Add SQL, Erlang, and Forth highlighter implementations and tests for LSP process and transport handling.

- Added highlighters for new languages (SQL, Erlang, Forth) with filetype recognition. - Updated and reorganized syntax files to maintain consistency and modularity. - Introduced LSP transport framing unit tests and JSON decoding/dispatch tests. - Refactored `LspManager`, integrating UTF-16/UTF-8 position conversions and robust diagnostics handling. - Enhanced server start/restart logic with workspace root detection and logging to improve LSP usability.
2025-12-02 00:15:15 -08:00
parent e089c6e4d1
commit 33bbb5b98f
68 changed files with 29571 additions and 945 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 !.idea
 cmake-build*
 build
+build-*
 /imgui.ini
 result
--- a/Buffer.cc
+++ b/Buffer.cc
@@ -7,8 +7,8 @@
 #include "UndoSystem.h"
 #include "UndoTree.h"
 // For reconstructing highlighter state on copies
-#include "HighlighterRegistry.h"
-#include "NullHighlighter.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"
 #include "lsp/BufferChangeTracker.h"


--- a/Buffer.h
+++ b/Buffer.h
@@ -14,7 +14,7 @@
 #include "UndoSystem.h"
 #include <cstdint>
 #include <memory>
-#include "HighlighterEngine.h"
+#include "syntax/HighlighterEngine.h"
 #include "Highlight.h"

 // Forward declarations to avoid heavy includes
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -54,6 +54,35 @@ set(CURSES_NEED_WIDE)
 find_package(Curses REQUIRED)
 include_directories(${CURSES_INCLUDE_DIR})

+# Detect availability of get_wch (wide-char input) in the curses headers
+include(CheckSymbolExists)
+set(CMAKE_REQUIRED_INCLUDES ${CURSES_INCLUDE_DIR})
+check_symbol_exists(get_wch "ncurses.h" KTE_HAVE_GET_WCH_IN_NCURSES)
+if (NOT KTE_HAVE_GET_WCH_IN_NCURSES)
+	# Some systems expose curses headers as <curses.h>
+	check_symbol_exists(get_wch "curses.h" KTE_HAVE_GET_WCH_IN_CURSES)
+endif ()
+if (KTE_HAVE_GET_WCH_IN_NCURSES OR KTE_HAVE_GET_WCH_IN_CURSES)
+	add_compile_definitions(KTE_HAVE_GET_WCH)
+endif ()
+
+set(SYNTAX_SOURCES
+	syntax/HighlighterEngine.cc
+	syntax/CppHighlighter.cc
+	syntax/HighlighterRegistry.cc
+	syntax/NullHighlighter.cc
+	syntax/JsonHighlighter.cc
+	syntax/MarkdownHighlighter.cc
+	syntax/ShellHighlighter.cc
+	syntax/GoHighlighter.cc
+	syntax/PythonHighlighter.cc
+	syntax/RustHighlighter.cc
+	syntax/LispHighlighter.cc
+	syntax/SqlHighlighter.cc
+	syntax/ErlangHighlighter.cc
+	syntax/ForthHighlighter.cc
+)
+
 set(COMMON_SOURCES
 	GapBuffer.cc
 	PieceTable.cc
@@ -71,28 +100,49 @@ set(COMMON_SOURCES
 	UndoNode.cc
 	UndoTree.cc
 	UndoSystem.cc
-	HighlighterEngine.cc
-	CppHighlighter.cc
-	HighlighterRegistry.cc
-	NullHighlighter.cc
-	JsonHighlighter.cc
-	MarkdownHighlighter.cc
-	ShellHighlighter.cc
-	GoHighlighter.cc
-	PythonHighlighter.cc
-	RustHighlighter.cc
-	LispHighlighter.cc
+	lsp/UtfCodec.cc
 	lsp/BufferChangeTracker.cc
 	lsp/JsonRpcTransport.cc
 	lsp/LspProcessClient.cc
 	lsp/DiagnosticStore.cc
 	lsp/TerminalDiagnosticDisplay.cc
 	lsp/LspManager.cc
+
+	${SYNTAX_SOURCES}
 )

 if (KTE_ENABLE_TREESITTER)
-	list(APPEND COMMON_SOURCES
-		TreeSitterHighlighter.cc)
+	list(APPEND SYNTAX_SOURCES
+		syntax/TreeSitterHighlighter.cc)
+endif ()
+
+set(THEME_HEADERS
+	themes/EInk.h
+	themes/Gruvbox.h
+	themes/Nord.h
+	themes/Plan9.h
+	themes/Solarized.h
+	themes/ThemeHelpers.h
+)
+
+set(SYNTAX_HEADERS
+	syntax/LanguageHighlighter.h
+	syntax/HighlighterEngine.h
+	syntax/CppHighlighter.h
+	syntax/HighlighterRegistry.h
+	syntax/NullHighlighter.h
+	syntax/JsonHighlighter.h
+	syntax/MarkdownHighlighter.h
+	syntax/ShellHighlighter.h
+	syntax/GoHighlighter.h
+	syntax/PythonHighlighter.h
+	syntax/RustHighlighter.h
+	syntax/LispHighlighter.h
+)
+
+if (KTE_ENABLE_TREESITTER)
+	list(APPEND SYNTAX_HEADERS
+		syntax/TreeSitterHighlighter.h)
 endif ()

 set(COMMON_HEADERS
@@ -117,18 +167,7 @@ set(COMMON_HEADERS
 	UndoTree.h
 	UndoSystem.h
 	Highlight.h
-	LanguageHighlighter.h
-	HighlighterEngine.h
-	CppHighlighter.h
-	HighlighterRegistry.h
-	NullHighlighter.h
-	JsonHighlighter.h
-	MarkdownHighlighter.h
-	ShellHighlighter.h
-	GoHighlighter.h
-	PythonHighlighter.h
-	RustHighlighter.h
-	LispHighlighter.h
+	lsp/UtfCodec.h
 	lsp/LspTypes.h
 	lsp/BufferChangeTracker.h
 	lsp/JsonRpcTransport.h
@@ -140,12 +179,12 @@ set(COMMON_HEADERS
 	lsp/TerminalDiagnosticDisplay.h
 	lsp/LspManager.h
 	lsp/LspServerConfig.h
-)
+	ext/json.h
+	ext/json_fwd.h

-if (KTE_ENABLE_TREESITTER)
-	list(APPEND COMMON_HEADERS
-		TreeSitterHighlighter.h)
-endif ()
+	${THEME_HEADERS}
+	${SYNTAX_HEADERS}
+)

 # kte (terminal-first) executable
 add_executable(kte
@@ -162,6 +201,8 @@ if (KTE_UNDO_DEBUG)
 endif ()

 target_link_libraries(kte ${CURSES_LIBRARIES})
+# Ensure vendored headers (e.g., ext/json.h) are on the include path
+target_include_directories(kte PRIVATE ${CMAKE_SOURCE_DIR}/ext)

 if (KTE_ENABLE_TREESITTER)
 	# Users can provide their own tree-sitter include/lib via cache variables
@@ -200,6 +241,8 @@ if (BUILD_TESTS)


 	target_link_libraries(test_undo ${CURSES_LIBRARIES})
+	# Ensure vendored headers (e.g., ext/json.h) are on the include path for tests as well
+	target_include_directories(test_undo PRIVATE ${CMAKE_SOURCE_DIR}/ext)
 	if (KTE_ENABLE_TREESITTER)
 		if (TREESITTER_INCLUDE_DIR)
 			target_include_directories(test_undo PRIVATE ${TREESITTER_INCLUDE_DIR})
@@ -208,6 +251,90 @@ if (BUILD_TESTS)
 			target_link_libraries(test_undo ${TREESITTER_LIBRARY})
 		endif ()
 	endif ()
+
+	# test_utfcodec executable for UTF conversion helpers
+	add_executable(test_utfcodec
+		test_utfcodec.cc
+		${COMMON_SOURCES}
+		${COMMON_HEADERS}
+	)
+
+	if (KTE_USE_PIECE_TABLE)
+		target_compile_definitions(test_utfcodec PRIVATE KTE_USE_PIECE_TABLE=1)
+	endif ()
+
+	if (KTE_UNDO_DEBUG)
+		target_compile_definitions(test_utfcodec PRIVATE KTE_UNDO_DEBUG=1)
+	endif ()
+
+
+	target_link_libraries(test_utfcodec ${CURSES_LIBRARIES})
+	# Ensure vendored headers (e.g., ext/json.h) are on the include path for tests as well
+	target_include_directories(test_utfcodec PRIVATE ${CMAKE_SOURCE_DIR}/ext)
+	if (KTE_ENABLE_TREESITTER)
+		if (TREESITTER_INCLUDE_DIR)
+			target_include_directories(test_utfcodec PRIVATE ${TREESITTER_INCLUDE_DIR})
+		endif ()
+		if (TREESITTER_LIBRARY)
+			target_link_libraries(test_utfcodec ${TREESITTER_LIBRARY})
+		endif ()
+	endif ()
+
+	# test_transport executable for JSON-RPC framing
+	add_executable(test_transport
+		test_transport.cc
+		${COMMON_SOURCES}
+		${COMMON_HEADERS}
+	)
+
+	if (KTE_USE_PIECE_TABLE)
+		target_compile_definitions(test_transport PRIVATE KTE_USE_PIECE_TABLE=1)
+	endif ()
+
+	if (KTE_UNDO_DEBUG)
+		target_compile_definitions(test_transport PRIVATE KTE_UNDO_DEBUG=1)
+	endif ()
+
+
+	target_link_libraries(test_transport ${CURSES_LIBRARIES})
+	# Ensure vendored headers (e.g., ext/json.h) are on the include path for tests as well
+	target_include_directories(test_transport PRIVATE ${CMAKE_SOURCE_DIR}/ext)
+	if (KTE_ENABLE_TREESITTER)
+		if (TREESITTER_INCLUDE_DIR)
+			target_include_directories(test_transport PRIVATE ${TREESITTER_INCLUDE_DIR})
+		endif ()
+		if (TREESITTER_LIBRARY)
+			target_link_libraries(test_transport ${TREESITTER_LIBRARY})
+		endif ()
+	endif ()
+
+	# test_lsp_decode executable for dispatcher decoding
+	add_executable(test_lsp_decode
+		test_lsp_decode.cc
+		${COMMON_SOURCES}
+		${COMMON_HEADERS}
+	)
+
+	if (KTE_USE_PIECE_TABLE)
+		target_compile_definitions(test_lsp_decode PRIVATE KTE_USE_PIECE_TABLE=1)
+	endif ()
+
+	if (KTE_UNDO_DEBUG)
+		target_compile_definitions(test_lsp_decode PRIVATE KTE_UNDO_DEBUG=1)
+	endif ()
+
+
+	target_link_libraries(test_lsp_decode ${CURSES_LIBRARIES})
+	# Ensure vendored headers (e.g., ext/json.h) are on the include path for tests as well
+	target_include_directories(test_lsp_decode PRIVATE ${CMAKE_SOURCE_DIR}/ext)
+	if (KTE_ENABLE_TREESITTER)
+		if (TREESITTER_INCLUDE_DIR)
+			target_include_directories(test_lsp_decode PRIVATE ${TREESITTER_INCLUDE_DIR})
+		endif ()
+		if (TREESITTER_LIBRARY)
+			target_link_libraries(test_lsp_decode ${TREESITTER_LIBRARY})
+		endif ()
+	endif ()
 endif ()

 if (${BUILD_GUI})
@@ -242,6 +369,7 @@ if (${BUILD_GUI})
 		target_compile_definitions(kge PRIVATE KTE_UNDO_DEBUG=1)
 	endif ()
 	target_link_libraries(kge ${CURSES_LIBRARIES} imgui)
+	target_include_directories(kge PRIVATE ${CMAKE_SOURCE_DIR}/ext)

 	# On macOS, build kge as a proper .app bundle
 	if (APPLE)
--- a/Command.cc
+++ b/Command.cc
@@ -7,15 +7,15 @@
 #include <cctype>

 #include "Command.h"
-#include "HighlighterRegistry.h"
-#include "NullHighlighter.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"
 #include "Editor.h"
 #include "Buffer.h"
 #include "UndoSystem.h"
 #include "HelpText.h"
-#include "LanguageHighlighter.h"
-#include "HighlighterEngine.h"
-#include "CppHighlighter.h"
+#include "syntax/LanguageHighlighter.h"
+#include "syntax/HighlighterEngine.h"
+#include "syntax/CppHighlighter.h"
 #ifdef KTE_BUILD_GUI
 #include "GUITheme.h"
 #endif
@@ -554,6 +554,8 @@ cmd_save(CommandContext &ctx)
 	ctx.editor.SetStatus("Saved " + buf->Filename());
 	if (auto *u = buf->Undo())
 		u->mark_saved();
+	// Notify LSP of save
+	ctx.editor.NotifyBufferSaved(buf);
 	return true;
 }

@@ -608,6 +610,8 @@ cmd_save_as(CommandContext &ctx)
 	ctx.editor.SetStatus("Saved as " + ctx.arg);
 	if (auto *u = buf->Undo())
 		u->mark_saved();
+	// Notify LSP of save
+	ctx.editor.NotifyBufferSaved(buf);
 	return true;
 }

--- a/Editor.cc
+++ b/Editor.cc
@@ -1,13 +1,14 @@
 #include <algorithm>
 #include <utility>
 #include <filesystem>
-#include "HighlighterRegistry.h"
-#include "NullHighlighter.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"

 #include "Editor.h"
-#include "HighlighterRegistry.h"
-#include "CppHighlighter.h"
-#include "NullHighlighter.h"
+#include "lsp/LspManager.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/CppHighlighter.h"
+#include "syntax/NullHighlighter.h"


 Editor::Editor() = default;
@@ -29,6 +30,15 @@ Editor::SetStatus(const std::string &message)
 }


+void
+Editor::NotifyBufferSaved(Buffer *buf)
+{
+	if (lsp_manager_ && buf) {
+		lsp_manager_->onBufferSaved(buf);
+	}
+}
+
+
 Buffer *
 Editor::CurrentBuffer()
 {
@@ -181,6 +191,10 @@ Editor::OpenFile(const std::string &path, std::string &err)
 					eng->InvalidateFrom(0);
 				}
 			}
+			// Notify LSP (if wired) for current buffer open
+			if (lsp_manager_) {
+				lsp_manager_->onBufferOpened(&cur);
+			}
 			return true;
 		}
 	}
@@ -216,6 +230,10 @@ 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);
+	// Notify LSP (if wired) for current buffer open
+	if (lsp_manager_) {
+		lsp_manager_->onBufferOpened(&buffers_[curbuf_]);
+	}
 	return true;
 }

--- a/Editor.h
+++ b/Editor.h
@@ -11,6 +11,13 @@

 #include "Buffer.h"

+// fwd decl for LSP wiring
+namespace kte {
+namespace lsp {
+class LspManager;
+}
+}
+

 class Editor {
 public:
@@ -436,6 +443,16 @@ public:

 	bool OpenFile(const std::string &path, std::string &err);

+	// LSP: attach/detach manager
+	void SetLspManager(kte::lsp::LspManager *mgr)
+	{
+		lsp_manager_ = mgr;
+	}
+
+
+	// LSP: notify buffer saved (used by commands)
+	void NotifyBufferSaved(Buffer *buf);
+
 	// Buffer switching/closing
 	bool SwitchTo(std::size_t index);

@@ -551,6 +568,9 @@ public:
 private:
 	std::string replace_find_tmp_;
 	std::string replace_with_tmp_;
+
+	// Non-owning pointer to LSP manager (if provided)
+	kte::lsp::LspManager *lsp_manager_ = nullptr;
 };

-#endif // KTE_EDITOR_H
+#endif // KTE_EDITOR_H
--- a/GUIFrontend.cc
+++ b/GUIFrontend.cc
@@ -16,8 +16,8 @@
 #include "Font.h" // embedded default font (DefaultFontRegular)
 #include "GUIConfig.h"
 #include "GUITheme.h"
-#include "HighlighterRegistry.h"
-#include "NullHighlighter.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"


 #ifndef KTE_FONT_SIZE
--- a/GUITheme.h
+++ b/GUITheme.h
--- a/TerminalFrontend.cc
+++ b/TerminalFrontend.cc
@@ -1,6 +1,12 @@
 #include <ncurses.h>
+#include <clocale>
 #include <termios.h>
 #include <unistd.h>
+#ifdef __APPLE__
+#include <xlocale.h>
+#endif
+#include <langinfo.h>
+#include <cctype>

 #include "TerminalFrontend.h"
 #include "Command.h"
@@ -10,6 +16,35 @@
 bool
 TerminalFrontend::Init(Editor &ed)
 {
+	// Enable UTF-8 locale so ncurses and the terminal handle multibyte correctly
+	// This relies on the user's environment (e.g., LANG/LC_ALL) being set to a UTF-8 locale.
+	// If not set, try a couple of common UTF-8 fallbacks.
+	const char *loc      = std::setlocale(LC_ALL, "");
+	auto is_utf8_codeset = []() -> bool {
+		const char *cs = nl_langinfo(CODESET);
+		if (!cs)
+			return false;
+		std::string s(cs);
+		for (auto &ch: s)
+			ch = static_cast<char>(std::toupper(static_cast<unsigned char>(ch)));
+		return (s.find("UTF-8") != std::string::npos) || (s.find("UTF8") != std::string::npos);
+	};
+	bool utf8_ok = (MB_CUR_MAX > 1) && is_utf8_codeset();
+	if (!utf8_ok) {
+		// Try common UTF-8 locales
+		loc     = std::setlocale(LC_CTYPE, "C.UTF-8");
+		utf8_ok = (loc != nullptr) && (MB_CUR_MAX > 1) && is_utf8_codeset();
+		if (!utf8_ok) {
+			loc     = std::setlocale(LC_CTYPE, "en_US.UTF-8");
+			utf8_ok = (loc != nullptr) && (MB_CUR_MAX > 1) && is_utf8_codeset();
+		}
+		if (!utf8_ok) {
+			// macOS often uses plain "UTF-8" locale identifier
+			loc     = std::setlocale(LC_CTYPE, "UTF-8");
+			utf8_ok = (loc != nullptr) && (MB_CUR_MAX > 1) && is_utf8_codeset();
+		}
+	}
+
 	// Ensure Control keys reach the app: disable XON/XOFF and dsusp/susp bindings (e.g., ^S/^Q, ^Y on macOS)
 	{
 		struct termios tio{};
@@ -55,6 +90,9 @@ TerminalFrontend::Init(Editor &ed)
 	prev_r_ = r;
 	prev_c_ = c;
 	ed.SetDimensions(static_cast<std::size_t>(r), static_cast<std::size_t>(c));
+	// Inform renderer of UTF-8 capability so it can choose proper output path
+	renderer_.SetUtf8Enabled(utf8_ok);
+	input_.SetUtf8Enabled(utf8_ok);
 	return true;
 }

@@ -100,4 +138,4 @@ TerminalFrontend::Shutdown()
 		have_orig_tio_ = false;
 	}
 	endwin();
-}
+}
--- a/TerminalInputHandler.cc
+++ b/TerminalInputHandler.cc
@@ -1,4 +1,6 @@
 #include <cstdio>
+#include <cwchar>
+#include <climits>
 #include <ncurses.h>

 #include "TerminalInputHandler.h"
@@ -281,6 +283,77 @@ map_key_to_command(const int ch,
 bool
 TerminalInputHandler::decode_(MappedInput &out)
 {
+#if defined(KTE_HAVE_GET_WCH)
+	if (utf8_enabled_) {
+		// Prefer wide-character input so we can capture Unicode code points
+		wint_t wch = 0;
+		int rc     = get_wch(&wch);
+		if (rc == ERR) {
+			return false;
+		}
+		if (rc == KEY_CODE_YES) {
+			// Function/special key; pass through existing mapper
+			int sk        = static_cast<int>(wch);
+			bool consumed = map_key_to_command(
+				sk,
+				k_prefix_, esc_meta_,
+				uarg_active_, uarg_collecting_, uarg_negative_, uarg_had_digits_, uarg_value_,
+				uarg_text_,
+				out);
+			if (!consumed)
+				return false;
+		} else {
+			// Regular character
+			if (wch <= 0x7F) {
+				// ASCII path -> reuse existing mapping (handles control, ESC, etc.)
+				int ch        = static_cast<int>(wch);
+				bool consumed = map_key_to_command(
+					ch,
+					k_prefix_, esc_meta_,
+					uarg_active_, uarg_collecting_, uarg_negative_, uarg_had_digits_, uarg_value_,
+					uarg_text_,
+					out);
+				if (!consumed)
+					return false;
+			} else {
+				// Non-ASCII printable -> insert UTF-8 text directly
+				if (iswcntrl(static_cast<wint_t>(wch))) {
+					out.hasCommand = false;
+					return true;
+				}
+				char mb[MB_LEN_MAX];
+				mbstate_t st{};
+				std::size_t n = wcrtomb(mb, static_cast<wchar_t>(wch), &st);
+				if (n == static_cast<std::size_t>(-1)) {
+					// Fallback placeholder if encoding failed
+					out.hasCommand = true;
+					out.id         = CommandId::InsertText;
+					out.arg        = "?";
+					out.count      = 0;
+				} else {
+					out.hasCommand = true;
+					out.id         = CommandId::InsertText;
+					out.arg.assign(mb, mb + n);
+					out.count = 0;
+				}
+			}
+		}
+	} else {
+		int ch = getch();
+		if (ch == ERR) {
+			return false; // no input
+		}
+		bool consumed = map_key_to_command(
+			ch,
+			k_prefix_, esc_meta_,
+			uarg_active_, uarg_collecting_, uarg_negative_, uarg_had_digits_, uarg_value_, uarg_text_,
+			out);
+		if (!consumed)
+			return false;
+	}
+#else
+	// Wide-character input not available in this curses; fall back to byte-wise getch
+	(void) utf8_enabled_;
 	int ch = getch();
 	if (ch == ERR) {
 		return false; // no input
@@ -292,6 +365,7 @@ TerminalInputHandler::decode_(MappedInput &out)
 		out);
 	if (!consumed)
 		return false;
+#endif
 	// If a command was produced and a universal argument is active, attach it and clear state
 	if (out.hasCommand && uarg_active_ && out.id != CommandId::UArgStatus) {
 		int count = 0;
@@ -320,4 +394,4 @@ TerminalInputHandler::Poll(MappedInput &out)
 {
 	out = {};
 	return decode_(out) && out.hasCommand;
-}
+}
--- a/TerminalInputHandler.h
+++ b/TerminalInputHandler.h
@@ -15,6 +15,12 @@ public:

 	bool Poll(MappedInput &out) override;

+
+	void SetUtf8Enabled(bool on)
+	{
+		utf8_enabled_ = on;
+	}
+
 private:
 	bool decode_(MappedInput &out);

@@ -30,6 +36,8 @@ private:
 	bool uarg_had_digits_ = false; // whether any digits were supplied
 	int uarg_value_       = 0; // current absolute value (>=0)
 	std::string uarg_text_; // raw digits/minus typed for status display
+
+	bool utf8_enabled_ = true;
 };

-#endif // KTE_TERMINAL_INPUT_HANDLER_H
+#endif // KTE_TERMINAL_INPUT_HANDLER_H
--- a/TerminalRenderer.cc
+++ b/TerminalRenderer.cc
@@ -4,6 +4,7 @@
 #include <cstdlib>
 #include <ncurses.h>
 #include <regex>
+#include <cwchar>
 #include <string>

 #include "TerminalRenderer.h"
@@ -150,8 +151,10 @@ TerminalRenderer::Draw(Editor &ed)
 					}
 				};
 				while (written < cols) {
-					char ch       = ' ';
-					bool from_src = false;
+					// Default to space when beyond EOL
+					bool from_src             = false;
+					int wcw                   = 1; // display width
+					std::size_t advance_bytes = 0;
 					if (src_i < line.size()) {
 						unsigned char c = static_cast<unsigned char>(line[src_i]);
 						if (c == '\t') {
@@ -209,18 +212,46 @@ TerminalRenderer::Draw(Editor &ed)
 							++src_i;
 							continue;
 						} else {
-							// normal char
-							if (render_col < coloffs) {
-								++render_col;
-								++src_i;
-								continue;
+							if (!Utf8Enabled()) {
+								// ASCII fallback: treat each byte as single width
+								if (render_col + 1 <= coloffs) {
+									++render_col;
+									++src_i;
+									continue;
+								}
+								wcw           = 1;
+								advance_bytes = 1;
+								from_src      = true;
+							} else {
+								// Decode one UTF-8 codepoint
+								mbstate_t st{};
+								const char *p   = line.data() + src_i;
+								std::size_t rem = line.size() - src_i;
+								wchar_t tmp_wc  = 0;
+								std::size_t n   = mbrtowc(&tmp_wc, p, rem, &st);
+								if (n == static_cast<std::size_t>(-1) || n ==
+								    static_cast<std::size_t>(-2) || n == 0) {
+									// Invalid/incomplete -> treat as single-byte placeholder
+									tmp_wc = L'?';
+									n      = 1;
+								}
+								int w = wcwidth(tmp_wc);
+								if (w < 0)
+									w = 1;
+								// If this codepoint is scrolled off to the left, skip it
+								if (render_col + static_cast<std::size_t>(w) <=
+								    coloffs) {
+									render_col += static_cast<std::size_t>(w);
+									src_i += n;
+									continue;
+								}
+								wcw           = w;
+								advance_bytes = n;
+								from_src      = true;
 							}
-							ch       = static_cast<char>(c);
-							from_src = true;
 						}
 					} else {
 						// beyond EOL, fill spaces
-						ch       = ' ';
 						from_src = false;
 					}
 					bool in_hl  = search_mode && from_src && is_src_in_hl(src_i);
@@ -246,11 +277,20 @@ TerminalRenderer::Draw(Editor &ed)
 					if (!in_hl && from_src) {
 						apply_token_attr(token_at(src_i));
 					}
-					addch(static_cast<unsigned char>(ch));
-					++written;
-					++render_col;
-					if (from_src)
-						++src_i;
+					if (written + wcw > cols) {
+						break;
+					}
+					if (from_src) {
+						// Output original bytes for this unit (UTF-8 codepoint or ASCII byte)
+						const char *cp = line.data() + (src_i);
+						int out_n      = Utf8Enabled() ? static_cast<int>(advance_bytes) : 1;
+						addnstr(cp, out_n);
+						src_i += static_cast<std::size_t>(out_n);
+					} else {
+						addch(' ');
+					}
+					written += wcw;
+					render_col += wcw;
 					if (src_i >= line.size() && written >= cols)
 						break;
 				}
@@ -422,6 +462,10 @@ TerminalRenderer::Draw(Editor &ed)
 		else
 			std::snprintf(rbuf, sizeof(rbuf), "%d,%d | M: not set", row1, col1);
 		right = rbuf;
+		// If UTF-8 is not enabled (ASCII fallback), append a short hint
+		if (!Utf8Enabled()) {
+			right += " | ASCII";
+		}
 	}

 	// Compute placements with truncation rules: prioritize left and right; middle gets remaining
--- a/TerminalRenderer.h
+++ b/TerminalRenderer.h
@@ -14,6 +14,21 @@ public:
 	~TerminalRenderer() override;

 	void Draw(Editor &ed) override;
+
+	// Enable/disable UTF-8 aware rendering (set by TerminalFrontend after locale init)
+	void SetUtf8Enabled(bool on)
+	{
+		utf8_enabled_ = on;
+	}
+
+
+	[[nodiscard]] bool Utf8Enabled() const
+	{
+		return utf8_enabled_;
+	}
+
+private:
+	bool utf8_enabled_ = true;
 };

-#endif // KTE_TERMINAL_RENDERER_H
+#endif // KTE_TERMINAL_RENDERER_H
--- a/ext/json.h
+++ b/ext/json.h
--- a/ext/json_fwd.h
+++ b/ext/json_fwd.h
@@ -0,0 +1,185 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2025 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#ifndef INCLUDE_NLOHMANN_JSON_FWD_HPP_
+#define INCLUDE_NLOHMANN_JSON_FWD_HPP_
+
+#include <cstdint> // int64_t, uint64_t
+#include <map> // map
+#include <memory> // allocator
+#include <string> // string
+#include <vector> // vector
+
+// #include <nlohmann/detail/abi_macros.hpp>
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2025 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+
+// This file contains all macro definitions affecting or depending on the ABI
+
+#ifndef JSON_SKIP_LIBRARY_VERSION_CHECK
+#if defined(NLOHMANN_JSON_VERSION_MAJOR) && defined(NLOHMANN_JSON_VERSION_MINOR) && defined(NLOHMANN_JSON_VERSION_PATCH)
+#if NLOHMANN_JSON_VERSION_MAJOR != 3 || NLOHMANN_JSON_VERSION_MINOR != 12 || NLOHMANN_JSON_VERSION_PATCH != 0
+#warning "Already included a different version of the library!"
+#endif
+#endif
+#endif
+
+#define NLOHMANN_JSON_VERSION_MAJOR 3   // NOLINT(modernize-macro-to-enum)
+#define NLOHMANN_JSON_VERSION_MINOR 12  // NOLINT(modernize-macro-to-enum)
+#define NLOHMANN_JSON_VERSION_PATCH 0   // NOLINT(modernize-macro-to-enum)
+
+#ifndef JSON_DIAGNOSTICS
+#define JSON_DIAGNOSTICS 0
+#endif
+
+#ifndef JSON_DIAGNOSTIC_POSITIONS
+#define JSON_DIAGNOSTIC_POSITIONS 0
+#endif
+
+#ifndef JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 0
+#endif
+
+#if JSON_DIAGNOSTICS
+#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS _diag
+#else
+#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS
+#endif
+
+#if JSON_DIAGNOSTIC_POSITIONS
+#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS _dp
+#else
+#define NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS
+#endif
+
+#if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON
+#define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON _ldvcmp
+#else
+#define NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON
+#endif
+
+#ifndef NLOHMANN_JSON_NAMESPACE_NO_VERSION
+#define NLOHMANN_JSON_NAMESPACE_NO_VERSION 0
+#endif
+
+// Construct the namespace ABI tags component
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c) json_abi ## a ## b ## c
+#define NLOHMANN_JSON_ABI_TAGS_CONCAT(a, b, c) \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT_EX(a, b, c)
+
+#define NLOHMANN_JSON_ABI_TAGS                                       \
+    NLOHMANN_JSON_ABI_TAGS_CONCAT(                                   \
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS,                       \
+            NLOHMANN_JSON_ABI_TAG_LEGACY_DISCARDED_VALUE_COMPARISON, \
+            NLOHMANN_JSON_ABI_TAG_DIAGNOSTIC_POSITIONS)
+
+// Construct the namespace version component
+#define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch) \
+    _v ## major ## _ ## minor ## _ ## patch
+#define NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT(major, minor, patch) \
+    NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT_EX(major, minor, patch)
+
+#if NLOHMANN_JSON_NAMESPACE_NO_VERSION
+#define NLOHMANN_JSON_NAMESPACE_VERSION
+#else
+#define NLOHMANN_JSON_NAMESPACE_VERSION                                 \
+    NLOHMANN_JSON_NAMESPACE_VERSION_CONCAT(NLOHMANN_JSON_VERSION_MAJOR, \
+                                           NLOHMANN_JSON_VERSION_MINOR, \
+                                           NLOHMANN_JSON_VERSION_PATCH)
+#endif
+
+// Combine namespace components
+#define NLOHMANN_JSON_NAMESPACE_CONCAT_EX(a, b) a ## b
+#define NLOHMANN_JSON_NAMESPACE_CONCAT(a, b) \
+    NLOHMANN_JSON_NAMESPACE_CONCAT_EX(a, b)
+
+#ifndef NLOHMANN_JSON_NAMESPACE
+#define NLOHMANN_JSON_NAMESPACE               \
+    nlohmann::NLOHMANN_JSON_NAMESPACE_CONCAT( \
+            NLOHMANN_JSON_ABI_TAGS,           \
+            NLOHMANN_JSON_NAMESPACE_VERSION)
+#endif
+
+#ifndef NLOHMANN_JSON_NAMESPACE_BEGIN
+#define NLOHMANN_JSON_NAMESPACE_BEGIN                \
+    namespace nlohmann                               \
+    {                                                \
+    inline namespace NLOHMANN_JSON_NAMESPACE_CONCAT( \
+                NLOHMANN_JSON_ABI_TAGS,              \
+                NLOHMANN_JSON_NAMESPACE_VERSION)     \
+    {
+#endif
+
+#ifndef NLOHMANN_JSON_NAMESPACE_END
+#define NLOHMANN_JSON_NAMESPACE_END                                     \
+    }  /* namespace (inline namespace) NOLINT(readability/namespace) */ \
+    }  // namespace nlohmann
+#endif
+
+
+/*!
+@brief namespace for Niels Lohmann
+@see https://github.com/nlohmann
+@since version 1.0.0
+*/
+NLOHMANN_JSON_NAMESPACE_BEGIN
+/*!
+@brief default JSONSerializer template argument
+
+This serializer ignores the template arguments and uses ADL
+([argument-dependent lookup](https://en.cppreference.com/w/cpp/language/adl))
+for serialization.
+*/
+template<typename T = void, typename SFINAE = void>
+struct adl_serializer;
+
+/// a class to store JSON values
+/// @sa https://json.nlohmann.me/api/basic_json/
+template<template<typename U, typename V, typename... Args> class ObjectType =
+	std::map,
+	template<typename U, typename... Args> class ArrayType = std::vector,
+	class StringType = std::string, class BooleanType = bool,
+	class NumberIntegerType = std::int64_t,
+	class NumberUnsignedType = std::uint64_t,
+	class NumberFloatType = double,
+	template<typename U> class AllocatorType = std::allocator,
+	template<typename T, typename SFINAE = void> class JSONSerializer =
+	adl_serializer,
+	class BinaryType = std::vector<std::uint8_t>, // cppcheck-suppress syntaxError
+	class CustomBaseClass = void>
+class basic_json;
+
+/// @brief JSON Pointer defines a string syntax for identifying a specific value within a JSON document
+/// @sa https://json.nlohmann.me/api/json_pointer/
+template<typename RefStringType>
+class json_pointer;
+
+/*!
+@brief default specialization
+@sa https://json.nlohmann.me/api/json/
+*/
+using json = basic_json<>;
+
+/// @brief a minimal map-like container that preserves insertion order
+/// @sa https://json.nlohmann.me/api/ordered_map/
+template<class Key, class T, class IgnoredLess, class Allocator>
+struct ordered_map;
+
+/// @brief specialization that maintains the insertion order of object keys
+/// @sa https://json.nlohmann.me/api/ordered_json/
+using ordered_json = basic_json<nlohmann::ordered_map>;
+
+NLOHMANN_JSON_NAMESPACE_END
+
+#endif  // INCLUDE_NLOHMANN_JSON_FWD_HPP_
--- a/2
+++ b/2
@@ -6,4 +6,4 @@ then
 	fmt_args="-fmt 3"
 fi

-ls -1 *.cc *.h | grep -v '^Font.h$' | xargs cloc ${fmt_args}
+ls -1 *.cc *.h lsp/*.{cc,h} | grep -v '^Font.h$' | xargs cloc ${fmt_args}
--- a/lsp/JsonRpcTransport.cc
+++ b/lsp/JsonRpcTransport.cc
@@ -1,19 +1,147 @@
 /*
- * JsonRpcTransport.cc - placeholder
+ * JsonRpcTransport.cc - minimal stdio JSON-RPC framing (Content-Length)
 */
 #include "JsonRpcTransport.h"

+#include <cerrno>
+#include <cstddef>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+#include <optional>
+#include <unistd.h>
+
 namespace kte::lsp {
 void
-JsonRpcTransport::send(const std::string &/*method*/, const std::string &/*payload*/)
+JsonRpcTransport::connect(int inFd, int outFd)
 {
-	// stub: no-op
+	inFd_  = inFd;
+	outFd_ = outFd;
+}
+
+
+void
+JsonRpcTransport::send(const std::string &/*method*/, const std::string &payload)
+{
+	if (outFd_ < 0)
+		return;
+	const std::string header = "Content-Length: " + std::to_string(payload.size()) + "\r\n\r\n";
+	std::lock_guard<std::mutex> lk(writeMutex_);
+	// write header
+	const char *hbuf = header.data();
+	size_t hleft     = header.size();
+	while (hleft > 0) {
+		ssize_t n = ::write(outFd_, hbuf, hleft);
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			return;
+		}
+		hbuf += static_cast<size_t>(n);
+		hleft -= static_cast<size_t>(n);
+	}
+	// write payload
+	const char *pbuf = payload.data();
+	size_t pleft     = payload.size();
+	while (pleft > 0) {
+		ssize_t n = ::write(outFd_, pbuf, pleft);
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			return;
+		}
+		pbuf += static_cast<size_t>(n);
+		pleft -= static_cast<size_t>(n);
+	}
+}
+
+
+static bool
+readLineCrlf(int fd, std::string &out, size_t maxLen)
+{
+	out.clear();
+	char ch;
+	while (true) {
+		ssize_t n = ::read(fd, &ch, 1);
+		if (n == 0)
+			return false; // EOF
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			return false;
+		}
+		out.push_back(ch);
+		// Handle CRLF or bare LF as end-of-line
+		if ((out.size() >= 2 && out[out.size() - 2] == '\r' && out[out.size() - 1] == '\n') ||
+		    (out.size() >= 1 && out[out.size() - 1] == '\n')) {
+			return true;
+		}
+		if (out.size() > maxLen) {
+			// sanity cap
+			return false;
+		}
+	}
 }


 std::optional<JsonRpcMessage>
 JsonRpcTransport::read()
 {
-	return std::nullopt; // stub
+	if (inFd_ < 0)
+		return std::nullopt;
+	// Parse headers (case-insensitive), accept/ignore extras
+	size_t contentLength = 0;
+	while (true) {
+		std::string line;
+		if (!readLineCrlf(inFd_, line, kMaxHeaderLine))
+			return std::nullopt;
+		// Normalize end-of-line handling: consider blank line as end of headers
+		if (line == "\r\n" || line == "\n" || line == "\r")
+			break;
+		// Trim trailing CRLF
+		if (!line.empty() && (line.back() == '\n' || line.back() == '\r')) {
+			while (!line.empty() && (line.back() == '\n' || line.back() == '\r'))
+				line.pop_back();
+		}
+		// Find colon
+		auto pos = line.find(':');
+		if (pos == std::string::npos)
+			continue;
+		std::string name  = line.substr(0, pos);
+		std::string value = line.substr(pos + 1);
+		// trim leading spaces in value
+		size_t i = 0;
+		while (i < value.size() && (value[i] == ' ' || value[i] == '\t'))
+			++i;
+		value.erase(0, i);
+		// lower-case name for comparison
+		for (auto &c: name)
+			c = static_cast<char>(::tolower(static_cast<unsigned char>(c)));
+		if (name == "content-length") {
+			size_t len = static_cast<size_t>(std::strtoull(value.c_str(), nullptr, 10));
+			if (len > kMaxBody) {
+				return std::nullopt; // drop too-large message
+			}
+			contentLength = len;
+		}
+		// else: ignore other headers
+	}
+	if (contentLength == 0)
+		return std::nullopt;
+	std::string body;
+	body.resize(contentLength);
+	size_t readTotal = 0;
+	while (readTotal < contentLength) {
+		ssize_t n = ::read(inFd_, &body[readTotal], contentLength - readTotal);
+		if (n == 0)
+			return std::nullopt;
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			return std::nullopt;
+		}
+		readTotal += static_cast<size_t>(n);
+	}
+	return JsonRpcMessage{std::move(body)};
 }
 } // namespace kte::lsp
--- a/lsp/JsonRpcTransport.h
+++ b/lsp/JsonRpcTransport.h
@@ -1,11 +1,12 @@
 /*
- * JsonRpcTransport.h - placeholder transport for JSON-RPC over stdio (stub)
+ * JsonRpcTransport.h - minimal JSON-RPC over stdio transport
 */
 #ifndef KTE_JSON_RPC_TRANSPORT_H
 #define KTE_JSON_RPC_TRANSPORT_H

 #include <optional>
 #include <string>
+#include <mutex>

 namespace kte::lsp {
 struct JsonRpcMessage {
@@ -18,11 +19,24 @@ public:

 	~JsonRpcTransport() = default;

-	// Send a method call (request or notification) - stub does nothing
+	// Connect this transport to file descriptors (read from inFd, write to outFd)
+	void connect(int inFd, int outFd);
+
+	// Send a method call (request or notification)
+	// 'payload' should be a complete JSON object string to send as the message body.
 	void send(const std::string &method, const std::string &payload);

-	// Blocking read next message (stub => returns nullopt)
+	// Blocking read next message; returns nullopt on EOF or error
 	std::optional<JsonRpcMessage> read();
+
+private:
+	int inFd_  = -1;
+	int outFd_ = -1;
+	std::mutex writeMutex_;
+
+	// Limits to keep the transport resilient
+	static constexpr size_t kMaxHeaderLine = 16 * 1024; // 16 KiB per header line
+	static constexpr size_t kMaxBody       = 64ull * 1024ull * 1024ull; // 64 MiB body cap
 };
 } // namespace kte::lsp

--- a/lsp/LspClient.h
+++ b/lsp/LspClient.h
@@ -11,6 +11,7 @@
 #include <vector>

 #include "LspTypes.h"
+#include "Diagnostic.h"

 namespace kte::lsp {
 // Callback types (stubs for future phases)
@@ -55,6 +56,18 @@ public:
 	virtual bool isRunning() const = 0;

 	virtual std::string getServerName() const = 0;
+
+	// Handlers (optional; set by manager)
+	using DiagnosticsHandler = std::function<void(const std::string & uri,
+	const std::vector<Diagnostic> &diagnostics
+	)
+	>;
+
+
+	virtual void setDiagnosticsHandler(DiagnosticsHandler h)
+	{
+		(void) h;
+	}
 };
 } // namespace kte::lsp

--- a/lsp/LspManager.cc
+++ b/lsp/LspManager.cc
@@ -7,16 +7,42 @@
 #include <algorithm>
 #include <cctype>
 #include <filesystem>
+#include <fstream>
 #include <utility>
+#include <cstdio>
+#include <cstdlib>
+#include <ctime>
+#include <cstdarg>

 #include "../Buffer.h"
 #include "../Editor.h"
 #include "BufferChangeTracker.h"
 #include "LspProcessClient.h"
+#include "UtfCodec.h"

 namespace fs = std::filesystem;

 namespace kte::lsp {
+static void
+lsp_debug_file(const char *fmt, ...)
+{
+	FILE *f = std::fopen("/tmp/kte-lsp.log", "a");
+	if (!f)
+		return;
+	// prepend timestamp
+	std::time_t t = std::time(nullptr);
+	char ts[32];
+	std::strftime(ts, sizeof(ts), "%Y-%m-%d %H:%M:%S", std::localtime(&t));
+	std::fprintf(f, "[%s] ", ts);
+	va_list ap;
+	va_start(ap, fmt);
+	std::vfprintf(f, fmt, ap);
+	va_end(ap);
+	std::fputc('\n', f);
+	std::fclose(f);
+}
+
+
 LspManager::LspManager(Editor *editor, DiagnosticDisplay *display)
 	: editor_(editor), display_(display)
 {
@@ -53,14 +79,50 @@ LspManager::startServerForBuffer(Buffer *buffer)
 	if (!cfg.autostart) {
 		return false;
 	}
-	auto client = std::make_unique<LspProcessClient>(cfg.command, cfg.args);
-	// Determine root as parent of file for now; future: walk rootPatterns
+	// Allow env override of server path
+	std::string command = cfg.command;
+	if (lang == "cpp") {
+		if (const char *p = std::getenv("KTE_LSP_CLANGD"); p && *p)
+			command   = p;
+	} else if (lang == "go") {
+		if (const char *p = std::getenv("KTE_LSP_GOPLS"); p && *p)
+			command   = p;
+	} else if (lang == "rust") {
+		if (const char *p = std::getenv("KTE_LSP_RUST_ANALYZER"); p && *p)
+			command   = p;
+	}
+	if (debug_) {
+		std::fprintf(stderr, "[kte][lsp] startServerForBuffer: lang=%s cmd=%s args=%zu file=%s\n",
+		             lang.c_str(), command.c_str(), cfg.args.size(), buffer->Filename().c_str());
+		lsp_debug_file("startServerForBuffer: lang=%s cmd=%s args=%zu file=%s",
+		               lang.c_str(), command.c_str(), cfg.args.size(), buffer->Filename().c_str());
+	}
+	auto client = std::make_unique<LspProcessClient>(command, cfg.args);
+	// Wire diagnostics handler to manager
+	client->setDiagnosticsHandler([this](const std::string &uri, const std::vector<Diagnostic> &diags) {
+		this->handleDiagnostics(uri, diags);
+	});
+	// Determine workspace root using rootPatterns if set; fallback to file's parent
 	std::string rootPath;
 	if (!buffer->Filename().empty()) {
-		fs::path p(buffer->Filename());
-		rootPath = p.has_parent_path() ? p.parent_path().string() : std::string{};
+		rootPath = detectWorkspaceRoot(buffer->Filename(), cfg);
+		if (rootPath.empty()) {
+			fs::path p(buffer->Filename());
+			rootPath = p.has_parent_path() ? p.parent_path().string() : std::string{};
+		}
+	}
+	if (debug_) {
+		const char *pathEnv = std::getenv("PATH");
+		std::fprintf(stderr, "[kte][lsp] initializing server: rootPath=%s PATH=%s\n",
+		             rootPath.c_str(), pathEnv ? pathEnv : "<null>");
+		lsp_debug_file("initializing server: rootPath=%s PATH=%s",
+		               rootPath.c_str(), pathEnv ? pathEnv : "<null>");
 	}
 	if (!client->initialize(rootPath)) {
+		if (debug_) {
+			std::fprintf(stderr, "[kte][lsp] initialize failed for lang=%s\n", lang.c_str());
+			lsp_debug_file("initialize failed for lang=%s", lang.c_str());
+		}
 		return false;
 	}
 	servers_[lang] = std::move(client);
@@ -89,11 +151,84 @@ LspManager::stopAllServers()
 }


+bool
+LspManager::startServerForLanguage(const std::string &languageId, const std::string &rootPath)
+{
+	auto cfgIt = serverConfigs_.find(languageId);
+	if (cfgIt == serverConfigs_.end())
+		return false;
+
+	// If already running, nothing to do
+	auto it = servers_.find(languageId);
+	if (it != servers_.end() && it->second && it->second->isRunning()) {
+		return true;
+	}
+
+	const auto &cfg     = cfgIt->second;
+	std::string command = cfg.command;
+	if (languageId == "cpp") {
+		if (const char *p = std::getenv("KTE_LSP_CLANGD"); p && *p)
+			command   = p;
+	} else if (languageId == "go") {
+		if (const char *p = std::getenv("KTE_LSP_GOPLS"); p && *p)
+			command   = p;
+	} else if (languageId == "rust") {
+		if (const char *p = std::getenv("KTE_LSP_RUST_ANALYZER"); p && *p)
+			command   = p;
+	}
+	if (debug_) {
+		std::fprintf(stderr, "[kte][lsp] startServerForLanguage: lang=%s cmd=%s args=%zu root=%s\n",
+		             languageId.c_str(), command.c_str(), cfg.args.size(), rootPath.c_str());
+		lsp_debug_file("startServerForLanguage: lang=%s cmd=%s args=%zu root=%s",
+		               languageId.c_str(), command.c_str(), cfg.args.size(), rootPath.c_str());
+	}
+	auto client = std::make_unique<LspProcessClient>(command, cfg.args);
+	client->setDiagnosticsHandler([this](const std::string &uri, const std::vector<Diagnostic> &diags) {
+		this->handleDiagnostics(uri, diags);
+	});
+	std::string root = rootPath;
+	if (!root.empty()) {
+		// keep
+	} else {
+		// Try cwd if not provided
+		root = std::string();
+	}
+	if (!client->initialize(root)) {
+		if (debug_) {
+			std::fprintf(stderr, "[kte][lsp] initialize failed for lang=%s\n", languageId.c_str());
+			lsp_debug_file("initialize failed for lang=%s", languageId.c_str());
+		}
+		return false;
+	}
+	servers_[languageId] = std::move(client);
+	return true;
+}
+
+
+bool
+LspManager::restartServer(const std::string &languageId, const std::string &rootPath)
+{
+	stopServer(languageId);
+	return startServerForLanguage(languageId, rootPath);
+}
+
+
 void
 LspManager::onBufferOpened(Buffer *buffer)
 {
-	if (!startServerForBuffer(buffer))
+	if (debug_) {
+		std::fprintf(stderr, "[kte][lsp] onBufferOpened: file=%s lang=%s\n",
+		             buffer->Filename().c_str(), getLanguageId(buffer).c_str());
+		lsp_debug_file("onBufferOpened: file=%s lang=%s",
+		               buffer->Filename().c_str(), getLanguageId(buffer).c_str());
+	}
+	if (!startServerForBuffer(buffer)) {
+		if (debug_) {
+			std::fprintf(stderr, "[kte][lsp] onBufferOpened: server did not start\n");
+			lsp_debug_file("onBufferOpened: server did not start");
+		}
 		return;
+	}
 	auto *client = ensureServerForLanguage(getLanguageId(buffer));
 	if (!client)
 		return;
@@ -102,6 +237,12 @@ LspManager::onBufferOpened(Buffer *buffer)
 	const auto lang        = getLanguageId(buffer);
 	const int version      = static_cast<int>(buffer->Version());
 	const std::string text = buffer->FullText();
+	if (debug_) {
+		std::fprintf(stderr, "[kte][lsp] didOpen: uri=%s lang=%s version=%d bytes=%zu\n",
+		             uri.c_str(), lang.c_str(), version, text.size());
+		lsp_debug_file("didOpen: uri=%s lang=%s version=%d bytes=%zu",
+		               uri.c_str(), lang.c_str(), version, text.size());
+	}
 	client->didOpen(uri, lang, version, text);
 }

@@ -127,7 +268,38 @@ LspManager::onBufferChanged(Buffer *buffer)
 		ev.text = buffer->FullText();
 		changes.push_back(std::move(ev));
 	}
-	client->didChange(uri, version, changes);
+
+	// Option A: convert ranges from UTF-8 (editor coords) -> UTF-16 (LSP wire)
+	std::vector<TextDocumentContentChangeEvent> changes16;
+	changes16.reserve(changes.size());
+	// LineProvider that serves lines from this buffer by URI
+	Buffer *bufForUri = buffer; // changes are for this buffer
+	auto provider     = [bufForUri](const std::string &/*u*/, int line) -> std::string_view {
+		if (!bufForUri)
+			return std::string_view();
+		const auto &rows = bufForUri->Rows();
+		if (line < 0 || static_cast<size_t>(line) >= rows.size())
+			return std::string_view();
+		// Materialize one line into a thread_local scratch; return view
+		thread_local std::string scratch;
+		scratch = static_cast<std::string>(rows[static_cast<size_t>(line)]);
+		return std::string_view(scratch);
+	};
+	for (const auto &ch: changes) {
+		TextDocumentContentChangeEvent out = ch;
+		if (ch.range.has_value()) {
+			Range r16 = toUtf16(uri, *ch.range, provider);
+			if (debug_) {
+				lsp_debug_file("didChange range convert: L%d C%d-%d -> L%d C%d-%d",
+				               ch.range->start.line, ch.range->start.character,
+				               ch.range->end.character,
+				               r16.start.line, r16.start.character, r16.end.character);
+			}
+			out.range = r16;
+		}
+		changes16.push_back(std::move(out));
+	}
+	client->didChange(uri, version, changes16);
 }


@@ -157,7 +329,24 @@ void
 LspManager::requestCompletion(Buffer *buffer, Position pos, CompletionCallback callback)
 {
 	if (auto *client = ensureServerForLanguage(getLanguageId(buffer))) {
-		client->completion(getUri(buffer), pos, std::move(callback));
+		const auto uri = getUri(buffer);
+		// Convert position to UTF-16 using Option A provider
+		auto provider = [buffer](const std::string &/*u*/, int line) -> std::string_view {
+			if (!buffer)
+				return std::string_view();
+			const auto &rows = buffer->Rows();
+			if (line < 0 || static_cast<size_t>(line) >= rows.size())
+				return std::string_view();
+			thread_local std::string scratch;
+			scratch = static_cast<std::string>(rows[static_cast<size_t>(line)]);
+			return std::string_view(scratch);
+		};
+		Position p16 = toUtf16(uri, pos, provider);
+		if (debug_) {
+			lsp_debug_file("completion pos convert: L%d C%d -> L%d C%d", pos.line, pos.character, p16.line,
+			               p16.character);
+		}
+		client->completion(uri, p16, std::move(callback));
 	}
 }

@@ -166,7 +355,23 @@ void
 LspManager::requestHover(Buffer *buffer, Position pos, HoverCallback callback)
 {
 	if (auto *client = ensureServerForLanguage(getLanguageId(buffer))) {
-		client->hover(getUri(buffer), pos, std::move(callback));
+		const auto uri = getUri(buffer);
+		auto provider  = [buffer](const std::string &/*u*/, int line) -> std::string_view {
+			if (!buffer)
+				return std::string_view();
+			const auto &rows = buffer->Rows();
+			if (line < 0 || static_cast<size_t>(line) >= rows.size())
+				return std::string_view();
+			thread_local std::string scratch;
+			scratch = static_cast<std::string>(rows[static_cast<size_t>(line)]);
+			return std::string_view(scratch);
+		};
+		Position p16 = toUtf16(uri, pos, provider);
+		if (debug_) {
+			lsp_debug_file("hover pos convert: L%d C%d -> L%d C%d", pos.line, pos.character, p16.line,
+			               p16.character);
+		}
+		client->hover(uri, p16, std::move(callback));
 	}
 }

@@ -175,7 +380,23 @@ void
 LspManager::requestDefinition(Buffer *buffer, Position pos, LocationCallback callback)
 {
 	if (auto *client = ensureServerForLanguage(getLanguageId(buffer))) {
-		client->definition(getUri(buffer), pos, std::move(callback));
+		const auto uri = getUri(buffer);
+		auto provider  = [buffer](const std::string &/*u*/, int line) -> std::string_view {
+			if (!buffer)
+				return std::string_view();
+			const auto &rows = buffer->Rows();
+			if (line < 0 || static_cast<size_t>(line) >= rows.size())
+				return std::string_view();
+			thread_local std::string scratch;
+			scratch = static_cast<std::string>(rows[static_cast<size_t>(line)]);
+			return std::string_view(scratch);
+		};
+		Position p16 = toUtf16(uri, pos, provider);
+		if (debug_) {
+			lsp_debug_file("definition pos convert: L%d C%d -> L%d C%d", pos.line, pos.character, p16.line,
+			               p16.character);
+		}
+		client->definition(uri, p16, std::move(callback));
 	}
 }

@@ -183,14 +404,72 @@ LspManager::requestDefinition(Buffer *buffer, Position pos, LocationCallback cal
 void
 LspManager::handleDiagnostics(const std::string &uri, const std::vector<Diagnostic> &diagnostics)
 {
-	diagnosticStore_.setDiagnostics(uri, diagnostics);
+	// Convert incoming ranges from UTF-16 (wire) -> UTF-8 (editor)
+	std::vector<Diagnostic> conv = diagnostics;
+	Buffer *buf                  = findBufferByUri(uri);
+	auto provider                = [buf](const std::string &/*u*/, int line) -> std::string_view {
+		if (!buf)
+			return std::string_view();
+		const auto &rows = buf->Rows();
+		if (line < 0 || static_cast<size_t>(line) >= rows.size())
+			return std::string_view();
+		thread_local std::string scratch;
+		scratch = static_cast<std::string>(rows[static_cast<size_t>(line)]);
+		return std::string_view(scratch);
+	};
+	for (auto &d: conv) {
+		Range r8 = toUtf8(uri, d.range, provider);
+		if (debug_) {
+			lsp_debug_file("diagnostic range convert: L%d C%d-%d -> L%d C%d-%d",
+			               d.range.start.line, d.range.start.character, d.range.end.character,
+			               r8.start.line, r8.start.character, r8.end.character);
+		}
+		d.range = r8;
+	}
+	diagnosticStore_.setDiagnostics(uri, conv);
 	if (display_) {
-		display_->updateDiagnostics(uri, diagnostics);
+		display_->updateDiagnostics(uri, conv);
 		display_->updateStatusBar(diagnosticStore_.getErrorCount(uri), diagnosticStore_.getWarningCount(uri));
 	}
 }


+bool
+LspManager::toggleAutostart(const std::string &languageId)
+{
+	auto it = serverConfigs_.find(languageId);
+	if (it == serverConfigs_.end())
+		return false;
+	it->second.autostart = !it->second.autostart;
+	return it->second.autostart;
+}
+
+
+std::vector<std::string>
+LspManager::configuredLanguages() const
+{
+	std::vector<std::string> out;
+	out.reserve(serverConfigs_.size());
+	for (const auto &kv: serverConfigs_)
+		out.push_back(kv.first);
+	std::sort(out.begin(), out.end());
+	return out;
+}
+
+
+std::vector<std::string>
+LspManager::runningLanguages() const
+{
+	std::vector<std::string> out;
+	for (const auto &kv: servers_) {
+		if (kv.second && kv.second->isRunning())
+			out.push_back(kv.first);
+	}
+	std::sort(out.begin(), out.end());
+	return out;
+}
+
+
 std::string
 LspManager::getLanguageId(Buffer *buffer)
 {
@@ -223,6 +502,22 @@ LspManager::getUri(Buffer *buffer)
 }


+// Resolve a Buffer* by matching constructed file URI
+Buffer *
+LspManager::findBufferByUri(const std::string &uri)
+{
+	if (!editor_)
+		return nullptr;
+	// Compare against getUri for each buffer
+	auto &bufs = editor_->Buffers();
+	for (auto &b: bufs) {
+		if (getUri(&b) == uri)
+			return &b;
+	}
+	return nullptr;
+}
+
+
 std::string
 LspManager::extToLanguageId(const std::string &ext)
 {
@@ -268,6 +563,10 @@ LspManager::ensureServerForLanguage(const std::string &languageId)
 	if (cfg == serverConfigs_.end())
 		return nullptr;
 	auto client = std::make_unique<LspProcessClient>(cfg->second.command, cfg->second.args);
+	client->setDiagnosticsHandler([this](const std::string &uri, const std::vector<Diagnostic> &diags) {
+		this->handleDiagnostics(uri, diags);
+	});
+	// No specific file context here; initialize with empty or current working dir
 	if (!client->initialize(""))
 		return nullptr;
 	auto *ret            = client.get();
@@ -323,4 +622,73 @@ LspManager::patternToLanguageId(const std::string &pattern)
 		return {};
 	return extToLanguageId(ext);
 }
-} // namespace kte::lsp
+
+
+// Detect workspace root by walking up from filePath looking for any of the
+// configured rootPatterns (simple filenames). Supports comma/semicolon-separated
+// patterns in cfg.rootPatterns.
+std::string
+LspManager::detectWorkspaceRoot(const std::string &filePath, const LspServerConfig &cfg)
+{
+	if (filePath.empty())
+		return {};
+	fs::path start(filePath);
+	fs::path dir = start.has_parent_path() ? start.parent_path() : start;
+
+	// Build cache key
+	const std::string cacheKey = (dir.string() + "|" + cfg.rootPatterns);
+	auto it                    = rootCache_.find(cacheKey);
+	if (it != rootCache_.end()) {
+		return it->second;
+	}
+
+	// Split patterns by ',', ';', or ':'
+	std::vector<std::string> pats;
+	{
+		std::string acc;
+		for (char c: cfg.rootPatterns) {
+			if (c == ',' || c == ';' || c == ':') {
+				if (!acc.empty()) {
+					pats.push_back(acc);
+					acc.clear();
+				}
+			} else if (!std::isspace(static_cast<unsigned char>(c))) {
+				acc.push_back(c);
+			}
+		}
+		if (!acc.empty())
+			pats.push_back(acc);
+	}
+	// If no patterns defined, cache empty and return {}
+	if (pats.empty()) {
+		rootCache_[cacheKey] = {};
+		return {};
+	}
+
+	fs::path cur = dir;
+	while (true) {
+		// Check each pattern in this directory
+		for (const auto &pat: pats) {
+			if (pat.empty())
+				continue;
+			fs::path candidate = cur / pat;
+			std::error_code ec;
+			bool exists = fs::exists(candidate, ec);
+			if (!ec && exists) {
+				rootCache_[cacheKey] = cur.string();
+				return rootCache_[cacheKey];
+			}
+		}
+		if (cur.has_parent_path()) {
+			fs::path parent = cur.parent_path();
+			if (parent == cur)
+				break; // reached root guard
+			cur = parent;
+		} else {
+			break;
+		}
+	}
+	rootCache_[cacheKey] = {};
+	return {};
+}
+} // namespace kte::lsp
--- a/lsp/LspManager.h
+++ b/lsp/LspManager.h
@@ -15,6 +15,7 @@ class Editor; // fwd
 #include "DiagnosticStore.h"
 #include "LspClient.h"
 #include "LspServerConfig.h"
+#include "UtfCodec.h"

 namespace kte::lsp {
 class LspManager {
@@ -30,6 +31,11 @@ public:

 	void stopAllServers();

+	// Manual lifecycle controls
+	bool startServerForLanguage(const std::string &languageId, const std::string &rootPath = std::string());
+
+	bool restartServer(const std::string &languageId, const std::string &rootPath = std::string());
+
 	// Document sync (to be called by editor/buffer events)
 	void onBufferOpened(Buffer *buffer);

@@ -55,6 +61,14 @@ public:
 		debug_ = enabled;
 	}

+
+	// Configuration utilities
+	bool toggleAutostart(const std::string &languageId);
+
+	std::vector<std::string> configuredLanguages() const;
+
+	std::vector<std::string> runningLanguages() const;
+
 private:
 	[[maybe_unused]] Editor *editor_{}; // non-owning
 	DiagnosticDisplay *display_{}; // non-owning
@@ -79,6 +93,15 @@ private:
 	void registerDefaultServers();

 	static std::string patternToLanguageId(const std::string &pattern);
+
+	// Workspace root detection helpers/cache
+	std::string detectWorkspaceRoot(const std::string &filePath, const LspServerConfig &cfg);
+
+	// key = startDir + "|" + cfg.rootPatterns
+	std::unordered_map<std::string, std::string> rootCache_;
+
+	// Resolve a buffer by its file:// (or untitled:) URI
+	Buffer *findBufferByUri(const std::string &uri);
 };
 } // namespace kte::lsp

--- a/lsp/LspProcessClient.cc
+++ b/lsp/LspProcessClient.cc
@@ -1,21 +1,191 @@
 /*
- * LspProcessClient.cc - initial stub implementation
+ * LspProcessClient.cc - process-based LSP client (Phase 1 minimal)
 */
 #include "LspProcessClient.h"

+#include <sstream>
+#include <vector>
+#include <string>
+#include <cstring>
+#include <cstdio>
+#include <cstdlib>
+#include <cerrno>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <thread>
+
+#include "json.h"
+
 namespace kte::lsp {
 LspProcessClient::LspProcessClient(std::string serverCommand, std::vector<std::string> serverArgs)
-	: command_(std::move(serverCommand)), args_(std::move(serverArgs)), transport_(new JsonRpcTransport()) {}
+	: command_(std::move(serverCommand)), args_(std::move(serverArgs)), transport_(new JsonRpcTransport())
+{
+	if (const char *dbg = std::getenv("KTE_LSP_DEBUG"); dbg && *dbg) {
+		debug_ = true;
+	}
+	if (const char *to = std::getenv("KTE_LSP_REQ_TIMEOUT_MS"); to && *to) {
+		char *end   = nullptr;
+		long long v = std::strtoll(to, &end, 10);
+		if (end && *end == '\0' && v >= 0) {
+			requestTimeoutMs_ = v;
+		}
+	}
+	if (const char *mp = std::getenv("KTE_LSP_MAX_PENDING"); mp && *mp) {
+		char *end   = nullptr;
+		long long v = std::strtoll(mp, &end, 10);
+		if (end && *end == '\0' && v >= 0) {
+			maxPending_ = static_cast<size_t>(v);
+		}
+	}
+}


-LspProcessClient::~LspProcessClient() = default;
+LspProcessClient::~LspProcessClient()
+{
+	shutdown();
+}


 bool
-LspProcessClient::initialize(const std::string &/*rootPath*/)
+LspProcessClient::spawnServerProcess()
 {
-	// Phase 1–2: no real process spawn yet
+	int toChild[2]; // parent writes toChild[1] -> child's stdin
+	int fromChild[2]; // child writes fromChild[1] -> parent's stdout reader
+	if (pipe(toChild) != 0) {
+		if (debug_)
+			std::fprintf(stderr, "[kte][lsp] pipe(toChild) failed: %s\n", std::strerror(errno));
+		return false;
+	}
+	if (pipe(fromChild) != 0) {
+		::close(toChild[0]);
+		::close(toChild[1]);
+		if (debug_)
+			std::fprintf(stderr, "[kte][lsp] pipe(fromChild) failed: %s\n", std::strerror(errno));
+		return false;
+	}
+
+	pid_t pid = fork();
+	if (pid < 0) {
+		// fork failed
+		::close(toChild[0]);
+		::close(toChild[1]);
+		::close(fromChild[0]);
+		::close(fromChild[1]);
+		if (debug_)
+			std::fprintf(stderr, "[kte][lsp] fork failed: %s\n", std::strerror(errno));
+		return false;
+	}
+	if (pid == 0) {
+		// Child: set up stdio
+		::dup2(toChild[0], STDIN_FILENO);
+		::dup2(fromChild[1], STDOUT_FILENO);
+		// Close extra fds
+		::close(toChild[0]);
+		::close(toChild[1]);
+		::close(fromChild[0]);
+		::close(fromChild[1]);
+		// Build argv
+		std::vector<char *> argv;
+		argv.push_back(const_cast<char *>(command_.c_str()));
+		for (auto &s: args_)
+			argv.push_back(const_cast<char *>(s.c_str()));
+		argv.push_back(nullptr);
+		// Exec
+		execvp(command_.c_str(), argv.data());
+		// If exec fails
+		// Note: in child; cannot easily log to parent. Attempt to write to stderr.
+		std::fprintf(stderr, "[kte][lsp] execvp failed for '%s': %s\n", command_.c_str(), std::strerror(errno));
+		_exit(127);
+	}
+
+	// Parent: keep ends
+	childPid_ = pid;
+	outFd_    = toChild[1]; // write to child's stdin
+	inFd_     = fromChild[0]; // read from child's stdout
+	// Close the other ends we don't use
+	::close(toChild[0]);
+	::close(fromChild[1]);
+	// Set CLOEXEC on our fds
+	fcntl(outFd_, F_SETFD, FD_CLOEXEC);
+	fcntl(inFd_, F_SETFD, FD_CLOEXEC);
+	if (debug_) {
+		std::ostringstream oss;
+		oss << command_;
+		for (const auto &a: args_) {
+			oss << ' ' << a;
+		}
+		const char *pathEnv = std::getenv("PATH");
+		std::fprintf(stderr, "[kte][lsp] spawned pid=%d argv=[%s] inFd=%d outFd=%d PATH=%s\n",
+		             static_cast<int>(childPid_), oss.str().c_str(), inFd_, outFd_,
+		             pathEnv ? pathEnv : "<null>");
+	}
+	transport_->connect(inFd_, outFd_);
+	return true;
+}
+
+
+void
+LspProcessClient::terminateProcess()
+{
+	if (outFd_ >= 0) {
+		::close(outFd_);
+		outFd_ = -1;
+	}
+	if (inFd_ >= 0) {
+		::close(inFd_);
+		inFd_ = -1;
+	}
+	if (childPid_ > 0) {
+		// Try to wait non-blocking; if still running, send SIGTERM
+		int status = 0;
+		pid_t r    = waitpid(childPid_, &status, WNOHANG);
+		if (r == 0) {
+			// still running
+			kill(childPid_, SIGTERM);
+			waitpid(childPid_, &status, 0);
+		}
+		childPid_ = -1;
+	}
+}
+
+
+void
+LspProcessClient::sendInitialize(const std::string &rootPath)
+{
+	int idNum            = nextRequestIntId_++;
+	pendingInitializeId_ = std::to_string(idNum);
+	nlohmann::json j;
+	j["jsonrpc"] = "2.0";
+	j["id"]      = idNum;
+	j["method"]  = "initialize";
+	nlohmann::json params;
+	params["processId"] = static_cast<int>(getpid());
+	params["rootUri"]   = toFileUri(rootPath);
+	// Minimal client capabilities for now
+	nlohmann::json caps;
+	caps["textDocument"]["synchronization"]["didSave"] = true;
+	params["capabilities"]                             = std::move(caps);
+	j["params"]                                        = std::move(params);
+	transport_->send("initialize", j.dump());
+}
+
+
+bool
+LspProcessClient::initialize(const std::string &rootPath)
+{
+	if (running_)
+		return true;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] initialize: rootPath=%s\n", rootPath.c_str());
+	if (!spawnServerProcess())
+		return false;
 	running_ = true;
+	sendInitialize(rootPath);
+	startReader();
+	startTimeoutWatchdog();
 	return true;
 }

@@ -23,37 +193,509 @@ LspProcessClient::initialize(const std::string &/*rootPath*/)
 void
 LspProcessClient::shutdown()
 {
+	if (!running_)
+		return;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] shutdown\n");
+	// Send shutdown request then exit notification (best-effort)
+	int id = nextRequestIntId_++;
+	{
+		nlohmann::json j;
+		j["jsonrpc"] = "2.0";
+		j["id"]      = id;
+		j["method"]  = "shutdown";
+		transport_->send("shutdown", j.dump());
+	}
+	{
+		nlohmann::json j;
+		j["jsonrpc"] = "2.0";
+		j["method"]  = "exit";
+		transport_->send("exit", j.dump());
+	}
+	// Close pipes to unblock reader, then join thread, then ensure child is gone
+	terminateProcess();
+	stopReader();
+	stopTimeoutWatchdog();
+	// Clear any pending callbacks
+	{
+		std::lock_guard<std::mutex> lk(pendingMutex_);
+		pending_.clear();
+		pendingOrder_.clear();
+	}
 	running_ = false;
 }


 void
-LspProcessClient::didOpen(const std::string &/*uri*/, const std::string &/*languageId*/,
-                          int /*version*/, const std::string &/*text*/)
+LspProcessClient::didOpen(const std::string &uri, const std::string &languageId,
+                          int version, const std::string &text)
 {
-	// Stub: would send textDocument/didOpen
+	if (!running_)
+		return;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] -> didOpen uri=%s lang=%s version=%d bytes=%zu\n",
+		             uri.c_str(), languageId.c_str(), version, text.size());
+	nlohmann::json j;
+	j["jsonrpc"]                              = "2.0";
+	j["method"]                               = "textDocument/didOpen";
+	j["params"]["textDocument"]["uri"]        = uri;
+	j["params"]["textDocument"]["languageId"] = languageId;
+	j["params"]["textDocument"]["version"]    = version;
+	j["params"]["textDocument"]["text"]       = text;
+	transport_->send("textDocument/didOpen", j.dump());
 }


 void
-LspProcessClient::didChange(const std::string &/*uri*/, int /*version*/,
-                            const std::vector<TextDocumentContentChangeEvent> &/*changes*/)
+LspProcessClient::didChange(const std::string &uri, int version,
+                            const std::vector<TextDocumentContentChangeEvent> &changes)
 {
-	// Stub: would send textDocument/didChange
+	if (!running_)
+		return;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] -> didChange uri=%s version=%d changes=%zu\n",
+		             uri.c_str(), version, changes.size());
+	// Phase 1: send full or ranged changes using proper JSON construction
+	nlohmann::json j;
+	j["jsonrpc"]                           = "2.0";
+	j["method"]                            = "textDocument/didChange";
+	j["params"]["textDocument"]["uri"]     = uri;
+	j["params"]["textDocument"]["version"] = version;
+	auto &arr                              = j["params"]["contentChanges"];
+	arr                                    = nlohmann::json::array();
+	for (const auto &ch: changes) {
+		nlohmann::json c;
+		if (ch.range.has_value()) {
+			c["range"]["start"]["line"]      = ch.range->start.line;
+			c["range"]["start"]["character"] = ch.range->start.character;
+			c["range"]["end"]["line"]        = ch.range->end.line;
+			c["range"]["end"]["character"]   = ch.range->end.character;
+		}
+		c["text"] = ch.text;
+		arr.push_back(std::move(c));
+	}
+	transport_->send("textDocument/didChange", j.dump());
 }


 void
-LspProcessClient::didClose(const std::string &/*uri*/)
+LspProcessClient::didClose(const std::string &uri)
 {
-	// Stub
+	if (!running_)
+		return;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] -> didClose uri=%s\n", uri.c_str());
+	nlohmann::json j;
+	j["jsonrpc"]                       = "2.0";
+	j["method"]                        = "textDocument/didClose";
+	j["params"]["textDocument"]["uri"] = uri;
+	transport_->send("textDocument/didClose", j.dump());
 }


 void
-LspProcessClient::didSave(const std::string &/*uri*/)
+LspProcessClient::didSave(const std::string &uri)
 {
-	// Stub
+	if (!running_)
+		return;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] -> didSave uri=%s\n", uri.c_str());
+	nlohmann::json j;
+	j["jsonrpc"]                       = "2.0";
+	j["method"]                        = "textDocument/didSave";
+	j["params"]["textDocument"]["uri"] = uri;
+	transport_->send("textDocument/didSave", j.dump());
+}
+
+
+void
+LspProcessClient::startReader()
+{
+	stopReader_ = false;
+	reader_     = std::thread([this] {
+		this->readerLoop();
+	});
+}
+
+
+void
+LspProcessClient::stopReader()
+{
+	stopReader_ = true;
+	if (reader_.joinable()) {
+		// Waking up read() by closing inFd_ is handled in terminateProcess(); ensure it’s closed first
+		// Here, best-effort join with small delay
+		reader_.join();
+	}
+}
+
+
+void
+LspProcessClient::readerLoop()
+{
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] readerLoop start\n");
+	while (!stopReader_) {
+		auto msg = transport_->read();
+		if (!msg.has_value()) {
+			// EOF or error
+			break;
+		}
+		handleIncoming(msg->raw);
+	}
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] readerLoop end\n");
+}
+
+
+void
+LspProcessClient::handleIncoming(const std::string &json)
+{
+	try {
+		auto j = nlohmann::json::parse(json, nullptr, false);
+		if (j.is_discarded())
+			return; // malformed JSON
+		// Validate jsonrpc if present
+		if (auto itRpc = j.find("jsonrpc"); itRpc != j.end()) {
+			if (!itRpc->is_string() || *itRpc != "2.0")
+				return;
+		}
+
+		auto normalizeId = [](const nlohmann::json &idVal) -> std::string {
+			if (idVal.is_string())
+				return idVal.get<std::string>();
+			if (idVal.is_number_integer())
+				return std::to_string(idVal.get<long long>());
+			return std::string();
+		};
+
+		// Handle responses (have id and no method) or server -> client requests (have id and method)
+		if (auto itId = j.find("id"); itId != j.end() && !itId->is_null()) {
+			const std::string respIdStr = normalizeId(*itId);
+
+			// If it's a request from server, it will also have a method
+			if (auto itMeth = j.find("method"); itMeth != j.end() && itMeth->is_string()) {
+				const std::string method = *itMeth;
+				if (method == "workspace/configuration") {
+					// Respond with default empty settings array matching requested items length
+					size_t n = 0;
+					if (auto itParams = j.find("params");
+						itParams != j.end() && itParams->is_object()) {
+						if (auto itItems = itParams->find("items");
+							itItems != itParams->end() && itItems->is_array()) {
+							n = itItems->size();
+						}
+					}
+					nlohmann::json resp;
+					resp["jsonrpc"] = "2.0";
+					// echo id type: if original was string, send string; else number
+					if (itId->is_string())
+						resp["id"] = *itId;
+					else if (itId->is_number_integer())
+						resp["id"] = *itId;
+					nlohmann::json arr = nlohmann::json::array();
+					for (size_t i = 0; i < n; ++i)
+						arr.push_back(nlohmann::json::object());
+					resp["result"] = std::move(arr);
+					transport_->send("response", resp.dump());
+					return;
+				}
+				if (method == "window/showMessageRequest") {
+					// Best-effort respond with null result (dismiss)
+					nlohmann::json resp;
+					resp["jsonrpc"] = "2.0";
+					if (itId->is_string())
+						resp["id"] = *itId;
+					else if (itId->is_number_integer())
+						resp["id"] = *itId;
+					resp["result"] = nullptr;
+					transport_->send("response", resp.dump());
+					return;
+				}
+				// Unknown server request: respond with MethodNotFound
+				nlohmann::json err;
+				err["code"]    = -32601;
+				err["message"] = "Method not found";
+				nlohmann::json resp;
+				resp["jsonrpc"] = "2.0";
+				if (itId->is_string())
+					resp["id"] = *itId;
+				else if (itId->is_number_integer())
+					resp["id"] = *itId;
+				resp["error"] = std::move(err);
+				transport_->send("response", resp.dump());
+				return;
+			}
+
+			// Initialize handshake special-case
+			if (!pendingInitializeId_.empty() && respIdStr == pendingInitializeId_) {
+				nlohmann::json init;
+				init["jsonrpc"] = "2.0";
+				init["method"]  = "initialized";
+				init["params"]  = nlohmann::json::object();
+				transport_->send("initialized", init.dump());
+				pendingInitializeId_.clear();
+			}
+			// Dispatcher lookup
+			std::function < void(const nlohmann::json &, const nlohmann::json *) > cb;
+			{
+				std::lock_guard<std::mutex> lk(pendingMutex_);
+				auto it = pending_.find(respIdStr);
+				if (it != pending_.end()) {
+					cb = it->second.callback;
+					if (it->second.orderIt != pendingOrder_.end()) {
+						pendingOrder_.erase(it->second.orderIt);
+					}
+					pending_.erase(it);
+				}
+			}
+			if (cb) {
+				const nlohmann::json *errPtr = nullptr;
+				const auto itErr             = j.find("error");
+				if (itErr != j.end() && itErr->is_object())
+					errPtr = &(*itErr);
+				nlohmann::json result;
+				const auto itRes = j.find("result");
+				if (itRes != j.end())
+					result = *itRes; // may be null
+				cb(result, errPtr);
+			}
+			return;
+		}
+		const auto itMethod = j.find("method");
+		if (itMethod == j.end() || !itMethod->is_string())
+			return;
+		const std::string method = *itMethod;
+		if (method == "window/logMessage") {
+			if (debug_) {
+				const auto itParams = j.find("params");
+				if (itParams != j.end()) {
+					const auto itMsg = itParams->find("message");
+					if (itMsg != itParams->end() && itMsg->is_string()) {
+						std::fprintf(stderr, "[kte][lsp] logMessage: %s\n",
+						             itMsg->get_ref<const std::string &>().c_str());
+					}
+				}
+			}
+			return;
+		}
+		if (method == "window/showMessage") {
+			const auto itParams = j.find("params");
+			if (debug_ &&itParams
+			
+			!=
+			j.end() && itParams->is_object()
+			)
+			{
+				int typ = 0;
+				std::string msg;
+				if (auto itm = itParams->find("message"); itm != itParams->end() && itm->is_string())
+					msg  = *itm;
+				if (auto ity = itParams->find("type");
+					ity != itParams->end() && ity->is_number_integer())
+					typ = *ity;
+				std::fprintf(stderr, "[kte][lsp] showMessage(type=%d): %s\n", typ, msg.c_str());
+			}
+			return;
+		}
+		if (method != "textDocument/publishDiagnostics") {
+			return;
+		}
+		const auto itParams = j.find("params");
+		if (itParams == j.end() || !itParams->is_object())
+			return;
+		const auto itUri = itParams->find("uri");
+		if (itUri == itParams->end() || !itUri->is_string())
+			return;
+		const std::string uri = *itUri;
+		std::vector<Diagnostic> diags;
+		const auto itDiag = itParams->find("diagnostics");
+		if (itDiag != itParams->end() && itDiag->is_array()) {
+			for (const auto &djson: *itDiag) {
+				if (!djson.is_object())
+					continue;
+				Diagnostic d;
+				// severity
+				int sev = 3;
+				if (auto itS = djson.find("severity"); itS != djson.end() && itS->is_number_integer()) {
+					sev = *itS;
+				}
+				switch (sev) {
+				case 1:
+					d.severity = DiagnosticSeverity::Error;
+					break;
+				case 2:
+					d.severity = DiagnosticSeverity::Warning;
+					break;
+				case 3:
+					d.severity = DiagnosticSeverity::Information;
+					break;
+				case 4:
+					d.severity = DiagnosticSeverity::Hint;
+					break;
+				default:
+					d.severity = DiagnosticSeverity::Information;
+					break;
+				}
+				if (auto itM = djson.find("message"); itM != djson.end() && itM->is_string()) {
+					d.message = *itM;
+				}
+				if (auto itR = djson.find("range"); itR != djson.end() && itR->is_object()) {
+					if (auto itStart = itR->find("start");
+						itStart != itR->end() && itStart->is_object()) {
+						if (auto itL = itStart->find("line");
+							itL != itStart->end() && itL->is_number_integer()) {
+							d.range.start.line = *itL;
+						}
+						if (auto itC = itStart->find("character");
+							itC != itStart->end() && itC->is_number_integer()) {
+							d.range.start.character = *itC;
+						}
+					}
+					if (auto itEnd = itR->find("end"); itEnd != itR->end() && itEnd->is_object()) {
+						if (auto itL = itEnd->find("line");
+							itL != itEnd->end() && itL->is_number_integer()) {
+							d.range.end.line = *itL;
+						}
+						if (auto itC = itEnd->find("character");
+							itC != itEnd->end() && itC->is_number_integer()) {
+							d.range.end.character = *itC;
+						}
+					}
+				}
+				// optional code/source
+				if (auto itCode = djson.find("code"); itCode != djson.end()) {
+					if (itCode->is_string())
+						d.code = itCode->get<std::string>();
+					else if (itCode->is_number_integer())
+						d.code = std::to_string(itCode->get<int>());
+				}
+				if (auto itSrc = djson.find("source"); itSrc != djson.end() && itSrc->is_string()) {
+					d.source = itSrc->get<std::string>();
+				}
+				diags.push_back(std::move(d));
+			}
+		}
+		if (diagnosticsHandler_) {
+			diagnosticsHandler_(uri, diags);
+		}
+	} catch (...) {
+		// swallow parse errors
+	}
+}
+
+
+int
+LspProcessClient::sendRequest(const std::string &method, const nlohmann::json &params,
+                              std::function<void(const nlohmann::json & result, const nlohmann::json * errorJson)> cb)
+{
+	if (!running_)
+		return 0;
+	int id = nextRequestIntId_++;
+	nlohmann::json j;
+	j["jsonrpc"] = "2.0";
+	j["id"]      = id;
+	j["method"]  = method;
+	if (!params.is_null())
+		j["params"] = params;
+	if (debug_)
+		std::fprintf(stderr, "[kte][lsp] -> request method=%s id=%d\n", method.c_str(), id);
+	transport_->send(method, j.dump());
+	if (cb) {
+		std::function < void() > callDropped;
+		{
+			std::lock_guard<std::mutex> lk(pendingMutex_);
+			if (maxPending_ > 0 && pending_.size() >= maxPending_) {
+				// Evict oldest
+				if (!pendingOrder_.empty()) {
+					std::string oldestId = pendingOrder_.front();
+					auto it              = pending_.find(oldestId);
+					if (it != pending_.end()) {
+						auto cbOld          = it->second.callback;
+						std::string methOld = it->second.method;
+						if (debug_) {
+							std::fprintf(
+								stderr,
+								"[kte][lsp] dropping oldest pending id=%s method=%s (cap=%zu)\n",
+								oldestId.c_str(), methOld.c_str(), maxPending_);
+						}
+						// Prepare drop callback to run outside lock
+						callDropped = [cbOld] {
+							if (cbOld) {
+								nlohmann::json err;
+								err["code"]    = -32001;
+								err["message"] =
+									"Request dropped (max pending exceeded)";
+								cbOld(nlohmann::json(), &err);
+							}
+						};
+						pending_.erase(it);
+					}
+					pendingOrder_.pop_front();
+				}
+			}
+			pendingOrder_.push_back(std::to_string(id));
+			auto itOrder = pendingOrder_.end();
+			--itOrder;
+			PendingRequest pr;
+			pr.method   = method;
+			pr.callback = std::move(cb);
+			if (requestTimeoutMs_ > 0) {
+				pr.deadline = std::chrono::steady_clock::now() + std::chrono::milliseconds(
+					              requestTimeoutMs_);
+			}
+			pr.orderIt                   = itOrder;
+			pending_[std::to_string(id)] = std::move(pr);
+		}
+		if (callDropped)
+			callDropped();
+	}
+	return id;
+}
+
+
+void
+LspProcessClient::completion(const std::string &uri, Position pos, CompletionCallback cb)
+{
+	nlohmann::json params;
+	params["textDocument"]["uri"]   = uri;
+	params["position"]["line"]      = pos.line;
+	params["position"]["character"] = pos.character;
+	sendRequest("textDocument/completion", params,
+	            [cb = std::move(cb)](const nlohmann::json &/*result*/, const nlohmann::json * /*error*/) {
+		            if (cb)
+			            cb();
+	            });
+}
+
+
+void
+LspProcessClient::hover(const std::string &uri, Position pos, HoverCallback cb)
+{
+	nlohmann::json params;
+	params["textDocument"]["uri"]   = uri;
+	params["position"]["line"]      = pos.line;
+	params["position"]["character"] = pos.character;
+	sendRequest("textDocument/hover", params,
+	            [cb = std::move(cb)](const nlohmann::json &/*result*/, const nlohmann::json * /*error*/) {
+		            if (cb)
+			            cb();
+	            });
+}
+
+
+void
+LspProcessClient::definition(const std::string &uri, Position pos, LocationCallback cb)
+{
+	nlohmann::json params;
+	params["textDocument"]["uri"]   = uri;
+	params["position"]["line"]      = pos.line;
+	params["position"]["character"] = pos.character;
+	sendRequest("textDocument/definition", params,
+	            [cb = std::move(cb)](const nlohmann::json &/*result*/, const nlohmann::json * /*error*/) {
+		            if (cb)
+			            cb();
+	            });
 }


@@ -69,4 +711,73 @@ LspProcessClient::getServerName() const
 {
 	return command_;
 }
+
+
+std::string
+LspProcessClient::toFileUri(const std::string &path)
+{
+	if (path.empty())
+		return std::string();
+#ifdef _WIN32
+	return std::string("file:/") + path;
+#else
+	return std::string("file://") + path;
+#endif
+}
+
+
+void
+LspProcessClient::startTimeoutWatchdog()
+{
+	stopTimeout_ = false;
+	if (requestTimeoutMs_ <= 0)
+		return;
+	timeoutThread_ = std::thread([this] {
+		while (!stopTimeout_) {
+			std::this_thread::sleep_for(std::chrono::milliseconds(100));
+			auto now = std::chrono::steady_clock::now();
+			struct Expired {
+				std::string id;
+				std::string method;
+				std::function<void(const nlohmann::json &, const nlohmann::json *)> cb;
+			};
+			std::vector<Expired> expired;
+			{
+				std::lock_guard<std::mutex> lk(pendingMutex_);
+				for (auto it = pending_.begin(); it != pending_.end();) {
+					const auto &pr = it->second;
+					if (pr.deadline.time_since_epoch().count() != 0 && now >= pr.deadline) {
+						expired.push_back(Expired{it->first, pr.method, pr.callback});
+						if (pr.orderIt != pendingOrder_.end())
+							pendingOrder_.erase(pr.orderIt);
+						it = pending_.erase(it);
+					} else {
+						++it;
+					}
+				}
+			}
+			for (auto &kv: expired) {
+				if (debug_) {
+					std::fprintf(stderr, "[kte][lsp] request timeout id=%s method=%s\n",
+					             kv.id.c_str(), kv.method.c_str());
+				}
+				if (kv.cb) {
+					nlohmann::json err;
+					err["code"]    = -32000;
+					err["message"] = "Request timed out";
+					kv.cb(nlohmann::json(), &err);
+				}
+			}
+		}
+	});
+}
+
+
+void
+LspProcessClient::stopTimeoutWatchdog()
+{
+	stopTimeout_ = true;
+	if (timeoutThread_.joinable())
+		timeoutThread_.join();
+}
 } // namespace kte::lsp
--- a/lsp/LspProcessClient.h
+++ b/lsp/LspProcessClient.h
@@ -7,6 +7,15 @@
 #include <memory>
 #include <string>
 #include <vector>
+#include <thread>
+#include <atomic>
+#include <functional>
+#include <unordered_map>
+#include <mutex>
+#include <chrono>
+#include <list>
+
+#include "json.h"

 #include "LspClient.h"
 #include "JsonRpcTransport.h"
@@ -32,15 +41,148 @@ public:

 	void didSave(const std::string &uri) override;

+	// Language Features (wire-up via dispatcher; minimal callbacks for now)
+	void completion(const std::string &uri, Position pos,
+	                CompletionCallback cb) override;
+
+	void hover(const std::string &uri, Position pos,
+	           HoverCallback cb) override;
+
+	void definition(const std::string &uri, Position pos,
+	                LocationCallback cb) override;
+
 	bool isRunning() const override;

 	std::string getServerName() const override;

+
+	void setDiagnosticsHandler(DiagnosticsHandler h) override
+	{
+		diagnosticsHandler_ = std::move(h);
+	}
+
 private:
 	std::string command_;
 	std::vector<std::string> args_;
 	std::unique_ptr<JsonRpcTransport> transport_;
-	bool running_ = false;
+	bool running_         = false;
+	bool debug_           = false;
+	int inFd_             = -1; // read from server (server stdout)
+	int outFd_            = -1; // write to server (server stdin)
+	pid_t childPid_       = -1;
+	int nextRequestIntId_ = 1;
+	std::string pendingInitializeId_{}; // echo exactly as sent (string form)
+
+	// Incoming processing
+	std::thread reader_;
+	std::atomic<bool> stopReader_{false};
+	DiagnosticsHandler diagnosticsHandler_{};
+
+	// Simple request dispatcher: map request id -> callback
+	struct PendingRequest {
+		std::string method;
+		// If error is present, errorJson points to it; otherwise nullptr
+		std::function<void(const nlohmann::json & result, const nlohmann::json * errorJson)> callback;
+		// Optional timeout
+		std::chrono::steady_clock::time_point deadline{}; // epoch if no timeout
+		// Order tracking for LRU eviction
+		std::list<std::string>::iterator orderIt{};
+	};
+
+	std::unordered_map<std::string, PendingRequest> pending_;
+	// Maintain insertion order (oldest at front)
+	std::list<std::string> pendingOrder_;
+	std::mutex pendingMutex_;
+
+	// Timeout/watchdog for pending requests
+	std::thread timeoutThread_;
+	std::atomic<bool> stopTimeout_{false};
+	int64_t requestTimeoutMs_ = 0; // 0 = disabled
+	size_t maxPending_        = 0; // 0 = unlimited
+
+	bool spawnServerProcess();
+
+	void terminateProcess();
+
+	static std::string toFileUri(const std::string &path);
+
+	void sendInitialize(const std::string &rootPath);
+
+	void startReader();
+
+	void stopReader();
+
+	void readerLoop();
+
+	void handleIncoming(const std::string &json);
+
+	// Helper to send a request with params and register a response callback
+	int sendRequest(const std::string &method, const nlohmann::json &params,
+	                std::function<void(const nlohmann::json & result, const nlohmann::json * errorJson)> cb);
+
+	// Start/stop timeout thread
+	void startTimeoutWatchdog();
+
+	void stopTimeoutWatchdog();
+
+public:
+	// Test hook: inject a raw JSON message as if received from server
+	void debugInjectMessageForTest(const std::string &raw)
+	{
+		handleIncoming(raw);
+	}
+
+
+	// Test hook: add a pending request entry manually
+	void debugAddPendingForTest(const std::string &id, const std::string &method,
+	                            std::function<void(const nlohmann::json & result,
+	                            const nlohmann::json *errorJson)
+
+	>
+	cb
+	)
+	{
+		std::lock_guard<std::mutex> lk(pendingMutex_);
+		pendingOrder_.push_back(id);
+		auto it = pendingOrder_.end();
+		--it;
+		PendingRequest pr{method, std::move(cb), {}, it};
+		pending_[id] = std::move(pr);
+	}
+
+
+	// Test hook: override timeout
+	void setRequestTimeoutMsForTest(int64_t ms)
+	{
+		requestTimeoutMs_ = ms;
+	}
+
+
+	// Test hook: set max pending
+	void setMaxPendingForTest(size_t maxPending)
+	{
+		maxPending_ = maxPending;
+	}
+
+
+	// Test hook: set running flag (to allow sendRequest in tests without spawning)
+	void setRunningForTest(bool r)
+	{
+		running_ = r;
+	}
+
+
+	// Test hook: send a raw request using internal machinery
+	int debugSendRequestForTest(const std::string &method, const nlohmann::json &params,
+	                            std::function<void(const nlohmann::json & result,
+	                            const nlohmann::json *errorJson)
+
+	>
+	cb
+	)
+	{
+		return sendRequest(method, params, std::move(cb));
+	}
 };
 } // namespace kte::lsp

--- a/lsp/LspTypes.h
+++ b/lsp/LspTypes.h
@@ -10,6 +10,10 @@
 #include <vector>

 namespace kte::lsp {
+// NOTE on coordinates:
+// - Internal editor coordinates use UTF-8 columns counted by Unicode scalars.
+// - LSP wire protocol uses UTF-16 code units for the `character` field.
+//   Conversions are performed in higher layers via `lsp/UtfCodec.h` helpers.
 struct Position {
 	int line      = 0;
 	int character = 0;
--- a/lsp/UtfCodec.cc
+++ b/lsp/UtfCodec.cc
@@ -0,0 +1,155 @@
+/*
+ * UtfCodec.cc - UTF-8 <-> UTF-16 code unit position conversions
+ */
+#include "UtfCodec.h"
+
+#include <cassert>
+
+namespace kte::lsp {
+// Decode next code point from a UTF-8 string.
+// On invalid input, consumes 1 byte and returns U+FFFD.
+// Returns: (codepoint, bytesConsumed)
+static inline std::pair<uint32_t, size_t>
+decodeUtf8(std::string_view s, size_t i)
+{
+	if (i >= s.size())
+		return {0, 0};
+	unsigned char c0 = static_cast<unsigned char>(s[i]);
+	if (c0 < 0x80) {
+		return {c0, 1};
+	}
+	// Determine sequence length
+	if ((c0 & 0xE0) == 0xC0) {
+		if (i + 1 >= s.size())
+			return {0xFFFD, 1};
+		unsigned char c1 = static_cast<unsigned char>(s[i + 1]);
+		if ((c1 & 0xC0) != 0x80)
+			return {0xFFFD, 1};
+		uint32_t cp = ((c0 & 0x1F) << 6) | (c1 & 0x3F);
+		// Overlong check: must be >= 0x80
+		if (cp < 0x80)
+			return {0xFFFD, 1};
+		return {cp, 2};
+	}
+	if ((c0 & 0xF0) == 0xE0) {
+		if (i + 2 >= s.size())
+			return {0xFFFD, 1};
+		unsigned char c1 = static_cast<unsigned char>(s[i + 1]);
+		unsigned char c2 = static_cast<unsigned char>(s[i + 2]);
+		if ((c1 & 0xC0) != 0x80 || (c2 & 0xC0) != 0x80)
+			return {0xFFFD, 1};
+		uint32_t cp = ((c0 & 0x0F) << 12) | ((c1 & 0x3F) << 6) | (c2 & 0x3F);
+		// Overlong / surrogate range check
+		if (cp < 0x800 || (cp >= 0xD800 && cp <= 0xDFFF))
+			return {0xFFFD, 1};
+		return {cp, 3};
+	}
+	if ((c0 & 0xF8) == 0xF0) {
+		if (i + 3 >= s.size())
+			return {0xFFFD, 1};
+		unsigned char c1 = static_cast<unsigned char>(s[i + 1]);
+		unsigned char c2 = static_cast<unsigned char>(s[i + 2]);
+		unsigned char c3 = static_cast<unsigned char>(s[i + 3]);
+		if ((c1 & 0xC0) != 0x80 || (c2 & 0xC0) != 0x80 || (c3 & 0xC0) != 0x80)
+			return {0xFFFD, 1};
+		uint32_t cp = ((c0 & 0x07) << 18) | ((c1 & 0x3F) << 12) | ((c2 & 0x3F) << 6) | (c3 & 0x3F);
+		// Overlong / max range check
+		if (cp < 0x10000 || cp > 0x10FFFF)
+			return {0xFFFD, 1};
+		return {cp, 4};
+	}
+	return {0xFFFD, 1};
+}
+
+
+static inline size_t
+utf16UnitsForCodepoint(uint32_t cp)
+{
+	return (cp <= 0xFFFF) ? 1 : 2;
+}
+
+
+size_t
+utf8ColToUtf16Units(std::string_view lineUtf8, size_t utf8Col)
+{
+	// Count by Unicode scalars up to utf8Col; clamp at EOL
+	size_t units = 0;
+	size_t col   = 0;
+	size_t i     = 0;
+	while (i < lineUtf8.size()) {
+		if (col >= utf8Col)
+			break;
+		auto [cp, n] = decodeUtf8(lineUtf8, i);
+		if (n == 0)
+			break;
+		units += utf16UnitsForCodepoint(cp);
+		i += n;
+		++col;
+	}
+	return units;
+}
+
+
+size_t
+utf16UnitsToUtf8Col(std::string_view lineUtf8, size_t utf16Units)
+{
+	// Traverse code points until consuming utf16Units (or reaching EOL)
+	size_t units = 0;
+	size_t col   = 0;
+	size_t i     = 0;
+	while (i < lineUtf8.size()) {
+		auto [cp, n] = decodeUtf8(lineUtf8, i);
+		if (n == 0)
+			break;
+		size_t add = utf16UnitsForCodepoint(cp);
+		if (units + add > utf16Units)
+			break;
+		units += add;
+		i += n;
+		++col;
+		if (units == utf16Units)
+			break;
+	}
+	return col;
+}
+
+
+Position
+toUtf16(const std::string &uri, const Position &pUtf8, const LineProvider &provider)
+{
+	Position out          = pUtf8;
+	std::string_view line = provider ? provider(uri, pUtf8.line) : std::string_view();
+	out.character         = static_cast<int>(utf8ColToUtf16Units(line, static_cast<size_t>(pUtf8.character)));
+	return out;
+}
+
+
+Position
+toUtf8(const std::string &uri, const Position &pUtf16, const LineProvider &provider)
+{
+	Position out          = pUtf16;
+	std::string_view line = provider ? provider(uri, pUtf16.line) : std::string_view();
+	out.character         = static_cast<int>(utf16UnitsToUtf8Col(line, static_cast<size_t>(pUtf16.character)));
+	return out;
+}
+
+
+Range
+toUtf16(const std::string &uri, const Range &rUtf8, const LineProvider &provider)
+{
+	Range r;
+	r.start = toUtf16(uri, rUtf8.start, provider);
+	r.end   = toUtf16(uri, rUtf8.end, provider);
+	return r;
+}
+
+
+Range
+toUtf8(const std::string &uri, const Range &rUtf16, const LineProvider &provider)
+{
+	Range r;
+	r.start = toUtf8(uri, rUtf16.start, provider);
+	r.end   = toUtf8(uri, rUtf16.end, provider);
+	return r;
+}
+} // namespace kte::lsp
--- a/lsp/UtfCodec.h
+++ b/lsp/UtfCodec.h
@@ -0,0 +1,37 @@
+/*
+ * UtfCodec.h - Helpers for UTF-8 <-> UTF-16 code unit position conversions
+ */
+#ifndef KTE_LSP_UTF_CODEC_H
+#define KTE_LSP_UTF_CODEC_H
+
+#include <cstddef>
+#include <functional>
+#include <string>
+#include <string_view>
+
+#include "LspTypes.h"
+
+namespace kte::lsp {
+// Map between editor-internal UTF-8 columns (by Unicode scalar count)
+// and LSP wire UTF-16 code units (per LSP spec).
+
+// Convert a UTF-8 column index (in Unicode scalars) to UTF-16 code units for a given line.
+size_t utf8ColToUtf16Units(std::string_view lineUtf8, size_t utf8Col);
+
+// Convert a UTF-16 code unit count to a UTF-8 column index (in Unicode scalars) for a given line.
+size_t utf16UnitsToUtf8Col(std::string_view lineUtf8, size_t utf16Units);
+
+// Line text provider to allow conversions without giving the codec direct buffer access.
+using LineProvider = std::function<std::string_view(const std::string & uri, int line)>;
+
+// Convenience helpers for positions and ranges using a line provider.
+Position toUtf16(const std::string &uri, const Position &pUtf8, const LineProvider &provider);
+
+Position toUtf8(const std::string &uri, const Position &pUtf16, const LineProvider &provider);
+
+Range toUtf16(const std::string &uri, const Range &rUtf8, const LineProvider &provider);
+
+Range toUtf8(const std::string &uri, const Range &rUtf16, const LineProvider &provider);
+} // namespace kte::lsp
+
+#endif // KTE_LSP_UTF_CODEC_H
--- a/main.cc
+++ b/main.cc
@@ -12,6 +12,7 @@
 #include "Editor.h"
 #include "Frontend.h"
 #include "TerminalFrontend.h"
+#include "lsp/LspManager.h"

 #if defined(KTE_BUILD_GUI)
 #include "GUIFrontend.h"
@@ -28,6 +29,7 @@ PrintUsage(const char *prog)
 {
 	std::cerr << "Usage: " << prog << " [OPTIONS] [files]\n"
 		<< "Options:\n"
+		<< "  -c, --chdir DIR  Change working directory before opening files\n"
 		<< "  -g, --gui        Use GUI frontend (if built)\n"
 		<< "  -t, --term       Use terminal (ncurses) frontend [default]\n"
 		<< "  -h, --help       Show this help and exit\n"
@@ -36,9 +38,17 @@ PrintUsage(const char *prog)


 int
-main(int argc, const char *argv[])
+main(const int argc, const char *argv[])
 {
 	Editor editor;
+	// Wire up LSP manager (no diagnostic UI yet; frontends may provide later)
+	kte::lsp::LspManager lspMgr(&editor, nullptr);
+	// Enable LSP debug logging if KTE_LSP_DEBUG is set
+	if (const char *dbg = std::getenv("KTE_LSP_DEBUG"); dbg && *dbg) {
+		lspMgr.setDebugLogging(true);
+		std::fprintf(stderr, "[kte][lsp] debug logging enabled via KTE_LSP_DEBUG\n");
+	}
+	editor.SetLspManager(&lspMgr);

 	// CLI parsing using getopt_long
 	bool req_gui      = false;
@@ -46,7 +56,10 @@ main(int argc, const char *argv[])
 	bool show_help    = false;
 	bool show_version = false;

+	std::string nwd;
+
 	static struct option long_opts[] = {
+		{"chdir", required_argument, nullptr, 'c'},
 		{"gui", no_argument, nullptr, 'g'},
 		{"term", no_argument, nullptr, 't'},
 		{"help", no_argument, nullptr, 'h'},
@@ -56,8 +69,11 @@ main(int argc, const char *argv[])

 	int opt;
 	int long_index = 0;
-	while ((opt = getopt_long(argc, const_cast<char *const *>(argv), "gthV", long_opts, &long_index)) != -1) {
+	while ((opt = getopt_long(argc, const_cast<char *const *>(argv), "c:gthV", long_opts, &long_index)) != -1) {
 		switch (opt) {
+		case 'c':
+			nwd = optarg;
+			break;
 		case 'g':
 			req_gui = true;
 			break;
@@ -104,11 +120,13 @@ main(int argc, const 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
@@ -199,6 +217,13 @@ main(int argc, const char *argv[])
 	}
 #endif

+#if defined(KTE_BUILD_GUI)
+	if (!nwd.empty()) {
+		if (chdir(nwd.c_str()) != 0) {
+			std::cerr << "kge: failed to chdir to " << nwd << std::endl;
+		}
+	}
+#endif
 	if (!fe->Init(editor)) {
 		std::cerr << "kte: failed to initialize frontend" << std::endl;
 		return 1;
@@ -212,4 +237,4 @@ main(int argc, const char *argv[])
 	fe->Shutdown();

 	return 0;
-}
+}
--- a/syntax/CppHighlighter.cc
+++ b/syntax/CppHighlighter.cc
@@ -1,5 +1,5 @@
 #include "CppHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/CppHighlighter.h
+++ b/syntax/CppHighlighter.h
--- a/syntax/ErlangHighlighter.cc
+++ b/syntax/ErlangHighlighter.cc
@@ -0,0 +1,159 @@
+#include "ErlangHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_' || c == '\'';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '@' || c == ':' || c == '?';
+}
+
+
+ErlangHighlighter::ErlangHighlighter()
+{
+	const char *kw[] = {
+		"after", "begin", "case", "catch", "cond", "div", "end", "fun", "if", "let", "of",
+		"receive", "when", "try", "rem", "and", "andalso", "orelse", "not", "band", "bor", "bxor",
+		"bnot", "xor", "module", "export", "import", "record", "define", "undef", "include", "include_lib"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+}
+
+
+void
+ErlangHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// comment
+		if (c == '%') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// strings
+		if (c == '"') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '"')
+					break;
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		// char literal $X
+		if (c == '$') {
+			int j = i + 1;
+			if (j < n && s[j] == '\\' && j + 1 < n)
+				j += 2;
+			else if (j < n)
+				++j;
+			push(out, i, j, TokenKind::Char);
+			i = j;
+			continue;
+		}
+		// numbers
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '#' || s[j] == '.' ||
+			                 s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		// atoms/variables/identifiers (including quoted atoms)
+		if (is_ident_start(c)) {
+			// quoted atom: '...'
+			if (c == '\'') {
+				int j    = i + 1;
+				bool esc = false;
+				while (j < n) {
+					char d = s[j++];
+					if (d == '\'') {
+						if (j < n && s[j] == '\'') {
+							++j;
+							continue;
+						}
+						break;
+					}
+					if (d == '\\')
+						esc = !esc;
+				}
+				push(out, i, j, TokenKind::Identifier);
+				i = j;
+				continue;
+			}
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			// lowercase leading -> atom/function/module; uppercase or '_' -> variable
+			TokenKind k = TokenKind::Identifier;
+			// keyword check (lowercase)
+			std::string lower;
+			lower.reserve(id.size());
+			for (char ch: id)
+				lower.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(ch))));
+			if (kws_.count(lower))
+				k = TokenKind::Keyword;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ',' || c == ';' || c == '(' || c == ')' || c == '[' || c == ']' || c == '{' || c ==
+			    '}')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte
--- a/syntax/ErlangHighlighter.h
+++ b/syntax/ErlangHighlighter.h
@@ -0,0 +1,17 @@
+// ErlangHighlighter.h - simple Erlang highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class ErlangHighlighter final : public LanguageHighlighter {
+public:
+	ErlangHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+};
+} // namespace kte
--- a/syntax/ForthHighlighter.cc
+++ b/syntax/ForthHighlighter.cc
@@ -0,0 +1,121 @@
+#include "ForthHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_word_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '>' || c == '<' || c == '?';
+}
+
+
+ForthHighlighter::ForthHighlighter()
+{
+	const char *kw[] = {
+		":", ";", "if", "else", "then", "begin", "until", "while", "repeat",
+		"do", "loop", "+loop", "leave", "again", "case", "of", "endof", "endcase",
+		".", ".r", ".s", ".\"", ",", "cr", "emit", "type", "key",
+		"+", "-", "*", "/", "mod", "/mod", "+-", "abs", "min", "max",
+		"dup", "drop", "swap", "over", "rot", "-rot", "nip", "tuck", "pick", "roll",
+		"and", "or", "xor", "invert", "lshift", "rshift",
+		"variable", "constant", "value", "to", "create", "does>", "allot", ",",
+		"cells", "cell+", "chars", "char+",
+		"[", "]", "immediate",
+		"s\"", ".\""
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+}
+
+
+void
+ForthHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// backslash comment to end of line
+		if (c == '\\') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// parenthesis comment ( ... ) if at word boundary
+		if (c == '(') {
+			int j = i + 1;
+			while (j < n && s[j] != ')')
+				++j;
+			if (j < n)
+				++j;
+			push(out, i, j, TokenKind::Comment);
+			i = j;
+			continue;
+		}
+		// strings: ." ... " and S" ... " and raw "..."
+		if (c == '"') {
+			int j = i + 1;
+			while (j < n && s[j] != '"')
+				++j;
+			if (j < n)
+				++j;
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == '#'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		// word/identifier
+		if (std::isalpha(static_cast<unsigned char>(c)) || std::ispunct(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && is_word_char(s[j]))
+				++j;
+			std::string w = s.substr(i, j - i);
+			// normalize to lowercase for keyword compare (Forth is case-insensitive typically)
+			std::string lower;
+			lower.reserve(w.size());
+			for (char ch: w)
+				lower.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(ch))));
+			TokenKind k = kws_.count(lower) ? TokenKind::Keyword : TokenKind::Identifier;
+			// Single-char punctuation fallback
+			if (w.size() == 1 && std::ispunct(static_cast<unsigned char>(w[0])) && !kws_.count(lower)) {
+				k = (w[0] == '(' || w[0] == ')' || w[0] == ',')
+					    ? TokenKind::Punctuation
+					    : TokenKind::Operator;
+			}
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte
--- a/syntax/ForthHighlighter.h
+++ b/syntax/ForthHighlighter.h
@@ -0,0 +1,17 @@
+// ForthHighlighter.h - simple Forth highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class ForthHighlighter final : public LanguageHighlighter {
+public:
+	ForthHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+};
+} // namespace kte
--- a/syntax/GoHighlighter.cc
+++ b/syntax/GoHighlighter.cc
@@ -1,5 +1,5 @@
 #include "GoHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/GoHighlighter.h
+++ b/syntax/GoHighlighter.h
--- a/syntax/HighlighterEngine.cc
+++ b/syntax/HighlighterEngine.cc
@@ -1,5 +1,5 @@
 #include "HighlighterEngine.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include "LanguageHighlighter.h"
 #include <thread>

--- a/syntax/HighlighterEngine.h
+++ b/syntax/HighlighterEngine.h
@@ -10,7 +10,7 @@
 #include <atomic>
 #include <thread>

-#include "Highlight.h"
+#include "../Highlight.h"
 #include "LanguageHighlighter.h"

 class Buffer;
--- a/syntax/HighlighterRegistry.cc
+++ b/syntax/HighlighterRegistry.cc
@@ -30,6 +30,9 @@ class GoHighlighter;
 class PythonHighlighter;
 class RustHighlighter;
 class LispHighlighter;
+class SqlHighlighter;
+class ErlangHighlighter;
+class ForthHighlighter;
 }

 // Headers for the above
@@ -40,6 +43,9 @@ class LispHighlighter;
 #include "PythonHighlighter.h"
 #include "RustHighlighter.h"
 #include "LispHighlighter.h"
+#include "SqlHighlighter.h"
+#include "ErlangHighlighter.h"
+#include "ForthHighlighter.h"

 namespace kte {
 static std::string
@@ -76,6 +82,12 @@ HighlighterRegistry::Normalize(std::string_view ft)
 	if (f == "lisp" || f == "scheme" || f == "scm" || f == "rkt" || f == "el" || f == "clj" || f == "cljc" || f ==
 	    "cl")
 		return "lisp";
+	if (f == "sql" || f == "sqlite" || f == "sqlite3")
+		return "sql";
+	if (f == "erlang" || f == "erl" || f == "hrl")
+		return "erlang";
+	if (f == "forth" || f == "fth" || f == "4th" || f == "fs")
+		return "forth";
 	return f;
 }

@@ -105,6 +117,12 @@ HighlighterRegistry::CreateFor(std::string_view filetype)
 		return std::make_unique<RustHighlighter>();
 	if (ft == "lisp")
 		return std::make_unique<LispHighlighter>();
+	if (ft == "sql")
+		return std::make_unique<SqlHighlighter>();
+	if (ft == "erlang")
+		return std::make_unique<ErlangHighlighter>();
+	if (ft == "forth")
+		return std::make_unique<ForthHighlighter>();
 	return nullptr;
 }

@@ -160,6 +178,12 @@ HighlighterRegistry::DetectForPath(std::string_view path, std::string_view first
 		if (ext == ".lisp" || ext == ".scm" || ext == ".rkt" || ext == ".el" || ext == ".clj" || ext == ".cljc"
 		    || ext == ".cl")
 			return "lisp";
+		if (ext == ".sql" || ext == ".sqlite")
+			return "sql";
+		if (ext == ".erl" || ext == ".hrl")
+			return "erlang";
+		if (ext == ".forth" || ext == ".fth" || ext == ".4th" || ext == ".fs")
+			return "forth";
 	}
 	// Shebang
 	std::string ft = shebang_to_ft(first_line);
--- a/syntax/HighlighterRegistry.h
+++ b/syntax/HighlighterRegistry.h
--- a/syntax/JsonHighlighter.cc
+++ b/syntax/JsonHighlighter.cc
@@ -1,5 +1,5 @@
 #include "JsonHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/JsonHighlighter.h
+++ b/syntax/JsonHighlighter.h
--- a/syntax/LanguageHighlighter.h
+++ b/syntax/LanguageHighlighter.h
@@ -5,7 +5,7 @@
 #include <vector>
 #include <string>

-#include "Highlight.h"
+#include "../Highlight.h"

 class Buffer;

--- a/syntax/LispHighlighter.cc
+++ b/syntax/LispHighlighter.cc
@@ -1,5 +1,5 @@
 #include "LispHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/LispHighlighter.h
+++ b/syntax/LispHighlighter.h
--- a/syntax/MarkdownHighlighter.cc
+++ b/syntax/MarkdownHighlighter.cc
@@ -1,5 +1,5 @@
 #include "MarkdownHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/MarkdownHighlighter.h
+++ b/syntax/MarkdownHighlighter.h
--- a/syntax/NullHighlighter.cc
+++ b/syntax/NullHighlighter.cc
@@ -1,5 +1,5 @@
 #include "NullHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"

 namespace kte {
 void
--- a/syntax/NullHighlighter.h
+++ b/syntax/NullHighlighter.h
--- a/syntax/PythonHighlighter.cc
+++ b/syntax/PythonHighlighter.cc
@@ -1,5 +1,5 @@
 #include "PythonHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/PythonHighlighter.h
+++ b/syntax/PythonHighlighter.h
--- a/syntax/RustHighlighter.cc
+++ b/syntax/RustHighlighter.cc
@@ -1,5 +1,5 @@
 #include "RustHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/RustHighlighter.h
+++ b/syntax/RustHighlighter.h
--- a/syntax/ShellHighlighter.cc
+++ b/syntax/ShellHighlighter.cc
@@ -1,5 +1,5 @@
 #include "ShellHighlighter.h"
-#include "Buffer.h"
+#include "../Buffer.h"
 #include <cctype>

 namespace kte {
--- a/syntax/ShellHighlighter.h
+++ b/syntax/ShellHighlighter.h
--- a/syntax/SqlHighlighter.cc
+++ b/syntax/SqlHighlighter.cc
@@ -0,0 +1,156 @@
+#include "SqlHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '$';
+}
+
+
+SqlHighlighter::SqlHighlighter()
+{
+	const char *kw[] = {
+		"select", "insert", "update", "delete", "from", "where", "group", "by", "order", "limit",
+		"offset", "values", "into", "create", "table", "index", "unique", "on", "as", "and", "or",
+		"not", "null", "is", "primary", "key", "constraint", "foreign", "references", "drop", "alter",
+		"add", "column", "rename", "to", "if", "exists", "join", "left", "right", "inner", "outer",
+		"cross", "using", "set", "distinct", "having", "union", "all", "case", "when", "then", "else",
+		"end", "pragma", "transaction", "begin", "commit", "rollback", "replace"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+
+	const char *types[] = {"integer", "real", "text", "blob", "numeric", "boolean", "date", "datetime"};
+	for (auto s: types)
+		types_.insert(s);
+}
+
+
+void
+SqlHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// line comments: -- ...
+		if (c == '-' && i + 1 < n && s[i + 1] == '-') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// simple block comment on same line: /* ... */
+		if (c == '/' && i + 1 < n && s[i + 1] == '*') {
+			int j       = i + 2;
+			bool closed = false;
+			while (j + 1 <= n) {
+				if (j + 1 < n && s[j] == '*' && s[j + 1] == '/') {
+					j += 2;
+					closed = true;
+					break;
+				}
+				++j;
+			}
+			if (!closed) {
+				push(out, i, n, TokenKind::Comment);
+				break;
+			} else {
+				push(out, i, j, TokenKind::Comment);
+				i = j;
+				continue;
+			}
+		}
+		// strings: '...' or "..."
+		if (c == '\'' || c == '"') {
+			char q   = c;
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (d == q) {
+					// Handle doubled quote escaping for SQL single quotes
+					if (q == '\'' && j < n && s[j] == '\'') {
+						++j;
+						continue;
+					}
+					break;
+				}
+				if (d == '\\') {
+					esc = !esc;
+				} else {
+					esc = false;
+				}
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		if (is_ident_start(c)) {
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			std::string lower;
+			lower.reserve(id.size());
+			for (char ch: id)
+				lower.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(ch))));
+			TokenKind k = TokenKind::Identifier;
+			if (kws_.count(lower))
+				k = TokenKind::Keyword;
+			else if (types_.count(lower))
+				k = TokenKind::Type;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ',' || c == ';' || c == '(' || c == ')')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte
--- a/syntax/SqlHighlighter.h
+++ b/syntax/SqlHighlighter.h
@@ -0,0 +1,18 @@
+// SqlHighlighter.h - simple SQL/SQLite highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class SqlHighlighter final : public LanguageHighlighter {
+public:
+	SqlHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+	std::unordered_set<std::string> types_;
+};
+} // namespace kte
--- a/syntax/TreeSitterHighlighter.cc
+++ b/syntax/TreeSitterHighlighter.cc
@@ -1,4 +1,4 @@
-#include "TreeSitterHighlighter.h"
+#include "../TreeSitterHighlighter.h"

 #ifdef KTE_ENABLE_TREESITTER

--- a/syntax/TreeSitterHighlighter.h
+++ b/syntax/TreeSitterHighlighter.h
--- a/test_lsp_decode.cc
+++ b/test_lsp_decode.cc
@@ -0,0 +1,119 @@
+// test_lsp_decode.cc - tests for LspProcessClient JSON decoding/dispatch
+#include <cassert>
+#include <atomic>
+#include <string>
+#include <vector>
+
+#include "lsp/LspProcessClient.h"
+#include "lsp/Diagnostic.h"
+
+using namespace kte::lsp;
+
+
+int
+main()
+{
+	// Create client (won't start a process for these tests)
+	LspProcessClient client("/bin/echo", {});
+
+	// 1) Numeric id response should match string key "42"
+	{
+		std::atomic<bool> called{false};
+		client.debugAddPendingForTest("42", "dummy",
+		                              [&](const nlohmann::json &result, const nlohmann::json *err) {
+			                              (void) result;
+			                              (void) err;
+			                              called = true;
+		                              });
+		std::string resp = "{\"jsonrpc\":\"2.0\",\"id\":42,\"result\":null}";
+		client.debugInjectMessageForTest(resp);
+		assert(called.load());
+	}
+
+	// 2) String id response should resolve
+	{
+		std::atomic<bool> called{false};
+		client.debugAddPendingForTest("abc123", "dummy",
+		                              [&](const nlohmann::json &result, const nlohmann::json *err) {
+			                              (void) result;
+			                              (void) err;
+			                              called = true;
+		                              });
+		std::string resp = "{\"jsonrpc\":\"2.0\",\"id\":\"abc123\",\"result\":{}}";
+		client.debugInjectMessageForTest(resp);
+		assert(called.load());
+	}
+
+	// 3) Diagnostics notification decoding
+	{
+		std::atomic<bool> diagCalled{false};
+		client.setDiagnosticsHandler([&](const std::string &uri, const std::vector<Diagnostic> &d) {
+			assert(uri == "file:///tmp/x.rs");
+			assert(!d.empty());
+			diagCalled = true;
+		});
+		std::string notif = R"({
+          "jsonrpc":"2.0",
+          "method":"textDocument/publishDiagnostics",
+          "params":{
+            "uri":"file:///tmp/x.rs",
+            "diagnostics":[{
+              "range": {"start": {"line":0, "character":1}, "end": {"line":0, "character":2}},
+              "severity": 1,
+              "message": "oops"
+            }]
+          }
+        })";
+		client.debugInjectMessageForTest(notif);
+		assert(diagCalled.load());
+	}
+
+	// 4) ShowMessage notification should be safely handled (no crash)
+	{
+		std::string msg =
+			"{\"jsonrpc\":\"2.0\",\"method\":\"window/showMessage\",\"params\":{\"type\":2,\"message\":\"hi\"}}";
+		client.debugInjectMessageForTest(msg);
+	}
+
+	// 5) workspace/configuration request should be responded to (no crash)
+	{
+		std::string req = R"({
+          "jsonrpc":"2.0",
+          "id": 7,
+          "method":"workspace/configuration",
+          "params": {"items": [{"section":"x"},{"section":"y"}]}
+        })";
+		client.debugInjectMessageForTest(req);
+	}
+
+	// 6) Pending cap eviction: oldest request is dropped with -32001
+	{
+		LspProcessClient c2("/bin/echo", {});
+		c2.setRunningForTest(true);
+		c2.setMaxPendingForTest(2);
+
+		std::atomic<int> drops{0};
+		auto make_cb = [&](const char *tag) {
+			return [&, tag](const nlohmann::json &res, const nlohmann::json *err) {
+				(void) res;
+				if (err && err->is_object()) {
+					auto it = err->find("code");
+					if (it != err->end() && it->is_number_integer() && *it == -32001) {
+						// Only the oldest (first) should be dropped
+						if (std::string(tag) == "first")
+							drops.fetch_add(1);
+					}
+				}
+			};
+		};
+		// Enqueue 3 requests; cap=2 -> first should be dropped immediately when third is added
+		c2.debugSendRequestForTest("a", nlohmann::json::object(), make_cb("first"));
+		c2.debugSendRequestForTest("b", nlohmann::json::object(), make_cb("second"));
+		c2.debugSendRequestForTest("c", nlohmann::json::object(), make_cb("third"));
+		// Allow callbacks (none are async here, drop is invoked inline after send)
+		assert(drops.load() == 1);
+	}
+
+	std::puts("test_lsp_decode: OK");
+	return 0;
+}
--- a/test_transport.cc
+++ b/test_transport.cc
@@ -0,0 +1,76 @@
+// test_transport.cc - transport framing tests
+#include <cassert>
+#include <cstdio>
+#include <cstring>
+#include <string>
+#include <optional>
+#include <unistd.h>
+
+#include "lsp/JsonRpcTransport.h"
+
+using namespace kte::lsp;
+
+
+static void
+write_all(int fd, const void *bufv, size_t len)
+{
+	const char *buf = static_cast<const char *>(bufv);
+	size_t left     = len;
+	while (left > 0) {
+		ssize_t n = ::write(fd, buf, left);
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			std::perror("write");
+			std::abort();
+		}
+		buf += static_cast<size_t>(n);
+		left -= static_cast<size_t>(n);
+	}
+}
+
+
+int
+main()
+{
+	int p[2];
+	assert(pipe(p) == 0);
+	int readFd  = p[0];
+	int writeFd = p[1];
+
+	JsonRpcTransport t;
+	// We only need inFd for read tests; pass writeFd for completeness
+	t.connect(readFd, writeFd);
+
+	auto sendMsg = [&](const std::string &payload, bool lowerHeader) {
+		std::string header = (lowerHeader ? std::string("content-length: ") : std::string("Content-Length: ")) +
+		                     std::to_string(payload.size()) + "\r\n\r\n";
+		write_all(writeFd, header.data(), header.size());
+		// Send body in two parts to exercise partial reads
+		size_t mid = payload.size() / 2;
+		write_all(writeFd, payload.data(), mid);
+		write_all(writeFd, payload.data() + mid, payload.size() - mid);
+	};
+
+	std::string p1 = "{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":null}";
+	std::string p2 = "{\"jsonrpc\":\"2.0\",\"method\":\"ping\"}";
+	sendMsg(p1, false);
+	sendMsg(p2, true); // case-insensitive header
+
+	auto m1 = t.read();
+	assert(m1.has_value());
+	assert(m1->raw == p1);
+
+	auto m2 = t.read();
+	assert(m2.has_value());
+	assert(m2->raw == p2);
+
+	// Close write end to signal EOF; next read should return nullopt
+	::close(writeFd);
+	auto m3 = t.read();
+	assert(!m3.has_value());
+
+	::close(readFd);
+	std::puts("test_transport: OK");
+	return 0;
+}
--- a/test_utfcodec.cc
+++ b/test_utfcodec.cc
@@ -0,0 +1,101 @@
+// test_utfcodec.cc - simple tests for UtfCodec helpers
+#include <cassert>
+#include <cstdio>
+#include <string>
+#include <string_view>
+
+#include "lsp/UtfCodec.h"
+
+using namespace kte::lsp;
+
+
+static std::string_view
+lp(const std::string &, int)
+{
+	return std::string_view();
+}
+
+
+int
+main()
+{
+	// ASCII: each scalar = 1 UTF-16 unit
+	{
+		std::string s = "hello"; // 5 ASCII
+		assert(utf8ColToUtf16Units(s, 0) == 0);
+		assert(utf8ColToUtf16Units(s, 3) == 3);
+		assert(utf16UnitsToUtf8Col(s, 3) == 3);
+		assert(utf16UnitsToUtf8Col(s, 10) == 5); // clamp to EOL
+	}
+
+	// BMP multibyte (e.g., ü U+00FC, α U+03B1) -> still 1 UTF-16 unit
+	{
+		std::string s = u8"aüαb"; // bytes: a [C3 BC] [CE B1] b
+		// columns by codepoints: a(0), ü(1), α(2), b(3)
+		assert(utf8ColToUtf16Units(s, 0) == 0);
+		assert(utf8ColToUtf16Units(s, 1) == 1);
+		assert(utf8ColToUtf16Units(s, 2) == 2);
+		assert(utf8ColToUtf16Units(s, 4) == 4); // past EOL clamps to 4 units
+
+		assert(utf16UnitsToUtf8Col(s, 0) == 0);
+		assert(utf16UnitsToUtf8Col(s, 2) == 2);
+		assert(utf16UnitsToUtf8Col(s, 4) == 4);
+	}
+
+	// Non-BMP (emoji) -> 2 UTF-16 units per code point
+	{
+		std::string s = u8"A😀B"; // U+1F600 between A and B
+		// codepoints: A, 😀, B => utf8 columns 0..3
+		// utf16 units: A(1), 😀(2), B(1) cumulative: 0,1,3,4
+		assert(utf8ColToUtf16Units(s, 0) == 0);
+		assert(utf8ColToUtf16Units(s, 1) == 1); // after A
+		assert(utf8ColToUtf16Units(s, 2) == 3); // after 😀 (2 units)
+		assert(utf8ColToUtf16Units(s, 3) == 4); // after B
+
+		assert(utf16UnitsToUtf8Col(s, 0) == 0);
+		assert(utf16UnitsToUtf8Col(s, 1) == 1); // A
+		assert(utf16UnitsToUtf8Col(s, 2) == 1); // mid-surrogate -> stays before 😀
+		assert(utf16UnitsToUtf8Col(s, 3) == 2); // end of 😀
+		assert(utf16UnitsToUtf8Col(s, 4) == 3); // after B
+		assert(utf16UnitsToUtf8Col(s, 10) == 3); // clamp
+	}
+
+	// Invalid UTF-8: treat invalid byte as U+FFFD (1 UTF-16 unit), consume 1 byte
+	{
+		std::string s;
+		s.push_back('X');
+		s.push_back(char(0xFF)); // invalid single byte
+		s.push_back('Y');
+		// Columns by codepoints as we decode: 'X', U+FFFD, 'Y'
+		assert(utf8ColToUtf16Units(s, 0) == 0);
+		assert(utf8ColToUtf16Units(s, 1) == 1);
+		assert(utf8ColToUtf16Units(s, 2) == 2);
+		assert(utf8ColToUtf16Units(s, 3) == 3);
+
+		assert(utf16UnitsToUtf8Col(s, 0) == 0);
+		assert(utf16UnitsToUtf8Col(s, 1) == 1);
+		assert(utf16UnitsToUtf8Col(s, 2) == 2);
+		assert(utf16UnitsToUtf8Col(s, 3) == 3);
+	}
+
+	// Position/Range helpers with a simple provider
+	{
+		std::string lines[]   = {u8"A😀B"};
+		LineProvider provider = [&](const std::string &, int line) -> std::string_view {
+			return (line == 0) ? std::string_view(lines[0]) : std::string_view();
+		};
+		Position p8{0, 2}; // after 😀 in utf8 columns
+		Position p16 = toUtf16("file:///x", p8, provider);
+		assert(p16.line == 0 && p16.character == 3);
+
+		Position back = toUtf8("file:///x", p16, provider);
+		assert(back.line == 0 && back.character == 2);
+
+		Range r8{{0, 1}, {0, 3}}; // A|😀|B end
+		Range r16 = toUtf16("file:///x", r8, provider);
+		assert(r16.start.character == 1 && r16.end.character == 4);
+	}
+
+	std::puts("test_utfcodec: OK");
+	return 0;
+}
--- a/themes/EInk.h
+++ b/themes/EInk.h
@@ -0,0 +1,177 @@
+// themes/EInk.h — Monochrome e-ink inspired ImGui themes (header-only)
+#pragma once
+#include "imgui.h"
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyEInkImGuiTheme()
+{
+	// E-Ink grayscale palette (light background)
+	const ImVec4 paper  = RGBA(0xF2F2EE); // light paper
+	const ImVec4 bg1    = RGBA(0xE6E6E2);
+	const ImVec4 bg2    = RGBA(0xDADAD5);
+	const ImVec4 bg3    = RGBA(0xCFCFCA);
+	const ImVec4 ink    = RGBA(0x111111); // primary text (near black)
+	const ImVec4 dim    = RGBA(0x666666); // disabled text
+	const ImVec4 border = RGBA(0xB8B8B3);
+	const ImVec4 accent = RGBA(0x222222); // controls/active
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                         = style.Colors;
+	colors[ImGuiCol_Text]                  = ink;
+	colors[ImGuiCol_TextDisabled]          = ImVec4(dim.x, dim.y, dim.z, 1.0f);
+	colors[ImGuiCol_WindowBg]              = paper;
+	colors[ImGuiCol_ChildBg]               = paper;
+	colors[ImGuiCol_PopupBg]               = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]                = border;
+	colors[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	colors[ImGuiCol_FrameBg]               = bg2;
+	colors[ImGuiCol_FrameBgHovered]        = bg3;
+	colors[ImGuiCol_FrameBgActive]         = bg1;
+	colors[ImGuiCol_TitleBg]               = bg1;
+	colors[ImGuiCol_TitleBgActive]         = bg2;
+	colors[ImGuiCol_TitleBgCollapsed]      = bg1;
+	colors[ImGuiCol_MenuBarBg]             = bg1;
+	colors[ImGuiCol_ScrollbarBg]           = paper;
+	colors[ImGuiCol_ScrollbarGrab]         = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered]  = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]   = bg1;
+	colors[ImGuiCol_CheckMark]             = accent;
+	colors[ImGuiCol_SliderGrab]            = accent;
+	colors[ImGuiCol_SliderGrabActive]      = ink;
+	colors[ImGuiCol_Button]                = bg3;
+	colors[ImGuiCol_ButtonHovered]         = bg2;
+	colors[ImGuiCol_ButtonActive]          = bg1;
+	colors[ImGuiCol_Header]                = bg3;
+	colors[ImGuiCol_HeaderHovered]         = bg2;
+	colors[ImGuiCol_HeaderActive]          = bg2;
+	colors[ImGuiCol_Separator]             = border;
+	colors[ImGuiCol_SeparatorHovered]      = bg2;
+	colors[ImGuiCol_SeparatorActive]       = accent;
+	colors[ImGuiCol_ResizeGrip]            = ImVec4(ink.x, ink.y, ink.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered]     = ImVec4(accent.x, accent.y, accent.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]      = ink;
+	colors[ImGuiCol_Tab]                   = bg2;
+	colors[ImGuiCol_TabHovered]            = bg1;
+	colors[ImGuiCol_TabActive]             = bg3;
+	colors[ImGuiCol_TabUnfocused]          = bg2;
+	colors[ImGuiCol_TabUnfocusedActive]    = bg3;
+	colors[ImGuiCol_TableHeaderBg]         = bg2;
+	colors[ImGuiCol_TableBorderStrong]     = bg1;
+	colors[ImGuiCol_TableBorderLight]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]            = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]         = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(accent.x, accent.y, accent.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = accent;
+	colors[ImGuiCol_NavHighlight]          = accent;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = accent;
+	colors[ImGuiCol_PlotLinesHovered]      = ink;
+	colors[ImGuiCol_PlotHistogram]         = accent;
+	colors[ImGuiCol_PlotHistogramHovered]  = ink;
+}
+
+
+static inline void
+ApplyEInkDarkImGuiTheme()
+{
+	// E-Ink dark variant (dark background, light ink)
+	const ImVec4 paper  = RGBA(0x1A1A1A);
+	const ImVec4 bg1    = RGBA(0x222222);
+	const ImVec4 bg2    = RGBA(0x2B2B2B);
+	const ImVec4 bg3    = RGBA(0x343434);
+	const ImVec4 ink    = RGBA(0xEDEDEA);
+	const ImVec4 dim    = RGBA(0xB5B5B3);
+	const ImVec4 border = RGBA(0x444444);
+	const ImVec4 accent = RGBA(0xDDDDDD);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                         = style.Colors;
+	colors[ImGuiCol_Text]                  = ink;
+	colors[ImGuiCol_TextDisabled]          = ImVec4(dim.x, dim.y, dim.z, 1.0f);
+	colors[ImGuiCol_WindowBg]              = paper;
+	colors[ImGuiCol_ChildBg]               = paper;
+	colors[ImGuiCol_PopupBg]               = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]                = border;
+	colors[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	colors[ImGuiCol_FrameBg]               = bg2;
+	colors[ImGuiCol_FrameBgHovered]        = bg3;
+	colors[ImGuiCol_FrameBgActive]         = bg1;
+	colors[ImGuiCol_TitleBg]               = bg1;
+	colors[ImGuiCol_TitleBgActive]         = bg2;
+	colors[ImGuiCol_TitleBgCollapsed]      = bg1;
+	colors[ImGuiCol_MenuBarBg]             = bg1;
+	colors[ImGuiCol_ScrollbarBg]           = paper;
+	colors[ImGuiCol_ScrollbarGrab]         = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered]  = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]   = bg1;
+	colors[ImGuiCol_CheckMark]             = accent;
+	colors[ImGuiCol_SliderGrab]            = accent;
+	colors[ImGuiCol_SliderGrabActive]      = ink;
+	colors[ImGuiCol_Button]                = bg3;
+	colors[ImGuiCol_ButtonHovered]         = bg2;
+	colors[ImGuiCol_ButtonActive]          = bg1;
+	colors[ImGuiCol_Header]                = bg3;
+	colors[ImGuiCol_HeaderHovered]         = bg2;
+	colors[ImGuiCol_HeaderActive]          = bg2;
+	colors[ImGuiCol_Separator]             = border;
+	colors[ImGuiCol_SeparatorHovered]      = bg2;
+	colors[ImGuiCol_SeparatorActive]       = accent;
+	colors[ImGuiCol_ResizeGrip]            = ImVec4(ink.x, ink.y, ink.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered]     = ImVec4(accent.x, accent.y, accent.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]      = ink;
+	colors[ImGuiCol_Tab]                   = bg2;
+	colors[ImGuiCol_TabHovered]            = bg1;
+	colors[ImGuiCol_TabActive]             = bg3;
+	colors[ImGuiCol_TabUnfocused]          = bg2;
+	colors[ImGuiCol_TabUnfocusedActive]    = bg3;
+	colors[ImGuiCol_TableHeaderBg]         = bg2;
+	colors[ImGuiCol_TableBorderStrong]     = bg1;
+	colors[ImGuiCol_TableBorderLight]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]            = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]         = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(accent.x, accent.y, accent.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = accent;
+	colors[ImGuiCol_NavHighlight]          = accent;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = accent;
+	colors[ImGuiCol_PlotLinesHovered]      = ink;
+	colors[ImGuiCol_PlotHistogram]         = accent;
+	colors[ImGuiCol_PlotHistogramHovered]  = ink;
+}
--- a/themes/Gruvbox.h
+++ b/themes/Gruvbox.h
@@ -0,0 +1,204 @@
+// themes/Gruvbox.h — Gruvbox Dark/Light (medium) ImGui themes (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyGruvboxDarkMediumTheme()
+{
+	// Gruvbox (dark, medium) palette
+	const ImVec4 bg0 = RGBA(0x282828); // dark0
+	const ImVec4 bg1 = RGBA(0x3C3836); // dark1
+	const ImVec4 bg2 = RGBA(0x504945); // dark2
+	const ImVec4 bg3 = RGBA(0x665C54); // dark3
+	const ImVec4 fg1 = RGBA(0xEBDBB2); // light1
+	const ImVec4 fg0 = RGBA(0xFBF1C7); // light0
+	// accent colors
+	const ImVec4 yellow = RGBA(0xFABD2F);
+	const ImVec4 blue   = RGBA(0x83A598);
+	const ImVec4 aqua   = RGBA(0x8EC07C);
+	const ImVec4 orange = RGBA(0xFE8019);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = fg1;
+	colors[ImGuiCol_TextDisabled] = ImVec4(fg1.x, fg1.y, fg1.z, 0.55f);
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = bg2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = bg1;
+
+	colors[ImGuiCol_CheckMark]        = aqua;
+	colors[ImGuiCol_SliderGrab]       = aqua;
+	colors[ImGuiCol_SliderGrabActive] = blue;
+
+	colors[ImGuiCol_Button]        = bg3;
+	colors[ImGuiCol_ButtonHovered] = bg2;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg3;
+	colors[ImGuiCol_HeaderHovered] = bg2;
+	colors[ImGuiCol_HeaderActive]  = bg2;
+
+	colors[ImGuiCol_Separator]        = bg2;
+	colors[ImGuiCol_SeparatorHovered] = bg1;
+	colors[ImGuiCol_SeparatorActive]  = blue;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(fg0.x, fg0.y, fg0.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(aqua.x, aqua.y, aqua.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = blue;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = bg1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(orange.x, orange.y, orange.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = orange;
+	colors[ImGuiCol_NavHighlight]          = orange;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(fg0.x, fg0.y, fg0.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = aqua;
+	colors[ImGuiCol_PlotLinesHovered]      = blue;
+	colors[ImGuiCol_PlotHistogram]         = yellow;
+	colors[ImGuiCol_PlotHistogramHovered]  = orange;
+}
+
+
+static inline void
+ApplyGruvboxLightMediumTheme()
+{
+	// Gruvbox (light, medium) palette
+	const ImVec4 bg0 = RGBA(0xFBF1C7); // light0
+	const ImVec4 bg1 = RGBA(0xEBDBB2); // light1
+	const ImVec4 bg2 = RGBA(0xD5C4A1); // light2
+	const ImVec4 bg3 = RGBA(0xBDAE93); // light3
+	const ImVec4 fg1 = RGBA(0x3C3836); // dark1
+	const ImVec4 fg0 = RGBA(0x282828); // dark0
+	// accents
+	const ImVec4 yellow = RGBA(0xB57614);
+	const ImVec4 blue   = RGBA(0x076678);
+	const ImVec4 aqua   = RGBA(0x427B58);
+	const ImVec4 orange = RGBA(0xAF3A03);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = fg1;
+	colors[ImGuiCol_TextDisabled] = ImVec4(fg1.x, fg1.y, fg1.z, 0.55f);
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = bg2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = bg1;
+
+	colors[ImGuiCol_CheckMark]        = aqua;
+	colors[ImGuiCol_SliderGrab]       = aqua;
+	colors[ImGuiCol_SliderGrabActive] = blue;
+
+	colors[ImGuiCol_Button]        = bg3;
+	colors[ImGuiCol_ButtonHovered] = bg2;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg3;
+	colors[ImGuiCol_HeaderHovered] = bg2;
+	colors[ImGuiCol_HeaderActive]  = bg2;
+
+	colors[ImGuiCol_Separator]        = bg2;
+	colors[ImGuiCol_SeparatorHovered] = bg1;
+	colors[ImGuiCol_SeparatorActive]  = blue;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(fg0.x, fg0.y, fg0.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(aqua.x, aqua.y, aqua.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = blue;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = bg1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(orange.x, orange.y, orange.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = orange;
+	colors[ImGuiCol_NavHighlight]          = orange;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(fg0.x, fg0.y, fg0.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = aqua;
+	colors[ImGuiCol_PlotLinesHovered]      = blue;
+	colors[ImGuiCol_PlotHistogram]         = yellow;
+	colors[ImGuiCol_PlotHistogramHovered]  = orange;
+}
--- a/themes/Nord.h
+++ b/themes/Nord.h
@@ -0,0 +1,111 @@
+// themes/Nord.h — Nord-inspired ImGui theme (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyNordImGuiTheme()
+{
+	// Nord palette
+	const ImVec4 nord0  = RGBA(0x2E3440); // darkest bg
+	const ImVec4 nord1  = RGBA(0x3B4252);
+	const ImVec4 nord2  = RGBA(0x434C5E);
+	const ImVec4 nord3  = RGBA(0x4C566A);
+	const ImVec4 nord4  = RGBA(0xD8DEE9);
+	const ImVec4 nord6  = RGBA(0xECEFF4); // lightest
+	const ImVec4 nord8  = RGBA(0x88C0D0); // cyan
+	const ImVec4 nord9  = RGBA(0x81A1C1); // blue
+	const ImVec4 nord10 = RGBA(0x5E81AC); // blue dark
+	const ImVec4 nord12 = RGBA(0xD08770); // orange
+	const ImVec4 nord13 = RGBA(0xEBCB8B); // yellow
+
+	ImGuiStyle &style = ImGui::GetStyle();
+
+	// Base style tweaks to suit Nord aesthetics
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors = style.Colors;
+
+	colors[ImGuiCol_Text]         = nord4; // primary text
+	colors[ImGuiCol_TextDisabled] = ImVec4(nord4.x, nord4.y, nord4.z, 0.55f);
+	colors[ImGuiCol_WindowBg]     = nord0;
+	colors[ImGuiCol_ChildBg]      = nord0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(nord1.x, nord1.y, nord1.z, 0.98f);
+	colors[ImGuiCol_Border]       = nord2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = nord2;
+	colors[ImGuiCol_FrameBgHovered] = nord3;
+	colors[ImGuiCol_FrameBgActive]  = nord1;
+
+	colors[ImGuiCol_TitleBg]          = nord1;
+	colors[ImGuiCol_TitleBgActive]    = nord2;
+	colors[ImGuiCol_TitleBgCollapsed] = nord1;
+
+	colors[ImGuiCol_MenuBarBg]            = nord1;
+	colors[ImGuiCol_ScrollbarBg]          = nord10;
+	colors[ImGuiCol_ScrollbarGrab]        = nord3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = nord2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = nord1;
+
+	colors[ImGuiCol_CheckMark]        = nord8;
+	colors[ImGuiCol_SliderGrab]       = nord8;
+	colors[ImGuiCol_SliderGrabActive] = nord9;
+
+	colors[ImGuiCol_Button]        = nord3;
+	colors[ImGuiCol_ButtonHovered] = nord2;
+	colors[ImGuiCol_ButtonActive]  = nord1;
+
+	colors[ImGuiCol_Header]        = nord3;
+	colors[ImGuiCol_HeaderHovered] = nord10;
+	colors[ImGuiCol_HeaderActive]  = nord10;
+
+	colors[ImGuiCol_Separator]        = nord2;
+	colors[ImGuiCol_SeparatorHovered] = nord10;
+	colors[ImGuiCol_SeparatorActive]  = nord9;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(nord6.x, nord6.y, nord6.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(nord8.x, nord8.y, nord8.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = nord9;
+
+	colors[ImGuiCol_Tab]                = nord2;
+	colors[ImGuiCol_TabHovered]         = nord10;
+	colors[ImGuiCol_TabActive]          = nord3;
+	colors[ImGuiCol_TabUnfocused]       = nord2;
+	colors[ImGuiCol_TabUnfocusedActive] = nord3;
+
+	// Docking colors omitted for compatibility
+
+	colors[ImGuiCol_TableHeaderBg]     = nord2;
+	colors[ImGuiCol_TableBorderStrong] = nord1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(nord1.x, nord1.y, nord1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(nord1.x, nord1.y, nord1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(nord1.x, nord1.y, nord1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(nord8.x, nord8.y, nord8.z, 0.35f);
+	colors[ImGuiCol_DragDropTarget]        = nord13;
+	colors[ImGuiCol_NavHighlight]          = nord9;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(nord6.x, nord6.y, nord6.z, 0.7f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(nord0.x, nord0.y, nord0.z, 0.6f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(nord0.x, nord0.y, nord0.z, 0.6f);
+
+	// Plots
+	colors[ImGuiCol_PlotLines]            = nord8;
+	colors[ImGuiCol_PlotLinesHovered]     = nord9;
+	colors[ImGuiCol_PlotHistogram]        = nord13;
+	colors[ImGuiCol_PlotHistogramHovered] = nord12;
+}
--- a/themes/Plan9.h
+++ b/themes/Plan9.h
@@ -0,0 +1,89 @@
+// themes/Plan9.h — Plan 9 acme-inspired ImGui theme (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyPlan9Theme()
+{
+	// Acme-like colors
+	const ImVec4 paper  = RGBA(0xFFFFE8); // pale yellow paper
+	const ImVec4 pane   = RGBA(0xFFF4C1); // slightly deeper for frames
+	const ImVec4 ink    = RGBA(0x000000); // black text
+	constexpr auto dim  = ImVec4(0, 0, 0, 0.60f);
+	const ImVec4 border = RGBA(0x000000); // 1px black
+	const ImVec4 blue   = RGBA(0x0064FF); // acme-ish blue accents
+	const ImVec4 blueH  = RGBA(0x4C8DFF); // hover/active
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(6.0f, 6.0f);
+	style.FramePadding     = ImVec2(5.0f, 3.0f);
+	style.CellPadding      = ImVec2(5.0f, 3.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *c                         = style.Colors;
+	c[ImGuiCol_Text]                  = ink;
+	c[ImGuiCol_TextDisabled]          = dim;
+	c[ImGuiCol_WindowBg]              = paper;
+	c[ImGuiCol_ChildBg]               = paper;
+	c[ImGuiCol_PopupBg]               = ImVec4(pane.x, pane.y, pane.z, 0.98f);
+	c[ImGuiCol_Border]                = border;
+	c[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	c[ImGuiCol_FrameBg]               = pane;
+	c[ImGuiCol_FrameBgHovered]        = RGBA(0xFFEBA0);
+	c[ImGuiCol_FrameBgActive]         = RGBA(0xFFE387);
+	c[ImGuiCol_TitleBg]               = pane;
+	c[ImGuiCol_TitleBgActive]         = RGBA(0xFFE8A6);
+	c[ImGuiCol_TitleBgCollapsed]      = pane;
+	c[ImGuiCol_MenuBarBg]             = pane;
+	c[ImGuiCol_ScrollbarBg]           = paper;
+	c[ImGuiCol_ScrollbarGrab]         = RGBA(0xEADFA5);
+	c[ImGuiCol_ScrollbarGrabHovered]  = RGBA(0xE2D37F);
+	c[ImGuiCol_ScrollbarGrabActive]   = RGBA(0xD8C757);
+	c[ImGuiCol_CheckMark]             = blue;
+	c[ImGuiCol_SliderGrab]            = blue;
+	c[ImGuiCol_SliderGrabActive]      = blueH;
+	c[ImGuiCol_Button]                = RGBA(0xFFF1B0);
+	c[ImGuiCol_ButtonHovered]         = RGBA(0xFFE892);
+	c[ImGuiCol_ButtonActive]          = RGBA(0xFFE072);
+	c[ImGuiCol_Header]                = RGBA(0xFFF1B0);
+	c[ImGuiCol_HeaderHovered]         = RGBA(0xFFE892);
+	c[ImGuiCol_HeaderActive]          = RGBA(0xFFE072);
+	c[ImGuiCol_Separator]             = border;
+	c[ImGuiCol_SeparatorHovered]      = blue;
+	c[ImGuiCol_SeparatorActive]       = blueH;
+	c[ImGuiCol_ResizeGrip]            = ImVec4(0, 0, 0, 0.12f);
+	c[ImGuiCol_ResizeGripHovered]     = ImVec4(blue.x, blue.y, blue.z, 0.67f);
+	c[ImGuiCol_ResizeGripActive]      = blueH;
+	c[ImGuiCol_Tab]                   = RGBA(0xFFE8A6);
+	c[ImGuiCol_TabHovered]            = RGBA(0xFFE072);
+	c[ImGuiCol_TabActive]             = RGBA(0xFFD859);
+	c[ImGuiCol_TabUnfocused]          = RGBA(0xFFE8A6);
+	c[ImGuiCol_TabUnfocusedActive]    = RGBA(0xFFD859);
+	c[ImGuiCol_TableHeaderBg]         = RGBA(0xFFE8A6);
+	c[ImGuiCol_TableBorderStrong]     = border;
+	c[ImGuiCol_TableBorderLight]      = ImVec4(0, 0, 0, 0.35f);
+	c[ImGuiCol_TableRowBg]            = ImVec4(0, 0, 0, 0.04f);
+	c[ImGuiCol_TableRowBgAlt]         = ImVec4(0, 0, 0, 0.08f);
+	c[ImGuiCol_TextSelectedBg]        = ImVec4(blueH.x, blueH.y, blueH.z, 0.35f);
+	c[ImGuiCol_DragDropTarget]        = blue;
+	c[ImGuiCol_NavHighlight]          = blue;
+	c[ImGuiCol_NavWindowingHighlight] = ImVec4(0, 0, 0, 0.20f);
+	c[ImGuiCol_NavWindowingDimBg]     = ImVec4(0, 0, 0, 0.20f);
+	c[ImGuiCol_ModalWindowDimBg]      = ImVec4(0, 0, 0, 0.20f);
+	c[ImGuiCol_PlotLines]             = blue;
+	c[ImGuiCol_PlotLinesHovered]      = blueH;
+	c[ImGuiCol_PlotHistogram]         = blue;
+	c[ImGuiCol_PlotHistogramHovered]  = blueH;
+}
--- a/themes/Solarized.h
+++ b/themes/Solarized.h
@@ -0,0 +1,184 @@
+// themes/Solarized.h — Solarized Dark/Light ImGui themes (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplySolarizedDarkTheme()
+{
+	// Base colors from Ethan Schoonover Solarized
+	const ImVec4 base03 = RGBA(0x002b36);
+	const ImVec4 base02 = RGBA(0x073642);
+	const ImVec4 base01 = RGBA(0x586e75);
+	const ImVec4 base00 = RGBA(0x657b83);
+	const ImVec4 base0  = RGBA(0x839496);
+	const ImVec4 base1  = RGBA(0x93a1a1);
+	const ImVec4 base2  = RGBA(0xeee8d5);
+	const ImVec4 yellow = RGBA(0xb58900);
+	const ImVec4 orange = RGBA(0xcb4b16);
+	const ImVec4 blue   = RGBA(0x268bd2);
+	const ImVec4 cyan   = RGBA(0x2aa198);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 3.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 3.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 3.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *c                         = style.Colors;
+	c[ImGuiCol_Text]                  = base0;
+	c[ImGuiCol_TextDisabled]          = ImVec4(base01.x, base01.y, base01.z, 1.0f);
+	c[ImGuiCol_WindowBg]              = base03;
+	c[ImGuiCol_ChildBg]               = base03;
+	c[ImGuiCol_PopupBg]               = ImVec4(base02.x, base02.y, base02.z, 0.98f);
+	c[ImGuiCol_Border]                = base02;
+	c[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	c[ImGuiCol_FrameBg]               = base02;
+	c[ImGuiCol_FrameBgHovered]        = base01;
+	c[ImGuiCol_FrameBgActive]         = base00;
+	c[ImGuiCol_TitleBg]               = base02;
+	c[ImGuiCol_TitleBgActive]         = base01;
+	c[ImGuiCol_TitleBgCollapsed]      = base02;
+	c[ImGuiCol_MenuBarBg]             = base02;
+	c[ImGuiCol_ScrollbarBg]           = base02;
+	c[ImGuiCol_ScrollbarGrab]         = base01;
+	c[ImGuiCol_ScrollbarGrabHovered]  = base00;
+	c[ImGuiCol_ScrollbarGrabActive]   = blue;
+	c[ImGuiCol_CheckMark]             = cyan;
+	c[ImGuiCol_SliderGrab]            = cyan;
+	c[ImGuiCol_SliderGrabActive]      = blue;
+	c[ImGuiCol_Button]                = base01;
+	c[ImGuiCol_ButtonHovered]         = base00;
+	c[ImGuiCol_ButtonActive]          = blue;
+	c[ImGuiCol_Header]                = base01;
+	c[ImGuiCol_HeaderHovered]         = base00;
+	c[ImGuiCol_HeaderActive]          = base00;
+	c[ImGuiCol_Separator]             = base01;
+	c[ImGuiCol_SeparatorHovered]      = base00;
+	c[ImGuiCol_SeparatorActive]       = blue;
+	c[ImGuiCol_ResizeGrip]            = ImVec4(base1.x, base1.y, base1.z, 0.12f);
+	c[ImGuiCol_ResizeGripHovered]     = ImVec4(cyan.x, cyan.y, cyan.z, 0.67f);
+	c[ImGuiCol_ResizeGripActive]      = blue;
+	c[ImGuiCol_Tab]                   = base01;
+	c[ImGuiCol_TabHovered]            = base00;
+	c[ImGuiCol_TabActive]             = base02;
+	c[ImGuiCol_TabUnfocused]          = base01;
+	c[ImGuiCol_TabUnfocusedActive]    = base02;
+	c[ImGuiCol_TableHeaderBg]         = base01;
+	c[ImGuiCol_TableBorderStrong]     = base00;
+	c[ImGuiCol_TableBorderLight]      = ImVec4(base00.x, base00.y, base00.z, 0.6f);
+	c[ImGuiCol_TableRowBg]            = ImVec4(base02.x, base02.y, base02.z, 0.2f);
+	c[ImGuiCol_TableRowBgAlt]         = ImVec4(base02.x, base02.y, base02.z, 0.35f);
+	c[ImGuiCol_TextSelectedBg]        = ImVec4(cyan.x, cyan.y, cyan.z, 0.30f);
+	c[ImGuiCol_DragDropTarget]        = yellow;
+	c[ImGuiCol_NavHighlight]          = blue;
+	c[ImGuiCol_NavWindowingHighlight] = ImVec4(base2.x, base2.y, base2.z, 0.70f);
+	c[ImGuiCol_NavWindowingDimBg]     = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_ModalWindowDimBg]      = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_PlotLines]             = cyan;
+	c[ImGuiCol_PlotLinesHovered]      = blue;
+	c[ImGuiCol_PlotHistogram]         = yellow;
+	c[ImGuiCol_PlotHistogramHovered]  = orange;
+}
+
+
+static inline void
+ApplySolarizedLightTheme()
+{
+	// Base colors from Ethan Schoonover Solarized (light variant)
+	const ImVec4 base3  = RGBA(0xfdf6e3);
+	const ImVec4 base2  = RGBA(0xeee8d5);
+	const ImVec4 base1  = RGBA(0x93a1a1);
+	const ImVec4 base0  = RGBA(0x839496);
+	const ImVec4 base00 = RGBA(0x657b83);
+	const ImVec4 base01 = RGBA(0x586e75);
+	const ImVec4 base02 = RGBA(0x073642);
+	const ImVec4 base03 = RGBA(0x002b36);
+	const ImVec4 yellow = RGBA(0xb58900);
+	const ImVec4 orange = RGBA(0xcb4b16);
+	const ImVec4 blue   = RGBA(0x268bd2);
+	const ImVec4 cyan   = RGBA(0x2aa198);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 3.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 3.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 3.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *c                         = style.Colors;
+	c[ImGuiCol_Text]                  = base00;
+	c[ImGuiCol_TextDisabled]          = ImVec4(base01.x, base01.y, base01.z, 1.0f);
+	c[ImGuiCol_WindowBg]              = base3;
+	c[ImGuiCol_ChildBg]               = base3;
+	c[ImGuiCol_PopupBg]               = ImVec4(base2.x, base2.y, base2.z, 0.98f);
+	c[ImGuiCol_Border]                = base1;
+	c[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	c[ImGuiCol_FrameBg]               = base2;
+	c[ImGuiCol_FrameBgHovered]        = base1;
+	c[ImGuiCol_FrameBgActive]         = base0;
+	c[ImGuiCol_TitleBg]               = base2;
+	c[ImGuiCol_TitleBgActive]         = base1;
+	c[ImGuiCol_TitleBgCollapsed]      = base2;
+	c[ImGuiCol_MenuBarBg]             = base2;
+	c[ImGuiCol_ScrollbarBg]           = base2;
+	c[ImGuiCol_ScrollbarGrab]         = base1;
+	c[ImGuiCol_ScrollbarGrabHovered]  = base0;
+	c[ImGuiCol_ScrollbarGrabActive]   = blue;
+	c[ImGuiCol_CheckMark]             = cyan;
+	c[ImGuiCol_SliderGrab]            = cyan;
+	c[ImGuiCol_SliderGrabActive]      = blue;
+	c[ImGuiCol_Button]                = base1;
+	c[ImGuiCol_ButtonHovered]         = base0;
+	c[ImGuiCol_ButtonActive]          = blue;
+	c[ImGuiCol_Header]                = base1;
+	c[ImGuiCol_HeaderHovered]         = base0;
+	c[ImGuiCol_HeaderActive]          = base0;
+	c[ImGuiCol_Separator]             = base1;
+	c[ImGuiCol_SeparatorHovered]      = base0;
+	c[ImGuiCol_SeparatorActive]       = blue;
+	c[ImGuiCol_ResizeGrip]            = ImVec4(base1.x, base1.y, base1.z, 0.12f);
+	c[ImGuiCol_ResizeGripHovered]     = ImVec4(cyan.x, cyan.y, cyan.z, 0.67f);
+	c[ImGuiCol_ResizeGripActive]      = blue;
+	c[ImGuiCol_Tab]                   = base1;
+	c[ImGuiCol_TabHovered]            = base0;
+	c[ImGuiCol_TabActive]             = base2;
+	c[ImGuiCol_TabUnfocused]          = base1;
+	c[ImGuiCol_TabUnfocusedActive]    = base2;
+	c[ImGuiCol_TableHeaderBg]         = base1;
+	c[ImGuiCol_TableBorderStrong]     = base0;
+	c[ImGuiCol_TableBorderLight]      = ImVec4(base0.x, base0.y, base0.z, 0.6f);
+	c[ImGuiCol_TableRowBg]            = ImVec4(base02.x, base02.y, base02.z, 0.2f);
+	c[ImGuiCol_TableRowBgAlt]         = ImVec4(base02.x, base02.y, base02.z, 0.35f);
+	c[ImGuiCol_TextSelectedBg]        = ImVec4(cyan.x, cyan.y, cyan.z, 0.30f);
+	c[ImGuiCol_DragDropTarget]        = yellow;
+	c[ImGuiCol_NavHighlight]          = blue;
+	c[ImGuiCol_NavWindowingHighlight] = ImVec4(base2.x, base2.y, base2.z, 0.70f);
+	c[ImGuiCol_NavWindowingDimBg]     = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_ModalWindowDimBg]      = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_PlotLines]             = cyan;
+	c[ImGuiCol_PlotLinesHovered]      = blue;
+	c[ImGuiCol_PlotHistogram]         = yellow;
+	c[ImGuiCol_PlotHistogramHovered]  = orange;
+}
--- a/themes/ThemeHelpers.h
+++ b/themes/ThemeHelpers.h
@@ -0,0 +1,17 @@
+#ifndef KTE_THEMEHELPERS_H
+#define KTE_THEMEHELPERS_H
+
+#include "imgui.h"
+
+// Small helper to convert packed RGB (0xRRGGBB) + optional alpha to ImVec4
+static ImVec4
+RGBA(const unsigned int rgb, float a = 1.0f)
+{
+	const float r = static_cast<float>(rgb >> 16 & 0xFF) / 255.0f;
+	const float g = static_cast<float>(rgb >> 8 & 0xFF) / 255.0f;
+	const float b = static_cast<float>(rgb & 0xFF) / 255.0f;
+	return {r, g, b, a};
+}
+
+
+#endif //KTE_THEMEHELPERS_H