diff --git a/files/client/custom/modules/knowledge-base/res/templates/kb/index.tpl b/files/client/custom/modules/knowledge-base/res/templates/kb/index.tpl
index 8a9cc08..535c8e9 100644
--- a/files/client/custom/modules/knowledge-base/res/templates/kb/index.tpl
+++ b/files/client/custom/modules/knowledge-base/res/templates/kb/index.tpl
@@ -1,6 +1,13 @@
 <div class="kb-page" dir="rtl">
-    <div class="page-header">
-        <h3>בסיס ידע — ביטוח לאומי</h3>
+    <div class="page-header" style="display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:12px;">
+        <h3 style="margin:0;">בסיס ידע<span class="kb-topic-name-suffix"></span></h3>
+        <div class="kb-topic-picker" style="display:flex;align-items:center;gap:8px;">
+            <label for="kb-topic-select" class="text-muted" style="margin:0;font-weight:normal;">נושא:</label>
+            <select id="kb-topic-select" class="form-control kb-topic-select" data-name="topic"
+                    style="min-width:180px;">
+                <option value="">טוען…</option>
+            </select>
+        </div>
     </div>
 
     <ul class="nav nav-tabs" style="margin-bottom:12px;">
diff --git a/files/client/custom/modules/knowledge-base/src/views/kb/index.js b/files/client/custom/modules/knowledge-base/src/views/kb/index.js
index 57a21b0..5d27511 100644
--- a/files/client/custom/modules/knowledge-base/src/views/kb/index.js
+++ b/files/client/custom/modules/knowledge-base/src/views/kb/index.js
@@ -6,14 +6,17 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
     // it. sessionStorage backs the last completed answer so a hard reload
     // also recovers it. None of this leaks to the next browser session —
     // ask history is intentionally ephemeral.
-    let _activeAsk = null;     // {question, promise, startedAt} while in flight
-    let _lastAsk = null;       // {question, text, sources, completedAt} after success
-    let _activeSearch = null;  // {query, kind, promise} while in flight
-    let _lastSearch = null;    // {query, kind, hits, selectedIdx, completedAt}
+    let _activeAsk = null;     // {question, topicId, promise, startedAt} while in flight
+    let _lastAsk = null;       // {question, topicId, text, sources, completedAt} after success
+    let _activeSearch = null;  // {query, kind, topicId, promise} while in flight
+    let _lastSearch = null;    // {query, kind, topicId, hits, selectedIdx, completedAt}
+    let _topics = null;        // [{id, slug, name, description, is_active}]
+    let _topicsPromise = null; // dedupe concurrent fetches across mounts
 
     const SS_ASK = 'kb-last-ask';
     const SS_SEARCH = 'kb-last-search';
     const LS_SPLIT = 'kb-split-pct';   // long-lived UI preference (not session)
+    const LS_TOPIC = 'kb-topic';        // selected topic id, persists across sessions
     // Cached results auto-expire after this long. The user explicitly asked
     // for a clear button, but auto-clearing also handles the case where they
     // come back hours later and the prior result is no longer relevant.
@@ -46,6 +49,21 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
         _lastSearch = _loadJson(sessionStorage, SS_SEARCH, x => x && typeof x.query === 'string' && Array.isArray(x.hits));
     }
 
+    function _readPersistedTopicId() {
+        try {
+            const raw = localStorage.getItem(LS_TOPIC);
+            if (!raw) return null;
+            const v = parseInt(raw, 10);
+            return Number.isFinite(v) ? v : null;
+        } catch (e) { return null; }
+    }
+    function _writePersistedTopicId(id) {
+        try {
+            if (id == null) localStorage.removeItem(LS_TOPIC);
+            else localStorage.setItem(LS_TOPIC, String(id));
+        } catch (e) { /* ignore */ }
+    }
+
     return Dep.extend({
 
         template: 'knowledge-base:kb/index',
@@ -53,11 +71,13 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
         // Active mode: 'search' (default) | 'ask' | 'browse'
         mode: 'search',
         kind: 'any',
+        topicId: null,
 
         data: function () {
             return {
                 mode: this.mode,
                 kind: this.kind,
+                topicId: this.topicId,
             };
         },
 
@@ -91,6 +111,12 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
                 e.preventDefault();
                 this.clearResults();
             },
+            'change select[data-name="topic"]': function (e) {
+                const raw = $(e.currentTarget).val();
+                const id = parseInt(raw, 10);
+                if (!Number.isFinite(id) || id === this.topicId) return;
+                this.switchTopic(id);
+            },
         },
 
         // Cancel any in-flight ask/search, drop the cached last-result for
@@ -133,28 +159,150 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
             if (label && label !== 'KnowledgeBase') {
                 document.title = label;
             }
+
+            // Best-effort initial topic id from localStorage. Reconciled with
+            // the actual topics list once it loads (a stale id from a deleted
+            // topic falls back to the first active topic).
+            this.topicId = _readPersistedTopicId();
+
+            // Kick off the topics fetch before first render so the <select>
+            // can be populated in the first afterRender pass without flicker.
+            this._ensureTopicsLoaded();
+        },
+
+        _ensureSourcesLoaded: function () {
+            const self = this;
+            if (this._sources) {
+                this.renderSourcesList();
+                return;
+            }
+            if (this._sourcesPromise || this.topicId == null) return;
+            const topicAtFetch = this.topicId;
+            this._sourcesPromise = Espo.Ajax.getRequest('KnowledgeBase/action/sources', {topicId: topicAtFetch})
+                .then(res => {
+                    // Bail if the user switched topic before we landed.
+                    if (self.topicId !== topicAtFetch) return;
+                    self._sources = res.sources || [];
+                    self.renderSourcesList();
+                })
+                .catch(err => {
+                    console.error('KB: failed to load sources', err);
+                });
+        },
+
+        _ensureTopicsLoaded: function () {
+            if (_topics) return Promise.resolve(_topics);
+            if (_topicsPromise) return _topicsPromise;
+            _topicsPromise = Espo.Ajax.getRequest('KnowledgeBase/action/topics')
+                .then(res => {
+                    _topics = (res && res.topics) || [];
+                    return _topics;
+                })
+                .catch(err => {
+                    console.error('KB: failed to load topics', err);
+                    _topics = [];
+                    return _topics;
+                })
+                .finally(() => { _topicsPromise = null; });
+            return _topicsPromise;
+        },
+
+        // Replace the <select> options with the loaded topics, reconcile
+        // this.topicId against the active list, and fire afterRender's
+        // mode-specific render path now that scope is known.
+        _populateTopicPicker: function () {
+            const $sel = this.$el.find('.kb-topic-select');
+            if (!$sel.length || !_topics) return;
+            const topics = _topics.filter(t => t.is_active !== false);
+            if (!topics.length) {
+                $sel.html('<option value="">אין נושאים פעילים</option>');
+                return;
+            }
+            // Reconcile: drop persisted id if it's not in the list any more.
+            const ids = topics.map(t => t.id);
+            if (!ids.includes(this.topicId)) {
+                this.topicId = topics[0].id;
+                _writePersistedTopicId(this.topicId);
+            }
+            const opts = topics.map(t => {
+                const sel = t.id === this.topicId ? ' selected' : '';
+                return '<option value="' + t.id + '"' + sel + '>' +
+                    this.escape(t.name || ('#' + t.id)) + '</option>';
+            }).join('');
+            $sel.html(opts);
+            // Header suffix shows the active domain so the page title stays
+            // self-explanatory across topics.
+            const active = topics.find(t => t.id === this.topicId);
+            const $suffix = this.$el.find('.kb-topic-name-suffix');
+            if ($suffix.length) {
+                $suffix.text(active ? ' — ' + active.name : '');
+            }
+        },
+
+        // Called from the topic <select>'s change handler. Tear down anything
+        // scoped to the prior topic so cross-topic results never bleed in.
+        switchTopic: function (newTopicId) {
+            this.topicId = newTopicId;
+            _writePersistedTopicId(newTopicId);
+            // Invalidate everything scoped to the old topic.
+            _activeAsk = null;
+            _activeSearch = null;
+            _lastAsk = null;
+            _lastSearch = null;
+            _clear(sessionStorage, SS_ASK);
+            _clear(sessionStorage, SS_SEARCH);
+            this._sources = null;
+            this._sourcesPromise = null;
+            this.stopAskProgress();
+            this.setLoading(false);
+            this.$el.find('.kb-results').empty();
+            // Re-render the page so mode-specific markup picks up the new
+            // topic header. afterRender will re-fetch /sources for it.
+            this.reRender();
         },
 
         afterRender: function () {
-            // Load the source list up front so the browse tab is instant when
-            // the user clicks it.
-            if (!this._sourcesPromise) {
-                this._sourcesPromise = Espo.Ajax.getRequest('KnowledgeBase/action/sources')
-                    .then(res => {
-                        this._sources = res.sources || [];
-                        this.renderSourcesList();
-                    })
-                    .catch(err => {
-                        console.error('KB: failed to load sources', err);
-                    });
-            } else if (this._sources) {
-                this.renderSourcesList();
+            const self = this;
+
+            // Populate picker + scope-dependent fetches gate on topics being
+            // loaded so a stale localStorage id (deleted topic) doesn't fire
+            // a /sources?topicId=99 that 400s. Once topics resolve, the
+            // .then path reconciles this.topicId then runs the fetch.
+            const afterTopics = () => {
+                if (!self.$el || !self.$el.length) return;
+                self._populateTopicPicker();
+                self._ensureSourcesLoaded();
+            };
+            if (_topics) {
+                afterTopics();
+            } else {
+                this._ensureTopicsLoaded().then(afterTopics);
             }
 
             // Recover prior state across view remounts (user navigated away and
             // back). Active in-flight wins; otherwise replay the last result
             // from sessionStorage so the work the user already did doesn't
             // disappear behind a tab switch.
+            //
+            // CROSS-TOPIC GUARD: any cached state whose topicId doesn't match
+            // the current topic is silently dropped — its hits/answer were
+            // computed against a different domain.
+            if (_activeAsk && _activeAsk.topicId != null && _activeAsk.topicId !== this.topicId) {
+                try { if (_activeAsk.es) _activeAsk.es.close(); } catch (e) { /* ignore */ }
+                _activeAsk = null;
+            }
+            if (_lastAsk && _lastAsk.topicId != null && _lastAsk.topicId !== this.topicId) {
+                _lastAsk = null;
+                _clear(sessionStorage, SS_ASK);
+            }
+            if (_activeSearch && _activeSearch.topicId != null && _activeSearch.topicId !== this.topicId) {
+                _activeSearch = null;
+            }
+            if (_lastSearch && _lastSearch.topicId != null && _lastSearch.topicId !== this.topicId) {
+                _lastSearch = null;
+                _clear(sessionStorage, SS_SEARCH);
+            }
+
             if (this.mode === 'ask') {
                 if (_activeAsk) {
                     const $input = this.$el.find('input[data-name="query"]');
@@ -208,12 +356,14 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
             _clear(sessionStorage, SS_SEARCH);
 
             this.setLoading(true);
+            const topicId = this.topicId;
             const promise = Espo.Ajax.postRequest('KnowledgeBase/action/search', {
                 query: query,
                 kind: kind,
                 topK: 8,
+                topicId: topicId,
             });
-            _activeSearch = {query: query, kind: kind, promise: promise};
+            _activeSearch = {query: query, kind: kind, topicId: topicId, promise: promise};
             this._attachSearchHandlers(_activeSearch);
         },
 
@@ -224,6 +374,7 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
                 const entry = {
                     query: search.query,
                     kind: search.kind,
+                    topicId: search.topicId,
                     hits: hits,
                     selectedIdx: 0,
                     completedAt: Date.now(),
@@ -252,15 +403,20 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
             _clear(sessionStorage, SS_ASK);
 
             this.setLoading(true);
+            const topicId = this.topicId;
             // Streaming via Server-Sent Events. The browser opens an
             // EventSource against KnowledgeBaseAskStream which proxies
             // /kb/ask/stream on shira-hermes; one SSE event per agent step
             // (thinking, tool_start, tool_done) plus a final answer event.
-            const url = '?entryPoint=KnowledgeBaseAskStream&message='
+            let url = '?entryPoint=KnowledgeBaseAskStream&message='
                 + encodeURIComponent(message);
+            if (topicId != null) {
+                url += '&topicId=' + encodeURIComponent(topicId);
+            }
             const es = new EventSource(url);
             _activeAsk = {
                 question: message,
+                topicId: topicId,
                 es: es,
                 events: [],
                 startedAt: Date.now(),
@@ -286,6 +442,7 @@ define('modules/knowledge-base/views/kb/index', ['view'], function (Dep) {
                 if (data.type === 'answer') {
                     self._finishAsk(ask, {
                         question: ask.question,
+                        topicId: ask.topicId,
                         text: data.text || '',
                         sources: data.sources || [],
                         completedAt: Date.now(),
diff --git a/files/custom/Espo/Modules/KnowledgeBase/Controllers/KnowledgeBase.php b/files/custom/Espo/Modules/KnowledgeBase/Controllers/KnowledgeBase.php
index 0a325b4..48d7b03 100644
--- a/files/custom/Espo/Modules/KnowledgeBase/Controllers/KnowledgeBase.php
+++ b/files/custom/Espo/Modules/KnowledgeBase/Controllers/KnowledgeBase.php
@@ -42,6 +42,27 @@ class KnowledgeBase
         }
     }
 
+    /**
+     * Coerce a request-supplied topic id (string from query, int from JSON body)
+     * to int|null. Lets the upstream resolver decide what an unknown id means.
+     */
+    private function coerceTopicId($raw): ?int
+    {
+        if ($raw === null || $raw === '' || $raw === false) {
+            return null;
+        }
+        if (is_numeric($raw)) {
+            return (int) $raw;
+        }
+        return null;
+    }
+
+    public function getActionTopics(Request $request, Response $response): array
+    {
+        $this->checkAccess();
+        return $this->getService()->listTopics();
+    }
+
     public function postActionSearch(Request $request, Response $response): array
     {
         $this->checkAccess();
@@ -54,14 +75,17 @@ class KnowledgeBase
         return $this->getService()->search(
             trim($data->query),
             $data->kind ?? 'any',
-            (int) ($data->top_k ?? $data->topK ?? 8)
+            (int) ($data->top_k ?? $data->topK ?? 8),
+            $this->coerceTopicId($data->topicId ?? $data->topic_id ?? null)
         );
     }
 
     public function getActionSources(Request $request, Response $response): array
     {
         $this->checkAccess();
-        return $this->getService()->listSources();
+        return $this->getService()->listSources(
+            $this->coerceTopicId($request->getQueryParam('topicId'))
+        );
     }
 
     public function getActionChunks(Request $request, Response $response): array
@@ -93,7 +117,8 @@ class KnowledgeBase
         return $this->getService()->ask(
             trim($data->message),
             $data->conversationId ?? null,
-            $data->conversationHistory ?? []
+            $data->conversationHistory ?? [],
+            $this->coerceTopicId($data->topicId ?? $data->topic_id ?? null)
         );
     }
 }
diff --git a/files/custom/Espo/Modules/KnowledgeBase/EntryPoints/KnowledgeBaseAskStream.php b/files/custom/Espo/Modules/KnowledgeBase/EntryPoints/KnowledgeBaseAskStream.php
index 0059c7f..1033a00 100644
--- a/files/custom/Espo/Modules/KnowledgeBase/EntryPoints/KnowledgeBaseAskStream.php
+++ b/files/custom/Espo/Modules/KnowledgeBase/EntryPoints/KnowledgeBaseAskStream.php
@@ -46,6 +46,14 @@ class KnowledgeBaseAskStream implements EntryPoint
             throw new BadRequest('message is too long.');
         }
 
+        // Optional topic scope. EventSource is GET-only so the client passes
+        // it via ?topicId=N; we forward it as topic_id in the JSON body to
+        // /kb/ask/stream. Bad ints just become null and the upstream falls
+        // back to the lowest active topic.
+        $topicIdRaw = $request->getQueryParam('topicId');
+        $topicId = (is_string($topicIdRaw) && is_numeric($topicIdRaw))
+            ? (int) $topicIdRaw : null;
+
         $service = $this->injectableFactory->create(KnowledgeBaseService::class);
         try {
             $upstreamUrl = $service->getStreamingUrl('/kb/ask/stream');
@@ -77,7 +85,11 @@ class KnowledgeBaseAskStream implements EntryPoint
         // Defense in depth: same locked-down CSP we use for the PDF entry.
         header("Content-Security-Policy: default-src 'self'");
 
-        $payload = json_encode(['message' => $message], JSON_UNESCAPED_UNICODE);
+        $payloadArr = ['message' => $message];
+        if ($topicId !== null) {
+            $payloadArr['topic_id'] = $topicId;
+        }
+        $payload = json_encode($payloadArr, JSON_UNESCAPED_UNICODE);
 
         $ch = curl_init();
         curl_setopt_array($ch, [
diff --git a/files/custom/Espo/Modules/KnowledgeBase/Resources/routes.json b/files/custom/Espo/Modules/KnowledgeBase/Resources/routes.json
index 4b624ce..f411dbe 100644
--- a/files/custom/Espo/Modules/KnowledgeBase/Resources/routes.json
+++ b/files/custom/Espo/Modules/KnowledgeBase/Resources/routes.json
@@ -1,4 +1,12 @@
 [
+    {
+        "route": "/KnowledgeBase/action/topics",
+        "method": "get",
+        "params": {
+            "controller": "KnowledgeBase",
+            "action": "topics"
+        }
+    },
     {
         "route": "/KnowledgeBase/action/search",
         "method": "post",
diff --git a/files/custom/Espo/Modules/KnowledgeBase/Services/KnowledgeBaseService.php b/files/custom/Espo/Modules/KnowledgeBase/Services/KnowledgeBaseService.php
index 6bff3f8..bbc7aa9 100644
--- a/files/custom/Espo/Modules/KnowledgeBase/Services/KnowledgeBaseService.php
+++ b/files/custom/Espo/Modules/KnowledgeBase/Services/KnowledgeBaseService.php
@@ -29,23 +29,36 @@ class KnowledgeBaseService
         $this->log = $log;
     }
 
-    public function search(string $query, string $kind, int $topK): array
+    public function listTopics(): array
+    {
+        return $this->get('/kb/topics');
+    }
+
+    public function search(string $query, string $kind, int $topK, ?int $topicId = null): array
     {
         $topK = max(1, min(15, $topK));
         if (!in_array($kind, ['any', 'law', 'regulation', 'circular'], true)) {
             $kind = 'any';
         }
 
-        return $this->post('/kb/search', [
+        $payload = [
             'query' => $query,
             'kind' => $kind,
             'top_k' => $topK,
-        ]);
+        ];
+        if ($topicId !== null) {
+            $payload['topic_id'] = $topicId;
+        }
+        return $this->post('/kb/search', $payload);
     }
 
-    public function listSources(): array
+    public function listSources(?int $topicId = null): array
     {
-        return $this->get('/kb/sources');
+        $path = '/kb/sources';
+        if ($topicId !== null) {
+            $path .= '?topic_id=' . rawurlencode((string) $topicId);
+        }
+        return $this->get($path);
     }
 
     public function sourceChunks(int $sourceId, ?int $around = null, int $ctx = 2): array
@@ -57,13 +70,21 @@ class KnowledgeBaseService
         return $this->get($path);
     }
 
-    public function ask(string $message, ?string $conversationId, array $history): array
-    {
-        return $this->post('/kb/ask', [
+    public function ask(
+        string $message,
+        ?string $conversationId,
+        array $history,
+        ?int $topicId = null
+    ): array {
+        $payload = [
             'message' => $message,
             'conversation_id' => $conversationId,
             'conversation_history' => $history,
-        ]);
+        ];
+        if ($topicId !== null) {
+            $payload['topic_id'] = $topicId;
+        }
+        return $this->post('/kb/ask', $payload);
     }
 
     /**