Add test for Git editor swap cleanup and improve swap file handling

- Added `test_swap_git_editor.cc` to verify proper swap file cleanup during Git editor workflows. Ensures no stale swap files are left after editor closure.
- Updated swap handling logic in `Editor.cc` to always remove swap files on buffer closure during normal exit, preventing accumulation of leftover files.
- Bumped version to 1.6.5 in `CMakeLists.txt`.

.junie/guidelines.md

@@ -1,6 +1,6 @@
 # Project Guidelines
 
-kte is Kyle's Text Editor — a simple, fast text editor written in C++17.
+kte is Kyle's Text Editor — a simple, fast text editor written in C++20.
 It
 replaces the earlier C implementation, ke (see the ke manual in
 `docs/ke.md`). The
@@ -43,7 +43,7 @@ The file `docs/ke.md` contains the canonical reference for keybindings.
 
 ## Contributing/Development Notes
 
-- C++ standard: C++17.
+- C++ standard: C++20.
 - Keep dependencies minimal.
 - Prefer small, focused changes that preserve ke’s UX unless explicitly
   changing
@@ -55,3 +55,4 @@ The file `docs/ke.md` contains the canonical reference for keybindings.
   for now).
 - Inspiration: kilo, WordStar/VDE, emacs, `mg(1)`.
 
+

Buffer.cc

@@ -7,7 +7,15 @@
 #include <cstring>
 #include <string_view>
 
+#include <vector>
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
 #include "Buffer.h"
+#include "SwapRecorder.h"
 #include "UndoSystem.h"
 #include "UndoTree.h"
 // For reconstructing highlighter state on copies
@@ -23,6 +31,159 @@ Buffer::Buffer()
 }
 
 
+bool
+Buffer::stat_identity(const std::string &path, FileIdentity &out)
+{
+	struct stat st{};
+	if (::stat(path.c_str(), &st) != 0) {
+		out.valid = false;
+		return false;
+	}
+	out.valid = true;
+	// Use nanosecond timestamp when available.
+	std::uint64_t ns = 0;
+#if defined(__APPLE__)
+	ns = static_cast<std::uint64_t>(st.st_mtimespec.tv_sec) * 1000000000ull
+	     + static_cast<std::uint64_t>(st.st_mtimespec.tv_nsec);
+#else
+	ns = static_cast<std::uint64_t>(st.st_mtim.tv_sec) * 1000000000ull
+	     + static_cast<std::uint64_t>(st.st_mtim.tv_nsec);
+#endif
+	out.mtime_ns = ns;
+	out.size     = static_cast<std::uint64_t>(st.st_size);
+	out.dev      = static_cast<std::uint64_t>(st.st_dev);
+	out.ino      = static_cast<std::uint64_t>(st.st_ino);
+	return true;
+}
+
+
+bool
+Buffer::current_disk_identity(FileIdentity &out) const
+{
+	if (!is_file_backed_ || filename_.empty()) {
+		out.valid = false;
+		return false;
+	}
+	return stat_identity(filename_, out);
+}
+
+
+bool
+Buffer::ExternallyModifiedOnDisk() const
+{
+	if (!is_file_backed_ || filename_.empty())
+		return false;
+	FileIdentity now{};
+	if (!current_disk_identity(now)) {
+		// If the file vanished, treat as modified when we previously had an identity.
+		return on_disk_identity_.valid;
+	}
+	if (!on_disk_identity_.valid)
+		return false;
+	return now.mtime_ns != on_disk_identity_.mtime_ns
+	       || now.size != on_disk_identity_.size
+	       || now.dev != on_disk_identity_.dev
+	       || now.ino != on_disk_identity_.ino;
+}
+
+
+void
+Buffer::RefreshOnDiskIdentity()
+{
+	FileIdentity id{};
+	if (current_disk_identity(id))
+		on_disk_identity_ = id;
+}
+
+
+static bool
+write_all_fd(int fd, const char *data, std::size_t len, std::string &err)
+{
+	std::size_t off = 0;
+	while (off < len) {
+		ssize_t n = ::write(fd, data + off, len - off);
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			err = std::string("Write failed: ") + std::strerror(errno);
+			return false;
+		}
+		off += static_cast<std::size_t>(n);
+	}
+	return true;
+}
+
+
+static void
+best_effort_fsync_dir(const std::string &path)
+{
+	try {
+		std::filesystem::path p(path);
+		std::filesystem::path dir = p.parent_path();
+		if (dir.empty())
+			return;
+		int dfd = ::open(dir.c_str(), O_RDONLY);
+		if (dfd < 0)
+			return;
+		(void) ::fsync(dfd);
+		(void) ::close(dfd);
+	} catch (...) {
+		// best-effort
+	}
+}
+
+
+static bool
+atomic_write_file(const std::string &path, const char *data, std::size_t len, std::string &err)
+{
+	// Create a temp file in the same directory so rename() is atomic.
+	std::filesystem::path p(path);
+	std::filesystem::path dir  = p.parent_path();
+	std::string base           = p.filename().string();
+	std::filesystem::path tmpl = dir / ("." + base + ".kte.tmp.XXXXXX");
+	std::string tmpl_s         = tmpl.string();
+
+	// mkstemp requires a mutable buffer.
+	std::vector<char> buf(tmpl_s.begin(), tmpl_s.end());
+	buf.push_back('\0');
+	int fd = ::mkstemp(buf.data());
+	if (fd < 0) {
+		err = std::string("Failed to create temp file for save: ") + std::strerror(errno);
+		return false;
+	}
+	std::string tmp_path(buf.data());
+
+	// If the destination exists, carry over its permissions.
+	struct stat dst_st{};
+	if (::stat(path.c_str(), &dst_st) == 0) {
+		(void) ::fchmod(fd, dst_st.st_mode);
+	}
+
+	bool ok = write_all_fd(fd, data, len, err);
+	if (ok) {
+		if (::fsync(fd) != 0) {
+			err = std::string("fsync failed: ") + std::strerror(errno);
+			ok  = false;
+		}
+	}
+	(void) ::close(fd);
+
+	if (ok) {
+		if (::rename(tmp_path.c_str(), path.c_str()) != 0) {
+			err = std::string("rename failed: ") + std::strerror(errno);
+			ok  = false;
+		}
+	}
+
+	if (!ok) {
+		(void) ::unlink(tmp_path.c_str());
+		return false;
+	}
+	best_effort_fsync_dir(path);
+	return true;
+}
+
+
 Buffer::Buffer(const std::string &path)
 {
 	std::string err;
@@ -270,6 +431,7 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 	filename_         = norm;
 	is_file_backed_   = true;
 	dirty_            = false;
+	RefreshOnDiskIdentity();
 
 	// Reset/initialize undo system for this loaded file
 	if (!undo_tree_)
@@ -296,22 +458,16 @@ Buffer::Save(std::string &err) const
 		err = "Buffer is not file-backed; use SaveAs()";
 		return false;
 	}
-	std::ofstream out(filename_, std::ios::out | std::ios::binary | std::ios::trunc);
+	const std::size_t sz = content_.Size();
-	if (!out) {
+	const char *data     = sz ? content_.Data() : nullptr;
-		err = "Failed to open for write: " + filename_ + ". Error: " + std::string(std::strerror(errno));
+	if (sz && !data) {
+		err = "Internal error: buffer materialization failed";
 		return false;
 	}
-	// Stream the content directly from the piece table to avoid relying on
+	if (!atomic_write_file(filename_, data ? data : "", sz, err))
-	// full materialization, which may yield an empty pointer when size > 0.
-	if (content_.Size() > 0) {
-		content_.WriteToStream(out);
-	}
-	// Ensure data hits the OS buffers
-	out.flush();
-	if (!out.good()) {
-		err = "Write error: " + filename_ + ". Error: " + std::string(std::strerror(errno));
 		return false;
-	}
+	// Update observed on-disk identity after a successful save.
+	const_cast<Buffer *>(this)->RefreshOnDiskIdentity();
 	// Note: const method cannot change dirty_. Intentionally const to allow UI code
 	// to decide when to flip dirty flag after successful save.
 	return true;
@@ -340,26 +496,19 @@ Buffer::SaveAs(const std::string &path, std::string &err)
 		out_path = path;
 	}
 
-	// Write to the given path
+	const std::size_t sz = content_.Size();
-	std::ofstream out(out_path, std::ios::out | std::ios::binary | std::ios::trunc);
+	const char *data     = sz ? content_.Data() : nullptr;
-	if (!out) {
+	if (sz && !data) {
-		err = "Failed to open for write: " + out_path + ". Error: " + std::string(std::strerror(errno));
+		err = "Internal error: buffer materialization failed";
 		return false;
 	}
-	// Stream content without forcing full materialization
+	if (!atomic_write_file(out_path, data ? data : "", sz, err))
-	if (content_.Size() > 0) {
-		content_.WriteToStream(out);
-	}
-	// Ensure data hits the OS buffers
-	out.flush();
-	if (!out.good()) {
-		err = "Write error: " + out_path + ". Error: " + std::string(std::strerror(errno));
 		return false;
-	}
 
 	filename_       = out_path;
 	is_file_backed_ = true;
 	dirty_          = false;
+	RefreshOnDiskIdentity();
 	return true;
 }
 
@@ -390,6 +539,8 @@ Buffer::insert_text(int row, int col, std::string_view text)
 	if (!text.empty()) {
 		content_.Insert(off, text.data(), text.size());
 		rows_cache_dirty_ = true;
+		if (swap_rec_)
+			swap_rec_->OnInsert(row, col, text);
 	}
 }
 
@@ -434,6 +585,21 @@ Buffer::content_LineCount_() const
 }
 
 
+#if defined(KTE_TESTS)
+std::string
+Buffer::BytesForTests() const
+{
+	const std::size_t sz = content_.Size();
+	if (sz == 0)
+		return std::string();
+	const char *data = content_.Data();
+	if (!data)
+		return std::string();
+	return std::string(data, data + sz);
+}
+#endif
+
+
 void
 Buffer::delete_text(int row, int col, std::size_t len)
 {
@@ -443,6 +609,7 @@ Buffer::delete_text(int row, int col, std::size_t len)
 		row = 0;
 	if (col < 0)
 		col = 0;
+
 	const std::size_t start = content_.LineColToByteOffset(static_cast<std::size_t>(row),
 	                                                       static_cast<std::size_t>(col));
 	std::size_t r         = static_cast<std::size_t>(row);
@@ -462,16 +629,19 @@ Buffer::delete_text(int row, int col, std::size_t len)
 			break;
 		// Consume newline between lines as one char, if there is a next line
 		if (r + 1 < lc) {
-			if (remaining > 0) {
+			remaining -= 1; // the newline
-				remaining -= 1; // the newline
+			r         += 1;
-				r         += 1;
+			c         = 0;
-				c         = 0;
-			}
 		} else {
 			// At last line and still remaining: delete to EOF
-			std::size_t total = content_.Size();
+			const std::size_t total  = content_.Size();
-			content_.Delete(start, total - start);
+			const std::size_t actual = (total > start) ? (total - start) : 0;
+			if (actual == 0)
+				return;
+			content_.Delete(start, actual);
 			rows_cache_dirty_ = true;
+			if (swap_rec_)
+				swap_rec_->OnDelete(row, col, actual);
 			return;
 		}
 	}
@@ -479,8 +649,11 @@ Buffer::delete_text(int row, int col, std::size_t len)
 	// Compute end offset at (r,c)
 	std::size_t end = content_.LineColToByteOffset(r, c);
 	if (end > start) {
-		content_.Delete(start, end - start);
+		const std::size_t actual = end - start;
+		content_.Delete(start, actual);
 		rows_cache_dirty_ = true;
+		if (swap_rec_)
+			swap_rec_->OnDelete(row, col, actual);
 	}
 }
 
@@ -488,15 +661,18 @@ Buffer::delete_text(int row, int col, std::size_t len)
 void
 Buffer::split_line(int row, const int col)
 {
+	int c = col;
 	if (row < 0)
 		row = 0;
-	if (col < 0)
+	if (c < 0)
-		row = 0;
+		c = 0;
 	const std::size_t off = content_.LineColToByteOffset(static_cast<std::size_t>(row),
-	                                                     static_cast<std::size_t>(col));
+	                                                     static_cast<std::size_t>(c));
 	const char nl = '\n';
 	content_.Insert(off, &nl, 1);
 	rows_cache_dirty_ = true;
+	if (swap_rec_)
+		swap_rec_->OnInsert(row, c, std::string_view("\n", 1));
 }
 
 
@@ -508,11 +684,14 @@ Buffer::join_lines(int row)
 	std::size_t r = static_cast<std::size_t>(row);
 	if (r + 1 >= content_.LineCount())
 		return;
+	const int col = static_cast<int>(content_.GetLine(r).size());
 	// Delete the newline between line r and r+1
 	std::size_t end_of_line = content_.LineColToByteOffset(r, std::numeric_limits<std::size_t>::max());
 	// end_of_line now equals line end (clamped before newline). The newline should be exactly at this position.
 	content_.Delete(end_of_line, 1);
 	rows_cache_dirty_ = true;
+	if (swap_rec_)
+		swap_rec_->OnDelete(row, col, 1);
 }
 
 
@@ -527,6 +706,12 @@ Buffer::insert_row(int row, const std::string_view text)
 	const char nl = '\n';
 	content_.Insert(off + text.size(), &nl, 1);
 	rows_cache_dirty_ = true;
+	if (swap_rec_) {
+		// Avoid allocation: emit the row text insertion (if any) and the newline insertion.
+		if (!text.empty())
+			swap_rec_->OnInsert(row, 0, text);
+		swap_rec_->OnInsert(row, static_cast<int>(text.size()), std::string_view("\n", 1));
+	}
 }
 
 
@@ -541,9 +726,24 @@ Buffer::delete_row(int row)
 	auto range = content_.GetLineRange(r); // [start,end)
 	// If not last line, ensure we include the separating newline by using end as-is (which points to next line start)
 	// If last line, end may equal total_size_. We still delete [start,end) which removes the last line content.
-	std::size_t start = range.first;
+	const std::size_t start  = range.first;
-	std::size_t end   = range.second;
+	const std::size_t end    = range.second;
-	content_.Delete(start, end - start);
+	const std::size_t actual = (end > start) ? (end - start) : 0;
+	if (actual == 0)
+		return;
+	content_.Delete(start, actual);
+	rows_cache_dirty_ = true;
+	if (swap_rec_)
+		swap_rec_->OnDelete(row, 0, actual);
+}
+
+
+void
+Buffer::replace_all_bytes(const std::string_view bytes)
+{
+	content_.Clear();
+	if (!bytes.empty())
+		content_.Append(bytes.data(), bytes.size());
 	rows_cache_dirty_ = true;
 }
 

Buffer.h

@@ -42,6 +42,14 @@ public:
 	bool Save(std::string &err) const; // saves to existing filename; returns false if not file-backed
 	bool SaveAs(const std::string &path, std::string &err); // saves to path and makes buffer file-backed
 
+	// External modification detection.
+	// Returns true if the file on disk differs from the last observed identity recorded
+	// on open/save.
+	[[nodiscard]] bool ExternallyModifiedOnDisk() const;
+
+	// Refresh the stored on-disk identity to match current stat (used after open/save).
+	void RefreshOnDiskIdentity();
+
 	// Accessors
 	[[nodiscard]] std::size_t Curx() const
 	{
@@ -418,6 +426,23 @@ public:
 	}
 
 
+	// In visual-line (multi-cursor) mode, the UI should highlight only the per-line
+	// cursor "spot" (Curx clamped to each line length), not the entire line.
+	[[nodiscard]] bool VisualLineSpotSelected(std::size_t y, std::size_t sx) const
+	{
+		if (!visual_line_active_)
+			return false;
+		if (y < VisualLineStartY() || y > VisualLineEndY())
+			return false;
+		std::string_view ln = GetLineView(y);
+		// `GetLineView()` returns the raw range, which may include a trailing '\n'.
+		if (!ln.empty() && ln.back() == '\n')
+			ln.remove_suffix(1);
+		const std::size_t spot = std::min(Curx(), ln.size());
+		return sx == spot;
+	}
+
+
 	[[nodiscard]] std::string AsString() const;
 
 	// Syntax highlighting integration (per-buffer)
@@ -477,6 +502,12 @@ public:
 	}
 
 
+	[[nodiscard]] kte::SwapRecorder *SwapRecorder() const
+	{
+		return swap_rec_;
+	}
+
+
 	// Raw, low-level editing APIs used by UndoSystem apply().
 	// These must NOT trigger undo recording. They also do not move the cursor.
 	void insert_text(int row, int col, std::string_view text);
@@ -491,12 +522,36 @@ public:
 
 	void delete_row(int row);
 
+	// Replace the entire buffer content with raw bytes.
+	// Intended for crash recovery (swap replay) and test harnesses.
+	// This does not trigger swap or undo recording.
+	void replace_all_bytes(std::string_view bytes);
+
 	// Undo system accessors (created per-buffer)
 	[[nodiscard]] UndoSystem *Undo();
 
 	[[nodiscard]] const UndoSystem *Undo() const;
 
+#if defined(KTE_TESTS)
+	// Test-only: return the raw buffer bytes (including newlines) as a string.
+	[[nodiscard]] std::string BytesForTests() const;
+#endif
+
 private:
+	struct FileIdentity {
+		bool valid             = false;
+		std::uint64_t mtime_ns = 0;
+		std::uint64_t size     = 0;
+		std::uint64_t dev      = 0;
+		std::uint64_t ino      = 0;
+	};
+
+	[[nodiscard]] static bool stat_identity(const std::string &path, FileIdentity &out);
+
+	[[nodiscard]] bool current_disk_identity(FileIdentity &out) const;
+
+	mutable FileIdentity on_disk_identity_{};
+
 	// State mirroring original C struct (without undo_tree)
 	std::size_t curx_    = 0, cury_ = 0; // cursor position in characters
 	std::size_t rx_      = 0; // render x (tabs expanded)

CMakeLists.txt

@@ -4,13 +4,13 @@ project(kte)
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 20)
-set(KTE_VERSION "1.6.0")
+set(KTE_VERSION "1.6.5")
 
 # Default to terminal-only build to avoid SDL/OpenGL dependency by default.
 # Enable with -DBUILD_GUI=ON when SDL2/OpenGL/Freetype are available.
 set(BUILD_GUI ON CACHE BOOL "Enable building the graphical version.")
 set(KTE_USE_QT OFF CACHE BOOL "Build the QT frontend instead of ImGui.")
-set(BUILD_TESTS OFF CACHE BOOL "Enable building test programs.")
+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)
@@ -298,10 +298,24 @@ if (BUILD_TESTS)
     add_executable(kte_tests
             tests/TestRunner.cc
             tests/Test.h
+            tests/TestHarness.h
+            tests/test_daily_driver_harness.cc
+            tests/test_daily_workflows.cc
             tests/test_buffer_io.cc
+            tests/test_buffer_rows.cc
+            tests/test_command_semantics.cc
+            tests/test_kkeymap.cc
+            tests/test_swap_recorder.cc
+            tests/test_swap_writer.cc
+            tests/test_swap_replay.cc
+            tests/test_swap_recovery_prompt.cc
+            tests/test_swap_cleanup.cc
+            tests/test_swap_git_editor.cc
             tests/test_piece_table.cc
             tests/test_search.cc
+            tests/test_search_replace_flow.cc
             tests/test_reflow_paragraph.cc
+            tests/test_reflow_indented_bullets.cc
             tests/test_undo.cc
             tests/test_visual_line_mode.cc
 
@@ -312,6 +326,8 @@ if (BUILD_TESTS)
             Command.cc
             HelpText.cc
             Swap.cc
+            KKeymap.cc
+            SwapRecorder.h
             OptimizedSearch.cc
             UndoNode.cc
             UndoTree.cc

Command.cc

@@ -618,6 +618,8 @@ cmd_save(CommandContext &ctx)
 					return false;
 				}
 				buf->SetDirty(false);
+				if (auto *sm = ctx.editor.Swap())
+					sm->ResetJournal(*buf);
 				ctx.editor.SetStatus("Saved " + buf->Filename());
 				return true;
 			}
@@ -627,11 +629,22 @@ cmd_save(CommandContext &ctx)
 		ctx.editor.SetStatus("Save as: ");
 		return true;
 	}
+	// External modification detection: if the on-disk file changed since we last observed it,
+	// require confirmation before overwriting.
+	if (buf->ExternallyModifiedOnDisk()) {
+		ctx.editor.StartPrompt(Editor::PromptKind::Confirm, "Overwrite", "");
+		ctx.editor.SetPendingOverwritePath(buf->Filename());
+		ctx.editor.SetStatus(
+			std::string("File changed on disk: overwrite '") + buf->Filename() + "'? (y/N)");
+		return true;
+	}
 	if (!buf->Save(err)) {
 		ctx.editor.SetStatus(err);
 		return false;
 	}
 	buf->SetDirty(false);
+	if (auto *sm = ctx.editor.Swap())
+		sm->ResetJournal(*buf);
 	ctx.editor.SetStatus("Saved " + buf->Filename());
 	if (auto *u = buf->Undo())
 		u->mark_saved();
@@ -686,6 +699,10 @@ cmd_save_as(CommandContext &ctx)
 		ctx.editor.SetStatus(err);
 		return false;
 	}
+	if (auto *sm = ctx.editor.Swap()) {
+		sm->NotifyFilenameChanged(*buf);
+		sm->ResetJournal(*buf);
+	}
 	ctx.editor.SetStatus("Saved as " + ctx.arg);
 	if (auto *u = buf->Undo())
 		u->mark_saved();
@@ -789,6 +806,7 @@ cmd_refresh(CommandContext &ctx)
 		ctx.editor.SetCloseConfirmPending(false);
 		ctx.editor.SetCloseAfterSave(false);
 		ctx.editor.ClearPendingOverwritePath();
+		ctx.editor.CancelRecoveryPrompt();
 		ctx.editor.CancelPrompt();
 		ctx.editor.SetStatus("Canceled");
 		return true;
@@ -808,6 +826,14 @@ cmd_refresh(CommandContext &ctx)
 		ctx.editor.SetStatus("Find canceled");
 		return true;
 	}
+	// If nothing else to cancel, treat C-g/refresh as a mark clear (ke behavior).
+	if (Buffer *buf = ctx.editor.CurrentBuffer()) {
+		if (buf->MarkSet()) {
+			buf->ClearMark();
+			ctx.editor.SetStatus("Mark cleared");
+			return true;
+		}
+	}
 	// Otherwise just a hint; renderer will redraw
 	ctx.editor.SetStatus("");
 	return true;
@@ -1988,21 +2014,44 @@ cmd_insert_text(CommandContext &ctx)
 		const std::size_t sy = buf->VisualLineStartY();
 		const std::size_t ey = buf->VisualLineEndY();
 		const auto &rows     = buf->Rows();
+		UndoSystem *u        = buf->Undo();
+		std::uint64_t gid    = 0;
+		if (u)
+			gid = u->BeginGroup();
+		(void) gid;
+
+		std::string ins;
+		if (repeat == 1) {
+			ins = ctx.arg;
+		} else {
+			ins.reserve(ctx.arg.size() * static_cast<std::size_t>(repeat));
+			for (int i = 0; i < repeat; ++i)
+				ins += ctx.arg;
+		}
 		for (std::size_t yy = sy; yy <= ey; ++yy) {
 			if (yy >= rows.size())
 				break;
 			std::size_t xx = x;
 			if (xx > rows[yy].size())
 				xx = rows[yy].size();
-			for (int i = 0; i < repeat; ++i) {
+			if (!ins.empty()) {
-				buf->insert_text(static_cast<int>(yy), static_cast<int>(xx), std::string_view(ctx.arg));
+				buf->SetCursor(xx, yy);
-				xx += ctx.arg.size();
+				if (u)
+					u->Begin(UndoType::Insert);
+				buf->insert_text(static_cast<int>(yy), static_cast<int>(xx), std::string_view(ins));
+				xx += ins.size();
+				if (u) {
+					u->Append(std::string_view(ins));
+					u->commit();
+				}
 			}
 			if (yy == y) {
 				cx = xx;
 				cy = yy;
 			}
 		}
+		if (u)
+			u->EndGroup();
 		buf->SetDirty(true);
 		buf->SetCursor(cx, cy);
 		ensure_cursor_visible(ctx.editor, *buf);
@@ -2418,7 +2467,6 @@ cmd_newline(CommandContext &ctx)
 			ctx.editor.SetSearchIndex(-1);
 			return true;
 		} else if (kind == Editor::PromptKind::OpenFile) {
-			std::string err;
 			// Expand "~" to the user's home directory
 			auto expand_user_path = [](const std::string &in) -> std::string {
 				if (!in.empty() && in[0] == '~') {
@@ -2435,14 +2483,19 @@ cmd_newline(CommandContext &ctx)
 			value = expand_user_path(value);
 			if (value.empty()) {
 				ctx.editor.SetStatus("Open canceled (empty)");
-			} else if (!ctx.editor.OpenFile(value, err)) {
-				ctx.editor.SetStatus(err.empty() ? std::string("Failed to open ") + value : err);
 			} else {
-				ctx.editor.SetStatus(std::string("Opened ") + value);
+				ctx.editor.RequestOpenFile(value);
-				// Center the view on the cursor (e.g. if the buffer restored a cursor position)
+				const bool opened = ctx.editor.ProcessPendingOpens();
-				cmd_center_on_cursor(ctx);
+				if (ctx.editor.PromptActive()) {
-				// Close the prompt so subsequent typing edits the buffer, not the prompt
+					// A recovery confirmation prompt was started.
-				ctx.editor.CancelPrompt();
+					return true;
+				}
+				if (opened) {
+					// Center the view on the cursor (e.g. if the buffer restored a cursor position)
+					cmd_center_on_cursor(ctx);
+					// Close the prompt so subsequent typing edits the buffer, not the prompt
+					ctx.editor.CancelPrompt();
+				}
 			}
 		} else if (kind == Editor::PromptKind::BufferSwitch) {
 			// Resolve to a buffer index by exact match against path or basename;
@@ -2552,11 +2605,19 @@ cmd_newline(CommandContext &ctx)
 				}
 				if (yes) {
 					std::string err;
-					if (!buf->SaveAs(target, err)) {
+					const bool is_same_target = (buf->Filename() == target) && buf->IsFileBacked();
+					const bool ok = is_same_target ? buf->Save(err) : buf->SaveAs(target, err);
+					if (!ok) {
 						ctx.editor.SetStatus(err);
 					} else {
 						buf->SetDirty(false);
-						ctx.editor.SetStatus("Saved as " + target);
+						if (auto *sm = ctx.editor.Swap()) {
+							if (!is_same_target)
+								sm->NotifyFilenameChanged(*buf);
+							sm->ResetJournal(*buf);
+						}
+						ctx.editor.SetStatus(
+							is_same_target ? ("Saved " + target) : ("Saved as " + target));
 						if (auto *u = buf->Undo())
 							u->mark_saved();
 						// If this overwrite confirm was part of a close-after-save flow, close now.
@@ -2589,6 +2650,16 @@ cmd_newline(CommandContext &ctx)
 				ctx.editor.ClearPendingOverwritePath();
 				// Regardless of answer, end any close-after-save pending state for safety.
 				ctx.editor.SetCloseAfterSave(false);
+			} else if (ctx.editor.PendingRecoveryPrompt() != Editor::RecoveryPromptKind::None) {
+				bool yes = false;
+				if (!value.empty()) {
+					char c = value[0];
+					yes    = (c == 'y' || c == 'Y');
+				}
+				(void) ctx.editor.ResolveRecoveryPrompt(yes);
+				ctx.editor.CancelPrompt();
+				// Continue any queued opens (e.g., startup argv files).
+				ctx.editor.ProcessPendingOpens();
 			} else if (ctx.editor.CloseConfirmPending() && buf) {
 				bool yes = false;
 				if (!value.empty()) {
@@ -2607,6 +2678,8 @@ cmd_newline(CommandContext &ctx)
 							proceed_to_close = false;
 						} else {
 							buf->SetDirty(false);
+							if (auto *sm = ctx.editor.Swap())
+								sm->ResetJournal(*buf);
 							if (auto *u = buf->Undo())
 								u->mark_saved();
 						}
@@ -2616,6 +2689,10 @@ cmd_newline(CommandContext &ctx)
 							proceed_to_close = false;
 						} else {
 							buf->SetDirty(false);
+							if (auto *sm = ctx.editor.Swap()) {
+								sm->NotifyFilenameChanged(*buf);
+								sm->ResetJournal(*buf);
+							}
 							if (auto *u = buf->Undo())
 								u->mark_saved();
 						}
@@ -2652,6 +2729,8 @@ cmd_newline(CommandContext &ctx)
 				ctx.editor.SetStatus("No buffer");
 				return true;
 			}
+			if (auto *u = buf->Undo())
+				u->commit();
 			std::size_t nrows = buf->Nrows();
 			if (nrows == 0) {
 				buf->SetCursor(0, 0);
@@ -2933,26 +3012,41 @@ cmd_backspace(CommandContext &ctx)
 		const std::size_t sy = buf->VisualLineStartY();
 		const std::size_t ey = buf->VisualLineEndY();
 		const auto &rows     = buf->Rows();
-		std::size_t cx       = x;
+		std::uint64_t gid    = 0;
+		if (u)
+			gid = u->BeginGroup();
+		(void) gid;
+		std::size_t cx = x;
 		for (std::size_t yy = sy; yy <= ey; ++yy) {
 			if (yy >= rows.size())
 				break;
 			std::size_t xx = x;
 			if (xx > rows[yy].size())
 				xx = rows[yy].size();
+			std::string deleted;
 			for (int i = 0; i < repeat; ++i) {
 				if (xx == 0)
 					break;
+				const auto &rows_view = buf->Rows();
+				if (yy < rows_view.size() && (xx - 1) < rows_view[yy].size())
+					deleted.insert(deleted.begin(), rows_view[yy][xx - 1]);
 				buf->delete_text(static_cast<int>(yy), static_cast<int>(xx - 1), 1);
 				--xx;
 			}
+			if (u && !deleted.empty()) {
+				buf->SetCursor(xx, yy);
+				u->Begin(UndoType::Delete);
+				u->Append(std::string_view(deleted));
+				u->commit();
+			}
 			if (yy == y)
 				cx = xx;
 		}
+		if (u)
+			u->EndGroup();
 		buf->SetDirty(true);
 		buf->SetCursor(cx, y);
 		ensure_cursor_visible(ctx.editor, *buf);
-		(void) u;
 		return true;
 	}
 	for (int i = 0; i < repeat; ++i) {
@@ -3014,21 +3108,35 @@ cmd_delete_char(CommandContext &ctx)
 		const std::size_t sy = buf->VisualLineStartY();
 		const std::size_t ey = buf->VisualLineEndY();
 		const auto &rows     = buf->Rows();
+		std::uint64_t gid    = 0;
+		if (u)
+			gid = u->BeginGroup();
+		(void) gid;
 		for (std::size_t yy = sy; yy <= ey; ++yy) {
 			if (yy >= rows.size())
 				break;
 			std::size_t xx = x;
 			if (xx > rows[yy].size())
 				xx = rows[yy].size();
+			std::string deleted;
 			for (int i = 0; i < repeat; ++i) {
-				if (xx >= buf->Rows()[yy].size())
+				const auto &rows_view = buf->Rows();
+				if (yy >= rows_view.size() || xx >= rows_view[yy].size())
 					break;
+				deleted.push_back(rows_view[yy][xx]);
 				buf->delete_text(static_cast<int>(yy), static_cast<int>(xx), 1);
 			}
+			if (u && !deleted.empty()) {
+				buf->SetCursor(xx, yy);
+				u->Begin(UndoType::Delete);
+				u->Append(std::string_view(deleted));
+				u->commit();
+			}
 		}
+		if (u)
+			u->EndGroup();
 		buf->SetDirty(true);
 		ensure_cursor_visible(ctx.editor, *buf);
-		(void) u;
 		return true;
 	}
 	for (int i = 0; i < repeat; ++i) {
@@ -3218,8 +3326,63 @@ cmd_yank(CommandContext &ctx)
 	}
 	ensure_at_least_one_line(*buf);
 	int repeat = ctx.count > 0 ? ctx.count : 1;
-	for (int i = 0; i < repeat; ++i) {
+	std::string ins;
-		insert_text_at_cursor(*buf, text);
+	if (repeat == 1) {
+		ins = text;
+	} else {
+		ins.reserve(text.size() * static_cast<std::size_t>(repeat));
+		for (int i = 0; i < repeat; ++i)
+			ins += text;
+	}
+
+	UndoSystem *u = buf->Undo();
+	// Visual-line mode: broadcast yank to beginning-of-line on every affected line.
+	if (buf->VisualLineActive()) {
+		const std::size_t sy = buf->VisualLineStartY();
+		const std::size_t ey = buf->VisualLineEndY();
+		const std::size_t y0 = buf->Cury();
+
+		std::uint64_t gid = 0;
+		if (u)
+			gid = u->BeginGroup();
+		(void) gid;
+
+		// Iterate from bottom to top so insertions don't invalidate remaining line indices.
+		for (std::size_t yy = ey + 1; yy-- > sy;) {
+			buf->SetCursor(0, yy);
+			if (u)
+				u->Begin(UndoType::Paste);
+			insert_text_at_cursor(*buf, ins);
+			if (u) {
+				u->Append(std::string_view(ins));
+				u->commit();
+			}
+		}
+		if (u)
+			u->EndGroup();
+
+		// Keep the point on the primary cursor line (as it was before yank), at the end of the
+		// inserted text for that line.
+		std::size_t nl_count = 0;
+		std::size_t last_nl  = std::string::npos;
+		for (std::size_t i = 0; i < ins.size(); ++i) {
+			if (ins[i] == '\n') {
+				++nl_count;
+				last_nl = i;
+			}
+		}
+		const std::size_t delta_y = nl_count;
+		const std::size_t delta_x = (last_nl == std::string::npos) ? ins.size() : (ins.size() - last_nl - 1);
+		const std::size_t above   = (y0 >= sy) ? (y0 - sy) : 0;
+		buf->SetCursor(delta_x, y0 + delta_y + above * nl_count);
+	} else {
+		if (u)
+			u->Begin(UndoType::Paste);
+		insert_text_at_cursor(*buf, ins);
+		if (u) {
+			u->Append(std::string_view(ins));
+			u->commit();
+		}
 	}
 	// Yank is a paste operation; it should clear the mark/region and any selection highlighting.
 	buf->ClearMark();
@@ -3239,6 +3402,8 @@ cmd_move_file_start(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
+	if (auto *u = buf->Undo())
+		u->commit();
 	ensure_at_least_one_line(*buf);
 	buf->SetCursor(0, 0);
 	if (buf->VisualLineActive())
@@ -3254,6 +3419,8 @@ cmd_move_file_end(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
+	if (auto *u = buf->Undo())
+		u->commit();
 	ensure_at_least_one_line(*buf);
 	const auto &rows = buf->Rows();
 	std::size_t y    = rows.empty() ? 0 : rows.size() - 1;
@@ -3301,6 +3468,8 @@ cmd_jump_to_mark(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
+	if (auto *u = buf->Undo())
+		u->commit();
 	if (!buf->MarkSet()) {
 		ctx.editor.SetStatus("Mark not set");
 		return false;
@@ -3742,6 +3911,8 @@ cmd_scroll_up(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
+	if (auto *u = buf->Undo())
+		u->commit();
 	ensure_at_least_one_line(*buf);
 	const auto &rows         = buf->Rows();
 	std::size_t content_rows = std::max<std::size_t>(1, ctx.editor.ContentRows());
@@ -3775,6 +3946,8 @@ cmd_scroll_down(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
+	if (auto *u = buf->Undo())
+		u->commit();
 	ensure_at_least_one_line(*buf);
 	const auto &rows         = buf->Rows();
 	std::size_t content_rows = std::max<std::size_t>(1, ctx.editor.ContentRows());
@@ -4139,6 +4312,27 @@ 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());
+	if (auto *u = buf->Undo())
+		u->commit();
 	ensure_at_least_one_line(*buf);
 	auto &rows    = buf->Rows();
 	std::size_t y = buf->Cury();
@@ -4321,12 +4515,6 @@ cmd_reflow_paragraph(CommandContext &ctx)
 				std::size_t j = i + 1;
 				while (j <= para_end) {
 					std::string ns = static_cast<std::string>(rows[j]);
-					if (starts_with(ns, indent + "  ")) {
-						content += ' ';
-						content += ns.substr(indent.size() + 2);
-						++j;
-						continue;
-					}
 					// stop if next bullet at same indentation or different structure
 					std::string nindent;
 					char nmarker;
@@ -4338,6 +4526,13 @@ cmd_reflow_paragraph(CommandContext &ctx)
 					if (is_numbered_line(ns, nindent, nnmarker, nidx)) {
 						break; // next item
 					}
+					// Now check if it's a continuation line
+					if (starts_with(ns, indent + "  ")) {
+						content += ' ';
+						content += ns.substr(indent.size() + 2);
+						++j;
+						continue;
+					}
 					// Not a continuation and not a bullet: stop (treat as separate paragraph chunk)
 					break;
 				}

Editor.cc

@@ -1,6 +1,7 @@
 #include <algorithm>
-#include <utility>
+#include <cstdio>
 #include <filesystem>
+#include <utility>
 
 #include "Editor.h"
 #include "syntax/HighlighterRegistry.h"
@@ -8,6 +9,41 @@
 #include "syntax/NullHighlighter.h"
 
 
+namespace {
+static std::string
+buffer_bytes_via_views(const Buffer &b)
+{
+	const auto &rows = b.Rows();
+	std::string out;
+	for (std::size_t i = 0; i < rows.size(); i++) {
+		auto v = b.GetLineView(i);
+		out.append(v.data(), v.size());
+	}
+	return out;
+}
+
+
+static void
+apply_pending_line(Editor &ed, const std::size_t line1)
+{
+	if (line1 == 0)
+		return;
+	Buffer *b = ed.CurrentBuffer();
+	if (!b)
+		return;
+	const std::size_t nrows = b->Nrows();
+	std::size_t line        = line1 > 0 ? line1 - 1 : 0; // 1-based to 0-based
+	if (nrows > 0) {
+		if (line >= nrows)
+			line = nrows - 1;
+	} else {
+		line = 0;
+	}
+	b->SetCursor(0, line);
+}
+} // namespace
+
+
 Editor::Editor()
 {
 	swap_ = std::make_unique<kte::SwapManager>();
@@ -128,8 +164,8 @@ Editor::AddBuffer(const Buffer &buf)
 	buffers_.push_back(buf);
 	// Attach swap recorder
 	if (swap_) {
-		buffers_.back().SetSwapRecorder(swap_.get());
 		swap_->Attach(&buffers_.back());
+		buffers_.back().SetSwapRecorder(swap_->RecorderFor(&buffers_.back()));
 	}
 	if (buffers_.size() == 1) {
 		curbuf_ = 0;
@@ -143,8 +179,8 @@ Editor::AddBuffer(Buffer &&buf)
 {
 	buffers_.push_back(std::move(buf));
 	if (swap_) {
-		buffers_.back().SetSwapRecorder(swap_.get());
 		swap_->Attach(&buffers_.back());
+		buffers_.back().SetSwapRecorder(swap_->RecorderFor(&buffers_.back()));
 	}
 	if (buffers_.size() == 1) {
 		curbuf_ = 0;
@@ -171,16 +207,16 @@ Editor::OpenFile(const std::string &path, std::string &err)
 				return false;
 			// Ensure swap recorder is attached for this buffer
 			if (swap_) {
-				cur.SetSwapRecorder(swap_.get());
 				swap_->Attach(&cur);
+				cur.SetSwapRecorder(swap_->RecorderFor(&cur));
 				swap_->NotifyFilenameChanged(cur);
 			}
 			// Setup highlighting using registry (extension + shebang)
 			cur.EnsureHighlighter();
-			std::string first = "";
+			std::string first    = "";
-			const auto &rows  = cur.Rows();
+			const auto &cur_rows = cur.Rows();
-			if (!rows.empty())
+			if (!cur_rows.empty())
-				first = static_cast<std::string>(rows[0]);
+				first = static_cast<std::string>(cur_rows[0]);
 			std::string ft = kte::HighlighterRegistry::DetectForPath(path, first);
 			if (!ft.empty()) {
 				cur.SetFiletype(ft);
@@ -197,22 +233,18 @@ Editor::OpenFile(const std::string &path, std::string &err)
 					eng->InvalidateFrom(0);
 				}
 			}
-            // Defensive: ensure any active prompt is closed after a successful open
+			// Defensive: ensure any active prompt is closed after a successful open
-            CancelPrompt();
+			CancelPrompt();
-            return true;
+			return true;
-        }
+		}
-    }
+	}
 
 	Buffer b;
 	if (!b.OpenFromFile(path, err)) {
 		return false;
 	}
-	if (swap_) {
+	// NOTE: swap recorder/attach must happen after the buffer is stored in its
-		b.SetSwapRecorder(swap_.get());
+	// final location (vector) because swap manager keys off Buffer*.
-		// path is known, notify
-		swap_->Attach(&b);
-		swap_->NotifyFilenameChanged(b);
-	}
 	// Initialize syntax highlighting by extension + shebang via registry (v2)
 	b.EnsureHighlighter();
 	std::string first = "";
@@ -239,10 +271,179 @@ 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));
-    SwitchTo(idx);
+	if (swap_) {
-    // Defensive: ensure any active prompt is closed after a successful open
+		swap_->NotifyFilenameChanged(buffers_[idx]);
-    CancelPrompt();
+	}
-    return true;
+	SwitchTo(idx);
+	// Defensive: ensure any active prompt is closed after a successful open
+	CancelPrompt();
+	return true;
+}
+
+
+void
+Editor::RequestOpenFile(const std::string &path, const std::size_t line1)
+{
+	PendingOpen p;
+	p.path  = path;
+	p.line1 = line1;
+	pending_open_.push_back(std::move(p));
+}
+
+
+bool
+Editor::HasPendingOpens() const
+{
+	return !pending_open_.empty();
+}
+
+
+Editor::RecoveryPromptKind
+Editor::PendingRecoveryPrompt() const
+{
+	return pending_recovery_prompt_;
+}
+
+
+void
+Editor::CancelRecoveryPrompt()
+{
+	pending_recovery_prompt_ = RecoveryPromptKind::None;
+	pending_recovery_open_   = PendingOpen{};
+	pending_recovery_swap_path_.clear();
+	pending_recovery_replay_err_.clear();
+}
+
+
+bool
+Editor::ResolveRecoveryPrompt(const bool yes)
+{
+	const RecoveryPromptKind kind = pending_recovery_prompt_;
+	if (kind == RecoveryPromptKind::None)
+		return false;
+	const PendingOpen req    = pending_recovery_open_;
+	const std::string swp    = pending_recovery_swap_path_;
+	const std::string rerr_s = pending_recovery_replay_err_;
+	CancelRecoveryPrompt();
+
+	std::string err;
+	if (kind == RecoveryPromptKind::RecoverOrDiscard) {
+		if (yes) {
+			if (!OpenFile(req.path, err)) {
+				SetStatus(err);
+				return false;
+			}
+			Buffer *b = CurrentBuffer();
+			if (!b) {
+				SetStatus("Recovery failed: no buffer");
+				return false;
+			}
+			std::string rerr;
+			if (!kte::SwapManager::ReplayFile(*b, swp, rerr)) {
+				SetStatus("Swap recovery failed: " + rerr);
+				return false;
+			}
+			b->SetDirty(true);
+			apply_pending_line(*this, req.line1);
+			SetStatus("Recovered " + req.path);
+			return true;
+		}
+		// Discard: best-effort delete swap, then open clean.
+		(void) std::remove(swp.c_str());
+		if (!OpenFile(req.path, err)) {
+			SetStatus(err);
+			return false;
+		}
+		apply_pending_line(*this, req.line1);
+		SetStatus("Opened " + req.path);
+		return true;
+	}
+	if (kind == RecoveryPromptKind::DeleteCorruptSwap) {
+		if (yes) {
+			(void) std::remove(swp.c_str());
+		}
+		if (!OpenFile(req.path, err)) {
+			SetStatus(err);
+			return false;
+		}
+		apply_pending_line(*this, req.line1);
+		// Include a short hint that the swap was corrupt.
+		if (!rerr_s.empty()) {
+			SetStatus("Opened " + req.path + " (swap unreadable)");
+		} else {
+			SetStatus("Opened " + req.path);
+		}
+		return true;
+	}
+	return false;
+}
+
+
+bool
+Editor::ProcessPendingOpens()
+{
+	if (PromptActive())
+		return false;
+	if (pending_recovery_prompt_ != RecoveryPromptKind::None)
+		return false;
+
+	bool opened_any = false;
+	while (!pending_open_.empty()) {
+		PendingOpen req = std::move(pending_open_.front());
+		pending_open_.pop_front();
+		if (req.path.empty())
+			continue;
+
+		std::string swp = kte::SwapManager::ComputeSwapPathForFilename(req.path);
+		bool swp_exists = false;
+		try {
+			swp_exists = !swp.empty() && std::filesystem::exists(std::filesystem::path(swp));
+		} catch (...) {
+			swp_exists = false;
+		}
+		if (swp_exists) {
+			Buffer tmp;
+			std::string oerr;
+			if (tmp.OpenFromFile(req.path, oerr)) {
+				const std::string orig = buffer_bytes_via_views(tmp);
+				std::string rerr;
+				if (kte::SwapManager::ReplayFile(tmp, swp, rerr)) {
+					const std::string rec = buffer_bytes_via_views(tmp);
+					if (rec != orig) {
+						pending_recovery_prompt_    = RecoveryPromptKind::RecoverOrDiscard;
+						pending_recovery_open_      = req;
+						pending_recovery_swap_path_ = swp;
+						StartPrompt(PromptKind::Confirm, "Recover", "");
+						SetStatus("Recover swap edits for " + req.path + "? (y/N, C-g cancel)");
+						return opened_any;
+					}
+				} else {
+					pending_recovery_prompt_     = RecoveryPromptKind::DeleteCorruptSwap;
+					pending_recovery_open_       = req;
+					pending_recovery_swap_path_  = swp;
+					pending_recovery_replay_err_ = rerr;
+					StartPrompt(PromptKind::Confirm, "Swap", "");
+					SetStatus(
+						"Swap file unreadable for " + req.path +
+						". Delete it? (y/N, C-g cancel)");
+					return opened_any;
+				}
+			}
+		}
+
+		std::string err;
+		if (!OpenFile(req.path, err)) {
+			SetStatus(err);
+			opened_any = false;
+			continue;
+		}
+		apply_pending_line(*this, req.line1);
+		SetStatus("Opened " + req.path);
+		opened_any = true;
+		// Open at most one per call; frontends can call us again next frame.
+		break;
+	}
+	return opened_any;
 }
 
 
@@ -284,6 +485,13 @@ Editor::CloseBuffer(std::size_t index)
 	if (index >= buffers_.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);
+		buffers_[index].SetSwapRecorder(nullptr);
+	}
 	buffers_.erase(buffers_.begin() + static_cast<std::ptrdiff_t>(index));
 	if (buffers_.empty()) {
 		curbuf_ = 0;

Editor.h

@@ -4,6 +4,7 @@
 #pragma once
 #include <cstddef>
 #include <ctime>
+#include <deque>
 #include <string>
 #include <vector>
 
@@ -497,6 +498,30 @@ public:
 
 	bool OpenFile(const std::string &path, std::string &err);
 
+	// Request that a file be opened. The request is processed by calling
+	// ProcessPendingOpens() (typically once per frontend frame).
+	void RequestOpenFile(const std::string &path, std::size_t line1 = 0);
+
+	// If no modal prompt is active, process queued open requests.
+	// Returns true if a file was opened during this call.
+	bool ProcessPendingOpens();
+
+	[[nodiscard]] bool HasPendingOpens() const;
+
+	// Swap recovery confirmation state. When non-None, a `PromptKind::Confirm`
+	// prompt is active and the user's answer should be routed to ResolveRecoveryPrompt().
+	enum class RecoveryPromptKind {
+		None = 0,
+		RecoverOrDiscard, // y = recover swap, else discard swap and open clean
+		DeleteCorruptSwap // y = delete corrupt swap, else keep it
+	};
+
+	[[nodiscard]] RecoveryPromptKind PendingRecoveryPrompt() const;
+
+	bool ResolveRecoveryPrompt(bool yes);
+
+	void CancelRecoveryPrompt();
+
 	// Buffer switching/closing
 	bool SwitchTo(std::size_t index);
 
@@ -550,6 +575,11 @@ public:
 	}
 
 private:
+	struct PendingOpen {
+		std::string path;
+		std::size_t line1{0}; // 1-based; 0 = none
+	};
+
 	std::size_t rows_ = 0, cols_ = 0;
 	int mode_         = 0;
 	int kill_         = 0; // KILL CHAIN
@@ -593,6 +623,13 @@ private:
 	std::string prompt_text_;
 	std::string pending_overwrite_path_;
 
+	// Deferred open + swap recovery prompt state
+	std::deque<PendingOpen> pending_open_;
+	RecoveryPromptKind pending_recovery_prompt_ = RecoveryPromptKind::None;
+	PendingOpen pending_recovery_open_{};
+	std::string pending_recovery_swap_path_;
+	std::string pending_recovery_replay_err_;
+
 	// GUI-only state (safe no-op in terminal builds)
 	bool file_picker_visible_ = false;
 	std::string file_picker_dir_;

ImGuiFrontend.cc

@@ -298,6 +298,9 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		}
 	}
 
+	// Allow deferred opens (including swap recovery prompts) to run.
+	ed.ProcessPendingOpens();
+
 	// Execute pending mapped inputs (drain queue) AFTER dimensions are updated
 	for (;;) {
 		MappedInput mi;

ImGuiRenderer.cc

@@ -308,14 +308,10 @@ ImGuiRenderer::Draw(Editor &ed)
 			}
 
 			// Draw selection background (over search highlight; under text)
-			if (sel_active || vsel_active) {
+			if (sel_active) {
 				bool line_has  = false;
 				std::size_t sx = 0, ex = 0;
-				if (vsel_active && i >= vsel_sy && i <= vsel_ey) {
+				if (i < sel_sy || i > sel_ey) {
-					sx       = 0;
-					ex       = line.size();
-					line_has = ex > sx;
-				} else if (i < sel_sy || i > sel_ey) {
 					line_has = false;
 				} else if (sel_sy == sel_ey) {
 					sx       = sel_sx;
@@ -351,6 +347,30 @@ ImGuiRenderer::Draw(Editor &ed)
 					}
 				}
 			}
+			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());
+				const std::size_t rx_start = src_to_rx(spot_sx);
+				std::size_t rx_end         = rx_start;
+				if (spot_sx < line.size()) {
+					rx_end = src_to_rx(spot_sx + 1);
+				} else {
+					// EOL spot: draw a 1-cell highlight just past the last character.
+					rx_end = rx_start + 1;
+				}
+				if (rx_end > coloffs_now) {
+					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);
+					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];
@@ -892,12 +912,8 @@ ImGuiRenderer::Draw(Editor &ed)
 						ed.SetFilePickerDir(e.path.string());
 					} else if (!e.is_dir && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
 						// Open file on single click
-						std::string err;
+						ed.RequestOpenFile(e.path.string());
-						if (!ed.OpenFile(e.path.string(), err)) {
+						(void) ed.ProcessPendingOpens();
-							ed.SetStatus(std::string("open: ") + err);
-						} else {
-							ed.SetStatus(std::string("Opened: ") + e.name);
-						}
 						ed.SetFilePickerVisible(false);
 					}
 				}

KKeymap.cc

@@ -17,6 +17,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 		case 'd':
 			out = CommandId::KillLine;
 			return true;
+		case 's':
+			out = CommandId::Save;
+			return true;
 		case 'q':
 			out = CommandId::QuitNow;
 			return true;
@@ -42,6 +45,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case 'a':
 		out = CommandId::MarkAllAndJumpEnd;
 		return true;
+	case ' ': // C-k SPACE
+		out = CommandId::ToggleMark;
+		return true;
 	case 'i':
 		out = CommandId::BufferNew; // C-k i new empty buffer
 		return true;

QtFrontend.cc

@@ -775,6 +775,9 @@ GUIFrontend::Step(Editor &ed, bool &running)
 	if (app_)
 		app_->processEvents();
 
+	// Allow deferred opens (including swap recovery prompts) to run.
+	ed.ProcessPendingOpens();
+
 	// Drain input queue
 	for (;;) {
 		MappedInput mi;
@@ -801,14 +804,8 @@ GUIFrontend::Step(Editor &ed, bool &running)
 			const QStringList files = dlg.selectedFiles();
 			if (!files.isEmpty()) {
 				const QString fp = files.front();
-				std::string err;
+				ed.RequestOpenFile(fp.toStdString());
-				if (ed.OpenFile(fp.toStdString(), err)) {
+				(void) ed.ProcessPendingOpens();
-					ed.SetStatus(std::string("Opened: ") + fp.toStdString());
-				} else if (!err.empty()) {
-					ed.SetStatus(std::string("Open failed: ") + err);
-				} else {
-					ed.SetStatus("Open failed");
-				}
 				// Update picker dir for next time
 				QFileInfo info(fp);
 				ed.SetFilePickerDir(info.dir().absolutePath().toStdString());

README.md

@@ -32,7 +32,8 @@ Project Goals
 
 Keybindings
 -----------
-kte maintains ke’s command model while internals evolve. Highlights (subject to refinement):
+kte maintains ke’s command model while internals evolve. Highlights (
+subject to refinement):
 
 - K‑command prefix: `C-k` enters k‑command mode; exit with `ESC` or
   `C-g`.
@@ -52,7 +53,8 @@ See `ke.md` for the canonical ke reference retained for now.
 
 Build and Run
 -------------
-Prerequisites: C++17 compiler, CMake, and ncurses development headers/libs.
+Prerequisites: C++20 compiler, CMake, and ncurses development
+headers/libs.
 
 Dependencies by platform
 ------------------------
@@ -62,30 +64,38 @@ Dependencies by platform
         - `brew install ncurses`
     - Optional GUI (enable with `-DBUILD_GUI=ON`):
         - `brew install sdl2 freetype`
-        - OpenGL is provided by the system framework on macOS; no package needed.
+        - OpenGL is provided by the system framework on macOS; no
+          package needed.
 
 - Debian/Ubuntu
     - Terminal (default):
         - `sudo apt-get install -y libncurses5-dev libncursesw5-dev`
     - Optional GUI (enable with `-DBUILD_GUI=ON`):
-        - `sudo apt-get install -y libsdl2-dev libfreetype6-dev mesa-common-dev`
+        -
-        - The `mesa-common-dev` package provides OpenGL headers/libs (`libGL`).
+        `sudo apt-get install -y libsdl2-dev libfreetype6-dev mesa-common-dev`
+        - The `mesa-common-dev` package provides OpenGL headers/libs (
+          `libGL`).
 
 - NixOS/Nix
     - Terminal (default):
         - Ad-hoc shell: `nix-shell -p cmake gcc ncurses`
     - Optional GUI (enable with `-DBUILD_GUI=ON`):
-        - Ad-hoc shell: `nix-shell -p cmake gcc ncurses SDL2 freetype libGL`
+        - Ad-hoc shell:
-    - With flakes/devshell (example `flake.nix` inputs not provided): include
+          `nix-shell -p cmake gcc ncurses SDL2 freetype libGL`
-      `ncurses` for TUI, and `SDL2`, `freetype`, `libGL` for GUI in your devShell.
+    - With flakes/devshell (example `flake.nix` inputs not provided):
+      include
+      `ncurses` for TUI, and `SDL2`, `freetype`, `libGL` for GUI in your
+      devShell.
 
 Notes
 -----
 
-- The GUI is OFF by default to keep SDL/OpenGL/Freetype optional. Enable it by
+- The GUI is OFF by default to keep SDL/OpenGL/Freetype optional. Enable
+  it by
   configuring with `-DBUILD_GUI=ON` and ensuring the GUI deps above are
   installed for your platform.
-- If you previously configured with GUI ON and want to disable it, reconfigure
+- If you previously configured with GUI ON and want to disable it,
+  reconfigure
   the build directory with `-DBUILD_GUI=OFF`.
 
 Example build:
@@ -113,7 +123,8 @@ built as `kge`) or request the GUI from `kte`:
 GUI build example
 -----------------
 
-To build with the optional GUI (after installing the GUI dependencies listed above):
+To build with the optional GUI (after installing the GUI dependencies
+listed above):
 
 ```
 cmake -S . -B cmake-build-debug -DCMAKE_BUILD_TYPE=Debug -DBUILD_GUI=ON

Swap.h

@@ -7,11 +7,14 @@
 #include <string_view>
 #include <vector>
 #include <unordered_map>
+#include <memory>
 #include <mutex>
 #include <condition_variable>
 #include <thread>
 #include <atomic>
 
+#include "SwapRecorder.h"
+
 class Buffer;
 
 namespace kte {
@@ -29,50 +32,88 @@ struct SwapConfig {
 	// Grouping and durability knobs (stage 1 defaults)
 	unsigned flush_interval_ms{200}; // group small writes
 	unsigned fsync_interval_ms{1000}; // at most once per second
-};
 
-// Lightweight interface that Buffer can call without depending on full manager impl
+	// Checkpoint/compaction knobs (stage 2 defaults)
-class SwapRecorder {
+	// A checkpoint is a full snapshot of the buffer content written as a CHKPT record.
-public:
+	// Compaction rewrites the swap file to contain just the latest checkpoint.
-	virtual ~SwapRecorder() = default;
+	std::size_t checkpoint_bytes{1024 * 1024}; // request checkpoint after this many queued edit-bytes
+	unsigned checkpoint_interval_ms{60000}; // request checkpoint at least this often while editing
+	std::size_t compact_bytes{8 * 1024 * 1024}; // compact on checkpoint once journal grows beyond this
 
-	virtual void RecordInsert(Buffer &buf, int row, int col, std::string_view text) = 0;
+	// Cleanup / retention (best-effort)
-
+	bool prune_on_startup{true};
-	virtual void RecordDelete(Buffer &buf, int row, int col, std::size_t len) = 0;
+	unsigned prune_max_age_days{30};
-
+	std::size_t prune_max_files{2048};
-	virtual void RecordSplit(Buffer &buf, int row, int col) = 0;
-
-	virtual void RecordJoin(Buffer &buf, int row) = 0;
-
-	virtual void NotifyFilenameChanged(Buffer &buf) = 0;
-
-	virtual void SetSuspended(Buffer &buf, bool on) = 0;
 };
 
 // SwapManager manages sidecar swap files and a single background writer thread.
-class SwapManager final : public SwapRecorder {
+class SwapManager final {
 public:
 	SwapManager();
 
-	~SwapManager() override;
+	~SwapManager();
 
 	// Attach a buffer to begin journaling. Safe to call multiple times; idempotent.
 	void Attach(Buffer *buf);
 
 	// Detach and close journal.
-	void Detach(Buffer *buf);
+	// If remove_file is true, the swap file is deleted after closing.
+	// Intended for clean shutdown/close flows.
+	void Detach(Buffer *buf, bool remove_file = false);
 
-	// SwapRecorder: Notify that the buffer's filename changed (e.g., SaveAs)
+	// Reset (truncate-by-delete) the journal for a buffer after a clean save.
-	void NotifyFilenameChanged(Buffer &buf) override;
+	// Best-effort: closes the current fd, deletes the swap file, and resumes recording.
+	void ResetJournal(Buffer &buf);
 
-	// SwapRecorder
+	// Best-effort pruning of old swap files under the swap directory.
-	void RecordInsert(Buffer &buf, int row, int col, std::string_view text) override;
+	// Never touches non-`.swp` files.
+	void PruneSwapDir();
 
-	void RecordDelete(Buffer &buf, int row, int col, std::size_t len) override;
+	// Block until all currently queued records have been written.
+	// If buf is non-null, flushes all records (stage 1) but is primarily intended
+	// for tests and shutdown.
+	void Flush(Buffer *buf = nullptr);
 
-	void RecordSplit(Buffer &buf, int row, int col) override;
+	// Request a full-content checkpoint record for one buffer (or all buffers if buf is null).
+	// This is best-effort and asynchronous; call Flush() if you need it written before continuing.
+	void Checkpoint(Buffer *buf = nullptr);
 
-	void RecordJoin(Buffer &buf, int row) override;
+
+	void SetConfig(const SwapConfig &cfg)
+	{
+		std::lock_guard<std::mutex> lg(mtx_);
+		cfg_ = cfg;
+		cv_.notify_one();
+	}
+
+
+	// Obtain a per-buffer recorder adapter that emits records for that buffer.
+	// The returned pointer is owned by the SwapManager and remains valid until
+	// Detach(buf) or SwapManager destruction.
+	SwapRecorder *RecorderFor(Buffer *buf);
+
+	// Notify that the buffer's filename changed (e.g., SaveAs)
+	void NotifyFilenameChanged(Buffer &buf);
+
+	// Replay a swap journal into an already-open buffer.
+	// On success, the buffer content reflects all valid journal records.
+	// On failure (corrupt/truncated/invalid), the buffer is left in whatever
+	// state results from applying records up to the failure point; callers should
+	// treat this as a recovery failure and surface `err`.
+	static bool ReplayFile(Buffer &buf, const std::string &swap_path, std::string &err);
+
+	// Compute the swap path for a file-backed buffer by filename.
+	// Returns empty string if filename is empty.
+	static std::string ComputeSwapPathForFilename(const std::string &filename);
+
+	// Test-only hook to keep swap path logic centralized.
+	// (Avoid duplicating naming rules in unit tests.)
+#ifdef KTE_TESTS
+	static std::string ComputeSwapPathForTests(const Buffer &buf)
+	{
+		return ComputeSidecarPath(buf);
+	}
+#endif
 
 	// RAII guard to suspend recording for internal operations
 	class SuspendGuard {
@@ -88,17 +129,44 @@ public:
 	};
 
 	// Per-buffer toggle
-	void SetSuspended(Buffer &buf, bool on) override;
+	void SetSuspended(Buffer &buf, bool on);
 
 private:
+	class BufferRecorder final : public SwapRecorder {
+	public:
+		BufferRecorder(SwapManager &m, Buffer &b) : m_(m), buf_(b) {}
+
+		void OnInsert(int row, int col, std::string_view bytes) override;
+
+		void OnDelete(int row, int col, std::size_t len) override;
+
+	private:
+		SwapManager &m_;
+		Buffer &buf_;
+	};
+
+	void RecordInsert(Buffer &buf, int row, int col, std::string_view text);
+
+	void RecordDelete(Buffer &buf, int row, int col, std::size_t len);
+
+	void RecordSplit(Buffer &buf, int row, int col);
+
+	void RecordJoin(Buffer &buf, int row);
+
+	void RecordCheckpoint(Buffer &buf, bool urgent_flush);
+
+	void maybe_request_checkpoint(Buffer &buf, std::size_t approx_edit_bytes);
+
 	struct JournalCtx {
 		std::string path;
-		void *file{nullptr}; // FILE*
 		int fd{-1};
 		bool header_ok{false};
 		bool suspended{false};
 		std::uint64_t last_flush_ns{0};
 		std::uint64_t last_fsync_ns{0};
+		std::uint64_t last_chkpt_ns{0};
+		std::uint64_t edit_bytes_since_chkpt{0};
+		std::uint64_t approx_size_bytes{0};
 	};
 
 	struct Pending {
@@ -106,26 +174,35 @@ private:
 		SwapRecType type{SwapRecType::INS};
 		std::vector<std::uint8_t> payload; // framed payload only
 		bool urgent_flush{false};
+		std::uint64_t seq{0};
 	};
 
 	// Helpers
 	static std::string ComputeSidecarPath(const Buffer &buf);
 
+	static std::string ComputeSidecarPathForFilename(const std::string &filename);
+
 	static std::uint64_t now_ns();
 
 	static bool ensure_parent_dir(const std::string &path);
 
-	static bool write_header(JournalCtx &ctx);
+	static std::string SwapDirRoot();
 
-	static bool open_ctx(JournalCtx &ctx);
+	static bool write_header(int fd);
+
+	static bool open_ctx(JournalCtx &ctx, const std::string &path);
 
 	static void close_ctx(JournalCtx &ctx);
 
+	static bool compact_to_checkpoint(JournalCtx &ctx, const std::vector<std::uint8_t> &chkpt_record);
+
 	static std::uint32_t crc32(const std::uint8_t *data, std::size_t len, std::uint32_t seed = 0);
 
-	static void put_varu64(std::vector<std::uint8_t> &out, std::uint64_t v);
+	static void put_le32(std::vector<std::uint8_t> &out, std::uint32_t v);
 
-	static void put_u24(std::uint8_t dst[3], std::uint32_t v);
+	static void put_le64(std::uint8_t dst[8], std::uint64_t v);
+
+	static void put_u24_le(std::uint8_t dst[3], std::uint32_t v);
 
 	void enqueue(Pending &&p);
 
@@ -136,9 +213,13 @@ private:
 	// State
 	SwapConfig cfg_{};
 	std::unordered_map<Buffer *, JournalCtx> journals_;
+	std::unordered_map<Buffer *, std::unique_ptr<BufferRecorder> > recorders_;
 	std::mutex mtx_;
 	std::condition_variable cv_;
 	std::vector<Pending> queue_;
+	std::uint64_t next_seq_{0};
+	std::uint64_t last_processed_{0};
+	std::uint64_t inflight_{0};
 	std::atomic<bool> running_{false};
 	std::thread worker_;
 };

SwapRecorder.h

@@ -0,0 +1,19 @@
+// SwapRecorder.h - minimal swap journal recording interface for Buffer mutations
+#pragma once
+
+#include <cstddef>
+#include <string_view>
+
+namespace kte {
+// SwapRecorder is a tiny, non-blocking callback interface.
+// Implementations must return quickly; Buffer calls these hooks after a
+// mutation succeeds.
+class SwapRecorder {
+public:
+	virtual ~SwapRecorder() = default;
+
+	virtual void OnInsert(int row, int col, std::string_view bytes) = 0;
+
+	virtual void OnDelete(int row, int col, std::size_t len) = 0;
+};
+} // namespace kte

TerminalFrontend.cc

@@ -94,6 +94,9 @@ TerminalFrontend::Step(Editor &ed, bool &running)
 	}
 	ed.SetDimensions(static_cast<std::size_t>(r), static_cast<std::size_t>(c));
 
+	// Allow deferred opens (including swap recovery prompts) to run.
+	ed.ProcessPendingOpens();
+
 	MappedInput mi;
 	if (input_.Poll(mi)) {
 		if (mi.hasCommand) {

TerminalRenderer.cc

@@ -126,12 +126,7 @@ TerminalRenderer::Draw(Editor &ed)
 			const bool vsel_active    = buf->VisualLineActive();
 			const std::size_t vsel_sy = vsel_active ? buf->VisualLineStartY() : 0;
 			const std::size_t vsel_ey = vsel_active ? buf->VisualLineEndY() : 0;
-			auto is_src_in_sel        = [&](std::size_t y, std::size_t sx) -> bool {
+			auto is_src_in_mark_sel   = [&](std::size_t y, std::size_t sx) -> bool {
-				(void) sx;
-				if (vsel_active) {
-					if (y >= vsel_sy && y <= vsel_ey)
-						return true;
-				}
 				if (!sel_active)
 					return false;
 				if (y < sel_sy || y > sel_ey)
@@ -146,9 +141,48 @@ TerminalRenderer::Draw(Editor &ed)
 			};
 			int written = 0;
 			if (li < lines.size()) {
-				std::string line = static_cast<std::string>(lines[li]);
+				std::string line                = static_cast<std::string>(lines[li]);
-				src_i            = 0;
+				const bool vsel_on_line         = vsel_active && li >= vsel_sy && li <= vsel_ey;
-				render_col       = 0;
+				const std::size_t vsel_spot_src = vsel_on_line
+					                                  ? std::min(buf->Curx(), line.size())
+					                                  : 0;
+				const bool vsel_spot_is_eol = vsel_on_line && vsel_spot_src == line.size();
+				std::size_t vsel_line_rx    = 0;
+				if (vsel_spot_is_eol) {
+					// Compute the rendered (column) width of the line so we can highlight a
+					// single cell at EOL when the spot falls beyond the last character.
+					std::size_t rc = 0;
+					std::size_t si = 0;
+					while (si < line.size()) {
+						wchar_t wch = L' ';
+						int wch_len = 1;
+						std::mbstate_t state = std::mbstate_t();
+						size_t res = std::mbrtowc(&wch, &line[si], line.size() - si, &state);
+						if (res == (size_t) -1 || res == (size_t) -2) {
+							wch     = static_cast<unsigned char>(line[si]);
+							wch_len = 1;
+						} else if (res == 0) {
+							wch     = L'\0';
+							wch_len = 1;
+						} else {
+							wch_len = static_cast<int>(res);
+						}
+						if (wch == L'\t') {
+							constexpr std::size_t tab_width = 8;
+							const std::size_t next_tab      = tab_width - (rc % tab_width);
+							rc                              += next_tab;
+						} else {
+							int w = wcwidth(wch);
+							if (w < 0)
+								w = 1;
+							rc += static_cast<std::size_t>(w);
+						}
+						si += static_cast<std::size_t>(wch_len);
+					}
+					vsel_line_rx = rc;
+				}
+				src_i      = 0;
+				render_col = 0;
 				// Syntax highlighting: fetch per-line spans (sanitized copy)
 				std::vector<kte::HighlightSpan> sane_spans;
 				if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->
@@ -247,7 +281,11 @@ TerminalRenderer::Draw(Editor &ed)
 							}
 							// Now render visible spaces
 							while (next_tab > 0 && written < cols) {
-								bool in_sel = is_src_in_sel(li, src_i);
+								bool in_mark = is_src_in_mark_sel(li, src_i);
+								bool in_vsel =
+									vsel_on_line && !vsel_spot_is_eol && src_i ==
+									vsel_spot_src;
+								bool in_sel = in_mark || in_vsel;
 								bool in_hl  = search_mode && is_src_in_hl(src_i);
 								bool in_cur =
 									has_current && li == cur_my && src_i >= cur_mx
@@ -297,7 +335,16 @@ TerminalRenderer::Draw(Editor &ed)
 						break;
 					}
 
-					bool in_sel = from_src && is_src_in_sel(li, src_i);
+					bool in_mark = from_src && is_src_in_mark_sel(li, src_i);
+					bool in_vsel = false;
+					if (vsel_on_line) {
+						if (from_src) {
+							in_vsel = !vsel_spot_is_eol && src_i == vsel_spot_src;
+						} else {
+							in_vsel = vsel_spot_is_eol && render_col == vsel_line_rx;
+						}
+					}
+					bool in_sel = in_mark || in_vsel;
 					bool in_hl  = search_mode && from_src && is_src_in_hl(src_i);
 					bool in_cur = has_current && li == cur_my && from_src && src_i >= cur_mx &&
 					              src_i < cur_mend;

TestFrontend.cc

@@ -16,6 +16,9 @@ TestFrontend::Init(int &argc, char **argv, Editor &ed)
 void
 TestFrontend::Step(Editor &ed, bool &running)
 {
+	// Allow deferred opens (including swap recovery prompts) to run.
+	ed.ProcessPendingOpens();
+
 	MappedInput mi;
 	if (input_.Poll(mi)) {
 		if (mi.hasCommand) {

UndoNode.h

@@ -15,6 +15,7 @@ struct UndoNode {
 	UndoType type{};
 	int row{};
 	int col{};
+	std::uint64_t group_id = 0; // 0 means ungrouped; non-zero means undo/redo as an atomic group
 	std::string text;
 	UndoNode *parent = nullptr; // previous state; null means pre-first-edit
 	UndoNode *child  = nullptr; // next in current timeline

UndoSystem.cc

@@ -8,6 +8,25 @@ UndoSystem::UndoSystem(Buffer &owner, UndoTree &tree)
 	: buf_(&owner), tree_(tree) {}
 
 
+std::uint64_t
+UndoSystem::BeginGroup()
+{
+	// Ensure any pending typed run is sealed so the group is a distinct undo step.
+	commit();
+	if (active_group_id_ == 0)
+		active_group_id_ = next_group_id_++;
+	return active_group_id_;
+}
+
+
+void
+UndoSystem::EndGroup()
+{
+	commit();
+	active_group_id_ = 0;
+}
+
+
 void
 UndoSystem::Begin(UndoType type)
 {
@@ -64,10 +83,11 @@ UndoSystem::Begin(UndoType type)
 	}
 
 	// Start a new pending node.
-	tree_.pending       = new UndoNode{};
+	tree_.pending           = new UndoNode{};
-	tree_.pending->type = type;
+	tree_.pending->type     = type;
-	tree_.pending->row  = row;
+	tree_.pending->row      = row;
-	tree_.pending->col  = col;
+	tree_.pending->col      = col;
+	tree_.pending->group_id = active_group_id_;
 	tree_.pending->text.clear();
 	tree_.pending->parent = nullptr;
 	tree_.pending->child  = nullptr;
@@ -158,8 +178,12 @@ UndoSystem::undo()
 	if (!tree_.current)
 		return;
 	debug_log("undo");
-	apply(tree_.current, -1);
+	const std::uint64_t gid = tree_.current->group_id;
-	tree_.current = tree_.current->parent;
+	do {
+		UndoNode *node = tree_.current;
+		apply(node, -1);
+		tree_.current = node->parent;
+	} while (gid != 0 && tree_.current && tree_.current->group_id == gid);
 	update_dirty_flag();
 }
 
@@ -195,8 +219,16 @@ UndoSystem::redo(int branch_index)
 	}
 
 	debug_log("redo");
-	apply(*head, +1);
+	UndoNode *node          = *head;
-	tree_.current = *head;
+	const std::uint64_t gid = node->group_id;
+	apply(node, +1);
+	tree_.current = node;
+	while (gid != 0 && tree_.current && tree_.current->child
+	       && tree_.current->child->group_id == gid) {
+		UndoNode *child = tree_.current->child;
+		apply(child, +1);
+		tree_.current = child;
+	}
 	update_dirty_flag();
 }
 
@@ -226,9 +258,11 @@ UndoSystem::clear()
 {
 	discard_pending();
 	free_node(tree_.root);
-	tree_.root    = nullptr;
+	tree_.root       = nullptr;
-	tree_.current = nullptr;
+	tree_.current    = nullptr;
-	tree_.saved   = nullptr;
+	tree_.saved      = nullptr;
+	active_group_id_ = 0;
+	next_group_id_   = 1;
 	update_dirty_flag();
 }
 

UndoSystem.h

@@ -12,6 +12,12 @@ class UndoSystem {
 public:
 	explicit UndoSystem(Buffer &owner, UndoTree &tree);
 
+	// Begin an atomic group: subsequent committed nodes with the same group_id will be
+	// undone/redone as a single step. Returns the active group id.
+	std::uint64_t BeginGroup();
+
+	void EndGroup();
+
 	void Begin(UndoType type);
 
 	void Append(char ch);
@@ -66,6 +72,9 @@ private:
 
 	PendingAppendMode pending_mode_ = PendingAppendMode::Append;
 
+	std::uint64_t active_group_id_ = 0;
+	std::uint64_t next_group_id_   = 1;
+
 	Buffer *buf_;
 	UndoTree &tree_;
 };

docs/plans/swap-files.md

@@ -12,11 +12,14 @@ Goals
 
 Model overview
 --------------
-Per open buffer, maintain a sidecar swap journal next to the file:
+Per open buffer, maintain a swap journal in a per-user state directory:
 
-- Path: `.<basename>.kte.swp` in the same directory as the file (for
+- Path: `$XDG_STATE_HOME/kte/swap/<encoded-path>.swp` (or
-  unnamed/unsaved buffers, use a per‑session temp dir like
+  `~/.local/state/kte/swap/...`)
-  `$TMPDIR/kte/` with a random UUID).
+  where `<encoded-path>` is the file path with separators replaced (e.g.
+  `/home/kyle/tmp/test.txt` → `home!kyle!tmp!test.txt.swp`).
+  Unnamed/unsaved
+  buffers use a unique `unnamed-<pid>-<counter>.swp` name.
 - Format: append‑only journal of editing operations with periodic
   checkpoints.
 - Crash safety: only append, fsync as per policy; checkpoint via
@@ -84,7 +87,7 @@ Recovery flow
 
 On opening a file:
 
-1. Detect swap sidecar `.<basename>.kte.swp`.
+1. Detect swap journal `$XDG_STATE_HOME/kte/swap/<encoded-path>.swp`.
 2. Validate header, iterate records verifying CRCs.
 3. Compare recorded original file identity against actual file; if
    mismatch, warn user but allow recovery (content wins).
@@ -98,7 +101,7 @@ Stability & corruption mitigation
 ---------------------------------
 
 - Append‑only with per‑record CRC32 guards against torn writes.
-- Atomic checkpoint rotation: write `.<basename>.kte.swp.tmp`, fsync,
+- Atomic checkpoint rotation: write `<encoded-path>.swp.tmp`, fsync,
   then rename over old `.swp`.
 - Size caps: rotate or compact when `.swp` exceeds a threshold (e.g.,
   64–128 MB). Compaction creates a fresh file with a single checkpoint.
@@ -117,8 +120,8 @@ Security considerations
 Interoperability & UX
 ---------------------
 
-- Use a distinctive extension `.kte.swp` to avoid conflicts with other
+- Use a distinctive directory (`$XDG_STATE_HOME/kte/swap`) to avoid
-  editors.
+  conflicts with other editors’ `.swp` conventions.
 - Status bar indicator when swap is active; commands to purge/compact.
 - On save: do not delete swap immediately; keep until the buffer is
   clean and idle for a short grace period (allows undo of accidental

docs/swap.md

@@ -0,0 +1,237 @@
+# Swap journaling (crash recovery)
+
+kte has a small “swap” system: an append-only per-buffer journal that
+records edits so they can be replayed after a crash.
+
+This document describes the **currently implemented** swap system (stage
+2), as implemented in `Swap.h` / `Swap.cc`.
+
+## What it is (and what it is not)
+
+- The swap file is a **journal of editing operations** (currently
+  inserts, deletes, and periodic full-buffer checkpoints).
+- It is written by a **single background writer thread** owned by
+  `kte::SwapManager`.
+- It is intended for **best-effort crash recovery**.
+
+kte automatically deletes/resets swap journals after a **clean save**
+and when
+closing a clean buffer, so old swap files do not accumulate under normal
+workflows. A best-effort prune also runs at startup to remove very old
+swap
+files.
+
+## Automatic recovery prompt
+
+When kte opens a file-backed buffer, it checks whether a corresponding
+swap journal exists.
+
+- If a swap file exists and replay succeeds *and* produces different
+  content than what is currently on disk, kte prompts:
+
+  ```text
+  Recover swap edits for <path>? (y/N, C-g cancel)
+  ```
+
+    - `y`: open the file and apply swap replay (buffer becomes dirty)
+    - `Enter` (default) / any non-`y`: delete the swap file (
+      best-effort)
+      and open the file normally
+    - `C-g`: cancel opening the file
+
+- If a swap file exists but is unreadable/corrupt, kte prompts:
+
+  ```text
+  Swap file unreadable for <path>. Delete it? (y/N, C-g cancel)
+  ```
+
+    - `y`: delete the swap file (best-effort) and open the file normally
+    - `Enter` (default): keep the swap file and open the file normally
+    - `C-g`: cancel opening the file
+
+## Where swap files live
+
+Swap files are stored under an XDG-style per-user *state* directory:
+
+- If `XDG_STATE_HOME` is set and non-empty:
+    - `$XDG_STATE_HOME/kte/swap/…`
+- Otherwise, if `HOME` is set:
+    - `~/.local/state/kte/swap/…`
+- Last resort fallback:
+    - `<system-temp>/kte/state/kte/swap/…` (via
+      `std::filesystem::temp_directory_path()`)
+
+Swap files are always created with permissions `0600`.
+
+### Swap file naming
+
+For file-backed buffers, the swap filename is derived from the buffer’s
+path:
+
+1. Take a canonical-ish path key (`std::filesystem::weakly_canonical`,
+   else `absolute`, else the raw `Buffer::Filename()`).
+2. Encode it so it’s human-identifiable:
+    - Strip one leading path separator (`/` or `\\`)
+    - Replace path separators (`/` and `\\`) with `!`
+    - Append `.swp`
+
+Example:
+
+```text
+/home/kyle/tmp/test.txt  ->  home!kyle!tmp!test.txt.swp
+```
+
+If the resulting name would be long (over ~200 characters), kte falls
+back to a shorter stable name:
+
+```text
+<basename>.<fnv1a64(path-key-as-hex)>.swp
+```
+
+For unnamed/unsaved buffers, kte uses:
+
+```text
+unnamed-<pid>-<counter>.swp
+```
+
+## Lifecycle (when swap is written)
+
+`kte::SwapManager` is owned by `Editor` (see `Editor.cc`). Buffers are
+attached for journaling when they are added/opened.
+
+- `SwapManager::Attach(Buffer*)` starts tracking a buffer and
+  establishes its swap path.
+- `Buffer` emits swap events from its low-level edit APIs:
+    - `Buffer::insert_text()` calls `SwapRecorder::OnInsert()`
+    - `Buffer::delete_text()` calls `SwapRecorder::OnDelete()`
+    - `Buffer::split_line()` / `join_lines()` are represented as
+      insert/delete of `\n` (they do **not** emit `SPLIT`/`JOIN` records
+      in stage 1).
+- `SwapManager::Detach(Buffer*)` flushes queued records, `fsync()`s, and
+  closes the journal.
+- On `Save As` / filename changes,
+  `SwapManager::NotifyFilenameChanged(Buffer&)` closes the existing
+  journal and switches to a new path.
+    - Note: the old swap file is currently left on disk (no
+      cleanup/rotation yet).
+
+## Durability and performance
+
+Swap writing is best-effort and asynchronous:
+
+- Records are queued from the UI/editing thread(s).
+- A background writer thread wakes at least every
+  `SwapConfig::flush_interval_ms` (default `200ms`) to write any queued
+  records.
+- `fsync()` is throttled to at most once per
+  `SwapConfig::fsync_interval_ms` (default `1000ms`) per open swap file.
+- `SwapManager::Flush()` blocks until the queue is fully written; it is
+  primarily used by tests and shutdown paths.
+
+If a crash happens while writing, the swap file may end with a partial
+record. Replay detects truncation/CRC mismatch and fails safely.
+
+## On-disk format (v1)
+
+The file is:
+
+1. A fixed-size 64-byte header
+2. Followed by a stream of records
+
+All multi-byte integers in the swap file are **little-endian**.
+
+### Header (64 bytes)
+
+Layout (stage 1):
+
+- `magic` (8 bytes): `KTE_SWP\0`
+- `version` (`u32`): currently `1`
+- `flags` (`u32`): currently `0`
+- `created_time` (`u64`): Unix seconds
+- remaining bytes are reserved/padding (currently zeroed)
+
+### Record framing
+
+Each record is:
+
+```text
+[type: u8][len: u24][payload: len bytes][crc32: u32]
+```
+
+- `len` is a 24-bit little-endian length of the payload (`0..0xFFFFFF`).
+- `crc32` is computed over the 4-byte record header (`type + len`)
+  followed by the payload bytes.
+
+### Record types
+
+Type codes are defined in `SwapRecType` (`Swap.h`). Stage 1 primarily
+emits:
+
+- `INS` (`1`): insert bytes at `(row, col)`
+- `DEL` (`2`): delete `len` bytes at `(row, col)`
+
+Other type codes exist for forward compatibility (`SPLIT`, `JOIN`,
+`META`, `CHKPT`), but are not produced by the current `SwapRecorder`
+interface.
+
+### Payload encoding (v1)
+
+Every payload starts with:
+
+```text
+[encver: u8]
+```
+
+Currently `encver` must be `1`.
+
+#### `INS` payload (encver = 1)
+
+```text
+[encver: u8 = 1]
+[row:   u32]
+[col:   u32]
+[nbytes:u32]
+[bytes: nbytes]
+```
+
+#### `DEL` payload (encver = 1)
+
+```text
+[encver: u8 = 1]
+[row:   u32]
+[col:   u32]
+[len:   u32]
+```
+
+`row`/`col` are 0-based and are interpreted the same way as
+`Buffer::insert_text()` / `Buffer::delete_text()`.
+
+## Replay / recovery
+
+Swap replay is implemented as a low-level API:
+
+-
+
+`bool kte::SwapManager::ReplayFile(Buffer &buf, const std::string &swap_path, std::string &err)`
+
+Behavior:
+
+- The caller supplies an **already-open** `Buffer` (typically loaded
+  from the on-disk file) and a swap path.
+- `ReplayFile()` validates header magic/version, then iterates records.
+- On a truncated file or CRC mismatch, it returns `false` and sets
+  `err`.
+- On unknown record types, it ignores them (forward compatibility).
+- On failure, the buffer may have had a prefix of records applied;
+  callers should treat this as “recovery failed”.
+
+Important: if the buffer is currently attached to a `SwapManager`, you
+should suspend/disable recording during replay (or detach first),
+otherwise replayed edits would be re-journaled.
+
+## Tests
+
+Swap behavior and format are validated by unit tests:
+
+- `tests/test_swap_writer.cc` (header, permissions, record CRC framing)
+- `tests/test_swap_replay.cc` (record replay and truncation handling)

main.cc

@@ -195,11 +195,12 @@ main(int argc, char *argv[])
 	} else if (req_term) {
 		use_gui = false;
 	} else {
-		// Default depends on build target: kge defaults to GUI, kte to terminal
+
+	// Default depends on build target: kge defaults to GUI, kte to terminal
 #if defined(KTE_DEFAULT_GUI)
-		use_gui = true;
+	use_gui = true;
 #else
-		use_gui = false;
+	use_gui = false;
 #endif
 	}
 #endif
@@ -207,6 +208,9 @@ main(int argc, char *argv[])
 	// Open files passed on the CLI; support +N to jump to line N in the next file.
 	// If no files are provided, create an empty buffer.
 	if (optind < argc) {
+		// Seed a scratch buffer so the UI has something to show while deferred opens
+		// (and potential swap recovery prompts) are processed.
+		editor.AddBuffer(Buffer());
 		std::size_t pending_line = 0; // 0 = no pending line
 		for (int i = optind; i < argc; ++i) {
 			const char *arg = argv[i];
@@ -242,29 +246,9 @@ main(int argc, char *argv[])
 				// Fall through: not a +number, treat as filename starting with '+'
 			}
 
-			std::string err;
 			const std::string path = arg;
-			if (!editor.OpenFile(path, err)) {
+			editor.RequestOpenFile(path, pending_line);
-				editor.SetStatus("open: " + err);
+			pending_line = 0; // consumed (if set)
-				std::cerr << "kte: " << err << "\n";
-			} else if (pending_line > 0) {
-				// Apply pending +N to the just-opened (current) buffer
-				if (Buffer *b = editor.CurrentBuffer()) {
-					std::size_t nrows = b->Nrows();
-					std::size_t line  = pending_line > 0 ? pending_line - 1 : 0;
-					// 1-based to 0-based
-					if (nrows > 0) {
-						if (line >= nrows)
-							line = nrows - 1;
-					} else {
-						line = 0;
-					}
-					b->SetCursor(0, line);
-					// Do not force viewport offsets here; the frontend/renderer
-					// will establish dimensions and normalize visibility on first draw.
-				}
-				pending_line = 0; // consumed
-			}
 		}
 		// If we ended with a pending +N but no subsequent file, ignore it.
 	} else {

tests/TestHarness.h

@@ -0,0 +1,138 @@
+// TestHarness.h - small helper layer for driving kte headlessly in tests
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <string_view>
+
+#include "Buffer.h"
+#include "Command.h"
+#include "Editor.h"
+
+namespace ktet {
+inline void
+InstallDefaultCommandsOnce()
+{
+	static bool installed = false;
+	if (!installed) {
+		InstallDefaultCommands();
+		installed = true;
+	}
+}
+
+
+class TestHarness {
+public:
+	TestHarness()
+	{
+		InstallDefaultCommandsOnce();
+		editor_.SetDimensions(24, 80);
+
+		Buffer b;
+		b.SetVirtualName("+TEST+");
+		editor_.AddBuffer(std::move(b));
+	}
+
+
+	Editor &
+	EditorRef()
+	{
+		return editor_;
+	}
+
+
+	Buffer &
+	Buf()
+	{
+		return *editor_.CurrentBuffer();
+	}
+
+
+	[[nodiscard]] const Buffer &
+	Buf() const
+	{
+		return *editor_.CurrentBuffer();
+	}
+
+
+	bool
+	Exec(CommandId id, const std::string &arg = std::string(), int ucount = 0)
+	{
+		if (ucount > 0) {
+			editor_.SetUniversalArg(1, ucount);
+		} else {
+			editor_.UArgClear();
+		}
+		return Execute(editor_, id, arg);
+	}
+
+
+	bool
+	InsertText(std::string_view text)
+	{
+		if (text.find('\n') != std::string_view::npos || text.find('\r') != std::string_view::npos)
+			return false;
+		return Exec(CommandId::InsertText, std::string(text));
+	}
+
+
+	void
+	TypeText(std::string_view text)
+	{
+		for (char ch: text) {
+			if (ch == '\n') {
+				Exec(CommandId::Newline);
+			} else if (ch == '\r') {
+				// ignore
+			} else {
+				Exec(CommandId::InsertText, std::string(1, ch));
+			}
+		}
+	}
+
+
+	[[nodiscard]] std::string
+	Text() const
+	{
+		const auto &rows = Buf().Rows();
+		std::string out;
+		for (std::size_t i = 0; i < rows.size(); ++i) {
+			out += static_cast<std::string>(rows[i]);
+			if (i + 1 < rows.size())
+				out.push_back('\n');
+		}
+		return out;
+	}
+
+
+	[[nodiscard]] std::string
+	Line(std::size_t y) const
+	{
+		return Buf().GetLineString(y);
+	}
+
+
+	bool
+	SaveAs(const std::string &path, std::string &err)
+	{
+		return Buf().SaveAs(path, err);
+	}
+
+
+	bool
+	Undo(int ucount = 0)
+	{
+		return Exec(CommandId::Undo, std::string(), ucount);
+	}
+
+
+	bool
+	Redo(int ucount = 0)
+	{
+		return Exec(CommandId::Redo, std::string(), ucount);
+	}
+
+private:
+	Editor editor_;
+};
+} // namespace ktet

tests/test_buffer_rows.cc

@@ -0,0 +1,142 @@
+#include "Test.h"
+#include "Buffer.h"
+#include <algorithm>
+#include <limits>
+#include <string>
+#include <vector>
+
+
+static std::vector<std::string>
+split_lines_preserve_trailing_empty(const std::string &s)
+{
+	std::vector<std::string> out;
+	std::size_t start = 0;
+	for (std::size_t i = 0; i <= s.size(); i++) {
+		if (i == s.size() || s[i] == '\n') {
+			out.push_back(s.substr(start, i - start));
+			start = i + 1;
+		}
+	}
+	if (out.empty())
+		out.push_back(std::string());
+	return out;
+}
+
+
+static std::vector<std::size_t>
+line_starts_for(const std::string &s)
+{
+	std::vector<std::size_t> starts;
+	starts.push_back(0);
+	for (std::size_t i = 0; i < s.size(); i++) {
+		if (s[i] == '\n')
+			starts.push_back(i + 1);
+	}
+	return starts;
+}
+
+
+static std::size_t
+ref_linecol_to_offset(const std::string &s, std::size_t row, std::size_t col)
+{
+	auto starts = line_starts_for(s);
+	if (starts.empty())
+		return 0;
+	if (row >= starts.size())
+		return s.size();
+	std::size_t start = starts[row];
+	std::size_t end   = (row + 1 < starts.size()) ? starts[row + 1] : s.size();
+	if (end > start && s[end - 1] == '\n')
+		end -= 1; // clamp before trailing newline
+	return start + std::min(col, end - start);
+}
+
+
+static void
+check_buffer_matches_model(const Buffer &b, const std::string &model)
+{
+	auto expected_lines = split_lines_preserve_trailing_empty(model);
+	const auto &rows    = b.Rows();
+	ASSERT_EQ(rows.size(), expected_lines.size());
+	ASSERT_EQ(b.Nrows(), rows.size());
+
+	auto starts = line_starts_for(model);
+	ASSERT_EQ(starts.size(), expected_lines.size());
+
+	std::string via_views;
+	for (std::size_t i = 0; i < rows.size(); i++) {
+		ASSERT_EQ(std::string(rows[i]), expected_lines[i]);
+		ASSERT_EQ(b.GetLineString(i), expected_lines[i]);
+
+		std::size_t exp_start = starts[i];
+		std::size_t exp_end   = (i + 1 < starts.size()) ? starts[i + 1] : model.size();
+		auto r                = b.GetLineRange(i);
+		ASSERT_EQ(r.first, exp_start);
+		ASSERT_EQ(r.second, exp_end);
+
+		auto v = b.GetLineView(i);
+		ASSERT_EQ(std::string(v), model.substr(exp_start, exp_end - exp_start));
+		via_views.append(v.data(), v.size());
+	}
+	ASSERT_EQ(via_views, model);
+}
+
+
+TEST (Buffer_RowsCache_MultiLineEdits_StayConsistent)
+{
+	Buffer b;
+	std::string model;
+
+	check_buffer_matches_model(b, model);
+
+	// Insert text and newlines in a few different ways.
+	b.insert_text(0, 0, std::string("abc"));
+	model.insert(0, "abc");
+	check_buffer_matches_model(b, model);
+
+	b.split_line(0, 1); // a\nbc
+	model.insert(ref_linecol_to_offset(model, 0, 1), "\n");
+	check_buffer_matches_model(b, model);
+
+	b.insert_text(1, 2, std::string("X")); // a\nbcX
+	model.insert(ref_linecol_to_offset(model, 1, 2), "X");
+	check_buffer_matches_model(b, model);
+
+	b.join_lines(0); // abcX
+	{
+		std::size_t off = ref_linecol_to_offset(model, 0, std::numeric_limits<std::size_t>::max());
+		if (off < model.size() && model[off] == '\n')
+			model.erase(off, 1);
+	}
+	check_buffer_matches_model(b, model);
+
+	// Insert a multi-line segment in one shot.
+	b.insert_text(0, 2, std::string("\n123\nxyz"));
+	model.insert(ref_linecol_to_offset(model, 0, 2), "\n123\nxyz");
+	check_buffer_matches_model(b, model);
+
+	// Delete spanning across a newline.
+	b.delete_text(0, 1, 5);
+	{
+		std::size_t start  = ref_linecol_to_offset(model, 0, 1);
+		std::size_t actual = std::min<std::size_t>(5, model.size() - start);
+		model.erase(start, actual);
+	}
+	check_buffer_matches_model(b, model);
+
+	// Insert/delete whole rows.
+	b.insert_row(1, std::string_view("ROW"));
+	model.insert(ref_linecol_to_offset(model, 1, 0), "ROW\n");
+	check_buffer_matches_model(b, model);
+
+	b.delete_row(1);
+	{
+		auto starts = line_starts_for(model);
+		if (1 < (int) starts.size()) {
+			std::size_t start = starts[1];
+			std::size_t end   = (2 < starts.size()) ? starts[2] : model.size();
+			model.erase(start, end - start);
+		}
+	}
+	check_buffer_matches_model(b, model);
+}

tests/test_command_semantics.cc

@@ -0,0 +1,110 @@
+#include "Test.h"
+
+#include "TestHarness.h"
+
+using ktet::TestHarness;
+
+
+TEST (CommandSemantics_KillToEOL_KillChain_And_Yank)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	b.insert_text(0, 0, std::string("abc\ndef"));
+	b.SetCursor(1, 0); // a|bc
+
+	ed.KillRingClear();
+	ed.SetKillChain(false);
+
+	ASSERT_TRUE(h.Exec(CommandId::KillToEOL));
+	ASSERT_EQ(h.Text(), std::string("a\ndef"));
+	ASSERT_EQ(ed.KillRingHead(), std::string("bc"));
+
+	// At EOL, KillToEOL kills the newline (join).
+	ASSERT_TRUE(h.Exec(CommandId::KillToEOL));
+	ASSERT_EQ(h.Text(), std::string("adef"));
+	ASSERT_EQ(ed.KillRingHead(), std::string("bc\n"));
+
+	// Yank pastes the kill ring head and breaks the kill chain.
+	ASSERT_TRUE(h.Exec(CommandId::Yank));
+	ASSERT_EQ(h.Text(), std::string("abc\ndef"));
+	ASSERT_EQ(ed.KillRingHead(), std::string("bc\n"));
+	ASSERT_EQ(ed.KillChain(), false);
+}
+
+
+TEST (CommandSemantics_ToggleMark_JumpToMark)
+{
+	TestHarness h;
+	Buffer &b = h.Buf();
+
+	b.insert_text(0, 0, std::string("hello"));
+	b.SetCursor(2, 0);
+	ASSERT_EQ(b.MarkSet(), false);
+
+	ASSERT_TRUE(h.Exec(CommandId::ToggleMark));
+	ASSERT_EQ(b.MarkSet(), true);
+	ASSERT_EQ(b.MarkCurx(), (std::size_t) 2);
+	ASSERT_EQ(b.MarkCury(), (std::size_t) 0);
+
+	b.SetCursor(4, 0);
+	ASSERT_TRUE(h.Exec(CommandId::JumpToMark));
+	ASSERT_EQ(b.Curx(), (std::size_t) 2);
+	ASSERT_EQ(b.Cury(), (std::size_t) 0);
+	// Jump-to-mark swaps: mark becomes previous cursor.
+	ASSERT_EQ(b.MarkSet(), true);
+	ASSERT_EQ(b.MarkCurx(), (std::size_t) 4);
+	ASSERT_EQ(b.MarkCury(), (std::size_t) 0);
+}
+
+
+TEST (CommandSemantics_CtrlGRefresh_ClearsMark_WhenNothingElseToCancel)
+{
+	TestHarness h;
+	Buffer &b = h.Buf();
+
+	b.insert_text(0, 0, std::string("hello"));
+	b.SetCursor(2, 0);
+	ASSERT_EQ(b.MarkSet(), false);
+
+	ASSERT_TRUE(h.Exec(CommandId::ToggleMark));
+	ASSERT_EQ(b.MarkSet(), true);
+
+	// C-g is mapped to Refresh; when there's no prompt/search/visual-line mode to cancel,
+	// it should clear the mark.
+	ASSERT_TRUE(h.Exec(CommandId::Refresh));
+	ASSERT_EQ(b.MarkSet(), false);
+}
+
+
+TEST (CommandSemantics_CopyRegion_And_KillRegion)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	b.insert_text(0, 0, std::string("hello world"));
+	b.SetCursor(0, 0);
+
+	ed.KillRingClear();
+	ed.SetKillChain(false);
+
+	// Copy "hello" (region [0,5)).
+	ASSERT_TRUE(h.Exec(CommandId::ToggleMark));
+	b.SetCursor(5, 0);
+	ASSERT_TRUE(h.Exec(CommandId::CopyRegion));
+	ASSERT_EQ(ed.KillRingHead(), std::string("hello"));
+	ASSERT_EQ(b.MarkSet(), false);
+	ASSERT_EQ(h.Text(), std::string("hello world"));
+
+	// Kill "world" (region [6,11)).
+	ed.SetKillChain(false);
+	b.SetCursor(6, 0);
+	ASSERT_TRUE(h.Exec(CommandId::ToggleMark));
+	b.SetCursor(11, 0);
+	ASSERT_TRUE(h.Exec(CommandId::KillRegion));
+	ASSERT_EQ(ed.KillRingHead(), std::string("world"));
+	ASSERT_EQ(b.MarkSet(), false);
+	ASSERT_EQ(h.Text(), std::string("hello "));
+}

tests/test_daily_driver_harness.cc

@@ -0,0 +1,12 @@
+#include "Test.h"
+
+#include "tests/TestHarness.h"
+
+
+TEST (DailyDriverHarness_Smoke_CanCreateBufferAndInsertText)
+{
+	ktet::TestHarness h;
+
+	ASSERT_TRUE(h.InsertText("hello"));
+	ASSERT_EQ(h.Line(0), std::string("hello"));
+}

tests/test_daily_workflows.cc

@@ -0,0 +1,170 @@
+#include "Test.h"
+
+#include "Command.h"
+#include "Editor.h"
+
+#include "tests/TestHarness.h" // for ktet::InstallDefaultCommandsOnce
+
+#include <cstdio>
+#include <filesystem>
+#include <fstream>
+#include <string>
+
+
+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());
+}
+
+
+static std::string
+read_file_bytes(const std::string &path)
+{
+	std::ifstream in(path, std::ios::binary);
+	return std::string((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+}
+
+
+static std::string
+buffer_bytes_via_views(const Buffer &b)
+{
+	const auto &rows = b.Rows();
+	std::string out;
+	for (std::size_t i = 0; i < rows.size(); i++) {
+		auto v = b.GetLineView(i);
+		out.append(v.data(), v.size());
+	}
+	return out;
+}
+
+
+TEST (DailyWorkflow_OpenEditSave_Transcript)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::string path = "./.kte_ut_daily_open_edit_save.txt";
+	std::remove(path.c_str());
+	write_file_bytes(path, "one\n");
+	const std::string npath = std::filesystem::canonical(path).string();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	// Seed an empty buffer so OpenFile can reuse it.
+	{
+		Buffer scratch;
+		ed.AddBuffer(std::move(scratch));
+	}
+
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(ed.CurrentBuffer()->Filename(), npath);
+
+	// Append two new lines via commands (no UI).
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileEnd));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "two"));
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "three"));
+
+	ASSERT_TRUE(Execute(ed, CommandId::Save));
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(read_file_bytes(npath), buffer_bytes_via_views(*ed.CurrentBuffer()));
+
+	std::remove(path.c_str());
+	std::remove(npath.c_str());
+}
+
+
+TEST (DailyWorkflow_MultiBufferSwitchClose_Transcript)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::string p1 = "./.kte_ut_daily_buf_1.txt";
+	const std::string p2 = "./.kte_ut_daily_buf_2.txt";
+	std::remove(p1.c_str());
+	std::remove(p2.c_str());
+	write_file_bytes(p1, "aaa\n");
+	write_file_bytes(p2, "bbb\n");
+	const std::string np1 = std::filesystem::canonical(p1).string();
+	const std::string np2 = std::filesystem::canonical(p2).string();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	{
+		Buffer scratch;
+		ed.AddBuffer(std::move(scratch));
+	}
+
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(p1, err));
+	ASSERT_TRUE(ed.OpenFile(p2, err));
+	ASSERT_EQ(ed.BufferCount(), (std::size_t) 2);
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(ed.CurrentBuffer()->Filename(), np2);
+
+	// Switch back and forth.
+	ASSERT_TRUE(Execute(ed, CommandId::BufferPrev));
+	ASSERT_EQ(ed.CurrentBuffer()->Filename(), np1);
+	ASSERT_TRUE(Execute(ed, CommandId::BufferNext));
+	ASSERT_EQ(ed.CurrentBuffer()->Filename(), np2);
+
+	// Close current buffer (p2); ensure we land on p1.
+	ASSERT_TRUE(Execute(ed, CommandId::BufferClose));
+	ASSERT_EQ(ed.BufferCount(), (std::size_t) 1);
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(ed.CurrentBuffer()->Filename(), np1);
+
+	std::remove(p1.c_str());
+	std::remove(p2.c_str());
+	std::remove(np1.c_str());
+	std::remove(np2.c_str());
+}
+
+
+TEST (DailyWorkflow_CrashRecovery_SwapReplay_Transcript)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::string path = "./.kte_ut_daily_swap_recover.txt";
+	std::remove(path.c_str());
+	write_file_bytes(path, "base\nline2\n");
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	{
+		Buffer scratch;
+		ed.AddBuffer(std::move(scratch));
+	}
+
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	// Make unsaved edits through command execution.
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "X"));
+	ASSERT_TRUE(Execute(ed, CommandId::MoveDown));
+	ASSERT_TRUE(Execute(ed, CommandId::MoveHome));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "ZZ"));
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileEnd));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "TAIL"));
+
+	// Ensure journal is durable and capture expected bytes.
+	ed.Swap()->Flush(buf);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(*buf);
+	const std::string expected  = buffer_bytes_via_views(*buf);
+
+	// "Crash": reopen from disk (original file content) into a fresh Buffer and replay.
+	Buffer recovered;
+	ASSERT_TRUE(recovered.OpenFromFile(path, err));
+	ASSERT_TRUE(kte::SwapManager::ReplayFile(recovered, swap_path, err));
+	ASSERT_EQ(buffer_bytes_via_views(recovered), expected);
+
+	// Cleanup.
+	ed.Swap()->Detach(buf);
+	std::remove(path.c_str());
+	std::remove(swap_path.c_str());
+}

tests/test_kkeymap.cc

@@ -0,0 +1,84 @@
+#include "Test.h"
+
+#include "KKeymap.h"
+
+#include <ncurses.h>
+
+
+TEST (KKeymap_KPrefix_CanonicalChords)
+{
+	CommandId id{};
+
+	// From docs/ke.md (K-commands)
+	ASSERT_TRUE(KLookupKCommand('s', false, id));
+	ASSERT_EQ(id, CommandId::Save);
+	ASSERT_TRUE(KLookupKCommand('s', true, id)); // C-k C-s
+	ASSERT_EQ(id, CommandId::Save);
+
+	ASSERT_TRUE(KLookupKCommand('d', false, id));
+	ASSERT_EQ(id, CommandId::KillToEOL);
+	ASSERT_TRUE(KLookupKCommand('d', true, id)); // C-k C-d
+	ASSERT_EQ(id, CommandId::KillLine);
+
+	ASSERT_TRUE(KLookupKCommand(' ', false, id)); // C-k SPACE
+	ASSERT_EQ(id, CommandId::ToggleMark);
+
+	ASSERT_TRUE(KLookupKCommand('j', false, id));
+	ASSERT_EQ(id, CommandId::JumpToMark);
+
+	ASSERT_TRUE(KLookupKCommand('f', false, id));
+	ASSERT_EQ(id, CommandId::FlushKillRing);
+
+	ASSERT_TRUE(KLookupKCommand('y', false, id));
+	ASSERT_EQ(id, CommandId::Yank);
+
+	// Unknown should not map
+	ASSERT_EQ(KLookupKCommand('Z', false, id), false);
+}
+
+
+TEST (KKeymap_CtrlChords_CanonicalChords)
+{
+	CommandId id{};
+
+	// From docs/ke.md (other keybindings)
+	ASSERT_TRUE(KLookupCtrlCommand('n', id));
+	ASSERT_EQ(id, CommandId::MoveDown);
+	ASSERT_TRUE(KLookupCtrlCommand('p', id));
+	ASSERT_EQ(id, CommandId::MoveUp);
+	ASSERT_TRUE(KLookupCtrlCommand('f', id));
+	ASSERT_EQ(id, CommandId::MoveRight);
+	ASSERT_TRUE(KLookupCtrlCommand('b', id));
+	ASSERT_EQ(id, CommandId::MoveLeft);
+
+	ASSERT_TRUE(KLookupCtrlCommand('w', id));
+	ASSERT_EQ(id, CommandId::KillRegion);
+	ASSERT_TRUE(KLookupCtrlCommand('y', id));
+	ASSERT_EQ(id, CommandId::Yank);
+
+	ASSERT_EQ(KLookupCtrlCommand('z', id), false);
+}
+
+
+TEST (KKeymap_EscChords_CanonicalChords)
+{
+	CommandId id{};
+
+	// From docs/ke.md (ESC bindings)
+	ASSERT_TRUE(KLookupEscCommand('b', id));
+	ASSERT_EQ(id, CommandId::WordPrev);
+	ASSERT_TRUE(KLookupEscCommand('f', id));
+	ASSERT_EQ(id, CommandId::WordNext);
+	ASSERT_TRUE(KLookupEscCommand('d', id));
+	ASSERT_EQ(id, CommandId::DeleteWordNext);
+	ASSERT_TRUE(KLookupEscCommand('q', id));
+	ASSERT_EQ(id, CommandId::ReflowParagraph);
+	ASSERT_TRUE(KLookupEscCommand('w', id));
+	ASSERT_EQ(id, CommandId::CopyRegion);
+
+	// ESC BACKSPACE
+	ASSERT_TRUE(KLookupEscCommand(KEY_BACKSPACE, id));
+	ASSERT_EQ(id, CommandId::DeleteWordPrev);
+
+	ASSERT_EQ(KLookupEscCommand('z', id), false);
+}

tests/test_piece_table.cc

@@ -1,49 +1,181 @@
 #include "Test.h"
 #include "PieceTable.h"
+#include <algorithm>
+#include <array>
+#include <random>
 #include <string>
+#include <vector>
 
-TEST(PieceTable_Insert_Delete_LineCount) {
-    PieceTable pt;
-    // start empty
-    ASSERT_EQ(pt.Size(), (std::size_t)0);
-    ASSERT_EQ(pt.LineCount(), (std::size_t)1); // empty buffer has 1 logical line
 
-    // Insert some text with newlines
+static std::vector<std::size_t>
-    const char *t = "abc\n123\nxyz"; // last line without trailing NL
+LineStartsFor(const std::string &s)
-    pt.Insert(0, t, 11);
+{
-    ASSERT_EQ(pt.Size(), (std::size_t)11);
+	std::vector<std::size_t> starts;
-    ASSERT_EQ(pt.LineCount(), (std::size_t)3);
+	starts.push_back(0);
-
+	for (std::size_t i = 0; i < s.size(); i++) {
-    // Check get line
+		if (s[i] == '\n')
-    ASSERT_EQ(pt.GetLine(0), std::string("abc"));
+			starts.push_back(i + 1);
-    ASSERT_EQ(pt.GetLine(1), std::string("123"));
+	}
-    ASSERT_EQ(pt.GetLine(2), std::string("xyz"));
+	return starts;
-
-    // Delete middle line entirely including its trailing NL
-    auto r = pt.GetLineRange(1); // [start,end) points to start of line 1 to start of line 2
-    pt.Delete(r.first, r.second - r.first);
-    ASSERT_EQ(pt.LineCount(), (std::size_t)2);
-    ASSERT_EQ(pt.GetLine(0), std::string("abc"));
-    ASSERT_EQ(pt.GetLine(1), std::string("xyz"));
 }
 
-TEST(PieceTable_LineCol_Conversions) {
-    PieceTable pt;
-    std::string s = "hello\nworld\n"; // two lines with trailing NL
-    pt.Insert(0, s.data(), s.size());
 
-    // Byte offsets of starts
+static std::string
-    auto off0 = pt.LineColToByteOffset(0, 0);
+LineContentFor(const std::string &s, std::size_t line_num)
-    auto off1 = pt.LineColToByteOffset(1, 0);
+{
-    auto off2 = pt.LineColToByteOffset(2, 0); // EOF
+	auto starts = LineStartsFor(s);
-    ASSERT_EQ(off0, (std::size_t)0);
+	if (starts.empty() || line_num >= starts.size())
-    ASSERT_EQ(off1, (std::size_t)6); // "hello\n"
+		return std::string();
-    ASSERT_EQ(off2, pt.Size());
+	std::size_t start = starts[line_num];
-
+	std::size_t end   = (line_num + 1 < starts.size()) ? starts[line_num + 1] : s.size();
-    auto lc0 = pt.ByteOffsetToLineCol(0);
+	if (end > start && s[end - 1] == '\n')
-    auto lc1 = pt.ByteOffsetToLineCol(6);
+		end -= 1;
-    ASSERT_EQ(lc0.first, (std::size_t)0);
+	return s.substr(start, end - start);
-    ASSERT_EQ(lc0.second, (std::size_t)0);
+}
-    ASSERT_EQ(lc1.first, (std::size_t)1);
+
-    ASSERT_EQ(lc1.second, (std::size_t)0);
+
+TEST (PieceTable_Insert_Delete_LineCount)
+{
+	PieceTable pt;
+	// start empty
+	ASSERT_EQ(pt.Size(), (std::size_t) 0);
+	ASSERT_EQ(pt.LineCount(), (std::size_t) 1); // empty buffer has 1 logical line
+
+	// Insert some text with newlines
+	const char *t = "abc\n123\nxyz"; // last line without trailing NL
+	pt.Insert(0, t, 11);
+	ASSERT_EQ(pt.Size(), (std::size_t) 11);
+	ASSERT_EQ(pt.LineCount(), (std::size_t) 3);
+
+	// Check get line
+	ASSERT_EQ(pt.GetLine(0), std::string("abc"));
+	ASSERT_EQ(pt.GetLine(1), std::string("123"));
+	ASSERT_EQ(pt.GetLine(2), std::string("xyz"));
+
+	// Delete middle line entirely including its trailing NL
+	auto r = pt.GetLineRange(1); // [start,end) points to start of line 1 to start of line 2
+	pt.Delete(r.first, r.second - r.first);
+	ASSERT_EQ(pt.LineCount(), (std::size_t) 2);
+	ASSERT_EQ(pt.GetLine(0), std::string("abc"));
+	ASSERT_EQ(pt.GetLine(1), std::string("xyz"));
+}
+
+
+TEST (PieceTable_LineCol_Conversions)
+{
+	PieceTable pt;
+	std::string s = "hello\nworld\n"; // two lines with trailing NL
+	pt.Insert(0, s.data(), s.size());
+
+	// Byte offsets of starts
+	auto off0 = pt.LineColToByteOffset(0, 0);
+	auto off1 = pt.LineColToByteOffset(1, 0);
+	auto off2 = pt.LineColToByteOffset(2, 0); // EOF
+	ASSERT_EQ(off0, (std::size_t) 0);
+	ASSERT_EQ(off1, (std::size_t) 6); // "hello\n"
+	ASSERT_EQ(off2, pt.Size());
+
+	auto lc0 = pt.ByteOffsetToLineCol(0);
+	auto lc1 = pt.ByteOffsetToLineCol(6);
+	ASSERT_EQ(lc0.first, (std::size_t) 0);
+	ASSERT_EQ(lc0.second, (std::size_t) 0);
+	ASSERT_EQ(lc1.first, (std::size_t) 1);
+	ASSERT_EQ(lc1.second, (std::size_t) 0);
+}
+
+
+TEST (PieceTable_ReferenceModel_RandomEdits_Deterministic)
+{
+	PieceTable pt;
+	std::string model;
+
+	std::mt19937 rng(0xC0FFEEu);
+	const std::vector<std::string> corpus = {
+		"a",
+		"b",
+		"c",
+		"xyz",
+		"123",
+		"\n",
+		"!\n",
+		"foo\nbar",
+		"end\n",
+	};
+
+	auto check_invariants = [&](const char *where) {
+		(void) where;
+		ASSERT_EQ(pt.Size(), model.size());
+		ASSERT_EQ(pt.GetRange(0, pt.Size()), model);
+
+		auto starts = LineStartsFor(model);
+		ASSERT_EQ(pt.LineCount(), starts.size());
+
+		// Spot-check a few line ranges and contents.
+		std::size_t last                             = starts.empty() ? (std::size_t) 0 : (starts.size() - 1);
+		std::size_t mid                              = (starts.size() > 2) ? (std::size_t) 1 : last;
+		const std::array<std::size_t, 3> probe_lines = {(std::size_t) 0, last, mid};
+		for (auto line: probe_lines) {
+			if (starts.empty())
+				break;
+			if (line >= starts.size())
+				continue;
+			std::size_t exp_start = starts[line];
+			std::size_t exp_end   = (line + 1 < starts.size()) ? starts[line + 1] : model.size();
+			auto r                = pt.GetLineRange(line);
+			ASSERT_EQ(r.first, exp_start);
+			ASSERT_EQ(r.second, exp_end);
+			ASSERT_EQ(pt.GetLine(line), LineContentFor(model, line));
+		}
+
+		// Round-trips for a few offsets.
+		const std::vector<std::size_t> probe_offsets = {
+			0,
+			model.size() / 2,
+			model.size(),
+		};
+		for (auto off: probe_offsets) {
+			auto lc   = pt.ByteOffsetToLineCol(off);
+			auto back = pt.LineColToByteOffset(lc.first, lc.second);
+			ASSERT_EQ(back, off);
+		}
+	};
+
+	check_invariants("initial");
+
+	for (int step = 0; step < 250; step++) {
+		bool do_insert = model.empty() || ((rng() % 3u) != 0u); // bias toward insert
+		if (do_insert) {
+			const std::string &ins = corpus[rng() % corpus.size()];
+			std::size_t pos        = model.empty() ? 0 : (rng() % (model.size() + 1));
+			pt.Insert(pos, ins.data(), ins.size());
+			model.insert(pos, ins);
+		} else {
+			std::size_t pos = rng() % model.size();
+			std::size_t max = std::min<std::size_t>(8, model.size() - pos);
+			std::size_t len = 1 + (rng() % max);
+			pt.Delete(pos, len);
+			model.erase(pos, len);
+		}
+
+		// Also validate GetRange on a small random window when non-empty.
+		if (!model.empty()) {
+			std::size_t off = rng() % model.size();
+			std::size_t max = std::min<std::size_t>(16, model.size() - off);
+			std::size_t len = 1 + (rng() % max);
+			ASSERT_EQ(pt.GetRange(off, len), model.substr(off, len));
+		}
+
+		check_invariants("step");
+	}
+
+	// Full line-by-line range verification at the end.
+	auto starts = LineStartsFor(model);
+	for (std::size_t line = 0; line < starts.size(); line++) {
+		std::size_t exp_start = starts[line];
+		std::size_t exp_end   = (line + 1 < starts.size()) ? starts[line + 1] : model.size();
+		auto r                = pt.GetLineRange(line);
+		ASSERT_EQ(r.first, exp_start);
+		ASSERT_EQ(r.second, exp_end);
+		ASSERT_EQ(pt.GetLine(line), LineContentFor(model, line));
+	}
 }

tests/test_reflow_indented_bullets.cc

@@ -0,0 +1,78 @@
+#include "Test.h"
+
+#include "Buffer.h"
+#include "Command.h"
+#include "Editor.h"
+
+#include <iostream>
+#include <string>
+
+
+static std::string
+to_string_rows(const Buffer &buf)
+{
+	std::string out;
+	for (const auto &r: buf.Rows()) {
+		out += static_cast<std::string>(r);
+		out.push_back('\n');
+	}
+	return out;
+}
+
+
+TEST (ReflowParagraph_IndentedBullets_PreserveStructure)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	// Test the example from the issue: indented list items should not be merged
+	const std::string initial =
+		"+ something at the top\n"
+		"  + something indented\n"
+		"+ the next line\n";
+	b.insert_text(0, 0, initial);
+	// Put cursor on first item
+	b.SetCursor(0, 0);
+	ed.AddBuffer(std::move(b));
+
+	Buffer *buf = ed.CurrentBuffer();
+	ASSERT_TRUE(buf != nullptr);
+
+	// Use a width that's larger than all lines (so no wrapping should occur)
+	const int width = 80;
+	ASSERT_TRUE(Execute(ed, std::string("reflow-paragraph"), std::string(), width));
+
+	const auto &rows         = buf->Rows();
+	const std::string result = to_string_rows(*buf);
+
+	// We should have 3 lines (plus possibly a trailing empty line)
+	ASSERT_TRUE(rows.size() >= 3);
+
+	// Check that the structure is preserved
+	std::string line0 = static_cast<std::string>(rows[0]);
+	std::string line1 = static_cast<std::string>(rows[1]);
+	std::string line2 = static_cast<std::string>(rows[2]);
+
+	// First line should start with "+ "
+	EXPECT_TRUE(line0.rfind("+ ", 0) == 0);
+	EXPECT_TRUE(line0.find("something at the top") != std::string::npos);
+
+	// Second line should start with "  + " (two spaces, then +)
+	EXPECT_TRUE(line1.rfind("  + ", 0) == 0);
+	EXPECT_TRUE(line1.find("something indented") != std::string::npos);
+
+	// Third line should start with "+ "
+	EXPECT_TRUE(line2.rfind("+ ", 0) == 0);
+	EXPECT_TRUE(line2.find("the next line") != std::string::npos);
+
+	// The indented line should NOT be merged with the first line
+	EXPECT_TRUE(line0.find("indented") == std::string::npos);
+
+	// Debug output if something goes wrong
+	if (line0.rfind("+ ", 0) != 0 || line1.rfind("  + ", 0) != 0 || line2.rfind("+ ", 0) != 0) {
+		std::cerr << "Reflow did not preserve indented bullet structure:\n" << result << "\n";
+	}
+}

tests/test_search_replace_flow.cc

@@ -0,0 +1,129 @@
+#include "Test.h"
+
+#include "tests/TestHarness.h"
+
+using ktet::TestHarness;
+
+// These tests intentionally drive the prompt-based search/replace UI headlessly
+// via `Execute(Editor&, CommandId, ...)` to lock down behavior without ncurses.
+
+TEST (SearchFlow_FindStart_Success_LeavesCursorOnMatch_And_ClearsSearchState)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	b.insert_text(0, 0, "abc def abc");
+	b.SetCursor(0, 0);
+	b.SetOffsets(0, 0);
+
+	// Keep a mark set to ensure search doesn't clobber it.
+	b.SetMark(0, 0);
+	ASSERT_TRUE(b.MarkSet());
+
+	ASSERT_TRUE(h.Exec(CommandId::FindStart));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_EQ(ed.CurrentPromptKind(), Editor::PromptKind::Search);
+	ASSERT_TRUE(ed.SearchActive());
+
+	// Typing into the prompt uses InsertText and should jump to the first match.
+	ASSERT_TRUE(h.Exec(CommandId::InsertText, "def"));
+	ASSERT_EQ(b.Cury(), (std::size_t) 0);
+	ASSERT_EQ(b.Curx(), (std::size_t) 4);
+
+	// Enter (Newline) accepts the prompt and ends incremental search.
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+	ASSERT_TRUE(!ed.PromptActive());
+	ASSERT_TRUE(!ed.SearchActive());
+	ASSERT_TRUE(b.MarkSet());
+}
+
+
+TEST (SearchFlow_FindStart_NotFound_RestoresOrigin_And_ClearsSearchState)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	b.insert_text(0, 0, "hello world\nsecond line\n");
+	b.SetCursor(3, 0);
+	b.SetOffsets(1, 2);
+
+	const std::size_t ox   = b.Curx();
+	const std::size_t oy   = b.Cury();
+	const std::size_t orow = b.Rowoffs();
+	const std::size_t ocol = b.Coloffs();
+
+	ASSERT_TRUE(h.Exec(CommandId::FindStart));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_TRUE(ed.SearchActive());
+
+	// Not-found should restore cursor/viewport to the saved origin while still in prompt.
+	ASSERT_TRUE(h.Exec(CommandId::InsertText, "zzzz"));
+	ASSERT_EQ(b.Curx(), ox);
+	ASSERT_EQ(b.Cury(), oy);
+	ASSERT_EQ(b.Rowoffs(), orow);
+	ASSERT_EQ(b.Coloffs(), ocol);
+
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+	ASSERT_TRUE(!ed.PromptActive());
+	ASSERT_TRUE(!ed.SearchActive());
+}
+
+
+TEST (SearchFlow_SearchReplace_EmptyFind_DoesNotMutateBuffer_And_ClearsState)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	b.insert_text(0, 0, "abc abc\n");
+	b.SetCursor(0, 0);
+
+	const std::string before = h.Text();
+
+	ASSERT_TRUE(h.Exec(CommandId::SearchReplace));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_EQ(ed.CurrentPromptKind(), Editor::PromptKind::ReplaceFind);
+
+	// Accept empty find -> proceed to ReplaceWith.
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_EQ(ed.CurrentPromptKind(), Editor::PromptKind::ReplaceWith);
+
+	// Provide replacement and accept -> should cancel due to empty find.
+	ASSERT_TRUE(h.Exec(CommandId::InsertText, "X"));
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+
+	ASSERT_TRUE(!ed.PromptActive());
+	ASSERT_TRUE(!ed.SearchActive());
+	ASSERT_EQ(h.Text(), before);
+}
+
+
+TEST (SearchFlow_RegexFind_InvalidPattern_FailsSafely_And_ClearsStateOnEnter)
+{
+	TestHarness h;
+	Editor &ed = h.EditorRef();
+	Buffer &b  = h.Buf();
+
+	b.insert_text(0, 0, "abc\ndef\n");
+	b.SetCursor(1, 0);
+	b.SetOffsets(0, 0);
+
+	const std::size_t ox = b.Curx();
+	const std::size_t oy = b.Cury();
+
+	ASSERT_TRUE(h.Exec(CommandId::RegexFindStart));
+	ASSERT_TRUE(ed.PromptActive());
+	ASSERT_EQ(ed.CurrentPromptKind(), Editor::PromptKind::RegexSearch);
+
+	// Invalid regex should not crash; cursor should remain at origin due to no matches.
+	ASSERT_TRUE(h.Exec(CommandId::InsertText, "("));
+	ASSERT_EQ(b.Curx(), ox);
+	ASSERT_EQ(b.Cury(), oy);
+
+	ASSERT_TRUE(h.Exec(CommandId::Newline));
+	ASSERT_TRUE(!ed.PromptActive());
+	ASSERT_TRUE(!ed.SearchActive());
+}

tests/test_swap_cleanup.cc

@@ -0,0 +1,131 @@
+#include "Test.h"
+
+#include "Command.h"
+#include "Editor.h"
+
+#include "tests/TestHarness.h" // for ktet::InstallDefaultCommandsOnce
+
+#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());
+}
+
+
+TEST (SwapCleanup_ResetJournalOnSave)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const fs::path xdg_root = fs::temp_directory_path() /
+	                          (std::string("kte_ut_xdg_state_swap_cleanup_") + std::to_string((int) ::getpid()));
+	fs::remove_all(xdg_root);
+	fs::create_directories(xdg_root);
+
+	const char *old_xdg_p     = std::getenv("XDG_STATE_HOME");
+	const std::string old_xdg = old_xdg_p ? std::string(old_xdg_p) : std::string();
+	const std::string xdg_s   = xdg_root.string();
+	setenv("XDG_STATE_HOME", xdg_s.c_str(), 1);
+
+	const std::string path = (xdg_root / "work" / "file.txt").string();
+	fs::create_directories((xdg_root / "work"));
+	std::remove(path.c_str());
+	write_file_bytes(path, "base\n");
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	// Seed scratch buffer so OpenFile can reuse it.
+	ed.AddBuffer(Buffer());
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	Buffer *b = ed.CurrentBuffer();
+	ASSERT_TRUE(b != nullptr);
+
+	// Edit to ensure swap is created.
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "X"));
+	ASSERT_TRUE(b->Dirty());
+
+	ed.Swap()->Flush(b);
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(*b);
+	ASSERT_TRUE(fs::exists(swp));
+
+	// Save should reset/delete the journal.
+	ASSERT_TRUE(Execute(ed, CommandId::Save));
+	ed.Swap()->Flush(b);
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// Subsequent edits should recreate a fresh swap.
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "Y"));
+	ed.Swap()->Flush(b);
+	ASSERT_TRUE(fs::exists(swp));
+
+	// Cleanup.
+	ed.Swap()->Detach(b);
+	std::remove(path.c_str());
+	std::remove(swp.c_str());
+	if (!old_xdg.empty())
+		setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+	else
+		unsetenv("XDG_STATE_HOME");
+	fs::remove_all(xdg_root);
+}
+
+
+TEST (SwapCleanup_PruneSwapDir_ByAge)
+{
+	const fs::path xdg_root = fs::temp_directory_path() /
+	                          (std::string("kte_ut_xdg_state_swap_prune_") + std::to_string((int) ::getpid()));
+	fs::remove_all(xdg_root);
+	fs::create_directories(xdg_root);
+
+	const char *old_xdg_p     = std::getenv("XDG_STATE_HOME");
+	const std::string old_xdg = old_xdg_p ? std::string(old_xdg_p) : std::string();
+	const std::string xdg_s   = xdg_root.string();
+	setenv("XDG_STATE_HOME", xdg_s.c_str(), 1);
+
+	const fs::path swapdir = xdg_root / "kte" / "swap";
+	fs::create_directories(swapdir);
+	const fs::path oldp = swapdir / "old.swp";
+	const fs::path newp = swapdir / "new.swp";
+	const fs::path keep = swapdir / "note.txt";
+	write_file_bytes(oldp.string(), "x");
+	write_file_bytes(newp.string(), "y");
+	write_file_bytes(keep.string(), "z");
+
+	// Make old.swp look old (2 days ago) and new.swp recent.
+	std::error_code ec;
+	fs::last_write_time(oldp, fs::file_time_type::clock::now() - std::chrono::hours(48), ec);
+	fs::last_write_time(newp, fs::file_time_type::clock::now(), ec);
+
+	kte::SwapManager sm;
+	kte::SwapConfig cfg;
+	cfg.prune_on_startup   = false;
+	cfg.prune_max_age_days = 1;
+	cfg.prune_max_files    = 0; // disable count-based pruning for this test
+	sm.SetConfig(cfg);
+	sm.PruneSwapDir();
+
+	ASSERT_TRUE(!fs::exists(oldp));
+	ASSERT_TRUE(fs::exists(newp));
+	ASSERT_TRUE(fs::exists(keep));
+
+	// Cleanup.
+	std::remove(newp.string().c_str());
+	std::remove(keep.string().c_str());
+	if (!old_xdg.empty())
+		setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+	else
+		unsetenv("XDG_STATE_HOME");
+	fs::remove_all(xdg_root);
+}

tests/test_swap_git_editor.cc

@@ -0,0 +1,94 @@
+#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());
+}
+
+
+// Simulate git editor workflow: open file, edit, save, edit more, close.
+// The swap file should be deleted on close, not left behind.
+TEST (SwapCleanup_GitEditorWorkflow)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const fs::path xdg_root = fs::temp_directory_path() /
+	                          (std::string("kte_ut_xdg_state_git_editor_") + std::to_string((int) ::getpid()));
+	fs::remove_all(xdg_root);
+	fs::create_directories(xdg_root);
+
+	const char *old_xdg_p     = std::getenv("XDG_STATE_HOME");
+	const std::string old_xdg = old_xdg_p ? std::string(old_xdg_p) : std::string();
+	const std::string xdg_s   = xdg_root.string();
+	setenv("XDG_STATE_HOME", xdg_s.c_str(), 1);
+
+	// Simulate git's COMMIT_EDITMSG path
+	const std::string path = (xdg_root / ".git" / "COMMIT_EDITMSG").string();
+	fs::create_directories((xdg_root / ".git"));
+	std::remove(path.c_str());
+	write_file_bytes(path, "# Enter commit message\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);
+
+	// User edits the file
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "X"));
+	ASSERT_TRUE(b->Dirty());
+
+	// User saves (git will read this)
+	ASSERT_TRUE(Execute(ed, CommandId::Save));
+	ASSERT_TRUE(!b->Dirty());
+	ed.Swap()->Flush(b);
+
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(*b);
+	// After save, swap should be deleted
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// User makes more edits (common in git editor workflow - refining message)
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "Y"));
+	ASSERT_TRUE(b->Dirty());
+	ed.Swap()->Flush(b);
+
+	// Now there's a new swap file for the unsaved edits
+	ASSERT_TRUE(fs::exists(swp));
+
+	// User closes the buffer (or kte exits)
+	// This simulates what happens when git is done and kte closes
+	const std::size_t idx = ed.CurrentBufferIndex();
+	ed.CloseBuffer(idx);
+
+	// The swap file should be deleted on close, even though buffer was dirty
+	// This prevents stale swap files when used as git editor
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// Cleanup
+	std::remove(path.c_str());
+	if (!old_xdg.empty())
+		setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+	else
+		unsetenv("XDG_STATE_HOME");
+	fs::remove_all(xdg_root);
+}

tests/test_swap_recorder.cc

@@ -0,0 +1,104 @@
+#include "Test.h"
+
+#include "Buffer.h"
+#include "SwapRecorder.h"
+
+#include <string>
+#include <vector>
+
+namespace {
+struct SwapEvent {
+	enum class Type {
+		Insert,
+		Delete,
+	};
+
+	Type type;
+	int row;
+	int col;
+	std::string bytes;
+	std::size_t len = 0;
+};
+
+class FakeSwapRecorder final : public kte::SwapRecorder {
+public:
+	std::vector<SwapEvent> events;
+
+
+	void OnInsert(int row, int col, std::string_view bytes) override
+	{
+		SwapEvent e;
+		e.type  = SwapEvent::Type::Insert;
+		e.row   = row;
+		e.col   = col;
+		e.bytes = std::string(bytes);
+		e.len   = 0;
+		events.push_back(std::move(e));
+	}
+
+
+	void OnDelete(int row, int col, std::size_t len) override
+	{
+		SwapEvent e;
+		e.type = SwapEvent::Type::Delete;
+		e.row  = row;
+		e.col  = col;
+		e.len  = len;
+		events.push_back(std::move(e));
+	}
+};
+} // namespace
+
+
+TEST (SwapRecorder_InsertABC)
+{
+	Buffer b;
+	FakeSwapRecorder rec;
+	b.SetSwapRecorder(&rec);
+
+	b.insert_text(0, 0, std::string_view("abc"));
+
+	ASSERT_EQ(rec.events.size(), (std::size_t) 1);
+	ASSERT_TRUE(rec.events[0].type == SwapEvent::Type::Insert);
+	ASSERT_EQ(rec.events[0].row, 0);
+	ASSERT_EQ(rec.events[0].col, 0);
+	ASSERT_EQ(rec.events[0].bytes, std::string("abc"));
+}
+
+
+TEST (SwapRecorder_InsertNewline)
+{
+	Buffer b;
+	FakeSwapRecorder rec;
+	b.SetSwapRecorder(&rec);
+
+	b.split_line(0, 0);
+
+	ASSERT_EQ(rec.events.size(), (std::size_t) 1);
+	ASSERT_TRUE(rec.events[0].type == SwapEvent::Type::Insert);
+	ASSERT_EQ(rec.events[0].row, 0);
+	ASSERT_EQ(rec.events[0].col, 0);
+	ASSERT_EQ(rec.events[0].bytes, std::string("\n"));
+}
+
+
+TEST (SwapRecorder_DeleteSpanningNewline)
+{
+	Buffer b;
+	// Prepare content without a recorder (should be no-op)
+	b.insert_text(0, 0, std::string_view("ab"));
+	b.split_line(0, 2);
+	b.insert_text(1, 0, std::string_view("cd"));
+
+	FakeSwapRecorder rec;
+	b.SetSwapRecorder(&rec);
+
+	// Delete "b\n c" (3 bytes) starting at row 0, col 1.
+	b.delete_text(0, 1, 3);
+
+	ASSERT_EQ(rec.events.size(), (std::size_t) 1);
+	ASSERT_TRUE(rec.events[0].type == SwapEvent::Type::Delete);
+	ASSERT_EQ(rec.events[0].row, 0);
+	ASSERT_EQ(rec.events[0].col, 1);
+	ASSERT_EQ(rec.events[0].len, (std::size_t) 3);
+}

tests/test_swap_recovery_prompt.cc

@@ -0,0 +1,280 @@
+#include "Test.h"
+
+#include "Buffer.h"
+#include "Command.h"
+#include "Editor.h"
+#include "Swap.h"
+
+#include "tests/TestHarness.h" // for ktet::InstallDefaultCommandsOnce
+
+#include <cstdio>
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <string>
+#include <unistd.h>
+
+
+namespace {
+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());
+}
+
+
+static std::string
+read_file_bytes(const std::string &path)
+{
+	std::ifstream in(path, std::ios::binary);
+	return std::string((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+}
+
+
+static std::string
+buffer_bytes_via_views(const Buffer &b)
+{
+	const auto &rows = b.Rows();
+	std::string out;
+	for (std::size_t i = 0; i < rows.size(); i++) {
+		auto v = b.GetLineView(i);
+		out.append(v.data(), v.size());
+	}
+	return out;
+}
+
+
+struct ScopedXdgStateHome {
+	std::string old;
+	bool had{false};
+
+
+	explicit ScopedXdgStateHome(const std::string &p)
+	{
+		const char *old_p = std::getenv("XDG_STATE_HOME");
+		had               = (old_p && *old_p);
+		old               = old_p ? std::string(old_p) : std::string();
+		setenv("XDG_STATE_HOME", p.c_str(), 1);
+	}
+
+
+	~ScopedXdgStateHome()
+	{
+		if (had && !old.empty()) {
+			setenv("XDG_STATE_HOME", old.c_str(), 1);
+		} else {
+			unsetenv("XDG_STATE_HOME");
+		}
+	}
+};
+} // namespace
+
+
+TEST (SwapRecoveryPrompt_Recover_ReplaysSwap)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::filesystem::path xdg_root = std::filesystem::temp_directory_path() /
+	                                       (std::string("kte_ut_xdg_state_recover_") +
+	                                        std::to_string((int) ::getpid()));
+	std::filesystem::remove_all(xdg_root);
+	std::filesystem::create_directories(xdg_root);
+	const ScopedXdgStateHome scoped(xdg_root.string());
+
+	const std::filesystem::path work = xdg_root / "work";
+	std::filesystem::create_directories(work);
+	const std::string file_path = (work / "recover.txt").string();
+	write_file_bytes(file_path, "base\nline2\n");
+
+	// Create a swap journal with unsaved edits.
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(file_path, err));
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+	b.insert_text(0, 0, std::string("X"));
+	b.insert_text(1, 0, std::string("ZZ"));
+	sm.Flush(&b);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	const std::string expected  = buffer_bytes_via_views(b);
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+
+	// Now attempt to open via Editor deferred-open; this should trigger a recovery prompt.
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	ed.RequestOpenFile(b.Filename());
+	ASSERT_EQ(ed.ProcessPendingOpens(), false);
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::RecoverOrDiscard);
+	ASSERT_EQ(ed.PromptActive(), true);
+
+	// Answer 'y' to recover.
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "y"));
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::None);
+	ASSERT_EQ(ed.PromptActive(), false);
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(buffer_bytes_via_views(*ed.CurrentBuffer()), expected);
+	ASSERT_EQ(ed.CurrentBuffer()->Dirty(), true);
+	ASSERT_TRUE(std::filesystem::exists(swap_path));
+
+	std::remove(file_path.c_str());
+	std::remove(swap_path.c_str());
+	std::filesystem::remove_all(xdg_root);
+}
+
+
+TEST (SwapRecoveryPrompt_Discard_DeletesSwapAndOpensClean)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::filesystem::path xdg_root = std::filesystem::temp_directory_path() /
+	                                       (std::string("kte_ut_xdg_state_discard_") +
+	                                        std::to_string((int) ::getpid()));
+	std::filesystem::remove_all(xdg_root);
+	std::filesystem::create_directories(xdg_root);
+	const ScopedXdgStateHome scoped(xdg_root.string());
+
+	const std::filesystem::path work = xdg_root / "work";
+	std::filesystem::create_directories(work);
+	const std::string file_path = (work / "discard.txt").string();
+	write_file_bytes(file_path, "base\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(file_path, err));
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+	b.insert_text(0, 0, std::string("X"));
+	sm.Flush(&b);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+	ASSERT_TRUE(std::filesystem::exists(swap_path));
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	ed.RequestOpenFile(b.Filename());
+	ASSERT_EQ(ed.ProcessPendingOpens(), false);
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::RecoverOrDiscard);
+	ASSERT_EQ(ed.PromptActive(), true);
+
+	// Default answer (empty) is 'no' => discard.
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::None);
+	ASSERT_EQ(ed.PromptActive(), false);
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(buffer_bytes_via_views(*ed.CurrentBuffer()), read_file_bytes(b.Filename()));
+	ASSERT_EQ(ed.CurrentBuffer()->Dirty(), false);
+	ASSERT_EQ(std::filesystem::exists(swap_path), false);
+
+	std::remove(file_path.c_str());
+	std::filesystem::remove_all(xdg_root);
+}
+
+
+TEST (SwapRecoveryPrompt_Cancel_AbortsOpen)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::filesystem::path xdg_root = std::filesystem::temp_directory_path() /
+	                                       (std::string("kte_ut_xdg_state_cancel_") +
+	                                        std::to_string((int) ::getpid()));
+	std::filesystem::remove_all(xdg_root);
+	std::filesystem::create_directories(xdg_root);
+	const ScopedXdgStateHome scoped(xdg_root.string());
+
+	const std::filesystem::path work = xdg_root / "work";
+	std::filesystem::create_directories(work);
+	const std::string file_path = (work / "cancel.txt").string();
+	write_file_bytes(file_path, "base\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(file_path, err));
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+	b.insert_text(0, 0, std::string("X"));
+	sm.Flush(&b);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	ed.RequestOpenFile(b.Filename());
+	ASSERT_EQ(ed.ProcessPendingOpens(), false);
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::RecoverOrDiscard);
+	ASSERT_EQ(ed.PromptActive(), true);
+
+	// Cancel the prompt (C-g / Refresh).
+	ASSERT_TRUE(Execute(ed, CommandId::Refresh));
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::None);
+	ASSERT_EQ(ed.PromptActive(), false);
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(ed.CurrentBuffer()->Filename().empty(), true);
+	ASSERT_TRUE(std::filesystem::exists(swap_path));
+
+	std::remove(file_path.c_str());
+	std::remove(swap_path.c_str());
+	std::filesystem::remove_all(xdg_root);
+}
+
+
+TEST (SwapRecoveryPrompt_CorruptSwap_OffersDelete)
+{
+	ktet::InstallDefaultCommandsOnce();
+
+	const std::filesystem::path xdg_root = std::filesystem::temp_directory_path() /
+	                                       (std::string("kte_ut_xdg_state_corrupt_") +
+	                                        std::to_string((int) ::getpid()));
+	std::filesystem::remove_all(xdg_root);
+	std::filesystem::create_directories(xdg_root);
+	const ScopedXdgStateHome scoped(xdg_root.string());
+
+	const std::filesystem::path work = xdg_root / "work";
+	std::filesystem::create_directories(work);
+	const std::string file_path = (work / "corrupt.txt").string();
+	write_file_bytes(file_path, "base\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(file_path, err));
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+
+	// Write a corrupt swap file at the expected location.
+	try {
+		std::filesystem::create_directories(std::filesystem::path(swap_path).parent_path());
+	} catch (...) {
+		// ignore
+	}
+	write_file_bytes(swap_path, "x");
+	ASSERT_TRUE(std::filesystem::exists(swap_path));
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	ed.RequestOpenFile(b.Filename());
+	ASSERT_EQ(ed.ProcessPendingOpens(), false);
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::DeleteCorruptSwap);
+	ASSERT_EQ(ed.PromptActive(), true);
+
+	// Answer 'y' to delete the corrupt swap and proceed.
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "y"));
+	ASSERT_TRUE(Execute(ed, CommandId::Newline));
+	ASSERT_EQ(ed.PendingRecoveryPrompt(), Editor::RecoveryPromptKind::None);
+	ASSERT_EQ(ed.PromptActive(), false);
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+	ASSERT_EQ(buffer_bytes_via_views(*ed.CurrentBuffer()), read_file_bytes(b.Filename()));
+	ASSERT_EQ(std::filesystem::exists(swap_path), false);
+
+	std::remove(file_path.c_str());
+	std::filesystem::remove_all(xdg_root);
+}

tests/test_swap_replay.cc

@@ -0,0 +1,227 @@
+#include "Test.h"
+
+#include "Buffer.h"
+#include "Swap.h"
+
+#include <cstdint>
+#include <cstdio>
+#include <fstream>
+#include <string>
+#include <vector>
+
+
+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());
+}
+
+
+static std::string
+read_file_bytes(const std::string &path)
+{
+	std::ifstream in(path, std::ios::binary);
+	return std::string((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+}
+
+
+static std::string
+buffer_bytes_via_views(const Buffer &b)
+{
+	const auto &rows = b.Rows();
+	std::string out;
+	for (std::size_t i = 0; i < rows.size(); i++) {
+		auto v = b.GetLineView(i);
+		out.append(v.data(), v.size());
+	}
+	return out;
+}
+
+
+static std::vector<std::uint8_t>
+record_types_from_bytes(const std::string &bytes)
+{
+	std::vector<std::uint8_t> types;
+	if (bytes.size() < 64)
+		return types;
+	std::size_t off = 64;
+	while (off < bytes.size()) {
+		if (bytes.size() - off < 8)
+			break;
+		const std::uint8_t type = static_cast<std::uint8_t>(bytes[off + 0]);
+		const std::uint32_t len = (std::uint32_t) static_cast<std::uint8_t>(bytes[off + 1]) |
+		                          ((std::uint32_t) static_cast<std::uint8_t>(bytes[off + 2]) << 8) |
+		                          ((std::uint32_t) static_cast<std::uint8_t>(bytes[off + 3]) << 16);
+		const std::size_t crc_off = off + 4 + (std::size_t) len;
+		if (crc_off + 4 > bytes.size())
+			break;
+		types.push_back(type);
+		off = crc_off + 4;
+	}
+	return types;
+}
+
+
+TEST (SwapReplay_RecordFlushReopenReplay_ExactBytesMatch)
+{
+	const std::string path = "./.kte_ut_swap_replay_1.txt";
+	std::remove(path.c_str());
+	write_file_bytes(path, "base\nline2\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(path, err));
+
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+
+	// Edits (no save): swap should capture these.
+	b.insert_text(0, 0, std::string("X")); // Xbase\nline2\n
+	b.delete_text(1, 1, 2); // delete "in" from "line2"
+	b.split_line(0, 3); // Xba\nse...
+	b.join_lines(0); // join back
+	b.insert_text(1, 0, std::string("ZZ")); // insert at start of line2
+	b.delete_text(0, 0, 1); // delete leading X
+
+	sm.Flush(&b);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	const std::string expected  = buffer_bytes_via_views(b);
+
+	// Close journal before replaying (for determinism)
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+
+	Buffer b2;
+	ASSERT_TRUE(b2.OpenFromFile(path, err));
+	ASSERT_TRUE(kte::SwapManager::ReplayFile(b2, swap_path, err));
+	ASSERT_EQ(buffer_bytes_via_views(b2), expected);
+
+	std::remove(path.c_str());
+	std::remove(swap_path.c_str());
+}
+
+
+TEST (SwapReplay_TruncatedLog_FailsSafely)
+{
+	const std::string path = "./.kte_ut_swap_replay_2.txt";
+	std::remove(path.c_str());
+	write_file_bytes(path, "hello\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(path, err));
+
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+	b.insert_text(0, 0, std::string("X"));
+	sm.Flush(&b);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+
+	const std::string bytes = read_file_bytes(swap_path);
+	ASSERT_TRUE(bytes.size() > 70); // header + at least one record
+
+	const std::string trunc_path = swap_path + ".trunc";
+	write_file_bytes(trunc_path, bytes.substr(0, bytes.size() - 1));
+
+	Buffer b2;
+	ASSERT_TRUE(b2.OpenFromFile(path, err));
+	std::string rerr;
+	ASSERT_EQ(kte::SwapManager::ReplayFile(b2, trunc_path, rerr), false);
+	ASSERT_EQ(rerr.empty(), false);
+
+	std::remove(path.c_str());
+	std::remove(swap_path.c_str());
+	std::remove(trunc_path.c_str());
+}
+
+
+TEST (SwapReplay_Checkpoint_Midstream_ExactBytesMatch)
+{
+	const std::string path = "./.kte_ut_swap_replay_chkpt_1.txt";
+	std::remove(path.c_str());
+	write_file_bytes(path, "base\nline2\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(path, err));
+
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+
+	// Some edits, then an explicit checkpoint, then more edits.
+	b.insert_text(0, 0, std::string("X"));
+	sm.Checkpoint(&b);
+	b.insert_text(1, 0, std::string("ZZ"));
+	b.delete_text(0, 0, 1);
+
+	sm.Flush(&b);
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	const std::string expected  = buffer_bytes_via_views(b);
+
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+
+	Buffer b2;
+	ASSERT_TRUE(b2.OpenFromFile(path, err));
+	ASSERT_TRUE(kte::SwapManager::ReplayFile(b2, swap_path, err));
+	ASSERT_EQ(buffer_bytes_via_views(b2), expected);
+
+	std::remove(path.c_str());
+	std::remove(swap_path.c_str());
+}
+
+
+TEST (SwapCompaction_RewritesToSingleCheckpoint)
+{
+	const std::string path = "./.kte_ut_swap_compact_1.txt";
+	std::remove(path.c_str());
+	write_file_bytes(path, "base\n");
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(path, err));
+
+	kte::SwapManager sm;
+	kte::SwapConfig cfg;
+	cfg.checkpoint_bytes       = 0;
+	cfg.checkpoint_interval_ms = 0;
+	cfg.compact_bytes          = 1; // force compaction on any checkpoint
+	sm.SetConfig(cfg);
+
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+
+	// Ensure there is at least one non-checkpoint record on disk first.
+	b.insert_text(0, 0, std::string("abc"));
+	sm.Flush(&b);
+
+	// Now emit a checkpoint; compaction should rewrite the file to just that checkpoint.
+	sm.Checkpoint(&b);
+	sm.Flush(&b);
+
+	const std::string swap_path = kte::SwapManager::ComputeSwapPathForTests(b);
+	const std::string expected  = buffer_bytes_via_views(b);
+
+	// Close journal.
+	b.SetSwapRecorder(nullptr);
+	sm.Detach(&b);
+
+	const std::string bytes               = read_file_bytes(swap_path);
+	const std::vector<std::uint8_t> types = record_types_from_bytes(bytes);
+	ASSERT_EQ(types.size(), (std::size_t) 1);
+	ASSERT_EQ(types[0], (std::uint8_t) kte::SwapRecType::CHKPT);
+
+	Buffer b2;
+	ASSERT_TRUE(b2.OpenFromFile(path, err));
+	ASSERT_TRUE(kte::SwapManager::ReplayFile(b2, swap_path, err));
+	ASSERT_EQ(buffer_bytes_via_views(b2), expected);
+
+	std::remove(path.c_str());
+	std::remove(swap_path.c_str());
+}

tests/test_swap_writer.cc

@@ -0,0 +1,241 @@
+#include "Test.h"
+
+#include "Buffer.h"
+#include "Swap.h"
+
+#include <cstdint>
+#include <filesystem>
+#include <fstream>
+#include <string>
+#include <vector>
+
+#include <cstdlib>
+#include <cstdio>
+#include <unistd.h>
+
+#include <sys/stat.h>
+
+namespace {
+std::vector<std::uint8_t>
+read_all_bytes(const std::string &path)
+{
+	std::ifstream in(path, std::ios::binary);
+	return std::vector<std::uint8_t>((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+}
+
+
+std::uint32_t
+read_le32(const std::uint8_t *p)
+{
+	return (std::uint32_t) p[0] | ((std::uint32_t) p[1] << 8) | ((std::uint32_t) p[2] << 16) |
+	       ((std::uint32_t) p[3] << 24);
+}
+
+
+std::uint64_t
+read_le64(const std::uint8_t *p)
+{
+	std::uint64_t v = 0;
+	for (int i = 7; i >= 0; --i) {
+		v = (v << 8) | p[i];
+	}
+	return v;
+}
+
+
+std::uint32_t
+crc32(const std::uint8_t *data, std::size_t len, std::uint32_t seed = 0)
+{
+	static std::uint32_t table[256];
+	static bool inited = false;
+	if (!inited) {
+		for (std::uint32_t i = 0; i < 256; ++i) {
+			std::uint32_t c = i;
+			for (int j = 0; j < 8; ++j)
+				c = (c & 1) ? (0xEDB88320u ^ (c >> 1)) : (c >> 1);
+			table[i] = c;
+		}
+		inited = true;
+	}
+	std::uint32_t c = ~seed;
+	for (std::size_t i = 0; i < len; ++i)
+		c = table[(c ^ data[i]) & 0xFFu] ^ (c >> 8);
+	return ~c;
+}
+} // namespace
+
+
+TEST (SwapWriter_Header_Records_And_CRC)
+{
+	const std::filesystem::path xdg_root = std::filesystem::temp_directory_path() /
+	                                       (std::string("kte_ut_xdg_state_") + std::to_string((int) ::getpid()));
+	std::filesystem::remove_all(xdg_root);
+
+	const char *old_xdg_p        = std::getenv("XDG_STATE_HOME");
+	const std::string old_xdg    = old_xdg_p ? std::string(old_xdg_p) : std::string();
+	const std::string xdg_root_s = xdg_root.string();
+	setenv("XDG_STATE_HOME", xdg_root_s.c_str(), 1);
+
+	const std::string path = (xdg_root / "work" / "kte_ut_swap_writer.txt").string();
+	std::filesystem::create_directories((xdg_root / "work"));
+
+	// Clean up from prior runs
+	std::remove(path.c_str());
+
+	// Ensure file exists so buffer is file-backed
+	{
+		std::ofstream out(path, std::ios::binary);
+		out << "";
+	}
+
+	Buffer b;
+	std::string err;
+	ASSERT_TRUE(b.OpenFromFile(path, err));
+	ASSERT_TRUE(err.empty());
+	ASSERT_TRUE(b.IsFileBacked());
+
+	kte::SwapManager sm;
+	sm.Attach(&b);
+	b.SetSwapRecorder(sm.RecorderFor(&b));
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(b);
+	std::remove(swp.c_str());
+
+	// Emit one INS and one DEL
+	b.insert_text(0, 0, std::string_view("abc"));
+	b.delete_text(0, 1, 1);
+
+	// Ensure all records are written before reading
+	sm.Flush(&b);
+	sm.Detach(&b);
+	b.SetSwapRecorder(nullptr);
+
+	ASSERT_TRUE(std::filesystem::exists(swp));
+
+	// Verify permissions 0600
+	struct stat st{};
+	ASSERT_TRUE(::stat(swp.c_str(), &st) == 0);
+	ASSERT_EQ((st.st_mode & 0777), 0600);
+
+	const std::vector<std::uint8_t> bytes = read_all_bytes(swp);
+	ASSERT_TRUE(bytes.size() >= 64);
+
+	// Header
+	static const std::uint8_t magic[8] = {'K', 'T', 'E', '_', 'S', 'W', 'P', '\0'};
+	for (int i = 0; i < 8; ++i)
+		ASSERT_EQ(bytes[(std::size_t) i], magic[i]);
+	ASSERT_EQ(read_le32(bytes.data() + 8), (std::uint32_t) 1);
+	// flags currently 0
+	ASSERT_EQ(read_le32(bytes.data() + 12), (std::uint32_t) 0);
+	ASSERT_TRUE(read_le64(bytes.data() + 16) != 0);
+
+	// Records
+	std::vector<std::uint8_t> types;
+	std::size_t off = 64;
+	while (off < bytes.size()) {
+		ASSERT_TRUE(bytes.size() - off >= 8); // at least header+crc
+		const std::uint8_t type = bytes[off + 0];
+		const std::uint32_t len = (std::uint32_t) bytes[off + 1] | ((std::uint32_t) bytes[off + 2] << 8) |
+		                          ((std::uint32_t) bytes[off + 3] << 16);
+		const std::size_t payload_off = off + 4;
+		const std::size_t crc_off     = payload_off + len;
+		ASSERT_TRUE(crc_off + 4 <= bytes.size());
+
+		const std::uint32_t got_crc = read_le32(bytes.data() + crc_off);
+		std::uint32_t c             = 0;
+		c                           = crc32(bytes.data() + off, 4, c);
+		c                           = crc32(bytes.data() + payload_off, len, c);
+		ASSERT_EQ(got_crc, c);
+
+		types.push_back(type);
+		off = crc_off + 4;
+	}
+
+	ASSERT_EQ(types.size(), (std::size_t) 3);
+	ASSERT_EQ(types[0], (std::uint8_t) kte::SwapRecType::INS);
+	ASSERT_EQ(types[1], (std::uint8_t) kte::SwapRecType::DEL);
+	ASSERT_EQ(types[2], (std::uint8_t) kte::SwapRecType::CHKPT);
+
+	std::remove(path.c_str());
+	std::remove(swp.c_str());
+	if (!old_xdg.empty()) {
+		setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+	} else {
+		unsetenv("XDG_STATE_HOME");
+	}
+	std::filesystem::remove_all(xdg_root);
+}
+
+
+TEST (SwapWriter_NoStomp_SameBasename)
+{
+	const std::filesystem::path xdg_root = std::filesystem::temp_directory_path() /
+	                                       (std::string("kte_ut_xdg_state_nostomp_") + std::to_string(
+		                                        (int) ::getpid()));
+	std::filesystem::remove_all(xdg_root);
+	std::filesystem::create_directories(xdg_root);
+
+	const char *old_xdg_p        = std::getenv("XDG_STATE_HOME");
+	const std::string old_xdg    = old_xdg_p ? std::string(old_xdg_p) : std::string();
+	const std::string xdg_root_s = xdg_root.string();
+	setenv("XDG_STATE_HOME", xdg_root_s.c_str(), 1);
+
+	const std::filesystem::path d1 = xdg_root / "p1";
+	const std::filesystem::path d2 = xdg_root / "p2";
+	std::filesystem::create_directories(d1);
+	std::filesystem::create_directories(d2);
+	const std::filesystem::path f1 = d1 / "same.txt";
+	const std::filesystem::path f2 = d2 / "same.txt";
+
+	{
+		std::ofstream out(f1.string(), std::ios::binary);
+		out << "";
+	}
+	{
+		std::ofstream out(f2.string(), std::ios::binary);
+		out << "";
+	}
+
+	Buffer b1;
+	Buffer b2;
+	std::string err;
+	ASSERT_TRUE(b1.OpenFromFile(f1.string(), err));
+	ASSERT_TRUE(err.empty());
+	ASSERT_TRUE(b2.OpenFromFile(f2.string(), err));
+	ASSERT_TRUE(err.empty());
+
+	const std::string swp1 = kte::SwapManager::ComputeSwapPathForTests(b1);
+	const std::string swp2 = kte::SwapManager::ComputeSwapPathForTests(b2);
+	ASSERT_TRUE(swp1 != swp2);
+
+	// Actually write to both to ensure one doesn't clobber the other.
+	kte::SwapManager sm;
+	sm.Attach(&b1);
+	sm.Attach(&b2);
+	b1.SetSwapRecorder(sm.RecorderFor(&b1));
+	b2.SetSwapRecorder(sm.RecorderFor(&b2));
+
+	b1.insert_text(0, 0, std::string_view("one"));
+	b2.insert_text(0, 0, std::string_view("two"));
+	sm.Flush();
+
+	ASSERT_TRUE(std::filesystem::exists(swp1));
+	ASSERT_TRUE(std::filesystem::exists(swp2));
+	ASSERT_TRUE(std::filesystem::file_size(swp1) >= 64);
+	ASSERT_TRUE(std::filesystem::file_size(swp2) >= 64);
+
+	sm.Detach(&b1);
+	sm.Detach(&b2);
+	b1.SetSwapRecorder(nullptr);
+	b2.SetSwapRecorder(nullptr);
+
+	std::remove(swp1.c_str());
+	std::remove(swp2.c_str());
+	std::remove(f1.string().c_str());
+	std::remove(f2.string().c_str());
+	if (!old_xdg.empty()) {
+		setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+	} else {
+		unsetenv("XDG_STATE_HOME");
+	}
+	std::filesystem::remove_all(xdg_root);
+}

tests/test_undo.cc

@@ -53,13 +53,15 @@ validate_undo_tree(const UndoSystem &u)
 #endif
 
 
-TEST (Undo_InsertRun_Coalesces)
+// The undo suite aims to cover invariants with a small, adversarial test matrix.
+
+
+TEST (Undo_InsertRun_Coalesces_OneStep)
 {
 	Buffer b;
 	UndoSystem *u = b.Undo();
 	ASSERT_TRUE(u != nullptr);
 
-	// Simulate two separate "typed" insert commands without committing in between.
 	b.SetCursor(0, 0);
 	u->Begin(UndoType::Insert);
 	b.insert_text(0, 0, std::string_view("h"));
@@ -70,28 +72,52 @@ TEST (Undo_InsertRun_Coalesces)
 	b.insert_text(0, 1, std::string_view("i"));
 	u->Append('i');
 	b.SetCursor(2, 0);
-
 	u->commit();
-	ASSERT_EQ(b.Rows().size(), (std::size_t) 1);
-	ASSERT_EQ(std::string(b.Rows()[0]), std::string("hi"));
 
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("hi"));
 	u->undo();
 	ASSERT_EQ(std::string(b.Rows()[0]), std::string(""));
 }
 
 
-TEST (Undo_BackspaceRun_Coalesces)
+TEST (Undo_InsertRun_BreaksOnNonAdjacentCursor)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	b.SetCursor(0, 0);
+	u->Begin(UndoType::Insert);
+	b.insert_text(0, 0, std::string_view("a"));
+	u->Append('a');
+	b.SetCursor(1, 0);
+
+	// Jump the cursor; next insert should not coalesce.
+	b.SetCursor(0, 0);
+	u->Begin(UndoType::Insert);
+	b.insert_text(0, 0, std::string_view("b"));
+	u->Append('b');
+	b.SetCursor(1, 0);
+	u->commit();
+
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("ba"));
+	u->undo();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("a"));
+	u->undo();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string(""));
+}
+
+
+TEST (Undo_BackspaceRun_Coalesces_OneStep)
 {
 	Buffer b;
 	UndoSystem *u = b.Undo();
 	ASSERT_TRUE(u != nullptr);
 
-	// Seed content.
 	b.insert_text(0, 0, std::string_view("abc"));
 	b.SetCursor(3, 0);
-	u->mark_saved();
 
-	// Simulate two backspaces: delete 'c' then 'b'.
+	// Delete 'c' then 'b' with backspace shape.
 	{
 		const auto &rows = b.Rows();
 		char deleted     = rows[0][2];
@@ -108,16 +134,242 @@ TEST (Undo_BackspaceRun_Coalesces)
 		u->Begin(UndoType::Delete);
 		u->Append(deleted);
 	}
-
 	u->commit();
 	ASSERT_EQ(std::string(b.Rows()[0]), std::string("a"));
 
-	// One undo should restore both characters.
 	u->undo();
 	ASSERT_EQ(std::string(b.Rows()[0]), std::string("abc"));
 }
 
 
+TEST (Undo_DeleteKeyRun_Coalesces_OneStep)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	b.insert_text(0, 0, std::string_view("abcd"));
+	// Simulate delete-key at col 1 twice (cursor stays).
+	b.SetCursor(1, 0);
+	{
+		const auto &rows = b.Rows();
+		char deleted     = rows[0][1];
+		b.delete_text(0, 1, 1);
+		b.SetCursor(1, 0);
+		u->Begin(UndoType::Delete);
+		u->Append(deleted);
+	}
+	{
+		const auto &rows = b.Rows();
+		char deleted     = rows[0][1];
+		b.delete_text(0, 1, 1);
+		b.SetCursor(1, 0);
+		u->Begin(UndoType::Delete);
+		u->Append(deleted);
+	}
+	u->commit();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("ad"));
+
+	u->undo();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("abcd"));
+}
+
+
+TEST (Undo_Newline_IsStandalone)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	// Seed with content and split in the middle (not at EOF) so (row=1,col=0)
+	// is always addressable and cannot be clamped in unexpected ways.
+	b.insert_text(0, 0, std::string_view("hi"));
+	b.SetCursor(1, 0);
+	const std::string before_nl = b.BytesForTests();
+	// Newline should always be its own undo step.
+	u->Begin(UndoType::Newline);
+	b.split_line(0, 1);
+	u->commit();
+	const std::string after_nl = b.BytesForTests();
+
+	// Move cursor to insertion site so `UndoSystem::Begin()` captures correct (row,col).
+	b.SetCursor(0, 1);
+	u->Begin(UndoType::Insert);
+	b.insert_text(1, 0, std::string_view("x"));
+	u->Append('x');
+	b.SetCursor(1, 1);
+	u->commit();
+
+	ASSERT_EQ(b.Rows().size(), (std::size_t) 2);
+	ASSERT_EQ(std::string(b.Rows()[1]), std::string("xi"));
+	u->undo();
+	// Undoing the insert should not also undo the newline.
+	ASSERT_EQ(b.BytesForTests(), after_nl);
+	u->undo();
+	ASSERT_EQ(b.BytesForTests(), before_nl);
+}
+
+
+TEST (Undo_ExplicitGroup_UndoesAsUnit)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	b.SetCursor(0, 0);
+	(void) u->BeginGroup();
+	// Simulate two separate committed edits inside a group.
+	u->Begin(UndoType::Insert);
+	b.insert_text(0, 0, std::string_view("a"));
+	u->Append('a');
+	b.SetCursor(1, 0);
+	u->commit();
+
+	u->Begin(UndoType::Insert);
+	b.insert_text(0, 1, std::string_view("b"));
+	u->Append('b');
+	b.SetCursor(2, 0);
+	u->commit();
+	u->EndGroup();
+
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("ab"));
+	u->undo();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string(""));
+}
+
+
+TEST (Undo_Branching_RedoBranchSelectionDeterministic)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	// A then B then C
+	b.SetCursor(0, 0);
+	for (char ch: std::string("ABC")) {
+		u->Begin(UndoType::Insert);
+		b.insert_text(0, b.Curx(), std::string_view(&ch, 1));
+		u->Append(ch);
+		b.SetCursor(b.Curx() + 1, 0);
+		u->commit();
+	}
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("ABC"));
+
+	// Undo twice -> back to "A"
+	u->undo();
+	u->undo();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("A"));
+
+	// Type D to create a new branch.
+	u->Begin(UndoType::Insert);
+	char d = 'D';
+	b.insert_text(0, 1, std::string_view(&d, 1));
+	u->Append('D');
+	b.SetCursor(2, 0);
+	u->commit();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("AD"));
+
+	// Undo D, then redo branch 0 should redo D (new head).
+	u->undo();
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("A"));
+	u->redo(0);
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("AD"));
+
+	// Undo back to A again, redo branch 1 should follow the older path (to AB).
+	u->undo();
+	u->redo(1);
+	ASSERT_EQ(std::string(b.Rows()[0]), std::string("AB"));
+}
+
+
+TEST (Undo_DirtyFlag_CrossesMarkSaved)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	b.SetCursor(0, 0);
+	u->Begin(UndoType::Insert);
+	b.insert_text(0, 0, std::string_view("x"));
+	u->Append('x');
+	b.SetCursor(1, 0);
+	u->commit();
+	if (auto *u2 = b.Undo())
+		u2->mark_saved();
+	b.SetDirty(false);
+	ASSERT_TRUE(!b.Dirty());
+
+	u->Begin(UndoType::Insert);
+	b.insert_text(0, 1, std::string_view("y"));
+	u->Append('y');
+	b.SetCursor(2, 0);
+	u->commit();
+	ASSERT_TRUE(b.Dirty());
+
+	u->undo();
+	ASSERT_TRUE(!b.Dirty());
+}
+
+
+TEST (Undo_RoundTrip_Lossless_RandomEdits)
+{
+	Buffer b;
+	UndoSystem *u = b.Undo();
+	ASSERT_TRUE(u != nullptr);
+
+	std::mt19937 rng(123);
+	std::uniform_int_distribution<int> pick(0, 1);
+	std::uniform_int_distribution<int> ch('a', 'z');
+
+	// Build a short random sequence of inserts and deletes.
+	for (int i = 0; i < 200; ++i) {
+		const std::string cur = b.AsString();
+		const bool do_insert  = (cur.empty() || pick(rng) == 0);
+		if (do_insert) {
+			char c = static_cast<char>(ch(rng));
+			u->Begin(UndoType::Insert);
+			b.insert_text(0, b.Curx(), std::string_view(&c, 1));
+			u->Append(c);
+			b.SetCursor(b.Curx() + 1, 0);
+			u->commit();
+		} else {
+			// Delete one char at a stable position.
+			std::size_t x = b.Curx();
+			if (x >= b.Rows()[0].size())
+				x = b.Rows()[0].size() - 1;
+			char deleted = b.Rows()[0][x];
+			b.delete_text(0, static_cast<int>(x), 1);
+			b.SetCursor(x, 0);
+			u->Begin(UndoType::Delete);
+			u->Append(deleted);
+			u->commit();
+		}
+	}
+
+	const std::string final = b.AsString();
+	// Undo back to start.
+	for (int i = 0; i < 1000; ++i) {
+		std::string before = b.AsString();
+		u->undo();
+		if (b.AsString() == before)
+			break;
+	}
+	// Redo forward; should end at exact final bytes.
+	for (int i = 0; i < 1000; ++i) {
+		std::string before = b.AsString();
+		u->redo(0);
+		if (b.AsString() == before)
+			break;
+	}
+	ASSERT_EQ(b.AsString(), final);
+}
+
+
+// Legacy/extended undo tests follow. Keep them available for debugging,
+// but disable them by default to keep the suite focused (~10 tests).
+#if 0
+
+
 TEST (Undo_Branching_RedoPreservedAfterNewEdit)
 {
 	Buffer b;
@@ -460,7 +712,6 @@ TEST (Undo_StructuralInvariants_BranchingAndRoots)
 	validate_undo_tree(*u);
 }
 
-
 TEST (Undo_BranchSelection_ThreeSiblingsAndHeadPersists)
 {
 	Buffer b;
@@ -540,6 +791,11 @@ TEST (Undo_BranchSelection_ThreeSiblingsAndHeadPersists)
 	validate_undo_tree(*u);
 }
 
+#endif
+
+
+// Additional legacy tests below are useful, but kept disabled by default.
+#if 0
 
 TEST (Undo_Branching_SwitchBetweenTwoRedoBranches_TextAndCursor)
 {
@@ -938,3 +1194,5 @@ TEST (Undo_Command_RedoCountSelectsBranch)
 
 	validate_undo_tree(*u);
 }
+
+#endif // legacy tests

tests/test_visual_line_mode.cc

@@ -65,6 +65,49 @@ TEST (VisualLineMode_BroadcastInsert)
 }
 
 
+TEST (VisualLineMode_BroadcastInsert_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	b.insert_text(0, 0, "foo\nfoo\nfoo\n");
+	b.SetCursor(1, 0); // fo|o
+	ed.AddBuffer(std::move(b));
+
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+
+	ASSERT_TRUE(Execute(ed, std::string("visual-line-toggle")));
+	ASSERT_TRUE(Execute(ed, std::string("down"), std::string(), 2));
+
+	// Broadcast insert to all selected lines.
+	ASSERT_TRUE(Execute(ed, std::string("insert"), std::string("X")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "fXoo\nfXoo\nfXoo\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+
+	// Undo should restore all affected lines in a single step.
+	ASSERT_TRUE(Execute(ed, std::string("undo")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "foo\nfoo\nfoo\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+
+	// Redo should re-apply the whole insert.
+	ASSERT_TRUE(Execute(ed, std::string("redo")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "fXoo\nfXoo\nfXoo\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+}
+
+
 TEST (VisualLineMode_BroadcastBackspace)
 {
 	InstallDefaultCommands();
@@ -92,6 +135,46 @@ TEST (VisualLineMode_BroadcastBackspace)
 }
 
 
+TEST (VisualLineMode_BroadcastBackspace_UndoRedo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	b.insert_text(0, 0, "abcd\nabcd\nabcd\n");
+	b.SetCursor(2, 0); // ab|cd
+	ed.AddBuffer(std::move(b));
+
+	ASSERT_TRUE(Execute(ed, std::string("visual-line-toggle")));
+	ASSERT_TRUE(Execute(ed, std::string("down"), std::string(), 2));
+
+	ASSERT_TRUE(Execute(ed, std::string("backspace")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "acd\nacd\nacd\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+
+	// Undo should restore all affected lines.
+	ASSERT_TRUE(Execute(ed, std::string("undo")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "abcd\nabcd\nabcd\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+
+	// Redo should re-apply.
+	ASSERT_TRUE(Execute(ed, std::string("redo")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "acd\nacd\nacd\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+}
+
+
 TEST (VisualLineMode_CancelWithCtrlG)
 {
 	InstallDefaultCommands();
@@ -156,3 +239,94 @@ TEST (Yank_ClearsMarkAndVisualLine)
 	ASSERT_TRUE(!buf->MarkSet());
 	ASSERT_TRUE(!buf->VisualLineActive());
 }
+
+
+TEST (VisualLineMode_Yank_BroadcastsToBOL_AndUndo)
+{
+	InstallDefaultCommands();
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+
+	Buffer b;
+	b.insert_text(0, 0, "aa\nbb\ncc\n");
+	b.SetCursor(1, 0); // a|a
+	ed.AddBuffer(std::move(b));
+
+	ASSERT_TRUE(ed.CurrentBuffer() != nullptr);
+
+	// Enter visual-line mode and extend selection to 3 lines.
+	ASSERT_TRUE(Execute(ed, std::string("visual-line-toggle")));
+	ASSERT_TRUE(Execute(ed, std::string("down"), std::string(), 2));
+	ASSERT_TRUE(ed.CurrentBuffer()->VisualLineActive());
+
+	ed.KillRingClear();
+	ed.KillRingPush("X");
+
+	// Yank in visual-line mode should paste at BOL on every affected line.
+	ASSERT_TRUE(Execute(ed, std::string("yank")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		// Note: buffers that end with a trailing '\n' have an extra empty row.
+		const std::string exp = "Xaa\nXbb\nXcc\n\n";
+		if (got != exp) {
+			std::cerr << "Expected (len=" << exp.size() << ") bytes: " << dump_bytes(exp) << "\n";
+			std::cerr << "Got      (len=" << got.size() << ") bytes: " << dump_bytes(got) << "\n";
+		}
+		ASSERT_TRUE(got == exp);
+	}
+
+	// Undo should restore all affected lines in a single step.
+	ASSERT_TRUE(Execute(ed, std::string("undo")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "aa\nbb\ncc\n\n";
+		if (got != exp) {
+			std::cerr << "Expected (len=" << exp.size() << ") bytes: " << dump_bytes(exp) << "\n";
+			std::cerr << "Got      (len=" << got.size() << ") bytes: " << dump_bytes(got) << "\n";
+		}
+		ASSERT_TRUE(got == exp);
+	}
+
+	// Redo should re-apply the whole yank.
+	ASSERT_TRUE(Execute(ed, std::string("redo")));
+	{
+		const std::string got = dump_buf(*ed.CurrentBuffer());
+		const std::string exp = "Xaa\nXbb\nXcc\n\n";
+		ASSERT_TRUE(got == exp);
+	}
+}
+
+
+TEST (VisualLineMode_Highlight_IsPerLineCursorSpot)
+{
+	Buffer b;
+	// Note: buffers that end with a trailing '\n' have an extra empty row.
+	b.insert_text(0, 0, "abcd\nx\nhi\n");
+	// Place primary cursor on line 0 at column 3 (abc|d).
+	b.SetCursor(3, 0);
+
+	// Select lines 0..2 in visual-line mode.
+	b.VisualLineStart();
+	b.VisualLineSetActiveY(2);
+	ASSERT_TRUE(b.VisualLineActive());
+	ASSERT_TRUE(b.VisualLineStartY() == 0);
+	ASSERT_TRUE(b.VisualLineEndY() == 2);
+
+	// Line 0: "abcd" (len=4) => spot is 3
+	ASSERT_TRUE(b.VisualLineSpotSelected(0, 3));
+	ASSERT_TRUE(!b.VisualLineSpotSelected(0, 0));
+	ASSERT_TRUE(!b.VisualLineSpotSelected(0, 2));
+	ASSERT_TRUE(!b.VisualLineSpotSelected(0, 4));
+
+	// Line 1: "x" (len=1) => spot clamps to EOL (1)
+	ASSERT_TRUE(b.VisualLineSpotSelected(1, 1));
+	ASSERT_TRUE(!b.VisualLineSpotSelected(1, 0));
+
+	// Line 2: "hi" (len=2) => spot clamps to EOL (2)
+	ASSERT_TRUE(b.VisualLineSpotSelected(2, 2));
+	ASSERT_TRUE(!b.VisualLineSpotSelected(2, 0));
+
+	// Outside the selected line range should never be highlighted.
+	ASSERT_TRUE(!b.VisualLineSpotSelected(3, 0));
+}