From 1a77f28ce414e286436b64014afff03128a2ec0e Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Mon, 1 Dec 2025 18:20:36 -0800
Subject: [PATCH] Add syntax highlighting infrastructure

- Introduced `HighlighterRegistry` with support for multiple language highlighters (e.g., JSON, Markdown, Python).
- Added `JsonHighlighter` implementation for basic JSON syntax highlighting.
---
 .idea/workspace.xml    | 390 -----------------------------------------
 Buffer.h               |  33 ++++
 CMakeLists.txt         |  24 +++
 Command.cc             | 132 +++++++++++++-
 Command.h              |   5 +-
 CppHighlighter.cc      | 170 ++++++++++++++++++
 CppHighlighter.h       |  34 ++++
 Editor.cc              |  87 +++++++--
 GUIConfig.cc           |  34 ++--
 GUIConfig.h            |  20 ++-
 GUIFrontend.cc         |  44 ++++-
 GUIRenderer.cc         |  59 +++++--
 GUITheme.h             | 133 +++++++-------
 GoHighlighter.cc       |  48 +++++
 GoHighlighter.h        |  18 ++
 Highlight.h            |  39 +++++
 HighlighterEngine.cc   |  94 ++++++++++
 HighlighterEngine.h    |  45 +++++
 HighlighterRegistry.cc |  93 ++++++++++
 HighlighterRegistry.h  |  26 +++
 JsonHighlighter.cc     |  42 +++++
 JsonHighlighter.h      |  14 ++
 LanguageHighlighter.h  |  43 +++++
 LispHighlighter.cc     |  41 +++++
 LispHighlighter.h      |  17 ++
 MarkdownHighlighter.cc |  88 ++++++++++
 MarkdownHighlighter.h  |  14 ++
 NullHighlighter.cc     |  16 ++
 NullHighlighter.h      |  13 ++
 PythonHighlighter.cc   |  85 +++++++++
 PythonHighlighter.h    |  18 ++
 RustHighlighter.cc     |  39 +++++
 RustHighlighter.h      |  18 ++
 ShellHighlighter.cc    |  43 +++++
 ShellHighlighter.h     |  13 ++
 TerminalRenderer.cc    | 199 +++++++++++++--------
 docs/syntax.md         |  52 ++++++
 kte-cloc               |   8 +-
 38 files changed, 1701 insertions(+), 590 deletions(-)
 delete mode 100644 .idea/workspace.xml
 create mode 100644 CppHighlighter.cc
 create mode 100644 CppHighlighter.h
 create mode 100644 GoHighlighter.cc
 create mode 100644 GoHighlighter.h
 create mode 100644 Highlight.h
 create mode 100644 HighlighterEngine.cc
 create mode 100644 HighlighterEngine.h
 create mode 100644 HighlighterRegistry.cc
 create mode 100644 HighlighterRegistry.h
 create mode 100644 JsonHighlighter.cc
 create mode 100644 JsonHighlighter.h
 create mode 100644 LanguageHighlighter.h
 create mode 100644 LispHighlighter.cc
 create mode 100644 LispHighlighter.h
 create mode 100644 MarkdownHighlighter.cc
 create mode 100644 MarkdownHighlighter.h
 create mode 100644 NullHighlighter.cc
 create mode 100644 NullHighlighter.h
 create mode 100644 PythonHighlighter.cc
 create mode 100644 PythonHighlighter.h
 create mode 100644 RustHighlighter.cc
 create mode 100644 RustHighlighter.h
 create mode 100644 ShellHighlighter.cc
 create mode 100644 ShellHighlighter.h
 create mode 100644 docs/syntax.md

diff --git a/.idea/workspace.xml b/.idea/workspace.xml
deleted file mode 100644
index 5ddee4a..0000000
--- a/.idea/workspace.xml
+++ /dev/null
@@ -1,390 +0,0 @@
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-    <option name="/Default/Housekeeping/LiveTemplatesHousekeeping/HotspotSessionHintIsShown/@EntryValue" value="true" type="bool" />
-    <option name="/Default/Housekeeping/OptionsDialog/SelectedPageId/@EntryValue" value="CppFormatterOtherPage" type="string" />
-    <option name="/Default/Housekeeping/RefactoringsMru/RenameRefactoring/DoSearchForTextInStrings/@EntryValue" value="true" type="bool" />
-    <option name="/Default/RiderDebugger/RiderRestoreDecompile/RestoreDecompileSetting/@EntryValue" value="false" type="bool" />
-  </component>
-  <component name="CMakePresetLoader">{
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-}</component>
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-    <option name="flavorId" value="CMakePlainProjectFlavor" />
-  </component>
-  <component name="CMakeReloadState">
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-  </component>
-  <component name="CMakeRunConfigurationManager">
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-      <config projectName="kte" targetName="imgui" />
-      <config projectName="kte" targetName="kge" />
-    </generated>
-  </component>
-  <component name="CMakeSettings" AUTO_RELOAD="true">
-    <configurations>
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-      <option name="closed" value="true" />
-      <created>1764635874362</created>
-      <option name="number" value="00020" />
-      <option name="presentableId" value="LOCAL-00020" />
-      <option name="project" value="LOCAL" />
-      <updated>1764635874362</updated>
-    </task>
-    <task id="LOCAL-00021" summary="bump version">
-      <option name="closed" value="true" />
-      <created>1764635891710</created>
-      <option name="number" value="00021" />
-      <option name="presentableId" value="LOCAL-00021" />
-      <option name="project" value="LOCAL" />
-      <updated>1764635891710</updated>
-    </task>
-    <option name="localTasksCounter" value="22" />
-    <servers />
-  </component>
-  <component name="TypeScriptGeneratedFilesManager">
-    <option name="version" value="3" />
-  </component>
-  <component name="VCPKGProject">
-    <isAutomaticCheckingOnLaunch value="false" />
-    <isAutomaticFoundErrors value="true" />
-    <isAutomaticReloadCMake value="true" />
-  </component>
-  <component name="VcsManagerConfiguration">
-    <MESSAGE value="Refactoring" />
-    <MESSAGE value="Add undo/redo infrastructure and buffer management additions." />
-    <MESSAGE value="Refactor `Buffer` to use `Line` abstraction and improve handling of row operations.&#10;&#10;This uses either a GapBuffer or PieceTable depending on the compilation." />
-    <MESSAGE value="Handle end-of-file newline semantics and improve scroll alignment logic." />
-    <MESSAGE value="Enable installation targets." />
-    <MESSAGE value="Add `UndoSystem` implementation and refactor `UndoNode` for simplicity." />
-    <MESSAGE value="Add non-linear undo/redo design documentation and improve `UndoSystem` with backspace batching and GUI integration fixes." />
-    <MESSAGE value="Add `TestFrontend` documentation and `UndoSystem` buffer reference update.&#10;&#10;- Document `TestFrontend` for programmatic testing, including examples and usage details.&#10;- Add `UpdateBufferReference` to `UndoSystem` to support updating buffer associations." />
-    <MESSAGE value="Remove `packaging.cmake`, deprecate `test_undo` setup, and add new testing infrastructure.&#10;&#10;- Delete `packaging.cmake` to streamline build system.&#10;- Deprecate `test_undo` in CMake setup; condition builds on `BUILD_TESTS`.&#10;- Introduce `TestFrontend`, `TestRenderer`, and `TestInputHandler` for structured testing.&#10;- Update `GUIInputHandler` and `Command` for enhanced buffer save handling and overwrite confirmation.&#10;- Enhance kill ring operations and new prompt workflows in `Editor`." />
-    <MESSAGE value="Add man pages for `kge` and `kte` with installation targets in CMake.&#10;&#10;- Introduce `docs/kge.1` and `docs/kte.1` man pages covering usage, options, keybindings, and examples.&#10;- Update `CMakeLists.txt` to install man pages under `${CMAKE_INSTALL_MANDIR}/man1`.&#10;- Ensure `kge` man page installation is conditional on GUI being built." />
-    <MESSAGE value="Add GUI initialization updates and improve navigation commands.&#10;&#10;- Implement terminal detachment for GUI mode to enable terminal closure post-launch.&#10;- Add `+N` support for opening files at specific line numbers and refine cursor positioning.&#10;- Introduce `JumpToLine` command for direct navigation by line number.&#10;- Enhance mouse wheel handling for line-wise scrolling." />
-    <MESSAGE value="Refactor code for consistency and enhanced functionality.&#10;&#10;- Normalize path handling for buffer operations, supporting tilde expansion and absolute paths.&#10;- Introduce `DisplayNameFor` to uniquely resolve buffer display names, minimizing filename clashes.&#10;- Add new commands: `ShowWorkingDirectory` and `ChangeWorkingDirectory`.&#10;- Refine keybindings and enhance existing commands for improved command flow.&#10;- Adjust GUI and terminal renderers to display total line counts alongside filenames.&#10;- Update coding style to align with project guidelines." />
-    <MESSAGE value="Add horizontal scrolling support and refactor mouse click handling in GUI.&#10;&#10;- Introduce horizontal scrolling with column offset synchronization in GUI.&#10;- Refactor mouse click handling for improved accuracy and viewport alignment.&#10;- Enhance tab expansion and cursor rendering logic for better user experience.&#10;- Replace redundant variable declarations in `Buffer` for cleaner code." />
-    <MESSAGE value="Introduce file picker and GUI configuration with enhancements.&#10;&#10;- Add visual file picker for GUI with toggle support.&#10;- Introduce `GUIConfig` class for loading GUI settings from configuration file.&#10;- Refactor window initialization to support dynamic sizing based on configuration.&#10;- Add macOS-specific handling for fullscreen behavior.&#10;- Improve header inclusion order and minor code cleanup." />
-    <MESSAGE value="Add buffer position display and documentation improvements.&#10;&#10;- Display buffer position prefix &quot;[x/N]&quot; in GUI and terminal renderers.&#10;- Improve `kte` and `kge` man pages with frontend usage details and project homepage.&#10;- Update README with GUI invocation instructions.&#10;- Bump version to 1.0.0." />
-    <MESSAGE value="Actually add the screenshot." />
-    <MESSAGE value="Fix void crash in kge." />
-    <MESSAGE value="add regex and search/replace functionality to editor" />
-    <MESSAGE value="Add regex search, search/replace, and buffer read-only mode functionality with help text" />
-    <MESSAGE value="Nord theme and undo system refinements&#10;&#10;- Improve text input/event batching&#10;- Enhance debugging with optional instrumentation&#10;- Begin implementation of non-linear undo tree structure." />
-    <MESSAGE value="Add Nord theme for real" />
-    <MESSAGE value="Fix double scroll issue." />
-    <MESSAGE value="bump version" />
-    <option name="LAST_COMMIT_MESSAGE" value="bump version" />
-  </component>
-  <component name="XSLT-Support.FileAssociations.UIState">
-    <expand />
-    <select />
-  </component>
-</project>
\ No newline at end of file
diff --git a/Buffer.h b/Buffer.h
index 59e8525..926f67c 100644
--- a/Buffer.h
+++ b/Buffer.h
@@ -12,6 +12,10 @@
 
 #include "AppendBuffer.h"
 #include "UndoSystem.h"
+#include <cstdint>
+#include <memory>
+#include "HighlighterEngine.h"
+#include "Highlight.h"
 
 
 class Buffer {
@@ -326,6 +330,12 @@ public:
 	void SetDirty(bool d)
 	{
 		dirty_ = d;
+		if (d) {
+			++version_;
+			if (highlighter_) {
+				highlighter_->InvalidateFrom(0);
+			}
+		}
 	}
 
 
@@ -364,6 +374,23 @@ public:
 
 	[[nodiscard]] std::string AsString() const;
 
+	// Syntax highlighting integration (per-buffer)
+	[[nodiscard]] std::uint64_t Version() const { return version_; }
+
+	void SetSyntaxEnabled(bool on) { syntax_enabled_ = on; }
+	[[nodiscard]] bool SyntaxEnabled() const { return syntax_enabled_; }
+
+	void SetFiletype(const std::string &ft) { filetype_ = ft; }
+	[[nodiscard]] const std::string &Filetype() const { return filetype_; }
+
+	kte::HighlighterEngine *Highlighter() { return highlighter_.get(); }
+	const kte::HighlighterEngine *Highlighter() const { return highlighter_.get(); }
+
+	void EnsureHighlighter()
+	{
+		if (!highlighter_) highlighter_ = std::make_unique<kte::HighlighterEngine>();
+	}
+
 	// Raw, low-level editing APIs used by UndoSystem apply().
 	// These must NOT trigger undo recording. They also do not move the cursor.
 	void insert_text(int row, int col, std::string_view text);
@@ -400,6 +427,12 @@ private:
 	// Per-buffer undo state
 	std::unique_ptr<struct UndoTree> undo_tree_;
 	std::unique_ptr<UndoSystem> undo_sys_;
+
+	// Syntax/highlighting state
+	std::uint64_t version_ = 0; // increment on edits
+ bool syntax_enabled_    = true;
+	std::string filetype_;
+	std::unique_ptr<kte::HighlighterEngine> highlighter_;
 };
 
 #endif // KTE_BUFFER_H
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2aba041..6b95e77 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,6 +67,17 @@ 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
 )
 
 set(COMMON_HEADERS
@@ -90,6 +101,19 @@ set(COMMON_HEADERS
         UndoNode.h
         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
 )
 
 # kte (terminal-first) executable
diff --git a/Command.cc b/Command.cc
index 44a0ccb..3b5a12f 100644
--- a/Command.cc
+++ b/Command.cc
@@ -7,10 +7,15 @@
 #include <cctype>
 
 #include "Command.h"
+#include "HighlighterRegistry.h"
+#include "NullHighlighter.h"
 #include "Editor.h"
 #include "Buffer.h"
 #include "UndoSystem.h"
 #include "HelpText.h"
+#include "LanguageHighlighter.h"
+#include "HighlighterEngine.h"
+#include "CppHighlighter.h"
 #ifdef KTE_BUILD_GUI
 #include "GUITheme.h"
 #endif
@@ -757,6 +762,124 @@ cmd_unknown_kcommand(CommandContext &ctx)
 	return true;
 }
 
+// --- Syntax highlighting commands ---
+static void apply_filetype(Buffer &buf, const std::string &ft)
+{
+    buf.EnsureHighlighter();
+    auto *eng = buf.Highlighter();
+    if (!eng) return;
+    std::string val = ft;
+    // trim + lower
+    auto trim = [](const std::string &s){
+        std::string r = s;
+        auto notsp = [](int ch){ return !std::isspace(ch); };
+        r.erase(r.begin(), std::find_if(r.begin(), r.end(), notsp));
+        r.erase(std::find_if(r.rbegin(), r.rend(), notsp).base(), r.end());
+        return r;
+    };
+    val = trim(val);
+    for (auto &ch: val) ch = static_cast<char>(std::tolower(static_cast<unsigned char>(ch)));
+    if (val == "off") {
+        eng->SetHighlighter(nullptr);
+        buf.SetFiletype("");
+        buf.SetSyntaxEnabled(false);
+        return;
+    }
+    if (val.empty()) {
+        // Empty means unknown/unspecified -> use NullHighlighter but keep syntax enabled
+        buf.SetFiletype("");
+        buf.SetSyntaxEnabled(true);
+        eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+        eng->InvalidateFrom(0);
+        return;
+    }
+    // Normalize and create via registry
+    std::string norm = kte::HighlighterRegistry::Normalize(val);
+    auto hl = kte::HighlighterRegistry::CreateFor(norm);
+    if (hl) {
+        eng->SetHighlighter(std::move(hl));
+        buf.SetFiletype(norm);
+        buf.SetSyntaxEnabled(true);
+        eng->InvalidateFrom(0);
+    } else {
+        // Unknown -> install NullHighlighter and keep syntax enabled
+        eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+        buf.SetFiletype(val); // record what user asked even if unsupported
+        buf.SetSyntaxEnabled(true);
+        eng->InvalidateFrom(0);
+    }
+}
+
+static bool cmd_syntax(CommandContext &ctx)
+{
+    Buffer *b = ctx.editor.CurrentBuffer();
+    if (!b) {
+        ctx.editor.SetStatus("No buffer");
+        return true;
+    }
+    std::string arg = ctx.arg;
+    // trim
+    auto trim = [](std::string &s){
+        auto notsp = [](int ch){ return !std::isspace(ch); };
+        s.erase(s.begin(), std::find_if(s.begin(), s.end(), notsp));
+        s.erase(std::find_if(s.rbegin(), s.rend(), notsp).base(), s.end());
+    };
+    trim(arg);
+    if (arg == "on") {
+        b->SetSyntaxEnabled(true);
+        // If no highlighter but filetype is cpp by extension, set it
+        if (!b->Highlighter() || !b->Highlighter()->HasHighlighter()) {
+            apply_filetype(*b, b->Filetype().empty() ? std::string("cpp") : b->Filetype());
+        }
+        ctx.editor.SetStatus("syntax: on");
+    } else if (arg == "off") {
+        b->SetSyntaxEnabled(false);
+        ctx.editor.SetStatus("syntax: off");
+    } else if (arg == "reload") {
+        if (auto *eng = b->Highlighter()) eng->InvalidateFrom(0);
+        ctx.editor.SetStatus("syntax: reloaded");
+    } else {
+        ctx.editor.SetStatus("usage: :syntax on|off|reload");
+    }
+    return true;
+}
+
+static bool cmd_set_option(CommandContext &ctx)
+{
+    Buffer *b = ctx.editor.CurrentBuffer();
+    if (!b) {
+        ctx.editor.SetStatus("No buffer");
+        return true;
+    }
+    // Expect key=value
+    auto eq = ctx.arg.find('=');
+    if (eq == std::string::npos) {
+        ctx.editor.SetStatus("usage: :set key=value");
+        return true;
+    }
+    std::string key = ctx.arg.substr(0, eq);
+    std::string val = ctx.arg.substr(eq + 1);
+    // trim
+    auto trim = [](std::string &s){
+        auto notsp = [](int ch){ return !std::isspace(ch); };
+        s.erase(s.begin(), std::find_if(s.begin(), s.end(), notsp));
+        s.erase(std::find_if(s.rbegin(), s.rend(), notsp).base(), s.end());
+    };
+    trim(key); trim(val);
+    // lower-case value for filetype
+    for (auto &ch: val) ch = static_cast<char>(std::tolower(static_cast<unsigned char>(ch)));
+    if (key == "filetype") {
+        apply_filetype(*b, val);
+        if (b->SyntaxEnabled())
+            ctx.editor.SetStatus(std::string("filetype: ") + (b->Filetype().empty()?"off":b->Filetype()));
+        else
+            ctx.editor.SetStatus("filetype: off");
+        return true;
+    }
+    ctx.editor.SetStatus("unknown option: " + key);
+    return true;
+}
+
 
 // GUI theme cycling commands (available in GUI build; show message otherwise)
 #ifdef KTE_BUILD_GUI
@@ -3611,9 +3734,12 @@ InstallDefaultCommands()
 		CommandId::ChangeWorkingDirectory, "change-working-directory", "Change current working directory",
 		cmd_change_working_directory_start
 	});
-	// UI helpers
-	CommandRegistry::Register(
-		{CommandId::UArgStatus, "uarg-status", "Update universal-arg status", cmd_uarg_status});
+    // UI helpers
+    CommandRegistry::Register(
+        {CommandId::UArgStatus, "uarg-status", "Update universal-arg status", cmd_uarg_status});
+    // Syntax highlighting (public commands)
+    CommandRegistry::Register({CommandId::Syntax, "syntax", "Syntax: on|off|reload", cmd_syntax, true});
+    CommandRegistry::Register({CommandId::SetOption, "set", "Set option: key=value", cmd_set_option, true});
 }
 
 
diff --git a/Command.h b/Command.h
index e08f85e..7ee15eb 100644
--- a/Command.h
+++ b/Command.h
@@ -94,7 +94,10 @@ enum class CommandId {
 	// Theme by name
 	ThemeSetByName,
 	// Background mode (GUI)
-	BackgroundSet,
+    BackgroundSet,
+    // Syntax highlighting
+    Syntax,        // ":syntax on|off|reload"
+    SetOption,     // generic ":set key=value" (v1: filetype=<lang>)
 };
 
 
diff --git a/CppHighlighter.cc b/CppHighlighter.cc
new file mode 100644
index 0000000..c1e0f9c
--- /dev/null
+++ b/CppHighlighter.cc
@@ -0,0 +1,170 @@
+#include "CppHighlighter.h"
+#include "Buffer.h"
+#include <cctype>
+
+namespace kte {
+
+static bool is_digit(char c) { return c >= '0' && c <= '9'; }
+
+CppHighlighter::CppHighlighter()
+{
+    const char *kw[] = {
+        "if","else","for","while","do","switch","case","default","break","continue",
+        "return","goto","struct","class","namespace","using","template","typename",
+        "public","private","protected","virtual","override","const","constexpr","auto",
+        "static","inline","operator","new","delete","try","catch","throw","friend",
+        "enum","union","extern","volatile","mutable","noexcept","sizeof","this"
+    };
+    for (auto s: kw) keywords_.insert(s);
+    const char *types[] = {
+        "int","long","short","char","signed","unsigned","float","double","void",
+        "bool","wchar_t","size_t","ptrdiff_t","uint8_t","uint16_t","uint32_t","uint64_t",
+        "int8_t","int16_t","int32_t","int64_t"
+    };
+    for (auto s: types) types_.insert(s);
+}
+
+bool CppHighlighter::is_ident_start(char c) { return std::isalpha(static_cast<unsigned char>(c)) || c == '_'; }
+bool CppHighlighter::is_ident_char(char c) { return std::isalnum(static_cast<unsigned char>(c)) || c == '_'; }
+
+void CppHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+    // Stateless entry simply delegates to stateful with a clean previous state
+    StatefulHighlighter::LineState prev;
+    (void)HighlightLineStateful(buf, row, prev, out);
+}
+
+StatefulHighlighter::LineState CppHighlighter::HighlightLineStateful(const Buffer &buf,
+                                    int row,
+                                    const LineState &prev,
+                                    std::vector<HighlightSpan> &out) const
+{
+    const auto &rows = buf.Rows();
+    StatefulHighlighter::LineState state = prev;
+    if (row < 0 || static_cast<std::size_t>(row) >= rows.size()) return state;
+    std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+    if (s.empty()) return state;
+
+    auto push = [&](int a, int b, TokenKind k){ if (b> a) out.push_back({a,b,k}); };
+    int n = static_cast<int>(s.size());
+    int bol = 0; while (bol < n && (s[bol] == ' ' || s[bol] == '\t')) ++bol;
+    int i = 0;
+
+    // Continue multi-line raw string from previous line
+    if (state.in_raw_string) {
+        std::string needle = ")" + state.raw_delim + "\"";
+        auto pos = s.find(needle);
+        if (pos == std::string::npos) {
+            push(0, n, TokenKind::String);
+            state.in_raw_string = true;
+            return state;
+        } else {
+            int end = static_cast<int>(pos + needle.size());
+            push(0, end, TokenKind::String);
+            i = end;
+            state.in_raw_string = false;
+            state.raw_delim.clear();
+        }
+    }
+
+    // Continue multi-line block comment from previous line
+    if (state.in_block_comment) {
+        int j = i;
+        while (i + 1 < n) {
+            if (s[i] == '*' && s[i+1] == '/') { i += 2; push(j, i, TokenKind::Comment); state.in_block_comment = false; break; }
+            ++i;
+        }
+        if (state.in_block_comment) { push(j, n, TokenKind::Comment); return state; }
+    }
+
+    while (i < n) {
+        char c = s[i];
+        // Preprocessor at beginning of line (after leading whitespace)
+        if (i == bol && c == '#') { push(0, n, TokenKind::Preproc); break; }
+
+        // Whitespace
+        if (c == ' ' || c == '\t') {
+            int j = i+1; while (j < n && (s[j] == ' ' || s[j] == '\t')) ++j; push(i,j,TokenKind::Whitespace); i=j; continue;
+        }
+
+        // Line comment
+        if (c == '/' && i+1 < n && s[i+1] == '/') { push(i, n, TokenKind::Comment); break; }
+
+        // Block comment
+        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(i, j, TokenKind::Comment); i = j; continue; }
+            // Spill to next lines
+            push(i, n, TokenKind::Comment);
+            state.in_block_comment = true;
+            return state;
+        }
+
+        // Raw string start: very simple detection: R"delim(
+        if (c == 'R' && i+1 < n && s[i+1] == '"') {
+            int k = i + 2;
+            std::string delim;
+            while (k < n && s[k] != '(') { delim.push_back(s[k]); ++k; }
+            if (k < n && s[k] == '(') {
+                int body_start = k + 1;
+                std::string needle = ")" + delim + "\"";
+                auto pos = s.find(needle, static_cast<std::size_t>(body_start));
+                if (pos == std::string::npos) {
+                    push(i, n, TokenKind::String);
+                    state.in_raw_string = true;
+                    state.raw_delim = delim;
+                    return state;
+                } else {
+                    int end = static_cast<int>(pos + needle.size());
+                    push(i, end, TokenKind::String);
+                    i = end;
+                    continue;
+                }
+            }
+            // If malformed, just treat 'R' as identifier fallback
+        }
+
+        // Regular string literal
+        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(i, j, TokenKind::String); i = j; continue;
+        }
+
+        // Char literal
+        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(i, j, TokenKind::Char); i = j; continue;
+        }
+
+        // Number literal (simple)
+        if (is_digit(c) || (c == '.' && i+1 < n && is_digit(s[i+1]))) {
+            int j = i+1; while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j]=='.' || s[j]=='x' || s[j]=='X' || s[j]=='b' || s[j]=='B' || s[j]=='_')) ++j;
+            push(i, j, TokenKind::Number); i = j; continue;
+        }
+
+        // Identifier / keyword / type
+        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);
+            TokenKind k = TokenKind::Identifier; if (keywords_.count(id)) k = TokenKind::Keyword; else if (types_.count(id)) k = TokenKind::Type; push(i, j, k); i = j; continue;
+        }
+
+        // Operators and punctuation (single char for now)
+        TokenKind kind = TokenKind::Operator;
+        if (std::ispunct(static_cast<unsigned char>(c)) && c != '_' && c != '#') {
+            if (c==';' || c==',' || c=='(' || c==')' || c=='{' || c=='}' || c=='[' || c==']') kind = TokenKind::Punctuation;
+            push(i, i+1, kind); ++i; continue;
+        }
+
+        // Fallback
+        push(i, i+1, TokenKind::Default); ++i;
+    }
+
+    return state;
+}
+
+} // namespace kte
diff --git a/CppHighlighter.h b/CppHighlighter.h
new file mode 100644
index 0000000..9b63bff
--- /dev/null
+++ b/CppHighlighter.h
@@ -0,0 +1,34 @@
+// CppHighlighter.h - minimal stateless C/C++ line highlighter
+#pragma once
+
+#include <regex>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "LanguageHighlighter.h"
+
+class Buffer;
+
+namespace kte {
+
+class CppHighlighter final : public StatefulHighlighter {
+public:
+    CppHighlighter();
+    ~CppHighlighter() override = default;
+
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+    LineState HighlightLineStateful(const Buffer &buf,
+                                    int row,
+                                    const LineState &prev,
+                                    std::vector<HighlightSpan> &out) const override;
+
+private:
+    std::unordered_set<std::string> keywords_;
+    std::unordered_set<std::string> types_;
+
+    static bool is_ident_start(char c);
+    static bool is_ident_char(char c);
+};
+
+} // namespace kte
diff --git a/Editor.cc b/Editor.cc
index cc0f01e..5695a29 100644
--- a/Editor.cc
+++ b/Editor.cc
@@ -3,6 +3,9 @@
 #include <filesystem>
 
 #include "Editor.h"
+#include "HighlighterRegistry.h"
+#include "CppHighlighter.h"
+#include "NullHighlighter.h"
 
 
 Editor::Editor() = default;
@@ -143,26 +146,72 @@ Editor::OpenFile(const std::string &path, std::string &err)
 {
 	// If there is exactly one unnamed, empty, clean buffer, reuse it instead
 	// of creating a new one.
-	if (buffers_.size() == 1) {
-		Buffer &cur                  = buffers_[curbuf_];
-		const bool unnamed           = cur.Filename().empty() && !cur.IsFileBacked();
-		const bool clean             = !cur.Dirty();
-		const auto &rows             = cur.Rows();
-		const bool rows_empty        = rows.empty();
-		const bool single_empty_line = (!rows.empty() && rows.size() == 1 && rows[0].size() == 0);
-		if (unnamed && clean && (rows_empty || single_empty_line)) {
-			return cur.OpenFromFile(path, err);
-		}
-	}
+ if (buffers_.size() == 1) {
+        Buffer &cur                  = buffers_[curbuf_];
+        const bool unnamed           = cur.Filename().empty() && !cur.IsFileBacked();
+        const bool clean             = !cur.Dirty();
+        const auto &rows             = cur.Rows();
+        const bool rows_empty        = rows.empty();
+        const bool single_empty_line = (!rows.empty() && rows.size() == 1 && rows[0].size() == 0);
+        if (unnamed && clean && (rows_empty || single_empty_line)) {
+            bool ok = cur.OpenFromFile(path, err);
+            if (!ok) return false;
+            // Setup highlighting using registry (extension + shebang)
+            cur.EnsureHighlighter();
+            std::string first = "";
+            const auto &rows = cur.Rows();
+            if (!rows.empty()) first = static_cast<std::string>(rows[0]);
+            std::string ft = kte::HighlighterRegistry::DetectForPath(path, first);
+            if (!ft.empty()) {
+                cur.SetFiletype(ft);
+                cur.SetSyntaxEnabled(true);
+                if (auto *eng = cur.Highlighter()) {
+                    eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
+                    eng->InvalidateFrom(0);
+                }
+            } else {
+                cur.SetFiletype("");
+                cur.SetSyntaxEnabled(true);
+                if (auto *eng = cur.Highlighter()) {
+                    eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+                    eng->InvalidateFrom(0);
+                }
+            }
+            return true;
+        }
+    }
 
-	Buffer b;
-	if (!b.OpenFromFile(path, err)) {
-		return false;
-	}
-	// Add as a new buffer and switch to it
-	std::size_t idx = AddBuffer(std::move(b));
-	SwitchTo(idx);
-	return true;
+    Buffer b;
+    if (!b.OpenFromFile(path, err)) {
+        return false;
+    }
+    // Initialize syntax highlighting by extension + shebang via registry (v2)
+    b.EnsureHighlighter();
+    std::string first = "";
+    {
+        const auto &rows = b.Rows();
+        if (!rows.empty()) first = static_cast<std::string>(rows[0]);
+    }
+    std::string ft = kte::HighlighterRegistry::DetectForPath(path, first);
+    if (!ft.empty()) {
+        b.SetFiletype(ft);
+        b.SetSyntaxEnabled(true);
+        if (auto *eng = b.Highlighter()) {
+            eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
+            eng->InvalidateFrom(0);
+        }
+    } else {
+        b.SetFiletype("");
+        b.SetSyntaxEnabled(true);
+        if (auto *eng = b.Highlighter()) {
+            eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+            eng->InvalidateFrom(0);
+        }
+    }
+    // Add as a new buffer and switch to it
+    std::size_t idx = AddBuffer(std::move(b));
+    SwitchTo(idx);
+    return true;
 }
 
 
diff --git a/GUIConfig.cc b/GUIConfig.cc
index 4dd5651..9820ef0 100644
--- a/GUIConfig.cc
+++ b/GUIConfig.cc
@@ -102,17 +102,27 @@ GUIConfig::LoadFromFile(const std::string &path)
 			if (v > 0.0f) {
 				font_size = v;
 			}
-		} else if (key == "theme") {
-			theme = val;
-		} else if (key == "background" || key == "bg") {
-			std::string v = val;
-			std::transform(v.begin(), v.end(), v.begin(), [](unsigned char c) {
-				return (char) std::tolower(c);
-			});
-			if (v == "light" || v == "dark")
-				background = v;
-		}
-	}
+        } else if (key == "theme") {
+            theme = val;
+        } else if (key == "background" || key == "bg") {
+            std::string v = val;
+            std::transform(v.begin(), v.end(), v.begin(), [](unsigned char c) {
+                return (char) std::tolower(c);
+            });
+            if (v == "light" || v == "dark")
+                background = v;
+        } else if (key == "syntax") {
+            std::string v = val;
+            std::transform(v.begin(), v.end(), v.begin(), [](unsigned char c) {
+                return (char) std::tolower(c);
+            });
+            if (v == "1" || v == "on" || v == "true" || v == "yes") {
+                syntax = true;
+            } else if (v == "0" || v == "off" || v == "false" || v == "no") {
+                syntax = false;
+            }
+        }
+    }
 
-	return true;
+    return true;
 }
diff --git a/GUIConfig.h b/GUIConfig.h
index f43e97f..63799e1 100644
--- a/GUIConfig.h
+++ b/GUIConfig.h
@@ -12,14 +12,18 @@
 
 class GUIConfig {
 public:
-	bool fullscreen   = false;
-	int columns       = 80;
-	int rows          = 42;
-	float font_size   = (float) KTE_FONT_SIZE;
-	std::string theme = "nord";
-	// Background mode for themes that support light/dark variants
-	// Values: "dark" (default), "light"
-	std::string background = "dark";
+    bool fullscreen   = false;
+    int columns       = 80;
+    int rows          = 42;
+    float font_size   = (float) KTE_FONT_SIZE;
+    std::string theme = "nord";
+    // Background mode for themes that support light/dark variants
+    // Values: "dark" (default), "light"
+    std::string background = "dark";
+
+    // Default syntax highlighting state for GUI (kge): on/off
+    // Accepts: on/off/true/false/yes/no/1/0 in the ini file.
+    bool syntax = true; // default: enabled
 
 	// Load from default path: $HOME/.config/kte/kge.ini
 	static GUIConfig Load();
diff --git a/GUIFrontend.cc b/GUIFrontend.cc
index 560521f..afd0dcc 100644
--- a/GUIFrontend.cc
+++ b/GUIFrontend.cc
@@ -16,6 +16,8 @@
 #include "Font.h" // embedded default font (DefaultFontRegular)
 #include "GUIConfig.h"
 #include "GUITheme.h"
+#include "HighlighterRegistry.h"
+#include "NullHighlighter.h"
 
 
 #ifndef KTE_FONT_SIZE
@@ -106,12 +108,42 @@ GUIFrontend::Init(Editor &ed)
 	(void) io;
 	ImGui::StyleColorsDark();
 
-	// Apply background mode and selected theme (default: Nord). Can be changed at runtime via commands.
-	if (cfg.background == "light")
-		kte::SetBackgroundMode(kte::BackgroundMode::Light);
-	else
-		kte::SetBackgroundMode(kte::BackgroundMode::Dark);
-	kte::ApplyThemeByName(cfg.theme);
+ // Apply background mode and selected theme (default: Nord). Can be changed at runtime via commands.
+ if (cfg.background == "light")
+     kte::SetBackgroundMode(kte::BackgroundMode::Light);
+ else
+     kte::SetBackgroundMode(kte::BackgroundMode::Dark);
+ kte::ApplyThemeByName(cfg.theme);
+
+ // Apply default syntax highlighting preference from GUI config to the current buffer
+ if (Buffer *b = ed.CurrentBuffer()) {
+     if (cfg.syntax) {
+         b->SetSyntaxEnabled(true);
+         // Ensure a highlighter is available if possible
+         b->EnsureHighlighter();
+         if (auto *eng = b->Highlighter()) {
+             if (!eng->HasHighlighter()) {
+                 // Try detect from filename and first line; fall back to cpp or existing filetype
+                 std::string first_line;
+                 const auto &rows = b->Rows();
+                 if (!rows.empty()) first_line = static_cast<std::string>(rows[0]);
+                 std::string ft = kte::HighlighterRegistry::DetectForPath(b->Filename(), first_line);
+                 if (!ft.empty()) {
+                     eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
+                     b->SetFiletype(ft);
+                     eng->InvalidateFrom(0);
+                 } else {
+                     // Unknown/unsupported -> install a null highlighter to keep syntax enabled
+                     eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+                     b->SetFiletype("");
+                     eng->InvalidateFrom(0);
+                 }
+             }
+         }
+     } else {
+         b->SetSyntaxEnabled(false);
+     }
+ }
 
 	if (!ImGui_ImplSDL2_InitForOpenGL(window_, gl_ctx_))
 		return false;
diff --git a/GUIRenderer.cc b/GUIRenderer.cc
index d8d6d3e..e3b8f74 100644
--- a/GUIRenderer.cc
+++ b/GUIRenderer.cc
@@ -10,6 +10,8 @@
 #include <regex>
 
 #include "GUIRenderer.h"
+#include "Highlight.h"
+#include "GUITheme.h"
 #include "Buffer.h"
 #include "Command.h"
 #include "Editor.h"
@@ -321,21 +323,50 @@ GUIRenderer::Draw(Editor &ed)
 					ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
 				}
 			}
-			// Emit entire line (ImGui child scrolling will handle clipping)
-			for (std::size_t src = 0; src < line.size(); ++src) {
-				char c = line[src];
-				if (c == '\t') {
-					std::size_t adv = (tabw - (rx_abs_draw % tabw));
-					// Emit spaces for the tab
-					expanded.append(adv, ' ');
-					rx_abs_draw += adv;
-				} else {
-					expanded.push_back(c);
-					rx_abs_draw += 1;
-				}
-			}
+   // Emit entire line to an expanded buffer (tabs -> spaces)
+   for (std::size_t src = 0; src < line.size(); ++src) {
+       char c = line[src];
+       if (c == '\t') {
+           std::size_t adv = (tabw - (rx_abs_draw % tabw));
+           expanded.append(adv, ' ');
+           rx_abs_draw += adv;
+       } else {
+           expanded.push_back(c);
+           rx_abs_draw += 1;
+       }
+   }
 
-			ImGui::TextUnformatted(expanded.c_str());
+   // Draw syntax-colored runs (text above background highlights)
+   if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
+       const kte::LineHighlight &lh = buf->Highlighter()->GetLine(*buf, static_cast<int>(i), buf->Version());
+       // Helper to convert a src column to expanded rx position
+       auto src_to_rx_full = [&](std::size_t sidx) -> std::size_t {
+           std::size_t rx = 0;
+           for (std::size_t k = 0; k < sidx && k < line.size(); ++k) {
+               rx += (line[k] == '\t') ? (tabw - (rx % tabw)) : 1;
+           }
+           return rx;
+       };
+       for (const auto &sp: lh.spans) {
+           std::size_t rx_s = src_to_rx_full(static_cast<std::size_t>(std::max(0, sp.col_start)));
+           std::size_t rx_e = src_to_rx_full(static_cast<std::size_t>(std::max(sp.col_start, sp.col_end)));
+           if (rx_e <= coloffs_now)
+               continue;
+           std::size_t vx0 = (rx_s > coloffs_now) ? (rx_s - coloffs_now) : 0;
+           std::size_t vx1 = (rx_e > coloffs_now) ? (rx_e - coloffs_now) : 0;
+           if (vx0 >= expanded.size()) continue;
+           vx1 = std::min<std::size_t>(vx1, expanded.size());
+           if (vx1 <= vx0) continue;
+           ImU32 col = ImGui::GetColorU32(kte::SyntaxInk(sp.kind));
+           ImVec2 p = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w, line_pos.y);
+           ImGui::GetWindowDrawList()->AddText(p, col, expanded.c_str() + vx0, expanded.c_str() + vx1);
+       }
+       // We drew text via draw list (no layout advance). Manually advance the cursor to the next line.
+       ImGui::SetCursorScreenPos(ImVec2(line_pos.x, line_pos.y + line_h));
+   } else {
+       // No syntax: draw as one run
+       ImGui::TextUnformatted(expanded.c_str());
+   }
 
 			// Draw a visible cursor indicator on the current line
 			if (i == cy) {
diff --git a/GUITheme.h b/GUITheme.h
index afc0d6c..1606c4a 100644
--- a/GUITheme.h
+++ b/GUITheme.h
@@ -1,57 +1,48 @@
-// GUITheme.h - ImGui theme configuration for kte GUI
-// Provides theme palettes and style settings (Nord + Gruvbox variants).
-
+// GUITheme.h — ImGui theming helpers and background mode
 #pragma once
 
 #include <imgui.h>
-#include <algorithm>
-#include <memory>
 #include <vector>
+#include <memory>
 #include <string>
+#include <cstddef>
+#include <algorithm>
+#include <cctype>
 
-namespace kte {
-// Theme identifiers (legacy API kept for compatibility)
-enum class ThemeId {
-	Nord,
-	GruvboxDarkMedium,
-	GruvboxLightMedium,
-	EInk, // monochrome e-ink style
-	Solarized, // solarized (light/dark via background)
-	Plan9, // plan9-inspired minimal theme (single acme-like palette)
-};
-
-// Background mode for themes that support light/dark variants
-enum class BackgroundMode {
-	Dark,
-	Light,
-};
-
-// Forward declaration of registry helpers
-class Theme;
-
-static inline const std::vector<std::unique_ptr<Theme> > &ThemeRegistry();
-
-static inline size_t ThemeIndexFromId(ThemeId id);
-
-static inline ThemeId ThemeIdFromIndex(size_t idx);
-
-// Keep track of current theme (program-wide)
-static inline ThemeId gCurrentTheme = ThemeId::Nord;
-// Background preference (defaults to Dark)
-static inline BackgroundMode gBackgroundMode = BackgroundMode::Dark;
-// Mirror index of current theme in the registry; keep it consistent with gCurrentTheme
-// Current alphabetical order: 0=eink, 1=gruvbox, 2=nord, 3=solarized
-static inline size_t gCurrentThemeIndex = ThemeIndexFromId(gCurrentTheme);
-// Convert RGB hex (0xRRGGBB) to ImVec4 with optional alpha
-static inline ImVec4
-RGBA(unsigned int rgb, float a = 1.0f)
+// Small helper to convert packed RGB (0xRRGGBB) + optional alpha to ImVec4
+static inline ImVec4 RGBA(unsigned int rgb, float a = 1.0f)
 {
-	float r = ((rgb >> 16) & 0xFF) / 255.0f;
-	float g = ((rgb >> 8) & 0xFF) / 255.0f;
-	float b = ((rgb) & 0xFF) / 255.0f;
-	return ImVec4(r, g, b, a);
+    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 ImVec4(r, g, b, a);
 }
 
+namespace kte {
+
+// Background mode selection for light/dark palettes
+enum class BackgroundMode { Light, Dark };
+
+// Global background mode; default to Dark to match prior defaults
+static inline BackgroundMode gBackgroundMode = BackgroundMode::Dark;
+
+// Basic theme identifier (kept minimal; some ids are aliases)
+enum class ThemeId {
+    EInk = 0,
+    GruvboxDarkMedium = 1,
+    GruvboxLightMedium = 1, // alias to unified gruvbox index
+    Nord = 2,
+    Plan9 = 3,
+    Solarized = 4,
+};
+
+// Current theme tracking
+static inline ThemeId gCurrentTheme = ThemeId::Nord;
+static inline std::size_t gCurrentThemeIndex = 0;
+
+// Forward declarations for helpers used below
+static inline size_t ThemeIndexFromId(ThemeId id);
+static inline ThemeId ThemeIdFromIndex(size_t idx);
 
 // Helpers to set/query background mode
 static inline void
@@ -1107,20 +1098,18 @@ CurrentThemeName()
 static inline size_t
 ThemeIndexFromId(ThemeId id)
 {
-	switch (id) {
-	case ThemeId::EInk:
-		return 0;
-	case ThemeId::GruvboxDarkMedium:
-		return 1;
-	case ThemeId::GruvboxLightMedium: // legacy alias maps to unified gruvbox index
-		return 1;
-	case ThemeId::Nord:
-		return 2;
-	case ThemeId::Plan9:
-		return 3;
-	case ThemeId::Solarized:
-		return 4;
-	}
+ switch (id) {
+ case ThemeId::EInk:
+     return 0;
+ case ThemeId::GruvboxDarkMedium:
+     return 1;
+ case ThemeId::Nord:
+     return 2;
+ case ThemeId::Plan9:
+     return 3;
+ case ThemeId::Solarized:
+     return 4;
+ }
 	return 0;
 }
 
@@ -1142,4 +1131,30 @@ ThemeIdFromIndex(size_t idx)
 		return ThemeId::Solarized;
 	}
 }
+
+// --- Syntax palette (v1): map TokenKind to ink color per current theme/background ---
+static inline ImVec4 SyntaxInk(TokenKind k)
+{
+    // Basic palettes for dark/light backgrounds; tuned for Nord-ish defaults
+    const bool dark = (GetBackgroundMode() == BackgroundMode::Dark);
+    // Base text
+    ImVec4 def = dark ? RGBA(0xD8DEE9) : RGBA(0x2E3440);
+    switch (k) {
+        case TokenKind::Keyword:      return dark ? RGBA(0x81A1C1) : RGBA(0x5E81AC);
+        case TokenKind::Type:         return dark ? RGBA(0x8FBCBB) : RGBA(0x4C566A);
+        case TokenKind::String:       return dark ? RGBA(0xA3BE8C) : RGBA(0x6C8E5E);
+        case TokenKind::Char:         return dark ? RGBA(0xA3BE8C) : RGBA(0x6C8E5E);
+        case TokenKind::Comment:      return dark ? RGBA(0x616E88) : RGBA(0x7A869A);
+        case TokenKind::Number:       return dark ? RGBA(0xEBCB8B) : RGBA(0xB58900);
+        case TokenKind::Preproc:      return dark ? RGBA(0xD08770) : RGBA(0xAF3A03);
+        case TokenKind::Constant:     return dark ? RGBA(0xB48EAD) : RGBA(0x7B4B7F);
+        case TokenKind::Function:     return dark ? RGBA(0x88C0D0) : RGBA(0x3465A4);
+        case TokenKind::Operator:     return dark ? RGBA(0xECEFF4) : RGBA(0x2E3440);
+        case TokenKind::Punctuation:  return dark ? RGBA(0xECEFF4) : RGBA(0x2E3440);
+        case TokenKind::Identifier:   return def;
+        case TokenKind::Whitespace:   return def;
+        case TokenKind::Error:        return dark ? RGBA(0xBF616A) : RGBA(0xCC0000);
+        case TokenKind::Default:      default: return def;
+    }
+}
 } // namespace kte
diff --git a/GoHighlighter.cc b/GoHighlighter.cc
new file mode 100644
index 0000000..d63e240
--- /dev/null
+++ b/GoHighlighter.cc
@@ -0,0 +1,48 @@
+#include "GoHighlighter.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=='_'; }
+
+GoHighlighter::GoHighlighter()
+{
+    const char* kw[] = {"break","case","chan","const","continue","default","defer","else","fallthrough","for","func","go","goto","if","import","interface","map","package","range","return","select","struct","switch","type","var"};
+    for (auto s: kw) kws_.insert(s);
+    const char* tp[] = {"bool","byte","complex64","complex128","error","float32","float64","int","int8","int16","int32","int64","rune","string","uint","uint8","uint16","uint32","uint64","uintptr"};
+    for (auto s: tp) types_.insert(s);
+}
+
+void GoHighlighter::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;
+    int bol=0; while (bol<n && (s[bol]==' '||s[bol]=='\t')) ++bol;
+    // line comment
+    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; }
+        if (c=='/' && i+1<n && s[i+1]=='/') { push(out,i,n,TokenKind::Comment); break; }
+        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; }
+        }
+        if (c=='"' || c=='`') {
+            char q=c; int j=i+1; bool esc=false; if (q=='`') { while (j<n && s[j] != '`') ++j; if (j<n) ++j; }
+            else { 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;
+        }
+        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]=='x'||s[j]=='X'||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); TokenKind k=TokenKind::Identifier; if (kws_.count(id)) k=TokenKind::Keyword; else if (types_.count(id)) 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==')'||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
diff --git a/GoHighlighter.h b/GoHighlighter.h
new file mode 100644
index 0000000..89ec530
--- /dev/null
+++ b/GoHighlighter.h
@@ -0,0 +1,18 @@
+// GoHighlighter.h - simple Go highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+
+class GoHighlighter final : public LanguageHighlighter {
+public:
+    GoHighlighter();
+    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
diff --git a/Highlight.h b/Highlight.h
new file mode 100644
index 0000000..f10961b
--- /dev/null
+++ b/Highlight.h
@@ -0,0 +1,39 @@
+// Highlight.h - core syntax highlighting types for kte
+#pragma once
+
+#include <cstdint>
+#include <vector>
+
+namespace kte {
+
+// Token kinds shared between renderers and highlighters
+enum class TokenKind {
+    Default,
+    Keyword,
+    Type,
+    String,
+    Char,
+    Comment,
+    Number,
+    Preproc,
+    Constant,
+    Function,
+    Operator,
+    Punctuation,
+    Identifier,
+    Whitespace,
+    Error
+};
+
+struct HighlightSpan {
+    int col_start{0}; // inclusive, 0-based columns in buffer indices
+    int col_end{0};   // exclusive
+    TokenKind kind{TokenKind::Default};
+};
+
+struct LineHighlight {
+    std::vector<HighlightSpan> spans;
+    std::uint64_t version{0}; // buffer version used for this line
+};
+
+} // namespace kte
diff --git a/HighlighterEngine.cc b/HighlighterEngine.cc
new file mode 100644
index 0000000..6db0b56
--- /dev/null
+++ b/HighlighterEngine.cc
@@ -0,0 +1,94 @@
+#include "HighlighterEngine.h"
+#include "Buffer.h"
+#include "LanguageHighlighter.h"
+
+namespace kte {
+
+HighlighterEngine::HighlighterEngine() = default;
+HighlighterEngine::~HighlighterEngine() = default;
+
+void
+HighlighterEngine::SetHighlighter(std::unique_ptr<LanguageHighlighter> hl)
+{
+    hl_ = std::move(hl);
+    cache_.clear();
+    state_cache_.clear();
+}
+
+const LineHighlight &
+HighlighterEngine::GetLine(const Buffer &buf, int row, std::uint64_t buf_version) const
+{
+    auto it = cache_.find(row);
+    if (it != cache_.end()) {
+        if (it->second.version == buf_version) {
+            return it->second;
+        }
+    }
+    LineHighlight updated;
+    updated.version = buf_version;
+    updated.spans.clear();
+    if (!hl_) {
+        auto &slot = cache_[row];
+        slot = std::move(updated);
+        return cache_[row];
+    }
+
+    if (auto *stateful = dynamic_cast<StatefulHighlighter *>(hl_.get())) {
+        // Find nearest cached state at or before row-1 with matching version
+        StatefulHighlighter::LineState prev_state;
+        int start_row = -1;
+        if (!state_cache_.empty()) {
+            // linear search over map (unordered), track best candidate
+            int best = -1;
+            for (const auto &kv : state_cache_) {
+                int r = kv.first;
+                if (r <= row - 1 && kv.second.version == buf_version) {
+                    if (r > best) {
+                        best = r;
+                    }
+                }
+            }
+            if (best >= 0) {
+                start_row = best;
+                prev_state = state_cache_.at(best).state;
+            }
+        }
+
+        // Walk from start_row+1 up to row computing states; only collect spans at the target row
+        for (int r = start_row + 1; r <= row; ++r) {
+            std::vector<HighlightSpan> tmp;
+            std::vector<HighlightSpan> &out = (r == row) ? updated.spans : tmp;
+            auto next_state = stateful->HighlightLineStateful(buf, r, prev_state, out);
+            // store state for this row (state after finishing r)
+            StateEntry se;
+            se.version = buf_version;
+            se.state = next_state;
+            state_cache_[r] = se;
+            prev_state = next_state;
+        }
+    } else {
+        // Stateless path
+        hl_->HighlightLine(buf, row, updated.spans);
+    }
+
+    auto &slot = cache_[row];
+    slot = std::move(updated);
+    return cache_[row];
+}
+
+void
+HighlighterEngine::InvalidateFrom(int row)
+{
+    if (cache_.empty()) return;
+    // Simple implementation: erase all rows >= row
+    for (auto it = cache_.begin(); it != cache_.end(); ) {
+        if (it->first >= row) it = cache_.erase(it); else ++it;
+    }
+    if (!state_cache_.empty()) {
+        for (auto it = state_cache_.begin(); it != state_cache_.end(); ) {
+            if (it->first >= row) it = state_cache_.erase(it); else ++it;
+        }
+    }
+}
+
+} // namespace kte
diff --git a/HighlighterEngine.h b/HighlighterEngine.h
new file mode 100644
index 0000000..544b6cf
--- /dev/null
+++ b/HighlighterEngine.h
@@ -0,0 +1,45 @@
+// HighlighterEngine.h - caching layer for per-line highlights
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <unordered_map>
+#include <vector>
+
+#include "Highlight.h"
+#include "LanguageHighlighter.h"
+
+class Buffer;
+
+namespace kte {
+
+class HighlighterEngine {
+public:
+    HighlighterEngine();
+    ~HighlighterEngine();
+
+    void SetHighlighter(std::unique_ptr<LanguageHighlighter> hl);
+
+    // Retrieve highlights for a given line and buffer version.
+    // If cache is stale, recompute using the current highlighter.
+    const LineHighlight &GetLine(const Buffer &buf, int row, std::uint64_t buf_version) const;
+
+    // Invalidate cached lines from row (inclusive)
+    void InvalidateFrom(int row);
+
+    bool HasHighlighter() const { return static_cast<bool>(hl_); }
+
+private:
+    std::unique_ptr<LanguageHighlighter> hl_;
+    // Simple cache by row index (mutable to allow caching in const GetLine)
+    mutable std::unordered_map<int, LineHighlight> cache_;
+    // For stateful highlighters, remember per-line state (state after finishing that row)
+    struct StateEntry {
+        std::uint64_t version{0};
+        // Using the interface type; forward-declare via header
+        StatefulHighlighter::LineState state;
+    };
+    mutable std::unordered_map<int, StateEntry> state_cache_;
+};
+
+} // namespace kte
diff --git a/HighlighterRegistry.cc b/HighlighterRegistry.cc
new file mode 100644
index 0000000..66141fd
--- /dev/null
+++ b/HighlighterRegistry.cc
@@ -0,0 +1,93 @@
+#include "HighlighterRegistry.h"
+#include "CppHighlighter.h"
+
+#include <algorithm>
+#include <filesystem>
+
+// Forward declare simple highlighters implemented in this project
+namespace kte {
+class JSONHighlighter; class MarkdownHighlighter; class ShellHighlighter;
+class GoHighlighter; class PythonHighlighter; class RustHighlighter; class LispHighlighter;
+}
+
+// Headers for the above
+#include "JsonHighlighter.h"
+#include "MarkdownHighlighter.h"
+#include "ShellHighlighter.h"
+#include "GoHighlighter.h"
+#include "PythonHighlighter.h"
+#include "RustHighlighter.h"
+#include "LispHighlighter.h"
+
+namespace kte {
+
+static std::string to_lower(std::string_view s) {
+    std::string r(s);
+    std::transform(r.begin(), r.end(), r.begin(), [](unsigned char c){ return static_cast<char>(std::tolower(c)); });
+    return r;
+}
+
+std::string HighlighterRegistry::Normalize(std::string_view ft)
+{
+    std::string f = to_lower(ft);
+    if (f == "c" || f == "c++" || f == "cc" || f == "hpp" || f == "hh" || f == "h" || f == "cxx") return "cpp";
+    if (f == "cpp") return "cpp";
+    if (f == "json") return "json";
+    if (f == "markdown" || f == "md" || f == "mkd" || f == "mdown") return "markdown";
+    if (f == "shell" || f == "sh" || f == "bash" || f == "zsh" || f == "ksh" || f == "fish") return "shell";
+    if (f == "go" || f == "golang") return "go";
+    if (f == "py" || f == "python") return "python";
+    if (f == "rs" || f == "rust") return "rust";
+    if (f == "lisp" || f == "scheme" || f == "scm" || f == "rkt" || f == "el" || f == "clj" || f == "cljc" || f == "cl") return "lisp";
+    return f;
+}
+
+std::unique_ptr<LanguageHighlighter> HighlighterRegistry::CreateFor(std::string_view filetype)
+{
+    std::string ft = Normalize(filetype);
+    if (ft == "cpp") return std::make_unique<CppHighlighter>();
+    if (ft == "json") return std::make_unique<JSONHighlighter>();
+    if (ft == "markdown") return std::make_unique<MarkdownHighlighter>();
+    if (ft == "shell") return std::make_unique<ShellHighlighter>();
+    if (ft == "go") return std::make_unique<GoHighlighter>();
+    if (ft == "python") return std::make_unique<PythonHighlighter>();
+    if (ft == "rust") return std::make_unique<RustHighlighter>();
+    if (ft == "lisp") return std::make_unique<LispHighlighter>();
+    return nullptr;
+}
+
+static std::string shebang_to_ft(std::string_view first_line) {
+    if (first_line.size() < 2 || first_line.substr(0,2) != "#!") return "";
+    std::string low = to_lower(first_line);
+    if (low.find("python") != std::string::npos) return "python";
+    if (low.find("bash") != std::string::npos) return "shell";
+    if (low.find("sh") != std::string::npos) return "shell";
+    if (low.find("zsh") != std::string::npos) return "shell";
+    if (low.find("fish") != std::string::npos) return "shell";
+    if (low.find("scheme") != std::string::npos || low.find("racket") != std::string::npos || low.find("guile") != std::string::npos) return "lisp";
+    return "";
+}
+
+std::string HighlighterRegistry::DetectForPath(std::string_view path, std::string_view first_line)
+{
+    // Extension
+    std::string p(path);
+    std::error_code ec;
+    std::string ext = std::filesystem::path(p).extension().string();
+    for (auto &ch: ext) ch = static_cast<char>(std::tolower(static_cast<unsigned char>(ch)));
+    if (!ext.empty()) {
+        if (ext == ".c" || ext == ".cc" || ext == ".cpp" || ext == ".cxx" || ext == ".h" || ext == ".hpp" || ext == ".hh") return "cpp";
+        if (ext == ".json") return "json";
+        if (ext == ".md" || ext == ".markdown" || ext == ".mkd") return "markdown";
+        if (ext == ".sh" || ext == ".bash" || ext == ".zsh" || ext == ".ksh" || ext == ".fish") return "shell";
+        if (ext == ".go") return "go";
+        if (ext == ".py") return "python";
+        if (ext == ".rs") return "rust";
+        if (ext == ".lisp" || ext == ".scm" || ext == ".rkt" || ext == ".el" || ext == ".clj" || ext == ".cljc" || ext == ".cl") return "lisp";
+    }
+    // Shebang
+    std::string ft = shebang_to_ft(first_line);
+    return ft;
+}
+
+} // namespace kte
diff --git a/HighlighterRegistry.h b/HighlighterRegistry.h
new file mode 100644
index 0000000..f4985bd
--- /dev/null
+++ b/HighlighterRegistry.h
@@ -0,0 +1,26 @@
+// HighlighterRegistry.h - create/detect language highlighters
+#pragma once
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <string_view>
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+
+class HighlighterRegistry {
+public:
+    // Create a highlighter for normalized filetype id (e.g., "cpp", "json", "markdown", "shell", "go", "python", "rust", "lisp").
+    static std::unique_ptr<LanguageHighlighter> CreateFor(std::string_view filetype);
+
+    // Detect filetype by path extension and shebang (first line).
+    // Returns normalized id or empty string if unknown.
+    static std::string DetectForPath(std::string_view path, std::string_view first_line);
+
+    // Normalize various aliases/extensions to canonical ids.
+    static std::string Normalize(std::string_view ft);
+};
+
+} // namespace kte
diff --git a/JsonHighlighter.cc b/JsonHighlighter.cc
new file mode 100644
index 0000000..693d3ff
--- /dev/null
+++ b/JsonHighlighter.cc
@@ -0,0 +1,42 @@
+#include "JsonHighlighter.h"
+#include "Buffer.h"
+#include <cctype>
+
+namespace kte {
+
+static bool is_digit(char c) { return c >= '0' && c <= '9'; }
+
+void JSONHighlighter::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());
+    auto push = [&](int a, int b, TokenKind k){ if (b> a) out.push_back({a,b,k}); };
+
+    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(i,j,TokenKind::Whitespace); i=j; continue; }
+        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(i, j, TokenKind::String); i = j; continue;
+        }
+        if (is_digit(c) || (c=='-' && i+1<n && is_digit(s[i+1]))) {
+            int j=i+1; while (j<n && (std::isdigit(static_cast<unsigned char>(s[j]))||s[j]=='.'||s[j]=='e'||s[j]=='E'||s[j]=='+'||s[j]=='-'||s[j]=='_')) ++j; push(i,j,TokenKind::Number); i=j; continue;
+        }
+        // booleans/null
+        if (std::isalpha(static_cast<unsigned char>(c))) {
+            int j=i+1; while (j<n && std::isalpha(static_cast<unsigned char>(s[j]))) ++j;
+            std::string id = s.substr(i, j-i);
+            if (id == "true" || id == "false" || id == "null") push(i,j,TokenKind::Constant); else push(i,j,TokenKind::Identifier);
+            i=j; continue;
+        }
+        // punctuation
+        if (c=='{'||c=='}'||c=='['||c==']'||c==','||c==':' ) { push(i,i+1,TokenKind::Punctuation); ++i; continue; }
+        // fallback
+        push(i,i+1,TokenKind::Default); ++i;
+    }
+}
+
+} // namespace kte
diff --git a/JsonHighlighter.h b/JsonHighlighter.h
new file mode 100644
index 0000000..314619f
--- /dev/null
+++ b/JsonHighlighter.h
@@ -0,0 +1,14 @@
+// JsonHighlighter.h - simple JSON line highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <vector>
+
+namespace kte {
+
+class JSONHighlighter final : public LanguageHighlighter {
+public:
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+
+} // namespace kte
diff --git a/LanguageHighlighter.h b/LanguageHighlighter.h
new file mode 100644
index 0000000..cdd0d45
--- /dev/null
+++ b/LanguageHighlighter.h
@@ -0,0 +1,43 @@
+// LanguageHighlighter.h - interface for line-based highlighters
+#pragma once
+
+#include <memory>
+#include <vector>
+#include <string>
+
+#include "Highlight.h"
+
+class Buffer;
+
+namespace kte {
+
+class LanguageHighlighter {
+public:
+    virtual ~LanguageHighlighter() = default;
+    // Produce highlight spans for a given buffer row. Implementations should append to out.
+    virtual void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const = 0;
+    virtual bool Stateful() const { return false; }
+};
+
+// Optional extension for stateful highlighters (e.g., multi-line comments/strings).
+// Engines may detect and use this via dynamic_cast without breaking stateless impls.
+class StatefulHighlighter : public LanguageHighlighter {
+public:
+    struct LineState {
+        bool in_block_comment{false};
+        bool in_raw_string{false};
+        // For raw strings, remember the delimiter between the opening R"delim( and closing )delim"
+        std::string raw_delim;
+    };
+
+    // Highlight one line given the previous line state; return the resulting state after this line.
+    // Implementations should append spans for this line to out and compute the next state.
+    virtual LineState HighlightLineStateful(const Buffer &buf,
+                                            int row,
+                                            const LineState &prev,
+                                            std::vector<HighlightSpan> &out) const = 0;
+
+    bool Stateful() const override { return true; }
+};
+
+} // namespace kte
diff --git a/LispHighlighter.cc b/LispHighlighter.cc
new file mode 100644
index 0000000..e8b0763
--- /dev/null
+++ b/LispHighlighter.cc
@@ -0,0 +1,41 @@
+#include "LispHighlighter.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}); }
+
+LispHighlighter::LispHighlighter()
+{
+    const char* kw[] = {"defun","lambda","let","let*","define","set!","if","cond","begin","quote","quasiquote","unquote","unquote-splicing","loop","do","and","or","not"};
+    for (auto s: kw) kws_.insert(s);
+}
+
+void LispHighlighter::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;
+    int bol = 0; while (bol<n && (s[bol]==' '||s[bol]=='\t')) ++bol;
+    if (bol < n && s[bol] == ';') { push(out, bol, n, TokenKind::Comment); if (bol>0) push(out,0,bol,TokenKind::Whitespace); return; }
+    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; }
+        if (c==';') { push(out,i,n,TokenKind::Comment); break; }
+        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; }
+        if (std::isalpha(static_cast<unsigned char>(c)) || c=='*' || c=='-' || c=='+' || c=='/' || c=='_' ) {
+            int j=i+1; while (j<n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j]=='*' || s[j]=='-' || s[j]=='+' || s[j]=='/' || s[j]=='_' || s[j]=='!')) ++j;
+            std::string id=s.substr(i,j-i);
+            TokenKind k = kws_.count(id) ? TokenKind::Keyword : TokenKind::Identifier;
+            push(out,i,j,k); i=j; continue;
+        }
+        if (std::isdigit(static_cast<unsigned char>(c))) { int j=i+1; while (j<n && (std::isdigit(static_cast<unsigned char>(s[j]))||s[j]=='.')) ++j; push(out,i,j,TokenKind::Number); i=j; continue; }
+        if (std::ispunct(static_cast<unsigned char>(c))) { TokenKind k=TokenKind::Punctuation; push(out,i,i+1,k); ++i; continue; }
+        push(out,i,i+1,TokenKind::Default); ++i;
+    }
+}
+
+} // namespace kte
diff --git a/LispHighlighter.h b/LispHighlighter.h
new file mode 100644
index 0000000..35f6b52
--- /dev/null
+++ b/LispHighlighter.h
@@ -0,0 +1,17 @@
+// LispHighlighter.h - simple Lisp/Scheme family highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+
+class LispHighlighter final : public LanguageHighlighter {
+public:
+    LispHighlighter();
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+private:
+    std::unordered_set<std::string> kws_;
+};
+
+} // namespace kte
diff --git a/MarkdownHighlighter.cc b/MarkdownHighlighter.cc
new file mode 100644
index 0000000..6314dfb
--- /dev/null
+++ b/MarkdownHighlighter.cc
@@ -0,0 +1,88 @@
+#include "MarkdownHighlighter.h"
+#include "Buffer.h"
+#include <cctype>
+
+namespace kte {
+
+static void push_span(std::vector<HighlightSpan> &out, int a, int b, TokenKind k) {
+    if (b > a) out.push_back({a,b,k});
+}
+
+void MarkdownHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+    LineState st; // not used in stateless entry
+    (void)HighlightLineStateful(buf, row, st, out);
+}
+
+StatefulHighlighter::LineState MarkdownHighlighter::HighlightLineStateful(const Buffer &buf, int row, const LineState &prev, std::vector<HighlightSpan> &out) const
+{
+    StatefulHighlighter::LineState state = prev;
+    const auto &rows = buf.Rows();
+    if (row < 0 || static_cast<std::size_t>(row) >= rows.size()) return state;
+    std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+    int n = static_cast<int>(s.size());
+
+    // Reuse in_block_comment flag as "in fenced code" state.
+    if (state.in_block_comment) {
+        // If line contains closing fence ``` then close after it
+        auto pos = s.find("```");
+        if (pos == std::string::npos) {
+            push_span(out, 0, n, TokenKind::String);
+            state.in_block_comment = true;
+            return state;
+        } else {
+            int end = static_cast<int>(pos + 3);
+            push_span(out, 0, end, TokenKind::String);
+            // rest of line processed normally after fence
+            int i = end;
+            // whitespace
+            if (i < n) push_span(out, i, n, TokenKind::Default);
+            state.in_block_comment = false;
+            return state;
+        }
+    }
+
+    // Detect fenced code block start at beginning (allow leading spaces)
+    int bol = 0; while (bol < n && (s[bol]==' '||s[bol]=='\t')) ++bol;
+    if (bol + 3 <= n && s.compare(bol, 3, "```") == 0) {
+        push_span(out, bol, n, TokenKind::String);
+        state.in_block_comment = true; // enter fenced mode
+        return state;
+    }
+
+    // Headings: lines starting with 1-6 '#'
+    if (bol < n && s[bol] == '#') {
+        int j = bol; while (j < n && s[j] == '#') ++j; // hashes
+        // include following space and text as Keyword to stand out
+        push_span(out, bol, n, TokenKind::Keyword);
+        return state;
+    }
+
+    // Process inline: emphasis and code spans
+    int i = 0;
+    while (i < n) {
+        char c = s[i];
+        if (c == '`') {
+            int j = i + 1; while (j < n && s[j] != '`') ++j; if (j < n) ++j;
+            push_span(out, i, j, TokenKind::String); i = j; continue;
+        }
+        if (c == '*' || c == '_') {
+            // bold/italic markers: treat the marker and until next same marker as Type to highlight
+            char m = c; int j = i + 1; while (j < n && s[j] != m) ++j; if (j < n) ++j;
+            push_span(out, i, j, TokenKind::Type); i = j; continue;
+        }
+        // links []() minimal: treat [text](url) as Function
+        if (c == '[') {
+            int j = i + 1; while (j < n && s[j] != ']') ++j; if (j < n) ++j; // include ]
+            if (j < n && s[j] == '(') { while (j < n && s[j] != ')') ++j; if (j < n) ++j; }
+            push_span(out, i, j, TokenKind::Function); i = j; continue;
+        }
+        // whitespace
+        if (c == ' ' || c == '\t') { int j=i+1; while (j<n && (s[j]==' '||s[j]=='\t')) ++j; push_span(out, i, j, TokenKind::Whitespace); i=j; continue; }
+        // fallback: default single char
+        push_span(out, i, i+1, TokenKind::Default); ++i;
+    }
+    return state;
+}
+
+} // namespace kte
diff --git a/MarkdownHighlighter.h b/MarkdownHighlighter.h
new file mode 100644
index 0000000..5e1c12e
--- /dev/null
+++ b/MarkdownHighlighter.h
@@ -0,0 +1,14 @@
+// MarkdownHighlighter.h - simple Markdown highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+
+class MarkdownHighlighter final : public StatefulHighlighter {
+public:
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+    LineState HighlightLineStateful(const Buffer &buf, int row, const LineState &prev, std::vector<HighlightSpan> &out) const override;
+};
+
+} // namespace kte
diff --git a/NullHighlighter.cc b/NullHighlighter.cc
new file mode 100644
index 0000000..9a59036
--- /dev/null
+++ b/NullHighlighter.cc
@@ -0,0 +1,16 @@
+#include "NullHighlighter.h"
+#include "Buffer.h"
+
+namespace kte {
+
+void NullHighlighter::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());
+    if (n <= 0) return;
+    out.push_back({0, n, TokenKind::Default});
+}
+
+} // namespace kte
diff --git a/NullHighlighter.h b/NullHighlighter.h
new file mode 100644
index 0000000..64e82d0
--- /dev/null
+++ b/NullHighlighter.h
@@ -0,0 +1,13 @@
+// NullHighlighter.h - default highlighter that emits a single Default span per line
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+
+class NullHighlighter final : public LanguageHighlighter {
+public:
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+
+} // namespace kte
diff --git a/PythonHighlighter.cc b/PythonHighlighter.cc
new file mode 100644
index 0000000..ffc9235
--- /dev/null
+++ b/PythonHighlighter.cc
@@ -0,0 +1,85 @@
+#include "PythonHighlighter.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=='_'; }
+
+PythonHighlighter::PythonHighlighter()
+{
+    const char* kw[] = {"and","as","assert","break","class","continue","def","del","elif","else","except","False","finally","for","from","global","if","import","in","is","lambda","None","nonlocal","not","or","pass","raise","return","True","try","while","with","yield"};
+    for (auto s: kw) kws_.insert(s);
+}
+
+void PythonHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+    LineState st; (void)HighlightLineStateful(buf, row, st, out);
+}
+
+StatefulHighlighter::LineState PythonHighlighter::HighlightLineStateful(const Buffer &buf, int row, const LineState &prev, std::vector<HighlightSpan> &out) const
+{
+    StatefulHighlighter::LineState state = prev;
+    const auto &rows = buf.Rows();
+    if (row < 0 || static_cast<std::size_t>(row) >= rows.size()) return state;
+    std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+    int n = static_cast<int>(s.size());
+
+    // Triple-quoted string continuation uses in_raw_string with raw_delim either "'''" or "\"\"\""
+    if (state.in_raw_string && (state.raw_delim == "'''" || state.raw_delim == "\"\"\"")) {
+        auto pos = s.find(state.raw_delim);
+        if (pos == std::string::npos) {
+            push(out, 0, n, TokenKind::String);
+            return state; // still inside
+        } else {
+            int end = static_cast<int>(pos + static_cast<int>(state.raw_delim.size()));
+            push(out, 0, end, TokenKind::String);
+            // remainder processed normally
+            s = s.substr(end);
+            n = static_cast<int>(s.size());
+            state.in_raw_string = false; state.raw_delim.clear();
+            // Continue parsing remainder as a separate small loop
+            int base = end; // original offset, but we already emitted to 'out' with base=0; following spans should be from 'end'
+            // For simplicity, mark rest as Default
+            if (n>0) push(out, base, base + n, TokenKind::Default);
+            return state;
+        }
+    }
+
+    int i = 0;
+    // Detect comment start '#', ignoring inside strings
+    while (i < n) {
+        char c = s[i];
+        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; }
+        if (c=='#') { push(out,i,n,TokenKind::Comment); break; }
+        // Strings: triple quotes and single-line
+        if (c=='"' || c=='\'') {
+            char q=c;
+            // triple?
+            if (i+2 < n && s[i+1]==q && s[i+2]==q) {
+                std::string delim(3, q);
+                int j = i+3; // search for closing triple
+                auto pos = s.find(delim, static_cast<std::size_t>(j));
+                if (pos == std::string::npos) {
+                    push(out,i,n,TokenKind::String);
+                    state.in_raw_string = true; state.raw_delim = delim; return state;
+                } else {
+                    int end = static_cast<int>(pos + 3);
+                    push(out,i,end,TokenKind::String); i=end; continue;
+                }
+            } else {
+                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==q) break; }
+                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); TokenKind k=TokenKind::Identifier; if (kws_.count(id)) 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==']') k=TokenKind::Punctuation; push(out,i,i+1,k); ++i; continue; }
+        push(out,i,i+1,TokenKind::Default); ++i;
+    }
+    return state;
+}
+
+} // namespace kte
diff --git a/PythonHighlighter.h b/PythonHighlighter.h
new file mode 100644
index 0000000..d7d2d3c
--- /dev/null
+++ b/PythonHighlighter.h
@@ -0,0 +1,18 @@
+// PythonHighlighter.h - simple Python highlighter with triple-quote state
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+
+class PythonHighlighter final : public StatefulHighlighter {
+public:
+    PythonHighlighter();
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+    LineState HighlightLineStateful(const Buffer &buf, int row, const LineState &prev, std::vector<HighlightSpan> &out) const override;
+private:
+    std::unordered_set<std::string> kws_;
+};
+
+} // namespace kte
diff --git a/RustHighlighter.cc b/RustHighlighter.cc
new file mode 100644
index 0000000..8e51007
--- /dev/null
+++ b/RustHighlighter.cc
@@ -0,0 +1,39 @@
+#include "RustHighlighter.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=='_'; }
+
+RustHighlighter::RustHighlighter()
+{
+    const char* kw[] = {"as","break","const","continue","crate","else","enum","extern","false","fn","for","if","impl","in","let","loop","match","mod","move","mut","pub","ref","return","self","Self","static","struct","super","trait","true","type","unsafe","use","where","while","dyn","async","await","try"};
+    for (auto s: kw) kws_.insert(s);
+    const char* tp[] = {"u8","u16","u32","u64","u128","usize","i8","i16","i32","i64","i128","isize","f32","f64","bool","char","str"};
+    for (auto s: tp) types_.insert(s);
+}
+
+void RustHighlighter::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; }
+        if (c=='/' && i+1<n && s[i+1]=='/') { push(out,i,n,TokenKind::Comment); break; }
+        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; } }
+        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; }
+        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); TokenKind k=TokenKind::Identifier; if (kws_.count(id)) k=TokenKind::Keyword; else if (types_.count(id)) 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==')'||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
diff --git a/RustHighlighter.h b/RustHighlighter.h
new file mode 100644
index 0000000..6b75c77
--- /dev/null
+++ b/RustHighlighter.h
@@ -0,0 +1,18 @@
+// RustHighlighter.h - simple Rust highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+
+class RustHighlighter final : public LanguageHighlighter {
+public:
+    RustHighlighter();
+    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
diff --git a/ShellHighlighter.cc b/ShellHighlighter.cc
new file mode 100644
index 0000000..2061601
--- /dev/null
+++ b/ShellHighlighter.cc
@@ -0,0 +1,43 @@
+#include "ShellHighlighter.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}); }
+
+void ShellHighlighter::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;
+    // if first non-space is '#', whole line is comment
+    int bol = 0; while (bol < n && (s[bol]==' '||s[bol]=='\t')) ++bol;
+    if (bol < n && s[bol] == '#') { push(out, bol, n, TokenKind::Comment); if (bol>0) push(out,0,bol,TokenKind::Whitespace); return; }
+    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; }
+        if (c == '#') { push(out, i, n, TokenKind::Comment); break; }
+        if (c == '\'' || c == '"') {
+            char q = c; int j = i+1; bool esc=false; while (j<n) { char d=s[j++]; if (q=='"') { if (esc) {esc=false; continue;} if (d=='\\'){esc=true; continue;} if (d=='"') break; } else { if (d=='\'') break; } }
+            push(out,i,j,TokenKind::String); i=j; continue;
+        }
+        // simple keywords
+        if (std::isalpha(static_cast<unsigned char>(c))) {
+            int j=i+1; while (j<n && (std::isalnum(static_cast<unsigned char>(s[j]))||s[j]=='_')) ++j; std::string id=s.substr(i,j-i);
+            static const char* kws[] = {"if","then","fi","for","in","do","done","case","esac","while","function","elif","else"};
+            bool kw=false; for (auto k: kws) if (id==k) { kw=true; break; }
+            push(out,i,j, kw?TokenKind::Keyword:TokenKind::Identifier); i=j; continue;
+        }
+        if (std::ispunct(static_cast<unsigned char>(c))) {
+            TokenKind k = TokenKind::Operator;
+            if (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
diff --git a/ShellHighlighter.h b/ShellHighlighter.h
new file mode 100644
index 0000000..c819bb7
--- /dev/null
+++ b/ShellHighlighter.h
@@ -0,0 +1,13 @@
+// ShellHighlighter.h - simple POSIX shell highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+
+class ShellHighlighter final : public LanguageHighlighter {
+public:
+    void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+
+} // namespace kte
diff --git a/TerminalRenderer.cc b/TerminalRenderer.cc
index 860fade..a8f4423 100644
--- a/TerminalRenderer.cc
+++ b/TerminalRenderer.cc
@@ -9,6 +9,7 @@
 #include "TerminalRenderer.h"
 #include "Buffer.h"
 #include "Editor.h"
+#include "Highlight.h"
 
 // Version string expected to be provided by build system as KTE_VERSION_STR
 #ifndef KTE_VERSION_STR
@@ -97,13 +98,49 @@ TerminalRenderer::Draw(Editor &ed)
 			bool hl_on                 = false;
 			bool cur_on                = false;
 			int written                = 0;
-			if (li < lines.size()) {
-				std::string line = static_cast<std::string>(lines[li]);
-				src_i            = 0;
-				render_col       = 0;
-				while (written < cols) {
-					char ch       = ' ';
-					bool from_src = false;
+   if (li < lines.size()) {
+                std::string line = static_cast<std::string>(lines[li]);
+                src_i            = 0;
+                render_col       = 0;
+                // Syntax highlighting: fetch per-line spans
+                const kte::LineHighlight *lh_ptr = nullptr;
+                if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
+                    lh_ptr = &buf->Highlighter()->GetLine(*buf, static_cast<int>(li), buf->Version());
+                }
+                auto token_at = [&](std::size_t src_index) -> kte::TokenKind {
+                    if (!lh_ptr) return kte::TokenKind::Default;
+                    for (const auto &sp: lh_ptr->spans) {
+                        if (static_cast<int>(src_index) >= sp.col_start && static_cast<int>(src_index) < sp.col_end)
+                            return sp.kind;
+                    }
+                    return kte::TokenKind::Default;
+                };
+                auto apply_token_attr = [&](kte::TokenKind k) {
+                    // Map to simple attributes; search highlight uses A_STANDOUT which takes precedence below
+                    attrset(A_NORMAL);
+                    switch (k) {
+                        case kte::TokenKind::Keyword:
+                        case kte::TokenKind::Type:
+                        case kte::TokenKind::Constant:
+                        case kte::TokenKind::Function:
+                            attron(A_BOLD);
+                            break;
+                        case kte::TokenKind::Comment:
+                            attron(A_DIM);
+                            break;
+                        case kte::TokenKind::String:
+                        case kte::TokenKind::Char:
+                        case kte::TokenKind::Number:
+                            // standout a bit using A_UNDERLINE if available
+                            attron(A_UNDERLINE);
+                            break;
+                        default:
+                            break;
+                    }
+                };
+                while (written < cols) {
+                    char ch       = ' ';
+                    bool from_src = false;
 					if (src_i < line.size()) {
 						unsigned char c = static_cast<unsigned char>(line[src_i]);
 						if (c == '\t') {
@@ -122,41 +159,45 @@ TerminalRenderer::Draw(Editor &ed)
 								next_tab -= to_skip;
 							}
 							// Now render visible spaces
-							while (next_tab > 0 && written < cols) {
-								bool in_hl  = search_mode && is_src_in_hl(src_i);
-								bool in_cur =
-									has_current && li == cur_my && src_i >= cur_mx
-									&& src_i < cur_mend;
-								// Toggle highlight attributes
-								int attr = 0;
-								if (in_hl)
-									attr |= A_STANDOUT;
-								if (in_cur)
-									attr |= A_BOLD;
-								if ((attr & A_STANDOUT) && !hl_on) {
-									attron(A_STANDOUT);
-									hl_on = true;
-								}
-								if (!(attr & A_STANDOUT) && hl_on) {
-									attroff(A_STANDOUT);
-									hl_on = false;
-								}
-								if ((attr & A_BOLD) && !cur_on) {
-									attron(A_BOLD);
-									cur_on = true;
-								}
-								if (!(attr & A_BOLD) && cur_on) {
-									attroff(A_BOLD);
-									cur_on = false;
-								}
-								addch(' ');
-								++written;
-								++render_col;
-								--next_tab;
-							}
-							++src_i;
-							continue;
-						} else {
+       while (next_tab > 0 && written < cols) {
+                                bool in_hl  = search_mode && is_src_in_hl(src_i);
+                                bool in_cur =
+                                    has_current && li == cur_my && src_i >= cur_mx
+                                    && src_i < cur_mend;
+                                // Toggle highlight attributes
+                                int attr = 0;
+                                if (in_hl)
+                                    attr |= A_STANDOUT;
+                                if (in_cur)
+                                    attr |= A_BOLD;
+                                if ((attr & A_STANDOUT) && !hl_on) {
+                                    attron(A_STANDOUT);
+                                    hl_on = true;
+                                }
+                                if (!(attr & A_STANDOUT) && hl_on) {
+                                    attroff(A_STANDOUT);
+                                    hl_on = false;
+                                }
+                                if ((attr & A_BOLD) && !cur_on) {
+                                    attron(A_BOLD);
+                                    cur_on = true;
+                                }
+                                if (!(attr & A_BOLD) && cur_on) {
+                                    attroff(A_BOLD);
+                                    cur_on = false;
+                                }
+                                // Apply syntax attribute only if not in search highlight
+                                if (!in_hl) {
+                                    apply_token_attr(token_at(src_i));
+                                }
+                                addch(' ');
+                                ++written;
+                                ++render_col;
+                                --next_tab;
+                            }
+                            ++src_i;
+                            continue;
+                        } else {
 							// normal char
 							if (render_col < coloffs) {
 								++render_col;
@@ -171,45 +212,49 @@ TerminalRenderer::Draw(Editor &ed)
 						ch       = ' ';
 						from_src = false;
 					}
-					bool in_hl  = search_mode && from_src && is_src_in_hl(src_i);
-					bool in_cur =
-						has_current && li == cur_my && from_src && src_i >= cur_mx && src_i <
-						cur_mend;
-					if (in_hl && !hl_on) {
-						attron(A_STANDOUT);
-						hl_on = true;
-					}
-					if (!in_hl && hl_on) {
-						attroff(A_STANDOUT);
-						hl_on = false;
-					}
-					if (in_cur && !cur_on) {
-						attron(A_BOLD);
-						cur_on = true;
-					}
-					if (!in_cur && cur_on) {
-						attroff(A_BOLD);
-						cur_on = false;
-					}
-					addch(static_cast<unsigned char>(ch));
-					++written;
-					++render_col;
-					if (from_src)
-						++src_i;
+     bool in_hl  = search_mode && from_src && is_src_in_hl(src_i);
+     bool in_cur =
+         has_current && li == cur_my && from_src && src_i >= cur_mx && src_i <
+         cur_mend;
+     if (in_hl && !hl_on) {
+         attron(A_STANDOUT);
+         hl_on = true;
+     }
+     if (!in_hl && hl_on) {
+         attroff(A_STANDOUT);
+         hl_on = false;
+     }
+     if (in_cur && !cur_on) {
+         attron(A_BOLD);
+         cur_on = true;
+     }
+     if (!in_cur && cur_on) {
+         attroff(A_BOLD);
+         cur_on = false;
+     }
+     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 (src_i >= line.size() && written >= cols)
 						break;
 				}
 			}
-			if (hl_on) {
-				attroff(A_STANDOUT);
-				hl_on = false;
-			}
-			if (cur_on) {
-				attroff(A_BOLD);
-				cur_on = false;
-			}
-			clrtoeol();
-		}
+            if (hl_on) {
+                attroff(A_STANDOUT);
+                hl_on = false;
+            }
+            if (cur_on) {
+                attroff(A_BOLD);
+                cur_on = false;
+            }
+            attrset(A_NORMAL);
+            clrtoeol();
+        }
 
 		// Place terminal cursor at logical position accounting for tabs and coloffs
 		std::size_t cy = buf->Cury();
diff --git a/docs/syntax.md b/docs/syntax.md
new file mode 100644
index 0000000..6d55ddc
--- /dev/null
+++ b/docs/syntax.md
@@ -0,0 +1,52 @@
+Syntax highlighting in kte
+==========================
+
+Overview
+--------
+
+kte provides lightweight syntax highlighting with a pluggable highlighter interface. The initial implementation targets C/C++ and focuses on speed and responsiveness.
+
+Core types
+----------
+
+- `TokenKind` — token categories (keywords, types, strings, comments, numbers, preprocessor, operators, punctuation, identifiers, whitespace, etc.).
+- `HighlightSpan` — a half-open column range `[col_start, col_end)` with a `TokenKind`.
+- `LineHighlight` — a vector of `HighlightSpan` and the buffer `version` used to compute it.
+
+Engine and caching
+------------------
+
+- `HighlighterEngine` maintains a per-line cache of `LineHighlight` keyed by row and buffer version.
+- Cache invalidation occurs when the buffer version changes or when the buffer calls `InvalidateFrom(row)`, which clears cached lines and line states from `row` downward.
+- The engine supports both stateless and stateful highlighters. For stateful highlighters, it memoizes a simple per-line state and computes lines sequentially when necessary.
+
+Stateful highlighters
+---------------------
+
+- `LanguageHighlighter` is the base interface for stateless per-line tokenization.
+- `StatefulHighlighter` extends it with a `LineState` and the method `HighlightLineStateful(buf, row, prev_state, out)`.
+- The engine detects `StatefulHighlighter` via dynamic_cast and feeds each line the previous line’s state, caching the resulting state per line.
+
+C/C++ highlighter
+-----------------
+
+- `CppHighlighter` implements `StatefulHighlighter`.
+- Stateless constructs: line comments `//`, strings `"..."`, chars `'...'`, numbers, identifiers (keywords/types), preprocessor at beginning of line after leading whitespace, operators/punctuation, and whitespace.
+- Stateful constructs (v2):
+  - Multi-line block comments `/* ... */` — the state records whether the next line continues a comment.
+  - Raw strings `R"delim(... )delim"` — the state tracks whether we are inside a raw string and its delimiter `delim` until the closing sequence appears.
+
+Limitations and TODOs
+---------------------
+
+- Raw string detection is intentionally simple and does not handle all corner cases of the C++ standard.
+- Preprocessor handling is line-based; continuation lines with `\\` are not yet tracked.
+- No semantic analysis; identifiers are classified via small keyword/type sets.
+- Additional languages (JSON, Markdown, Shell, Python, Go, Rust, Lisp, …) are planned.
+- Terminal color mapping is conservative to support 8/16-color terminals. Rich color-pair themes can be added later.
+
+Renderer integration
+--------------------
+
+- Terminal and GUI renderers request line spans via `Highlighter()->GetLine(buf, row, buf.Version())`.
+- Search highlight and cursor overlays take precedence over syntax colors.
diff --git a/kte-cloc b/kte-cloc
index 08bc3b1..865d039 100755
--- a/kte-cloc
+++ b/kte-cloc
@@ -1,3 +1,9 @@
 #!/usr/bin/env bash
 
-ls -1 *.cc *.h | grep -v '^Font.h$' | xargs cloc -fmt 3
+fmt_arg=""
+if [ "${V}" = "1" ]
+then
+	fmt_args="-fmt 3"
+fi
+
+ls -1 *.cc *.h | grep -v '^Font.h$' | xargs cloc ${fmt_args}