diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e84a9b9
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+build/
+*.db
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..8804fe7
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,57 @@
+cmake_minimum_required(VERSION 3.14)
+project(LLS VERSION 1.0 LANGUAGES C CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
+  set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type" FORCE)
+endif()
+
+# --- SQLite ------------------------------------------------------------------
+# Use the system SQLite if present, otherwise download the amalgamation.
+find_package(SQLite3)
+
+if(NOT SQLite3_FOUND)
+  message(STATUS "System SQLite3 not found - fetching the amalgamation")
+  include(FetchContent)
+  if(POLICY CMP0135)
+    cmake_policy(SET CMP0135 NEW)
+  endif()
+  FetchContent_Declare(sqlite3_amalgamation
+    URL https://www.sqlite.org/2024/sqlite-amalgamation-3450100.zip)
+  FetchContent_MakeAvailable(sqlite3_amalgamation)
+
+  find_package(Threads REQUIRED)
+  add_library(sqlite3_local STATIC ${sqlite3_amalgamation_SOURCE_DIR}/sqlite3.c)
+  target_include_directories(sqlite3_local PUBLIC ${sqlite3_amalgamation_SOURCE_DIR})
+  target_link_libraries(sqlite3_local PUBLIC Threads::Threads ${CMAKE_DL_LIBS})
+  add_library(SQLite::SQLite3 ALIAS sqlite3_local)
+endif()
+
+# --- Application -------------------------------------------------------------
+add_executable(lls
+  src/main.cpp
+  src/Completer.cpp
+  src/Config.cpp
+  src/Database.cpp
+  src/Display.cpp
+  src/ExternalEditor.cpp
+  src/LineEditor.cpp
+  src/Repl.cpp
+  src/Status.cpp
+  src/StringUtil.cpp
+  src/Table.cpp
+  src/Terminal.cpp
+  src/Tokenizer.cpp
+)
+
+target_include_directories(lls PRIVATE include)
+target_link_libraries(lls PRIVATE SQLite::SQLite3)
+
+if(MSVC)
+  target_compile_options(lls PRIVATE /W4)
+else()
+  target_compile_options(lls PRIVATE -Wall -Wextra -Wpedantic)
+endif()
diff --git a/build.sh b/build.sh
new file mode 100644
index 0000000..9b6cfd7
--- /dev/null
+++ b/build.sh
@@ -0,0 +1 @@
+cmake -B build && cmake --build build --parallel -j 8
diff --git a/include/CommandSpec.h b/include/CommandSpec.h
new file mode 100644
index 0000000..7f62275
--- /dev/null
+++ b/include/CommandSpec.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+// What kind of value an argument holds (drives tab completion).
+enum class ArgKind {
+    None,
+    Task,
+    Account,
+    AccountOrDash,
+    AccountOrStatus,
+    Status,
+    Visibility,
+    TaskLevel,
+    AccountLevel,
+    File,
+    Editor
+};
+
+struct CommandSpec {
+    std::string key;    // e.g. "tsk add"
+    std::string usage;  // e.g. "tsk add <name> [acc] [status]"
+    std::string help;
+    std::size_t minArgs = 0;
+    std::size_t maxArgs = 0;
+    std::vector<ArgKind> argKinds;
+};
diff --git a/include/Completer.h b/include/Completer.h
new file mode 100644
index 0000000..684b603
--- /dev/null
+++ b/include/Completer.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "CommandSpec.h"
+#include "Completion.h"
+#include "Database.h"
+
+// Works out tab-completion candidates for the text typed so far: command
+// words first, then arguments (task names, account names, statuses, ...).
+class Completer {
+public:
+    Completer(const Database& db, const std::vector<CommandSpec>& specs);
+
+    Completion complete(const std::string& textBeforeCursor) const;
+
+private:
+    std::vector<std::string> valuesFor(ArgKind kind, const std::string& current) const;
+
+    const Database& db_;
+    const std::vector<CommandSpec>& specs_;
+};
diff --git a/include/Completion.h b/include/Completion.h
new file mode 100644
index 0000000..2950c71
--- /dev/null
+++ b/include/Completion.h
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+// Result of a tab-completion request: the text from `start` up to the cursor
+// can be replaced by any of `candidates`.
+struct Completion {
+    std::size_t start = 0;
+    std::vector<std::string> candidates;
+};
diff --git a/include/Config.h b/include/Config.h
new file mode 100644
index 0000000..6e6b7c4
--- /dev/null
+++ b/include/Config.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include <string>
+
+// User preferences stored outside the database, in
+// $XDG_CONFIG_HOME/task_tracker (or ~/.config/task_tracker, or %APPDATA%).
+class Config {
+public:
+    Config();
+
+    void load();
+    void save() const;
+
+    const std::string& editor() const;  // empty = use the default
+    void setEditor(const std::string& command);
+
+    std::string historyPath() const;
+
+    static std::string directory();
+
+private:
+    std::string directory_;
+    std::string editor_;
+};
diff --git a/include/Database.h b/include/Database.h
new file mode 100644
index 0000000..ccec73d
--- /dev/null
+++ b/include/Database.h
@@ -0,0 +1,59 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "Models.h"
+
+struct sqlite3;
+
+// Works on an in-memory SQLite database that is loaded from, and saved to, a
+// file on request (db save / backup / restore).
+class Database {
+public:
+    Database();
+    ~Database();
+    Database(const Database&) = delete;
+    Database& operator=(const Database&) = delete;
+
+    // Loads `path` into memory if it exists, otherwise starts empty.
+    void open(const std::string& path);
+    void save();
+    std::string backup(const std::string& file);  // empty = timestamped name; returns the file used
+    void restore(const std::string& file);
+
+    bool dirty() const;
+    const std::string& path() const;
+
+    // Accounts
+    std::optional<std::string> findAccount(const std::string& name) const;  // canonical spelling
+    std::vector<std::string> listAccounts() const;
+    void addAccount(const std::string& name);
+    void removeAccount(const std::string& name);
+    void renameAccount(const std::string& name, const std::string& newName);
+
+    // Tasks
+    std::optional<std::string> findTask(const std::string& name) const;  // canonical spelling
+    std::optional<TaskRow> getTask(const std::string& name) const;
+    std::vector<TaskRow> listTasks() const;
+    void addTask(const std::string& name, const std::optional<std::string>& account, const std::string& status);
+    void removeTask(const std::string& name);
+    void renameTask(const std::string& name, const std::string& newName);
+    void setTaskAccount(const std::string& name, const std::optional<std::string>& account);
+    void setTaskStatus(const std::string& name, const std::string& status);
+    void setTaskNotes(const std::string& name, const std::string& notes);
+
+private:
+    using Param = std::optional<std::string>;
+    using Row = std::vector<std::optional<std::string>>;
+
+    void createSchema();
+    void exec(const std::string& sql);
+    std::vector<Row> query(const std::string& sql, const std::vector<Param>& params = {}) const;
+    void run(const std::string& sql, const std::vector<Param>& params);
+
+    sqlite3* db_;
+    std::string path_;
+    bool dirty_;
+};
diff --git a/include/Display.h b/include/Display.h
new file mode 100644
index 0000000..1c5a3cf
--- /dev/null
+++ b/include/Display.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <ctime>
+#include <set>
+#include <string>
+
+#include "Database.h"
+#include "Status.h"
+
+enum class AccountLevel { Busy, Free };
+
+struct DisplaySettings {
+    bool showTasks = true;     // auto-print the task table after each change
+    bool showAccounts = true;  // auto-print the account table after each change
+    std::set<StatusKind> hiddenTaskLevels;
+    std::set<AccountLevel> hiddenAccountLevels;
+};
+
+// Builds the computed views. The status shown is derived from the stored
+// status and the current time, never copied straight from the database.
+class Display {
+public:
+    explicit Display(const Database& db);
+
+    DisplaySettings& settings();
+    const DisplaySettings& settings() const;
+
+    std::string renderTasks(std::time_t now) const;
+    std::string renderAccounts(std::time_t now) const;
+
+private:
+    const Database& db_;
+    DisplaySettings settings_;
+};
diff --git a/include/ExternalEditor.h b/include/ExternalEditor.h
new file mode 100644
index 0000000..82ff517
--- /dev/null
+++ b/include/ExternalEditor.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+namespace ExternalEditor {
+
+// $VISUAL, then $EDITOR, then the first of nano/vim/vi found on PATH.
+// Empty if nothing was found.
+std::string defaultCommand();
+
+// Is the first word of `command` an executable we can find?
+bool commandExists(const std::string& command);
+
+// Well-known editors that are installed (used for tab completion).
+std::vector<std::string> installedEditors();
+
+// Opens `initialText` in the editor and returns the edited text.
+// Throws std::runtime_error if the editor cannot be run or exits with an error.
+std::string edit(const std::string& command, const std::string& initialText);
+
+}  // namespace ExternalEditor
diff --git a/include/LineEditor.h b/include/LineEditor.h
new file mode 100644
index 0000000..ec45b06
--- /dev/null
+++ b/include/LineEditor.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <functional>
+#include <string>
+#include <vector>
+
+#include "Completion.h"
+
+// Reads one line with cursor editing, history (up/down) and tab completion.
+// Falls back to plain std::getline when stdin/stdout are not a terminal.
+class LineEditor {
+public:
+    using CompletionFn = std::function<Completion(const std::string& textBeforeCursor)>;
+
+    LineEditor();
+
+    void setCompleter(const CompletionFn& completer);
+    void setHistoryFile(const std::string& path);  // loads it and appends new entries
+    void addHistory(const std::string& line);
+
+    // Returns false on end of input (Ctrl-D on an empty line, or closed stdin).
+    bool readLine(const std::string& prompt, std::string& line);
+
+private:
+    bool readPlain(const std::string& prompt, std::string& line);
+    bool readInteractive(const std::string& prompt, std::string& line);
+
+    CompletionFn completer_;
+    std::vector<std::string> history_;
+    std::string historyFile_;
+};
diff --git a/include/Models.h b/include/Models.h
new file mode 100644
index 0000000..dcd162d
--- /dev/null
+++ b/include/Models.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#include <optional>
+#include <string>
+
+struct TaskRow {
+    std::string id;
+    std::optional<std::string> account;
+    std::string status;  // serialized, see StatusUtil::serialize
+    std::string notes;   // free text, any length (stored as SQLite TEXT)
+};
diff --git a/include/Repl.h b/include/Repl.h
new file mode 100644
index 0000000..7b35b80
--- /dev/null
+++ b/include/Repl.h
@@ -0,0 +1,89 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+#include "CommandSpec.h"
+#include "Completer.h"
+#include "Config.h"
+#include "Database.h"
+#include "Display.h"
+#include "LineEditor.h"
+#include "Status.h"
+
+// Interactive prompt: commands are typed live, one per line.
+class Repl {
+public:
+    Repl(Database& db, Display& display, Config& config);
+
+    int run();
+
+private:
+    using Args = std::vector<std::string>;
+    using Handler = bool (Repl::*)(const Args&);  // returns true if the panels should be redrawn
+
+    struct Command {
+        CommandSpec spec;
+        Handler handler;
+    };
+
+    void registerCommands();
+    void add(const std::string& key, const std::string& usage, const std::string& help,
+             std::size_t minArgs, std::size_t maxArgs, const std::vector<ArgKind>& argKinds,
+             Handler handler);
+    const Command* find(const Args& tokens, std::size_t& consumed) const;
+
+    void execute(const std::string& line);
+    void refresh() const;
+    void say(const std::string& message);
+    void flushMessages();
+    void endOfInput();
+    bool confirm(const std::string& question) const;
+
+    // Helpers
+    static void requireName(const std::string& name);
+    static Status parseStatusFrom(const Args& args, std::size_t from);
+
+    // Account commands
+    bool cmdAccAdd(const Args& args);
+    bool cmdAccDel(const Args& args);
+    bool cmdAccRename(const Args& args);
+    bool cmdAccLs(const Args& args);
+
+    // Task commands
+    bool cmdTskAdd(const Args& args);
+    bool cmdTskDel(const Args& args);
+    bool cmdTskLs(const Args& args);
+    bool cmdTskRename(const Args& args);
+    bool cmdTskReacc(const Args& args);
+    bool cmdTskRestat(const Args& args);
+    bool cmdTskNotes(const Args& args);
+
+    // Display commands
+    bool cmdDisp(const Args& args);
+    bool cmdDispTsk(const Args& args);
+    bool cmdDispTskLevel(const Args& args);
+    bool cmdDispAcc(const Args& args);
+    bool cmdDispAccLevel(const Args& args);
+
+    // Database commands
+    bool cmdDbSave(const Args& args);
+    bool cmdDbBackup(const Args& args);
+    bool cmdDbRestore(const Args& args);
+
+    // Misc
+    bool cmdEditor(const Args& args);
+    bool cmdHelp(const Args& args);
+    bool cmdQuit(const Args& args);
+
+    Database& db_;
+    Display& display_;
+    Config& config_;
+    std::vector<Command> commands_;
+    std::vector<CommandSpec> specs_;
+    Completer completer_;
+    LineEditor lineEditor_;
+    std::vector<std::string> messages_;
+    bool quit_;
+};
diff --git a/include/Status.h b/include/Status.h
new file mode 100644
index 0000000..f2fc041
--- /dev/null
+++ b/include/Status.h
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <ctime>
+#include <optional>
+#include <string>
+#include <vector>
+
+// Prompt:      free to accept prompts.
+// LimitReset:  computed - a Wait whose time has passed (can also be set by hand).
+// The enum order is the sort order of the panels.
+enum class StatusKind { Prompt, LimitReset, Testing, Wait, Uploading, Frozen, Done };
+
+struct Status {
+    StatusKind kind = StatusKind::Prompt;
+    std::time_t waitUntil = 0;  // only meaningful when kind == Wait
+};
+
+namespace StatusUtil {
+
+Status make(StatusKind kind);
+
+// User input such as "testing" or "wait 16:30". A wait time that has already
+// passed today is taken to mean tomorrow.
+std::optional<Status> parse(const std::string& text, std::time_t now);
+
+// Database representation, e.g. "testing" or "wait 2026-10-17T16:30".
+std::string serialize(const Status& status);
+std::optional<Status> deserialize(const std::string& text);
+
+// The status shown to the user: an expired wait becomes LimitReset.
+Status effective(const Status& status, std::time_t now);
+
+std::string label(const Status& status);  // "Prompt", "Limit reset", "Wait 16:30", ...
+std::string kindName(StatusKind kind);    // lowercase token: "prompt", "limit-reset", ...
+std::vector<StatusKind> allKinds();
+// Accepts "limit-reset", "limit_reset", "limitreset", "reset"; "available" is an
+// old name for "prompt".
+std::optional<StatusKind> kindFromName(const std::string& name);
+int rank(StatusKind kind);                // sort order
+bool isBusy(StatusKind kind);             // does this status hold the account?
+
+}  // namespace StatusUtil
diff --git a/include/StringUtil.h b/include/StringUtil.h
new file mode 100644
index 0000000..46ce758
--- /dev/null
+++ b/include/StringUtil.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+namespace StringUtil {
+
+std::string lower(const std::string& text);
+std::string trim(const std::string& text);
+bool equalsIgnoreCase(const std::string& a, const std::string& b);
+bool startsWithIgnoreCase(const std::string& text, const std::string& prefix);
+std::string join(const std::vector<std::string>& parts, std::size_t from, const std::string& separator);
+
+// Number of characters (UTF-8 code points) in the text.
+std::size_t displayWidth(const std::string& text);
+
+// Collapses line breaks into " / ". If `maxChars` > 0 the text is cut to that
+// many characters; 0 means no limit.
+std::string singleLine(const std::string& text, std::size_t maxChars);
+
+}  // namespace StringUtil
diff --git a/include/Table.h b/include/Table.h
new file mode 100644
index 0000000..c1c109b
--- /dev/null
+++ b/include/Table.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+class TextTable {
+public:
+    explicit TextTable(const std::vector<std::string>& headers);
+
+    void addRow(const std::vector<std::string>& cells);
+    std::size_t rowCount() const;
+    std::string render() const;
+
+private:
+    std::vector<std::string> headers_;
+    std::vector<std::vector<std::string>> rows_;
+};
diff --git a/include/Terminal.h b/include/Terminal.h
new file mode 100644
index 0000000..d147cf9
--- /dev/null
+++ b/include/Terminal.h
@@ -0,0 +1,11 @@
+#pragma once
+
+namespace Terminal {
+
+bool stdinIsInteractive();
+bool stdoutIsInteractive();
+
+// Clears the screen. Does nothing when stdout is not a terminal.
+void clearScreen();
+
+}  // namespace Terminal
diff --git a/include/Tokenizer.h b/include/Tokenizer.h
new file mode 100644
index 0000000..679f073
--- /dev/null
+++ b/include/Tokenizer.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+namespace Tokenizer {
+
+// Splits a command line on whitespace. Double quotes group words into a single
+// token ("Breeze A"). Throws std::invalid_argument on an unterminated quote.
+std::vector<std::string> split(const std::string& line);
+
+// Lenient split for tab completion: completed words, plus the word being typed.
+struct PartialLine {
+    std::vector<std::string> words;  // completed words (quotes removed)
+    std::string current;             // word being typed (quotes removed, may be empty)
+    std::size_t start = 0;           // index in the text where that word begins
+};
+
+PartialLine splitPartial(const std::string& text);
+
+}  // namespace Tokenizer
diff --git a/src/Completer.cpp b/src/Completer.cpp
new file mode 100644
index 0000000..e4bb00c
--- /dev/null
+++ b/src/Completer.cpp
@@ -0,0 +1,178 @@
+#include "Completer.h"
+
+#include <algorithm>
+#include <cctype>
+#include <filesystem>
+#include <sstream>
+
+#include "ExternalEditor.h"
+#include "Status.h"
+#include "StringUtil.h"
+#include "Tokenizer.h"
+
+namespace {
+
+std::string quoteIfNeeded(const std::string& name, bool force) {
+    const bool hasSpace = std::any_of(name.begin(), name.end(),
+                                      [](unsigned char c) { return std::isspace(c) != 0; });
+    return (force || hasSpace) ? "\"" + name + "\"" : name;
+}
+
+std::vector<std::string> splitWords(const std::string& text) {
+    std::vector<std::string> words;
+    std::istringstream in(text);
+    std::string word;
+    while (in >> word) {
+        words.push_back(word);
+    }
+    return words;
+}
+
+std::vector<std::string> statusNames() {
+    std::vector<std::string> names;
+    for (StatusKind kind : StatusUtil::allKinds()) {
+        names.push_back(StatusUtil::kindName(kind));
+    }
+    return names;
+}
+
+std::vector<std::string> fileNames(const std::string& partial) {
+    namespace fs = std::filesystem;
+
+    std::string directoryPart;
+    std::string prefix = partial;
+    const std::size_t slash = partial.find_last_of("/\\");
+    if (slash != std::string::npos) {
+        directoryPart = partial.substr(0, slash + 1);
+        prefix = partial.substr(slash + 1);
+    }
+
+    std::vector<std::string> names;
+    std::error_code error;
+    fs::directory_iterator it(directoryPart.empty() ? fs::path(".") : fs::path(directoryPart), error);
+    for (fs::directory_iterator end; !error && it != end; it.increment(error)) {
+        const std::string name = it->path().filename().string();
+        if (!name.empty() && name[0] == '.' && prefix.empty()) {
+            continue;  // hide dotfiles unless asked for
+        }
+        std::error_code statusError;
+        const bool isDirectory = it->is_directory(statusError);
+        names.push_back(directoryPart + name + (isDirectory ? "/" : ""));
+    }
+    return names;
+}
+
+}  // namespace
+
+Completer::Completer(const Database& db, const std::vector<CommandSpec>& specs)
+    : db_(db), specs_(specs) {}
+
+std::vector<std::string> Completer::valuesFor(ArgKind kind, const std::string& current) const {
+    std::vector<std::string> values;
+    switch (kind) {
+        case ArgKind::None:
+            break;
+        case ArgKind::Task:
+            for (const TaskRow& task : db_.listTasks()) {
+                values.push_back(task.id);
+            }
+            break;
+        case ArgKind::Account:
+            values = db_.listAccounts();
+            break;
+        case ArgKind::AccountOrDash:
+            values = db_.listAccounts();
+            values.push_back("-");
+            break;
+        case ArgKind::AccountOrStatus:
+            values = db_.listAccounts();
+            for (const std::string& name : statusNames()) {
+                values.push_back(name);
+            }
+            break;
+        case ArgKind::Status:
+            values = statusNames();
+            break;
+        case ArgKind::Visibility:
+            values = {"show", "hide"};
+            break;
+        case ArgKind::TaskLevel:
+            values = statusNames();
+            values.push_back("all");
+            break;
+        case ArgKind::AccountLevel:
+            values = {"busy", "free", "all"};
+            break;
+        case ArgKind::File:
+            values = fileNames(current);
+            break;
+        case ArgKind::Editor:
+            values = ExternalEditor::installedEditors();
+            values.push_back("default");
+            break;
+    }
+    return values;
+}
+
+Completion Completer::complete(const std::string& textBeforeCursor) const {
+    const Tokenizer::PartialLine line = Tokenizer::splitPartial(textBeforeCursor);
+
+    std::vector<std::string> words;
+    for (const std::string& word : line.words) {
+        words.push_back(StringUtil::lower(word));
+    }
+
+    std::vector<std::string> raw;
+
+    // 1. Continue a command name: "tsk" -> add/del/ls/..., "disp tsk" -> level
+    for (const CommandSpec& spec : specs_) {
+        const std::vector<std::string> parts = splitWords(spec.key);
+        if (parts.size() <= words.size()) {
+            continue;
+        }
+        bool matches = true;
+        for (std::size_t i = 0; i < words.size(); ++i) {
+            matches = matches && (parts[i] == words[i]);
+        }
+        if (matches) {
+            raw.push_back(parts[words.size()]);
+        }
+    }
+
+    // 2. Complete an argument of the command typed so far (longest match wins).
+    for (std::size_t consumed = std::min<std::size_t>(3, words.size()); consumed >= 1; --consumed) {
+        const std::string key = StringUtil::join(
+            std::vector<std::string>(words.begin(), words.begin() + static_cast<std::ptrdiff_t>(consumed)), 0, " ");
+        const CommandSpec* found = nullptr;
+        for (const CommandSpec& spec : specs_) {
+            if (spec.key == key) {
+                found = &spec;
+                break;
+            }
+        }
+        if (!found) {
+            continue;
+        }
+        const std::size_t argIndex = words.size() - consumed;
+        if (argIndex < found->argKinds.size()) {
+            for (const std::string& value : valuesFor(found->argKinds[argIndex], line.current)) {
+                raw.push_back(value);
+            }
+        }
+        break;
+    }
+
+    const bool forceQuote = line.start < textBeforeCursor.size() && textBeforeCursor[line.start] == '"';
+
+    Completion completion;
+    completion.start = line.start;
+    for (const std::string& value : raw) {
+        if (StringUtil::startsWithIgnoreCase(value, line.current)) {
+            completion.candidates.push_back(quoteIfNeeded(value, forceQuote));
+        }
+    }
+    std::sort(completion.candidates.begin(), completion.candidates.end());
+    completion.candidates.erase(std::unique(completion.candidates.begin(), completion.candidates.end()),
+                                completion.candidates.end());
+    return completion;
+}
diff --git a/src/Config.cpp b/src/Config.cpp
new file mode 100644
index 0000000..1abaa56
--- /dev/null
+++ b/src/Config.cpp
@@ -0,0 +1,69 @@
+#include "Config.h"
+
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <stdexcept>
+
+#include "StringUtil.h"
+
+namespace fs = std::filesystem;
+
+Config::Config() : directory_(directory()) {}
+
+std::string Config::directory() {
+    fs::path base;
+#ifdef _WIN32
+    const char* appData = std::getenv("APPDATA");
+    base = (appData && *appData) ? fs::path(appData) : fs::current_path();
+#else
+    const char* xdg = std::getenv("XDG_CONFIG_HOME");
+    const char* home = std::getenv("HOME");
+    if (xdg && *xdg) {
+        base = xdg;
+    } else if (home && *home) {
+        base = fs::path(home) / ".config";
+    } else {
+        base = fs::current_path();
+    }
+#endif
+    return (base / "task_tracker").string();
+}
+
+void Config::load() {
+    std::ifstream in(fs::path(directory_) / "config");
+    std::string line;
+    while (std::getline(in, line)) {
+        const std::size_t equals = line.find('=');
+        if (equals == std::string::npos) {
+            continue;
+        }
+        const std::string key = StringUtil::trim(line.substr(0, equals));
+        const std::string value = StringUtil::trim(line.substr(equals + 1));
+        if (key == "editor") {
+            editor_ = value;
+        }
+    }
+}
+
+void Config::save() const {
+    std::error_code error;
+    fs::create_directories(directory_, error);
+    std::ofstream out(fs::path(directory_) / "config", std::ios::trunc);
+    if (!out) {
+        throw std::runtime_error("Cannot write the config file in " + directory_);
+    }
+    out << "editor=" << editor_ << "\n";
+}
+
+const std::string& Config::editor() const {
+    return editor_;
+}
+
+void Config::setEditor(const std::string& command) {
+    editor_ = command;
+}
+
+std::string Config::historyPath() const {
+    return (fs::path(directory_) / "history").string();
+}
diff --git a/src/Database.cpp b/src/Database.cpp
new file mode 100644
index 0000000..6b9b745
--- /dev/null
+++ b/src/Database.cpp
@@ -0,0 +1,294 @@
+#include "Database.h"
+
+#include <sqlite3.h>
+
+#include <cstdio>
+#include <ctime>
+#include <iomanip>
+#include <memory>
+#include <sstream>
+#include <stdexcept>
+
+namespace {
+
+const char* const kSchema =
+    "CREATE TABLE IF NOT EXISTS Account ("
+    "  id TEXT NOT NULL PRIMARY KEY COLLATE NOCASE"
+    ");"
+    "CREATE TABLE IF NOT EXISTS Task ("
+    "  id TEXT NOT NULL PRIMARY KEY COLLATE NOCASE,"
+    "  account TEXT COLLATE NOCASE REFERENCES Account(id) ON UPDATE CASCADE ON DELETE SET NULL,"
+    "  status TEXT NOT NULL DEFAULT 'prompt',"
+    "  notes TEXT NOT NULL DEFAULT ''"
+    ");"
+    "CREATE INDEX IF NOT EXISTS idx_task_account ON Task(account);";
+
+using Connection = std::unique_ptr<sqlite3, int (*)(sqlite3*)>;
+
+Connection openFile(const std::string& path, int flags) {
+    sqlite3* raw = nullptr;
+    int rc = sqlite3_open_v2(path.c_str(), &raw, flags, nullptr);
+    Connection connection(raw, &sqlite3_close);
+    if (rc != SQLITE_OK) {
+        throw std::runtime_error("Cannot open '" + path + "': " +
+                                 (raw ? sqlite3_errmsg(raw) : "out of memory"));
+    }
+    return connection;
+}
+
+void copyDatabase(sqlite3* from, sqlite3* to) {
+    sqlite3_backup* backup = sqlite3_backup_init(to, "main", from, "main");
+    if (!backup) {
+        throw std::runtime_error(std::string("Copy failed: ") + sqlite3_errmsg(to));
+    }
+    int rc = sqlite3_backup_step(backup, -1);
+    sqlite3_backup_finish(backup);
+    if (rc != SQLITE_DONE) {
+        throw std::runtime_error(std::string("Copy failed: ") + sqlite3_errmsg(to));
+    }
+}
+
+// True if the connection holds a database with our two tables.
+bool hasExpectedTables(sqlite3* db) {
+    sqlite3_stmt* stmt = nullptr;
+    const char* sql = "SELECT count(*) FROM sqlite_master WHERE type = 'table' AND name IN ('Task', 'Account')";
+    if (sqlite3_prepare_v2(db, sql, -1, &stmt, nullptr) != SQLITE_OK) {
+        return false;
+    }
+    int count = 0;
+    if (sqlite3_step(stmt) == SQLITE_ROW) {
+        count = sqlite3_column_int(stmt, 0);
+    }
+    sqlite3_finalize(stmt);
+    return count == 2;
+}
+
+std::string timestampedName(const std::string& basePath) {
+    std::time_t now = std::time(nullptr);
+    std::tm parts{};
+#ifdef _WIN32
+    localtime_s(&parts, &now);
+#else
+    localtime_r(&now, &parts);
+#endif
+    std::ostringstream out;
+    out << basePath << "." << std::put_time(&parts, "%Y%m%d-%H%M%S") << ".bak";
+    return out.str();
+}
+
+}  // namespace
+
+Database::Database() : db_(nullptr), dirty_(false) {
+    if (sqlite3_open(":memory:", &db_) != SQLITE_OK) {
+        std::string message = db_ ? sqlite3_errmsg(db_) : "out of memory";
+        sqlite3_close(db_);
+        db_ = nullptr;
+        throw std::runtime_error("Cannot create in-memory database: " + message);
+    }
+    exec("PRAGMA foreign_keys = ON;");
+    createSchema();
+}
+
+Database::~Database() {
+    sqlite3_close(db_);
+}
+
+void Database::createSchema() {
+    exec(kSchema);
+    // "available" was split into "prompt" and "limit-reset"; old files still say "available".
+    exec("UPDATE Task SET status = 'prompt' WHERE status = 'available';");
+}
+
+void Database::exec(const std::string& sql) {
+    char* error = nullptr;
+    if (sqlite3_exec(db_, sql.c_str(), nullptr, nullptr, &error) != SQLITE_OK) {
+        std::string message = error ? error : "unknown error";
+        sqlite3_free(error);
+        throw std::runtime_error(message);
+    }
+}
+
+std::vector<Database::Row> Database::query(const std::string& sql, const std::vector<Param>& params) const {
+    sqlite3_stmt* stmt = nullptr;
+    if (sqlite3_prepare_v2(db_, sql.c_str(), -1, &stmt, nullptr) != SQLITE_OK) {
+        throw std::runtime_error(sqlite3_errmsg(db_));
+    }
+
+    for (std::size_t i = 0; i < params.size(); ++i) {
+        int index = static_cast<int>(i) + 1;
+        if (params[i]) {
+            sqlite3_bind_text64(stmt, index, params[i]->data(), params[i]->size(), SQLITE_TRANSIENT, SQLITE_UTF8);
+        } else {
+            sqlite3_bind_null(stmt, index);
+        }
+    }
+
+    std::vector<Row> rows;
+    int rc = SQLITE_OK;
+    while ((rc = sqlite3_step(stmt)) == SQLITE_ROW) {
+        Row row;
+        int columns = sqlite3_column_count(stmt);
+        for (int c = 0; c < columns; ++c) {
+            if (sqlite3_column_type(stmt, c) == SQLITE_NULL) {
+                row.emplace_back(std::nullopt);
+            } else {
+                const unsigned char* text = sqlite3_column_text(stmt, c);
+                const int bytes = sqlite3_column_bytes(stmt, c);
+                row.emplace_back(std::string(reinterpret_cast<const char*>(text), static_cast<std::size_t>(bytes)));
+            }
+        }
+        rows.push_back(row);
+    }
+
+    std::string error = (rc == SQLITE_DONE) ? "" : sqlite3_errmsg(db_);
+    sqlite3_finalize(stmt);
+    if (rc != SQLITE_DONE) {
+        throw std::runtime_error(error);
+    }
+    return rows;
+}
+
+void Database::run(const std::string& sql, const std::vector<Param>& params) {
+    query(sql, params);
+    dirty_ = true;
+}
+
+void Database::open(const std::string& path) {
+    path_ = path;
+    dirty_ = false;
+
+    std::FILE* probe = std::fopen(path.c_str(), "rb");
+    if (!probe) {
+        return;  // new database, will be created on first save
+    }
+    std::fclose(probe);
+
+    restore(path);
+    dirty_ = false;
+}
+
+void Database::save() {
+    if (path_.empty()) {
+        throw std::runtime_error("No database file set.");
+    }
+    Connection file = openFile(path_, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE);
+    copyDatabase(db_, file.get());
+    dirty_ = false;
+}
+
+std::string Database::backup(const std::string& fileName) {
+    std::string target = fileName.empty() ? timestampedName(path_.empty() ? "tasks.db" : path_) : fileName;
+    Connection file = openFile(target, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE);
+    copyDatabase(db_, file.get());
+    return target;
+}
+
+void Database::restore(const std::string& fileName) {
+    Connection file = openFile(fileName, SQLITE_OPEN_READONLY);
+    if (!hasExpectedTables(file.get())) {
+        throw std::runtime_error("'" + fileName + "' is not a task database.");
+    }
+    copyDatabase(file.get(), db_);
+    exec("PRAGMA foreign_keys = ON;");
+    createSchema();
+    dirty_ = true;
+}
+
+bool Database::dirty() const {
+    return dirty_;
+}
+
+const std::string& Database::path() const {
+    return path_;
+}
+
+// ---- Accounts ---------------------------------------------------------------
+
+std::optional<std::string> Database::findAccount(const std::string& name) const {
+    std::vector<Row> rows = query("SELECT id FROM Account WHERE id = ?1", {name});
+    if (rows.empty()) {
+        return std::nullopt;
+    }
+    return rows[0][0];
+}
+
+std::vector<std::string> Database::listAccounts() const {
+    std::vector<std::string> names;
+    for (const Row& row : query("SELECT id FROM Account ORDER BY id")) {
+        names.push_back(*row[0]);
+    }
+    return names;
+}
+
+void Database::addAccount(const std::string& name) {
+    run("INSERT INTO Account (id) VALUES (?1)", {name});
+}
+
+void Database::removeAccount(const std::string& name) {
+    run("DELETE FROM Account WHERE id = ?1", {name});
+}
+
+void Database::renameAccount(const std::string& name, const std::string& newName) {
+    run("UPDATE Account SET id = ?2 WHERE id = ?1", {name, newName});
+}
+
+// ---- Tasks ------------------------------------------------------------------
+
+std::optional<std::string> Database::findTask(const std::string& name) const {
+    std::vector<Row> rows = query("SELECT id FROM Task WHERE id = ?1", {name});
+    if (rows.empty()) {
+        return std::nullopt;
+    }
+    return rows[0][0];
+}
+
+std::optional<TaskRow> Database::getTask(const std::string& name) const {
+    std::vector<Row> rows = query("SELECT id, account, status, notes FROM Task WHERE id = ?1", {name});
+    if (rows.empty()) {
+        return std::nullopt;
+    }
+    TaskRow task;
+    task.id = *rows[0][0];
+    task.account = rows[0][1];
+    task.status = *rows[0][2];
+    task.notes = *rows[0][3];
+    return task;
+}
+
+std::vector<TaskRow> Database::listTasks() const {
+    std::vector<TaskRow> tasks;
+    for (const Row& row : query("SELECT id, account, status, notes FROM Task ORDER BY id")) {
+        TaskRow task;
+        task.id = *row[0];
+        task.account = row[1];
+        task.status = *row[2];
+        task.notes = *row[3];
+        tasks.push_back(task);
+    }
+    return tasks;
+}
+
+void Database::addTask(const std::string& name, const std::optional<std::string>& account,
+                       const std::string& status) {
+    run("INSERT INTO Task (id, account, status) VALUES (?1, ?2, ?3)", {name, account, status});
+}
+
+void Database::removeTask(const std::string& name) {
+    run("DELETE FROM Task WHERE id = ?1", {name});
+}
+
+void Database::renameTask(const std::string& name, const std::string& newName) {
+    run("UPDATE Task SET id = ?2 WHERE id = ?1", {name, newName});
+}
+
+void Database::setTaskAccount(const std::string& name, const std::optional<std::string>& account) {
+    run("UPDATE Task SET account = ?2 WHERE id = ?1", {name, account});
+}
+
+void Database::setTaskStatus(const std::string& name, const std::string& status) {
+    run("UPDATE Task SET status = ?2 WHERE id = ?1", {name, status});
+}
+
+void Database::setTaskNotes(const std::string& name, const std::string& notes) {
+    run("UPDATE Task SET notes = ?2 WHERE id = ?1", {name, notes});
+}
diff --git a/src/Display.cpp b/src/Display.cpp
new file mode 100644
index 0000000..993d97c
--- /dev/null
+++ b/src/Display.cpp
@@ -0,0 +1,98 @@
+#include "Display.h"
+
+#include <algorithm>
+#include <optional>
+#include <vector>
+
+#include "StringUtil.h"
+#include "Table.h"
+
+namespace {
+
+struct TaskView {
+    std::string name;
+    std::string account;  // empty = unassigned
+    std::string notes;
+    Status status;        // effective status at render time
+};
+
+std::vector<TaskView> loadViews(const Database& db, std::time_t now) {
+    std::vector<TaskView> views;
+    for (const TaskRow& row : db.listTasks()) {
+        TaskView view;
+        view.name = row.id;
+        view.account = row.account.value_or("");
+        view.notes = row.notes;
+        std::optional<Status> stored = StatusUtil::deserialize(row.status);
+        view.status = StatusUtil::effective(stored.value_or(StatusUtil::make(StatusKind::Prompt)), now);
+        views.push_back(view);
+    }
+    return views;
+}
+
+bool taskLess(const TaskView& a, const TaskView& b) {
+    int rankA = StatusUtil::rank(a.status.kind);
+    int rankB = StatusUtil::rank(b.status.kind);
+    if (rankA != rankB) {
+        return rankA < rankB;
+    }
+    if (a.status.kind == StatusKind::Wait && a.status.waitUntil != b.status.waitUntil) {
+        return a.status.waitUntil < b.status.waitUntil;
+    }
+    return StringUtil::lower(a.name) < StringUtil::lower(b.name);
+}
+
+}  // namespace
+
+Display::Display(const Database& db) : db_(db) {}
+
+DisplaySettings& Display::settings() {
+    return settings_;
+}
+
+const DisplaySettings& Display::settings() const {
+    return settings_;
+}
+
+std::string Display::renderTasks(std::time_t now) const {
+    std::vector<TaskView> views = loadViews(db_, now);
+    std::sort(views.begin(), views.end(), taskLess);
+
+    TextTable table({"TASK", "ACCOUNT", "STATUS", "NOTES"});
+    for (const TaskView& view : views) {
+        if (settings_.hiddenTaskLevels.count(view.status.kind) > 0) {
+            continue;
+        }
+        table.addRow({view.name,
+                      view.account.empty() ? "-" : view.account,
+                      StatusUtil::label(view.status),
+                      view.notes.empty() ? "-" : StringUtil::singleLine(view.notes, 0)});
+    }
+    return table.render();
+}
+
+std::string Display::renderAccounts(std::time_t now) const {
+    std::vector<TaskView> views = loadViews(db_, now);
+    std::sort(views.begin(), views.end(), taskLess);
+
+    // One row per account. It is Busy while any of its tasks is Testing or
+    // Wait (those tasks are listed); otherwise it is Free.
+    TextTable table({"ACCOUNT", "STATUS", "TASKS"});
+    for (const std::string& account : db_.listAccounts()) {
+        std::vector<std::string> busyTasks;
+        for (const TaskView& view : views) {
+            if (view.account == account && StatusUtil::isBusy(view.status.kind)) {
+                busyTasks.push_back(view.name);
+            }
+        }
+
+        const AccountLevel level = busyTasks.empty() ? AccountLevel::Free : AccountLevel::Busy;
+        if (settings_.hiddenAccountLevels.count(level) > 0) {
+            continue;
+        }
+        table.addRow({account,
+                      level == AccountLevel::Busy ? "Busy" : "Free",
+                      busyTasks.empty() ? "-" : StringUtil::join(busyTasks, 0, ", ")});
+    }
+    return table.render();
+}
diff --git a/src/ExternalEditor.cpp b/src/ExternalEditor.cpp
new file mode 100644
index 0000000..68574f0
--- /dev/null
+++ b/src/ExternalEditor.cpp
@@ -0,0 +1,170 @@
+#include "ExternalEditor.h"
+
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <iterator>
+#include <sstream>
+#include <stdexcept>
+
+#if defined(__unix__) || defined(__APPLE__)
+#include <unistd.h>
+#endif
+
+namespace fs = std::filesystem;
+
+namespace {
+
+#ifdef _WIN32
+const char kPathSeparator = ';';
+#else
+const char kPathSeparator = ':';
+#endif
+
+bool isExecutableFile(const fs::path& path) {
+    std::error_code error;
+    if (!fs::is_regular_file(path, error)) {
+        return false;
+    }
+#if defined(__unix__) || defined(__APPLE__)
+    return access(path.c_str(), X_OK) == 0;
+#else
+    return true;
+#endif
+}
+
+bool findInPath(const std::string& program) {
+    if (program.find('/') != std::string::npos || program.find('\\') != std::string::npos) {
+        return isExecutableFile(program);
+    }
+
+    const char* pathVariable = std::getenv("PATH");
+    if (!pathVariable) {
+        return false;
+    }
+
+    std::stringstream paths(pathVariable);
+    std::string directory;
+    while (std::getline(paths, directory, kPathSeparator)) {
+        if (directory.empty()) {
+            continue;
+        }
+        if (isExecutableFile(fs::path(directory) / program)) {
+            return true;
+        }
+#ifdef _WIN32
+        if (isExecutableFile(fs::path(directory) / (program + ".exe"))) {
+            return true;
+        }
+#endif
+    }
+    return false;
+}
+
+std::string firstWord(const std::string& command) {
+    std::istringstream in(command);
+    std::string word;
+    in >> word;
+    return word;
+}
+
+std::string quotePath(const std::string& path) {
+#ifdef _WIN32
+    return "\"" + path + "\"";
+#else
+    std::string quoted = "'";
+    for (char c : path) {
+        if (c == '\'') {
+            quoted += "'\\''";
+        } else {
+            quoted.push_back(c);
+        }
+    }
+    return quoted + "'";
+#endif
+}
+
+std::string makeTempFile(const std::string& content) {
+#if defined(__unix__) || defined(__APPLE__)
+    std::string pattern = (fs::temp_directory_path() / "task-tracker-XXXXXX.txt").string();
+    std::vector<char> buffer(pattern.begin(), pattern.end());
+    buffer.push_back('\0');
+
+    int fd = mkstemps(buffer.data(), 4);
+    if (fd < 0) {
+        throw std::runtime_error("Cannot create a temporary file for the editor.");
+    }
+    std::size_t written = 0;
+    while (written < content.size()) {
+        ssize_t n = ::write(fd, content.data() + written, content.size() - written);
+        if (n <= 0) {
+            ::close(fd);
+            throw std::runtime_error("Cannot write the temporary file for the editor.");
+        }
+        written += static_cast<std::size_t>(n);
+    }
+    ::close(fd);
+    return std::string(buffer.data());
+#else
+    fs::path path = fs::temp_directory_path() / ("task-tracker-" + std::to_string(std::rand()) + ".txt");
+    std::ofstream out(path, std::ios::binary);
+    out << content;
+    if (!out) {
+        throw std::runtime_error("Cannot write the temporary file for the editor.");
+    }
+    return path.string();
+#endif
+}
+
+}  // namespace
+
+namespace ExternalEditor {
+
+std::string defaultCommand() {
+    for (const char* variable : {"VISUAL", "EDITOR"}) {
+        const char* value = std::getenv(variable);
+        if (value && *value) {
+            return value;
+        }
+    }
+    for (const char* candidate : {"nano", "vim", "vi"}) {
+        if (findInPath(candidate)) {
+            return candidate;
+        }
+    }
+    return "";
+}
+
+bool commandExists(const std::string& command) {
+    const std::string program = firstWord(command);
+    return !program.empty() && findInPath(program);
+}
+
+std::vector<std::string> installedEditors() {
+    std::vector<std::string> found;
+    for (const char* candidate : {"nano", "vim", "nvim", "vi", "emacs", "micro", "helix", "hx", "code", "kate", "gedit"}) {
+        if (findInPath(candidate)) {
+            found.push_back(candidate);
+        }
+    }
+    return found;
+}
+
+std::string edit(const std::string& command, const std::string& initialText) {
+    const std::string path = makeTempFile(initialText);
+    const std::string commandLine = command + " " + quotePath(path);
+    const int status = std::system(commandLine.c_str());
+
+    std::ifstream in(path, std::ios::binary);
+    std::string content((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+    in.close();
+    std::error_code error;
+    fs::remove(path, error);
+
+    if (status != 0) {
+        throw std::runtime_error("The editor exited with an error; nothing was changed.");
+    }
+    return content;
+}
+
+}  // namespace ExternalEditor
diff --git a/src/LineEditor.cpp b/src/LineEditor.cpp
new file mode 100644
index 0000000..04fb0be
--- /dev/null
+++ b/src/LineEditor.cpp
@@ -0,0 +1,367 @@
+#include "LineEditor.h"
+
+#include <cctype>
+#include <fstream>
+#include <iostream>
+
+#include "StringUtil.h"
+#include "Terminal.h"
+
+#if defined(__unix__) || defined(__APPLE__)
+#define TT_HAVE_TERMIOS 1
+#include <poll.h>
+#include <termios.h>
+#include <unistd.h>
+
+#include <cerrno>
+#endif
+
+namespace {
+
+const std::size_t kMaxHistory = 500;
+
+#ifdef TT_HAVE_TERMIOS
+
+// Puts the terminal into raw-ish mode and restores it on destruction.
+class RawMode {
+public:
+    RawMode();
+    ~RawMode();
+    bool active() const;
+
+private:
+    termios saved_;
+    bool active_;
+};
+
+RawMode::RawMode() : saved_(), active_(false) {
+    if (tcgetattr(STDIN_FILENO, &saved_) != 0) {
+        return;
+    }
+    termios raw = saved_;
+    raw.c_lflag &= static_cast<tcflag_t>(~(ICANON | ECHO | ISIG | IEXTEN));
+    raw.c_cc[VMIN] = 1;
+    raw.c_cc[VTIME] = 0;
+    active_ = (tcsetattr(STDIN_FILENO, TCSADRAIN, &raw) == 0);
+}
+
+RawMode::~RawMode() {
+    if (active_) {
+        tcsetattr(STDIN_FILENO, TCSADRAIN, &saved_);
+    }
+}
+
+bool RawMode::active() const {
+    return active_;
+}
+
+int readByte() {
+    unsigned char c = 0;
+    for (;;) {
+        ssize_t n = ::read(STDIN_FILENO, &c, 1);
+        if (n == 1) {
+            return c;
+        }
+        if (n == 0 || errno != EINTR) {
+            return -1;
+        }
+    }
+}
+
+bool byteAvailable(int milliseconds) {
+    pollfd descriptor;
+    descriptor.fd = STDIN_FILENO;
+    descriptor.events = POLLIN;
+    descriptor.revents = 0;
+    return poll(&descriptor, 1, milliseconds) > 0;
+}
+
+std::size_t previousChar(const std::string& text, std::size_t position) {
+    if (position == 0) {
+        return 0;
+    }
+    --position;
+    while (position > 0 && (static_cast<unsigned char>(text[position]) & 0xC0) == 0x80) {
+        --position;
+    }
+    return position;
+}
+
+std::size_t nextChar(const std::string& text, std::size_t position) {
+    if (position >= text.size()) {
+        return text.size();
+    }
+    ++position;
+    while (position < text.size() && (static_cast<unsigned char>(text[position]) & 0xC0) == 0x80) {
+        ++position;
+    }
+    return position;
+}
+
+std::size_t previousWord(const std::string& text, std::size_t position) {
+    while (position > 0 && std::isspace(static_cast<unsigned char>(text[position - 1]))) {
+        --position;
+    }
+    while (position > 0 && !std::isspace(static_cast<unsigned char>(text[position - 1]))) {
+        --position;
+    }
+    return position;
+}
+
+std::size_t nextWord(const std::string& text, std::size_t position) {
+    while (position < text.size() && std::isspace(static_cast<unsigned char>(text[position]))) {
+        ++position;
+    }
+    while (position < text.size() && !std::isspace(static_cast<unsigned char>(text[position]))) {
+        ++position;
+    }
+    return position;
+}
+
+void redraw(const std::string& prompt, const std::string& buffer, std::size_t cursor) {
+    std::string out = "\r" + prompt + buffer + "\x1b[K";
+    const std::size_t back = StringUtil::displayWidth(buffer.substr(cursor));
+    if (back > 0) {
+        out += "\x1b[" + std::to_string(back) + "D";
+    }
+    std::cout << out << std::flush;
+}
+
+std::string commonPrefix(const std::vector<std::string>& values) {
+    std::string prefix = values.front();
+    for (const std::string& value : values) {
+        std::size_t n = 0;
+        while (n < prefix.size() && n < value.size() && prefix[n] == value[n]) {
+            ++n;
+        }
+        prefix.resize(n);
+    }
+    // never cut a UTF-8 character in half
+    while (!prefix.empty() && prefix.size() < values.front().size() &&
+           (static_cast<unsigned char>(values.front()[prefix.size()]) & 0xC0) == 0x80) {
+        prefix.pop_back();
+    }
+    return prefix;
+}
+
+void printCandidates(const std::vector<std::string>& candidates) {
+    const std::size_t lineWidth = 78;
+    std::string line;
+    std::cout << "\n";
+    for (const std::string& candidate : candidates) {
+        if (!line.empty() && StringUtil::displayWidth(line) + 2 + StringUtil::displayWidth(candidate) > lineWidth) {
+            std::cout << line << "\n";
+            line.clear();
+        }
+        line += line.empty() ? candidate : "  " + candidate;
+    }
+    std::cout << line << "\n";
+}
+
+#endif  // TT_HAVE_TERMIOS
+
+}  // namespace
+
+LineEditor::LineEditor() = default;
+
+void LineEditor::setCompleter(const CompletionFn& completer) {
+    completer_ = completer;
+}
+
+void LineEditor::setHistoryFile(const std::string& path) {
+    historyFile_ = path;
+    history_.clear();
+
+    std::ifstream in(path);
+    std::string line;
+    while (std::getline(in, line)) {
+        if (!line.empty()) {
+            history_.push_back(line);
+        }
+    }
+    in.close();
+
+    if (history_.size() > kMaxHistory) {
+        history_.erase(history_.begin(), history_.end() - static_cast<std::ptrdiff_t>(kMaxHistory));
+        std::ofstream out(path, std::ios::trunc);
+        for (const std::string& entry : history_) {
+            out << entry << "\n";
+        }
+    }
+}
+
+void LineEditor::addHistory(const std::string& line) {
+    if (StringUtil::trim(line).empty() || (!history_.empty() && history_.back() == line)) {
+        return;
+    }
+    history_.push_back(line);
+    if (history_.size() > kMaxHistory) {
+        history_.erase(history_.begin());
+    }
+    if (!historyFile_.empty()) {
+        std::ofstream out(historyFile_, std::ios::app);
+        out << line << "\n";
+    }
+}
+
+bool LineEditor::readLine(const std::string& prompt, std::string& line) {
+#ifdef TT_HAVE_TERMIOS
+    if (Terminal::stdinIsInteractive() && Terminal::stdoutIsInteractive()) {
+        return readInteractive(prompt, line);
+    }
+#endif
+    return readPlain(prompt, line);
+}
+
+bool LineEditor::readPlain(const std::string& prompt, std::string& line) {
+    std::cout << prompt << std::flush;
+    return static_cast<bool>(std::getline(std::cin, line));
+}
+
+#ifdef TT_HAVE_TERMIOS
+
+bool LineEditor::readInteractive(const std::string& prompt, std::string& line) {
+    RawMode raw;
+    if (!raw.active()) {
+        return readPlain(prompt, line);
+    }
+
+    std::string buffer;
+    std::size_t cursor = 0;
+    std::size_t historyIndex = history_.size();
+    std::string pending;  // the line being typed while browsing history
+
+    redraw(prompt, buffer, cursor);
+
+    for (;;) {
+        const int c = readByte();
+        if (c < 0) {
+            std::cout << "\n";
+            return false;
+        }
+
+        if (c == '\n' || c == '\r') {
+            std::cout << "\n" << std::flush;
+            line = buffer;
+            addHistory(buffer);
+            return true;
+        }
+
+        if (c == 4) {  // Ctrl-D
+            if (buffer.empty()) {
+                std::cout << "\n";
+                return false;
+            }
+            buffer.erase(cursor, nextChar(buffer, cursor) - cursor);
+        } else if (c == 3) {  // Ctrl-C
+            std::cout << "^C\n" << std::flush;
+            line.clear();
+            return true;
+        } else if (c == 1) {  // Ctrl-A
+            cursor = 0;
+        } else if (c == 5) {  // Ctrl-E
+            cursor = buffer.size();
+        } else if (c == 2) {  // Ctrl-B
+            cursor = previousChar(buffer, cursor);
+        } else if (c == 6) {  // Ctrl-F
+            cursor = nextChar(buffer, cursor);
+        } else if (c == 11) {  // Ctrl-K
+            buffer.erase(cursor);
+        } else if (c == 21) {  // Ctrl-U
+            buffer.erase(0, cursor);
+            cursor = 0;
+        } else if (c == 23) {  // Ctrl-W
+            const std::size_t start = previousWord(buffer, cursor);
+            buffer.erase(start, cursor - start);
+            cursor = start;
+        } else if (c == 12) {  // Ctrl-L
+            Terminal::clearScreen();
+        } else if (c == 127 || c == 8) {  // Backspace
+            const std::size_t start = previousChar(buffer, cursor);
+            buffer.erase(start, cursor - start);
+            cursor = start;
+        } else if (c == 9) {  // Tab
+            if (!completer_) {
+                continue;
+            }
+            const Completion completion = completer_(buffer.substr(0, cursor));
+            if (completion.candidates.empty()) {
+                std::cout << "\a" << std::flush;
+                continue;
+            }
+
+            const std::string word = buffer.substr(completion.start, cursor - completion.start);
+            std::string replacement = commonPrefix(completion.candidates);
+            bool showList = false;
+            if (completion.candidates.size() == 1) {
+                if (replacement.empty() || replacement.back() != '/') {
+                    replacement += ' ';
+                }
+            } else if (replacement.size() <= word.size()) {
+                showList = true;
+            }
+
+            buffer.replace(completion.start, cursor - completion.start, replacement);
+            cursor = completion.start + replacement.size();
+            if (showList) {
+                printCandidates(completion.candidates);
+            }
+        } else if (c == 27) {  // Escape sequences (arrows, home, end, delete...)
+            if (!byteAvailable(30)) {
+                continue;
+            }
+            const int introducer = readByte();
+            if (introducer != '[' && introducer != 'O') {
+                continue;
+            }
+
+            std::string parameters;
+            int lastByte = readByte();
+            while (lastByte >= 0 && (std::isdigit(lastByte) || lastByte == ';')) {
+                parameters.push_back(static_cast<char>(lastByte));
+                lastByte = readByte();
+            }
+
+            const bool withModifier = parameters.find(';') != std::string::npos;
+            if (lastByte == '~') {
+                if (parameters == "3") {
+                    buffer.erase(cursor, nextChar(buffer, cursor) - cursor);
+                } else if (parameters == "1" || parameters == "7") {
+                    cursor = 0;
+                } else if (parameters == "4" || parameters == "8") {
+                    cursor = buffer.size();
+                }
+            } else if (lastByte == 'A') {  // Up
+                if (historyIndex > 0) {
+                    if (historyIndex == history_.size()) {
+                        pending = buffer;
+                    }
+                    --historyIndex;
+                    buffer = history_[historyIndex];
+                    cursor = buffer.size();
+                }
+            } else if (lastByte == 'B') {  // Down
+                if (historyIndex < history_.size()) {
+                    ++historyIndex;
+                    buffer = (historyIndex == history_.size()) ? pending : history_[historyIndex];
+                    cursor = buffer.size();
+                }
+            } else if (lastByte == 'C') {  // Right
+                cursor = withModifier ? nextWord(buffer, cursor) : nextChar(buffer, cursor);
+            } else if (lastByte == 'D') {  // Left
+                cursor = withModifier ? previousWord(buffer, cursor) : previousChar(buffer, cursor);
+            } else if (lastByte == 'H') {
+                cursor = 0;
+            } else if (lastByte == 'F') {
+                cursor = buffer.size();
+            }
+        } else if (c >= 32) {  // Printable (including UTF-8 bytes)
+            buffer.insert(cursor, 1, static_cast<char>(c));
+            ++cursor;
+        }
+
+        redraw(prompt, buffer, cursor);
+    }
+}
+
+#endif  // TT_HAVE_TERMIOS
diff --git a/src/Repl.cpp b/src/Repl.cpp
new file mode 100644
index 0000000..7f3c365
--- /dev/null
+++ b/src/Repl.cpp
@@ -0,0 +1,570 @@
+#include "Repl.h"
+
+#include <algorithm>
+#include <ctime>
+#include <iostream>
+#include <limits>
+#include <optional>
+#include <stdexcept>
+
+#include "ExternalEditor.h"
+#include "StringUtil.h"
+#include "Terminal.h"
+#include "Tokenizer.h"
+
+namespace {
+
+const std::size_t kUnlimited = std::numeric_limits<std::size_t>::max();
+
+const char* const kStatusHelp =
+    "prompt, limit-reset, testing, wait <time>, uploading, frozen, done "
+    "(time: 16:30, 4:30pm, 4pm)";
+
+bool parseVisibility(const std::string& word) {
+    const std::string value = StringUtil::lower(word);
+    if (value == "show") {
+        return true;
+    }
+    if (value == "hide") {
+        return false;
+    }
+    throw std::runtime_error("Expected 'show' or 'hide', got '" + word + "'.");
+}
+
+}  // namespace
+
+Repl::Repl(Database& db, Display& display, Config& config)
+    : db_(db), display_(display), config_(config), completer_(db, specs_), quit_(false) {
+    registerCommands();
+}
+
+void Repl::add(const std::string& key, const std::string& usage, const std::string& help,
+               std::size_t minArgs, std::size_t maxArgs, const std::vector<ArgKind>& argKinds,
+               Handler handler) {
+    CommandSpec spec;
+    spec.key = key;
+    spec.usage = usage;
+    spec.help = help;
+    spec.minArgs = minArgs;
+    spec.maxArgs = maxArgs;
+    spec.argKinds = argKinds;
+
+    Command command;
+    command.spec = spec;
+    command.handler = handler;
+    commands_.push_back(command);
+    specs_.push_back(spec);
+}
+
+void Repl::registerCommands() {
+    add("acc add", "acc add <name>", "create an account", 1, 1, {ArgKind::None}, &Repl::cmdAccAdd);
+    add("acc del", "acc del <name>", "delete an account (its tasks become unassigned)", 1, 1,
+        {ArgKind::Account}, &Repl::cmdAccDel);
+    add("acc rename", "acc rename <name> <new>", "rename an account", 2, 2,
+        {ArgKind::Account, ArgKind::None}, &Repl::cmdAccRename);
+    add("acc ls", "acc ls", "show the account table", 0, 0, {}, &Repl::cmdAccLs);
+
+    add("tsk add", "tsk add <name> [acc] [status]", "create a task", 1, kUnlimited,
+        {ArgKind::None, ArgKind::AccountOrStatus, ArgKind::Status}, &Repl::cmdTskAdd);
+    add("tsk del", "tsk del <name>", "delete a task", 1, 1, {ArgKind::Task}, &Repl::cmdTskDel);
+    add("tsk ls", "tsk ls", "show the task table", 0, 0, {}, &Repl::cmdTskLs);
+    add("tsk rename", "tsk rename <name> <new>", "rename a task", 2, 2,
+        {ArgKind::Task, ArgKind::None}, &Repl::cmdTskRename);
+    add("tsk reacc", "tsk reacc <name> <new>", "move a task to another account ('-' = none)", 2, 2,
+        {ArgKind::Task, ArgKind::AccountOrDash}, &Repl::cmdTskReacc);
+    add("tsk restat", "tsk restat <name> <new>", "change a task's status", 2, kUnlimited,
+        {ArgKind::Task, ArgKind::Status}, &Repl::cmdTskRestat);
+    add("tsk notes", "tsk notes <name>", "edit a task's notes in your editor (see 'editor')", 1, 1,
+        {ArgKind::Task}, &Repl::cmdTskNotes);
+
+    add("disp", "disp", "show the current display settings", 0, 0, {}, &Repl::cmdDisp);
+    add("disp tsk", "disp tsk (hide|show)", "auto-print the task table after changes", 1, 1,
+        {ArgKind::Visibility}, &Repl::cmdDispTsk);
+    add("disp tsk level", "disp tsk level (hide|show) (prompt|limit-reset|testing|wait|uploading|frozen|done|all)",
+        "hide or show task rows by status", 2, 2,
+        {ArgKind::Visibility, ArgKind::TaskLevel}, &Repl::cmdDispTskLevel);
+    add("disp acc", "disp acc (hide|show)", "auto-print the account table after changes", 1, 1,
+        {ArgKind::Visibility}, &Repl::cmdDispAcc);
+    add("disp acc level", "disp acc level (hide|show) (busy|free|all)",
+        "hide or show account rows by status", 2, 2,
+        {ArgKind::Visibility, ArgKind::AccountLevel}, &Repl::cmdDispAccLevel);
+
+    add("db save", "db save", "write the database to its file", 0, 0, {}, &Repl::cmdDbSave);
+    add("db backup", "db backup [file]", "write a copy (timestamped name if no file given)", 0, 1,
+        {ArgKind::File}, &Repl::cmdDbBackup);
+    add("db restore", "db restore <file>", "replace the current data with a file's contents", 1, 1,
+        {ArgKind::File}, &Repl::cmdDbRestore);
+
+    add("editor", "editor [command | default]", "show or set the editor used by 'tsk notes'", 0, kUnlimited,
+        {ArgKind::Editor}, &Repl::cmdEditor);
+    add("help", "help", "list the commands", 0, 0, {}, &Repl::cmdHelp);
+    add("quit", "quit", "exit (also: exit, Ctrl-D)", 0, 0, {}, &Repl::cmdQuit);
+    add("exit", "exit", "exit", 0, 0, {}, &Repl::cmdQuit);
+}
+
+const Repl::Command* Repl::find(const Args& tokens, std::size_t& consumed) const {
+    // Longest match wins: "disp tsk level" before "disp tsk" before "disp".
+    for (std::size_t words = std::min<std::size_t>(3, tokens.size()); words >= 1; --words) {
+        std::string key;
+        for (std::size_t i = 0; i < words; ++i) {
+            if (i > 0) {
+                key += " ";
+            }
+            key += StringUtil::lower(tokens[i]);
+        }
+        for (const Command& command : commands_) {
+            if (command.spec.key == key) {
+                consumed = words;
+                return &command;
+            }
+        }
+    }
+    return nullptr;
+}
+
+int Repl::run() {
+    lineEditor_.setCompleter([this](const std::string& before) { return completer_.complete(before); });
+    lineEditor_.setHistoryFile(config_.historyPath());
+
+    refresh();
+    std::cout << "Task tracker - database: " << db_.path()
+              << "   ('help' for commands, Tab completes, Enter on an empty line refreshes)\n";
+
+    std::string line;
+    while (!quit_) {
+        if (!lineEditor_.readLine("> ", line)) {
+            endOfInput();
+            return 0;
+        }
+        execute(line);
+    }
+    return 0;
+}
+
+void Repl::endOfInput() {
+    if (!db_.dirty()) {
+        return;
+    }
+    if (Terminal::stdinIsInteractive()) {
+        if (confirm("Save changes before exiting?")) {
+            db_.save();
+            std::cout << "Saved to " << db_.path() << ".\n";
+        }
+    } else {
+        db_.save();
+        std::cout << "Input closed - changes saved to " << db_.path() << ".\n";
+    }
+}
+
+void Repl::say(const std::string& message) {
+    messages_.push_back(message);
+}
+
+void Repl::flushMessages() {
+    for (const std::string& message : messages_) {
+        std::cout << message << "\n";
+    }
+    messages_.clear();
+}
+
+void Repl::execute(const std::string& line) {
+    messages_.clear();
+    try {
+        Args tokens = Tokenizer::split(line);
+        if (tokens.empty()) {
+            refresh();
+            return;
+        }
+
+        std::size_t consumed = 0;
+        const Command* command = find(tokens, consumed);
+        if (!command) {
+            std::cout << "Unknown command. Type 'help' for the list.\n";
+            return;
+        }
+
+        Args args(tokens.begin() + static_cast<std::ptrdiff_t>(consumed), tokens.end());
+        if (args.size() < command->spec.minArgs || args.size() > command->spec.maxArgs) {
+            std::cout << "Usage: " << command->spec.usage << "\n"
+                      << "(wrap names containing spaces in double quotes)\n";
+            return;
+        }
+
+        if ((this->*command->handler)(args)) {
+            refresh();
+        }
+        flushMessages();
+    } catch (const std::exception& error) {
+        messages_.clear();
+        std::cout << "Error: " << error.what() << "\n";
+    }
+}
+
+void Repl::refresh() const {
+    const DisplaySettings& settings = display_.settings();
+    if (!settings.showTasks && !settings.showAccounts) {
+        return;
+    }
+
+    const std::time_t now = std::time(nullptr);
+    Terminal::clearScreen();
+    if (settings.showTasks) {
+        std::cout << display_.renderTasks(now) << "\n";
+    }
+    if (settings.showAccounts) {
+        std::cout << display_.renderAccounts(now) << "\n";
+    }
+}
+
+bool Repl::confirm(const std::string& question) const {
+    std::cout << question << " (y/n): " << std::flush;
+    std::string answer;
+    if (!std::getline(std::cin, answer)) {
+        return false;
+    }
+    answer = StringUtil::lower(StringUtil::trim(answer));
+    return answer == "y" || answer == "yes";
+}
+
+void Repl::requireName(const std::string& name) {
+    if (name.empty() || name == "-") {
+        throw std::runtime_error("'" + name + "' is not a valid name.");
+    }
+}
+
+Status Repl::parseStatusFrom(const Args& args, std::size_t from) {
+    const std::string text = StringUtil::join(args, from, " ");
+    std::optional<Status> status = StatusUtil::parse(text, std::time(nullptr));
+    if (!status) {
+        throw std::runtime_error("Invalid status '" + text + "'. Use: " + kStatusHelp);
+    }
+    return *status;
+}
+
+// ---- Accounts ---------------------------------------------------------------
+
+bool Repl::cmdAccAdd(const Args& args) {
+    requireName(args[0]);
+    if (db_.findAccount(args[0])) {
+        throw std::runtime_error("Account '" + args[0] + "' already exists.");
+    }
+    db_.addAccount(args[0]);
+    say("Account '" + args[0] + "' added.");
+    return true;
+}
+
+bool Repl::cmdAccDel(const Args& args) {
+    std::optional<std::string> name = db_.findAccount(args[0]);
+    if (!name) {
+        throw std::runtime_error("No account named '" + args[0] + "'.");
+    }
+    db_.removeAccount(*name);
+    say("Account '" + *name + "' deleted.");
+    return true;
+}
+
+bool Repl::cmdAccRename(const Args& args) {
+    std::optional<std::string> name = db_.findAccount(args[0]);
+    if (!name) {
+        throw std::runtime_error("No account named '" + args[0] + "'.");
+    }
+    requireName(args[1]);
+    if (!StringUtil::equalsIgnoreCase(*name, args[1]) && db_.findAccount(args[1])) {
+        throw std::runtime_error("Account '" + args[1] + "' already exists.");
+    }
+    db_.renameAccount(*name, args[1]);
+    say("Account '" + *name + "' renamed to '" + args[1] + "'.");
+    return true;
+}
+
+bool Repl::cmdAccLs(const Args&) {
+    Terminal::clearScreen();
+    std::cout << display_.renderAccounts(std::time(nullptr)) << "\n";
+    return false;
+}
+
+// ---- Tasks ------------------------------------------------------------------
+
+bool Repl::cmdTskAdd(const Args& args) {
+    const std::string& name = args[0];
+    requireName(name);
+    if (db_.findTask(name)) {
+        throw std::runtime_error("Task '" + name + "' already exists.");
+    }
+
+    std::size_t next = 1;
+    std::optional<std::string> account;
+    if (next < args.size()) {
+        if (std::optional<std::string> found = db_.findAccount(args[next])) {
+            account = found;
+            ++next;
+        } else if (args[next] == "-") {
+            ++next;
+        } else if (!StatusUtil::parse(StringUtil::join(args, next, " "), std::time(nullptr))) {
+            throw std::runtime_error("'" + args[next] + "' is neither an existing account nor a valid status (" +
+                                     kStatusHelp + ").");
+        }
+    }
+
+    Status status = StatusUtil::make(StatusKind::Prompt);
+    if (next < args.size()) {
+        status = parseStatusFrom(args, next);
+    }
+
+    db_.addTask(name, account, StatusUtil::serialize(status));
+    say("Task '" + name + "' added.");
+    return true;
+}
+
+bool Repl::cmdTskDel(const Args& args) {
+    std::optional<std::string> name = db_.findTask(args[0]);
+    if (!name) {
+        throw std::runtime_error("No task named '" + args[0] + "'.");
+    }
+    db_.removeTask(*name);
+    say("Task '" + *name + "' deleted.");
+    return true;
+}
+
+bool Repl::cmdTskLs(const Args&) {
+    Terminal::clearScreen();
+    std::cout << display_.renderTasks(std::time(nullptr)) << "\n";
+    return false;
+}
+
+bool Repl::cmdTskRename(const Args& args) {
+    std::optional<std::string> name = db_.findTask(args[0]);
+    if (!name) {
+        throw std::runtime_error("No task named '" + args[0] + "'.");
+    }
+    requireName(args[1]);
+    if (!StringUtil::equalsIgnoreCase(*name, args[1]) && db_.findTask(args[1])) {
+        throw std::runtime_error("Task '" + args[1] + "' already exists.");
+    }
+    db_.renameTask(*name, args[1]);
+    say("Task '" + *name + "' renamed to '" + args[1] + "'.");
+    return true;
+}
+
+bool Repl::cmdTskReacc(const Args& args) {
+    std::optional<std::string> name = db_.findTask(args[0]);
+    if (!name) {
+        throw std::runtime_error("No task named '" + args[0] + "'.");
+    }
+
+    std::optional<std::string> account;
+    if (args[1] != "-") {
+        account = db_.findAccount(args[1]);
+        if (!account) {
+            throw std::runtime_error("No account named '" + args[1] + "'.");
+        }
+    }
+    db_.setTaskAccount(*name, account);
+    say("Task '" + *name + "' now on account " + (account ? "'" + *account + "'" : std::string("(none)")) + ".");
+    return true;
+}
+
+bool Repl::cmdTskRestat(const Args& args) {
+    std::optional<std::string> name = db_.findTask(args[0]);
+    if (!name) {
+        throw std::runtime_error("No task named '" + args[0] + "'.");
+    }
+    Status status = parseStatusFrom(args, 1);
+    db_.setTaskStatus(*name, StatusUtil::serialize(status));
+    say("Task '" + *name + "' set to " + StatusUtil::label(status) + ".");
+    return true;
+}
+
+bool Repl::cmdTskNotes(const Args& args) {
+    std::optional<TaskRow> task = db_.getTask(args[0]);
+    if (!task) {
+        throw std::runtime_error("No task named '" + args[0] + "'.");
+    }
+
+    std::string command = config_.editor();
+    if (command.empty()) {
+        command = ExternalEditor::defaultCommand();
+    }
+    if (command.empty()) {
+        throw std::runtime_error("No editor found. Set one with: editor <command>  (e.g. editor nano)");
+    }
+
+    const std::string initial = task->notes.empty() ? "" : task->notes + "\n";
+    const std::string edited = StringUtil::trim(ExternalEditor::edit(command, initial));
+
+    if (edited == StringUtil::trim(task->notes)) {
+        say("Notes unchanged.");
+        return false;
+    }
+    db_.setTaskNotes(task->id, edited);
+    say(edited.empty() ? "Notes cleared." : "Notes updated.");
+    return true;
+}
+
+// ---- Display ----------------------------------------------------------------
+
+bool Repl::cmdDisp(const Args&) {
+    const DisplaySettings& settings = display_.settings();
+    std::cout << "Task table:    " << (settings.showTasks ? "shown" : "hidden") << " after changes\n";
+    std::cout << "Account table: " << (settings.showAccounts ? "shown" : "hidden") << " after changes\n";
+
+    std::cout << "Hidden task levels:";
+    if (settings.hiddenTaskLevels.empty()) {
+        std::cout << " none";
+    }
+    for (StatusKind kind : settings.hiddenTaskLevels) {
+        std::cout << " " << StatusUtil::kindName(kind);
+    }
+
+    std::cout << "\nHidden account levels:";
+    if (settings.hiddenAccountLevels.empty()) {
+        std::cout << " none";
+    }
+    for (AccountLevel level : settings.hiddenAccountLevels) {
+        std::cout << (level == AccountLevel::Busy ? " busy" : " free");
+    }
+    std::cout << "\n";
+    return false;
+}
+
+bool Repl::cmdDispTsk(const Args& args) {
+    display_.settings().showTasks = parseVisibility(args[0]);
+    return true;
+}
+
+bool Repl::cmdDispTskLevel(const Args& args) {
+    const bool visible = parseVisibility(args[0]);
+    const std::string level = StringUtil::lower(args[1]);
+
+    std::set<StatusKind>& hidden = display_.settings().hiddenTaskLevels;
+    std::vector<StatusKind> targets;
+    if (level == "all") {
+        targets = StatusUtil::allKinds();
+    } else {
+        std::optional<StatusKind> kind = StatusUtil::kindFromName(level);
+        if (!kind) {
+            throw std::runtime_error("Unknown level '" + args[1] +
+                                     "'. Use: prompt, limit-reset, testing, wait, uploading, frozen, done, all");
+        }
+        targets = {*kind};
+    }
+
+    for (StatusKind target : targets) {
+        if (visible) {
+            hidden.erase(target);
+        } else {
+            hidden.insert(target);
+        }
+    }
+    return true;
+}
+
+bool Repl::cmdDispAcc(const Args& args) {
+    display_.settings().showAccounts = parseVisibility(args[0]);
+    return true;
+}
+
+bool Repl::cmdDispAccLevel(const Args& args) {
+    const bool visible = parseVisibility(args[0]);
+    const std::string level = StringUtil::lower(args[1]);
+
+    std::set<AccountLevel>& hidden = display_.settings().hiddenAccountLevels;
+    std::vector<AccountLevel> targets;
+    if (level == "all") {
+        targets = {AccountLevel::Busy, AccountLevel::Free};
+    } else if (level == "busy") {
+        targets = {AccountLevel::Busy};
+    } else if (level == "free") {
+        targets = {AccountLevel::Free};
+    } else {
+        throw std::runtime_error("Unknown level '" + args[1] + "'. Use: busy, free, all");
+    }
+
+    for (AccountLevel target : targets) {
+        if (visible) {
+            hidden.erase(target);
+        } else {
+            hidden.insert(target);
+        }
+    }
+    return true;
+}
+
+// ---- Database ---------------------------------------------------------------
+
+bool Repl::cmdDbSave(const Args&) {
+    db_.save();
+    say("Saved to " + db_.path() + ".");
+    return false;
+}
+
+bool Repl::cmdDbBackup(const Args& args) {
+    const std::string target = db_.backup(args.empty() ? "" : args[0]);
+    say("Backup written to " + target + ".");
+    return false;
+}
+
+bool Repl::cmdDbRestore(const Args& args) {
+    if (db_.dirty() && !confirm("Unsaved changes will be replaced. Continue?")) {
+        say("Restore cancelled.");
+        return false;
+    }
+    db_.restore(args[0]);
+    say("Restored from " + args[0] + ". Use 'db save' to keep it as the current database.");
+    return true;
+}
+
+// ---- Misc -------------------------------------------------------------------
+
+bool Repl::cmdEditor(const Args& args) {
+    if (args.empty()) {
+        if (!config_.editor().empty()) {
+            say("Editor: " + config_.editor());
+        } else {
+            const std::string fallback = ExternalEditor::defaultCommand();
+            say(fallback.empty()
+                    ? "No editor configured and none found. Set one with: editor <command>"
+                    : "Editor: " + fallback + " (default, from $VISUAL / $EDITOR / PATH)");
+        }
+        return false;
+    }
+
+    const std::string command = StringUtil::join(args, 0, " ");
+    if (StringUtil::lower(command) == "default") {
+        config_.setEditor("");
+        config_.save();
+        say("Editor reset to the default.");
+        return false;
+    }
+
+    if (!ExternalEditor::commandExists(command)) {
+        throw std::runtime_error("'" + args[0] + "' was not found on your PATH.");
+    }
+    config_.setEditor(command);
+    config_.save();
+    say("Editor set to: " + command);
+    return false;
+}
+
+bool Repl::cmdHelp(const Args&) {
+    std::cout << "\nCommands (wrap names with spaces in double quotes):\n";
+    for (const Command& command : commands_) {
+        if (command.spec.key == "exit") {
+            continue;
+        }
+        std::cout << "  " << command.spec.usage << "\n      " << command.spec.help << "\n";
+    }
+    std::cout << "\nStatuses: " << kStatusHelp << "\n"
+              << "Keys: Up/Down history, Left/Right edit, Tab completes, Ctrl-A/E start/end, "
+                 "Ctrl-U/K/W delete, Ctrl-L clear\n\n";
+    return false;
+}
+
+bool Repl::cmdQuit(const Args&) {
+    if (db_.dirty() && confirm("Save changes before exiting?")) {
+        db_.save();
+        say("Saved to " + db_.path() + ".");
+    }
+    quit_ = true;
+    return false;
+}
diff --git a/src/Status.cpp b/src/Status.cpp
new file mode 100644
index 0000000..5ba7fb8
--- /dev/null
+++ b/src/Status.cpp
@@ -0,0 +1,253 @@
+#include "Status.h"
+
+#include <cctype>
+#include <iomanip>
+#include <sstream>
+#include <utility>
+
+#include "StringUtil.h"
+
+namespace {
+
+std::tm toLocal(std::time_t value) {
+    std::tm out{};
+#ifdef _WIN32
+    localtime_s(&out, &value);
+#else
+    localtime_r(&value, &out);
+#endif
+    return out;
+}
+
+std::string alphanumeric(const std::string& text) {
+    std::string out;
+    for (char c : text) {
+        if (std::isalnum(static_cast<unsigned char>(c))) {
+            out.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(c))));
+        }
+    }
+    return out;
+}
+
+std::string formatTime(std::time_t value, const char* format) {
+    std::tm parts = toLocal(value);
+    std::ostringstream out;
+    out << std::put_time(&parts, format);
+    return out.str();
+}
+
+
+// Accepts 24-hour ("16:30", "6:40") and 12-hour ("4:30pm", "4pm", "12:05 am")
+// clock times. Returns {hour, minute} in 24-hour form.
+std::optional<std::pair<int, int>> parseClock(const std::string& text) {
+    std::string t;
+    for (char c : text) {
+        if (!std::isspace(static_cast<unsigned char>(c))) {
+            t.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(c))));
+        }
+    }
+
+    std::size_t i = 0;
+    auto readNumber = [&t, &i](int& value) {
+        const std::size_t begin = i;
+        value = 0;
+        while (i < t.size() && std::isdigit(static_cast<unsigned char>(t[i])) && i - begin < 2) {
+            value = value * 10 + (t[i] - '0');
+            ++i;
+        }
+        return i > begin;
+    };
+
+    int hour = 0;
+    int minute = 0;
+    bool hasColon = false;
+    if (!readNumber(hour)) {
+        return std::nullopt;
+    }
+    if (i < t.size() && t[i] == ':') {
+        ++i;
+        hasColon = true;
+        if (!readNumber(minute)) {
+            return std::nullopt;
+        }
+    }
+
+    const std::string suffix = t.substr(i);
+    const bool hasMeridiem = (suffix == "am" || suffix == "pm");
+    if (!suffix.empty() && !hasMeridiem) {
+        return std::nullopt;
+    }
+    if (!hasColon && !hasMeridiem) {
+        return std::nullopt;  // a bare "6" is ambiguous
+    }
+    if (minute > 59) {
+        return std::nullopt;
+    }
+
+    if (hasMeridiem) {
+        if (hour < 1 || hour > 12) {
+            return std::nullopt;
+        }
+        hour = hour % 12 + (suffix == "pm" ? 12 : 0);
+    } else if (hour > 23) {
+        return std::nullopt;
+    }
+    return std::make_pair(hour, minute);
+}
+}  // namespace
+
+namespace StatusUtil {
+
+Status make(StatusKind kind) {
+    Status status;
+    status.kind = kind;
+    return status;
+}
+
+std::string kindName(StatusKind kind) {
+    switch (kind) {
+        case StatusKind::Prompt:     return "prompt";
+        case StatusKind::LimitReset: return "limit-reset";
+        case StatusKind::Testing:    return "testing";
+        case StatusKind::Wait:       return "wait";
+        case StatusKind::Uploading:  return "uploading";
+        case StatusKind::Frozen:     return "frozen";
+        case StatusKind::Done:       return "done";
+    }
+    return "prompt";
+}
+
+std::vector<StatusKind> allKinds() {
+    return {StatusKind::Prompt,    StatusKind::LimitReset, StatusKind::Testing, StatusKind::Wait,
+            StatusKind::Uploading, StatusKind::Frozen,     StatusKind::Done};
+}
+
+std::optional<StatusKind> kindFromName(const std::string& name) {
+    const std::string wanted = alphanumeric(name);
+    if (wanted == "available") {
+        return StatusKind::Prompt;  // old name
+    }
+    if (wanted == "reset") {
+        return StatusKind::LimitReset;
+    }
+    for (StatusKind kind : allKinds()) {
+        if (alphanumeric(kindName(kind)) == wanted) {
+            return kind;
+        }
+    }
+    return std::nullopt;
+}
+
+int rank(StatusKind kind) {
+    return static_cast<int>(kind);
+}
+
+bool isBusy(StatusKind kind) {
+    return kind == StatusKind::Testing || kind == StatusKind::Wait;
+}
+
+std::optional<Status> parse(const std::string& text, std::time_t now) {
+    std::istringstream in(text);
+    std::string word;
+    in >> word;
+    if (StringUtil::lower(word) == "limit") {  // "limit reset" typed as two words
+        std::string second;
+        in >> second;
+        word += second;
+    }
+
+    std::optional<StatusKind> kind = kindFromName(word);
+    if (!kind) {
+        return std::nullopt;
+    }
+
+    // Everything after the status word, with spaces removed: "6:40 pm" -> "6:40pm".
+    std::string rest;
+    std::string piece;
+    while (in >> piece) {
+        rest += piece;
+    }
+
+    if (*kind != StatusKind::Wait) {
+        if (!rest.empty()) {
+            return std::nullopt;
+        }
+        return make(*kind);
+    }
+
+    std::optional<std::pair<int, int>> clock = parseClock(rest);
+    if (!clock) {
+        return std::nullopt;
+    }
+
+    std::tm target = toLocal(now);
+    target.tm_hour = clock->first;
+    target.tm_min = clock->second;
+    target.tm_sec = 0;
+    target.tm_isdst = -1;
+    std::time_t when = std::mktime(&target);
+    if (when <= now) {
+        target.tm_mday += 1;  // already passed today -> tomorrow
+        target.tm_isdst = -1;
+        when = std::mktime(&target);
+    }
+
+    Status status = make(StatusKind::Wait);
+    status.waitUntil = when;
+    return status;
+}
+
+std::string serialize(const Status& status) {
+    if (status.kind == StatusKind::Wait) {
+        return "wait " + formatTime(status.waitUntil, "%Y-%m-%dT%H:%M");
+    }
+    return kindName(status.kind);
+}
+
+std::optional<Status> deserialize(const std::string& text) {
+    std::istringstream in(text);
+    std::string word;
+    std::string argument;
+    in >> word >> argument;
+
+    std::optional<StatusKind> kind = kindFromName(word);
+    if (!kind) {
+        return std::nullopt;
+    }
+    if (*kind != StatusKind::Wait) {
+        return make(*kind);
+    }
+
+    std::tm parts{};
+    std::istringstream timeIn(argument);
+    timeIn >> std::get_time(&parts, "%Y-%m-%dT%H:%M");
+    if (timeIn.fail()) {
+        return std::nullopt;
+    }
+    parts.tm_isdst = -1;
+
+    Status status = make(StatusKind::Wait);
+    status.waitUntil = std::mktime(&parts);
+    return status;
+}
+
+Status effective(const Status& status, std::time_t now) {
+    if (status.kind == StatusKind::Wait && now >= status.waitUntil) {
+        return make(StatusKind::LimitReset);
+    }
+    return status;
+}
+
+std::string label(const Status& status) {
+    if (status.kind == StatusKind::Wait) {
+        return "Wait " + formatTime(status.waitUntil, "%H:%M");
+    }
+    if (status.kind == StatusKind::LimitReset) {
+        return "Limit reset";
+    }
+    std::string name = kindName(status.kind);
+    name[0] = static_cast<char>(std::toupper(static_cast<unsigned char>(name[0])));
+    return name;
+}
+
+}  // namespace StatusUtil
diff --git a/src/StringUtil.cpp b/src/StringUtil.cpp
new file mode 100644
index 0000000..596e326
--- /dev/null
+++ b/src/StringUtil.cpp
@@ -0,0 +1,93 @@
+#include "StringUtil.h"
+
+#include <algorithm>
+#include <cctype>
+
+namespace StringUtil {
+
+std::string lower(const std::string& text) {
+    std::string out = text;
+    std::transform(out.begin(), out.end(), out.begin(),
+                   [](unsigned char c) { return static_cast<char>(std::tolower(c)); });
+    return out;
+}
+
+std::string trim(const std::string& text) {
+    std::size_t begin = 0;
+    std::size_t end = text.size();
+    while (begin < end && std::isspace(static_cast<unsigned char>(text[begin]))) {
+        ++begin;
+    }
+    while (end > begin && std::isspace(static_cast<unsigned char>(text[end - 1]))) {
+        --end;
+    }
+    return text.substr(begin, end - begin);
+}
+
+bool equalsIgnoreCase(const std::string& a, const std::string& b) {
+    return lower(a) == lower(b);
+}
+
+bool startsWithIgnoreCase(const std::string& text, const std::string& prefix) {
+    return lower(text).rfind(lower(prefix), 0) == 0;
+}
+
+std::string join(const std::vector<std::string>& parts, std::size_t from, const std::string& separator) {
+    std::string out;
+    for (std::size_t i = from; i < parts.size(); ++i) {
+        if (i > from) {
+            out += separator;
+        }
+        out += parts[i];
+    }
+    return out;
+}
+
+std::size_t displayWidth(const std::string& text) {
+    std::size_t width = 0;
+    for (char c : text) {
+        if ((static_cast<unsigned char>(c) & 0xC0) != 0x80) {
+            ++width;
+        }
+    }
+    return width;
+}
+
+std::string singleLine(const std::string& text, std::size_t maxChars) {
+    std::string out;
+    bool pendingBreak = false;
+    for (char c : text) {
+        if (c == '\n' || c == '\r') {
+            pendingBreak = true;
+            continue;
+        }
+        if (pendingBreak) {
+            if (!out.empty()) {
+                out += " / ";
+            }
+            pendingBreak = false;
+        }
+        out.push_back(c == '\t' ? ' ' : c);
+    }
+
+    if (maxChars == 0) {
+        return out;
+    }
+
+    std::size_t chars = 0;
+    std::size_t cut = 0;
+    for (; cut < out.size(); ++cut) {
+        if ((static_cast<unsigned char>(out[cut]) & 0xC0) != 0x80) {
+            if (chars == maxChars) {
+                break;
+            }
+            ++chars;
+        }
+    }
+    if (cut < out.size()) {
+        out = out.substr(0, cut) + "...";
+    }
+    return out;
+}
+
+}  // namespace StringUtil
diff --git a/src/Table.cpp b/src/Table.cpp
new file mode 100644
index 0000000..9697fd8
--- /dev/null
+++ b/src/Table.cpp
@@ -0,0 +1,57 @@
+#include "Table.h"
+
+#include <algorithm>
+
+#include "StringUtil.h"
+
+TextTable::TextTable(const std::vector<std::string>& headers) : headers_(headers) {}
+
+void TextTable::addRow(const std::vector<std::string>& cells) {
+    std::vector<std::string> row = cells;
+    row.resize(headers_.size());
+    rows_.push_back(row);
+}
+
+std::size_t TextTable::rowCount() const {
+    return rows_.size();
+}
+
+std::string TextTable::render() const {
+    std::vector<std::size_t> widths;
+    for (const std::string& header : headers_) {
+        widths.push_back(StringUtil::displayWidth(header));
+    }
+    for (const std::vector<std::string>& row : rows_) {
+        for (std::size_t c = 0; c < row.size(); ++c) {
+            widths[c] = std::max(widths[c], StringUtil::displayWidth(row[c]));
+        }
+    }
+
+    auto formatLine = [&widths](const std::vector<std::string>& cells) {
+        std::string line;
+        for (std::size_t c = 0; c < cells.size(); ++c) {
+            if (c > 0) {
+                line += " | ";
+            }
+            line += cells[c];
+            line.append(widths[c] - StringUtil::displayWidth(cells[c]), ' ');
+        }
+        return line + "\n";
+    };
+
+    std::string out = formatLine(headers_);
+    for (std::size_t c = 0; c < widths.size(); ++c) {
+        if (c > 0) {
+            out += "-+-";
+        }
+        out.append(widths[c], '-');
+    }
+    out += "\n";
+    for (const std::vector<std::string>& row : rows_) {
+        out += formatLine(row);
+    }
+    if (rows_.empty()) {
+        out += "(none)\n";
+    }
+    return out;
+}
diff --git a/src/Terminal.cpp b/src/Terminal.cpp
new file mode 100644
index 0000000..b2b5c13
--- /dev/null
+++ b/src/Terminal.cpp
@@ -0,0 +1,35 @@
+#include "Terminal.h"
+
+#include <iostream>
+
+#ifdef _WIN32
+#include <io.h>
+#else
+#include <unistd.h>
+#endif
+
+namespace Terminal {
+
+bool stdinIsInteractive() {
+#ifdef _WIN32
+    return _isatty(_fileno(stdin)) != 0;
+#else
+    return isatty(STDIN_FILENO) != 0;
+#endif
+}
+
+bool stdoutIsInteractive() {
+#ifdef _WIN32
+    return _isatty(_fileno(stdout)) != 0;
+#else
+    return isatty(STDOUT_FILENO) != 0;
+#endif
+}
+
+void clearScreen() {
+    if (stdoutIsInteractive()) {
+        std::cout << "\x1b[H\x1b[2J" << std::flush;
+    }
+}
+
+}  // namespace Terminal
diff --git a/src/Tokenizer.cpp b/src/Tokenizer.cpp
new file mode 100644
index 0000000..2756016
--- /dev/null
+++ b/src/Tokenizer.cpp
@@ -0,0 +1,90 @@
+#include "Tokenizer.h"
+
+#include <cctype>
+#include <stdexcept>
+
+namespace Tokenizer {
+
+std::vector<std::string> split(const std::string& line) {
+    std::vector<std::string> tokens;
+    std::string current;
+    bool inToken = false;
+    bool inQuotes = false;
+
+    for (char c : line) {
+        if (inQuotes) {
+            if (c == '"') {
+                inQuotes = false;
+            } else {
+                current.push_back(c);
+            }
+        } else if (c == '"') {
+            inQuotes = true;
+            inToken = true;
+        } else if (std::isspace(static_cast<unsigned char>(c))) {
+            if (inToken) {
+                tokens.push_back(current);
+                current.clear();
+                inToken = false;
+            }
+        } else {
+            current.push_back(c);
+            inToken = true;
+        }
+    }
+
+    if (inQuotes) {
+        throw std::invalid_argument("Unterminated quote.");
+    }
+    if (inToken) {
+        tokens.push_back(current);
+    }
+    return tokens;
+}
+
+PartialLine splitPartial(const std::string& text) {
+    PartialLine result;
+    std::string current;
+    std::size_t currentStart = 0;
+    bool inToken = false;
+    bool inQuotes = false;
+
+    for (std::size_t i = 0; i < text.size(); ++i) {
+        const char c = text[i];
+        if (inQuotes) {
+            if (c == '"') {
+                inQuotes = false;
+            } else {
+                current.push_back(c);
+            }
+        } else if (c == '"') {
+            if (!inToken) {
+                inToken = true;
+                currentStart = i;
+            }
+            inQuotes = true;
+        } else if (std::isspace(static_cast<unsigned char>(c))) {
+            if (inToken) {
+                result.words.push_back(current);
+                current.clear();
+                inToken = false;
+            }
+        } else {
+            if (!inToken) {
+                inToken = true;
+                currentStart = i;
+            }
+            current.push_back(c);
+        }
+    }
+
+    if (inToken) {
+        result.current = current;
+        result.start = currentStart;
+    } else {
+        result.start = text.size();
+    }
+    return result;
+}
+
+}  // namespace Tokenizer
diff --git a/src/main.cpp b/src/main.cpp
new file mode 100644
index 0000000..46fe7b5
--- /dev/null
+++ b/src/main.cpp
@@ -0,0 +1,26 @@
+#include <exception>
+#include <iostream>
+#include <string>
+
+#include "Config.h"
+#include "Database.h"
+#include "Display.h"
+#include "Repl.h"
+
+int main(int argc, char** argv) {
+    const std::string path = (argc > 1) ? argv[1] : "tasks.db";
+
+    try {
+        Config config;
+        config.load();
+
+        Database db;
+        db.open(path);
+        Display display(db);
+        Repl repl(db, display, config);
+        return repl.run();
+    } catch (const std::exception& error) {
+        std::cerr << "Fatal: " << error.what() << "\n";
+        return 1;
+    }
+}