Fix macOS build: use CURSES_INCLUDE_DIRS and enable wide-char decls

Two latent defects broke the kte target on macOS once TerminalInputHandler
switched from getch() to get_wch().

include_directories() referenced CURSES_INCLUDE_DIR, a name FindCurses never
sets (it exports CURSES_INCLUDE_DIRS). The variable expanded to nothing, so
no curses include path was added and the compiler silently fell back to the
macOS SDK's narrow-char header on the default include path.

Both the SDK and Homebrew headers declare get_wch and friends only when
NCURSES_WIDECHAR is set, defaulting it to 0 absent a feature-test macro, so
the build failed with "use of undeclared identifier 'get_wch'". We always
request and link the wide library, so define NCURSES_WIDECHAR=1; redefining
it identically is benign on platforms whose headers already set it.

kte and kge now compile and link against libncursesw, and the app bundle
vendors it. Full test suite passes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Buffer.cc

@@ -231,9 +231,12 @@ Buffer::Buffer(const Buffer &other)
 	mark_set_         = other.mark_set_;
 	mark_curx_        = other.mark_curx_;
 	mark_cury_        = other.mark_cury_;
-	// Copy syntax/highlighting flags
+	// Copy edit mode + syntax/highlighting flags
+	edit_mode_          = other.edit_mode_;
+	edit_mode_detected_ = other.edit_mode_detected_;
 	version_            = other.version_;
 	syntax_enabled_        = other.syntax_enabled_;
+	syntax_user_override_  = other.syntax_user_override_;
 	filetype_           = other.filetype_;
 	// Fresh undo system for the copy
 	undo_tree_ = std::make_unique<UndoTree>();
@@ -281,8 +284,11 @@ Buffer::operator=(const Buffer &other)
 	mark_set_         = other.mark_set_;
 	mark_curx_          = other.mark_curx_;
 	mark_cury_          = other.mark_cury_;
+	edit_mode_          = other.edit_mode_;
+	edit_mode_detected_ = other.edit_mode_detected_;
 	version_            = other.version_;
 	syntax_enabled_        = other.syntax_enabled_;
+	syntax_user_override_  = other.syntax_user_override_;
 	filetype_           = other.filetype_;
 	// Recreate undo system for this instance
 	undo_tree_ = std::make_unique<UndoTree>();
@@ -323,16 +329,28 @@ Buffer::Buffer(Buffer &&other) noexcept
 	  mark_set_(other.mark_set_),
 	  mark_curx_(other.mark_curx_),
 	  mark_cury_(other.mark_cury_),
+	  visual_line_active_(other.visual_line_active_),
+	  visual_line_anchor_y_(other.visual_line_anchor_y_),
+	  visual_line_active_y_(other.visual_line_active_y_),
 	  undo_tree_(std::move(other.undo_tree_)),
 	  undo_sys_(std::move(other.undo_sys_))
 {
-	// Move syntax/highlighting state
+	// Move edit mode + syntax/highlighting state
+	edit_mode_          = other.edit_mode_;
+	edit_mode_detected_ = other.edit_mode_detected_;
 	version_            = other.version_;
 	syntax_enabled_        = other.syntax_enabled_;
+	syntax_user_override_  = other.syntax_user_override_;
 	filetype_           = std::move(other.filetype_);
 	highlighter_        = std::move(other.highlighter_);
 	content_            = std::move(other.content_);
 	rows_cache_dirty_   = other.rows_cache_dirty_;
+	on_disk_identity_   = other.on_disk_identity_;
+	// Non-owning: the recorder object itself is owned by SwapManager and outlives
+	// this move. The caller (Editor) is responsible for calling SwapManager::Rehome()
+	// so the journal's Buffer* key follows this object to its new address.
+	swap_rec_       = other.swap_rec_;
+	other.swap_rec_ = nullptr;
 	// Update UndoSystem's buffer reference to point to this object
 	if (undo_sys_) {
 		undo_sys_->UpdateBufferReference(*this);
@@ -361,16 +379,28 @@ Buffer::operator=(Buffer &&other) noexcept
 	mark_set_             = other.mark_set_;
 	mark_curx_            = other.mark_curx_;
 	mark_cury_            = other.mark_cury_;
+	visual_line_active_   = other.visual_line_active_;
+	visual_line_anchor_y_ = other.visual_line_anchor_y_;
+	visual_line_active_y_ = other.visual_line_active_y_;
 	undo_tree_            = std::move(other.undo_tree_);
 	undo_sys_             = std::move(other.undo_sys_);
 
-	// Move syntax/highlighting state
+	// Move edit mode + syntax/highlighting state
+	edit_mode_          = other.edit_mode_;
+	edit_mode_detected_ = other.edit_mode_detected_;
 	version_            = other.version_;
 	syntax_enabled_        = other.syntax_enabled_;
+	syntax_user_override_  = other.syntax_user_override_;
 	filetype_           = std::move(other.filetype_);
 	highlighter_        = std::move(other.highlighter_);
 	content_            = std::move(other.content_);
 	rows_cache_dirty_   = other.rows_cache_dirty_;
+	on_disk_identity_   = other.on_disk_identity_;
+	// Non-owning: the recorder object itself is owned by SwapManager and outlives
+	// this move. The caller (Editor) is responsible for calling SwapManager::Rehome()
+	// so the journal's Buffer* key follows this object to its new address.
+	swap_rec_       = other.swap_rec_;
+	other.swap_rec_ = nullptr;
 	// Update UndoSystem's buffer reference to point to this object
 	if (undo_sys_) {
 		undo_sys_->UpdateBufferReference(*this);

Buffer.h

@@ -35,9 +35,12 @@
  */
 #pragma once
 
+#include <algorithm>
 #include <cstddef>
+#include <filesystem>
 #include <memory>
 #include <string>
+#include <unordered_set>
 #include <vector>
 #include <string_view>
 
@@ -48,6 +51,26 @@
 #include "Highlight.h"
 #include <mutex>
 
+// Edit mode determines which font class is used for a buffer.
+enum class EditMode { Code, Writing };
+
+// Detect edit mode from a filename's extension.
+inline EditMode
+DetectEditMode(const std::string &filename)
+{
+	std::string ext = std::filesystem::path(filename).extension().string();
+	std::transform(ext.begin(), ext.end(), ext.begin(), [](unsigned char c) {
+		return static_cast<char>(std::tolower(c));
+	});
+	static const std::unordered_set<std::string> writing_exts = {
+		".txt", ".md", ".markdown", ".rst", ".org",
+		".tex", ".adoc", ".asciidoc",
+	};
+	if (writing_exts.count(ext))
+		return EditMode::Writing;
+	return EditMode::Code;
+}
+
 // Forward declaration for swap journal integration
 namespace kte {
 class SwapRecorder;
@@ -484,6 +507,35 @@ public:
 	}
 
 
+	// Edit mode (code vs writing)
+	[[nodiscard]] EditMode GetEditMode() const
+	{
+		return edit_mode_;
+	}
+
+
+	void SetEditMode(EditMode m)
+	{
+		edit_mode_ = m;
+		edit_mode_detected_ = true;
+	}
+
+
+	void ToggleEditMode()
+	{
+		edit_mode_ = (edit_mode_ == EditMode::Code)
+			             ? EditMode::Writing
+			             : EditMode::Code;
+		edit_mode_detected_ = true;
+	}
+
+
+	[[nodiscard]] bool EditModeDetected() const
+	{
+		return edit_mode_detected_;
+	}
+
+
 	void SetSyntaxEnabled(bool on)
 	{
 		syntax_enabled_ = on;
@@ -496,6 +548,25 @@ public:
 	}
 
 
+	// Marks that the user explicitly set syntax state via a command (:syntax
+	// on/off, :set filetype=...), as opposed to it being auto-applied from
+	// GUIConfig. Frontends that re-apply the config-driven default every
+	// frame (e.g. ImGuiFrontend::apply_syntax_to_buffer) must check this
+	// first, mirroring EditModeDetected()'s "don't stomp a manual toggle"
+	// pattern - otherwise a manual :syntax off is silently undone on the very
+	// next frame.
+	void SetSyntaxUserOverride(bool on)
+	{
+		syntax_user_override_ = on;
+	}
+
+
+	[[nodiscard]] bool SyntaxUserOverride() const
+	{
+		return syntax_user_override_;
+	}
+
+
 	void SetFiletype(const std::string &ft)
 	{
 		filetype_ = ft;
@@ -614,9 +685,14 @@ private:
 	std::unique_ptr<struct UndoTree> undo_tree_;
 	std::unique_ptr<UndoSystem> undo_sys_;
 
+	// Edit mode (code vs writing)
+	EditMode edit_mode_ = EditMode::Code;
+	bool edit_mode_detected_ = false; // true after initial auto-detection
+
 	// Syntax/highlighting state
 	std::uint64_t version_ = 0; // increment on edits
 	bool syntax_enabled_   = true;
+	bool syntax_user_override_ = false; // true once user explicitly set syntax state via a command
 	std::string filetype_;
 	std::unique_ptr<kte::HighlighterEngine> highlighter_;
 	// Non-owning pointer to swap recorder managed by Editor/SwapManager

CLAUDE.md

@@ -0,0 +1,115 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+**kte** (Kyle's Text Editor) is a C++20 text editor with a terminal-first design (ncurses) and optional GUI frontends (ImGui via SDL2/OpenGL/Freetype, or Qt6). It uses a WordStar/VDE-style command model. The terminal editor is `kte`; the GUI editor is `kge`.
+
+## Build Commands
+
+```bash
+# Configure (from project root, build dir is "build")
+cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DBUILD_GUI=ON -DBUILD_TESTS=ON
+
+# Build everything
+cmake --build build
+
+# Build specific targets
+cmake --build build --target kte        # terminal editor
+cmake --build build --target kge        # GUI editor (requires -DBUILD_GUI=ON)
+cmake --build build --target kte_tests  # test suite
+
+# Run all tests
+cmake --build build --target kte_tests && ./build/kte_tests
+```
+
+There is no single-test runner; the test binary runs all tests. Tests use a minimal custom framework in `tests/Test.h` with `TEST()`, `ASSERT_EQ()`, `ASSERT_TRUE()`, `EXPECT_TRUE()` macros.
+
+### Key CMake Options
+
+| Flag | Default | Purpose |
+|------|---------|---------|
+| `BUILD_GUI` | ON | Build `kge` (ImGui GUI) |
+| `KTE_USE_QT` | OFF | Use Qt6 instead of ImGui for GUI |
+| `BUILD_TESTS` | ON | Build test suite |
+| `ENABLE_ASAN` | OFF | AddressSanitizer |
+| `KTE_STATIC_LINK` | OFF | Static linking (Linux only) |
+| `KTE_ENABLE_TREESITTER` | OFF | Tree-sitter syntax highlighting |
+
+### Nix
+
+`flake.nix` provides devshells: `default` (ImGui+debug tools), `terminal`, `qt`.
+
+### Docker (cross-platform Linux testing)
+
+```bash
+docker build -t kte-linux . && docker run --rm -v "$(pwd):/kte" kte-linux
+```
+
+## Architecture
+
+Three-layer design with strict frontend independence:
+
+```
+Frontend Layer (Terminal / ImGui / Qt / Test)
+  InputHandler.h, Renderer.h, Frontend.h interfaces
+        ↓
+Command Layer
+  CommandId enum → CommandRegistry → handler functions in Command.cc
+        ↓
+Core Model Layer
+  Editor → Buffer → PieceTable
+  UndoSystem (tree-based, records at PieceTable level)
+  SwapManager (crash recovery journal per buffer)
+```
+
+### Core Components
+
+- **PieceTable** (`PieceTable.h/.cc`) - Text storage. Lazy materialization; most ops work on the piece list directly. Line index and materialization caches must be invalidated on content changes.
+- **Buffer** (`Buffer.h/.cc`) - Wraps PieceTable. Prefer `GetLineView(row)` (zero-copy) or `GetLineString(row)` over `Rows()` (legacy, materializes all lines). All text mutations must go through PieceTable API (`insert_text`, `delete_text`) to ensure undo and swap recording work.
+- **Editor** (`Editor.h/.cc`) - Top-level state container. Primarily getters/setters; editing logic lives in commands.
+- **Command** (`Command.h/.cc`) - 120+ editing commands. This is the main place to add new editing operations. Register via `CommandRegistry::Register()` in `InstallDefaultCommands()`.
+- **UndoSystem/UndoTree/UndoNode** - Tree-based undo with branching. Group related ops with `buf.Undo()->BeginGroup()` / `EndGroup()`.
+- **Swap** (`Swap.h/.cc`) - Append-only crash recovery journal. Uses circuit breaker pattern for resilience. Files in `~/.local/state/kte/`.
+- **Syntax highlighting** (`syntax/`) - Pluggable per-language highlighters registered in `HighlighterRegistry`. Per-line caching with buffer version tracking.
+
+### Frontend Implementations
+
+Each frontend implements three interfaces (`Frontend.h`, `InputHandler.h`, `Renderer.h`):
+- **Terminal**: ncurses-based (always built)
+- **ImGui**: SDL2+OpenGL+Freetype (built with `-DBUILD_GUI=ON`)
+- **Qt**: Qt6 (built with `-DBUILD_GUI=ON -DKTE_USE_QT=ON`)
+- **Test**: Programmatic frontend for testing (always built, no UI deps)
+
+## Code Style
+
+- **C++20**, compiled with `-Wall -Wextra -Werror -pedantic`
+- **Clang** uses `-stdlib=libc++`
+- **Naming**: PascalCase for classes/methods, snake_case for variables, trailing underscore for private members (e.g., `pieces_`)
+- **Indentation**: Tabs
+- **Error handling**: Fallible ops use `bool func(args..., std::string &err)` pattern. Always clear `err` at start, capture `errno` immediately after syscall failure. Use EINTR-safe wrappers from `SyscallWrappers.h` instead of raw syscalls.
+- **ErrorHandler**: Centralized logging to `~/.local/state/kte/error.log` with severity levels (Info/Warning/Error/Critical).
+
+## Testing
+
+Tests live in `tests/test_*.cc`. Use `TestFrontend`/`TestInputHandler`/`TestRenderer` for integration tests that exercise the full Editor+Buffer+Command stack without UI dependencies.
+
+Key test files by area:
+- PieceTable: `test_piece_table.cc`
+- Buffer I/O: `test_buffer_io.cc`
+- Commands: `test_command_semantics.cc`
+- Search/replace: `test_search.cc`, `test_search_replace_flow.cc`
+- Undo: `test_undo.cc`
+- Swap (crash recovery): `test_swap_*.cc` (7 files)
+- Reflow: `test_reflow_paragraph.cc`, `test_reflow_indented_bullets.cc`
+- Integration: `test_daily_workflows.cc`
+
+## Important Caveats
+
+- `Buffer::Rows()` is legacy; use `GetLineView()` / `GetLineString()` in new code
+- `GetLineView()` returns a `string_view` valid only until next buffer modification
+- After editing ops, call `ensure_cursor_visible()` to update viewport
+- All source files are in the project root (no `src/` directory); tests are in `tests/`; syntax highlighters in `syntax/`; themes in `themes/`; embedded fonts in `fonts/`
+- External deps: `ext/imgui/` (Dear ImGui), `ext/tomlplusplus/` (TOML parser)
+- GUI config: `~/.config/kte/kge.toml` (TOML preferred over legacy INI)

CMakeLists.txt

@@ -4,7 +4,7 @@ project(kte)
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 20)
-set(KTE_VERSION "1.8.0")
+set(KTE_VERSION "1.12.0")
 
 # Default to terminal-only build to avoid SDL/OpenGL dependency by default.
 # Enable with -DBUILD_GUI=ON when SDL2/OpenGL/Freetype are available.
@@ -14,7 +14,7 @@ set(BUILD_TESTS ON CACHE BOOL "Enable building test programs.")
 set(KTE_FONT_SIZE "18.0" CACHE STRING "Default font size for GUI")
 option(KTE_UNDO_DEBUG "Enable undo instrumentation logs" OFF)
 option(KTE_ENABLE_TREESITTER "Enable optional Tree-sitter highlighter adapter" OFF)
-option(KTE_STATIC_LINK "Enable static linking on Linux" ON)
+option(KTE_STATIC_LINK "Enable static linking on Linux" OFF)
 
 # Optionally enable AddressSanitizer (ASan)
 option(ENABLE_ASAN "Enable AddressSanitizer for builds" OFF)
@@ -51,6 +51,7 @@ else ()
     )
     if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
         add_compile_options("-stdlib=libc++")
+        add_link_options("-stdlib=libc++")
     else ()
         # nothing special for gcc at the moment
     endif ()
@@ -70,8 +71,34 @@ endif ()
 # NCurses for terminal mode
 set(CURSES_NEED_NCURSES TRUE)
 set(CURSES_NEED_WIDE TRUE)
+
+# macOS ships only a narrow-char ncurses in the SDK, and Homebrew's wide-char
+# build is keg-only, so FindCurses can't see it without a hint.
+if (APPLE)
+    find_program(BREW_EXECUTABLE brew)
+    if (BREW_EXECUTABLE)
+        execute_process(COMMAND "${BREW_EXECUTABLE}" --prefix ncurses
+                OUTPUT_VARIABLE HOMEBREW_NCURSES_PREFIX
+                OUTPUT_STRIP_TRAILING_WHITESPACE
+                ERROR_QUIET)
+        if (HOMEBREW_NCURSES_PREFIX AND IS_DIRECTORY "${HOMEBREW_NCURSES_PREFIX}")
+            message(STATUS "Using Homebrew ncursesw: ${HOMEBREW_NCURSES_PREFIX}")
+            list(PREPEND CMAKE_PREFIX_PATH "${HOMEBREW_NCURSES_PREFIX}")
+        endif ()
+    endif ()
+endif ()
+
 find_package(Curses REQUIRED)
-include_directories(${CURSES_INCLUDE_DIR})
+
+# FindCurses exports CURSES_INCLUDE_DIRS; the singular CURSES_INCLUDE_DIR was
+# never set, so this silently expanded to nothing and the compiler fell back
+# to whatever curses header happened to be on the default include path.
+include_directories(${CURSES_INCLUDE_DIRS})
+
+# The wide-char entry points we rely on (get_wch, etc.) are declared only when
+# NCURSES_WIDECHAR is set; the header defaults it to 0 unless a feature-test
+# macro says otherwise. We always link the wide library, so ask for them.
+add_compile_definitions(NCURSES_WIDECHAR=1)
 
 # On Alpine Linux, CMake's FindCurses looks in wrong paths
 # Manually find the correct ncurses library
@@ -205,6 +232,8 @@ set(FONT_HEADERS
         fonts/FontList.h
         fonts/B612Mono.h
         fonts/BrassMono.h
+        fonts/CrimsonPro.h
+        fonts/ETBook.h
         fonts/BrassMonoCode.h
         fonts/FiraCode.h
         fonts/Go.h
@@ -216,6 +245,7 @@ set(FONT_HEADERS
         fonts/IosevkaExtended.h
         fonts/ShareTech.h
         fonts/SpaceMono.h
+        fonts/Spectral.h
         fonts/Syne.h
         fonts/Triplicate.h
         fonts/Unispace.h
@@ -327,6 +357,7 @@ if (BUILD_TESTS)
             tests/test_swap_edge_cases.cc
             tests/test_swap_recovery_prompt.cc
             tests/test_swap_cleanup.cc
+            tests/test_swap_cleanup2.cc
             tests/test_swap_git_editor.cc
             tests/test_piece_table.cc
             tests/test_search.cc
@@ -339,6 +370,8 @@ if (BUILD_TESTS)
             tests/test_migration_coverage.cc
             tests/test_smart_newline.cc
             tests/test_reflow_undo.cc
+            tests/test_syntax_highlighting.cc
+            tests/test_paste_split.cc
 
             # minimal engine sources required by Buffer
             PieceTable.cc

CONFIG.md

@@ -0,0 +1,116 @@
+# kge Configuration
+
+kge loads configuration from `~/.config/kte/kge.toml`. If no TOML file is
+found, it falls back to the legacy `kge.ini` format.
+
+## TOML Format
+
+```toml
+[window]
+fullscreen = false
+columns = 80
+rows = 42
+
+[font]
+# Default font and size
+name = "default"
+size = 18.0
+# Font used in code mode (monospace)
+code = "default"
+# Font used in writing mode (proportional)
+writing = "crimsonpro"
+
+[appearance]
+theme = "nord"
+# "dark" or "light" for themes with variants
+background = "dark"
+
+[editor]
+syntax = true
+```
+
+## Sections
+
+### `[window]`
+
+| Key          | Type | Default | Description                     |
+|--------------|------|---------|---------------------------------|
+| `fullscreen` | bool | false   | Start in fullscreen mode        |
+| `columns`    | int  | 80      | Initial window width in columns |
+| `rows`       | int  | 42      | Initial window height in rows   |
+
+### `[font]`
+
+| Key       | Type   | Default      | Description                              |
+|-----------|--------|--------------|------------------------------------------|
+| `name`    | string | "default"    | Default font loaded at startup           |
+| `size`    | float  | 18.0         | Font size in pixels                      |
+| `code`    | string | "default"    | Font for code mode (monospace)           |
+| `writing` | string | "crimsonpro" | Font for writing mode (proportional)     |
+
+### `[appearance]`
+
+| Key          | Type   | Default | Description                             |
+|--------------|--------|---------|-----------------------------------------|
+| `theme`      | string | "nord"  | Color theme                             |
+| `background` | string | "dark"  | Background mode: "dark" or "light"      |
+
+### `[editor]`
+
+| Key      | Type | Default | Description                  |
+|----------|------|---------|------------------------------|
+| `syntax` | bool | true    | Enable syntax highlighting   |
+
+## Edit Modes
+
+kge has two edit modes that control which font is used:
+
+- **code** — Uses the monospace font (`font.code`). Default for source files.
+- **writing** — Uses the proportional font (`font.writing`). Auto-detected
+  for `.txt`, `.md`, `.markdown`, `.rst`, `.org`, `.tex`, `.adoc`, and
+  `.asciidoc` files.
+
+Toggle with `C-k m` or `: mode [code|writing]`.
+
+## Available Fonts
+
+### Monospace
+
+b612, berkeley, berkeley-bold, brassmono, brassmono-bold, brassmonocode,
+brassmonocode-bold, fira, go, ibm, idealist, inconsolata, inconsolataex,
+iosevka, iosevkaex, sharetech, space, syne, triplicate, unispace
+
+### Proportional (Serif)
+
+crimsonpro, etbook, spectral
+
+## Available Themes
+
+amber, eink, everforest, gruvbox, kanagawa-paper, lcars, leuchtturm, nord,
+old-book, orbital, plan9, solarized, tufte, weyland-yutani, zenburn
+
+Themes with light/dark variants: eink, gruvbox, leuchtturm, old-book,
+solarized. Set `background = "light"` or use `: background light`.
+
+## Migrating from kge.ini
+
+If you have an existing `kge.ini`, kge will still read it but prints a
+notice to stderr suggesting migration. To migrate, create `kge.toml` in the
+same directory (`~/.config/kte/`) using the format above. The TOML file
+takes priority when both exist.
+
+The INI keys map to TOML as follows:
+
+| INI key       | TOML equivalent          |
+|---------------|--------------------------|
+| `fullscreen`  | `window.fullscreen`      |
+| `columns`     | `window.columns`         |
+| `rows`        | `window.rows`            |
+| `font`        | `font.name`              |
+| `font_size`   | `font.size`              |
+| `theme`       | `appearance.theme`       |
+| `background`  | `appearance.background`  |
+| `syntax`      | `editor.syntax`          |
+
+New keys `font.code` and `font.writing` have no INI equivalent (the INI
+parser accepts `code_font` and `writing_font` if needed).

Command.cc

@@ -159,6 +159,27 @@ ensure_at_least_one_line(Buffer &buf)
 }
 
 
+// RAII helper: brackets a multi-edit command so its individual undo nodes
+// undo/redo as a single atomic step, per the project's undo-grouping convention.
+struct UndoGroupGuard {
+	UndoSystem *u;
+
+
+	explicit UndoGroupGuard(UndoSystem *u_) : u(u_)
+	{
+		if (u)
+			u->BeginGroup();
+	}
+
+
+	~UndoGroupGuard()
+	{
+		if (u)
+			u->EndGroup();
+	}
+};
+
+
 // Determine if a command mutates the buffer contents (text edits)
 static bool
 is_mutating_command(CommandId id)
@@ -264,8 +285,12 @@ extract_region_text(const Buffer &buf, std::size_t sx, std::size_t sy, std::size
 
 
 // Helper: delete region and leave cursor at start (sx,sy). Adjust lines appropriately.
+// If `u` is non-null, each underlying mutation is recorded as its own undo node;
+// callers that want the whole region-delete to undo/redo as one step should
+// wrap the call in an UndoGroupGuard.
 static void
-delete_region(Buffer &buf, std::size_t sx, std::size_t sy, std::size_t ex, std::size_t ey)
+delete_region(Buffer &buf, std::size_t sx, std::size_t sy, std::size_t ex, std::size_t ey,
+              UndoSystem *u = nullptr)
 {
 	std::size_t nrows = buf.Nrows();
 	if (nrows == 0)
@@ -282,7 +307,14 @@ delete_region(Buffer &buf, std::size_t sx, std::size_t sy, std::size_t ex, std::
 		std::size_t xe   = std::min(ex, line.size());
 		if (xe < xs)
 			std::swap(xs, xe);
+		std::string deleted = std::string(line.substr(xs, xe - xs));
 		buf.delete_text(static_cast<int>(sy), static_cast<int>(xs), xe - xs);
+		if (u && !deleted.empty()) {
+			buf.SetCursor(xs, sy);
+			u->Begin(UndoType::Delete);
+			u->Append(std::string_view(deleted));
+			u->commit();
+		}
 	} else {
 		// Multi-line: delete from (sx,sy) to (ex,ey)
 		// Strategy:
@@ -303,11 +335,25 @@ delete_region(Buffer &buf, std::size_t sx, std::size_t sy, std::size_t ex, std::
 
 		// Delete tail of first line (from xs to end)
 		if (xs < first_line_len) {
+			std::string tail = std::string(rows[sy].substr(xs));
 			buf.delete_text(static_cast<int>(sy), static_cast<int>(xs), first_line_len - xs);
+			if (u && !tail.empty()) {
+				buf.SetCursor(xs, sy);
+				u->Begin(UndoType::Delete);
+				u->Append(std::string_view(tail));
+				u->commit();
+			}
 		}
 
 		// Delete lines from ey down to sy+1 (reverse order to preserve indices)
 		for (std::size_t i = ey; i > sy; --i) {
+			if (u) {
+				std::string row_text = static_cast<std::string>(buf.Rows()[i]);
+				buf.SetCursor(0, i);
+				u->Begin(UndoType::DeleteRow);
+				u->Append(std::string_view(row_text));
+				u->commit();
+			}
 			buf.delete_row(static_cast<int>(i));
 		}
 
@@ -317,6 +363,12 @@ delete_region(Buffer &buf, std::size_t sx, std::size_t sy, std::size_t ex, std::
 			const auto &rows_after = buf.Rows();
 			std::size_t line_len   = rows_after[sy].size();
 			buf.insert_text(static_cast<int>(sy), static_cast<int>(line_len), suffix);
+			if (u) {
+				buf.SetCursor(line_len, sy);
+				u->Begin(UndoType::Insert);
+				u->Append(std::string_view(suffix));
+				u->commit();
+			}
 		}
 	}
 	buf.SetCursor(sx, sy);
@@ -752,6 +804,8 @@ cmd_save_and_quit(CommandContext &ctx)
 		if (buf->IsFileBacked()) {
 			if (buf->Save(err)) {
 				buf->SetDirty(false);
+				if (auto *sm = ctx.editor.Swap())
+					sm->ResetJournal(*buf);
 			} else {
 				ctx.editor.SetStatus(err);
 				return false;
@@ -759,6 +813,8 @@ cmd_save_and_quit(CommandContext &ctx)
 		} else if (!buf->Filename().empty()) {
 			if (buf->SaveAs(buf->Filename(), err)) {
 				buf->SetDirty(false);
+				if (auto *sm = ctx.editor.Swap())
+					sm->ResetJournal(*buf);
 			} else {
 				ctx.editor.SetStatus(err);
 				return false;
@@ -904,6 +960,10 @@ cmd_unknown_esc_command(CommandContext &ctx)
 static void
 apply_filetype(Buffer &buf, const std::string &ft)
 {
+	// Only reachable from explicit user commands (:syntax on, :set
+	// filetype=...) - mark so frontends that re-apply config-driven syntax
+	// defaults every frame (e.g. ImGuiFrontend) don't stomp this choice.
+	buf.SetSyntaxUserOverride(true);
 	buf.EnsureHighlighter();
 	auto *eng = buf.Highlighter();
 	if (!eng)
@@ -973,6 +1033,7 @@ cmd_syntax(CommandContext &ctx)
 	};
 	trim(arg);
 	if (arg == "on") {
+		b->SetSyntaxUserOverride(true);
 		b->SetSyntaxEnabled(true);
 		// If no highlighter but filetype is cpp by extension, set it
 		if (!b->Highlighter() || !b->Highlighter()->HasHighlighter()) {
@@ -980,6 +1041,7 @@ cmd_syntax(CommandContext &ctx)
 		}
 		ctx.editor.SetStatus("syntax: on");
 	} else if (arg == "off") {
+		b->SetSyntaxUserOverride(true);
 		b->SetSyntaxEnabled(false);
 		ctx.editor.SetStatus("syntax: off");
 	} else if (arg == "reload") {
@@ -1331,6 +1393,43 @@ cmd_font_set_size(CommandContext &ctx)
 #endif
 
 
+// Toggle edit mode (code/writing) for current buffer
+static bool
+cmd_toggle_edit_mode(const CommandContext &ctx)
+{
+	Buffer *b = ctx.editor.CurrentBuffer();
+	if (!b)
+		return false;
+
+	std::string arg = ctx.arg;
+	std::transform(arg.begin(), arg.end(), arg.begin(), [](unsigned char c) {
+		return static_cast<char>(std::tolower(c));
+	});
+	// Trim whitespace
+	auto start = arg.find_first_not_of(" \t");
+	if (start != std::string::npos)
+		arg = arg.substr(start);
+	auto end = arg.find_last_not_of(" \t");
+	if (end != std::string::npos)
+		arg = arg.substr(0, end + 1);
+
+	if (arg == "code") {
+		b->SetEditMode(EditMode::Code);
+	} else if (arg == "writing") {
+		b->SetEditMode(EditMode::Writing);
+	} else {
+		b->ToggleEditMode();
+	}
+
+	// Writing mode disables syntax highlighting; code mode re-enables it.
+	b->SetSyntaxEnabled(b->GetEditMode() == EditMode::Code);
+
+	const char *mode_str = (b->GetEditMode() == EditMode::Writing) ? "writing" : "code";
+	ctx.editor.SetStatus(std::string("Mode: ") + mode_str);
+	return true;
+}
+
+
 // Background set command (GUI, ImGui-only for now)
 #if defined(KTE_BUILD_GUI) && !defined(KTE_USE_QT)
 static bool
@@ -1353,6 +1452,10 @@ cmd_background_set(const CommandContext &ctx)
 	std::transform(mode.begin(), mode.end(), mode.begin(), [](unsigned char c) {
 		return (char) std::tolower(c);
 	});
+	if (mode.empty()) {
+		ctx.editor.SetStatus(std::string("Background: ") + kte::BackgroundModeName());
+		return true;
+	}
 	if (mode != "light" && mode != "dark") {
 		ctx.editor.SetStatus("background: expected 'light' or 'dark'");
 		return true;
@@ -1880,15 +1983,15 @@ cmd_insert_text(CommandContext &ctx)
 #endif
 					}
 					if (cmd == "font") {
-#if defined(KTE_BUILD_GUI) && defined(KTE_USE_QT)
-						// Complete against installed font families (case-insensitive prefix)
 						std::vector<std::string> cands;
-						QStringList fams       = QFontDatabase::families();
 						std::string apfx_lower = argprefix;
 						std::transform(apfx_lower.begin(), apfx_lower.end(), apfx_lower.begin(),
 						               [](unsigned char c) {
 							               return (char) std::tolower(c);
 						               });
+#if defined(KTE_BUILD_GUI) && defined(KTE_USE_QT)
+						// Qt: complete against system font families
+						QStringList fams = QFontDatabase::families();
 						for (const auto &fam: fams) {
 							std::string n      = fam.toStdString();
 							std::string nlower = n;
@@ -1899,6 +2002,13 @@ cmd_insert_text(CommandContext &ctx)
 							if (apfx_lower.empty() || nlower.rfind(apfx_lower, 0) == 0)
 								cands.push_back(n);
 						}
+#elif defined(KTE_BUILD_GUI)
+						// ImGui: complete against embedded font registry
+						for (const auto &n : kte::Fonts::FontRegistry::Instance().FontNames()) {
+							if (apfx_lower.empty() || n.rfind(apfx_lower, 0) == 0)
+								cands.push_back(n);
+						}
+#endif
 						if (cands.empty()) {
 							// no change
 						} else if (cands.size() == 1) {
@@ -1919,9 +2029,19 @@ cmd_insert_text(CommandContext &ctx)
 						}
 						ctx.editor.SetStatus(std::string(": ") + ctx.editor.PromptText());
 						return true;
-#else
+					}
-						(void) argprefix;
+					if (cmd == "mode") {
-#endif
+						std::vector<std::string> modes = {"code", "writing"};
+						std::vector<std::string> cands;
+						for (const auto &m : modes) {
+							if (argprefix.empty() || m.rfind(argprefix, 0) == 0)
+								cands.push_back(m);
+						}
+						if (cands.size() == 1) {
+							ctx.editor.SetPromptText(cmd + std::string(" ") + cands[0]);
+						}
+						ctx.editor.SetStatus(std::string(": ") + ctx.editor.PromptText());
+						return true;
 					}
 					// default: no special arg completion
 					ctx.editor.SetStatus(std::string(": ") + ctx.editor.PromptText());
@@ -2447,12 +2567,10 @@ cmd_newline(CommandContext &ctx)
 						}
 						pos = p + with.size();
 					} else {
-						// When replacing with empty, continue after the deletion point to avoid re-matching
+						// Replacing with empty leaves nothing inserted at the deletion
+						// point, so resume scanning from `p` itself (not p+1) to catch
+						// adjacent/overlapping matches, e.g. "aaaa" -> "" replacing "aa".
 						pos = p;
-						if (pos < static_cast<std::size_t>(buf->Rows()[y].size()))
-							++pos;
-						else
-							break;
 					}
 					++total;
 				}
@@ -2568,6 +2686,10 @@ cmd_newline(CommandContext &ctx)
 							ctx.editor.SetStatus(err);
 						} else {
 							buf->SetDirty(false);
+							if (auto *sm = ctx.editor.Swap()) {
+								sm->NotifyFilenameChanged(*buf);
+								sm->ResetJournal(*buf);
+							}
 							ctx.editor.SetStatus("Saved as " + value);
 							if (auto *u = buf->Undo())
 								u->mark_saved();
@@ -2857,14 +2979,28 @@ cmd_newline(CommandContext &ctx)
 				return true;
 			}
 			std::size_t changed = 0;
+			UndoSystem *ru      = buf->Undo();
+			UndoGroupGuard rguard(ru);
 			// Iterate by index to allow modifications via PieceTable helpers
 			for (std::size_t y = 0; y < buf->Rows().size(); ++y) {
 				std::string before = static_cast<std::string>(buf->Rows()[y]);
 				std::string after  = std::regex_replace(before, rx, repl);
 				if (after != before) {
 					// Replace entire line y with 'after' using PieceTable ops
+					if (ru) {
+						buf->SetCursor(0, y);
+						ru->Begin(UndoType::DeleteRow);
+						ru->Append(std::string_view(before));
+						ru->commit();
+					}
 					buf->delete_row(static_cast<int>(y));
 					buf->insert_row(static_cast<int>(y), std::string_view(after));
+					if (ru) {
+						buf->SetCursor(0, y);
+						ru->Begin(UndoType::InsertRow);
+						ru->Append(std::string_view(after));
+						ru->commit();
+					}
 					++changed;
 				}
 			}
@@ -2937,18 +3073,28 @@ cmd_newline(CommandContext &ctx)
 		ensure_cursor_visible(ctx.editor, *buf);
 		return true;
 	}
+	UndoSystem *u = buf->Undo();
+	if (u && repeat > 1)
+		u->BeginGroup();
 	for (int i = 0; i < repeat; ++i) {
+		// Sync the buffer's cursor to the split point before Begin(), which
+		// records its node's row/col from the buffer's *current* cursor. Undo
+		// must reverse this exact split, not wherever the cursor ends up after
+		// the whole loop finishes.
+		buf->SetCursor(x, y);
+		if (u) {
+			u->Begin(UndoType::Newline);
+			u->commit();
+		}
 		buf->split_line(static_cast<int>(y), static_cast<int>(x));
 		// Move to start of next line
 		y += 1;
 		x = 0;
 	}
+	if (u && repeat > 1)
+		u->EndGroup();
 	buf->SetCursor(x, y);
 	buf->SetDirty(true);
-	if (auto *u = buf->Undo()) {
-		u->Begin(UndoType::Newline);
-		u->commit();
-	}
 	ensure_cursor_visible(ctx.editor, *buf);
 	return true;
 }
@@ -3132,7 +3278,9 @@ cmd_backspace(CommandContext &ctx)
 			x = prev_len;
 			buf->SetCursor(x, y);
 			if (u) {
-				u->Begin(UndoType::Newline);
+				// Forward action here is a join, not a split: JoinLines has the
+				// correct (inverted) apply() semantics, unlike Newline.
+				u->Begin(UndoType::JoinLines);
 				u->commit();
 			}
 		} else {
@@ -3211,7 +3359,9 @@ cmd_delete_char(CommandContext &ctx)
 		} else if (y + 1 < rows_view.size()) {
 			buf->join_lines(static_cast<int>(y));
 			if (u) {
-				u->Begin(UndoType::Newline);
+				// Forward action here is a join, not a split: JoinLines has the
+				// correct (inverted) apply() semantics, unlike Newline.
+				u->Begin(UndoType::JoinLines);
 				u->commit();
 			}
 		} else {
@@ -3284,18 +3434,32 @@ cmd_kill_to_eol(CommandContext &ctx)
 	std::size_t x = buf->Curx();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
+	UndoSystem *u = buf->Undo();
+	UndoGroupGuard guard(u);
 	for (int i = 0; i < repeat; ++i) {
 		const auto &rows_view = buf->Rows();
 		if (y >= rows_view.size())
 			break;
 		if (x < rows_view[y].size()) {
 			// delete from cursor to end of line
-			killed_total    += rows_view[y].substr(x);
+			std::string seg = static_cast<std::string>(rows_view[y].substr(x));
+			killed_total    += seg;
 			std::size_t len = rows_view[y].size() - x;
 			buf->delete_text(static_cast<int>(y), static_cast<int>(x), len);
+			if (u) {
+				buf->SetCursor(x, y);
+				u->Begin(UndoType::Delete);
+				u->Append(std::string_view(seg));
+				u->commit();
+			}
 		} else if (y + 1 < rows_view.size()) {
 			// at EOL: delete the newline (join with next line)
 			killed_total += "\n";
+			if (u) {
+				buf->SetCursor(x, y);
+				u->Begin(UndoType::JoinLines);
+				u->commit();
+			}
 			buf->join_lines(static_cast<int>(y));
 		} else {
 			// nothing to delete
@@ -3329,20 +3493,37 @@ cmd_kill_line(CommandContext &ctx)
 	(void) x; // cursor x will be reset to 0
 	int repeat = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
+	UndoSystem *u = buf->Undo();
+	UndoGroupGuard guard(u);
 	for (int i = 0; i < repeat; ++i) {
 		const auto &rows_view = buf->Rows();
 		if (rows_view.empty())
 			break;
 		if (rows_view.size() == 1) {
 			// last remaining line: clear its contents
-			killed_total += static_cast<std::string>(rows_view[0]);
+			std::string content = static_cast<std::string>(rows_view[0]);
-			if (!rows_view[0].empty())
+			killed_total += content;
-				buf->delete_text(0, 0, rows_view[0].size());
+			if (!content.empty()) {
+				buf->delete_text(0, 0, content.size());
+				if (u) {
+					buf->SetCursor(0, 0);
+					u->Begin(UndoType::Delete);
+					u->Append(std::string_view(content));
+					u->commit();
+				}
+			}
 			y = 0;
 		} else if (y < rows_view.size()) {
 			// erase current line; keep y pointing at the next line
-			killed_total += static_cast<std::string>(rows_view[y]);
+			std::string content = static_cast<std::string>(rows_view[y]);
+			killed_total += content;
 			killed_total += "\n";
+			if (u) {
+				buf->SetCursor(0, y);
+				u->Begin(UndoType::DeleteRow);
+				u->Append(std::string_view(content));
+				u->commit();
+			}
 			buf->delete_row(static_cast<int>(y));
 			const auto &rows_after = buf->Rows();
 			if (y >= rows_after.size()) {
@@ -3556,7 +3737,10 @@ cmd_kill_region(CommandContext &ctx)
 		return false;
 	}
 	std::string text = extract_region_text(*buf, sx, sy, ex, ey);
-	delete_region(*buf, sx, sy, ex, ey);
+	{
+		UndoGroupGuard guard(buf->Undo());
+		delete_region(*buf, sx, sy, ex, ey, buf->Undo());
+	}
 	ensure_cursor_visible(ctx.editor, *buf);
 	if (!text.empty()) {
 		if (ctx.editor.KillChain())
@@ -4168,6 +4352,7 @@ cmd_delete_word_prev(CommandContext &ctx)
 	std::size_t x = buf->Curx();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
+	UndoGroupGuard guard(buf->Undo());
 	for (int i = 0; i < repeat; ++i) {
 		if (y >= rows.size()) {
 			y = rows.empty() ? 0 : rows.size() - 1;
@@ -4209,7 +4394,7 @@ cmd_delete_word_prev(CommandContext &ctx)
 		}
 		// Now delete from (x, y) to (start_x, start_y) using PieceTable
 		std::string deleted = extract_region_text(*buf, x, y, start_x, start_y);
-		delete_region(*buf, x, y, start_x, start_y);
+		delete_region(*buf, x, y, start_x, start_y, buf->Undo());
 		// Prepend to killed_total (since we're deleting backwards)
 		killed_total = deleted + killed_total;
 	}
@@ -4241,6 +4426,7 @@ cmd_delete_word_next(CommandContext &ctx)
 	std::size_t x    = buf->Curx();
 	int repeat       = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
+	UndoGroupGuard guard(buf->Undo());
 	for (int i = 0; i < repeat; ++i) {
 		if (y >= rows.size())
 			break;
@@ -4280,7 +4466,7 @@ cmd_delete_word_next(CommandContext &ctx)
 		}
 		// Now delete from (start_x, start_y) to (x, y) using PieceTable
 		std::string deleted = extract_region_text(*buf, start_x, start_y, x, y);
-		delete_region(*buf, start_x, start_y, x, y);
+		delete_region(*buf, start_x, start_y, x, y, buf->Undo());
 		y            = start_y;
 		x            = start_x;
 		killed_total += deleted;
@@ -4314,8 +4500,16 @@ cmd_indent_region(CommandContext &ctx)
 		ctx.editor.SetStatus("No region to indent");
 		return false;
 	}
+	UndoSystem *u = buf->Undo();
+	UndoGroupGuard guard(u);
 	for (std::size_t y = sy; y <= ey && y < buf->Rows().size(); ++y) {
 		buf->insert_text(static_cast<int>(y), 0, std::string_view("\t"));
+		if (u) {
+			buf->SetCursor(0, y);
+			u->Begin(UndoType::Insert);
+			u->Append('\t');
+			u->commit();
+		}
 	}
 	buf->SetDirty(true);
 	buf->ClearMark();
@@ -4339,6 +4533,8 @@ cmd_unindent_region(CommandContext &ctx)
 		ctx.editor.SetStatus("No region to unindent");
 		return false;
 	}
+	UndoSystem *u = buf->Undo();
+	UndoGroupGuard guard(u);
 	for (std::size_t y = sy; y <= ey && y < buf->Rows().size(); ++y) {
 		const auto &rows_view = buf->Rows();
 		if (y >= rows_view.size())
@@ -4347,13 +4543,26 @@ cmd_unindent_region(CommandContext &ctx)
 		if (!line.empty()) {
 			if (line[0] == '\t') {
 				buf->delete_text(static_cast<int>(y), 0, 1);
+				if (u) {
+					buf->SetCursor(0, y);
+					u->Begin(UndoType::Delete);
+					u->Append('\t');
+					u->commit();
+				}
 			} else if (line[0] == ' ') {
 				std::size_t spaces = 0;
 				while (spaces < line.size() && spaces < 8 && line[spaces] == ' ') {
 					++spaces;
 				}
-				if (spaces > 0)
+				if (spaces > 0) {
 					buf->delete_text(static_cast<int>(y), 0, spaces);
+					if (u) {
+						buf->SetCursor(0, y);
+						u->Begin(UndoType::Delete);
+						u->Append(line.substr(0, spaces));
+						u->commit();
+					}
+				}
 			}
 		}
 	}
@@ -4370,25 +4579,8 @@ cmd_reflow_paragraph(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
-	struct GroupGuard {
-		UndoSystem *u;
-
-
-		explicit GroupGuard(UndoSystem *u_) : u(u_)
-		{
-			if (u)
-				u->BeginGroup();
-		}
-
-
-		~GroupGuard()
-		{
-			if (u)
-				u->EndGroup();
-		}
-	};
 	// Reflow performs a multi-edit transformation; make it a single standalone undo/redo step.
-	GroupGuard guard(buf->Undo());
+	UndoGroupGuard guard(buf->Undo());
 	if (auto *u = buf->Undo())
 		u->commit();
 	ensure_at_least_one_line(*buf);
@@ -5013,6 +5205,11 @@ InstallDefaultCommands()
 		CommandId::NewWindow, "new-window", "Open a new editor window (GUI only)", cmd_new_window,
 		false, false
 	});
+	// Edit mode toggle (public)
+	CommandRegistry::Register({
+		CommandId::ToggleEditMode, "mode", "Toggle or set edit mode: code|writing",
+		cmd_toggle_edit_mode, true, false
+	});
 }
 
 

Command.h

@@ -113,6 +113,12 @@ enum class CommandId {
 	CenterOnCursor, // center the viewport on the current cursor line (C-k k)
 	// GUI: open a new editor window sharing the same buffer list
 	NewWindow,
+	// GUI: font size controls
+	FontZoomIn,
+	FontZoomOut,
+	FontZoomReset,
+	// Edit mode (code/writing)
+	ToggleEditMode,
 };
 
 

Editor.cc

@@ -69,20 +69,22 @@ Editor::SetStatus(const std::string &message)
 Buffer *
 Editor::CurrentBuffer()
 {
-	if (buffers_.empty() || curbuf_ >= buffers_.size()) {
+	auto &bufs = Buffers();
+	if (bufs.empty() || curbuf_ >= bufs.size()) {
 		return nullptr;
 	}
-	return &buffers_[curbuf_];
+	return &bufs[curbuf_];
 }
 
 
 const Buffer *
 Editor::CurrentBuffer() const
 {
-	if (buffers_.empty() || curbuf_ >= buffers_.size()) {
+	const auto &bufs = Buffers();
+	if (bufs.empty() || curbuf_ >= bufs.size()) {
 		return nullptr;
 	}
-	return &buffers_[curbuf_];
+	return &bufs[curbuf_];
 }
 
 
@@ -117,8 +119,9 @@ Editor::DisplayNameFor(const Buffer &buf) const
 
 	// Prepare list of other buffer paths
 	std::vector<std::vector<std::filesystem::path> > others;
-	others.reserve(buffers_.size());
+	const auto &bufs = Buffers();
-	for (const auto &b: buffers_) {
+	others.reserve(bufs.size());
+	for (const auto &b: bufs) {
 		if (&b == &buf)
 			continue;
 		if (b.Filename().empty())
@@ -161,41 +164,69 @@ Editor::DisplayNameFor(const Buffer &buf) const
 std::size_t
 Editor::AddBuffer(const Buffer &buf)
 {
-	buffers_.push_back(buf);
+	auto &bufs = Buffers();
-	// Attach swap recorder
+	// push_back may reallocate the vector's storage, moving every existing
+	// Buffer to a new address. Drain any in-flight swap records first so the
+	// writer thread never dereferences an address that's about to move, then
+	// rehome each attached buffer that actually moved.
+	if (swap_ && !bufs.empty())
+		swap_->Flush();
+	std::vector<Buffer *> old_addrs;
+	old_addrs.reserve(bufs.size());
+	for (auto &b: bufs)
+		old_addrs.push_back(&b);
+	bufs.push_back(buf);
 	if (swap_) {
-		swap_->Attach(&buffers_.back());
+		for (std::size_t i = 0; i < old_addrs.size(); ++i) {
-		buffers_.back().SetSwapRecorder(swap_->RecorderFor(&buffers_.back()));
+			Buffer *new_addr = &bufs[i];
+			if (new_addr != old_addrs[i])
+				bufs[i].SetSwapRecorder(swap_->Rehome(old_addrs[i], new_addr));
 		}
-	if (buffers_.size() == 1) {
+		swap_->Attach(&bufs.back());
+		bufs.back().SetSwapRecorder(swap_->RecorderFor(&bufs.back()));
+	}
+	if (bufs.size() == 1) {
 		curbuf_ = 0;
 	}
-	return buffers_.size() - 1;
+	return bufs.size() - 1;
 }
 
 
 std::size_t
 Editor::AddBuffer(Buffer &&buf)
 {
-	buffers_.push_back(std::move(buf));
+	auto &bufs = Buffers();
+	if (swap_ && !bufs.empty())
+		swap_->Flush();
+	std::vector<Buffer *> old_addrs;
+	old_addrs.reserve(bufs.size());
+	for (auto &b: bufs)
+		old_addrs.push_back(&b);
+	bufs.push_back(std::move(buf));
 	if (swap_) {
-		swap_->Attach(&buffers_.back());
+		for (std::size_t i = 0; i < old_addrs.size(); ++i) {
-		buffers_.back().SetSwapRecorder(swap_->RecorderFor(&buffers_.back()));
+			Buffer *new_addr = &bufs[i];
+			if (new_addr != old_addrs[i])
+				bufs[i].SetSwapRecorder(swap_->Rehome(old_addrs[i], new_addr));
 		}
-	if (buffers_.size() == 1) {
+		swap_->Attach(&bufs.back());
+		bufs.back().SetSwapRecorder(swap_->RecorderFor(&bufs.back()));
+	}
+	if (bufs.size() == 1) {
 		curbuf_ = 0;
 	}
-	return buffers_.size() - 1;
+	return bufs.size() - 1;
 }
 
 
 bool
 Editor::OpenFile(const std::string &path, std::string &err)
 {
-	// If there is exactly one unnamed, empty, clean buffer, reuse it instead
+	// If the current buffer is an unnamed, empty, clean scratch buffer, reuse
-	// of creating a new one.
+	// it instead of creating a new one.
-	if (buffers_.size() == 1) {
+	auto &bufs_ref = Buffers();
-		Buffer &cur                  = buffers_[curbuf_];
+	if (!bufs_ref.empty() && curbuf_ < bufs_ref.size()) {
+		Buffer &cur                  = bufs_ref[curbuf_];
 		const bool unnamed           = cur.Filename().empty() && !cur.IsFileBacked();
 		const bool clean             = !cur.Dirty();
 		const std::size_t nrows      = cur.Nrows();
@@ -268,7 +299,7 @@ Editor::OpenFile(const std::string &path, std::string &err)
 	// Add as a new buffer and switch to it
 	std::size_t idx = AddBuffer(std::move(b));
 	if (swap_) {
-		swap_->NotifyFilenameChanged(buffers_[idx]);
+		swap_->NotifyFilenameChanged(Buffers()[idx]);
 	}
 	SwitchTo(idx);
 	// Defensive: ensure any active prompt is closed after a successful open
@@ -446,12 +477,13 @@ Editor::ProcessPendingOpens()
 bool
 Editor::SwitchTo(std::size_t index)
 {
-	if (index >= buffers_.size()) {
+	auto &bufs = Buffers();
+	if (index >= bufs.size()) {
 		return false;
 	}
 	curbuf_ = index;
 	// Robustness: ensure a valid highlighter is installed when switching buffers
-	Buffer &b = buffers_[curbuf_];
+	Buffer &b = bufs[curbuf_];
 	if (b.SyntaxEnabled()) {
 		b.EnsureHighlighter();
 		if (auto *eng = b.Highlighter()) {
@@ -478,21 +510,36 @@ Editor::SwitchTo(std::size_t index)
 bool
 Editor::CloseBuffer(std::size_t index)
 {
-	if (index >= buffers_.size()) {
+	auto &bufs = Buffers();
+	if (index >= bufs.size()) {
 		return false;
 	}
 	if (swap_) {
 		// Always remove swap file when closing a buffer on normal exit.
 		// Swap files are for crash recovery; on clean close, we don't need them.
 		// This prevents stale swap files from accumulating (e.g., when used as git editor).
-		swap_->Detach(&buffers_[index], true);
+		swap_->Detach(&bufs[index], true);
-		buffers_[index].SetSwapRecorder(nullptr);
+		bufs[index].SetSwapRecorder(nullptr);
+		// Drain in-flight records before the erase-shift below moves other
+		// buffers to new addresses (vector::erase never reallocates, but it does
+		// move-assign each trailing buffer into the previous slot).
+		swap_->Flush();
 	}
-	buffers_.erase(buffers_.begin() + static_cast<std::ptrdiff_t>(index));
+	bufs.erase(bufs.begin() + static_cast<std::ptrdiff_t>(index));
-	if (buffers_.empty()) {
+	if (swap_) {
+		// erase() shifts every buffer after `index` down by one slot in-place
+		// (no reallocation), so the buffer now at slot i used to live at slot
+		// i+1 (same underlying storage, since data() doesn't move on erase).
+		for (std::size_t i = index; i < bufs.size(); ++i) {
+			Buffer *new_addr = &bufs[i];
+			Buffer *old_addr = new_addr + 1;
+			bufs[i].SetSwapRecorder(swap_->Rehome(old_addr, new_addr));
+		}
+	}
+	if (bufs.empty()) {
 		curbuf_ = 0;
-	} else if (curbuf_ >= buffers_.size()) {
+	} else if (curbuf_ >= bufs.size()) {
-		curbuf_ = buffers_.size() - 1;
+		curbuf_ = bufs.size() - 1;
 	}
 	return true;
 }
@@ -516,7 +563,12 @@ Editor::Reset()
 	// Reset close-confirm/save state
 	close_confirm_pending_ = false;
 	close_after_save_      = false;
-	buffers_.clear();
+	auto &bufs = Buffers();
+	if (swap_) {
+		for (auto &buf : bufs)
+			swap_->Detach(&buf, true);
+	}
+	bufs.clear();
 	curbuf_ = 0;
 }
 

Editor.h

@@ -521,7 +521,7 @@ public:
 	// Buffers
 	[[nodiscard]] std::size_t BufferCount() const
 	{
-		return buffers_.size();
+		return Buffers().size();
 	}
 
 
@@ -531,6 +531,19 @@ public:
 	}
 
 
+	// Clamp curbuf_ to valid range. Call when the shared buffer list may
+	// have been modified by another editor (e.g., buffer closed in another window).
+	void ValidateBufferIndex()
+	{
+		const auto &bufs = Buffers();
+		if (bufs.empty()) {
+			curbuf_ = 0;
+		} else if (curbuf_ >= bufs.size()) {
+			curbuf_ = bufs.size() - 1;
+		}
+	}
+
+
 	Buffer *CurrentBuffer();
 
 	const Buffer *CurrentBuffer() const;

GUIConfig.cc

@@ -3,9 +3,29 @@
 #include <fstream>
 #include <sstream>
 #include <algorithm>
+#include <filesystem>
+#include <iostream>
 
 #include "GUIConfig.h"
 
+// toml++ for TOML config parsing
+#if defined(__clang__)
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Weverything"
+#elif defined(__GNUC__)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wall"
+#  pragma GCC diagnostic ignored "-Wextra"
+#endif
+
+#include "ext/tomlplusplus/toml.hpp"
+
+#if defined(__clang__)
+#  pragma clang diagnostic pop
+#elif defined(__GNUC__)
+#  pragma GCC diagnostic pop
+#endif
+
 
 static void
 trim(std::string &s)
@@ -19,37 +39,124 @@ trim(std::string &s)
 
 
 static std::string
-default_config_path()
+config_dir()
 {
 	const char *home = std::getenv("HOME");
 	if (!home || !*home)
 		return {};
-	std::string path(home);
+	return std::string(home) + "/.config/kte";
-	path += "/.config/kte/kge.ini";
-	return path;
 }
 
 
 GUIConfig
 GUIConfig::Load()
 {
-	GUIConfig cfg; // defaults already set
+	GUIConfig cfg;
-	const std::string path = default_config_path();
+	std::string dir = config_dir();
+	if (dir.empty())
+		return cfg;
 
-	if (!path.empty()) {
+	// Try TOML first
-		cfg.LoadFromFile(path);
+	std::string toml_path = dir + "/kge.toml";
+	if (cfg.LoadFromTOML(toml_path))
+		return cfg;
+
+	// Fall back to legacy INI
+	std::string ini_path = dir + "/kge.ini";
+	if (cfg.LoadFromINI(ini_path)) {
+		std::cerr << "kge: loaded legacy kge.ini; consider migrating to kge.toml\n";
+		return cfg;
 	}
+
 	return cfg;
 }
 
 
 bool
-GUIConfig::LoadFromFile(const std::string &path)
+GUIConfig::LoadFromTOML(const std::string &path)
+{
+	if (!std::filesystem::exists(path))
+		return false;
+
+	toml::table tbl;
+	try {
+		tbl = toml::parse_file(path);
+	} catch (const toml::parse_error &err) {
+		std::cerr << "kge: TOML parse error in " << path << ": " << err.what() << "\n";
+		return false;
+	}
+
+	// [window]
+	if (auto win = tbl["window"].as_table()) {
+		if (auto v = (*win)["fullscreen"].value<bool>())
+			fullscreen = *v;
+		if (auto v = (*win)["columns"].value<int64_t>()) {
+			if (*v > 0) columns = static_cast<int>(*v);
+		}
+		if (auto v = (*win)["rows"].value<int64_t>()) {
+			if (*v > 0) rows = static_cast<int>(*v);
+		}
+	}
+
+	// [font]
+	bool explicit_code_font    = false;
+	bool explicit_writing_font = false;
+	if (auto sec = tbl["font"].as_table()) {
+		if (auto v = (*sec)["name"].value<std::string>())
+			font = *v;
+		if (auto v = (*sec)["size"].value<double>()) {
+			if (*v > 0.0) font_size = static_cast<float>(*v);
+		}
+		if (auto v = (*sec)["code"].value<std::string>()) {
+			code_font = *v;
+			explicit_code_font = true;
+		}
+		if (auto v = (*sec)["writing"].value<std::string>()) {
+			writing_font = *v;
+			explicit_writing_font = true;
+		}
+	}
+
+	// [appearance]
+	if (auto sec = tbl["appearance"].as_table()) {
+		if (auto v = (*sec)["theme"].value<std::string>())
+			theme = *v;
+		if (auto v = (*sec)["background"].value<std::string>()) {
+			std::string bg = *v;
+			std::transform(bg.begin(), bg.end(), bg.begin(), [](unsigned char c) {
+				return (char) std::tolower(c);
+			});
+			if (bg == "light" || bg == "dark")
+				background = bg;
+		}
+	}
+
+	// [editor]
+	if (auto sec = tbl["editor"].as_table()) {
+		if (auto v = (*sec)["syntax"].value<bool>())
+			syntax = *v;
+	}
+
+	// Default code_font to the main font if not explicitly set
+	if (!explicit_code_font)
+		code_font = font;
+	if (!explicit_writing_font && writing_font == "crimsonpro" && font != "default")
+		writing_font = font;
+
+	return true;
+}
+
+
+bool
+GUIConfig::LoadFromINI(const std::string &path)
 {
 	std::ifstream in(path);
 	if (!in.good())
 		return false;
 
+	bool explicit_code_font    = false;
+	bool explicit_writing_font = false;
+
 	std::string line;
 	while (std::getline(in, line)) {
 		// Remove comments starting with '#' or ';'
@@ -104,6 +211,12 @@ GUIConfig::LoadFromFile(const std::string &path)
 			}
 		} else if (key == "font") {
 			font = val;
+		} else if (key == "code_font") {
+			code_font = val;
+			explicit_code_font = true;
+		} else if (key == "writing_font") {
+			writing_font = val;
+			explicit_writing_font = true;
 		} else if (key == "theme") {
 			theme = val;
 		} else if (key == "background" || key == "bg") {
@@ -126,5 +239,13 @@ GUIConfig::LoadFromFile(const std::string &path)
 		}
 	}
 
+	// If code_font was not explicitly set, default it to the main font
+	// so that the edit-mode font switcher doesn't immediately switch away
+	// from the font loaded during Init.
+	if (!explicit_code_font)
+		code_font = font;
+	if (!explicit_writing_font && writing_font == "crimsonpro" && font != "default")
+		writing_font = font;
+
 	return true;
 }

GUIConfig.h

@@ -1,5 +1,7 @@
 /*
- * GUIConfig - loads simple GUI configuration from $HOME/.config/kte/kge.ini
+ * GUIConfig - loads GUI configuration from $HOME/.config/kte/kge.toml
+ *
+ * Falls back to legacy kge.ini if no TOML config is found.
  */
 #pragma once
 
@@ -22,12 +24,18 @@ public:
 	std::string background = "dark";
 
 	// Default syntax highlighting state for GUI (kge): on/off
-	// Accepts: on/off/true/false/yes/no/1/0 in the ini file.
+	bool syntax = true;
-	bool syntax = true; // default: enabled
 
-	// Load from default path: $HOME/.config/kte/kge.ini
+	// Per-mode font defaults
+	std::string code_font    = "default";
+	std::string writing_font = "crimsonpro";
+
+	// Load from default paths: try kge.toml first, fall back to kge.ini
 	static GUIConfig Load();
 
-	// Load from explicit path. Returns true if file existed and was parsed.
+	// Load from explicit TOML path. Returns true if file existed and was parsed.
-	bool LoadFromFile(const std::string &path);
+	bool LoadFromTOML(const std::string &path);
+
+	// Load from explicit INI path (legacy). Returns true if file existed and was parsed.
+	bool LoadFromINI(const std::string &path);
 };

GUITheme.h

@@ -312,7 +312,7 @@ namespace kte {
 enum class BackgroundMode { Light, Dark };
 
 // Global background mode; default to Dark to match prior defaults
-static inline auto gBackgroundMode = BackgroundMode::Dark;
+inline auto gBackgroundMode = BackgroundMode::Dark;
 
 // Basic theme identifier (kept minimal; some ids are aliases)
 enum class ThemeId {
@@ -330,11 +330,13 @@ enum class ThemeId {
 	Amber = 10,
 	WeylandYutani = 11,
 	Orbital = 12,
+	Tufte = 13,
+	Leuchtturm = 14,
 };
 
 // Current theme tracking
-static inline auto gCurrentTheme             = ThemeId::Nord;
+inline auto gCurrentTheme             = ThemeId::Nord;
-static inline std::size_t gCurrentThemeIndex = 6; // Nord index
+inline std::size_t gCurrentThemeIndex = 7; // Nord index
 
 // Forward declarations for helpers used below
 static size_t ThemeIndexFromId(ThemeId id);
@@ -372,11 +374,13 @@ BackgroundModeName()
 #include "themes/Everforest.h"
 #include "themes/KanagawaPaper.h"
 #include "themes/LCARS.h"
+#include "themes/Leuchtturm.h"
 #include "themes/OldBook.h"
 #include "themes/Amber.h"
 #include "themes/WeylandYutani.h"
 #include "themes/Zenburn.h"
 #include "themes/Orbital.h"
+#include "themes/Tufte.h"
 
 
 // Theme abstraction and registry (generalized theme system)
@@ -409,6 +413,28 @@ struct LCARSTheme final : Theme {
 	}
 };
 
+struct LeuchtturmTheme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "leuchtturm";
+	}
+
+
+	void Apply() const override
+	{
+		if (gBackgroundMode == BackgroundMode::Dark)
+			ApplyLeuchtturmDarkTheme();
+		else
+			ApplyLeuchtturmLightTheme();
+	}
+
+
+	ThemeId Id() override
+	{
+		return ThemeId::Leuchtturm;
+	}
+};
+
 struct EverforestTheme final : Theme {
 	[[nodiscard]] const char *Name() const override
 	{
@@ -488,6 +514,28 @@ struct OrbitalTheme final : Theme {
 	}
 };
 
+struct TufteTheme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "tufte";
+	}
+
+
+	void Apply() const override
+	{
+		if (gBackgroundMode == BackgroundMode::Dark)
+			ApplyTufteDarkTheme();
+		else
+			ApplyTufteLightTheme();
+	}
+
+
+	ThemeId Id() override
+	{
+		return ThemeId::Tufte;
+	}
+};
+
 struct ZenburnTheme final : Theme {
 	[[nodiscard]] const char *Name() const override
 	{
@@ -657,18 +705,20 @@ ThemeRegistry()
 	static std::vector<std::unique_ptr<Theme> > reg;
 	if (reg.empty()) {
 		// Alphabetical by canonical name:
-		// amber, eink, everforest, gruvbox, kanagawa-paper, lcars, nord, old-book, orbital, plan9, solarized, weyland-yutani, zenburn
+		// amber, eink, everforest, gruvbox, kanagawa-paper, lcars, leuchtturm, nord, old-book, orbital, plan9, solarized, tufte, weyland-yutani, zenburn
 		reg.emplace_back(std::make_unique<detail::AmberTheme>());
 		reg.emplace_back(std::make_unique<detail::EInkTheme>());
 		reg.emplace_back(std::make_unique<detail::EverforestTheme>());
 		reg.emplace_back(std::make_unique<detail::GruvboxTheme>());
 		reg.emplace_back(std::make_unique<detail::KanagawaPaperTheme>());
 		reg.emplace_back(std::make_unique<detail::LCARSTheme>());
+		reg.emplace_back(std::make_unique<detail::LeuchtturmTheme>());
 		reg.emplace_back(std::make_unique<detail::NordTheme>());
 		reg.emplace_back(std::make_unique<detail::OldBookTheme>());
 		reg.emplace_back(std::make_unique<detail::OrbitalTheme>());
 		reg.emplace_back(std::make_unique<detail::Plan9Theme>());
 		reg.emplace_back(std::make_unique<detail::SolarizedTheme>());
+		reg.emplace_back(std::make_unique<detail::TufteTheme>());
 		reg.emplace_back(std::make_unique<detail::WeylandYutaniTheme>());
 		reg.emplace_back(std::make_unique<detail::ZenburnTheme>());
 	}
@@ -845,20 +895,24 @@ ThemeIndexFromId(const ThemeId id)
 		return 4;
 	case ThemeId::LCARS:
 		return 5;
-	case ThemeId::Nord:
+	case ThemeId::Leuchtturm:
 		return 6;
-	case ThemeId::OldBook:
+	case ThemeId::Nord:
 		return 7;
-	case ThemeId::Orbital:
+	case ThemeId::OldBook:
 		return 8;
-	case ThemeId::Plan9:
+	case ThemeId::Orbital:
 		return 9;
-	case ThemeId::Solarized:
+	case ThemeId::Plan9:
 		return 10;
-	case ThemeId::WeylandYutani:
+	case ThemeId::Solarized:
 		return 11;
-	case ThemeId::Zenburn:
+	case ThemeId::Tufte:
 		return 12;
+	case ThemeId::WeylandYutani:
+		return 13;
+	case ThemeId::Zenburn:
+		return 14;
 	}
 	return 0;
 }
@@ -882,30 +936,144 @@ ThemeIdFromIndex(const size_t idx)
 	case 5:
 		return ThemeId::LCARS;
 	case 6:
-		return ThemeId::Nord;
+		return ThemeId::Leuchtturm;
 	case 7:
-		return ThemeId::OldBook;
+		return ThemeId::Nord;
 	case 8:
-		return ThemeId::Orbital;
+		return ThemeId::OldBook;
 	case 9:
-		return ThemeId::Plan9;
+		return ThemeId::Orbital;
 	case 10:
-		return ThemeId::Solarized;
+		return ThemeId::Plan9;
 	case 11:
-		return ThemeId::WeylandYutani;
+		return ThemeId::Solarized;
 	case 12:
+		return ThemeId::Tufte;
+	case 13:
+		return ThemeId::WeylandYutani;
+	case 14:
 		return ThemeId::Zenburn;
 	}
 }
 
 
 // --- Syntax palette (v1): map TokenKind to ink color per current theme/background ---
+
+// Tufte palette: high-contrast, restrained color. Body text is true black on
+// cream; only keywords and links get subtle color to avoid a "christmas tree."
+static ImVec4
+SyntaxInkTufte(const TokenKind k, const bool dark)
+{
+	const ImVec4 ink  = dark ? RGBA(0xEAE6DE) : RGBA(0x111111); // body text
+	const ImVec4 dim  = dark ? RGBA(0x8A8680) : RGBA(0x555555); // comments
+	const ImVec4 red  = dark ? RGBA(0xD06060) : RGBA(0x8B0000); // keywords/preproc
+	const ImVec4 navy = dark ? RGBA(0x7098C0) : RGBA(0x1A3A5C); // functions/links
+	const ImVec4 grn  = dark ? RGBA(0x8AAA6E) : RGBA(0x2E5E2E); // strings
+	switch (k) {
+	case TokenKind::Keyword:
+	case TokenKind::Preproc:
+		return red;
+	case TokenKind::String:
+	case TokenKind::Char:
+		return grn;
+	case TokenKind::Comment:
+		return dim;
+	case TokenKind::Function:
+		return navy;
+	case TokenKind::Number:
+	case TokenKind::Constant:
+		return dark ? RGBA(0xC8A85A) : RGBA(0x6B4C00);
+	case TokenKind::Type:
+		return dark ? RGBA(0xBBAA90) : RGBA(0x333333);
+	case TokenKind::Error:
+		return dark ? RGBA(0xD06060) : RGBA(0xCC0000);
+	default:
+		return ink;
+	}
+}
+
+
+// Leuchtturm palette: blue-black fountain pen ink with brass and bronze accents.
+// Body text is ink-colored; accents drawn from the pen metals.
+static ImVec4
+SyntaxInkLeuchtturm(const TokenKind k, const bool dark)
+{
+	const ImVec4 ink   = dark ? RGBA(0xE5DDD0) : RGBA(0x040720); // fountain pen ink
+	const ImVec4 dim   = dark ? RGBA(0x7A7060) : RGBA(0x6A6558); // comments
+	const ImVec4 brass = dark ? RGBA(0xB8A060) : RGBA(0x504518); // patinated brass
+	const ImVec4 bronze= dark ? RGBA(0xC08050) : RGBA(0x5C3010); // dark bronze
+	const ImVec4 navy  = dark ? RGBA(0x8898B0) : RGBA(0x1C2E4A); // deep navy
+	switch (k) {
+	case TokenKind::Keyword:
+	case TokenKind::Preproc:
+		return brass;
+	case TokenKind::String:
+	case TokenKind::Char:
+		return bronze;
+	case TokenKind::Comment:
+		return dim;
+	case TokenKind::Function:
+		return navy;
+	case TokenKind::Number:
+	case TokenKind::Constant:
+		return dark ? RGBA(0xA89060) : RGBA(0x483C10);
+	case TokenKind::Type:
+		return dark ? RGBA(0xC0B898) : RGBA(0x222238);
+	case TokenKind::Error:
+		return dark ? RGBA(0xD06060) : RGBA(0xA02020);
+	default:
+		return ink;
+	}
+}
+
+
+// Everforest: warm forest palette on dark green-gray (bg 0x2B3339).
+// Default comment color (0x616E88) is too dim; boost it and tune others.
+static ImVec4
+SyntaxInkEverforest(const TokenKind k)
+{
+	switch (k) {
+	case TokenKind::Keyword:
+		return RGBA(0xE67E80); // everforest red
+	case TokenKind::Type:
+		return RGBA(0xD699B6); // everforest purple
+	case TokenKind::String:
+	case TokenKind::Char:
+		return RGBA(0xA7C080); // everforest green
+	case TokenKind::Comment:
+		return RGBA(0x859289); // boosted from 0x616E88 for contrast
+	case TokenKind::Number:
+	case TokenKind::Constant:
+		return RGBA(0xD8A657); // everforest yellow/orange
+	case TokenKind::Preproc:
+		return RGBA(0xE69875); // everforest orange
+	case TokenKind::Function:
+		return RGBA(0x83C092); // everforest aqua
+	case TokenKind::Operator:
+	case TokenKind::Punctuation:
+		return RGBA(0xD3C6AA); // everforest fg
+	case TokenKind::Error:
+		return RGBA(0xE67E80);
+	default:
+		return RGBA(0xD3C6AA); // everforest fg
+	}
+}
+
+
 [[maybe_unused]] static ImVec4
 SyntaxInk(const TokenKind k)
 {
-	// Basic palettes for dark/light backgrounds; tuned for Nord-ish defaults
 	const bool dark = (GetBackgroundMode() == BackgroundMode::Dark);
-	// Base text
+
+	// Per-theme syntax palettes
+	if (gCurrentTheme == ThemeId::Tufte)
+		return SyntaxInkTufte(k, dark);
+	if (gCurrentTheme == ThemeId::Leuchtturm)
+		return SyntaxInkLeuchtturm(k, dark);
+	if (gCurrentTheme == ThemeId::Everforest)
+		return SyntaxInkEverforest(k);
+
+	// Default palettes tuned for Nord-ish themes
 	const ImVec4 def = dark ? RGBA(0xD8DEE9) : RGBA(0x2E3440);
 	switch (k) {
 	case TokenKind::Keyword:

HelpText.cc

@@ -41,6 +41,7 @@ HelpText::Text()
 		"  C-k j        Jump to mark\n"
 		"  C-k k        Center viewport on cursor\n"
 		"  C-k l        Reload buffer from disk\n"
+		"  C-k m        Toggle edit mode (code/writing)\n"
 		"  C-k n        Previous buffer\n"
 		"  C-k o        Change working directory (prompt)\n"
 		"  C-k p        Next buffer\n"
@@ -82,12 +83,24 @@ HelpText::Text()
 		"\n"
 		"Buffers:\n  +HELP+ is read-only. Press C-k ' to toggle; C-k h restores it.\n"
 		"\n"
-		"GUI appearance (command prompt):\n"
+		"Edit modes:\n"
-		"  : theme NAME         Set GUI theme (amber, eink, everforest, gruvbox, kanagawa-paper, lcars, nord, old-book, plan9, solarized, weyland-yutani, zenburn)\n"
+		"  code         Monospace font (default for source files)\n"
-		"  : background MODE    Set background: light | dark (affects eink, gruvbox, old-book, solarized)\n"
+		"  writing      Proportional font (auto for .txt, .md, .rst, .org, .tex)\n"
+		"  C-k m or : mode [code|writing] to toggle\n"
 		"\n"
-		"GUI config file options:\n"
+		"GUI commands (command prompt):\n"
-		"  font_size=NUM        Set font size in pixels (default: 16; e.g., font_size=18)\n"
+		"  : theme NAME         Set theme (amber, eink, everforest, gruvbox,\n"
+		"                       kanagawa-paper, lcars, leuchtturm, nord, old-book,\n"
+		"                       orbital, plan9, solarized, tufte, weyland-yutani,\n"
+		"                       zenburn)\n"
+		"  : background MODE    Background: light | dark\n"
+		"  : font NAME          Set font (tab completes)\n"
+		"  : font-size NUM      Set font size in pixels\n"
+		"  : mode [code|writing] Toggle or set edit mode\n"
+		"\n"
+		"Configuration:\n"
+		"  Config file: ~/.config/kte/kge.toml (see CONFIG.md)\n"
+		"  Legacy kge.ini is also supported.\n"
 		"\n"
 		"GUI window management:\n"
 		"  Cmd+N (macOS)        Open a new editor window sharing the same buffers\n"

ImGuiFrontend.cc

@@ -30,7 +30,7 @@
 static auto kGlslVersion = "#version 150"; // GL 3.2 core (macOS compatible)
 
 // ---------------------------------------------------------------------------
-// Helpers shared between Init and OpenNewWindow_
+// Helpers
 // ---------------------------------------------------------------------------
 
 static void
@@ -38,7 +38,20 @@ apply_syntax_to_buffer(Buffer *b, const GUIConfig &cfg)
 {
 	if (!b)
 		return;
-	if (cfg.syntax) {
+
+	// Auto-detect edit mode from file extension once per buffer so that
+	// manual toggles (C-k m / : mode) are not overridden every frame.
+	if (!b->EditModeDetected() && !b->Filename().empty())
+		b->SetEditMode(DetectEditMode(b->Filename()));
+
+	// If the user explicitly set syntax state via a command (:syntax on/off,
+	// :set filetype=...), leave it alone - otherwise this runs every frame
+	// and silently undoes a manual ":syntax off" on the very next frame.
+	if (b->SyntaxUserOverride())
+		return;
+
+	// Writing mode disables syntax; otherwise follow the global config.
+	if (cfg.syntax && b->GetEditMode() != EditMode::Writing) {
 		b->SetSyntaxEnabled(true);
 		b->EnsureHighlighter();
 		if (auto *eng = b->Highlighter()) {
@@ -71,7 +84,9 @@ static void
 update_editor_dimensions(Editor &ed, float disp_w, float disp_h)
 {
 	float row_h = ImGui::GetTextLineHeightWithSpacing();
-	float ch_w  = ImGui::CalcTextSize("M").x;
+	// Use average character width rather than "M" (the widest character)
+	// so that column count is reasonable for proportional fonts too.
+	float ch_w  = ImGui::CalcTextSize("abcdefghijklmnopqrstuvwxyz").x / 26.0f;
 	if (row_h <= 0.0f)
 		row_h = 16.0f;
 	if (ch_w <= 0.0f)
@@ -96,6 +111,63 @@ update_editor_dimensions(Editor &ed, float disp_w, float disp_h)
 }
 
 
+// ---------------------------------------------------------------------------
+// SetupImGuiStyle_ — apply theme, fonts, and flags to the current ImGui context
+// ---------------------------------------------------------------------------
+void
+GUIFrontend::SetupImGuiStyle_()
+{
+	ImGuiIO &io = ImGui::GetIO();
+
+	// Disable imgui.ini for secondary windows (primary sets its own path in Init)
+	io.IniFilename = nullptr;
+
+	io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
+	io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
+	ImGui::StyleColorsDark();
+
+	if (config_.background == "light")
+		kte::SetBackgroundMode(kte::BackgroundMode::Light);
+	else
+		kte::SetBackgroundMode(kte::BackgroundMode::Dark);
+	kte::ApplyThemeByName(config_.theme);
+
+	// Load fonts into this context's font atlas.
+	// Font registry is global and already populated by Init; just load into this atlas.
+	if (!kte::Fonts::FontRegistry::Instance().LoadFont(config_.font, (float) config_.font_size)) {
+		LoadGuiFont_(nullptr, (float) config_.font_size);
+	}
+}
+
+
+// ---------------------------------------------------------------------------
+// Destroy a single window's ImGui context + SDL/GL resources
+// ---------------------------------------------------------------------------
+void
+GUIFrontend::DestroyWindowResources_(WindowState &ws)
+{
+	if (ws.imgui_ctx) {
+		// Must activate this window's GL context before shutting down the
+		// OpenGL3 backend, otherwise it deletes another context's resources.
+		if (ws.window && ws.gl_ctx)
+			SDL_GL_MakeCurrent(ws.window, ws.gl_ctx);
+		ImGui::SetCurrentContext(ws.imgui_ctx);
+		ImGui_ImplOpenGL3_Shutdown();
+		ImGui_ImplSDL2_Shutdown();
+		ImGui::DestroyContext(ws.imgui_ctx);
+		ws.imgui_ctx = nullptr;
+	}
+	if (ws.gl_ctx) {
+		SDL_GL_DeleteContext(ws.gl_ctx);
+		ws.gl_ctx = nullptr;
+	}
+	if (ws.window) {
+		SDL_DestroyWindow(ws.window);
+		ws.window = nullptr;
+	}
+}
+
+
 bool
 GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 {
@@ -172,8 +244,9 @@ GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 	SDL_GL_MakeCurrent(win, gl_ctx);
 	SDL_GL_SetSwapInterval(1); // vsync
 
+	// Create primary ImGui context
 	IMGUI_CHECKVERSION();
-	ImGui::CreateContext();
+	ImGuiContext *imgui_ctx = ImGui::CreateContext();
 	ImGuiIO &io             = ImGui::GetIO();
 
 	// Set custom ini filename path to ~/.config/kte/imgui.ini
@@ -239,6 +312,7 @@ GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 	auto ws       = std::make_unique<WindowState>();
 	ws->window    = win;
 	ws->gl_ctx    = gl_ctx;
+	ws->imgui_ctx = imgui_ctx;
 	ws->width     = init_w;
 	ws->height    = init_h;
 	// The primary window's editor IS the editor passed in from main; we don't
@@ -255,8 +329,6 @@ GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 bool
 GUIFrontend::OpenNewWindow_(Editor &primary)
 {
-	SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
-
 	Uint32 win_flags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;
 	int w            = windows_[0]->width;
 	int h            = windows_[0]->height;
@@ -277,25 +349,48 @@ GUIFrontend::OpenNewWindow_(Editor &primary)
 	SDL_GL_MakeCurrent(win, gl_ctx);
 	SDL_GL_SetSwapInterval(1);
 
-	// Secondary windows share the ImGui context already created in Init.
+	// Each window gets its own ImGui context — ImGui requires exactly one
-	// We need to init the SDL2/OpenGL backends for this new window.
+	// NewFrame/Render cycle per context per frame.
-	// ImGui_ImplSDL2 supports multiple windows via SDL_GetWindowID checks.
+	ImGuiContext *imgui_ctx = ImGui::CreateContext();
-	ImGui_ImplOpenGL3_Init(kGlslVersion);
+	ImGui::SetCurrentContext(imgui_ctx);
+
+	SetupImGuiStyle_();
+
+	if (!ImGui_ImplSDL2_InitForOpenGL(win, gl_ctx)) {
+		ImGui::DestroyContext(imgui_ctx);
+		SDL_GL_DeleteContext(gl_ctx);
+		SDL_DestroyWindow(win);
+		return false;
+	}
+	if (!ImGui_ImplOpenGL3_Init(kGlslVersion)) {
+		ImGui_ImplSDL2_Shutdown();
+		ImGui::DestroyContext(imgui_ctx);
+		SDL_GL_DeleteContext(gl_ctx);
+		SDL_DestroyWindow(win);
+		return false;
+	}
 
 	auto ws       = std::make_unique<WindowState>();
 	ws->window    = win;
 	ws->gl_ctx    = gl_ctx;
+	ws->imgui_ctx = imgui_ctx;
 	ws->width     = w;
 	ws->height    = h;
 
 	// Secondary editor shares the primary's buffer list
 	ws->editor.SetSharedBuffers(&primary.Buffers());
 	ws->editor.SetDimensions(primary.Rows(), primary.Cols());
+
+	// Open a new untitled buffer and switch to it in the new window.
+	ws->editor.AddBuffer(Buffer());
+	ws->editor.SwitchTo(ws->editor.BufferCount() - 1);
+
 	ws->input.Attach(&ws->editor);
 
 	windows_.push_back(std::move(ws));
 
-	// Restore primary GL context as current
+	// Restore primary context
+	ImGui::SetCurrentContext(windows_[0]->imgui_ctx);
 	SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
 	return true;
 }
@@ -305,10 +400,10 @@ void
 GUIFrontend::Step(Editor &ed, bool &running)
 {
 	// --- Event processing ---
+	// SDL events carry a window ID. Route each event to the correct window's
+	// ImGui context (for ImGui_ImplSDL2_ProcessEvent) and input handler.
 	SDL_Event e;
 	while (SDL_PollEvent(&e)) {
-		ImGui_ImplSDL2_ProcessEvent(&e);
-
 		// Determine which window this event belongs to
 		Uint32 event_win_id = 0;
 		switch (e.type) {
@@ -329,6 +424,9 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		case SDL_MOUSEWHEEL:
 			event_win_id = e.wheel.windowID;
 			break;
+		case SDL_MOUSEMOTION:
+			event_win_id = e.motion.windowID;
+			break;
 		default:
 			break;
 		}
@@ -338,43 +436,57 @@ GUIFrontend::Step(Editor &ed, bool &running)
 			break;
 		}
 
+		// Find the target window and route the event to its ImGui context
+		WindowState *target = nullptr;
+		std::size_t target_idx = 0;
+		if (event_win_id != 0) {
+			for (std::size_t i = 0; i < windows_.size(); ++i) {
+				if (SDL_GetWindowID(windows_[i]->window) == event_win_id) {
+					target     = windows_[i].get();
+					target_idx = i;
+					break;
+				}
+			}
+		}
+
+		if (target && target->imgui_ctx) {
+			// Set this window's ImGui context so ImGui_ImplSDL2_ProcessEvent
+			// updates the correct IO state.
+			ImGui::SetCurrentContext(target->imgui_ctx);
+			ImGui_ImplSDL2_ProcessEvent(&e);
+		}
+
 		if (e.type == SDL_WINDOWEVENT) {
 			if (e.window.event == SDL_WINDOWEVENT_CLOSE) {
-				// Mark the window as dead; primary window close = quit
+				if (target) {
-				for (std::size_t i = 0; i < windows_.size(); ++i) {
+					if (target_idx == 0) {
-					if (SDL_GetWindowID(windows_[i]->window) == e.window.windowID) {
-						if (i == 0) {
 						running = false;
 					} else {
-							windows_[i]->alive = false;
+						target->alive = false;
-						}
-						break;
 					}
 				}
 			} else if (e.window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
-				for (auto &ws: windows_) {
+				if (target) {
-					if (SDL_GetWindowID(ws->window) == e.window.windowID) {
+					target->width  = e.window.data1;
-						ws->width  = e.window.data1;
+					target->height = e.window.data2;
-						ws->height = e.window.data2;
-						break;
-					}
 				}
 			}
 		}
 
 		// Route input events to the correct window's input handler
-		if (event_win_id != 0) {
+		if (target) {
-			// Primary window (index 0) uses the external editor &ed
+			Editor &tgt_ed = (target_idx == 0) ? ed : target->editor;
-			if (windows_.size() > 0 &&
+			if (tgt_ed.FilePickerVisible()) {
-			    SDL_GetWindowID(windows_[0]->window) == event_win_id) {
+				// Modal: don't let keystrokes fall through as edit commands
-				windows_[0]->input.ProcessSDLEvent(e);
+				// to the buffer underneath. Escape closes the picker;
+				// everything else (navigation, filtering, double-click) is
+				// handled by the picker's own ImGui widgets via
+				// ImGui_ImplSDL2_ProcessEvent above.
+				if (e.type == SDL_KEYDOWN && e.key.keysym.sym == SDLK_ESCAPE) {
+					tgt_ed.SetFilePickerVisible(false);
+				}
 			} else {
-				for (std::size_t i = 1; i < windows_.size(); ++i) {
+				target->input.ProcessSDLEvent(e);
-					if (SDL_GetWindowID(windows_[i]->window) == event_win_id) {
-						windows_[i]->input.ProcessSDLEvent(e);
-						break;
-					}
-				}
 			}
 		}
 	}
@@ -382,18 +494,24 @@ GUIFrontend::Step(Editor &ed, bool &running)
 	if (!running)
 		return;
 
-	// --- Apply pending font change ---
+	// --- Apply pending font change (to all contexts) ---
 	{
 		std::string fname;
 		float fsize = 0.0f;
 		if (kte::Fonts::FontRegistry::Instance().ConsumePendingFontRequest(fname, fsize)) {
 			if (!fname.empty() && fsize > 0.0f) {
+				for (auto &ws : windows_) {
+					if (!ws->alive || !ws->imgui_ctx)
+						continue;
+					ImGui::SetCurrentContext(ws->imgui_ctx);
+					SDL_GL_MakeCurrent(ws->window, ws->gl_ctx);
 					kte::Fonts::FontRegistry::Instance().LoadFont(fname, fsize);
 					ImGui_ImplOpenGL3_DestroyFontsTexture();
 					ImGui_ImplOpenGL3_CreateFontsTexture();
 				}
 			}
 		}
+	}
 
 	// --- Step each window ---
 	// We iterate by index because OpenNewWindow_ may append to windows_.
@@ -404,7 +522,12 @@ GUIFrontend::Step(Editor &ed, bool &running)
 
 		Editor &wed = (wi == 0) ? ed : ws.editor;
 
+		// Shared buffer list may have been modified by another window.
+		wed.ValidateBufferIndex();
+
+		// Activate this window's GL and ImGui contexts
 		SDL_GL_MakeCurrent(ws.window, ws.gl_ctx);
+		ImGui::SetCurrentContext(ws.imgui_ctx);
 
 		// Start a new ImGui frame
 		ImGui_ImplOpenGL3_NewFrame();
@@ -422,6 +545,9 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		// Allow deferred opens
 		wed.ProcessPendingOpens();
 
+		// Ensure newly opened buffers get syntax + edit mode detection
+		apply_syntax_to_buffer(wed.CurrentBuffer(), config_);
+
 		// Drain input queue
 		for (;;) {
 			MappedInput mi;
@@ -431,6 +557,21 @@ GUIFrontend::Step(Editor &ed, bool &running)
 				if (mi.id == CommandId::NewWindow) {
 					// Open a new window; handled after this loop
 					wed.SetNewWindowRequested(true);
+				} else if (mi.id == CommandId::FontZoomIn ||
+				           mi.id == CommandId::FontZoomOut ||
+				           mi.id == CommandId::FontZoomReset) {
+					auto &fr = kte::Fonts::FontRegistry::Instance();
+					float cur = fr.CurrentFontSize();
+					if (cur <= 0.0f) cur = config_.font_size;
+					float next = cur;
+					if (mi.id == CommandId::FontZoomIn)
+						next = std::min(cur + 2.0f, 72.0f);
+					else if (mi.id == CommandId::FontZoomOut)
+						next = std::max(cur - 2.0f, 8.0f);
+					else
+						next = config_.font_size; // reset to config default
+					if (next != cur)
+						fr.RequestLoadFont(fr.CurrentFontName(), next);
 				} else {
 					const std::string before = wed.KillRingHead();
 					Execute(wed, mi.id, mi.arg, mi.count);
@@ -442,16 +583,27 @@ GUIFrontend::Step(Editor &ed, bool &running)
 			}
 		}
 
-		// Handle new-window request
-		if (wed.NewWindowRequested()) {
-			wed.SetNewWindowRequested(false);
-			OpenNewWindow_(ed); // always share primary editor's buffers
-		}
-
 		if (wi == 0 && wed.QuitRequested()) {
 			running = false;
 		}
 
+		// Switch font based on current buffer's edit mode (deferred to next frame)
+		{
+			Buffer *cur = wed.CurrentBuffer();
+			if (cur) {
+				auto &fr = kte::Fonts::FontRegistry::Instance();
+				const std::string &expected =
+					(cur->GetEditMode() == EditMode::Writing)
+						? config_.writing_font
+						: config_.code_font;
+				if (fr.CurrentFontName() != expected && fr.HasFont(expected)) {
+					float sz = fr.CurrentFontSize();
+					if (sz <= 0.0f) sz = config_.font_size;
+					fr.RequestLoadFont(expected, sz);
+				}
+			}
+		}
+
 		// Draw
 		ws.renderer.Draw(wed);
 
@@ -466,52 +618,40 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		SDL_GL_SwapWindow(ws.window);
 	}
 
+	// Handle deferred new-window requests (must happen outside the render loop
+	// to avoid corrupting an in-progress ImGui frame).
+	for (std::size_t wi = 0; wi < windows_.size(); ++wi) {
+		Editor &wed = (wi == 0) ? ed : windows_[wi]->editor;
+		if (wed.NewWindowRequested()) {
+			wed.SetNewWindowRequested(false);
+			OpenNewWindow_(ed);
+		}
+	}
+
 	// Remove dead secondary windows
 	for (auto it = windows_.begin() + 1; it != windows_.end();) {
 		if (!(*it)->alive) {
-			SDL_GL_MakeCurrent((*it)->window, (*it)->gl_ctx);
+			DestroyWindowResources_(**it);
-			ImGui_ImplOpenGL3_Shutdown();
-			SDL_GL_DeleteContext((*it)->gl_ctx);
-			SDL_DestroyWindow((*it)->window);
 			it = windows_.erase(it);
-			// Restore primary context
-			SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
 		} else {
 			++it;
 		}
 	}
+
+	// Restore primary context
+	if (!windows_.empty()) {
+		ImGui::SetCurrentContext(windows_[0]->imgui_ctx);
+		SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
+	}
 }
 
 
 void
 GUIFrontend::Shutdown()
 {
-	// Destroy secondary windows first
+	// Destroy all windows (secondary first, then primary)
-	for (std::size_t i = 1; i < windows_.size(); ++i) {
+	for (auto it = windows_.rbegin(); it != windows_.rend(); ++it) {
-		SDL_GL_MakeCurrent(windows_[i]->window, windows_[i]->gl_ctx);
+		DestroyWindowResources_(**it);
-		ImGui_ImplOpenGL3_Shutdown();
-		SDL_GL_DeleteContext(windows_[i]->gl_ctx);
-		SDL_DestroyWindow(windows_[i]->window);
-	}
-	windows_.resize(std::min(windows_.size(), std::size_t(1)));
-
-	// Destroy primary window
-	if (!windows_.empty()) {
-		SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
-	}
-	ImGui_ImplOpenGL3_Shutdown();
-	ImGui_ImplSDL2_Shutdown();
-	ImGui::DestroyContext();
-
-	if (!windows_.empty()) {
-		if (windows_[0]->gl_ctx) {
-			SDL_GL_DeleteContext(windows_[0]->gl_ctx);
-			windows_[0]->gl_ctx = nullptr;
-		}
-		if (windows_[0]->window) {
-			SDL_DestroyWindow(windows_[0]->window);
-			windows_[0]->window = nullptr;
-		}
 	}
 	windows_.clear();
 	SDL_Quit();

ImGuiFrontend.h

@@ -13,6 +13,7 @@
 
 
 struct SDL_Window;
+struct ImGuiContext;
 typedef void *SDL_GLContext;
 
 class GUIFrontend final : public Frontend {
@@ -28,10 +29,13 @@ public:
 	void Shutdown() override;
 
 private:
-	// Per-window state
+	// Per-window state — each window owns its own ImGui context so that
+	// NewFrame/Render cycles are fully independent (ImGui requires exactly
+	// one NewFrame per Render per context).
 	struct WindowState {
 		SDL_Window *window       = nullptr;
 		SDL_GLContext gl_ctx     = nullptr;
+		ImGuiContext *imgui_ctx  = nullptr;
 		ImGuiInputHandler input{};
 		ImGuiRenderer renderer{};
 		Editor editor{};
@@ -44,6 +48,9 @@ private:
 	// Returns false if window creation fails.
 	bool OpenNewWindow_(Editor &primary);
 
+	// Initialize fonts and theme for a given ImGui context (must be current).
+	void SetupImGuiStyle_();
+	static void DestroyWindowResources_(WindowState &ws);
 	static bool LoadGuiFont_(const char *path, float size_px);
 
 	GUIConfig config_{};

ImGuiInputHandler.cc

@@ -8,6 +8,20 @@
 #include "ImGuiInputHandler.h"
 #include "KKeymap.h"
 #include "Editor.h"
+#include "PasteSplit.h"
+
+// Verbose k-prefix suffix logging for debugging macOS/SDL key translation
+// issues. Default to off; enable by defining IMGUI_IH_DEBUG=1 at compile
+// time. Mirrors QtInputHandler.cc's QT_IH_DEBUG gate.
+#ifndef IMGUI_IH_DEBUG
+#define IMGUI_IH_DEBUG 0
+#endif
+
+#if IMGUI_IH_DEBUG
+#define IH_LOGF(...) do { std::fprintf(stderr, __VA_ARGS__); std::fflush(stderr); } while (0)
+#else
+#define IH_LOGF(...) ((void) 0)
+#endif
 
 
 static bool
@@ -182,18 +196,19 @@ map_key(const SDL_Keycode key,
 			k_ctrl_pending             = false;
 			CommandId id;
 			bool mapped = KLookupKCommand(ascii_key, pass_ctrl, id);
+#if IMGUI_IH_DEBUG
 			// Diagnostics for u/U
 			if (lower == 'u') {
 				char disp = (ascii_key >= 0x20 && ascii_key <= 0x7e)
 					            ? static_cast<char>(ascii_key)
 					            : '?';
-				std::fprintf(stderr,
+				IH_LOGF(
 					"[kge] k-prefix suffix: sym=%d mods=0x%x ascii=%d '%c' ctrl2=%d pass_ctrl=%d mapped=%d id=%d\n",
 					static_cast<int>(key), static_cast<unsigned int>(mod), ascii_key, disp,
 					ctrl2 ? 1 : 0, pass_ctrl ? 1 : 0, mapped ? 1 : 0,
 					mapped ? static_cast<int>(id) : -1);
-				std::fflush(stderr);
 			}
+#endif
 			if (mapped) {
 				out = {true, id, "", 0};
 				if (ed)
@@ -349,6 +364,26 @@ ImGuiInputHandler::ProcessSDLEvent(const SDL_Event &e)
 			}
 		}
 
+		// Font zoom: Cmd+=/Cmd+-/Cmd+0 (macOS) or Ctrl+=/Ctrl+-/Ctrl+0
+		if ((mods & (KMOD_CTRL | KMOD_GUI)) && !(mods & KMOD_SHIFT)) {
+			bool is_zoom = true;
+			CommandId zoom_cmd = CommandId::FontZoomIn;
+			if (key == SDLK_EQUALS || key == SDLK_PLUS)
+				zoom_cmd = CommandId::FontZoomIn;
+			else if (key == SDLK_MINUS)
+				zoom_cmd = CommandId::FontZoomOut;
+			else if (key == SDLK_0)
+				zoom_cmd = CommandId::FontZoomReset;
+			else
+				is_zoom = false;
+			if (is_zoom) {
+				std::lock_guard<std::mutex> lk(mu_);
+				q_.push(MappedInput{true, zoom_cmd, std::string(), 0});
+				suppress_text_input_once_ = true;
+				return true;
+			}
+		}
+
 		// Handle Paste: Ctrl+V (Windows/Linux) or Cmd+V (macOS)
 		// Note: SDL defines letter keycodes in lowercase only (e.g., SDLK_v). Shift does not change keycode.
 		if ((mods & (KMOD_CTRL | KMOD_GUI)) && (key == SDLK_v)) {
@@ -356,32 +391,12 @@ ImGuiInputHandler::ProcessSDLEvent(const SDL_Event &e)
 			if (clip) {
 				std::string text(clip);
 				SDL_free(clip);
-				// Split on '\n' and enqueue as InsertText/Newline commands
+				// Turn line breaks (\n, \r\n, or bare \r) into Newline
+				// commands and the rest into InsertText; InsertText itself
+				// rejects any embedded '\r'/'\n'.
 				std::lock_guard<std::mutex> lk(mu_);
-				std::size_t start = 0;
+				for (const auto &cmd : SplitPasteIntoCommands(text))
-				while (start <= text.size()) {
+					q_.push(cmd);
-					std::size_t pos = text.find('\n', start);
-					std::string_view segment;
-					bool has_nl = (pos != std::string::npos);
-					if (has_nl) {
-						segment = std::string_view(text).substr(start, pos - start);
-					} else {
-						segment = std::string_view(text).substr(start);
-					}
-					if (!segment.empty()) {
-						MappedInput ins{
-							true, CommandId::InsertText, std::string(segment), 0
-						};
-						q_.push(ins);
-					}
-					if (has_nl) {
-						MappedInput nl{true, CommandId::Newline, std::string(), 0};
-						q_.push(nl);
-						start = pos + 1;
-					} else {
-						break;
-					}
-				}
 				// Suppress the corresponding TEXTINPUT that may follow
 				suppress_text_input_once_ = true;
 				return true; // consumed
@@ -504,15 +519,17 @@ ImGuiInputHandler::ProcessSDLEvent(const SDL_Event &e)
 					bool pass_ctrl  = k_ctrl_pending_;
 					k_ctrl_pending_ = false;
 					bool mapped     = KLookupKCommand(ascii_key, pass_ctrl, id);
+#if IMGUI_IH_DEBUG
 					// Diagnostics: log any k-prefix TEXTINPUT suffix mapping
+					{
 						char disp = (ascii_key >= 0x20 && ascii_key <= 0x7e)
 							            ? static_cast<char>(ascii_key)
 							            : '?';
-					std::fprintf(stderr,
+						IH_LOGF("[kge] k-prefix TEXTINPUT suffix: ascii=%d '%c' mapped=%d id=%d\n",
-					             "[kge] k-prefix TEXTINPUT suffix: ascii=%d '%c' mapped=%d id=%d\n",
 						       ascii_key, disp, mapped ? 1 : 0,
 						       mapped ? static_cast<int>(id) : -1);
-					std::fflush(stderr);
+					}
+#endif
 					if (mapped) {
 						mi = {true, id, "", 0};
 						if (ed_)

ImGuiRenderer.cc

@@ -76,23 +76,18 @@ ImGuiRenderer::Draw(Editor &ed)
 		// Two-way sync between Buffer::Rowoffs and ImGui scroll position:
 		// - If command layer changed Buffer::Rowoffs since last frame, drive ImGui scroll from it.
 		// - Otherwise, propagate ImGui scroll to Buffer::Rowoffs so command layer has an up-to-date view.
-		static long prev_buf_rowoffs = -1; // previous frame's Buffer::Rowoffs
-		static long prev_buf_coloffs = -1; // previous frame's Buffer::Coloffs
-
 		const long buf_rowoffs = static_cast<long>(buf->Rowoffs());
 		const long buf_coloffs = static_cast<long>(buf->Coloffs());
 
 		// Detect programmatic change (e.g., page_down command changed rowoffs)
 		// Use SetNextWindowScroll BEFORE BeginChild to set initial scroll position
-		if (prev_buf_rowoffs >= 0 && buf_rowoffs != prev_buf_rowoffs) {
+		if (prev_buf_rowoffs_ >= 0 && buf_rowoffs != prev_buf_rowoffs_) {
 			float target_y = static_cast<float>(buf_rowoffs) * row_h;
 			ImGui::SetNextWindowScroll(ImVec2(-1.0f, target_y));
 		}
-		if (prev_buf_coloffs >= 0 && buf_coloffs != prev_buf_coloffs) {
+		// Horizontal scroll is handled purely in pixel space (see
-			float target_x = static_cast<float>(buf_coloffs) * space_w;
+		// cursor-visibility block after the line loop) so we don't
-			float target_y = static_cast<float>(buf_rowoffs) * row_h;
+		// convert the character-based coloffs to an ImGui scroll here.
-			ImGui::SetNextWindowScroll(ImVec2(target_x, target_y));
-		}
 
 		// Reserve space for status bar at bottom.
 		// We calculate a height that is an exact multiple of the line height
@@ -111,44 +106,92 @@ ImGuiRenderer::Draw(Editor &ed)
 		ImVec2 child_window_pos = ImGui::GetWindowPos();
 		float scroll_y          = ImGui::GetScrollY();
 		float scroll_x          = ImGui::GetScrollX();
-		std::size_t rowoffs     = 0; // we render from the first line; scrolling is handled by ImGui
 
 		// Synchronize buffer offsets from ImGui scroll if user scrolled manually
 		bool forced_scroll = false;
 		{
-			static float prev_scroll_y = -1.0f; // previous frame's ImGui scroll Y in pixels
-			static float prev_scroll_x = -1.0f; // previous frame's ImGui scroll X in pixels
-
 			const long scroll_top  = static_cast<long>(scroll_y / row_h);
-			const long scroll_left = static_cast<long>(scroll_x / space_w);
 
 			// Check if rowoffs was programmatically changed this frame
-			if (prev_buf_rowoffs >= 0 && buf_rowoffs != prev_buf_rowoffs) {
+			if (prev_buf_rowoffs_ >= 0 && buf_rowoffs != prev_buf_rowoffs_) {
 				forced_scroll = true;
 			}
 
-			// If user scrolled (not programmatic), update buffer offsets accordingly
+			// If user scrolled vertically (not programmatic), update buffer row offset
-			if (prev_scroll_y >= 0.0f && scroll_y != prev_scroll_y && !forced_scroll) {
+			if (prev_scroll_y_ >= 0.0f && scroll_y != prev_scroll_y_ && !forced_scroll) {
 				if (Buffer *mbuf = const_cast<Buffer *>(buf)) {
 					mbuf->SetOffsets(static_cast<std::size_t>(std::max(0L, scroll_top)),
 					                 mbuf->Coloffs());
 				}
 			}
-			if (prev_scroll_x >= 0.0f && scroll_x != prev_scroll_x && !forced_scroll) {
+			// Horizontal scroll is pixel-based and managed by the cursor
-				if (Buffer *mbuf = const_cast<Buffer *>(buf)) {
+			// visibility block below; we don't sync it back to coloffs.
-					mbuf->SetOffsets(mbuf->Rowoffs(),
+
-					                 static_cast<std::size_t>(std::max(0L, scroll_left)));
+			// Update trackers for next frame
+			prev_scroll_y_ = scroll_y;
+			prev_scroll_x_ = scroll_x;
+		}
+		prev_buf_rowoffs_ = buf_rowoffs;
+		prev_buf_coloffs_ = buf_coloffs;
+
+		// Max-line-width cache: reset when the buffer or font changes. We only
+		// measure visible lines per frame and maintain a running max, so the
+		// scrollbar may be slightly conservative on first view of a file until
+		// the user scrolls, but idle CPU drops dramatically on large files.
+		// Edits bump the buffer version but we intentionally do NOT reset the
+		// max on version changes — keeping a conservative (possibly too-wide)
+		// scrollbar is preferable to per-keystroke jitter.
+		{
+			ImFont *cur_font = ImGui::GetFont();
+			float cur_fsize  = ImGui::GetFontSize();
+			if (buf != max_width_buf_
+			    || cur_font != max_width_font_
+			    || cur_fsize != max_width_font_size_) {
+				max_width_buf_       = buf;
+				max_width_font_      = cur_font;
+				max_width_font_size_ = cur_fsize;
+				max_width_px_        = 0.0f;
+			}
+			max_width_version_ = buf->Version();
+		}
+
+		// Hoist the search-regex compilation out of the per-line loop. Compiling
+		// std::regex per line per frame was a large source of idle CPU on macOS.
+		const bool search_mode = ed.SearchActive() && !ed.SearchQuery().empty();
+		const bool regex_mode  = search_mode && ed.PromptActive() && (
+			ed.CurrentPromptKind() == Editor::PromptKind::RegexSearch ||
+			ed.CurrentPromptKind() == Editor::PromptKind::RegexReplaceFind);
+		std::regex search_rx;
+		bool search_rx_valid = false;
+		if (regex_mode) {
+			try {
+				search_rx       = std::regex(ed.SearchQuery());
+				search_rx_valid = true;
+			} catch (const std::regex_error &) {
+				search_rx_valid = false;
 			}
 		}
 
-			// Update trackers for next frame
+		// Compute the visible row range and skip rendering work for off-screen
-			prev_scroll_y = scroll_y;
+		// lines. ImGui clips drawing, but string allocation, tab expansion,
-			prev_scroll_x = scroll_x;
+		// syntax-highlight lookups, and width measurement are not free.
+		const std::size_t total_rows = lines.size();
+		std::size_t first_vis = 0;
+		std::size_t last_vis  = total_rows; // exclusive
+		if (row_h > 0.0f && total_rows > 0) {
+			const long margin = 4; // render a few extra rows above/below for smoother scrolling
+			long fv           = static_cast<long>(std::floor(scroll_y / row_h)) - margin;
+			long lv           = static_cast<long>(
+				std::ceil((scroll_y + child_h_plan) / row_h)) + margin;
+			if (fv < 0) fv = 0;
+			if (lv < 0) lv = 0;
+			if (static_cast<std::size_t>(fv) > total_rows)
+				fv = static_cast<long>(total_rows);
+			if (static_cast<std::size_t>(lv) > total_rows)
+				lv = static_cast<long>(total_rows);
+			first_vis = static_cast<std::size_t>(fv);
+			last_vis  = static_cast<std::size_t>(lv);
 		}
-		prev_buf_rowoffs = buf_rowoffs;
-		prev_buf_coloffs = buf_coloffs;
-		// Cache current horizontal offset in rendered columns for click handling
-		const std::size_t coloffs_now = buf->Coloffs();
 
 		// Mark selection state (mark -> cursor), in source coordinates
 		bool sel_active    = false;
@@ -169,7 +212,7 @@ ImGuiRenderer::Draw(Editor &ed)
 		const std::size_t vsel_sy = vsel_active ? buf->VisualLineStartY() : 0;
 		const std::size_t vsel_ey = vsel_active ? buf->VisualLineEndY() : 0;
 
-		static bool mouse_selecting = false;
+		// (mouse_selecting__ is a member variable)
 		auto mouse_pos_to_buf       = [&]() -> std::pair<std::size_t, std::size_t> {
 			ImVec2 mp = ImGui::GetIO().MousePos;
 			// Convert mouse pos to buffer row
@@ -181,29 +224,54 @@ ImGuiRenderer::Draw(Editor &ed)
 			if (by >= lines.size())
 				by = lines.empty() ? 0 : (lines.size() - 1);
 
-			// Convert mouse pos to rendered x
+			if (lines.empty())
+				return {0, 0};
+
+			// Expand tabs for the clicked line
+			std::string line_clicked = static_cast<std::string>(lines[by]);
+			const std::size_t tabw   = 8;
+			std::string click_expanded;
+			click_expanded.reserve(line_clicked.size() + 16);
+			std::size_t click_rx = 0;
+			// Map: source column -> expanded column
+			std::vector<std::size_t> src_to_exp;
+			src_to_exp.reserve(line_clicked.size() + 1);
+			for (std::size_t ci = 0; ci < line_clicked.size(); ++ci) {
+				src_to_exp.push_back(click_rx);
+				if (line_clicked[ci] == '\t') {
+					std::size_t adv = (tabw - (click_rx % tabw));
+					click_expanded.append(adv, ' ');
+					click_rx += adv;
+				} else {
+					click_expanded.push_back(line_clicked[ci]);
+					click_rx += 1;
+				}
+			}
+			src_to_exp.push_back(click_rx); // past-end position
+
+			// Pixel x relative to the line start (accounting for scroll)
 			float visual_x = mp.x - child_window_pos.x;
 			if (visual_x < 0.0f)
 				visual_x = 0.0f;
-			std::size_t clicked_rx = static_cast<std::size_t>(visual_x / space_w) + coloffs_now;
+			// Add scroll offset in pixels
+			visual_x += scroll_x;
 
-			// Convert rendered column to source column
+			// Find the source column whose expanded position is closest
-			if (lines.empty())
+			// to the click pixel, using actual text measurement.
-				return {0, 0};
-			std::string line_clicked = static_cast<std::string>(lines[by]);
-			const std::size_t tabw   = 8;
-			std::size_t rx           = 0;
 			std::size_t best_col  = 0;
 			float best_dist       = std::numeric_limits<float>::infinity();
-			float clicked_rx_f       = static_cast<float>(clicked_rx);
+			for (std::size_t ci = 0; ci <= line_clicked.size(); ++ci) {
-			for (std::size_t i = 0; i <= line_clicked.size(); ++i) {
+				std::size_t exp_col = src_to_exp[ci];
-				float dist = std::fabs(clicked_rx_f - static_cast<float>(rx));
+				float px = 0.0f;
+				if (exp_col > 0 && !click_expanded.empty()) {
+					std::size_t end = std::min(click_expanded.size(), exp_col);
+					px = ImGui::CalcTextSize(click_expanded.c_str(),
+					                         click_expanded.c_str() + end).x;
+				}
+				float dist = std::fabs(visual_x - px);
 				if (dist < best_dist) {
 					best_dist = dist;
-					best_col  = i;
+					best_col  = ci;
-				}
-				if (i < line_clicked.size()) {
-					rx += (line_clicked[i] == '\t') ? (tabw - (rx % tabw)) : 1;
 				}
 			}
 			return {by, best_col};
@@ -211,7 +279,7 @@ ImGuiRenderer::Draw(Editor &ed)
 
 		// Mouse-driven selection: set mark on double-click or drag, update cursor on any press/drag
 		if (ImGui::IsWindowHovered() && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
-			mouse_selecting = true;
+			mouse_selecting_ = true;
 			auto [by, bx]   = mouse_pos_to_buf();
 			char tmp[64];
 			std::snprintf(tmp, sizeof(tmp), "%zu:%zu", by, bx);
@@ -225,7 +293,7 @@ ImGuiRenderer::Draw(Editor &ed)
 				}
 			}
 		}
-		if (mouse_selecting && ImGui::IsWindowHovered() && ImGui::IsMouseDown(ImGuiMouseButton_Left)) {
+		if (mouse_selecting_ && ImGui::IsWindowHovered() && ImGui::IsMouseDown(ImGuiMouseButton_Left)) {
 			auto [by, bx] = mouse_pos_to_buf();
 			// If we are dragging (mouse moved while down), ensure mark is set to start selection
 			if (ImGui::IsMouseDragging(ImGuiMouseButton_Left, 1.0f)) {
@@ -242,30 +310,56 @@ ImGuiRenderer::Draw(Editor &ed)
 			std::snprintf(tmp, sizeof(tmp), "%zu:%zu", by, bx);
 			Execute(ed, CommandId::MoveCursorTo, std::string(tmp));
 		}
-		if (mouse_selecting && ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
+		if (mouse_selecting_ && ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
-			mouse_selecting = false;
+			mouse_selecting_ = false;
 		}
-		for (std::size_t i = rowoffs; i < lines.size(); ++i) {
+		// Advance the cursor Y so the first visible line draws at its correct
+		// scroll position. Skipped rows simply leave the layout cursor untouched.
+		if (first_vis > 0) {
+			ImGui::SetCursorPosY(ImGui::GetCursorPosY() +
+			                     static_cast<float>(first_vis) * row_h);
+		}
+		for (std::size_t i = first_vis; i < last_vis; ++i) {
 			// Capture the screen position before drawing the line
 			ImVec2 line_pos  = ImGui::GetCursorScreenPos();
 			std::string line = static_cast<std::string>(lines[i]);
 
-			// Expand tabs to spaces with width=8 and apply horizontal scroll offset
+			// Expand tabs to spaces with width=8
 			const std::size_t tabw = 8;
 			std::string expanded;
 			expanded.reserve(line.size() + 16);
-			std::size_t rx_abs_draw = 0; // rendered column for drawing
+			std::size_t rx_abs_draw = 0;
+			for (std::size_t src = 0; src < line.size(); ++src) {
+				char c = line[src];
+				if (c == '\t') {
+					std::size_t adv = (tabw - (rx_abs_draw % tabw));
+					expanded.append(adv, ' ');
+					rx_abs_draw += adv;
+				} else {
+					expanded.push_back(c);
+					rx_abs_draw += 1;
+				}
+			}
+
+			// Helper: convert a rendered column position to an absolute
+			// pixel x offset from the start of the line.  ImGui's scroll
+			// handles viewport clipping so we measure from column 0.
+			auto rx_to_px = [&](std::size_t rx_col) -> float {
+				std::size_t end = std::min(expanded.size(), rx_col);
+				if (end == 0)
+					return 0.0f;
+				return ImGui::CalcTextSize(expanded.c_str(),
+				                           expanded.c_str() + end).x;
+			};
+
 			// Compute search highlight ranges for this line in source indices
-			bool search_mode = ed.SearchActive() && !ed.SearchQuery().empty();
 			std::vector<std::pair<std::size_t, std::size_t> > hl_src_ranges;
 			if (search_mode) {
-				// If we're in RegexSearch or RegexReplaceFind mode, compute ranges using regex; otherwise plain substring
+				// In regex mode, reuse the compiled regex hoisted above the loop.
-				if (ed.PromptActive() && (
+				if (regex_mode) {
-					    ed.CurrentPromptKind() == Editor::PromptKind::RegexSearch || ed.
+					if (search_rx_valid) {
-					    CurrentPromptKind() == Editor::PromptKind::RegexReplaceFind)) {
 						try {
-						std::regex rx(ed.SearchQuery());
+							for (auto it = std::sregex_iterator(line.begin(), line.end(), search_rx);
-						for (auto it = std::sregex_iterator(line.begin(), line.end(), rx);
 							     it != std::sregex_iterator(); ++it) {
 								const auto &m  = *it;
 								std::size_t sx = static_cast<std::size_t>(m.position());
@@ -275,6 +369,7 @@ ImGuiRenderer::Draw(Editor &ed)
 						} catch (const std::regex_error &) {
 							// ignore invalid patterns here; status line already shows the error
 						}
+					}
 				} else {
 					const std::string &q = ed.SearchQuery();
 					std::size_t pos      = 0;
@@ -306,13 +401,8 @@ ImGuiRenderer::Draw(Editor &ed)
 					std::size_t sx       = rg.first, ex = rg.second;
 					std::size_t rx_start = src_to_rx(sx);
 					std::size_t rx_end   = src_to_rx(ex);
-					// Apply horizontal scroll offset
+					ImVec2 p0 = ImVec2(line_pos.x + rx_to_px(rx_start), line_pos.y);
-					if (rx_end <= coloffs_now)
+					ImVec2 p1 = ImVec2(line_pos.x + rx_to_px(rx_end),
-						continue; // fully left of view
-					std::size_t vx0 = (rx_start > coloffs_now) ? (rx_start - coloffs_now) : 0;
-					std::size_t vx1 = rx_end - coloffs_now;
-					ImVec2 p0 = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w, line_pos.y);
-					ImVec2 p1 = ImVec2(line_pos.x + static_cast<float>(vx1) * space_w,
 					                   line_pos.y + line_h);
 					// Choose color: current match stronger
 					bool is_current = has_current && sx == cur_x && ex == cur_end;
@@ -349,20 +439,14 @@ ImGuiRenderer::Draw(Editor &ed)
 				if (line_has) {
 					std::size_t rx_start = src_to_rx(sx);
 					std::size_t rx_end   = src_to_rx(ex);
-					if (rx_end > coloffs_now) {
+					ImVec2 p0 = ImVec2(line_pos.x + rx_to_px(rx_start),
-						std::size_t vx0 = (rx_start > coloffs_now)
-							                  ? (rx_start - coloffs_now)
-							                  : 0;
-						std::size_t vx1 = rx_end - coloffs_now;
-						ImVec2 p0       = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w,
 					                   line_pos.y);
-						ImVec2 p1 = ImVec2(line_pos.x + static_cast<float>(vx1) * space_w,
+					ImVec2 p1 = ImVec2(line_pos.x + rx_to_px(rx_end),
 					                   line_pos.y + line_h);
 					ImU32 col = ImGui::GetColorU32(ImGuiCol_TextSelectedBg);
 					ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
 				}
 			}
-			}
 			if (vsel_active && i >= vsel_sy && i <= vsel_ey) {
 				// Visual-line (multi-cursor) mode: highlight only the per-line cursor spot.
 				const std::size_t spot_sx  = std::min(buf->Curx(), line.size());
@@ -374,32 +458,13 @@ ImGuiRenderer::Draw(Editor &ed)
 					// EOL spot: draw a 1-cell highlight just past the last character.
 					rx_end = rx_start + 1;
 				}
-				if (rx_end > coloffs_now) {
+				ImVec2 p0 = ImVec2(line_pos.x + rx_to_px(rx_start),
-					std::size_t vx0 = (rx_start > coloffs_now)
-						                  ? (rx_start - coloffs_now)
-						                  : 0;
-					std::size_t vx1 = rx_end - coloffs_now;
-					ImVec2 p0       = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w,
 				                   line_pos.y);
-					ImVec2 p1 = ImVec2(line_pos.x + static_cast<float>(vx1) * space_w,
+				ImVec2 p1 = ImVec2(line_pos.x + rx_to_px(rx_end),
 				                   line_pos.y + line_h);
 				ImU32 col = ImGui::GetColorU32(ImGuiCol_TextSelectedBg);
 				ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
 			}
-			}
-			// Emit entire line to an expanded buffer (tabs -> spaces)
-			for (std::size_t src = 0; src < line.size(); ++src) {
-				char c = line[src];
-				if (c == '\t') {
-					std::size_t adv = (tabw - (rx_abs_draw % tabw));
-					expanded.append(adv, ' ');
-					rx_abs_draw += adv;
-				} else {
-					expanded.push_back(c);
-					rx_abs_draw += 1;
-				}
-			}
-
 			// Draw syntax-colored runs (text above background highlights)
 			if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
 				kte::LineHighlight lh = buf->Highlighter()->GetLine(
@@ -442,19 +507,14 @@ ImGuiRenderer::Draw(Editor &ed)
 				for (const auto &sp: spans) {
 					std::size_t rx_s = src_to_rx_full(sp.s);
 					std::size_t rx_e = src_to_rx_full(sp.e);
-					if (rx_e <= coloffs_now)
+					std::size_t draw_start = rx_s;
-						continue; // fully left of viewport
-					// Clamp to visible portion and expanded length
-					std::size_t draw_start = (rx_s > coloffs_now) ? rx_s : coloffs_now;
 					if (draw_start >= expanded.size())
-						continue; // fully right of expanded text
+						continue;
 					std::size_t draw_end = std::min<std::size_t>(rx_e, expanded.size());
 					if (draw_end <= draw_start)
 						continue;
-					// Screen position is relative to coloffs_now
-					std::size_t screen_x = draw_start - coloffs_now;
 					ImU32 col = ImGui::GetColorU32(kte::SyntaxInk(sp.k));
-					ImVec2 p = ImVec2(line_pos.x + static_cast<float>(screen_x) * space_w,
+					ImVec2 p = ImVec2(line_pos.x + rx_to_px(draw_start),
 					                  line_pos.y);
 					ImGui::GetWindowDrawList()->AddText(
 						p, col, expanded.c_str() + draw_start, expanded.c_str() + draw_end);
@@ -463,49 +523,49 @@ ImGuiRenderer::Draw(Editor &ed)
 				// Use row_h (with spacing) to match click calculation and ensure consistent line positions.
 				ImGui::SetCursorScreenPos(ImVec2(line_pos.x, line_pos.y + row_h));
 			} else {
-				// No syntax: draw as one run, accounting for horizontal scroll offset
+				// No syntax: draw the full line; ImGui scroll handles clipping.
-				if (coloffs_now < expanded.size()) {
+				if (!expanded.empty()) {
 					ImVec2 p = ImVec2(line_pos.x, line_pos.y);
 					ImGui::GetWindowDrawList()->AddText(
 						p, ImGui::GetColorU32(ImGuiCol_Text),
-						expanded.c_str() + coloffs_now);
+						expanded.c_str());
-					ImGui::SetCursorScreenPos(ImVec2(line_pos.x, line_pos.y + row_h));
-				} else {
-					// Line is fully scrolled out of view horizontally
-					ImGui::SetCursorScreenPos(ImVec2(line_pos.x, line_pos.y + row_h));
 				}
+				ImGui::SetCursorScreenPos(ImVec2(line_pos.x, line_pos.y + row_h));
 			}
 
 			// Draw a visible cursor indicator on the current line
 			if (i == cy) {
-				// Compute rendered X (rx) from source column with tab expansion
+				std::size_t rx_abs = src_to_rx(cx);
-				std::size_t rx_abs = 0;
+				float cursor_px = rx_to_px(rx_abs);
-				for (std::size_t k = 0; k < std::min(cx, line.size()); ++k) {
-					if (line[k] == '\t')
-						rx_abs += (tabw - (rx_abs % tabw));
-					else
-						rx_abs += 1;
-				}
-				// Convert to viewport x by subtracting horizontal col offset
-				std::size_t rx_viewport = (rx_abs > coloffs_now) ? (rx_abs - coloffs_now) : 0;
-				// For proportional fonts (Linux GUI), avoid accumulating drift by computing
-				// the exact pixel width of the expanded substring up to the cursor.
-				// expanded contains the line with tabs expanded to spaces and is what we draw.
-				float cursor_px = 0.0f;
-				if (rx_viewport > 0 && coloffs_now < expanded.size()) {
-					std::size_t start = coloffs_now;
-					std::size_t end   = std::min(expanded.size(), start + rx_viewport);
-					// Measure substring width in pixels
-					ImVec2 sz = ImGui::CalcTextSize(expanded.c_str() + start,
-					                                expanded.c_str() + end);
-					cursor_px = sz.x;
-				}
 				ImVec2 p0 = ImVec2(line_pos.x + cursor_px, line_pos.y);
 				ImVec2 p1 = ImVec2(p0.x + space_w, p0.y + line_h);
 				ImU32 col = IM_COL32(200, 200, 255, 128); // soft highlight
 				ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
 			}
+
+			// Track widest line for content width reporting. We only measure
+			// visible lines and fold the result into a monotonic max cached on
+			// the renderer (see max_width_* members). Off-screen lines are not
+			// measured per frame; if the user scrolls or edits, the cache is
+			// refreshed accordingly.
+			if (!expanded.empty()) {
+				float line_w = ImGui::CalcTextSize(expanded.c_str()).x;
+				if (line_w > max_width_px_)
+					max_width_px_ = line_w;
 			}
+		}
+		// After the visible-range loop, advance the layout cursor to the end of
+		// the (virtual) content so ImGui sees the correct total size. Vertical
+		// height comes from total_rows; horizontal width comes from the cached
+		// max line width. A Dummy at the final position records both.
+		if (total_rows > last_vis) {
+			ImGui::SetCursorPosY(ImGui::GetCursorPosY() +
+			                     static_cast<float>(total_rows - last_vis) * row_h);
+		}
+		if (max_width_px_ > 0.0f) {
+			ImGui::SetCursorPosX(max_width_px_);
+		}
+		ImGui::Dummy(ImVec2(0, 0));
 		// Synchronize cursor and scrolling after rendering all lines so content size is known.
 		{
 			float child_h_actual = ImGui::GetWindowHeight();
@@ -545,29 +605,40 @@ ImGuiRenderer::Draw(Editor &ed)
 				last_row  = first_row + vis_rows - 1;
 			}
 
-			// Horizontal scroll: ensure cursor column is visible
+			// Horizontal scroll: ensure cursor is visible (pixel-based for proportional fonts)
-			long vis_cols = static_cast<long>(std::round(child_w_actual / space_w));
+			float cursor_px_abs = 0.0f;
-			if (vis_cols < 1)
-				vis_cols = 1;
-			long first_col = static_cast<long>(scroll_x_now / space_w);
-			long last_col  = first_col + vis_cols - 1;
-
-			std::size_t cursor_rx = 0;
 			if (cy < lines.size()) {
 				std::string cur_line   = static_cast<std::string>(lines[cy]);
 				const std::size_t tabw = 8;
-				for (std::size_t i = 0; i < cx && i < cur_line.size(); ++i) {
+				// Expand tabs for cursor line to measure pixel position
-					if (cur_line[i] == '\t') {
+				std::string cur_expanded;
-						cursor_rx += tabw - (cursor_rx % tabw);
+				cur_expanded.reserve(cur_line.size() + 16);
+				std::size_t cur_rx = 0;
+				for (std::size_t ci = 0; ci < cur_line.size(); ++ci) {
+					if (cur_line[ci] == '\t') {
+						std::size_t adv = tabw - (cur_rx % tabw);
+						cur_expanded.append(adv, ' ');
+						cur_rx += adv;
 					} else {
+						cur_expanded.push_back(cur_line[ci]);
+						cur_rx += 1;
+					}
+				}
+				// Compute rendered column of cursor
+				std::size_t cursor_rx = 0;
+				for (std::size_t ci = 0; ci < cx && ci < cur_line.size(); ++ci) {
+					if (cur_line[ci] == '\t')
+						cursor_rx += tabw - (cursor_rx % tabw);
+					else
 						cursor_rx += 1;
 				}
+				std::size_t exp_end = std::min(cur_expanded.size(), cursor_rx);
+				if (exp_end > 0)
+					cursor_px_abs = ImGui::CalcTextSize(cur_expanded.c_str(),
+					                                    cur_expanded.c_str() + exp_end).x;
 			}
-			}
+			if (cursor_px_abs < scroll_x_now || cursor_px_abs > scroll_x_now + child_w_actual) {
-			long cxr = static_cast<long>(cursor_rx);
+				float target_x = cursor_px_abs - (child_w_actual / 2.0f);
-			if (cxr < first_col || cxr > last_col) {
-				float target_x = static_cast<float>(cxr) * space_w;
-				target_x       -= (child_w_actual / 2.0f);
 				if (target_x < 0.f)
 					target_x = 0.f;
 				float max_x = ImGui::GetScrollMaxX();

ImGuiRenderer.h

@@ -2,8 +2,13 @@
  * ImGuiRenderer - ImGui-based renderer for GUI mode
  */
 #pragma once
+#include <cstdint>
+#include <string>
 #include "Renderer.h"
 
+struct ImFont;
+class Buffer;
+
 class ImGuiRenderer final : public Renderer {
 public:
 	ImGuiRenderer() = default;
@@ -11,4 +16,22 @@ public:
 	~ImGuiRenderer() override = default;
 
 	void Draw(Editor &ed) override;
+
+private:
+	// Per-window scroll tracking for two-way sync between Buffer offsets and ImGui scroll.
+	// These must be per-instance (not static) so each window maintains independent state.
+	long prev_buf_rowoffs_ = -1;
+	long prev_buf_coloffs_ = -1;
+	float prev_scroll_y_   = -1.0f;
+	float prev_scroll_x_   = -1.0f;
+	bool mouse_selecting_  = false;
+
+	// Max-line-width cache for the horizontal scrollbar. Measuring every line
+	// every frame is prohibitively expensive on large files; we only update the
+	// running max from visible lines and reset when buffer/version/font changes.
+	const Buffer *max_width_buf_ = nullptr;
+	std::uint64_t max_width_version_ = 0;
+	ImFont *max_width_font_ = nullptr;
+	float max_width_font_size_ = 0.0f;
+	float max_width_px_ = 0.0f;
 };

KKeymap.cc

@@ -1,6 +1,4 @@
-#include <iostream>
 #include <ncurses.h>
-#include <ostream>
 
 #include "KKeymap.h"
 
@@ -40,6 +38,15 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 		out = CommandId::ToggleReadOnly; // C-k ' (toggle read-only)
 		return true;
 	}
+	if (ascii_key == 'E') {
+		// Explicitly rejected and kept distinct from 'e' (OpenFileStart): the
+		// switch below operates on the lowercased key, so it can't otherwise
+		// tell 'E' and 'e' apart. Return false and let the caller show its
+		// normal "unknown k-command" status-line message - curses already
+		// owns the terminal here, so writing to stderr would corrupt the
+		// screen.
+		return false;
+	}
 
 	switch (k_lower) {
 	case 'a':
@@ -66,9 +73,6 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case 'e':
 		out = CommandId::OpenFileStart;
 		return true;
-	case 'E':
-		std::cerr << "E is not a valid command" << std::endl;
-		return false;
 	case 'f':
 		out = CommandId::FlushKillRing;
 		return true;
@@ -84,6 +88,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case 'l':
 		out = CommandId::ReloadBuffer;
 		return true;
+	case 'm':
+		out = CommandId::ToggleEditMode;
+		return true;
 	case 'n':
 		out = CommandId::BufferPrev;
 		return true;

PasteSplit.h

@@ -0,0 +1,48 @@
+/*
+ * PasteSplit.h - split pasted/clipboard text into editor commands
+ *
+ * Pure logic (no SDL/GUI dependencies) so it can be unit tested and shared
+ * across frontends. Line breaks in the pasted text must become Newline
+ * commands; InsertText itself rejects embedded '\r'/'\n' (see Command.cc).
+ */
+#pragma once
+#include <string>
+#include <vector>
+
+#include "InputHandler.h"
+
+
+// Translate a block of pasted text into a sequence of editor commands.
+//
+// Any of "\n", "\r\n", or a bare "\r" is treated as a single line break and
+// emitted as a Newline command; the text between breaks becomes InsertText
+// commands. Empty text segments are skipped, but line breaks are always
+// emitted so blank lines round-trip correctly.
+inline std::vector<MappedInput> SplitPasteIntoCommands(const std::string &text)
+{
+	std::vector<MappedInput> out;
+	std::string segment;
+
+	auto flush_segment = [&]() {
+		if (!segment.empty()) {
+			out.push_back(MappedInput{true, CommandId::InsertText, segment, 0});
+			segment.clear();
+		}
+	};
+
+	for (std::size_t i = 0; i < text.size(); ++i) {
+		const char c = text[i];
+		if (c == '\n' || c == '\r') {
+			flush_segment();
+			out.push_back(MappedInput{true, CommandId::Newline, std::string(), 0});
+			// Collapse a "\r\n" pair into one line break.
+			if (c == '\r' && i + 1 < text.size() && text[i + 1] == '\n')
+				++i;
+		} else {
+			segment.push_back(c);
+		}
+	}
+	flush_segment();
+
+	return out;
+}

Swap.cc

@@ -268,6 +268,43 @@ SwapManager::RecorderFor(Buffer *buf)
 }
 
 
+SwapRecorder *
+SwapManager::Rehome(Buffer *old_addr, Buffer *new_addr)
+{
+	if (!old_addr || !new_addr || old_addr == new_addr)
+		return nullptr;
+	std::lock_guard<std::mutex> lg(mtx_);
+	SwapRecorder *result = nullptr;
+
+	auto jit = journals_.find(old_addr);
+	if (jit != journals_.end()) {
+		JournalCtx ctx = std::move(jit->second);
+		journals_.erase(jit);
+		journals_[new_addr] = std::move(ctx);
+	}
+
+	auto rit = recorders_.find(old_addr);
+	if (rit != recorders_.end()) {
+		recorders_.erase(rit);
+		// BufferRecorder binds a Buffer& at construction, so it can't be
+		// repointed in place; rebuild it against the buffer's new address.
+		auto rec              = std::make_unique<BufferRecorder>(*this, *new_addr);
+		result                = rec.get();
+		recorders_[new_addr] = std::move(rec);
+	}
+
+	// Defensive: any record still queued (not yet drained by the writer thread)
+	// for the old address must follow the buffer to its new location. Callers
+	// are expected to Flush() before rehoming so this should normally be a no-op.
+	for (auto &p: queue_) {
+		if (p.buf == old_addr)
+			p.buf = new_addr;
+	}
+
+	return result;
+}
+
+
 void
 SwapManager::Attach(Buffer *buf)
 {

Swap.h

@@ -94,6 +94,15 @@ public:
 	// Detach(buf) or SwapManager destruction.
 	SwapRecorder *RecorderFor(Buffer *buf);
 
+	// Re-key an attached buffer's journal/recorder entries after its Buffer object
+	// has moved to a new address (e.g. std::vector<Buffer> reallocation/erase-shift).
+	// Callers must ensure no swap records for old_addr are in flight (see Flush())
+	// before calling this, and must not call it with an address that isn't
+	// currently attached. Returns the recorder for new_addr (nullptr if old_addr
+	// wasn't attached); the caller is responsible for calling
+	// new_buf->SetSwapRecorder() with the result.
+	SwapRecorder *Rehome(Buffer *old_addr, Buffer *new_addr);
+
 	// Notify that the buffer's filename changed (e.g., SaveAs)
 	void NotifyFilenameChanged(Buffer &buf);
 

TerminalInputHandler.cc

@@ -1,4 +1,6 @@
 #include <cstdio>
+#include <climits>
+#include <cwchar>
 #include <ncurses.h>
 
 #include "TerminalInputHandler.h"
@@ -12,6 +14,22 @@ CTRL(char c)
 {
 	return c & 0x1F;
 }
+
+
+// Encode a single wide character in the process locale's multibyte encoding
+// (UTF-8, given main.cc's setlocale(LC_ALL, "")). Returns false if the
+// codepoint can't be represented, leaving `out` untouched.
+bool
+wchar_to_mb(wchar_t wc, std::string &out)
+{
+	std::mbstate_t state{};
+	char buf[MB_LEN_MAX];
+	std::size_t n = std::wcrtomb(buf, wc, &state);
+	if (n == static_cast<std::size_t>(-1))
+		return false;
+	out.assign(buf, n);
+	return true;
+}
 }
 
 TerminalInputHandler::TerminalInputHandler() = default;
@@ -21,6 +39,7 @@ TerminalInputHandler::~TerminalInputHandler() = default;
 
 static bool
 map_key_to_command(const int ch,
+                   const bool is_keycode,
                    bool &k_prefix,
                    bool &esc_meta,
                    bool &k_ctrl_pending,
@@ -28,9 +47,13 @@ map_key_to_command(const int ch,
                    Editor *ed,
                    MappedInput &out)
 {
-	// Handle special keys from ncurses
+	// Handle special keys from ncurses. These are only meaningful when
+	// get_wch() reported KEY_CODE_YES: a regular (possibly non-ASCII) wide
+	// character can numerically collide with a KEY_* constant otherwise
+	// (e.g. U+0107 'ć' equals KEY_BACKSPACE's value), which would wrongly
+	// swallow it as a special key instead of inserting it.
 	// These keys exit k-prefix mode if active (user pressed C-k then a special key).
-	switch (ch) {
+	switch (is_keycode ? ch : -1) {
 	case KEY_ENTER:
 		// Some terminals send KEY_ENTER distinct from '\n'/'\r'
 		k_prefix = false;
@@ -259,7 +282,7 @@ map_key_to_command(const int ch,
 		esc_meta      = false;
 		int ascii_key = ch;
 		// Handle ESC + BACKSPACE (meta-backspace, Alt-Backspace)
-		if (ch == KEY_BACKSPACE || ch == 127 || ch == CTRL('H')) {
+		if ((is_keycode && ch == KEY_BACKSPACE) || ch == 127 || ch == CTRL('H')) {
 			ascii_key = KEY_BACKSPACE; // normalized value for lookup
 		} else if (ch == ',') {
 			// Some terminals emit ',' when Shift state is lost after ESC; treat as '<'
@@ -281,7 +304,7 @@ map_key_to_command(const int ch,
 	}
 
 	// Backspace in ncurses can be KEY_BACKSPACE or 127
-	if (ch == KEY_BACKSPACE || ch == 127 || ch == CTRL('H')) {
+	if ((is_keycode && ch == KEY_BACKSPACE) || ch == 127 || ch == CTRL('H')) {
 		k_prefix       = false;
 		k_ctrl_pending = false;
 		out            = {true, CommandId::Backspace, "", 0};
@@ -297,11 +320,20 @@ map_key_to_command(const int ch,
 		return true;
 	}
 
-	// Printable ASCII
+	// Printable character: ASCII, or (for a regular decoded wide character,
-	if (ch >= 0x20 && ch <= 0x7E) {
+	// not a keycode) any other printable Unicode codepoint - e.g. accented
+	// Latin, Cyrillic, CJK, etc.
+	if (!is_keycode && ch >= 0x20 && ch != 0x7F) {
+		std::string mb;
+		if (ch <= 0x7E) {
+			mb.assign(1, static_cast<char>(ch));
+		} else if (!wchar_to_mb(static_cast<wchar_t>(ch), mb)) {
+			out.hasCommand = false;
+			return true;
+		}
 		out.hasCommand = true;
 		out.id         = CommandId::InsertText;
-		out.arg.assign(1, static_cast<char>(ch));
+		out.arg        = mb;
 		out.count      = 0;
 		return true;
 	}
@@ -314,12 +346,15 @@ map_key_to_command(const int ch,
 bool
 TerminalInputHandler::decode_(MappedInput &out)
 {
-	int ch = getch();
+	wint_t wch;
-	if (ch == ERR) {
+	int ret = get_wch(&wch);
+	if (ret == ERR) {
 		return false; // no input
 	}
+	const bool is_keycode = (ret == KEY_CODE_YES);
+	const int ch          = static_cast<int>(wch);
 	bool consumed = map_key_to_command(
-		ch,
+		ch, is_keycode,
 		k_prefix_, esc_meta_,
 		k_ctrl_pending_,
 		mouse_selecting_,

UndoNode.h

@@ -10,6 +10,12 @@ enum class UndoType : std::uint8_t {
 	Newline,
 	DeleteRow,
 	InsertRow,
+	// Inverse of Newline: forward = join_lines(row) [removes the newline at the
+	// end of `row`], backward = split_line(row, col) [recreates the original
+	// two lines]. Used by backspace-at-col-0 and delete-at-eol, whose forward
+	// action is a join, not a split — Newline's apply() semantics are the
+	// wrong direction for those.
+	JoinLines,
 };
 
 struct UndoNode {

UndoSystem.cc

@@ -37,7 +37,7 @@ UndoSystem::Begin(UndoType type)
 
 	// Some operations should always be standalone undo steps.
 	const bool always_standalone = (type == UndoType::Newline || type == UndoType::DeleteRow || type ==
-	                                UndoType::InsertRow);
+	                                UndoType::InsertRow || type == UndoType::JoinLines);
 	if (always_standalone) {
 		commit();
 	}
@@ -77,6 +77,7 @@ UndoSystem::Begin(UndoType type)
 			case UndoType::Newline:
 			case UndoType::DeleteRow:
 			case UndoType::InsertRow:
+			case UndoType::JoinLines:
 				break;
 			}
 		}
@@ -325,6 +326,16 @@ UndoSystem::apply(const UndoNode *node, int direction)
 			buf_->SetCursor(0, static_cast<std::size_t>(node->row));
 		}
 		break;
+	case UndoType::JoinLines:
+		// Mirror image of Newline: forward removes a newline, backward restores it.
+		if (direction > 0) {
+			buf_->join_lines(node->row);
+			buf_->SetCursor(static_cast<std::size_t>(node->col), static_cast<std::size_t>(node->row));
+		} else {
+			buf_->split_line(node->row, node->col);
+			buf_->SetCursor(0, static_cast<std::size_t>(node->row + 1));
+		}
+		break;
 	}
 }
 
@@ -424,6 +435,8 @@ UndoSystem::type_str(UndoType t)
 		return "DeleteRow";
 	case UndoType::InsertRow:
 		return "InsertRow";
+	case UndoType::JoinLines:
+		return "JoinLines";
 	}
 	return "?";
 }

UndoTree.cc

@@ -1,3 +1,24 @@
-// Placeholder translation unit for UndoTree struct definition.
+// Undo logic is implemented in UndoSystem; this file only owns node lifetime.
-// Undo logic is implemented in UndoSystem.
 #include "UndoTree.h"
+
+namespace {
+void
+free_node_graph(UndoNode *node)
+{
+	// Walk the sibling (redo-branch) list; for each node, recursively free its
+	// child subtree first, then the node itself.
+	while (node) {
+		UndoNode *next = node->next;
+		free_node_graph(node->child);
+		delete node;
+		node = next;
+	}
+}
+} // namespace
+
+
+UndoTree::~UndoTree()
+{
+	free_node_graph(root);
+	delete pending;
+}

UndoTree.h

@@ -7,4 +7,11 @@ struct UndoTree {
 	UndoNode *current = nullptr; // current state of buffer
 	UndoNode *saved   = nullptr; // points to node matching last save (for dirty flag)
 	UndoNode *pending = nullptr; // in-progress batch (detached)
+
+	// Frees the entire node graph (root's subtree/branches plus any detached
+	// pending node). `current`/`saved` are aliases into that same graph, not
+	// separately owned. Without this, closing/reloading/resetting a buffer
+	// (which replaces or destroys its UndoTree) leaks every UndoNode ever
+	// created for it.
+	~UndoTree();
 };

default.nix

@@ -1,6 +1,5 @@
 {
-  pkgs ? import <nixpkgs> {},
+  lib,
-  lib ? pkgs.lib,
   stdenv,
   cmake,
   ncurses,
@@ -10,9 +9,10 @@
   kdePackages,
   qt6Packages ? kdePackages.qt6Packages,
   installShellFiles,
+  copyDesktopItems,
+  makeDesktopItem,
   graphical ? false,
   graphical-qt ? false,
-  ...
 }:
 let
   cmakeContent = builtins.readFile ./CMakeLists.txt;
@@ -23,25 +23,29 @@ let
   version = builtins.head (builtins.match ".*set\\(KTE_VERSION \"(.+)\"\\).*" versionLine);
 in
 stdenv.mkDerivation {
-  pname = "kte";
+  pname = if graphical then (if graphical-qt then "kge-qt" else "kge") else "kte";
   inherit version;
 
   src = lib.cleanSource ./.;
 
   nativeBuildInputs = [
     cmake
-    ncurses
     installShellFiles
-  ]
+  ] ++ lib.optionals graphical [
-  ++ lib.optionals graphical [
+    copyDesktopItems
+  ] ++ lib.optionals graphical-qt [
+    qt6Packages.wrapQtAppsHook
+  ];
+
+  buildInputs = [
+    ncurses
+  ] ++ lib.optionals graphical [
     SDL2
     libGL
     xorg.libX11
-  ]
+  ] ++ lib.optionals graphical-qt [
-  ++ lib.optionals graphical-qt [
     kdePackages.qt6ct
     qt6Packages.qtbase
-    qt6Packages.wrapQtAppsHook
   ];
 
   cmakeFlags = [
@@ -51,6 +55,30 @@ stdenv.mkDerivation {
     "-DKTE_STATIC_LINK=OFF"
   ];
 
+  desktopItems = lib.optionals graphical [
+    (makeDesktopItem {
+      name = "kge";
+      desktopName = "kge";
+      genericName = "Text Editor";
+      comment = "kyle's graphical text editor";
+      exec = if graphical-qt then "kge-qt %F" else "kge %F";
+      icon = "kge";
+      terminal = false;
+      categories = [ "Utility" "TextEditor" "Development" ];
+      mimeTypes = [
+        "text/plain"
+        "text/x-c"
+        "text/x-c++"
+        "text/x-python"
+        "text/x-go"
+        "text/x-rust"
+        "application/json"
+        "text/markdown"
+        "text/x-shellscript"
+      ];
+    })
+  ];
+
   installPhase = ''
     runHook preInstall
 
@@ -59,14 +87,11 @@ stdenv.mkDerivation {
     installManPage ../docs/kte.1
 
     ${lib.optionalString graphical ''
-      mkdir -p $out/bin
-  
       ${if graphical-qt then ''
         cp kge $out/bin/kge-qt
       '' else ''
         cp kge $out/bin/kge
       ''}
-
       installManPage ../docs/kge.1
 
       mkdir -p $out/share/icons/hicolor/256x256/apps
@@ -75,4 +100,10 @@ stdenv.mkDerivation {
 
     runHook postInstall
   '';
+
+  meta = {
+    description = "kyle's text editor" + lib.optionalString graphical " (graphical)";
+    platforms = lib.platforms.unix;
+    mainProgram = if graphical then (if graphical-qt then "kge-qt" else "kge") else "kte";
+  };
 }

docs/themes.md

@@ -23,29 +23,34 @@ Current themes (alphabetically):
 - **gruvbox** — Retro groove color scheme (light/dark variants)
 - **kanagawa-paper** — Inspired by traditional Japanese art
 - **lcars** — Star Trek LCARS interface style
+- **leuchtturm** — Modern, clean theme (light/dark variants)
 - **nord** — Arctic, north-bluish color palette
 - **old-book** — Sepia-toned vintage book aesthetic (light/dark
   variants)
 - **orbital** — Space-themed dark palette
 - **plan9** — Minimalist Plan 9 from Bell Labs inspired
 - **solarized** — Ethan Schoonover's Solarized (light/dark variants)
+- **tufte** — Edward Tufte-inspired minimalist theme (light/dark variants)
 - **weyland-yutani** — Alien franchise corporate aesthetic
 - **zenburn** — Low-contrast, easy-on-the-eyes theme
 
 Configuration
 -------------
 
-Themes are configured via `$HOME/.config/kte/kge.ini`:
+Themes are configured via `$HOME/.config/kte/kge.toml`:
 
-```ini
+```toml
-theme = nord
+[appearance]
-background = dark
+theme = "nord"
+background = "dark"
 ```
 
 - `theme` — The theme name (e.g., "nord", "gruvbox", "solarized")
 - `background` — Either "dark" or "light" (for themes supporting both
   variants)
 
+Legacy `kge.ini` format is also supported (see CONFIG.md).
+
 Themes can also be switched at runtime using the `:theme <name>`
 command.
 

flake.nix

@@ -3,8 +3,7 @@
 
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
 
-  outputs =
+  outputs = { self, nixpkgs, ... }:
-    inputs@{ self, nixpkgs, ... }:
     let
       eachSystem = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
       pkgsFor = system: import nixpkgs { inherit system; };
@@ -17,5 +16,27 @@
         kge = (pkgsFor system).callPackage ./default.nix { graphical = true;  graphical-qt = false; };
         qt  = (pkgsFor system).callPackage ./default.nix { graphical = true;  graphical-qt = true;  };
       });
+
+      devShells = eachSystem (system:
+        let pkgs = pkgsFor system;
+        in {
+          default = pkgs.mkShell {
+            inputsFrom = [ self.packages.${system}.kge ];
+            packages = with pkgs; [ gdb valgrind ];
+          };
+          terminal = pkgs.mkShell {
+            inputsFrom = [ self.packages.${system}.kte ];
+          };
+          qt = pkgs.mkShell {
+            inputsFrom = [ self.packages.${system}.qt ];
+            packages = with pkgs; [ gdb valgrind ];
+          };
+        }
+      );
+
+      overlays.default = final: prev: {
+        kte = self.packages.${final.system}.kte;
+        kge = self.packages.${final.system}.kge;
+      };
     };
 }

fonts/FontList.h

@@ -3,6 +3,8 @@
 #include "BerkeleyMono.h"
 #include "BrassMono.h"
 #include "BrassMonoCode.h"
+#include "CrimsonPro.h"
+#include "ETBook.h"
 #include "FiraCode.h"
 #include "Go.h"
 #include "IBMPlexMono.h"
@@ -13,6 +15,7 @@
 #include "IosevkaExtended.h"
 #include "ShareTech.h"
 #include "SpaceMono.h"
+#include "Spectral.h"
 #include "Syne.h"
 #include "Triplicate.h"
 #include "Unispace.h"

fonts/FontRegistry.cc

@@ -45,6 +45,16 @@ InstallDefaultFonts()
 		BrassMonoCode::DefaultFontBoldCompressedData,
 		BrassMonoCode::DefaultFontBoldCompressedSize
 	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+		"crimsonpro",
+		CrimsonPro::DefaultFontRegularCompressedData,
+		CrimsonPro::DefaultFontRegularCompressedSize
+	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+		"etbook",
+		ETBook::DefaultFontRegularCompressedData,
+		ETBook::DefaultFontRegularCompressedSize
+	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"fira",
 		FiraCode::DefaultFontRegularCompressedData,
@@ -95,6 +105,11 @@ InstallDefaultFonts()
 		SpaceMono::DefaultFontRegularCompressedData,
 		SpaceMono::DefaultFontRegularCompressedSize
 	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+		"spectral",
+		Spectral::DefaultFontRegularCompressedData,
+		Spectral::DefaultFontRegularCompressedSize
+	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"syne",
 		Syne::DefaultFontRegularCompressedData,

fonts/FontRegistry.h

@@ -1,10 +1,12 @@
 #pragma once
 
+#include <algorithm>
 #include <cassert>
 #include <memory>
 #include <mutex>
 #include <string>
 #include <unordered_map>
+#include <vector>
 
 #include "Font.h"
 
@@ -87,6 +89,19 @@ public:
 	}
 
 
+	// Return all registered font names (sorted)
+	std::vector<std::string> FontNames() const
+	{
+		std::lock_guard lock(mutex_);
+		std::vector<std::string> names;
+		names.reserve(fonts_.size());
+		for (const auto &[name, _] : fonts_)
+			names.push_back(name);
+		std::sort(names.begin(), names.end());
+		return names;
+	}
+
+
 	// Current font name/size as last successfully loaded via LoadFont()
 	std::string CurrentFontName() const
 	{

kge.toml.example

@@ -0,0 +1,24 @@
+# kge configuration
+# Place at ~/.config/kte/kge.toml
+
+[window]
+fullscreen = false
+columns = 80
+rows = 42
+
+[font]
+# Default font and size
+name = "default"
+size = 18.0
+# Font used in code mode (monospace)
+code = "default"
+# Font used in writing mode (proportional) — for .txt, .md, .rst, .org, .tex, etc.
+writing = "crimsonpro"
+
+[appearance]
+theme = "nord"
+# "dark" or "light" for themes with variants
+background = "dark"
+
+[editor]
+syntax = true

main.cc

@@ -12,6 +12,7 @@
 #include <random>
 #include <thread>
 #include <signal.h>
+#include <filesystem>
 #include <string>
 #include <unistd.h>
 #include <sys/stat.h>
@@ -255,7 +256,18 @@ main(int argc, char *argv[])
 					// Fall through: not a +number, treat as filename starting with '+'
 				}
 
-				const std::string path = arg;
+				// Resolve to absolute path now, before any
+				// chdir (macOS GUI changes CWD to HOME before
+				// deferred opens are processed).
+				std::string path = arg;
+				try {
+					std::filesystem::path p(path);
+					if (p.is_relative()) {
+						path = std::filesystem::absolute(p).string();
+					}
+				} catch (...) {
+					// Fall through with original path
+				}
 				editor.RequestOpenFile(path, pending_line);
 				pending_line = 0; // consumed (if set)
 			}
@@ -280,6 +292,20 @@ main(int argc, char *argv[])
 			fe = std::make_unique<TerminalFrontend>();
 		}
 
+		// Guarantee Shutdown() runs on every exit path from here on (normal
+		// return, early return, or exception unwinding e.g. from Init/Execute/
+		// Step) so a crash never leaves the terminal in raw/cbreak mode.
+		struct FrontendShutdownGuard {
+			Frontend *fe;
+
+
+			~FrontendShutdownGuard()
+			{
+				if (fe)
+					fe->Shutdown();
+			}
+		} shutdown_guard{fe.get()};
+
 #if defined(KTE_BUILD_GUI) && defined(__APPLE__)
 		if (use_gui) {
 			/* likely using the .app, so need to cd */
@@ -308,8 +334,6 @@ main(int argc, char *argv[])
 			fe->Step(editor, running);
 		}
 
-		fe->Shutdown();
-
 		return 0;
 	} catch (const std::exception &e) {
 		std::string msg = std::string("Unhandled exception: ") + e.what();

make-app-release

@@ -15,20 +15,18 @@ sha256sum kge.app.zip
 open .
 cd ..
 
-mkdir -p cmake-build-release-qt
+# Qt build disabled — ImGui frontend is the primary GUI.
-cmake -S . -B cmake-build-release-qt -DBUILD_GUI=ON -DKTE_USE_QT=ON -DCMAKE_BUILD_TYPE=Release -DENABLE_ASAN=OFF
+# mkdir -p cmake-build-release-qt
-
+# cmake -S . -B cmake-build-release-qt -DBUILD_GUI=ON -DKTE_USE_QT=ON -DCMAKE_BUILD_TYPE=Release -DENABLE_ASAN=OFF
-cd cmake-build-release-qt
+#
-make clean
+# cd cmake-build-release-qt
-rm -fr kge.app* kge-qt.app*
+# make clean
-make
+# rm -fr kge.app* kge-qt.app*
-mv -f kge.app kge-qt.app
+# make
-# Use the same Qt's macdeployqt as used for building; ensure it overwrites in-bundle paths
+# mv -f kge.app kge-qt.app
-macdeployqt kge-qt.app -always-overwrite -verbose=3
+# macdeployqt kge-qt.app -always-overwrite -verbose=3
-
+# cmake -DAPP_BUNDLE="$(pwd)/kge-qt.app" -P "${PWD%/*}/cmake/fix_bundle.cmake"
-# Run CMake BundleUtilities fixup to internalize non-Qt dylibs and rewrite install names
+# zip -r kge-qt.app.zip kge-qt.app
-cmake -DAPP_BUNDLE="$(pwd)/kge-qt.app" -P "${PWD%/*}/cmake/fix_bundle.cmake"
+# sha256sum kge-qt.app.zip
-zip -r kge-qt.app.zip kge-qt.app 
+# open .
-sha256sum kge-qt.app.zip
+# cd ..
-open .
-cd ..

make-release

@@ -22,5 +22,6 @@ fi
 
 git tag "${KTE_VERSION}"
 git push && git push --tags
+git push github && git push github --tags
 
 ( ./make-app-release )

syntax/GoHighlighter.cc

@@ -46,14 +46,45 @@ GoHighlighter::GoHighlighter()
 void
 GoHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
 {
+	StatefulHighlighter::LineState prev;
+	(void) HighlightLineStateful(buf, row, prev, out);
+}
+
+
+StatefulHighlighter::LineState
+GoHighlighter::HighlightLineStateful(const Buffer &buf,
+                                     int row,
+                                     const LineState &prev,
+                                     std::vector<HighlightSpan> &out) const
+{
+	StatefulHighlighter::LineState state = prev;
 	if (row < 0 || static_cast<std::size_t>(row) >= buf.Nrows())
-		return;
+		return state;
 	std::string s = buf.GetLineString(static_cast<std::size_t>(row));
 	int n         = static_cast<int>(s.size());
 	int i         = 0;
 	int bol       = 0;
 	while (bol < n && (s[bol] == ' ' || s[bol] == '\t'))
 		++bol;
+
+	// Continue a multi-line block comment from the previous line.
+	if (state.in_block_comment) {
+		int j = i;
+		while (i + 1 < n) {
+			if (s[i] == '*' && s[i + 1] == '/') {
+				i += 2;
+				push(out, j, i, TokenKind::Comment);
+				state.in_block_comment = false;
+				break;
+			}
+			++i;
+		}
+		if (state.in_block_comment) {
+			push(out, j, n, TokenKind::Comment);
+			return state;
+		}
+	}
+
 	// line comment
 	while (i < n) {
 		char c = s[i];
@@ -82,7 +113,8 @@ GoHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSp
 			}
 			if (!closed) {
 				push(out, i, n, TokenKind::Comment);
-				break;
+				state.in_block_comment = true;
+				return state;
 			} else {
 				push(out, i, j, TokenKind::Comment);
 				i = j;
@@ -152,5 +184,6 @@ GoHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSp
 		push(out, i, i + 1, TokenKind::Default);
 		++i;
 	}
+	return state;
 }
 } // namespace kte

syntax/GoHighlighter.h

@@ -5,12 +5,17 @@
 #include <unordered_set>
 
 namespace kte {
-class GoHighlighter final : public LanguageHighlighter {
+class GoHighlighter final : public StatefulHighlighter {
 public:
 	GoHighlighter();
 
 	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
 
+	LineState HighlightLineStateful(const Buffer &buf,
+	                                int row,
+	                                const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+
 private:
 	std::unordered_set<std::string> kws_;
 	std::unordered_set<std::string> types_;

syntax/HighlighterEngine.cc

@@ -74,7 +74,22 @@ HighlighterEngine::GetLine(const Buffer &buf, int row, std::uint64_t buf_version
 
 	StatefulHighlighter::LineState prev_state;
 	int start_row = -1;
-	if (!state_cache_.empty()) {
+
+	// Fast path: state_last_contig_ tracks the highest row we've cached state
+	// for, per version. If that row is already below our target, it's
+	// necessarily the best anchor the O(n) scan below would have found, so we
+	// can skip the scan entirely. Re-validated against state_cache_ before
+	// use since InvalidateFrom()/SetHighlighter() may have raced/cleared it.
+	auto contig_it = state_last_contig_.find(buf_version);
+	if (contig_it != state_last_contig_.end() && contig_it->second < row) {
+		auto sc_it = state_cache_.find(contig_it->second);
+		if (sc_it != state_cache_.end() && sc_it->second.version == buf_version) {
+			start_row  = contig_it->second;
+			prev_state = sc_it->second.state;
+		}
+	}
+
+	if (start_row < 0 && !state_cache_.empty()) {
 		// linear search over map (unordered), track best candidate
 		int best = -1;
 		for (const auto &kv: state_cache_) {
@@ -109,6 +124,9 @@ HighlighterEngine::GetLine(const Buffer &buf, int row, std::uint64_t buf_version
 		se.state        = next_state;
 		state_cache_[r] = se;
 		cur_state       = next_state;
+		int &contig     = state_last_contig_[buf_version];
+		if (r > contig)
+			contig = r;
 	}
 
 	// Store in cache and return by value
@@ -139,6 +157,14 @@ HighlighterEngine::InvalidateFrom(int row)
 				++it;
 		}
 	}
+	// A version's tracked contiguous-state row is no longer valid once any
+	// row at or above it has been evicted from state_cache_ above.
+	for (auto it = state_last_contig_.begin(); it != state_last_contig_.end();) {
+		if (it->second >= row)
+			it = state_last_contig_.erase(it);
+		else
+			++it;
+	}
 }
 
 

syntax/PythonHighlighter.cc

@@ -55,31 +55,26 @@ PythonHighlighter::HighlightLineStateful(const Buffer &buf, int row, const LineS
 	std::string s = buf.GetLineString(static_cast<std::size_t>(row));
 	int n         = static_cast<int>(s.size());
 
+	int i = 0;
+
 	// Triple-quoted string continuation uses in_raw_string with raw_delim either "'''" or "\"\"\""
 	if (state.in_raw_string && (state.raw_delim == "'''" || state.raw_delim == "\"\"\"")) {
 		auto pos = s.find(state.raw_delim);
 		if (pos == std::string::npos) {
 			push(out, 0, n, TokenKind::String);
 			return state; // still inside
-		} else {
+		}
 		int end = static_cast<int>(pos + static_cast<int>(state.raw_delim.size()));
 		push(out, 0, end, TokenKind::String);
-			// remainder processed normally
-			s                   = s.substr(end);
-			n                   = static_cast<int>(s.size());
 		state.in_raw_string = false;
 		state.raw_delim.clear();
-			// Continue parsing remainder as a separate small loop
+		// Resume the normal tokenizer at the closing delimiter's end, on the
-			int base = end;
+		// same (unmodified) `s`/`n`, so anything after it - including a new
-			// original offset, but we already emitted to 'out' with base=0; following spans should be from 'end'
+		// triple-quoted string opening on this same line - is re-scanned
-			// For simplicity, mark rest as Default
+		// instead of being dumped into a single opaque Default span.
-			if (n > 0)
+		i = end;
-				push(out, base, base + n, TokenKind::Default);
-			return state;
-		}
 	}
 
-	int i = 0;
 	// Detect comment start '#', ignoring inside strings
 	while (i < n) {
 		char c = s[i];

syntax/RustHighlighter.cc

@@ -47,11 +47,42 @@ RustHighlighter::RustHighlighter()
 void
 RustHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
 {
+	StatefulHighlighter::LineState prev;
+	(void) HighlightLineStateful(buf, row, prev, out);
+}
+
+
+StatefulHighlighter::LineState
+RustHighlighter::HighlightLineStateful(const Buffer &buf,
+                                       int row,
+                                       const LineState &prev,
+                                       std::vector<HighlightSpan> &out) const
+{
+	StatefulHighlighter::LineState state = prev;
 	if (row < 0 || static_cast<std::size_t>(row) >= buf.Nrows())
-		return;
+		return state;
 	std::string s = buf.GetLineString(static_cast<std::size_t>(row));
 	int n         = static_cast<int>(s.size());
 	int i         = 0;
+
+	// Continue a multi-line block comment from the previous line.
+	if (state.in_block_comment) {
+		int j = i;
+		while (i + 1 < n) {
+			if (s[i] == '*' && s[i + 1] == '/') {
+				i += 2;
+				push(out, j, i, TokenKind::Comment);
+				state.in_block_comment = false;
+				break;
+			}
+			++i;
+		}
+		if (state.in_block_comment) {
+			push(out, j, n, TokenKind::Comment);
+			return state;
+		}
+	}
+
 	while (i < n) {
 		char c = s[i];
 		if (c == ' ' || c == '\t') {
@@ -79,7 +110,8 @@ RustHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<Highlight
 			}
 			if (!closed) {
 				push(out, i, n, TokenKind::Comment);
-				break;
+				state.in_block_comment = true;
+				return state;
 			} else {
 				push(out, i, j, TokenKind::Comment);
 				i = j;
@@ -140,5 +172,6 @@ RustHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<Highlight
 		push(out, i, i + 1, TokenKind::Default);
 		++i;
 	}
+	return state;
 }
 } // namespace kte

syntax/RustHighlighter.h

@@ -5,12 +5,17 @@
 #include <unordered_set>
 
 namespace kte {
-class RustHighlighter final : public LanguageHighlighter {
+class RustHighlighter final : public StatefulHighlighter {
 public:
 	RustHighlighter();
 
 	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
 
+	LineState HighlightLineStateful(const Buffer &buf,
+	                                int row,
+	                                const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+
 private:
 	std::unordered_set<std::string> kws_;
 	std::unordered_set<std::string> types_;

syntax/SqlHighlighter.cc

@@ -47,12 +47,42 @@ SqlHighlighter::SqlHighlighter()
 void
 SqlHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
 {
+	StatefulHighlighter::LineState prev;
+	(void) HighlightLineStateful(buf, row, prev, out);
+}
+
+
+StatefulHighlighter::LineState
+SqlHighlighter::HighlightLineStateful(const Buffer &buf,
+                                      int row,
+                                      const LineState &prev,
+                                      std::vector<HighlightSpan> &out) const
+{
+	StatefulHighlighter::LineState state = prev;
 	if (row < 0 || static_cast<std::size_t>(row) >= buf.Nrows())
-		return;
+		return state;
 	std::string s = buf.GetLineString(static_cast<std::size_t>(row));
 	int n         = static_cast<int>(s.size());
 	int i         = 0;
 
+	// Continue a multi-line block comment from the previous line.
+	if (state.in_block_comment) {
+		int j = i;
+		while (i + 1 < n) {
+			if (s[i] == '*' && s[i + 1] == '/') {
+				i += 2;
+				push(out, j, i, TokenKind::Comment);
+				state.in_block_comment = false;
+				break;
+			}
+			++i;
+		}
+		if (state.in_block_comment) {
+			push(out, j, n, TokenKind::Comment);
+			return state;
+		}
+	}
+
 	while (i < n) {
 		char c = s[i];
 		if (c == ' ' || c == '\t') {
@@ -68,7 +98,7 @@ SqlHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightS
 			push(out, i, n, TokenKind::Comment);
 			break;
 		}
-		// simple block comment on same line: /* ... */
+		// block comment: /* ... */ (may span multiple lines)
 		if (c == '/' && i + 1 < n && s[i + 1] == '*') {
 			int j       = i + 2;
 			bool closed = false;
@@ -82,7 +112,8 @@ SqlHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightS
 			}
 			if (!closed) {
 				push(out, i, n, TokenKind::Comment);
-				break;
+				state.in_block_comment = true;
+				return state;
 			} else {
 				push(out, i, j, TokenKind::Comment);
 				i = j;
@@ -151,5 +182,6 @@ SqlHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightS
 		push(out, i, i + 1, TokenKind::Default);
 		++i;
 	}
+	return state;
 }
 } // namespace kte

syntax/SqlHighlighter.h

@@ -5,12 +5,17 @@
 #include <unordered_set>
 
 namespace kte {
-class SqlHighlighter final : public LanguageHighlighter {
+class SqlHighlighter final : public StatefulHighlighter {
 public:
 	SqlHighlighter();
 
 	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
 
+	LineState HighlightLineStateful(const Buffer &buf,
+	                                int row,
+	                                const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+
 private:
 	std::unordered_set<std::string> kws_;
 	std::unordered_set<std::string> types_;

tests/test_command_semantics.cc

@@ -108,3 +108,26 @@ TEST(CommandSemantics_CopyRegion_And_KillRegion)
 	ASSERT_EQ(b.MarkSet(), false);
 	ASSERT_EQ(h.Text(), std::string("hello "));
 }
+
+
+TEST(CommandSemantics_Syntax_OnOff_SetsUserOverride)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	// Before any explicit :syntax command, nothing has overridden the
+	// frontend's config-driven default.
+	ASSERT_EQ(b.SyntaxUserOverride(), false);
+
+	ASSERT_TRUE(Execute(ed, CommandId::Syntax, "off"));
+	ASSERT_EQ(b.SyntaxEnabled(), false);
+	// This flag is what a frontend's per-frame "apply config default" pass
+	// must check before re-enabling syntax, or a manual :syntax off gets
+	// silently undone on the next frame.
+	ASSERT_EQ(b.SyntaxUserOverride(), true);
+
+	ASSERT_TRUE(Execute(ed, CommandId::Syntax, "on"));
+	ASSERT_EQ(b.SyntaxEnabled(), true);
+	ASSERT_EQ(b.SyntaxUserOverride(), true);
+}

tests/test_kkeymap.cc

@@ -37,6 +37,21 @@ TEST(KKeymap_KPrefix_CanonicalChords)
 }
 
 
+TEST(KKeymap_KPrefix_UppercaseE_RejectedAndDistinctFromLowercaseE)
+{
+	CommandId id{};
+
+	// 'e' is a real binding (OpenFileStart).
+	ASSERT_TRUE(KLookupKCommand('e', false, id));
+	ASSERT_EQ(id, CommandId::OpenFileStart);
+
+	// 'E' must be rejected, not silently aliased to 'e' via case-insensitive
+	// lookup (the switch normalizes to lowercase, so this has to be special-
+	// cased before it).
+	ASSERT_EQ(KLookupKCommand('E', false, id), false);
+}
+
+
 TEST(KKeymap_CtrlChords_CanonicalChords)
 {
 	CommandId id{};

tests/test_migration_coverage.cc

@@ -414,17 +414,21 @@ TEST (Migration_EmptyBufferCheck_Pattern)
 
 TEST (Migration_SyntaxHighlighter_Pattern)
 {
-	// Test the pattern used in syntax highlighters
+	// Test the pattern used in syntax highlighters: loop Nrows(), fetch each
+	// line via GetLineString(row). Assert the pattern actually returns the
+	// right content, not just that it doesn't crash - see syntax highlighter
+	// correctness tests (test_syntax_highlighting.cc) for tokenization coverage.
 	Buffer buf;
 	buf.insert_text(0, 0, std::string("int main() {\n    return 0;\n}"));
 
+	ASSERT_EQ(buf.Nrows(), static_cast<std::size_t>(3));
+	const std::vector<std::string> expected = {"int main() {", "    return 0;", "}"};
 	for (std::size_t row = 0; row < buf.Nrows(); ++row) {
-		// This is the pattern used in all migrated highlighters
 		if (row >= buf.Nrows()) {
 			break; // Should never happen
 		}
 		std::string line = buf.GetLineString(row);
-		// Successfully accessed line - size() is always valid for std::string
+		ASSERT_EQ(line, expected[row]);
 	}
 }
 

tests/test_paste_split.cc

@@ -0,0 +1,104 @@
+// Tests for SplitPasteIntoCommands: pasted text must turn embedded line
+// breaks into Newline commands so InsertText never receives a '\r' or '\n'.
+#include "Test.h"
+
+#include "PasteSplit.h"
+
+
+namespace {
+
+// Assert that no InsertText command carries an embedded newline/carriage
+// return, mirroring the rejection in Command.cc's InsertText handler.
+void
+assert_no_newlines_in_inserts(const std::vector<MappedInput> &cmds)
+{
+	for (const auto &c : cmds) {
+		if (c.id == CommandId::InsertText) {
+			ASSERT_TRUE(c.arg.find('\n') == std::string::npos);
+			ASSERT_TRUE(c.arg.find('\r') == std::string::npos);
+		}
+	}
+}
+
+} // namespace
+
+
+TEST(PasteSplit_PlainTextNoNewline)
+{
+	auto cmds = SplitPasteIntoCommands("hello world");
+	ASSERT_EQ(cmds.size(), 1u);
+	ASSERT_TRUE(cmds[0].id == CommandId::InsertText);
+	ASSERT_TRUE(cmds[0].arg == "hello world");
+}
+
+
+TEST(PasteSplit_UnixNewlines)
+{
+	auto cmds = SplitPasteIntoCommands("a\nb");
+	assert_no_newlines_in_inserts(cmds);
+	ASSERT_EQ(cmds.size(), 3u);
+	ASSERT_TRUE(cmds[0].id == CommandId::InsertText && cmds[0].arg == "a");
+	ASSERT_TRUE(cmds[1].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[2].id == CommandId::InsertText && cmds[2].arg == "b");
+}
+
+
+// Regression: CRLF clipboards left a '\r' in the InsertText segment, which
+// InsertText rejected with "InsertText arg must not contain newlines".
+TEST(PasteSplit_WindowsCRLF)
+{
+	auto cmds = SplitPasteIntoCommands("a\r\nb");
+	assert_no_newlines_in_inserts(cmds);
+	ASSERT_EQ(cmds.size(), 3u);
+	ASSERT_TRUE(cmds[0].id == CommandId::InsertText && cmds[0].arg == "a");
+	ASSERT_TRUE(cmds[1].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[2].id == CommandId::InsertText && cmds[2].arg == "b");
+}
+
+
+// Regression: a bare '\r' (classic Mac / some macOS apps) must also break lines.
+TEST(PasteSplit_BareCR)
+{
+	auto cmds = SplitPasteIntoCommands("a\rb");
+	assert_no_newlines_in_inserts(cmds);
+	ASSERT_EQ(cmds.size(), 3u);
+	ASSERT_TRUE(cmds[0].id == CommandId::InsertText && cmds[0].arg == "a");
+	ASSERT_TRUE(cmds[1].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[2].id == CommandId::InsertText && cmds[2].arg == "b");
+}
+
+
+TEST(PasteSplit_BlankLinesPreserved)
+{
+	// Two line breaks between "a" and "b" => one empty line.
+	auto cmds = SplitPasteIntoCommands("a\n\nb");
+	assert_no_newlines_in_inserts(cmds);
+	ASSERT_EQ(cmds.size(), 4u);
+	ASSERT_TRUE(cmds[0].id == CommandId::InsertText && cmds[0].arg == "a");
+	ASSERT_TRUE(cmds[1].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[2].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[3].id == CommandId::InsertText && cmds[3].arg == "b");
+}
+
+
+TEST(PasteSplit_TrailingNewline)
+{
+	auto cmds = SplitPasteIntoCommands("abc\n");
+	assert_no_newlines_in_inserts(cmds);
+	ASSERT_EQ(cmds.size(), 2u);
+	ASSERT_TRUE(cmds[0].id == CommandId::InsertText && cmds[0].arg == "abc");
+	ASSERT_TRUE(cmds[1].id == CommandId::Newline);
+}
+
+
+TEST(PasteSplit_MultilineCRLF)
+{
+	auto cmds = SplitPasteIntoCommands("line1\r\nline2\r\nline3");
+	assert_no_newlines_in_inserts(cmds);
+	ASSERT_EQ(cmds.size(), 5u);
+	ASSERT_TRUE(cmds[0].arg == "line1");
+	ASSERT_TRUE(cmds[1].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[2].arg == "line2");
+	ASSERT_TRUE(cmds[3].id == CommandId::Newline);
+	ASSERT_TRUE(cmds[4].arg == "line3");
+}

tests/test_search_replace_flow.cc

@@ -101,6 +101,36 @@ TEST(SearchFlow_SearchReplace_EmptyFind_DoesNotMutateBuffer_And_ClearsState)
 }
 
 
+TEST(SearchFlow_SearchReplace_EmptyWith_ReplacesAdjacentOverlappingMatches)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	// "aaaa" with "aa" -> "" must remove both non-overlapping occurrences, not
+	// just the first: after deleting the match at column 0, the next "aa" now
+	// sits at column 0 too (not column 1), so the scan must resume at the
+	// deletion point rather than one character past it.
+	b.insert_text(0, 0, "aaaa\n");
+	b.SetCursor(0, 0);
+
+	ASSERT_TRUE(h.Exec(CommandId::SearchReplace));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_EQ(ed.CurrentPromptKind(), Editor::PromptKind::ReplaceFind);
+
+	ASSERT_TRUE(h.Exec(CommandId::InsertText, "aa"));
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_EQ(ed.CurrentPromptKind(), Editor::PromptKind::ReplaceWith);
+
+	// Leave the replacement empty and accept.
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+
+	ASSERT_TRUE(!ed.PromptActive());
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string(""));
+}
+
+
 TEST(SearchFlow_RegexFind_InvalidPattern_FailsSafely_And_ClearsStateOnEnter)
 {
 	TestHarness h;

tests/test_swap_cleanup2.cc

@@ -0,0 +1,125 @@
+#include "Test.h"
+
+#include "Command.h"
+#include "Editor.h"
+
+#include "tests/TestHarness.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <string>
+#include <unistd.h>
+
+namespace fs = std::filesystem;
+
+
+static void
+write_file_bytes(const std::string &path, const std::string &bytes)
+{
+	std::ofstream out(path, std::ios::binary | std::ios::trunc);
+	out.write(bytes.data(), (std::streamsize) bytes.size());
+}
+
+
+// RAII helper to set XDG_STATE_HOME for the duration of a test and clean up.
+struct XdgStateGuard {
+	fs::path root;
+	std::string old_xdg;
+	bool had_old;
+
+	explicit XdgStateGuard(const std::string &suffix)
+	{
+		root = fs::temp_directory_path() /
+		       (std::string("kte_ut_xdg_") + suffix + "_" + std::to_string((int) ::getpid()));
+		fs::remove_all(root);
+		fs::create_directories(root);
+
+		const char *p = std::getenv("XDG_STATE_HOME");
+		had_old       = (p != nullptr);
+		if (p)
+			old_xdg = p;
+		setenv("XDG_STATE_HOME", root.string().c_str(), 1);
+	}
+
+	~XdgStateGuard()
+	{
+		if (had_old)
+			setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+		else
+			unsetenv("XDG_STATE_HOME");
+		fs::remove_all(root);
+	}
+};
+
+
+TEST(SwapCleanup_SaveAndQuit)
+{
+	ktet::InstallDefaultCommandsOnce();
+	XdgStateGuard xdg("save_quit");
+
+	const std::string path = (xdg.root / "work" / "file.txt").string();
+	fs::create_directories(xdg.root / "work");
+	write_file_bytes(path, "hello\n");
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	Buffer *b = ed.CurrentBuffer();
+	ASSERT_TRUE(b != nullptr);
+
+	// Edit to create swap file
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "Z"));
+	ASSERT_TRUE(b->Dirty());
+
+	ed.Swap()->Flush(b);
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(*b);
+	ASSERT_TRUE(fs::exists(swp));
+
+	// Save-and-quit should clean up the swap file
+	ASSERT_TRUE(Execute(ed, CommandId::SaveAndQuit));
+	ed.Swap()->Flush(b);
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// Cleanup
+	std::remove(path.c_str());
+}
+
+
+TEST(SwapCleanup_EditorReset)
+{
+	ktet::InstallDefaultCommandsOnce();
+	XdgStateGuard xdg("editor_reset");
+
+	const std::string path = (xdg.root / "work" / "file.txt").string();
+	fs::create_directories(xdg.root / "work");
+	write_file_bytes(path, "hello\n");
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	Buffer *b = ed.CurrentBuffer();
+	ASSERT_TRUE(b != nullptr);
+
+	// Edit to create swap file
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "W"));
+	ASSERT_TRUE(b->Dirty());
+
+	ed.Swap()->Flush(b);
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(*b);
+	ASSERT_TRUE(fs::exists(swp));
+
+	// Reset (simulates clean editor exit) should remove swap files
+	ed.Reset();
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// Cleanup
+	std::remove(path.c_str());
+}

tests/test_syntax_highlighting.cc

@@ -0,0 +1,167 @@
+// test_syntax_highlighting.cc - tokenization correctness for LanguageHighlighter
+// implementations, focused on multi-line state propagation (block comments,
+// triple-quoted strings) that stateless-looking per-line scans easily get wrong.
+#include "Test.h"
+#include "Buffer.h"
+#include "Highlight.h"
+#include "syntax/LanguageHighlighter.h"
+#include "syntax/GoHighlighter.h"
+#include "syntax/RustHighlighter.h"
+#include "syntax/SqlHighlighter.h"
+#include "syntax/PythonHighlighter.h"
+
+#include <string>
+#include <vector>
+
+using kte::HighlightSpan;
+using kte::StatefulHighlighter;
+using kte::TokenKind;
+
+namespace {
+bool
+has_kind(const std::vector<HighlightSpan> &spans, TokenKind k)
+{
+	for (const auto &sp: spans) {
+		if (sp.kind == k)
+			return true;
+	}
+	return false;
+}
+} // namespace
+
+
+TEST (Syntax_Go_MultiLineBlockComment_PropagatesAcrossLines)
+{
+	Buffer b;
+	b.replace_all_bytes("/* start\nmiddle line\nend */\nfunc foo() {}\n");
+
+	kte::GoHighlighter hl;
+	StatefulHighlighter::LineState state;
+	std::vector<HighlightSpan> spans;
+
+	// Line 0 opens an unclosed block comment; state must carry forward.
+	state = hl.HighlightLineStateful(b, 0, state, spans);
+	ASSERT_TRUE(state.in_block_comment);
+
+	// Line 1 is entirely inside the comment; the whole line must be Comment,
+	// not re-tokenized as code (this is the bug: without state propagation
+	// "middle" and "line" would come back as identifiers).
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 1, state, spans);
+	ASSERT_TRUE(state.in_block_comment);
+	ASSERT_TRUE(!spans.empty());
+	for (const auto &sp: spans) {
+		ASSERT_TRUE(sp.kind == TokenKind::Comment);
+	}
+
+	// Line 2 closes the comment.
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 2, state, spans);
+	ASSERT_TRUE(!state.in_block_comment);
+	ASSERT_TRUE(has_kind(spans, TokenKind::Comment));
+
+	// Line 3 is ordinary code again: "func" must be a Keyword, not a Comment.
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 3, state, spans);
+	ASSERT_TRUE(!state.in_block_comment);
+	ASSERT_TRUE(has_kind(spans, TokenKind::Keyword));
+	ASSERT_TRUE(!has_kind(spans, TokenKind::Comment));
+}
+
+
+TEST (Syntax_Rust_MultiLineBlockComment_PropagatesAcrossLines)
+{
+	Buffer b;
+	b.replace_all_bytes("/* start\nmiddle line\nend */\nfn foo() {}\n");
+
+	kte::RustHighlighter hl;
+	StatefulHighlighter::LineState state;
+	std::vector<HighlightSpan> spans;
+
+	state = hl.HighlightLineStateful(b, 0, state, spans);
+	ASSERT_TRUE(state.in_block_comment);
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 1, state, spans);
+	ASSERT_TRUE(state.in_block_comment);
+	for (const auto &sp: spans) {
+		ASSERT_TRUE(sp.kind == TokenKind::Comment);
+	}
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 2, state, spans);
+	ASSERT_TRUE(!state.in_block_comment);
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 3, state, spans);
+	ASSERT_TRUE(has_kind(spans, TokenKind::Keyword));
+	ASSERT_TRUE(!has_kind(spans, TokenKind::Comment));
+}
+
+
+TEST (Syntax_Sql_MultiLineBlockComment_PropagatesAcrossLines)
+{
+	Buffer b;
+	b.replace_all_bytes("/* start\nmiddle line\nend */\nSELECT 1;\n");
+
+	kte::SqlHighlighter hl;
+	StatefulHighlighter::LineState state;
+	std::vector<HighlightSpan> spans;
+
+	state = hl.HighlightLineStateful(b, 0, state, spans);
+	ASSERT_TRUE(state.in_block_comment);
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 1, state, spans);
+	ASSERT_TRUE(state.in_block_comment);
+	for (const auto &sp: spans) {
+		ASSERT_TRUE(sp.kind == TokenKind::Comment);
+	}
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 2, state, spans);
+	ASSERT_TRUE(!state.in_block_comment);
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 3, state, spans);
+	ASSERT_TRUE(has_kind(spans, TokenKind::Keyword));
+	ASSERT_TRUE(!has_kind(spans, TokenKind::Comment));
+}
+
+
+TEST (Syntax_Python_TripleQuote_ClosesAndReopensOnSameLine)
+{
+	Buffer b;
+	// Line 0 opens a triple-quoted string that stays open.
+	// Line 1 closes the first string ("end'''") and, on the SAME line, opens a
+	// second triple-quoted string ("'''start of") that stays open into line 2.
+	b.replace_all_bytes("x = '''abc\nend''' + '''start of\nnext string'''\n");
+
+	kte::PythonHighlighter hl;
+	StatefulHighlighter::LineState state;
+	std::vector<HighlightSpan> spans;
+
+	state = hl.HighlightLineStateful(b, 0, state, spans);
+	ASSERT_TRUE(state.in_raw_string);
+	ASSERT_EQ(state.raw_delim, std::string("'''"));
+
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 1, state, spans);
+	// The bug: without re-scanning the remainder after the closing '''  the
+	// second opening ''' on this line is never noticed, so state.in_raw_string
+	// would incorrectly come back false here.
+	ASSERT_TRUE(state.in_raw_string);
+	ASSERT_EQ(state.raw_delim, std::string("'''"));
+
+	// Line 2 is inside the second string; it must be highlighted as String,
+	// not as ordinary code.
+	spans.clear();
+	state = hl.HighlightLineStateful(b, 2, state, spans);
+	ASSERT_TRUE(!spans.empty());
+	bool all_string = true;
+	for (const auto &sp: spans) {
+		if (sp.kind != TokenKind::String)
+			all_string = false;
+	}
+	ASSERT_TRUE(all_string);
+}

tests/test_undo.cc

@@ -1198,6 +1198,312 @@ TEST (Undo_Command_RedoCountSelectsBranch)
 }
 
 
+TEST (Undo_Command_Newline_UndoRejoinsCorrectLines)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abcdef\nghijkl");
+	buf->SetCursor(3, 0);
+
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(3));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("def"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("ghijkl"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(2));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abcdef"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("ghijkl"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_Backspace_JoinUndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abc\ndef");
+	buf->SetCursor(0, 1);
+
+	ASSERT_TRUE(Execute(ed, CommandId::Backspace));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(1));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abcdef"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(2));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("def"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(1));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abcdef"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_DeleteChar_JoinUndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abc\ndef");
+	buf->SetCursor(3, 0);
+
+	ASSERT_TRUE(Execute(ed, CommandId::DeleteChar));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(1));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abcdef"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(2));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("def"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(1));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abcdef"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_RegexReplaceAll_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("foo one\nfoo two\nbar three");
+	buf->SetCursor(0, 0);
+
+	ASSERT_TRUE(Execute(ed, CommandId::RegexpReplace));
+	ASSERT_TRUE(ed.PromptActive());
+	ed.SetPromptText("foo");
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+	ASSERT_TRUE(ed.PromptActive());
+	ed.SetPromptText("baz");
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("baz one"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("baz two"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("bar three"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("foo one"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("foo two"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("bar three"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("baz one"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("baz two"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("bar three"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_IndentUnindentRegion_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("one\ntwo\nthree");
+	buf->SetMark(0, 0);
+	buf->SetCursor(0, 2);
+
+	ASSERT_TRUE(Execute(ed, CommandId::IndentRegion));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("\tone"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("\ttwo"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("\tthree"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("one"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("two"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("three"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("\tone"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("\ttwo"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("\tthree"));
+
+	buf->SetMark(0, 0);
+	buf->SetCursor(0, 2);
+	ASSERT_TRUE(Execute(ed, CommandId::UnindentRegion));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("one"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("two"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("three"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("\tone"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("\ttwo"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("\tthree"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_KillToEol_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abcdef\nghijkl");
+	buf->SetCursor(3, 0);
+
+	ASSERT_TRUE(Execute(ed, CommandId::KillToEOL));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(2));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abcdef"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("ghijkl"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_KillLine_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abc\ndef\nghi");
+	buf->SetCursor(0, 1);
+
+	ASSERT_TRUE(Execute(ed, CommandId::KillLine));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(2));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("ghi"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(3));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("def"));
+	ASSERT_EQ(std::string(buf->Rows()[2]), std::string("ghi"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(buf->Nrows(), static_cast<std::size_t>(2));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc"));
+	ASSERT_EQ(std::string(buf->Rows()[1]), std::string("ghi"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_KillRegion_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abc def ghi");
+	buf->SetMark(4, 0);
+	buf->SetCursor(8, 0);
+
+	ASSERT_TRUE(Execute(ed, CommandId::KillRegion));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc ghi"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc def ghi"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Redo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc ghi"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
+TEST (Undo_Command_DeleteWordPrevNext_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	ed.AddBuffer(std::move(b));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	buf->replace_all_bytes("abc def ghi");
+	buf->SetCursor(8, 0);
+
+	ASSERT_TRUE(Execute(ed, CommandId::DeleteWordPrev));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc ghi"));
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc def ghi"));
+
+	buf->SetCursor(4, 0);
+	ASSERT_TRUE(Execute(ed, CommandId::DeleteWordNext));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc ghi"));
+	ASSERT_TRUE(Execute(ed, CommandId::Undo));
+	ASSERT_EQ(std::string(buf->Rows()[0]), std::string("abc def ghi"));
+
+	validate_undo_tree(*buf->Undo());
+}
+
+
 TEST (Undo_InsertRow_UndoDeletesRow)
 {
 	Buffer b;

themes/Leuchtturm.h

@@ -0,0 +1,204 @@
+// themes/Leuchtturm.h — Fountain pen on cream paper, brass and leather (header-only)
+// Inspired by Kaweco Brass/Bronze Sport pens on Leuchtturm1917 notebook paper.
+// Light: warm cream paper with blue-black fountain pen ink.
+// Dark: leather case and patinated metal.
+#pragma once
+#include "ThemeHelpers.h"
+
+static inline void
+ApplyLeuchtturmLightTheme()
+{
+	// Notebook paper and fountain pen ink
+	const ImVec4 paper  = RGBA(0xF2ECDF); // Leuchtturm cream paper
+	const ImVec4 bg1    = RGBA(0xE8E2D5); // slightly darker cream
+	const ImVec4 bg2    = RGBA(0xDDD7CA); // UI elements
+	const ImVec4 bg3    = RGBA(0xD1CBBD); // hover/active
+	const ImVec4 ink    = RGBA(0x040720); // blue-black fountain pen ink
+	const ImVec4 dim    = RGBA(0x7A756A); // faded text (like printed headers)
+	const ImVec4 border = RGBA(0xCCC6B4); // faint ruled lines
+
+	// Metal accents from the pens
+	const ImVec4 brass = RGBA(0x6B5E2A); // dark patinated brass
+	const ImVec4 brown = RGBA(0x5C3D28); // leather/bronze
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 12.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 0.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = ink;
+	colors[ImGuiCol_TextDisabled] = dim;
+	colors[ImGuiCol_WindowBg]     = paper;
+	colors[ImGuiCol_ChildBg]      = paper;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = border;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = paper;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = border;
+
+	colors[ImGuiCol_CheckMark]        = ink;
+	colors[ImGuiCol_SliderGrab]       = ink;
+	colors[ImGuiCol_SliderGrabActive] = brass;
+
+	colors[ImGuiCol_Button]        = bg2;
+	colors[ImGuiCol_ButtonHovered] = bg3;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg2;
+	colors[ImGuiCol_HeaderHovered] = bg3;
+	colors[ImGuiCol_HeaderActive]  = bg3;
+
+	colors[ImGuiCol_Separator]        = border;
+	colors[ImGuiCol_SeparatorHovered] = bg3;
+	colors[ImGuiCol_SeparatorActive]  = brass;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(ink.x, ink.y, ink.z, 0.10f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(brass.x, brass.y, brass.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]  = brass;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = border;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(border.x, border.y, border.z, 0.5f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.0f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.30f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(brass.x, brass.y, brass.z, 0.18f);
+	colors[ImGuiCol_DragDropTarget]        = brass;
+	colors[ImGuiCol_NavHighlight]          = brass;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.15f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.15f);
+	colors[ImGuiCol_PlotLines]             = brown;
+	colors[ImGuiCol_PlotLinesHovered]      = brass;
+	colors[ImGuiCol_PlotHistogram]         = brown;
+	colors[ImGuiCol_PlotHistogramHovered]  = brass;
+}
+
+
+// Dark variant — leather pen case with warm metal and cream accents
+static inline void
+ApplyLeuchtturmDarkTheme()
+{
+	const ImVec4 bg0    = RGBA(0x1C1610); // dark leather
+	const ImVec4 bg1    = RGBA(0x251E16); // slightly lighter
+	const ImVec4 bg2    = RGBA(0x30281E); // UI elements
+	const ImVec4 bg3    = RGBA(0x3E3428); // hover/active
+	const ImVec4 ink    = RGBA(0xE5DDD0); // warm cream text
+	const ImVec4 dim    = RGBA(0x978E7C); // secondary text
+	const ImVec4 border = RGBA(0x4A3E30); // subtle borders
+
+	const ImVec4 brass = RGBA(0xB8A060); // polished brass
+	const ImVec4 brown = RGBA(0x8B6848); // bronze pen
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 12.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 0.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = ink;
+	colors[ImGuiCol_TextDisabled] = dim;
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = border;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = border;
+	colors[ImGuiCol_ScrollbarGrabActive]  = dim;
+
+	colors[ImGuiCol_CheckMark]        = brass;
+	colors[ImGuiCol_SliderGrab]       = brass;
+	colors[ImGuiCol_SliderGrabActive] = brown;
+
+	colors[ImGuiCol_Button]        = bg2;
+	colors[ImGuiCol_ButtonHovered] = bg3;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg2;
+	colors[ImGuiCol_HeaderHovered] = bg3;
+	colors[ImGuiCol_HeaderActive]  = bg3;
+
+	colors[ImGuiCol_Separator]        = border;
+	colors[ImGuiCol_SeparatorHovered] = bg3;
+	colors[ImGuiCol_SeparatorActive]  = brass;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(ink.x, ink.y, ink.z, 0.10f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(brass.x, brass.y, brass.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]  = brass;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = border;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(border.x, border.y, border.z, 0.5f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.0f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.30f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(brass.x, brass.y, brass.z, 0.22f);
+	colors[ImGuiCol_DragDropTarget]        = brass;
+	colors[ImGuiCol_NavHighlight]          = brass;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.35f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.35f);
+	colors[ImGuiCol_PlotLines]             = brass;
+	colors[ImGuiCol_PlotLinesHovered]      = brown;
+	colors[ImGuiCol_PlotHistogram]         = brass;
+	colors[ImGuiCol_PlotHistogramHovered]  = brown;
+}

themes/Tufte.h

@@ -0,0 +1,203 @@
+// themes/Tufte.h — Edward Tufte inspired ImGui theme (header-only)
+// Warm cream paper, dark ink, minimal chrome, restrained accent colors.
+#pragma once
+#include "ThemeHelpers.h"
+
+// Light variant (primary — Tufte's books are fundamentally light)
+static inline void
+ApplyTufteLightTheme()
+{
+	// Tufte palette: warm cream paper with near-black ink
+	const ImVec4 paper  = RGBA(0xFFFFF8); // Tufte's signature warm white
+	const ImVec4 bg1    = RGBA(0xF4F0E8); // slightly darker cream
+	const ImVec4 bg2    = RGBA(0xEAE6DE); // UI elements
+	const ImVec4 bg3    = RGBA(0xDDD9D1); // hover/active
+	const ImVec4 ink    = RGBA(0x111111); // near-black text
+	const ImVec4 dim    = RGBA(0x6B6B6B); // disabled/secondary text
+	const ImVec4 border = RGBA(0xD0CCC4); // subtle borders
+
+	// Tufte uses color sparingly: muted red for emphasis, navy for links
+	const ImVec4 red  = RGBA(0xA00000); // restrained dark red
+	const ImVec4 blue = RGBA(0x1F3F6F); // dark navy
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 12.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f; // sharp edges — typographic, not app-like
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 0.0f; // minimal frame borders
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = ink;
+	colors[ImGuiCol_TextDisabled] = dim;
+	colors[ImGuiCol_WindowBg]     = paper;
+	colors[ImGuiCol_ChildBg]      = paper;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = border;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = paper;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = border;
+
+	colors[ImGuiCol_CheckMark]        = ink;
+	colors[ImGuiCol_SliderGrab]       = ink;
+	colors[ImGuiCol_SliderGrabActive] = blue;
+
+	colors[ImGuiCol_Button]        = bg2;
+	colors[ImGuiCol_ButtonHovered] = bg3;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg2;
+	colors[ImGuiCol_HeaderHovered] = bg3;
+	colors[ImGuiCol_HeaderActive]  = bg3;
+
+	colors[ImGuiCol_Separator]        = border;
+	colors[ImGuiCol_SeparatorHovered] = bg3;
+	colors[ImGuiCol_SeparatorActive]  = red;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(ink.x, ink.y, ink.z, 0.10f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(red.x, red.y, red.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]  = red;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = border;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(border.x, border.y, border.z, 0.5f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.0f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.30f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(red.x, red.y, red.z, 0.15f);
+	colors[ImGuiCol_DragDropTarget]        = red;
+	colors[ImGuiCol_NavHighlight]          = red;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.15f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.15f);
+	colors[ImGuiCol_PlotLines]             = blue;
+	colors[ImGuiCol_PlotLinesHovered]      = red;
+	colors[ImGuiCol_PlotHistogram]         = blue;
+	colors[ImGuiCol_PlotHistogramHovered]  = red;
+}
+
+
+// Dark variant — warm charcoal with cream ink, same restrained accents
+static inline void
+ApplyTufteDarkTheme()
+{
+	const ImVec4 bg0    = RGBA(0x1C1B19); // warm near-black
+	const ImVec4 bg1    = RGBA(0x252420); // slightly lighter
+	const ImVec4 bg2    = RGBA(0x302F2A); // UI elements
+	const ImVec4 bg3    = RGBA(0x3D3C36); // hover/active
+	const ImVec4 ink    = RGBA(0xEAE6DE); // cream text (inverted paper)
+	const ImVec4 dim    = RGBA(0x9A9690); // disabled text
+	const ImVec4 border = RGBA(0x4A4840); // subtle borders
+
+	const ImVec4 red  = RGBA(0xD06060); // warmer red for dark bg
+	const ImVec4 blue = RGBA(0x7098C0); // lighter navy for dark bg
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 12.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 0.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = ink;
+	colors[ImGuiCol_TextDisabled] = dim;
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = border;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = border;
+	colors[ImGuiCol_ScrollbarGrabActive]  = dim;
+
+	colors[ImGuiCol_CheckMark]        = ink;
+	colors[ImGuiCol_SliderGrab]       = ink;
+	colors[ImGuiCol_SliderGrabActive] = blue;
+
+	colors[ImGuiCol_Button]        = bg2;
+	colors[ImGuiCol_ButtonHovered] = bg3;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg2;
+	colors[ImGuiCol_HeaderHovered] = bg3;
+	colors[ImGuiCol_HeaderActive]  = bg3;
+
+	colors[ImGuiCol_Separator]        = border;
+	colors[ImGuiCol_SeparatorHovered] = bg3;
+	colors[ImGuiCol_SeparatorActive]  = red;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(ink.x, ink.y, ink.z, 0.10f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(red.x, red.y, red.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]  = red;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = border;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(border.x, border.y, border.z, 0.5f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.0f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.30f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(red.x, red.y, red.z, 0.20f);
+	colors[ImGuiCol_DragDropTarget]        = red;
+	colors[ImGuiCol_NavHighlight]          = red;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.35f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.35f);
+	colors[ImGuiCol_PlotLines]             = blue;
+	colors[ImGuiCol_PlotLinesHovered]      = red;
+	colors[ImGuiCol_PlotHistogram]         = blue;
+	colors[ImGuiCol_PlotHistogramHovered]  = red;
+}