diff --git a/internal/server/server.go b/internal/server/server.go
index bfb1255..feb35df 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -716,16 +716,21 @@ func toHomePageSessions(docs []session.DocumentInfo) []homePageSession {
 func buildClearURL(u *url.URL, removeKey string) string {
 	q := u.Query()
 	q.Del(removeKey)
-	if len(q) == 0 {
-		return "/"
-	}
-	return "/?" + q.Encode()
+	return (&url.URL{
+		Path:     "/",
+		RawQuery: q.Encode(),
+		Fragment: u.Fragment,
+	}).String()
 }
 
 func buildPageURL(u *url.URL, page int) string {
 	q := u.Query()
 	q.Set("page", fmt.Sprintf("%d", page))
-	return "/?" + q.Encode()
+	return (&url.URL{
+		Path:     "/",
+		RawQuery: q.Encode(),
+		Fragment: u.Fragment,
+	}).String()
 }
 
 func (s *Server) handleCreateSession(w http.ResponseWriter, r *http.Request) {
diff --git a/internal/server/server_test.go b/internal/server/server_test.go
index 077dee3..d3a3393 100644
--- a/internal/server/server_test.go
+++ b/internal/server/server_test.go
@@ -715,3 +715,133 @@ func TestDownloadSessionNotFound(t *testing.T) {
 		t.Fatalf("expected 404, got %d", resp.StatusCode)
 	}
 }
+
+func TestBuildClearURL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name      string
+		rawURL    string
+		removeKey string
+		want      string
+	}{
+		{
+			name:      "no query no fragment",
+			rawURL:    "/",
+			removeKey: "q",
+			want:      "/",
+		},
+		{
+			name:      "remove only param leaves root",
+			rawURL:    "/?q=test",
+			removeKey: "q",
+			want:      "/",
+		},
+		{
+			name:      "remove one param keeps others",
+			rawURL:    "/?q=test&tag=foo",
+			removeKey: "q",
+			want:      "/?tag=foo",
+		},
+		{
+			name:      "fragment preserved with no remaining params",
+			rawURL:    "/?q=test#section",
+			removeKey: "q",
+			want:      "/#section",
+		},
+		{
+			name:      "fragment preserved with remaining params",
+			rawURL:    "/?q=test&tag=foo#section",
+			removeKey: "q",
+			want:      "/?tag=foo#section",
+		},
+		{
+			name:      "fragment preserved when key not present",
+			rawURL:    "/?tag=foo#section",
+			removeKey: "q",
+			want:      "/?tag=foo#section",
+		},
+		{
+			name:      "fragment only no query params",
+			rawURL:    "/#section",
+			removeKey: "q",
+			want:      "/#section",
+		},
+		{
+			name:      "fragment with special characters encoded safely",
+			rawURL:    "/?q=test#sec%20tion",
+			removeKey: "q",
+			want:      "/#sec%20tion",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			u, err := url.Parse(tt.rawURL)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got := buildClearURL(u, tt.removeKey)
+			if got != tt.want {
+				t.Errorf("buildClearURL(%q, %q) = %q, want %q", tt.rawURL, tt.removeKey, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestBuildPageURL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name   string
+		rawURL string
+		page   int
+		want   string
+	}{
+		{
+			name:   "basic page",
+			rawURL: "/",
+			page:   2,
+			want:   "/?page=2",
+		},
+		{
+			name:   "preserves existing params",
+			rawURL: "/?q=test",
+			page:   3,
+			want:   "/?page=3&q=test",
+		},
+		{
+			name:   "preserves fragment",
+			rawURL: "/?q=test#section",
+			page:   2,
+			want:   "/?page=2&q=test#section",
+		},
+		{
+			name:   "fragment only no query",
+			rawURL: "/#section",
+			page:   1,
+			want:   "/?page=1#section",
+		},
+		{
+			name:   "replaces existing page param",
+			rawURL: "/?page=1&q=test",
+			page:   5,
+			want:   "/?page=5&q=test",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			u, err := url.Parse(tt.rawURL)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got := buildPageURL(u, tt.page)
+			if got != tt.want {
+				t.Errorf("buildPageURL(%q, %d) = %q, want %q", tt.rawURL, tt.page, got, tt.want)
+			}
+		})
+	}
+}