tui: fix nested source abandoning the calling script

Tui::Source kept the script position in single member fields
(loading_lines/idx/...), so a sourced line that was itself `source inner`
overwrote them: when the inner file finished, the outer script's remaining
lines were silently dropped.

The state is now a stack of SourceFrames — the stack is the call chain. A
nested source just pushes a frame (the running driver, ticker thread or
headless drain, picks it up next line) and the caller's frame resumes when
it pops. Each frame still prints its own "source: <file> (N line(s))"
summary; an interactive-line abort clears the whole chain; depth capped at
32 like the core script engine. The Computing modal shows the top frame.

Regression-tested headless via BootDispatch (tests/tui/test_source.cpp):
nested-then-continue, and self-recursion hitting the depth guard.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -1 +1 @@
-build/
+build*/

CMakeLists.txt

@@ -11,49 +11,64 @@ project(essim
 
 include(FetchContent)
 
-set(FTXUI_BUILD_DOCS OFF CACHE INTERNAL "")
+# Shared CMake helpers (essim_add_frontend — per-frontend target boilerplate).
-set(FTXUI_BUILD_EXAMPLES OFF CACHE INTERNAL "")
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
-set(FTXUI_BUILD_TESTS OFF CACHE INTERNAL "")
+include(EssimFrontend)
-set(FTXUI_ENABLE_INSTALL OFF CACHE INTERNAL "")
 
-FetchContent_Declare(ftxui
+# ----------------------------------------------------------------- core deps
-  GIT_REPOSITORY https://github.com/ArthurSonzogni/FTXUI.git
+# libbsdl — standalone BSDL parser (LGPL-2.1), dynamically linked (EUPL-1.2,
-  GIT_TAG v6.1.9
+# which the LGPL permits). Override its path with -DBSDL_DIR=...
-  GIT_SHALLOW TRUE
-)
-FetchContent_MakeAvailable(ftxui)
-
-find_package(libzip REQUIRED)
-find_package(pugixml REQUIRED)
-
-# libbsdl — standalone BSDL parser (LGPL-2.1), dynamically linked from essim
-# (EUPL-1.2, which the LGPL permits). Path overridable via -DBSDL_DIR=...;
-# its CLI and tests are not needed inside essim's build.
 set(BSDL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../libbsdl" CACHE PATH "libbsdl source tree")
 set(BSDL_BUILD_CLI   OFF CACHE BOOL "" FORCE)
 set(BSDL_BUILD_TESTS OFF CACHE BOOL "" FORCE)
 add_subdirectory(${BSDL_DIR} ${CMAKE_BINARY_DIR}/libbsdl)
 
-# Library target = everything except main.cpp; reused by `essim` and `essim_tests`.
+find_package(libzip REQUIRED)
-file(GLOB_RECURSE LIB_SOURCES "src/*.cpp")
+find_package(pugixml REQUIRED)
-list(REMOVE_ITEM LIB_SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/src/main.cpp")
 
-add_library(essim_lib STATIC ${LIB_SOURCES})
+# =============================================================== essim_core
-target_include_directories(essim_lib PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/src)
+# All business logic — domain model, importers, application operations
-target_link_libraries(essim_lib
+# (src/core/{domain,imports,app}). Frontend-agnostic: it links NO GUI/TUI
+# toolkit, so every frontend and the test suite share the exact same core.
+file(GLOB_RECURSE CORE_SOURCES "src/core/*.cpp")
+add_library(essim_core STATIC ${CORE_SOURCES})
+target_include_directories(essim_core PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/src)
+target_link_libraries(essim_core
   PUBLIC
-    ftxui::screen
-    ftxui::dom
-    ftxui::component
     libzip::zip
     pugixml::pugixml
     bsdl::bsdl
 )
 
-add_executable(essim src/main.cpp)
+# =============================================================== frontend(s)
-target_link_libraries(essim PRIVATE essim_lib)
+# Pick the GUI/TUI frontend to build the `essim` binary against. Each frontend
+# is a self-contained src/frontends/<name>/ (own CMakeLists, GUI toolkit, and
+# main.cpp) that links essim_core. "none" builds the core + tests only — no GUI
+# toolkit is fetched. To add a frontend (e.g. a Qt GUI), create
+# src/frontends/gui/ and configure with -DESSIM_FRONTEND=gui.
+set(ESSIM_FRONTEND "tui" CACHE STRING
+    "Frontend to build: a directory name under src/frontends/, or 'none'")
+set_property(CACHE ESSIM_FRONTEND PROPERTY STRINGS tui wx none)
 
-# Tests
+if(ESSIM_FRONTEND STREQUAL "none")
+  message(STATUS "essim: ESSIM_FRONTEND=none — core + tests only (no frontend, no GUI toolkit)")
+elseif(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/src/frontends/${ESSIM_FRONTEND}/CMakeLists.txt")
+  message(STATUS "essim: building frontend '${ESSIM_FRONTEND}'")
+  # Shared, GUI-toolkit-free frontend support: the abstract Frontend interface
+  # (header-only) and the frontend-agnostic launcher frontend_main(). Every
+  # frontend's main() links this and forwards argv to it.
+  add_library(essim_frontend STATIC
+    "${CMAKE_CURRENT_SOURCE_DIR}/src/frontends/frontend_main.cpp")
+  target_include_directories(essim_frontend PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/src)
+  add_subdirectory(src/frontends/${ESSIM_FRONTEND})
+else()
+  message(FATAL_ERROR
+    "Unknown ESSIM_FRONTEND '${ESSIM_FRONTEND}' — expected "
+    "src/frontends/${ESSIM_FRONTEND}/CMakeLists.txt, or 'none'.")
+endif()
+
+# =============================================================== tests (core)
+# The suite exercises essim_core only — no frontend, no GUI toolkit.
 include(CTest)
 if(BUILD_TESTING)
   set(CMAKE_POLICY_VERSION_MINIMUM 3.5)
@@ -65,20 +80,35 @@ if(BUILD_TESTING)
   FetchContent_MakeAvailable(doctest)
   unset(CMAKE_POLICY_VERSION_MINIMUM)
 
+  # Core tests — exercise essim_core only (tests/*.cpp, non-recursive, so the
+  # per-frontend tests under tests/<frontend>/ are not pulled in here).
   file(GLOB TEST_SOURCES "tests/*.cpp")
   if(TEST_SOURCES)
     add_executable(essim_tests ${TEST_SOURCES})
-    target_link_libraries(essim_tests PRIVATE essim_lib doctest::doctest)
+    target_link_libraries(essim_tests PRIVATE essim_core doctest::doctest)
     add_test(NAME essim_tests COMMAND essim_tests)
   endif()
+
+  # Per-frontend tests — tests/<frontend>/*.cpp, built and linked against that
+  # frontend's library only when the frontend itself is built.
+  if(TARGET essim_tui)
+    file(GLOB TUI_TEST_SOURCES "tests/tui/*.cpp")
+    if(TUI_TEST_SOURCES)
+      add_executable(essim_tui_tests
+        "${CMAKE_CURRENT_SOURCE_DIR}/tests/doctest_main.cpp" ${TUI_TEST_SOURCES})
+      target_link_libraries(essim_tui_tests PRIVATE essim_tui doctest::doctest)
+      add_test(NAME essim_tui_tests COMMAND essim_tui_tests)
+    endif()
+  endif()
 endif()
 
-# Documentation: Doxygen → XML → custom Python script → doc/api/ (Markdown rendered by gitea).
+# =============================================================== documentation
-# Optional — `doc` target is only created if Doxygen and Python 3 are present.
+# Doxygen → XML → gen_api_md.py → doc/api/, plus `essim --commands-md`. Needs the
+# `essim` binary, so it's only wired when a frontend that provides one is built.
 find_package(Doxygen COMPONENTS doxygen)
 find_package(Python3 COMPONENTS Interpreter)
 
-if(DOXYGEN_FOUND AND Python3_Interpreter_FOUND)
+if(TARGET essim AND DOXYGEN_FOUND AND Python3_Interpreter_FOUND)
   set(DOXYGEN_OUTPUT_DIR "${CMAKE_BINARY_DIR}/doc")
   file(MAKE_DIRECTORY "${DOXYGEN_OUTPUT_DIR}")
   configure_file(
@@ -103,11 +133,10 @@ if(DOXYGEN_FOUND AND Python3_Interpreter_FOUND)
     WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
     COMMENT "Generating documentation (doxygen → gen_api_md.py → doc/api/, essim --commands-md → doc/user/commands.md)"
     VERBATIM)
-elseif(NOT DOXYGEN_FOUND AND NOT Python3_Interpreter_FOUND)
+elseif(NOT TARGET essim)
-  message(STATUS "doc: Doxygen and Python 3 not found — `doc` target disabled.")
+  message(STATUS "doc: no `essim` binary (ESSIM_FRONTEND=none) — `doc` target disabled.")
 elseif(NOT DOXYGEN_FOUND)
-  message(STATUS "doc: Doxygen not found — `doc` target disabled "
+  message(STATUS "doc: Doxygen not found — `doc` target disabled.")
-                 "(install via `pacman -S doxygen`).")
 else()
   message(STATUS "doc: Python 3 interpreter not found — `doc` target disabled.")
 endif()

DESIGN.md

@@ -10,72 +10,120 @@ cmake --build build -j
 ./build/essim
 ```
 
-- CMake **3.14+** required (uses `FetchContent_MakeAvailable`).
+- CMake **3.14+** (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/`.
+- **Layered build** (see *Architecture* below). `essim_core` is the
-- **System dependencies** (resolved via `find_package`): `libzip` (target `libzip::zip`) and `pugixml` (target `pugixml::pugixml`). Used by the ODS importer. Arch: `pacman -S libzip pugixml`; Debian/Ubuntu: `libzip-dev libpugixml-dev`.
+  frontend-agnostic business library; a frontend under `src/frontends/<name>/`
-- **`libbsdl`** (standalone BSDL parser, LGPL-2.1) is the sibling repo at `../libbsdl`, pulled in via `add_subdirectory` (path overridable with `-DBSDL_DIR=...`) and linked dynamically (`bsdl::bsdl`; an LGPL `.so` is fine from EUPL essim). Powers the BSDL ingest behind `attach-bsdl`.
+  links it and produces the `essim` binary. Choose it with
-- 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".
+  `-DESSIM_FRONTEND=<name>` (default `tui`). **`-DESSIM_FRONTEND=none` builds the
+  core + tests only — no GUI toolkit is fetched.**
+- **Core system dependencies** (via `find_package`): `libzip` (`libzip::zip`)
+  and `pugixml` (`pugixml::pugixml`) for the ODS importer. Arch:
+  `pacman -S libzip pugixml`; Debian/Ubuntu: `libzip-dev libpugixml-dev`.
+- **`libbsdl`** (standalone BSDL parser, LGPL-2.1) — sibling repo at
+  `../libbsdl`, `add_subdirectory` (override `-DBSDL_DIR=...`), linked
+  dynamically **into the core** (`bsdl::bsdl`).
+- **FTXUI** is fetched by the **tui frontend only**
+  (`src/frontends/tui/CMakeLists.txt`), never by the core.
+- Sources are globbed per layer: `src/core/*.cpp` → `essim_core`,
+  `src/frontends/<fe>/*.cpp` → that frontend's lib + the `essim` binary.
+  **After adding a `.cpp`, re-run `cmake -S . -B build`** — CMake doesn't re-glob.
+- **Tests** are split: `essim_tests` links `essim_core` (no FTXUI) from
+  `tests/*.cpp`; per-frontend tests like `essim_tui_tests` link `essim_tui` from
+  `tests/<frontend>/*.cpp`.
 - **Headless / batch**: `essim --batch --source FILE` runs a script and prints its console output to stdout, then exits without the TUI (good for CI / capturing `verify`). Also `--restore FILE` and `--commands-md [FILE]`. `BootDispatch` runs `--restore`/`--source` synchronously before the event loop (`Source` takes its headless drain branch when no screen is attached), so the console buffer is complete by the time `--batch` dumps it (`Tui::DumpOutput`).
 
 ## Layout
 
 ```
 src/
-  main.cpp               -- launches Tui
+  core/                  -- business logic; NO GUI toolkit (builds libessim_core)
-  system/                -- domain model
+    domain/              -- the model + read-only analyses
-    syselmts.hpp           SystemElement + SystemElementContainer<T> (templated, get/merge/iterate)
+      syselmts.hpp         SystemElement + SystemElementContainer<T> (get/merge/iterate)
-    modules.{hpp,cpp}      Module, Modules
+      modules.{hpp,cpp}    Module, Modules
-    parts.{hpp,cpp}        Part (carries `kind` + `connector_type`), Parts
+      parts.{hpp,cpp}      Part (kind, connector_type, bsdl_path; PinSpec per pin)
-    pins.{hpp,cpp}         Pin (carries PinSpec `spec`), Pins
+      pins.{hpp,cpp}       Pin (carries PinSpec `spec`), Pins
-    signals.{hpp,cpp}      Signal, Signals
+      signals.{hpp,cpp}    Signal, Signals
-    signal_type.hpp        SignalType + helpers
+      signal_type.hpp      SignalType + helpers
-    pin_spec.hpp           PinSpec (function/direction/pad/source) + SignalType mapping
+      pin_spec.hpp         PinSpec (function/direction/pad/source), mappings, spec_source_rank
-    component_kind.{hpp,cpp} ComponentKind enum + infer_component_kind(name)
+      component_kind.{hpp,cpp}  ComponentKind + infer_component_kind(name)
-    pin_name.{hpp,cpp}     canonical_pin_name(s) — zero-pad digit suffix to 3
+      pin_name.{hpp,cpp}   canonical_pin_name (zero-pad digit suffix to 3)
-    connect.{hpp,cpp}      Connection, Connections
+      connect.{hpp,cpp}    Connection, Connections
-    transform.{hpp,cpp}    Transform / IdentityTransform / TransformRegistry +
+      transform*.{hpp,cpp} Transform / IdentityTransform / TransformRegistry, VPX transform
-                           CheckIdentityCompatible + FillIdentityNCs
+      pin_role.{hpp,cpp}   pin_role(kind,name) -> PinSpec, pin_layout, FillPartFromLayout
-    pin_role.{hpp,cpp}     pin_role(kind, name) → PinSpec, pin_layout(kind),
+      pin_model.{hpp,cpp}  PinModel + apply_model(Part*, model) + ConnectorModel
-                           FillPartFromLayout(part, kind)
+      bsdl_model.{hpp,cpp} BsdlModel (libbsdl wrapper) + BsdlPinModel + apply_bsdl
-    pin_model.{hpp,cpp}    PinModel + apply_model(Part*, model) + ConnectorModel
+      bsdl_check.{hpp,cpp} check_pin_specs / _jtag_chain / _source_conflicts / _bsdl_completeness
-    bsdl_model.{hpp,cpp}   BsdlModel (libbsdl wrapper) + BsdlPinModel + apply_bsdl
+      nets.{hpp,cpp}       find_net / compute_all_nets / net_type_consistent
-    bsdl_check.{hpp,cpp}   check_pin_specs / check_jtag_chain → vector<Anomaly>
+      analysis.{hpp,cpp}   analyze_system -> AnalysisReport (diff pairs, buses, anomalies)
-    nets.{hpp,cpp}         find_net / compute_all_nets / net_type_consistent
+      persist.{hpp,cpp}    save / restore (tab-delimited; `B` tag = bsdl_path)
-    analysis.{hpp,cpp}     analyze_system → AnalysisReport (diff pairs, buses, anomalies)
+      system.{hpp,cpp}     System: owns Modules + Connections, Load()
-    persist.{hpp,cpp}      save / restore (tab-delimited)
+    imports/             -- netlist / pinout adapters
-    system.{hpp,cpp}       System: owns Modules + Connections, exposes Load()
+      import_base.hpp / import_{mentor,altium,ods}.{hpp,cpp} / ods_writer.{hpp,cpp}
-  imports/               -- adapters that populate or emit the domain
+    app/                 -- application operations (UI-independent use cases)
-    import_base.hpp        ImportBase interface
+      export.{hpp,cpp}     export_connections(System*, path, format) -> ExportResult
-    import_mentor.{hpp,cpp} Mentor Graphics netlist parser
+      verify.{hpp,cpp}     verify(System*) -> VerifyReport (the 7 verify passes)
-    import_altium.{hpp,cpp} Altium netlist parser (`[ ]` parts, `( )` signals)
+      connect.{hpp,cpp}    connect_parts(System*, m1,p1, m2,p2) -> ConnectResult
-    import_ods.{hpp,cpp}   ODS spreadsheet pinout (libzip + pugixml)
+      load.{hpp,cpp}       load_module(System*, name, path, ImportType) -> LoadResult
-    ods_writer.{hpp,cpp}   Minimal .ods writer (multi-sheet, string cells)
+  frontends/             -- one directory per GUI/TUI engine; each links essim_core
-  tui/                   -- FTXUI shell, split by responsibility
+    frontend.hpp         -- abstract Frontend interface (BootDispatch/Dump*/Run)
-    tui.{hpp,cpp}          Class Tui (state + Run() orchestrator + screen-mode event dispatcher)
+    frontend_main.{hpp,cpp} -- frontend_main(argc,argv,Frontend&): argv + boot/batch/run
-    tui_helpers.{hpp,cpp}  Free helpers: ToLower, NaturalLess, LongestCommonPrefix
+    tui/                 -- FTXUI shell (builds libessim_tui + the `essim` binary)
-    shell.cpp              Print, Submit, Dispatch, Finalize, Tokenize, history persistence
+      CMakeLists.txt       fetches FTXUI; builds essim_tui + essim
-    completion.cpp         CompleteCommand, CompletePath, CompleteInline
+      main.cpp             entry point: construct Tui, call frontend_main
-    commands.cpp           RegisterCommands (orchestrator + lifecycle / shell / topology commands)
+      tui.{hpp,cpp}        class Tui (state + Run() + screen-mode event dispatch)
-    commands_export.cpp    RegisterExportCommands (export → CSV / ODS, file-dialog hook)
+      tui_helpers.{hpp,cpp}  ToLower, NaturalLess, RenderHelpPanel
-    screen_main.cpp        BuildMainScreen (visualisation area + bottom input)
+      shell.cpp            Print, Submit, Dispatch, Source / ProcessNextSourceLine
-    screen_connect.cpp     BuildConnectScreen + shared RefreshFilteredPartList helper
+      completion.cpp       CompleteCommand / CompletePath / CompleteInline
-    screen_settype.cpp     BuildSettypeScreen
+      commands.cpp         RegisterCommands (thin: resolve args -> call core -> render)
-    screen_explore.cpp     BuildExploreScreen (browse modules → parts/signals/connections → details; not scriptable)
+      commands_export.cpp  thin wrapper over app::export_connections
-    screen_dashboard.cpp   BuildDashboardScreen (read-only system overview)
+      screen_*.cpp         dashboard, connect, settype, explore, analyze, help, main
-    screen_analyze.cpp     BuildAnalyzeScreen (anomalies / groups / power decisions)
+                           (console), palette, file dialog, error/confirm, sigtype modal
-    screen_palette.cpp     BuildPaletteModal (global Ctrl-P fuzzy launcher)
+    wx/                  -- wxWidgets GUI (builds libessim_wx + the `essim` binary)
-    screen_filedialog.cpp  BuildFileDialog + OpenFileDialog (reusable file picker)
+      CMakeLists.txt       find_package(wxWidgets) + essim_add_frontend(wx ...)
-    screen_error.cpp       BuildErrorModal + ShowError (centred error popup)
+      main.cpp             entry point: construct WxFrontend, call frontend_main
-    screen_help.cpp        BuildHelpScreen (topic-driven feature reference)
+      wx_frontend.{hpp,cpp}  WxFrontend : Frontend (owns System; boots wx in Run())
-    screen_sigtype_modal.cpp BuildSignalTypeModal (popup attached to explore via Modal())
+      wx_frame.{hpp,cpp}   EssimFrame: menu/tree/overview/log over core + app::*
-doc/classes.puml         -- PlantUML class diagram
+cmake/EssimFrontend.cmake  -- essim_add_frontend(name LIBS ...) per-frontend wiring
+tests/                   -- core tests (link essim_core)
+  tui/                   -- frontend tests (link essim_tui)
+doc/ , test/             -- docs; sample netlists + system.essim bring-up script
 ```
 
-`include/` and `lib/` are kept empty by design — FTXUI used to live there as precompiled `.a` + headers, now it comes through FetchContent.
+## Architecture — core vs frontends
+
+The hard rule: **`src/core/` never depends on a frontend** — no `#include
+"frontends/…"`, no GUI toolkit. Frontends depend on the core, never the reverse
+(`essim_core` links libzip / pugixml / bsdl only).
+
+- **Domain** (`core/domain/`) — the model and the read-only analyses
+  (`analyze_system`, the `check_*` passes, `compute_all_nets`).
+- **Application** (`core/app/`) — use-case operations a frontend invokes, e.g.
+  `export_connections(System*, path, format) -> ExportResult`. An operation
+  builds its artefact and returns data/stats; it **never** prints or opens a
+  dialog. (Anti-pattern being removed: the export command used to build the file
+  inside its lambda. The TUI command is now a thin wrapper — resolve args/dialog
+  → call the core op → render the result.)
+- **Frontends** (`frontends/<name>/`) — thin: map UI events to core calls and
+  render results. Each implements the **`Frontend`** interface
+  (`frontends/frontend.hpp`: `BootDispatch`, `DumpCommandsMd`, `DumpOutput`,
+  `Run`). The process entry is shared and frontend-agnostic:
+  `frontend_main(argc, argv, Frontend&)` (`frontends/frontend_main.cpp`, built
+  into the toolkit-free `essim_frontend` lib) parses the CLI flags and drives the
+  boot → batch/run flow through the interface; a frontend's `main()` is just
+  *construct the concrete Frontend, call `frontend_main`*. Two frontends ship
+  today: **tui** (FTXUI, default) and **wx** (a wxWidgets GUI, menu-driven over
+  `app::*`). Add another by creating `src/frontends/<name>/CMakeLists.txt` — its
+  toolkit setup (FetchContent / find_package) plus one call to
+  `essim_add_frontend(<name> LIBS …)` (the shared helper in
+  `cmake/EssimFrontend.cmake` that builds `essim_<name>` + the `essim` binary) —
+  and configuring `-DESSIM_FRONTEND=<name>`.
+
+Because the core links no toolkit, the suite links `essim_core` directly and
+`-DESSIM_FRONTEND=none` builds + tests the whole core with FTXUI never fetched.
 
 ## Domain conventions
 
-- Everything in `system/` is **pointer-based** (commit `d8122d1`: "everything is pointer"). Containers store `T*`, ownership lives with the container.
+- Everything in `core/domain/` is **pointer-based** (commit `d8122d1`: "everything is pointer"). Containers store `T*`, ownership lives with the container.
 - `SystemElementContainer<T>::merge(name)` is the get-or-create primitive — call it instead of `add` when you don't know whether the element already exists. `add` throws on duplicate names or empty names.
 - `using namespace std;` is present in `syselmts.hpp` — pre-existing, don't add more `using namespace` in headers.
 - Include guards `_NAME_HPP_` *and* `#pragma once` are both used. Match the existing style.
@@ -110,11 +158,11 @@ Built-in commands: `new`, `set`, `load`, `duplicate`, `save`, `restore`, `source
 
 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`), `B` (part's attached BSDL `.bsd` path — re-parsed and re-applied on restore; the path is persisted, **not** the derived pin specs), `N` (pin → signal name; empty = NC; optional 4th field carries `nc_origin_tag()`: `U` = ImportedUnconnected, `D` = DroppedSingleton — omitted when the pin has a signal or when origin is `None`), `S` (signal → type override; only emitted for non-default), `C` (connection header with endpoints + `transform_name`), `W` (wire pair within the current connection). The 4th N field is backward-compatible: pre-existing snapshots without it restore with `nc_origin = None`.
+`save` / `restore` (`src/core/domain/persist.{hpp,cpp}`): tab-delimited line format, no extra deps. Tags: `M` (module), `P` (part with `connector_type`), `B` (part's attached BSDL `.bsd` path — re-parsed and re-applied on restore; the path is persisted, **not** the derived pin specs), `N` (pin → signal name; empty = NC; optional 4th field carries `nc_origin_tag()`: `U` = ImportedUnconnected, `D` = DroppedSingleton — omitted when the pin has a signal or when origin is `None`), `S` (signal → type override; only emitted for non-default), `C` (connection header with endpoints + `transform_name`), `W` (wire pair within the current connection). The 4th N field is backward-compatible: pre-existing snapshots without it restore with `nc_origin = None`.
 
 **Signals** carry a `type` (`SignalType::Power | GndShield | Other`). The `Signal` constructor **defaults to `Other`** — auto-inference no longer happens at construction. Types are set in three ways, in priority order:
 
-1. **`infer_signal_types(System*)`** (`src/system/analysis.{hpp,cpp}`) runs at the end of every `load` (after `drop_singleton_signals`). It assigns:
+1. **`infer_signal_types(System*)`** (`src/core/domain/analysis.{hpp,cpp}`) runs at the end of every `load` (after `drop_singleton_signals`). It assigns:
    - `GndShield` when the **name alone** is unambiguous (`GND`, `SHIELD`, `CHASSIS`, `EARTH`, …) — false-positive rate is essentially zero on these.
    - `Power` requires (a) the name heuristic (`infer_signal_type` says Power), (b) a **hard fan-out floor**: signals with fewer than `POWER_FANOUT_HARD_FLOOR = 3` pins are *always* refused, regardless of name or voltage pattern (a real rail physically cannot land on just 1-2 pads), and (c) at least one positive structural signal — fan-out ≥ `POWER_FANOUT_CONFIRM_MIN = 4` **or** a voltage pattern in the name (`3V3`, `5V`, `12V`, …; detector: a `V` adjacent to a digit). This catches `VSEL_*`, `PWR_OK`, `_VDD_SENSE` etc. which look like Power by name but aren't real rails. Both thresholds are exposed in `analysis.hpp` so the analyze screen can render the same reasoning without duplicating constants.
    - `Other` otherwise. The "name-said-Power-but-refuted-by-structure" count is reported by `load`.
@@ -123,17 +171,17 @@ Pending prompts (from incomplete inline commands) are NOT considered interactive
 
 The explore screen shows the type in the signal detail header.
 
-**Pin spec (expected attributes)**: every Pin carries a `PinSpec spec` (`src/system/pin_spec.hpp`) — the *expected* half of verification, set from a model: `function` (Power/Ground/Signal/Clock/NoConnect/Jtag*), `direction` (In/Out/Bidir/Passive/Power), `pad` (physical package terminal, e.g. a BSDL ball), and `source` (which model wrote it). `set-connector-type` populates it via `pin_role(connector_type, pin_name) → PinSpec`. `Pin::expected_signal_type()` is now a **derived accessor** — `to_signal_type(spec.function)` (Power→Power, Ground→GndShield, else Other) — not a stored field; the *observed* half stays `Pin::signal()` + the net + inference, and `verify` diffs the two. The VPX 3U connector lookup (`vpx_3u_role`) is still a stub returning Other, so connector-typed pins resolve to function Unknown until that table is filled. **`direction`/`function`/`pad` are populated from BSDL** via `attach-bsdl` (see below) and consumed by the model-driven checks (`check_pin_specs`: contention / undriven / NC-wired) and the JTAG chain check (`check_jtag_chain`), both run by `verify`.
+**Pin spec (expected attributes)**: every Pin carries a `PinSpec spec` (`src/core/domain/pin_spec.hpp`) — the *expected* half of verification, set from a model: `function` (Power/Ground/Signal/Clock/NoConnect/Jtag*), `direction` (In/Out/Bidir/Passive/Power), `pad` (physical package terminal, e.g. a BSDL ball), and `source` (which model wrote it). `set-connector-type` populates it via `pin_role(connector_type, pin_name) → PinSpec`. `Pin::expected_signal_type()` is now a **derived accessor** — `to_signal_type(spec.function)` (Power→Power, Ground→GndShield, else Other) — not a stored field; the *observed* half stays `Pin::signal()` + the net + inference, and `verify` diffs the two. The VPX 3U connector lookup (`vpx_3u_role`) is still a stub returning Other, so connector-typed pins resolve to function Unknown until that table is filled. **`direction`/`function`/`pad` are populated from BSDL** via `attach-bsdl` (see below) and consumed by the model-driven checks (`check_pin_specs`: contention / undriven / NC-wired) and the JTAG chain check (`check_jtag_chain`), both run by `verify`.
 
 **Connector pin layout (preparation)**: `pin_layout(connector_type)` returns the canonical full pin-name list for a known connector kind, and `FillPartFromLayout(part, kind)` materialises NC pins for any layout position absent from the imported netlist. `set-connector-type` calls it after setting `connector_type` (no-op today since `pin_layout` is a stub returning `{}` for everything — populate alongside `vpx_3u_role`). End-to-end chain in place: `set-connector-type → FillPartFromLayout → pin_role`.
 
-**BSDL models (`attach-bsdl`)**: `attach-bsdl <module> <part> <file.bsd>` parses a BSDL device through `libbsdl` (wrapped by `BsdlModel`, `src/system/bsdl_model.{hpp,cpp}`), then `apply_bsdl(part, model)` binds each port to a Pin **by port name first, then by physical pad** — so a netlist that names IC pins either by signal or by package ball both bind. Each bound pin gets its `spec` set: `direction` (BSDL in/out/inout/linkage), `function` (TAP role → Jtag\*, `linkage` → Power/Ground/NoConnect by name, else Signal), `pad` (PIN_MAP ball), `source = Bsdl`. The `.bsd` path is stored on `Part::bsdl_path`, persisted via the `B` tag and re-applied on `restore`. Real-world check: an `xcku15p` FPGA in a VPX system binds 1517/1517 ports.
+**BSDL models (`attach-bsdl`)**: `attach-bsdl <module> <part> <file.bsd>` parses a BSDL device through `libbsdl` (wrapped by `BsdlModel`, `src/core/domain/bsdl_model.{hpp,cpp}`), then `apply_bsdl(part, model)` binds each port to a Pin **by port name first, then by physical pad** — so a netlist that names IC pins either by signal or by package ball both bind. Each bound pin gets its `spec` set: `direction` (BSDL in/out/inout/linkage), `function` (TAP role → Jtag\*, `linkage` → Power/Ground/NoConnect by name, else Signal), `pad` (PIN_MAP ball), `source = Bsdl`. The `.bsd` path is stored on `Part::bsdl_path`, persisted via the `B` tag and re-applied on `restore`. Real-world check: an `xcku15p` FPGA in a VPX system binds 1517/1517 ports.
 
-**Unified application (`apply_model`)**: connector layout and BSDL are two implementations of one `PinModel` interface (`src/system/pin_model.{hpp,cpp}`: `spec_for(pin_name)`, `layout()`, `source()`). `ConnectorModel` wraps `pin_role`/`pin_layout`; `BsdlPinModel` wraps a parsed `BsdlModel`, indexed by both port name and physical pad. A single `apply_model(Part*, const PinModel&)` materialises the layout pins missing from the netlist, then sets each pin's `spec` **only where the model speaks** (`spec.source != None`). Sources are ranked (`spec_source_rank` in `pin_spec.hpp`: UserOverride > Bsdl > ConnectorModel > Inferred > Imported) and apply_model refuses to overwrite a spec owned by a higher-rank source — so one source never clobbers a more authoritative one, which is also the basis for `check_source_conflicts`. `set-connector-type` and `attach-bsdl` both funnel through it (the latter via the thin `apply_bsdl` adapter); `verify` stays agnostic of where a spec came from. A future SPICE/Modelica source would be a third `PinModel`.
+**Unified application (`apply_model`)**: connector layout and BSDL are two implementations of one `PinModel` interface (`src/core/domain/pin_model.{hpp,cpp}`: `spec_for(pin_name)`, `layout()`, `source()`). `ConnectorModel` wraps `pin_role`/`pin_layout`; `BsdlPinModel` wraps a parsed `BsdlModel`, indexed by both port name and physical pad. A single `apply_model(Part*, const PinModel&)` materialises the layout pins missing from the netlist, then sets each pin's `spec` **only where the model speaks** (`spec.source != None`). Sources are ranked (`spec_source_rank` in `pin_spec.hpp`: UserOverride > Bsdl > ConnectorModel > Inferred > Imported) and apply_model refuses to overwrite a spec owned by a higher-rank source — so one source never clobbers a more authoritative one, which is also the basis for `check_source_conflicts`. `set-connector-type` and `attach-bsdl` both funnel through it (the latter via the thin `apply_bsdl` adapter); `verify` stays agnostic of where a spec came from. A future SPICE/Modelica source would be a third `PinModel`.
 
 **`verify` (seven passes)**: (1) typed pins — local mismatch between each pin's `expected_signal_type()` (derived from its `PinSpec`) and the actual signal type; (2) bridged nets — Power↔GndShield inconsistencies; (3) orphan summary `N orphan pin(s) at import (X imported NC, Y dropped singleton)` (filters out pins bridged via any `Connection::pin_map` — typically `FillIdentityNCs`-materialised); (4) **model-driven pin checks** (`check_pin_specs`): `DriveContention` (≥2 push-pull `Out` on a net), `UndrivenNet` (a **fully-modelled** net with input(s) but no driver — nets with any Unknown-direction pin are skipped, so un-modelled drivers don't cause false positives), `NcWired` (a no-connect pin on a multi-pin net); (5) **JTAG chain** (`check_jtag_chain`): collects TAP pins by `spec.function`, maps each to its net, emits `JtagTapIncomplete` / `JtagBusUnbridged` (TMS or TCK not common to all TAP devices) / `JtagChainBreak` (dangling TDO/TDI, chain fan-out, or not a single head→tail daisy chain); (6) **source conflicts** (`check_source_conflicts`): a pin the BSDL declares power/ground (a must-connect rail) that the netlist leaves unconnected — a rail floated in the schematic (`SourceConflict`; the reverse, a BSDL no-connect that *is* wired, is the `NcWired` check); (7) **BSDL completeness** (`check_bsdl_completeness`): device power/ground ports (from the attached `.bsd`, re-parsed) with no matching pin on the netlist part — a rail the schematic symbol is missing (`BsdlPinMissing`, one aggregated finding per part). The BFS-reached `(module, signal)` set for any signal is shown live in `explore`'s detail pane when a signal entry is selected.
 
-**`analyze` (post-processing pass)**: `analyze_system(System*) → AnalysisReport` (`src/system/analysis.{hpp,cpp}`) is a stateless read-only pass that detects structural signal groups and anomalies. Per-module (signals are module-scoped):
+**`analyze` (post-processing pass)**: `analyze_system(System*) → AnalysisReport` (`src/core/domain/analysis.{hpp,cpp}`) is a stateless read-only pass that detects structural signal groups and anomalies. Per-module (signals are module-scoped):
 
 - **Diff pairs**: signal names ending `_P` / `_N` (case-insensitive) grouped by stem. Both halves present → candidate matched pair.
 - **Diff buses**: ≥ 2 matched diff pairs whose pair-stems share a common outer-stem after stripping a trailing integer (`MDI0` / `MDI1` / `MDI2` → outer `MDI` + indices). The strict `_` rule from plain buses does NOT apply to this trailing-index split: `_P`/`_N` was already stripped, so we know remaining digits are an index. Two index variants accepted: contiguous (`MDI0`) and underscore-separated (`PCIE_TX_0`). Emitted as `SignalGroup{kind=DiffBus, lo, hi}` with label `OUTER[lo..hi]_P/N`. Members include all 2·N constituent signals. A "bus" of size 1 falls back to `DiffPair` (single index does not a bus make).
@@ -145,13 +193,13 @@ Exposed as the `analyze` shell command which prints groups (sorted by module + l
 
 **Component classification**: every `Part` carries a `ComponentKind kind` (`Passive | Semiconductor | IntegratedCircuit | Connector | TestPoint | Switch | Crystal | Mechanical | Other`) inferred at construction by `infer_component_kind(name)` from the leading reference-designator letter(s) (longest-match: `LED/TP/SW/FB/MK/MP/MH/HS/RA/RN/RP/RV` first, then single-letter R/C/L/F/D/Q/U/J/P/Y/X/S). Recomputed on `restore` (no persistence tag). Not yet exposed in TUI commands — branchpoints will be `set-connector-type` guard, `explore` filter, and `explore` header.
 
-`SignalType` lives in its own header `src/system/signal_type.hpp` (extracted from signals to avoid a pins↔signals include cycle).
+`SignalType` lives in its own header `src/core/domain/signal_type.hpp` (extracted from signals to avoid a pins↔signals include cycle).
 
 **Pins** are either NC (`signal() == nullptr`) or connected to exactly one signal. The ODS importer creates a Pin for every row that has a non-empty pin name, even when the signal column is empty or `"NC"` — the pin stays in the Part as NC. `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.
 
 **NC origin tag**: each `Pin` carries `NcOrigin nc_origin` (`None | ImportedUnconnected | DroppedSingleton`, default `None`). Set in three places: (a) Mentor importer when the signal field starts with `unconnected` → `ImportedUnconnected`; (b) `drop_singleton_signals(Signals*)` called at the end of `load` → `DroppedSingleton` on each detached pin (signals with exactly one pin are NC by definition — see commits motivating this); (c) `duplicate` propagates the tag. Pins materialised by `FillIdentityNCs` keep `None` — they have no local signal but are bridged via `pin_map` and shouldn't be counted as orphans. The tag is persisted (see `N` record), reported as a total in `verify`, and tested in `tests/test_nc_origin.cpp`.
 
-**Connector types & transforms**: every `Part` carries a `connector_type` string (default `""`, set via the `set-connector-type` command — inline `set-connector-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 canonical-equivalent 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.
+**Connector types & transforms**: every `Part` carries a `connector_type` string (default `""`, set via the `set-connector-type` command — inline `set-connector-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/core/domain/transform.{hpp,cpp}`) — both directions of the pair are tried. If neither is registered, an `IdentityTransform` fallback wires each pin of A to the canonical-equivalent 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.
 
 **Identity wiring uses canonical names**: `IdentityTransform::apply` builds `unordered_map<canonical, Pin*>` for side B and looks up each side-A pin by its canonical form. So `A1` (one card) auto-pairs with `A001` (the other) thanks to `canonical_pin_name` (`pre + zero-padded(3) digit suffix`; mixed/non-numeric returns the original). Same canonicalisation in `CheckIdentityCompatible`. **`pin_role` doesn't need canonicalisation** because `parse_pin` extracts `(col, row)` via `stoi` which already strips leading zeros.
 
@@ -188,7 +236,7 @@ Today the only caller is `export` (`{"CSV", ".csv"}, {"ODS", ".ods"}` filters, k
 
 **Per-key path persistence** (`SaveLastUsed(key, dir, filename)` / `LoadLastUsed(key, &dir, &filename)` in `shell.cpp`): each key writes a tiny two-line file (`dir\nfilename\n`) under `UserDataDir() / <key>.last`. `UserDataDir()` is the cross-platform `XDG_DATA_HOME` / `LOCALAPPDATA` etc. helper also used by the command history file. Free functions, not Tui members, so any module (the file dialog today; could be the script-save buffer or the save command tomorrow) can use them with the same minimal API.
 
-**ODS writer** (`src/imports/ods_writer.{hpp,cpp}`): minimal OpenDocument Spreadsheet writer. Backed by libzip + pugixml (both already pulled in by the ODS importer). Class hierarchy is two structs:
+**ODS writer** (`src/core/imports/ods_writer.{hpp,cpp}`): minimal OpenDocument Spreadsheet writer. Backed by libzip + pugixml (both already pulled in by the ODS importer). Class hierarchy is two structs:
 
 - `OdsSheet` — sparse row-major grid of string cells (`set(row, col, value)`).
 - `OdsWriter` — owns the sheets, emits a valid `.ods` archive with `mimetype` (stored uncompressed, magic header), `META-INF/manifest.xml`, and `content.xml`.
@@ -248,9 +296,9 @@ Everything in this section is a precise description of how signals, pins, parts,
 
 Default: `Signal::type = SignalType::Other` (constructor does no inference).
 
-Type is set by `infer_signal_types(System*)` (`src/system/analysis.cpp`), called at the end of every `load` and after `duplicate`. The decision per signal:
+Type is set by `infer_signal_types(System*)` (`src/core/domain/analysis.cpp`), called at the end of every `load` and after `duplicate`. The decision per signal:
 
-1. Compute `named = infer_signal_type(name)` (`src/system/signals.cpp`):
+1. Compute `named = infer_signal_type(name)` (`src/core/domain/signals.cpp`):
    - `GndShield` if name matches **case-insensitively**: `GND`, `GROUND`, `EARTH`, `SHIELD`, `CHASSIS`, or starts with `GND_` / `GROUND_` / `EARTH_` / `SHIELD_` / `CHASSIS_`.
    - `Power` if the name contains any of `PWR`, `POWER`, `VCC`, `VDD`, `VEE`, `VSS`, `VBAT`, or starts with `VS_`, `VS3_`, `+`, `-` followed by a digit.
    - Else `Other`.
@@ -264,15 +312,15 @@ Type is set by `infer_signal_types(System*)` (`src/system/analysis.cpp`), called
 
 ### NC pin origin
 
-`Pin::nc_origin` (`src/system/pins.hpp`). Default `NcOrigin::None`. Set by:
+`Pin::nc_origin` (`src/core/domain/pins.hpp`). Default `NcOrigin::None`. Set by:
 
-- **`NcOrigin::ImportedUnconnected`** — Mentor importer (`src/imports/import_mentor.cpp`): the signal field of an `Explicit Pin:` row starts case-insensitively with `unconnected` (e.g. `'unconnected'`, `'unconnected (by TERM)'`). The pin is kept on the part with no signal.
+- **`NcOrigin::ImportedUnconnected`** — Mentor importer (`src/core/imports/import_mentor.cpp`): the signal field of an `Explicit Pin:` row starts case-insensitively with `unconnected` (e.g. `'unconnected'`, `'unconnected (by TERM)'`). The pin is kept on the part with no signal.
-- **`NcOrigin::DroppedSingleton`** — `drop_singleton_signals(Signals*)` (`src/system/signals.cpp`) called at the end of `load`: any signal whose pin set has size exactly 1 is unconnected by definition. The pin is detached (`sig = nullptr`) and tagged; the `Signal` object is deleted.
+- **`NcOrigin::DroppedSingleton`** — `drop_singleton_signals(Signals*)` (`src/core/domain/signals.cpp`) called at the end of `load`: any signal whose pin set has size exactly 1 is unconnected by definition. The pin is detached (`sig = nullptr`) and tagged; the `Signal` object is deleted.
 - **`NcOrigin::None` (no tag)** — pins materialised by `FillIdentityNCs` at `connect` time. These are unconnected locally but bridged to a real signal on the peer module via `Connection::pin_map`; they are explicitly excluded from the "orphan" count in `verify` and the analyze screen.
 
 ### Signal groups
 
-`analyze_system(System*)` (`src/system/analysis.cpp`) emits `SignalGroup`s **per module** (signals are module-scoped). Internal names (starting with `$` — Mentor's `$Nxxxx` convention) are skipped wholesale at every step.
+`analyze_system(System*)` (`src/core/domain/analysis.cpp`) emits `SignalGroup`s **per module** (signals are module-scoped). Internal names (starting with `$` — Mentor's `$Nxxxx` convention) are skipped wholesale at every step.
 
 **DiffPair** (`GroupKind::DiffPair`):
 - Signal name ends `_P` or `_N` (case-insensitive). The character before the suffix must be `_`.
@@ -303,7 +351,7 @@ The `verify` command (not the analyze screen, yet) also emits the **model-driven
 
 ### Component kind
 
-`Part::kind` is inferred at construction (`src/system/component_kind.cpp`) from the leading reference-designator letter(s) of the part name. **Longest-match wins**:
+`Part::kind` is inferred at construction (`src/core/domain/component_kind.cpp`) from the leading reference-designator letter(s) of the part name. **Longest-match wins**:
 
 - Two-letter prefixes (checked first, case-insensitive): `LED → Semiconductor`, `TP → TestPoint`, `SW → Switch`, `FB → Passive`, `MK / MP / MH → Mechanical`, `HS → Mechanical`, `RA / RN / RP / RV → Passive`.
 - Single-letter fallback: `R / C / L / F → Passive`, `D / Q → Semiconductor`, `U → IntegratedCircuit`, `J / P → Connector`, `Y / X → Crystal`, `S → Switch`.
@@ -315,7 +363,7 @@ Recomputed on `restore` (no persistence tag). Currently not used by any decision
 
 `connect` looks up a registered transform for `(p1->connector_type, p2->connector_type)` via `TransformRegistry::lookup`, tried in both directions. Fall-through is `IdentityTransform`:
 
-- Compares pin sets by **canonical name** (`canonical_pin_name(s)`, `src/system/pin_name.cpp`): split into prefix + digit suffix; if the suffix is pure digits, zero-pad to width 3 (`A1` → `A001`, `A001` → `A001`, `A1B` → `A1B`, `VCC` → `VCC`).
+- Compares pin sets by **canonical name** (`canonical_pin_name(s)`, `src/core/domain/pin_name.cpp`): split into prefix + digit suffix; if the suffix is pure digits, zero-pad to width 3 (`A1` → `A001`, `A001` → `A001`, `A1B` → `A1B`, `VCC` → `VCC`).
 - `CheckIdentityCompatible(a, b)` accepts the **subset case** (one side's canonical set is a subset of the other's — typical because Altium drops NC, Mentor doesn't). Bidirectional mismatch (both sides have orphans) is refused.
 - After acceptance, `FillIdentityNCs(p1, p2)` **materialises** the missing canonical positions on the smaller side as new NC pins (`new Pin(other_side_name)`, no signal attached, `nc_origin = None`). Idempotent.
 

README.md

@@ -15,6 +15,13 @@ cmake --build build -j
 ./build/essim
 ```
 
+The build is **layered**: `essim_core` is the frontend-agnostic business
+library (domain + importers + operations); the `essim` binary comes from a
+**frontend** under `src/frontends/<name>/` that links it. Select one with
+`-DESSIM_FRONTEND=<name>` (default `tui`); `-DESSIM_FRONTEND=none` builds the
+core + tests only, with no GUI toolkit fetched. Architecture in
+[`DESIGN.md`](DESIGN.md).
+
 Inside the shell, type `help` for the live command list — or read the
 auto-generated reference at [`doc/user/commands.md`](doc/user/commands.md).
 A worked bring-up script is at [`test/system.essim`](test/system.essim);
@@ -41,10 +48,21 @@ Step-by-step walkthroughs for both the batch and TUI workflows are in
   `../libbsdl`, pulled in via `add_subdirectory` and linked dynamically.
   Override its location with `-DBSDL_DIR=/path/to/libbsdl`. Powers the
   `attach-bsdl` command and the pin/JTAG checks.
-- Fetched automatically at configure time via `FetchContent` (nothing to
+- Fetched automatically via `FetchContent` (nothing to install): **FTXUI**
-  install): **FTXUI** v6.1.9 and **doctest** v2.4.11.
+  v6.1.9 — only when building the **tui** frontend — and **doctest** v2.4.11
+  for the tests.
+- **wxWidgets** (≥ 3.2) — only for the **wx** GUI frontend
+  (`-DESSIM_FRONTEND=wx`). Install the development package:
+  - Debian/Ubuntu — `sudo apt install libwxgtk3.2-dev`
+  - Arch — `sudo pacman -S wxwidgets-gtk3`
+  - Fedora — `sudo dnf install wxGTK-devel`
 - Optional, only for the `doc` target: **doxygen** and **python3**.
 
+libzip, pugixml and libbsdl are the **core** dependencies; each frontend pulls
+its own toolkit (FTXUI for tui, wxWidgets for wx), so a `-DESSIM_FRONTEND=none`
+build needs neither. Pick a GUI/TUI with `-DESSIM_FRONTEND=tui|wx` (default
+`tui`).
+
 ## Tests
 
 ```sh
@@ -53,6 +71,9 @@ Step-by-step walkthroughs for both the batch and TUI workflows are in
 ctest --test-dir build
 ```
 
+`ctest` runs `essim_tests` (core — links `essim_core`, no GUI toolkit) and
+`essim_tui_tests` (the FTXUI frontend's tests, under `tests/tui/`).
+
 Skip building tests entirely:
 
 ```sh
@@ -76,12 +97,17 @@ cmake --build build --target doc      # needs doxygen + python3
 ## Project layout
 
 ```
-src/system/   domain model (Module/Part/Pin/Signal, Connection, Transform, …)
+src/
-src/imports/  Mentor / Altium / ODS netlist importers
+  core/                 business logic, NO GUI toolkit (→ libessim_core)
-src/tui/      FTXUI shell (commands, screens, completion, history)
+    domain/             model (Module/Part/Pin/Signal, Connection, Transform…) + analyses
-tests/        doctest suite
+    imports/            Mentor / Altium / ODS netlist importers + ODS writer
-doc/          api/ + user/ Markdown trees, Doxyfile.in, gen_api_md.py
+    app/                use-case operations (export → CSV/ODS, …)
-test/         sample netlists + system.essim bring-up script
+  frontends/            one dir per GUI/TUI engine, each links essim_core
+    tui/                FTXUI shell + main.cpp (→ libessim_tui + the `essim` binary)
+tests/                  core tests (link essim_core)
+  tui/                  frontend tests (link essim_tui)
+doc/                    api/ + user/ Markdown, Doxyfile.in, gen_api_md.py
+test/                   sample netlists + system.essim bring-up script
 ```
 
 Full layout & rationale in [`DESIGN.md`](DESIGN.md).

cmake/EssimFrontend.cmake

@@ -0,0 +1,30 @@
+# essim_add_frontend(<name> [LIBS <toolkit link targets>...])
+#
+# Builds the boilerplate shared by every frontend under src/frontends/<name>/:
+#   * a static library essim_<name> from every .cpp in the current directory
+#     except main.cpp, linking essim_core plus the frontend's own GUI/TUI
+#     toolkit (LIBS);
+#   * the `essim` executable from main.cpp, linking essim_<name> and the shared,
+#     toolkit-free launcher essim_frontend, emitted at the top of the build tree
+#     (./build/essim) whichever frontend produced it.
+#
+# A per-frontend CMakeLists only sets up its toolkit (FetchContent /
+# find_package, and any directory-scoped include dirs / definitions) and then
+# calls this with the toolkit's link targets — no target wiring repeated.
+function(essim_add_frontend name)
+  cmake_parse_arguments(FE "" "" "LIBS" ${ARGN})
+
+  set(dir "${CMAKE_CURRENT_SOURCE_DIR}")
+
+  # Frontend library = every .cpp here except the entry point.
+  file(GLOB FE_SOURCES "${dir}/*.cpp")
+  list(REMOVE_ITEM FE_SOURCES "${dir}/main.cpp")
+
+  add_library(essim_${name} STATIC ${FE_SOURCES})
+  target_link_libraries(essim_${name} PUBLIC essim_core ${FE_LIBS})
+
+  add_executable(essim "${dir}/main.cpp")
+  target_link_libraries(essim PRIVATE essim_${name} essim_frontend)
+  set_target_properties(essim PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}")
+endfunction()

src/core/app/connect.cpp

@@ -0,0 +1,67 @@
+#include "core/app/connect.hpp"
+
+#include "core/domain/connect.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/parts.hpp"
+#include "core/domain/system.hpp"
+#include "core/domain/transform.hpp"
+
+#include <exception>
+#include <utility>
+
+namespace app {
+
+ConnectResult connect_parts(System *sys, Module *m1, Part *p1,
+                            Module *m2, Part *p2)
+{
+    ConnectResult r;
+
+    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) {
+            r.refused = true;
+            r.error = "no transform for types '"
+                    + (p1->connector_type.empty() ? std::string("(none)")
+                                                   : p1->connector_type)
+                    + "' ↔ '"
+                    + (p2->connector_type.empty() ? std::string("(none)")
+                                                   : p2->connector_type)
+                    + "'. Set matching types via 'set-connector-type' first.";
+            return r;
+        }
+        std::string info;
+        std::string err = CheckIdentityCompatible(p1, p2, &info);
+        if (!err.empty()) {
+            r.refused = true;
+            r.error = err;
+            return r;
+        }
+        if (!info.empty()) {
+            r.identity_info = info;
+            r.nc_added = FillIdentityNCs(p1, p2);
+        }
+    }
+
+    auto pin_map = t->apply(p1, p2);
+
+    r.connection_name = m1->name + "/" + p1->name
+                      + " <-> " + m2->name + "/" + p2->name;
+    r.transform_name = t->name;
+    try {
+        Connection *c = new Connection(r.connection_name, m1, p1, m2, p2);
+        c->transform_name = t->name;
+        c->pin_map = std::move(pin_map);
+        sys->connections()->add(c);
+        r.wires = (int)c->pin_map.size();
+        r.ok = true;
+    } catch (const std::exception &e) {
+        r.error = e.what();
+    }
+
+    return r;
+}
+
+}  // namespace app

src/core/app/connect.hpp

@@ -0,0 +1,42 @@
+#ifndef _APP_CONNECT_HPP_
+#define _APP_CONNECT_HPP_
+
+#include <string>
+
+class System;
+class Module;
+class Part;
+
+// Application layer: UI-independent operations that any frontend (TUI, GUI, …)
+// can call. No console, no dialogs, no FTXUI — just System in, result out.
+namespace app {
+
+// Outcome of connecting two parts. The side effects (filling identity NC pins,
+// creating the Connection and adding it to the system) all happen in core; the
+// caller only renders the fields.
+struct ConnectResult {
+    bool ok = false;            ///< a Connection was created and added
+    bool refused = false;       ///< a business rule rejected it (vs. an exception)
+    std::string error;          ///< why refused/failed; empty when ok
+
+    std::string connection_name;
+    std::string transform_name;
+    int wires = 0;              ///< pin_map size of the created connection
+
+    // Identity-transform path only: the compatibility info line and how many NC
+    // pins were materialised so both sides match. Empty / 0 otherwise.
+    std::string identity_info;
+    int nc_added = 0;
+};
+
+// Wire part `p1` (in module `m1`) to part `p2` (in module `m2`): look up the
+// transform for their connector types, refuse on an unknown pairing or an
+// identity-incompatible layout, fill identity NC pins when needed, apply the
+// transform and create the Connection. Pure core — no resolution of names or
+// patterns (the frontend turns user input into the Module*/Part* it passes).
+ConnectResult connect_parts(System *sys, Module *m1, Part *p1,
+                            Module *m2, Part *p2);
+
+}  // namespace app
+
+#endif  // _APP_CONNECT_HPP_

src/core/app/edit.cpp

@@ -0,0 +1,137 @@
+#include "core/app/edit.hpp"
+
+#include "core/domain/bsdl_model.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/parts.hpp"
+#include "core/domain/pin_model.hpp"
+#include "core/domain/pins.hpp"
+#include "core/domain/signals.hpp"
+#include "core/domain/system.hpp"
+#include "core/domain/transform_vpx.hpp"  // ValidatePartForKind
+
+#include <exception>
+
+namespace app {
+
+SetConnectorTypeResult set_connector_type(Part *part, const std::string &kind)
+{
+    SetConnectorTypeResult r;
+    if (!part) {
+        r.error = "no part";
+        return r;
+    }
+
+    std::string err = ValidatePartForKind(part, kind);
+    if (!err.empty()) {
+        r.error = err;
+        return r;
+    }
+
+    part->connector_type = kind;
+    ConnectorModel model(kind);
+    ApplyReport rep = apply_model(part, model);
+    r.materialised = rep.materialised;
+    r.ok = true;
+    return r;
+}
+
+AttachBsdlResult attach_bsdl(Part *part, const std::string &path)
+{
+    AttachBsdlResult r;
+    if (!part) {
+        r.error = "no part";
+        return r;
+    }
+
+    BsdlModel model = BsdlModel::from_file(path);
+    if (!model.valid()) {
+        r.error = "cannot parse " + path
+                + (model.error().empty() ? "" : (": " + model.error()));
+        return r;
+    }
+
+    BsdlApplyReport rep = apply_bsdl(part, model);
+    part->bsdl_path = path;
+    r.entity      = model.entity();
+    r.bound       = rep.bound;
+    r.unbound     = rep.unbound;
+    r.ports_total = (int)model.ports().size();
+    r.ok = true;
+    return r;
+}
+
+SetSignalTypeResult set_signal_type(Signal *sig, const std::string &type_name)
+{
+    SetSignalTypeResult r;
+    if (!sig) {
+        r.error = "no signal";
+        return r;
+    }
+
+    SignalType t;
+    if (!signal_type_from_name(type_name, t)) {
+        r.error = "type must be one of: power, gnd, other (got: " + type_name + ")";
+        return r;
+    }
+
+    sig->type = t;
+    r.type = t;
+    r.ok = true;
+    return r;
+}
+
+DuplicateResult duplicate_module(System *sys, const std::string &src_name,
+                                 const std::string &dst_name)
+{
+    DuplicateResult r;
+    if (!sys) { r.error = "no system"; return r; }
+
+    Module *src;
+    try { src = sys->modules()->get(src_name); }
+    catch (const std::exception &) {
+        r.error = "unknown module: " + src_name;
+        return r;
+    }
+    if (sys->modules()->exists(dst_name)) {
+        r.error = "duplicate refused: module '" + dst_name + "' already exists.";
+        return r;
+    }
+
+    Module *dst = new Module(dst_name);
+
+    // Signals first (preserve type overrides), so pins can re-wire to them.
+    for (auto &skv : *src->signals) {
+        Signal *ss = skv.second;
+        Signal *ds = new Signal(ss->name);
+        ds->type = ss->type;
+        dst->signals->add(ds);
+    }
+
+    // Parts, pins (spec + nc_origin), and the pin→signal wiring.
+    for (auto &pkv : *src) {
+        Part *sp = pkv.second;
+        Part *dp = new Part(sp->name);
+        dp->connector_type = sp->connector_type;
+        for (auto &nkv : *sp) {
+            Pin *sn = nkv.second;
+            Pin *dn = new Pin(sn->name);
+            dn->spec = sn->spec;
+            dn->nc_origin = sn->nc_origin;
+            dp->add(dn);
+            if (sn->signal()) {
+                Signal *ds = dst->signals->get(sn->signal()->name);
+                ds->add(dn);
+                dn->connect(ds);
+            }
+        }
+        dst->add(dp);
+    }
+
+    sys->modules()->add(dst);
+    r.parts   = (int)dst->size();
+    r.signals = (int)dst->signals->size();
+    r.ok = true;
+    return r;
+}
+
+}  // namespace app

src/core/app/edit.hpp

@@ -0,0 +1,73 @@
+#ifndef _APP_EDIT_HPP_
+#define _APP_EDIT_HPP_
+
+#include "core/domain/signal_type.hpp"  // SignalType
+
+#include <string>
+
+class Part;
+class Signal;
+class System;
+
+// Application layer: UI-independent part-editing operations any frontend can
+// call. No console, no dialogs, no FTXUI — Part in, result struct out.
+namespace app {
+
+// Outcome of tagging a part's connector type. The op validates the kind, sets
+// the type and applies the connector model (which may materialise the layout's
+// missing NC pins); the caller renders the result.
+struct SetConnectorTypeResult {
+    bool ok = false;
+    std::string error;     ///< set when refused (kind invalid for the part)
+    int materialised = 0;  ///< NC pins created from the connector layout
+};
+
+// Tag `part`'s connector type and apply the matching connector model. Refuses
+// (ok=false, error set, no mutation) when the kind is invalid for the part.
+SetConnectorTypeResult set_connector_type(Part *part, const std::string &kind);
+
+// Outcome of attaching a BSDL model to a part. On success the part's pin specs
+// are filled from the model and its bsdl_path is recorded.
+struct AttachBsdlResult {
+    bool ok = false;
+    std::string error;     ///< set when the .bsd cannot be parsed
+    std::string entity;    ///< the BSDL entity name
+    int bound = 0;         ///< ports matched to a pin
+    int unbound = 0;       ///< ports with no matching pin
+    int ports_total = 0;   ///< ports declared in the model
+};
+
+// Parse the BSDL file at `path` and apply it to `part` (fills each pin's role
+// and direction; records bsdl_path). Fails (ok=false, error set, no mutation)
+// when the file cannot be parsed.
+AttachBsdlResult attach_bsdl(Part *part, const std::string &path);
+
+// Outcome of overriding a signal's type from a user-supplied name.
+struct SetSignalTypeResult {
+    bool ok = false;
+    std::string error;                 ///< set when the name isn't power/gnd/other
+    SignalType type = SignalType::Other;  ///< the resolved type (for rendering)
+};
+
+// Set `sig`'s type from `type_name` (power | gnd | other, case-insensitive).
+// Fails (ok=false, error set, no mutation) on an unrecognised name.
+SetSignalTypeResult set_signal_type(Signal *sig, const std::string &type_name);
+
+// Outcome of cloning a module under a new name.
+struct DuplicateResult {
+    bool ok = false;
+    std::string error;  ///< unknown source, or destination name already taken
+    int parts = 0;
+    int signals = 0;
+};
+
+// Deep-clone module `src_name` as `dst_name`: parts, pins (spec + nc_origin),
+// signals (with type overrides) and the pin→signal wiring — but not the
+// system's connections. Fails (ok=false, error set, no change) when the source
+// is unknown or the destination name already exists.
+DuplicateResult duplicate_module(System *sys, const std::string &src_name,
+                                 const std::string &dst_name);
+
+}  // namespace app
+
+#endif  // _APP_EDIT_HPP_

src/core/app/export.cpp

@@ -0,0 +1,190 @@
+#include "core/app/export.hpp"
+
+#include "core/imports/ods_writer.hpp"
+#include "core/domain/connect.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/parts.hpp"
+#include "core/domain/pins.hpp"
+#include "core/domain/signal_type.hpp"
+#include "core/domain/signals.hpp"
+#include "core/domain/system.hpp"
+
+#include <cctype>
+#include <fstream>
+#include <string>
+
+namespace app {
+
+namespace {
+
+std::string to_lower(std::string s)
+{
+    for (char &c : s) c = (char)std::tolower((unsigned char)c);
+    return s;
+}
+
+// Minimal CSV quoter — wraps in "…" and doubles internal quotes when the field
+// contains a comma, quote, or newline.
+std::string csv_quote(const std::string &s)
+{
+    if (s.find_first_of(",\"\n") == std::string::npos)
+        return s;
+    std::string out = "\"";
+    for (char c : s) { if (c == '"') out += '"'; out += c; }
+    out += '"';
+    return out;
+}
+
+// Flatten one pin into the string slots an export row uses.
+void pin_side(Pin *p, std::string &mod, std::string &part, std::string &pin,
+              std::string &sig, std::string &type, std::string &suspect)
+{
+    if (!p) { mod = part = pin = sig = type = suspect = ""; return; }
+    mod  = (p->prnt && p->prnt->prnt) ? p->prnt->prnt->name : "";
+    part = p->prnt ? p->prnt->name : "";
+    pin  = p->name;
+    Signal *s = p->signal();
+    if (!s) {
+        sig = ""; type = "(NC)"; suspect = "";
+    } else {
+        sig = s->name;
+        type = signal_type_name(s->type);
+        suspect = (infer_signal_type(s->name) == SignalType::Power
+                   && s->type == SignalType::Other) ? "yes" : "no";
+    }
+}
+
+// Excel rejects /\?*:[] in sheet names; ODS forbids < > & in raw table names.
+// Sanitise to underscores and clip to Excel's 31-char hard limit.
+std::string sanitise_sheet_name(std::string name)
+{
+    for (char &ch : name)
+        if (ch == '/' || ch == '\\' || ch == '?' || ch == '*' || ch == ':'
+            || ch == '[' || ch == ']' || ch == '<' || ch == '>' || ch == '&')
+            ch = '_';
+    if (name.size() > 31) name = name.substr(0, 31);
+    return name;
+}
+
+ExportResult write_ods(const System *sys, const std::string &path)
+{
+    ExportResult r;
+    OdsWriter w;
+    for (auto &ckv : *sys->connections()) {
+        Connection *c = ckv.second;
+        OdsSheet *s = w.add_sheet(sanitise_sheet_name(c->name));
+
+        std::string lmod = c->m1 ? c->m1->name : "";
+        std::string lprt = c->p1 ? c->p1->name : "";
+        std::string rmod = c->m2 ? c->m2->name : "";
+        std::string rprt = c->p2 ? c->p2->name : "";
+
+        // Meta header: label/value rows, a blank row, then the column headers.
+        auto meta = [&](int row, const std::string &k, const std::string &v) {
+            s->set(row, 0, k);
+            s->set(row, 1, v);
+        };
+        meta(0, "Connection", c->name);
+        meta(1, "Transform",  c->transform_name);
+        meta(2, "Left",       lmod + " / " + lprt);
+        meta(3, "Right",      rmod + " / " + rprt);
+        // Row 4 left blank by design.
+
+        const int HDR = 5;
+        s->set_header_row(HDR);
+        const char *hdr[] = {
+            "left_pin", "left_signal", "left_type", "left_suspect",
+            "right_pin", "right_signal", "right_type", "right_suspect",
+            "type_mismatch"};
+        for (int i = 0; i < 9; ++i) s->set(HDR, i, hdr[i]);
+
+        int row = HDR + 1;
+        for (auto &wp : c->pin_map) {
+            std::string lm, lp, ln, ls, lt, lsus;
+            std::string rm, rp, rn, rs, rt, rsus;
+            pin_side(wp.first,  lm, lp, ln, ls, lt, lsus);
+            pin_side(wp.second, rm, rp, rn, rs, rt, rsus);
+            std::string tm = (lt != "(NC)" && rt != "(NC)" && lt != rt) ? "yes" : "no";
+            s->set(row, 0, ln); s->set(row, 1, ls);
+            s->set(row, 2, lt); s->set(row, 3, lsus);
+            s->set(row, 4, rn); s->set(row, 5, rs);
+            s->set(row, 6, rt); s->set(row, 7, rsus);
+            s->set(row, 8, tm);
+            ++row; ++r.rows;
+        }
+    }
+
+    std::string err;
+    if (!w.save(path, err)) {
+        r.error = err;
+        return r;
+    }
+    r.ok = true;
+    r.sheets = (int)sys->connections()->size();
+    return r;
+}
+
+ExportResult write_csv(const System *sys, const std::string &path)
+{
+    ExportResult r;
+    std::ofstream f(path);
+    if (!f) {
+        r.error = "cannot open '" + path + "' for writing";
+        return r;
+    }
+
+    // One rectangular table: each row repeats the per-connection constants so
+    // the file stays parser-friendly (pandas / awk / spreadsheet).
+    f << "connection,transform,"
+         "left_module,left_part,"
+         "left_pin,left_signal,left_type,left_suspect,"
+         "right_module,right_part,"
+         "right_pin,right_signal,right_type,right_suspect,"
+         "type_mismatch\n";
+
+    for (auto &ckv : *sys->connections()) {
+        Connection *c = ckv.second;
+        for (auto &wp : c->pin_map) {
+            std::string lm, lp, ln, ls, lt, lsus;
+            std::string rm, rp, rn, rs, rt, rsus;
+            pin_side(wp.first,  lm, lp, ln, ls, lt, lsus);
+            pin_side(wp.second, rm, rp, rn, rs, rt, rsus);
+            std::string tm = (lt != "(NC)" && rt != "(NC)" && lt != rt) ? "yes" : "no";
+            f << csv_quote(c->name)           << ','
+              << csv_quote(c->transform_name) << ','
+              << csv_quote(lm) << ',' << csv_quote(lp) << ','
+              << csv_quote(ln) << ',' << csv_quote(ls) << ','
+              << csv_quote(lt) << ',' << csv_quote(lsus) << ','
+              << csv_quote(rm) << ',' << csv_quote(rp) << ','
+              << csv_quote(rn) << ',' << csv_quote(rs) << ','
+              << csv_quote(rt) << ',' << csv_quote(rsus) << ','
+              << tm << '\n';
+            ++r.rows;
+        }
+    }
+    r.ok = f.good();
+    if (!r.ok) r.error = "write error on '" + path + "'";
+    return r;
+}
+
+}  // namespace
+
+bool export_format_from_path(const std::string &path, ExportFormat &out)
+{
+    size_t dot = path.rfind('.');
+    std::string ext = (dot == std::string::npos) ? "" : to_lower(path.substr(dot));
+    if (ext == ".csv") { out = ExportFormat::Csv; return true; }
+    if (ext == ".ods") { out = ExportFormat::Ods; return true; }
+    return false;
+}
+
+ExportResult export_connections(const System *sys, const std::string &path,
+                                ExportFormat format)
+{
+    ExportResult r;
+    if (!sys) { r.error = "no system"; return r; }
+    return (format == ExportFormat::Ods) ? write_ods(sys, path)
+                                         : write_csv(sys, path);
+}
+
+}  // namespace app

src/core/app/export.hpp

@@ -0,0 +1,34 @@
+#ifndef _APP_EXPORT_HPP_
+#define _APP_EXPORT_HPP_
+
+#include <string>
+
+class System;
+
+// Application layer: UI-independent operations that any frontend (TUI, GUI, …)
+// can call. No console, no dialogs, no FTXUI — just System in, result out.
+namespace app {
+
+enum class ExportFormat { Csv, Ods };
+
+// Outcome of an export. The only side effect is writing the target file; the
+// caller renders `error` / the stats however it likes.
+struct ExportResult {
+    bool ok = false;
+    std::string error;  ///< human-readable, set when !ok
+    int sheets = 0;     ///< ODS: number of sheets (one per connection); 0 for CSV
+    int rows = 0;       ///< wires written
+};
+
+// Map a filename extension (.csv / .ods, case-insensitive) to a format.
+// Returns false if the extension is neither.
+bool export_format_from_path(const std::string &path, ExportFormat &out);
+
+// Export the system's connections to `path` in `format`. Builds the file and
+// returns stats or an error. Pure core — safe to call from any frontend.
+ExportResult export_connections(const System *sys, const std::string &path,
+                                ExportFormat format);
+
+}  // namespace app
+
+#endif  // _APP_EXPORT_HPP_

src/core/app/load.cpp

@@ -0,0 +1,47 @@
+#include "core/app/load.hpp"
+
+#include "core/domain/analysis.hpp"  // infer_signal_types, SignalTypeInferenceStats
+#include "core/domain/modules.hpp"
+#include "core/domain/signals.hpp"   // drop_singleton_signals
+#include "core/domain/system.hpp"
+
+#include <cctype>
+#include <exception>
+
+namespace app {
+
+bool import_type_from_name(const std::string &name, ImportType &out)
+{
+    std::string ls;
+    ls.reserve(name.size());
+    for (char c : name) ls += (char)std::tolower((unsigned char)c);
+    if (ls == "mentor") { out = ImportType::IMPORT_MENTOR; return true; }
+    if (ls == "altium") { out = ImportType::IMPORT_ALTIUM; return true; }
+    if (ls == "ods")    { out = ImportType::IMPORT_ODS;    return true; }
+    return false;
+}
+
+LoadResult load_module(System *sys, const std::string &module_name,
+                       const std::string &path, ImportType type)
+{
+    LoadResult r;
+    if (!sys) { r.error = "no system"; return r; }
+    try {
+        sys->Load(module_name, path, type);
+        Module *mod = sys->modules()->get(module_name);
+        r.dropped = drop_singleton_signals(mod->signals);
+        SignalTypeInferenceStats inf = infer_signal_types(sys);
+        r.parts      = (int)mod->size();
+        r.signals    = (int)mod->signals->size();
+        r.power      = inf.power;
+        r.gnd        = inf.gnd;
+        r.kept_other = inf.kept_other;
+        r.mgmt       = inf.mgmt;
+        r.ok = true;
+    } catch (const std::exception &e) {
+        r.error = e.what();
+    }
+    return r;
+}
+
+}  // namespace app

src/core/app/load.hpp

@@ -0,0 +1,37 @@
+#ifndef _APP_LOAD_HPP_
+#define _APP_LOAD_HPP_
+
+#include "core/domain/system.hpp"  // ImportType
+
+#include <string>
+
+// Application layer: UI-independent operations that any frontend (TUI, GUI, …)
+// can call. No console, no dialogs, no FTXUI — just System in, result out.
+namespace app {
+
+// Map an import-type name (mentor / altium / ods, case-insensitive) to an
+// ImportType. Returns false if the name is none of those.
+bool import_type_from_name(const std::string &name, ImportType &out);
+
+// Outcome of loading a module: the post-import counts the caller renders.
+struct LoadResult {
+    bool ok = false;
+    std::string error;   ///< human-readable, set when !ok
+    int parts = 0;
+    int signals = 0;
+    int dropped = 0;     ///< singleton/NC signals removed after import
+    int power = 0;       ///< signals inferred Power (name + structure)
+    int gnd = 0;         ///< signals inferred GndShield (name)
+    int kept_other = 0;  ///< name said Power but evidence too weak → kept Other
+    int mgmt = 0;        ///< power-management signal (rail + SENSE/EN/PG/… token) → Other, not suspect
+};
+
+// Import a module from a netlist/pinout file into `sys`, drop singleton signals,
+// then infer signal types. Returns the counts or an error. Pure core — safe to
+// call from any frontend.
+LoadResult load_module(System *sys, const std::string &module_name,
+                       const std::string &path, ImportType type);
+
+}  // namespace app
+
+#endif  // _APP_LOAD_HPP_

src/core/app/script.cpp

@@ -0,0 +1,332 @@
+#include "core/app/script.hpp"
+
+#include "core/app/connect.hpp"
+#include "core/app/edit.hpp"
+#include "core/app/export.hpp"
+#include "core/app/load.hpp"
+#include "core/app/verify.hpp"
+
+#include "core/domain/analysis.hpp"
+#include "core/domain/connect.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/parts.hpp"
+#include "core/domain/persist.hpp"
+#include "core/domain/signal_type.hpp"
+#include "core/domain/signals.hpp"
+#include "core/domain/system.hpp"
+
+#include <cctype>
+#include <fstream>
+#include <map>
+#include <ostream>
+#include <string>
+#include <vector>
+
+namespace app {
+
+namespace {
+
+// Whitespace split with "double quotes" grouping — same rules as the TUI shell.
+std::vector<std::string> tokenize(const std::string &s) {
+    std::vector<std::string> out;
+    std::string cur;
+    bool in_q = false;
+    bool has = false;
+    for (char c : s) {
+        if (c == '"') { in_q = !in_q; has = true; continue; }
+        if (!in_q && std::isspace((unsigned char)c)) {
+            if (has) { out.push_back(std::move(cur)); cur.clear(); has = false; }
+        } else {
+            cur.push_back(c);
+            has = true;
+        }
+    }
+    if (has) out.push_back(std::move(cur));
+    return out;
+}
+
+// One script execution: holds the variable table, the System reference (so new/
+// restore can replace it) and the output stream.
+class Runner {
+public:
+    Runner(std::unique_ptr<System> &sys, std::ostream &out) : sys_(sys), out_(out) {}
+
+    // Run a file; `opened` reports whether it could be opened. Returns the count
+    // of effective lines; accumulates command errors into `r.errors`.
+    int run_file(const std::string &path, int depth, ScriptResult &r, bool &opened) {
+        opened = false;
+        if (depth > 32) {
+            emit("source: nesting too deep, skipping " + path);
+            return 0;
+        }
+        std::ifstream f(path);
+        if (!f) return 0;
+        opened = true;
+
+        int count = 0;
+        std::string line;
+        while (std::getline(f, line)) {
+            std::size_t s = line.find_first_not_of(" \t");
+            if (s == std::string::npos) continue;
+            if (line[s] == '#') continue;
+            std::string t = line.substr(s);
+            while (!t.empty() && std::isspace((unsigned char)t.back())) t.pop_back();
+            if (t.empty()) continue;
+            ++count;
+            if (!exec(t, depth, r)) ++r.errors;
+        }
+        return count;
+    }
+
+private:
+    void emit(const std::string &line) { out_ << line << '\n'; }
+
+    // $name / ${name} → variable value; unknown names kept literally.
+    std::string expand(const std::string &s) const {
+        std::string out;
+        std::size_t i = 0;
+        while (i < s.size()) {
+            if (s[i] != '$') { out.push_back(s[i++]); continue; }
+            std::size_t j = i + 1;
+            bool braces = (j < s.size() && s[j] == '{');
+            if (braces) ++j;
+            std::size_t start = j;
+            while (j < s.size() && (std::isalnum((unsigned char)s[j]) || s[j] == '_')) ++j;
+            std::string name = s.substr(start, j - start);
+            if (braces) {
+                if (j >= s.size() || s[j] != '}') { out.push_back('$'); ++i; continue; }
+                ++j;
+            }
+            if (name.empty()) { out.push_back('$'); ++i; continue; }
+            auto it = vars_.find(name);
+            if (it != vars_.end()) out += it->second;
+            else                   out += s.substr(i, j - i);
+            i = j;
+        }
+        return out;
+    }
+
+    Module *resolve_module(const std::string &name) {
+        try { return sys_->modules()->get(name); }
+        catch (const std::exception &) { emit("unknown module: " + name); return nullptr; }
+    }
+    Part *resolve_part(Module *m, const std::string &name) {
+        try { return m->get(name); }
+        catch (const std::exception &) {
+            emit("part in " + m->name + " not found: " + name);
+            return nullptr;
+        }
+    }
+
+    void render_verify() {
+        VerifyReport r = verify(sys_.get());
+        for (const auto &m : r.role_mismatches)
+            emit("  " + m.module + "/" + m.part + "/" + m.pin + ": expected "
+                 + signal_type_name(m.expected) + ", got " + signal_type_name(m.actual)
+                 + " (signal: " + m.signal + ")");
+        emit("verify: " + std::to_string(r.role_mismatches.size())
+             + " local mismatch(es) over " + std::to_string(r.typed_pins)
+             + " typed pin(s).");
+        for (const auto &ni : r.net_inconsistencies) {
+            std::string line = "  net mixes Power and GndShield:";
+            for (const auto &mem : ni.members)
+                line += " " + mem.module + "/" + mem.signal
+                      + "(" + signal_type_name(mem.type) + ")";
+            emit(line);
+        }
+        emit("verify: " + std::to_string(r.net_inconsistencies.size())
+             + " inconsistent net(s) over " + std::to_string(r.bridged_nets)
+             + " bridged net(s) (" + std::to_string(r.total_nets) + " total).");
+        emit("verify: " + std::to_string(r.orphan_total())
+             + " orphan pin(s) at import (" + std::to_string(r.orphan_imported)
+             + " imported NC, " + std::to_string(r.orphan_dropped)
+             + " dropped singleton).");
+        auto grp = [&](const std::vector<Anomaly> &v, const char *tail) {
+            for (const auto &a : v)
+                emit("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
+            emit("verify: " + std::to_string(v.size()) + tail);
+        };
+        grp(r.pin_anomalies,          " model-driven pin anomaly(ies).");
+        grp(r.jtag_anomalies,         " JTAG chain anomaly(ies).");
+        grp(r.conflict_anomalies,     " source-conflict(s).");
+        grp(r.completeness_anomalies, " BSDL completeness issue(s).");
+        grp(r.diff_anomalies,         " diff-pair crossing anomaly(ies).");
+    }
+
+    // Execute one already-trimmed line. Returns false on a hard error.
+    bool exec(const std::string &raw, int depth, ScriptResult &top) {
+        std::vector<std::string> tok = tokenize(raw);
+        if (tok.empty()) return true;
+        const std::string cmd = tok[0];
+        std::vector<std::string> a;
+        for (std::size_t i = 1; i < tok.size(); ++i) a.push_back(expand(tok[i]));
+
+        auto need = [&](std::size_t n) {
+            if (a.size() == n) return true;
+            emit(cmd + ": expected " + std::to_string(n) + " argument(s)");
+            return false;
+        };
+
+        if (cmd == "set") {
+            if (a.size() != 2) { emit("set: usage: set <name> <value>"); return false; }
+            vars_[a[0]] = a[1];
+            return true;
+        }
+        if (cmd == "new") {
+            sys_ = std::make_unique<System>();
+            emit("system created.");
+            return true;
+        }
+        if (cmd == "load") {
+            if (!need(3)) return false;
+            ImportType t;
+            if (!import_type_from_name(a[2], t)) { emit("unknown import type: " + a[2]); return false; }
+            LoadResult r = load_module(sys_.get(), a[0], a[1], t);
+            if (!r.ok) { emit("load failed: " + r.error); return false; }
+            emit("loaded '" + a[0] + "' from " + a[1]);
+            emit("  parts:   " + std::to_string(r.parts));
+            emit("  signals: " + std::to_string(r.signals)
+                 + (r.dropped ? " (dropped " + std::to_string(r.dropped)
+                                + " singleton/NC signal(s))" : ""));
+            emit("  types:   " + std::to_string(r.power) + " power, "
+                 + std::to_string(r.gnd) + " gnd, " + std::to_string(r.kept_other)
+                 + " suspect Power (name only — kept as Other), "
+                 + std::to_string(r.mgmt)
+                 + " power-management (control/measure — kept as Other)");
+            return true;
+        }
+        if (cmd == "connect" || cmd == "plug") {
+            if (!need(4)) return false;
+            Module *m1 = resolve_module(a[0]); if (!m1) return false;
+            Part   *p1 = resolve_part(m1, a[1]); if (!p1) return false;
+            Module *m2 = resolve_module(a[2]); if (!m2) return false;
+            Part   *p2 = resolve_part(m2, a[3]); if (!p2) return false;
+            ConnectResult r = connect_parts(sys_.get(), m1, p1, m2, p2);
+            if (r.refused) { emit("connect refused: " + r.error); return false; }
+            if (!r.identity_info.empty()) {
+                emit("connect: " + r.identity_info);
+                if (r.nc_added > 0)
+                    emit("connect: added " + std::to_string(r.nc_added)
+                         + " NC pin(s) so both sides match");
+            }
+            if (!r.ok) { emit("connect failed: " + r.error); return false; }
+            emit("connected: " + r.connection_name + "  via " + r.transform_name
+                 + " (" + std::to_string(r.wires) + " wires)");
+            return true;
+        }
+        if (cmd == "set-connector-type") {
+            if (!need(3)) return false;
+            Module *m = resolve_module(a[0]); if (!m) return false;
+            Part   *p = resolve_part(m, a[1]); if (!p) return false;
+            SetConnectorTypeResult r = set_connector_type(p, a[2]);
+            if (!r.ok) { emit("set-connector-type refused: " + r.error); return false; }
+            emit(m->name + "/" + p->name + ": connector_type = "
+                 + (a[2].empty() ? "(none)" : a[2]));
+            if (r.materialised > 0)
+                emit("set-connector-type: added " + std::to_string(r.materialised)
+                     + " NC pin(s) from the connector layout");
+            return true;
+        }
+        if (cmd == "set-signal-type") {
+            if (!need(3)) return false;
+            Module *m = resolve_module(a[0]); if (!m) return false;
+            Signal *sig;
+            try { sig = m->signals->get(a[1]); }
+            catch (const std::exception &) {
+                emit("unknown signal: " + m->name + "/" + a[1]); return false;
+            }
+            SetSignalTypeResult r = set_signal_type(sig, a[2]);
+            if (!r.ok) { emit(r.error); return false; }
+            emit(m->name + "/" + sig->name + ": signal type = " + signal_type_name(r.type));
+            return true;
+        }
+        if (cmd == "attach-bsdl") {
+            if (!need(3)) return false;
+            Module *m = resolve_module(a[0]); if (!m) return false;
+            Part   *p = resolve_part(m, a[1]); if (!p) return false;
+            AttachBsdlResult r = attach_bsdl(p, a[2]);
+            if (!r.ok) { emit("attach-bsdl: " + r.error); return false; }
+            emit(m->name + "/" + p->name + ": attached BSDL '" + r.entity + "' — "
+                 + std::to_string(r.bound) + "/" + std::to_string(r.ports_total)
+                 + " ports bound" + (r.unbound ? (", " + std::to_string(r.unbound) + " unbound") : ""));
+            return true;
+        }
+        if (cmd == "duplicate") {
+            if (!need(2)) return false;
+            DuplicateResult r = duplicate_module(sys_.get(), a[0], a[1]);
+            if (!r.ok) { emit(r.error); return false; }
+            emit("duplicate: '" + a[0] + "' → '" + a[1] + "'  ("
+                 + std::to_string(r.parts) + " part(s), "
+                 + std::to_string(r.signals) + " signal(s))");
+            return true;
+        }
+        if (cmd == "verify") {
+            render_verify();
+            return true;
+        }
+        if (cmd == "export") {
+            if (!need(1)) return false;
+            ExportFormat fmt;
+            if (!export_format_from_path(a[0], fmt)) {
+                emit("export: unknown extension (use .csv or .ods): " + a[0]); return false;
+            }
+            ExportResult r = export_connections(sys_.get(), a[0], fmt);
+            if (!r.ok) { emit("export failed: " + r.error); return false; }
+            emit("exported " + std::to_string(r.rows) + " row(s) to " + a[0]);
+            return true;
+        }
+        if (cmd == "save") {
+            if (!need(1)) return false;
+            std::string err;
+            if (!save_system(sys_.get(), a[0], err)) { emit("save failed: " + err); return false; }
+            emit("saved to " + a[0]);
+            return true;
+        }
+        if (cmd == "restore") {
+            if (!need(1)) return false;
+            std::string err;
+            System *fresh = restore_system(a[0], err);
+            if (!fresh) { emit("restore failed: " + err); return false; }
+            sys_.reset(fresh);
+            emit("restored from " + a[0] + "  ("
+                 + std::to_string(sys_->modules()->size()) + " module(s), "
+                 + std::to_string(sys_->connections()->size()) + " connection(s))");
+            return true;
+        }
+        if (cmd == "source") {
+            if (!need(1)) return false;
+            bool opened;
+            int n = run_file(a[0], depth + 1, top, opened);
+            if (!opened) { emit("source: cannot open " + a[0]); return false; }
+            emit("source: " + a[0] + "  (" + std::to_string(n) + " line(s))");
+            return true;
+        }
+
+        emit("script: unsupported command '" + cmd + "'");
+        return false;
+    }
+
+    std::unique_ptr<System> &sys_;
+    std::ostream &out_;
+    std::map<std::string, std::string> vars_;
+};
+
+}  // namespace
+
+ScriptResult run_script(std::unique_ptr<System> &sys, const std::string &path,
+                        std::ostream &out)
+{
+    ScriptResult r;
+    Runner runner(sys, out);
+    bool opened = false;
+    int n = runner.run_file(path, 0, r, opened);
+    if (!opened) {
+        r.error = "cannot open " + path;
+        return r;
+    }
+    r.ok = true;
+    r.lines = n;
+    return r;
+}
+
+}  // namespace app

src/core/app/script.hpp

@@ -0,0 +1,35 @@
+#ifndef _APP_SCRIPT_HPP_
+#define _APP_SCRIPT_HPP_
+
+#include <iosfwd>
+#include <memory>
+#include <string>
+
+class System;
+
+// Application layer: a frontend-agnostic runner for essim command scripts.
+// Dispatches the scriptable, system-building commands to the app::* operations
+// and writes their output to a stream — no console, no dialogs, no FTXUI. Any
+// frontend (and batch mode) can drive a script through it.
+namespace app {
+
+// Outcome of running a script file.
+struct ScriptResult {
+    bool ok = false;       ///< the top-level file opened and ran
+    std::string error;     ///< set when the top-level file can't be opened
+    int lines = 0;         ///< effective (non-comment, non-blank) lines run
+    int errors = 0;        ///< commands that failed / were unsupported
+};
+
+// Run the script at `path` against `sys`, writing per-command output to `out`.
+// `sys` is taken by reference because `new` / `restore` replace the System.
+// Supported: # comments, blank lines, set + $var/${var} expansion, new, load,
+// connect, set-connector-type, set-signal-type, attach-bsdl, verify, export,
+// save, restore, source (nested). Unsupported commands are reported and counted
+// in `errors`, and execution continues.
+ScriptResult run_script(std::unique_ptr<System> &sys, const std::string &path,
+                        std::ostream &out);
+
+}  // namespace app
+
+#endif  // _APP_SCRIPT_HPP_

src/core/app/verify.cpp

@@ -0,0 +1,107 @@
+#include "core/app/verify.hpp"
+
+#include "core/domain/bsdl_check.hpp"
+#include "core/domain/connect.hpp"
+#include "core/domain/diff_check.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/nets.hpp"
+#include "core/domain/parts.hpp"
+#include "core/domain/pins.hpp"
+#include "core/domain/signals.hpp"
+#include "core/domain/system.hpp"
+
+#include <unordered_set>
+#include <utility>
+#include <vector>
+
+namespace app {
+
+VerifyReport verify(System *sys)
+{
+    VerifyReport r;
+    if (!sys)
+        return r;
+
+    // Pass 1 — typed pins: expected (model) vs actual (net) signal type.
+    for (auto &mkv : *sys->modules()) {
+        Module *mod = mkv.second;
+        for (auto &pkv : *mod) {
+            Part *prt = pkv.second;
+            if (prt->connector_type.empty())
+                continue;
+            for (auto &nkv : *prt) {
+                Pin *pin = nkv.second;
+                ++r.typed_pins;
+                SignalType expected = pin->expected_signal_type();
+                if (expected == SignalType::Other)
+                    continue;
+                Signal *s = pin->signal();
+                SignalType actual = s ? s->type : SignalType::Other;
+                if (actual == expected)
+                    continue;
+                RoleMismatch m;
+                m.module = mod->name;
+                m.part = prt->name;
+                m.pin = pin->name;
+                m.signal = s ? s->name : std::string("(NC)");
+                m.expected = expected;
+                m.actual = actual;
+                r.role_mismatches.push_back(std::move(m));
+            }
+        }
+    }
+
+    // Pass 2 — bridged nets: flag Power/GndShield mixing. Compute the nets once
+    // here and reuse them for the model checks below.
+    std::vector<Net> nets = compute_all_nets(sys);
+    r.total_nets = (int)nets.size();
+    for (const Net &n : nets) {
+        if (n.members.size() < 2)
+            continue;
+        ++r.bridged_nets;
+        SignalType dom;
+        if (net_type_consistent(n, dom))
+            continue;
+        NetInconsistency ni;
+        for (const auto &mp : n.members)
+            ni.members.push_back({mp.first->name, mp.second->name, mp.second->type});
+        r.net_inconsistencies.push_back(std::move(ni));
+    }
+
+    // Pass 3 — orphans: pins with no signal and not bridged via a connection.
+    std::unordered_set<Pin *> bridged_pins;
+    for (auto &ckv : *sys->connections())
+        for (auto &wp : ckv.second->pin_map) {
+            if (wp.first)  bridged_pins.insert(wp.first);
+            if (wp.second) bridged_pins.insert(wp.second);
+        }
+    for (auto &mkv : *sys->modules())
+        for (auto &pkv : *mkv.second)
+            for (auto &nkv : *pkv.second) {
+                Pin *pin = nkv.second;
+                if (pin->signal() || bridged_pins.count(pin))
+                    continue;
+                bool dropped;
+                if (pin->nc_origin == NcOrigin::ImportedUnconnected) {
+                    ++r.orphan_imported;
+                    dropped = false;
+                } else if (pin->nc_origin == NcOrigin::DroppedSingleton) {
+                    ++r.orphan_dropped;
+                    dropped = true;
+                } else {
+                    continue;
+                }
+                r.orphans.push_back({mkv.first, pkv.first, nkv.first, dropped});
+            }
+
+    // Passes 4-8 — model-driven checks (reuse the nets from pass 2).
+    r.pin_anomalies          = check_pin_specs(sys, &nets);
+    r.jtag_anomalies         = check_jtag_chain(sys, &nets);
+    r.conflict_anomalies     = check_source_conflicts(sys);
+    r.completeness_anomalies = check_bsdl_completeness(sys);
+    r.diff_anomalies         = check_diff_crossings(sys, &nets);
+
+    return r;
+}
+
+}  // namespace app

src/core/app/verify.hpp

@@ -0,0 +1,71 @@
+#ifndef _APP_VERIFY_HPP_
+#define _APP_VERIFY_HPP_
+
+#include "core/domain/analysis.hpp"     // Anomaly
+#include "core/domain/signal_type.hpp"  // SignalType
+
+#include <string>
+#include <vector>
+
+class System;
+
+namespace app {
+
+// One typed-pin role mismatch: the connector/BSDL expectation disagrees with
+// the actual net type.
+struct RoleMismatch {
+    std::string module, part, pin;
+    std::string signal;        ///< signal name, or "(NC)"
+    SignalType expected = SignalType::Other;
+    SignalType actual   = SignalType::Other;
+};
+
+// One bridged net mixing Power and GndShield, with its members for display.
+struct NetInconsistency {
+    struct Member { std::string module, signal; SignalType type; };
+    std::vector<Member> members;
+};
+
+// One orphan pin: no signal and not bridged via a connection. `dropped` is true
+// for a dropped singleton (essim detached it), false for an import-time NC.
+struct OrphanPin {
+    std::string module, part, pin;
+    bool dropped = false;
+};
+
+// The full result of `verify`: structured data only — no strings beyond the
+// names, no formatting. Frontends (the verify command, the analyze screen, the
+// dashboard) render it however they like.
+struct VerifyReport {
+    int typed_pins = 0;                          ///< pins with a non-Other expectation considered
+    std::vector<RoleMismatch> role_mismatches;
+
+    int total_nets = 0;
+    int bridged_nets = 0;
+    std::vector<NetInconsistency> net_inconsistencies;
+
+    int orphan_imported = 0;
+    int orphan_dropped = 0;
+    std::vector<OrphanPin> orphans;              ///< per-pin detail (both origins)
+
+    std::vector<Anomaly> pin_anomalies;          ///< check_pin_specs
+    std::vector<Anomaly> jtag_anomalies;         ///< check_jtag_chain
+    std::vector<Anomaly> conflict_anomalies;     ///< check_source_conflicts
+    std::vector<Anomaly> completeness_anomalies; ///< check_bsdl_completeness
+    std::vector<Anomaly> diff_anomalies;         ///< check_diff_crossings
+
+    int orphan_total() const { return orphan_imported + orphan_dropped; }
+    int model_total() const {
+        return (int)(pin_anomalies.size() + jtag_anomalies.size()
+                     + conflict_anomalies.size() + completeness_anomalies.size()
+                     + diff_anomalies.size());
+    }
+};
+
+// Run every verify pass over the system and return the findings. Pure core —
+// computes the nets once and feeds them to the net-based checks.
+VerifyReport verify(System *sys);
+
+}  // namespace app
+
+#endif  // _APP_VERIFY_HPP_

src/core/domain/analysis.cpp

@@ -31,15 +31,15 @@ const char *anomaly_kind_name(AnomalyKind k) {
     case AnomalyKind::JtagBusUnbridged:  return "jtag-bus-unbridged";
     case AnomalyKind::SourceConflict:    return "source-conflict";
     case AnomalyKind::BsdlPinMissing:    return "bsdl-pin-missing";
+    case AnomalyKind::DiffPolaritySwap:    return "diff-polarity-swap";
+    case AnomalyKind::DiffCrossIncomplete: return "diff-cross-incomplete";
     }
     return "?";
 }
 
-namespace {
-
 // Diff-pair suffix detection. Returns true and fills <stem, polarity> if
 // `name` ends with one of {_P, _N, _p, _n} preceded by a non-suffix char.
-// 'P' / 'N' result is normalised to uppercase.
+// 'P' / 'N' result is normalised to uppercase. Shared with diff_check.cpp.
 bool diff_suffix(const std::string &name, std::string &stem, char &pol) {
     if (name.size() < 3) return false;
     char last = name.back();
@@ -52,6 +52,29 @@ bool diff_suffix(const std::string &name, std::string &stem, char &pol) {
     return true;
 }
 
+// Tool-internal net names we never want to surface to the user (Mentor's
+// `$Nxxxx` convention, ODS placeholders, etc.). Cheap prefix check.
+bool is_internal_name(const std::string &n) {
+    return !n.empty() && n[0] == '$';
+}
+
+// Trailing-integer split: "MDI0" → ("MDI", 0); "PCIE_TX_3" → ("PCIE_TX_", 3);
+// "USB" → false (no trailing digits). Used for diff-bus aggregation only —
+// the strict `_` rule from `numeric_suffix` does NOT apply here because the
+// caller has already stripped a `_P` / `_N` polarity suffix, so we know the
+// remaining digits are an index rather than part of a longer name.
+bool split_trailing_index(const std::string &s, std::string &outer, int &idx) {
+    if (s.empty()) return false;
+    size_t i = s.size();
+    while (i > 0 && std::isdigit((unsigned char)s[i - 1])) --i;
+    if (i == s.size() || i == 0) return false;
+    idx = std::atoi(s.c_str() + i);
+    outer = s.substr(0, i);
+    return true;
+}
+
+namespace {
+
 // Bus suffix detection. Two accepted forms:
 //   - bracketed:    NAME[12]   → stem "NAME",  idx 12
 //   - underscore:   NAME_12    → stem "NAME_", idx 12 (underscore is REQUIRED
@@ -81,27 +104,6 @@ bool numeric_suffix(const std::string &name, std::string &stem, int &idx,
     return true;
 }
 
-// Tool-internal net names we never want to surface to the user (Mentor's
-// `$Nxxxx` convention, ODS placeholders, etc.). Cheap prefix check.
-bool is_internal_name(const std::string &n) {
-    return !n.empty() && n[0] == '$';
-}
-
-// Trailing-integer split: "MDI0" → ("MDI", 0); "PCIE_TX_3" → ("PCIE_TX_", 3);
-// "USB" → false (no trailing digits). Used for diff-bus aggregation only —
-// the strict `_` rule from `numeric_suffix` does NOT apply here because the
-// caller has already stripped a `_P` / `_N` polarity suffix, so we know the
-// remaining digits are an index rather than part of a longer name.
-bool split_trailing_index(const std::string &s, std::string &outer, int &idx) {
-    if (s.empty()) return false;
-    size_t i = s.size();
-    while (i > 0 && std::isdigit((unsigned char)s[i - 1])) --i;
-    if (i == s.size() || i == 0) return false;
-    idx = std::atoi(s.c_str() + i);
-    outer = s.substr(0, i);
-    return true;
-}
-
 void analyse_module(Module *mod, AnalysisReport &out) {
     // ---- Pass 1: diff pairs ----
     std::unordered_map<std::string, std::pair<Signal *, Signal *>> dp;  // stem -> {P, N}
@@ -276,13 +278,21 @@ SignalTypeInferenceStats infer_signal_types(System *sys) {
         Module *mod = mkv.second;
         for (auto &skv : *mod->signals) {
             Signal *s = skv.second;
-            SignalType named = infer_signal_type(s->name);
+            NameClassification ncl = classify_signal_name(s->name);
-            if (named == SignalType::GndShield) {
+            if (ncl.verdict == NameVerdict::GndShield) {
                 s->type = SignalType::GndShield;
                 ++st.gnd;
                 continue;
             }
-            if (named == SignalType::Power) {
+            if (ncl.verdict == NameVerdict::PowerMgmt) {
+                // A rail token next to a control token (SENSE, EN, PG, …):
+                // a signal about a rail, confidently NOT the rail — never
+                // suspect, whatever the fan-out.
+                s->type = SignalType::Other;
+                ++st.mgmt;
+                continue;
+            }
+            if (ncl.verdict == NameVerdict::Rail) {
                 int fanout = (int)s->size();
                 // Hard rule: a "power" net that touches fewer than three
                 // pins cannot physically be a rail (a real rail goes to

src/core/domain/analysis.hpp

@@ -39,6 +39,8 @@ enum class AnomalyKind {
     JtagBusUnbridged,  ///< TMS or TCK is not common to all TAP devices.
     SourceConflict,    ///< A model contradicts the netlist (e.g. BSDL power pin left NC).
     BsdlPinMissing,    ///< A BSDL power/ground port has no pin on the netlist part.
+    DiffPolaritySwap,    ///< A diff pair crosses a connection with P and N swapped.
+    DiffCrossIncomplete, ///< A diff pair/bus only partially crosses a connection.
 };
 
 struct Anomaly {
@@ -62,6 +64,8 @@ struct SignalTypeInferenceStats {
     int power = 0;        ///< Signals promoted to Power (name + structural).
     int gnd   = 0;        ///< Signals promoted to GndShield (name only).
     int kept_other = 0;   ///< Name said Power but structural evidence too weak.
+    int mgmt = 0;         ///< Power-management signal (rail + SENSE/EN/PG/…
+                          ///< token) → confidently Other, never suspect.
 };
 
 // Thresholds used by `infer_signal_types` (re-exposed so the analyze screen
@@ -71,6 +75,15 @@ inline constexpr int POWER_FANOUT_CONFIRM_MIN  = 4;  ///< ≥ this confirms Powe
 
 bool has_voltage_pattern(const std::string &name);
 
+// Name-parsing helpers shared with the diff-crossing check (diff_check.cpp).
+// diff_suffix: true if `name` ends with _P/_N (case-insensitive); fills the
+// stem and the polarity normalised to uppercase 'P'/'N'.
+// split_trailing_index: "MDI0" → ("MDI", 0); false without trailing digits.
+// is_internal_name: tool-internal net names never surfaced ($Nxxxx …).
+bool diff_suffix(const std::string &name, std::string &stem, char &pol);
+bool split_trailing_index(const std::string &s, std::string &outer, int &idx);
+bool is_internal_name(const std::string &n);
+
 // Best-effort signal-type inference. Sets `Signal::type`:
 //   - GndShield when the name unambiguously matches GND/SHIELD/CHASSIS/EARTH.
 //   - Power when the name suggests Power AND there is structural evidence

src/core/domain/component_kind.cpp

@@ -1,4 +1,4 @@
-#include "system/component_kind.hpp"
+#include "core/domain/component_kind.hpp"
 
 #include <cctype>
 #include <string>

src/core/domain/diff_check.cpp

@@ -0,0 +1,194 @@
+#include "diff_check.hpp"
+
+#include "modules.hpp"
+#include "signals.hpp"
+#include "system.hpp"
+
+#include <algorithm>
+#include <map>
+#include <set>
+#include <string>
+#include <unordered_map>
+#include <utility>
+
+namespace {
+
+// One complete local diff pair with the net ids of its two legs.
+struct LocalPair {
+    Module *mod = nullptr;
+    std::string stem;
+    Signal *p = nullptr, *n = nullptr;
+    int np = -1, nn = -1;
+};
+
+std::string pair_label(const LocalPair &lp) {
+    return lp.mod->name + "/" + lp.stem + "_P/N";
+}
+
+}  // namespace
+
+std::vector<Anomaly> check_diff_crossings(System *sys,
+                                          const std::vector<Net> *nets)
+{
+    std::vector<Anomaly> out;
+    if (!sys || !nets) return out;
+
+    // Signal → net id (compute_all_nets covers every signal, singletons too).
+    std::unordered_map<Signal *, int> net_of;
+    for (size_t i = 0; i < nets->size(); ++i)
+        for (const auto &mp : (*nets)[i].members)
+            net_of[mp.second] = (int)i;
+
+    // Complete local pairs, module by module. Orphan halves (X_P without
+    // X_N) are analysis's DiffPairOrphan business — skipped here.
+    std::vector<LocalPair> pairs;
+    std::unordered_map<Signal *, int> pair_of;  // leg signal → index in `pairs`
+    for (auto &mkv : *sys->modules()) {
+        Module *mod = mkv.second;
+        std::map<std::string, LocalPair> by_stem;
+        for (auto &skv : *mod->signals) {
+            if (is_internal_name(skv.first)) continue;
+            std::string stem; char pol;
+            if (!diff_suffix(skv.first, stem, pol)) continue;
+            LocalPair &lp = by_stem[stem];
+            lp.mod = mod; lp.stem = stem;
+            if (pol == 'P') lp.p = skv.second;
+            else            lp.n = skv.second;
+        }
+        for (auto &kv : by_stem) {
+            LocalPair lp = kv.second;
+            if (!lp.p || !lp.n) continue;
+            auto ip = net_of.find(lp.p), in = net_of.find(lp.n);
+            if (ip == net_of.end() || in == net_of.end()) continue;
+            lp.np = ip->second;
+            lp.nn = in->second;
+            int idx = (int)pairs.size();
+            pairs.push_back(lp);
+            pair_of[lp.p] = idx;
+            pair_of[lp.n] = idx;
+        }
+    }
+
+    // Pass 1 — pair against pair. Each unordered couple of pairs is judged
+    // once (dedup set), so A↔B is never also reported as B↔A.
+    std::set<std::pair<int, int>> seen;
+    for (int i = 0; i < (int)pairs.size(); ++i) {
+        const LocalPair &a = pairs[i];
+        if (a.np == a.nn) {
+            // Degenerate: both legs land on one net — only the connections
+            // can do that (two module-local signals are distinct by nature).
+            Anomaly an;
+            an.kind = AnomalyKind::DiffPolaritySwap;
+            an.module = a.mod;
+            an.message = a.mod->name + ": " + a.stem + "_P and " + a.stem
+                       + "_N join the same net (through the connections)";
+            an.involved = {a.p, a.n};
+            out.push_back(std::move(an));
+            continue;
+        }
+        // Candidate peers: pairs of OTHER modules with a leg on net np or nn.
+        std::set<int> cands;
+        for (int net : {a.np, a.nn})
+            for (const auto &mp : (*nets)[net].members) {
+                auto it = pair_of.find(mp.second);
+                if (it == pair_of.end()) continue;
+                const LocalPair &b = pairs[it->second];
+                if (b.mod == a.mod) continue;   // intra-module: nothing to say
+                if (b.np == b.nn) continue;     // degenerate: own anomaly above
+                cands.insert(it->second);
+            }
+        for (int j : cands) {
+            std::pair<int, int> key = std::minmax(i, j);
+            if (!seen.insert(key).second) continue;
+            const LocalPair &b = pairs[j];
+            if (a.np == b.np && a.nn == b.nn) continue;   // straight: all good
+            Anomaly an;
+            an.module = a.mod;
+            an.involved = {a.p, a.n, b.p, b.n};
+            if (a.np == b.nn && a.nn == b.np) {
+                an.kind = AnomalyKind::DiffPolaritySwap;
+                an.message = pair_label(a) + " <-> " + pair_label(b)
+                           + ": polarity swapped (P legs meet N legs)";
+            } else {
+                an.kind = AnomalyKind::DiffCrossIncomplete;
+                std::string how;
+                if      (a.np == b.np) how = "only the P legs are bridged";
+                else if (a.nn == b.nn) how = "only the N legs are bridged";
+                else if (a.np == b.nn) how = "P leg bridged to N leg; "
+                                             "the other legs are not";
+                else                   how = "N leg bridged to P leg; "
+                                             "the other legs are not";
+                an.message = pair_label(a) + " <-> " + pair_label(b)
+                           + ": " + how;
+            }
+            out.push_back(std::move(an));
+        }
+    }
+
+    // Pass 2 — diff buses at a crossing. Lanes grouped by outer stem. A lane
+    // is "dangling" when it crosses to NO module at all while sibling lanes
+    // do cross — distributed buses (lanes fanned out to different peers, a
+    // backplane classic) are legitimate and stay silent. Lanes crossing
+    // partially are already reported above, so they don't count as dangling.
+    // One aggregated anomaly per bus, per side (each side names its lanes).
+    std::map<std::pair<Module *, std::string>, std::map<int, int>> groups;
+    for (int i = 0; i < (int)pairs.size(); ++i) {
+        std::string outer; int idx;
+        if (!split_trailing_index(pairs[i].stem, outer, idx)) continue;
+        groups[{pairs[i].mod, outer}][idx] = i;
+    }
+    for (auto &gkv : groups) {
+        auto &lanes = gkv.second;          // lane index → pair index
+        if (lanes.size() < 2) continue;
+        std::set<int> touching_any;        // lanes sharing ≥1 net with a peer
+        std::set<int> complete_any;        // lanes fully crossing somewhere
+        std::set<Module *> reached;
+        for (auto &lkv : lanes) {
+            const LocalPair &a = pairs[lkv.second];
+            if (a.np == a.nn) continue;
+            for (int net : {a.np, a.nn})
+                for (const auto &mp : (*nets)[net].members) {
+                    auto it = pair_of.find(mp.second);
+                    if (it == pair_of.end()) continue;
+                    const LocalPair &b = pairs[it->second];
+                    if (b.mod == a.mod) continue;
+                    touching_any.insert(lkv.first);
+                    bool straight = (a.np == b.np && a.nn == b.nn);
+                    bool swapped  = (a.np == b.nn && a.nn == b.np);
+                    if (straight || swapped) {
+                        complete_any.insert(lkv.first);
+                        reached.insert(b.mod);
+                    }
+                }
+        }
+        if (complete_any.empty()) continue;   // fully local bus: fine
+        std::vector<int> dangling;
+        for (auto &lkv : lanes)
+            if (!touching_any.count(lkv.first))
+                dangling.push_back(lkv.first);
+        if (dangling.empty()) continue;
+        int lo = lanes.begin()->first;
+        int hi = lanes.rbegin()->first;
+        Anomaly an;
+        an.kind = AnomalyKind::DiffCrossIncomplete;
+        an.module = gkv.first.first;
+        std::string m = gkv.first.first->name + ": " + gkv.first.second
+                      + "[" + std::to_string(lo) + ".."
+                      + std::to_string(hi) + "]_P/N: lane(s)";
+        for (int ix : dangling) m += " " + std::to_string(ix);
+        m += " do not cross (others reach";
+        std::vector<std::string> names;
+        for (Module *mod : reached) names.push_back(mod->name);
+        std::sort(names.begin(), names.end());
+        for (const std::string &nm : names) m += " " + nm;
+        m += ")";
+        an.message = std::move(m);
+        for (auto &lkv : lanes) {
+            an.involved.push_back(pairs[lkv.second].p);
+            an.involved.push_back(pairs[lkv.second].n);
+        }
+        out.push_back(std::move(an));
+    }
+
+    return out;
+}

src/core/domain/diff_check.hpp

@@ -0,0 +1,27 @@
+#ifndef _DIFF_CHECK_HPP_
+#define _DIFF_CHECK_HPP_
+
+#include "analysis.hpp"  // Anomaly, diff_suffix, split_trailing_index
+#include "nets.hpp"      // Net
+
+#include <vector>
+
+class System;
+
+// Differential-pair crossing checks. Every complete local diff pair
+// (X_P / X_N, name-based) resolves its two legs to two bridged nets; any
+// other module whose own pair sits on those nets must match them leg for
+// leg. Findings:
+//   - DiffPolaritySwap: the peer pair is wired P→N / N→P, or a pair's two
+//     legs end up joined onto one single net through the connections.
+//   - DiffCrossIncomplete: the two pairs share only one leg (the other does
+//     not cross), or some lanes of a diff bus do not reach a module the
+//     other lanes reach.
+// Name-based on BOTH sides: a peer whose signals carry no _P/_N suffix is
+// not judged (silent). Polarity swaps are sometimes intentional (routing
+// compensation, SerDes with configurable polarity) — these are findings to
+// review, not hard errors. `nets` must come from compute_all_nets(sys).
+std::vector<Anomaly> check_diff_crossings(System *sys,
+                                          const std::vector<Net> *nets);
+
+#endif  // _DIFF_CHECK_HPP_

src/core/domain/nets.cpp

@@ -1,11 +1,11 @@
-#include "system/nets.hpp"
+#include "core/domain/nets.hpp"
 
-#include "system/connect.hpp"
+#include "core/domain/connect.hpp"
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
-#include "system/pins.hpp"
+#include "core/domain/pins.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
 
 #include <queue>
 #include <unordered_map>

src/core/domain/pin_name.cpp

@@ -1,4 +1,4 @@
-#include "system/pin_name.hpp"
+#include "core/domain/pin_name.hpp"
 
 #include <cstdio>
 #include <stdexcept>

src/core/domain/signal_type.hpp

@@ -0,0 +1,30 @@
+#ifndef _SIGNAL_TYPE_HPP_
+#define _SIGNAL_TYPE_HPP_
+
+#include <string>
+
+enum class SignalType { Power, GndShield, Other };
+
+// Name-level verdict, richer than SignalType. `PowerMgmt` is the key
+// addition: a name holding BOTH a rail token (VCC/VDD/PWR/…) and a control
+// token (SENSE/EN/PG/FB/…) is a power-management signal — measurement,
+// enable, power-good — not the rail itself. Its non-Power classification is
+// therefore confident, where a bare rail name without structural evidence
+// stays suspect.
+enum class NameVerdict { Rail, GndShield, PowerMgmt, Other };
+
+struct NameClassification {
+    NameVerdict verdict = NameVerdict::Other;
+    std::string token;   ///< PowerMgmt only: the control token that decided it.
+};
+
+NameClassification classify_signal_name(const std::string &signal_name);
+
+const char *signal_type_name(SignalType t);
+bool        signal_type_from_name(const std::string &s, SignalType &out);
+// Thin wrapper over classify_signal_name: Rail → Power, GndShield → GndShield,
+// PowerMgmt/Other → Other.
+SignalType  infer_signal_type(const std::string &signal_name);
+SignalType  next_signal_type(SignalType t);  // Power → GndShield → Other → Power
+
+#endif // _SIGNAL_TYPE_HPP_

src/core/domain/signals.cpp

@@ -0,0 +1,198 @@
+
+#include "signals.hpp"
+#include "parts.hpp"
+
+#include <algorithm>
+#include <cctype>
+#include <cstring>
+#include <vector>
+
+const char *signal_type_name(SignalType t) {
+    switch (t) {
+    case SignalType::Power:     return "power";
+    case SignalType::GndShield: return "gnd";
+    case SignalType::Other:     return "other";
+    }
+    return "other";
+}
+
+SignalType next_signal_type(SignalType t) {
+    switch (t) {
+    case SignalType::Power:     return SignalType::GndShield;
+    case SignalType::GndShield: return SignalType::Other;
+    case SignalType::Other:     return SignalType::Power;
+    }
+    return SignalType::Other;
+}
+
+bool signal_type_from_name(const std::string &s, SignalType &out) {
+    std::string l = s;
+    std::transform(l.begin(), l.end(), l.begin(),
+                   [](unsigned char c) { return std::tolower(c); });
+    if (l == "power" || l == "p")          { out = SignalType::Power;     return true; }
+    if (l == "gnd" || l == "g" || l == "shield" || l == "ground")
+                                           { out = SignalType::GndShield; return true; }
+    if (l == "other" || l == "o" || l == "signal")
+                                           { out = SignalType::Other;     return true; }
+    return false;
+}
+
+namespace {
+
+// Control/monitoring vocabulary: a name holding both a rail token and one of
+// these is a signal ABOUT a rail (feedback, enable, power-good, fault, …) —
+// not the rail itself. Matched against whole separator-delimited tokens
+// (uppercase, trailing digits stripped so EN1/PG0 still hit). Entries of
+// length ≥ 4 also match as a token *suffix*, catching fused (VSENSE, PWRGOOD)
+// and active-low (NFAULT) forms; short entries match exactly, so GREEN or
+// SENSOR never trip on EN / SENSE.
+const char *const kPowerControlTokens[] = {
+    "SENSE", "SNS", "KELVIN",                  // remote / Kelvin sense
+    "FB", "FBK", "FDB", "FDBK", "VFB",         // regulator feedback
+    "FEEDBACK",
+    "EN", "ENA", "ENABLE", "INH", "INHIBIT",   // enable / inhibit
+    "PG", "PGOOD", "PWRGD", "PWROK",           // power-good
+    "GOOD", "OK", "FAIL", "FAULT", "FLT",      // status / fault
+    "ALERT", "ALRT", "WARN",
+    "MON", "IMON", "VMON", "PMON",             // monitoring
+    "DET", "DETECT", "PRSNT", "PRESENT",       // presence detection
+    "OC", "OCP", "OV", "OVP", "UV", "UVP",     // protection trips
+    "TRIP", "SHDN", "SHUTDOWN",
+    "ADJ", "ADJUST", "VADJ", "TRIM",           // regulator adjust / trim
+    "MARG", "MARGIN",                          // voltage margining
+    "SET", "VSET", "ISET",                     // set-point pins
+    "SEQ", "CTRL", "CTL", "CMD",               // sequencing / control / command
+    "STAT", "STATUS",
+    "ON", "OFF", "BTN",                        // on/off request
+    "REF", "VREF",                             // voltage reference
+    "LED",                                     // indicator drive
+    "CS", "IRQ",
+};
+
+bool is_power_control_token(std::string tok) {
+    while (!tok.empty() && std::isdigit((unsigned char)tok.back()))
+        tok.pop_back();                          // EN1, PG0, FB2 …
+    if (tok.empty()) return false;
+    for (const char *lex : kPowerControlTokens) {
+        size_t n = std::strlen(lex);
+        if (tok == lex) return true;
+        if (n >= 4 && tok.size() > n
+            && tok.compare(tok.size() - n, n, lex) == 0)
+            return true;                         // VSENSE, PWRGOOD, NFAULT …
+    }
+    return false;
+}
+
+// Split on every non-alphanumeric character. `u` is already uppercase.
+std::vector<std::string> alnum_tokens(const std::string &u) {
+    std::vector<std::string> out;
+    std::string cur;
+    for (char c : u) {
+        if (std::isalnum((unsigned char)c)) { cur += c; continue; }
+        if (!cur.empty()) { out.push_back(std::move(cur)); cur.clear(); }
+    }
+    if (!cur.empty()) out.push_back(std::move(cur));
+    return out;
+}
+
+}  // namespace
+
+// Heuristic. Names like GND, GNDA, SHIELD, CHASSIS → GndShield (name alone is
+// reliable there — left out of the control-token logic on purpose). Names
+// containing PWR/POWER/VCC/VDD/VEE/VSS, or starting with VS_/VBAT/+/− → rail
+// candidates; a rail candidate whose tokens include a control word (SENSE,
+// EN, PG, …) is downgraded to PowerMgmt. Else Other.
+NameClassification classify_signal_name(const std::string &name) {
+    NameClassification out;
+    if (name.empty()) return out;
+    std::string u = name;
+    std::transform(u.begin(), u.end(), u.begin(),
+                   [](unsigned char c) { return std::toupper(c); });
+
+    auto contains = [&](const char *needle) {
+        return u.find(needle) != std::string::npos;
+    };
+    auto starts_with = [&](const char *needle) {
+        return u.rfind(needle, 0) == 0;
+    };
+
+    if (u == "GND" || u == "GROUND"
+        || starts_with("GND_")
+        || (starts_with("GND") && u.size() >= 4
+            && std::isalpha((unsigned char)u[3]))
+        || contains("SHIELD") || contains("CHASSIS") || contains("EARTH")) {
+        out.verdict = NameVerdict::GndShield;
+        return out;
+    }
+
+    if (contains("PWR") || contains("POWER")
+        || contains("VCC") || contains("VDD") || contains("VEE") || contains("VSS")
+        || starts_with("VS_") || starts_with("VS1_") || starts_with("VS2_")
+        || starts_with("VS3_") || starts_with("VS4_")
+        || starts_with("VBAT") || starts_with("VBUS")
+        || starts_with("+") || starts_with("-")) {
+        for (const std::string &tok : alnum_tokens(u)) {
+            if (is_power_control_token(tok)) {
+                out.verdict = NameVerdict::PowerMgmt;
+                out.token = tok;
+                return out;
+            }
+        }
+        out.verdict = NameVerdict::Rail;
+        return out;
+    }
+    return out;
+}
+
+SignalType infer_signal_type(const std::string &name) {
+    switch (classify_signal_name(name).verdict) {
+    case NameVerdict::Rail:      return SignalType::Power;
+    case NameVerdict::GndShield: return SignalType::GndShield;
+    case NameVerdict::PowerMgmt:
+    case NameVerdict::Other:     break;
+    }
+    return SignalType::Other;
+}
+
+Signal::Signal(std::string name)
+    : SystemElementContainer<Pin>(name), prnt(nullptr),
+      type(SignalType::Other) {};
+
+void Signal::add(Pin *pin)
+{
+    string pname = pin->prnt->name + "." + pin->name;
+    SystemElementContainer<Pin>::add(pname, pin);
+}
+
+Signals::Signals(void): SystemElementContainer<Signal>("signals") {}
+
+Signals::Signals(std::vector<Signal *> signals): SystemElementContainer<Signal>("signals", signals) {}
+
+Signals::~Signals() {
+    for (const auto& [key, value] : content) {
+        delete value;
+    }
+}
+
+int drop_singleton_signals(Signals *signals) {
+    if (!signals) return 0;
+    std::vector<Signal *> doomed;
+    for (auto &kv : *signals)
+        if (kv.second->size() == 1) doomed.push_back(kv.second);
+    for (Signal *s : doomed) {
+        // Detach the lone pin so it surfaces as `(NC)` in views.
+        for (auto &pkv : *s) {
+            pkv.second->connect(nullptr);
+            pkv.second->nc_origin = NcOrigin::DroppedSingleton;
+        }
+        signals->remove(s->name);
+        delete s;
+    }
+    return (int)doomed.size();
+}
+
+void Signals::add(Signal *signal)
+{
+    SystemElementContainer<Signal>::add(signal);
+    signal->prnt = this;
+}

src/core/domain/system.cpp

@@ -0,0 +1,56 @@
+
+#include "system.hpp"
+
+#include "connect.hpp"
+#include "modules.hpp"
+#include "core/imports/import_altium.hpp"
+#include "core/imports/import_mentor.hpp"
+#include "core/imports/import_ods.hpp"
+
+System::System() : mods(nullptr), conns(nullptr)
+{
+    mods = new Modules();
+    conns = new Connections();
+}
+
+System::~System()
+{
+    delete mods;
+    delete conns;
+}
+
+void System::Load(std::string module_name, std::string file_name, ImportType type)
+{
+    // Build the importer first, based on the import type.
+    ImportBase *imp;
+    if (type == ImportType::IMPORT_MENTOR)
+    {
+        imp = new ImportMentor(file_name);
+    } else if (type == ImportType::IMPORT_ALTIUM)
+    {
+        imp = new ImportAltium(file_name);
+    } else if (type == ImportType::IMPORT_ODS)
+    {
+        imp = new ImportOds(file_name);
+    }
+    else
+    {
+        throw std::runtime_error("Unknown import type");
+    }
+
+    // Fail fast on a missing/unreadable file, before touching the module table,
+    // so a failed load never leaves behind an empty module.
+    if (!imp->is_open())
+    {
+        delete imp;
+        throw std::runtime_error("cannot open file: " + file_name);
+    }
+
+    // Creation or retrieval of the module, then parse into it. add() copies the
+    // Part pointers into the module, which takes ownership; deleting the
+    // importer then frees the (now drained) Parts container, not the parts.
+    Module *mod = mods->merge(module_name);
+    imp->parse(mod->signals);
+    mod->add(imp->parts());
+    delete imp;
+}

src/core/domain/system.hpp

@@ -1,7 +1,7 @@
 #ifndef _SYSTEM_HPP_
 #define _SYSTEM_HPP_
 
-#include "imports/import_base.hpp"
+#include "core/imports/import_base.hpp"
 
 #pragma once
 class Modules; ///< Forward declaration of the Modules class.

src/core/imports/import_altium.cpp

@@ -1,8 +1,8 @@
 #include "import_altium.hpp"
 
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
-#include "system/pins.hpp"
+#include "core/domain/pins.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
 
 #include <cctype>
 #include <string>

src/core/imports/import_base.hpp

@@ -4,8 +4,8 @@
 #include <string>
 #include <fstream>
 
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
 
 /**
  * @brief Base class for importing data from a file.
@@ -27,11 +27,22 @@ public:
      *
      * @param file_name Name of the file to be imported.
      */
-    ImportBase(std::string file_name) : file_lines(std::fstream(file_name))
+    ImportBase(std::string file_name) : file_lines(file_name, std::ios::in)
     {
         prts = new Parts();
     };
 
+    /**
+     * @brief Whether the input file was opened successfully.
+     *
+     * Opened read-only, so this is false only when the file is genuinely
+     * missing or unreadable (a read-only but present file still opens).
+     * System::Load checks it to fail fast instead of producing an empty module.
+     *
+     * @return true if the file stream is open.
+     */
+    bool is_open() const { return file_lines.is_open(); }
+
     /**
      * @brief Pure virtual method for parsing the file.
      *
@@ -53,9 +64,13 @@ public:
     /**
      * @brief Virtual destructor for ImportBase.
      *
-     * Ensures proper cleanup of derived classes.
+     * Frees the Parts container object. Only the container is deleted, not the
+     * Part objects it holds: by the time the importer is destroyed those have
+     * been transferred to a Module (SystemElementContainer::add copies the
+     * pointers), which owns and deletes them. The default ~Parts frees the map
+     * without touching the elements, so there is no double free.
      */
-    virtual ~ImportBase() = default;
+    virtual ~ImportBase() { delete prts; }
 };
 
 #endif // _IMPORT_BASE_HPP_

src/core/imports/import_mentor.cpp

@@ -1,6 +1,6 @@
 #include "import_mentor.hpp"
-#include "system/pins.hpp"
+#include "core/domain/pins.hpp"
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
 
 #include <cctype>
 #include <vector>
@@ -43,16 +43,6 @@ enum class State
  */
 ImportMentor::ImportMentor(string filename) : ImportBase(filename) {}
 
-/**
- * @brief Destructor for ImportMentor.
- *
- * Ensures proper cleanup by calling the base class destructor.
- */
-ImportMentor::~ImportMentor()
-{
-    ImportBase::~ImportBase();
-}
-
 /**
  * @brief Parses the file to extract parts, pins, and signals.
  *

src/core/imports/import_mentor.hpp

@@ -10,7 +10,6 @@ class ImportMentor : public ImportBase
 public:
     ImportMentor(std::string filename);
     void parse(Signals *signals) override;
-    ~ImportMentor();
 };
 
 #endif // _IMPORT_MENTOR_HPP_

src/core/imports/import_ods.cpp

@@ -1,8 +1,8 @@
 #include "import_ods.hpp"
 
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
-#include "system/pins.hpp"
+#include "core/domain/pins.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
 
 #include <pugixml.hpp>
 #include <zip.h>

src/frontends/frontend.hpp

@@ -0,0 +1,30 @@
+#ifndef _FRONTEND_HPP_
+#define _FRONTEND_HPP_
+
+#include <iosfwd>
+#include <string>
+
+// Abstract entry-point interface every frontend (TUI, GUI, …) implements, so
+// one shared launcher (frontend_main) can drive any of them: parse argv, run
+// boot commands, optionally dump output (batch / docs) and enter the event
+// loop. Lives in the frontends layer — essim_core never depends on it.
+class Frontend {
+public:
+    virtual ~Frontend() = default;
+
+    // Dispatch one command synchronously, exactly as if the user typed it
+    // (e.g. "restore foo.essim" or "source bring-up.essim"), before the event
+    // loop starts — used to seed the system at boot.
+    virtual void BootDispatch(const std::string &raw) = 0;
+
+    // Write the command registry as Markdown (used for doc generation).
+    virtual void DumpCommandsMd(std::ostream &out) const = 0;
+
+    // Write the accumulated console output (batch mode: no event loop).
+    virtual void DumpOutput(std::ostream &out) const = 0;
+
+    // Enter the interactive event loop.
+    virtual void Run() = 0;
+};
+
+#endif  // _FRONTEND_HPP_

src/frontends/frontend_main.cpp

@@ -1,4 +1,6 @@
-#include "tui/tui.hpp"
+#include "frontends/frontend_main.hpp"
+
+#include "frontends/frontend.hpp"
 
 #include <fstream>
 #include <iostream>
@@ -11,16 +13,17 @@ void print_usage(const char *prog) {
         "usage: " << prog << " [--batch] [--source FILE] [--restore FILE]\n"
         "       " << prog << " --commands-md [FILE]\n"
         "       " << prog << " --help\n"
-        "  (no args)             launch the TUI on an empty system.\n"
+        "  (no args)             launch the interface on an empty system.\n"
         "  --source FILE         after boot, run FILE as an essim script\n"
         "                        (one command per line; same as the `source`\n"
-        "                        command). Output is in the console screen.\n"
+        "                        command). Output goes to the console.\n"
         "  --restore FILE        after boot, restore the system snapshot in\n"
         "                        FILE (same as the `restore` command).\n"
         "                        Combine with --source to layer a script on\n"
         "                        top of a restored snapshot.\n"
         "  --batch               run --restore/--source, print the console\n"
-        "                        output to stdout, and exit without the TUI.\n"
+        "                        output to stdout, and exit without launching\n"
+        "                        the interface.\n"
         "  --commands-md [FILE]  dump the command registry as Markdown.\n"
         "                        With FILE: write there. Without: stdout.\n"
         "                        (Used by `cmake --build build --target doc`.)\n"
@@ -29,7 +32,7 @@ void print_usage(const char *prog) {
 
 }  // namespace
 
-int main(int argc, char **argv) {
+int frontend_main(int argc, char **argv, Frontend &fe) {
     std::string boot_restore;
     std::string boot_source;
     bool batch = false;
@@ -37,16 +40,15 @@ int main(int argc, char **argv) {
     for (int i = 1; i < argc; ++i) {
         std::string a = argv[i];
         if (a == "--commands-md") {
-            Tui tui;
             if (i + 1 < argc) {
                 std::ofstream f(argv[++i]);
                 if (!f) {
                     std::cerr << "essim: cannot open " << argv[i] << " for writing\n";
                     return 1;
                 }
-                tui.DumpCommandsMd(f);
+                fe.DumpCommandsMd(f);
             } else {
-                tui.DumpCommandsMd(std::cout);
+                fe.DumpCommandsMd(std::cout);
             }
             return 0;
         }
@@ -79,20 +81,19 @@ int main(int argc, char **argv) {
         return 2;
     }
 
-    Tui tui;
     // Order matters: a `--restore` brings up a snapshot, then `--source`
     // can layer additional commands on top of it (useful e.g. for "load
     // snapshot, then re-run a small script that adds a new card").
-    if (!boot_restore.empty()) tui.BootDispatch("restore " + boot_restore);
+    if (!boot_restore.empty()) fe.BootDispatch("restore " + boot_restore);
-    if (!boot_source.empty())  tui.BootDispatch("source "  + boot_source);
+    if (!boot_source.empty())  fe.BootDispatch("source "  + boot_source);
 
-    // Batch mode: the boot dispatch already ran synchronously (no screen yet),
+    // Batch mode: the boot dispatch already ran synchronously (no event loop
-    // so the console output is complete. Print it and exit without the TUI.
+    // yet), so the console output is complete. Print it and exit.
     if (batch) {
-        tui.DumpOutput(std::cout);
+        fe.DumpOutput(std::cout);
         return 0;
     }
 
-    tui.Run();
+    fe.Run();
     return 0;
 }

src/frontends/frontend_main.hpp

@@ -0,0 +1,13 @@
+#ifndef _FRONTEND_MAIN_HPP_
+#define _FRONTEND_MAIN_HPP_
+
+class Frontend;
+
+// Shared process entry point, frontend-agnostic. Parses argv
+// (--source / --restore / --batch / --commands-md / --help), drives `fe`
+// through the boot commands and then either dumps output (batch) or enters its
+// event loop, and returns the process exit code. Each frontend's main() just
+// constructs its concrete Frontend and forwards to this.
+int frontend_main(int argc, char **argv, Frontend &fe);
+
+#endif  // _FRONTEND_MAIN_HPP_

src/frontends/tui/CMakeLists.txt

@@ -0,0 +1,22 @@
+# TUI frontend (FTXUI). Builds the `essim` executable against essim_core.
+#
+# A frontend is self-contained here: it pulls its own GUI toolkit, compiles its
+# sources into a library that links essim_core, and produces the `essim` binary
+# from its own entry point (main.cpp). To add another frontend, create a sibling
+# src/frontends/<name>/ with the same shape and select it with
+# -DESSIM_FRONTEND=<name>.
+
+set(FTXUI_BUILD_DOCS OFF CACHE INTERNAL "")
+set(FTXUI_BUILD_EXAMPLES OFF CACHE INTERNAL "")
+set(FTXUI_BUILD_TESTS OFF CACHE INTERNAL "")
+set(FTXUI_ENABLE_INSTALL OFF CACHE INTERNAL "")
+
+FetchContent_Declare(ftxui
+  GIT_REPOSITORY https://github.com/ArthurSonzogni/FTXUI.git
+  GIT_TAG v6.1.9
+  GIT_SHALLOW TRUE
+)
+FetchContent_MakeAvailable(ftxui)
+
+# Library essim_tui (sources here minus main.cpp) + the `essim` binary.
+essim_add_frontend(tui LIBS ftxui::screen ftxui::dom ftxui::component)

src/frontends/tui/commands.cpp

@@ -1,28 +1,26 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/analysis.hpp"
+#include "core/domain/analysis.hpp"
-#include "system/connect.hpp"
+#include "core/domain/connect.hpp"
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/nets.hpp"
+#include "core/domain/parts.hpp"
-#include "system/parts.hpp"
+#include "core/domain/persist.hpp"
-#include "system/persist.hpp"
+#include "core/domain/pin_role.hpp"
-#include "system/pin_role.hpp"
+#include "core/domain/pins.hpp"
-#include "system/pin_model.hpp"
+#include "core/domain/signals.hpp"
-#include "system/bsdl_model.hpp"
+#include "core/domain/system.hpp"
-#include "system/bsdl_check.hpp"
+
-#include "system/pins.hpp"
+#include "core/app/connect.hpp"
-#include "system/signals.hpp"
+#include "core/app/edit.hpp"
-#include "system/system.hpp"
+#include "core/app/load.hpp"
-#include "system/transform.hpp"
+#include "core/app/verify.hpp"
-#include "system/transform_vpx.hpp"
 
 #include <algorithm>
 #include <cctype>
 #include <cstdlib>
 #include <exception>
 #include <fstream>
-#include <unordered_set>
 #include <utility>
 
 void Tui::RegisterCommands() {
@@ -138,29 +136,25 @@ void Tui::RegisterCommands() {
          {"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;
+            if (!app::import_type_from_name(args[2], t)) {
-            else if (ls == "altium") t = ImportType::IMPORT_ALTIUM;
+                Print("unknown import type: " + args[2]); return;
-            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]);
-                int dropped = drop_singleton_signals(mod->signals);
-                auto inf = infer_signal_types(sys.get());
-                Print("loaded '" + args[0] + "' from " + args[1]);
-                Print("  parts:   " + std::to_string(mod->size()));
-                Print("  signals: " + std::to_string(mod->signals->size())
-                      + (dropped ? " (dropped " + std::to_string(dropped)
-                                   + " singleton/NC signal(s))" : ""));
-                Print("  types:   " + std::to_string(inf.power) + " power, "
-                      + std::to_string(inf.gnd)   + " gnd, "
-                      + std::to_string(inf.kept_other)
-                      + " suspect Power (name only — kept as Other)");
-            } catch (const std::exception &e) {
-                Print(std::string("load failed: ") + e.what());
             }
+            // Import + drop-singletons + infer-types is one core op; the command
+            // only parses the type and renders the counts.
+            app::LoadResult r = app::load_module(sys.get(), args[0], args[1], t);
+            if (!r.ok) { Print(std::string("load failed: ") + r.error); return; }
+            Print("loaded '" + args[0] + "' from " + args[1]);
+            Print("  parts:   " + std::to_string(r.parts));
+            Print("  signals: " + std::to_string(r.signals)
+                  + (r.dropped ? " (dropped " + std::to_string(r.dropped)
+                               + " singleton/NC signal(s))" : ""));
+            Print("  types:   " + std::to_string(r.power) + " power, "
+                  + std::to_string(r.gnd)   + " gnd, "
+                  + std::to_string(r.kept_other)
+                  + " suspect Power (name only — kept as Other), "
+                  + std::to_string(r.mgmt)
+                  + " power-management (control/measure — kept as Other)");
         },
         /*prompt_for_missing=*/ true,
         "load a module from a netlist / pinout file (mentor, altium, ods)",
@@ -228,104 +222,44 @@ void Tui::RegisterCommands() {
 
     commands["verify"] = { {}, [this](auto &) {
         if (!sys) { Print("no system: run 'new' first."); return; }
-        int checked = 0;
+        app::VerifyReport r = app::verify(sys.get());
-        int mismatches = 0;
-        for (auto &mkv : *sys->modules()) {
-            Module *mod = mkv.second;
-            for (auto &pkv : *mod) {
-                Part *prt = pkv.second;
-                if (prt->connector_type.empty()) continue;
-                for (auto &nkv : *prt) {
-                    Pin *pin = nkv.second;
-                    ++checked;
-                    SignalType expected = pin->expected_signal_type();
-                    if (expected == SignalType::Other) continue;
-                    Signal *s = pin->signal();
-                    SignalType actual = s ? s->type : SignalType::Other;
-                    if (actual == expected) continue;
-                    ++mismatches;
-                    std::string sig_label = s ? s->name : std::string("(NC)");
-                    Print("  " + mod->name + "/" + prt->name + "/" + pin->name
-                          + ": expected " + signal_type_name(expected)
-                          + ", got " + signal_type_name(actual)
-                          + " (signal: " + sig_label + ")");
-                }
-            }
-        }
-        Print("verify: " + std::to_string(mismatches) + " local mismatch(es) over "
-              + std::to_string(checked) + " typed pin(s).");
 
-        auto nets = compute_all_nets(sys.get());
+        for (const auto &m : r.role_mismatches)
-        int bridged = 0, inconsistent = 0;
+            Print("  " + m.module + "/" + m.part + "/" + m.pin
-        for (const auto &n : nets) {
+                  + ": expected " + signal_type_name(m.expected)
-            if (n.members.size() < 2) continue;
+                  + ", got " + signal_type_name(m.actual)
-            ++bridged;
+                  + " (signal: " + m.signal + ")");
-            SignalType dom;
+        Print("verify: " + std::to_string(r.role_mismatches.size())
-            if (net_type_consistent(n, dom)) continue;
+              + " local mismatch(es) over " + std::to_string(r.typed_pins)
-            ++inconsistent;
+              + " typed pin(s).");
+
+        for (const auto &ni : r.net_inconsistencies) {
             std::string line = "  net mixes Power and GndShield:";
-            for (const auto &mp : n.members) {
+            for (const auto &mem : ni.members)
-                line += " " + mp.first->name + "/" + mp.second->name
+                line += " " + mem.module + "/" + mem.signal
-                      + "(" + signal_type_name(mp.second->type) + ")";
+                      + "(" + signal_type_name(mem.type) + ")";
-            }
             Print(line);
         }
-        Print("verify: " + std::to_string(inconsistent) + " inconsistent net(s) over "
+        Print("verify: " + std::to_string(r.net_inconsistencies.size())
-              + std::to_string(bridged) + " bridged net(s) ("
+              + " inconsistent net(s) over " + std::to_string(r.bridged_nets)
-              + std::to_string(nets.size()) + " total).");
+              + " bridged net(s) (" + std::to_string(r.total_nets) + " total).");
 
-        // Orphan pin report. A pin is "orphan" if it came out of import (or
+        Print("verify: " + std::to_string(r.orphan_total())
-        // post-import drop) with no signal, and is still not bridged to a
+              + " orphan pin(s) at import (" + std::to_string(r.orphan_imported)
-        // real signal via any Connection::pin_map. Use `nc-export` for the
+              + " imported NC, " + std::to_string(r.orphan_dropped)
-        // per-pin list.
+              + " dropped singleton).");
-        std::unordered_set<Pin *> bridged_pins;
-        for (auto &ckv : *sys->connections())
-            for (auto &wp : ckv.second->pin_map) {
-                if (wp.first)  bridged_pins.insert(wp.first);
-                if (wp.second) bridged_pins.insert(wp.second);
-            }
-        int orph_imported = 0, orph_dropped = 0;
-        for (auto &mkv : *sys->modules())
-            for (auto &pkv : *mkv.second)
-                for (auto &nkv : *pkv.second) {
-                    Pin *pin = nkv.second;
-                    if (pin->signal() || bridged_pins.count(pin)) continue;
-                    if (pin->nc_origin == NcOrigin::ImportedUnconnected) ++orph_imported;
-                    else if (pin->nc_origin == NcOrigin::DroppedSingleton) ++orph_dropped;
-                }
-        Print("verify: " + std::to_string(orph_imported + orph_dropped)
-              + " orphan pin(s) at import ("
-              + std::to_string(orph_imported) + " imported NC, "
-              + std::to_string(orph_dropped)  + " dropped singleton).");
 
-        // Model-driven pin checks (drive contention / undriven net / NC-wired)
+        // Each model-driven group: per-finding lines + a one-line summary.
-        // from the PinSpec direction/function populated by connector/BSDL models.
+        auto render = [this](const std::vector<Anomaly> &v, const char *tail) {
-        auto pin_anoms = check_pin_specs(sys.get(), &nets);
+            for (const auto &a : v)
-        for (const auto &a : pin_anoms)
+                Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
-            Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
+            Print("verify: " + std::to_string(v.size()) + tail);
-        Print("verify: " + std::to_string(pin_anoms.size())
+        };
-              + " model-driven pin anomaly(ies).");
+        render(r.pin_anomalies,          " model-driven pin anomaly(ies).");
-
+        render(r.jtag_anomalies,         " JTAG chain anomaly(ies).");
-        // JTAG boundary-scan chain integrity (TAP pins → nets).
+        render(r.conflict_anomalies,     " source-conflict(s).");
-        auto jtag_anoms = check_jtag_chain(sys.get(), &nets);
+        render(r.completeness_anomalies, " BSDL completeness issue(s).");
-        for (const auto &a : jtag_anoms)
+        render(r.diff_anomalies,         " diff-pair crossing anomaly(ies).");
-            Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
-        Print("verify: " + std::to_string(jtag_anoms.size())
-              + " JTAG chain anomaly(ies).");
-
-        // Model-vs-netlist conflicts (e.g. a BSDL power pin left unconnected).
-        auto conflict_anoms = check_source_conflicts(sys.get());
-        for (const auto &a : conflict_anoms)
-            Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
-        Print("verify: " + std::to_string(conflict_anoms.size())
-              + " source-conflict(s).");
-
-        // BSDL completeness: device power/ground pins missing from the netlist.
-        auto missing_anoms = check_bsdl_completeness(sys.get());
-        for (const auto &a : missing_anoms)
-            Print("  [" + std::string(anomaly_kind_name(a.kind)) + "] " + a.message);
-        Print("verify: " + std::to_string(missing_anoms.size())
-              + " BSDL completeness issue(s).");
     }, true,
        "check pin roles, power/gnd net consistency, and (with BSDL) pin and JTAG checks" };
 
@@ -403,14 +337,10 @@ void Tui::RegisterCommands() {
             catch (const std::exception &) {
                 Print("unknown signal: " + mod->name + "/" + args[1]); return;
             }
-            SignalType t;
+            app::SetSignalTypeResult r = app::set_signal_type(sig, args[2]);
-            if (!signal_type_from_name(args[2], t)) {
+            if (!r.ok) { Print(r.error); return; }
-                Print("type must be one of: power, gnd, other (got: " + args[2] + ")");
-                return;
-            }
-            sig->type = t;
             Print(mod->name + "/" + sig->name + ": signal type = "
-                  + signal_type_name(t));
+                  + signal_type_name(r.type));
         },
         /*prompt_for_missing=*/ true,
         "override the auto-detected signal type (power | gnd | other)",
@@ -464,18 +394,15 @@ void Tui::RegisterCommands() {
                     return;
                 }
             }
-            std::string err = ValidatePartForKind(prt, args[2]);
+            app::SetConnectorTypeResult r = app::set_connector_type(prt, args[2]);
-            if (!err.empty()) {
+            if (!r.ok) {
-                Print("set-connector-type refused: " + err);
+                Print("set-connector-type refused: " + r.error);
                 return;
             }
-            prt->connector_type = args[2];
-            ConnectorModel model(args[2]);
-            ApplyReport rep = apply_model(prt, model);
             Print(mod->name + "/" + prt->name + ": connector_type = "
                   + (args[2].empty() ? "(none)" : args[2]));
-            if (rep.materialised > 0)
+            if (r.materialised > 0)
-                Print("set-connector-type: added " + std::to_string(rep.materialised)
+                Print("set-connector-type: added " + std::to_string(r.materialised)
                       + " NC pin(s) from the connector layout");
         },
         /*prompt_for_missing=*/ false,
@@ -516,17 +443,11 @@ void Tui::RegisterCommands() {
                 }
             }
 
-            BsdlModel model = BsdlModel::from_file(args[2]);
+            app::AttachBsdlResult r = app::attach_bsdl(prt, args[2]);
-            if (!model.valid()) {
+            if (!r.ok) { Print("attach-bsdl: " + r.error); return; }
-                Print("attach-bsdl: cannot parse " + args[2]
+            Print(mod->name + "/" + prt->name + ": attached BSDL '" + r.entity
-                      + (model.error().empty() ? "" : (": " + model.error())));
-                return;
-            }
-            BsdlApplyReport r = apply_bsdl(prt, model);
-            prt->bsdl_path = args[2];
-            Print(mod->name + "/" + prt->name + ": attached BSDL '" + model.entity()
                   + "' — " + std::to_string(r.bound) + "/"
-                  + std::to_string((int)model.ports().size()) + " ports bound"
+                  + std::to_string(r.ports_total) + " ports bound"
                   + (r.unbound ? (", " + std::to_string(r.unbound) + " unbound") : ""));
         },
         /*prompt_for_missing=*/ false,
@@ -622,47 +543,23 @@ void Tui::RegisterCommands() {
             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();
+            // Resolution above is arg-parsing (user text → objects); the wiring
-            Transform *t = reg.lookup(p1->connector_type, p2->connector_type);
+            // itself — transform lookup, identity NC fill, Connection creation —
-            bool both_empty = p1->connector_type.empty() && p2->connector_type.empty();
+            // is app::connect_parts.
-            if (t == reg.identity()) {
+            app::ConnectResult cr = app::connect_parts(sys.get(), m1, p1, m2, p2);
-                if (!both_empty) {
+            if (cr.refused) { Print("connect refused: " + cr.error); return; }
-                    Print("connect refused: no transform for types '"
+            if (!cr.identity_info.empty()) {
-                          + (p1->connector_type.empty() ? "(none)" : p1->connector_type)
+                Print("connect: " + cr.identity_info);
-                          + "' ↔ '"
+                if (cr.nc_added > 0)
-                          + (p2->connector_type.empty() ? "(none)" : p2->connector_type)
+                    Print("connect: added " + std::to_string(cr.nc_added)
-                          + "'. Set matching types via 'set-connector-type' first.");
+                          + " NC pin(s) so both sides match");
-                    return;
-                }
-                std::string info;
-                std::string err = CheckIdentityCompatible(p1, p2, &info);
-                if (!err.empty()) {
-                    Print("connect refused: " + err);
-                    return;
-                }
-                if (!info.empty()) {
-                    int added = FillIdentityNCs(p1, p2);
-                    Print("connect: " + info);
-                    if (added > 0)
-                        Print("connect: added " + std::to_string(added)
-                              + " NC pin(s) so both sides match");
-                }
-            }
-            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());
             }
+            if (cr.ok)
+                Print("connected: " + cr.connection_name
+                      + "  via " + cr.transform_name
+                      + " (" + std::to_string(cr.wires) + " wires)");
+            else
+                Print(std::string("connect failed: ") + cr.error);
         },
         /*prompt_for_missing=*/ false,
         "connect a part across two modules (interactive screen if no args)",
@@ -701,51 +598,12 @@ void Tui::RegisterCommands() {
          {"new module name", Completion::None}},
         [this](const std::vector<std::string> &args) {
             if (!sys) { Print("no system: run 'new' first."); return; }
-
+            app::DuplicateResult r =
-            Module *src;
+                app::duplicate_module(sys.get(), args[0], args[1]);
-            try { src = sys->modules()->get(args[0]); }
+            if (!r.ok) { Print(r.error); return; }
-            catch (const std::exception &) {
-                Print("unknown module: " + args[0]); return;
-            }
-            if (sys->modules()->exists(args[1])) {
-                Print("duplicate refused: module '" + args[1] + "' already exists.");
-                return;
-            }
-
-            Module *dst = new Module(args[1]);
-
-            // 1. Copy signals (preserve type overrides).
-            for (auto &skv : *src->signals) {
-                Signal *ss = skv.second;
-                Signal *ds = new Signal(ss->name);
-                ds->type = ss->type;
-                dst->signals->add(ds);
-            }
-
-            // 2. Copy parts, pins, and re-wire pin→signal.
-            for (auto &pkv : *src) {
-                Part *sp = pkv.second;
-                Part *dp = new Part(sp->name);
-                dp->connector_type = sp->connector_type;
-                for (auto &nkv : *sp) {
-                    Pin *sn = nkv.second;
-                    Pin *dn = new Pin(sn->name);
-                    dn->spec = sn->spec;
-                    dn->nc_origin = sn->nc_origin;
-                    dp->add(dn);
-                    if (sn->signal()) {
-                        Signal *ds = dst->signals->get(sn->signal()->name);
-                        ds->add(dn);
-                        dn->connect(ds);
-                    }
-                }
-                dst->add(dp);
-            }
-
-            sys->modules()->add(dst);
             Print("duplicate: '" + args[0] + "' → '" + args[1] + "'"
-                  + "  (" + std::to_string(dst->size()) + " part(s), "
+                  + "  (" + std::to_string(r.parts) + " part(s), "
-                  + std::to_string(dst->signals->size()) + " signal(s))");
+                  + std::to_string(r.signals) + " signal(s))");
         },
         /*prompt_for_missing=*/ true,
         "clone a module under a new name (parts, pins, signals; no connections)",

src/frontends/tui/commands_export.cpp

@@ -0,0 +1,70 @@
+#include "frontends/tui/tui.hpp"
+
+#include "core/app/export.hpp"
+#include "core/domain/connect.hpp"
+#include "core/domain/system.hpp"
+
+#include <string>
+#include <vector>
+
+// Thin UI wrapper around app::export_connections — this file only resolves
+// arguments / the file dialog and renders the result. All the actual export
+// (CSV / ODS building, file writing) lives in src/app/export.cpp.
+void Tui::RegisterExportCommands() {
+    commands["export"] = {
+        {{"kind [connections]", Completion::None},
+         {"filename (.csv)",    Completion::Path}},
+        [this](const std::vector<std::string> &args) {
+            if (!sys) { Print("no system: run 'new' first."); return; }
+
+            if (args.empty()) {
+                // Bare → the generic file dialog. The CSV/ODS filter rewrites
+                // the extension; the action below dispatches on it.
+                OpenFileDialog(
+                    "Export — connections",
+                    "export.connections",
+                    "connections.csv",
+                    {{"CSV", ".csv"}, {"ODS", ".ods"}},
+                    [this](const std::string &path) {
+                        Dispatch("export connections " + path);
+                    });
+                return;
+            }
+            if (args.size() != 2) {
+                Print("usage: export <kind> <file>   (or no args for the dialog)");
+                return;
+            }
+            const std::string &kind = args[0];
+            const std::string &path = args[1];
+
+            if (kind != "connections") {
+                ShowError("export: unknown kind '" + kind + "'\n"
+                          "Known kinds: connections");
+                return;
+            }
+
+            app::ExportFormat fmt;
+            if (!app::export_format_from_path(path, fmt)) {
+                ShowError("export: unknown extension — accepted: .csv, .ods");
+                return;
+            }
+
+            app::ExportResult r = app::export_connections(sys.get(), path, fmt);
+            if (!r.ok) {
+                ShowError("export failed:\n" + r.error);
+                return;
+            }
+
+            const bool ods = (fmt == app::ExportFormat::Ods);
+            std::string msg = ods ? "export connections (.ods): "
+                                  : "export connections (.csv): ";
+            if (ods) msg += std::to_string(r.sheets) + " sheet(s), ";
+            Print(msg + std::to_string(r.rows) + " wire(s) → " + path);
+        },
+        /*prompt_for_missing=*/ false,
+        "export structured data to CSV / ODS (kinds: connections; "
+        "bare form opens the file-picker dialog)",
+        /*scriptable=*/ true,
+        /*interactive=*/ true,
+    };
+}

src/frontends/tui/completion.cpp

@@ -1,5 +1,5 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
 #include <cctype>
 #include <cstdlib>

src/frontends/tui/main.cpp

@@ -0,0 +1,11 @@
+#include "frontends/frontend_main.hpp"
+#include "frontends/tui/tui.hpp"
+
+// The TUI frontend's entry point: construct the concrete Frontend (Tui) and
+// hand off to the shared, frontend-agnostic launcher. All argv parsing and the
+// boot/batch/run flow live in frontend_main(); a second frontend's main() looks
+// exactly like this with its own Frontend type.
+int main(int argc, char **argv) {
+    Tui tui;
+    return frontend_main(argc, argv, tui);
+}

src/frontends/tui/screen_analyze.cpp

@@ -1,15 +1,11 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/analysis.hpp"
+#include "core/app/verify.hpp"
-#include "system/bsdl_check.hpp"
+#include "core/domain/analysis.hpp"
-#include "system/connect.hpp"
+#include "core/domain/modules.hpp"
-#include "system/modules.hpp"
+#include "core/domain/signals.hpp"
-#include "system/nets.hpp"
+#include "core/domain/system.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>
@@ -17,7 +13,6 @@
 
 #include <algorithm>
 #include <array>
-#include <unordered_set>
 
 using namespace ftxui;
 
@@ -57,41 +52,23 @@ Component Tui::BuildAnalyzeScreen() {
         // connection), then structural anomalies from the analysis pass.
         analyze_issues.clear();
 
-        int n_role_mismatches = 0, n_typed_pins = 0;
+        // verify + structural anomalies. The verify passes (pin-role, net-mix,
-        for (auto &mkv : *sys->modules())
+        // orphans, model checks) come from the shared core op; the structural
-            for (auto &pkv : *mkv.second) {
+        // anomalies (diff-pair/bus) come from analyze_system above.
-                Part *prt = pkv.second;
+        app::VerifyReport vr = app::verify(sys.get());
-                if (prt->connector_type.empty()) continue;
-                for (auto &nkv : *prt) {
-                    Pin *pin = nkv.second;
-                    ++n_typed_pins;
-                    SignalType expected = pin->expected_signal_type();
-                    if (expected == SignalType::Other) continue;
-                    Signal *s = pin->signal();
-                    SignalType actual = s ? s->type : SignalType::Other;
-                    if (actual == expected) continue;
-                    ++n_role_mismatches;
-                    std::string sig_label = s ? s->name : std::string("(NC)");
-                    analyze_issues.push_back(
-                        "[pin-role] " + mkv.first + "/" + prt->name + "/"
-                        + pin->name + ": expected " + signal_type_name(expected)
-                        + ", got " + signal_type_name(actual)
-                        + " (signal: " + sig_label + ")");
-                }
-            }
 
-        auto nets = compute_all_nets(sys.get());
+        for (const auto &m : vr.role_mismatches)
-        int n_bridged = 0, n_inconsistent = 0;
+            analyze_issues.push_back(
-        for (const auto &n : nets) {
+                "[pin-role] " + m.module + "/" + m.part + "/" + m.pin
-            if (n.members.size() < 2) continue;
+                + ": expected " + signal_type_name(m.expected)
-            ++n_bridged;
+                + ", got " + signal_type_name(m.actual)
-            SignalType dom;
+                + " (signal: " + m.signal + ")");
-            if (net_type_consistent(n, dom)) continue;
+
-            ++n_inconsistent;
+        for (const auto &ni : vr.net_inconsistencies) {
             std::string line = "[net-mix] mixes Power and Gnd:";
-            for (const auto &mp : n.members)
+            for (const auto &mem : ni.members)
-                line += " " + mp.first->name + "/" + mp.second->name
+                line += " " + mem.module + "/" + mem.signal
-                      + "(" + signal_type_name(mp.second->type) + ")";
+                      + "(" + signal_type_name(mem.type) + ")";
             analyze_issues.push_back(std::move(line));
         }
 
@@ -100,28 +77,26 @@ Component Tui::BuildAnalyzeScreen() {
                                      + anomaly_kind_name(a.kind) + "] "
                                      + a.message);
 
-        // Model-driven checks (same as `verify`), reusing the nets above.
+        // Model-driven checks (pin / JTAG / source-conflict / completeness).
-        std::vector<Anomaly> model_anoms;
+        auto push_anoms = [this](const std::vector<Anomaly> &v) {
-        {
+            for (const auto &a : v)
-            auto a1 = check_pin_specs(sys.get(), &nets);
+                analyze_issues.push_back(std::string("[")
-            auto a2 = check_jtag_chain(sys.get(), &nets);
+                                         + anomaly_kind_name(a.kind) + "] "
-            auto a3 = check_source_conflicts(sys.get());
+                                         + a.message);
-            auto a4 = check_bsdl_completeness(sys.get());
+        };
-            model_anoms.insert(model_anoms.end(), a1.begin(), a1.end());
+        push_anoms(vr.pin_anomalies);
-            model_anoms.insert(model_anoms.end(), a2.begin(), a2.end());
+        push_anoms(vr.jtag_anomalies);
-            model_anoms.insert(model_anoms.end(), a3.begin(), a3.end());
+        push_anoms(vr.conflict_anomalies);
-            model_anoms.insert(model_anoms.end(), a4.begin(), a4.end());
+        push_anoms(vr.completeness_anomalies);
-        }
+        push_anoms(vr.diff_anomalies);
-        for (const auto &a : model_anoms)
+        int n_model = vr.model_total();
-            analyze_issues.push_back(std::string("[")
-                                     + anomaly_kind_name(a.kind) + "] "
-                                     + a.message);
-        int n_model = (int)model_anoms.size();
 
         if (analyze_issues.empty()) analyze_issues.push_back("(no issue found)");
         if (analyze_issue_idx >= (int)analyze_issues.size())
             analyze_issue_idx = (int)analyze_issues.size() - 1;
 
+        int n_role_mismatches = (int)vr.role_mismatches.size();
+        int n_inconsistent    = (int)vr.net_inconsistencies.size();
         std::string issues_header = "Issues ("
             + std::to_string(n_role_mismatches + n_inconsistent
                              + (int)rep.anomalies.size() + n_model)
@@ -157,29 +132,39 @@ Component Tui::BuildAnalyzeScreen() {
         // ============================================================= Types
         // Power decisions (confirmed / refuted) and NC orphan breakdown.
         analyze_types.clear();
-        int conf_pwr = 0, ref_pwr = 0, gnd = 0;
+        int conf_pwr = 0, ref_pwr = 0, mgmt = 0, gnd = 0;
-        struct Row { char kind; std::string mod, sig; int fanout; bool voltage; };
+        struct Row { char kind; std::string mod, sig; int fanout; bool voltage;
+                     std::string token; };
         std::vector<Row> rows;
         for (auto &mkv : *sys->modules()) {
             Module *mod = mkv.second;
             for (auto &skv : *mod->signals) {
                 Signal *s = skv.second;
-                SignalType named = infer_signal_type(s->name);
+                NameClassification ncl = classify_signal_name(s->name);
                 char kind = 0;
-                if (named == SignalType::GndShield && s->type == SignalType::GndShield) {
+                std::string token;
+                if (ncl.verdict == NameVerdict::GndShield && s->type == SignalType::GndShield) {
                     kind = 'G'; ++gnd;
-                } else if (named == SignalType::Power && s->type == SignalType::Power) {
+                } else if (ncl.verdict == NameVerdict::Rail && s->type == SignalType::Power) {
                     kind = 'P'; ++conf_pwr;
-                } else if (named == SignalType::Power && s->type == SignalType::Other) {
+                } else if (ncl.verdict == NameVerdict::Rail && s->type == SignalType::Other) {
                     kind = 'R'; ++ref_pwr;
+                } else if (ncl.verdict == NameVerdict::PowerMgmt) {
+                    kind = 'M'; ++mgmt; token = ncl.token;
                 } else continue;
                 rows.push_back({kind, mod->name, s->name,
-                                (int)s->size(), has_voltage_pattern(s->name)});
+                                (int)s->size(), has_voltage_pattern(s->name),
+                                token});
             }
         }
+        // Deliberate display order: confirmed rails, then the suspects (the
+        // actionable residue), then the power-management signals, gnd last.
+        auto rank = [](char k) {
+            return k == 'P' ? 0 : k == 'R' ? 1 : k == 'M' ? 2 : 3;
+        };
         std::sort(rows.begin(), rows.end(),
-                  [](const Row &a, const Row &b) {
+                  [&](const Row &a, const Row &b) {
-                      if (a.kind != b.kind) return a.kind < b.kind;
+                      if (a.kind != b.kind) return rank(a.kind) < rank(b.kind);
                       if (a.mod  != b.mod)  return a.mod  < b.mod;
                       return a.sig < b.sig;
                   });
@@ -207,6 +192,10 @@ Component Tui::BuildAnalyzeScreen() {
                 else                  reason = "name only — fan-out "
                                              + std::to_string(r.fanout)
                                              + ", no voltage";
+            } else if (r.kind == 'M') {
+                tag = "[Power mgmt]    ";
+                reason = "control token '" + r.token
+                       + "' in name — kept as Other";
             } else {
                 tag = "[Gnd]           ";
                 reason = "name match (fan-out " + std::to_string(r.fanout) + ")";
@@ -215,33 +204,19 @@ Component Tui::BuildAnalyzeScreen() {
                 std::string(tag) + r.mod + "/" + r.sig + "  —  " + reason);
         }
 
-        // NC orphan rollup — same filter as the verify pass.
+        // NC orphan rollup — from the shared verify report.
-        std::unordered_set<Pin *> bridged_pins;
-        for (auto &ckv : *sys->connections())
-            for (auto &wp : ckv.second->pin_map) {
-                if (wp.first)  bridged_pins.insert(wp.first);
-                if (wp.second) bridged_pins.insert(wp.second);
-            }
-        int orph_imported = 0, orph_dropped = 0;
-        for (auto &mkv : *sys->modules())
-            for (auto &pkv : *mkv.second)
-                for (auto &nkv : *pkv.second) {
-                    Pin *pin = nkv.second;
-                    if (pin->signal() || bridged_pins.count(pin)) continue;
-                    if (pin->nc_origin == NcOrigin::ImportedUnconnected) ++orph_imported;
-                    else if (pin->nc_origin == NcOrigin::DroppedSingleton) ++orph_dropped;
-                }
         analyze_types.push_back(
-            "[NC] orphan pin(s): " + std::to_string(orph_imported + orph_dropped)
+            "[NC] orphan pin(s): " + std::to_string(vr.orphan_total())
-            + " (" + std::to_string(orph_imported) + " imported, "
+            + " (" + std::to_string(vr.orphan_imported) + " imported, "
-            + std::to_string(orph_dropped) + " dropped)");
+            + std::to_string(vr.orphan_dropped) + " dropped)");
 
         if (analyze_type_idx >= (int)analyze_types.size())
             analyze_type_idx = (int)analyze_types.size() - 1;
 
         std::string types_header = "Types: " + std::to_string(conf_pwr)
                                  + " Power, " + std::to_string(ref_pwr)
-                                 + " Suspect, " + std::to_string(gnd)
+                                 + " Suspect, " + std::to_string(mgmt)
+                                 + " Pwr-mgmt, " + std::to_string(gnd)
                                  + " Gnd";
 
         // Tab bar — horizontal headers, active one inverted.
@@ -281,8 +256,14 @@ Component Tui::BuildAnalyzeScreen() {
                  "Name suggests Power AND structure agrees: fan-out ≥ 4 pins, "
                  "or a voltage pattern in the name (e.g. 3V3, 5V, 12V)."),
             term("Suspect Power",
-                 "Name suggests Power but the structural check failed — "
+                 "Name suggests Power, no control token explains it, but the "
-                 "fan-out too low and no voltage in the name."),
+                 "structural check failed — fan-out too low and no voltage "
+                 "in the name."),
+            term("Power mgmt",
+                 "Name holds a rail token AND a control token (SENSE, EN, PG, "
+                 "FB, …): a power-management signal — measurement or control "
+                 "of a rail — not the rail itself. Confidently Other, never "
+                 "suspect."),
             term("Hard floor",
                  "Fan-out below 3 pins forces Other regardless of the name. "
                  "A real rail physically cannot live on 1-2 pads."),

src/frontends/tui/screen_confirm.cpp

@@ -1,4 +1,4 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/event.hpp>

src/frontends/tui/screen_connect.cpp

@@ -1,11 +1,10 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/connect.hpp"
+#include "core/app/connect.hpp"
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
-#include "system/transform.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>
@@ -67,37 +66,24 @@ Component Tui::BuildConnectScreen() {
             Part *p1 = m1->get(connect_p1_list[connect_p1_idx]);
             Part *p2 = m2->get(connect_p2_list[connect_p2_idx]);
 
-            auto &reg = TransformRegistry::get();
+            // Same wiring op as the `connect` command — see app::connect_parts.
-            Transform *t = reg.lookup(p1->connector_type, p2->connector_type);
+            app::ConnectResult cr = app::connect_parts(sys.get(), m1, p1, m2, p2);
-            bool both_empty = p1->connector_type.empty() && p2->connector_type.empty();
+            if (cr.refused) {
-            if (t == reg.identity()) {
+                Print("connect refused: " + cr.error);
-                if (!both_empty) {
+            } else {
-                    Print("connect refused: no transform for types '"
+                if (!cr.identity_info.empty()) {
-                          + (p1->connector_type.empty() ? "(none)" : p1->connector_type)
+                    Print("connect: " + cr.identity_info);
-                          + "' ↔ '"
+                    if (cr.nc_added > 0)
-                          + (p2->connector_type.empty() ? "(none)" : p2->connector_type)
+                        Print("connect: added " + std::to_string(cr.nc_added)
-                          + "'. Set matching types via 'set-connector-type' first.");
+                              + " NC pin(s) so both sides match");
-                    screen_idx = 0;
-                    return;
-                }
-                std::string err = CheckIdentityCompatible(p1, p2);
-                if (!err.empty()) {
-                    Print("connect refused: " + err);
-                    screen_idx = 0;
-                    return;
                 }
+                if (cr.ok)
+                    Print("connected: " + cr.connection_name
+                          + "  via " + cr.transform_name
+                          + " (" + std::to_string(cr.wires) + " wires)");
+                else
+                    Print(std::string("connect failed: ") + cr.error);
             }
-            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());
         }

src/frontends/tui/screen_dashboard.cpp

@@ -1,22 +1,19 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/analysis.hpp"
+#include "core/app/verify.hpp"
-#include "system/bsdl_check.hpp"
+#include "core/domain/analysis.hpp"
-#include "system/connect.hpp"
+#include "core/domain/connect.hpp"
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/nets.hpp"
+#include "core/domain/parts.hpp"
-#include "system/parts.hpp"
+#include "core/domain/signals.hpp"
-#include "system/pins.hpp"
+#include "core/domain/system.hpp"
-#include "system/signals.hpp"
-#include "system/system.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/dom/elements.hpp>
 
 #include <algorithm>
 #include <map>
-#include <unordered_set>
 #include <vector>
 
 using namespace ftxui;
@@ -44,6 +41,8 @@ Component Tui::BuildDashboardScreen() {
 
       Element early_help = RenderHelpPanel("dashboard", {
           {"c",      "console"},
+          {"o",      "open/run a script"},
+          {"r",      "restore a snapshot"},
           {"a",      "analyze"},
           {"h",      "help screen"},
           {"q",      "quit"},
@@ -56,8 +55,8 @@ Component Tui::BuildDashboardScreen() {
               separator(),
               hbox({
                   vbox({
-                      text("  no system loaded — run 'new' or 'restore <file>'") | dim,
+                      text("  no system loaded") | dim,
-                      text("  (press 'c' for the console, or Ctrl-P for the palette)") | dim,
+                      text("  (press 'o' open a script · 'r' restore a snapshot · 'c' console · Ctrl-P palette)") | dim,
                       filler(),
                   }) | flex,
                   separator(),
@@ -75,58 +74,23 @@ Component Tui::BuildDashboardScreen() {
       }
       int n_conn = (int)sys->connections()->size();
 
-      // ---- verify-style health (recomputed; cheap on realistic sizes) ----
+      // ---- verify-style health (shared core op; cheap on realistic sizes) ----
-      int n_role_mismatches = 0, n_typed_pins = 0;
+      app::VerifyReport vr = app::verify(sys.get());
-      for (auto &mkv : *sys->modules())
+      int n_role_mismatches = (int)vr.role_mismatches.size();
-          for (auto &pkv : *mkv.second) {
+      int n_typed_pins      = vr.typed_pins;
-              Part *prt = pkv.second;
+      int n_inconsistent    = (int)vr.net_inconsistencies.size();
-              if (prt->connector_type.empty()) continue;
+      int n_bridged         = vr.bridged_nets;
-              for (auto &nkv : *prt) {
+      int orph_imported     = vr.orphan_imported;
-                  Pin *pin = nkv.second;
+      int orph_dropped      = vr.orphan_dropped;
-                  ++n_typed_pins;
-                  SignalType expected = pin->expected_signal_type();
-                  if (expected == SignalType::Other) continue;
-                  Signal *s = pin->signal();
-                  SignalType actual = s ? s->type : SignalType::Other;
-                  if (actual != expected) ++n_role_mismatches;
-              }
-          }
 
-      auto nets = compute_all_nets(sys.get());
-      int n_bridged = 0, n_inconsistent = 0;
-      for (const auto &n : nets) {
-          if (n.members.size() < 2) continue;
-          ++n_bridged;
-          SignalType dom;
-          if (!net_type_consistent(n, dom)) ++n_inconsistent;
-      }
-
-      // ---- NC orphan summary (matches verify pass 3) ----
-      std::unordered_set<Pin *> bridged_pins;
-      for (auto &ckv : *sys->connections())
-          for (auto &wp : ckv.second->pin_map) {
-              if (wp.first)  bridged_pins.insert(wp.first);
-              if (wp.second) bridged_pins.insert(wp.second);
-          }
-      int orph_imported = 0, orph_dropped = 0;
       // Per-module list of dropped-singleton pins, for the detail rows below
       // the NC health line. The signal name is gone (the Signal object was
       // deleted by `drop_singleton_signals`), but the pin's full path is
       // enough to locate it in `explore`.
       std::map<std::string, std::vector<std::string>> dropped_by_module;
-      for (auto &mkv : *sys->modules())
+      for (const auto &o : vr.orphans)
-          for (auto &pkv : *mkv.second)
+          if (o.dropped)
-              for (auto &nkv : *pkv.second) {
+              dropped_by_module[o.module].push_back(o.part + "/" + o.pin);
-                  Pin *pin = nkv.second;
-                  if (pin->signal() || bridged_pins.count(pin)) continue;
-                  if (pin->nc_origin == NcOrigin::ImportedUnconnected) {
-                      ++orph_imported;
-                  } else if (pin->nc_origin == NcOrigin::DroppedSingleton) {
-                      ++orph_dropped;
-                      dropped_by_module[mkv.first].push_back(
-                          pkv.first + "/" + nkv.first);
-                  }
-              }
 
       auto health_line = [](bool ok, const std::string &s) {
           return hbox({
@@ -142,7 +106,7 @@ Component Tui::BuildDashboardScreen() {
           + " typed pin(s)"));
       health_rows.push_back(health_line(n_inconsistent == 0,
           "nets:    " + std::to_string(n_inconsistent) + " inconsistent over "
-          + std::to_string(n_bridged) + " bridged (" + std::to_string(nets.size())
+          + std::to_string(n_bridged) + " bridged (" + std::to_string(vr.total_nets)
           + " total)"));
       int orph_total = orph_imported + orph_dropped;
       health_rows.push_back(health_line(orph_total == 0,
@@ -170,12 +134,9 @@ Component Tui::BuildDashboardScreen() {
           }
       }
 
-      // Model-driven checks (BSDL pin specs, JTAG chain, source conflicts),
+      // Model-driven checks (BSDL pin specs, JTAG chain, source conflicts,
-      // reusing the nets computed above.
+      // completeness) — from the shared verify report.
-      int n_model = (int)(check_pin_specs(sys.get(), &nets).size()
+      int n_model = vr.model_total();
-                          + check_jtag_chain(sys.get(), &nets).size()
-                          + check_source_conflicts(sys.get()).size()
-                          + check_bsdl_completeness(sys.get()).size());
       health_rows.push_back(health_line(n_model == 0,
           "model:   " + std::to_string(n_model) + " BSDL/JTAG anomaly(ies)"));
 
@@ -311,6 +272,7 @@ Component Tui::BuildDashboardScreen() {
           {"x",      "export"},
           {"o",      "open/run a script"},
           {"s",      "save system"},
+          {"r",      "restore a snapshot"},
           {"PgUp",   "scroll up"},
           {"PgDn",   "scroll down"},
           {"Home",   "scroll top"},

src/frontends/tui/screen_error.cpp

@@ -1,4 +1,4 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/event.hpp>

src/frontends/tui/screen_explore.cpp

@@ -1,13 +1,13 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/connect.hpp"
+#include "core/domain/connect.hpp"
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/nets.hpp"
+#include "core/domain/nets.hpp"
-#include "system/parts.hpp"
+#include "core/domain/parts.hpp"
-#include "system/pins.hpp"
+#include "core/domain/pins.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>

src/frontends/tui/screen_filedialog.cpp

@@ -1,5 +1,5 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>
@@ -54,11 +54,13 @@ void Tui::OpenFileDialog(std::string title,
                          std::string persist_key,
                          std::string default_filename,
                          std::vector<FilenameFilter> filters,
-                         std::function<void(const std::string &)> on_confirm) {
+                         std::function<void(const std::string &)> on_confirm,
+                         bool confirm_overwrite) {
     file_dialog.title       = std::move(title);
     file_dialog.persist_key = std::move(persist_key);
     file_dialog.on_confirm  = std::move(on_confirm);
     file_dialog.filters     = std::move(filters);
+    file_dialog.confirm_overwrite = confirm_overwrite;
     file_dialog.filter_labels.clear();
     for (const auto &f : file_dialog.filters)
         file_dialog.filter_labels.push_back(f.label);
@@ -122,7 +124,7 @@ void Tui::ConfirmFileDialog() {
     // Overwrite guard: if the file already exists, ask before letting
     // the action proceed. Esc / No cancels; Yes runs the action.
     std::error_code ec;
-    if (fs::exists(full, ec) && !ec) {
+    if (file_dialog.confirm_overwrite && fs::exists(full, ec) && !ec) {
         ShowConfirm("File '" + full.string() + "' already exists.\n"
                     "Overwrite?",
                     invoke);

src/frontends/tui/screen_help.cpp

@@ -1,5 +1,5 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>

src/frontends/tui/screen_main.cpp

@@ -1,5 +1,5 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>
@@ -89,18 +89,8 @@ Component Tui::BuildMainScreen(ScreenInteractive &screen) {
             }) | flex,
         }) | border;
 
-        if (loading) {
+        // The "Computing…" overlay is rendered globally in Run(), so it shows
-            int total = (int)loading_lines.size();
+        // on whatever screen is active while a script loads.
-            std::string progress = std::to_string(loading_executed) + " / "
-                                 + std::to_string(total) + " lines";
-            auto modal = vbox({
-                text(" Computing… ") | bold | center,
-                separator(),
-                text(loading_filename) | center,
-                text(progress) | center,
-            }) | borderDouble | size(WIDTH, GREATER_THAN, 40);
-            return dbox({base, modal | center});
-        }
         return base;
     });
 }

src/frontends/tui/screen_palette.cpp

@@ -1,9 +1,9 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>

src/frontends/tui/screen_settype.cpp

@@ -1,13 +1,12 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/modules.hpp"
+#include "core/app/edit.hpp"
-#include "system/parts.hpp"
+#include "core/domain/modules.hpp"
-#include "system/pin_model.hpp"
+#include "core/domain/parts.hpp"
-#include "system/pin_role.hpp"
+#include "core/domain/pin_role.hpp"
-#include "system/pins.hpp"
+#include "core/domain/pins.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
-#include "system/transform_vpx.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>
@@ -63,14 +62,11 @@ Component Tui::BuildSettypeScreen() {
         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);
+            app::SetConnectorTypeResult r = app::set_connector_type(prt, settype_type);
-            if (!err.empty()) {
+            if (!r.ok) {
-                settype_status = "refused: " + err;
+                settype_status = "refused: " + r.error;
                 return;
             }
-            prt->connector_type = settype_type;
-            ConnectorModel model(settype_type);
-            apply_model(prt, model);
             std::string msg = mod->name + "/" + prt->name + " = "
                             + (settype_type.empty() ? "(none)" : settype_type);
             settype_status = "applied: " + msg;

src/frontends/tui/screen_sigtype_modal.cpp

@@ -1,8 +1,8 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
 
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/component_options.hpp>

src/frontends/tui/shell.cpp

@@ -1,9 +1,9 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
-#include "system/modules.hpp"
+#include "core/domain/modules.hpp"
-#include "system/signals.hpp"
+#include "core/domain/signals.hpp"
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
 
 #include <cctype>
 #include <chrono>
@@ -281,23 +281,34 @@ void Tui::Source(const std::string &filename) {
         if (const char *home = std::getenv("HOME"))
             expanded = std::string(home) + expanded.substr(1);
     }
+    if (source_stack.size() >= 32) {   // same depth guard as the core engine
+        Print("source: nesting too deep, skipping " + filename);
+        return;
+    }
     std::ifstream f(expanded);
     if (!f) { Print("source failed: cannot open " + filename); return; }
 
     // Slurp the whole file so we can drive line-by-line processing from the
     // event loop (one line per posted task). This lets the screen redraw
     // between lines and surface the "Computing…" modal.
-    loading_lines.clear();
+    SourceFrame fr;
+    fr.filename = filename;
     std::string line;
-    while (std::getline(f, line)) loading_lines.push_back(line);
+    while (std::getline(f, line)) fr.lines.push_back(std::move(line));
+
+    // Nested source (a sourced line is itself `source …`): just stack the
+    // frame — the driver already running (ticker thread or headless drain)
+    // picks it up on the next ProcessNextSourceLine, and the caller's frame
+    // resumes when it finishes.
+    bool nested = !source_stack.empty();
+    source_stack.push_back(std::move(fr));
+    if (nested) return;
 
-    loading_filename = filename;
-    loading_idx = 0;
-    loading_executed = 0;
-    loading_lineno = 0;
     loading_prev_in_source = in_source;
+    source_origin_screen = screen_idx;  // a sourced line that leaves this screen aborts
     in_source = true;
     loading = true;
+    computing_open = true;  // raise the global "Computing…" progress modal
 
     if (!screen_ptr) {
         // Headless fallback (e.g. tests): drain synchronously.
@@ -330,9 +341,18 @@ void Tui::Source(const std::string &filename) {
 
 void Tui::ProcessNextSourceLine() {
     if (!loading.load()) return;
-    while (loading_idx < loading_lines.size()) {
+    while (!source_stack.empty()) {
-        const std::string &raw = loading_lines[loading_idx++];
+        if (source_stack.back().idx >= source_stack.back().lines.size()) {
-        ++loading_lineno;
+            // Frame done: summarise it and resume the caller's frame.
+            const SourceFrame &done = source_stack.back();
+            Print("source: " + done.filename
+                  + "  (" + std::to_string(done.executed) + " line(s))");
+            source_stack.pop_back();
+            continue;
+        }
+        SourceFrame &fr = source_stack.back();
+        const std::string raw = fr.lines[fr.idx++];
+        ++fr.lineno;
         size_t start = raw.find_first_not_of(" \t");
         if (start == std::string::npos) continue;
         if (raw[start] == '#') continue;
@@ -341,28 +361,28 @@ void Tui::ProcessNextSourceLine() {
             trimmed.pop_back();
         if (trimmed.empty()) continue;
 
+        ++fr.executed;
+        int lineno = fr.lineno;   // copies: Submit can push a nested frame,
+                                  // which may reallocate and invalidate `fr`.
         input = trimmed;
         cursor_pos = (int)input.size();
         Submit();
-        ++loading_executed;
 
-        if (screen_idx != 0) {
+        if (screen_idx != source_origin_screen) {
-            Print("source: line " + std::to_string(loading_lineno)
+            Print("source: line " + std::to_string(lineno)
                   + " is interactive (would open a screen) — aborting.");
-            screen_idx = 0;
+            screen_idx = source_origin_screen;
-            loading.store(false);
+            source_stack.clear();   // an abort cancels the whole chain
-            tick_in_flight.store(false);
+            break;
-            in_source = loading_prev_in_source;
-            return;
         }
         // One effective line per tick — ack so the ticker can pace the next.
         tick_in_flight.store(false);
         return;
     }
 
-    Print("source: " + loading_filename
+    // Stack drained (or aborted): close up.
-          + "  (" + std::to_string(loading_executed) + " line(s))");
     loading.store(false);
+    computing_open = false;
     tick_in_flight.store(false);
     in_source = loading_prev_in_source;
 }

src/frontends/tui/tui.cpp

@@ -1,17 +1,17 @@
-#include "tui/tui.hpp"
+#include "frontends/tui/tui.hpp"
 
-#include "system/system.hpp"
+#include "core/domain/system.hpp"
 
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/event.hpp>
 #include <ftxui/component/screen_interactive.hpp>
+#include <ftxui/dom/elements.hpp>
 
 using namespace ftxui;
 
 Tui::Tui()
     : cursor_pos(0), history_idx(-1), scroll_offset(0), quit(false), in_source(false),
       loading(false), tick_in_flight(false),
-      loading_idx(0), loading_executed(0), loading_lineno(0),
       loading_prev_in_source(false), screen_ptr(nullptr),
       screen_idx(4),  // boot to the dashboard; console (screen 0) is now a sub-screen
       connect_m1_idx(0), connect_m2_idx(0),
@@ -58,10 +58,36 @@ void Tui::Run() {
     auto with_error   = with_confirm
                       | Modal(BuildErrorModal(), &error_open);
 
-    auto root = CatchEvent(with_error, [this](Event e) {
+    // Global "Computing…" progress modal while a script loads — a proper Modal
+    // (like the palette / file dialog), so it shows on any screen, e.g. when a
+    // script is opened from the dashboard. The Renderer re-reads the live
+    // progress every frame.
+    auto computing_modal = Renderer([this] {
+        std::string fname, progress;
+        if (!source_stack.empty()) {   // top frame = the file currently running
+            const SourceFrame &fr = source_stack.back();
+            fname = fr.filename;
+            progress = std::to_string(fr.executed) + " / "
+                     + std::to_string((int)fr.lines.size()) + " lines";
+        }
+        return vbox({
+                   text(" Computing… ") | bold | center,
+                   separator(),
+                   text(fname) | center,
+                   text(progress) | center,
+               }) | borderDouble | size(WIDTH, GREATER_THAN, 40);
+    });
+    auto with_loading = with_error | Modal(computing_modal, &computing_open);
+
+    auto root = CatchEvent(with_loading, [this](Event e) {
+        // Source ticks drive the line-by-line loader; handle them on ANY screen
+        // (and before the modal guard) so `source` keeps running while the
+        // Computing modal is up.
+        if (e == Event::Special("\x02tick")) { ProcessNextSourceLine(); return true; }
+
         // Modals own their events while open. Error modal sits on top.
         if (error_open || confirm_open || palette_open
-            || sigtype_dialog_open || file_dialog.open) return false;
+            || sigtype_dialog_open || file_dialog.open || computing_open) return false;
 
         // Ctrl-P opens the palette from any screen.
         if (e == Event::CtrlP) { OpenPalette(); return true; }
@@ -106,7 +132,8 @@ void Tui::Run() {
                                "dashboard.source", "", {},
                                [this](const std::string &path) {
                                    Dispatch("source " + path);
-                               });
+                               },
+                               /*confirm_overwrite=*/false);  // opening, not saving
                 return true;
             }
             if (e == Event::Character("s")) {   // save the system snapshot
@@ -118,6 +145,15 @@ void Tui::Run() {
                                    });
                 return true;
             }
+            if (e == Event::Character("r")) {   // restore a saved system
+                OpenFileDialog("Restore system — load a snapshot",
+                               "dashboard.restore", "", {},
+                               [this](const std::string &path) {
+                                   Dispatch("restore " + path);
+                               },
+                               /*confirm_overwrite=*/false);  // opening, not saving
+                return true;
+            }
             return false;
 
         case 3:  // explore
@@ -152,7 +188,6 @@ void Tui::Run() {
             return false;
 
         default:  // 0: main (console / log view)
-            if (e == Event::Special("\x02tick")) { ProcessNextSourceLine(); return true; }
             if (e == Event::Escape) {
                 if (!pending.empty()) { CancelPending(); return true; }
                 screen_idx = 4; return true;

src/frontends/tui/tui.hpp

@@ -13,9 +13,11 @@
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/screen_interactive.hpp>
 
+#include "frontends/frontend.hpp"
+
 class System;
 
-class Tui {
+class Tui : public Frontend {
     enum class Completion { None, Path, Command };
 
     struct Prompt {
@@ -97,12 +99,19 @@ class Tui {
     // ---- Source-file loading (event-driven, one line per tick) ----
     std::atomic<bool> loading;         ///< true while a script is being processed; read by tick thread.
     std::atomic<bool> tick_in_flight;  ///< main thread acks each tick by clearing this; ticker waits.
-    std::string loading_filename;
+    // One script being processed. Nested `source` pushes a frame so the
-    std::vector<std::string> loading_lines;
+    // caller resumes where it left off — the stack IS the call chain.
-    size_t loading_idx;
+    struct SourceFrame {
-    int loading_executed;
+        std::string filename;
-    int loading_lineno;
+        std::vector<std::string> lines;
+        size_t idx = 0;    ///< next line to process
+        int executed = 0;  ///< effective (non-blank, non-comment) lines run
+        int lineno = 0;    ///< current 1-based line, for messages
+    };
+    std::vector<SourceFrame> source_stack;
     bool loading_prev_in_source;
+    int source_origin_screen = 0;  ///< screen a `source` started from; a sourced line that navigates away (opens an interactive screen) aborts it.
+    bool computing_open = false;   ///< drives the global "Computing…" progress modal while a script loads.
     ftxui::ScreenInteractive *screen_ptr;  ///< set in Run() so Source() can post events.
 
     // ---- Dashboard scroll state (0 = top; grows as the user scrolls down) ----
@@ -149,6 +158,7 @@ private:
         std::vector<std::string> filter_labels;  ///< parallel to `filters`
         int filter_idx = 0;
         std::function<void(const std::string &)> on_confirm;
+        bool confirm_overwrite = true;  ///< false in "open" mode — skip the overwrite prompt.
     };
     FileDialogState file_dialog;
 
@@ -195,16 +205,16 @@ private:
 public:
     Tui();
     ~Tui();
-    void Run();
+    void Run() override;
-    void DumpCommandsMd(std::ostream &out) const;
+    void DumpCommandsMd(std::ostream &out) const override;
     // Write the accumulated console output to `out`. Used by batch mode to
     // surface a script's output without starting the TUI.
-    void DumpOutput(std::ostream &out) const;
+    void DumpOutput(std::ostream &out) const override;
 
     // Boot-time hook: dispatch a single command exactly as if the user
     // typed it (e.g. `restore foo.essim` or `source bring-up.essim`).
     // Call before `Run()` to seed the system before the event loop starts.
-    void BootDispatch(const std::string &raw);
+    void BootDispatch(const std::string &raw) override;
 
 private:
     // Lifecycle (commands.cpp)
@@ -272,11 +282,14 @@ private:
     // dir + filename are stored (one tiny file per key under the user
     // data directory). `on_confirm` runs when the user presses Enter on
     // the action button — it receives the absolute path the user picked.
+    // `confirm_overwrite = false` puts the dialog in "open" mode: it skips the
+    // "file exists — overwrite?" prompt (you *want* an existing file to open).
     void OpenFileDialog(std::string title,
                         std::string persist_key,
                         std::string default_filename,
                         std::vector<FilenameFilter> filters,
-                        std::function<void(const std::string &)> on_confirm);
+                        std::function<void(const std::string &)> on_confirm,
+                        bool confirm_overwrite = true);
     void ConfirmFileDialog();
     ftxui::Component BuildSignalTypeModal();
     ftxui::Component BuildPaletteModal();

src/frontends/tui/tui_helpers.cpp

@@ -1,4 +1,4 @@
-#include "tui/tui_helpers.hpp"
+#include "frontends/tui/tui_helpers.hpp"
 
 #include <ftxui/dom/elements.hpp>
 

src/frontends/wx/CMakeLists.txt

@@ -0,0 +1,16 @@
+# wxWidgets GUI frontend. Builds the `essim` executable against essim_core.
+#
+# Self-contained like every frontend: it pulls its own GUI toolkit (here a
+# system wxWidgets via find_package), then defers the target wiring to the
+# shared essim_add_frontend() helper. Select it with -DESSIM_FRONTEND=wx.
+#
+# Needs the wxWidgets development package, e.g. on Debian/Ubuntu:
+#   sudo apt install libwxgtk3.2-dev
+
+find_package(wxWidgets REQUIRED COMPONENTS core base)
+
+# UsewxWidgets sets the include dirs and compile definitions for targets defined
+# afterwards in this directory — so it must come before essim_add_frontend().
+include(${wxWidgets_USE_FILE})
+
+essim_add_frontend(wx LIBS ${wxWidgets_LIBRARIES})

src/frontends/wx/main.cpp

@@ -0,0 +1,10 @@
+#include "frontends/frontend_main.hpp"
+#include "frontends/wx/wx_frontend.hpp"
+
+// The wx frontend's entry point: construct the concrete Frontend (WxFrontend)
+// and hand off to the shared, frontend-agnostic launcher. Identical in shape to
+// the tui frontend's main — only the Frontend type differs.
+int main(int argc, char **argv) {
+    WxFrontend fe;
+    return frontend_main(argc, argv, fe);
+}

src/frontends/wx/wx_frame.cpp

@@ -0,0 +1,680 @@
+#include "frontends/wx/wx_frame.hpp"
+
+#include "frontends/wx/wx_frontend.hpp"
+
+#include "core/app/connect.hpp"
+#include "core/app/edit.hpp"
+#include "core/app/export.hpp"
+#include "core/app/load.hpp"
+#include "core/app/script.hpp"
+#include "core/app/verify.hpp"
+#include "core/domain/analysis.hpp"
+#include "core/domain/connect.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/parts.hpp"
+#include "core/domain/persist.hpp"
+#include "core/domain/pins.hpp"
+#include "core/domain/signal_type.hpp"
+#include "core/domain/signals.hpp"
+#include "core/domain/system.hpp"
+
+#include <wx/wx.h>
+#include <wx/choicdlg.h>
+#include <wx/filedlg.h>
+#include <wx/filename.h>
+#include <wx/textdlg.h>
+#include <wx/treectrl.h>
+
+#include <algorithm>
+#include <cctype>
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace {
+enum {
+    ID_LOAD = wxID_HIGHEST + 1,
+    ID_RESTORE,
+    ID_RUN_SCRIPT,
+    ID_SAVE,
+    ID_EXPORT,
+    ID_SET_CONNECTOR_TYPE,
+    ID_ATTACH_BSDL,
+    ID_SET_SIGNAL_TYPE,
+    ID_CONNECT,
+    ID_DUPLICATE,
+    ID_VERIFY,
+    ID_QUIT,
+    ID_ABOUT,
+};
+
+// Core (UTF-8 std::string) -> wxString, and back for paths.
+inline wxString wx(const std::string &s) { return wxString::FromUTF8(s.c_str()); }
+
+// Natural order ("2" < "10", "A2" < "A10") so pin/part lists read intuitively.
+bool natural_less(const std::string &a, const std::string &b) {
+    size_t i = 0, j = 0;
+    while (i < a.size() && j < b.size()) {
+        unsigned char ca = a[i], cb = b[j];
+        if (std::isdigit(ca) && std::isdigit(cb)) {
+            size_t i0 = i, j0 = j;
+            while (i < a.size() && std::isdigit((unsigned char)a[i])) ++i;
+            while (j < b.size() && std::isdigit((unsigned char)b[j])) ++j;
+            std::string na = a.substr(i0, i - i0), nb = b.substr(j0, j - j0);
+            na.erase(0, na.find_first_not_of('0'));  // ignore leading zeros
+            nb.erase(0, nb.find_first_not_of('0'));
+            if (na.size() != nb.size()) return na.size() < nb.size();
+            if (na != nb) return na < nb;
+        } else {
+            if (ca != cb) return ca < cb;
+            ++i; ++j;
+        }
+    }
+    return a.size() < b.size();
+}
+
+// " (Power)" / " (Gnd)" — only for the meaningful types; "" for Other.
+wxString type_suffix(SignalType t) {
+    return t == SignalType::Other ? wxString()
+                                  : " (" + wxString(signal_type_name(t)) + ")";
+}
+
+// What a tree node stands for, attached to the item so a selection or a
+// right-click can drive the edit operations on the right domain object.
+struct NodeData : public wxTreeItemData {
+    enum class Kind { Other, Module, Part, Pin, Signal };
+    Kind kind;
+    Module *module = nullptr;
+    Part   *part   = nullptr;
+    Signal *signal = nullptr;
+    explicit NodeData(Kind k) : kind(k) {}
+};
+
+NodeData *node_of(wxTreeCtrl *tree, const wxTreeItemId &id) {
+    return id.IsOk() ? static_cast<NodeData *>(tree->GetItemData(id)) : nullptr;
+}
+
+// The part of the current selection — a Part node, or the Pin's owning part.
+Part *selected_part(wxTreeCtrl *tree) {
+    NodeData *d = node_of(tree, tree->GetSelection());
+    if (d && (d->kind == NodeData::Kind::Part || d->kind == NodeData::Kind::Pin))
+        return d->part;
+    return nullptr;
+}
+
+// The signal of the current selection (and, via `mod`, its module).
+Signal *selected_signal(wxTreeCtrl *tree, Module **mod) {
+    NodeData *d = node_of(tree, tree->GetSelection());
+    if (d && d->kind == NodeData::Kind::Signal) {
+        if (mod) *mod = d->module;
+        return d->signal;
+    }
+    return nullptr;
+}
+}  // namespace
+
+EssimFrame::EssimFrame(WxFrontend &fe)
+    : wxFrame(nullptr, wxID_ANY, "essim — system digital twin",
+              wxDefaultPosition, wxSize(960, 640)),
+      fe_(fe) {
+    auto *file = new wxMenu;
+    file->Append(ID_LOAD,    "&Load module…\tCtrl-L");
+    file->Append(ID_RESTORE, "&Restore snapshot…\tCtrl-R");
+    file->Append(ID_RUN_SCRIPT, "&Run script…\tCtrl-U");
+    file->Append(ID_SAVE,    "&Save snapshot…\tCtrl-S");
+    file->AppendSeparator();
+    file->Append(ID_EXPORT,  "&Export connections…\tCtrl-E");
+    file->AppendSeparator();
+    file->Append(ID_QUIT, "&Quit\tCtrl-Q");
+
+    auto *edit = new wxMenu;
+    edit->Append(ID_SET_CONNECTOR_TYPE, "Set &connector type…\tCtrl-T");
+    edit->Append(ID_ATTACH_BSDL, "Attach &BSDL…\tCtrl-B");
+    edit->Append(ID_SET_SIGNAL_TYPE, "Set &signal type…\tCtrl-G");
+    edit->AppendSeparator();
+    edit->Append(ID_CONNECT, "C&onnect parts…\tCtrl-O");
+    edit->AppendSeparator();
+    edit->Append(ID_DUPLICATE, "&Duplicate module…\tCtrl-D");
+
+    auto *sysm = new wxMenu;
+    sysm->Append(ID_VERIFY, "&Verify\tCtrl-K");
+
+    auto *help = new wxMenu;
+    help->Append(ID_ABOUT, "&About");
+
+    auto *bar = new wxMenuBar;
+    bar->Append(file, "&File");
+    bar->Append(edit, "&Edit");
+    bar->Append(sysm, "&System");
+    bar->Append(help, "&Help");
+    SetMenuBar(bar);
+
+    CreateStatusBar();
+    SetStatusText("essim — wx frontend");
+
+    auto *panel = new wxPanel(this);
+    tree_     = new wxTreeCtrl(panel, wxID_ANY);
+    overview_ = new wxTextCtrl(panel, wxID_ANY, "", wxDefaultPosition,
+                               wxDefaultSize, wxTE_MULTILINE | wxTE_READONLY);
+    log_      = new wxTextCtrl(panel, wxID_ANY, "", wxDefaultPosition,
+                               wxDefaultSize, wxTE_MULTILINE | wxTE_READONLY);
+
+    wxFont mono(wxFontInfo().Family(wxFONTFAMILY_TELETYPE));
+    overview_->SetFont(mono);
+    log_->SetFont(mono);
+
+    // Cap each control's minimum so its *content* can't inflate the layout's
+    // minimum size: on GTK a full tree/text reports a large natural size, which
+    // would otherwise eat all the vertical space and freeze the log at its
+    // minimum (it stopped resizing once a script populated the tree). With a
+    // modest min, the sizer proportions govern and content scrolls inside.
+    tree_->SetMinSize(wxSize(260, 120));
+    overview_->SetMinSize(wxSize(260, 120));
+    log_->SetMinSize(wxSize(420, 90));
+
+    auto *top = new wxBoxSizer(wxHORIZONTAL);
+    top->Add(tree_,     1, wxEXPAND | wxALL, 4);
+    top->Add(overview_, 1, wxEXPAND | wxALL, 4);
+
+    auto *root = new wxBoxSizer(wxVERTICAL);
+    root->Add(top, 2, wxEXPAND);
+    root->Add(new wxStaticText(panel, wxID_ANY, " Log"), 0, wxLEFT | wxTOP, 6);
+    root->Add(log_, 1, wxEXPAND | wxALL, 4);
+    panel->SetSizer(root);
+
+    // Drive the panel from a frame sizer so it fills the client area and
+    // re-lays-out on every resize (the implicit single-child fill is not
+    // reliable here — without this the log keeps its size when the window grows).
+    auto *frame_sizer = new wxBoxSizer(wxVERTICAL);
+    frame_sizer->Add(panel, 1, wxEXPAND);
+    SetSizer(frame_sizer);
+
+    Bind(wxEVT_MENU, &EssimFrame::OnLoad,    this, ID_LOAD);
+    Bind(wxEVT_MENU, &EssimFrame::OnRestore, this, ID_RESTORE);
+    Bind(wxEVT_MENU, &EssimFrame::OnSave,    this, ID_SAVE);
+    Bind(wxEVT_MENU, &EssimFrame::OnRunScript, this, ID_RUN_SCRIPT);
+    Bind(wxEVT_MENU, &EssimFrame::OnExport,  this, ID_EXPORT);
+    Bind(wxEVT_MENU, &EssimFrame::OnSetConnectorType, this, ID_SET_CONNECTOR_TYPE);
+    Bind(wxEVT_MENU, &EssimFrame::OnAttachBsdl, this, ID_ATTACH_BSDL);
+    Bind(wxEVT_MENU, &EssimFrame::OnSetSignalType, this, ID_SET_SIGNAL_TYPE);
+    Bind(wxEVT_MENU, &EssimFrame::OnConnect, this, ID_CONNECT);
+    Bind(wxEVT_MENU, &EssimFrame::OnDuplicateModule, this, ID_DUPLICATE);
+    Bind(wxEVT_MENU, &EssimFrame::OnVerify,  this, ID_VERIFY);
+    Bind(wxEVT_MENU, &EssimFrame::OnQuit,    this, ID_QUIT);
+    Bind(wxEVT_MENU, &EssimFrame::OnAbout,   this, ID_ABOUT);
+
+    tree_->Bind(wxEVT_TREE_ITEM_MENU, &EssimFrame::OnTreeContextMenu, this);
+
+    RebuildModelView();
+}
+
+void EssimFrame::Log(const wxString &line) {
+    log_->AppendText(line + "\n");
+}
+
+void EssimFrame::RebuildModelView() {
+    System *sys = fe_.system();
+
+    tree_->DeleteAllItems();
+    wxTreeItemId root = tree_->AddRoot("System");
+
+    int n_mods = 0, n_parts = 0, n_sigs = 0;
+    if (sys) {
+        std::vector<std::string> mods;
+        for (auto &mkv : *sys->modules()) mods.push_back(mkv.first);
+        std::sort(mods.begin(), mods.end());
+        n_mods = (int)mods.size();
+        for (const auto &mname : mods) {
+            Module *m = sys->modules()->get(mname);
+            int mp = (int)m->size();
+            int ms = (int)m->signals->size();
+            n_parts += mp;
+            n_sigs  += ms;
+            wxTreeItemId mid = tree_->AppendItem(
+                root, wx(mname) + wxString::Format(" — %d part(s), %d signal(s)",
+                                                   mp, ms));
+            {
+                auto *d = new NodeData(NodeData::Kind::Module);
+                d->module = m;
+                tree_->SetItemData(mid, d);
+            }
+
+            // Parts → pins (each pin shows the signal it is wired to, or NC).
+            std::vector<std::string> parts;
+            for (auto &pkv : *m) parts.push_back(pkv.first);
+            std::sort(parts.begin(), parts.end(), natural_less);
+            for (const auto &pname : parts) {
+                Part *p = m->get(pname);
+                wxString label = wx(pname)
+                    + wxString::Format(" (%d pin(s))", (int)p->size());
+                if (!p->connector_type.empty())
+                    label += " [" + wx(p->connector_type) + "]";
+                wxTreeItemId pid = tree_->AppendItem(mid, label);
+                {
+                    auto *d = new NodeData(NodeData::Kind::Part);
+                    d->module = m;
+                    d->part = p;
+                    tree_->SetItemData(pid, d);
+                }
+
+                std::vector<std::string> pins;
+                for (auto &nkv : *p) pins.push_back(nkv.first);
+                std::sort(pins.begin(), pins.end(), natural_less);
+                for (const auto &pinname : pins) {
+                    Pin *pin = p->get(pinname);
+                    wxString pl = wx(pinname) + " -> ";
+                    if (Signal *s = pin->signal()) {
+                        pl += wx(s->name) + type_suffix(s->type);
+                    } else {
+                        pl += "(NC";
+                        if (pin->nc_origin == NcOrigin::ImportedUnconnected)
+                            pl += ", imported";
+                        else if (pin->nc_origin == NcOrigin::DroppedSingleton)
+                            pl += ", dropped";
+                        pl += ")";
+                    }
+                    wxTreeItemId nid = tree_->AppendItem(pid, pl);
+                    auto *d = new NodeData(NodeData::Kind::Pin);
+                    d->module = m;
+                    d->part = p;
+                    tree_->SetItemData(nid, d);
+                }
+            }
+
+            // Signals branch (the per-module net view: type + fan-out).
+            if (ms > 0) {
+                wxTreeItemId sid =
+                    tree_->AppendItem(mid, wxString::Format("Signals (%d)", ms));
+                std::vector<std::string> sigs;
+                for (auto &skv : *m->signals) sigs.push_back(skv.first);
+                std::sort(sigs.begin(), sigs.end(), natural_less);
+                for (const auto &sname : sigs) {
+                    Signal *s = m->signals->get(sname);
+                    wxTreeItemId nid = tree_->AppendItem(
+                        sid, wx(sname) + type_suffix(s->type)
+                                 + wxString::Format(" — %d pin(s)", (int)s->size()));
+                    auto *d = new NodeData(NodeData::Kind::Signal);
+                    d->module = m;
+                    d->signal = s;
+                    tree_->SetItemData(nid, d);
+                }
+            }
+
+            tree_->Expand(mid);   // parts + Signals visible; pins/nets on demand
+        }
+    }
+    tree_->Expand(root);
+
+    int n_conn = sys ? (int)sys->connections()->size() : 0;
+
+    wxString ov;
+    ov << "Modules:      " << n_mods << "\n"
+       << "Parts:        " << n_parts << "\n"
+       << "Signals:      " << n_sigs << "\n"
+       << "Connections:  " << n_conn << "\n";
+    if (sys) {
+        app::VerifyReport r = app::verify(sys);
+        ov << "\nHealth (verify):\n"
+           << wxString::Format("  pin-role mismatches: %d / %d typed pin(s)\n",
+                               (int)r.role_mismatches.size(), r.typed_pins)
+           << wxString::Format("  net inconsistencies: %d / %d bridged net(s)\n",
+                               (int)r.net_inconsistencies.size(), r.bridged_nets)
+           << wxString::Format("  orphan pins:         %d (%d imported, %d dropped)\n",
+                               r.orphan_total(), r.orphan_imported, r.orphan_dropped)
+           << wxString::Format("  model anomalies:     %d\n", r.model_total());
+    }
+    overview_->SetValue(ov);
+}
+
+void EssimFrame::OnLoad(wxCommandEvent &) {
+    wxFileDialog dlg(this, "Load a netlist / pinout file", "", "",
+                     "All files (*.*)|*.*", wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK) return;
+    const wxString path = dlg.GetPath();
+
+    wxString modname = wxGetTextFromUser("Module name:", "Load module",
+                                         wxFileName(path).GetName(), this);
+    if (modname.empty()) return;
+
+    static const wxString kinds[] = {"mentor", "altium", "ods"};
+    int ki = wxGetSingleChoiceIndex("Import type:", "Load module",
+                                    WXSIZEOF(kinds), kinds, this);
+    if (ki < 0) return;
+
+    ImportType type;
+    app::import_type_from_name(kinds[ki].ToStdString(), type);  // choice is valid
+    app::LoadResult r = app::load_module(
+        fe_.system(), modname.utf8_string(), path.utf8_string(), type);
+    if (!r.ok) {
+        Log("load failed: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Load failed", wxOK | wxICON_ERROR, this);
+        return;
+    }
+    Log(wxString::Format(
+        "loaded '%s' from %s — %d part(s), %d signal(s)"
+        " (dropped %d; types: %d power / %d gnd / %d suspect / %d pwr-mgmt)",
+        modname, path, r.parts, r.signals, r.dropped, r.power, r.gnd,
+        r.kept_other, r.mgmt));
+    RebuildModelView();
+}
+
+void EssimFrame::OnRestore(wxCommandEvent &) {
+    wxFileDialog dlg(this, "Restore a system snapshot", "", "",
+                     "essim snapshots (*.essim)|*.essim|All files (*.*)|*.*",
+                     wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK) return;
+    std::string err;
+    System *fresh = restore_system(dlg.GetPath().utf8_string(), err);
+    if (!fresh) {
+        Log("restore failed: " + wx(err));
+        wxMessageBox(wx(err), "Restore failed", wxOK | wxICON_ERROR, this);
+        return;
+    }
+    fe_.set_system(fresh);
+    Log("restored from " + dlg.GetPath());
+    RebuildModelView();
+}
+
+void EssimFrame::OnRunScript(wxCommandEvent &) {
+    wxFileDialog dlg(this, "Run an essim script", "", "",
+                     "essim scripts (*.essim)|*.essim|All files (*.*)|*.*",
+                     wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK) return;
+
+    fe_.ensure_system();
+    std::ostringstream out;
+    app::ScriptResult r =
+        app::run_script(fe_.system_ptr(), dlg.GetPath().utf8_string(), out);
+
+    if (!r.ok) {
+        Log("run script: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Run script", wxOK | wxICON_ERROR, this);
+        return;
+    }
+
+    // Echo each line of the script's output into the log pane.
+    std::istringstream lines(out.str());
+    std::string line;
+    while (std::getline(lines, line)) Log(wx(line));
+    Log(wxString::Format("source: %s  (%d line(s), %d error(s))",
+                         dlg.GetPath(), r.lines, r.errors));
+    RebuildModelView();
+}
+
+void EssimFrame::OnSave(wxCommandEvent &) {
+    wxFileDialog dlg(this, "Save system snapshot", "", "system.essim",
+                     "essim snapshots (*.essim)|*.essim|All files (*.*)|*.*",
+                     wxFD_SAVE | wxFD_OVERWRITE_PROMPT);
+    if (dlg.ShowModal() != wxID_OK) return;
+    std::string err;
+    if (save_system(fe_.system(), dlg.GetPath().utf8_string(), err)) {
+        Log("saved to " + dlg.GetPath());
+    } else {
+        Log("save failed: " + wx(err));
+        wxMessageBox(wx(err), "Save failed", wxOK | wxICON_ERROR, this);
+    }
+}
+
+void EssimFrame::OnExport(wxCommandEvent &) {
+    wxFileDialog dlg(this, "Export connections", "", "connections.csv",
+                     "CSV (*.csv)|*.csv|OpenDocument sheet (*.ods)|*.ods",
+                     wxFD_SAVE | wxFD_OVERWRITE_PROMPT);
+    if (dlg.ShowModal() != wxID_OK) return;
+    const std::string path = dlg.GetPath().utf8_string();
+
+    app::ExportFormat fmt;
+    if (!app::export_format_from_path(path, fmt)) {
+        wxMessageBox("Unknown export extension (use .csv or .ods).",
+                     "Export failed", wxOK | wxICON_ERROR, this);
+        return;
+    }
+    app::ExportResult r = app::export_connections(fe_.system(), path, fmt);
+    if (r.ok) {
+        Log(wxString::Format("exported %d row(s) to %s", r.rows, dlg.GetPath()));
+    } else {
+        Log("export failed: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Export failed", wxOK | wxICON_ERROR, this);
+    }
+}
+
+Module *EssimFrame::PickModule(const wxString &caption) {
+    System *sys = fe_.system();
+    if (!sys || sys->modules()->size() == 0) {
+        wxMessageBox("No modules loaded.", caption,
+                     wxOK | wxICON_INFORMATION, this);
+        return nullptr;
+    }
+    std::vector<std::string> mods;
+    for (auto &mkv : *sys->modules()) mods.push_back(mkv.first);
+    std::sort(mods.begin(), mods.end());
+    wxArrayString choices;
+    for (const auto &m : mods) choices.Add(wx(m));
+    int mi = wxGetSingleChoiceIndex("Module:", caption, choices, this);
+    if (mi < 0) return nullptr;
+    return sys->modules()->get(mods[mi]);
+}
+
+Part *EssimFrame::PickPart(const wxString &caption) {
+    Module *m = PickModule(caption);
+    if (!m) return nullptr;
+    if (m->size() == 0) {
+        wxMessageBox("That module has no parts.", caption,
+                     wxOK | wxICON_INFORMATION, this);
+        return nullptr;
+    }
+    std::vector<std::string> parts;
+    for (auto &pkv : *m) parts.push_back(pkv.first);
+    std::sort(parts.begin(), parts.end());
+    wxArrayString choices;
+    for (const auto &p : parts) choices.Add(wx(p));
+    int pi = wxGetSingleChoiceIndex("Part:", caption, choices, this);
+    if (pi < 0) return nullptr;
+    return m->get(parts[pi]);
+}
+
+
+void EssimFrame::OnSetConnectorType(wxCommandEvent &) {
+    Part *p = selected_part(tree_);
+    if (!p) p = PickPart();
+    if (!p) return;
+
+    wxTextEntryDialog dlg(this, "Connector type (empty = none):",
+                          "Set connector type", wx(p->connector_type));
+    if (dlg.ShowModal() != wxID_OK) return;
+    const std::string kind = dlg.GetValue().utf8_string();
+
+    app::SetConnectorTypeResult r = app::set_connector_type(p, kind);
+    if (!r.ok) {
+        Log("set-connector-type refused: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Refused", wxOK | wxICON_ERROR, this);
+        return;
+    }
+
+    wxString who = (p->prnt ? wx(p->prnt->name) + "/" : wxString()) + wx(p->name);
+    Log(who + ": connector_type = " + (kind.empty() ? wxString("(none)") : wx(kind)));
+    if (r.materialised > 0)
+        Log(wxString::Format("  added %d NC pin(s) from the connector layout",
+                             r.materialised));
+    RebuildModelView();
+}
+
+void EssimFrame::OnAttachBsdl(wxCommandEvent &) {
+    Part *p = selected_part(tree_);
+    if (!p) p = PickPart();
+    if (!p) return;
+
+    wxFileDialog dlg(this, "Attach a BSDL model", "", "",
+                     "BSDL files (*.bsd)|*.bsd|All files (*.*)|*.*",
+                     wxFD_OPEN | wxFD_FILE_MUST_EXIST);
+    if (dlg.ShowModal() != wxID_OK) return;
+
+    app::AttachBsdlResult r = app::attach_bsdl(p, dlg.GetPath().utf8_string());
+    if (!r.ok) {
+        Log("attach-bsdl: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Attach BSDL failed", wxOK | wxICON_ERROR, this);
+        return;
+    }
+
+    wxString who = (p->prnt ? wx(p->prnt->name) + "/" : wxString()) + wx(p->name);
+    wxString tail = r.unbound ? wxString::Format(", %d unbound", r.unbound)
+                              : wxString();
+    Log(wxString::Format("%s: attached BSDL '%s' — %d/%d ports bound%s",
+                         who, wx(r.entity), r.bound, r.ports_total, tail));
+    RebuildModelView();
+}
+
+void EssimFrame::OnConnect(wxCommandEvent &) {
+    Part *p1 = selected_part(tree_);
+    if (!p1) p1 = PickPart("Connect — first part");
+    if (!p1) return;
+    Part *p2 = PickPart("Connect — second part");
+    if (!p2) return;
+    if (p1 == p2) {
+        wxMessageBox("Pick two different parts.", "Connect",
+                     wxOK | wxICON_INFORMATION, this);
+        return;
+    }
+
+    // m1/m2 are the parts' parent modules — connect_parts needs them for the
+    // Connection name and ownership.
+    app::ConnectResult r =
+        app::connect_parts(fe_.system(), p1->prnt, p1, p2->prnt, p2);
+
+    if (r.refused) {
+        Log("connect refused: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Connect refused", wxOK | wxICON_ERROR, this);
+        return;
+    }
+    if (!r.identity_info.empty()) {
+        Log("connect: " + wx(r.identity_info));
+        if (r.nc_added > 0)
+            Log(wxString::Format("connect: added %d NC pin(s) so both sides match",
+                                 r.nc_added));
+    }
+    if (r.ok) {
+        Log(wxString::Format("connected: %s  via %s (%d wires)",
+                             wx(r.connection_name), wx(r.transform_name), r.wires));
+    } else {
+        Log("connect failed: " + wx(r.error));
+        wxMessageBox(wx(r.error), "Connect failed", wxOK | wxICON_ERROR, this);
+    }
+    RebuildModelView();
+}
+
+void EssimFrame::OnSetSignalType(wxCommandEvent &) {
+    Module *m = nullptr;
+    Signal *sig = selected_signal(tree_, &m);
+    if (!sig) {
+        m = PickModule("Set signal type");
+        if (!m) return;
+        if (m->signals->size() == 0) {
+            wxMessageBox("That module has no signals.", "Set signal type",
+                         wxOK | wxICON_INFORMATION, this);
+            return;
+        }
+        std::vector<std::string> sigs;
+        for (auto &skv : *m->signals) sigs.push_back(skv.first);
+        std::sort(sigs.begin(), sigs.end(), natural_less);
+        wxArrayString schoices;
+        for (const auto &s : sigs) schoices.Add(wx(s));
+        int si = wxGetSingleChoiceIndex("Signal:", "Set signal type", schoices, this);
+        if (si < 0) return;
+        sig = m->signals->get(sigs[si]);
+    }
+
+    static const wxString types[] = {"power", "gnd", "other"};
+    int ti = wxGetSingleChoiceIndex("Type:", "Set signal type",
+                                    WXSIZEOF(types), types, this);
+    if (ti < 0) return;
+
+    app::SetSignalTypeResult r = app::set_signal_type(sig, types[ti].ToStdString());
+    if (!r.ok) {
+        Log(wx(r.error));
+        wxMessageBox(wx(r.error), "Set signal type", wxOK | wxICON_ERROR, this);
+        return;
+    }
+    Log(wxString::Format("%s/%s: signal type = %s", wx(m->name), wx(sig->name),
+                         wx(signal_type_name(r.type))));
+    RebuildModelView();
+}
+
+void EssimFrame::OnDuplicateModule(wxCommandEvent &) {
+    Module *m = PickModule("Duplicate module");
+    if (!m) return;
+    const std::string src = m->name;   // m may move in the table after the add
+
+    wxTextEntryDialog dlg(this, "New module name:", "Duplicate module",
+                          wx(src) + "_copy");
+    if (dlg.ShowModal() != wxID_OK) return;
+    const std::string dst = dlg.GetValue().utf8_string();
+    if (dst.empty()) return;
+
+    app::DuplicateResult r = app::duplicate_module(fe_.system(), src, dst);
+    if (!r.ok) {
+        Log(wx(r.error));
+        wxMessageBox(wx(r.error), "Duplicate module", wxOK | wxICON_ERROR, this);
+        return;
+    }
+    Log(wx("duplicate: '" + src + "' → '" + dst + "'  ("
+           + std::to_string(r.parts) + " part(s), "
+           + std::to_string(r.signals) + " signal(s))"));
+    RebuildModelView();
+}
+
+void EssimFrame::OnVerify(wxCommandEvent &) {
+    app::VerifyReport r = app::verify(fe_.system());
+
+    Log("verify:");
+    Log(wxString::Format("  %d pin-role mismatch(es) over %d typed pin(s)",
+                         (int)r.role_mismatches.size(), r.typed_pins));
+    for (const auto &m : r.role_mismatches)
+        Log(wx("    " + m.module + "/" + m.part + "/" + m.pin + ": expected "
+               + signal_type_name(m.expected) + ", got "
+               + signal_type_name(m.actual)));
+
+    Log(wxString::Format("  %d inconsistent net(s) over %d bridged net(s)",
+                         (int)r.net_inconsistencies.size(), r.bridged_nets));
+    Log(wxString::Format("  %d orphan pin(s) (%d imported, %d dropped)",
+                         r.orphan_total(), r.orphan_imported, r.orphan_dropped));
+
+    auto log_anoms = [this](const std::vector<Anomaly> &v, const char *tail) {
+        Log(wxString::Format("  %d %s", (int)v.size(), tail));
+        for (const auto &a : v)
+            Log(wx(std::string("    [") + anomaly_kind_name(a.kind) + "] "
+                   + a.message));
+    };
+    log_anoms(r.pin_anomalies,          "model-driven pin anomaly(ies)");
+    log_anoms(r.jtag_anomalies,         "JTAG chain anomaly(ies)");
+    log_anoms(r.conflict_anomalies,     "source-conflict(s)");
+    log_anoms(r.completeness_anomalies, "BSDL completeness issue(s)");
+    log_anoms(r.diff_anomalies,         "diff-pair crossing anomaly(ies)");
+
+    RebuildModelView();
+}
+
+void EssimFrame::OnQuit(wxCommandEvent &) { Close(true); }
+
+void EssimFrame::OnAbout(wxCommandEvent &) {
+    wxMessageBox("essim — system digital twin\n\n"
+                 "wxWidgets frontend over essim_core.",
+                 "About essim", wxOK | wxICON_INFORMATION, this);
+}
+
+void EssimFrame::OnTreeContextMenu(wxTreeEvent &ev) {
+    wxTreeItemId id = ev.GetItem();
+    if (id.IsOk()) tree_->SelectItem(id);   // the edit handlers read the selection
+    NodeData *d = node_of(tree_, id);
+    if (!d) return;
+
+    // Reuse the menu IDs so these route to the same handlers, which now act on
+    // the (just-selected) tree item.
+    wxMenu menu;
+    if (d->kind == NodeData::Kind::Part || d->kind == NodeData::Kind::Pin) {
+        menu.Append(ID_SET_CONNECTOR_TYPE, "Set connector type…");
+        menu.Append(ID_ATTACH_BSDL, "Attach BSDL…");
+        menu.Append(ID_CONNECT, "Connect to…");
+    } else if (d->kind == NodeData::Kind::Signal) {
+        menu.Append(ID_SET_SIGNAL_TYPE, "Set signal type…");
+    }
+    if (menu.GetMenuItemCount() > 0) PopupMenu(&menu);
+}

src/frontends/wx/wx_frame.hpp

@@ -0,0 +1,56 @@
+#ifndef _WX_FRAME_HPP_
+#define _WX_FRAME_HPP_
+
+#include <wx/frame.h>
+
+class WxFrontend;
+class wxTreeCtrl;
+class wxTextCtrl;
+class wxCommandEvent;
+class wxTreeEvent;
+
+// The essim main window. Holds no domain state of its own: it reads and mutates
+// the System owned by the WxFrontend, calling the core/app operations directly
+// (load, verify, export, save, restore) and rendering their results into a
+// model tree, an overview panel and a log.
+class EssimFrame : public wxFrame {
+public:
+    explicit EssimFrame(WxFrontend &fe);
+
+private:
+    // Menu handlers — each is a thin wrapper over a core/app operation.
+    void OnLoad(wxCommandEvent &);
+    void OnRestore(wxCommandEvent &);
+    void OnRunScript(wxCommandEvent &);
+    void OnSave(wxCommandEvent &);
+    void OnExport(wxCommandEvent &);
+    void OnSetConnectorType(wxCommandEvent &);
+    void OnAttachBsdl(wxCommandEvent &);
+    void OnConnect(wxCommandEvent &);
+    void OnSetSignalType(wxCommandEvent &);
+    void OnDuplicateModule(wxCommandEvent &);
+    void OnVerify(wxCommandEvent &);
+    void OnQuit(wxCommandEvent &);
+    void OnAbout(wxCommandEvent &);
+
+    // Right-click on a tree item → context menu of the edit actions valid for
+    // that node (part / signal). The actions reuse the menu IDs, so they run
+    // the same handlers — which read the tree selection.
+    void OnTreeContextMenu(wxTreeEvent &);
+
+    // Modal pickers over the current System. `caption` titles the dialogs (e.g.
+    // to distinguish two picks). Each returns nullptr if there is nothing to
+    // pick or the user cancels.
+    class Module *PickModule(const wxString &caption);
+    class Part   *PickPart(const wxString &caption = "Select part");
+
+    void RebuildModelView();          ///< refresh tree + overview from the System
+    void Log(const wxString &line);   ///< append a line to the log pane
+
+    WxFrontend &fe_;
+    wxTreeCtrl *tree_ = nullptr;
+    wxTextCtrl *overview_ = nullptr;
+    wxTextCtrl *log_ = nullptr;
+};
+
+#endif  // _WX_FRAME_HPP_

src/frontends/wx/wx_frontend.cpp

@@ -0,0 +1,113 @@
+#include "frontends/wx/wx_frontend.hpp"
+
+#include "frontends/wx/wx_frame.hpp"
+
+#include "core/app/script.hpp"
+#include "core/domain/connect.hpp"
+#include "core/domain/modules.hpp"
+#include "core/domain/persist.hpp"
+#include "core/domain/system.hpp"
+
+#include <wx/app.h>
+#include <wx/init.h>
+
+#include <clocale>
+#include <ostream>
+#include <sstream>
+#include <string>
+
+namespace {
+
+// Minimal wxApp: on init it shows the main window bound to the frontend.
+class EssimApp : public wxApp {
+public:
+    explicit EssimApp(WxFrontend &fe) : fe_(fe) {}
+    bool OnInit() override {
+        // Decode the UTF-8 in our narrow string literals (em dash, ellipsis…)
+        // correctly: wxString converts const char* via the C locale, which is
+        // "C" (ASCII) at startup. Set only LC_CTYPE — leave LC_NUMERIC as "C"
+        // so number formatting stays dot-decimal.
+        std::setlocale(LC_CTYPE, "");
+        (new EssimFrame(fe_))->Show(true);
+        return true;
+    }
+
+private:
+    WxFrontend &fe_;
+};
+
+}  // namespace
+
+WxFrontend::WxFrontend() = default;
+WxFrontend::~WxFrontend() = default;
+
+void WxFrontend::ensure_system() {
+    if (!sys_) sys_.reset(new System());
+}
+
+void WxFrontend::set_system(System *fresh) {
+    sys_.reset(fresh);
+}
+
+void WxFrontend::BootDispatch(const std::string &raw) {
+    // The GUI has no command shell. Honour the boot commands that make sense
+    // headlessly: `restore <file>` seeds a snapshot; anything else is noted.
+    std::istringstream iss(raw);
+    std::string cmd;
+    iss >> cmd;
+    std::string arg;
+    std::getline(iss, arg);
+    if (std::size_t b = arg.find_first_not_of(" \t"); b != std::string::npos)
+        arg = arg.substr(b);
+    else
+        arg.clear();
+
+    if (cmd == "restore") {
+        std::string err;
+        System *fresh = restore_system(arg, err);
+        if (!fresh) {
+            output_ += "restore failed: " + err + "\n";
+            return;
+        }
+        sys_.reset(fresh);
+        output_ += "restored from " + arg + "  ("
+                 + std::to_string(sys_->modules()->size()) + " module(s), "
+                 + std::to_string(sys_->connections()->size())
+                 + " connection(s))\n";
+    } else if (cmd == "source") {
+        ensure_system();
+        std::ostringstream out;
+        app::ScriptResult r = app::run_script(sys_, arg, out);
+        output_ += out.str();
+        if (!r.ok)
+            output_ += "source: " + r.error + "\n";
+        else
+            output_ += "source: " + arg + "  (" + std::to_string(r.lines)
+                     + " line(s), " + std::to_string(r.errors) + " error(s))\n";
+    } else if (!cmd.empty()) {
+        output_ += "boot: ignored '" + raw + "'.\n";
+    }
+}
+
+void WxFrontend::DumpCommandsMd(std::ostream &out) const {
+    out << "# essim — wx frontend\n\n"
+        << "The wx frontend is menu-driven and exposes no textual command "
+        << "registry. Generate the command reference from the tui frontend "
+        << "(`-DESSIM_FRONTEND=tui`, then `essim --commands-md`).\n";
+}
+
+void WxFrontend::DumpOutput(std::ostream &out) const {
+    out << output_;
+}
+
+void WxFrontend::Run() {
+    ensure_system();
+
+    wxApp::SetInstance(new EssimApp(*this));
+    int argc = 0;
+    wxEntryStart(argc, static_cast<char **>(nullptr));
+    if (wxTheApp->CallOnInit())
+        wxTheApp->OnRun();
+    wxTheApp->OnExit();
+    wxEntryCleanup();
+}

src/frontends/wx/wx_frontend.hpp

@@ -0,0 +1,38 @@
+#ifndef _WX_FRONTEND_HPP_
+#define _WX_FRONTEND_HPP_
+
+#include "frontends/frontend.hpp"
+
+#include <memory>
+#include <string>
+
+class System;
+
+// wxWidgets GUI frontend. Implements the shared Frontend interface so the same
+// launcher (frontend_main) drives it: it owns the System and a console buffer,
+// handles boot commands headlessly (for --restore/--batch), and Run() opens the
+// wxWidgets window. The window itself (EssimFrame) drives essim_core / app::*
+// operations directly — no command shell, no TUI reuse.
+class WxFrontend : public Frontend {
+public:
+    WxFrontend();
+    ~WxFrontend() override;
+
+    // --- Frontend interface ---
+    void BootDispatch(const std::string &raw) override;
+    void DumpCommandsMd(std::ostream &out) const override;
+    void DumpOutput(std::ostream &out) const override;
+    void Run() override;
+
+    // --- used by the window (EssimFrame) ---
+    System *system() const { return sys_.get(); }
+    std::unique_ptr<System> &system_ptr() { return sys_; }  ///< for run_script (new/restore replace it)
+    void set_system(System *fresh);   ///< take ownership (used by Restore)
+    void ensure_system();             ///< create an empty System if none yet
+
+private:
+    std::unique_ptr<System> sys_;
+    std::string output_;   ///< console buffer surfaced by DumpOutput (batch)
+};
+
+#endif  // _WX_FRONTEND_HPP_

src/system/signal_type.hpp

@@ -1,13 +0,0 @@
-#ifndef _SIGNAL_TYPE_HPP_
-#define _SIGNAL_TYPE_HPP_
-
-#include <string>
-
-enum class SignalType { Power, GndShield, Other };
-
-const char *signal_type_name(SignalType t);
-bool        signal_type_from_name(const std::string &s, SignalType &out);
-SignalType  infer_signal_type(const std::string &signal_name);
-SignalType  next_signal_type(SignalType t);  // Power → GndShield → Other → Power
-
-#endif // _SIGNAL_TYPE_HPP_

src/system/signals.cpp

@@ -1,116 +0,0 @@
-
-#include "signals.hpp"
-#include "parts.hpp"
-
-#include <algorithm>
-#include <cctype>
-#include <vector>
-
-const char *signal_type_name(SignalType t) {
-    switch (t) {
-    case SignalType::Power:     return "power";
-    case SignalType::GndShield: return "gnd";
-    case SignalType::Other:     return "other";
-    }
-    return "other";
-}
-
-SignalType next_signal_type(SignalType t) {
-    switch (t) {
-    case SignalType::Power:     return SignalType::GndShield;
-    case SignalType::GndShield: return SignalType::Other;
-    case SignalType::Other:     return SignalType::Power;
-    }
-    return SignalType::Other;
-}
-
-bool signal_type_from_name(const std::string &s, SignalType &out) {
-    std::string l = s;
-    std::transform(l.begin(), l.end(), l.begin(),
-                   [](unsigned char c) { return std::tolower(c); });
-    if (l == "power" || l == "p")          { out = SignalType::Power;     return true; }
-    if (l == "gnd" || l == "g" || l == "shield" || l == "ground")
-                                           { out = SignalType::GndShield; return true; }
-    if (l == "other" || l == "o" || l == "signal")
-                                           { out = SignalType::Other;     return true; }
-    return false;
-}
-
-// Heuristic. Names like GND, GNDA, SHIELD, CHASSIS → GndShield.
-// Names containing PWR/POWER/VCC/VDD/VEE/VSS, or matching V±N or +N.NV
-// patterns, or starting with VS_/VS3_ → Power. Else Other.
-SignalType infer_signal_type(const std::string &name) {
-    if (name.empty()) return SignalType::Other;
-    std::string u = name;
-    std::transform(u.begin(), u.end(), u.begin(),
-                   [](unsigned char c) { return std::toupper(c); });
-
-    auto contains = [&](const char *needle) {
-        return u.find(needle) != std::string::npos;
-    };
-    auto starts_with = [&](const char *needle) {
-        return u.rfind(needle, 0) == 0;
-    };
-
-    if (u == "GND" || u == "GROUND") return SignalType::GndShield;
-    if (starts_with("GND_")
-        || (starts_with("GND") && u.size() >= 4
-            && std::isalpha((unsigned char)u[3]))) {
-        return SignalType::GndShield;
-    }
-    if (contains("SHIELD") || contains("CHASSIS") || contains("EARTH"))
-        return SignalType::GndShield;
-
-    if (contains("PWR") || contains("POWER")
-        || contains("VCC") || contains("VDD") || contains("VEE") || contains("VSS")
-        || starts_with("VS_") || starts_with("VS1_") || starts_with("VS2_")
-        || starts_with("VS3_") || starts_with("VS4_")
-        || starts_with("VBAT") || starts_with("VBUS")
-        || starts_with("+") || starts_with("-")) {
-        return SignalType::Power;
-    }
-    return SignalType::Other;
-}
-
-Signal::Signal(std::string name)
-    : SystemElementContainer<Pin>(name), prnt(nullptr),
-      type(SignalType::Other) {};
-
-void Signal::add(Pin *pin)
-{
-    string pname = pin->prnt->name + "." + pin->name;
-    SystemElementContainer<Pin>::add(pname, pin);
-}
-
-Signals::Signals(void): SystemElementContainer<Signal>("signals") {}
-
-Signals::Signals(std::vector<Signal *> signals): SystemElementContainer<Signal>("signals", signals) {}
-
-Signals::~Signals() {
-    for (const auto& [key, value] : content) {
-        delete value;
-    }
-}
-
-int drop_singleton_signals(Signals *signals) {
-    if (!signals) return 0;
-    std::vector<Signal *> doomed;
-    for (auto &kv : *signals)
-        if (kv.second->size() == 1) doomed.push_back(kv.second);
-    for (Signal *s : doomed) {
-        // Detach the lone pin so it surfaces as `(NC)` in views.
-        for (auto &pkv : *s) {
-            pkv.second->connect(nullptr);
-            pkv.second->nc_origin = NcOrigin::DroppedSingleton;
-        }
-        signals->remove(s->name);
-        delete s;
-    }
-    return (int)doomed.size();
-}
-
-void Signals::add(Signal *signal)
-{
-    SystemElementContainer<Signal>::add(signal);
-    signal->prnt = this;
-}

src/system/system.cpp

@@ -1,49 +0,0 @@
-
-#include "system.hpp"
-
-#include "connect.hpp"
-#include "modules.hpp"
-#include "imports/import_altium.hpp"
-#include "imports/import_mentor.hpp"
-#include "imports/import_ods.hpp"
-
-System::System() : mods(nullptr), conns(nullptr)
-{
-    mods = new Modules();
-    conns = new Connections();
-}
-
-System::~System()
-{
-    delete mods;
-    delete conns;
-}
-
-void System::Load(std::string module_name, std::string file_name, ImportType type)
-{
-    ImportBase *imp;
-    Module *mod = nullptr;
-    Parts *prts = nullptr;
-
-    // Creation or retrieval of the module.
-    mod = mods->merge(module_name);
-
-    // Parsing of the file based on the import type.
-    if (type == ImportType::IMPORT_MENTOR)
-    {
-        imp = new ImportMentor(file_name);
-    } else if (type == ImportType::IMPORT_ALTIUM)
-    {
-        imp = new ImportAltium(file_name);
-    } else if (type == ImportType::IMPORT_ODS)
-    {
-        imp = new ImportOds(file_name);
-    }
-    else
-    {
-        throw std::runtime_error("Unknown import type");
-    }
-    imp->parse(mod->signals);
-    prts = imp->parts();
-    mod->add(prts);
-}

src/tui/commands_export.cpp

@@ -1,235 +0,0 @@
-#include "tui/tui.hpp"
-#include "tui/tui_helpers.hpp"
-
-#include "imports/ods_writer.hpp"
-#include "system/connect.hpp"
-#include "system/modules.hpp"
-#include "system/parts.hpp"
-#include "system/pins.hpp"
-#include "system/signal_type.hpp"
-#include "system/signals.hpp"
-#include "system/system.hpp"
-
-#include <fstream>
-#include <string>
-#include <vector>
-
-namespace {
-
-// Minimal CSV quoter — wraps in `"…"` and doubles internal quotes when
-// the field contains a comma, quote, or newline. Local to this file.
-std::string csv_quote(const std::string &s) {
-    bool needs = s.find_first_of(",\"\n") != std::string::npos;
-    if (!needs) return s;
-    std::string out = "\"";
-    for (char c : s) { if (c == '"') out += '"'; out += c; }
-    out += '"';
-    return out;
-}
-
-// Flatten one pin into the 6 string slots the export row uses.
-void pin_side(Pin *p, std::string &mod, std::string &part,
-              std::string &pin, std::string &sig,
-              std::string &type, std::string &suspect) {
-    if (!p) { mod = part = pin = sig = type = suspect = ""; return; }
-    mod  = (p->prnt && p->prnt->prnt) ? p->prnt->prnt->name : "";
-    part = p->prnt ? p->prnt->name : "";
-    pin  = p->name;
-    Signal *s = p->signal();
-    if (!s) {
-        sig = ""; type = "(NC)"; suspect = "";
-    } else {
-        sig = s->name;
-        type = signal_type_name(s->type);
-        suspect = (infer_signal_type(s->name) == SignalType::Power
-                   && s->type == SignalType::Other) ? "yes" : "no";
-    }
-}
-
-}  // namespace
-
-void Tui::RegisterExportCommands() {
-    commands["export"] = {
-        {{"kind [connections]", Completion::None},
-         {"filename (.csv)",    Completion::Path}},
-        [this](const std::vector<std::string> &args) {
-            if (!sys) { Print("no system: run 'new' first."); return; }
-            if (args.empty()) {
-                // Bare → reuse the generic file dialog. Filters give a
-                // one-keystroke CSV/ODS toggle; picking either rewrites
-                // the filename's extension, and the action below
-                // dispatches on that extension.
-                OpenFileDialog(
-                    "Export — connections",
-                    "export.connections",
-                    "connections.csv",
-                    {{"CSV", ".csv"}, {"ODS", ".ods"}},
-                    [this](const std::string &path) {
-                        Dispatch("export connections " + path);
-                    });
-                return;
-            }
-            if (args.size() != 2) {
-                Print("usage: export <kind> <file>   (or no args for the dialog)");
-                return;
-            }
-            const std::string &kind = args[0];
-            const std::string &path = args[1];
-
-            if (kind == "connections") {
-                // Accepted extensions: `.csv` (flat file) and `.ods`
-                // (one sheet per connection). Anything else is an error.
-                std::string ext;
-                {
-                    size_t dot = path.rfind('.');
-                    if (dot != std::string::npos) ext = ToLower(path.substr(dot));
-                }
-                bool ods = (ext == ".ods");
-                bool csv = (ext == ".csv");
-                if (!ods && !csv) {
-                    ShowError("export: unknown extension '"
-                              + (ext.empty() ? std::string("(none)") : ext)
-                              + "'\nAccepted: .csv, .ods");
-                    return;
-                }
-
-                if (ods) {
-                    OdsWriter w;
-                    int total = 0;
-                    for (auto &ckv : *sys->connections()) {
-                        Connection *c = ckv.second;
-                        // Sheet names: Excel rejects /\?*:[] characters,
-                        // ODS forbids < > & in raw cell/table names.
-                        // Sanitise to underscores; clip to 31 chars
-                        // (Excel's hard limit).
-                        std::string sname = c->name;
-                        for (char &ch : sname)
-                            if (ch == '/' || ch == '\\' || ch == '?' || ch == '*'
-                                || ch == ':' || ch == '[' || ch == ']'
-                                || ch == '<' || ch == '>' || ch == '&') ch = '_';
-                        if (sname.size() > 31) sname = sname.substr(0, 31);
-                        OdsSheet *s = w.add_sheet(sname);
-
-                        // Pull the constants for this connection once.
-                        // `transform`, the left module/part, and the
-                        // right module/part don't vary across the wires
-                        // of a single connection — putting them in
-                        // every row was repetitive.
-                        std::string lmod, lprt;
-                        std::string rmod, rprt;
-                        if (c->m1) lmod = c->m1->name;
-                        if (c->p1) lprt = c->p1->name;
-                        if (c->m2) rmod = c->m2->name;
-                        if (c->p2) rprt = c->p2->name;
-
-                        // Meta header above the table: 5 rows of label /
-                        // value, then a blank, then the column headers
-                        // on row 6 (index 5).
-                        auto meta = [&](int r, const std::string &k,
-                                         const std::string &v) {
-                            s->set(r, 0, k);
-                            s->set(r, 1, v);
-                        };
-                        meta(0, "Connection", c->name);
-                        meta(1, "Transform",  c->transform_name);
-                        meta(2, "Left",       lmod + " / " + lprt);
-                        meta(3, "Right",      rmod + " / " + rprt);
-                        // Row 4 left blank by design.
-
-                        const int HDR = 5;
-                        s->set_header_row(HDR);
-                        const char *hdr[] = {
-                            "left_pin", "left_signal", "left_type", "left_suspect",
-                            "right_pin", "right_signal", "right_type", "right_suspect",
-                            "type_mismatch"};
-                        for (int i = 0; i < 9; ++i) s->set(HDR, i, hdr[i]);
-
-                        int row = HDR + 1;
-                        for (auto &wp : c->pin_map) {
-                            std::string lm, lp, ln, ls, lt, lsus;
-                            std::string rm, rp, rn, rs, rt, rsus;
-                            pin_side(wp.first,  lm, lp, ln, ls, lt, lsus);
-                            pin_side(wp.second, rm, rp, rn, rs, rt, rsus);
-                            // `type_mismatch = yes` when both sides have a
-                            // real signal AND their types disagree (e.g.
-                            // Power ↔ Gnd, or Power ↔ Other).
-                            std::string tm = (lt != "(NC)" && rt != "(NC)" && lt != rt)
-                                            ? "yes" : "no";
-                            s->set(row, 0, ln); s->set(row, 1, ls);
-                            s->set(row, 2, lt); s->set(row, 3, lsus);
-                            s->set(row, 4, rn); s->set(row, 5, rs);
-                            s->set(row, 6, rt); s->set(row, 7, rsus);
-                            s->set(row, 8, tm);
-                            ++row; ++total;
-                        }
-                    }
-                    std::string err;
-                    if (!w.save(path, err)) {
-                        ShowError("export (.ods) failed:\n" + err);
-                        return;
-                    }
-                    Print("export connections (.ods): "
-                          + std::to_string(sys->connections()->size())
-                          + " sheet(s), " + std::to_string(total)
-                          + " wire(s) → " + path);
-                    return;
-                }
-
-                // Classic flat CSV: a single rectangular table — one
-                // header line, N data rows, every row carries the per-
-                // connection constants too. The 9 right-most column
-                // names match the ODS sheet headers exactly; the 5
-                // leading ones (connection, transform, left_module,
-                // left_part, right_module, right_part) correspond to
-                // the ODS meta block (Connection, Transform, Left,
-                // Right). Repeating the constants per row keeps the
-                // file parser-friendly (pandas / awk / spreadsheet).
-                std::ofstream f(path);
-                if (!f) {
-                    ShowError("export: cannot open '" + path + "' for writing");
-                    return;
-                }
-                f << "connection,transform,"
-                     "left_module,left_part,"
-                     "left_pin,left_signal,left_type,left_suspect,"
-                     "right_module,right_part,"
-                     "right_pin,right_signal,right_type,right_suspect,"
-                     "type_mismatch\n";
-
-                int rows = 0;
-                for (auto &ckv : *sys->connections()) {
-                    Connection *c = ckv.second;
-                    for (auto &wp : c->pin_map) {
-                        std::string lm, lp, ln, ls, lt, lsus;
-                        std::string rm, rp, rn, rs, rt, rsus;
-                        pin_side(wp.first,  lm, lp, ln, ls, lt, lsus);
-                        pin_side(wp.second, rm, rp, rn, rs, rt, rsus);
-                        std::string tm = "no";
-                        if (lt != "(NC)" && rt != "(NC)" && lt != rt) tm = "yes";
-                        f << csv_quote(c->name)           << ','
-                          << csv_quote(c->transform_name) << ','
-                          << csv_quote(lm) << ',' << csv_quote(lp) << ','
-                          << csv_quote(ln) << ',' << csv_quote(ls) << ','
-                          << csv_quote(lt) << ',' << csv_quote(lsus) << ','
-                          << csv_quote(rm) << ',' << csv_quote(rp) << ','
-                          << csv_quote(rn) << ',' << csv_quote(rs) << ','
-                          << csv_quote(rt) << ',' << csv_quote(rsus) << ','
-                          << tm << '\n';
-                        ++rows;
-                    }
-                }
-                Print("export connections (.csv): " + std::to_string(rows)
-                      + " wire(s) → " + path);
-                return;
-            }
-
-            ShowError("export: unknown kind '" + kind + "'\n"
-                      "Known kinds: connections");
-        },
-        /*prompt_for_missing=*/ false,
-        "export structured data to CSV / ODS (kinds: connections; "
-        "bare form opens the file-picker dialog)",
-        /*scriptable=*/ true,
-        /*interactive=*/ true,
-    };
-}