STEP import takes up for Y-up files and names for the bodies' names (#1312)

file.insert_step and doc.open on a STEP file take `up` (turn a Y-up file so its up is +Z) and `names` (names for the imported bodies). The MCP tool and the app's control requests pass them through; an import without them works as before. Tests in the kernel's STEP reader, the engine, MCP and the file-load UI; docs/step-import.md and docs/mcp.md describe both.

crates/mcp/src/tests.rs

@@ -196,6 +196,34 @@ fn agent_builds_box_fillet_hole() {
     let _ = std::fs::remove_dir_all(&dir);
 }
 
+/// `open` hands `up` and `names` to the STEP import, and the tool's schema refuses other values.
+#[test]
+fn open_stands_a_y_up_step_file_up() {
+    let mut s = server();
+    tool(&mut s, "execute", json!({"command": "solid.box", "params": {"length": 10, "width": 40, "height": 5}}));
+    let dir = std::env::temp_dir().join(format!("solidcraft-mcp-up-{}", std::process::id()));
+    std::fs::create_dir_all(&dir).unwrap();
+    let step = dir.join("tall.step").to_string_lossy().to_string();
+    tool(&mut s, "export", json!({"path": step}));
+    let height = |s: &mut Server| {
+        let bbox = tool(s, "measure", json!({}))["bodies"][0]["bbox"].clone();
+        bbox["max"][2].as_f64().unwrap() - bbox["min"][2].as_f64().unwrap()
+    };
+
+    let r = tool(&mut s, "open", json!({"path": step}));
+    assert_eq!(r["features"], 1, "{r}");
+    assert!((height(&mut s) - 5.0).abs() < 1e-6, "as written");
+    let r = tool(&mut s, "open", json!({"path": step, "up": "y", "names": "product"}));
+    assert_eq!(r["features"], 2, "the import and the turn: {r}");
+    assert!((height(&mut s) - 40.0).abs() < 1e-6, "Y became Z");
+
+    for args in [json!({"path": step, "up": "x"}), json!({"path": step, "names": "label"}), json!({"path": step, "up": 1})] {
+        let r = raw_tool(&mut s, "open", args.clone());
+        assert_eq!(r["error"]["code"], -32602, "{args}: {r}");
+    }
+    let _ = std::fs::remove_dir_all(&dir);
+}
+
 #[test]
 fn save_selects_container_or_json_and_reopens_by_contents() {
     let mut s = server();

crates/mcp/src/tools.rs

@@ -238,8 +238,17 @@ pub fn tool_definitions() -> Vec<Value> {
             "Open a design",
             "Open a .solidcraft design file, a STEP file (.step/.stp: a new design whose bodies come from the file, as an \
              Import base feature) or a 3MF/STL mesh (.3mf/.stl: mesh bodies). Replaces the current design; insert into it \
-             instead with the file.insert_step (STEP) or file.insert_mesh (3MF/STL) commands.",
-            obj(json!({"path": string("Path to a .solidcraft, .step/.stp, .3mf or .stl file")}), &["path"]),
+             instead with the file.insert_step (STEP) or file.insert_mesh (3MF/STL) commands. A STEP file from a system \
+             that has Y up opens lying on its back: `up: \"y\"` turns it a quarter turn about X (Y becomes Z) with a Move \
+             feature. `names` picks what the bodies are named after when the solids' own names say nothing useful.",
+            obj(
+                json!({
+                    "path": string("Path to a .solidcraft, .step/.stp, .3mf or .stl file"),
+                    "up": {"type": "string", "enum": ["z", "y"], "description": "STEP only. z (default) keeps the file's axes; y: the file has Y up, so its bodies are turned to stand Z up"},
+                    "names": {"type": "string", "enum": ["solid", "product", "instance"], "description": "STEP only. What the bodies are named after: solid (default: the solid's own name, else the product's), product (the part's name) or instance (the assembly occurrence's name, else the product's)"},
+                }),
+                &["path"],
+            ),
             Effect::Files,
         ),
         tool(
@@ -401,7 +410,7 @@ fn dispatch(b: &mut dyn Backend, name: &str, a: &Map<String, Value>) -> Result<V
         "undo" => exec(b, "edit.undo", json!({})),
         "redo" => exec(b, "edit.redo", json!({})),
         "new_design" => exec(b, "file.new", pick(a, &["name"])),
-        "open" => exec(b, "doc.open", pick(a, &["path"])),
+        "open" => exec(b, "doc.open", pick(a, &["path", "up", "names"])),
         "save" => exec(b, "file.save", pick(a, &["path", "format"])),
         other => Err(format!("unknown tool `{other}`")),
     }