6 files changed, 170 insertions, 0 deletions
diff --git a/vendor/libghostty-vt.patches.md b/vendor/libghostty-vt.patches.md
index 10596292..cd7f44f6 100644
--- a/vendor/libghostty-vt.patches.md
+++ b/vendor/libghostty-vt.patches.md
@@ -132,3 +132,41 @@ just test-one link_activation
 just test-one ctrl_click
 just check
 ```
+
+## 0006 clear screen while preserving the cursor line
+
+status: active
+
+patch: `vendor/patches/libghostty-vt/0006-clear-screen-preserving-cursor-line.patch`
+
+herdr issue: none; requested in https://github.com/herdrdev/herdr/discussions/545
+
+upstream discussion: not opened
+
+upstream pr: not opened
+
+vendored base: `44f2a44df7e8c4a0c6df3f7d872ef3d7ead88e51`
+
+local files:
+
+- `vendor/libghostty-vt/include/ghostty/vt/terminal.h`
+- `vendor/libghostty-vt/src/lib_vt.zig`
+- `vendor/libghostty-vt/src/terminal/c/main.zig`
+- `vendor/libghostty-vt/src/terminal/c/terminal.zig`
+
+reason: Herdr needs an explicit screen/history clear that preserves the cursor's
+visible soft-wrapped line without writing to the child or interrupting a partial
+VT sequence. The new C function operates directly on the screen, leaves alternate
+screens untouched, clears image placements, and marks the result dirty.
+
+remove when: the vendored C API provides an equivalent parser-independent clear
+operation preserving the visible cursor line, and Herdr passes the checks below
+using it without this patch.
+
+verification:
+
+```sh
+just test-one clear_pane
+just maintenance-test
+just check
+```
diff --git a/vendor/libghostty-vt/include/ghostty/vt/terminal.h b/vendor/libghostty-vt/include/ghostty/vt/terminal.h
index ad5eec54..81f9ebd0 100644
--- a/vendor/libghostty-vt/include/ghostty/vt/terminal.h
+++ b/vendor/libghostty-vt/include/ghostty/vt/terminal.h
@@ -2008,6 +2008,14 @@ GHOSTTY_API void ghostty_terminal_free(GhosttyTerminal terminal);
 GHOSTTY_API void ghostty_terminal_reset(GhosttyTerminal terminal);
 
 /**
+ * Clear screen and history, retaining the cursor's soft-wrapped active line.
+ * Does not alter the VT parser or write to the child process. Returns false
+ * without changing the terminal on the alternate screen or for a NULL handle.
+ * Otherwise returns true and moves the retained line to the top of the screen.
+ */
+GHOSTTY_API bool ghostty_terminal_clear_screen(GhosttyTerminal terminal);
+
+/**
  * Resize the terminal to the given dimensions.
  *
  * Changes the number of columns and rows in the terminal. The primary
diff --git a/vendor/libghostty-vt/src/lib_vt.zig b/vendor/libghostty-vt/src/lib_vt.zig
index 48536568..05bc0baa 100644
--- a/vendor/libghostty-vt/src/lib_vt.zig
+++ b/vendor/libghostty-vt/src/lib_vt.zig
@@ -317,6 +317,7 @@ comptime {
         @export(&c.terminal_new, .{ .name = "ghostty_terminal_new" });
         @export(&c.terminal_free, .{ .name = "ghostty_terminal_free" });
         @export(&c.terminal_reset, .{ .name = "ghostty_terminal_reset" });
+        @export(&c.terminal_clear_screen, .{ .name = "ghostty_terminal_clear_screen" });
         @export(&c.terminal_resize, .{ .name = "ghostty_terminal_resize" });
         @export(&c.terminal_set, .{ .name = "ghostty_terminal_set" });
         @export(&c.terminal_vt_write, .{ .name = "ghostty_terminal_vt_write" });
diff --git a/vendor/libghostty-vt/src/terminal/c/main.zig b/vendor/libghostty-vt/src/terminal/c/main.zig
index 0ba1224a..5ac299ab 100644
--- a/vendor/libghostty-vt/src/terminal/c/main.zig
+++ b/vendor/libghostty-vt/src/terminal/c/main.zig
@@ -183,6 +183,7 @@ pub const sys_set = sys.set;
 pub const terminal_new = terminal.new;
 pub const terminal_free = terminal.free;
 pub const terminal_reset = terminal.reset;
+pub const terminal_clear_screen = terminal.clearScreen;
 pub const terminal_resize = terminal.resize;
 pub const terminal_set = terminal.set;
 pub const terminal_vt_write = terminal.vt_write;
diff --git a/vendor/libghostty-vt/src/terminal/c/terminal.zig b/vendor/libghostty-vt/src/terminal/c/terminal.zig
index 73097573..91bbe310 100644
--- a/vendor/libghostty-vt/src/terminal/c/terminal.zig
+++ b/vendor/libghostty-vt/src/terminal/c/terminal.zig
@@ -1504,6 +1504,40 @@ pub fn reset(terminal_: Terminal) callconv(lib.calling_conv) void {
     t.fullReset();
 }
 
+/// Clear output without feeding synthetic bytes into the child's VT stream.
+pub fn clearScreen(terminal_: Terminal) callconv(lib.calling_conv) bool {
+    const t: *ZigTerminal = (terminal_ orelse return false).terminal;
+    if (t.screens.active_key == .alternate) return false;
+    const screen = t.screens.active;
+
+    var first = screen.cursor.y;
+    while (first > 0) {
+        const pin = screen.pages.pin(.{ .active = .{ .y = first } }).?;
+        if (!pin.rowAndCell().row.wrap_continuation) break;
+        first -= 1;
+    }
+    var last = screen.cursor.y;
+    while (last + 1 < t.rows) {
+        const pin = screen.pages.pin(.{ .active = .{ .y = last } }).?;
+        if (!pin.rowAndCell().row.wrap) break;
+        last += 1;
+    }
+
+    screen.clearSelection();
+    if (last + 1 < t.rows) {
+        screen.clearRows(.{ .active = .{ .y = last + 1 } }, null, false);
+    }
+    screen.eraseHistory(null);
+    if (first > 0) screen.eraseActive(first - 1);
+    screen.pages.pin(.{ .active = .{} }).?.rowAndCell().row.wrap_continuation = false;
+    screen.scroll(.active);
+    if (comptime build_options.kitty_graphics) {
+        screen.kitty_images.delete(t.io(), screen.alloc, t, .{ .all = true });
+    }
+    t.flags.dirty.clear = true;
+    return true;
+}
+
 /// C: GhosttyKittyGraphics
 pub const KittyGraphics = kitty_gfx_c.KittyGraphics;
 
diff --git a/vendor/patches/libghostty-vt/0006-clear-screen-preserving-cursor-line.patch b/vendor/patches/libghostty-vt/0006-clear-screen-preserving-cursor-line.patch
new file mode 100644
index 00000000..86fcee9a
--- /dev/null
+++ b/vendor/patches/libghostty-vt/0006-clear-screen-preserving-cursor-line.patch
@@ -0,0 +1,88 @@
+diff --git a/vendor/libghostty-vt/include/ghostty/vt/terminal.h b/vendor/libghostty-vt/include/ghostty/vt/terminal.h
+index ad5eec54..81f9ebd0 100644
+--- a/vendor/libghostty-vt/include/ghostty/vt/terminal.h
++++ b/vendor/libghostty-vt/include/ghostty/vt/terminal.h
+@@ -2007,6 +2007,14 @@ GHOSTTY_API void ghostty_terminal_free(GhosttyTerminal terminal);
+  */
+ GHOSTTY_API void ghostty_terminal_reset(GhosttyTerminal terminal);
+ 
++/**
++ * Clear screen and history, retaining the cursor's soft-wrapped active line.
++ * Does not alter the VT parser or write to the child process. Returns false
++ * without changing the terminal on the alternate screen or for a NULL handle.
++ * Otherwise returns true and moves the retained line to the top of the screen.
++ */
++GHOSTTY_API bool ghostty_terminal_clear_screen(GhosttyTerminal terminal);
++
+ /**
+  * Resize the terminal to the given dimensions.
+  *
+diff --git a/vendor/libghostty-vt/src/lib_vt.zig b/vendor/libghostty-vt/src/lib_vt.zig
+index 48536568..05bc0baa 100644
+--- a/vendor/libghostty-vt/src/lib_vt.zig
++++ b/vendor/libghostty-vt/src/lib_vt.zig
+@@ -317,6 +317,7 @@ comptime {
+         @export(&c.terminal_new, .{ .name = "ghostty_terminal_new" });
+         @export(&c.terminal_free, .{ .name = "ghostty_terminal_free" });
+         @export(&c.terminal_reset, .{ .name = "ghostty_terminal_reset" });
++        @export(&c.terminal_clear_screen, .{ .name = "ghostty_terminal_clear_screen" });
+         @export(&c.terminal_resize, .{ .name = "ghostty_terminal_resize" });
+         @export(&c.terminal_set, .{ .name = "ghostty_terminal_set" });
+         @export(&c.terminal_vt_write, .{ .name = "ghostty_terminal_vt_write" });
+diff --git a/vendor/libghostty-vt/src/terminal/c/main.zig b/vendor/libghostty-vt/src/terminal/c/main.zig
+index 0ba1224a..5ac299ab 100644
+--- a/vendor/libghostty-vt/src/terminal/c/main.zig
++++ b/vendor/libghostty-vt/src/terminal/c/main.zig
+@@ -183,6 +183,7 @@ pub const sys_set = sys.set;
+ pub const terminal_new = terminal.new;
+ pub const terminal_free = terminal.free;
+ pub const terminal_reset = terminal.reset;
++pub const terminal_clear_screen = terminal.clearScreen;
+ pub const terminal_resize = terminal.resize;
+ pub const terminal_set = terminal.set;
+ pub const terminal_vt_write = terminal.vt_write;
+diff --git a/vendor/libghostty-vt/src/terminal/c/terminal.zig b/vendor/libghostty-vt/src/terminal/c/terminal.zig
+index 73097573..91bbe310 100644
+--- a/vendor/libghostty-vt/src/terminal/c/terminal.zig
++++ b/vendor/libghostty-vt/src/terminal/c/terminal.zig
+@@ -1504,6 +1504,40 @@ pub fn reset(terminal_: Terminal) callconv(lib.calling_conv) void {
+     t.fullReset();
+ }
+ 
++/// Clear output without feeding synthetic bytes into the child's VT stream.
++pub fn clearScreen(terminal_: Terminal) callconv(lib.calling_conv) bool {
++    const t: *ZigTerminal = (terminal_ orelse return false).terminal;
++    if (t.screens.active_key == .alternate) return false;
++    const screen = t.screens.active;
++
++    var first = screen.cursor.y;
++    while (first > 0) {
++        const pin = screen.pages.pin(.{ .active = .{ .y = first } }).?;
++        if (!pin.rowAndCell().row.wrap_continuation) break;
++        first -= 1;
++    }
++    var last = screen.cursor.y;
++    while (last + 1 < t.rows) {
++        const pin = screen.pages.pin(.{ .active = .{ .y = last } }).?;
++        if (!pin.rowAndCell().row.wrap) break;
++        last += 1;
++    }
++
++    screen.clearSelection();
++    if (last + 1 < t.rows) {
++        screen.clearRows(.{ .active = .{ .y = last + 1 } }, null, false);
++    }
++    screen.eraseHistory(null);
++    if (first > 0) screen.eraseActive(first - 1);
++    screen.pages.pin(.{ .active = .{} }).?.rowAndCell().row.wrap_continuation = false;
++    screen.scroll(.active);
++    if (comptime build_options.kitty_graphics) {
++        screen.kitty_images.delete(t.io(), screen.alloc, t, .{ .all = true });
++    }
++    t.flags.dirty.clear = true;
++    return true;
++}
++
+ /// C: GhosttyKittyGraphics
+ pub const KittyGraphics = kitty_gfx_c.KittyGraphics;
+