#include "io/abaqus/domain_mapping_context.h"

#include <algorithm>
#include <array>
#include <cerrno>
#include <charconv>
#include <cmath>
#include <cstdlib>
#include <limits>
#include <map>
#include <optional>
#include <set>
#include <string>
#include <string_view>
#include <system_error>
#include <tuple>
#include <utility>
#include <vector>

#include "fesa/analysis/thermal_time_grid.h"
#include "fesa/core/ascii.h"
#include "fesa/math/vector3.h"
#include "fesa/model/shell_geometry.h"
#include "fesa/model/source_target_resolver.h"

namespace fesa::abaqus_internal {
namespace {

std::vector<std::string> WithoutTrailingEmpty(std::vector<std::string> fields) {
  while (!fields.empty() && fields.back().empty()) {
    fields.pop_back();
  }
  return fields;
}

std::string CanonicalizeAscii(std::string value) {
  for (char& character : value) {
    if (character >= 'a' && character <= 'z') {
      character = static_cast<char>(character - 'a' + 'A');
    }
  }
  return value;
}

struct RawNode {
  std::int64_t label;
  std::string label_text;
  std::array<double, 3> coordinates;
  SourceLocation location;
};

struct RawElement {
  enum class Type { kB33, kS4, kS4r, kDs4, kC3d8 };

  std::int64_t label;
  std::string label_text;
  Type type;
  std::vector<std::int64_t> node_labels;
  SourceLocation location;
};

enum class ElementFamily { kBeam, kShell, kThermalShell, kSolid };

struct RawSet {
  std::string name;
  std::vector<std::int64_t> members;
  SourceLocation location;
};

struct RawSection {
  std::string element_set_name;
  std::string material_name;
  std::array<double, 5> properties;
  std::array<double, 3> first_axis;
  std::vector<std::array<double, 2>> section_points;
  SourceLocation location;
};

struct RawShellSection {
  std::string element_set_name;
  std::string material_name;
  double thickness;
  SourceLocation location;
};

struct RawSolidSection {
  std::string element_set_name;
  std::string material_name;
  SourceLocation location;
};

struct RawPart {
  std::string name;
  SourceLocation location;
  std::vector<RawNode> nodes;
  std::vector<RawElement> elements;
  std::vector<RawSet> node_sets;
  std::vector<RawSet> element_sets;
  std::vector<RawSection> sections;
  std::vector<RawShellSection> shell_sections;
  std::vector<RawSolidSection> solid_sections;
};

struct RawInstance {
  std::string name;
  std::string part_name;
  SourceLocation location;
};

struct RawAssemblySet {
  bool is_node_set;
  std::string name;
  std::string instance_name;
  std::vector<std::int64_t> members;
  SourceLocation location;
};

struct RawSurfaceMember {
  std::string target;
  ShellSurfaceSide side;
  SourceLocation location;
  std::size_t ordinal;
};

struct RawElementSurface {
  std::string name;
  SourceLocation location;
  std::size_t declaration_ordinal;
  std::vector<RawSurfaceMember> members;
};

struct RawSurfacePressureLoad {
  std::string surface_name;
  double magnitude;
  std::string magnitude_raw;
  SourceLocation keyword_location;
  SourceLocation data_location;
  std::size_t data_ordinal;
  std::size_t load_ordinal;
};

struct RawMaterial {
  std::string name;
  double youngs_modulus{0.0};
  double poisson_ratio{0.0};
  bool has_elastic{false};
  std::optional<double> density;
  std::optional<double> conductivity;
  std::optional<double> specific_heat;
  SourceLocation location;
  SourceLocation elastic_location;
  SourceLocation density_location;
};

struct RawThermalBoundary {
  std::string target;
  int dof;
  double value;
  SourceLocation location;
};

struct RawThermalInitial {
  std::string target;
  double value;
  SourceLocation location;
};

struct RawThermalFlux {
  std::string target;
  int dof;
  double power;
  SourceLocation location;
};

struct RawStep {
  SourceLocation location;
  std::string name_raw;
  std::string name_canonical;
  bool has_static{false};
  bool static_direct{false};
  std::uint32_t static_increment_count{0U};
  std::optional<DynamicStepDefinition> dynamic;
  bool perturbation_explicit{false};
  bool nlgeom_explicit{false};
  StaticProcedureKind procedure_kind{
      StaticProcedureKind::kLinearSmallDisplacement};
  bool nlgeom{false};
  std::uint32_t maximum_increments{0U};
  std::array<double, 4> static_values{};
  std::optional<FrequencyStepDefinition> frequency;
  bool has_heat_transfer{false};
  double thermal_increment{0.0};
  double thermal_period{0.0};
  std::vector<RawThermalBoundary> thermal_boundaries;
  std::vector<RawThermalFlux> thermal_fluxes;
  std::vector<PrescribedDisplacementDefinition> boundaries;
  std::vector<NodalLoad> loads;
  std::vector<RawSurfacePressureLoad> surface_pressure_loads;
  std::size_t next_load_ordinal{0U};
};

struct MappingFailure {
  FailureCategory category;
  Diagnostic diagnostic;
};

}  // namespace

/// @brief Builds one complete Domain candidate while retaining source identity.
/// @note The candidate is committed only after all blocks and cross-references
/// have been validated.
class DomainMappingContext::Impl {
 public:
  explicit Impl(const ParsedInput& input) : input_{input} {}

  Status ParseSyntax() {
    ParseBlocks();
    return CurrentStatus();
  }

  Status FinalizeMaterialProperties() {
    if (failure_) {
      return CurrentStatus();
    }
    ValidateCardinality();
    if (!failure_) {
      FinalizeMaterials();
    }
    if (!failure_) {
      FinalizePartsAndSections();
    }
    if (!failure_) {
      FinalizeDensities();
    }
    return CurrentStatus();
  }

  Status FinalizeTopology() {
    if (failure_) {
      return CurrentStatus();
    }
    ExpandInstances();
    if (!failure_ && !definition_.shell_elements.empty()) {
      auto geometry =
          PreprocessShellGeometry(definition_.nodes, definition_.shell_elements,
                                  definition_.shell_sections);
      if (!geometry.HasValue()) {
        const auto& status = geometry.GetStatus();
        failure_ =
            MappingFailure{status.Category().value_or(FailureCategory::kModel),
                           status.Diagnostics().front()};
      } else {
        definition_.shell_node_initial_frames =
            std::move(geometry.Value().nodal_frames);
      }
    }
    if (!failure_) {
      ExpandAssemblySets();
    }
    return CurrentStatus();
  }

  Status FinalizeElementSurfaces() {
    if (!failure_) {
      ResolveElementSurfaces();
    }
    return CurrentStatus();
  }

  Status FinalizeStepCandidate() {
    if (!failure_) {
      FinalizeStep();
    }
    return CurrentStatus();
  }

  Result<Domain> Commit() {
    if (failure_) {
      return Result<Domain>::Failure(Status::Failure(
          failure_->category, {std::move(failure_->diagnostic)}));
    }
    SortDiagnostics(definition_.warnings);
    return Domain::Create(std::move(definition_));
  }

  DomainMappingCandidateSummary CandidateSummary() const noexcept {
    DomainMappingCandidateSummary summary{};
    summary.part_count = parts_.size();
    summary.instance_count = instances_.size();
    summary.material_count = materials_.size();
    summary.model_boundary_count = model_boundaries_.size();
    summary.step_boundary_count = step_.boundaries.size();
    summary.step_load_count = step_.loads.size();
    summary.has_static_step = step_.has_static;
    for (const auto& part : parts_) {
      summary.node_count += part.nodes.size();
      summary.element_count += part.elements.size();
      summary.node_set_count += part.node_sets.size();
      summary.element_set_count += part.element_sets.size();
      summary.beam_section_count += part.sections.size();
      summary.shell_section_count += part.shell_sections.size();
    }
    for (const auto& set : assembly_sets_) {
      if (set.is_node_set) {
        ++summary.node_set_count;
      } else {
        ++summary.element_set_count;
      }
    }
    return summary;
  }

 private:
  Status CurrentStatus() const {
    if (!failure_) {
      return Status::Ok();
    }
    return Status::Failure(failure_->category, {failure_->diagnostic});
  }

  const KeywordParameter* Parameter(const KeywordBlock& block,
                                    std::string_view name) const {
    const auto found =
        std::find_if(block.parameters.begin(), block.parameters.end(),
                     [name](const KeywordParameter& candidate) {
                       return candidate.name == name;
                     });
    return found == block.parameters.end() ? nullptr : &*found;
  }

  bool Fail(FailureCategory category, std::string code,
            const SourceLocation& location, std::string keyword,
            std::string entity_identity, std::string message) {
    if (!failure_) {
      failure_ = MappingFailure{
          category,
          {Severity::kError, std::move(code), location, std::move(keyword),
           std::move(entity_identity), std::move(message)}};
    }
    return false;
  }

  bool InputFailure(std::string code, const SourceLocation& location,
                    std::string keyword, std::string entity_identity,
                    std::string message) {
    return Fail(FailureCategory::kInput, std::move(code), location,
                std::move(keyword), std::move(entity_identity),
                std::move(message));
  }

  bool ModelFailure(std::string code, const SourceLocation& location,
                    std::string keyword, std::string entity_identity,
                    std::string message) {
    return Fail(FailureCategory::kModel, std::move(code), location,
                std::move(keyword), std::move(entity_identity),
                std::move(message));
  }

  bool InvalidKeywordLocation(const KeywordBlock& block, std::string message) {
    return InputFailure("invalid-keyword-location", block.location,
                        block.canonical_name, "", std::move(message));
  }

  bool ValidateParameters(
      const KeywordBlock& block, const std::vector<std::string_view>& allowed,
      std::string_view unsupported_code = "invalid-keyword-parameter") {
    std::set<std::string> seen;
    for (const auto& candidate : block.parameters) {
      if (!seen.insert(candidate.name).second) {
        return InputFailure("duplicate-entity", block.location,
                            block.canonical_name, candidate.name,
                            "A keyword parameter may be declared only once.");
      }
      if (std::find(allowed.begin(), allowed.end(), candidate.name) ==
          allowed.end()) {
        return InputFailure(std::string{unsupported_code}, block.location,
                            block.canonical_name, candidate.name,
                            "The keyword parameter is outside the approved "
                            "subset.");
      }
    }
    return true;
  }

  const std::string* RequiredParameterValue(const KeywordBlock& block,
                                            std::string_view name) {
    const auto* found = Parameter(block, name);
    if (found == nullptr || !found->value || found->value->empty()) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, std::string{name},
                   "The keyword requires a non-empty parameter value.");
      return nullptr;
    }
    return &*found->value;
  }

  bool RequireNoData(const KeywordBlock& block) {
    if (!block.data.empty()) {
      return InputFailure("invalid-data-arity", block.data.front().location,
                          block.canonical_name, "",
                          "This keyword does not accept data rows.");
    }
    return true;
  }

  bool ParseInteger(const std::string& text, std::int64_t& value,
                    const SourceLocation& location, const std::string& keyword,
                    bool positive) {
    if (text.empty()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A numeric field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const long long parsed = std::strtoll(text.c_str(), &end, 10);
    if (errno == ERANGE || end != text.c_str() + text.size() ||
        (positive && parsed <= 0)) {
      return InputFailure(
          "invalid-numeric-value", location, keyword, text,
          "The field must be a valid positive base-10 integer.");
    }
    value = static_cast<std::int64_t>(parsed);
    return true;
  }

  bool ParseDouble(const std::string& text, double& value,
                   const SourceLocation& location, const std::string& keyword) {
    if (text.empty()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A numeric field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const double parsed = std::strtod(text.c_str(), &end);
    if (errno == ERANGE || end != text.c_str() + text.size() ||
        !std::isfinite(parsed)) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "The field must be a finite floating-point value.");
    }
    value = parsed;
    return true;
  }

  /// @brief Parses finite thermal decimal scalars without strtod underflow
  /// flags.
  /// @note from_chars preserves representable subnormals and rejects values
  /// outside binary64 range; structural scalar parsing remains unchanged.
  bool ParseThermalDouble(const std::string& text, double& value,
                          const SourceLocation& location,
                          const std::string& keyword) {
    if (text.empty() ||
        (text.front() == '+' &&
         (text.size() == 1U || text[1U] == '+' || text[1U] == '-'))) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A thermal scalar requires finite decimal syntax.");
    }
    const char* begin = text.data() + (text.front() == '+' ? 1U : 0U);
    const char* end = text.data() + text.size();
    const auto parsed =
        std::from_chars(begin, end, value, std::chars_format::general);
    if (parsed.ec != std::errc{} || parsed.ptr != end ||
        !std::isfinite(value)) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A thermal scalar must be representable and finite.");
    }
    return true;
  }

  bool ParseSurfacePressureDouble(const std::string& text, double& value,
                                  const SourceLocation& location,
                                  const std::string& keyword) {
    std::size_t cursor = 0U;
    if (cursor < text.size() && (text[cursor] == '+' || text[cursor] == '-')) {
      ++cursor;
    }
    const std::size_t integer_start = cursor;
    while (cursor < text.size() && text[cursor] >= '0' && text[cursor] <= '9') {
      ++cursor;
    }
    const bool has_integer_digits = cursor != integer_start;
    bool has_fraction_digits = false;
    if (cursor < text.size() && text[cursor] == '.') {
      ++cursor;
      const std::size_t fraction_start = cursor;
      while (cursor < text.size() && text[cursor] >= '0' &&
             text[cursor] <= '9') {
        ++cursor;
      }
      has_fraction_digits = cursor != fraction_start;
    }
    if (!has_integer_digits && !has_fraction_digits) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "Pressure values require C-locale decimal syntax.");
    }
    if (cursor < text.size() && (text[cursor] == 'E' || text[cursor] == 'e')) {
      ++cursor;
      if (cursor < text.size() &&
          (text[cursor] == '+' || text[cursor] == '-')) {
        ++cursor;
      }
      const std::size_t exponent_start = cursor;
      while (cursor < text.size() && text[cursor] >= '0' &&
             text[cursor] <= '9') {
        ++cursor;
      }
      if (cursor == exponent_start) {
        return InputFailure("invalid-numeric-value", location, keyword, text,
                            "Pressure exponents require one or more digits.");
      }
    }
    if (cursor != text.size()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "Pressure values require C-locale decimal syntax.");
    }
    const char* const begin = text.data();
    const char* const end = begin + text.size();
    const char* const numeric_begin = *begin == '+' ? begin + 1U : begin;
    const auto parsed =
        std::from_chars(numeric_begin, end, value, std::chars_format::general);
    if (parsed.ec != std::errc{} || parsed.ptr != end ||
        !std::isfinite(value)) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "Pressure values must be finite C-locale values.");
    }
    return true;
  }

  bool ParseNonlinearStaticDouble(const std::string& text, double& value,
                                  const SourceLocation& location,
                                  const std::string& keyword) {
    if (text.empty()) {
      return InputFailure("invalid-nonlinear-static-data", location, keyword,
                          text, "A nonlinear STATIC field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const double parsed = std::strtod(text.c_str(), &end);
    if (errno == ERANGE || end != text.c_str() + text.size() ||
        !std::isfinite(parsed)) {
      return InputFailure("invalid-nonlinear-static-data", location, keyword,
                          text,
                          "All four nonlinear STATIC fields must be finite.");
    }
    value = parsed;
    return true;
  }

  bool ParseDynamicDouble(const std::string& text, double& value,
                          const SourceLocation& location,
                          const std::string& keyword) {
    if (text.empty()) {
      return InputFailure("invalid-dynamic-data", location, keyword, text,
                          "Dynamic data fields cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const double parsed = std::strtod(text.c_str(), &end);
    if (errno == ERANGE || end != text.c_str() + text.size() ||
        !std::isfinite(parsed)) {
      return InputFailure("invalid-dynamic-data", location, keyword, text,
                          "Dynamic data fields must be finite.");
    }
    value = parsed;
    return true;
  }

  bool ParseModelDouble(const std::string& text, double& value,
                        const SourceLocation& location,
                        const std::string& keyword,
                        const std::string& diagnostic_code,
                        const std::string& message) {
    if (text.empty()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "A numeric field cannot be empty.");
    }
    char* end = nullptr;
    errno = 0;
    const double parsed = std::strtod(text.c_str(), &end);
    if (end != text.c_str() + text.size()) {
      return InputFailure("invalid-numeric-value", location, keyword, text,
                          "The field must use floating-point syntax.");
    }
    if (errno == ERANGE || !std::isfinite(parsed)) {
      return ModelFailure(diagnostic_code, location, keyword, text, message);
    }
    value = parsed;
    return true;
  }

  bool ContainsName(const std::vector<RawPart>& values,
                    const std::string& name) const {
    return std::any_of(values.begin(), values.end(),
                       [&name](const RawPart& value) {
                         return AsciiCaseInsensitiveEquals(value.name, name);
                       });
  }

  bool ContainsName(const std::vector<RawInstance>& values,
                    const std::string& name) const {
    return std::any_of(values.begin(), values.end(),
                       [&name](const RawInstance& value) {
                         return AsciiCaseInsensitiveEquals(value.name, name);
                       });
  }

  bool ContainsName(const std::vector<RawMaterial>& values,
                    const std::string& name) const {
    return std::any_of(values.begin(), values.end(),
                       [&name](const RawMaterial& value) {
                         return AsciiCaseInsensitiveEquals(value.name, name);
                       });
  }

  bool ContainsSetName(const std::vector<RawSet>& sets,
                       const std::string& name) const {
    const auto matches = [&name](const RawSet& set) {
      return AsciiCaseInsensitiveEquals(set.name, name);
    };
    return std::any_of(sets.begin(), sets.end(), matches);
  }

  bool ContainsAssemblySetName(bool node_set, const std::string& name) const {
    return std::any_of(assembly_sets_.begin(), assembly_sets_.end(),
                       [node_set, &name](const RawAssemblySet& set) {
                         return set.is_node_set == node_set &&
                                AsciiCaseInsensitiveEquals(set.name, name);
                       });
  }

  bool ContainsSurfaceName(const std::string& name) const {
    return std::any_of(element_surfaces_.begin(), element_surfaces_.end(),
                       [&name](const RawElementSurface& surface) {
                         return AsciiCaseInsensitiveEquals(surface.name, name);
                       });
  }

  bool IsPressureNameToken(const std::string_view text) const noexcept {
    if (text.empty() || text.size() > 80U) {
      return false;
    }
    const auto is_initial = [](const char value) {
      return (value >= 'A' && value <= 'Z') || (value >= 'a' && value <= 'z') ||
             value == '_';
    };
    const auto is_subsequent = [is_initial](const char value) {
      return is_initial(value) || (value >= '0' && value <= '9') ||
             value == '-' || value == '_';
    };
    return is_initial(text.front()) &&
           std::all_of(text.begin() + 1, text.end(), is_subsequent);
  }

  void ParseBlocks() {
    definition_.source_path = input_.source_path;
    definition_.source_content_identity = input_.source_content_identity;

    for (std::size_t index = 0U; index < input_.blocks.size() && !failure_;
         ++index) {
      const auto& block = input_.blocks[index];
      if (in_instance_) {
        ParseInstanceBlock(block);
      } else if (current_part_) {
        ParsePartBlock(block);
      } else if (in_assembly_) {
        ParseAssemblyBlock(block);
      } else if (in_step_) {
        ParseStepBlock(block);
      } else {
        ParseTopLevelBlock(block, index);
      }
    }

    if (!failure_ &&
        (current_part_ || in_assembly_ || in_instance_ || in_step_)) {
      const auto location = input_.blocks.empty()
                                ? SourceLocation{input_.source_path, 0U}
                                : input_.blocks.back().location;
      InputFailure("unclosed-keyword-block", location, "", "",
                   "A part, assembly, instance, or step block was not closed.");
    }
  }

  void ParseTopLevelBlock(const KeywordBlock& block, std::size_t index) {
    if (step_seen_) {
      if (block.canonical_name == "STEP") {
        ParseStepStart(block);
      } else {
        InvalidKeywordLocation(
            block, "The sole analysis step must be the final top-level block.");
      }
      return;
    }

    if (block.canonical_name != "ELASTIC" &&
        block.canonical_name != "DENSITY" &&
        block.canonical_name != "CONDUCTIVITY" &&
        block.canonical_name != "SPECIFIC HEAT") {
      material_eligible_.reset();
    }
    pending_section_.reset();
    active_output_ = false;

    if (block.canonical_name == "HEADING") {
      if (index != 0U || heading_seen_ || !ValidateParameters(block, {})) {
        if (!failure_) {
          InputFailure("invalid-keyword-location", block.location,
                       block.canonical_name, "",
                       "HEADING is optional only as the first keyword.");
        }
        return;
      }
      heading_seen_ = true;
      for (std::size_t row = 0U; row < block.data.size(); ++row) {
        if (row != 0U) {
          definition_.heading.push_back('\n');
        }
        for (std::size_t field = 0U; field < block.data[row].fields.size();
             ++field) {
          if (field != 0U) {
            definition_.heading.push_back(',');
          }
          definition_.heading += block.data[row].fields[field];
        }
      }
      return;
    }
    if (block.canonical_name == "PREPRINT") {
      if (!RequireNoData(block)) {
        return;
      }
      AddIgnoredWarning(block);
      return;
    }
    if (block.canonical_name == "PHYSICAL CONSTANTS") {
      if (!ValidateParameters(block, {"ABSOLUTE ZERO"}) ||
          !RequireNoData(block))
        return;
      const auto* absolute_zero =
          RequiredParameterValue(block, "ABSOLUTE ZERO");
      if (absolute_zero == nullptr) return;
      double value = 0.0;
      if (ParseThermalDouble(*absolute_zero, value, block.location,
                             block.canonical_name)) {
        if (!physical_constants_location_)
          physical_constants_location_ = block.location;
        AddIgnoredWarning(block);
      }
      return;
    }
    if (block.canonical_name == "PART") {
      ParsePartStart(block);
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      ParseAssemblyStart(block);
      return;
    }
    if (block.canonical_name == "AMPLITUDE") {
      ParseAmplitude(block);
      return;
    }
    if (block.canonical_name == "MATERIAL") {
      ParseMaterial(block);
      return;
    }
    if (block.canonical_name == "ELASTIC") {
      ParseElastic(block);
      return;
    }
    if (block.canonical_name == "DENSITY") {
      if (!material_eligible_) {
        RejectUnknown(block);
        return;
      }
      ParseDensity(block);
      return;
    }
    if (block.canonical_name == "CONDUCTIVITY") {
      ParseThermalProperty(block, true);
      return;
    }
    if (block.canonical_name == "SPECIFIC HEAT") {
      ParseThermalProperty(block, false);
      return;
    }
    if (block.canonical_name == "INITIAL CONDITIONS") {
      ParseInitialConditions(block);
      return;
    }
    if (block.canonical_name == "BOUNDARY") {
      if (!assembly_seen_ || materials_.empty()) {
        InvalidKeywordLocation(
            block, "Model boundary data follows the assembly and materials.");
        return;
      }
      model_boundary_seen_ = true;
      if (model_element_family_ == ElementFamily::kThermalShell) {
        ParseThermalBoundary(block, thermal_model_boundaries_);
      } else {
        ParseBoundary(block, model_boundaries_);
      }
      return;
    }
    if (block.canonical_name == "STEP") {
      ParseStepStart(block);
      return;
    }
    if (block.canonical_name == "END PART" ||
        block.canonical_name == "END ASSEMBLY" ||
        block.canonical_name == "END INSTANCE" ||
        block.canonical_name == "END STEP") {
      InputFailure("invalid-keyword-location", block.location,
                   block.canonical_name, "",
                   "The closing keyword has no matching open block.");
      return;
    }
    RejectUnknown(block);
  }

  void ParsePartStart(const KeywordBlock& block) {
    if (assembly_seen_ || !materials_.empty() || model_boundary_seen_) {
      InvalidKeywordLocation(
          block, "All part blocks must precede the sole assembly block.");
      return;
    }
    if (!ValidateParameters(block, {"NAME"}) || !RequireNoData(block)) {
      return;
    }
    const auto* name = RequiredParameterValue(block, "NAME");
    if (name == nullptr) {
      return;
    }
    if (ContainsName(parts_, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Part names are unique under case-insensitive lookup.");
      return;
    }
    parts_.push_back({*name, block.location, {}, {}, {}, {}, {}, {}});
    current_part_ = parts_.size() - 1U;
    part_elements_seen_ = false;
    part_sets_seen_ = false;
    part_sections_seen_ = false;
    beam_section_context_active_ = false;
  }

  void ParsePartBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END PART") {
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      const RawPart& part = parts_[*current_part_];
      const bool shell_part =
          model_element_family_ == ElementFamily::kShell ||
          model_element_family_ == ElementFamily::kThermalShell;
      if (part.nodes.empty() || part.elements.empty() ||
          (!shell_part && model_element_family_ != ElementFamily::kSolid &&
           part.sections.empty())) {
        InvalidKeywordLocation(block,
                               "A part closes only after node, element, "
                               "and matching section blocks.");
        return;
      }
      current_part_.reset();
      pending_section_.reset();
      beam_section_context_active_ = false;
      return;
    }
    if (block.canonical_name == "PART") {
      InputFailure("invalid-keyword-location", block.location,
                   block.canonical_name, "",
                   "Nested part blocks are not supported.");
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "An assembly cannot be nested in a part.");
      return;
    }

    RawPart& part = parts_[*current_part_];
    if (block.canonical_name == "NODE") {
      beam_section_context_active_ = false;
      if (part_elements_seen_ || part_sets_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(
            block,
            "NODE blocks must precede element, set, and section blocks.");
        return;
      }
      pending_section_.reset();
      ParseNodes(block, part);
    } else if (block.canonical_name == "ELEMENT") {
      beam_section_context_active_ = false;
      if (part.nodes.empty() || part_sets_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(block,
                               "ELEMENT blocks follow at least one NODE block "
                               "and precede sets and sections.");
        return;
      }
      pending_section_.reset();
      ParseElements(block, part);
      part_elements_seen_ = !failure_;
    } else if (block.canonical_name == "NSET") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(
            block,
            "Part sets follow element blocks and precede beam sections.");
        return;
      }
      pending_section_.reset();
      ParseSet(block, true, part);
      part_sets_seen_ = !failure_;
    } else if (block.canonical_name == "ELSET") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_ || part_sections_seen_) {
        InvalidKeywordLocation(
            block,
            "Part sets follow element blocks and precede beam sections.");
        return;
      }
      pending_section_.reset();
      ParseSet(block, false, part);
      part_sets_seen_ = !failure_;
    } else if (block.canonical_name == "BEAM GENERAL SECTION") {
      if (!part_elements_seen_) {
        InvalidKeywordLocation(
            block,
            "BEAM GENERAL SECTION follows the part mesh and optional sets.");
        return;
      }
      if (model_element_family_ == ElementFamily::kShell ||
          model_element_family_ == ElementFamily::kThermalShell ||
          model_element_family_ == ElementFamily::kSolid) {
        InputFailure(
            "unsupported-mixed-element-model", block.location,
            block.canonical_name, "",
            "Beam-section semantics cannot be mixed with shell elements.");
        return;
      }
      ParseBeamSection(block, part);
      part_sections_seen_ = !failure_;
      beam_section_context_active_ = !failure_;
    } else if (block.canonical_name == "SHELL SECTION") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_) {
        InvalidKeywordLocation(
            block, "SHELL SECTION follows the part mesh and optional sets.");
        return;
      }
      if (model_element_family_ == ElementFamily::kBeam ||
          model_element_family_ == ElementFamily::kSolid) {
        InputFailure(
            "unsupported-mixed-element-model", block.location,
            block.canonical_name, "",
            "Shell-section semantics cannot be mixed with beam elements.");
        return;
      }
      ParseShellSection(block, part);
      part_sections_seen_ = !failure_;
    } else if (block.canonical_name == "SOLID SECTION") {
      beam_section_context_active_ = false;
      if (!part_elements_seen_ ||
          model_element_family_ != ElementFamily::kSolid) {
        InputFailure("invalid-solid-section", block.location,
                     block.canonical_name, "",
                     "SOLID SECTION requires an exclusive C3D8 mesh.");
        return;
      }
      ParseSolidSection(block, part);
      part_sections_seen_ = !failure_;
    } else if (block.canonical_name == "SECTION POINTS") {
      ParseSectionPoints(block, part);
    } else if (block.canonical_name == "TRANSVERSE SHEAR STIFFNESS") {
      pending_section_.reset();
      if (!beam_section_context_active_) {
        InputFailure(
            "invalid-keyword-location", block.location, block.canonical_name,
            "",
            "The ignored shear keyword still requires beam-section context.");
        return;
      }
      AddIgnoredWarning(block);
    } else if (block.canonical_name == "SURFACE") {
      InputFailure("unsupported-surface-scope", block.location,
                   block.canonical_name, "",
                   "Pressure surfaces are supported only at assembly scope.");
    } else {
      pending_section_.reset();
      beam_section_context_active_ = false;
      RejectUnknown(block);
    }
  }

  void ParseNodes(const KeywordBlock& block, RawPart& part) {
    if (!ValidateParameters(block, {}) || block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "NODE requires at least one four-field data row.");
      }
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 4U) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "NODE rows require label, x, y, z.");
        return;
      }
      RawNode node{};
      node.label_text = row.fields[0];
      node.location = row.location;
      if (!ParseInteger(row.fields[0], node.label, row.location,
                        block.canonical_name, true)) {
        return;
      }
      if (std::any_of(part.nodes.begin(), part.nodes.end(),
                      [&node](const RawNode& existing) {
                        return existing.label == node.label;
                      })) {
        InputFailure("duplicate-entity", row.location, block.canonical_name,
                     node.label_text, "Node labels are unique within a part.");
        return;
      }
      for (std::size_t coordinate = 0U; coordinate < 3U; ++coordinate) {
        if (!ParseDouble(row.fields[coordinate + 1U],
                         node.coordinates[coordinate], row.location,
                         block.canonical_name)) {
          return;
        }
      }
      part.nodes.push_back(std::move(node));
    }
  }

  void ParseElements(const KeywordBlock& block, RawPart& part) {
    const auto* type_parameter = Parameter(block, "TYPE");
    const bool thermal_block =
        type_parameter && type_parameter->value &&
        AsciiCaseInsensitiveEquals(*type_parameter->value, "DS4");
    if (!ValidateParameters(
            block, (thermal_block || (type_parameter && type_parameter->value &&
                                      AsciiCaseInsensitiveEquals(
                                          *type_parameter->value, "C3D8")))
                       ? std::vector<std::string_view>{"TYPE", "ELSET"}
                       : std::vector<std::string_view>{"TYPE"})) {
      return;
    }
    const auto* type = RequiredParameterValue(block, "TYPE");
    if (type == nullptr) {
      return;
    }
    RawElement::Type element_type{};
    ElementFamily element_family{};
    std::size_t expected_field_count = 0U;
    if (AsciiCaseInsensitiveEquals(*type, "B33")) {
      element_type = RawElement::Type::kB33;
      element_family = ElementFamily::kBeam;
      expected_field_count = 3U;
    } else if (AsciiCaseInsensitiveEquals(*type, "S4")) {
      element_type = RawElement::Type::kS4;
      element_family = ElementFamily::kShell;
      expected_field_count = 5U;
    } else if (AsciiCaseInsensitiveEquals(*type, "S4R")) {
      element_type = RawElement::Type::kS4r;
      element_family = ElementFamily::kShell;
      expected_field_count = 5U;
    } else if (AsciiCaseInsensitiveEquals(*type, "C3D8")) {
      element_type = RawElement::Type::kC3d8;
      element_family = ElementFamily::kSolid;
      expected_field_count = 9U;
    } else if (AsciiCaseInsensitiveEquals(*type, "DS4")) {
      element_type = RawElement::Type::kDs4;
      element_family = ElementFamily::kThermalShell;
      expected_field_count = 5U;
    } else {
      InputFailure("unsupported-element-formulation", block.location,
                   block.canonical_name, *type,
                   "Only B33, S4, S4R, DS4, and C3D8 belong to "
                   "the approved "
                   "element subsets.");
      return;
    }
    if (model_element_family_ && *model_element_family_ != element_family) {
      InputFailure(
          "unsupported-mixed-element-model", block.location,
          block.canonical_name, *type,
          "Beam, Shell, thermal, and Solid families cannot mix in one model.");
      return;
    }
    model_element_family_ = element_family;
    std::optional<RawSet> inline_set;
    if (Parameter(block, "ELSET")) {
      const auto* name = RequiredParameterValue(block, "ELSET");
      if (name == nullptr) return;
      if (ContainsSetName(part.element_sets, *name)) {
        InputFailure("duplicate-entity", block.location, block.canonical_name,
                     *name, "Element-set names are unique within their part.");
        return;
      }
      inline_set = RawSet{*name, {}, block.location};
    }
    if (block.data.empty()) {
      InputFailure(element_family == ElementFamily::kSolid
                       ? "invalid-solid-connectivity"
                       : (element_family == ElementFamily::kShell
                              ? "invalid-shell-connectivity"
                              : "invalid-data-arity"),
                   block.location, block.canonical_name, "",
                   "ELEMENT requires at least one row with the approved "
                   "connectivity arity.");
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != expected_field_count) {
        InputFailure(
            element_family == ElementFamily::kSolid
                ? "invalid-solid-connectivity"
                : (element_family == ElementFamily::kShell
                       ? "invalid-shell-connectivity"
                       : "invalid-data-arity"),
            row.location, block.canonical_name, "",
            element_family == ElementFamily::kShell
                ? "S4 and S4R rows require a label and exactly four nodes."
                : "B33 rows require label, node 1, node 2.");
        return;
      }
      RawElement element{};
      element.label_text = row.fields[0];
      element.type = element_type;
      element.location = row.location;
      if (!ParseInteger(row.fields[0], element.label, row.location,
                        block.canonical_name, true)) {
        return;
      }
      element.node_labels.reserve(expected_field_count - 1U);
      for (std::size_t field = 1U; field < expected_field_count; ++field) {
        std::int64_t node_label = 0;
        if (!ParseInteger(row.fields[field], node_label, row.location,
                          block.canonical_name, true)) {
          return;
        }
        element.node_labels.push_back(node_label);
      }
      if (element_family != ElementFamily::kBeam) {
        const std::set<std::int64_t> distinct_nodes{element.node_labels.begin(),
                                                    element.node_labels.end()};
        if (distinct_nodes.size() != element.node_labels.size()) {
          InputFailure(element_family == ElementFamily::kSolid
                           ? "invalid-solid-connectivity"
                           : "invalid-shell-connectivity",
                       row.location, block.canonical_name, element.label_text,
                       "Connectivity requires the specified number of distinct "
                       "source nodes.");
          return;
        }
      }
      if (std::any_of(part.elements.begin(), part.elements.end(),
                      [&element](const RawElement& existing) {
                        return existing.label == element.label;
                      })) {
        InputFailure("duplicate-entity", row.location, block.canonical_name,
                     element.label_text,
                     "Element labels are unique within a part.");
        return;
      }
      if (inline_set) inline_set->members.push_back(element.label);
      part.elements.push_back(std::move(element));
    }
    // Inline membership follows the block's source rows and uses the same
    // part-set namespace and section resolution as an explicit ELSET.
    if (inline_set) part.element_sets.push_back(std::move(*inline_set));
  }

  /// @brief Parses material-only Solid assignment without thickness defaults.
  void ParseSolidSection(const KeywordBlock& block, RawPart& part) {
    if (!ValidateParameters(block, {"ELSET", "MATERIAL"})) return;
    const auto* elset = RequiredParameterValue(block, "ELSET");
    const auto* material = RequiredParameterValue(block, "MATERIAL");
    if (!elset || !material) return;
    if (block.data.size() > 1U ||
        (!block.data.empty() &&
         std::any_of(block.data[0].fields.begin(), block.data[0].fields.end(),
                     [](const auto& field) { return !field.empty(); }))) {
      InputFailure("invalid-solid-section", block.location,
                   block.canonical_name, *elset,
                   "SOLID SECTION permits omitted or blank data only.");
      return;
    }
    part.solid_sections.push_back({*elset, *material, block.location});
  }

  /// @brief Validates and owns one model-level supported load amplitude.
  void ParseAmplitude(const KeywordBlock& block) {
    const bool dynamic_source = std::any_of(
        input_.blocks.begin(), input_.blocks.end(), [](const auto& candidate) {
          return candidate.canonical_name == "DYNAMIC";
        });
    if (model_element_family_ != ElementFamily::kSolid || !dynamic_source) {
      InputFailure("unsupported-load-amplitude", block.location,
                   block.canonical_name, "",
                   "Amplitude is supported only in Solid dynamic models.");
      return;
    }
    if (!ValidateParameters(block, {"NAME", "DEFINITION", "TIME", "VALUE"}))
      return;
    const auto* name = RequiredParameterValue(block, "NAME");
    if (!name) return;
    for (const auto& option :
         std::array<std::pair<const char*, const char*>, 3>{
             {{"DEFINITION", "TABULAR"},
              {"TIME", "STEP TIME"},
              {"VALUE", "RELATIVE"}}}) {
      const auto* parameter = Parameter(block, option.first);
      if (parameter &&
          (!parameter->value ||
           !AsciiCaseInsensitiveEquals(*parameter->value, option.second))) {
        InputFailure("unsupported-amplitude-option", block.location,
                     block.canonical_name, option.first,
                     "Only TABULAR STEP TIME RELATIVE amplitude is supported.");
        return;
      }
    }
    const std::string canonical = CanonicalizeAscii(*name);
    if (std::any_of(definition_.amplitudes.begin(),
                    definition_.amplitudes.end(), [&canonical](const auto& a) {
                      return a.name_canonical == canonical;
                    })) {
      InputFailure("duplicate-amplitude", block.location, block.canonical_name,
                   *name,
                   "Amplitude names must be unique ignoring ASCII case.");
      return;
    }
    TabularAmplitudeDefinition amplitude{*name, canonical, block.location, {}};
    for (const auto& row : block.data) {
      if (row.fields.empty() || row.fields.size() % 2U != 0U) {
        InputFailure("invalid-amplitude-data", row.location,
                     block.canonical_name, *name,
                     "Amplitude rows require complete time/value pairs.");
        return;
      }
      for (std::size_t field = 0U; field < row.fields.size(); field += 2U) {
        double time = 0.0;
        double value = 0.0;
        if (!ParseDouble(row.fields[field], time, row.location,
                         block.canonical_name) ||
            !ParseDouble(row.fields[field + 1U], value, row.location,
                         block.canonical_name))
          return;
        if (time < 0.0 || (!amplitude.points.empty() &&
                           !(time > amplitude.points.back()[0]))) {
          InputFailure(
              "invalid-amplitude-data", row.location, block.canonical_name,
              *name,
              "Amplitude times must be nonnegative and strictly increasing.");
          return;
        }
        amplitude.points.push_back({time, value});
      }
    }
    if (amplitude.points.empty()) {
      InputFailure("invalid-amplitude-data", block.location,
                   block.canonical_name, *name,
                   "Amplitude requires at least one finite time/value pair.");
      return;
    }
    definition_.amplitudes.push_back(std::move(amplitude));
  }

  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.canonical_name, candidate.name,
                     "The shell-section option is outside the centered "
                     "single-layer subset.");
        return;
      }
    }
    if (!ValidateParameters(block, {"ELSET", "MATERIAL"})) {
      return;
    }
    const auto* element_set = RequiredParameterValue(block, "ELSET");
    const auto* material = RequiredParameterValue(block, "MATERIAL");
    if (element_set == 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.canonical_name, *element_set,
                   "SHELL SECTION requires one thickness row with one optional "
                   "integration-point field.");
      return;
    }
    double thickness = 0.0;
    const bool parsed_thickness =
        model_element_family_ == ElementFamily::kThermalShell
            ? ParseThermalDouble(block.data[0].fields[0], thickness,
                                 block.data[0].location, block.canonical_name)
            : ParseModelDouble(block.data[0].fields[0], thickness,
                               block.data[0].location, block.canonical_name,
                               "invalid-shell-thickness",
                               "Shell thickness must be finite and positive.");
    if (!parsed_thickness) {
      return;
    }
    if (!(thickness > 0.0)) {
      ModelFailure("invalid-shell-thickness", block.data[0].location,
                   block.canonical_name, *element_set,
                   "Shell thickness must be finite and positive.");
      return;
    }
    if (block.data[0].fields.size() == 2U) {
      const auto integration_points =
          ParsePositiveSourceLabel(block.data[0].fields[1]);
      if (!integration_points.HasValue()) {
        InputFailure("unsupported-shell-section-option", block.data[0].location,
                     block.canonical_name, block.data[0].fields[1],
                     "The optional shell integration-point field must be a "
                     "positive integer.");
        return;
      }
      if (model_element_family_ == ElementFamily::kThermalShell &&
          integration_points.Value() != 5) {
        InputFailure(
            "unsupported-shell-section-option", block.data[0].location,
            block.canonical_name, block.data[0].fields[1],
            "Thermal DS4 sections require exactly five integration points.");
        return;
      }
    }
    part.shell_sections.push_back(
        {*element_set, *material, thickness, block.location});
  }

  bool ParseSetMembers(const KeywordBlock& block, bool generate,
                       std::vector<std::int64_t>& members) {
    if (block.data.empty()) {
      return InputFailure("invalid-data-arity", block.location,
                          block.canonical_name, "",
                          "A set requires at least one member row.");
    }
    for (const auto& data : block.data) {
      auto fields = WithoutTrailingEmpty(data.fields);
      if (generate) {
        if (fields.size() != 3U) {
          return InputFailure("invalid-data-arity", data.location,
                              block.canonical_name, "",
                              "GENERATE rows require first, last, increment.");
        }
        std::int64_t first = 0;
        std::int64_t last = 0;
        std::int64_t increment = 0;
        if (!ParseInteger(fields[0], first, data.location, block.canonical_name,
                          true) ||
            !ParseInteger(fields[1], last, data.location, block.canonical_name,
                          true)) {
          return false;
        }
        if (!ParseInteger(fields[2], increment, data.location,
                          block.canonical_name, false) ||
            increment <= 0 || first > last || (last - first) % increment != 0) {
          return InputFailure("invalid-set-range", data.location,
                              block.canonical_name, "",
                              "GENERATE requires an inclusive range reached by "
                              "a positive increment.");
        }
        for (std::int64_t label = first; label <= last;) {
          members.push_back(label);
          if (label > last - increment) {
            break;
          }
          label += increment;
        }
      } else {
        if (fields.empty() || std::any_of(fields.begin(), fields.end(),
                                          [](const std::string& field) {
                                            return field.empty();
                                          })) {
          return InputFailure(
              "invalid-data-arity", data.location, block.canonical_name, "",
              "Explicit set rows require non-empty member labels.");
        }
        for (const auto& field : fields) {
          std::int64_t label = 0;
          if (!ParseInteger(field, label, data.location, block.canonical_name,
                            true)) {
            return false;
          }
          members.push_back(label);
        }
      }
    }
    std::set<std::int64_t> unique;
    if (model_element_family_ == ElementFamily::kThermalShell) {
      // Thermal sets expand each source member once, in first-seen order.
      members.erase(std::remove_if(members.begin(), members.end(),
                                   [&unique](const auto member) {
                                     return !unique.insert(member).second;
                                   }),
                    members.end());
      return true;
    }
    for (const auto member : members) {
      if (!unique.insert(member).second) {
        return InputFailure("duplicate-entity", block.location,
                            block.canonical_name, std::to_string(member),
                            "A set cannot repeat the same source member.");
      }
    }
    return true;
  }

  void ParseSet(const KeywordBlock& block, bool node_set, RawPart& part) {
    const std::string_view name_parameter = node_set ? "NSET" : "ELSET";
    if (!ValidateParameters(block, {name_parameter, "GENERATE"})) {
      return;
    }
    const auto* name = RequiredParameterValue(block, name_parameter);
    if (name == nullptr) {
      return;
    }
    const auto* generate_parameter = Parameter(block, "GENERATE");
    if (generate_parameter != nullptr && generate_parameter->value) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "GENERATE",
                   "GENERATE is a valueless flag.");
      return;
    }
    const auto& sets = node_set ? part.node_sets : part.element_sets;
    if (ContainsSetName(sets, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Set names are unique within their node-set or element-set "
                   "namespace.");
      return;
    }
    RawSet set{*name, {}, block.location};
    if (!ParseSetMembers(block, generate_parameter != nullptr, set.members)) {
      return;
    }
    if (node_set) {
      part.node_sets.push_back(std::move(set));
    } else {
      part.element_sets.push_back(std::move(set));
    }
  }

  void ParseBeamSection(const KeywordBlock& block, RawPart& part) {
    pending_section_.reset();
    if (!ValidateParameters(block, {"ELSET", "MATERIAL", "SECTION"})) {
      return;
    }
    const auto* element_set = RequiredParameterValue(block, "ELSET");
    const auto* material = RequiredParameterValue(block, "MATERIAL");
    const auto* section = RequiredParameterValue(block, "SECTION");
    if (element_set == nullptr || material == nullptr || section == nullptr) {
      return;
    }
    if (!AsciiCaseInsensitiveEquals(*section, "GENERAL")) {
      InputFailure("unsupported-section-formulation", block.location,
                   block.canonical_name, *section,
                   "Only SECTION=GENERAL belongs to the approved subset.");
      return;
    }
    if (std::any_of(part.sections.begin(), part.sections.end(),
                    [element_set](const RawSection& existing) {
                      return AsciiCaseInsensitiveEquals(
                          existing.element_set_name, *element_set);
                    })) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *element_set,
                   "An element set can receive only one beam section.");
      return;
    }
    if (block.data.size() != 2U || block.data[0].fields.size() != 5U ||
        block.data[1].fields.size() != 3U) {
      InputFailure("invalid-data-arity", block.location, block.canonical_name,
                   *element_set,
                   "A general section requires one five-field property row and "
                   "one three-field axis row.");
      return;
    }
    RawSection raw{*element_set, *material, {}, {}, {}, block.location};
    for (std::size_t property = 0U; property < 5U; ++property) {
      if (!ParseModelDouble(block.data[0].fields[property],
                            raw.properties[property], block.data[0].location,
                            block.canonical_name, "invalid-beam-property",
                            "Beam section properties must be finite.")) {
        return;
      }
    }
    for (std::size_t coordinate = 0U; coordinate < 3U; ++coordinate) {
      if (!ParseModelDouble(block.data[1].fields[coordinate],
                            raw.first_axis[coordinate], block.data[1].location,
                            block.canonical_name, "invalid-beam-guide-vector",
                            "The beam guide vector must be finite.")) {
        return;
      }
    }
    part.sections.push_back(std::move(raw));
    pending_section_ = part.sections.size() - 1U;
  }

  void ParseSectionPoints(const KeywordBlock& block, RawPart& part) {
    if (!pending_section_ || !ValidateParameters(block, {}) ||
        block.data.empty()) {
      if (!failure_) {
        InputFailure(
            "invalid-keyword-location", block.location, block.canonical_name,
            "", "SECTION POINTS must immediately follow a general section.");
      }
      return;
    }
    RawSection& section = part.sections[*pending_section_];
    for (const auto& row : block.data) {
      if (row.fields.size() != 2U) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     section.element_set_name,
                     "Section-point rows require x1 and x2.");
        return;
      }
      std::array<double, 2> point{};
      if (!ParseDouble(row.fields[0], point[0], row.location,
                       block.canonical_name) ||
          !ParseDouble(row.fields[1], point[1], row.location,
                       block.canonical_name)) {
        return;
      }
      if (std::find(section.section_points.begin(),
                    section.section_points.end(),
                    point) != section.section_points.end()) {
        InputFailure("duplicate-entity", row.location, block.canonical_name,
                     section.element_set_name,
                     "Section points must be unique within a section.");
        return;
      }
      section.section_points.push_back(point);
    }
    pending_section_.reset();
  }

  void ParseAssemblyStart(const KeywordBlock& block) {
    if (assembly_seen_) {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "V0 accepts exactly one non-nested assembly.");
      return;
    }
    if (parts_.empty() || !materials_.empty() || model_boundary_seen_) {
      InvalidKeywordLocation(
          block,
          "The sole assembly follows all part blocks and precedes model data.");
      return;
    }
    if (!ValidateParameters(block, {"NAME"}) || !RequireNoData(block)) {
      return;
    }
    if (RequiredParameterValue(block, "NAME") == nullptr) {
      return;
    }
    assembly_seen_ = true;
    in_assembly_ = true;
    assembly_set_seen_ = false;
  }

  void ParseAssemblyBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END ASSEMBLY") {
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "The assembly requires at least one identity instance.");
        return;
      }
      in_assembly_ = false;
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "Nested or duplicate assembly blocks are unsupported.");
    } else if (block.canonical_name == "INSTANCE") {
      if (assembly_set_seen_) {
        InvalidKeywordLocation(
            block, "All identity instances must precede assembly-level sets.");
        return;
      }
      ParseInstanceStart(block);
    } else if (block.canonical_name == "NSET") {
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "Assembly sets follow at least one identity instance.");
        return;
      }
      assembly_set_seen_ = true;
      ParseAssemblySet(block, true);
    } else if (block.canonical_name == "ELSET") {
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "Assembly sets follow at least one identity instance.");
        return;
      }
      assembly_set_seen_ = true;
      ParseAssemblySet(block, false);
    } else if (block.canonical_name == "SURFACE") {
      if (instances_.empty()) {
        InvalidKeywordLocation(
            block, "Assembly surfaces follow at least one identity instance.");
        return;
      }
      ParseElementSurface(block);
    } else {
      RejectUnknown(block);
    }
  }

  void ParseInstanceStart(const KeywordBlock& block) {
    if (Parameter(block, "DEPENDENT") != nullptr ||
        Parameter(block, "INDEPENDENT") != nullptr) {
      InputFailure(
          "unsupported-instance-mesh-semantics", block.location,
          block.canonical_name, "",
          "Dependent and independent instance mesh semantics are unsupported.");
      return;
    }
    if (!ValidateParameters(block, {"NAME", "PART"})) {
      return;
    }
    const auto* name = RequiredParameterValue(block, "NAME");
    const auto* part = RequiredParameterValue(block, "PART");
    if (name == nullptr || part == nullptr) {
      return;
    }
    if (!block.data.empty()) {
      InputFailure("unsupported-instance-transform",
                   block.data.front().location, block.canonical_name, *name,
                   "Instance translation or rotation data is unsupported.");
      return;
    }
    if (ContainsName(instances_, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name, "Instance names are globally unique.");
      return;
    }
    instances_.push_back({*name, *part, block.location});
    in_instance_ = true;
  }

  void ParseInstanceBlock(const KeywordBlock& block) {
    if (block.canonical_name == "END INSTANCE") {
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      in_instance_ = false;
      return;
    }
    if (block.canonical_name == "ASSEMBLY") {
      InputFailure("unsupported-nested-assembly", block.location,
                   block.canonical_name, "",
                   "An assembly cannot be nested in an instance.");
      return;
    }
    if (block.canonical_name == "SURFACE") {
      InputFailure("unsupported-surface-scope", block.location,
                   block.canonical_name, instances_.back().name,
                   "Pressure surfaces are unsupported inside an instance.");
      return;
    }
    InputFailure("unsupported-instance-mesh-semantics", block.location,
                 block.canonical_name, instances_.back().name,
                 "Instance-local mesh definitions are unsupported.");
  }

  void ParseAssemblySet(const KeywordBlock& block, bool node_set) {
    const std::string_view name_parameter = node_set ? "NSET" : "ELSET";
    const std::vector<std::string_view> allowed_parameters =
        node_set ? std::vector<std::string_view>{"NSET", "INSTANCE", "GENERATE"}
                 : std::vector<std::string_view>{"ELSET", "INSTANCE",
                                                 "GENERATE", "INTERNAL"};
    if (!ValidateParameters(block, allowed_parameters)) {
      return;
    }
    const auto* name = RequiredParameterValue(block, name_parameter);
    if (name == nullptr) {
      return;
    }
    const auto* instance_parameter = Parameter(block, "INSTANCE");
    if (instance_parameter == nullptr || !instance_parameter->value ||
        instance_parameter->value->empty()) {
      InputFailure(
          node_set ? "invalid-keyword-parameter" : "implicit-instance-elset",
          block.location, block.canonical_name, "INSTANCE",
          "Assembly element sets require an explicit INSTANCE.");
      return;
    }
    const std::string& instance = *instance_parameter->value;
    const auto* generate_parameter = Parameter(block, "GENERATE");
    if (generate_parameter != nullptr && generate_parameter->value) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "GENERATE",
                   "GENERATE is a valueless flag.");
      return;
    }
    const auto* internal_parameter = Parameter(block, "INTERNAL");
    if (internal_parameter != nullptr && internal_parameter->value) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "INTERNAL",
                   "INTERNAL is a valueless result-membership flag.");
      return;
    }
    if (ContainsAssemblySetName(node_set, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Assembly set names are unique within their node-set or "
                   "element-set namespace.");
      return;
    }
    if (!node_set && generate_parameter == nullptr) {
      for (const auto& row : block.data) {
        for (const auto& field : WithoutTrailingEmpty(row.fields)) {
          if (field.empty()) {
            continue;
          }
          const bool numeric =
              !field.empty() &&
              std::all_of(field.begin(), field.end(), [](const char value) {
                return value >= '0' && value <= '9';
              });
          if (!numeric) {
            const std::string code = AsciiCaseInsensitiveEquals(field, *name)
                                         ? "cyclic-elset"
                                         : "nested-elset";
            InputFailure(code, row.location, block.canonical_name, field,
                         "Assembly ELSET members must be direct labels.");
            return;
          }
        }
      }
    }
    RawAssemblySet set{node_set, *name, instance, {}, block.location};
    if (!ParseSetMembers(block, generate_parameter != nullptr, set.members)) {
      return;
    }
    assembly_sets_.push_back(std::move(set));
  }

  void ParseElementSurface(const KeywordBlock& block) {
    if (!ValidateParameters(block, {"TYPE", "NAME"}, "unsupported-parameter")) {
      return;
    }
    const auto* type = RequiredParameterValue(block, "TYPE");
    const auto* name = RequiredParameterValue(block, "NAME");
    if (type == nullptr || name == nullptr) {
      return;
    }
    if (!IsPressureNameToken(*name)) {
      InputFailure("invalid-surface-name", block.location, block.canonical_name,
                   *name,
                   "Surface names must use the approved ASCII name syntax.");
      return;
    }
    if (!AsciiCaseInsensitiveEquals(*type, "ELEMENT")) {
      InputFailure("unsupported-surface-type", block.location,
                   block.canonical_name, *type,
                   "Only TYPE=ELEMENT belongs to the approved surface subset.");
      return;
    }
    if (ContainsSurfaceName(*name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name,
                   "Surface names are unique in the assembly namespace.");
      return;
    }
    if (block.data.empty()) {
      InputFailure("empty-surface", block.location, block.canonical_name, *name,
                   "An element surface requires at least one member.");
      return;
    }

    RawElementSurface surface{
        *name, block.location, element_surfaces_.size(), {}};
    for (std::size_t ordinal = 0U; ordinal < block.data.size(); ++ordinal) {
      const auto& row = block.data[ordinal];
      if (row.fields.size() != 2U || row.fields[0].empty() ||
          row.fields[1].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     *name,
                     "Surface rows require one member and SPOS or SNEG.");
        return;
      }
      ShellSurfaceSide side = ShellSurfaceSide::kSpos;
      if (AsciiCaseInsensitiveEquals(row.fields[1], "SPOS")) {
        side = ShellSurfaceSide::kSpos;
      } else if (AsciiCaseInsensitiveEquals(row.fields[1], "SNEG")) {
        side = ShellSurfaceSide::kSneg;
      } else {
        InputFailure("unsupported-surface-side", row.location,
                     block.canonical_name, row.fields[1],
                     "Surface sides must be SPOS or SNEG.");
        return;
      }
      surface.members.push_back({row.fields[0], side, row.location, ordinal});
    }
    element_surfaces_.push_back(std::move(surface));
    if (model_element_family_ == ElementFamily::kThermalShell)
      AddIgnoredWarning(block);
  }

  void ParseMaterial(const KeywordBlock& block) {
    if (!assembly_seen_ || model_boundary_seen_) {
      InvalidKeywordLocation(block,
                             "Material definitions follow the assembly and "
                             "precede model boundaries.");
      return;
    }
    if (!ValidateParameters(block, {"NAME"}) || !RequireNoData(block)) {
      return;
    }
    const auto* name = RequiredParameterValue(block, "NAME");
    if (name == nullptr) {
      return;
    }
    if (ContainsName(materials_, *name)) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   *name, "Material names are globally unique.");
      return;
    }
    materials_.push_back({*name,
                          0.0,
                          0.0,
                          false,
                          std::nullopt,
                          std::nullopt,
                          std::nullopt,
                          block.location,
                          {},
                          {}});
    material_eligible_ = materials_.size() - 1U;
  }

  void ParseElastic(const KeywordBlock& block) {
    if (model_element_family_ == ElementFamily::kThermalShell) {
      InputFailure("unsupported-keyword", block.location, block.canonical_name,
                   "", "ELASTIC is outside the thermal material subset.");
      return;
    }
    if (!material_eligible_) {
      InputFailure("invalid-keyword-location", block.location,
                   block.canonical_name, "",
                   "ELASTIC must immediately follow MATERIAL.");
      return;
    }
    if (!ValidateParameters(block, {}) || block.data.size() != 1U ||
        block.data[0].fields.size() != 2U) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     materials_[*material_eligible_].name,
                     "ELASTIC requires exactly one E, nu row.");
      }
      return;
    }
    RawMaterial& material = materials_[*material_eligible_];
    if (material.has_elastic) {
      InputFailure("duplicate-entity", block.location, block.canonical_name,
                   material.name, "A material accepts one ELASTIC definition.");
      return;
    }
    if (!ParseModelDouble(block.data[0].fields[0], material.youngs_modulus,
                          block.data[0].location, block.canonical_name,
                          model_element_family_ == ElementFamily::kSolid
                              ? "invalid-solid-material"
                          : model_element_family_ == ElementFamily::kShell
                              ? "invalid-shell-material"
                              : "invalid-beam-property",
                          "Elastic material values must be finite.") ||
        !ParseModelDouble(block.data[0].fields[1], material.poisson_ratio,
                          block.data[0].location, block.canonical_name,
                          model_element_family_ == ElementFamily::kSolid
                              ? "invalid-solid-material"
                          : model_element_family_ == ElementFamily::kShell
                              ? "invalid-shell-material"
                              : "invalid-beam-property",
                          "Elastic material values must be finite.")) {
      return;
    }
    material.has_elastic = true;
    material.elastic_location = block.data[0].location;
  }

  bool ParseDensityValue(const std::string& text, double& value,
                         const SourceLocation& location) {
    const std::string canonical = CanonicalizeAscii(text);
    if (canonical == "NAN" || canonical == "+NAN" || canonical == "-NAN" ||
        canonical == "INF" || canonical == "+INF" || canonical == "-INF" ||
        canonical == "INFINITY" || canonical == "+INFINITY" ||
        canonical == "-INFINITY") {
      return ModelFailure(
          "invalid-material-density", location, "DENSITY", text,
          "Density must convert to a finite value greater than zero.");
    }
    std::size_t cursor = 0U;
    if (cursor < text.size() && (text[cursor] == '+' || text[cursor] == '-')) {
      ++cursor;
    }
    const std::size_t integer_start = cursor;
    while (cursor < text.size() && text[cursor] >= '0' && text[cursor] <= '9') {
      ++cursor;
    }
    const bool has_integer_digits = cursor != integer_start;
    bool has_fraction_digits = false;
    if (cursor < text.size() && text[cursor] == '.') {
      ++cursor;
      const std::size_t fraction_start = cursor;
      while (cursor < text.size() && text[cursor] >= '0' &&
             text[cursor] <= '9') {
        ++cursor;
      }
      has_fraction_digits = cursor != fraction_start;
    }
    if (!has_integer_digits && !has_fraction_digits) {
      return InputFailure("invalid-density-data", location, "DENSITY", text,
                          "Density requires C-locale decimal syntax.");
    }
    if (cursor < text.size() && (text[cursor] == 'E' || text[cursor] == 'e')) {
      ++cursor;
      if (cursor < text.size() &&
          (text[cursor] == '+' || text[cursor] == '-')) {
        ++cursor;
      }
      const std::size_t exponent_start = cursor;
      while (cursor < text.size() && text[cursor] >= '0' &&
             text[cursor] <= '9') {
        ++cursor;
      }
      if (cursor == exponent_start) {
        return InputFailure("invalid-density-data", location, "DENSITY", text,
                            "Density exponents require one or more digits.");
      }
    }
    if (cursor != text.size()) {
      return InputFailure("invalid-density-data", location, "DENSITY", text,
                          "Density requires C-locale decimal syntax.");
    }
    const char* begin = text.data();
    if (*begin == '+') {
      ++begin;
    }
    double parsed = 0.0;
    const auto conversion = std::from_chars(begin, text.data() + text.size(),
                                            parsed, std::chars_format::general);
    if (conversion.ec != std::errc{} ||
        conversion.ptr != text.data() + text.size() || !std::isfinite(parsed) ||
        !(parsed > 0.0)) {
      return ModelFailure(
          "invalid-material-density", location, "DENSITY", text,
          "Density must convert to a finite value greater than zero.");
    }
    value = parsed;
    return true;
  }

  void ParseDensity(const KeywordBlock& block) {
    if (!material_eligible_) {
      InputFailure("invalid-density-data", block.location, block.canonical_name,
                   "", "DENSITY must be declared inside one MATERIAL.");
      return;
    }
    if (!ValidateParameters(block, {}, "unsupported-density-option")) {
      return;
    }
    RawMaterial& material = materials_[*material_eligible_];
    if (material.density) {
      InputFailure("duplicate-density", block.location, block.canonical_name,
                   material.name, "A material accepts one DENSITY definition.");
      return;
    }
    if (block.data.size() != 1U ||
        (block.data[0].fields.size() != 1U &&
         (block.data[0].fields.size() != 2U ||
          !block.data[0].fields[1].empty())) ||
        block.data[0].fields[0].empty()) {
      InputFailure("invalid-density-data", block.location, block.canonical_name,
                   material.name, "DENSITY requires exactly rho or rho,.");
      return;
    }
    double rho = 0.0;
    if (!ParseDensityValue(block.data[0].fields[0], rho,
                           block.data[0].location)) {
      return;
    }
    material.density = rho;
    material.density_location = block.data[0].location;
  }

  void ParseThermalProperty(const KeywordBlock& block, bool conductivity) {
    if (model_element_family_ != ElementFamily::kThermalShell ||
        !material_eligible_ || !ValidateParameters(block, {})) {
      if (!failure_) {
        InputFailure("invalid-keyword-location", block.location,
                     block.canonical_name, "",
                     "Thermal properties belong to a DS4 material.");
      }
      return;
    }
    RawMaterial& material = materials_[*material_eligible_];
    std::optional<double>& destination =
        conductivity ? material.conductivity : material.specific_heat;
    if (destination || block.data.size() != 1U ||
        (block.data[0].fields.size() != 1U &&
         (block.data[0].fields.size() != 2U ||
          !block.data[0].fields[1].empty()))) {
      InputFailure("invalid-data-arity", block.location, block.canonical_name,
                   material.name,
                   "Thermal property requires one constant row.");
      return;
    }
    double value = 0.0;
    if (!ParseThermalDouble(block.data[0].fields[0], value,
                            block.data[0].location, block.canonical_name) ||
        !(value > 0.0)) {
      if (!failure_) {
        ModelFailure("invalid-thermal-material", block.data[0].location,
                     block.canonical_name, material.name,
                     "Thermal material values must be finite and positive.");
      }
      return;
    }
    destination = value;
  }

  void ParseInitialConditions(const KeywordBlock& block) {
    if (model_element_family_ != ElementFamily::kThermalShell ||
        !ValidateParameters(block, {"TYPE"}) || block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "Thermal initial conditions require data rows.");
      }
      return;
    }
    const auto* type = RequiredParameterValue(block, "TYPE");
    if (type == nullptr || !AsciiCaseInsensitiveEquals(*type, "TEMPERATURE")) {
      if (!failure_)
        InputFailure("unsupported-keyword", block.location,
                     block.canonical_name, "TYPE",
                     "Only TYPE=TEMPERATURE is supported.");
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 2U || row.fields[0].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "Initial temperatures require target, value.");
        return;
      }
      double value = 0.0;
      if (!ParseThermalDouble(row.fields[1], value, row.location,
                              block.canonical_name))
        return;
      thermal_initial_conditions_.push_back(
          {row.fields[0], value, row.location});
    }
  }

  void ParseThermalBoundary(const KeywordBlock& block,
                            std::vector<RawThermalBoundary>& destination) {
    if (!ValidateParameters(block, {}) || block.data.empty()) {
      if (!failure_)
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "Thermal BOUNDARY requires data rows.");
      return;
    }
    for (const auto& row : block.data) {
      if ((row.fields.size() != 3U && row.fields.size() != 4U) ||
          row.fields[0].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "Thermal boundaries require target, DOF, DOF, value.");
        return;
      }
      std::int64_t first = 0;
      std::int64_t last = 0;
      if (!ParseInteger(row.fields[1], first, row.location,
                        block.canonical_name, true) ||
          !ParseInteger(row.fields[2], last, row.location, block.canonical_name,
                        true) ||
          first != last || (first != 11 && first != 15)) {
        InputFailure("invalid-dof", row.location, block.canonical_name,
                     row.fields[0], "Thermal boundaries support DOF 11 or 15.");
        return;
      }
      double value = 0.0;
      if (row.fields.size() == 4U &&
          !ParseThermalDouble(row.fields[3], value, row.location,
                              block.canonical_name))
        return;
      destination.push_back(
          {row.fields[0], static_cast<int>(first), value, row.location});
    }
  }

  void ParseBoundary(
      const KeywordBlock& block,
      std::vector<PrescribedDisplacementDefinition>& destination) {
    const bool dynamic_input = std::any_of(
        input_.blocks.begin(), input_.blocks.end(), [](const auto& candidate) {
          return candidate.canonical_name == "DYNAMIC";
        });
    if (!ValidateParameters(block, {},
                            dynamic_input ? "unsupported-dynamic-boundary"
                                          : "invalid-keyword-parameter") ||
        block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "BOUNDARY requires one or more data rows.");
      }
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 3U && row.fields.size() != 4U) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "",
                     "BOUNDARY rows require target, first DOF, last DOF, and "
                     "optional value.");
        return;
      }
      if (row.fields[0].empty()) {
        InputFailure("unresolved-reference", row.location, block.canonical_name,
                     "", "A boundary target cannot be empty.");
        return;
      }
      std::int64_t first = 0;
      std::int64_t last = 0;
      if (!ParseInteger(row.fields[1], first, row.location,
                        block.canonical_name, true) ||
          !ParseInteger(row.fields[2], last, row.location, block.canonical_name,
                        true)) {
        return;
      }
      if (first < 1 || first > 6 || last < first || last > 6) {
        InputFailure("invalid-dof", row.location, block.canonical_name,
                     row.fields[0],
                     "Boundary DOFs must be an ordered range in 1..6.");
        return;
      }
      double value = 0.0;
      if (row.fields.size() == 4U &&
          !(model_element_family_ == ElementFamily::kSolid &&
            row.fields[3].empty()) &&
          !ParseDouble(row.fields[3], value, row.location,
                       block.canonical_name)) {
        return;
      }
      destination.push_back({row.fields[0], static_cast<int>(first),
                             static_cast<int>(last), value, row.location});
    }
  }

  void ParseCload(const KeywordBlock& block, std::vector<NodalLoad>& loads) {
    if (step_.dynamic && model_element_family_ != ElementFamily::kSolid &&
        !block.parameters.empty()) {
      InputFailure("unsupported-dynamic-load", block.location,
                   block.canonical_name, "",
                   "Dynamic CLOAD does not support keyword parameters.");
      return;
    }
    const bool solid_dynamic =
        step_.dynamic && model_element_family_ == ElementFamily::kSolid;
    if (!ValidateParameters(
            block, solid_dynamic ? std::vector<std::string_view>{"AMPLITUDE"}
                                 : std::vector<std::string_view>{}) ||
        block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "CLOAD requires one or more rows.");
      }
      return;
    }
    std::optional<EntityIndex> amplitude_index;
    std::string amplitude_name;
    if (Parameter(block, "AMPLITUDE")) {
      const auto* name = RequiredParameterValue(block, "AMPLITUDE");
      if (!name) return;
      amplitude_name = *name;
      for (std::size_t index = 0U; index < definition_.amplitudes.size();
           ++index) {
        if (AsciiCaseInsensitiveEquals(definition_.amplitudes[index].name_raw,
                                       *name)) {
          amplitude_index = static_cast<EntityIndex>(index);
          break;
        }
      }
      if (!amplitude_index) {
        InputFailure("unresolved-amplitude", block.location,
                     block.canonical_name, *name,
                     "CLOAD amplitude must resolve to a model-level curve.");
        return;
      }
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 3U || row.fields[0].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "CLOAD rows require target, DOF, magnitude.");
        return;
      }
      std::int64_t dof = 0;
      double magnitude = 0.0;
      if (!ParseInteger(row.fields[1], dof, row.location, block.canonical_name,
                        true) ||
          !ParseDouble(row.fields[2], magnitude, row.location,
                       block.canonical_name)) {
        return;
      }
      if (dof < 1 || dof > 6) {
        InputFailure("invalid-dof", row.location, block.canonical_name,
                     row.fields[0], "CLOAD DOF must be in 1..6.");
        return;
      }
      if ((step_.dynamic || model_element_family_ == ElementFamily::kSolid) &&
          dof > 3) {
        InputFailure("unsupported-dynamic-load", row.location,
                     block.canonical_name, row.fields[1],
                     "Dynamic CLOAD supports global translational DOF 1 "
                     "through 3 only.");
        return;
      }
      loads.push_back({row.fields[0], static_cast<int>(dof), magnitude,
                       row.location, amplitude_index, amplitude_name,
                       block.location});
    }
  }

  void ParseDsload(const KeywordBlock& block) {
    if (!ValidateParameters(block, {}, "unsupported-dsload-parameter") ||
        block.data.empty()) {
      if (!failure_) {
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "DSLOAD requires one or more rows.");
      }
      return;
    }
    for (std::size_t ordinal = 0U; ordinal < block.data.size(); ++ordinal) {
      const auto& row = block.data[ordinal];
      if (row.fields.size() != 3U || row.fields[0].empty() ||
          row.fields[1].empty() || row.fields[2].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "DSLOAD rows require surface, P, magnitude.");
        return;
      }
      if (!IsPressureNameToken(row.fields[0])) {
        InputFailure("invalid-surface-name", row.location, block.canonical_name,
                     row.fields[0],
                     "DSLOAD surface names must use the approved ASCII name "
                     "syntax.");
        return;
      }
      if (!AsciiCaseInsensitiveEquals(row.fields[1], "P")) {
        InputFailure("unsupported-load-type", row.location,
                     block.canonical_name, row.fields[1],
                     "Only uniform surface pressure load type P is supported.");
        return;
      }
      double magnitude = 0.0;
      if (!ParseSurfacePressureDouble(row.fields[2], magnitude, row.location,
                                      block.canonical_name)) {
        return;
      }
      step_.surface_pressure_loads.push_back(
          {row.fields[0], magnitude, row.fields[2], block.location,
           row.location, ordinal, step_.next_load_ordinal++});
    }
  }

  void ParseStepStart(const KeywordBlock& block) {
    if (step_seen_) {
      if (step_.frequency || step_.dynamic) {
        InputFailure(
            "unsupported-analysis-procedure", block.location,
            block.canonical_name, "",
            "The frequency subset accepts exactly one procedure step.");
      } else {
        const auto* nlgeom = Parameter(block, "NLGEOM");
        const bool nonlinear_second_step =
            nlgeom != nullptr && nlgeom->value &&
            AsciiCaseInsensitiveEquals(*nlgeom->value, "YES");
        if (step_.nlgeom || nonlinear_second_step) {
          InputFailure("unsupported-analysis-procedure", block.location,
                       block.canonical_name, "",
                       "The nonlinear static subset accepts exactly one "
                       "procedure step.");
        } else {
          InputFailure("unsupported-multiple-step", block.location,
                       block.canonical_name, "",
                       "V0 accepts exactly one analysis step.");
        }
      }
      return;
    }
    if (!assembly_seen_ || materials_.empty()) {
      InvalidKeywordLocation(block,
                             "The sole step follows the complete assembly and "
                             "material definitions.");
      return;
    }
    if (!ValidateParameters(block, {"NAME", "NLGEOM", "PERTURBATION", "INC"}) ||
        !RequireNoData(block)) {
      return;
    }
    StaticProcedureKind procedure_kind =
        StaticProcedureKind::kLinearSmallDisplacement;
    bool nlgeom = false;
    const auto* nlgeom_parameter = Parameter(block, "NLGEOM");
    if (nlgeom_parameter != nullptr) {
      if (!nlgeom_parameter->value || nlgeom_parameter->value->empty()) {
        InputFailure("invalid-keyword-parameter", block.location,
                     block.canonical_name, "NLGEOM",
                     "NLGEOM requires YES or NO in the approved subset.");
        return;
      }
      if (AsciiCaseInsensitiveEquals(*nlgeom_parameter->value, "YES")) {
        if (model_element_family_ != ElementFamily::kShell &&
            model_element_family_ != ElementFamily::kSolid) {
          InputFailure("unsupported-analysis-procedure", block.location,
                       block.canonical_name, *nlgeom_parameter->value,
                       "NLGEOM=YES requires a supported Shell or Solid model.");
          return;
        }
        procedure_kind = StaticProcedureKind::kNonlinearFullNewton;
        nlgeom = true;
      } else if (!AsciiCaseInsensitiveEquals(*nlgeom_parameter->value, "NO")) {
        InputFailure("unsupported-analysis-procedure", block.location,
                     block.canonical_name, *nlgeom_parameter->value,
                     "NLGEOM must select YES or NO.");
        return;
      }
    }
    const auto* perturbation = Parameter(block, "PERTURBATION");
    if (perturbation != nullptr && perturbation->value) {
      InputFailure("unsupported-analysis-procedure", block.location,
                   block.canonical_name, "PERTURBATION",
                   "PERTURBATION is accepted only as a value-less flag.");
      return;
    }
    const auto* name = Parameter(block, "NAME");
    if (name != nullptr && (!name->value || name->value->empty())) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "NAME",
                   "STEP NAME must not be empty when it is present.");
      return;
    }
    const auto* increment_limit = Parameter(block, "INC");
    std::uint32_t maximum_increments = 100U;
    if (increment_limit != nullptr) {
      if (!increment_limit->value || increment_limit->value->empty()) {
        InputFailure("invalid-dynamic-data", block.location,
                     block.canonical_name, "INC",
                     "INC requires a positive uint32 value.");
        return;
      }
      std::int64_t parsed_limit = 0;
      if (!ParseInteger(*increment_limit->value, parsed_limit, block.location,
                        block.canonical_name, true) ||
          parsed_limit > static_cast<std::int64_t>(
                             std::numeric_limits<std::uint32_t>::max())) {
        if (!failure_) {
          InputFailure("invalid-dynamic-data", block.location,
                       block.canonical_name, "INC",
                       "INC requires a positive uint32 value.");
        }
        return;
      }
      maximum_increments = static_cast<std::uint32_t>(parsed_limit);
    }
    step_seen_ = true;
    in_step_ = true;
    step_ = {};
    step_.location = block.location;
    step_.name_raw = name == nullptr ? "Step-1" : *name->value;
    step_.name_canonical = CanonicalizeAscii(step_.name_raw);
    step_.procedure_kind = procedure_kind;
    step_.nlgeom = nlgeom;
    step_.nlgeom_explicit = nlgeom_parameter != nullptr;
    step_.perturbation_explicit = perturbation != nullptr;
    step_.maximum_increments = maximum_increments;
    step_load_seen_ = false;
    step_no_op_seen_ = false;
  }

  void ParseStepBlock(const KeywordBlock& block) {
    if (model_element_family_ == ElementFamily::kSolid &&
        (block.canonical_name == "STATIC" ||
         block.canonical_name == "FREQUENCY" ||
         block.canonical_name == "DYNAMIC") &&
        (step_.has_static || step_.frequency || step_.dynamic)) {
      InputFailure("unsupported-analysis-procedure", block.location,
                   block.canonical_name, step_.name_raw,
                   "Solid steps accept exactly one procedure.");
      return;
    }
    if (model_element_family_ == ElementFamily::kThermalShell &&
        (block.canonical_name == "STATIC" ||
         block.canonical_name == "FREQUENCY" ||
         block.canonical_name == "DYNAMIC")) {
      InputFailure("unsupported-analysis-procedure", block.location,
                   block.canonical_name, step_.name_raw,
                   "DS4 supports only one HEAT TRANSFER procedure.");
      return;
    }
    if (block.canonical_name == "END STEP") {
      active_output_ = false;
      if (!ValidateParameters(block, {}) || !RequireNoData(block)) {
        return;
      }
      if (!step_.has_static && !step_.frequency && !step_.dynamic &&
          !step_.has_heat_transfer) {
        InvalidKeywordLocation(
            block, "The sole step requires one supported procedure keyword.");
        return;
      }
      in_step_ = false;
      return;
    }
    if (block.canonical_name == "STEP") {
      InputFailure("unsupported-multiple-step", block.location,
                   block.canonical_name, "",
                   "A second or nested step is unsupported.");
      return;
    }
    if (block.canonical_name == "HEAT TRANSFER") {
      active_output_ = false;
      if (step_.has_static || step_.frequency || step_.dynamic ||
          step_.has_heat_transfer || !step_.boundaries.empty() ||
          !step_.loads.empty() || step_no_op_seen_) {
        InvalidKeywordLocation(block,
                               "HEAT TRANSFER must be the first procedure.");
        return;
      }
      ParseHeatTransfer(block);
    } else if (block.canonical_name == "STATIC") {
      active_output_ = false;
      if (!step_.boundaries.empty() || !step_.loads.empty() ||
          !step_.surface_pressure_loads.empty() || step_no_op_seen_) {
        InvalidKeywordLocation(
            block, "STATIC must be the first keyword in the sole step.");
        return;
      }
      ParseStatic(block);
    } else if (block.canonical_name == "FREQUENCY") {
      active_output_ = false;
      if (step_.has_static || step_.frequency || !step_.boundaries.empty() ||
          !step_.loads.empty() || !step_.surface_pressure_loads.empty() ||
          step_no_op_seen_) {
        InvalidKeywordLocation(
            block, "FREQUENCY must be the first procedure in the sole step.");
        return;
      }
      ParseFrequency(block);
    } else if (block.canonical_name == "DYNAMIC") {
      active_output_ = false;
      if (step_.has_static || step_.frequency || step_.dynamic ||
          !step_.boundaries.empty() || !step_.loads.empty() ||
          !step_.surface_pressure_loads.empty() || step_no_op_seen_) {
        InvalidKeywordLocation(
            block, "DYNAMIC must be the first procedure in the sole step.");
        return;
      }
      ParseDynamic(block);
    } else if (block.canonical_name == "BOUNDARY") {
      active_output_ = false;
      if ((!step_.has_static && !step_.frequency && !step_.dynamic &&
           !step_.has_heat_transfer) ||
          step_load_seen_ || step_no_op_seen_) {
        InvalidKeywordLocation(
            block,
            "Step boundaries follow STATIC and precede loads "
            "and no-op requests.");
        return;
      }
      if (step_.dynamic && !block.parameters.empty()) {
        InputFailure("unsupported-dynamic-boundary", block.location,
                     block.canonical_name, "",
                     "Dynamic BOUNDARY does not support keyword parameters.");
        return;
      }
      if (step_.has_heat_transfer) {
        ParseThermalBoundary(block, step_.thermal_boundaries);
      } else {
        ParseBoundary(block, step_.boundaries);
      }
      if (!failure_ && step_.frequency) {
        ValidateEigenBoundaries(step_.boundaries);
      }
      if (!failure_ && step_.dynamic) {
        ValidateDynamicBoundaries(step_.boundaries);
      }
    } else if (block.canonical_name == "CLOAD") {
      active_output_ = false;
      if ((!step_.has_static && !step_.dynamic) || step_no_op_seen_) {
        InvalidKeywordLocation(
            block,
            "CLOAD follows STATIC and boundaries and precedes no-op requests.");
        return;
      }
      ParseCload(block, step_.loads);
      if (!failure_) {
        step_.next_load_ordinal += block.data.size();
      }
      step_load_seen_ = !failure_;
    } else if (block.canonical_name == "CFLUX") {
      active_output_ = false;
      if (!step_.has_heat_transfer || step_no_op_seen_) {
        InvalidKeywordLocation(block,
                               "CFLUX follows HEAT TRANSFER and boundaries.");
        return;
      }
      ParseCflux(block);
      step_load_seen_ = !failure_;
    } else if (block.canonical_name == "DSLOAD") {
      active_output_ = false;
      if (!step_.has_static || step_.dynamic || step_no_op_seen_) {
        InvalidKeywordLocation(block,
                               "DSLOAD follows STATIC and boundaries and "
                               "precedes no-op requests.");
        return;
      }
      ParseDsload(block);
      step_load_seen_ = !failure_;
    } else if (block.canonical_name == "RESTART") {
      active_output_ = false;
      if (!step_.has_static && !step_.frequency && !step_.dynamic &&
          !step_.has_heat_transfer) {
        InvalidKeywordLocation(
            block, "Step no-op requests follow STATIC, boundaries, and loads.");
        return;
      }
      step_no_op_seen_ = true;
      if (step_.frequency || step_.has_heat_transfer ||
          model_element_family_ == ElementFamily::kSolid) {
        const auto* write = Parameter(block, "WRITE");
        const auto* frequency = Parameter(block, "FREQUENCY");
        if (!ValidateParameters(block, {"WRITE", "FREQUENCY"}) ||
            write == nullptr || write->value || frequency == nullptr ||
            !frequency->value || *frequency->value != "0") {
          if (!failure_) {
            InputFailure(
                "unsupported-keyword", block.location, block.canonical_name, "",
                "Supported RESTART no-op requires WRITE, FREQUENCY=0.");
          }
          return;
        }
      }
      if (RequireNoData(block)) {
        AddIgnoredWarning(block);
      }
    } else if (block.canonical_name == "OUTPUT") {
      if (!step_.has_static && !step_.frequency && !step_.dynamic &&
          !step_.has_heat_transfer) {
        InvalidKeywordLocation(
            block, "Step no-op requests follow STATIC, boundaries, and loads.");
        return;
      }
      step_no_op_seen_ = true;
      ParseOutputRoot(block);
    } else if (block.canonical_name == "NODE OUTPUT" ||
               block.canonical_name == "ELEMENT OUTPUT" ||
               block.canonical_name == "CONTACT OUTPUT" ||
               block.canonical_name == "ENERGY OUTPUT") {
      ParseOutputChild(block);
    } else {
      active_output_ = false;
      if (step_.procedure_kind == StaticProcedureKind::kNonlinearFullNewton &&
          !step_.has_static) {
        InputFailure("unsupported-analysis-procedure", block.location,
                     block.canonical_name, "",
                     "The nonlinear step supports only the STATIC procedure.");
        return;
      }
      RejectUnknown(block);
    }
  }

  bool ParseFrequencyModeCount(const std::string& text, std::int64_t& value,
                               const SourceLocation& location) {
    if (text.empty() ||
        !std::all_of(text.begin(), text.end(), [](char character) {
          return character >= '0' && character <= '9';
        })) {
      return InputFailure(
          "invalid-frequency-data", location, "FREQUENCY", text,
          "The requested mode count must be positive decimal digits.");
    }
    const auto parsed =
        std::from_chars(text.data(), text.data() + text.size(), value);
    if (parsed.ec != std::errc{} || parsed.ptr != text.data() + text.size() ||
        value <= 0) {
      return InputFailure(
          "invalid-frequency-data", location, "FREQUENCY", text,
          "The requested mode count must be a positive int64 value.");
    }
    return true;
  }

  void ParseFrequency(const KeywordBlock& block) {
    if (step_.nlgeom || (step_.perturbation_explicit && step_.has_static) ||
        !ValidateParameters(
            block, {"EIGENSOLVER", "SIM", "ACOUSTIC COUPLING", "NORMALIZATION"},
            "unsupported-frequency-option")) {
      if (!failure_) {
        InputFailure("unsupported-analysis-procedure", block.location,
                     block.canonical_name, "",
                     "FREQUENCY requires the original linear configuration.");
      }
      return;
    }
    if (block.data.size() != 1U || block.data[0].fields.empty() ||
        block.data[0].fields.size() > 7U) {
      InputFailure("invalid-frequency-data", block.location,
                   block.canonical_name, "",
                   "FREQUENCY requires one data row with one to seven fields.");
      return;
    }
    for (std::size_t field = 1U; field < block.data[0].fields.size(); ++field) {
      if (!block.data[0].fields[field].empty()) {
        InputFailure("invalid-frequency-data", block.data[0].location,
                     block.canonical_name, std::to_string(field + 1U),
                     "Only the requested mode-count field may be non-empty.");
        return;
      }
    }
    FrequencyStepDefinition frequency{step_.name_raw,
                                      step_.name_canonical,
                                      step_.location,
                                      block.location,
                                      block.data[0].location,
                                      0,
                                      step_.nlgeom_explicit,
                                      step_.perturbation_explicit,
                                      false,
                                      false,
                                      false,
                                      false,
                                      FrequencyEigensolver::kLanczos,
                                      FrequencyNormalization::kMass,
                                      {}};
    if (!ParseFrequencyModeCount(block.data[0].fields[0],
                                 frequency.requested_mode_count,
                                 block.data[0].location)) {
      return;
    }
    const auto* eigensolver = Parameter(block, "EIGENSOLVER");
    if (eigensolver != nullptr) {
      if (!eigensolver->value ||
          !AsciiCaseInsensitiveEquals(*eigensolver->value, "LANCZOS")) {
        InputFailure("unsupported-frequency-option", block.location,
                     block.canonical_name, "EIGENSOLVER",
                     "Only EIGENSOLVER=LANCZOS is accepted.");
        return;
      }
      frequency.eigensolver_explicit = true;
    }
    const auto* sim = Parameter(block, "SIM");
    if (sim != nullptr) {
      if (sim->value && !AsciiCaseInsensitiveEquals(*sim->value, "YES")) {
        InputFailure("unsupported-frequency-option", block.location,
                     block.canonical_name, "SIM",
                     "SIM accepts only a flag or YES.");
        return;
      }
      frequency.sim_explicit = true;
    }
    const auto* acoustic = Parameter(block, "ACOUSTIC COUPLING");
    if (acoustic != nullptr) {
      if (!acoustic->value ||
          !AsciiCaseInsensitiveEquals(*acoustic->value, "ON")) {
        InputFailure("unsupported-frequency-option", block.location,
                     block.canonical_name, "ACOUSTIC COUPLING",
                     "Only ACOUSTIC COUPLING=ON is accepted.");
        return;
      }
      frequency.acoustic_coupling_explicit = true;
    }
    const auto* normalization = Parameter(block, "NORMALIZATION");
    if (normalization != nullptr) {
      if (!normalization->value ||
          !AsciiCaseInsensitiveEquals(*normalization->value, "MASS")) {
        InputFailure("unsupported-frequency-option", block.location,
                     block.canonical_name, "NORMALIZATION",
                     "Only NORMALIZATION=MASS is accepted.");
        return;
      }
      frequency.normalization_explicit = true;
    }
    step_.frequency = std::move(frequency);
    definition_.warnings.push_back(
        {Severity::kWarning, "source-eigensolver-mapped-to-feast",
         block.location, block.canonical_name, step_.name_raw,
         "The accepted source eigensolver is mapped to the FEAST backend."});
    if (step_.frequency->sim_explicit) {
      definition_.warnings.push_back(
          {Severity::kWarning, "source-sim-option-not-applied", block.location,
           block.canonical_name, step_.name_raw,
           "The accepted source SIM option has no FESA runtime effect."});
    }
    if (step_.frequency->acoustic_coupling_explicit) {
      definition_.warnings.push_back(
          {Severity::kWarning, "acoustic-option-inapplicable-structural-only",
           block.location, block.canonical_name, step_.name_raw,
           "Acoustic coupling is inapplicable to this structural-only model."});
    }
  }

  void ValidateEigenBoundaries(
      const std::vector<PrescribedDisplacementDefinition>& boundaries) {
    for (const auto& boundary : boundaries) {
      if (boundary.value != 0.0) {
        InputFailure("unsupported-eigen-boundary", boundary.location,
                     "BOUNDARY", boundary.target,
                     "Frequency boundaries must prescribe exact zero.");
        return;
      }
    }
  }

  void ValidateDynamicBoundaries(
      const std::vector<PrescribedDisplacementDefinition>& boundaries) {
    for (const auto& boundary : boundaries) {
      if (boundary.value != 0.0) {
        InputFailure("unsupported-dynamic-boundary", boundary.location,
                     "BOUNDARY", boundary.target,
                     "Dynamic boundaries must be homogeneous and constant.");
        return;
      }
    }
  }

  void ParseDynamic(const KeywordBlock& block) {
    if (step_.perturbation_explicit ||
        (model_element_family_ != ElementFamily::kSolid &&
         (!step_.nlgeom || model_element_family_ != ElementFamily::kShell)) ||
        !ValidateParameters(block, {"DIRECT"},
                            "unsupported-dynamic-parameter")) {
      if (!failure_) {
        InputFailure("unsupported-analysis-procedure", block.location,
                     block.canonical_name, "",
                     "DYNAMIC requires nonlinear Shell or linear/nonlinear "
                     "Solid geometry.");
      }
      return;
    }
    if (model_element_family_ == ElementFamily::kSolid &&
        block.data.size() == 1U && block.data[0].fields.size() > 3U) {
      InputFailure("invalid-dynamic-data", block.data[0].location,
                   block.canonical_name, "",
                   "Solid DYNAMIC requires h,T with at most one blank field.");
      return;
    }
    const auto* direct = Parameter(block, "DIRECT");
    if (direct == nullptr || direct->value || block.data.size() != 1U ||
        block.data[0].fields.size() < 2U ||
        std::any_of(block.data[0].fields.begin() + 2,
                    block.data[0].fields.end(),
                    [](const auto& field) { return !field.empty(); })) {
      InputFailure(
          "invalid-dynamic-data", block.location, block.canonical_name, "",
          "DYNAMIC,DIRECT requires one row with increment and time period.");
      return;
    }
    DynamicStepDefinition dynamic{step_.name_raw,
                                  step_.name_canonical,
                                  step_.location,
                                  block.location,
                                  block.data[0].location,
                                  0.0,
                                  0.0,
                                  0U,
                                  step_.maximum_increments,
                                  -0.05,
                                  0.275625,
                                  0.55,
                                  {},
                                  {}};
    if (!ParseDynamicDouble(block.data[0].fields[0], dynamic.initial_increment,
                            block.data[0].location, block.canonical_name) ||
        !ParseDynamicDouble(block.data[0].fields[1], dynamic.time_period,
                            block.data[0].location, block.canonical_name) ||
        !(dynamic.initial_increment > 0.0) || !(dynamic.time_period > 0.0)) {
      if (!failure_) {
        InputFailure(
            "invalid-dynamic-data", block.data[0].location,
            block.canonical_name, "",
            "Dynamic increment and time period must be finite and positive.");
      }
      return;
    }
    const double count = dynamic.time_period / dynamic.initial_increment;
    const double rounded_count = std::round(count);
    if (!std::isfinite(count) || rounded_count < 1.0 ||
        rounded_count >
            static_cast<double>(std::numeric_limits<std::uint32_t>::max()) ||
        dynamic.initial_increment * rounded_count != dynamic.time_period) {
      InputFailure("invalid-dynamic-schedule", block.data[0].location,
                   block.canonical_name, "",
                   "DYNAMIC,DIRECT requires an exact positive integer number "
                   "of increments.");
      return;
    }
    dynamic.increment_count = static_cast<std::uint32_t>(rounded_count);
    if (dynamic.increment_count > dynamic.maximum_increments) {
      InputFailure("invalid-dynamic-schedule", block.data[0].location,
                   block.canonical_name, "",
                   "DYNAMIC,DIRECT increment count cannot exceed STEP INC.");
      return;
    }
    dynamic.nlgeom = step_.nlgeom;
    step_.dynamic = std::move(dynamic);
  }

  void ParseHeatTransfer(const KeywordBlock& block) {
    if (model_element_family_ != ElementFamily::kThermalShell || step_.nlgeom ||
        step_.perturbation_explicit ||
        !ValidateParameters(block, {"END"}, "unsupported-thermal-option") ||
        block.data.size() != 1U) {
      if (!failure_)
        InputFailure("unsupported-analysis-procedure", block.location,
                     block.canonical_name, "",
                     "HEAT TRANSFER requires the DS4 thermal subset.");
      return;
    }
    const auto* end = Parameter(block, "END");
    if (end != nullptr &&
        (!end->value || !AsciiCaseInsensitiveEquals(*end->value, "PERIOD"))) {
      InputFailure("unsupported-thermal-option", block.location,
                   block.canonical_name, "END",
                   "HEAT TRANSFER accepts only END=PERIOD.");
      return;
    }
    if (block.data[0].fields.size() > 5U) {
      InputFailure(
          "invalid-thermal-time-grid", block.data[0].location,
          block.canonical_name, "",
          "HEAT TRANSFER permits at most three trailing empty fields.");
      return;
    }
    const auto fields = WithoutTrailingEmpty(block.data[0].fields);
    if (fields.size() != 2U) {
      InputFailure("invalid-thermal-time-grid", block.data[0].location,
                   block.canonical_name, "",
                   "HEAT TRANSFER requires increment and time period.");
      return;
    }
    if (!ParseThermalDouble(fields[0], step_.thermal_increment,
                            block.data[0].location, block.canonical_name) ||
        !ParseThermalDouble(fields[1], step_.thermal_period,
                            block.data[0].location, block.canonical_name) ||
        !(step_.thermal_increment > 0.0) || !(step_.thermal_period > 0.0)) {
      if (!failure_)
        InputFailure(
            "invalid-thermal-time-grid", block.data[0].location,
            block.canonical_name, "",
            "Thermal increment and period must be finite and positive.");
      return;
    }
    const auto grid =
        ThermalTimeGrid::Create(step_.thermal_period, step_.thermal_increment,
                                step_.maximum_increments);
    if (!grid.HasValue()) {
      auto diagnostic = grid.GetStatus().Diagnostics().front();
      diagnostic.location = block.data[0].location;
      diagnostic.keyword = block.canonical_name;
      diagnostic.entity_identity = step_.name_raw;
      failure_ = MappingFailure{
          grid.GetStatus().Category().value_or(FailureCategory::kInput),
          std::move(diagnostic)};
      return;
    }
    step_.has_heat_transfer = true;
  }

  void ParseCflux(const KeywordBlock& block) {
    if (!ValidateParameters(block, {}) || block.data.empty()) {
      if (!failure_)
        InputFailure("invalid-data-arity", block.location, block.canonical_name,
                     "", "CFLUX requires target, DOF, power rows.");
      return;
    }
    for (const auto& row : block.data) {
      if (row.fields.size() != 3U || row.fields[0].empty()) {
        InputFailure("invalid-data-arity", row.location, block.canonical_name,
                     "", "CFLUX rows require target, DOF, power.");
        return;
      }
      std::int64_t dof = 0;
      double power = 0.0;
      if (!ParseInteger(row.fields[1], dof, row.location, block.canonical_name,
                        true) ||
          !ParseThermalDouble(row.fields[2], power, row.location,
                              block.canonical_name) ||
          (dof != 11 && dof != 15)) {
        InputFailure("invalid-dof", row.location, block.canonical_name,
                     row.fields[0], "CFLUX supports DOF 11 or 15.");
        return;
      }
      step_.thermal_fluxes.push_back(
          {row.fields[0], static_cast<int>(dof), power, row.location});
    }
  }

  void ParseStatic(const KeywordBlock& block) {
    if (model_element_family_ == ElementFamily::kSolid &&
        Parameter(block, "DIRECT")) {
      if (step_.perturbation_explicit || step_.has_static || step_.frequency ||
          step_.dynamic) {
        InputFailure("unsupported-analysis-procedure", block.location,
                     block.canonical_name, step_.name_raw,
                     "STATIC DIRECT requires one non-perturbation procedure.");
        return;
      }
      if (!ValidateParameters(block, {"DIRECT"})) return;
      const auto* direct = Parameter(block, "DIRECT");
      if (direct->value || block.data.size() != 1U ||
          (block.data[0].fields.size() < 2U ||
           block.data[0].fields.size() > 3U ||
           std::any_of(block.data[0].fields.begin() + 2,
                       block.data[0].fields.end(),
                       [](const auto& field) { return !field.empty(); }))) {
        InputFailure("invalid-static-data", block.location,
                     block.canonical_name, "DIRECT",
                     "STATIC DIRECT requires exactly h,T.");
        return;
      }
      double h = 0.0;
      double period = 0.0;
      if (!ParseDouble(block.data[0].fields[0], h, block.data[0].location,
                       "STATIC") ||
          !ParseDouble(block.data[0].fields[1], period, block.data[0].location,
                       "STATIC"))
        return;
      const double count = std::round(period / h);
      if (!(h > 0.0) || !(period > 0.0) || !std::isfinite(count) ||
          count < 1.0 ||
          count > static_cast<double>(step_.maximum_increments) ||
          h * count != period) {
        InputFailure("invalid-static-schedule", block.data[0].location,
                     block.canonical_name, "DIRECT",
                     "STATIC DIRECT requires positive exact N*h=T and N<=INC.");
        return;
      }
      step_.static_values = {h, period, h, h};
      step_.static_direct = true;
      step_.static_increment_count = static_cast<std::uint32_t>(count);
      step_.has_static = true;
      return;
    }
    if (step_.perturbation_explicit || step_.frequency) {
      InputFailure("unsupported-analysis-procedure", block.location,
                   block.canonical_name, "PERTURBATION",
                   "PERTURBATION is supported only with FREQUENCY.");
      return;
    }
    if (step_.has_heat_transfer || step_.has_static ||
        !ValidateParameters(block, {}) || block.data.size() != 1U ||
        block.data[0].fields.size() != 4U) {
      if (!failure_) {
        InputFailure(step_.nlgeom ? "invalid-nonlinear-static-data"
                                  : "invalid-static-data",
                     block.location, block.canonical_name, "",
                     "STATIC requires exactly one row of four values.");
      }
      return;
    }
    for (std::size_t field = 0U; field < 4U; ++field) {
      const std::string& text = block.data[0].fields[field];
      const bool parsed =
          step_.nlgeom
              ? ParseNonlinearStaticDouble(text, step_.static_values[field],
                                           block.data[0].location,
                                           block.canonical_name)
              : ParseDouble(text, step_.static_values[field],
                            block.data[0].location, block.canonical_name);
      if (!parsed) {
        return;
      }
      if (step_.static_values[field] <= 0.0) {
        InputFailure(step_.nlgeom ? "invalid-nonlinear-static-data"
                                  : "invalid-static-data",
                     block.data[0].location, block.canonical_name, "",
                     "All four STATIC fields must be positive.");
        return;
      }
    }
    if (step_.static_values[2] > step_.static_values[3]) {
      InputFailure(step_.nlgeom ? "invalid-nonlinear-static-data"
                                : "invalid-static-data",
                   block.data[0].location, block.canonical_name, "",
                   "STATIC minimum increment cannot exceed maximum increment.");
      return;
    }
    if (step_.nlgeom && step_.static_values[1] != 1.0) {
      InputFailure("invalid-nonlinear-static-data", block.data[0].location,
                   block.canonical_name, "",
                   "The nonlinear STATIC time period must be exactly 1.0.");
      return;
    }
    step_.has_static = true;
  }

  void ParseOutputRoot(const KeywordBlock& block) {
    if (step_.has_heat_transfer) {
      const auto* field = Parameter(block, "FIELD");
      const auto* history = Parameter(block, "HISTORY");
      const auto* variable = Parameter(block, "VARIABLE");
      const auto* frequency = Parameter(block, "FREQUENCY");
      const bool valid_field =
          field && !field->value && variable && variable->value &&
          AsciiCaseInsensitiveEquals(*variable->value, "PRESELECT");
      const bool valid_history = history && !history->value && frequency &&
                                 frequency->value && *frequency->value == "0";
      if (!RequireNoData(block)) return;
      if (block.parameters.size() != 2U || (!valid_field && !valid_history)) {
        InputFailure("unsupported-keyword", block.location,
                     block.canonical_name, "",
                     "Thermal OUTPUT accepts FIELD, VARIABLE=PRESELECT or "
                     "HISTORY, FREQUENCY=0.");
        return;
      }
      AddIgnoredWarning(block);
      return;
    }
    if (!ValidateParameters(
            block, (step_.dynamic || step_.has_heat_transfer)
                       ? std::vector<std::string_view>{"FIELD", "HISTORY",
                                                       "VARIABLE", "FREQUENCY"}
                       : std::vector<std::string_view>{"FIELD", "HISTORY",
                                                       "VARIABLE"})) {
      return;
    }
    const auto* field = Parameter(block, "FIELD");
    const auto* history = Parameter(block, "HISTORY");
    const auto* variable = Parameter(block, "VARIABLE");
    if ((field == nullptr) == (history == nullptr) ||
        (field != nullptr && field->value) ||
        (history != nullptr && history->value)) {
      InputFailure(
          step_.nlgeom ? "invalid-keyword-parameter" : "unsupported-keyword",
          block.location, block.canonical_name, "",
          "OUTPUT must select exactly FIELD or HISTORY.");
      return;
    }
    if (model_element_family_ == ElementFamily::kSolid &&
        ((variable &&
          (!variable->value ||
           !AsciiCaseInsensitiveEquals(*variable->value, "PRESELECT"))) ||
         !RequireNoData(block))) {
      if (!failure_)
        InputFailure("unsupported-keyword", block.location,
                     block.canonical_name, "VARIABLE",
                     "Solid OUTPUT accepts only PRESELECT requests.");
      return;
    }
    if (step_.nlgeom &&
        (variable == nullptr || !variable->value ||
         !AsciiCaseInsensitiveEquals(*variable->value, "PRESELECT"))) {
      InputFailure("invalid-keyword-parameter", block.location,
                   block.canonical_name, "VARIABLE",
                   "Nonlinear OUTPUT requires VARIABLE=PRESELECT.");
      return;
    }
    if (step_.dynamic) {
      const auto* frequency = Parameter(block, "FREQUENCY");
      if (!ValidateParameters(block,
                              {"FIELD", "HISTORY", "VARIABLE", "FREQUENCY"}) ||
          variable == nullptr || !variable->value ||
          !AsciiCaseInsensitiveEquals(*variable->value, "PRESELECT") ||
          (frequency != nullptr &&
           (!frequency->value || *frequency->value != "1")) ||
          !RequireNoData(block)) {
        if (!failure_) {
          InputFailure(
              "unsupported-keyword", block.location, block.canonical_name, "",
              "Dynamic OUTPUT accepts only VARIABLE=PRESELECT, FREQUENCY=1.");
        }
        return;
      }
    } else if (step_.frequency &&
               ((variable != nullptr &&
                 (!variable->value || !AsciiCaseInsensitiveEquals(
                                          *variable->value, "PRESELECT"))) ||
                !RequireNoData(block))) {
      if (!failure_) {
        InputFailure("unsupported-keyword", block.location,
                     block.canonical_name, "",
                     "Frequency OUTPUT accepts only VARIABLE=PRESELECT.");
      }
      return;
    }
    active_output_ = true;
    active_output_is_field_ = field != nullptr;
    AddIgnoredWarning(block);
  }

  void ParseOutputChild(const KeywordBlock& block) {
    if (step_.has_heat_transfer) {
      InputFailure("unsupported-keyword", block.location, block.canonical_name,
                   "",
                   "Thermal output children are outside the approved subset.");
      return;
    }
    if (!active_output_) {
      InputFailure(
          "invalid-keyword-location", block.location, block.canonical_name, "",
          "Output variable keywords require an active OUTPUT request.");
      return;
    }
    if (model_element_family_ == ElementFamily::kSolid && step_.dynamic) {
      InputFailure(
          "unsupported-keyword", block.location, block.canonical_name, "",
          "Solid dynamic output children are outside the approved subset.");
      return;
    }
    if (model_element_family_ == ElementFamily::kSolid && step_.has_static) {
      const auto* variable = Parameter(block, "VARIABLE");
      const auto* directions = Parameter(block, "DIRECTIONS");
      const bool node = block.canonical_name == "NODE OUTPUT";
      const bool element = block.canonical_name == "ELEMENT OUTPUT";
      const bool contact = block.canonical_name == "CONTACT OUTPUT";
      if (!active_output_is_field_ || (!node && !element && !contact) ||
          !ValidateParameters(
              block,
              element ? std::vector<std::string_view>{"VARIABLE", "DIRECTIONS"}
                      : std::vector<std::string_view>{"VARIABLE"}) ||
          (directions &&
           (!directions->value ||
            !AsciiCaseInsensitiveEquals(*directions->value, "YES"))) ||
          (variable &&
           (!variable->value ||
            !AsciiCaseInsensitiveEquals(*variable->value, "PRESELECT"))) ||
          (contact && (!variable || !block.data.empty()))) {
        if (!failure_)
          InputFailure("unsupported-keyword", block.location,
                       block.canonical_name, "",
                       "Solid static output child is unsupported.");
        return;
      }
      for (const auto& row : block.data) {
        for (const auto& field : row.fields) {
          const std::string token = CanonicalizeAscii(field);
          if (!(node ? (token == "U" || token == "RF")
                     : (token == "S" || token == "E"))) {
            InputFailure("unsupported-keyword", row.location,
                         block.canonical_name, field,
                         "Solid output quantities must be physical supported "
                         "components.");
            return;
          }
        }
      }
    }
    if (step_.frequency) {
      const std::string_view required_variable =
          block.canonical_name == "NODE OUTPUT" ? "PRESELECT" : "ALL";
      const auto* variable = Parameter(block, "VARIABLE");
      if ((block.canonical_name != "NODE OUTPUT" &&
           block.canonical_name != "ENERGY OUTPUT") ||
          (block.canonical_name == "NODE OUTPUT" && !active_output_is_field_) ||
          (block.canonical_name == "ENERGY OUTPUT" &&
           active_output_is_field_) ||
          !ValidateParameters(block, {"VARIABLE"}) || variable == nullptr ||
          !variable->value ||
          !AsciiCaseInsensitiveEquals(*variable->value, required_variable) ||
          !RequireNoData(block)) {
        if (!failure_) {
          InputFailure(
              "unsupported-keyword", block.location, block.canonical_name, "",
              "Frequency output child is outside the approved subset.");
        }
        return;
      }
    }
    AddIgnoredWarning(block);
  }

  void AddIgnoredWarning(const KeywordBlock& block) {
    // One warning per allowlisted keyword keeps no-op provenance stable;
    // subordinate variable rows remain attached to that keyword record.
    definition_.warnings.push_back(
        {Severity::kWarning,
         step_.dynamic ? "ignored-output-request" : "ignored-input-keyword",
         block.location, block.canonical_name, "",
         "The allowlisted Abaqus keyword is "
         "ignored without semantic effect."});
  }

  void RejectUnknown(const KeywordBlock& block) {
    if (block.canonical_name == "DLOAD" &&
        model_element_family_ == ElementFamily::kShell) {
      InputFailure("unsupported-distributed-load", block.location,
                   block.canonical_name, "",
                   "Distributed, pressure, gravity, body, edge, and follower "
                   "loads are unsupported.");
      return;
    }
    InputFailure("unsupported-keyword", block.location, block.canonical_name,
                 "", "The keyword is outside the approved Abaqus subset.");
  }

  const RawPart* FindPart(const std::string& name) const {
    const auto found = std::find_if(
        parts_.begin(), parts_.end(), [&name](const RawPart& part) {
          return AsciiCaseInsensitiveEquals(part.name, name);
        });
    return found == parts_.end() ? nullptr : &*found;
  }

  const RawInstance* FindInstance(const std::string& name) const {
    const auto found =
        std::find_if(instances_.begin(), instances_.end(),
                     [&name](const RawInstance& instance) {
                       return AsciiCaseInsensitiveEquals(instance.name, name);
                     });
    return found == instances_.end() ? nullptr : &*found;
  }

  std::optional<EntityIndex> FindMaterialIndex(const std::string& name) const {
    for (std::size_t index = 0U; index < materials_.size(); ++index) {
      if (AsciiCaseInsensitiveEquals(materials_[index].name, name)) {
        return static_cast<EntityIndex>(index);
      }
    }
    return std::nullopt;
  }

  const RawSet* FindSet(const std::vector<RawSet>& sets,
                        const std::string& name) const {
    const auto found =
        std::find_if(sets.begin(), sets.end(), [&name](const RawSet& set) {
          return AsciiCaseInsensitiveEquals(set.name, name);
        });
    return found == sets.end() ? nullptr : &*found;
  }

  const RawNode* FindNode(const RawPart& part, std::int64_t label) const {
    const auto found = std::find_if(
        part.nodes.begin(), part.nodes.end(),
        [label](const RawNode& node) { return node.label == label; });
    return found == part.nodes.end() ? nullptr : &*found;
  }

  const RawElement* FindElement(const RawPart& part, std::int64_t label) const {
    const auto found = std::find_if(
        part.elements.begin(), part.elements.end(),
        [label](const RawElement& element) { return element.label == label; });
    return found == part.elements.end() ? nullptr : &*found;
  }

  void ValidateCardinality() {
    if (parts_.empty() || !assembly_seen_ || instances_.empty() ||
        materials_.empty() || !step_seen_ ||
        (!step_.has_static && !step_.frequency && !step_.dynamic &&
         !step_.has_heat_transfer)) {
      const auto location = input_.blocks.empty()
                                ? SourceLocation{input_.source_path, 0U}
                                : input_.blocks.back().location;
      InputFailure("invalid-model-cardinality", location, "", "",
                   "The model requires part, assembly, identity instance, "
                   "material, and one supported procedure step.");
    }
  }

  void FinalizeMaterials() {
    for (const auto& material : materials_) {
      if (model_element_family_ == ElementFamily::kThermalShell) {
        if (!material.density || !material.conductivity ||
            !material.specific_heat) {
          ModelFailure("missing-thermal-material-property", material.location,
                       "MATERIAL", material.name,
                       "DS4 materials require DENSITY, CONDUCTIVITY, and "
                       "SPECIFIC HEAT.");
          return;
        }
        definition_.thermal_materials.push_back({{"", 0, material.name},
                                                 material.name,
                                                 *material.conductivity,
                                                 *material.density,
                                                 *material.specific_heat,
                                                 material.location});
        continue;
      }
      if (!material.has_elastic) {
        InputFailure("unresolved-reference", material.location, "MATERIAL",
                     material.name,
                     "A material must own exactly one ELASTIC row.");
        return;
      }
      if (model_element_family_ == ElementFamily::kShell ||
          model_element_family_ == ElementFamily::kSolid) {
        if (!(material.youngs_modulus > 0.0) ||
            !(material.poisson_ratio > -1.0) ||
            !(material.poisson_ratio < 0.5)) {
          ModelFailure(model_element_family_ == ElementFamily::kSolid
                           ? "invalid-solid-material"
                           : "invalid-shell-material",
                       material.elastic_location, "ELASTIC", material.name,
                       "Isotropic elasticity requires E>0 and -1<nu<0.5.");
          return;
        }
        if (model_element_family_ == ElementFamily::kSolid) {
          const double mu =
              material.youngs_modulus / (2.0 * (1.0 + material.poisson_ratio));
          const double lambda = material.youngs_modulus *
                                material.poisson_ratio /
                                ((1.0 + material.poisson_ratio) *
                                 (1.0 - 2.0 * material.poisson_ratio));
          if (!std::isfinite(mu) || !std::isfinite(lambda)) {
            ModelFailure("invalid-solid-material", material.elastic_location,
                         "ELASTIC", material.name,
                         "Solid Lame constants must be finite.");
            return;
          }
        }
        definition_.materials.push_back({material.name, material.youngs_modulus,
                                         material.poisson_ratio,
                                         material.location});
        continue;
      }
      const double denominator = 2.0 * (1.0 + material.poisson_ratio);
      const double shear_modulus = material.youngs_modulus / denominator;
      // The approved ledger deliberately validates derived G, not an
      // independent upper bound on Poisson's ratio.
      if (!(material.youngs_modulus > 0.0) || !std::isfinite(shear_modulus) ||
          !(shear_modulus > 0.0)) {
        ModelFailure("invalid-beam-property", material.elastic_location,
                     "ELASTIC", material.name,
                     "E and the derived G=E/(2*(1+nu)) must be positive.");
        return;
      }
      definition_.materials.push_back({material.name, material.youngs_modulus,
                                       material.poisson_ratio,
                                       material.location});
    }
  }

  void FinalizeDensities() {
    if (model_element_family_ == ElementFamily::kThermalShell) {
      for (const auto& block : input_.blocks) {
        if (block.canonical_name != "PREPRINT") continue;
        if (!ValidateParameters(block, {"ECHO", "MODEL", "HISTORY", "CONTACT"}))
          return;
        if (block.parameters.size() != 4U) {
          InputFailure("unsupported-keyword", block.location,
                       block.canonical_name, "",
                       "Thermal PREPRINT requires four NO parameters.");
          return;
        }
        for (const auto& parameter : block.parameters) {
          if (!parameter.value ||
              !AsciiCaseInsensitiveEquals(*parameter.value, "NO")) {
            InputFailure("unsupported-keyword", block.location,
                         block.canonical_name, parameter.name,
                         "Thermal PREPRINT parameters must equal NO.");
            return;
          }
        }
      }
      return;
    }
    if (physical_constants_location_) {
      InputFailure("unsupported-keyword", *physical_constants_location_,
                   "PHYSICAL CONSTANTS", "",
                   "PHYSICAL CONSTANTS is supported only by thermal input.");
      return;
    }
    if (!step_.frequency && !step_.dynamic &&
        model_element_family_ == ElementFamily::kSolid) {
      for (std::size_t index = 0U; index < materials_.size(); ++index) {
        if (materials_[index].density)
          definition_.densities.push_back({static_cast<EntityIndex>(index),
                                           *materials_[index].density,
                                           materials_[index].density_location});
      }
      return;
    }
    if (!step_.frequency && !step_.dynamic) {
      if (std::any_of(materials_.begin(), materials_.end(),
                      [](const RawMaterial& material) {
                        return material.density.has_value();
                      })) {
        InputFailure("invalid-density-data", step_.location, "DENSITY", "",
                     "DENSITY is supported only by the FREQUENCY procedure.");
      }
      return;
    }
    if (step_.frequency) {
      ValidateFrequencyPreprint();
      if (failure_) {
        return;
      }
    }
    if (step_.dynamic) {
      ValidateDynamicPreprint();
      if (failure_) {
        return;
      }
      for (auto& warning : definition_.warnings) {
        if (warning.keyword == "PREPRINT") {
          warning.code = "ignored-output-request";
        }
      }
    }
    if (model_element_family_ != ElementFamily::kShell &&
        model_element_family_ != ElementFamily::kSolid) {
      InputFailure("unsupported-analysis-procedure", step_.location,
                   step_.frequency ? "FREQUENCY" : "DYNAMIC", step_.name_raw,
                   "The procedure requires an approved Shell or Solid model.");
      return;
    }
    if (!element_surfaces_.empty()) {
      InputFailure("unsupported-keyword", element_surfaces_.front().location,
                   "SURFACE", element_surfaces_.front().name,
                   "The selected procedure does not support element surfaces.");
      return;
    }
    for (std::size_t index = 0U; index < materials_.size(); ++index) {
      const RawMaterial& material = materials_[index];
      if (!material.density) {
        bool active = false;
        for (const auto& section : definition_.shell_sections) {
          if (section.material_index == static_cast<EntityIndex>(index)) {
            active = true;
            break;
          }
        }
        for (const auto& section : definition_.solid_sections) {
          if (section.MaterialIndex() == static_cast<EntityIndex>(index))
            active = true;
        }
        if (active) {
          ModelFailure(
              "missing-material-density", material.location, "MATERIAL",
              material.name,
              "Each active dynamic or frequency material requires DENSITY.");
          return;
        }
        continue;
      }
      definition_.densities.push_back({static_cast<EntityIndex>(index),
                                       *material.density,
                                       material.density_location});
    }
  }

  void ValidateFrequencyPreprint() {
    for (const auto& block : input_.blocks) {
      if (block.canonical_name != "PREPRINT") {
        continue;
      }
      if (!ValidateParameters(block, {"ECHO", "MODEL", "HISTORY", "CONTACT"}) ||
          block.parameters.size() != 4U) {
        if (!failure_) {
          InputFailure("unsupported-keyword", block.location,
                       block.canonical_name, "",
                       "FREQUENCY requires PREPRINT with ECHO, MODEL, HISTORY, "
                       "and CONTACT parameters.");
        }
        return;
      }
      for (const auto& parameter : block.parameters) {
        if (!parameter.value ||
            !AsciiCaseInsensitiveEquals(*parameter.value, "NO")) {
          InputFailure("unsupported-keyword", block.location,
                       block.canonical_name, parameter.name,
                       "FREQUENCY requires PREPRINT parameters to equal NO.");
          return;
        }
      }
    }
    for (auto& warning : definition_.warnings) {
      if (warning.keyword == "PREPRINT") {
        warning.message = "mandatory-eigen-output-unchanged";
      }
    }
  }

  void ValidateDynamicPreprint() {
    for (const auto& block : input_.blocks) {
      if (block.canonical_name != "PREPRINT") {
        continue;
      }
      if (!ValidateParameters(block, {"ECHO", "MODEL", "HISTORY", "CONTACT"}) ||
          block.parameters.size() != 4U) {
        if (!failure_) {
          InputFailure("unsupported-keyword", block.location,
                       block.canonical_name, "",
                       "DYNAMIC requires PREPRINT with ECHO, MODEL, HISTORY, "
                       "and CONTACT parameters.");
        }
        return;
      }
      for (const auto& parameter : block.parameters) {
        if (!parameter.value ||
            !AsciiCaseInsensitiveEquals(*parameter.value, "NO")) {
          InputFailure("unsupported-keyword", block.location,
                       block.canonical_name, parameter.name,
                       "DYNAMIC requires PREPRINT parameters to equal NO.");
          return;
        }
      }
    }
  }

  void FinalizePartsAndSections() {
    part_section_assignments_.resize(parts_.size());
    part_shell_section_assignments_.resize(parts_.size());
    const bool shell_model =
        model_element_family_ == ElementFamily::kShell ||
        model_element_family_ == ElementFamily::kThermalShell;
    for (std::size_t part_index = 0U; part_index < parts_.size();
         ++part_index) {
      const RawPart& part = parts_[part_index];
      if (part.nodes.empty() || part.elements.empty() ||
          (!shell_model && model_element_family_ != ElementFamily::kSolid &&
           part.sections.empty())) {
        InputFailure("invalid-model-cardinality", part.location, "PART",
                     part.name,
                     "A part requires nodes, elements, and its approved "
                     "section form.");
        return;
      }

      PartDefinition part_definition{};
      part_definition.name = part.name;
      part_definition.location = part.location;
      for (const auto& node : part.nodes) {
        part_definition.node_source_labels.push_back(node.label);
      }
      for (const auto& element : part.elements) {
        part_definition.element_source_labels.push_back(element.label);
        for (const auto node_label : element.node_labels) {
          if (FindNode(part, node_label) == nullptr) {
            InputFailure(shell_model ? "invalid-shell-connectivity"
                                     : "unresolved-reference",
                         element.location, "ELEMENT", element.label_text,
                         "Element connectivity must resolve within its part.");
            return;
          }
        }
      }
      for (const auto& set : part.node_sets) {
        part_definition.node_set_names.push_back(set.name);
        for (const auto label : set.members) {
          if (FindNode(part, label) == nullptr) {
            InputFailure("unresolved-reference", set.location, "NSET", set.name,
                         "Every node-set member must resolve within its part.");
            return;
          }
        }
      }
      for (const auto& set : part.element_sets) {
        part_definition.element_set_names.push_back(set.name);
        for (const auto label : set.members) {
          if (FindElement(part, label) == nullptr) {
            InputFailure(
                "unresolved-reference", set.location, "ELSET", set.name,
                "Every element-set member must resolve within its part.");
            return;
          }
        }
      }
      definition_.parts.push_back(std::move(part_definition));

      if (model_element_family_ == ElementFamily::kSolid) {
        auto& assignments = part_shell_section_assignments_[part_index];
        for (const auto& section : part.solid_sections) {
          const auto* element_set =
              FindSet(part.element_sets, section.element_set_name);
          const auto material = FindMaterialIndex(section.material_name);
          if (!element_set || !material) {
            InputFailure("unresolved-solid-section", section.location,
                         "SOLID SECTION", section.element_set_name,
                         "Solid ELSET and MATERIAL must resolve.");
            return;
          }
          const auto index =
              static_cast<EntityIndex>(definition_.solid_sections.size());
          definition_.solid_sections.emplace_back(
              SourceEntityId{part.name, static_cast<std::int64_t>(index),
                             section.element_set_name},
              section.element_set_name, *material, section.location);
          for (const auto label : element_set->members) {
            if (!assignments.emplace(label, std::make_pair(index, *material))
                     .second) {
              InputFailure(
                  "invalid-solid-section-assignment", section.location,
                  "SOLID SECTION", std::to_string(label),
                  "Solid elements require exactly one section assignment.");
              return;
            }
          }
        }
        for (const auto& element : part.elements) {
          if (assignments.find(element.label) == assignments.end()) {
            InputFailure("invalid-solid-section-assignment", element.location,
                         "ELEMENT", element.label_text,
                         "A Solid section assignment is missing.");
            return;
          }
        }
        continue;
      }
      if (shell_model) {
        auto& assignments = part_shell_section_assignments_[part_index];
        for (const auto& section : part.shell_sections) {
          const auto* element_set =
              FindSet(part.element_sets, section.element_set_name);
          const auto material_index = FindMaterialIndex(section.material_name);
          if (element_set == nullptr || !material_index) {
            InputFailure("unresolved-shell-section", section.location,
                         "SHELL SECTION", section.element_set_name,
                         "Shell section ELSET and MATERIAL references "
                         "must resolve.");
            return;
          }
          const EntityIndex section_index =
              model_element_family_ == ElementFamily::kThermalShell
                  ? static_cast<EntityIndex>(
                        definition_.thermal_sections.size())
                  : static_cast<EntityIndex>(definition_.shell_sections.size());
          if (model_element_family_ == ElementFamily::kThermalShell) {
            definition_.thermal_sections.push_back(
                {{part.name, static_cast<std::int64_t>(section_index),
                  section.element_set_name},
                 section.element_set_name,
                 section.thickness,
                 *material_index,
                 section.location});
          } else {
            definition_.shell_sections.push_back(
                {section.element_set_name, section.thickness, *material_index,
                 section.location});
          }
          for (const auto element_label : element_set->members) {
            if (!assignments
                     .emplace(element_label,
                              std::make_pair(section_index, *material_index))
                     .second) {
              InputFailure("invalid-shell-section-assignment", section.location,
                           "SHELL SECTION", std::to_string(element_label),
                           "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.label_text,
                         "Every shell element requires exactly one "
                         "resolved section assignment.");
            return;
          }
        }
        continue;
      }

      auto& assignments = part_section_assignments_[part_index];
      for (const auto& section : part.sections) {
        const auto* element_set =
            FindSet(part.element_sets, section.element_set_name);
        const auto material_index = FindMaterialIndex(section.material_name);
        if (element_set == nullptr || !material_index) {
          InputFailure("unresolved-reference", section.location,
                       "BEAM GENERAL SECTION", section.element_set_name,
                       "Section ELSET and MATERIAL references must resolve.");
          return;
        }
        if (section.properties[2] != 0.0) {
          ModelFailure("unsupported-coupled-section", section.location,
                       "BEAM GENERAL SECTION", section.element_set_name,
                       "V0 requires exact I12=0.");
          return;
        }
        if (!(section.properties[0] > 0.0) || !(section.properties[1] > 0.0) ||
            !(section.properties[3] > 0.0) || !(section.properties[4] > 0.0)) {
          ModelFailure("invalid-beam-property", section.location,
                       "BEAM GENERAL SECTION", section.element_set_name,
                       "A, I11, I22, and J must be positive.");
          return;
        }
        const EntityIndex section_index =
            static_cast<EntityIndex>(definition_.sections.size());
        definition_.sections.push_back(
            {section.element_set_name, section.properties[0],
             section.properties[1], section.properties[2],
             section.properties[3], section.properties[4], section.first_axis,
             section.section_points, section.location});
        for (const auto element_label : element_set->members) {
          if (!assignments
                   .emplace(element_label,
                            std::make_pair(section_index, *material_index))
                   .second) {
            InputFailure("duplicate-entity", section.location,
                         "BEAM GENERAL SECTION", std::to_string(element_label),
                         "An element cannot receive multiple section "
                         "assignments.");
            return;
          }
        }
      }
      for (const auto& element : part.elements) {
        if (assignments.find(element.label) == assignments.end()) {
          InputFailure(
              "unresolved-reference", element.location, "ELEMENT",
              element.label_text,
              "Every B33 element requires a resolved section assignment.");
          return;
        }
      }
    }
  }

  std::size_t PartIndex(const RawPart& part) const {
    return static_cast<std::size_t>(&part - parts_.data());
  }

  bool ValidateGeometry(const RawElement& raw, const Node& first,
                        const Node& second, const GeneralBeamSection& section) {
    const auto maximum_absolute = [](const Vector3& vector) {
      return std::max(
          {std::abs(vector[0]), std::abs(vector[1]), std::abs(vector[2])});
    };
    const Vector3 first_position{first.coordinates};
    const Vector3 second_position{second.coordinates};

    // Compare both approved inequalities after a common scaling. This
    // preserves the exact ratios while avoiding overflow in x*x and in
    // subtraction between large finite coordinates.
    const double global_coordinate_scale =
        std::max({1.0, maximum_absolute(first_position),
                  maximum_absolute(second_position)});
    const Vector3 first_scaled = first_position / global_coordinate_scale;
    const Vector3 second_scaled = second_position / global_coordinate_scale;
    const Vector3 delta_scaled = second_scaled - first_scaled;
    const double length_ratio = delta_scaled.Norm();
    const double coordinate_norm_ratio =
        std::max({1.0 / global_coordinate_scale, first_scaled.Norm(),
                  second_scaled.Norm()});
    if (!(length_ratio > 1.0e-12 * coordinate_norm_ratio)) {
      return ModelFailure(
          "invalid-beam-length", raw.location, "ELEMENT", raw.label_text,
          "Beam length fails the approved scale-aware threshold.");
    }
    const Vector3 tangent = delta_scaled / length_ratio;

    const Vector3 guide{section.first_axis};
    const double global_guide_scale = std::max(1.0, maximum_absolute(guide));
    const Vector3 guide_scaled = guide / global_guide_scale;
    const double projection = guide_scaled.Dot(tangent);
    const Vector3 perpendicular = guide_scaled - projection * tangent;
    const double guide_norm_ratio =
        std::max(1.0 / global_guide_scale, guide_scaled.Norm());
    if (!(perpendicular.Norm() > 1.0e-12 * guide_norm_ratio)) {
      return ModelFailure(
          "invalid-beam-guide-vector", section.location, "BEAM GENERAL SECTION",
          raw.label_text,
          "The first section axis cannot be zero or tangent-parallel.");
    }
    return true;
  }

  void ExpandInstances() {
    for (const auto& raw_instance : instances_) {
      const RawPart* part = FindPart(raw_instance.part_name);
      if (part == nullptr) {
        InputFailure("unresolved-reference", raw_instance.location, "INSTANCE",
                     raw_instance.name,
                     "INSTANCE PART must resolve case-insensitively.");
        return;
      }
      InstanceDefinition instance{
          raw_instance.name, part->name, {}, {}, raw_instance.location};
      std::map<std::int64_t, EntityIndex> node_indices;
      std::map<std::int64_t, EntityIndex> element_indices;

      // Instance order, followed by part-local declaration order, is the
      // sole source of stable expanded internal IDs.
      for (const auto& raw_node : part->nodes) {
        if (definition_.nodes.size() >
            std::numeric_limits<EntityIndex>::max()) {
          InputFailure("entity-index-overflow", raw_node.location, "NODE",
                       raw_node.label_text,
                       "Expanded node count exceeds EntityIndex capacity.");
          return;
        }
        const EntityIndex index =
            static_cast<EntityIndex>(definition_.nodes.size());
        definition_.nodes.push_back(
            {{raw_instance.name, raw_node.label, raw_node.label_text},
             raw_node.coordinates,
             raw_node.location});
        node_indices.emplace(raw_node.label, index);
        instance.node_mappings.push_back({raw_node.label, index});
      }

      for (const auto& raw_element : part->elements) {
        EntityIndex index = 0U;
        if (raw_element.type == RawElement::Type::kB33) {
          const auto first = node_indices.find(raw_element.node_labels[0]);
          const auto second = node_indices.find(raw_element.node_labels[1]);
          const auto& assignments = part_section_assignments_[PartIndex(*part)];
          const auto assignment = assignments.find(raw_element.label);
          if (first == node_indices.end() || second == node_indices.end() ||
              assignment == assignments.end()) {
            InputFailure(
                "unresolved-reference", raw_element.location, "ELEMENT",
                raw_element.label_text,
                "Expanded connectivity and section assignment must resolve.");
            return;
          }
          if (definition_.elements.size() >
              std::numeric_limits<EntityIndex>::max()) {
            InputFailure(
                "entity-index-overflow", raw_element.location, "ELEMENT",
                raw_element.label_text,
                "Expanded element count exceeds EntityIndex capacity.");
            return;
          }
          index = static_cast<EntityIndex>(definition_.elements.size());
          const auto& section = definition_.sections[assignment->second.first];
          if (!ValidateGeometry(raw_element, definition_.nodes[first->second],
                                definition_.nodes[second->second], section)) {
            return;
          }
          definition_.elements.push_back(
              {{raw_instance.name, raw_element.label, raw_element.label_text},
               {first->second, second->second},
               assignment->second.second,
               assignment->second.first,
               raw_element.location});
        } else if (raw_element.type == RawElement::Type::kC3d8) {
          std::array<EntityIndex, 8> connected_nodes{};
          for (std::size_t node = 0U; node < connected_nodes.size(); ++node) {
            const auto found = node_indices.find(raw_element.node_labels[node]);
            if (found == node_indices.end()) {
              InputFailure("invalid-solid-connectivity", raw_element.location,
                           "ELEMENT", raw_element.label_text,
                           "Solid nodes must resolve.");
              return;
            }
            connected_nodes[node] = found->second;
          }
          const auto& assignments =
              part_shell_section_assignments_[PartIndex(*part)];
          const auto assignment = assignments.find(raw_element.label);
          if (assignment == assignments.end() ||
              definition_.solid_elements.size() >
                  std::numeric_limits<EntityIndex>::max()) {
            InputFailure("invalid-solid-section-assignment",
                         raw_element.location, "ELEMENT",
                         raw_element.label_text,
                         "Solid assignment must resolve.");
            return;
          }
          index = static_cast<EntityIndex>(definition_.solid_elements.size());
          definition_.solid_elements.emplace_back(
              SourceEntityId{raw_instance.name, raw_element.label,
                             raw_element.label_text},
              connected_nodes, assignment->second.second,
              assignment->second.first, raw_element.location);
        } else {
          std::array<EntityIndex, 4> connected_nodes{};
          for (std::size_t node = 0U; node < connected_nodes.size(); ++node) {
            const auto found = node_indices.find(raw_element.node_labels[node]);
            if (found == node_indices.end()) {
              InputFailure("invalid-shell-connectivity", raw_element.location,
                           "ELEMENT", raw_element.label_text,
                           "Expanded shell connectivity must resolve.");
              return;
            }
            connected_nodes[node] = found->second;
          }
          const auto& assignments =
              part_shell_section_assignments_[PartIndex(*part)];
          const auto assignment = assignments.find(raw_element.label);
          if (assignment == assignments.end()) {
            InputFailure(
                "invalid-shell-section-assignment", raw_element.location,
                "ELEMENT", raw_element.label_text,
                "Expanded shell section assignment must resolve exactly once.");
            return;
          }
          if (raw_element.type == RawElement::Type::kDs4) {
            if (definition_.thermal_elements.size() >
                std::numeric_limits<EntityIndex>::max()) {
              InputFailure("entity-index-overflow", raw_element.location,
                           "ELEMENT", raw_element.label_text,
                           "Expanded thermal element count exceeds EntityIndex "
                           "capacity.");
              return;
            }
            index =
                static_cast<EntityIndex>(definition_.thermal_elements.size());
            definition_.thermal_elements.push_back(
                {{raw_instance.name, raw_element.label, raw_element.label_text},
                 connected_nodes,
                 assignment->second.first,
                 raw_element.location});
            element_indices.emplace(raw_element.label, index);
            instance.element_mappings.push_back({raw_element.label, index});
            continue;
          }
          if (definition_.shell_elements.size() >
              std::numeric_limits<EntityIndex>::max()) {
            InputFailure(
                "entity-index-overflow", raw_element.location, "ELEMENT",
                raw_element.label_text,
                "Expanded shell element count exceeds EntityIndex capacity.");
            return;
          }
          index = static_cast<EntityIndex>(definition_.shell_elements.size());
          definition_.shell_elements.push_back(
              {{raw_instance.name, raw_element.label, raw_element.label_text},
               raw_element.type == RawElement::Type::kS4
                   ? ShellSourceElementType::kS4
                   : ShellSourceElementType::kS4r,
               connected_nodes,
               assignment->second.second,
               assignment->second.first,
               raw_element.location});
        }
        element_indices.emplace(raw_element.label, index);
        instance.element_mappings.push_back({raw_element.label, index});
      }

      for (const auto& raw_set : part->node_sets) {
        NodeSet set{raw_set.name, raw_instance.name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto found = node_indices.find(member);
          if (found == node_indices.end()) {
            InputFailure("unresolved-reference", raw_set.location, "NSET",
                         raw_set.name, "Part node-set expansion failed.");
            return;
          }
          set.node_indices.push_back(found->second);
        }
        definition_.node_sets.push_back(std::move(set));
      }
      for (const auto& raw_set : part->element_sets) {
        ElementSet set{raw_set.name, raw_instance.name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto found = element_indices.find(member);
          if (found == element_indices.end()) {
            InputFailure("unresolved-reference", raw_set.location, "ELSET",
                         raw_set.name, "Part element-set expansion failed.");
            return;
          }
          set.element_indices.push_back(found->second);
        }
        definition_.element_sets.push_back(std::move(set));
      }
      definition_.instances.push_back(std::move(instance));
    }
  }

  void ExpandAssemblySets() {
    for (const auto& raw_set : assembly_sets_) {
      const RawInstance* raw_instance = FindInstance(raw_set.instance_name);
      if (raw_instance == nullptr) {
        InputFailure("unresolved-reference", raw_set.location,
                     raw_set.is_node_set ? "NSET" : "ELSET", raw_set.name,
                     "Assembly set INSTANCE must resolve.");
        return;
      }
      const auto definition_instance = std::find_if(
          definition_.instances.begin(), definition_.instances.end(),
          [&raw_instance](const InstanceDefinition& instance) {
            return AsciiCaseInsensitiveEquals(instance.name,
                                              raw_instance->name);
          });
      if (definition_instance == definition_.instances.end()) {
        InputFailure("unresolved-reference", raw_set.location,
                     raw_set.is_node_set ? "NSET" : "ELSET", raw_set.name,
                     "Assembly set instance expansion is unavailable.");
        return;
      }
      if (raw_set.is_node_set) {
        definition_.node_sets.erase(
            std::remove_if(
                definition_.node_sets.begin(), definition_.node_sets.end(),
                [&raw_set](const NodeSet& set) {
                  return AsciiCaseInsensitiveEquals(set.name, raw_set.name);
                }),
            definition_.node_sets.end());
        NodeSet set{
            raw_set.name, definition_instance->name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto mapping =
              std::find_if(definition_instance->node_mappings.begin(),
                           definition_instance->node_mappings.end(),
                           [member](const SourceIndexMapping& value) {
                             return value.source_label == member;
                           });
          if (mapping == definition_instance->node_mappings.end()) {
            InputFailure("unresolved-reference", raw_set.location, "NSET",
                         raw_set.name,
                         "Assembly node-set member must resolve in its "
                         "instance.");
            return;
          }
          set.node_indices.push_back(mapping->internal_index);
        }
        definition_.node_sets.push_back(std::move(set));
      } else {
        definition_.element_sets.erase(
            std::remove_if(definition_.element_sets.begin(),
                           definition_.element_sets.end(),
                           [&raw_set](const ElementSet& set) {
                             return AsciiCaseInsensitiveEquals(set.name,
                                                               raw_set.name);
                           }),
            definition_.element_sets.end());
        ElementSet set{
            raw_set.name, definition_instance->name, {}, raw_set.location};
        for (const auto member : raw_set.members) {
          const auto mapping =
              std::find_if(definition_instance->element_mappings.begin(),
                           definition_instance->element_mappings.end(),
                           [member](const SourceIndexMapping& value) {
                             return value.source_label == member;
                           });
          if (mapping == definition_instance->element_mappings.end()) {
            InputFailure("unresolved-reference", raw_set.location, "ELSET",
                         raw_set.name,
                         "Assembly element-set member must resolve in "
                         "its instance.");
            return;
          }
          set.element_indices.push_back(mapping->internal_index);
        }
        definition_.element_sets.push_back(std::move(set));
      }
    }
  }

  bool AppendSurfaceFacet(
      const RawSurfaceMember& member, const RawInstance& raw_instance,
      std::size_t instance_ordinal, EntityIndex element_index,
      SurfaceMemberKind member_kind, const std::string& elset_name_raw,
      std::vector<std::pair<ElementSurfaceFacetDefinition, std::size_t>>*
          candidates) {
    const bool thermal = model_element_family_ == ElementFamily::kThermalShell;
    const auto element_count = thermal ? definition_.thermal_elements.size()
                                       : definition_.shell_elements.size();
    if (static_cast<std::size_t>(element_index) >= element_count) {
      return InputFailure(
          "unsupported-element-formulation", member.location, "SURFACE",
          member.target,
          "Element surfaces may resolve only to S4 or S4R shell elements.");
    }
    const RawPart* part = FindPart(raw_instance.part_name);
    if (part == nullptr) {
      return InputFailure(
          "unresolved-reference", member.location, "SURFACE", member.target,
          "The surface instance must resolve to its source part.");
    }
    const auto& source_id =
        thermal ? definition_.thermal_elements[element_index].source_id
                : definition_.shell_elements[element_index].source_id;
    const std::string source_type =
        thermal ? "DS4"
                : (definition_.shell_elements[element_index].source_type ==
                           ShellSourceElementType::kS4
                       ? "S4"
                       : "S4R");
    ElementSurfaceFacetDefinition facet{element_index,
                                        0U,
                                        part->name,
                                        CanonicalizeAscii(part->name),
                                        raw_instance.name,
                                        CanonicalizeAscii(raw_instance.name),
                                        source_id.source_label,
                                        source_id.source_label_text,
                                        source_type,
                                        member.side,
                                        member.location,
                                        member.ordinal,
                                        member_kind,
                                        elset_name_raw,
                                        member_kind == SurfaceMemberKind::kElset
                                            ? CanonicalizeAscii(elset_name_raw)
                                            : ""};
    candidates->push_back({std::move(facet), instance_ordinal});
    return true;
  }

  bool ResolveDirectSurfaceMember(
      const RawSurfaceMember& member,
      std::vector<std::pair<ElementSurfaceFacetDefinition, std::size_t>>*
          candidates) {
    const std::size_t dot = member.target.find('.');
    if (dot == std::string::npos || dot == 0U ||
        dot + 1U >= member.target.size() ||
        member.target.find('.', dot + 1U) != std::string::npos) {
      return InputFailure(
          "unresolved-reference", member.location, "SURFACE", member.target,
          "A direct surface member must be instance.positive-element-label.");
    }
    const std::string instance_name = member.target.substr(0U, dot);
    if (!IsPressureNameToken(instance_name)) {
      return InputFailure(
          "unsupported-surface-target", member.location, "SURFACE",
          member.target,
          "A direct surface member must use an identity instance name.");
    }
    std::int64_t source_label = 0;
    if (!ParseInteger(member.target.substr(dot + 1U), source_label,
                      member.location, "SURFACE", true)) {
      return false;
    }
    const auto raw_instance = std::find_if(
        instances_.begin(), instances_.end(),
        [&instance_name](const RawInstance& value) {
          return AsciiCaseInsensitiveEquals(value.name, instance_name);
        });
    if (raw_instance == instances_.end()) {
      if (FindPart(instance_name) != nullptr) {
        return InputFailure(
            "unsupported-surface-target", member.location, "SURFACE",
            member.target,
            "A direct surface member cannot use a part name as an instance.");
      }
      return InputFailure("unresolved-reference", member.location, "SURFACE",
                          member.target,
                          "A direct surface member instance must resolve.");
    }
    const auto instance = std::find_if(
        definition_.instances.begin(), definition_.instances.end(),
        [&raw_instance](const InstanceDefinition& value) {
          return AsciiCaseInsensitiveEquals(value.name, raw_instance->name);
        });
    const auto element = std::find_if(
        instance->element_mappings.begin(), instance->element_mappings.end(),
        [source_label](const SourceIndexMapping& value) {
          return value.source_label == source_label;
        });
    if (element == instance->element_mappings.end()) {
      return InputFailure(
          "unresolved-reference", member.location, "SURFACE", member.target,
          "A direct surface member must resolve to a supported shell element.");
    }
    return AppendSurfaceFacet(member, *raw_instance,
                              static_cast<std::size_t>(std::distance(
                                  instances_.begin(), raw_instance)),
                              element->internal_index,
                              SurfaceMemberKind::kDirect, "", candidates);
  }

  bool ResolveElsetSurfaceMember(
      const RawSurfaceMember& member,
      std::vector<std::pair<ElementSurfaceFacetDefinition, std::size_t>>*
          candidates) {
    if (!IsPressureNameToken(member.target)) {
      return InputFailure("unsupported-surface-target", member.location,
                          "SURFACE", member.target,
                          "A surface ELSET must use the approved name syntax.");
    }
    const auto raw_set = std::find_if(
        assembly_sets_.begin(), assembly_sets_.end(),
        [&member](const RawAssemblySet& value) {
          return !value.is_node_set &&
                 AsciiCaseInsensitiveEquals(value.name, member.target);
        });
    if (raw_set == assembly_sets_.end()) {
      const bool part_scoped = std::any_of(
          parts_.begin(), parts_.end(), [this, &member](const RawPart& part) {
            return FindSet(part.element_sets, member.target) != nullptr;
          });
      if (part_scoped) {
        return InputFailure(
            "cross-scope-target", member.location, "SURFACE", member.target,
            "A surface ELSET must be declared at assembly scope.");
      }
      return InputFailure(
          "missing-reference", member.location, "SURFACE", member.target,
          "A surface ELSET must be assembly-scoped and explicit-instance.");
    }
    const auto raw_instance = std::find_if(
        instances_.begin(), instances_.end(),
        [&raw_set](const RawInstance& value) {
          return AsciiCaseInsensitiveEquals(value.name, raw_set->instance_name);
        });
    if (raw_instance == instances_.end()) {
      return InputFailure("unresolved-reference", member.location, "SURFACE",
                          member.target,
                          "The surface ELSET instance must resolve.");
    }
    const auto element_set = std::find_if(
        definition_.element_sets.begin(), definition_.element_sets.end(),
        [&raw_set](const ElementSet& value) {
          return AsciiCaseInsensitiveEquals(value.name, raw_set->name) &&
                 value.instance_name &&
                 AsciiCaseInsensitiveEquals(*value.instance_name,
                                            raw_set->instance_name);
        });
    if (element_set == definition_.element_sets.end()) {
      return InputFailure(
          "unresolved-reference", member.location, "SURFACE", member.target,
          "The surface ELSET must expand in its explicit instance.");
    }
    for (const EntityIndex element_index : element_set->element_indices) {
      if (!AppendSurfaceFacet(member, *raw_instance,
                              static_cast<std::size_t>(std::distance(
                                  instances_.begin(), raw_instance)),
                              element_index, SurfaceMemberKind::kElset,
                              member.target, candidates)) {
        return false;
      }
    }
    return true;
  }

  void ResolveElementSurfaces() {
    std::vector<ElementSurfaceDefinition> resolved_surfaces;
    resolved_surfaces.reserve(element_surfaces_.size());
    for (const auto& surface : element_surfaces_) {
      std::vector<std::pair<ElementSurfaceFacetDefinition, std::size_t>>
          candidates;
      for (const auto& member : surface.members) {
        const bool is_direct = member.target.find('.') != std::string::npos;
        if (!(is_direct ? ResolveDirectSurfaceMember(member, &candidates)
                        : ResolveElsetSurfaceMember(member, &candidates))) {
          return;
        }
      }
      if (candidates.empty()) {
        InputFailure("empty-surface", surface.location, "SURFACE", surface.name,
                     "An element surface must resolve at least one facet.");
        return;
      }

      std::vector<std::pair<ElementSurfaceFacetDefinition, std::size_t>>
          unique_facets;
      for (auto& candidate : candidates) {
        const auto same_element =
            std::find_if(unique_facets.begin(), unique_facets.end(),
                         [&candidate](const auto& existing) {
                           return existing.first.instance_name_canonical ==
                                      candidate.first.instance_name_canonical &&
                                  existing.first.source_element_label ==
                                      candidate.first.source_element_label;
                         });
        if (same_element != unique_facets.end()) {
          if (same_element->first.side != candidate.first.side) {
            InputFailure(
                "conflicting-surface-membership",
                candidate.first.first_member_location, "SURFACE", surface.name,
                "One shell element cannot appear on both surface sides.");
            return;
          }
          if (model_element_family_ != ElementFamily::kThermalShell) {
            definition_.warnings.push_back(
                {Severity::kWarning, "duplicate-surface-member-normalized",
                 candidate.first.first_member_location, "SURFACE", surface.name,
                 "A repeated same-side surface member was normalized once."});
          }
          continue;
        }
        unique_facets.push_back(std::move(candidate));
      }
      std::sort(unique_facets.begin(), unique_facets.end(),
                [](const auto& lhs, const auto& rhs) {
                  const int lhs_side =
                      lhs.first.side == ShellSurfaceSide::kSpos ? 0 : 1;
                  const int rhs_side =
                      rhs.first.side == ShellSurfaceSide::kSpos ? 0 : 1;
                  return std::tie(lhs.second, lhs.first.source_element_label,
                                  lhs_side) <
                         std::tie(rhs.second, rhs.first.source_element_label,
                                  rhs_side);
                });

      ElementSurfaceDefinition resolved{surface.name,
                                        CanonicalizeAscii(surface.name),
                                        {},
                                        surface.location,
                                        surface.declaration_ordinal};
      resolved.facets.reserve(unique_facets.size());
      for (std::size_t ordinal = 0U; ordinal < unique_facets.size();
           ++ordinal) {
        unique_facets[ordinal].first.facet_ordinal = ordinal;
        resolved.facets.push_back(std::move(unique_facets[ordinal].first));
      }
      resolved_surfaces.push_back(std::move(resolved));
    }
    definition_.element_surfaces = std::move(resolved_surfaces);
  }

  /// @brief Builds one stable node-target index from the completed candidate.
  SourceTargetIndex BuildSourceTargetIndex() const {
    std::vector<SourceTargetIndexEntry> entries;
    std::size_t declaration_order = 0U;
    for (std::size_t node = 0U; node < definition_.nodes.size(); ++node) {
      const auto& source_id = definition_.nodes[node].source_id;
      entries.push_back({SourceEntityKind::kNode, source_id.instance_name, "",
                         source_id, static_cast<EntityIndex>(node),
                         declaration_order++});
    }
    for (const auto& set : definition_.node_sets) {
      for (const EntityIndex node : set.node_indices) {
        const auto& source_id = definition_.nodes[node].source_id;
        entries.push_back({SourceEntityKind::kNode,
                           set.instance_name.value_or(source_id.instance_name),
                           set.name, source_id, node, declaration_order++});
      }
    }
    return SourceTargetIndex{std::move(entries)};
  }

  std::optional<std::vector<EntityIndex>> ResolveNodeTarget(
      const SourceTargetResolver& resolver, const std::string& target,
      const SourceLocation& location, const std::string& keyword) {
    auto resolved = resolver.Resolve({SourceEntityKind::kNode, "", target});
    if (!resolved.HasValue()) {
      InputFailure(
          "unresolved-reference", location, keyword, target,
          "The boundary or load target must resolve unambiguously to one "
          "node or one node set.");
      return std::nullopt;
    }
    std::vector<EntityIndex> indices;
    indices.reserve(resolved.Value().size());
    for (const auto& entry : resolved.Value()) {
      if (model_element_family_ == ElementFamily::kThermalShell &&
          !thermal_active_nodes_[entry.entity_index]) {
        ModelFailure("inactive-thermal-target", location, keyword, target,
                     "Thermal targets must connect to an active DS4 element.");
        return std::nullopt;
      }
      indices.push_back(entry.entity_index);
    }
    return indices;
  }

  void FinalizeStep() {
    if (step_.has_heat_transfer) {
      thermal_active_nodes_.assign(definition_.nodes.size(), false);
      for (const auto& element : definition_.thermal_elements)
        for (const auto node : element.node_indices)
          thermal_active_nodes_[node] = true;
      const SourceTargetIndex target_index = BuildSourceTargetIndex();
      const SourceTargetResolver resolver{target_index};
      const auto append_boundaries =
          [this, &resolver](
              const std::vector<RawThermalBoundary>& rows,
              std::map<std::pair<EntityIndex, int>, double>* values,
              std::vector<ThermalBoundaryConditionDefinition>* out) {
            for (const auto& row : rows) {
              const auto nodes = ResolveNodeTarget(resolver, row.target,
                                                   row.location, "BOUNDARY");
              if (!nodes) return false;
              for (const EntityIndex node : *nodes) {
                const auto key = std::make_pair(node, row.dof);
                const auto existing = values->find(key);
                if (existing != values->end() &&
                    existing->second != row.value) {
                  return InputFailure("conflicting-boundary-condition",
                                      row.location, "BOUNDARY", row.target,
                                      "Expanded thermal boundaries prescribe "
                                      "different values.");
                }
                (*values)[key] = row.value;
                out->push_back({node, row.dof, row.value, row.location});
              }
            }
            return true;
          };
      std::map<std::pair<EntityIndex, int>, double> model_values;
      if (!append_boundaries(thermal_model_boundaries_, &model_values,
                             &definition_.thermal_model_boundaries))
        return;
      std::vector<ThermalBoundaryConditionDefinition> step_boundaries;
      std::map<std::pair<EntityIndex, int>, double> step_values;
      if (!append_boundaries(step_.thermal_boundaries, &step_values,
                             &step_boundaries))
        return;
      std::map<EntityIndex, double> initial_values;
      for (const auto& row : thermal_initial_conditions_) {
        const auto nodes = ResolveNodeTarget(resolver, row.target, row.location,
                                             "INITIAL CONDITIONS");
        if (!nodes) return;
        for (const EntityIndex node : *nodes) {
          const auto inserted = initial_values.emplace(node, row.value);
          if (!inserted.second && inserted.first->second != row.value) {
            InputFailure(
                "conflicting-initial-temperature", row.location,
                "INITIAL CONDITIONS", row.target,
                "Expanded initial temperatures prescribe different values.");
            return;
          }
          definition_.thermal_initial_conditions.push_back(
              {node, row.value, row.location});
        }
      }
      std::vector<ThermalFluxLoadDefinition> loads;
      for (const auto& row : step_.thermal_fluxes) {
        const auto nodes =
            ResolveNodeTarget(resolver, row.target, row.location, "CFLUX");
        if (!nodes) return;
        for (const EntityIndex node : *nodes) {
          loads.push_back(
              {node, row.dof, row.power, row.location, loads.size()});
        }
      }
      definition_.thermal_step = {step_.name_raw,
                                  step_.thermal_increment,
                                  step_.thermal_period,
                                  step_.maximum_increments,
                                  false,
                                  std::move(step_boundaries),
                                  std::move(loads),
                                  step_.location};
      return;
    }
    std::vector<PrescribedDisplacementDefinition> boundaries =
        model_boundaries_;
    boundaries.insert(boundaries.end(), step_.boundaries.begin(),
                      step_.boundaries.end());
    if (step_.frequency) {
      ValidateEigenBoundaries(boundaries);
      if (failure_) {
        return;
      }
    }
    if (step_.dynamic) {
      ValidateDynamicBoundaries(boundaries);
      if (failure_) {
        return;
      }
    }
    const SourceTargetIndex target_index = BuildSourceTargetIndex();
    const SourceTargetResolver target_resolver{target_index};

    if (model_element_family_ == ElementFamily::kSolid) {
      std::vector<PrescribedDisplacementDefinition> physical;
      for (auto boundary : boundaries) {
        if (!ResolveNodeTarget(target_resolver, boundary.target,
                               boundary.location, "BOUNDARY"))
          return;
        if (boundary.last_dof > 3) {
          if (boundary.value != 0.0) {
            InputFailure("unsupported-solid-rotation-boundary",
                         boundary.location, "BOUNDARY", boundary.target,
                         "Solid rotational boundaries must be exact zero to be "
                         "inactive.");
            return;
          }
          definition_.warnings.push_back(
              {Severity::kWarning, "inactive-solid-rotation-boundary",
               boundary.location, "BOUNDARY", boundary.target,
               "Exact-zero rotational boundary DOFs " +
                   std::to_string(std::max(4, boundary.first_dof)) + ".." +
                   std::to_string(boundary.last_dof) +
                   " are inactive; Solid equations contain translations "
                   "only."});
          boundary.last_dof = 3;
        }
        if (boundary.first_dof <= boundary.last_dof)
          physical.push_back(std::move(boundary));
      }
      boundaries = std::move(physical);
      std::vector<bool> active(definition_.nodes.size(), false);
      for (const auto& element : definition_.solid_elements)
        for (const auto node : element.node_indices) active[node] = true;
      for (std::size_t node = 0U; node < active.size(); ++node) {
        if (!active[node]) {
          ModelFailure("unused-solid-node", definition_.nodes[node].location,
                       "NODE",
                       definition_.nodes[node].source_id.source_label_text,
                       "Every Solid node must connect to a C3D8 element.");
          return;
        }
      }
    }
    std::map<std::pair<EntityIndex, int>, double> prescribed_values;
    for (const auto& boundary : boundaries) {
      auto target = ResolveNodeTarget(target_resolver, boundary.target,
                                      boundary.location, "BOUNDARY");
      if (!target) {
        return;
      }
      for (const auto node : *target) {
        for (int dof = boundary.first_dof; dof <= boundary.last_dof; ++dof) {
          const auto key = std::make_pair(node, dof);
          const auto existing = prescribed_values.find(key);
          if (existing != prescribed_values.end() &&
              existing->second != boundary.value) {
            InputFailure("conflicting-boundary-condition", boundary.location,
                         "BOUNDARY", boundary.target,
                         "Expanded boundary rows prescribe different values to "
                         "one node/DOF.");
            return;
          }
          prescribed_values[key] = boundary.value;
        }
      }
    }
    for (const auto& load : step_.loads) {
      if (!ResolveNodeTarget(target_resolver, load.target, load.location,
                             "CLOAD")) {
        return;
      }
    }
    if (step_.frequency) {
      step_.frequency->boundaries = std::move(boundaries);
      definition_.frequency_step = std::move(step_.frequency);
      return;
    }
    if (step_.dynamic) {
      step_.dynamic->boundaries = std::move(boundaries);
      step_.dynamic->loads = step_.loads;
      definition_.dynamic_step = std::move(step_.dynamic);
      return;
    }
    std::vector<SurfacePressureLoadDefinition> surface_pressure_loads;
    surface_pressure_loads.reserve(step_.surface_pressure_loads.size());
    for (const auto& load : step_.surface_pressure_loads) {
      const auto surface = std::find_if(
          definition_.element_surfaces.begin(),
          definition_.element_surfaces.end(), [&load](const auto& candidate) {
            return AsciiCaseInsensitiveEquals(candidate.surface_name_raw,
                                              load.surface_name);
          });
      if (surface == definition_.element_surfaces.end()) {
        InputFailure("missing-reference", load.data_location, "DSLOAD",
                     load.surface_name,
                     "A DSLOAD surface must resolve after surface validation.");
        return;
      }
      surface_pressure_loads.push_back(
          {step_.name_raw, step_.name_canonical,
           static_cast<EntityIndex>(
               std::distance(definition_.element_surfaces.begin(), surface)),
           load.surface_name, CanonicalizeAscii(load.surface_name), "P",
           load.magnitude, load.magnitude_raw, load.keyword_location,
           load.data_location, load.data_ordinal, load.load_ordinal});
    }

    // Static time-control values are provenance only: V0 creates exactly
    // the canonical final frame 0 and performs no increment loop here.
    definition_.steps.push_back(
        {model_element_family_ == ElementFamily::kSolid ? step_.name_raw
                                                        : "Step-1",
         std::move(boundaries), step_.loads, std::move(surface_pressure_loads),
         step_.procedure_kind, step_.nlgeom, step_.static_values[0],
         step_.static_values[1], step_.static_values[2], step_.static_values[3],
         step_.location});
    definition_.steps.back().direct = step_.static_direct;
    definition_.steps.back().increment_count = step_.static_increment_count;
    definition_.steps.back().maximum_increments = step_.maximum_increments;
  }

  const ParsedInput& input_;
  ModelDefinition definition_{};
  std::optional<MappingFailure> failure_;

  std::vector<RawPart> parts_;
  std::vector<RawInstance> instances_;
  std::vector<RawAssemblySet> assembly_sets_;
  std::vector<RawElementSurface> element_surfaces_;
  std::vector<RawMaterial> materials_;
  std::vector<PrescribedDisplacementDefinition> model_boundaries_;
  std::vector<RawThermalBoundary> thermal_model_boundaries_;
  std::vector<RawThermalInitial> thermal_initial_conditions_;
  std::vector<bool> thermal_active_nodes_;
  RawStep step_{};
  std::vector<std::map<std::int64_t, std::pair<EntityIndex, EntityIndex>>>
      part_section_assignments_;
  std::vector<std::map<std::int64_t, std::pair<EntityIndex, EntityIndex>>>
      part_shell_section_assignments_;

  std::optional<std::size_t> current_part_;
  std::optional<std::size_t> pending_section_;
  std::optional<std::size_t> material_eligible_;
  std::optional<ElementFamily> model_element_family_;
  bool heading_seen_{false};
  bool part_elements_seen_{false};
  bool part_sets_seen_{false};
  bool part_sections_seen_{false};
  bool beam_section_context_active_{false};
  bool assembly_seen_{false};
  bool assembly_set_seen_{false};
  bool model_boundary_seen_{false};
  bool in_assembly_{false};
  bool in_instance_{false};
  bool step_seen_{false};
  bool in_step_{false};
  bool step_load_seen_{false};
  bool step_no_op_seen_{false};
  bool active_output_{false};
  bool active_output_is_field_{false};
  std::optional<SourceLocation> physical_constants_location_;
};

DomainMappingContext::DomainMappingContext(const ParsedInput& input)
    : impl_{std::make_unique<Impl>(input)} {}

DomainMappingContext::~DomainMappingContext() = default;

DomainMappingCandidateSummary DomainMappingContext::CandidateSummary()
    const noexcept {
  return impl_->CandidateSummary();
}

Status DomainMappingContext::ParseSyntax() { return impl_->ParseSyntax(); }

Status DomainMappingContext::FinalizeMaterialProperties() {
  return impl_->FinalizeMaterialProperties();
}

Status DomainMappingContext::FinalizeTopology() {
  return impl_->FinalizeTopology();
}

Status DomainMappingContext::FinalizeElementSurfaces() {
  return impl_->FinalizeElementSurfaces();
}

Status DomainMappingContext::FinalizeStep() {
  return impl_->FinalizeStepCandidate();
}

Result<Domain> DomainMappingContext::Commit() { return impl_->Commit(); }

}  // namespace fesa::abaqus_internal