diff --git a/rust/crates/mnote-web/browser/sidebar-page-settings-runtime.js b/rust/crates/mnote-web/browser/sidebar-page-settings-runtime.js
index 649dbfc1..b6fa6927 100644
--- a/rust/crates/mnote-web/browser/sidebar-page-settings-runtime.js
+++ b/rust/crates/mnote-web/browser/sidebar-page-settings-runtime.js
@@ -670,7 +670,7 @@ export function createSidebarPageSettingsRuntime(context) {
             '</div>' +
             '<div class="wolai-page-settings-index-actions">' +
               '<button type="button" data-knowledge-rag-action="refresh">刷新状态</button>' +
-              '<button type="button" data-knowledge-rag-action="ingest">索引来源</button>' +
+              '<button type="button" data-knowledge-rag-action="ingest">索引/重建来源</button>' +
               '<button type="button" data-knowledge-rag-action="prune">清除失效记录</button>' +
               '<button type="button" data-knowledge-rag-action="open-dashboard">打开 LightRAG</button>' +
             '</div>' +
@@ -1058,6 +1058,17 @@ export function createSidebarPageSettingsRuntime(context) {
     });
   }
 
+  function knowledgeRagIndexedRootValues() {
+    var status = currentKnowledgeRagSummary().status || {};
+    var registry = status.registry && typeof status.registry === 'object' ? status.registry : {};
+    var roots = Array.isArray(registry.indexedRoots) ? registry.indexedRoots : [];
+    return roots.map(function(root) {
+      return String(root && (root.rootRelativePath || root.root_relative_path) || '').trim();
+    }).filter(Boolean).filter(function(value, index, list) {
+      return list.indexOf(value) === index;
+    });
+  }
+
   function knowledgeRagCurrentFilter() {
     return pageUiState.knowledgeRagSourceFilter || 'attention';
   }
@@ -1503,11 +1514,12 @@ export function createSidebarPageSettingsRuntime(context) {
   async function ingestKnowledgeRagSources() {
     if (!knowledgeRagIsAvailable()) return;
     var sources = knowledgeRagSourceInputValues();
+    if (!sources.length) sources = knowledgeRagIndexedRootValues();
     if (!sources.length) {
       pageUiState.knowledgeRagSummary = Object.assign({}, currentKnowledgeRagSummary(), {
         scopeKey: knowledgeRagScopeKey(),
         loading: false,
-        error: '请先填写要索引的资料路径'
+        error: '请先填写要索引的资料路径，或保留至少一个已保存的索引范围'
       });
       renderKnowledgeRagSettings();
       return;
diff --git a/rust/crates/mnote-web/browser/sidebar-tree-runtime.js b/rust/crates/mnote-web/browser/sidebar-tree-runtime.js
index 4efabc66..a0037954 100644
--- a/rust/crates/mnote-web/browser/sidebar-tree-runtime.js
+++ b/rust/crates/mnote-web/browser/sidebar-tree-runtime.js
@@ -2135,12 +2135,12 @@ import { createSidebarPageSettingsRuntime } from './sidebar-page-settings-runtim
           '<div class="wolai-search-options-left">' +
             '<span class="wolai-search-switch-control"><span>仅匹配标题</span><button type="button" class="wolai-search-switch" data-search-switch="title" role="switch" aria-checked="false" aria-label="仅匹配标题"></button></span>' +
             '<span class="wolai-search-switch-control"><span>精确匹配</span><button type="button" class="wolai-search-switch" data-search-switch="exact" role="switch" aria-checked="false" aria-label="精确匹配"></button></span>' +
-            '<span class="wolai-search-sort-control"><span>资料库模式</span><select class="wolai-search-sort-value" data-search-knowledge-mode aria-label="资料库检索模式"><option value="mix">综合</option><option value="hybrid">图谱混合</option><option value="naive">向量</option><option value="local">实体</option><option value="global">关系</option><option value="exact">关键词</option></select></span>' +
+            '<span class="wolai-search-sort-control"><span>资料库模式</span><select class="wolai-search-sort-value" data-search-knowledge-mode aria-label="资料库检索模式"><option value="exact" selected>关键词</option><option value="mix">综合</option><option value="hybrid">图谱混合</option><option value="naive">向量</option><option value="local">实体</option><option value="global">关系</option></select></span>' +
             '<span class="wolai-search-sort-control"><span>按编辑时间</span><button type="button" class="wolai-search-sort-value" data-search-sort="updated" aria-label="按编辑时间范围">所有</button></span>' +
             '<span class="wolai-search-sort-control"><span>按创建时间</span><button type="button" class="wolai-search-sort-value" data-search-sort="created" aria-label="按创建时间范围">所有</button></span>' +
           '</div>' +
           '<div class="wolai-search-options-right">' +
-            '<span class="wolai-search-switch-control"><span>全盘资料库</span><button type="button" class="wolai-search-switch" data-search-switch="knowledge" role="switch" aria-checked="false" aria-label="全盘资料库检索"></button></span>' +
+            '<span class="wolai-search-switch-control"><span>全盘资料库</span><button type="button" class="wolai-search-switch is-on" data-search-switch="knowledge" role="switch" aria-checked="true" aria-label="全盘资料库检索"></button></span>' +
             '<span class="wolai-search-switch-control"><span>页面内搜索</span><button type="button" class="wolai-search-switch" data-search-switch="page" role="switch" aria-checked="false" aria-label="页面内搜索"></button></span>' +
             '<span class="wolai-search-switch-control"><span>折叠同来源</span><button type="button" class="wolai-search-switch is-on" data-search-switch="collapseSource" role="switch" aria-checked="true" aria-label="默认折叠相同来源结果"></button></span>' +
           '</div>' +
@@ -2152,7 +2152,9 @@ import { createSidebarPageSettingsRuntime } from './sidebar-page-settings-runtim
     document.body.appendChild(overlay);
     var input = overlay.querySelector('[data-testid="wolai-search-input"]');
     var closeButton = overlay.querySelector('[data-testid="wolai-search-close"]');
-    applySearchSwitchState(overlay, { collapseSource: readSearchCollapseSourcesDefault() });
+    applySearchSwitchState(overlay, { knowledge: true, collapseSource: readSearchCollapseSourcesDefault() });
+    var initialKnowledgeModeSelect = overlay.querySelector('[data-search-knowledge-mode]');
+    if (initialKnowledgeModeSelect && 'value' in initialKnowledgeModeSelect) initialKnowledgeModeSelect.value = 'exact';
     if (input) input.addEventListener('input', function() {
       searchUiState.hasRendered = false;
       scheduleSearchResultsRender();
@@ -2194,7 +2196,7 @@ import { createSidebarPageSettingsRuntime } from './sidebar-page-settings-runtim
     metaHtml: '',
     resultsHtml: '',
     items: [],
-    knowledgeMode: 'mix',
+    knowledgeMode: 'exact',
     sourceCollapsed: {},
     scrollTop: 0,
     signature: '',
@@ -2345,7 +2347,7 @@ import { createSidebarPageSettingsRuntime } from './sidebar-page-settings-runtim
     if (input && 'value' in input) input.value = searchUiState.query || '';
     applySearchSwitchState(overlay, searchUiState.switches);
     var knowledgeModeSelect = overlay.querySelector('[data-search-knowledge-mode]');
-    if (knowledgeModeSelect && 'value' in knowledgeModeSelect) knowledgeModeSelect.value = searchUiState.knowledgeMode || 'mix';
+    if (knowledgeModeSelect && 'value' in knowledgeModeSelect) knowledgeModeSelect.value = searchUiState.knowledgeMode || 'exact';
     if (options instanceof HTMLElement) options.hidden = !searchText(searchUiState.query);
     if (meta && searchUiState.metaHtml) meta.innerHTML = searchUiState.metaHtml;
     if (results && searchUiState.resultsHtml) {
diff --git a/rust/crates/mnote-web/src/routes/knowledge_rag.rs b/rust/crates/mnote-web/src/routes/knowledge_rag.rs
index 468c0955..5e77268c 100644
--- a/rust/crates/mnote-web/src/routes/knowledge_rag.rs
+++ b/rust/crates/mnote-web/src/routes/knowledge_rag.rs
@@ -369,7 +369,27 @@ pub async fn ingest(
     let mut expanded_count = 0usize;
     let mut seen_sources = BTreeSet::<String>::new();
     let force = body.force.unwrap_or(false);
-    for source in body.sources {
+    let mut requested_sources = body.sources;
+    if requested_sources.is_empty() {
+        requested_sources = registry
+            .indexed_roots
+            .iter()
+            .map(|root| KnowledgeRagSourceInput {
+                source_path: Some(root.root_relative_path.clone()),
+                path: None,
+                parser_hint: None,
+            })
+            .collect();
+    }
+    if requested_sources.is_empty() {
+        return Err(WebError::bad_request_code(
+            "knowledge_rag_source_required",
+            "资料库索引缺少 sourcePath，且没有可重建的已保存索引范围",
+        )
+        .with_context(&context));
+    }
+
+    for source in requested_sources {
         let source_path = source.source_path.or(source.path).ok_or_else(|| {
             WebError::bad_request_code("knowledge_rag_source_required", "资料库索引缺少 sourcePath")
                 .with_context(&context)
@@ -1087,7 +1107,8 @@ fn normalize_knowledge_rag_search_mode(mode: Option<&str>) -> String {
         Some("hybrid") => "hybrid".into(),
         Some("naive" | "vector") => "naive".into(),
         Some("mix" | "mixed") => "mix".into(),
-        _ => "mix".into(),
+        Some(_) => "mix".into(),
+        None => "exact".into(),
     }
 }
 
@@ -4718,7 +4739,7 @@ mod tests {
             normalize_knowledge_rag_search_mode(Some("hybrid")),
             "hybrid"
         );
-        assert_eq!(normalize_knowledge_rag_search_mode(None), "mix");
+        assert_eq!(normalize_knowledge_rag_search_mode(None), "exact");
     }
 
     #[test]
diff --git a/rust/crates/mnote-web/src/ssr/pages/layout.rs b/rust/crates/mnote-web/src/ssr/pages/layout.rs
index 335d018b..c2fe9efb 100644
--- a/rust/crates/mnote-web/src/ssr/pages/layout.rs
+++ b/rust/crates/mnote-web/src/ssr/pages/layout.rs
@@ -568,6 +568,11 @@ mod tests {
         assert!(SIDEBAR_TREE_RUNTIME_JS.contains("pruneKnowledgeRagRegistry"));
         assert!(SIDEBAR_TREE_RUNTIME_JS.contains("setKnowledgeRagSourceFilter"));
         assert!(SIDEBAR_TREE_RUNTIME_JS.contains("mnote:knowledge-rag-source-updated"));
+        assert!(
+            SIDEBAR_TREE_RUNTIME_JS.contains(r#"<option value="exact" selected>关键词</option>"#)
+        );
+        assert!(SIDEBAR_TREE_RUNTIME_JS
+            .contains(r#"data-search-switch="knowledge" role="switch" aria-checked="true""#));
         assert!(SIDEBAR_FILETREE_COMMAND_RUNTIME_JS.contains("knowledgeRagSourceRelativePath"));
         assert!(SIDEBAR_FILETREE_COMMAND_RUNTIME_JS.contains("supportsKnowledgeRagSource"));
         assert!(!SIDEBAR_FILETREE_COMMAND_RUNTIME_JS.contains("runLocalOcr"));