[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"skill-jetbrains-mps-aspect-behavior":3,"mdc--q3ns8h-key":32,"related-repo-jetbrains-mps-aspect-behavior":1596,"related-org-jetbrains-mps-aspect-behavior":1666},{"slug":4,"name":4,"fn":5,"description":6,"org":7,"tags":11,"stars":19,"repoUrl":20,"updatedAt":21,"license":22,"forks":23,"topics":24,"repo":27,"sourceUrl":30,"mdContent":31},"mps-aspect-behavior","define and edit MPS concept behavior","Use when defining or editing MPS `ConceptBehavior` — per-concept methods (non-virtual \u002F virtual \u002F abstract \u002F static \u002F virtual static), constructors, virtual dispatch (MRO), super and interface-default calls (`super\u003CInterface>.method`), overriding methods from `lang.core.behavior` interfaces such as `ScopeProvider.getScope` \u002F `INamedConcept.getName` \u002F `BaseConcept.getPresentation`, calling sibling methods (`LocalBehaviorMethodCall`) and behavior methods from other aspects via `node.method(...)`. Reach for this skill whenever the task involves authoring or modifying `\u003Clang>\u002FlanguageModels\u002Fbehavior.mps`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},"jetbrains","JetBrains","https:\u002F\u002Fpexgzepcugksgbtrxkhf.supabase.co\u002Fstorage\u002Fv1\u002Fobject\u002Fpublic\u002Forg-logos\u002Fjetbrains.png",[12,16],{"name":13,"slug":14,"type":15},"Architecture","architecture","tag",{"name":17,"slug":18,"type":15},"Engineering","engineering",1650,"https:\u002F\u002Fgithub.com\u002FJetBrains\u002FMPS","2026-07-13T06:45:21.757084",null,311,[25,26],"domain-specific-language","dsl",{"repoUrl":20,"stars":19,"forks":23,"topics":28,"description":29},[25,26],"JetBrains Meta programming System","https:\u002F\u002Fgithub.com\u002FJetBrains\u002FMPS\u002Ftree\u002FHEAD\u002Fplugins\u002Fmcp-tools\u002Fresources\u002Fjetbrains\u002Fmps\u002Fagents\u002Fmcp\u002Fskills\u002Fmps-aspect-behavior","---\nname: mps-aspect-behavior\ndescription: Use when defining or editing MPS `ConceptBehavior` — per-concept methods (non-virtual \u002F virtual \u002F abstract \u002F static \u002F virtual static), constructors, virtual dispatch (MRO), super and interface-default calls (`super\u003CInterface>.method`), overriding methods from `lang.core.behavior` interfaces such as `ScopeProvider.getScope` \u002F `INamedConcept.getName` \u002F `BaseConcept.getPresentation`, calling sibling methods (`LocalBehaviorMethodCall`) and behavior methods from other aspects via `node.method(...)`. Reach for this skill whenever the task involves authoring or modifying `\u003Clang>\u002FlanguageModels\u002Fbehavior.mps`.\ntype: reference\n---\n\n# MPS Behavior Aspect\n\nThe **behavior** aspect attaches methods and a constructor to a concept, much like adding methods to a Java class. Bodies are written in BaseLanguage + smodel and are callable from any other aspect (editor, constraints, typesystem, generator, intentions, plugin) via `node.methodName(...)`. Lives in `\u003Clang>\u002FlanguageModels\u002Fbehavior.mps`, language `jetbrains.mps.lang.behavior`.\n\n## Critical Directives\n\n- One `ConceptBehavior` root per concept. The `constructor` child is **mandatory** (an empty body is fine).\n- Constructors run **before** the node is attached to the model. `parent`, ancestors, and all children\u002Fdescendants evaluate to `null`. Constructors can only set own property\u002Freference defaults and add mandatory children — use a `NodeFactory` (actions aspect) for anything that needs the parent\u002Fmodel context.\n- Quotations (`\u003CC()>`) bypass behavior constructors. Use `new node\u003CC>()` or `add new initialized C` when you need the constructor to fire.\n- Constructors are **not** inherited — each concept has at most one, and they do not chain (no `super()`). MPS runs each ancestor's constructor in ancestor-first order independently.\n- An overriding method must match the signature of the supertype\u002Finterface method exactly. When implementing an interface method (e.g. `ScopeProvider.getScope`), set `overriddenMethod` on the new method to the interface declaration — MPS uses it for dispatch and signature validation.\n- Behavior calls on a `null` node do **not** NPE — MPS returns `null` for reference\u002FString returns and the default for primitives. Still handle the `null` return for reference types.\n- Hoist shared methods to an abstract super-concept rather than duplicating per-sub-concept `ConceptBehavior` roots — virtual dispatch covers all non-abstract sub-concepts. (See `references\u002Finheritance-and-dispatch.md`.)\n- Methods are **non-virtual by default**: all modifier booleans (`isVirtual`, `isAbstract`, `isStatic`, `isFinal`) default to `false`. Only `virtual` methods can be overridden; mark a method `virtual` up front if sub-concepts may ever need to specialise it.\n- When the same piece of node-handling logic repeats across several places or several aspects of one concept (editor, constraints, typesystem, generator, intentions, textgen), **extract it into a behavior method** and call it everywhere via `node.m(...)` — this de-duplication is the behavior aspect's primary purpose. Pick the modifier with the table below.\n- Edit behavior models through MPS MCP tools (`mps_mcp_insert_root_node_from_json`, `mps_mcp_update_node`, `mps_mcp_parse_java_and_insert`). Do not hand-edit `.mps` files.\n- For MPS-typed return types (`sequence\u003Cnode\u003CX>>`, `list\u003Cnode\u003CX>>`), `mps_mcp_parse_java_and_insert` produces Java `List\u003CSNode>` — replace `returnType` afterwards with the correct MPS blueprint (see `mps-model-manipulation\u002Freferences\u002Fvariable-declarations.md`).\n- After edits run `mps_mcp_check_root_node_problems` and rebuild the language.\n\n## Common-Path Workflow\n\n1. Create a `behavior` model if missing (`mps_mcp_create_model` with `modelName: \"\u003Clang>.behavior\"` — aspect ID `behavior`, case-sensitive, no `@` suffix; see [aspect-model-stereotypes.md](..\u002Fmps-mcp-workflow\u002Freferences\u002Faspect-model-stereotypes.md)). Use languages: `jetbrains.mps.lang.behavior`, plus any languages referenced in bodies (`smodel`, `collections`, `closures`, `baseLanguage`).\n2. Add a `ConceptBehavior` root for the target concept; set `concept` ref. The minimal blueprint (with the mandatory empty `constructor`) is in `references\u002Fjson-blueprints.md`.\n3. Add `ConceptConstructorDeclaration` (at most one) and\u002For `ConceptMethodDeclaration` children.\n4. Write bodies. For non-trivial logic prefer `mps_mcp_parse_java_and_insert` with `featureKind: \"STATEMENTS\"` or `\"METHOD\"`, then fix MPS-typed return\u002Fparameter types.\n5. Validate with `mps_mcp_check_root_node_problems`, rebuild the language.\n\n## Method Modifier Quick Reference\n\n| Modifier | Call shape | Dispatch \u002F inheritance | Notes |\n|---|---|---|---|\n| *(none)* — non-virtual (**default**) | `node.m(...)` | Inherited by sub-concepts but **statically bound — cannot be overridden** | A same-named method in a sub-concept's behavior shadows it (hazard) instead of overriding. Most `Classifier_Behavior` utilities in baseLanguage are non-virtual. |\n| `virtual` | `node.m(...)` | Dispatched at runtime by the node's actual concept; overridable in sub-concept behaviors | Set `isVirtual: true` explicitly. E.g. `Expression.isLValue` and every method of `Type_Behavior` in baseLanguage. |\n| `abstract` | `node.m(...)` (virtually dispatched) | No body; every non-abstract sub-concept must provide an implementation | **Implies `virtual` — set both `isAbstract` and `isVirtual`.** Declare on abstract\u002Finterface concepts (e.g. `Classifier.findAncestor`, `IMemberContainer.getMembers` in baseLanguage). |\n| `final` | `node.m(...)` | A virtual method that cannot be overridden further down | Rarely needed — a plain non-virtual method is already non-overridable. |\n| `static` | `ConceptName.m(...)` (qualified by concept name) | Belongs to the concept; no `this`; no dispatch | Concept-wide utilities, e.g. `Classifier.getContextClassifier` in baseLanguage. Called as `LocalBehaviorMethodCall` when unqualified inside the same `ConceptBehavior`. |\n| `virtual static` | `conceptValue.m(...)` on a `concept\u003CX>` expression | Dispatched by the runtime **concept value**; overridable in sub-concept behaviors (link `overriddenMethod`) | Per-concept (not per-node) polymorphism — e.g. `Expression.getPrecedenceLevel`, `Type.isValueType` in baseLanguage, overridden across the smodel\u002Fcollections behaviors. |\n\n### Choosing a modifier for an extracted method\n\n- Invoked on a **node** (needs `this`, properties, children)? → instance method: `virtual` if sub-concepts must be able to override it (or the logic varies by concept), non-virtual for a fixed helper.\n- Invoked on a **concept** (no node instance at hand, concept-wide utility, or nodes passed as parameters)? → `static`; make it `virtual static` when the result must vary per concept (dispatch on a `concept\u003CX>` value).\n- Shared by several sub-concepts? → declare it once on their common (abstract) super-concept or interface; use `abstract` (+ `virtual`) when only sub-concepts can supply the body.\n\n## Related Skills\n\n- `mps-aspect-actions` — `NodeFactory` is the right place for initialization that needs parent\u002Fmodel context (constructors run before the node is attached).\n- `mps-aspect-intentions`, `mps-aspect-constraints`, `mps-aspect-generator`, `mps-aspect-typesystem` — call behavior methods via `node.m(...)`; behavior is one of the most-used aspects from these.\n- `mps-model-manipulation` — full BaseLanguage \u002F smodel \u002F collections reference. Covers the `LinkList_AddNewChildOperation` family and the `List\u003CSNode>` → `sequence\u003Cnode\u003CX>>` return-type fix.\n- `mps-aspect-constraints` — `ScopeProvider.getScope` is most often overridden in a behavior; constraints describe where the reference lives.\n- `mps-aspect-structure-concepts` — when introducing the concept that the behavior attaches to.\n- `mps-language-inheritance` — to design the abstract-super-concept refactors discussed in `references\u002Finheritance-and-dispatch.md`.\n- `mps-quotations` — quotations bypass behavior constructors; document the workaround in the generator.\n\n## Reference Index\n\n- Open `references\u002Fmethod-declarations.md` when authoring a `ConceptMethodDeclaration` — modifiers, parameters, `overriddenMethod`, `BaseConcept` overrides (`getPresentation` \u002F `getSideIcon`), implicit-return rule, and the MPS-typed return-type Java-parser caveat.\n- Open `references\u002Flocal-and-super-calls.md` when calling sibling methods of the same `ConceptBehavior` (`LocalBehaviorMethodCall`), distinguishing unqualified `m(args)` from `this.m(args)` (which generates `DotExpression { ThisNodeExpression, Node_ConceptMethodCall }`), or calling `super\u003CInterface>.method(...)` — includes the verbatim Stateful and Kaja `CommentLine_Behavior` examples and the `Stateful_Behavior.getScope` super-call JSON.\n- Open `references\u002Finheritance-and-dispatch.md` when designing or debugging virtual dispatch — the MRO algorithm (own → extended super → interfaces in definition order), how a method on an abstract super-concept covers every concrete sub-concept (Stateful pattern), and when to hoist shared behavior up vs. duplicate per concept.\n- Open `references\u002Fconstructors.md` when writing a `ConceptConstructorDeclaration` — what runs and what does not run a constructor, the \"node not yet attached\" constraint, scalar-default and seed-mandatory-child examples (ChemMastery `Compound_Behavior` and `ChemEquation_Behavior`) with full JSON blueprints, and the surface→FQN mapping for the surface syntax involved.\n- Open `references\u002Fcalling-from-other-aspects.md` when calling a behavior method from generator templates, typesystem rules, constraints, intentions, or hand-written Java — the descriptor invocation shape, the `_idXXXXX` stable suffix, and the null-safety behavior of `node.method()`.\n- Open `references\u002Fjson-blueprints.md` when inserting a behavior root or a method via MCP — minimal `ConceptBehavior` with the mandatory empty constructor, the `ConceptMethodDeclaration` skeleton, and the validated concept ref.\n- Open `references\u002Flang-core-behavior-overrides.md` for the validated node refs to set as `overriddenMethod` when implementing common `lang.core.behavior` methods (`getTextualRepresentation`, `isTODOComment`, `getScope`), plus the `IGenericComment` interface node ref used in `super\u003CIGenericComment>.isTODOComment()` calls.\n- Open `references\u002Fcommon-failures.md` when a behavior method isn't found, an override is ignored, a constructor's defaults don't stick, a descriptor returns `Object`, the return type fights the Java parser, or quotations bypass the constructor.\n",{"data":33,"body":35},{"name":4,"description":6,"type":34},"reference",{"type":36,"children":37},"root",[38,47,86,93,468,474,658,664,1041,1048,1127,1133,1281,1287],{"type":39,"tag":40,"props":41,"children":43},"element","h1",{"id":42},"mps-behavior-aspect",[44],{"type":45,"value":46},"text","MPS Behavior Aspect",{"type":39,"tag":48,"props":49,"children":50},"p",{},[51,53,59,61,68,70,76,78,84],{"type":45,"value":52},"The ",{"type":39,"tag":54,"props":55,"children":56},"strong",{},[57],{"type":45,"value":58},"behavior",{"type":45,"value":60}," aspect attaches methods and a constructor to a concept, much like adding methods to a Java class. 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Use ",{"type":39,"tag":62,"props":176,"children":178},{"className":177},[],[179],{"type":45,"value":180},"new node\u003CC>()",{"type":45,"value":182}," or ",{"type":39,"tag":62,"props":184,"children":186},{"className":185},[],[187],{"type":45,"value":188},"add new initialized C",{"type":45,"value":190}," when you need the constructor to fire.",{"type":39,"tag":98,"props":192,"children":193},{},[194,196,201,203,209],{"type":45,"value":195},"Constructors are ",{"type":39,"tag":54,"props":197,"children":198},{},[199],{"type":45,"value":200},"not",{"type":45,"value":202}," inherited — each concept has at most one, and they do not chain (no ",{"type":39,"tag":62,"props":204,"children":206},{"className":205},[],[207],{"type":45,"value":208},"super()",{"type":45,"value":210},"). MPS runs each ancestor's constructor in ancestor-first order independently.",{"type":39,"tag":98,"props":212,"children":213},{},[214,216,222,224,230],{"type":45,"value":215},"An overriding method must match the signature of the supertype\u002Finterface method exactly. When implementing an interface method (e.g. ",{"type":39,"tag":62,"props":217,"children":219},{"className":218},[],[220],{"type":45,"value":221},"ScopeProvider.getScope",{"type":45,"value":223},"), set ",{"type":39,"tag":62,"props":225,"children":227},{"className":226},[],[228],{"type":45,"value":229},"overriddenMethod",{"type":45,"value":231}," on the new method to the interface declaration — MPS uses it for dispatch and signature validation.",{"type":39,"tag":98,"props":233,"children":234},{},[235,237,242,244,248,250,255,257,262],{"type":45,"value":236},"Behavior calls on a ",{"type":39,"tag":62,"props":238,"children":240},{"className":239},[],[241],{"type":45,"value":151},{"type":45,"value":243}," node do ",{"type":39,"tag":54,"props":245,"children":246},{},[247],{"type":45,"value":200},{"type":45,"value":249}," NPE — MPS returns ",{"type":39,"tag":62,"props":251,"children":253},{"className":252},[],[254],{"type":45,"value":151},{"type":45,"value":256}," for reference\u002FString returns and the default for primitives. Still handle the ",{"type":39,"tag":62,"props":258,"children":260},{"className":259},[],[261],{"type":45,"value":151},{"type":45,"value":263}," return for reference types.",{"type":39,"tag":98,"props":265,"children":266},{},[267,269,274,276,282],{"type":45,"value":268},"Hoist shared methods to an abstract super-concept rather than duplicating per-sub-concept ",{"type":39,"tag":62,"props":270,"children":272},{"className":271},[],[273],{"type":45,"value":108},{"type":45,"value":275}," roots — virtual dispatch covers all non-abstract sub-concepts. (See ",{"type":39,"tag":62,"props":277,"children":279},{"className":278},[],[280],{"type":45,"value":281},"references\u002Finheritance-and-dispatch.md",{"type":45,"value":283},".)",{"type":39,"tag":98,"props":285,"children":286},{},[287,289,294,296,302,304,310,311,317,318,324,326,332,334,340,342,347],{"type":45,"value":288},"Methods are ",{"type":39,"tag":54,"props":290,"children":291},{},[292],{"type":45,"value":293},"non-virtual by default",{"type":45,"value":295},": all modifier booleans (",{"type":39,"tag":62,"props":297,"children":299},{"className":298},[],[300],{"type":45,"value":301},"isVirtual",{"type":45,"value":303},", ",{"type":39,"tag":62,"props":305,"children":307},{"className":306},[],[308],{"type":45,"value":309},"isAbstract",{"type":45,"value":303},{"type":39,"tag":62,"props":312,"children":314},{"className":313},[],[315],{"type":45,"value":316},"isStatic",{"type":45,"value":303},{"type":39,"tag":62,"props":319,"children":321},{"className":320},[],[322],{"type":45,"value":323},"isFinal",{"type":45,"value":325},") default to ",{"type":39,"tag":62,"props":327,"children":329},{"className":328},[],[330],{"type":45,"value":331},"false",{"type":45,"value":333},". Only ",{"type":39,"tag":62,"props":335,"children":337},{"className":336},[],[338],{"type":45,"value":339},"virtual",{"type":45,"value":341}," methods can be overridden; mark a method ",{"type":39,"tag":62,"props":343,"children":345},{"className":344},[],[346],{"type":45,"value":339},{"type":45,"value":348}," up front if sub-concepts may ever need to specialise it.",{"type":39,"tag":98,"props":350,"children":351},{},[352,354,359,361,367],{"type":45,"value":353},"When the same piece of node-handling logic repeats across several places or several aspects of one concept (editor, constraints, typesystem, generator, intentions, textgen), ",{"type":39,"tag":54,"props":355,"children":356},{},[357],{"type":45,"value":358},"extract it into a behavior method",{"type":45,"value":360}," and call it everywhere via ",{"type":39,"tag":62,"props":362,"children":364},{"className":363},[],[365],{"type":45,"value":366},"node.m(...)",{"type":45,"value":368}," — this de-duplication is the behavior aspect's primary purpose. 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",{"type":39,"tag":62,"props":1311,"children":1313},{"className":1312},[],[1314],{"type":45,"value":229},{"type":45,"value":303},{"type":39,"tag":62,"props":1317,"children":1319},{"className":1318},[],[1320],{"type":45,"value":1321},"BaseConcept",{"type":45,"value":1323}," overrides (",{"type":39,"tag":62,"props":1325,"children":1327},{"className":1326},[],[1328],{"type":45,"value":1329},"getPresentation",{"type":45,"value":1331}," \u002F ",{"type":39,"tag":62,"props":1333,"children":1335},{"className":1334},[],[1336],{"type":45,"value":1337},"getSideIcon",{"type":45,"value":1339},"), implicit-return rule, and the MPS-typed return-type Java-parser caveat.",{"type":39,"tag":98,"props":1341,"children":1342},{},[1343,1344,1350,1352,1357,1359,1364,1366,1372,1374,1380,1382,1388,1390,1396,1398,1404,1406,1412],{"type":45,"value":1294},{"type":39,"tag":62,"props":1345,"children":1347},{"className":1346},[],[1348],{"type":45,"value":1349},"references\u002Flocal-and-super-calls.md",{"type":45,"value":1351}," when calling sibling methods of the same ",{"type":39,"tag":62,"props":1353,"children":1355},{"className":1354},[],[1356],{"type":45,"value":108},{"type":45,"value":1358}," (",{"type":39,"tag":62,"props":1360,"children":1362},{"className":1361},[],[1363],{"type":45,"value":963},{"type":45,"value":1365},"), distinguishing unqualified ",{"type":39,"tag":62,"props":1367,"children":1369},{"className":1368},[],[1370],{"type":45,"value":1371},"m(args)",{"type":45,"value":1373}," from ",{"type":39,"tag":62,"props":1375,"children":1377},{"className":1376},[],[1378],{"type":45,"value":1379},"this.m(args)",{"type":45,"value":1381}," (which generates ",{"type":39,"tag":62,"props":1383,"children":1385},{"className":1384},[],[1386],{"type":45,"value":1387},"DotExpression { ThisNodeExpression, Node_ConceptMethodCall }",{"type":45,"value":1389},"), or calling ",{"type":39,"tag":62,"props":1391,"children":1393},{"className":1392},[],[1394],{"type":45,"value":1395},"super\u003CInterface>.method(...)",{"type":45,"value":1397}," — includes the verbatim Stateful and Kaja ",{"type":39,"tag":62,"props":1399,"children":1401},{"className":1400},[],[1402],{"type":45,"value":1403},"CommentLine_Behavior",{"type":45,"value":1405}," examples and the ",{"type":39,"tag":62,"props":1407,"children":1409},{"className":1408},[],[1410],{"type":45,"value":1411},"Stateful_Behavior.getScope",{"type":45,"value":1413}," super-call JSON.",{"type":39,"tag":98,"props":1415,"children":1416},{},[1417,1418,1423],{"type":45,"value":1294},{"type":39,"tag":62,"props":1419,"children":1421},{"className":1420},[],[1422],{"type":45,"value":281},{"type":45,"value":1424}," when designing or debugging virtual dispatch — the MRO algorithm (own → extended super → interfaces in definition order), how a method on an abstract super-concept covers every concrete sub-concept (Stateful pattern), and when to hoist shared behavior up vs. duplicate per concept.",{"type":39,"tag":98,"props":1426,"children":1427},{},[1428,1429,1435,1437,1442,1444,1450,1451,1457],{"type":45,"value":1294},{"type":39,"tag":62,"props":1430,"children":1432},{"className":1431},[],[1433],{"type":45,"value":1434},"references\u002Fconstructors.md",{"type":45,"value":1436}," when writing a ",{"type":39,"tag":62,"props":1438,"children":1440},{"className":1439},[],[1441],{"type":45,"value":609},{"type":45,"value":1443}," — what runs and what does not run a constructor, the \"node not yet attached\" constraint, scalar-default and seed-mandatory-child examples (ChemMastery ",{"type":39,"tag":62,"props":1445,"children":1447},{"className":1446},[],[1448],{"type":45,"value":1449},"Compound_Behavior",{"type":45,"value":855},{"type":39,"tag":62,"props":1452,"children":1454},{"className":1453},[],[1455],{"type":45,"value":1456},"ChemEquation_Behavior",{"type":45,"value":1458},") with full JSON blueprints, and the surface→FQN mapping for the surface syntax involved.",{"type":39,"tag":98,"props":1460,"children":1461},{},[1462,1463,1469,1471,1477,1479,1485],{"type":45,"value":1294},{"type":39,"tag":62,"props":1464,"children":1466},{"className":1465},[],[1467],{"type":45,"value":1468},"references\u002Fcalling-from-other-aspects.md",{"type":45,"value":1470}," when calling a behavior method from generator templates, typesystem rules, constraints, intentions, or hand-written Java — the descriptor invocation shape, the ",{"type":39,"tag":62,"props":1472,"children":1474},{"className":1473},[],[1475],{"type":45,"value":1476},"_idXXXXX",{"type":45,"value":1478}," stable suffix, and the null-safety behavior of ",{"type":39,"tag":62,"props":1480,"children":1482},{"className":1481},[],[1483],{"type":45,"value":1484},"node.method()",{"type":45,"value":85},{"type":39,"tag":98,"props":1487,"children":1488},{},[1489,1490,1495,1497,1502,1504,1509],{"type":45,"value":1294},{"type":39,"tag":62,"props":1491,"children":1493},{"className":1492},[],[1494],{"type":45,"value":597},{"type":45,"value":1496}," when inserting a behavior root or a method via MCP — minimal ",{"type":39,"tag":62,"props":1498,"children":1500},{"className":1499},[],[1501],{"type":45,"value":108},{"type":45,"value":1503}," with the mandatory empty constructor, the ",{"type":39,"tag":62,"props":1505,"children":1507},{"className":1506},[],[1508],{"type":45,"value":617},{"type":45,"value":1510}," skeleton, and the validated concept ref.",{"type":39,"tag":98,"props":1512,"children":1513},{},[1514,1515,1521,1523,1528,1530,1536,1538,1544,1545,1551,1552,1558,1560,1566,1568,1574],{"type":45,"value":1294},{"type":39,"tag":62,"props":1516,"children":1518},{"className":1517},[],[1519],{"type":45,"value":1520},"references\u002Flang-core-behavior-overrides.md",{"type":45,"value":1522}," for the validated node refs to set as ",{"type":39,"tag":62,"props":1524,"children":1526},{"className":1525},[],[1527],{"type":45,"value":229},{"type":45,"value":1529}," when implementing common ",{"type":39,"tag":62,"props":1531,"children":1533},{"className":1532},[],[1534],{"type":45,"value":1535},"lang.core.behavior",{"type":45,"value":1537}," methods (",{"type":39,"tag":62,"props":1539,"children":1541},{"className":1540},[],[1542],{"type":45,"value":1543},"getTextualRepresentation",{"type":45,"value":303},{"type":39,"tag":62,"props":1546,"children":1548},{"className":1547},[],[1549],{"type":45,"value":1550},"isTODOComment",{"type":45,"value":303},{"type":39,"tag":62,"props":1553,"children":1555},{"className":1554},[],[1556],{"type":45,"value":1557},"getScope",{"type":45,"value":1559},"), plus the ",{"type":39,"tag":62,"props":1561,"children":1563},{"className":1562},[],[1564],{"type":45,"value":1565},"IGenericComment",{"type":45,"value":1567}," interface node ref used in ",{"type":39,"tag":62,"props":1569,"children":1571},{"className":1570},[],[1572],{"type":45,"value":1573},"super\u003CIGenericComment>.isTODOComment()",{"type":45,"value":1575}," calls.",{"type":39,"tag":98,"props":1577,"children":1578},{},[1579,1580,1586,1588,1594],{"type":45,"value":1294},{"type":39,"tag":62,"props":1581,"children":1583},{"className":1582},[],[1584],{"type":45,"value":1585},"references\u002Fcommon-failures.md",{"type":45,"value":1587}," when a behavior method isn't found, an override is ignored, a constructor's defaults don't stick, a descriptor returns ",{"type":39,"tag":62,"props":1589,"children":1591},{"className":1590},[],[1592],{"type":45,"value":1593},"Object",{"type":45,"value":1595},", the return type fights the Java parser, or quotations bypass the constructor.",{"items":1597,"total":1665},[1598,1610,1618,1623,1633,1643,1656],{"slug":1599,"name":1599,"fn":1600,"description":1601,"org":1602,"tags":1603,"stars":19,"repoUrl":20,"updatedAt":1609},"mps-aspect-accessories","configure JetBrains MPS module dependencies","Wire MPS module and model dependencies, used languages, used devkits, extended languages, runtime solutions, accessory models, and language\u002Fdependency versions. Use when adding\u002Fremoving module dependencies, importing languages or devkits into a model, declaring runtime solutions, or shipping accessory content visible to consumers without explicit import.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1604,1605,1608],{"name":13,"slug":14,"type":15},{"name":1606,"slug":1607,"type":15},"Configuration","configuration",{"name":17,"slug":18,"type":15},"2026-07-17T06:06:57.311661",{"slug":1144,"name":1144,"fn":1611,"description":1612,"org":1613,"tags":1614,"stars":19,"repoUrl":20,"updatedAt":1617},"define and edit MPS node factories","Use when defining or editing MPS node factories (the \"actions\" aspect) — `NodeFactories` roots, per-concept `NodeFactory` setup functions that initialize a freshly created node and optionally copy data from a replaced `sampleNode`, plus the actions aspect's `CopyPasteHandlers` and `PasteWrappers` roots. Reach for this skill when a substitution, side transform, completion replacement, or `add new initialized(...)` should preserve fields from the node it is replacing, or when defaults set in a constructor are not enough.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1615,1616],{"name":13,"slug":14,"type":15},{"name":17,"slug":18,"type":15},"2026-07-17T06:04:48.066901",{"slug":4,"name":4,"fn":5,"description":6,"org":1619,"tags":1620,"stars":19,"repoUrl":20,"updatedAt":21},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1621,1622],{"name":13,"slug":14,"type":15},{"name":17,"slug":18,"type":15},{"slug":1169,"name":1169,"fn":1624,"description":1625,"org":1626,"tags":1627,"stars":19,"repoUrl":20,"updatedAt":1632},"define JetBrains MPS language constraints","Use when defining or editing MPS language constraints — property validators \u002F setters \u002F getters, referent search scopes (imperative or inherited via `ScopeProvider.getScope`), `referentSetHandler` side effects, default-scope blocks, `canBeChild` \u002F `canBeParent` \u002F `canBeAncestor` \u002F `canBeRoot` placement rules, `defaultConcreteConcept` for abstract concepts, `set \u003Cread-only>` and `{name}` aliasing, and scope helpers (`SimpleRoleScope`, `ListScope`, `CompositeScope`, `HidingByNameScope`). Reach for this skill whenever the task involves authoring or modifying `\u003Clang>\u002FlanguageModels\u002Fconstraints.mps`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1628,1629],{"name":13,"slug":14,"type":15},{"name":1630,"slug":1631,"type":15},"Code Analysis","code-analysis","2026-07-23T05:41:33.639365",{"slug":1634,"name":1634,"fn":1635,"description":1636,"org":1637,"tags":1638,"stars":19,"repoUrl":20,"updatedAt":1642},"mps-aspect-dataflow","define and debug MPS dataflow builders","Use when defining or debugging MPS dataflow builders for a concept — control\u002Fdata flow declarations that drive reachability analysis and variable-use checking. Covers DataFlowBuilderDeclaration, BuilderBlock, emit instructions (code for, jump, ifjump, label, read, write, ret, mayBeUnreachable), positions (AfterPosition, BeforePosition, LabelPosition), the jetbrains.mps.lang.dataFlow language, the NodeParameter implicit, BL+smodel usage inside builder bodies, and IBuilderMode for advanced analyses such as nullable\u002Fnon-null tracking.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1639],{"name":1640,"slug":1641,"type":15},"Data Analysis","data-analysis","2026-07-13T06:45:19.114674",{"slug":1644,"name":1644,"fn":1645,"description":1646,"org":1647,"tags":1648,"stars":19,"repoUrl":20,"updatedAt":1655},"mps-aspect-editor","define MPS editor layouts","Use when creating or changing MPS editor definitions — the overall workflow from scaffolding a `ConceptEditorDeclaration` through componentizing reusable `EditorComponentDeclaration`s, refining cell models and cell layouts, applying style sheets and indent-layout style items, wiring smart references, leveraging inheritance via super-concepts and interfaces, inspecting (`print_node_json`, `show_node_representation`) and validating (`check_root_node_problems`). Covers `jetbrains.mps.lang.editor` cell models (`CellModel_RefNode`\u002F`CellModel_RefNodeList`\u002F`CellModel_RefCell`\u002F`CellModel_Property`\u002F`CellModel_Constant`), layout choices, and JSON blueprints for common editor shapes. For the non-layout side (action maps, keymaps, transformation\u002Fsubstitute menus) use `mps-aspect-editor-menus-and-keymaps`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1649,1652],{"name":1650,"slug":1651,"type":15},"Design","design",{"name":1653,"slug":1654,"type":15},"UI Components","ui-components","2026-07-23T05:41:56.638151",{"slug":1657,"name":1657,"fn":1658,"description":1659,"org":1660,"tags":1661,"stars":19,"repoUrl":20,"updatedAt":1664},"mps-aspect-editor-menus-and-keymaps","author MPS editor menus and keymaps","Use when authoring the **non-layout** parts of the MPS editor aspect — what happens when the user types, presses a key, triggers completion, pastes, or invokes a context action. Covers action maps (`CellActionMapDeclaration`), cell keymaps (`CellKeyMapDeclaration`), transformation menus (`TransformationMenu_Default` \u002F `_Named` \u002F `_Contribution`), substitute menus (`SubstituteMenu_Default` \u002F `SubstituteMenu` \u002F contributions), side transforms (LEFT\u002FRIGHT), legacy cell menus, paste wrappers and copy-paste handlers (in the actions language), completion styling, reference presentation, two-step deletion, and the editor selection API. Trigger terms: `actionMap`, `keyMap`, `delete_action_id`, `transformationMenu`, `substituteMenu`, `Ctrl+Space`, `Ctrl+Alt+B`, side transform, paste wrapper, completion styling, `PasteWrappers`, `CopyPasteHandlers`. For the **layout** side (cells, layouts, style sheets) use `mps-aspect-editor` instead.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1662,1663],{"name":17,"slug":18,"type":15},{"name":1653,"slug":1654,"type":15},"2026-07-23T05:41:49.666535",31,{"items":1667,"total":1751},[1668,1674,1679,1684,1689,1693,1698,1703,1712,1721,1729,1742],{"slug":1599,"name":1599,"fn":1600,"description":1601,"org":1669,"tags":1670,"stars":19,"repoUrl":20,"updatedAt":1609},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1671,1672,1673],{"name":13,"slug":14,"type":15},{"name":1606,"slug":1607,"type":15},{"name":17,"slug":18,"type":15},{"slug":1144,"name":1144,"fn":1611,"description":1612,"org":1675,"tags":1676,"stars":19,"repoUrl":20,"updatedAt":1617},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1677,1678],{"name":13,"slug":14,"type":15},{"name":17,"slug":18,"type":15},{"slug":4,"name":4,"fn":5,"description":6,"org":1680,"tags":1681,"stars":19,"repoUrl":20,"updatedAt":21},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1682,1683],{"name":13,"slug":14,"type":15},{"name":17,"slug":18,"type":15},{"slug":1169,"name":1169,"fn":1624,"description":1625,"org":1685,"tags":1686,"stars":19,"repoUrl":20,"updatedAt":1632},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1687,1688],{"name":13,"slug":14,"type":15},{"name":1630,"slug":1631,"type":15},{"slug":1634,"name":1634,"fn":1635,"description":1636,"org":1690,"tags":1691,"stars":19,"repoUrl":20,"updatedAt":1642},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1692],{"name":1640,"slug":1641,"type":15},{"slug":1644,"name":1644,"fn":1645,"description":1646,"org":1694,"tags":1695,"stars":19,"repoUrl":20,"updatedAt":1655},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1696,1697],{"name":1650,"slug":1651,"type":15},{"name":1653,"slug":1654,"type":15},{"slug":1657,"name":1657,"fn":1658,"description":1659,"org":1699,"tags":1700,"stars":19,"repoUrl":20,"updatedAt":1664},{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1701,1702],{"name":17,"slug":18,"type":15},{"name":1653,"slug":1654,"type":15},{"slug":1704,"name":1704,"fn":1705,"description":1706,"org":1707,"tags":1708,"stars":19,"repoUrl":20,"updatedAt":1711},"mps-aspect-generation-plan","modify MPS generation plans","Use when defining or modifying an MPS generation plan — explicit ordering of generators, checkpoints for cross-model reference resolution, forks for parallel branches, IncludePlan composition, conditional PlanContribution activation, ParameterEquals\u002FConceptListSelector fork selectors, and InitModelAttributes for targetFacet routing. Apply when working with @genplan models, the jetbrains.mps.lang.generator.plan language, attaching plans via DevKits or the Custom generation facet, or debugging cross-model mapping label resolution.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1709,1710],{"name":13,"slug":14,"type":15},{"name":17,"slug":18,"type":15},"2026-07-13T06:44:59.507855",{"slug":1176,"name":1176,"fn":1713,"description":1714,"org":1715,"tags":1716,"stars":19,"repoUrl":20,"updatedAt":1720},"define JetBrains MPS generator rules","Use when defining or modifying MPS generators — author a generator module, add or edit root\u002Freduction\u002Fweaving\u002Fpattern mapping rules, attach template macros ($COPY_SRC, $LOOP, $IF, $PROPERTY, $REF, $SWITCH, $MAP_SRC, $WEAVE, $INSERT, $LABEL, $TRACE, $VAR), wire mapping labels, build template switches, write pre\u002Fpost mapping scripts, navigate `genContext`, or debug \"rule didn't fire\", missing references, empty output, infinite reduction loops, and generated-Java compile failures.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1717,1718,1719],{"name":13,"slug":14,"type":15},{"name":1630,"slug":1631,"type":15},{"name":17,"slug":18,"type":15},"2026-07-17T06:06:58.042999",{"slug":1162,"name":1162,"fn":1722,"description":1723,"org":1724,"tags":1725,"stars":19,"repoUrl":20,"updatedAt":1728},"define and edit MPS intentions","Use when defining or editing MPS intentions (the Alt+Enter context-action aspect) — adding `IntentionDeclaration` roots, parameterized or surround-with variants, description\u002FisApplicable\u002Fexecute blocks, child-filter functions, factory-initialized AST splicing, or debugging why an intention is not offered. Lives in the language's `intentions` model and uses `jetbrains.mps.lang.intentions`.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1726,1727],{"name":13,"slug":14,"type":15},{"name":17,"slug":18,"type":15},"2026-07-23T05:41:48.692899",{"slug":1730,"name":1730,"fn":1731,"description":1732,"org":1733,"tags":1734,"stars":19,"repoUrl":20,"updatedAt":1741},"mps-aspect-migrations","author and debug MPS migration scripts","Use when authoring or debugging MPS migration scripts that upgrade user models after a language definition changes — covers jetbrains.mps.lang.migration (MigrationScript class-based, PureMigrationScript declarative, MoveConcept\u002FMoveContainmentLink\u002FMoveReferenceLink\u002FMoveProperty, ordering via OrderDependency, data exchange via putData\u002FgetData, RefactoringLog, ConceptMigrationReference) and jetbrains.mps.lang.script Enhancement Scripts (MigrationScript with MigrationScriptPart_Instance, ExtractInterfaceMigration, FactoryMigrationScriptPart, CommentMigrationScriptPart) — when a model needs version-gated upgrade, concept rename or removal, link or property rename, instance-level transformation, or composition of migration steps.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1735,1738],{"name":1736,"slug":1737,"type":15},"Debugging","debugging",{"name":1739,"slug":1740,"type":15},"Migration","migration","2026-07-13T06:45:20.372122",{"slug":1250,"name":1250,"fn":1743,"description":1744,"org":1745,"tags":1746,"stars":19,"repoUrl":20,"updatedAt":1750},"define concepts in MPS structure aspect","Define concepts, interface concepts, enumerations, and constrained data types in an MPS language's `structure` aspect. Covers smart-reference detection, alias rules, cardinality, INamedConcept usage, bulk creation, and the full `mps_mcp_alter_structure` \u002F `mps_mcp_query_structure` reference. Use when authoring or modifying a language's structure model.",{"slug":8,"name":9,"logoUrl":10,"githubOrg":9},[1747],{"name":1748,"slug":1749,"type":15},"Data Modeling","data-modeling","2026-07-23T05:41:30.705975",188]