feat(iso): dedicated ZLayer::SystemsModel variant

Cargo.toml

@@ -28,6 +28,7 @@ members = [
   "crates/beankeeper-bridge",
   "crates/ledgerr-desktop-agent",
   "crates/sysml-derive",
+  "crates/reqif-mcp-spike",
 ]
 resolver = "2"
 

crates/arc-kit-au/src/node.rs

@@ -124,7 +124,7 @@ pub fn content_hash(parts: &[&str]) -> String {
 }
 
 /// Source document evidence.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct SourceDoc {
     /// Original filename (must follow VENDOR--ACCOUNT--YYYY-MM--DOCTYPE.ext)
     pub filename: String,
@@ -151,7 +151,7 @@ impl SourceDoc {
 }
 
 /// Extracted row from document parsing.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct ExtractedRow {
     pub account_id: String,
     pub date: String,
@@ -176,7 +176,7 @@ impl ExtractedRow {
 }
 
 /// Deterministic transaction record.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct Transaction {
     /// Blake3 hash of account/date/amount/description
     pub tx_id: String,
@@ -194,7 +194,7 @@ impl Transaction {
 }
 
 /// Classification applied to transaction.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct Classification {
     pub tx_id: String,
     pub category: String,
@@ -221,7 +221,7 @@ impl Classification {
 }
 
 /// Model-generated classification proposal.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct ModelProposal {
     pub tx_id: String,
     pub model_name: String,
@@ -247,7 +247,7 @@ impl ModelProposal {
 }
 
 /// Operator approval/rejection of model proposal.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct OperatorApproval {
     pub tx_id: String,
     pub operator_id: String,
@@ -275,7 +275,7 @@ impl OperatorApproval {
 /// Distinct from Classification — validation artifacts represent rule/constraint
 /// failures, not categorization decisions. PRD-4 Phase 2 requires
 /// classification_artifact → validation_artifact as a separate chain step.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct ValidationIssue {
     pub tx_id: String,
     pub rule: String,
@@ -301,7 +301,7 @@ impl ValidationIssue {
 }
 
 /// Final workbook row in CPA export.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, SysmlBlock)]
 pub struct WorkbookRow {
     pub tx_id: String,
     pub sheet_name: String,

crates/ledger-core/src/iso.rs

@@ -51,10 +51,16 @@ pub enum ZLayer {
     Legal,
     FormalProof,
     Attestation,
+    /// SysML-v2 systems-modeling primitives (Requirement/Decision/Cost) —
+    /// a dedicated layer rather than folded into the (still-unimplemented,
+    /// see `docs/ontological-implementation-spec.md` §6.1) proposed `Domain`
+    /// layer, per explicit decision: independent toggle/color in the
+    /// isometric renderer over reusing an ontological-concepts layer.
+    SystemsModel,
 }
 
 impl ZLayer {
-    /// 0-based layer index (max 5).
+    /// 0-based layer index (max 6).
     pub fn index(self) -> u8 {
         match self {
             ZLayer::Document => 0,
@@ -63,6 +69,7 @@ impl ZLayer {
             ZLayer::Legal => 3,
             ZLayer::FormalProof => 4,
             ZLayer::Attestation => 5,
+            ZLayer::SystemsModel => 6,
         }
     }
 
@@ -75,6 +82,7 @@ impl ZLayer {
             ZLayer::Legal => "#b91c1c",
             ZLayer::FormalProof => "#0f766e",
             ZLayer::Attestation => "#b45309",
+            ZLayer::SystemsModel => "#be185d",
         }
     }
 
@@ -87,6 +95,7 @@ impl ZLayer {
             ZLayer::Legal => 408.0,
             ZLayer::FormalProof => 544.0,
             ZLayer::Attestation => 680.0,
+            ZLayer::SystemsModel => 816.0,
         }
     }
 
@@ -99,6 +108,7 @@ impl ZLayer {
             ZLayer::Legal => "Legal",
             ZLayer::FormalProof => "FormalProof",
             ZLayer::Attestation => "Attestation",
+            ZLayer::SystemsModel => "SystemsModel",
         }
     }
 }
@@ -127,6 +137,12 @@ pub enum SemanticType {
     Issue,
     Proof,
     Attestation,
+    /// SysML-v2 systems-modeling requirement record — see `ZLayer::SystemsModel`.
+    Requirement,
+    /// SysML-v2 systems-modeling decision record — see `ZLayer::SystemsModel`.
+    Decision,
+    /// SysML-v2 systems-modeling cost record — see `ZLayer::SystemsModel`.
+    Cost,
     Unknown,
 }
 
@@ -145,6 +161,9 @@ impl SemanticType {
             SemanticType::Issue => "issue",
             SemanticType::Proof => "proof",
             SemanticType::Attestation => "attestation",
+            SemanticType::Requirement => "requirement",
+            SemanticType::Decision => "decision",
+            SemanticType::Cost => "cost",
             SemanticType::Unknown => "unknown",
         }
     }
@@ -641,17 +660,31 @@ mod tests {
             ZLayer::Legal,
             ZLayer::FormalProof,
             ZLayer::Attestation,
+            ZLayer::SystemsModel,
         ];
         for layer in all {
             assert!(
-                layer.index() <= 5,
-                "ZLayer::{:?} has index {} > 5",
+                layer.index() <= 6,
+                "ZLayer::{:?} has index {} > 6",
                 layer,
                 layer.index()
             );
         }
     }
 
+    #[test]
+    fn z_layer_systems_model_is_dedicated_not_pipeline() {
+        // Decision 2: Requirement/Decision/Cost content gets its own layer,
+        // not folded into an existing one (e.g. Pipeline or a future Domain).
+        assert_eq!(ZLayer::SystemsModel.index(), 6);
+        assert_eq!(ZLayer::SystemsModel.label(), "SystemsModel");
+        assert_ne!(ZLayer::SystemsModel.color(), ZLayer::Pipeline.color());
+        assert_eq!(
+            ZLayer::SystemsModel.base_z(),
+            ZLayer::Attestation.base_z() + 136.0
+        );
+    }
+
     #[test]
     fn semantic_type_known_name_nonempty() {
         let all = [
@@ -666,6 +699,9 @@ mod tests {
             SemanticType::Issue,
             SemanticType::Proof,
             SemanticType::Attestation,
+            SemanticType::Requirement,
+            SemanticType::Decision,
+            SemanticType::Cost,
             SemanticType::Unknown,
         ];
         for st in all {
@@ -771,6 +807,7 @@ mod tests {
             ZLayer::Legal,
             ZLayer::FormalProof,
             ZLayer::Attestation,
+            ZLayer::SystemsModel,
         ];
         for layer in all {
             assert!(!layer.to_string().is_empty());
@@ -791,6 +828,9 @@ mod tests {
             SemanticType::Issue,
             SemanticType::Proof,
             SemanticType::Attestation,
+            SemanticType::Requirement,
+            SemanticType::Decision,
+            SemanticType::Cost,
             SemanticType::Unknown,
         ];
         for st in all {

crates/ledger-core/src/iso_objects.rs

@@ -1,4 +1,4 @@
-//! `HasVisualization` implementations for the 28 domain types that participate
+//! `HasVisualization` implementations for the 31 domain types that participate
 //! in the isometric pipeline view.
 //!
 //! Every `impl HasVisualization` added here must also be registered in
@@ -469,9 +469,64 @@
     }
 }
 
+// ============================================================================
+// SYSTEMS MODEL — Requirement/Decision/Cost (z=6, SystemsModel layer)
+// ============================================================================
+
+#[cfg(feature = "arc-kit-au")]
+mod systems_model {
+    use arc_kit_au::node::{Cost, Decision, Requirement};
+
+    use crate::iso::{HasVisualization, RhaiDsl, SemanticType, VisualizationSpec, ZLayer};
+
+    impl HasVisualization for Requirement {
+        fn viz_spec() -> VisualizationSpec {
+            VisualizationSpec {
+                semantic_type: SemanticType::Requirement,
+                z_layer: ZLayer::SystemsModel,
+                rhai_dsl: RhaiDsl::new(
+                    r#"let req = load_requirement(source);
+if req.status == "active" { link_decisions(req.related_decisions) }"#,
+                ),
+                description: "SysML v2 systems-modeling requirement — traceable spec record, linked to the decisions it constrains",
+            }
+        }
+    }
+
+    impl HasVisualization for Decision {
+        fn viz_spec() -> VisualizationSpec {
+            VisualizationSpec {
+                semantic_type: SemanticType::Decision,
+                z_layer: ZLayer::SystemsModel,
+                rhai_dsl: RhaiDsl::new(
+                    r#"let decision = record_decision(subject, rationale, decided_by);
+link_requirements(decision.related_requirements);"#,
+                ),
+                description: "Version-controlled decision record — rationale + decider, linked back to the requirements it satisfies",
+            }
+        }
+    }
+
+    impl HasVisualization for Cost {
+        fn viz_spec() -> VisualizationSpec {
+            VisualizationSpec {
+                semantic_type: SemanticType::Cost,
+                z_layer: ZLayer::SystemsModel,
+                rhai_dsl: RhaiDsl::new(
+                    r#"let cost = record_cost(subject, amount, currency);
+if cost.related_decision.is_some() { attribute_to_decision(cost) }"#,
+                ),
+                description: "Version-controlled cost record — monetary amount attributed to a decision for systems-modeling cost traceability",
+            }
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(feature = "arc-kit-au")]
+    use arc_kit_au::node::{Cost, Decision, Requirement};
 
     #[test]
     fn all_viz_spec_rhai_dsl_has_valid_syntax() {
@@ -517,6 +572,13 @@
         check!(UsRdcCredit);
         check!(CryptoTx);
         check!(CryptoWallet);
+        // Systems-modeling domain
+        #[cfg(feature = "arc-kit-au")]
+        {
+            check!(Requirement);
+            check!(Decision);
+            check!(Cost);
+        }
     }
 }
 

crates/ledgerr-mcp/src/contract.rs

@@ -166,13 +166,16 @@ pub const PUBLISHED_TOOLS: [ToolContractSpec; 12] = [
     },
     ToolContractSpec {
         name: EVIDENCE_TOOL,
-        purpose: "evidence traceability: provenance gaps, transaction lineage, review badges, graph summary and node queries",
+        purpose: "evidence traceability: provenance gaps, transaction lineage, review badges, graph summary and node queries; requirement/decision/cost recording",
         actions: &[
             "provenance_gaps",
             "trace_tx",
             "summary",
             "list_nodes",
             "node_detail",
+            "import_requirement",
+            "record_decision",
+            "record_cost",
         ],
     },
     ToolContractSpec {
@@ -915,6 +918,46 @@ pub enum EvidenceArgs {
     },
     #[serde(rename = "node_detail")]
     NodeDetail { node_id: String },
+    /// Import a requirement record (e.g. from `reqif-mcp-spike`'s
+    /// `RequirementRecord`) as a `NodeType::Requirement` evidence node.
+    #[serde(rename = "import_requirement")]
+    ImportRequirement {
+        requirement_id: String,
+        title: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        rationale: Option<String>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        source: Option<String>,
+        #[serde(default = "default_requirement_status")]
+        status: String,
+        #[serde(default, skip_serializing_if = "Vec::is_empty")]
+        related_decisions: Vec<String>,
+    },
+    /// Record a decision as a `NodeType::Decision` evidence node.
+    #[serde(rename = "record_decision")]
+    RecordDecision {
+        decision_id: String,
+        subject: String,
+        rationale: String,
+        decided_by: String,
+        #[serde(default, skip_serializing_if = "Vec::is_empty")]
+        related_requirements: Vec<String>,
+    },
+    /// Record a cost as a `NodeType::Cost` evidence node.
+    #[serde(rename = "record_cost")]
+    RecordCost {
+        cost_id: String,
+        subject: String,
+        amount: String,
+        currency: String,
+        recorded_by: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        related_decision: Option<String>,
+    },
+}
+
+fn default_requirement_status() -> String {
+    "active".to_string()
 }
 
 pub fn parse_evidence(arguments: &Value) -> Result<EvidenceArgs, ToolError> {