 
-  <div id="modal" class="modal hidden" role="dialog" aria-modal="true" aria-labelledby="modalTitle" :class="{ 'hidden': !modalOpen }">
-    <div class="modal__content">
-      <div class="modal__header">
-        <h3 id="modalTitle">Raw Event</h3>
-        <button type="button" id="closeModal" class="ghost" @click="modalOpen = false">Close</button>
+    <div id="modal" class="modal hidden" role="dialog" aria-modal="true" aria-labelledby="modalTitle" :class="{ 'hidden': !modalOpen }">
+      <div class="modal__content">
+        <div class="modal__header">
+          <h3 id="modalTitle">Raw Event</h3>
+          <button type="button" id="closeModal" class="ghost" @click="modalOpen = false">Close</button>
+        </div>
+        <pre id="modalBody" x-text="modalBody"></pre>
       </div>
-      <pre id="modalBody" x-text="modalBody"></pre>
     </div>
   </div>
 
@@ -168,7 +188,7 @@
         accessToken: null,
         authScopes: [],
         filters: {
-          actor: '', service: '', search: '', operation: '', result: '', start: '', end: '', limit: 100,
+          actor: '', selectedServices: [], search: '', operation: '', result: '', start: '', end: '', limit: 100,
         },
         options: { actors: [], services: [], operations: [], results: [] },
 
@@ -186,7 +206,21 @@
         },
 
         pickToken(res) {
-          return res ? (res.accessToken || res.idToken || null) : null;
+          if (!res) return null;
+          const clientId = this.authConfig?.client_id;
+          // If accessToken is present and its audience matches our API, use it.
+          if (res.accessToken && clientId) {
+            try {
+              const base64 = res.accessToken.split('.')[1].replace(/-/g, '+').replace(/_/g, '/');
+              const padded = base64.padEnd(base64.length + (4 - base64.length % 4) % 4, '=');
+              const payload = JSON.parse(atob(padded));
+              if (payload.aud === clientId) {
+                return res.accessToken;
+              }
+            } catch {}
+          }
+          // Fall back to idToken (always aud=clientId) or accessToken
+          return res.idToken || res.accessToken || null;
         },
 
         async initAuth() {
@@ -279,10 +313,13 @@
         async loadEvents(cursor) {
           this.currentCursor = cursor || null;
           const params = new URLSearchParams();
-          ['actor', 'service', 'operation', 'result', 'search'].forEach((key) => {
+          ['actor', 'operation', 'result', 'search'].forEach((key) => {
             const val = this.filters[key];
             if (val) params.append(key, val);
           });
+          if (this.filters.selectedServices && this.filters.selectedServices.length) {
+            this.filters.selectedServices.forEach((s) => params.append('services', s));
+          }
           if (this.filters.start) {
             const d = new Date(this.filters.start);
             if (!isNaN(d.getTime())) params.append('start', d.toISOString());
@@ -345,6 +382,9 @@
             this.options.services = (opts.services || []).slice(0, 200);
             this.options.operations = (opts.operations || []).slice(0, 200);
             this.options.results = (opts.results || []).slice(0, 200);
+            if (!this.filters.selectedServices.length && this.options.services.length) {
+              this.filters.selectedServices = [...this.options.services];
+            }
           } catch {}
         },
 
@@ -377,12 +417,14 @@
         },
 
         clearFilters() {
-          this.filters = { actor: '', service: '', search: '', operation: '', result: '', start: '', end: '', limit: 100 };
+          this.filters = { actor: '', selectedServices: [...this.options.services], search: '', operation: '', result: '', start: '', end: '', limit: 100 };
           this.resetPagination();
           this.loadEvents();
         },
 
         displayActor(e) {
+          const app = e.actor?.application || e.actor?.app;
+          if (app?.displayName) return app.displayName;
           return e.actor_display ||
             (e.actor_resolved?.name) ||
             (e.actor?.user?.displayName && e.actor?.user?.userPrincipalName && e.actor?.user?.displayName !== e.actor?.user?.userPrincipalName
@@ -399,7 +441,18 @@
         },
 
         openModal(e) {
-          this.modalBody = JSON.stringify(e.raw || e, null, 2);
+          const seen = new WeakSet();
+          try {
+            this.modalBody = JSON.stringify(e.raw || e, (key, value) => {
+              if (typeof value === 'object' && value !== null) {
+                if (seen.has(value)) return '[Circular]';
+                seen.add(value);
+              }
+              return value;
+            }, 2);
+          } catch (err) {
+            this.modalBody = `Error serializing event:\n${err.message}\n\nEvent ID: ${e.id || 'N/A'}`;
+          }
           this.modalOpen = true;
         },
 
diff --git a/backend/frontend/style.css b/backend/frontend/style.css
index a2b71ad..e9afb2c 100644
--- a/backend/frontend/style.css
+++ b/backend/frontend/style.css
@@ -91,12 +91,51 @@ button.ghost {
 }
 
 .filters {
-  display: grid;
-  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
+  display: flex;
+  flex-direction: column;
   gap: 14px;
 }
 
-.filters label {
+.filter-row {
+  display: grid;
+  grid-template-columns: repeat(4, 1fr);
+  gap: 14px;
+  align-items: start;
+}
+
+.filter-row .span-2 {
+  grid-column: span 2;
+}
+
+.filter-row--tall {
+  align-items: stretch;
+}
+
+.actions-row {
+  display: flex;
+  justify-content: flex-start;
+}
+
+@media (max-width: 900px) {
+  .filter-row {
+    grid-template-columns: repeat(2, 1fr);
+  }
+  .filter-row .span-2 {
+    grid-column: span 2;
+  }
+}
+
+@media (max-width: 480px) {
+  .filter-row {
+    grid-template-columns: 1fr;
+  }
+  .filter-row .span-2 {
+    grid-column: span 1;
+  }
+}
+
+.filters label,
+.filter-group {
   display: flex;
   flex-direction: column;
   gap: 6px;
@@ -159,7 +198,7 @@ input {
 
 .events {
   display: grid;
-  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
+  grid-template-columns: repeat(auto-fit, minmax(min(260px, 100%), 1fr));
   gap: 12px;
 }
 
@@ -168,6 +207,8 @@ input {
   border-radius: 14px;
   padding: 14px;
   background: rgba(255, 255, 255, 0.02);
+  min-width: 0;
+  overflow-wrap: break-word;
 }
 
 .event__meta {
@@ -175,16 +216,19 @@ input {
   gap: 8px;
   align-items: center;
   margin-bottom: 8px;
+  flex-wrap: wrap;
 }
 
 .pill {
   display: inline-block;
-  padding: 6px 10px;
+  padding: 5px 10px;
   border-radius: 999px;
   background: rgba(125, 211, 252, 0.12);
   border: 1px solid rgba(125, 211, 252, 0.4);
   color: var(--text);
   font-size: 12px;
+  max-width: 100%;
+  overflow-wrap: break-word;
 }
 
 .pill--ok {
@@ -197,8 +241,17 @@ input {
   border-color: rgba(249, 115, 22, 0.5);
 }
 
+.pill--err {
+  background: rgba(239, 68, 68, 0.15);
+  border-color: rgba(239, 68, 68, 0.5);
+}
+
 .event h3 {
   margin: 0 0 6px;
+  font-size: 17px;
+  line-height: 1.25;
+  overflow-wrap: break-word;
+  word-break: break-word;
 }
 
 .event__detail {
@@ -211,6 +264,71 @@ input {
   margin-top: 10px;
 }
 
+.multi-select {
+  border: 1px solid var(--border);
+  border-radius: 10px;
+  background: rgba(255, 255, 255, 0.02);
+  overflow: hidden;
+}
+
+.multi-select__actions {
+  display: flex;
+  gap: 12px;
+  padding: 6px 10px;
+  border-bottom: 1px solid var(--border);
+  background: rgba(255, 255, 255, 0.03);
+}
+
+.multi-select__actions .link {
+  background: none;
+  border: none;
+  color: var(--accent-strong);
+  font-size: 12px;
+  padding: 0;
+  cursor: pointer;
+  font-weight: 500;
+  box-shadow: none;
+}
+
+.multi-select__actions .link:hover {
+  text-decoration: underline;
+}
+
+.multi-select__options {
+  max-height: 140px;
+  overflow-y: auto;
+  display: flex;
+  flex-direction: column;
+}
+
+.checkbox-label {
+  display: flex !important;
+  flex-direction: row !important;
+  align-items: center !important;
+  gap: 8px;
+  padding: 6px 10px;
+  font-size: 13px;
+  color: var(--text);
+  cursor: pointer;
+  border-bottom: 1px solid rgba(255, 255, 255, 0.04);
+}
+
+.checkbox-label:last-child {
+  border-bottom: none;
+}
+
+.checkbox-label:hover {
+  background: rgba(255, 255, 255, 0.04);
+}
+
+.checkbox-label input[type="checkbox"] {
+  accent-color: var(--accent-strong);
+  width: 14px;
+  height: 14px;
+  flex-shrink: 0;
+  margin: 0;
+}
+
 .modal {
   position: fixed;
   inset: 0;
diff --git a/backend/main.py b/backend/main.py
index 2167d01..a47255d 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -69,6 +69,17 @@ async def prometheus_middleware(request: Request, call_next):
     return response
 
 
+@app.middleware("http")
+async def cache_control_middleware(request: Request, call_next):
+    response = await call_next(request)
+    # Prevent caching of HTML and API responses by default
+    if request.url.path.startswith("/api/") or request.url.path in ("/", "/index.html"):
+        response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
+        response.headers["Pragma"] = "no-cache"
+        response.headers["Expires"] = "0"
+    return response
+
+
 @app.middleware("http")
 async def audit_middleware(request: Request, call_next):
     response = await call_next(request)
diff --git a/backend/models/api.py b/backend/models/api.py
index 3830988..35d816b 100644
--- a/backend/models/api.py
+++ b/backend/models/api.py
@@ -46,6 +46,7 @@ class FetchAuditLogsResponse(BaseModel):
 class SourceHealthResponse(BaseModel):
     source: str
     last_fetch_time: str | None = None
+    last_attempt_time: str | None = None
     status: str
 
 
diff --git a/backend/models/event_model.py b/backend/models/event_model.py
index ad02f36..1a7aa29 100644
--- a/backend/models/event_model.py
+++ b/backend/models/event_model.py
@@ -28,9 +28,11 @@ def _actor_display(actor: dict, resolved: dict = None, owners=None) -> str:
     user = actor.get("user", {}) or {}
     sp = actor.get("servicePrincipal", {}) or {}
     app = actor.get("app", {}) or {}
+    application = actor.get("application", {}) or {}
     upn = user.get("userPrincipalName") or user.get("mail")
     display = user.get("displayName")
-    app_display = app.get("displayName")
+    app_display = app.get("displayName") or application.get("displayName")
+    app_id = app.get("id") or application.get("id")
 
     if display and upn and display != upn:
         return f"{display} ({upn})"
@@ -41,6 +43,7 @@ def _actor_display(actor: dict, resolved: dict = None, owners=None) -> str:
         or app_display
         or sp.get("displayName")
         or sp.get("appId")
+        or app_id
         or actor.get("ipAddress")
         or user.get("id")
         or sp.get("id")
@@ -164,7 +167,8 @@ def normalize_event(e):
 
     display_conf = display_mapping.get(category) or display_mapping.get("default", {})
     actor_field_pref = display_conf.get("actor_field", "actor_display")
-    actor_label_text = display_conf.get("actor_label", "User")
+    default_actor_label = "Application" if (actor.get("application") or actor.get("app")) else "User"
+    actor_label_text = display_conf.get("actor_label", default_actor_label)
 
     if actor_field_pref == "actor_upn" and actor_upn:
         display_actor_value = actor_upn
diff --git a/backend/routes/events.py b/backend/routes/events.py
index 62191b3..a026fd6 100644
--- a/backend/routes/events.py
+++ b/backend/routes/events.py
@@ -34,6 +34,7 @@ def _decode_cursor(cursor: str) -> tuple[str, str]:
 @router.get("/events", response_model=PaginatedEventResponse)
 def list_events(
     service: str | None = None,
+    services: list[str] | None = Query(default=None),
     actor: str | None = None,
     operation: str | None = None,
     result: str | None = None,
@@ -48,6 +49,8 @@ def list_events(
 
     if service:
         filters.append({"service": service})
+    if services:
+        filters.append({"service": {"$in": services}})
     if actor:
         actor_safe = re.escape(actor)
         filters.append(
diff --git a/backend/routes/fetch.py b/backend/routes/fetch.py
index eed63e2..9fe0a70 100644
--- a/backend/routes/fetch.py
+++ b/backend/routes/fetch.py
@@ -31,12 +31,13 @@ def run_fetch(hours: int = 168):
         try:
             since = get_watermark(source_key)
             result = fn(since=since) if since else fn(hours=window)
-            set_watermark(source_key, now)
+            set_watermark(source_key, now, status="healthy")
             track_fetch(source_key, len(result))
             return result
         except Exception as exc:
             errors.append(f"{label}: {exc}")
             track_fetch_error(source_key)
+            set_watermark(source_key, now, status="error")
             return []
         finally:
             track_fetch_duration(source_key, time.time() - start_time)
diff --git a/backend/routes/health.py b/backend/routes/health.py
index d9227a0..608850b 100644
--- a/backend/routes/health.py
+++ b/backend/routes/health.py
@@ -15,16 +15,21 @@ def source_health():
     results = []
     for source in SOURCES:
         doc = watermarks_collection.find_one({"source": source})
-        if doc and doc.get("last_fetch_time"):
+        if doc:
+            status = doc.get("status")
+            if not status:
+                status = "healthy" if doc.get("last_fetch_time") else "unknown"
             results.append({
                 "source": source,
-                "last_fetch_time": doc["last_fetch_time"],
-                "status": "healthy",
+                "last_fetch_time": doc.get("last_fetch_time"),
+                "last_attempt_time": doc.get("last_attempt_time"),
+                "status": status,
             })
         else:
             results.append({
                 "source": source,
                 "last_fetch_time": None,
+                "last_attempt_time": None,
                 "status": "unknown",
             })
     return results
diff --git a/backend/sources/intune_audit.py b/backend/sources/intune_audit.py
index 2afcd6c..8e8f9ea 100644
--- a/backend/sources/intune_audit.py
+++ b/backend/sources/intune_audit.py
@@ -45,20 +45,27 @@ def _normalize_intune(e: dict) -> dict:
     actor = e.get("actor", {}) or {}
     target = e.get("resources", [{}])[0] if e.get("resources") else {}
 
+    initiated_by: dict = {"user": {}}
+    if actor.get("auditActorType") == "Application" or actor.get("applicationDisplayName"):
+        initiated_by["application"] = {
+            "id": actor.get("applicationId"),
+            "displayName": actor.get("applicationDisplayName"),
+        }
+    else:
+        initiated_by["user"] = {
+            "id": actor.get("userId"),
+            "userPrincipalName": actor.get("userPrincipalName"),
+            "displayName": actor.get("userName"),
+            "ipAddress": actor.get("ipAddress"),
+        }
+
     return {
         "id": e.get("id"),
         "activityDateTime": e.get("activityDateTime"),
         "category": e.get("category") or "Intune",
         "activityDisplayName": e.get("activity") or e.get("activityType"),
         "result": e.get("activityResult") or e.get("result"),
-        "initiatedBy": {
-            "user": {
-                "id": actor.get("userId"),
-                "userPrincipalName": actor.get("userPrincipalName"),
-                "displayName": actor.get("userName"),
-                "ipAddress": actor.get("ipAddress"),
-            }
-        },
+        "initiatedBy": initiated_by,
         "targetResources": [
             {
                 "id": target.get("id"),
diff --git a/backend/tests/test_api.py b/backend/tests/test_api.py
index 1b76a81..02041ee 100644
--- a/backend/tests/test_api.py
+++ b/backend/tests/test_api.py
@@ -73,6 +73,42 @@ def test_list_events_filter_by_service(client, mock_events_collection):
     assert data["items"][0]["service"] == "Exchange"
 
 
+def test_list_events_filter_by_services(client, mock_events_collection):
+    mock_events_collection.insert_one({
+        "id": "evt-1",
+        "timestamp": datetime.now(UTC).isoformat(),
+        "service": "Exchange",
+        "operation": "Update",
+        "result": "success",
+        "actor_display": "Alice",
+        "raw_text": "",
+    })
+    mock_events_collection.insert_one({
+        "id": "evt-2",
+        "timestamp": datetime.now(UTC).isoformat(),
+        "service": "Directory",
+        "operation": "Add",
+        "result": "success",
+        "actor_display": "Bob",
+        "raw_text": "",
+    })
+    mock_events_collection.insert_one({
+        "id": "evt-3",
+        "timestamp": datetime.now(UTC).isoformat(),
+        "service": "Teams",
+        "operation": "Delete",
+        "result": "success",
+        "actor_display": "Charlie",
+        "raw_text": "",
+    })
+    response = client.get("/api/events?service=Exchange&service=Directory")
+    assert response.status_code == 200
+    data = response.json()
+    assert len(data["items"]) == 2
+    returned_services = {item["service"] for item in data["items"]}
+    assert returned_services == {"Exchange", "Directory"}
+
+
 def test_list_events_page_size_validation(client):
     response = client.get("/api/events?page_size=0")
     assert response.status_code == 422
diff --git a/backend/watermark.py b/backend/watermark.py
index 9001f6f..a4a238a 100644
--- a/backend/watermark.py
+++ b/backend/watermark.py
@@ -9,10 +9,15 @@ def get_watermark(source: str) -> str | None:
     return doc.get("last_fetch_time") if doc else None
 
 
-def set_watermark(source: str, timestamp: str):
-    """Persist the latest successful fetch timestamp for a source."""
+def set_watermark(source: str, timestamp: str, status: str | None = None):
+    """Persist the latest fetch attempt timestamp and optional status for a source."""
+    doc: dict = {"last_attempt_time": timestamp}
+    if status == "healthy":
+        doc["last_fetch_time"] = timestamp
+    if status:
+        doc["status"] = status
     watermarks_collection.update_one(
         {"source": source},
-        {"$set": {"last_fetch_time": timestamp}},
+        {"$set": doc},
         upsert=True,
     )