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.

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

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
 

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
 

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

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
 

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

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
 

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;

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

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