diff --git a/apps/web/src/components/filters/FilterBar.test.tsx b/apps/web/src/components/filters/FilterBar.test.tsx
index 53a659b..8b077c4 100644
--- a/apps/web/src/components/filters/FilterBar.test.tsx
+++ b/apps/web/src/components/filters/FilterBar.test.tsx
@@ -132,4 +132,70 @@ describe("FilterBar", (): void => {
     // Should show 3 active filters (2 statuses + 1 priority)
     expect(screen.getByText(/3/)).toBeInTheDocument();
   });
+
+  describe("accessibility (CQ-WEB-11)", (): void => {
+    it("should have aria-label on search input", (): void => {
+      render(<FilterBar onFilterChange={mockOnFilterChange} />);
+      const searchInput = screen.getByRole("textbox", { name: /search tasks/i });
+      expect(searchInput).toBeInTheDocument();
+    });
+
+    it("should have aria-label on date inputs", (): void => {
+      render(<FilterBar onFilterChange={mockOnFilterChange} />);
+      expect(screen.getByLabelText(/filter from date/i)).toBeInTheDocument();
+      expect(screen.getByLabelText(/filter to date/i)).toBeInTheDocument();
+    });
+
+    it("should have aria-labels on status filter buttons", (): void => {
+      render(<FilterBar onFilterChange={mockOnFilterChange} />);
+      expect(screen.getByRole("button", { name: /status filter/i })).toBeInTheDocument();
+    });
+
+    it("should have aria-labels on priority filter buttons", (): void => {
+      render(<FilterBar onFilterChange={mockOnFilterChange} />);
+      expect(screen.getByRole("button", { name: /priority filter/i })).toBeInTheDocument();
+    });
+
+    it("should have id and htmlFor associations on status checkboxes", async (): Promise<void> => {
+      const user = userEvent.setup();
+      render(<FilterBar onFilterChange={mockOnFilterChange} />);
+
+      // Open status dropdown
+      await user.click(screen.getByRole("button", { name: /status filter/i }));
+
+      // Verify specific status checkboxes have proper id attributes
+      const notStartedCheckbox = screen.getByLabelText(/filter by status: not started/i);
+      expect(notStartedCheckbox).toHaveAttribute("id", "status-filter-NOT_STARTED");
+
+      const inProgressCheckbox = screen.getByLabelText(/filter by status: in progress/i);
+      expect(inProgressCheckbox).toHaveAttribute("id", "status-filter-IN_PROGRESS");
+
+      const completedCheckbox = screen.getByLabelText(/filter by status: completed/i);
+      expect(completedCheckbox).toHaveAttribute("id", "status-filter-COMPLETED");
+    });
+
+    it("should have id and htmlFor associations on priority checkboxes", async (): Promise<void> => {
+      const user = userEvent.setup();
+      render(<FilterBar onFilterChange={mockOnFilterChange} />);
+
+      // Open priority dropdown
+      await user.click(screen.getByRole("button", { name: /priority filter/i }));
+
+      // Verify specific priority checkboxes have proper id attributes
+      const lowCheckbox = screen.getByLabelText(/filter by priority: low/i);
+      expect(lowCheckbox).toHaveAttribute("id", "priority-filter-LOW");
+
+      const mediumCheckbox = screen.getByLabelText(/filter by priority: medium/i);
+      expect(mediumCheckbox).toHaveAttribute("id", "priority-filter-MEDIUM");
+
+      const highCheckbox = screen.getByLabelText(/filter by priority: high/i);
+      expect(highCheckbox).toHaveAttribute("id", "priority-filter-HIGH");
+    });
+
+    it("should have aria-label on clear filters button", (): void => {
+      const filtersWithSearch = { search: "test" };
+      render(<FilterBar onFilterChange={mockOnFilterChange} initialFilters={filtersWithSearch} />);
+      expect(screen.getByRole("button", { name: /clear filters/i })).toBeInTheDocument();
+    });
+  });
 });
diff --git a/apps/web/src/components/filters/FilterBar.tsx b/apps/web/src/components/filters/FilterBar.tsx
index 981060d..ccb541c 100644
--- a/apps/web/src/components/filters/FilterBar.tsx
+++ b/apps/web/src/components/filters/FilterBar.tsx
@@ -112,6 +112,7 @@ export function FilterBar({
         <input
           type="text"
           placeholder="Search tasks..."
+          aria-label="Search tasks"
           value={searchValue}
           onChange={(e) => {
             setSearchValue(e.target.value);
@@ -141,14 +142,17 @@ export function FilterBar({
             {Object.values(TaskStatus).map((status) => (
               <label
                 key={status}
+                htmlFor={`status-filter-${status}`}
                 className="flex items-center px-3 py-2 hover:bg-gray-100 cursor-pointer"
               >
                 <input
+                  id={`status-filter-${status}`}
                   type="checkbox"
                   checked={filters.status?.includes(status) ?? false}
                   onChange={() => {
                     handleStatusToggle(status);
                   }}
+                  aria-label={`Filter by status: ${status.replace(/_/g, " ")}`}
                   className="mr-2"
                 />
                 {status.replace(/_/g, " ")}
@@ -179,14 +183,17 @@ export function FilterBar({
             {Object.values(TaskPriority).map((priority) => (
               <label
                 key={priority}
+                htmlFor={`priority-filter-${priority}`}
                 className="flex items-center px-3 py-2 hover:bg-gray-100 cursor-pointer"
               >
                 <input
+                  id={`priority-filter-${priority}`}
                   type="checkbox"
                   checked={filters.priority?.includes(priority) ?? false}
                   onChange={() => {
                     handlePriorityToggle(priority);
                   }}
+                  aria-label={`Filter by priority: ${priority}`}
                   className="mr-2"
                 />
                 {priority}
@@ -201,6 +208,7 @@ export function FilterBar({
         <input
           type="date"
           placeholder="From date"
+          aria-label="Filter from date"
           value={filters.dateFrom ?? ""}
           onChange={(e) => {
             handleFilterChange("dateFrom", e.target.value || undefined);
@@ -211,6 +219,7 @@ export function FilterBar({
         <input
           type="date"
           placeholder="To date"
+          aria-label="Filter to date"
           value={filters.dateTo ?? ""}
           onChange={(e) => {
             handleFilterChange("dateTo", e.target.value || undefined);
diff --git a/apps/web/src/components/mindmap/ReactFlowEditor.tsx b/apps/web/src/components/mindmap/ReactFlowEditor.tsx
index 5801e1b..697de3e 100644
--- a/apps/web/src/components/mindmap/ReactFlowEditor.tsx
+++ b/apps/web/src/components/mindmap/ReactFlowEditor.tsx
@@ -222,7 +222,9 @@ export function ReactFlowEditor({
   }, [readOnly, selectedNode, onNodeDelete, setNodes, setEdges]);
 
   // Keyboard shortcuts
-  useEffect((): (() => void) => {
+  useEffect((): (() => void) | undefined => {
+    if (typeof window === "undefined") return undefined;
+
     const handleKeyDown = (event: KeyboardEvent): void => {
       if (readOnly) return;
 
@@ -240,8 +242,13 @@ export function ReactFlowEditor({
     };
   }, [readOnly, selectedNode, handleDeleteSelected]);
 
-  const isDark =
-    typeof window !== "undefined" && document.documentElement.classList.contains("dark");
+  // Dark mode detection - must be in state+effect to avoid SSR/hydration mismatch
+  const [isDark, setIsDark] = useState(false);
+  useEffect((): void => {
+    if (typeof window !== "undefined") {
+      setIsDark(document.documentElement.classList.contains("dark"));
+    }
+  }, []);
 
   return (
     <div className={`w-full h-full ${className}`} style={{ minHeight: "500px" }}>