diff --git a/experiments/core/edit_csi_test.cpp b/experiments/core/edit_csi_test.cpp
index 38c26cd4..ff7ee037 100644
--- a/experiments/core/edit_csi_test.cpp
+++ b/experiments/core/edit_csi_test.cpp
@@ -42,6 +42,28 @@ int main() {
     parser.feed("\x1b[1;1H");
     parser.feed("\x1b[99@");
     require(row_text(parser.screen, 0).empty(), "over-wide ICH should clear the row");
+
+    // IL opens blank rows at the cursor and lets the bottom rows fall off.
+    Parser lines(4, 10, 10, termforge::ParseMode::recovery);
+    lines.feed("a\r\nb\r\nc\r\nd");
+    lines.feed("\x1b[1;1H");
+    lines.feed("\x1b[2L");
+    require(row_text(lines.screen, 0).empty() && row_text(lines.screen, 1).empty() &&
+            row_text(lines.screen, 2) == "a" && row_text(lines.screen, 3) == "b",
+            "IL did not open blank rows");
+    require(lines.screen.row == 0 && lines.screen.column == 0, "IL moved the cursor");
+
+    // DL closes rows from the cursor and appends blanks at the bottom.
+    lines.feed("\x1b[M");
+    require(row_text(lines.screen, 0).empty() && row_text(lines.screen, 1) == "a" &&
+            row_text(lines.screen, 2) == "b" && row_text(lines.screen, 3).empty(),
+            "DL did not close a row");
+
+    // A count past the bottom only removes what remains.
+    lines.feed("\x1b[99L");
+    require(row_text(lines.screen, 0).empty() && row_text(lines.screen, 1).empty() &&
+            row_text(lines.screen, 2).empty() && row_text(lines.screen, 3).empty(),
+            "over-large IL should clear the screen");
     std::puts("edit csi contracts passed");
     return 0;
 }
diff --git a/experiments/core/screen.hpp b/experiments/core/screen.hpp
index e2c7ac8c..affaad39 100644
--- a/experiments/core/screen.hpp
+++ b/experiments/core/screen.hpp
@@ -438,6 +438,26 @@ class Screen {
         // Microsoft Terminal ECH contract explicitly cancels delayed wrapping.
         wrap_pending = false; invalidate_attachment();
     }
+    void insert_lines(int count) {
+        if (count < 1) throw InputError("invalid insert line count");
+        const int insert = (std::min)(count, height() - row);
+        if (insert <= 0) { wrap_pending = false; return; }
+        // Rows pushed past the bottom leave the screen; their identities stay
+        // spent. Inserted rows are new lines and get fresh identities.
+        for (int r = height() - 1; r >= row + insert; --r) lines[r] = std::move(lines[r - insert]);
+        for (int r = row; r < row + insert; ++r) lines[r] = make_line(width(), Cell{}, next_id_);
+        wrap_pending = false;
+        invalidate_attachment();
+    }
+    void delete_lines(int count) {
+        if (count < 1) throw InputError("invalid delete line count");
+        const int remove = (std::min)(count, height() - row);
+        if (remove <= 0) { wrap_pending = false; return; }
+        for (int r = row; r < height() - remove; ++r) lines[r] = std::move(lines[r + remove]);
+        for (int r = height() - remove; r < height(); ++r) lines[r] = make_line(width(), Cell{}, next_id_);
+        wrap_pending = false;
+        invalidate_attachment();
+    }
     void insert_characters(int count) {
         if (count < 1) throw InputError("invalid insert character count");
         const int shift = (std::min)(count, width() - column);
diff --git a/experiments/core/terminal.hpp b/experiments/core/terminal.hpp
index 4f6773fa..c0f523d0 100644
--- a/experiments/core/terminal.hpp
+++ b/experiments/core/terminal.hpp
@@ -72,6 +72,8 @@ class Parser {
         case 'H': case 'f': screen.move(n - 1, params.size() < 2 || params[1] == 0 ? 0 : params[1] - 1); break;
         case 'J': screen.erase_display(params[0]); break;
         case 'K': screen.erase_line(params[0]); break;
+        case 'L': screen.insert_lines(n); break;
+        case 'M': screen.delete_lines(n); break;
         case 'X': screen.erase_characters(n); break;
         case '@': screen.insert_characters(n); break;
         case 'P': screen.delete_characters(n); break;