JavaZeroo · Oct 30, 2026 · Oct 30, 2026 · Oct 30, 2026
diff --git a/experiments/core/edit_csi_test.cpp b/experiments/core/edit_csi_test.cpp
@@ -16,6 +16,7 @@ std::string row_text(const termforge::Screen& screen, int row) {
 }  // namespace
 
 int main() {
+    try {
     using termforge::Parser;
     Parser parser(3, 10, 10, termforge::ParseMode::recovery);
     parser.feed("abcdef");
@@ -75,6 +76,33 @@ int main() {
             row_text(region.screen, 2).empty() && row_text(region.screen, 3) == "d",
             "region scroll changed rows outside the margins");
     require(region.screen.row == 2, "region scroll moved the cursor past the margin");
+    // ED3 empties the scrollback without touching the visible rows.
+    {
+        Parser scrollback(2, 6, 10, termforge::ParseMode::recovery);
+        scrollback.feed("a\r\nb\r\nc");
+        require(scrollback.screen.scrollback_lines() > 0, "no scrollback was produced");
+        scrollback.feed("\x1b[3J");
+        require(scrollback.screen.scrollback_lines() == 0, "ED3 left scrollback behind");
+        require(row_text(scrollback.screen, 0) == "b" && row_text(scrollback.screen, 1) == "c",
+                "ED3 changed the visible screen");
+    }
+    // RIS returns attributes, cursor and modes to their start state.
+    {
+        Parser reset(2, 6, 10, termforge::ParseMode::recovery);
+        reset.feed("\x1b[31;1mX\x1b[?25l\x1b[?1h");
+        require(!reset.screen.visible_lines()[0][0].style.plain(), "test setup lost the style");
+        reset.feed("\x1b" "c");
+        require(reset.screen.row == 0 && reset.screen.column == 0, "RIS did not home the cursor");
+        require(reset.cursor_visible() && !reset.application_cursor_keys(), "RIS did not reset the modes");
+        require(row_text(reset.screen, 0).empty(), "RIS did not clear the screen");
+        reset.feed("Y");
+        require(reset.screen.visible_lines()[0][0].style.plain() &&
+                reset.screen.visible_lines()[0][0].style.fg == -1, "RIS did not reset attributes");
+    }
     std::puts("edit csi contracts passed");
     return 0;
+    } catch (const std::exception& error) {
+        std::fprintf(stderr, "edit csi contract failed: %s\n", error.what());
+        return 1;
+    }
 }
diff --git a/experiments/core/screen.hpp b/experiments/core/screen.hpp
@@ -515,7 +515,25 @@ class Screen {
         erase_range(line, width() - shift, width());
         wrap_pending = false; invalidate_attachment();
     }
+    void reset() {
+        // RIS: every mode, attribute, region and buffer returns to its start
+        // state; the identities already spent stay spent.
+        for (int r = 0; r < height(); ++r) erase_range(lines[r], 0, width());
+        history.clear();
+        style = Style{};
+        row = column = 0;
+        wrap_pending = false;
+        autowrap_enabled_ = true;
+        activate_buffer(ScreenBuffer::primary);
+        invalidate_attachment();
+    }
+    size_t scrollback_lines() const { return history.size(); }
+    void erase_scrollback() {
+        // ED3 drops scrollback only; the visible screen is untouched.
+        if (!history.empty() || discarded) { history.clear(); discarded = 0; }
+    }
     void erase_display(int mode) {
+        if (mode == 3) { erase_scrollback(); return; }
         if (mode > 2) throw InputError("unsupported erase mode");
         for (int r = 0; r < height(); ++r)
             if (mode == 2 || (mode == 0 && r > row) || (mode == 1 && r < row)) erase_range(lines[r], 0, width());

diff --git a/experiments/core/terminal.hpp b/experiments/core/terminal.hpp
@@ -106,6 +106,14 @@ class Parser {
                 continue;
             }
             if (state == State::escape) {
+                // RIS resets the parser-owned modes too, so it is handled here
+                // rather than inside Screen.
+                if (c == 'c') {
+                    screen.reset();
+                    mode_bits_ = 1u << 1;
+                    state = State::ground;
+                    continue;
+                }
                 if (c != '[') throw std::runtime_error("unsupported escape");
                 state = State::csi; params.assign(1, 0); sequence_bytes = 0; private_csi = false; continue;
             }
@@ -204,6 +212,13 @@ class Parser {
                     state = State::csi; sequence_bytes = 0; params.assign(1, 0);
                     stats.max_parameters = (std::max)(stats.max_parameters, params.size()); return;
                 }
+                if (state == State::escape && c == 'c') {
+                    // RIS also works on the recovery path the product uses.
+                    screen.reset();
+                    mode_bits_ = 1u << 1;
+                    reset_sequence();
+                    return;
+                }
                 if (state == State::escape &&
                     (c == ']' || c == 'P' || c == 'X' || c == '^' || c == '_')) {
                     count(stats.ignored_sequences); osc = c == ']';

diff --git a/experiments/core/test_recovery.py b/experiments/core/test_recovery.py
@@ -147,7 +147,8 @@ def test_known_alternate_mode_is_not_counted_as_ignored(self):
                     stats={"ignored_sequences": 0})
 
     def test_invalid_parameter_does_not_apply_prefix(self):
-        self.expect(b"A\x1b[2;3;4H\x1b[3J\x1b[3KZ", "AZ", stats={"ignored_sequences": 3})
+        # ED3 (CSI 3J) is implemented now, so only the bad CUP and CSI 3K count.
+        self.expect(b"A\x1b[2;3;4H\x1b[3J\x1b[3KZ", "AZ", stats={"ignored_sequences": 2})
 
     def test_invalid_sgr_is_atomic(self):
         for data in (b"\x1b[1;999mX", b"\x1b[31m\x1b[0;999mX"):