fix: forward pane cursor shape

fixes #116

8 files changed, 232 insertions, 9 deletions

diff --git a/src/api/schema.rs b/src/api/schema.rs
index cfd681ca..d2bf3ff6 100644
--- a/src/api/schema.rs
+++ b/src/api/schema.rs
@@ -994,7 +994,7 @@ mod tests {
             id: "req_1".into(),
             result: ResponseResult::Pong {
                 version: "0.1.2".into(),
-                protocol: 5,
+                protocol: 6,
             },
         };
 
diff --git a/src/client/blit.rs b/src/client/blit.rs
index 4a5c90c3..2196e1ff 100644
--- a/src/client/blit.rs
+++ b/src/client/blit.rs
@@ -18,6 +18,7 @@
 //! - `CSI H` (CUP) — move cursor to (row, col)
 //! - `CSI m` (SGR) — set graphic rendition (colors, bold, etc.)
 //! - `CSI ? 2026 h/l` — begin/end synchronized output
+//! - `CSI Ps SP q` — DECSCUSR cursor shape
 //! - `ESC ] 52 ; c ; <base64> BEL` — OSC 52 clipboard write
 //!
 //! The goal is minimal output: skip unchanged cells, batch adjacent changes,
@@ -37,6 +38,7 @@ pub(crate) struct EncodedBlit {
     /// Whether this frame was encoded as a full redraw.
     pub(crate) full: bool,
     next_last_visible_cursor: Option<(u16, u16)>,
+    next_last_cursor_shape: u8,
 }
 
 /// Stateful encoder that diffs semantic frames into terminal ANSI bytes.
@@ -44,6 +46,7 @@ pub(crate) struct EncodedBlit {
 pub(crate) struct BlitEncoder {
     last_frame: Option<FrameData>,
     last_visible_cursor: Option<(u16, u16)>,
+    last_cursor_shape: u8,
 }
 
 impl BlitEncoder {
@@ -62,16 +65,25 @@ impl BlitEncoder {
             || prev.is_some_and(|p| p.width != frame.width || p.height != frame.height);
         let mut bytes = Vec::new();
         let mut next_last_visible_cursor = self.last_visible_cursor;
-        blit_frame_to_with_cursor_memory(&mut bytes, frame, prev, &mut next_last_visible_cursor);
+        let mut next_last_cursor_shape = self.last_cursor_shape;
+        blit_frame_to_with_cursor_memory(
+            &mut bytes,
+            frame,
+            prev,
+            &mut next_last_visible_cursor,
+            &mut next_last_cursor_shape,
+        );
         EncodedBlit {
             bytes,
             full,
             next_last_visible_cursor,
+            next_last_cursor_shape,
         }
     }
 
     pub(crate) fn commit(&mut self, frame: FrameData, encoded: EncodedBlit) {
         self.last_visible_cursor = encoded.next_last_visible_cursor;
+        self.last_cursor_shape = encoded.next_last_cursor_shape;
         self.last_frame = Some(frame);
     }
 
@@ -244,7 +256,14 @@ fn cells_equal(a: &CellData, b: &CellData) -> bool {
 #[cfg(test)]
 fn blit_frame_to(writer: impl Write, frame: &FrameData, prev: Option<&FrameData>) {
     let mut last_visible_cursor = None;
-    blit_frame_to_with_cursor_memory(writer, frame, prev, &mut last_visible_cursor);
+    let mut last_cursor_shape = 0;
+    blit_frame_to_with_cursor_memory(
+        writer,
+        frame,
+        prev,
+        &mut last_visible_cursor,
+        &mut last_cursor_shape,
+    );
 }
 
 fn blit_frame_to_with_cursor_memory(
@@ -252,6 +271,7 @@ fn blit_frame_to_with_cursor_memory(
     frame: &FrameData,
     prev: Option<&FrameData>,
     last_visible_cursor: &mut Option<(u16, u16)>,
+    last_cursor_shape: &mut u8,
 ) {
     // On first frame or size change, do a full redraw.
     let full_redraw =
@@ -288,7 +308,7 @@ fn blit_frame_to_with_cursor_memory(
     // hides its cursor, still park the host cursor intentionally so IMEs do not
     // anchor to whichever cell happened to be painted last.
     let host_cursor = resolve_host_cursor_state(frame, last_visible_cursor);
-    write_host_cursor_state(&mut writer, host_cursor);
+    write_host_cursor_state(&mut writer, host_cursor, last_cursor_shape);
 
     // End the synchronized output block immediately after the final cursor
     // state is emitted so supporting terminals can present the frame atomically.
@@ -312,6 +332,8 @@ fn cell_width(cell: &CellData) -> usize {
 struct HostCursorState {
     position: (u16, u16),
     visible: bool,
+    /// DECSCUSR parameter (0–6). 0 means terminal default.
+    shape: u8,
 }
 
 fn resolve_host_cursor_state(
@@ -325,6 +347,7 @@ fn resolve_host_cursor_state(
             return HostCursorState {
                 position,
                 visible: true,
+                shape: normalize_cursor_shape(cursor.shape),
             };
         }
 
@@ -332,6 +355,7 @@ fn resolve_host_cursor_state(
         return HostCursorState {
             position,
             visible: false,
+            shape: normalize_cursor_shape(cursor.shape),
         };
     }
 
@@ -341,6 +365,15 @@ fn resolve_host_cursor_state(
     HostCursorState {
         position,
         visible: false,
+        shape: 0,
+    }
+}
+
+fn normalize_cursor_shape(shape: u8) -> u8 {
+    if shape <= 6 {
+        shape
+    } else {
+        0
     }
 }
 
@@ -363,8 +396,12 @@ fn write_cursor_position(writer: &mut impl Write, (x, y): (u16, u16)) {
     let _ = write!(writer, "\x1b[{};{}H", y + 1, x + 1);
 }
 
-fn write_host_cursor_state(writer: &mut impl Write, cursor: HostCursorState) {
+fn write_host_cursor_state(writer: &mut impl Write, cursor: HostCursorState, last_shape: &mut u8) {
     write_cursor_position(writer, cursor.position);
+    if cursor.shape != *last_shape {
+        let _ = write!(writer, "\x1b[{} q", cursor.shape);
+        *last_shape = cursor.shape;
+    }
     if cursor.visible {
         // Show cursor only after it is already at the final position.
         let _ = writer.write_all(b"\x1b[?25h");
@@ -780,6 +817,7 @@ mod tests {
                 x: 2,
                 y: 1,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -800,6 +838,43 @@ mod tests {
     }
 
     #[test]
+    fn blit_frame_emits_cursor_shape_before_visibility_without_touching_ime_anchor() {
+        let frame = FrameData {
+            cells: vec![make_cell("A", 0, 0, 0)],
+            width: 1,
+            height: 1,
+            cursor: Some(CursorState {
+                x: 0,
+                y: 0,
+                visible: true,
+                shape: 6,
+            }),
+            hyperlinks: Vec::new(),
+            graphics: Vec::new(),
+        };
+
+        let mut output = Vec::new();
+        blit_frame_to(&mut output, &frame, None);
+
+        let output_str = String::from_utf8(output).unwrap();
+        let final_cursor = output_str
+            .find("\x1b[1;1H\x1b[6 q\x1b[?25h")
+            .expect("should set cursor shape before showing cursor");
+        let sync_end = output_str
+            .find("\x1b[?2026l")
+            .expect("should end synchronized output");
+        assert!(
+            final_cursor < sync_end,
+            "shape should be part of the synchronized final cursor state"
+        );
+        let trailing_cursor = &output_str[sync_end + "\x1b[?2026l".len()..];
+        assert_eq!(
+            trailing_cursor, "\x1b[1;1H\x1b[?25h",
+            "IME anchor update should preserve the existing position/visibility-only contract"
+        );
+    }
+
+    #[test]
     fn blit_frame_repeats_explicit_hidden_cursor_anchor_after_synchronized_output() {
         let visible = FrameData {
             cells: vec![make_cell("A", 0, 0, 0); 9],
@@ -809,6 +884,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -821,20 +897,29 @@ mod tests {
                 x: 2,
                 y: 1,
                 visible: false,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
         };
         let mut last_visible_cursor = None;
+        let mut last_cursor_shape = 0;
         let mut output = Vec::new();
 
-        blit_frame_to_with_cursor_memory(&mut output, &visible, None, &mut last_visible_cursor);
+        blit_frame_to_with_cursor_memory(
+            &mut output,
+            &visible,
+            None,
+            &mut last_visible_cursor,
+            &mut last_cursor_shape,
+        );
         output.clear();
         blit_frame_to_with_cursor_memory(
             &mut output,
             &hidden,
             Some(&visible),
             &mut last_visible_cursor,
+            &mut last_cursor_shape,
         );
 
         let output_str = String::from_utf8(output).unwrap();
@@ -976,6 +1061,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1001,6 +1087,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: false,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1048,6 +1135,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: false,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1069,6 +1157,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1097,6 +1186,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1107,6 +1197,7 @@ mod tests {
             x: 2,
             y: 2,
             visible: true,
+            shape: 0,
         });
 
         let mut output = Vec::new();
@@ -1135,6 +1226,7 @@ mod tests {
                 x: 1,
                 y: 1,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1148,15 +1240,23 @@ mod tests {
             graphics: Vec::new(),
         };
         let mut last_visible_cursor = None;
+        let mut last_cursor_shape = 0;
         let mut output = Vec::new();
 
-        blit_frame_to_with_cursor_memory(&mut output, &visible, None, &mut last_visible_cursor);
+        blit_frame_to_with_cursor_memory(
+            &mut output,
+            &visible,
+            None,
+            &mut last_visible_cursor,
+            &mut last_cursor_shape,
+        );
         output.clear();
         blit_frame_to_with_cursor_memory(
             &mut output,
             &hidden,
             Some(&visible),
             &mut last_visible_cursor,
+            &mut last_cursor_shape,
         );
 
         let output_str = String::from_utf8(output).unwrap();
@@ -1180,9 +1280,16 @@ mod tests {
             graphics: Vec::new(),
         };
         let mut last_visible_cursor = None;
+        let mut last_cursor_shape = 0;
         let mut output = Vec::new();
 
-        blit_frame_to_with_cursor_memory(&mut output, &frame, None, &mut last_visible_cursor);
+        blit_frame_to_with_cursor_memory(
+            &mut output,
+            &frame,
+            None,
+            &mut last_visible_cursor,
+            &mut last_cursor_shape,
+        );
 
         let output_str = String::from_utf8(output).unwrap();
         assert!(
@@ -1201,6 +1308,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
diff --git a/src/ghostty/mod.rs b/src/ghostty/mod.rs
index a0ff3226..ef03716a 100644
--- a/src/ghostty/mod.rs
+++ b/src/ghostty/mod.rs
@@ -204,6 +204,31 @@ pub struct KittyPlacementRenderInfo {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CursorVisualStyle {
+    Bar,
+    Block,
+    Underline,
+    BlockHollow,
+}
+
+impl CursorVisualStyle {
+    fn from_raw(value: ffi::GhosttyRenderStateCursorVisualStyle) -> Self {
+        match value {
+            ffi::GhosttyRenderStateCursorVisualStyle_GHOSTTY_RENDER_STATE_CURSOR_VISUAL_STYLE_BLOCK => {
+                Self::Block
+            }
+            ffi::GhosttyRenderStateCursorVisualStyle_GHOSTTY_RENDER_STATE_CURSOR_VISUAL_STYLE_UNDERLINE => {
+                Self::Underline
+            }
+            ffi::GhosttyRenderStateCursorVisualStyle_GHOSTTY_RENDER_STATE_CURSOR_VISUAL_STYLE_BLOCK_HOLLOW => {
+                Self::BlockHollow
+            }
+            _ => Self::Bar,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum ActiveScreen {
     Primary,
     Alternate,
@@ -1278,6 +1303,24 @@ impl RenderState {
         self.get_bool(ffi::GhosttyRenderStateData_GHOSTTY_RENDER_STATE_DATA_CURSOR_VISIBLE)
     }
 
+    pub fn cursor_blinking(&self) -> Result<bool, Error> {
+        self.get_bool(ffi::GhosttyRenderStateData_GHOSTTY_RENDER_STATE_DATA_CURSOR_BLINKING)
+    }
+
+    pub fn cursor_visual_style(&self) -> Result<CursorVisualStyle, Error> {
+        let mut out: ffi::GhosttyRenderStateCursorVisualStyle = 0;
+        // SAFETY: out points to the matching enum storage for the requested data kind.
+        unsafe {
+            ffi::ghostty_render_state_get(
+                self.raw,
+                ffi::GhosttyRenderStateData_GHOSTTY_RENDER_STATE_DATA_CURSOR_VISUAL_STYLE,
+                (&mut out as *mut ffi::GhosttyRenderStateCursorVisualStyle).cast(),
+            )
+            .into_result()?;
+        }
+        Ok(CursorVisualStyle::from_raw(out))
+    }
+
     pub fn cursor_viewport(&self) -> Result<Option<CursorViewport>, Error> {
         if !self.get_bool(
             ffi::GhosttyRenderStateData_GHOSTTY_RENDER_STATE_DATA_CURSOR_VIEWPORT_HAS_VALUE,
diff --git a/src/pane.rs b/src/pane.rs
index d9b63fb9..522365df 100644
--- a/src/pane.rs
+++ b/src/pane.rs
@@ -790,6 +790,7 @@ impl PaneRuntime {
             x: area.x + cursor.x,
             y: area.y + cursor.y,
             visible: cursor.visible,
+            shape: cursor.shape,
         })
     }
 
diff --git a/src/pane/terminal.rs b/src/pane/terminal.rs
index 33cd8ed5..f0535c7a 100644
--- a/src/pane/terminal.rs
+++ b/src/pane/terminal.rs
@@ -39,6 +39,21 @@ pub struct TerminalCursorState {
     pub x: u16,
     pub y: u16,
     pub visible: bool,
+    /// DECSCUSR parameter (0–6). 0 means terminal default.
+    pub shape: u8,
+}
+
+fn decscusr_cursor_shape(style: crate::ghostty::CursorVisualStyle, blinking: bool) -> u8 {
+    match (style, blinking) {
+        (crate::ghostty::CursorVisualStyle::Block, true)
+        | (crate::ghostty::CursorVisualStyle::BlockHollow, true) => 1,
+        (crate::ghostty::CursorVisualStyle::Block, false)
+        | (crate::ghostty::CursorVisualStyle::BlockHollow, false) => 2,
+        (crate::ghostty::CursorVisualStyle::Underline, true) => 3,
+        (crate::ghostty::CursorVisualStyle::Underline, false) => 4,
+        (crate::ghostty::CursorVisualStyle::Bar, true) => 5,
+        (crate::ghostty::CursorVisualStyle::Bar, false) => 6,
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -530,10 +545,17 @@ impl GhosttyPaneTerminal {
         } = &mut *core;
         render_state.update(terminal).ok()?;
         let cursor = render_state.cursor_viewport().ok()??;
+        let shape = render_state
+            .cursor_visual_style()
+            .ok()
+            .zip(render_state.cursor_blinking().ok())
+            .map(|(style, blinking)| decscusr_cursor_shape(style, blinking))
+            .unwrap_or(0);
         Some(TerminalCursorState {
             x: cursor.x,
             y: cursor.y,
             visible: render_state.cursor_visible().ok()?,
+            shape,
         })
     }
 
@@ -1203,6 +1225,38 @@ mod tests {
     }
 
     #[test]
+    fn decscusr_cursor_shape_preserves_blinking_variants() {
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::Block, true),
+            1
+        );
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::Block, false),
+            2
+        );
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::Underline, true),
+            3
+        );
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::Underline, false),
+            4
+        );
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::Bar, true),
+            5
+        );
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::Bar, false),
+            6
+        );
+        assert_eq!(
+            decscusr_cursor_shape(crate::ghostty::CursorVisualStyle::BlockHollow, false),
+            2
+        );
+    }
+
+    #[test]
     fn host_terminal_theme_restore_probe_skips_when_no_transient_override() {
         let (tx, _rx) = mpsc::channel(4);
         let terminal = crate::ghostty::Terminal::new(80, 24, 0).unwrap();
diff --git a/src/server/headless.rs b/src/server/headless.rs
index cc57c1f5..9bb3181f 100644
--- a/src/server/headless.rs
+++ b/src/server/headless.rs
@@ -2137,6 +2137,7 @@ mod tests {
                 x: pane.inner_rect.x + 4,
                 y: pane.inner_rect.y,
                 visible: true,
+                shape: cursor.as_ref().map(|c| c.shape).unwrap_or(0),
             })
         );
     }
@@ -2172,6 +2173,7 @@ mod tests {
                 x: pane.inner_rect.x + 4,
                 y: pane.inner_rect.y,
                 visible: false,
+                shape: cursor.as_ref().map(|c| c.shape).unwrap_or(0),
             })
         );
     }
diff --git a/src/server/protocol.rs b/src/server/protocol.rs
index e9b7975e..7d0d3e2d 100644
--- a/src/server/protocol.rs
+++ b/src/server/protocol.rs
@@ -13,7 +13,7 @@ use serde::{Deserialize, Serialize};
 // ---------------------------------------------------------------------------
 
 /// Current protocol version. Bumped when wire format changes incompatibly.
-pub const PROTOCOL_VERSION: u32 = 5;
+pub const PROTOCOL_VERSION: u32 = 6;
 
 /// Maximum allowed frame payload size (2 MB). Frames larger than this are
 /// rejected to prevent denial-of-service via oversized length prefixes.
@@ -103,6 +103,13 @@ pub struct CellData {
     pub hyperlink: Option<u32>,
 }
 
+/// Cursor shape encoded as a DECSCUSR parameter.
+///
+/// 0 = terminal default, 1 = blinking block, 2 = steady block,
+/// 3 = blinking underline, 4 = steady underline, 5 = blinking bar,
+/// 6 = steady bar.
+pub type CursorShapeParam = u8;
+
 /// Cursor position within a rendered frame.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct CursorState {
@@ -112,6 +119,9 @@ pub struct CursorState {
     pub y: u16,
     /// Whether the cursor is visible.
     pub visible: bool,
+    /// Cursor shape as a DECSCUSR parameter.
+    #[serde(default)]
+    pub shape: CursorShapeParam,
 }
 
 /// A rendered frame to be displayed by the client.
@@ -725,6 +735,7 @@ mod tests {
                 x: 0,
                 y: 0,
                 visible: true,
+                shape: 6,
             }),
             hyperlinks: vec!["https://example.com".to_owned()],
             graphics: Vec::new(),
@@ -875,6 +886,7 @@ mod tests {
                 x: 10,
                 y: 5,
                 visible: true,
+                shape: 0,
             }),
             hyperlinks: Vec::new(),
             graphics: Vec::new(),
@@ -1151,6 +1163,7 @@ mod tests {
             x: 1,
             y: 0,
             visible: true,
+            shape: 0,
         };
         let frame = FrameData::from_ratatui_buffer(&buffer, Some(cursor.clone()));
 
diff --git a/src/server/render_stream.rs b/src/server/render_stream.rs
index ca0ecddd..a921960c 100644
--- a/src/server/render_stream.rs
+++ b/src/server/render_stream.rs
@@ -151,6 +151,7 @@ impl CursorTrackingBackend {
             x: pos.x,
             y: pos.y,
             visible: true,
+            shape: 0,
         })
     }
 }
@@ -296,5 +297,6 @@ fn focused_terminal_cursor(app_state: &AppState) -> Option<CursorState> {
         x: cursor.x,
         y: cursor.y,
         visible: cursor.visible && !crate::ui::pane_is_scrolled_back(rt),
+        shape: cursor.shape,
     })
 }