diff --git a/src/fesa/io/abaqus/domain_mapper.cpp b/src/fesa/io/abaqus/domain_mapper.cpp
index 66a7867..27dc04c 100644
--- a/src/fesa/io/abaqus/domain_mapper.cpp
+++ b/src/fesa/io/abaqus/domain_mapper.cpp
@@ -48,12 +48,24 @@ struct RawNode {
 };
 
 struct RawElement {
+    enum class Type {
+        b33,
+        s4,
+        s4r
+    };
+
     std::int64_t label;
     std::string labelText;
-    std::array<std::int64_t, 2> nodeLabels;
+    Type type;
+    std::vector<std::int64_t> nodeLabels;
     SourceLocation location;
 };
 
+enum class ElementFamily {
+    beam,
+    shell
+};
+
 struct RawSet {
     std::string name;
     std::vector<std::int64_t> members;
@@ -69,6 +81,13 @@ struct RawSection {
     SourceLocation location;
 };
 
+struct RawShellSection {
+    std::string elementSetName;
+    std::string materialName;
+    double thickness;
+    SourceLocation location;
+};
+
 struct RawPart {
     std::string name;
     SourceLocation location;
@@ -77,6 +96,7 @@ struct RawPart {
     std::vector<RawSet> nodeSets;
     std::vector<RawSet> elementSets;
     std::vector<RawSection> sections;
+    std::vector<RawShellSection> shellSections;
 };
 
 struct RawInstance {
@@ -551,7 +571,7 @@ private:
                 "Part names are unique under case-insensitive lookup.");
             return;
         }
-        parts_.push_back({*name, block.location, {}, {}, {}, {}, {}});
+        parts_.push_back({*name, block.location, {}, {}, {}, {}, {}, {}});
         currentPart_ = parts_.size() - 1U;
         partElementsSeen_ = false;
         partSetsSeen_ = false;
@@ -565,11 +585,12 @@ private:
                 return;
             }
             const RawPart& part = parts_[*currentPart_];
+            const bool shellPart = modelElementFamily_ == ElementFamily::shell;
             if (part.nodes.empty() || part.elements.empty() ||
-                part.sections.empty()) {
+                (!shellPart && part.sections.empty())) {
                 invalidKeywordLocation(
                     block,
-                    "A part closes only after node, element, and beam-section blocks.");
+                    "A part closes only after node, element, and matching section blocks.");
                 return;
             }
             currentPart_.reset();
@@ -647,9 +668,33 @@ private:
                     "BEAM GENERAL SECTION follows the part mesh and optional sets.");
                 return;
             }
+            if (modelElementFamily_ == ElementFamily::shell) {
+                inputFailure(
+                    "unsupported-mixed-element-model", block.location,
+                    block.canonicalName, "",
+                    "Beam-section semantics cannot be mixed with shell elements.");
+                return;
+            }
             parseBeamSection(block, part);
             partSectionsSeen_ = !failure_;
             beamSectionContextActive_ = !failure_;
+        } else if (block.canonicalName == "SHELL SECTION") {
+            beamSectionContextActive_ = false;
+            if (!partElementsSeen_) {
+                invalidKeywordLocation(
+                    block,
+                    "SHELL SECTION follows the part mesh and optional sets.");
+                return;
+            }
+            if (modelElementFamily_ == ElementFamily::beam) {
+                inputFailure(
+                    "unsupported-mixed-element-model", block.location,
+                    block.canonicalName, "",
+                    "Shell-section semantics cannot be mixed with beam elements.");
+                return;
+            }
+            parseShellSection(block, part);
+            partSectionsSeen_ = !failure_;
         } else if (block.canonicalName == "SECTION POINTS") {
             parseSectionPoints(block, part);
         } else if (block.canonicalName == "TRANSVERSE SHEAR STIFFNESS") {
@@ -726,42 +771,91 @@ private:
         if (type == nullptr) {
             return;
         }
-        if (!equalName(*type, "B33")) {
+        RawElement::Type elementType{};
+        ElementFamily elementFamily{};
+        std::size_t expectedFieldCount = 0U;
+        if (equalName(*type, "B33")) {
+            elementType = RawElement::Type::b33;
+            elementFamily = ElementFamily::beam;
+            expectedFieldCount = 3U;
+        } else if (equalName(*type, "S4")) {
+            elementType = RawElement::Type::s4;
+            elementFamily = ElementFamily::shell;
+            expectedFieldCount = 5U;
+        } else if (equalName(*type, "S4R")) {
+            elementType = RawElement::Type::s4r;
+            elementFamily = ElementFamily::shell;
+            expectedFieldCount = 5U;
+        } else {
             inputFailure(
                 "unsupported-element-formulation",
                 block.location,
                 block.canonicalName,
                 *type,
-                "Only TYPE=B33 maps to the V0 Euler beam.");
+                "Only TYPE=B33, TYPE=S4, and TYPE=S4R belong to the approved element subsets.");
             return;
         }
+        if (modelElementFamily_ && *modelElementFamily_ != elementFamily) {
+            inputFailure(
+                "unsupported-mixed-element-model",
+                block.location,
+                block.canonicalName,
+                *type,
+                "Beam and shell elements cannot be mixed in one model.");
+            return;
+        }
+        modelElementFamily_ = elementFamily;
         if (block.data.empty()) {
             inputFailure(
-                "invalid-data-arity", block.location, block.canonicalName,
-                "", "ELEMENT requires at least one three-field row.");
+                elementFamily == ElementFamily::shell
+                    ? "invalid-shell-connectivity"
+                    : "invalid-data-arity",
+                block.location, block.canonicalName, "",
+                "ELEMENT requires at least one row with the approved connectivity arity.");
             return;
         }
         for (const auto& row : block.data) {
-            if (row.fields.size() != 3U) {
+            if (row.fields.size() != expectedFieldCount) {
                 inputFailure(
-                    "invalid-data-arity", row.location, block.canonicalName,
-                    "", "B33 rows require label, node 1, node 2.");
+                    elementFamily == ElementFamily::shell
+                        ? "invalid-shell-connectivity"
+                        : "invalid-data-arity",
+                    row.location, block.canonicalName, "",
+                    elementFamily == ElementFamily::shell
+                        ? "S4 and S4R rows require a label and exactly four nodes."
+                        : "B33 rows require label, node 1, node 2.");
                 return;
             }
             RawElement element{};
             element.labelText = row.fields[0];
+            element.type = elementType;
             element.location = row.location;
             if (!parseInteger(
                     row.fields[0], element.label, row.location,
-                    block.canonicalName, true) ||
-                !parseInteger(
-                    row.fields[1], element.nodeLabels[0], row.location,
-                    block.canonicalName, true) ||
-                !parseInteger(
-                    row.fields[2], element.nodeLabels[1], row.location,
                     block.canonicalName, true)) {
                 return;
             }
+            element.nodeLabels.reserve(expectedFieldCount - 1U);
+            for (std::size_t field = 1U; field < expectedFieldCount; ++field) {
+                std::int64_t nodeLabel = 0;
+                if (!parseInteger(
+                        row.fields[field], nodeLabel, row.location,
+                        block.canonicalName, true)) {
+                    return;
+                }
+                element.nodeLabels.push_back(nodeLabel);
+            }
+            if (elementFamily == ElementFamily::shell) {
+                const std::set<std::int64_t> distinctNodes{
+                    element.nodeLabels.begin(), element.nodeLabels.end()};
+                if (distinctNodes.size() != element.nodeLabels.size()) {
+                    inputFailure(
+                        "invalid-shell-connectivity", row.location,
+                        block.canonicalName, element.labelText,
+                        "Shell connectivity requires four distinct source nodes.");
+                    return;
+                }
+            }
             if (std::any_of(
                     part.elements.begin(), part.elements.end(),
                     [&element](const RawElement& existing) {
@@ -777,6 +871,62 @@ private:
         }
     }
 
+    void parseShellSection(const KeywordBlock& block, RawPart& part) {
+        for (const auto& candidate : block.parameters) {
+            if (candidate.name != "ELSET" && candidate.name != "MATERIAL") {
+                inputFailure(
+                    "unsupported-shell-section-option", block.location,
+                    block.canonicalName, candidate.name,
+                    "The shell-section option is outside the centered single-layer subset.");
+                return;
+            }
+        }
+        if (!validateParameters(block, {"ELSET", "MATERIAL"})) {
+            return;
+        }
+        const auto* elementSet = requiredParameterValue(block, "ELSET");
+        const auto* material = requiredParameterValue(block, "MATERIAL");
+        if (elementSet == nullptr || material == nullptr) {
+            return;
+        }
+        if (block.data.size() != 1U || block.data[0].fields.empty() ||
+            block.data[0].fields.size() > 2U) {
+            inputFailure(
+                "unsupported-shell-section-option", block.location,
+                block.canonicalName, *elementSet,
+                "SHELL SECTION requires one thickness row with one optional integration-point field.");
+            return;
+        }
+        double thickness = 0.0;
+        if (!parseModelDouble(
+                block.data[0].fields[0], thickness,
+                block.data[0].location, block.canonicalName,
+                "invalid-shell-thickness",
+                "Shell thickness must be finite and positive.")) {
+            return;
+        }
+        if (!(thickness > 0.0)) {
+            modelFailure(
+                "invalid-shell-thickness", block.data[0].location,
+                block.canonicalName, *elementSet,
+                "Shell thickness must be finite and positive.");
+            return;
+        }
+        if (block.data[0].fields.size() == 2U) {
+            std::int64_t ignoredIntegrationPoints = 0;
+            if (!tryPositiveInteger(
+                    block.data[0].fields[1], ignoredIntegrationPoints)) {
+                inputFailure(
+                    "unsupported-shell-section-option", block.data[0].location,
+                    block.canonicalName, block.data[0].fields[1],
+                    "The optional shell integration-point field must be a positive integer.");
+                return;
+            }
+        }
+        part.shellSections.push_back(
+            {*elementSet, *material, thickness, block.location});
+    }
+
     bool parseSetMembers(
         const KeywordBlock& block,
         bool generate,
@@ -1208,12 +1358,16 @@ private:
         if (!parseModelDouble(
                 block.data[0].fields[0], material.youngsModulus,
                 block.data[0].location, block.canonicalName,
-                "invalid-beam-property",
+                modelElementFamily_ == ElementFamily::shell
+                    ? "invalid-shell-material"
+                    : "invalid-beam-property",
                 "Elastic material values must be finite.") ||
             !parseModelDouble(
                 block.data[0].fields[1], material.poissonRatio,
                 block.data[0].location, block.canonicalName,
-                "invalid-beam-property",
+                modelElementFamily_ == ElementFamily::shell
+                    ? "invalid-shell-material"
+                    : "invalid-beam-property",
                 "Elastic material values must be finite.")) {
             return;
         }
@@ -1346,10 +1500,17 @@ private:
                 return;
             }
             if (!equalName(*nlgeom->value, "NO")) {
-                modelFailure(
-                    "unsupported-nonlinear-geometry", block.location,
-                    block.canonicalName, *nlgeom->value,
-                    "Only absent NLGEOM or NLGEOM=NO is supported.");
+                if (modelElementFamily_ == ElementFamily::shell) {
+                    inputFailure(
+                        "unsupported-nonlinear-geometry", block.location,
+                        block.canonicalName, *nlgeom->value,
+                        "Only absent NLGEOM or NLGEOM=NO is supported.");
+                } else {
+                    modelFailure(
+                        "unsupported-nonlinear-geometry", block.location,
+                        block.canonicalName, *nlgeom->value,
+                        "Only absent NLGEOM or NLGEOM=NO is supported.");
+                }
                 return;
             }
         }
@@ -1517,6 +1678,14 @@ private:
     }
 
     void rejectUnknown(const KeywordBlock& block) {
+        if (block.canonicalName == "DLOAD" &&
+            modelElementFamily_ == ElementFamily::shell) {
+            inputFailure(
+                "unsupported-distributed-load", block.location,
+                block.canonicalName, "",
+                "Distributed, pressure, gravity, body, edge, and follower loads are unsupported.");
+            return;
+        }
         inputFailure(
             "unsupported-keyword", block.location,
             block.canonicalName, "",
@@ -1615,6 +1784,23 @@ private:
                     "A material must own exactly one ELASTIC row.");
                 return;
             }
+            if (modelElementFamily_ == ElementFamily::shell) {
+                if (!(material.youngsModulus > 0.0) ||
+                    !(material.poissonRatio > -1.0) ||
+                    !(material.poissonRatio < 0.5)) {
+                    modelFailure(
+                        "invalid-shell-material", material.elasticLocation,
+                        "ELASTIC", material.name,
+                        "Shell isotropic elasticity requires E>0 and -1<nu<0.5.");
+                    return;
+                }
+                definition_.materials.push_back({
+                    material.name,
+                    material.youngsModulus,
+                    material.poissonRatio,
+                    material.location});
+                continue;
+            }
             const double denominator = 2.0 * (1.0 + material.poissonRatio);
             const double shearModulus = material.youngsModulus / denominator;
             // The approved ledger deliberately validates derived G, not an
@@ -1637,14 +1823,16 @@ private:
 
     void finalizePartsAndSections() {
         partSectionAssignments_.resize(parts_.size());
+        partShellSectionAssignments_.resize(parts_.size());
+        const bool shellModel = modelElementFamily_ == ElementFamily::shell;
         for (std::size_t partIndex = 0U; partIndex < parts_.size(); ++partIndex) {
             const RawPart& part = parts_[partIndex];
             if (part.nodes.empty() || part.elements.empty() ||
-                part.sections.empty()) {
+                (!shellModel && part.sections.empty())) {
                 inputFailure(
                     "invalid-model-cardinality", part.location,
                     "PART", part.name,
-                    "A part requires nodes, B33 elements, and a beam section.");
+                    "A part requires nodes, elements, and its approved section form.");
                 return;
             }
 
@@ -1656,13 +1844,16 @@ private:
             }
             for (const auto& element : part.elements) {
                 partDefinition.elementSourceLabels.push_back(element.label);
-                if (findNode(part, element.nodeLabels[0]) == nullptr ||
-                    findNode(part, element.nodeLabels[1]) == nullptr) {
-                    inputFailure(
-                        "unresolved-reference", element.location,
-                        "ELEMENT", element.labelText,
-                        "Element connectivity must resolve within its part.");
-                    return;
+                for (const auto nodeLabel : element.nodeLabels) {
+                    if (findNode(part, nodeLabel) == nullptr) {
+                        inputFailure(
+                            shellModel
+                                ? "invalid-shell-connectivity"
+                                : "unresolved-reference",
+                            element.location, "ELEMENT", element.labelText,
+                            "Element connectivity must resolve within its part.");
+                        return;
+                    }
                 }
             }
             for (const auto& set : part.nodeSets) {
@@ -1691,6 +1882,52 @@ private:
             }
             definition_.parts.push_back(std::move(partDefinition));
 
+            if (shellModel) {
+                auto& assignments = partShellSectionAssignments_[partIndex];
+                for (const auto& section : part.shellSections) {
+                    const auto* elementSet = findSet(
+                        part.elementSets, section.elementSetName);
+                    const auto materialIndex = findMaterialIndex(section.materialName);
+                    if (elementSet == nullptr || !materialIndex) {
+                        inputFailure(
+                            "unresolved-shell-section", section.location,
+                            "SHELL SECTION", section.elementSetName,
+                            "Shell section ELSET and MATERIAL references must resolve.");
+                        return;
+                    }
+                    const EntityIndex sectionIndex =
+                        static_cast<EntityIndex>(definition_.shellSections.size());
+                    definition_.shellSections.push_back({
+                        section.elementSetName,
+                        section.thickness,
+                        *materialIndex,
+                        section.location});
+                    for (const auto elementLabel : elementSet->members) {
+                        if (!assignments.emplace(
+                                elementLabel,
+                                std::make_pair(
+                                    sectionIndex, *materialIndex)).second) {
+                            inputFailure(
+                                "invalid-shell-section-assignment",
+                                section.location, "SHELL SECTION",
+                                std::to_string(elementLabel),
+                                "A shell element cannot receive multiple section assignments.");
+                            return;
+                        }
+                    }
+                }
+                for (const auto& element : part.elements) {
+                    if (assignments.find(element.label) == assignments.end()) {
+                        inputFailure(
+                            "invalid-shell-section-assignment", element.location,
+                            "ELEMENT", element.labelText,
+                            "Every shell element requires exactly one resolved section assignment.");
+                        return;
+                    }
+                }
+                continue;
+            }
+
             auto& assignments = partSectionAssignments_[partIndex];
             for (const auto& section : part.sections) {
                 const auto* elementSet = findSet(
@@ -1873,44 +2110,92 @@ private:
                 instance.nodeMappings.push_back({rawNode.label, index});
             }
 
-            const auto& assignments =
-                partSectionAssignments_[partIndex(*part)];
             for (const auto& rawElement : part->elements) {
-                const auto first = nodeIndices.find(rawElement.nodeLabels[0]);
-                const auto second = nodeIndices.find(rawElement.nodeLabels[1]);
-                const auto assignment = assignments.find(rawElement.label);
-                if (first == nodeIndices.end() || second == nodeIndices.end() ||
-                    assignment == assignments.end()) {
-                    inputFailure(
-                        "unresolved-reference", rawElement.location,
-                        "ELEMENT", rawElement.labelText,
-                        "Expanded connectivity and section assignment must resolve.");
-                    return;
+                EntityIndex index = 0U;
+                if (rawElement.type == RawElement::Type::b33) {
+                    const auto first = nodeIndices.find(rawElement.nodeLabels[0]);
+                    const auto second = nodeIndices.find(rawElement.nodeLabels[1]);
+                    const auto& assignments =
+                        partSectionAssignments_[partIndex(*part)];
+                    const auto assignment = assignments.find(rawElement.label);
+                    if (first == nodeIndices.end() || second == nodeIndices.end() ||
+                        assignment == assignments.end()) {
+                        inputFailure(
+                            "unresolved-reference", rawElement.location,
+                            "ELEMENT", rawElement.labelText,
+                            "Expanded connectivity and section assignment must resolve.");
+                        return;
+                    }
+                    if (definition_.elements.size() >
+                        std::numeric_limits<EntityIndex>::max()) {
+                        inputFailure(
+                            "entity-index-overflow", rawElement.location,
+                            "ELEMENT", rawElement.labelText,
+                            "Expanded element count exceeds EntityIndex capacity.");
+                        return;
+                    }
+                    index = static_cast<EntityIndex>(definition_.elements.size());
+                    const auto& section =
+                        definition_.sections[assignment->second.first];
+                    if (!validateGeometry(
+                            rawElement,
+                            definition_.nodes[first->second],
+                            definition_.nodes[second->second],
+                            section)) {
+                        return;
+                    }
+                    definition_.elements.push_back({
+                        {rawInstance.name, rawElement.label, rawElement.labelText},
+                        {first->second, second->second},
+                        assignment->second.second,
+                        assignment->second.first,
+                        rawElement.location});
+                } else {
+                    std::array<EntityIndex, 4> connectedNodes{};
+                    for (std::size_t node = 0U;
+                         node < connectedNodes.size();
+                         ++node) {
+                        const auto found =
+                            nodeIndices.find(rawElement.nodeLabels[node]);
+                        if (found == nodeIndices.end()) {
+                            inputFailure(
+                                "invalid-shell-connectivity", rawElement.location,
+                                "ELEMENT", rawElement.labelText,
+                                "Expanded shell connectivity must resolve.");
+                            return;
+                        }
+                        connectedNodes[node] = found->second;
+                    }
+                    const auto& assignments =
+                        partShellSectionAssignments_[partIndex(*part)];
+                    const auto assignment = assignments.find(rawElement.label);
+                    if (assignment == assignments.end()) {
+                        inputFailure(
+                            "invalid-shell-section-assignment",
+                            rawElement.location, "ELEMENT", rawElement.labelText,
+                            "Expanded shell section assignment must resolve exactly once.");
+                        return;
+                    }
+                    if (definition_.shellElements.size() >
+                        std::numeric_limits<EntityIndex>::max()) {
+                        inputFailure(
+                            "entity-index-overflow", rawElement.location,
+                            "ELEMENT", rawElement.labelText,
+                            "Expanded shell element count exceeds EntityIndex capacity.");
+                        return;
+                    }
+                    index =
+                        static_cast<EntityIndex>(definition_.shellElements.size());
+                    definition_.shellElements.push_back({
+                        {rawInstance.name, rawElement.label, rawElement.labelText},
+                        rawElement.type == RawElement::Type::s4
+                            ? ShellSourceElementType::s4
+                            : ShellSourceElementType::s4r,
+                        connectedNodes,
+                        assignment->second.second,
+                        assignment->second.first,
+                        rawElement.location});
                 }
-                if (definition_.elements.size() >
-                    std::numeric_limits<EntityIndex>::max()) {
-                    inputFailure(
-                        "entity-index-overflow", rawElement.location,
-                        "ELEMENT", rawElement.labelText,
-                        "Expanded element count exceeds EntityIndex capacity.");
-                    return;
-                }
-                const EntityIndex index =
-                    static_cast<EntityIndex>(definition_.elements.size());
-                const auto& section = definition_.sections[assignment->second.first];
-                if (!validateGeometry(
-                        rawElement,
-                        definition_.nodes[first->second],
-                        definition_.nodes[second->second],
-                        section)) {
-                    return;
-                }
-                definition_.elements.push_back({
-                    {rawInstance.name, rawElement.label, rawElement.labelText},
-                    {first->second, second->second},
-                    assignment->second.second,
-                    assignment->second.first,
-                    rawElement.location});
                 elementIndices.emplace(rawElement.label, index);
                 instance.elementMappings.push_back({rawElement.label, index});
             }
@@ -2134,10 +2419,14 @@ private:
     std::vector<std::map<
         std::int64_t,
         std::pair<EntityIndex, EntityIndex>>> partSectionAssignments_;
+    std::vector<std::map<
+        std::int64_t,
+        std::pair<EntityIndex, EntityIndex>>> partShellSectionAssignments_;
 
     std::optional<std::size_t> currentPart_;
     std::optional<std::size_t> pendingSection_;
     std::optional<std::size_t> materialEligible_;
+    std::optional<ElementFamily> modelElementFamily_;
     bool headingSeen_{false};
     bool partElementsSeen_{false};
     bool partSetsSeen_{false};
diff --git a/tests/unit/io/abaqus/domain_mapper_test.cpp b/tests/unit/io/abaqus/domain_mapper_test.cpp
index 6c471ef..ca685f8 100644
--- a/tests/unit/io/abaqus/domain_mapper_test.cpp
+++ b/tests/unit/io/abaqus/domain_mapper_test.cpp
@@ -128,6 +128,55 @@ Tip, 2, -1.
 )inp";
 }
 
+std::string shellDeck() {
+    return R"inp(*Part, name=ShellPart
+*Node
+1, 0., 0., 0.
+2, 1., 0., 0.
+3, 1., 1., 0.
+4, 0., 1., 0.
+5, 2., 0., 0.
+6, 2., 1., 0.
+*Element, type=S4
+0010, 1, 2, 3, 4
+*Element, type=S4R
+0020, 2, 5, 6, 3
+*Elset, elset=ShellS4
+10
+*Elset, elset=ShellS4R
+20
+*Shell Section, elset=ShellS4, material=Steel
+0.1, 5
+*Shell Section, elset=ShellS4R, material=Aluminum
+0.2
+*End Part
+*Assembly, name=Assembly
+*Instance, name=First, part=ShellPart
+*End Instance
+*Instance, name=Second, part=ShellPart
+*End Instance
+*Nset, nset=RootFirst, instance=First
+1
+*Nset, nset=TipSecond, instance=Second
+6
+*End Assembly
+*Material, name=Steel
+*Elastic
+210000., 0.3
+*Material, name=Aluminum
+*Elastic
+70000., 0.25
+*Boundary
+RootFirst, 1, 6
+*Step, name=Load, nlgeom=NO
+*Static
+0.1, 1., 0.01, 1.
+*Cload
+TipSecond, 6, 1.
+*End Step
+)inp";
+}
+
 std::string supportedInventoryDeck(bool includeNoOps) {
     const std::string preprint = includeNoOps
         ? "*Preprint, echo=NO, model=NO, history=NO, contact=NO\n"
@@ -422,6 +471,188 @@ TEST(InpDomainMapping, NoOpAllowlistWarnsWithoutSemanticEffect) {
               plain.value().steps()[0].loads.size());
 }
 
+// MITC4-MAP-001
+TEST(InpDomainMapping, MapsS4AndS4rThroughOneMitc4Identity) {
+    auto result = mapText("mitc4-map-001", shellDeck());
+
+    ASSERT_TRUE(result.hasValue());
+    const fesa::Domain& domain = result.value();
+    EXPECT_TRUE(domain.elements().empty());
+    ASSERT_EQ(domain.shellElements().size(), 4U);
+    EXPECT_EQ(domain.shellElements()[0].sourceId.instanceName, "First");
+    EXPECT_EQ(domain.shellElements()[0].sourceId.sourceLabelText, "0010");
+    EXPECT_EQ(
+        domain.shellElements()[0].sourceType,
+        fesa::ShellSourceElementType::s4);
+    EXPECT_EQ(
+        domain.shellElements()[0].nodeIndices,
+        (std::array<fesa::EntityIndex, 4>{0U, 1U, 2U, 3U}));
+    EXPECT_EQ(domain.shellElements()[0].sectionIndex, 0U);
+    EXPECT_EQ(domain.shellElements()[0].materialIndex, 0U);
+
+    EXPECT_EQ(domain.shellElements()[1].sourceId.instanceName, "First");
+    EXPECT_EQ(
+        domain.shellElements()[1].sourceType,
+        fesa::ShellSourceElementType::s4r);
+    EXPECT_EQ(
+        domain.shellElements()[1].nodeIndices,
+        (std::array<fesa::EntityIndex, 4>{1U, 4U, 5U, 2U}));
+    EXPECT_EQ(domain.shellElements()[1].sectionIndex, 1U);
+    EXPECT_EQ(domain.shellElements()[1].materialIndex, 1U);
+
+    EXPECT_EQ(domain.shellElements()[2].sourceId.instanceName, "Second");
+    EXPECT_EQ(
+        domain.shellElements()[2].nodeIndices,
+        (std::array<fesa::EntityIndex, 4>{6U, 7U, 8U, 9U}));
+    EXPECT_EQ(domain.shellElements()[3].sourceId.instanceName, "Second");
+    EXPECT_EQ(
+        fesa::kMitc4InternalFormulation,
+        std::string_view{"FESA-MITC4"});
+
+    ASSERT_EQ(domain.shellSections().size(), 2U);
+    EXPECT_EQ(domain.shellSections()[0].name, "ShellS4");
+    EXPECT_DOUBLE_EQ(domain.shellSections()[0].thickness, 0.1);
+    EXPECT_EQ(domain.shellSections()[0].materialIndex, 0U);
+    EXPECT_EQ(domain.shellSections()[1].name, "ShellS4R");
+    EXPECT_DOUBLE_EQ(domain.shellSections()[1].thickness, 0.2);
+    EXPECT_EQ(domain.shellSections()[1].materialIndex, 1U);
+
+    ASSERT_EQ(domain.steps().size(), 1U);
+    ASSERT_EQ(domain.steps()[0].boundaries.size(), 1U);
+    EXPECT_EQ(domain.steps()[0].boundaries[0].lastDof, 6);
+    ASSERT_EQ(domain.steps()[0].loads.size(), 1U);
+    EXPECT_EQ(domain.steps()[0].loads[0].dof, 6);
+}
+
+// MITC4-MAP-002
+TEST(InpDomainMapping, RejectsInvalidShellAssignmentsAndProperties) {
+    struct InvalidCase {
+        std::string name;
+        std::string deck;
+        std::string expectedCode;
+        fesa::FailureCategory category;
+    };
+
+    const std::string base = shellDeck();
+    const std::vector<InvalidCase> cases{
+        {"unresolved-material",
+         replaceOnce(base, "material=Steel", "material=Missing"),
+         "unresolved-shell-section", fesa::FailureCategory::input},
+        {"unresolved-elset",
+         replaceOnce(base, "elset=ShellS4, material=Steel",
+                     "elset=Missing, material=Steel"),
+         "unresolved-shell-section", fesa::FailureCategory::input},
+        {"missing-assignment",
+         replaceOnce(
+             base,
+             "*Shell Section, elset=ShellS4R, material=Aluminum\n0.2\n",
+             ""),
+         "invalid-shell-section-assignment", fesa::FailureCategory::input},
+        {"conflicting-assignment",
+         replaceOnce(base, "elset=ShellS4R, material=Aluminum",
+                     "elset=ShellS4, material=Aluminum"),
+         "invalid-shell-section-assignment", fesa::FailureCategory::input},
+        {"invalid-thickness",
+         replaceOnce(base, "0.2\n*End Part", "0.\n*End Part"),
+         "invalid-shell-thickness", fesa::FailureCategory::model},
+        {"invalid-material",
+         replaceOnce(base, "70000., 0.25", "70000., 0.5"),
+         "invalid-shell-material", fesa::FailureCategory::model}};
+
+    for (const auto& testCase : cases) {
+        SCOPED_TRACE(testCase.name);
+        auto result = mapText("mitc4-map-002-" + testCase.name, testCase.deck);
+        ASSERT_FALSE(result.hasValue());
+        EXPECT_EQ(result.status().failureCategory(), testCase.category);
+        ASSERT_NE(findDiagnostic(result.status(), testCase.expectedCode), nullptr);
+    }
+}
+
+// MITC4-MAP-003
+TEST(InpDomainMapping, RejectsInvalidShellConnectivityOptionsAndMixedModels) {
+    struct InvalidCase {
+        std::string name;
+        std::string deck;
+        std::string expectedCode;
+    };
+
+    const std::string base = shellDeck();
+    const std::vector<InvalidCase> cases{
+        {"wrong-arity", replaceOnce(base, "0010, 1, 2, 3, 4", "0010, 1, 2, 3"),
+         "invalid-shell-connectivity"},
+        {"repeated-node", replaceOnce(base, "0010, 1, 2, 3, 4", "0010, 1, 2, 2, 4"),
+         "invalid-shell-connectivity"},
+        {"dangling-node", replaceOnce(base, "0010, 1, 2, 3, 4", "0010, 1, 2, 3, 99"),
+         "invalid-shell-connectivity"},
+        {"unsupported-section-option",
+         replaceOnce(base, "material=Steel\n0.1", "material=Steel, offset=0.1\n0.1"),
+         "unsupported-shell-section-option"},
+        {"unsupported-element",
+         replaceOnce(base, "type=S4R", "type=S8R"),
+         "unsupported-element-formulation"},
+        {"mixed-beam-shell",
+         replaceOnce(base,
+                     "0020, 2, 5, 6, 3\n*Elset",
+                     "0020, 2, 5, 6, 3\n*Element, type=B33\n30, 1, 2\n*Elset"),
+         "unsupported-mixed-element-model"}};
+
+    for (const auto& testCase : cases) {
+        SCOPED_TRACE(testCase.name);
+        auto result = mapText("mitc4-map-003-" + testCase.name, testCase.deck);
+        ASSERT_FALSE(result.hasValue());
+        EXPECT_EQ(
+            result.status().failureCategory(),
+            fesa::FailureCategory::input);
+        ASSERT_NE(findDiagnostic(result.status(), testCase.expectedCode), nullptr);
+    }
+}
+
+// MITC4-MAP-004
+TEST(InpDomainMapping, PreservesProcedureLoadAndOutputRequestBoundariesForShells) {
+    const std::string withNoOps = replaceOnce(
+        shellDeck(),
+        "*End Step\n",
+        "*Output, field\n*Node Output\nU, RF\n*Element Output\nS\n*End Step\n");
+    auto valid = mapText("mitc4-map-004-no-ops", withNoOps);
+    ASSERT_TRUE(valid.hasValue());
+    ASSERT_EQ(valid.value().warnings().size(), 3U);
+    EXPECT_EQ(valid.value().warnings()[0].keyword, "OUTPUT");
+    EXPECT_EQ(valid.value().warnings()[1].keyword, "NODE OUTPUT");
+    EXPECT_EQ(valid.value().warnings()[2].keyword, "ELEMENT OUTPUT");
+
+    struct InvalidCase {
+        std::string name;
+        std::string deck;
+        std::string expectedCode;
+    };
+    const std::string base = shellDeck();
+    const std::vector<InvalidCase> cases{
+        {"second-step",
+         base + "*Step\n*Static\n1., 1., 1., 1.\n*End Step\n",
+         "unsupported-multiple-step"},
+        {"nonlinear-step",
+         replaceOnce(base, "nlgeom=NO", "nlgeom=YES"),
+         "unsupported-nonlinear-geometry"},
+        {"other-procedure",
+         replaceOnce(base, "*Static\n0.1, 1., 0.01, 1.",
+                     "*Dynamic\n0.1, 1., 0.01, 1."),
+         "unsupported-keyword"},
+        {"distributed-load",
+         replaceOnce(base, "*Cload\nTipSecond, 6, 1.",
+                     "*Dload\nShellS4, P, 1."),
+         "unsupported-distributed-load"}};
+
+    for (const auto& testCase : cases) {
+        SCOPED_TRACE(testCase.name);
+        auto result = mapText("mitc4-map-004-" + testCase.name, testCase.deck);
+        ASSERT_FALSE(result.hasValue());
+        EXPECT_EQ(
+            result.status().failureCategory(),
+            fesa::FailureCategory::input);
+        ASSERT_NE(findDiagnostic(result.status(), testCase.expectedCode), nullptr);
+    }
+}
+
 TEST(InpDomainMapping, RejectsUnsupportedAndInvalidPortfolio) {
     struct InvalidCase {
         std::string name;