diff --git a/backend/main.py b/backend/main.py
index 9550d55..d5526f3 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -17,6 +17,7 @@ from backend.indexer import (
     reload_index,
     index,
     get_vault_data,
+    get_vault_names,
     find_file_in_index,
     parse_markdown_file,
     _extract_tags,
@@ -120,10 +121,20 @@ class TagsResponse(BaseModel):
     tags: Dict[str, int]
 
 
-class ReloadResponse(BaseModel):
-    """Index reload confirmation with per-vault stats."""
-    status: str
-    vaults: Dict[str, Any]
+class TreeSearchResult(BaseModel):
+    """A single tree search result item."""
+    vault: str
+    path: str
+    name: str
+    type: str = Field(description="'file' or 'directory'")
+    matched_path: str
+
+
+class TreeSearchResponse(BaseModel):
+    """Tree search response with matching paths."""
+    query: str
+    vault_filter: str
+    results: List[TreeSearchResult]
 
 
 class HealthResponse(BaseModel):
@@ -588,6 +599,74 @@ async def api_tags(vault: Optional[str] = Query(None, description="Vault filter"
     return {"vault_filter": vault, "tags": tags}
 
 
+@app.get("/api/tree-search", response_model=TreeSearchResponse)
+async def api_tree_search(
+    q: str = Query("", description="Search query"),
+    vault: str = Query("all", description="Vault filter"),
+):
+    """Search for files and directories in the tree structure.
+    
+    Searches through the file index for matching paths, returning
+    both files and their parent directories that match the query.
+    
+    Args:
+        q: Search string to match against file/directory paths.
+        vault: Vault name or "all" to search everywhere.
+        
+    Returns:
+        ``TreeSearchResponse`` with matching paths and their parent directories.
+    """
+    if not q:
+        return {"query": q, "vault_filter": vault, "results": []}
+    
+    query_lower = q.lower()
+    results = []
+    seen_paths = set()  # Avoid duplicates
+    
+    vaults_to_search = [vault] if vault != "all" else list(index.keys())
+    
+    for vault_name in vaults_to_search:
+        vault_data = get_vault_data(vault_name)
+        if not vault_data:
+            continue
+            
+        vault_root = Path(vault_data["path"])
+        if not vault_root.exists():
+            continue
+        
+        for fpath in vault_root.rglob("*"):
+            if fpath.name.startswith("."):
+                continue
+
+            try:
+                rel_path = str(fpath.relative_to(vault_root)).replace("\\", "/")
+                path_lower = rel_path.lower()
+                name_lower = fpath.name.lower()
+
+                if query_lower not in name_lower and query_lower not in path_lower:
+                    continue
+
+                entry_type = "directory" if fpath.is_dir() else "file"
+                entry_key = f"{vault_name}:{entry_type}:{rel_path}"
+                if entry_key in seen_paths:
+                    continue
+
+                seen_paths.add(entry_key)
+                results.append({
+                    "vault": vault_name,
+                    "path": rel_path,
+                    "name": fpath.name,
+                    "type": entry_type,
+                    "matched_path": rel_path,
+                })
+            except PermissionError:
+                continue
+            except Exception:
+                continue
+    
+    return {"query": q, "vault_filter": vault, "results": results}
+
+
 @app.get("/api/index/reload", response_model=ReloadResponse)
 async def api_reload():
     """Force a full re-index of all configured vaults.
diff --git a/frontend/app.js b/frontend/app.js
index 2fe70bf..a612617 100644
--- a/frontend/app.js
+++ b/frontend/app.js
@@ -710,24 +710,24 @@
       const hasText = input.value.length > 0;
       clearBtn.style.display = hasText ? "flex" : "none";
       
+      const q = sidebarFilterCaseSensitive ? input.value.trim() : input.value.trim().toLowerCase();
+      
       if (hasText) {
-        // Expand all vaults and load their contents for filtering
-        await expandAllVaultsForFiltering();
+        await performTreeSearch(q);
+      } else {
+        await restoreSidebarTree();
       }
       
-      const q = sidebarFilterCaseSensitive ? input.value.trim() : input.value.trim().toLowerCase();
-      filterSidebarTree(q);
       filterTagCloud(q);
     });
     
     caseBtn.addEventListener("click", async () => {
       sidebarFilterCaseSensitive = !sidebarFilterCaseSensitive;
       caseBtn.classList.toggle("active");
-      if (input.value.trim()) {
-        await expandAllVaultsForFiltering();
-      }
       const q = sidebarFilterCaseSensitive ? input.value.trim() : input.value.trim().toLowerCase();
-      filterSidebarTree(q);
+      if (input.value.trim()) {
+        await performTreeSearch(q);
+      }
       filterTagCloud(q);
     });
     
@@ -736,7 +736,7 @@
       clearBtn.style.display = "none";
       sidebarFilterCaseSensitive = false;
       caseBtn.classList.remove("active");
-      filterSidebarTree("");
+      restoreSidebarTree();
       filterTagCloud("");
     });
     
@@ -744,15 +744,101 @@
     clearBtn.style.display = "none";
   }
 
-  async function expandAllVaultsForFiltering() {
-    const vaultItems = document.querySelectorAll(".vault-item");
-    for (const vaultItem of vaultItems) {
-      const vaultName = vaultItem.getAttribute("data-vault");
-      const childContainer = document.getElementById(`vault-children-${vaultName}`);
-      if (childContainer && childContainer.classList.contains("collapsed")) {
-        await toggleVault(vaultItem, vaultName, true);
-      }
+  async function performTreeSearch(query) {
+    if (!query) {
+      await restoreSidebarTree();
+      return;
     }
+    
+    try {
+      const vaultParam = selectedContextVault === "all" ? "all" : selectedContextVault;
+      const url = `/api/tree-search?q=${encodeURIComponent(query)}&vault=${encodeURIComponent(vaultParam)}`;
+      const data = await api(url);
+      renderFilteredSidebarResults(query, data.results);
+    } catch (err) {
+      console.error("Tree search error:", err);
+      renderFilteredSidebarResults(query, []);
+    }
+  }
+
+  async function restoreSidebarTree() {
+    await refreshSidebarForContext();
+    if (currentVault) {
+      focusPathInSidebar(currentVault, currentPath || "", { alignToTop: false }).catch(() => {});
+    }
+  }
+
+  function renderFilteredSidebarResults(query, results) {
+    const container = document.getElementById("vault-tree");
+    container.innerHTML = "";
+
+    const grouped = new Map();
+    results.forEach((result) => {
+      if (!grouped.has(result.vault)) {
+        grouped.set(result.vault, []);
+      }
+      grouped.get(result.vault).push(result);
+    });
+
+    if (grouped.size === 0) {
+      container.appendChild(el("div", { class: "sidebar-filter-empty" }, [
+        document.createTextNode("Aucun répertoire ou fichier correspondant."),
+      ]));
+      return;
+    }
+
+    grouped.forEach((entries, vaultName) => {
+      entries.sort((a, b) => a.path.localeCompare(b.path, undefined, { sensitivity: "base" }));
+
+      const vaultHeader = el("div", { class: "tree-item vault-item filter-results-header", "data-vault": vaultName }, [
+        icon("database", 16),
+        document.createTextNode(` ${vaultName} `),
+        smallBadge(entries.length),
+      ]);
+      container.appendChild(vaultHeader);
+
+      const resultsWrapper = el("div", { class: "filter-results-group" });
+      entries.forEach((entry) => {
+        const resultItem = el("div", {
+          class: `tree-item filter-result-item filter-result-${entry.type}`,
+          "data-vault": entry.vault,
+          "data-path": entry.path,
+          "data-type": entry.type,
+        }, [
+          icon(entry.type === "directory" ? "folder" : getFileIcon(entry.name), 16),
+        ]);
+
+        const textWrap = el("div", { class: "filter-result-text" });
+        const primary = el("div", { class: "filter-result-primary" });
+        appendHighlightedText(primary, entry.name, query, sidebarFilterCaseSensitive);
+        const secondary = el("div", { class: "filter-result-secondary" });
+        appendHighlightedText(secondary, entry.path, query, sidebarFilterCaseSensitive);
+        textWrap.appendChild(primary);
+        textWrap.appendChild(secondary);
+        resultItem.appendChild(textWrap);
+
+        resultItem.addEventListener("click", async () => {
+          const input = document.getElementById("sidebar-filter-input");
+          const clearBtn = document.getElementById("sidebar-filter-clear-btn");
+          if (input) input.value = "";
+          if (clearBtn) clearBtn.style.display = "none";
+          await restoreSidebarTree();
+          if (entry.type === "directory") {
+            await focusPathInSidebar(entry.vault, entry.path, { alignToTop: true });
+          } else {
+            await openFile(entry.vault, entry.path);
+            await focusPathInSidebar(entry.vault, entry.path, { alignToTop: false });
+          }
+          closeMobileSidebar();
+        });
+
+        resultsWrapper.appendChild(resultItem);
+      });
+
+      container.appendChild(resultsWrapper);
+    });
+
+    flushIcons();
   }
 
   function filterSidebarTree(query) {
@@ -1644,6 +1730,40 @@
     return s;
   }
 
+  function appendHighlightedText(container, text, query, caseSensitive) {
+    container.textContent = "";
+    if (!query) {
+      container.appendChild(document.createTextNode(text));
+      return;
+    }
+
+    const source = caseSensitive ? text : text.toLowerCase();
+    const needle = caseSensitive ? query : query.toLowerCase();
+    let start = 0;
+    let index = source.indexOf(needle, start);
+
+    if (index === -1) {
+      container.appendChild(document.createTextNode(text));
+      return;
+    }
+
+    while (index !== -1) {
+      if (index > start) {
+        container.appendChild(document.createTextNode(text.slice(start, index)));
+      }
+      const mark = el("mark", { class: "filter-highlight" }, [
+        document.createTextNode(text.slice(index, index + query.length)),
+      ]);
+      container.appendChild(mark);
+      start = index + query.length;
+      index = source.indexOf(needle, start);
+    }
+
+    if (start < text.length) {
+      container.appendChild(document.createTextNode(text.slice(start)));
+    }
+  }
+
   function showWelcome() {
     const area = document.getElementById("content-area");
     area.innerHTML = `
diff --git a/frontend/style.css b/frontend/style.css
index 7eec72f..3ef91d9 100644
--- a/frontend/style.css
+++ b/frontend/style.css
@@ -804,6 +804,59 @@ select {
   display: none;
 }
 
+.filter-results-header {
+  margin-top: 8px;
+}
+
+.filter-results-group {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  padding: 4px 0 10px 12px;
+}
+
+.filter-result-item {
+  align-items: flex-start;
+  gap: 8px;
+  border-radius: 8px;
+}
+
+.filter-result-text {
+  min-width: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.filter-result-primary,
+.filter-result-secondary {
+  min-width: 0;
+  overflow-wrap: anywhere;
+  word-break: break-word;
+}
+
+.filter-result-primary {
+  color: var(--text-primary);
+}
+
+.filter-result-secondary {
+  color: var(--text-muted);
+  font-size: 0.78rem;
+}
+
+.sidebar-filter-empty {
+  padding: 12px 16px;
+  color: var(--text-muted);
+  font-size: 0.85rem;
+}
+
+.filter-highlight {
+  background: color-mix(in srgb, var(--accent) 22%, transparent);
+  color: var(--accent);
+  padding: 0 2px;
+  border-radius: 4px;
+}
+
 /* --- Tag resize handle --- */
 .tag-resize-handle {
   height: 5px;