ODS import, persistence, scripting, connector types + VPX transforms.

- ODS importer (libzip + pugixml): each sheet → Part, rows → Pin/Signal.
- save / restore commands: tab-delimited snapshot of modules, parts,
  signals, connections + pin_map. `restore` replaces the System.
- source / script-save: replay a file of commands; record canonical
  commands since last `new` for replay later. Interactive screens
  refused during source. `explore` marked non-scriptable.
- TUI screen_explore: 4 columns (modules, type, children, detail) with
  filters on children and detail; detail is a Menu so arrows scroll
  long pin lists.
- Connector types & transforms: each Part carries a `connector_type`
  string. `set-type` validates the part's pin layout against the type
  (cols set check). `connect` strict pair: rejects when lookup falls
  back to identity unless types are both empty AND pin sets match.
- VPX 3U transforms: 3 registered pairs (vpx-3u-bkp-pN ↔ vpx-3u-payload-pN,
  N=0/1/2) with row-pattern correspondence tables ported from the user's
  Python reference.
- Code split for maintainability: src/tui/{shell,completion,commands,
  screen_main,screen_search,screen_connect,screen_settype,screen_explore,
  tui_helpers}.cpp.
- Bug fixes: Module::add(Part*) override sets part->prnt (was always
  null, breaking save's W lines). Defensive guards in explore against
  empty Menu lists. Renderer wrapped in try/catch so domain throws
  surface as on-screen errors instead of SIGABRT.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CLAUDE.md

@@ -12,6 +12,7 @@ cmake --build build -j
 
 - CMake **3.14+** required (uses `FetchContent_MakeAvailable`).
 - FTXUI is fetched at configure time from GitHub (`v6.1.9`, shallow clone). First configure pays ~20 s for the clone; subsequent ones are cached in `build/_deps/`.
+- **System dependencies** (resolved via `find_package`): `libzip` (target `libzip::zip`) and `pugixml` (target `pugixml::pugixml`). Used by the ODS importer. Available on Arch via `pacman -S libzip pugixml`.
 - Sources are collected with `file(GLOB_RECURSE ALL_SOURCES "src/*.cpp")`. **After adding a new `.cpp`, re-run `cmake -S . -B build`** — CMake does not re-glob automatically and link will fail with "undefined reference".
 
 ## Layout
@@ -31,8 +32,17 @@ src/
   imports/               -- adapters that populate the domain
     import_base.hpp        ImportBase interface
     import_mentor.{hpp,cpp} Mentor Graphics netlist parser (done)
-  tui/                   -- FTXUI shell
-    tui.{hpp,cpp}          Tui: visualisation area on top, input + history at the bottom
+  tui/                   -- FTXUI shell, split by responsibility
+    tui.{hpp,cpp}          Class Tui (state + Run() orchestrator + screen-mode event dispatcher)
+    tui_helpers.{hpp,cpp}  Free helpers: ToLower, NaturalLess, LongestCommonPrefix
+    shell.cpp              Print, Submit, Dispatch, Finalize, Tokenize, history persistence
+    completion.cpp         CompleteCommand, CompletePath, CompleteInline
+    commands.cpp           RegisterCommands (all built-in commands declared here)
+    screen_main.cpp        BuildMainScreen (visualisation area + bottom input)
+    screen_search.cpp      BuildSearchScreen
+    screen_connect.cpp     BuildConnectScreen + shared RefreshFilteredPartList helper
+    screen_settype.cpp     BuildSettypeScreen
+    screen_explore.cpp     BuildExploreScreen (browse modules → parts/signals/connections → details; not scriptable)
 doc/classes.puml         -- PlantUML class diagram
 ```
 
@@ -54,12 +64,36 @@ doc/classes.puml         -- PlantUML class diagram
 - `CatchEvent` is wrapped **outside** the `Renderer` (not between `Renderer` and `Input`). Pattern: `Renderer(input_component, lambda)` then `CatchEvent(renderer, handler)`. Wrapping `CatchEvent(input, …)` inside a `Container::Vertical({…})` and then `Renderer(container, …)` was found to break the `Input`'s content rendering on at least one terminal — typed characters didn't show even though `on_enter` fired correctly.
 - `InputOption::transform` is overridden to avoid hard-coded colors (default sets `White on Black` when focused, which is unreadable on light terminal themes). The custom transform only applies `dim` to the placeholder; everything else inherits terminal default fg/bg, so the UI adapts to any theme.
 - `InputOption::multiline` **must** be set to `false` for the command prompt. Default is `true`, and FTXUI's `HandleReturn()` then both inserts `\n` into the content **and** fires `on_enter` — so `Submit()` would receive `"help\n"` instead of `"help"` and command lookups would all fall through to "unknown command".
-- Commands live in a `std::map<std::string, CommandSpec>` registry built in `RegisterCommands()`. Each `CommandSpec` declares a list of `Param{name, path_completion}` and an `action(args)` lambda. `Dispatch(raw)` tokenises the input (whitespace split with `"…"` quoting), takes inline args first, and pushes a `Prompt` onto the queue for each missing param. The last prompt's callback calls `Finalize()`.
+- Commands live in a `std::map<std::string, CommandSpec>` registry built in `RegisterCommands()`. Each `CommandSpec` carries `params` (list of `Param{name, completion}` where `completion` is the `Tui::Completion` enum: `None | Path | Command`), an `action(args)` lambda, a `prompt_for_missing` bool (default `true`), a one-line `description` string, and a `scriptable` bool (default `true`). Setting `scriptable = false` (e.g. `explore`) excludes the command from the script-save buffer; if a non-scriptable command is invoked from a sourced file the `Source` loop still aborts via the `screen_idx != 0` check, since these commands are typically screen-openers. `Dispatch(raw)` tokenises the input (whitespace split with `"…"` quoting), takes inline args first, and (only when `prompt_for_missing`) pushes a `Prompt` onto the queue for each missing param. The last prompt's callback calls `Finalize()`. Set `prompt_for_missing = false` for commands that accept either zero args or a full arg list (e.g. `search`: bare → interactive, full → inline) — the action gets called immediately with whatever it received and decides what to do.
+- `Tab` completes by `Param::completion`: `Path` triggers `CompletePath()` (filesystem listing with `~/` expansion), `Command` triggers `CompleteCommand()` (matches against the registry), `None` does nothing. Both work inline (`CompleteInline()` figures out the arg position) and inside a multi-step prompt.
+- `help` (no args) iterates the registry and prints `name — description` for every command. `help <command>` describes a single command, including each `Param`'s name. The argument has `Completion::Command`, so `help <Tab>` lists registered commands.
 - `Finalize()` rebuilds the **canonical inline form** (`name arg1 "arg with spaces" arg3`) and writes that to history — so a `load` command answered via interactive prompts still shows up in `history` (and on disk) as a single inline line, ready to be replayed via ↑.
 - Multi-step prompts work via a `std::deque<Prompt>` queue. `Submit()` pops them one by one before falling back to dispatch. Adding a new command = one entry in `RegisterCommands()`; the prompt-flow and inline-flow are both handled automatically.
 - Tab completion: at the top-level prompt (no `pending`), completes built-in command names. Inside a prompt with `path_completion = true` (e.g. the `filename` step of `load`), completes file paths via `std::filesystem::directory_iterator` (handles `~/`, dirs get a trailing `/`). Logic: 1 match → replace; multiple with progress on the longest common prefix → extend; multiple stuck at LCP → list candidates in the visualisation area.
 
-Built-in commands: `new`, `load`, `search`, `clear`, `help`, `quit`/`exit`. `Esc` cancels an in-progress multi-step prompt.
+Built-in commands: `new`, `load`, `save`, `restore`, `source`, `script-save`, `connect`, `set-type`, `search`, `explore`, `clear`, `help`, `quit`/`exit`. `Esc` cancels an in-progress multi-step prompt.
+
+`script-save <file>` writes a replay-ready script of every command issued since the last `new` (the `recorded` buffer is cleared inside the `new` action). The buffer is appended to inside `Finalize()` after the action runs, with a denylist of commands that aren't useful in a replay: `clear`, `help`, `quit`, `exit`, `source`, `script-save`. Note the `source` exclusion: when a script is sourced, the *individual lines inside* the script are recorded (because each goes through `Finalize`), so the saved script reproduces the same end state without the indirection.
+
+`source <file>` reads a script line by line and feeds each line through `Submit()`. While the script is running, `in_source = true` is set on the `Tui` and:
+- `Dispatch` / `Finalize` skip writing to memory + on-disk history.
+- After each `Submit`, if `screen_idx != 0` (a screen was opened by an "interactive" command like bare `connect`/`search`/`set-type`), the script is aborted with an error message and `screen_idx` is reset to 0 — interactive screen-opening commands are explicitly disallowed in scripts.
+
+Pending prompts (from incomplete inline commands) are NOT considered interactive and are filled by subsequent script lines, the way you'd expect. Lines starting with `#` and blank lines are skipped; leading/trailing whitespace is trimmed; `~/` is expanded.
+
+`save` / `restore` (`src/system/persist.{hpp,cpp}`): tab-delimited line format, no extra deps. Tags: `M` (module), `P` (part with `connector_type`), `N` (pin → signal name; empty = NC), `C` (connection header with endpoints + `transform_name`), `W` (wire pair within the current connection). `restore` replaces `Tui::sys` entirely (`unique_ptr::reset`). Names are stored as-is — must not contain TAB or newline (true for the EE netlists we ingest). Format is versioned by the `# essim system snapshot v1` header for future compatibility.
+
+**Connector types & transforms**: every `Part` carries a `connector_type` string (default `""`, set via the `set-type` command — inline `set-type m p kind` or bare which opens a TUI screen with module menu, part filter+menu, type input, list of types already in use, and an Apply button). When `connect` validates a pair, it consults `TransformRegistry::lookup(p1->connector_type, p2->connector_type)` (defined in `src/system/transform.{hpp,cpp}`) — both directions of the pair are tried. If neither is registered, an `IdentityTransform` fallback wires each pin of A to the same-name pin of B (when present). The resulting `(Pin*, Pin*)` list and the transform's name are stored on the `Connection` (`pin_map`, `transform_name`). To register a real transform: define a `Transform` subclass in `transform.cpp` and call `TransformRegistry::get().add("kindA", "kindB", new MyTransform())` at init — there's no startup hook for this yet, so a small `RegisterBuiltinTransforms()` helper is the natural place to add when more types appear.
+
+`screen_idx` mapping: 0 = main TUI, 1 = search, 2 = connect, 3 = set-type. Adding a new screen mode is the same recipe each time: state members, `Container::Vertical` of focusable components, a `Renderer` lambda that recomputes derived state per frame (e.g. filtered part lists), an entry in `Container::Tab`, and Tab/Esc handling in the outer `CatchEvent`.
+
+`connect` is dual-mode (`prompt_for_missing = false`):
+- Inline: `connect m1 p1 m2 p2`. Each part argument is resolved as exact name first, then case-insensitive substring; ambiguous → lists candidates and aborts.
+- Bare: opens a dedicated full-screen layout (`screen_idx = 2`) with two columns (`endpoint 1` / `endpoint 2`). Each column has a module `Menu`, a part filter `Input`, and a filtered part `Menu`. A `Button(" Connect ")` at the bottom commits. `Tab` cycles focus across the 7 components, `Esc` leaves.
+
+The connect screen rebuilds the filtered part lists inside the `Renderer` lambda each frame (cheap; lets the part menus react live to module changes and filter typing). Selection indices are clamped if a list shrinks below the previous index.
+
+The Connection record stores `Module*`/`Part*` for both endpoints (added to `Connection` for this — minimal struct fields, no behaviour change).
 
 `search` switches to a second full-screen layout (handled by `Container::Tab({main, search}, &screen_idx)`). Layout:
 - Left column: `Menu` for the module list and `Menu` for the type (`parts` / `signals`).
@@ -67,7 +101,7 @@ Built-in commands: `new`, `load`, `search`, `clear`, `help`, `quit`/`exit`. `Esc
 - `Tab` cycles focus between the query input and the menus. **Implemented manually** in the outer `CatchEvent`: `Menu::OnEvent` consumes `Event::Tab` to cycle its own entries and returns `true`, which prevents `Container::Vertical` from ever seeing the event (Container only cycles between children when the active child returns `false`). So we short-circuit Tab/TabReverse upstream and mutate `search_focus_idx` directly.
 - `Esc` exits the search mode (flips `screen_idx` back to 0). The search state (selected module/type, query) is preserved across re-entries until `search` is run again.
 
-Adding a new screen mode = add a child to `Container::Tab` and a `screen_idx` value; key handling already lives in the outer `CatchEvent`.
+Adding a new screen mode = drop a `screen_<name>.cpp` defining `Component Tui::BuildXxxScreen()`, add corresponding state members in `tui.hpp`, register a `BuildXxxScreen` declaration in the screen-builders block, then in `tui.cpp::Run()` add a child to `Container::Tab` and a case in the screen-mode `switch` of the outer `CatchEvent` (Tab cycling + Esc-leave). Commands lived in `commands.cpp` set `screen_idx` to enter the new mode.
 
 Command history is persisted on disk and loaded on startup. Path resolution is platform-aware:
 - Linux/macOS: `$XDG_DATA_HOME/essim/history`, falling back to `~/.local/share/essim/history`.
@@ -77,7 +111,8 @@ Each successful submission appends a single line to the file (so a crash doesn't
 
 ## Gotchas
 
-- `System::Load` for `IMPORT_ALTIUM` / `IMPORT_ODS`: the corresponding constructor lines are commented out, so `imp` stays uninitialised → UB on `imp->parse(...)`. Only `IMPORT_MENTOR` is safe today. Wrap calls in `try/catch` (the TUI does).
+- `System::Load` for `IMPORT_ALTIUM`: the corresponding constructor line is still commented out, so `imp` stays uninitialised → UB on `imp->parse(...)`. `IMPORT_MENTOR` and `IMPORT_ODS` are wired. Wrap calls in `try/catch` (the TUI does).
+- ODS importer: each spreadsheet sheet becomes a `Part` (sheet name = part name). Rows are pin/signal pairs; the **first non-empty row of each sheet is dropped as a header** (no validation of header content). Empty cells skip the row; `"NC"` keeps the pin in the part but doesn't connect it to a signal. Pins or parts whose name collides (rare in well-formed sheets) are silently dropped.
 - `System::Load` throws `std::runtime_error("Unknown import type")` for any value outside the three enum cases.
 - `Modules`/`Parts`/etc. have no const-correct iteration on the `*` accessor; iterators on `SystemElementContainer<T>` are available but `begin()`/`end()` are non-const-safe in some places.
 

CMakeLists.txt

@@ -23,6 +23,9 @@ FetchContent_Declare(ftxui
 )
 FetchContent_MakeAvailable(ftxui)
 
+find_package(libzip REQUIRED)
+find_package(pugixml REQUIRED)
+
 file(GLOB_RECURSE ALL_SOURCES "src/*.cpp")
 
 add_executable(essim ${ALL_SOURCES})
@@ -34,4 +37,6 @@ target_link_libraries(essim
     ftxui::screen
     ftxui::dom
     ftxui::component
+    libzip::zip
+    pugixml::pugixml
 )

src/imports/import_ods.cpp

@@ -0,0 +1,121 @@
+#include "import_ods.hpp"
+
+#include "system/parts.hpp"
+#include "system/pins.hpp"
+#include "system/signals.hpp"
+
+#include <pugixml.hpp>
+#include <zip.h>
+
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+ImportOds::ImportOds(std::string filename)
+    : ImportBase(filename), filename_(std::move(filename)) {}
+
+static std::string read_content_xml(const std::string &filename)
+{
+    int err = 0;
+    zip_t *zip = zip_open(filename.c_str(), ZIP_RDONLY, &err);
+    if (!zip) throw std::runtime_error("ods: cannot open " + filename);
+
+    zip_stat_t st;
+    if (zip_stat(zip, "content.xml", 0, &st) != 0) {
+        zip_close(zip);
+        throw std::runtime_error("ods: missing content.xml in " + filename);
+    }
+
+    zip_file_t *f = zip_fopen(zip, "content.xml", 0);
+    if (!f) {
+        zip_close(zip);
+        throw std::runtime_error("ods: cannot read content.xml");
+    }
+
+    std::string out;
+    out.resize(static_cast<size_t>(st.size));
+    zip_int64_t n = zip_fread(f, out.data(), st.size);
+    zip_fclose(f);
+    zip_close(zip);
+    if (n < 0) throw std::runtime_error("ods: read failed");
+    out.resize(static_cast<size_t>(n));
+    return out;
+}
+
+static std::string cell_text(pugi::xml_node cell)
+{
+    std::string out;
+    for (auto p : cell.children("text:p")) {
+        if (!out.empty()) out += " ";
+        for (auto n : p.children()) {
+            if (n.type() == pugi::node_pcdata) out += n.value();
+        }
+    }
+    return out;
+}
+
+static std::vector<std::string> expand_row(pugi::xml_node row)
+{
+    std::vector<std::string> cells;
+    for (auto cell : row.children()) {
+        std::string n = cell.name();
+        if (n != "table:table-cell" && n != "table:covered-table-cell") continue;
+        int rep = cell.attribute("table:number-columns-repeated").as_int(1);
+        std::string v = cell_text(cell);
+        for (int i = 0; i < rep; ++i) cells.push_back(v);
+    }
+    while (!cells.empty() && cells.back().empty()) cells.pop_back();
+    return cells;
+}
+
+void ImportOds::parse(Signals *signals)
+{
+    std::string xml = read_content_xml(filename_);
+
+    pugi::xml_document doc;
+    auto res = doc.load_string(xml.c_str());
+    if (!res) {
+        throw std::runtime_error(std::string("ods: xml parse: ") + res.description());
+    }
+
+    auto spreadsheet = doc.child("office:document-content")
+                          .child("office:body")
+                          .child("office:spreadsheet");
+    if (!spreadsheet) {
+        throw std::runtime_error("ods: no spreadsheet found");
+    }
+
+    for (auto t : spreadsheet.children("table:table")) {
+        std::string sheet = t.attribute("table:name").value();
+        if (sheet.empty()) continue;
+
+        Part *prt = new Part(sheet);
+        bool first_data = true;
+
+        for (auto row : t.children("table:table-row")) {
+            auto cells = expand_row(row);
+            if (cells.size() < 2) continue;
+
+            // Skip the first non-empty row (header).
+            if (first_data) { first_data = false; continue; }
+
+            const std::string &pin_name = cells[0];
+            const std::string &sig_name = cells[1];
+            if (pin_name.empty() || sig_name.empty()) continue;
+
+            Pin *pin = new Pin(pin_name);
+            try { prt->add(pin); }
+            catch (const std::exception &) { delete pin; continue; }
+
+            // "NC" = Not Connected: keep the pin in the part, no signal hookup.
+            if (sig_name == "NC") continue;
+
+            Signal *s = signals->merge(sig_name);
+            s->add(pin);
+            pin->connect(s);
+        }
+
+        try { prts->add(prt); }
+        catch (const std::exception &) { delete prt; }
+    }
+}

src/imports/import_ods.hpp

@@ -0,0 +1,15 @@
+#ifndef _IMPORT_ODS_HPP_
+#define _IMPORT_ODS_HPP_
+
+#include "import_base.hpp"
+
+class ImportOds : public ImportBase
+{
+    std::string filename_;
+
+public:
+    ImportOds(std::string filename);
+    void parse(Signals *signals) override;
+};
+
+#endif // _IMPORT_ODS_HPP_

src/system/connect.cpp

@@ -1,6 +1,10 @@
 #include "connect.hpp"
 
-Connection::Connection(std::string name) : SystemElement(name) {};
+Connection::Connection(std::string name)
+    : SystemElement(name), m1(nullptr), p1(nullptr), m2(nullptr), p2(nullptr) {}
+
+Connection::Connection(std::string name, Module *m1, Part *p1, Module *m2, Part *p2)
+    : SystemElement(name), m1(m1), p1(p1), m2(m2), p2(p2) {}
 
 Connections::Connections(void): SystemElementContainer<Connection>("connections") {}
 

src/system/connect.hpp

@@ -3,10 +3,25 @@
 
 #include "syselmts.hpp"
 
+#include <utility>
+#include <vector>
+
+class Module;
+class Part;
+class Pin;
+
 class Connection : public SystemElement
 {
 public:
+    Module *m1;
+    Part *p1;
+    Module *m2;
+    Part *p2;
+    std::string transform_name;
+    std::vector<std::pair<Pin *, Pin *>> pin_map;
+
     Connection(std::string name);
+    Connection(std::string name, Module *m1, Part *p1, Module *m2, Part *p2);
 };
 
 class Connections : public SystemElementContainer<Connection>

src/system/modules.cpp

@@ -13,6 +13,11 @@ Module::~Module() {
     delete signals;
 }
 
+void Module::add(Part *part) {
+    SystemElementContainer<Part>::add(part);
+    part->prnt = this;
+}
+
 Modules::Modules(void): SystemElementContainer<Module>("modules") {}
 
 Modules::Modules(std::vector<Module *> modules): SystemElementContainer<Module>("modules", modules) {}

src/system/modules.hpp

@@ -16,6 +16,8 @@ public:
     Modules *prnt;
     Module(std::string name);
     ~Module();
+    using SystemElementContainer<Part>::add;
+    void add(Part *part) override;
 };
 
 class Modules : public SystemElementContainer<Module>
@@ -27,4 +29,5 @@ public:
     ~Modules();
 };
 
+
 #endif // _MODULES_HPP_

src/system/parts.cpp

@@ -1,6 +1,6 @@
 #include "parts.hpp"
 
-Part::Part(std::string name) : SystemElementContainer<Pin>(name), prnt(nullptr) {};
+Part::Part(std::string name) : SystemElementContainer<Pin>(name), prnt(nullptr), connector_type() {};
 
 void Part::add(Pin *pin)
 {

src/system/parts.hpp

@@ -13,6 +13,7 @@ public:
     Part(std::string name);
     ~Part();
     Module *prnt; ///< Pointer to the parent module.
+    std::string connector_type; ///< Tag used by the transform registry; empty = untyped.
     void add(Pin *pin) override;
 };
 

src/system/persist.cpp

@@ -0,0 +1,153 @@
+#include "persist.hpp"
+
+#include "connect.hpp"
+#include "modules.hpp"
+#include "parts.hpp"
+#include "pins.hpp"
+#include "signals.hpp"
+#include "system.hpp"
+
+#include <fstream>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+namespace {
+
+// Tab-delimited tokeniser. Empty trailing fields are preserved.
+std::vector<std::string> split_tab(const std::string &line) {
+    std::vector<std::string> out;
+    std::string cur;
+    for (char c : line) {
+        if (c == '\t') { out.push_back(std::move(cur)); cur.clear(); }
+        else cur.push_back(c);
+    }
+    out.push_back(std::move(cur));
+    return out;
+}
+
+}  // namespace
+
+bool save_system(const System *sys, const std::string &filename, std::string &error)
+{
+    if (!sys) { error = "no system to save"; return false; }
+    std::ofstream f(filename);
+    if (!f) { error = "cannot open " + filename + " for writing"; return false; }
+
+    f << "# essim system snapshot v1\n";
+
+    for (auto &mkv : *sys->modules()) {
+        Module *mod = mkv.second;
+        f << "M\t" << mod->name << "\n";
+        for (auto &pkv : *mod) {
+            Part *p = pkv.second;
+            f << "P\t" << p->name << "\t" << p->connector_type << "\n";
+            for (auto &nkv : *p) {
+                Pin *pin = nkv.second;
+                Signal *s = pin->signal();
+                f << "N\t" << pin->name << "\t" << (s ? s->name : "") << "\n";
+            }
+        }
+    }
+
+    for (auto &ckv : *sys->connections()) {
+        Connection *c = ckv.second;
+        f << "C\t" << c->name
+          << "\t" << (c->m1 ? c->m1->name : "")
+          << "\t" << (c->p1 ? c->p1->name : "")
+          << "\t" << (c->m2 ? c->m2->name : "")
+          << "\t" << (c->p2 ? c->p2->name : "")
+          << "\t" << c->transform_name << "\n";
+        for (auto &wp : c->pin_map) {
+            Pin *a = wp.first;
+            Pin *b = wp.second;
+            f << "W"
+              << "\t" << (a && a->prnt && a->prnt->prnt ? a->prnt->prnt->name : "")
+              << "\t" << (a && a->prnt ? a->prnt->name : "")
+              << "\t" << (a ? a->name : "")
+              << "\t" << (b && b->prnt && b->prnt->prnt ? b->prnt->prnt->name : "")
+              << "\t" << (b && b->prnt ? b->prnt->name : "")
+              << "\t" << (b ? b->name : "")
+              << "\n";
+        }
+    }
+    return f.good();
+}
+
+System *restore_system(const std::string &filename, std::string &error)
+{
+    std::ifstream f(filename);
+    if (!f) { error = "cannot open " + filename; return nullptr; }
+
+    System *sys = new System();
+    Module *cur_mod = nullptr;
+    Part *cur_part = nullptr;
+    Connection *cur_conn = nullptr;
+
+    std::string line;
+    int lineno = 0;
+
+    auto fail = [&](const std::string &msg) {
+        error = "line " + std::to_string(lineno) + ": " + msg;
+        delete sys;
+        return nullptr;
+    };
+
+    while (std::getline(f, line)) {
+        ++lineno;
+        if (line.empty() || line[0] == '#') continue;
+        auto fs = split_tab(line);
+        if (fs.empty()) continue;
+        const std::string &tag = fs[0];
+
+        try {
+            if (tag == "M") {
+                if (fs.size() < 2) return fail("M needs <name>");
+                cur_mod = sys->modules()->merge(fs[1]);
+                cur_part = nullptr;
+            } else if (tag == "P") {
+                if (!cur_mod) return fail("P outside module");
+                if (fs.size() < 2) return fail("P needs <name>");
+                cur_part = new Part(fs[1]);
+                if (fs.size() >= 3) cur_part->connector_type = fs[2];
+                cur_mod->add(cur_part);
+            } else if (tag == "N") {
+                if (!cur_part || !cur_mod) return fail("N outside part");
+                if (fs.size() < 3) return fail("N needs <pin> <signal>");
+                Pin *pin = new Pin(fs[1]);
+                cur_part->add(pin);
+                if (!fs[2].empty()) {
+                    Signal *s = cur_mod->signals->merge(fs[2]);
+                    s->add(pin);
+                    pin->connect(s);
+                }
+            } else if (tag == "C") {
+                if (fs.size() < 7) return fail("C needs <name> <m1> <p1> <m2> <p2> <transform>");
+                Module *m1 = sys->modules()->get(fs[2]);
+                Module *m2 = sys->modules()->get(fs[4]);
+                Part *p1 = m1->get(fs[3]);
+                Part *p2 = m2->get(fs[5]);
+                cur_conn = new Connection(fs[1], m1, p1, m2, p2);
+                cur_conn->transform_name = fs[6];
+                sys->connections()->add(cur_conn);
+            } else if (tag == "W") {
+                if (!cur_conn) return fail("W outside connection");
+                if (fs.size() < 7) return fail("W needs <m1> <p1> <pin1> <m2> <p2> <pin2>");
+                Module *m1 = sys->modules()->get(fs[1]);
+                Module *m2 = sys->modules()->get(fs[4]);
+                Part *p1 = m1->get(fs[2]);
+                Part *p2 = m2->get(fs[5]);
+                Pin *pin1 = p1->get(fs[3]);
+                Pin *pin2 = p2->get(fs[6]);
+                cur_conn->pin_map.emplace_back(pin1, pin2);
+            } else {
+                return fail("unknown tag '" + tag + "'");
+            }
+        } catch (const std::exception &e) {
+            return fail(std::string(tag) + ": " + e.what());
+        }
+    }
+
+    return sys;
+}

src/system/persist.hpp

@@ -0,0 +1,16 @@
+#ifndef _PERSIST_HPP_
+#define _PERSIST_HPP_
+
+#include <string>
+
+class System;
+
+// Writes the system to `filename` using a tab-delimited line format.
+// Returns true on success; on failure, sets `error` and returns false.
+bool save_system(const System *sys, const std::string &filename, std::string &error);
+
+// Loads a system snapshot from `filename`. On success, returns a freshly allocated
+// System (caller takes ownership). On failure, returns nullptr and sets `error`.
+System *restore_system(const std::string &filename, std::string &error);
+
+#endif // _PERSIST_HPP_

src/system/pins.hpp

@@ -16,6 +16,7 @@ public:
     Pin(std::string name);
     Part *prnt; ///< Pointer to the parent part.
     bool connected();
+    Signal *signal() const { return sig; }
     void connect(Signal *signal);
 };
 

src/system/system.cpp

@@ -4,6 +4,7 @@
 #include "connect.hpp"
 #include "modules.hpp"
 #include "imports/import_mentor.hpp"
+#include "imports/import_ods.hpp"
 
 System::System() : mods(nullptr), conns(nullptr)
 {
@@ -35,7 +36,7 @@ void System::Load(std::string module_name, std::string file_name, ImportType typ
         // imp = new ImportAltium(file_name);
     } else if (type == ImportType::IMPORT_ODS)
     {
-        // imp = new ImportOds(file_name);
+        imp = new ImportOds(file_name);
     }
     else
     {

src/system/system.hpp

@@ -23,6 +23,7 @@ public:
     System();
     void Load(std::string module_name, std::string filename, ImportType type);
     Modules *modules() const { return mods; }
+    Connections *connections() const { return conns; }
     ~System();
 };
 

src/system/transform.cpp

@@ -0,0 +1,90 @@
+#include "transform.hpp"
+
+#include "parts.hpp"
+#include "pins.hpp"
+#include "transform_vpx.hpp"
+
+#include <set>
+#include <vector>
+
+#include <exception>
+#include <utility>
+
+Transform::Transform(std::string name) : name(std::move(name)) {}
+
+std::string CheckIdentityCompatible(const Part *a, const Part *b)
+{
+    if (!a || !b) return "missing part";
+    std::set<std::string> a_pins, b_pins;
+    for (auto &kv : *a) a_pins.insert(kv.first);
+    for (auto &kv : *b) b_pins.insert(kv.first);
+    if (a_pins == b_pins) return "";
+
+    std::vector<std::string> only_a, only_b;
+    for (const auto &n : a_pins) if (!b_pins.count(n)) only_a.push_back(n);
+    for (const auto &n : b_pins) if (!a_pins.count(n)) only_b.push_back(n);
+
+    std::string msg = "identity wiring requires same pin names on both sides";
+    if (!only_a.empty())
+        msg += "; only on '" + a->name + "': "
+             + std::to_string(only_a.size()) + " (e.g. " + only_a.front() + ")";
+    if (!only_b.empty())
+        msg += "; only on '" + b->name + "': "
+             + std::to_string(only_b.size()) + " (e.g. " + only_b.front() + ")";
+    return msg;
+}
+
+IdentityTransform::IdentityTransform() : Transform("identity") {}
+
+std::vector<std::pair<Pin *, Pin *>> IdentityTransform::apply(Part *a, Part *b) const
+{
+    std::vector<std::pair<Pin *, Pin *>> out;
+    for (auto &kv : *a) {
+        try {
+            Pin *pb = b->get(kv.first);
+            out.emplace_back(kv.second, pb);
+        } catch (const std::exception &) {
+            // No same-name pin on the other side — skip.
+        }
+    }
+    return out;
+}
+
+TransformRegistry::TransformRegistry() : identity_(new IdentityTransform()) {
+    RegisterVpxTransforms(*this);
+}
+
+TransformRegistry::~TransformRegistry()
+{
+    for (auto &kv : entries) delete kv.second;
+    delete identity_;
+}
+
+TransformRegistry &TransformRegistry::get()
+{
+    static TransformRegistry instance;
+    return instance;
+}
+
+void TransformRegistry::add(const std::string &kA, const std::string &kB, Transform *t)
+{
+    auto key = std::make_pair(kA, kB);
+    auto it = entries.find(key);
+    if (it != entries.end()) {
+        delete it->second;
+        it->second = t;
+    } else {
+        entries.emplace(key, t);
+    }
+}
+
+Transform *TransformRegistry::lookup(const std::string &kA, const std::string &kB) const
+{
+    auto it = entries.find({kA, kB});
+    if (it != entries.end()) return it->second;
+    auto it2 = entries.find({kB, kA});
+    if (it2 != entries.end()) return it2->second;
+    return identity_;
+}
+
+Transform *TransformRegistry::identity() const { return identity_; }

src/system/transform.hpp

@@ -0,0 +1,56 @@
+#ifndef _TRANSFORM_HPP_
+#define _TRANSFORM_HPP_
+
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+class Part;
+class Pin;
+
+// A Transform describes how a connector pair maps pins between two Parts.
+// Returning the list of (pin on side A, pin on side B) wired by this connection
+// is enough to record the wiring on the Connection.
+// Returns "" if a and b have identical pin name sets (so the identity
+// fallback would wire every pin), otherwise a description of the mismatch.
+std::string CheckIdentityCompatible(const Part *a, const Part *b);
+
+class Transform
+{
+public:
+    std::string name;
+    explicit Transform(std::string name);
+    virtual ~Transform() = default;
+    virtual std::vector<std::pair<Pin *, Pin *>> apply(Part *a, Part *b) const = 0;
+};
+
+// Identity: each pin on A is wired to the same-named pin on B, when present.
+// Used as the fallback when no specific transform is registered for the pair.
+class IdentityTransform : public Transform
+{
+public:
+    IdentityTransform();
+    std::vector<std::pair<Pin *, Pin *>> apply(Part *a, Part *b) const override;
+};
+
+class TransformRegistry
+{
+    std::map<std::pair<std::string, std::string>, Transform *> entries;
+    Transform *identity_;
+    TransformRegistry();
+    ~TransformRegistry();
+
+public:
+    static TransformRegistry &get();
+    void add(const std::string &kindA, const std::string &kindB, Transform *t);
+    // Returns the transform registered for (kindA, kindB). If neither (kindA, kindB)
+    // nor (kindB, kindA) is registered, returns the identity transform.
+    Transform *lookup(const std::string &kindA, const std::string &kindB) const;
+    Transform *identity() const;
+
+    TransformRegistry(const TransformRegistry &) = delete;
+    TransformRegistry &operator=(const TransformRegistry &) = delete;
+};
+
+#endif // _TRANSFORM_HPP_

src/system/transform_vpx.cpp

@@ -0,0 +1,204 @@
+#include "transform_vpx.hpp"
+
+#include "parts.hpp"
+#include "pins.hpp"
+
+#include <cctype>
+#include <exception>
+#include <set>
+#include <string>
+#include <utility>
+
+VpxTransform::VpxTransform(std::string name,
+                           std::string bkp_kind, std::string payload_kind,
+                           std::vector<ColTable> bkp_to_payload,
+                           std::vector<ColTable> payload_to_bkp)
+    : Transform(std::move(name)),
+      bkp_kind_(std::move(bkp_kind)),
+      payload_kind_(std::move(payload_kind)),
+      bkp_to_payload_(std::move(bkp_to_payload)),
+      payload_to_bkp_(std::move(payload_to_bkp)) {}
+
+namespace {
+
+struct ParsedPin {
+    char col;             // single-letter column
+    int row;              // numeric row (1-based)
+    std::string digits;   // original digit string (preserves leading zeros)
+    bool ok = false;
+};
+
+ParsedPin parse_pin(const std::string &name) {
+    ParsedPin out;
+    size_t i = 0;
+    while (i < name.size() && std::isalpha((unsigned char)name[i])) ++i;
+    if (i != 1) return out;  // single letter only (VPX 3U convention)
+    if (i == name.size()) return out;
+    for (size_t k = i; k < name.size(); ++k)
+        if (!std::isdigit((unsigned char)name[k])) return out;
+    out.col = (char)std::toupper((unsigned char)name[0]);
+    out.digits = name.substr(i);
+    try { out.row = std::stoi(out.digits); }
+    catch (const std::exception &) { return out; }
+    if (out.row <= 0) return out;
+    out.ok = true;
+    return out;
+}
+
+// Try to find a pin in `to` whose name matches the new column + the source
+// row, allowing for either the source's exact digit-string or the canonical
+// integer form (so "C01" finds either "C01" or "C1").
+Pin *find_target_pin(Part *to, char col, int row, const std::string &digits) {
+    std::string s1 = std::string(1, col) + digits;
+    try { return to->get(s1); } catch (const std::exception &) {}
+    std::string s2 = std::string(1, col) + std::to_string(row);
+    if (s2 != s1) {
+        try { return to->get(s2); } catch (const std::exception &) {}
+    }
+    return nullptr;
+}
+
+}  // namespace
+
+std::vector<std::pair<Pin *, Pin *>> VpxTransform::apply(Part *a, Part *b) const
+{
+    std::vector<std::pair<Pin *, Pin *>> out;
+    if (!a || !b) return out;
+
+    bool a_is_bkp;
+    if (a->connector_type == bkp_kind_ && b->connector_type == payload_kind_)
+        a_is_bkp = true;
+    else if (a->connector_type == payload_kind_ && b->connector_type == bkp_kind_)
+        a_is_bkp = false;
+    else
+        return out;  // not our pair
+
+    const std::vector<ColTable> &table = a_is_bkp ? bkp_to_payload_ : payload_to_bkp_;
+    if (table.empty()) return out;
+
+    for (auto &kv : *a) {
+        Pin *a_pin = kv.second;
+        ParsedPin p = parse_pin(kv.first);
+        if (!p.ok) continue;
+
+        size_t pat_idx = (size_t)((p.row - 1) % (int)table.size());
+        const ColTable &t = table[pat_idx];
+        auto it = t.find(p.col);
+        if (it == t.end()) continue;
+        char new_col = it->second;
+
+        Pin *b_pin = find_target_pin(b, new_col, p.row, p.digits);
+        if (!b_pin) continue;
+
+        out.emplace_back(a_pin, b_pin);
+    }
+    return out;
+}
+
+// ---- Built-in tables (translated verbatim from the user's Python reference) ----
+
+namespace {
+
+using Tbl = VpxTransform::ColTable;
+using Pat = std::vector<Tbl>;
+
+// Connector 0: 8 row-patterns each side.
+const Pat bkp_to_payload_0 = {
+    {{'A','A'},{'B','C'},{'C','C'},{'D','C'},{'E','D'},{'F','E'},{'G','E'},{'H','F'},{'I','G'}},
+    {{'A','A'},{'B','C'},{'C','C'},{'D','C'},{'E','D'},{'F','E'},{'G','E'},{'H','F'},{'I','G'}},
+    {{'A','A'},{'B','C'},{'C','C'},{'D','C'},{'E','D'},{'F','E'},{'G','E'},{'H','F'},{'I','G'}},
+    {{'A','C'},{'B','A'},{'C','B'},{'D','C'},{'E','D'},{'F','E'},{'G','F'},{'H','G'},{'I','E'}},
+    {{'A','C'},{'B','A'},{'C','B'},{'D','C'},{'E','D'},{'F','E'},{'G','F'},{'H','G'},{'I','E'}},
+    {{'A','C'},{'B','A'},{'C','B'},{'D','C'},{'E','D'},{'F','E'},{'G','F'},{'H','G'},{'I','E'}},
+    {{'A','A'},{'B','B'},{'C','C'},{'D','C'},{'E','D'},{'F','E'},{'G','F'},{'H','F'},{'I','G'}},
+    {{'A','A'},{'B','A'},{'C','B'},{'D','C'},{'E','D'},{'F','D'},{'G','E'},{'H','F'},{'I','G'}},
+};
+const Pat payload_to_bkp_0 = {
+    {{'A','A'},{'B','B'},{'C','C'},{'D','E'},{'E','G'},{'F','H'},{'G','I'}},
+    {{'A','A'},{'B','B'},{'C','C'},{'D','E'},{'E','G'},{'F','H'},{'G','I'}},
+    {{'A','A'},{'B','B'},{'C','C'},{'D','E'},{'E','G'},{'F','H'},{'G','I'}},
+    {{'A','B'},{'B','C'},{'C','D'},{'D','E'},{'E','F'},{'F','G'},{'G','H'}},
+    {{'A','B'},{'B','C'},{'C','D'},{'D','E'},{'E','F'},{'F','G'},{'G','H'}},
+    {{'A','B'},{'B','C'},{'C','D'},{'D','E'},{'E','F'},{'F','G'},{'G','H'}},
+    {{'A','A'},{'B','B'},{'C','C'},{'D','E'},{'E','F'},{'F','G'},{'G','I'}},
+    {{'A','B'},{'B','C'},{'C','D'},{'D','E'},{'E','G'},{'F','H'},{'G','I'}},
+};
+
+// Connectors 1 and 2: 2 row-patterns each side.
+const Pat bkp_to_payload_aux = {
+    {{'A','A'},{'B','B'},{'C','C'},{'D','C'},{'E','D'},{'F','E'},{'G','F'},{'H','F'},{'I','G'}},
+    {{'A','A'},{'B','A'},{'C','B'},{'D','C'},{'E','D'},{'F','D'},{'G','E'},{'H','F'},{'I','G'}},
+};
+const Pat payload_to_bkp_aux = {
+    {{'A','A'},{'B','B'},{'C','C'},{'D','E'},{'E','F'},{'F','G'},{'G','I'}},
+    {{'A','A'},{'B','C'},{'C','D'},{'D','E'},{'E','G'},{'F','H'},{'G','I'}},
+};
+
+}  // namespace
+
+namespace {
+
+// Returns the set of acceptable column letters for a known VPX kind, or
+// an empty set when `kind` is unknown (no built-in layout to enforce).
+std::set<char> expected_cols(const std::string &kind) {
+    if (kind == "vpx-3u-bkp-p0"
+        || kind == "vpx-3u-bkp-p1"
+        || kind == "vpx-3u-bkp-p2") {
+        return {'A','B','C','D','E','F','G','H','I'};
+    }
+    if (kind == "vpx-3u-payload-p0"
+        || kind == "vpx-3u-payload-p1"
+        || kind == "vpx-3u-payload-p2") {
+        return {'A','B','C','D','E','F','G'};
+    }
+    return {};
+}
+
+}  // namespace
+
+std::string ValidatePartForKind(const Part *p, const std::string &kind)
+{
+    if (!p) return "no part";
+    auto cols = expected_cols(kind);
+    if (cols.empty()) return "";  // unknown kind → caller handles freely
+
+    int bad_count = 0;
+    std::string sample;
+    std::set<char> seen;
+    for (auto &kv : *const_cast<Part*>(p)) {
+        ParsedPin pp = parse_pin(kv.first);
+        if (!pp.ok || !cols.count(pp.col)) {
+            ++bad_count;
+            if (sample.empty()) sample = kv.first;
+            continue;
+        }
+        seen.insert(pp.col);
+    }
+    if (bad_count > 0) {
+        return std::to_string(bad_count) + " pin(s) don't fit the '" + kind
+             + "' layout (e.g. '" + sample + "'); expected single-letter columns "
+             + "{" + std::string(cols.begin(), cols.end()) + "}.";
+    }
+    if (seen != cols) {
+        std::string missing;
+        for (char c : cols) if (!seen.count(c)) missing += c;
+        return "missing pin column(s) for '" + kind + "': " + missing;
+    }
+    return "";
+}
+
+void RegisterVpxTransforms(TransformRegistry &reg)
+{
+    reg.add("vpx-3u-bkp-p0", "vpx-3u-payload-p0",
+        new VpxTransform("vpx-3u-p0",
+                         "vpx-3u-bkp-p0", "vpx-3u-payload-p0",
+                         bkp_to_payload_0, payload_to_bkp_0));
+    reg.add("vpx-3u-bkp-p1", "vpx-3u-payload-p1",
+        new VpxTransform("vpx-3u-p1",
+                         "vpx-3u-bkp-p1", "vpx-3u-payload-p1",
+                         bkp_to_payload_aux, payload_to_bkp_aux));
+    reg.add("vpx-3u-bkp-p2", "vpx-3u-payload-p2",
+        new VpxTransform("vpx-3u-p2",
+                         "vpx-3u-bkp-p2", "vpx-3u-payload-p2",
+                         bkp_to_payload_aux, payload_to_bkp_aux));
+}

src/system/transform_vpx.hpp

@@ -0,0 +1,52 @@
+#ifndef _TRANSFORM_VPX_HPP_
+#define _TRANSFORM_VPX_HPP_
+
+#include "transform.hpp"
+
+#include <map>
+#include <string>
+#include <vector>
+
+// 3U-VPX connector pin-name transform.
+//
+// Each VPX 3U slot has 3 connectors per side: backplane (P0/P1/P2) and
+// payload (J0/J1/J2). The pin-name correspondence between the two sides
+// is *not* identity (differential-pair routing makes 9 backplane columns
+// map onto 7 payload columns, and the mapping cycles on a row-pattern
+// basis that depends on which connector index we're on).
+//
+// One VpxTransform handles a single connector index (0, 1 or 2). Three
+// instances are registered at startup, under the type pairs
+//   (vpx-3u-bkp-N, vpx-3u-payload-N)
+// for N in {0, 1, 2}. Tag each Part with the correct connector_type via
+// `set-type`, then `connect` will pick the right transform automatically.
+class VpxTransform : public Transform
+{
+public:
+    using ColTable = std::map<char, char>;
+
+    VpxTransform(std::string name,
+                 std::string bkp_kind, std::string payload_kind,
+                 std::vector<ColTable> bkp_to_payload,
+                 std::vector<ColTable> payload_to_bkp);
+
+    std::vector<std::pair<Pin *, Pin *>> apply(Part *a, Part *b) const override;
+
+private:
+    std::string bkp_kind_;
+    std::string payload_kind_;
+    std::vector<ColTable> bkp_to_payload_;  // pattern row → col→col map (cycling by row index)
+    std::vector<ColTable> payload_to_bkp_;
+};
+
+class TransformRegistry;
+void RegisterVpxTransforms(TransformRegistry &reg);
+
+class Part;
+
+// Returns "" if the part's pin layout is consistent with `kind`, otherwise an
+// error message describing the mismatch. Returns "" for unknown `kind`s
+// (no built-in layout to check against → caller-defined types).
+std::string ValidatePartForKind(const Part *p, const std::string &kind);
+
+#endif // _TRANSFORM_VPX_HPP_

src/tui/commands.cpp

@@ -0,0 +1,417 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include "system/connect.hpp"
+#include "system/modules.hpp"
+#include "system/parts.hpp"
+#include "system/persist.hpp"
+#include "system/signals.hpp"
+#include "system/system.hpp"
+#include "system/transform.hpp"
+#include "system/transform_vpx.hpp"
+
+#include <algorithm>
+#include <cctype>
+#include <cstdlib>
+#include <exception>
+#include <fstream>
+#include <utility>
+
+void Tui::RegisterCommands() {
+    commands["help"] = {
+        {{"command name (optional)", Completion::Command}},
+        [this](const std::vector<std::string> &args) {
+            if (args.empty()) {
+                Print("Commands — type `help <name>` for details.");
+                size_t maxw = 0;
+                for (const auto &kv : commands) maxw = std::max(maxw, kv.first.size());
+                for (const auto &kv : commands) {
+                    Print("  " + kv.first
+                          + std::string(maxw - kv.first.size() + 2, ' ')
+                          + kv.second.description);
+                }
+                Print("Keys: Esc cancels a multi-step prompt; Tab completes commands or paths.");
+                return;
+            }
+            const std::string &name = args[0];
+            auto it = commands.find(name);
+            if (it == commands.end()) { Print("unknown command: " + name); return; }
+            const auto &spec = it->second;
+            Print(name + " — " + spec.description);
+            if (spec.params.empty()) {
+                Print("  no arguments.");
+            } else {
+                for (size_t i = 0; i < spec.params.size(); ++i) {
+                    Print("  arg " + std::to_string(i + 1) + ": " + spec.params[i].name);
+                }
+            }
+            if (!spec.prompt_for_missing) {
+                Print("  run with no args for the interactive form.");
+            } else if (!spec.params.empty()) {
+                Print("  missing args trigger a prompt for each one.");
+            }
+        },
+        /*prompt_for_missing=*/ false,
+        "show command help (optionally for a specific command)",
+    };
+    commands["clear"] = { {}, [this](auto &) { output.clear(); }, true,
+                          "clear the visualization area" };
+    commands["quit"]  = { {}, [this](auto &) { quit = true; }, true,
+                          "leave essim" };
+    commands["exit"]  = { {}, [this](auto &) { quit = true; }, true,
+                          "leave essim (alias of quit)" };
+
+    commands["new"] = { {}, [this](auto &) {
+        sys = std::make_unique<System>();
+        recorded.clear();
+        Print("system created.");
+    }, true, "create a new (empty) system; resets the script-save buffer" };
+
+    commands["load"] = {
+        {{"module name", Completion::None},
+         {"filename", Completion::Path},
+         {"import type [mentor|altium|ods]", Completion::None}},
+        [this](const std::vector<std::string> &args) {
+            if (!sys) { Print("no system: run 'new' first."); return; }
+            std::string ls = ToLower(args[2]);
+            ImportType t;
+            if      (ls == "mentor") t = ImportType::IMPORT_MENTOR;
+            else if (ls == "altium") t = ImportType::IMPORT_ALTIUM;
+            else if (ls == "ods")    t = ImportType::IMPORT_ODS;
+            else { Print("unknown import type: " + args[2]); return; }
+            try {
+                sys->Load(args[0], args[1], t);
+                Module *mod = sys->modules()->get(args[0]);
+                Print("loaded '" + args[0] + "' from " + args[1]);
+                Print("  parts:   " + std::to_string(mod->size()));
+                Print("  signals: " + std::to_string(mod->signals->size()));
+            } catch (const std::exception &e) {
+                Print(std::string("load failed: ") + e.what());
+            }
+        },
+        /*prompt_for_missing=*/ true,
+        "load a module from a netlist / pinout file (mentor, altium, ods)",
+    };
+
+    commands["source"] = {
+        {{"filename", Completion::Path}},
+        [this](const std::vector<std::string> &args) {
+            Source(args[0]);
+        },
+        /*prompt_for_missing=*/ true,
+        "execute a file of commands line by line (interactive cmds rejected)",
+    };
+
+    commands["script-save"] = {
+        {{"filename", Completion::Path}},
+        [this](const std::vector<std::string> &args) {
+            std::string expanded = args[0];
+            if (!expanded.empty() && expanded[0] == '~') {
+                if (const char *home = std::getenv("HOME"))
+                    expanded = std::string(home) + expanded.substr(1);
+            }
+            std::ofstream f(expanded);
+            if (!f) { Print("script-save: cannot open " + args[0]); return; }
+            for (const auto &cmd : recorded) f << cmd << '\n';
+            Print("script-save: " + std::to_string(recorded.size())
+                  + " line(s) → " + args[0]);
+        },
+        /*prompt_for_missing=*/ true,
+        "write commands run since last 'new' as a replay-ready script",
+    };
+
+    commands["save"] = {
+        {{"filename", Completion::Path}},
+        [this](const std::vector<std::string> &args) {
+            if (!sys) { Print("no system: run 'new' first."); return; }
+            std::string err;
+            if (save_system(sys.get(), args[0], err)) {
+                Print("saved to " + args[0]);
+            } else {
+                Print("save failed: " + err);
+            }
+        },
+        /*prompt_for_missing=*/ true,
+        "write the current system snapshot to a file",
+    };
+
+    commands["restore"] = {
+        {{"filename", Completion::Path}},
+        [this](const std::vector<std::string> &args) {
+            std::string err;
+            System *fresh = restore_system(args[0], err);
+            if (!fresh) { Print("restore failed: " + err); return; }
+            sys.reset(fresh);
+            int mods = (int)sys->modules()->size();
+            int conns = (int)sys->connections()->size();
+            Print("restored from " + args[0]
+                  + "  (" + std::to_string(mods) + " module(s), "
+                  + std::to_string(conns) + " connection(s))");
+        },
+        /*prompt_for_missing=*/ true,
+        "replace the current system with a saved snapshot",
+    };
+
+    commands["set-type"] = {
+        {{"module", Completion::None},
+         {"part (name or pattern)", Completion::None},
+         {"connector type (free string, e.g. vpx-bp, vpx-payload)", Completion::None}},
+        [this](const std::vector<std::string> &args) {
+            if (!sys) { Print("no system: run 'new' first."); return; }
+
+            if (args.empty()) {
+                settype_modules.clear();
+                for (auto &m : *sys->modules()) settype_modules.push_back(m.first);
+                std::sort(settype_modules.begin(), settype_modules.end(), NaturalLess);
+                if (settype_modules.empty()) { Print("no modules loaded."); return; }
+                settype_m_idx = 0;
+                settype_p_filter.clear();
+                settype_p_idx = 0;
+                settype_type.clear();
+                settype_status.clear();
+                settype_focus_idx = 0;
+                screen_idx = 3;
+                return;
+            }
+
+            if (args.size() != 3) {
+                Print("usage: set-type <module> <part> <kind>   (or no args for interactive)");
+                return;
+            }
+
+            Module *mod;
+            try { mod = sys->modules()->get(args[0]); }
+            catch (const std::exception &) {
+                Print("unknown module: " + args[0]); return;
+            }
+            Part *prt = nullptr;
+            try { prt = mod->get(args[1]); }
+            catch (const std::exception &) {
+                std::string needle = ToLower(args[1]);
+                std::vector<Part *> matches;
+                for (auto &p : *mod)
+                    if (ToLower(p.first).find(needle) != std::string::npos)
+                        matches.push_back(p.second);
+                if (matches.size() == 1) prt = matches[0];
+                else {
+                    Print(std::to_string(matches.size())
+                          + " match(es) for part '" + args[1] + "' in " + mod->name);
+                    return;
+                }
+            }
+            std::string err = ValidatePartForKind(prt, args[2]);
+            if (!err.empty()) {
+                Print("set-type refused: " + err);
+                return;
+            }
+            prt->connector_type = args[2];
+            Print(mod->name + "/" + prt->name + ": connector_type = "
+                  + (args[2].empty() ? "(none)" : args[2]));
+        },
+        /*prompt_for_missing=*/ false,
+        "tag a part's connector type for transform lookup",
+    };
+
+    commands["connect"] = {
+        {{"module1", Completion::None},
+         {"part1 (name or pattern)", Completion::None},
+         {"module2", Completion::None},
+         {"part2 (name or pattern)", Completion::None}},
+        [this](const std::vector<std::string> &args) {
+            if (!sys) { Print("no system: run 'new' first."); return; }
+
+            if (args.empty()) {
+                connect_modules.clear();
+                for (auto &m : *sys->modules()) connect_modules.push_back(m.first);
+                std::sort(connect_modules.begin(), connect_modules.end(), NaturalLess);
+                if (connect_modules.empty()) { Print("no modules loaded."); return; }
+                connect_m1_idx = 0;
+                connect_m2_idx = std::min(1, (int)connect_modules.size() - 1);
+                connect_p1_filter.clear();
+                connect_p2_filter.clear();
+                connect_p1_idx = 0;
+                connect_p2_idx = 0;
+                connect_focus_idx = 0;
+                screen_idx = 2;
+                return;
+            }
+
+            if (args.size() != 4) {
+                Print("usage: connect <m1> <p1> <m2> <p2>   (or no args for interactive)");
+                return;
+            }
+
+            auto resolve_module = [this](const std::string &name)
+                    -> std::pair<Module*, std::vector<std::string>> {
+                try { return {sys->modules()->get(name), {}}; }
+                catch (const std::exception &) {}
+                std::string needle = ToLower(name);
+                std::vector<Module*> matches;
+                std::vector<std::string> names;
+                for (auto &m : *sys->modules()) {
+                    if (ToLower(m.first).find(needle) != std::string::npos) {
+                        matches.push_back(m.second);
+                        names.push_back(m.first);
+                    }
+                }
+                if (matches.size() == 1) return {matches[0], {}};
+                return {nullptr, names};
+            };
+
+            auto resolve_part = [](Module *mod, const std::string &name)
+                    -> std::pair<Part*, std::vector<std::string>> {
+                try { return {mod->get(name), {}}; }
+                catch (const std::exception &) {}
+                std::string needle = ToLower(name);
+                std::vector<Part*> matches;
+                std::vector<std::string> names;
+                for (auto &p : *mod) {
+                    if (ToLower(p.first).find(needle) != std::string::npos) {
+                        matches.push_back(p.second);
+                        names.push_back(p.first);
+                    }
+                }
+                if (matches.size() == 1) return {matches[0], {}};
+                return {nullptr, names};
+            };
+
+            auto report_ambiguous = [this](const std::string &what,
+                                           const std::string &needle,
+                                           const std::vector<std::string> &names) {
+                if (names.empty()) {
+                    Print(what + " not found: " + needle);
+                } else {
+                    Print(what + " ambiguous for '" + needle + "': "
+                          + std::to_string(names.size()) + " match(es)");
+                    int shown = 0;
+                    for (const auto &n : names) {
+                        if (shown++ >= 8) { Print("    …"); break; }
+                        Print("    " + n);
+                    }
+                }
+            };
+
+            auto [m1, m1_alts] = resolve_module(args[0]);
+            if (!m1) { report_ambiguous("module", args[0], m1_alts); return; }
+            auto [p1, p1_alts] = resolve_part(m1, args[1]);
+            if (!p1) { report_ambiguous("part in " + m1->name, args[1], p1_alts); return; }
+            auto [m2, m2_alts] = resolve_module(args[2]);
+            if (!m2) { report_ambiguous("module", args[2], m2_alts); return; }
+            auto [p2, p2_alts] = resolve_part(m2, args[3]);
+            if (!p2) { report_ambiguous("part in " + m2->name, args[3], p2_alts); return; }
+
+            auto &reg = TransformRegistry::get();
+            Transform *t = reg.lookup(p1->connector_type, p2->connector_type);
+            bool both_empty = p1->connector_type.empty() && p2->connector_type.empty();
+            if (t == reg.identity()) {
+                if (!both_empty) {
+                    Print("connect refused: no transform for types '"
+                          + (p1->connector_type.empty() ? "(none)" : p1->connector_type)
+                          + "' ↔ '"
+                          + (p2->connector_type.empty() ? "(none)" : p2->connector_type)
+                          + "'. Set matching types via 'set-type' first.");
+                    return;
+                }
+                std::string err = CheckIdentityCompatible(p1, p2);
+                if (!err.empty()) {
+                    Print("connect refused: " + err);
+                    return;
+                }
+            }
+            auto pin_map = t->apply(p1, p2);
+
+            std::string conn_name = m1->name + "/" + p1->name
+                                  + " <-> " + m2->name + "/" + p2->name;
+            try {
+                Connection *c = new Connection(conn_name, m1, p1, m2, p2);
+                c->transform_name = t->name;
+                c->pin_map = std::move(pin_map);
+                sys->connections()->add(c);
+                Print("connected: " + conn_name
+                      + "  via " + t->name
+                      + " (" + std::to_string(c->pin_map.size()) + " wires)");
+            } catch (const std::exception &e) {
+                Print(std::string("connect failed: ") + e.what());
+            }
+        },
+        /*prompt_for_missing=*/ false,
+        "connect a part across two modules (interactive screen if no args)",
+    };
+
+    commands["explore"] = { {}, [this](auto &) {
+        if (!sys) { Print("no system: run 'new' first."); return; }
+        explore_modules.clear();
+        for (auto &m : *sys->modules()) explore_modules.push_back(m.first);
+        std::sort(explore_modules.begin(), explore_modules.end(), NaturalLess);
+        if (explore_modules.empty()) { Print("no modules loaded."); return; }
+        explore_module_idx = 0;
+        explore_type_idx = 0;
+        explore_child_idx = 0;
+        explore_detail_idx = 0;
+        explore_child_filter.clear();
+        explore_detail_filter.clear();
+        explore_focus_idx = 0;
+        screen_idx = 4;
+    }, true, "browse modules → parts/signals/connections → details (interactive)",
+       /*scriptable=*/ false };
+
+    commands["search"] = {
+        {{"module", Completion::None},
+         {"kind [parts|signals]", Completion::None},
+         {"pattern", Completion::None}},
+        [this](const std::vector<std::string> &args) {
+            if (!sys) { Print("no system: run 'new' first."); return; }
+
+            if (args.empty()) {
+                search_modules.clear();
+                for (auto &m : *sys->modules()) search_modules.push_back(m.first);
+                std::sort(search_modules.begin(), search_modules.end(), NaturalLess);
+                if (search_modules.empty()) { Print("no modules loaded."); return; }
+                search_module_idx = 0;
+                search_type_idx = 0;
+                search_query.clear();
+                search_focus_idx = 0;
+                screen_idx = 1;
+                return;
+            }
+
+            if (args.size() != 3) {
+                Print("usage: search <module> <parts|signals> <pattern>");
+                Print("       search                                  (interactive)");
+                return;
+            }
+
+            Module *mod;
+            try { mod = sys->modules()->get(args[0]); }
+            catch (const std::exception &) {
+                Print("unknown module: " + args[0]); return;
+            }
+
+            std::string kind = ToLower(args[1]);
+            std::string needle = ToLower(args[2]);
+
+            std::vector<std::pair<std::string, size_t>> hits;
+            if (kind == "parts" || kind == "part") {
+                for (auto &pkv : *mod)
+                    if (ToLower(pkv.first).find(needle) != std::string::npos)
+                        hits.emplace_back(pkv.first, pkv.second->size());
+            } else if (kind == "signals" || kind == "signal") {
+                for (auto &skv : *mod->signals)
+                    if (ToLower(skv.first).find(needle) != std::string::npos)
+                        hits.emplace_back(skv.first, skv.second->size());
+            } else {
+                Print("kind must be 'parts' or 'signals' (got: " + args[1] + ")");
+                return;
+            }
+            std::sort(hits.begin(), hits.end(),
+                      [](const auto &a, const auto &b) { return NaturalLess(a.first, b.first); });
+            for (const auto &h : hits) {
+                Print("  " + args[0] + "/" + h.first
+                      + "  (" + std::to_string(h.second) + " pins)");
+            }
+            Print(std::to_string(hits.size()) + " match(es).");
+        },
+        /*prompt_for_missing=*/ false,
+        "list parts/signals matching a pattern (interactive screen if no args)",
+    };
+}

src/tui/completion.cpp

@@ -0,0 +1,111 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include <cctype>
+#include <cstdlib>
+#include <filesystem>
+
+void Tui::CompleteCommand(size_t start) {
+    std::string current = input.substr(start);
+    std::vector<std::string> matches;
+    for (const auto &kv : commands)
+        if (kv.first.rfind(current, 0) == 0) matches.push_back(kv.first);
+
+    if (matches.empty()) return;
+
+    auto replace_with = [&](const std::string &replacement) {
+        input.replace(start, std::string::npos, replacement);
+        cursor_pos = (int)input.size();
+    };
+
+    if (matches.size() == 1) { replace_with(matches[0]); return; }
+
+    std::string lcp = LongestCommonPrefix(matches);
+    if (lcp.size() > current.size()) { replace_with(lcp); return; }
+
+    std::string line = " ";
+    for (const auto &m : matches) line += " " + m;
+    Print(line);
+}
+
+void Tui::CompletePath(size_t start) {
+    namespace fs = std::filesystem;
+
+    std::string current = input.substr(start);
+
+    auto pos = current.rfind('/');
+    std::string disp, prefix;
+    if (pos == std::string::npos) { disp = ""; prefix = current; }
+    else { disp = current.substr(0, pos + 1); prefix = current.substr(pos + 1); }
+
+    std::string resolved = disp.empty() ? "." : disp;
+    if (!resolved.empty() && resolved[0] == '~') {
+        if (const char *home = std::getenv("HOME"))
+            resolved = std::string(home) + resolved.substr(1);
+    }
+
+    std::vector<std::string> names;
+    std::vector<bool> is_dir;
+    try {
+        for (const auto &e : fs::directory_iterator(resolved)) {
+            std::string n = e.path().filename().string();
+            if (n.rfind(prefix, 0) == 0) {
+                names.push_back(n);
+                is_dir.push_back(e.is_directory());
+            }
+        }
+    } catch (const std::exception &) {
+        return;
+    }
+    if (names.empty()) return;
+
+    auto replace_with = [&](const std::string &replacement) {
+        input.replace(start, std::string::npos, replacement);
+        cursor_pos = (int)input.size();
+    };
+
+    if (names.size() == 1) {
+        replace_with(disp + names[0] + (is_dir[0] ? "/" : ""));
+        return;
+    }
+
+    std::string lcp = LongestCommonPrefix(names);
+    if (lcp.size() > prefix.size()) { replace_with(disp + lcp); return; }
+
+    std::string line = " ";
+    for (size_t i = 0; i < names.size(); ++i)
+        line += " " + names[i] + (is_dir[i] ? "/" : "");
+    Print(line);
+}
+
+void Tui::CompleteInline() {
+    bool ends_with_ws = !input.empty()
+                        && std::isspace((unsigned char)input.back());
+
+    size_t arg_start;
+    if (input.empty() || ends_with_ws) {
+        arg_start = input.size();
+    } else {
+        size_t i = input.size();
+        while (i > 0 && !std::isspace((unsigned char)input[i - 1])) --i;
+        arg_start = i;
+    }
+
+    auto preceding = Tokenize(input.substr(0, arg_start));
+    int arg_index = (int)preceding.size();
+
+    if (arg_index == 0) { CompleteCommand(); return; }
+
+    if (preceding.empty()) return;
+    auto cmd_it = commands.find(preceding[0]);
+    if (cmd_it == commands.end()) return;
+    const auto &spec = cmd_it->second;
+
+    int param_idx = arg_index - 1;
+    if (param_idx >= (int)spec.params.size()) return;
+    switch (spec.params[param_idx].completion) {
+        case Completion::Path:    CompletePath(arg_start);    break;
+        case Completion::Command: CompleteCommand(arg_start); break;
+        case Completion::None:                                 break;
+    }
+}

src/tui/screen_connect.cpp

@@ -0,0 +1,146 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include "system/connect.hpp"
+#include "system/modules.hpp"
+#include "system/parts.hpp"
+#include "system/system.hpp"
+#include "system/transform.hpp"
+
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/component_options.hpp>
+#include <ftxui/dom/elements.hpp>
+
+#include <algorithm>
+#include <exception>
+#include <utility>
+
+using namespace ftxui;
+
+void Tui::RefreshFilteredPartList(const std::vector<std::string> &modules,
+                                   int m_idx,
+                                   const std::string &filter,
+                                   std::vector<std::string> &out,
+                                   int &sel_idx) {
+    out.clear();
+    if (!sys || modules.empty()) { sel_idx = 0; return; }
+    try {
+        Module *mod = sys->modules()->get(modules[m_idx]);
+        std::string needle = ToLower(filter);
+        for (auto &pkv : *mod) {
+            if (needle.empty()
+                || ToLower(pkv.first).find(needle) != std::string::npos) {
+                out.push_back(pkv.first);
+            }
+        }
+    } catch (const std::exception &) {}
+    std::sort(out.begin(), out.end(), NaturalLess);
+    if (sel_idx >= (int)out.size()) sel_idx = std::max(0, (int)out.size() - 1);
+}
+
+Component Tui::BuildConnectScreen() {
+    InputOption pf_opt;
+    pf_opt.multiline = false;
+    pf_opt.transform = [](InputState s) {
+        auto el = s.element;
+        if (s.is_placeholder) el |= dim;
+        return el;
+    };
+
+    auto m1_menu   = Menu(&connect_modules, &connect_m1_idx);
+    auto p1_filter = Input(&connect_p1_filter, "filter…", pf_opt);
+    auto p1_menu   = Menu(&connect_p1_list, &connect_p1_idx);
+    auto m2_menu   = Menu(&connect_modules, &connect_m2_idx);
+    auto p2_filter = Input(&connect_p2_filter, "filter…", pf_opt);
+    auto p2_menu   = Menu(&connect_p2_list, &connect_p2_idx);
+
+    auto do_connect = [this] {
+        if (!sys || connect_modules.empty()) { screen_idx = 0; return; }
+        if (connect_p1_list.empty() || connect_p2_list.empty()) {
+            Print("connect: select a part on each side first.");
+            screen_idx = 0;
+            return;
+        }
+        try {
+            Module *m1 = sys->modules()->get(connect_modules[connect_m1_idx]);
+            Module *m2 = sys->modules()->get(connect_modules[connect_m2_idx]);
+            Part *p1 = m1->get(connect_p1_list[connect_p1_idx]);
+            Part *p2 = m2->get(connect_p2_list[connect_p2_idx]);
+
+            auto &reg = TransformRegistry::get();
+            Transform *t = reg.lookup(p1->connector_type, p2->connector_type);
+            bool both_empty = p1->connector_type.empty() && p2->connector_type.empty();
+            if (t == reg.identity()) {
+                if (!both_empty) {
+                    Print("connect refused: no transform for types '"
+                          + (p1->connector_type.empty() ? "(none)" : p1->connector_type)
+                          + "' ↔ '"
+                          + (p2->connector_type.empty() ? "(none)" : p2->connector_type)
+                          + "'. Set matching types via 'set-type' first.");
+                    screen_idx = 0;
+                    return;
+                }
+                std::string err = CheckIdentityCompatible(p1, p2);
+                if (!err.empty()) {
+                    Print("connect refused: " + err);
+                    screen_idx = 0;
+                    return;
+                }
+            }
+            auto pin_map = t->apply(p1, p2);
+
+            std::string conn_name = m1->name + "/" + p1->name
+                                  + " <-> " + m2->name + "/" + p2->name;
+            Connection *c = new Connection(conn_name, m1, p1, m2, p2);
+            c->transform_name = t->name;
+            c->pin_map = std::move(pin_map);
+            sys->connections()->add(c);
+            Print("connected: " + conn_name
+                  + "  via " + t->name
+                  + " (" + std::to_string(c->pin_map.size()) + " wires)");
+        } catch (const std::exception &e) {
+            Print(std::string("connect failed: ") + e.what());
+        }
+        screen_idx = 0;
+    };
+    auto connect_button = Button(" Connect ", do_connect);
+
+    auto components = Container::Vertical({
+        m1_menu, p1_filter, p1_menu,
+        m2_menu, p2_filter, p2_menu,
+        connect_button,
+    }, &connect_focus_idx);
+
+    return Renderer(components,
+            [this, m1_menu, p1_filter, p1_menu,
+             m2_menu, p2_filter, p2_menu, connect_button] {
+        RefreshFilteredPartList(connect_modules, connect_m1_idx,
+                                connect_p1_filter, connect_p1_list, connect_p1_idx);
+        RefreshFilteredPartList(connect_modules, connect_m2_idx,
+                                connect_p2_filter, connect_p2_list, connect_p2_idx);
+
+        auto col = [&](const std::string &title,
+                       Component mm, Component pf, Component pm) {
+            return vbox({
+                text(title) | bold,
+                text("module") | dim,
+                mm->Render() | yframe | size(HEIGHT, LESS_THAN, 8),
+                separator(),
+                hbox({text(" filter: "), pf->Render() | flex}) | border,
+                text("part") | dim,
+                pm->Render() | yframe | flex,
+            }) | flex;
+        };
+
+        return vbox({
+            hbox({
+                col("endpoint 1", m1_menu, p1_filter, p1_menu),
+                separator(),
+                col("endpoint 2", m2_menu, p2_filter, p2_menu),
+            }) | flex,
+            separator(),
+            hbox({filler(), connect_button->Render(), filler()}),
+            text(" Tab: cycle focus   |   Enter on [Connect]: confirm   |   Esc: leave ") | dim,
+        }) | border;
+    });
+}

src/tui/screen_explore.cpp

@@ -0,0 +1,207 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include "system/connect.hpp"
+#include "system/modules.hpp"
+#include "system/parts.hpp"
+#include "system/pins.hpp"
+#include "system/signals.hpp"
+#include "system/system.hpp"
+
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/component_options.hpp>
+#include <ftxui/dom/elements.hpp>
+
+#include <algorithm>
+#include <exception>
+
+using namespace ftxui;
+
+Component Tui::BuildExploreScreen() {
+    InputOption pf_opt;
+    pf_opt.multiline = false;
+    pf_opt.transform = [](InputState s) {
+        auto el = s.element;
+        if (s.is_placeholder) el |= dim;
+        return el;
+    };
+
+    auto module_menu   = Menu(&explore_modules,  &explore_module_idx);
+    auto type_menu     = Menu(&explore_types,    &explore_type_idx);
+    auto child_filter  = Input(&explore_child_filter,  "filter…", pf_opt);
+    auto children_menu = Menu(&explore_children, &explore_child_idx);
+    auto detail_filter = Input(&explore_detail_filter, "filter…", pf_opt);
+    auto detail_menu   = Menu(&explore_detail,   &explore_detail_idx);
+
+    auto components = Container::Vertical(
+        {module_menu, type_menu, child_filter, children_menu, detail_filter, detail_menu},
+        &explore_focus_idx);
+
+    return Renderer(components,
+            [this, module_menu, type_menu, child_filter, children_menu, detail_filter, detail_menu] {
+      try {
+        // Clamp the module index defensively (covers fresh systems / restore).
+        if (explore_module_idx < 0
+            || explore_module_idx >= (int)explore_modules.size()) {
+            explore_module_idx = 0;
+        }
+
+        // Refresh the children list for the selected module + type, applying child filter.
+        explore_children.clear();
+        Module *cur_mod = nullptr;
+        std::string c_needle = ToLower(explore_child_filter);
+        if (sys && !explore_modules.empty()) {
+            try {
+                cur_mod = sys->modules()->get(explore_modules[explore_module_idx]);
+                auto keep = [&](const std::string &name) {
+                    return c_needle.empty()
+                        || ToLower(name).find(c_needle) != std::string::npos;
+                };
+                if (explore_type_idx == 0) {
+                    for (auto &pkv : *cur_mod)
+                        if (keep(pkv.first)) explore_children.push_back(pkv.first);
+                } else if (explore_type_idx == 1) {
+                    for (auto &skv : *cur_mod->signals)
+                        if (keep(skv.first)) explore_children.push_back(skv.first);
+                } else {
+                    for (auto &ckv : *sys->connections()) {
+                        Connection *c = ckv.second;
+                        if ((c->m1 == cur_mod || c->m2 == cur_mod) && keep(ckv.first))
+                            explore_children.push_back(ckv.first);
+                    }
+                }
+            } catch (const std::exception &) {}
+        }
+        std::sort(explore_children.begin(), explore_children.end(), NaturalLess);
+
+        // Never let the Menu see an empty list — FTXUI Menu's clamp(v, 0, size()-1)
+        // is brittle when size() == 0; a placeholder also gives the user feedback.
+        if (explore_children.empty()) explore_children.push_back("(no matches)");
+
+        if (explore_child_idx < 0
+            || explore_child_idx >= (int)explore_children.size()) {
+            explore_child_idx = 0;
+        }
+
+        std::string d_needle = ToLower(explore_detail_filter);
+        auto keep_detail = [&](const std::string &line) {
+            return d_needle.empty()
+                || ToLower(line).find(d_needle) != std::string::npos;
+        };
+
+        // Build the detail pane (lines stored in explore_detail so the Menu
+        // bound to it can scroll with arrow keys when focused).
+        explore_header = "(no system)";
+        explore_detail.clear();
+        if (cur_mod && !explore_children.empty()) {
+            const std::string &cname = explore_children[explore_child_idx];
+            try {
+                if (explore_type_idx == 0) {
+                    Part *p = cur_mod->get(cname);
+                    std::string type_str = p->connector_type.empty()
+                        ? "(no type)" : p->connector_type;
+                    explore_header = cur_mod->name + "/" + p->name
+                                   + "  —  " + std::to_string(p->size())
+                                   + " pins  •  type: " + type_str;
+                    std::vector<std::pair<std::string, std::string>> rows;
+                    for (auto &pin_kv : *p) {
+                        Signal *s = pin_kv.second->signal();
+                        rows.emplace_back(pin_kv.first, s ? s->name : std::string("—"));
+                    }
+                    std::sort(rows.begin(), rows.end(),
+                              [](const auto &a, const auto &b) { return NaturalLess(a.first, b.first); });
+                    size_t maxw = 0;
+                    for (const auto &r : rows) maxw = std::max(maxw, r.first.size());
+                    for (const auto &r : rows) {
+                        std::string line = "  " + r.first
+                                         + std::string(maxw - r.first.size() + 2, ' ')
+                                         + r.second;
+                        if (keep_detail(line))
+                            explore_detail.push_back(line);
+                    }
+                } else if (explore_type_idx == 1) {
+                    Signal *s = cur_mod->signals->get(cname);
+                    explore_header = cur_mod->name + "/" + s->name
+                                   + "  —  " + std::to_string(s->size())
+                                   + " pins";
+                    std::vector<std::string> rows;
+                    for (auto &pin_kv : *s) {
+                        Pin *pin = pin_kv.second;
+                        std::string mname = (pin->prnt && pin->prnt->prnt)
+                                          ? pin->prnt->prnt->name : std::string("?");
+                        std::string pname = pin->prnt ? pin->prnt->name : std::string("?");
+                        rows.push_back(mname + "/" + pname + "/" + pin->name);
+                    }
+                    std::sort(rows.begin(), rows.end(), NaturalLess);
+                    for (const auto &r : rows)
+                        if (keep_detail(r))
+                            explore_detail.push_back("  " + r);
+                } else {
+                    Connection *c = sys->connections()->get(cname);
+                    std::string tname = c->transform_name.empty()
+                        ? "(unknown)" : c->transform_name;
+                    explore_header = c->name
+                                   + "  —  " + std::to_string(c->pin_map.size())
+                                   + " wires  •  transform: " + tname;
+                    std::vector<std::string> rows;
+                    for (auto &wp : c->pin_map) {
+                        Pin *a = wp.first;
+                        Pin *b = wp.second;
+                        auto label = [](Pin *pin) {
+                            if (!pin) return std::string("?");
+                            std::string m = (pin->prnt && pin->prnt->prnt)
+                                          ? pin->prnt->prnt->name : "?";
+                            std::string p = pin->prnt ? pin->prnt->name : "?";
+                            return m + "/" + p + "/" + pin->name;
+                        };
+                        rows.push_back(label(a) + "  ↔  " + label(b));
+                    }
+                    std::sort(rows.begin(), rows.end(), NaturalLess);
+                    for (const auto &r : rows)
+                        if (keep_detail(r))
+                            explore_detail.push_back("  " + r);
+                }
+            } catch (const std::exception &) {}
+        }
+
+        if (explore_detail.empty()) explore_detail.push_back("(empty)");
+        if (explore_detail_idx < 0
+            || explore_detail_idx >= (int)explore_detail.size()) {
+            explore_detail_idx = 0;
+        }
+
+        auto col1 = vbox({
+            text("module") | bold,
+            module_menu->Render() | yframe | flex,
+        }) | size(WIDTH, EQUAL, 24);
+
+        auto col2 = vbox({
+            text("type") | bold,
+            type_menu->Render() | flex,
+        }) | size(WIDTH, EQUAL, 12);
+
+        auto col3 = vbox({
+            text(explore_types[explore_type_idx]) | bold,
+            hbox({text(" filter: "), child_filter->Render() | flex}) | border,
+            children_menu->Render() | yframe | flex,
+        }) | size(WIDTH, EQUAL, 36);
+
+        auto col4 = vbox({
+            text(explore_header) | bold,
+            hbox({text(" filter: "), detail_filter->Render() | flex}) | border,
+            detail_menu->Render() | vscroll_indicator | yframe | flex,
+        }) | flex;
+
+        return vbox({
+            hbox({col1, separator(), col2, separator(), col3, separator(), col4}) | flex,
+            text(" Tab: cycle focus (incl. detail to scroll)   |   Esc: leave explore ") | dim,
+        }) | border;
+      } catch (const std::exception &e) {
+        return vbox({
+            text("explore: render error") | bold,
+            text(std::string("  ") + e.what()) | dim,
+            text(" Esc: leave explore ") | dim,
+        }) | border;
+      }
+    });
+}

src/tui/screen_main.cpp

@@ -0,0 +1,42 @@
+#include "tui/tui.hpp"
+
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/component_options.hpp>
+#include <ftxui/component/screen_interactive.hpp>
+#include <ftxui/dom/elements.hpp>
+
+using namespace ftxui;
+
+Component Tui::BuildMainScreen(ScreenInteractive &screen) {
+    InputOption opt;
+    opt.multiline = false;
+    opt.cursor_position = &cursor_pos;
+    opt.on_enter = [this] { Submit(); };
+    opt.transform = [](InputState s) {
+        auto el = s.element;
+        if (s.is_placeholder) el |= dim;
+        return el;
+    };
+    auto input_component = Input(&input, "type a command…", opt);
+
+    return Renderer(input_component, [this, &screen, input_component] {
+        if (quit) screen.Exit();
+
+        Elements lines;
+        for (const auto &l : output) lines.push_back(text(l));
+        auto view = vbox(std::move(lines))
+                  | focusPositionRelative(0, 1)
+                  | yframe
+                  | flex;
+
+        std::string label = pending.empty()
+            ? "> "
+            : pending.front().question + "? ";
+
+        return vbox({
+            view,
+            separator(),
+            hbox({text(label), input_component->Render()}),
+        }) | border;
+    });
+}

src/tui/screen_search.cpp

@@ -0,0 +1,83 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include "system/modules.hpp"
+#include "system/parts.hpp"
+#include "system/signals.hpp"
+#include "system/system.hpp"
+
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/component_options.hpp>
+#include <ftxui/dom/elements.hpp>
+
+#include <algorithm>
+#include <exception>
+#include <utility>
+
+using namespace ftxui;
+
+Component Tui::BuildSearchScreen() {
+    InputOption query_opt;
+    query_opt.multiline = false;
+    query_opt.transform = [](InputState s) {
+        auto el = s.element;
+        if (s.is_placeholder) el |= dim;
+        return el;
+    };
+
+    auto query_input = Input(&search_query, "filter…", query_opt);
+    auto module_menu = Menu(&search_modules, &search_module_idx);
+    auto type_menu   = Menu(&search_types,   &search_type_idx);
+
+    auto components = Container::Vertical(
+        {query_input, module_menu, type_menu}, &search_focus_idx);
+
+    return Renderer(components,
+            [this, query_input, module_menu, type_menu] {
+        std::vector<std::pair<std::string, size_t>> hits;
+        if (!search_modules.empty() && sys) {
+            const std::string &mname = search_modules[search_module_idx];
+            try {
+                Module *mod = sys->modules()->get(mname);
+                std::string needle = ToLower(search_query);
+                if (search_type_idx == 0) {  // parts
+                    for (auto &pkv : *mod)
+                        if (needle.empty()
+                            || ToLower(pkv.first).find(needle) != std::string::npos)
+                            hits.emplace_back(pkv.first, pkv.second->size());
+                } else {  // signals
+                    for (auto &skv : *mod->signals)
+                        if (needle.empty()
+                            || ToLower(skv.first).find(needle) != std::string::npos)
+                            hits.emplace_back(skv.first, skv.second->size());
+                }
+            } catch (const std::exception &) {}
+        }
+        std::sort(hits.begin(), hits.end(),
+                  [](const auto &a, const auto &b) { return NaturalLess(a.first, b.first); });
+
+        Elements result_lines;
+        for (const auto &h : hits)
+            result_lines.push_back(
+                text("  " + h.first + "  (" + std::to_string(h.second) + " pins)"));
+
+        auto left = vbox({
+            text("module") | bold,
+            module_menu->Render() | yframe | flex,
+            separator(),
+            text("type") | bold,
+            type_menu->Render(),
+        }) | size(WIDTH, EQUAL, 28);
+
+        auto right = vbox({
+            hbox({text(" search: "), query_input->Render() | flex}) | border,
+            text(std::to_string(hits.size()) + " match(es)") | dim,
+            vbox(std::move(result_lines)) | yframe | flex,
+        }) | flex;
+
+        return vbox({
+            hbox({left, separator(), right}) | flex,
+            text(" Tab: cycle focus   |   Esc: leave search ") | dim,
+        }) | border;
+    });
+}

src/tui/screen_settype.cpp

@@ -0,0 +1,129 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include "system/modules.hpp"
+#include "system/parts.hpp"
+#include "system/system.hpp"
+#include "system/transform_vpx.hpp"
+
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/component_options.hpp>
+#include <ftxui/dom/elements.hpp>
+
+#include <algorithm>
+#include <exception>
+
+using namespace ftxui;
+
+Component Tui::BuildSettypeScreen() {
+    InputOption pf_opt;
+    pf_opt.multiline = false;
+    pf_opt.transform = [](InputState s) {
+        auto el = s.element;
+        if (s.is_placeholder) el |= dim;
+        return el;
+    };
+
+    auto module_menu = Menu(&settype_modules, &settype_m_idx);
+    auto part_filter = Input(&settype_p_filter, "filter…", pf_opt);
+    auto part_menu   = Menu(&settype_p_list,   &settype_p_idx);
+
+    InputOption type_opt;
+    type_opt.multiline = false;
+    type_opt.transform = pf_opt.transform;
+    auto type_input  = Input(&settype_type, "connector type (e.g. vpx-bp)", type_opt);
+
+    auto do_settype = [this] {
+        if (!sys || settype_modules.empty()) {
+            settype_status = "no system / no modules";
+            return;
+        }
+        if (settype_p_list.empty()) {
+            settype_status = "select a part first";
+            return;
+        }
+        try {
+            Module *mod = sys->modules()->get(settype_modules[settype_m_idx]);
+            Part *prt = mod->get(settype_p_list[settype_p_idx]);
+            std::string err = ValidatePartForKind(prt, settype_type);
+            if (!err.empty()) {
+                settype_status = "refused: " + err;
+                return;
+            }
+            prt->connector_type = settype_type;
+            std::string msg = mod->name + "/" + prt->name + " = "
+                            + (settype_type.empty() ? "(none)" : settype_type);
+            settype_status = "applied: " + msg;
+            Print("set-type " + msg);
+        } catch (const std::exception &e) {
+            settype_status = std::string("failed: ") + e.what();
+        }
+    };
+    auto button = Button(" Apply ", do_settype);
+
+    auto components = Container::Vertical({
+        module_menu, part_filter, part_menu, type_input, button,
+    }, &settype_focus_idx);
+
+    return Renderer(components,
+            [this, module_menu, part_filter, part_menu, type_input, button] {
+        RefreshFilteredPartList(settype_modules, settype_m_idx,
+                                settype_p_filter, settype_p_list, settype_p_idx);
+
+        std::string current = "(none)";
+        if (sys && !settype_modules.empty() && !settype_p_list.empty()) {
+            try {
+                Module *mod = sys->modules()->get(settype_modules[settype_m_idx]);
+                Part *prt = mod->get(settype_p_list[settype_p_idx]);
+                if (!prt->connector_type.empty()) current = prt->connector_type;
+            } catch (const std::exception &) {}
+        }
+
+        std::vector<std::string> known_types;
+        if (sys) {
+            for (auto &mkv : *sys->modules())
+                for (auto &pkv : *mkv.second)
+                    if (!pkv.second->connector_type.empty())
+                        known_types.push_back(pkv.second->connector_type);
+            std::sort(known_types.begin(), known_types.end(), NaturalLess);
+            known_types.erase(std::unique(known_types.begin(), known_types.end()),
+                              known_types.end());
+        }
+        std::string known_line = "in use:";
+        if (known_types.empty()) known_line += " (none yet)";
+        else for (const auto &k : known_types) known_line += "  " + k;
+
+        auto left = vbox({
+            text("module") | bold,
+            module_menu->Render() | yframe | flex,
+        }) | size(WIDTH, EQUAL, 28);
+
+        auto middle = vbox({
+            hbox({text(" filter: "), part_filter->Render() | flex}) | border,
+            text("part") | dim,
+            part_menu->Render() | yframe | flex,
+        }) | flex;
+
+        auto right = vbox({
+            text("current type: ") | bold,
+            text("  " + current),
+            separator(),
+            text("new type:") | bold,
+            hbox({text(" "), type_input->Render() | flex}) | border,
+            text(known_line) | dim,
+            filler(),
+            hbox({filler(), button->Render(), filler()}),
+        }) | size(WIDTH, EQUAL, 40);
+
+        Element status = settype_status.empty()
+            ? text("") | dim
+            : text(" " + settype_status) | bold;
+
+        return vbox({
+            hbox({left, separator(), middle, separator(), right}) | flex,
+            separator(),
+            status,
+            text(" Tab: cycle focus   |   Enter on [Apply]: apply (stay)   |   Esc: leave ") | dim,
+        }) | border;
+    });
+}

src/tui/shell.cpp

@@ -0,0 +1,236 @@
+#include "tui/tui.hpp"
+#include "tui/tui_helpers.hpp"
+
+#include <cctype>
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <set>
+#include <system_error>
+
+void Tui::Print(const std::string &line) {
+    output.push_back(line);
+}
+
+void Tui::HistoryUp() {
+    if (history.empty()) return;
+    if (history_idx == -1) history_idx = (int)history.size() - 1;
+    else if (history_idx > 0) history_idx--;
+    input = history[history_idx];
+    cursor_pos = (int)input.size();
+}
+
+void Tui::HistoryDown() {
+    if (history_idx == -1) return;
+    history_idx++;
+    if (history_idx >= (int)history.size()) {
+        history_idx = -1;
+        input.clear();
+    } else {
+        input = history[history_idx];
+    }
+    cursor_pos = (int)input.size();
+}
+
+void Tui::CancelPending() {
+    if (pending.empty()) return;
+    pending.clear();
+    input.clear();
+    cursor_pos = 0;
+    history_idx = -1;
+    Print("(cancelled)");
+}
+
+std::vector<std::string> Tui::Tokenize(const std::string &s) {
+    std::vector<std::string> out;
+    std::string cur;
+    bool in_q = false;
+    for (char c : s) {
+        if (c == '"') { in_q = !in_q; continue; }
+        if (!in_q && std::isspace((unsigned char)c)) {
+            if (!cur.empty()) { out.push_back(std::move(cur)); cur.clear(); }
+        } else {
+            cur.push_back(c);
+        }
+    }
+    if (!cur.empty()) out.push_back(std::move(cur));
+    return out;
+}
+
+void Tui::Submit() {
+    if (!pending.empty()) {
+        if (input.empty()) { Print("(empty — Esc to cancel)"); return; }
+        Prompt p = std::move(pending.front());
+        pending.pop_front();
+        Print("  " + p.question + ": " + input);
+        std::string answer = std::move(input);
+        input.clear();
+        cursor_pos = 0;
+        history_idx = -1;
+        p.on_answer(answer);
+        return;
+    }
+
+    if (input.empty()) return;
+    history_idx = -1;
+    Print("> " + input);
+    std::string raw = std::move(input);
+    input.clear();
+    cursor_pos = 0;
+    Dispatch(raw);
+}
+
+void Tui::Dispatch(const std::string &raw) {
+    auto tokens = Tokenize(raw);
+    if (tokens.empty()) return;
+
+    auto it = commands.find(tokens[0]);
+    if (it == commands.end()) {
+        Print("unknown command: " + tokens[0]);
+        if (!in_source) { history.push_back(raw); AppendHistory(raw); }
+        return;
+    }
+
+    const std::string name = it->first;
+    const CommandSpec &spec = it->second;
+
+    if (tokens.size() - 1 > spec.params.size()) {
+        Print("too many arguments for '" + name + "'");
+        if (!in_source) { history.push_back(raw); AppendHistory(raw); }
+        return;
+    }
+
+    auto args = std::make_shared<std::vector<std::string>>(
+        tokens.begin() + 1, tokens.end());
+
+    if (args->size() == spec.params.size() || !spec.prompt_for_missing) {
+        Finalize(name, spec, *args);
+        return;
+    }
+
+    for (size_t i = args->size(); i < spec.params.size(); ++i) {
+        bool last = (i + 1 == spec.params.size());
+        const auto &param = spec.params[i];
+        pending.push_back({
+            param.name,
+            [this, name, &spec, args, last](const std::string &s) {
+                args->push_back(s);
+                if (last) Finalize(name, spec, *args);
+            },
+            param.completion,
+        });
+    }
+}
+
+void Tui::Finalize(const std::string &name,
+                   const CommandSpec &spec,
+                   const std::vector<std::string> &args) {
+    std::string canonical = name;
+    for (const auto &a : args) {
+        if (a.find_first_of(" \t\"") != std::string::npos)
+            canonical += " \"" + a + "\"";
+        else
+            canonical += " " + a;
+    }
+    if (!in_source) {
+        history.push_back(canonical);
+        AppendHistory(canonical);
+    }
+    spec.action(args);
+
+    static const std::set<std::string> no_record = {
+        "clear", "help", "quit", "exit", "source", "script-save",
+    };
+    if (spec.scriptable && !no_record.count(name)) recorded.push_back(canonical);
+}
+
+namespace {
+
+std::filesystem::path HistoryPath() {
+    namespace fs = std::filesystem;
+#ifdef _WIN32
+    if (const char *p = std::getenv("LOCALAPPDATA"); p && *p)
+        return fs::path(p) / "essim" / "history";
+    if (const char *p = std::getenv("APPDATA"); p && *p)
+        return fs::path(p) / "essim" / "history";
+    if (const char *p = std::getenv("USERPROFILE"); p && *p)
+        return fs::path(p) / "AppData" / "Local" / "essim" / "history";
+#else
+    if (const char *p = std::getenv("XDG_DATA_HOME"); p && *p)
+        return fs::path(p) / "essim" / "history";
+    if (const char *p = std::getenv("HOME"); p && *p)
+        return fs::path(p) / ".local" / "share" / "essim" / "history";
+#endif
+    return {};
+}
+
+}  // namespace
+
+void Tui::LoadHistory() {
+    auto p = HistoryPath();
+    if (p.empty()) return;
+    std::ifstream f(p);
+    std::string line;
+    while (std::getline(f, line))
+        if (!line.empty()) history.push_back(line);
+}
+
+void Tui::Source(const std::string &filename) {
+    std::string expanded = filename;
+    if (!expanded.empty() && expanded[0] == '~') {
+        if (const char *home = std::getenv("HOME"))
+            expanded = std::string(home) + expanded.substr(1);
+    }
+    std::ifstream f(expanded);
+    if (!f) { Print("source failed: cannot open " + filename); return; }
+
+    bool prev = in_source;
+    in_source = true;
+
+    int executed = 0;
+    int lineno = 0;
+    bool aborted = false;
+    std::string line;
+    while (std::getline(f, line)) {
+        ++lineno;
+        size_t start = line.find_first_not_of(" \t");
+        if (start == std::string::npos) continue;
+        if (line[start] == '#') continue;
+        std::string trimmed = line.substr(start);
+        while (!trimmed.empty() && std::isspace((unsigned char)trimmed.back()))
+            trimmed.pop_back();
+        if (trimmed.empty()) continue;
+
+        input = trimmed;
+        cursor_pos = (int)input.size();
+        Submit();
+        ++executed;
+
+        if (screen_idx != 0) {
+            Print("source: line " + std::to_string(lineno)
+                  + " is interactive (would open a screen) — aborting.");
+            screen_idx = 0;
+            aborted = true;
+            break;
+        }
+    }
+
+    in_source = prev;
+
+    if (!aborted)
+        Print("source: " + filename + "  (" + std::to_string(executed) + " line(s))");
+}
+
+void Tui::AppendHistory(const std::string &cmd) {
+    auto p = HistoryPath();
+    if (p.empty()) return;
+    std::string trimmed = cmd;
+    while (!trimmed.empty() && std::isspace((unsigned char)trimmed.back()))
+        trimmed.pop_back();
+    if (trimmed.empty()) return;
+    std::error_code ec;
+    std::filesystem::create_directories(p.parent_path(), ec);
+    if (ec) return;
+    std::ofstream f(p, std::ios::app);
+    if (f) f << trimmed << '\n';
+}

src/tui/tui.cpp

@@ -1,29 +1,26 @@
 #include "tui/tui.hpp"
 
-#include "system/modules.hpp"
-#include "system/parts.hpp"
-#include "system/signals.hpp"
 #include "system/system.hpp"
 
 #include <ftxui/component/component.hpp>
+#include <ftxui/component/event.hpp>
 #include <ftxui/component/screen_interactive.hpp>
-#include <ftxui/dom/elements.hpp>
-
-#include <algorithm>
-#include <cctype>
-#include <cstdlib>
-#include <exception>
-#include <filesystem>
-#include <fstream>
-#include <system_error>
 
 using namespace ftxui;
 
 Tui::Tui()
-    : cursor_pos(0), history_idx(-1), quit(false),
+    : cursor_pos(0), history_idx(-1), quit(false), in_source(false),
       screen_idx(0),
       search_types{"parts", "signals"},
-      search_module_idx(0), search_type_idx(0), search_focus_idx(0)
+      search_module_idx(0), search_type_idx(0), search_focus_idx(0),
+      connect_m1_idx(0), connect_m2_idx(0),
+      connect_p1_idx(0), connect_p2_idx(0),
+      connect_focus_idx(0),
+      explore_module_idx(0),
+      explore_types{"parts", "signals", "connections"},
+      explore_type_idx(0), explore_child_idx(0),
+      explore_detail_idx(0), explore_focus_idx(0),
+      settype_m_idx(0), settype_p_idx(0), settype_focus_idx(0)
 {
     LoadHistory();
     RegisterCommands();
@@ -32,450 +29,68 @@ Tui::Tui()
 
 Tui::~Tui() = default;
 
-void Tui::Print(const std::string &line) {
-    output.push_back(line);
-}
-
-void Tui::HistoryUp() {
-    if (history.empty()) return;
-    if (history_idx == -1) history_idx = (int)history.size() - 1;
-    else if (history_idx > 0) history_idx--;
-    input = history[history_idx];
-    cursor_pos = (int)input.size();
-}
-
-void Tui::HistoryDown() {
-    if (history_idx == -1) return;
-    history_idx++;
-    if (history_idx >= (int)history.size()) {
-        history_idx = -1;
-        input.clear();
-    } else {
-        input = history[history_idx];
-    }
-    cursor_pos = (int)input.size();
-}
-
-void Tui::CancelPending() {
-    if (pending.empty()) return;
-    pending.clear();
-    input.clear();
-    cursor_pos = 0;
-    history_idx = -1;
-    Print("(cancelled)");
-}
-
-static std::string ToLower(std::string s) {
-    std::transform(s.begin(), s.end(), s.begin(),
-                   [](unsigned char c) { return std::tolower(c); });
-    return s;
-}
-
-std::vector<std::string> Tui::Tokenize(const std::string &s) {
-    std::vector<std::string> out;
-    std::string cur;
-    bool in_q = false;
-    for (char c : s) {
-        if (c == '"') { in_q = !in_q; continue; }
-        if (!in_q && std::isspace((unsigned char)c)) {
-            if (!cur.empty()) { out.push_back(std::move(cur)); cur.clear(); }
-        } else {
-            cur.push_back(c);
-        }
-    }
-    if (!cur.empty()) out.push_back(std::move(cur));
-    return out;
-}
-
-void Tui::RegisterCommands() {
-    commands["help"] = { {}, [this](auto &) {
-        Print("Commands (give params inline or fill them in via prompt):");
-        Print("  new                                       create a new (empty) system");
-        Print("  load <module> <file> <mentor|altium|ods>  load a module into the system");
-        Print("  search                                    interactive search (parts/signals, live filter)");
-        Print("  clear                                     clear the visualization area");
-        Print("  help                                      show this message");
-        Print("  quit / exit                               leave essim");
-        Print("  Esc                                       cancel a multi-step prompt");
-        Print("  Tab                                       complete command name / file path");
-    }};
-    commands["clear"] = { {}, [this](auto &) { output.clear(); }};
-    commands["quit"]  = { {}, [this](auto &) { quit = true; }};
-    commands["exit"]  = { {}, [this](auto &) { quit = true; }};
-    commands["new"]   = { {}, [this](auto &) {
-        sys = std::make_unique<System>();
-        Print("system created.");
-    }};
-    commands["load"]  = {
-        {{"module name", false},
-         {"filename", true},
-         {"import type [mentor|altium|ods]", false}},
-        [this](const std::vector<std::string> &args) {
-            if (!sys) { Print("no system: run 'new' first."); return; }
-            std::string ls = args[2];
-            std::transform(ls.begin(), ls.end(), ls.begin(),
-                           [](unsigned char c) { return std::tolower(c); });
-            ImportType t;
-            if      (ls == "mentor") t = ImportType::IMPORT_MENTOR;
-            else if (ls == "altium") t = ImportType::IMPORT_ALTIUM;
-            else if (ls == "ods")    t = ImportType::IMPORT_ODS;
-            else { Print("unknown import type: " + args[2]); return; }
-            try {
-                sys->Load(args[0], args[1], t);
-                Module *mod = sys->modules()->get(args[0]);
-                Print("loaded '" + args[0] + "' from " + args[1]);
-                Print("  parts:   " + std::to_string(mod->size()));
-                Print("  signals: " + std::to_string(mod->signals->size()));
-            } catch (const std::exception &e) {
-                Print(std::string("load failed: ") + e.what());
-            }
-        }
-    };
-    commands["search"] = { {}, [this](auto &) {
-        if (!sys) { Print("no system: run 'new' first."); return; }
-        search_modules.clear();
-        for (auto &m : *sys->modules()) search_modules.push_back(m.first);
-        if (search_modules.empty()) { Print("no modules loaded."); return; }
-        search_module_idx = 0;
-        search_type_idx = 0;
-        search_query.clear();
-        search_focus_idx = 0;  // start with the query input focused
-        screen_idx = 1;
-    }};
-}
-
-void Tui::Submit() {
-    if (!pending.empty()) {
-        if (input.empty()) { Print("(empty — Esc to cancel)"); return; }
-        Prompt p = std::move(pending.front());
-        pending.pop_front();
-        Print("  " + p.question + ": " + input);
-        std::string answer = std::move(input);
-        input.clear();
-        cursor_pos = 0;
-        history_idx = -1;
-        p.on_answer(answer);
-        return;
-    }
-
-    if (input.empty()) return;
-    history_idx = -1;
-    Print("> " + input);
-    std::string raw = std::move(input);
-    input.clear();
-    cursor_pos = 0;
-    Dispatch(raw);
-}
-
-void Tui::Dispatch(const std::string &raw) {
-    auto tokens = Tokenize(raw);
-    if (tokens.empty()) return;
-
-    auto it = commands.find(tokens[0]);
-    if (it == commands.end()) {
-        Print("unknown command: " + tokens[0]);
-        history.push_back(raw);
-        AppendHistory(raw);
-        return;
-    }
-
-    const std::string name = it->first;
-    const CommandSpec &spec = it->second;
-
-    if (tokens.size() - 1 > spec.params.size()) {
-        Print("too many arguments for '" + name + "'");
-        history.push_back(raw);
-        AppendHistory(raw);
-        return;
-    }
-
-    auto args = std::make_shared<std::vector<std::string>>(
-        tokens.begin() + 1, tokens.end());
-
-    if (args->size() == spec.params.size()) {
-        Finalize(name, spec, *args);
-        return;
-    }
-
-    for (size_t i = args->size(); i < spec.params.size(); ++i) {
-        bool last = (i + 1 == spec.params.size());
-        const auto &param = spec.params[i];
-        pending.push_back({
-            param.name,
-            [this, name, &spec, args, last](const std::string &s) {
-                args->push_back(s);
-                if (last) Finalize(name, spec, *args);
-            },
-            param.path_completion,
-        });
-    }
-}
-
-void Tui::Finalize(const std::string &name,
-                   const CommandSpec &spec,
-                   const std::vector<std::string> &args) {
-    std::string canonical = name;
-    for (const auto &a : args) {
-        if (a.find_first_of(" \t\"") != std::string::npos)
-            canonical += " \"" + a + "\"";
-        else
-            canonical += " " + a;
-    }
-    history.push_back(canonical);
-    AppendHistory(canonical);
-    spec.action(args);
-}
-
-static std::filesystem::path HistoryPath() {
-    namespace fs = std::filesystem;
-#ifdef _WIN32
-    if (const char *p = std::getenv("LOCALAPPDATA"); p && *p)
-        return fs::path(p) / "essim" / "history";
-    if (const char *p = std::getenv("APPDATA"); p && *p)
-        return fs::path(p) / "essim" / "history";
-    if (const char *p = std::getenv("USERPROFILE"); p && *p)
-        return fs::path(p) / "AppData" / "Local" / "essim" / "history";
-#else
-    if (const char *p = std::getenv("XDG_DATA_HOME"); p && *p)
-        return fs::path(p) / "essim" / "history";
-    if (const char *p = std::getenv("HOME"); p && *p)
-        return fs::path(p) / ".local" / "share" / "essim" / "history";
-#endif
-    return {};
-}
-
-void Tui::LoadHistory() {
-    auto p = HistoryPath();
-    if (p.empty()) return;
-    std::ifstream f(p);
-    std::string line;
-    while (std::getline(f, line))
-        if (!line.empty()) history.push_back(line);
-}
-
-void Tui::AppendHistory(const std::string &cmd) {
-    auto p = HistoryPath();
-    if (p.empty()) return;
-    std::string trimmed = cmd;
-    while (!trimmed.empty() && std::isspace((unsigned char)trimmed.back()))
-        trimmed.pop_back();
-    if (trimmed.empty()) return;
-    std::error_code ec;
-    std::filesystem::create_directories(p.parent_path(), ec);
-    if (ec) return;
-    std::ofstream f(p, std::ios::app);
-    if (f) f << trimmed << '\n';
-}
-
-static std::string LongestCommonPrefix(const std::vector<std::string> &v) {
-    if (v.empty()) return "";
-    std::string lcp = v[0];
-    for (size_t i = 1; i < v.size(); ++i) {
-        size_t k = 0;
-        while (k < lcp.size() && k < v[i].size() && lcp[k] == v[i][k]) ++k;
-        lcp.resize(k);
-    }
-    return lcp;
-}
-
-void Tui::CompleteCommand() {
-    std::vector<std::string> matches;
-    for (const auto &kv : commands)
-        if (kv.first.rfind(input, 0) == 0) matches.push_back(kv.first);
-
-    if (matches.empty()) return;
-    if (matches.size() == 1) { input = matches[0]; cursor_pos = (int)input.size(); return; }
-
-    std::string lcp = LongestCommonPrefix(matches);
-    if (lcp.size() > input.size()) { input = lcp; cursor_pos = (int)input.size(); return; }
-
-    std::string line = " ";
-    for (const auto &m : matches) line += " " + m;
-    Print(line);
-}
-
-void Tui::CompletePath() {
-    namespace fs = std::filesystem;
-
-    auto pos = input.rfind('/');
-    std::string disp, prefix;
-    if (pos == std::string::npos) { disp = ""; prefix = input; }
-    else { disp = input.substr(0, pos + 1); prefix = input.substr(pos + 1); }
-
-    std::string resolved = disp.empty() ? "." : disp;
-    if (!resolved.empty() && resolved[0] == '~') {
-        if (const char *home = std::getenv("HOME"))
-            resolved = std::string(home) + resolved.substr(1);
-    }
-
-    std::vector<std::string> names;
-    std::vector<bool> is_dir;
-    try {
-        for (const auto &e : fs::directory_iterator(resolved)) {
-            std::string n = e.path().filename().string();
-            if (n.rfind(prefix, 0) == 0) {
-                names.push_back(n);
-                is_dir.push_back(e.is_directory());
-            }
-        }
-    } catch (const std::exception &) {
-        return;
-    }
-    if (names.empty()) return;
-
-    if (names.size() == 1) {
-        input = disp + names[0] + (is_dir[0] ? "/" : "");
-        cursor_pos = (int)input.size();
-        return;
-    }
-
-    std::string lcp = LongestCommonPrefix(names);
-    if (lcp.size() > prefix.size()) { input = disp + lcp; cursor_pos = (int)input.size(); return; }
-
-    std::string line = " ";
-    for (size_t i = 0; i < names.size(); ++i)
-        line += " " + names[i] + (is_dir[i] ? "/" : "");
-    Print(line);
-}
-
 void Tui::Run() {
     auto screen = ScreenInteractive::Fullscreen();
 
-    // ---- Main TUI ----
-    InputOption opt;
-    opt.multiline = false;
-    opt.cursor_position = &cursor_pos;
-    opt.on_enter = [this] { Submit(); };
-    opt.transform = [](InputState s) {
-        auto el = s.element;
-        if (s.is_placeholder) el |= dim;
-        return el;
-    };
-    auto input_component = Input(&input, "type a command…", opt);
+    auto main_screen    = BuildMainScreen(screen);
+    auto search_screen  = BuildSearchScreen();
+    auto connect_screen = BuildConnectScreen();
+    auto settype_screen = BuildSettypeScreen();
+    auto explore_screen = BuildExploreScreen();
 
-    auto main_renderer = Renderer(input_component, [this, &screen, input_component] {
-        if (quit) screen.Exit();
-
-        Elements lines;
-        for (const auto &l : output) lines.push_back(text(l));
-        auto view = vbox(std::move(lines))
-                  | focusPositionRelative(0, 1)
-                  | yframe
-                  | flex;
-
-        std::string label = pending.empty()
-            ? "> "
-            : pending.front().question + "? ";
-
-        return vbox({
-            view,
-            separator(),
-            hbox({text(label), input_component->Render()}),
-        }) | border;
-    });
-
-    // ---- Search screen ----
-    InputOption query_opt;
-    query_opt.multiline = false;
-    query_opt.transform = opt.transform;
-    auto query_input = Input(&search_query, "filter…", query_opt);
-    auto module_menu = Menu(&search_modules, &search_module_idx);
-    auto type_menu   = Menu(&search_types,   &search_type_idx);
-
-    auto search_components = Container::Vertical(
-        {query_input, module_menu, type_menu}, &search_focus_idx);
-
-    auto search_renderer = Renderer(search_components,
-            [this, query_input, module_menu, type_menu] {
-        // Compute filtered list.
-        Elements result_lines;
-        int total = 0;
-        if (!search_modules.empty() && sys) {
-            const std::string &mname = search_modules[search_module_idx];
-            try {
-                Module *mod = sys->modules()->get(mname);
-                std::string needle = ToLower(search_query);
-                if (search_type_idx == 0) {  // parts
-                    for (auto &pkv : *mod) {
-                        if (needle.empty()
-                            || ToLower(pkv.first).find(needle) != std::string::npos) {
-                            result_lines.push_back(
-                                text("  " + pkv.first
-                                     + "  (" + std::to_string(pkv.second->size()) + " pins)"));
-                            ++total;
-                        }
-                    }
-                } else {  // signals
-                    for (auto &skv : *mod->signals) {
-                        if (needle.empty()
-                            || ToLower(skv.first).find(needle) != std::string::npos) {
-                            result_lines.push_back(
-                                text("  " + skv.first
-                                     + "  (" + std::to_string(skv.second->size()) + " pins)"));
-                            ++total;
-                        }
-                    }
-                }
-            } catch (const std::exception &) {}
-        }
-
-        auto left = vbox({
-            text("module") | bold,
-            module_menu->Render() | yframe | flex,
-            separator(),
-            text("type") | bold,
-            type_menu->Render(),
-        }) | size(WIDTH, EQUAL, 28);
-
-        auto right = vbox({
-            hbox({text(" search: "), query_input->Render() | flex}) | border,
-            text(std::to_string(total) + " match(es)") | dim,
-            vbox(std::move(result_lines)) | yframe | flex,
-        }) | flex;
-
-        return vbox({
-            hbox({left, separator(), right}) | flex,
-            text(" Tab: cycle focus   |   Esc: leave search ") | dim,
-        }) | border;
-    });
-
-    // ---- Screen tab + global key handling ----
-    auto tab = Container::Tab({main_renderer, search_renderer}, &screen_idx);
+    auto tab = Container::Tab(
+        {main_screen, search_screen, connect_screen, settype_screen, explore_screen},
+        &screen_idx);
 
     auto root = CatchEvent(tab, [this](Event e) {
-        if (screen_idx == 1) {
-            // Search mode
+        switch (screen_idx) {
+        case 4:  // explore
             if (e == Event::Escape) { screen_idx = 0; return true; }
-            // Cycle focus query → modules → type → query (Menu eats Tab otherwise).
-            if (e == Event::Tab) {
-                search_focus_idx = (search_focus_idx + 1) % 3;
-                return true;
-            }
-            if (e == Event::TabReverse) {
-                search_focus_idx = (search_focus_idx + 2) % 3;
-                return true;
-            }
-            return false;  // let menus / input handle the rest
-        }
+            if (e == Event::Tab)        { explore_focus_idx = (explore_focus_idx + 1) % 6; return true; }
+            if (e == Event::TabReverse) { explore_focus_idx = (explore_focus_idx + 5) % 6; return true; }
+            return false;
 
-        // Main mode
-        if (e == Event::Escape && !pending.empty()) { CancelPending(); return true; }
-        if (e == Event::ArrowUp || e == Event::ArrowDown) {
-            if (pending.empty()) {
-                if (e == Event::ArrowUp) HistoryUp();
-                else                     HistoryDown();
+        case 3:  // set-type
+            if (e == Event::Escape) { screen_idx = 0; return true; }
+            if (e == Event::Tab)        { settype_focus_idx = (settype_focus_idx + 1) % 5; return true; }
+            if (e == Event::TabReverse) { settype_focus_idx = (settype_focus_idx + 4) % 5; return true; }
+            return false;
+
+        case 2:  // connect
+            if (e == Event::Escape) { screen_idx = 0; return true; }
+            if (e == Event::Tab)        { connect_focus_idx = (connect_focus_idx + 1) % 7; return true; }
+            if (e == Event::TabReverse) { connect_focus_idx = (connect_focus_idx + 6) % 7; return true; }
+            return false;
+
+        case 1:  // search
+            if (e == Event::Escape) { screen_idx = 0; return true; }
+            if (e == Event::Tab)        { search_focus_idx = (search_focus_idx + 1) % 3; return true; }
+            if (e == Event::TabReverse) { search_focus_idx = (search_focus_idx + 2) % 3; return true; }
+            return false;
+
+        default:  // main
+            if (e == Event::Escape && !pending.empty()) { CancelPending(); return true; }
+            if (e == Event::ArrowUp || e == Event::ArrowDown) {
+                if (pending.empty()) {
+                    if (e == Event::ArrowUp) HistoryUp();
+                    else                     HistoryDown();
+                }
+                return true;
             }
-            return true;
-        }
-        if (e == Event::Tab) {
-            if (pending.empty()) {
-                if (input.find(' ') == std::string::npos) CompleteCommand();
-            } else if (pending.front().path_completion) {
-                CompletePath();
+            if (e == Event::Tab) {
+                if (pending.empty()) {
+                    CompleteInline();
+                } else {
+                    switch (pending.front().completion) {
+                        case Completion::Path:    CompletePath();    break;
+                        case Completion::Command: CompleteCommand(); break;
+                        case Completion::None:                       break;
+                    }
+                }
+                return true;
             }
-            return true;
+            return false;
         }
-        return false;
     });
 
     screen.Loop(root);

src/tui/tui.hpp

@@ -8,36 +8,50 @@
 #include <string>
 #include <vector>
 
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/screen_interactive.hpp>
+
 class System;
 
 class Tui {
+    enum class Completion { None, Path, Command };
+
     struct Prompt {
         std::string question;
         std::function<void(const std::string &)> on_answer;
-        bool path_completion = false;
+        Completion completion = Completion::None;
     };
 
     struct CommandSpec {
         struct Param {
             std::string name;
-            bool path_completion = false;
+            Completion completion = Completion::None;
         };
         std::vector<Param> params;
         std::function<void(const std::vector<std::string> &)> action;
+        bool prompt_for_missing = true;
+        std::string description;
+        bool scriptable = true;
     };
 
+    // ---- Shell state ----
     std::vector<std::string> history;
+    std::vector<std::string> recorded;  // commands since the last 'new', for script-save
     std::vector<std::string> output;
     std::string input;
     int cursor_pos;
     int history_idx;
     bool quit;
+    bool in_source;
 
     std::unique_ptr<System> sys;
     std::deque<Prompt> pending;
     std::map<std::string, CommandSpec> commands;
 
+    // ---- Screen orchestration ----
     int screen_idx;
+
+    // ---- Search screen state ----
     std::vector<std::string> search_modules;
     std::vector<std::string> search_types;
     int search_module_idx;
@@ -45,31 +59,84 @@ class Tui {
     int search_focus_idx;
     std::string search_query;
 
+    // ---- Connect screen state ----
+    std::vector<std::string> connect_modules;
+    int connect_m1_idx;
+    int connect_m2_idx;
+    std::string connect_p1_filter;
+    std::string connect_p2_filter;
+    std::vector<std::string> connect_p1_list;
+    std::vector<std::string> connect_p2_list;
+    int connect_p1_idx;
+    int connect_p2_idx;
+    int connect_focus_idx;
+
+    // ---- Explore screen state ----
+    std::vector<std::string> explore_modules;
+    int explore_module_idx;
+    std::vector<std::string> explore_types;
+    int explore_type_idx;
+    std::vector<std::string> explore_children;
+    int explore_child_idx;
+    std::string explore_child_filter;
+    std::string explore_detail_filter;
+    std::vector<std::string> explore_detail;
+    int explore_detail_idx;
+    std::string explore_header;
+    int explore_focus_idx;
+
+    // ---- Set-type screen state ----
+    std::vector<std::string> settype_modules;
+    int settype_m_idx;
+    std::string settype_p_filter;
+    std::vector<std::string> settype_p_list;
+    int settype_p_idx;
+    std::string settype_type;
+    std::string settype_status;
+    int settype_focus_idx;
+
 public:
     Tui();
     ~Tui();
     void Run();
 
 private:
+    // Lifecycle (commands.cpp)
     void RegisterCommands();
+
+    // Shell (shell.cpp)
+    void Print(const std::string &line);
     void Submit();
     void Dispatch(const std::string &raw);
     void Finalize(const std::string &name,
                   const CommandSpec &spec,
                   const std::vector<std::string> &args);
-
     void HistoryUp();
     void HistoryDown();
     void CancelPending();
-    void Print(const std::string &line);
-
-    void CompleteCommand();
-    void CompletePath();
-
     void LoadHistory();
     void AppendHistory(const std::string &cmd);
-
+    void Source(const std::string &filename);
     static std::vector<std::string> Tokenize(const std::string &s);
+
+    // Completion (completion.cpp)
+    void CompleteCommand(size_t start = 0);
+    void CompletePath(size_t start = 0);
+    void CompleteInline();
+
+    // Filtered part list rebuild (used by connect & set-type screens)
+    void RefreshFilteredPartList(const std::vector<std::string> &modules,
+                                  int m_idx,
+                                  const std::string &filter,
+                                  std::vector<std::string> &out,
+                                  int &sel_idx);
+
+    // Screen builders (screen_*.cpp)
+    ftxui::Component BuildMainScreen(ftxui::ScreenInteractive &screen);
+    ftxui::Component BuildSearchScreen();
+    ftxui::Component BuildConnectScreen();
+    ftxui::Component BuildSettypeScreen();
+    ftxui::Component BuildExploreScreen();
 };
 
 #endif // _TUI_HPP_

src/tui/tui_helpers.cpp

@@ -0,0 +1,54 @@
+#include "tui/tui_helpers.hpp"
+
+#include <algorithm>
+#include <cctype>
+
+std::string ToLower(std::string s) {
+    std::transform(s.begin(), s.end(), s.begin(),
+                   [](unsigned char c) { return std::tolower(c); });
+    return s;
+}
+
+bool NaturalLess(const std::string &a, const std::string &b) {
+    size_t i = 0, j = 0;
+    while (i < a.size() && j < b.size()) {
+        unsigned char ca = (unsigned char)a[i];
+        unsigned char cb = (unsigned char)b[j];
+        if (std::isdigit(ca) && std::isdigit(cb)) {
+            size_t za = 0, zb = 0;
+            while (i + za < a.size() && a[i + za] == '0') ++za;
+            while (j + zb < b.size() && b[j + zb] == '0') ++zb;
+            size_t ea = i + za;
+            while (ea < a.size() && std::isdigit((unsigned char)a[ea])) ++ea;
+            size_t eb = j + zb;
+            while (eb < b.size() && std::isdigit((unsigned char)b[eb])) ++eb;
+            size_t la = ea - (i + za);
+            size_t lb = eb - (j + zb);
+            if (la != lb) return la < lb;
+            int cmp = a.compare(i + za, la, b, j + zb, lb);
+            if (cmp != 0) return cmp < 0;
+            if (za != zb) return za > zb;
+            i = ea;
+            j = eb;
+        } else {
+            char la = (char)std::tolower(ca);
+            char lb = (char)std::tolower(cb);
+            if (la != lb) return la < lb;
+            ++i; ++j;
+        }
+    }
+    if (i < a.size()) return false;
+    if (j < b.size()) return true;
+    return false;
+}
+
+std::string LongestCommonPrefix(const std::vector<std::string> &v) {
+    if (v.empty()) return "";
+    std::string lcp = v[0];
+    for (size_t i = 1; i < v.size(); ++i) {
+        size_t k = 0;
+        while (k < lcp.size() && k < v[i].size() && lcp[k] == v[i][k]) ++k;
+        lcp.resize(k);
+    }
+    return lcp;
+}

src/tui/tui_helpers.hpp

@@ -0,0 +1,17 @@
+#ifndef _TUI_HELPERS_HPP_
+#define _TUI_HELPERS_HPP_
+
+#include <string>
+#include <vector>
+
+// Free helpers shared across the TUI translation units.
+
+std::string ToLower(std::string s);
+
+// Case-insensitive natural-order comparison: digit runs compared as integers,
+// letters compared after std::tolower.
+bool NaturalLess(const std::string &a, const std::string &b);
+
+std::string LongestCommonPrefix(const std::vector<std::string> &v);
+
+#endif // _TUI_HELPERS_HPP_