Require every track to name a track type and rework menu run flow

MODS.md

@@ -1289,7 +1289,7 @@ what it says and invents nothing:
     depth_map: Some("example/assets/track/ballast_disp.jpg"), // height map -> parallax relief
     occlusion_map: Some("example/assets/track/ballast_ao.jpg"),// ambient occlusion between the stones
     texture_scale: 2.2,          // metres one repeat of those four covers, along and across
-    color: (0.32, 0.30, 0.28),   // untextured fallback; the route editor tints sections its own way
+    color: (0.32, 0.30, 0.28),   // colour of a type that names no texture; the editor tints sections its own way
     roughness: 1.0,              // scales the rolling noise; jointed track > 1, slab track < 1
     reverb: 0.0,                 // how much the surroundings ring: 0 = open line, 1 = tunnel
     max_speed: 250.0,            // superstructure limit [km/h], caps the line's speed profile
@@ -1366,13 +1366,20 @@ linear; the loader is told so and does not gamma-decode them. A type that names
 textures is skinned in its `color`.
 
 A line assigns types per edge as steps over the arc length, so one edge changes its
-superstructure section by section; the reserved name `"default"` returns to the built-in
-default type:
+superstructure section by section:
 
 ```ron
 track_type: [(0.0, "example:hauptbahn"), (3000.0, "example:altbau")],
 ```
 
+**Every track has to name one.** There is no built-in type and no reserved
+`"default"` name: what a track is built of is part of the module, not of the
+engine, and a module that leaves it out does not compile — the compiler reports
+`MissingTrackType(<edge>)` and the route editor's rule check says the same thing
+before the run. A type from another mod is a dependency like any other; name that
+mod in `depends:`. This is deliberate: a silent fallback is how a line ends up on
+untextured grey ballast without anybody being told.
+
 `max_speed` merges into the speed profile every consumer already reads (AI, LZB, HUD,
 scoring); `roughness` reaches the sound table as the `Roughness` quantity (the default
 rolling entries carry a volume factor on it, see Sounds); `reverb` drives the reverb the
@@ -1381,8 +1388,9 @@ or a deep cutting sits around 0.3 … 0.6. Modelling the room on the track type
 on the terrain is the same trade `roughness` makes: a line says where its tunnels are by
 assigning the type, and nothing has to trace geometry at run time. The route editor edits the
 sections in the selection panel (a color chip per section, the map tints the track ribbon
-to match) and its rule check flags names no installed mod has, and LZB types on a line
-that places no line conductor.
+to match) and its rule check flags tracks that name no type at all, names no installed
+mod has, and LZB types on a line that places no line conductor. The lay tool arms itself
+with the first installed type, so track drawn in the editor carries one from the start.
 
 ### Electrification
 

STATUS.md

@@ -33,8 +33,10 @@ As of 2026-08-31 · `cargo test --workspace`: **1136 tests green** · clippy and
   **Track types** (superstructure classes, `track_types/*.ron` in a mod): texture, color,
   roughness, how much its surroundings ring (`reverb`, 0 = open line, 1 = tunnel),
   superstructure speed limit and an LZB flag — assigned per edge as a step
-  profile over `s`, so one edge changes its type section by section, with the reserved
-  name `"default"` returning to the built-in type. The mod runtime resolves the names
+  profile over `s`, so one edge changes its type section by section. **Every track has
+  to name one**: there is no built-in type and no reserved `"default"` name, and a
+  module that leaves it out does not compile (`CompileError::MissingTrackType`) —
+  a silent fallback is how a line ends up on untextured grey ballast unnoticed. The mod runtime resolves the names
   after compile (like signal types) and merges `max_speed` into the one speed profile AI,
   LZB, HUD and scoring already read; the app **builds the track the type describes**
   (`world_render::track`, rebuilt 2026-08-31 against the DB InfraGO dimensions and split

crates/app/src/audio.rs

@@ -476,10 +476,13 @@ pub fn update_audio(
                 SoundState::sample(vehicle, &cab, protection, audio.previous.get(&(t, v)), dt);
             // The sampler deliberately sees no track and no weather — both are filled in
             // here, where net and world state live.
+            // Track without a type is track nobody has laid a superstructure
+            // on — it cannot happen on a compiled line, and what rolls over it
+            // rolls as smoothly as welded main line.
             state.roughness = sim
                 .net
                 .track_type_at(vehicle.pos.edge, vehicle.pos.s)
-                .roughness;
+                .map_or(1.0, |ty| ty.roughness);
             // The rain quantity is how hard it falls, not whether it does: a
             // drizzle is not a downpour with the volume turned down.
             let weather = sim.weather.now;
@@ -530,10 +533,10 @@ pub fn update_audio(
         .trains
         .get(player.0)
         .and_then(|train| train.vehicles.first())
-        .map(|vehicle| {
+        .and_then(|vehicle| {
             sim.net
                 .track_type_at(vehicle.pos.edge, vehicle.pos.s)
-                .reverb
+                .map(|ty| ty.reverb)
         })
         .unwrap_or(0.0);
     audio

crates/app/src/main.rs

@@ -2049,7 +2049,7 @@ fn update_precipitation(
         .0
         .net
         .track_type_at(vehicle.pos.edge, vehicle.pos.s)
-        .reverb
+        .map_or(0.0, |ty| ty.reverb)
         .clamp(0.0, 1.0) as f32;
     // The wind the drops actually meet: the weather's own — swaying in strength
     // and direction with the gusts, because a curtain of rain never stands at one

crates/content/src/area_tests.rs

@@ -27,7 +27,7 @@ fn line() -> LineSource {
             grade: vec![],
             cant: vec![],
             speed: vec![],
-            track_type: vec![],
+            track_type: vec![(0.0, STARTER_TRACK_TYPE.into())],
             electrification: vec![],
             formation: true,
         }],
@@ -139,7 +139,7 @@ fn an_area_can_switch_the_wire_and_the_superstructure() {
     let inside = net.edges()[0].track_type.at(1500.0);
     let outside = net.edges()[0].track_type.at(500.0);
     assert_ne!(inside, outside);
-    assert_eq!(outside, 0, "outside the area, the default type");
+    assert_eq!(outside, 0, "outside the area, the track's own type");
     assert_eq!(net.types()[inside as usize].name, "example:nebenbahn");
 }
 
@@ -200,7 +200,7 @@ fn removing_a_track_takes_its_spans_with_it() {
         grade: vec![],
         cant: vec![],
         speed: vec![],
-        track_type: vec![],
+        track_type: vec![(0.0, STARTER_TRACK_TYPE.into())],
         electrification: vec![],
         formation: true,
     });
@@ -234,7 +234,12 @@ fn a_span_is_stored_the_way_round_it_was_marked() {
 #[test]
 fn the_rule_check_finds_a_marking_that_does_not_reach_the_line() {
     use std::collections::BTreeMap;
-    let types = BTreeMap::new();
+    // The line is laid with the starter type; the registry answers it, so the
+    // check reports the markings and not a missing mod.
+    let types = BTreeMap::from([(
+        STARTER_TRACK_TYPE.to_string(),
+        track_model::TrackType::placeholder(STARTER_TRACK_TYPE),
+    )]);
     let objects = BTreeMap::new();
 
     // A marking with no properties yet: useful while working, worth saying out loud.

crates/content/src/bin/import-line.rs

@@ -2,7 +2,8 @@
 //!
 //! ```text
 //! import-line line.json [--dgm dgm.xyz --epsg 25832] [--name "Musterbahn"]
-//!                       [--sample 20] [--smoothing 3] [--out line.ron]
+//!                       [--sample 20] [--smoothing 3] [--track-type example:hauptbahn]
+//!                       [--out line.ron]
 //! ```
 
 use content::import::dgm::TerrainSource;
@@ -14,7 +15,8 @@ fn main() -> ExitCode {
     if args.is_empty() || args[0] == "--help" {
         eprintln!(
             "Usage: import-line <overpass.json> [--dgm <file.xyz> --epsg <25832>] \
-             [--name <name>] [--sample <m>] [--smoothing <n>] [--no-snap]              [--max-cant <mm>] [--out <file.ron>]"
+             [--name <name>] [--sample <m>] [--smoothing <n>] [--no-snap] \
+             [--max-cant <mm>] [--track-type <mod:name>] [--out <file.ron>]"
         );
         return ExitCode::from(2);
     }
@@ -86,6 +88,11 @@ fn main() -> ExitCode {
     if let Some(v) = flag("--start-way").and_then(|v| v.parse().ok()) {
         options.start_way = Some(v);
     }
+    // What the imported track is built of. Every edge is written out with it —
+    // a line that names no type does not compile.
+    if let Some(v) = flag("--track-type") {
+        options.track_type = v;
+    }
 
     let (line, report) = match import_line(&osm_json, grid.as_ref(), &options) {
         Ok(v) => v,

crates/content/src/compose.rs

@@ -468,7 +468,8 @@ fn shift_payload(kind: &DeviceKind, payload: &str, off: ModuleOffsets) -> String
 mod tests {
     use super::*;
     use crate::route::{
-        BoundarySource, DeviceSource, EdgeSource, GeoPoint, SectionSource, SignalSource,
+        BoundarySource, DeviceSource, EdgeSource, GeoPoint, STARTER_TRACK_TYPE, SectionSource,
+        SignalSource,
     };
     use sim_core::interlock::{SignalKind, SignalSystem};
     use track_model::{Segment, TrackPosition};
@@ -493,7 +494,7 @@ mod tests {
                 grade: vec![],
                 cant: vec![],
                 speed: vec![(0.0, 120.0)],
-                track_type: vec![],
+                track_type: vec![(0.0, STARTER_TRACK_TYPE.into())],
                 electrification: Vec::new(),
                 formation: true,
             }],

crates/content/src/demo.rs

@@ -164,6 +164,10 @@ fn demo_trees() -> Vec<TreeSource> {
 ///
 /// Signalling: distant signal at km 1.0 and main signal at km 2.0 (end of block),
 /// plus the three PZB magnets. From the third section on there is a line cable (LZB).
+///
+/// It names its superstructure like any other line does
+/// ([`crate::route::STARTER_TRACK_TYPE`]) — there is no built-in type, so a
+/// demo line that said nothing would stand on no ballast at all.
 pub fn musterbahn() -> LineSource {
     let magnet = |p: &MagnetPayload| ron::to_string(p).unwrap();
 
@@ -189,7 +193,7 @@ pub fn musterbahn() -> LineSource {
                 grade: vec![],
                 cant: vec![],
                 speed: vec![(0.0, 160.0)],
-                track_type: vec![],
+                track_type: vec![(0.0, crate::route::STARTER_TRACK_TYPE.to_string())],
                 electrification: Vec::new(),
                 formation: true,
             },
@@ -205,7 +209,7 @@ pub fn musterbahn() -> LineSource {
                 grade: vec![],
                 cant: vec![(0.0, 0.0), (200.0, 80.0), (800.0, 0.0)],
                 speed: vec![(0.0, 130.0)],
-                track_type: vec![],
+                track_type: vec![(0.0, crate::route::STARTER_TRACK_TYPE.to_string())],
                 electrification: Vec::new(),
                 formation: true,
             },
@@ -217,7 +221,7 @@ pub fn musterbahn() -> LineSource {
                 grade: vec![(0.0, 0.0), (500.0, 8.0), (2500.0, 0.0)],
                 cant: vec![],
                 speed: vec![(0.0, 160.0)],
-                track_type: vec![],
+                track_type: vec![(0.0, crate::route::STARTER_TRACK_TYPE.to_string())],
                 electrification: Vec::new(),
                 formation: true,
             },

crates/content/src/import/mod.rs

@@ -36,6 +36,11 @@ pub struct ImportOptions {
     /// What the imported line is electrified with (an id of
     /// [`track_model::PowerSystem`], or `"none"`).
     pub electrification: String,
+    /// What the imported track is built of (`"<mod>:<name>"` of a
+    /// `track_types/*.ron`). Every edge is written out with it: there is no
+    /// built-in type, so an import that named none would produce a module
+    /// that does not compile.
+    pub track_type: String,
     /// Permitted speed when OSM does not give one [km/h].
     pub default_speed: f64,
     /// Height used when no DGM is available [m].
@@ -52,6 +57,7 @@ impl Default for ImportOptions {
             max_edge_length: 2_000.0,
             geoid_offset: 46.0,
             electrification: track_model::PowerSystem::Ac15kv.id().to_string(),
+            track_type: crate::route::STARTER_TRACK_TYPE.to_string(),
             default_speed: 100.0,
             default_height: 100.0,
             start_way: None,
@@ -183,7 +189,10 @@ pub fn import_line(
             grade: shift_profile(&fitted.grade, offset, len),
             cant: shift_profile(&fitted.cant, offset, len),
             speed: shift_profile(&fitted.speed, offset, len),
-            track_type: vec![],
+            // The superstructure belongs to the track the same way the wire
+            // does, and it is not optional: every imported edge is written out
+            // with the type the import was given.
+            track_type: vec![(0.0, options.track_type.clone())],
             // The wire belongs to the track: every imported edge starts out
             // saying so itself, so it can be changed one edge at a time.
             electrification: vec![(0.0, options.electrification.clone())],