diff --git a/ROADMAP.md b/ROADMAP.md
index f101971c..4d12ff1f 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -59,6 +59,14 @@ PCB / Package, Render, Animation, Simulation, Manufacture/CAM, Drawings.
 | M14 | Configurations: a table of rows (parameter expressions and feature suppressions per row) switched with config.activate (undoable, all or nothing), kept through parameter renames and feature deletes (config.configure, config.table, config.column/row/activate). Per-row body materials and appearances (library looks, custom colour/opacity and clearing overrides), undoable activation and save/reopen: done. Ordered typed configuration rules, atomic validation and structured rule editing: done. Component appearance and certified semantic face style columns, atomic preview/apply and independent-copy remapping: done. Exact constructed sketch-side and immutable imported-face lineage now preserve legacy names and reject retargeting. Left: ambiguous shifted/two-sided caps | in progress | 4 |
 | M13 | Never lose work: atomic saves (temporary file, flush, rename; a crash at any moment leaves the old file or the new one) with the replaced version kept as `<file>.bak`; autosave of unsaved changes to the recovery folder every 5 minutes (preference) and after big operations, only when something changed; "Recover unsaved design?" on the next launch (`doc.recovery_list`, `doc.recover`, `doc.recovery_discard`); a kill-mid-save test (process killed while saving a 0.5 MB design 25 times). File format: `"format": "solidcraft/12"`, older formats upgraded step by step (`doc::format`), newer ones refused with a message, out-of-range numbers and broken placements refused; a corpus of designs saved by M0, components-era, joints-era and current builds (apps/solidcraft-cli/tests/corpus) that must open and evaluate as saved; damaged and hostile variants (truncation, bit flips, hostile values, removed keys, repeated features, deep nesting) never panic | done | 6 |
 
+## Physical material data
+
+- Physical material card validation (#923/#922) provides typed SI mechanical and
+  thermal data, per-property sources/conditions and isotropic/orthotropic stability
+  checks through read-only `material.properties.validate`. It does not assign or
+  persist properties, provide a solver or enable rendering; see
+  [the contract and staged follow-ups](docs/physical-material-cards.md).
+
 ## Library foundations (#785, #786, #787)
 
 - Proposed phases cover offline bundled/project/user packs, physical materials and
diff --git a/assets/locales/en.json b/assets/locales/en.json
index 7bf21bd0..fd5a9dc6 100644
--- a/assets/locales/en.json
+++ b/assets/locales/en.json
@@ -956,5 +956,6 @@
   "Letter Spacing": "Letter Spacing",
   "Line Spacing": "Line Spacing",
   "Path": "Path",
-  "sketch_text.on_path": "The text follows its path: the curve places it"
+  "sketch_text.on_path": "The text follows its path: the curve places it",
+  "cmd.material_properties_validate":"Validate Physical Material Data"
 }
diff --git a/assets/locales/ja.json b/assets/locales/ja.json
index af8acbe5..4d79b510 100644
--- a/assets/locales/ja.json
+++ b/assets/locales/ja.json
@@ -956,5 +956,6 @@
   "Letter Spacing": "文字間隔",
   "Line Spacing": "行間",
   "Path": "パス",
-  "sketch_text.on_path": "文字はパスに沿います: 位置は曲線で決まります"
+  "sketch_text.on_path": "文字はパスに沿います: 位置は曲線で決まります",
+  "cmd.material_properties_validate":"物理材料データを検証"
 }
diff --git a/assets/locales/zh.json b/assets/locales/zh.json
index 813b6f74..1b2073e8 100644
--- a/assets/locales/zh.json
+++ b/assets/locales/zh.json
@@ -956,5 +956,6 @@
   "Path": "路径",
   "sketch_text.on_path": "文字沿路径排列：由曲线放置",
   "ui.analysis": "分析",
-  "ui.edit_section_analysis": "编辑截面分析"
+  "ui.edit_section_analysis": "编辑截面分析",
+  "cmd.material_properties_validate":"验证物理材料数据"
 }
diff --git a/crates/doc/src/lib.rs b/crates/doc/src/lib.rs
index eafc1dd3..6af31183 100644
--- a/crates/doc/src/lib.rs
+++ b/crates/doc/src/lib.rs
@@ -30,6 +30,7 @@ pub mod motion;
 mod name_lookup;
 pub mod naming;
 mod params;
+pub mod physical_material;
 mod piece_names;
 mod profile_refs;
 pub mod progress;
diff --git a/crates/doc/src/physical_material.rs b/crates/doc/src/physical_material.rs
new file mode 100644
index 00000000..b5f496b4
--- /dev/null
+++ b/crates/doc/src/physical_material.rs
@@ -0,0 +1,353 @@
+//! Candidate engineering data, separate from assigned density and visual appearance.
+//! Validation establishes numerical consistency, not certification or solver support.
+
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use std::collections::BTreeSet;
+
+use crate::{DocError, Result};
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct MaterialCard {
+    pub schema_version: u32,
+    pub designation: String,
+    pub family: Family,
+    pub sources: Vec<Source>,
+    pub properties: Vec<Property>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum Family {
+    Wood,
+    Polymer,
+    Glass,
+    Metal,
+    Other,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct Source {
+    pub id: String,
+    pub title: String,
+    pub kind: SourceKind,
+    /// A caller's claim, never an approval to redistribute or proof of authenticity.
+    pub license: Option<String>,
+    pub reference: Option<String>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum SourceKind {
+    UserSupplied,
+    Measurement,
+    PublicReference,
+    Illustrative,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct Property {
+    pub data: PropertyData,
+    pub source_id: String,
+    #[serde(default)]
+    pub conditions: Conditions,
+}
+
+#[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct Conditions {
+    pub temperature_k: Option<f64>,
+    /// kg water / kg dry material; unlike wet-basis fraction, may exceed one.
+    pub moisture_dry_basis_kg_kg: Option<f64>,
+    pub strain_rate_per_s: Option<f64>,
+    pub state: Option<String>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MaterialAxes {
+    Material123,
+    WoodLrt,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "kind", rename_all = "snake_case", deny_unknown_fields)]
+pub enum PropertyData {
+    Density { kg_m3: f64 },
+    Elasticity { model: Elasticity },
+    TensileStrength { pa: f64 },
+    CompressiveStrength { pa: f64 },
+    YieldStrength { pa: f64 },
+    ShearStrength { pa: f64 },
+    ThermalConductivity { w_m_k: [f64; 3], axes: MaterialAxes },
+    ThermalExpansion { per_k: [f64; 3], axes: MaterialAxes },
+    SpecificHeat { j_kg_k: f64 },
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "symmetry", rename_all = "snake_case", deny_unknown_fields)]
+pub enum Elasticity {
+    Isotropic {
+        young_modulus_pa: f64,
+        poisson_ratio: f64,
+    },
+    /// E1,E2,E3; G12,G23,G31; nu12,nu23,nu31, with nu_ij = -eps_j/eps_i
+    /// under uniaxial stress in i. Reciprocal ratios follow nu_ij/Ei = nu_ji/Ej.
+    Orthotropic {
+        axes: MaterialAxes,
+        young_moduli_pa: [f64; 3],
+        shear_moduli_pa: [f64; 3],
+        poisson_ratios: [f64; 3],
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct IsotropicModuli {
+    pub shear_pa: f64,
+    pub bulk_pa: f64,
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct Validation {
+    pub schema_version: u32,
+    pub property_kinds: Vec<String>,
+    pub isotropic_moduli: Option<IsotropicModuli>,
+    pub unspecified_conditions: Vec<String>,
+    pub source_review_required: Vec<String>,
+    pub analysis_solver_available: bool,
+    pub rendering_properties_available: bool,
+}
+
+fn invalid(message: impl Into<String>) -> DocError {
+    DocError::Invalid(message.into())
+}
+fn text(value: &str, limit: usize, field: &str) -> Result<()> {
+    if value.trim().is_empty() || value.len() > limit || value.chars().any(char::is_control) {
+        return Err(invalid(format!("{field}: expected nonempty text of at most {limit} UTF-8 bytes without controls")));
+    }
+    Ok(())
+}
+fn number(value: f64, low: f64, high: f64, field: &str) -> Result<()> {
+    if !value.is_finite() || value < low || value > high {
+        return Err(invalid(format!("{field}: expected a finite value in [{low}, {high}]")));
+    }
+    Ok(())
+}
+fn positive(value: f64, high: f64, field: &str) -> Result<()> {
+    number(value, 0., high, field)?;
+    if value == 0. {
+        return Err(invalid(format!("{field}: must be positive")));
+    }
+    Ok(())
+}
+
+impl Elasticity {
+    pub fn validate(&self) -> Result<Option<IsotropicModuli>> {
+        match self {
+            Self::Isotropic { young_modulus_pa: e, poisson_ratio: nu } => {
+                positive(*e, 1e15, "young_modulus_pa")?;
+                if !e.recip().is_finite() {
+                    return Err(invalid("young_modulus_pa produces unrepresentable compliance"));
+                }
+                if !nu.is_finite() || *nu <= -1. || *nu >= 0.5 {
+                    return Err(invalid("poisson_ratio: isotropic stability requires -1 < nu < 0.5"));
+                }
+                let result = IsotropicModuli { shear_pa: e / (2. * (1. + nu)), bulk_pa: e / (3. * (1. - 2. * nu)) };
+                if !result.shear_pa.is_finite()
+                    || !result.bulk_pa.is_finite()
+                    || result.shear_pa <= 0.
+                    || result.bulk_pa <= 0.
+                    || !result.shear_pa.recip().is_finite()
+                    || !result.bulk_pa.recip().is_finite()
+                {
+                    return Err(invalid("elastic moduli exceed numeric limits"));
+                }
+                Ok(Some(result))
+            }
+            Self::Orthotropic { young_moduli_pa: e, shear_moduli_pa: g, poisson_ratios: nu, .. } => {
+                for value in e.iter().chain(g) {
+                    positive(*value, 1e15, "orthotropic modulus_pa")?;
+                    if !value.recip().is_finite() {
+                        return Err(invalid("orthotropic modulus produces unrepresentable compliance"));
+                    }
+                }
+                for value in nu {
+                    number(*value, -1e6, 1e6, "orthotropic poisson_ratio")?;
+                }
+                // Diagonal scaling of the reciprocal, symmetric normal compliance
+                // gives unit diagonal and these off-diagonal entries. Sylvester's
+                // criterion proves positive definiteness without dimensional cutoffs.
+                let [e1, e2, e3] = *e;
+                let [n12, n23, n31] = *nu;
+                let [a, b, c] = [-n12 * (e2.sqrt() / e1.sqrt()), -n23 * (e3.sqrt() / e2.sqrt()), -n31 * (e1.sqrt() / e3.sqrt())];
+                let determinant = 1. + 2. * a * b * c - a * a - b * b - c * c;
+                if ![a, b, c, determinant].iter().all(|v| v.is_finite()) || 1. - a * a <= 0. || determinant <= 0. {
+                    return Err(invalid("orthotropic compliance must be finite and positive definite"));
+                }
+                Ok(None)
+            }
+        }
+    }
+}
+
+impl PropertyData {
+    pub fn kind(&self) -> &'static str {
+        match self {
+            Self::Density { .. } => "density",
+            Self::Elasticity { .. } => "elasticity",
+            Self::TensileStrength { .. } => "tensile_strength",
+            Self::CompressiveStrength { .. } => "compressive_strength",
+            Self::YieldStrength { .. } => "yield_strength",
+            Self::ShearStrength { .. } => "shear_strength",
+            Self::ThermalConductivity { .. } => "thermal_conductivity",
+            Self::ThermalExpansion { .. } => "thermal_expansion",
+            Self::SpecificHeat { .. } => "specific_heat",
+        }
+    }
+    fn validate(&self) -> Result<Option<IsotropicModuli>> {
+        match self {
+            Self::Density { kg_m3 } => positive(*kg_m3, 1e6, "density.kg_m3")?,
+            Self::Elasticity { model } => return model.validate(),
+            Self::TensileStrength { pa } | Self::CompressiveStrength { pa } | Self::YieldStrength { pa } | Self::ShearStrength { pa } => {
+                positive(*pa, 1e15, self.kind())?
+            }
+            Self::ThermalConductivity { w_m_k, .. } => {
+                for k in w_m_k {
+                    positive(*k, 1e9, "thermal_conductivity.w_m_k")?;
+                }
+            }
+            Self::ThermalExpansion { per_k, .. } => {
+                for a in per_k {
+                    number(*a, -1., 1., "thermal_expansion.per_k")?;
+                }
+            }
+            Self::SpecificHeat { j_kg_k } => positive(*j_kg_k, 1e9, "specific_heat.j_kg_k")?,
+        }
+        Ok(None)
+    }
+}
+
+impl MaterialCard {
+    pub fn validate(&self) -> Result<Validation> {
+        if self.schema_version != 1 {
+            return Err(invalid("unsupported material card schema_version (expected 1)"));
+        }
+        text(&self.designation, 256, "designation")?;
+        if self.sources.len() > 32 || self.properties.len() > 16 {
+            return Err(invalid("material card exceeds 32 sources or 16 properties"));
+        }
+        let mut sources = BTreeSet::new();
+        for source in &self.sources {
+            text(&source.id, 128, "source.id")?;
+            text(&source.title, 256, "source.title")?;
+            if let Some(value) = &source.license {
+                text(value, 512, "source.license")?;
+            }
+            if let Some(value) = &source.reference {
+                text(value, 2048, "source.reference")?;
+            }
+            if !sources.insert(source.id.clone()) {
+                return Err(invalid("duplicate source id"));
+            }
+        }
+        let mut kinds = BTreeSet::new();
+        let mut used_sources = BTreeSet::new();
+        let mut unspecified = Vec::new();
+        let mut isotropic_moduli = None;
+        for property in &self.properties {
+            let kind = property.data.kind();
+            if !kinds.insert(kind.to_string()) {
+                return Err(invalid(format!("duplicate property kind: {kind}")));
+            }
+            if !sources.contains(&property.source_id) {
+                return Err(invalid(format!("{kind}: unknown source_id")));
+            }
+            used_sources.insert(property.source_id.clone());
+            let conditions = &property.conditions;
+            if let Some(t) = conditions.temperature_k {
+                positive(t, 20000., "temperature_k")?;
+            }
+            if let Some(m) = conditions.moisture_dry_basis_kg_kg {
+                number(m, 0., 1e6, "moisture_dry_basis_kg_kg")?;
+            }
+            if let Some(r) = conditions.strain_rate_per_s {
+                positive(r, 1e12, "strain_rate_per_s")?;
+            }
+            if let Some(state) = &conditions.state {
+                text(state, 1024, "conditions.state")?;
+            }
+            if conditions.temperature_k.is_none()
+                || conditions.state.is_none()
+                || (self.family == Family::Wood && conditions.moisture_dry_basis_kg_kg.is_none())
+                || (self.family == Family::Polymer && conditions.strain_rate_per_s.is_none())
+            {
+                unspecified.push(kind.to_string());
+            }
+            if let Some(moduli) = property.data.validate()? {
+                isotropic_moduli = Some(moduli);
+            }
+        }
+        Ok(Validation {
+            schema_version: 1,
+            property_kinds: kinds.into_iter().collect(),
+            isotropic_moduli,
+            unspecified_conditions: unspecified,
+            source_review_required: used_sources.into_iter().collect(),
+            analysis_solver_available: false,
+            rendering_properties_available: false,
+        })
+    }
+}
+
+/// Bound JSON traversal before cloning/deserializing it. Metadata and numeric
+/// bounds are admission limits, not claims about a real material's valid range.
+pub fn validate_card(value: &Value) -> Result<Validation> {
+    let mut pending = vec![(value, 0usize)];
+    let (mut nodes, mut bytes) = (0usize, 0usize);
+    while let Some((value, depth)) = pending.pop() {
+        nodes += 1;
+        bytes += 32;
+        if nodes > 2048 || depth > 12 {
+            return Err(invalid("material card exceeds JSON node/depth budget"));
+        }
+        match value {
+            Value::String(s) => {
+                if s.len() > 256 * 1024 {
+                    return Err(invalid("material card string exceeds admission budget"));
+                }
+                bytes += s.len();
+            }
+            Value::Array(a) => {
+                if a.len() > 32 {
+                    return Err(invalid("material card array exceeds 32 entries"));
+                }
+                pending.extend(a.iter().map(|v| (v, depth + 1)));
+            }
+            Value::Object(o) => {
+                if o.len() > 32 {
+                    return Err(invalid("material card object exceeds 32 fields"));
+                }
+                for (key, v) in o {
+                    if key.len() > 256 * 1024 {
+                        return Err(invalid("material card key exceeds admission budget"));
+                    }
+                    bytes += key.len();
+                    pending.push((v, depth + 1));
+                }
+            }
+            _ => {}
+        }
+        if bytes > 256 * 1024 {
+            return Err(invalid("material card exceeds 256 KiB admission budget"));
+        }
+    }
+    let card: MaterialCard = serde_json::from_value(value.clone()).map_err(|e| invalid(format!("material card: {e}")))?;
+    card.validate()
+}
+
+#[cfg(test)]
+#[path = "physical_material_tests.rs"]
+mod tests;
diff --git a/crates/doc/src/physical_material_tests.rs b/crates/doc/src/physical_material_tests.rs
new file mode 100644
index 00000000..0b99a76c
--- /dev/null
+++ b/crates/doc/src/physical_material_tests.rs
@@ -0,0 +1,115 @@
+use super::*;
+use serde_json::json;
+
+fn card(data: Value) -> Value {
+    json!({"schema_version":1,"designation":"Original synthetic fixture","family":"wood",
+        "sources":[{"id":"test","title":"Analytic synthetic data, not a material specification","kind":"illustrative","license":"MIT OR Apache-2.0"}],
+        "properties":[{"data":data,"source_id":"test"}]})
+}
+fn isotropic(e: f64, nu: f64) -> Value {
+    json!({"kind":"elasticity","model":{"symmetry":"isotropic","young_modulus_pa":e,"poisson_ratio":nu}})
+}
+fn orthotropic(e: [f64; 3], nu: [f64; 3]) -> Value {
+    json!({"kind":"elasticity","model":{"symmetry":"orthotropic","axes":"wood_lrt",
+        "young_moduli_pa":e,"shear_moduli_pa":[4e9,4e9,4e9],"poisson_ratios":nu}})
+}
+
+#[test]
+fn isotropic_moduli_match_closed_form_and_auxetic_values_are_valid() {
+    let r = validate_card(&card(isotropic(12e9, 0.25))).unwrap();
+    assert_eq!(r.isotropic_moduli, Some(IsotropicModuli { shear_pa: 4.8e9, bulk_pa: 8e9 }));
+    let r = validate_card(&card(isotropic(12e9, -0.5))).unwrap();
+    assert_eq!(r.isotropic_moduli, Some(IsotropicModuli { shear_pa: 12e9, bulk_pa: 2e9 }));
+    for nu in [-2., -1., 0.5, 0.6] {
+        assert!(validate_card(&card(isotropic(12e9, nu))).is_err());
+    }
+    for e in [0., -1., 1e16] {
+        assert!(validate_card(&card(isotropic(e, 0.25))).is_err());
+    }
+    assert!(Elasticity::Isotropic { young_modulus_pa: f64::NAN, poisson_ratio: 0.25 }.validate().is_err());
+    assert!(Elasticity::Isotropic { young_modulus_pa: 1e-309, poisson_ratio: 0.25 }.validate().is_err());
+}
+
+#[test]
+fn orthotropy_uses_reciprocity_and_full_positive_definiteness() {
+    // With equal E and nu=.25 this is the same normal compliance as isotropy.
+    assert!(validate_card(&card(orthotropic([12e9; 3], [0.25; 3]))).is_ok());
+    // A general orthotropic ratio may exceed .5: reciprocal nu21 is .08 here.
+    assert!(validate_card(&card(orthotropic([10e9, 1e9, 1e9], [0.8, 0., 0.]))).is_ok());
+    // Every 2x2 principal minor is positive; the full determinant is negative.
+    assert!(validate_card(&card(orthotropic([12e9; 3], [0.6; 3]))).is_err());
+    assert!(validate_card(&card(orthotropic([10e9, 1e9, 1e9], [4., 0., 0.]))).is_err());
+    assert!(validate_card(&card(orthotropic([0., 1e9, 1e9], [0.; 3]))).is_err());
+    let mut bad = card(orthotropic([12e9; 3], [0.25; 3]));
+    bad["properties"][0]["data"]["model"]["shear_moduli_pa"] = json!([4e9, 0., 4e9]);
+    assert!(validate_card(&bad).is_err());
+    // Scaling all moduli changes units of compliance, not its stability verdict.
+    assert!(validate_card(&card(orthotropic([12.; 3], [0.25; 3]))).is_ok());
+    assert!(validate_card(&card(orthotropic([1e-300, 1e15, 1.], [0.; 3]))).is_ok());
+    assert!(validate_card(&card(orthotropic([1e-309, 1., 1.], [0.; 3]))).is_err());
+}
+
+#[test]
+fn conditions_missing_values_and_source_claims_remain_explicit() {
+    let mut value = card(json!({"kind":"density","kg_m3":600.}));
+    let r = validate_card(&value).unwrap();
+    assert_eq!(r.unspecified_conditions, vec!["density"]);
+    assert_eq!(r.source_review_required, vec!["test"]); // Even an explicit license is unverified.
+    assert!(!r.analysis_solver_available && !r.rendering_properties_available);
+    assert!(r.isotropic_moduli.is_none());
+    value["properties"][0]["conditions"] = json!({"temperature_k":293.15,"moisture_dry_basis_kg_kg":1.5,"state":"synthetic wet specimen"});
+    assert!(validate_card(&value).unwrap().unspecified_conditions.is_empty());
+    value["family"] = json!("polymer");
+    value["properties"][0]["conditions"]["moisture_dry_basis_kg_kg"] = json!(150.);
+    value["properties"][0]["conditions"]["strain_rate_per_s"] = json!(1.);
+    assert!(validate_card(&value).unwrap().unspecified_conditions.is_empty());
+    value["properties"] = json!([]);
+    let r = validate_card(&value).unwrap();
+    assert!(r.property_kinds.is_empty() && r.isotropic_moduli.is_none());
+    let parsed: MaterialCard = serde_json::from_value(value.clone()).unwrap();
+    assert_eq!(serde_json::from_value::<MaterialCard>(serde_json::to_value(&parsed).unwrap()).unwrap(), parsed);
+}
+
+#[test]
+fn thermal_properties_accept_negative_expansion_but_not_negative_conductivity() {
+    assert!(validate_card(&card(json!({"kind":"thermal_expansion","per_k":[-1e-6,0.,2e-6],"axes":"material123"}))).is_ok());
+    assert!(validate_card(&card(json!({"kind":"thermal_conductivity","w_m_k":[1.,0.,1.],"axes":"material123"}))).is_err());
+    assert!(validate_card(&card(json!({"kind":"specific_heat","j_kg_k":500.}))).is_ok());
+    for kind in ["tensile_strength", "compressive_strength", "yield_strength", "shear_strength"] {
+        assert!(validate_card(&card(json!({"kind":kind,"pa":1e8}))).is_ok());
+        assert!(validate_card(&card(json!({"kind":kind,"pa":-1.}))).is_err());
+    }
+}
+
+#[test]
+fn hostile_units_sources_fields_and_budgets_are_rejected() {
+    let valid = card(isotropic(12e9, 0.25));
+    let mut bad = valid.clone();
+    bad["properties"][0]["data"]["model"]["young_modulus_mpa"] = json!(12.);
+    assert!(validate_card(&bad).is_err());
+    let mut bad = valid.clone();
+    bad["properties"][0]["source_id"] = json!("unknown");
+    assert!(validate_card(&bad).is_err());
+    let mut bad = valid.clone();
+    bad["properties"] = json!([valid["properties"][0], valid["properties"][0]]);
+    assert!(validate_card(&bad).is_err());
+    let mut bad = valid.clone();
+    bad["sources"] = json!([valid["sources"][0], valid["sources"][0]]);
+    assert!(validate_card(&bad).is_err());
+    let mut bad = valid.clone();
+    bad["schema_version"] = json!(2);
+    assert!(validate_card(&bad).is_err());
+    let mut bad = valid.clone();
+    bad["designation"] = json!("x".repeat(257));
+    assert!(validate_card(&bad).is_err());
+    let mut bad = valid.clone();
+    bad["properties"][0]["conditions"] = json!({"moisture_dry_basis_kg_kg":-1.});
+    assert!(validate_card(&bad).is_err());
+    assert!(validate_card(&json!(vec![Value::Null; 33])).is_err());
+    assert!(validate_card(&json!("x".repeat(256 * 1024 + 1))).is_err());
+    let mut deep = Value::Null;
+    for _ in 0..14 {
+        deep = json!([deep]);
+    }
+    assert!(validate_card(&deep).is_err());
+}
diff --git a/crates/engine/src/cmd/material_properties.rs b/crates/engine/src/cmd/material_properties.rs
new file mode 100644
index 00000000..0e69aa9b
--- /dev/null
+++ b/crates/engine/src/cmd/material_properties.rs
@@ -0,0 +1,92 @@
+//! Read-only validation of candidate engineering data; no assignment or simulation.
+use super::CommandSpec;
+use crate::params::bad;
+use crate::{Result, Session};
+use serde_json::{Value, json};
+
+pub static COMMANDS: &[CommandSpec] = &[CommandSpec::new("material.properties.validate", "Validate Physical Material Data", validate)
+    .icon("material")
+    .noundo()
+    .doc_only()
+    .params("card: schema_version 1 engineering material card in SI units. Returns numerical consistency, derived isotropic moduli, missing conditions and sources needing review. Read-only; does not assign/save properties or provide an analysis solver. See docs/physical-material-cards.md")];
+
+fn validate(_: &mut Session, params: &Value) -> Result<Value> {
+    let object = params
+        .as_object()
+        .filter(|o| o.len() == 1 && o.contains_key("card"))
+        .ok_or_else(|| bad("material.properties.validate", "expected {card: ...}"))?;
+    let card = object.get("card").ok_or_else(|| bad("material.properties.validate", "missing card"))?;
+    let result = solidcraft_doc::physical_material::validate_card(card).map_err(|e| bad("material.properties.validate", e.to_string()))?;
+    Ok(json!({"valid":true,"validation":result}))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::Arc;
+
+    #[test]
+    fn command_reports_analytic_moduli_and_refuses_unstable_data() {
+        let mut s = Session::default();
+        let mut card = json!({"schema_version":1,"designation":"Synthetic elastic fixture","family":"other",
+            "sources":[{"id":"fixture","title":"Original analytic fixture","kind":"illustrative"}],
+            "properties":[{"source_id":"fixture","data":{"kind":"elasticity","model":{
+                "symmetry":"isotropic","young_modulus_pa":12e9,"poisson_ratio":0.25}}}]});
+        let result = s.execute("material.properties.validate", &json!({"card":card})).unwrap();
+        assert_eq!(result["validation"]["isotropic_moduli"], json!({"shear_pa":4.8e9,"bulk_pa":8e9}));
+        assert_eq!(result["validation"]["source_review_required"], json!(["fixture"]));
+        assert_eq!(result["validation"]["rendering_properties_available"], false);
+        card["properties"][0]["data"]["model"]["poisson_ratio"] = json!(0.6);
+        assert!(s.execute("material.properties.validate", &json!({"card":card})).is_err());
+    }
+    #[test]
+    fn validation_preserves_document_history_selection_and_evaluation() {
+        let mut s = Session::default();
+        s.execute("solid.box", &json!({"length":10,"width":20,"height":5})).unwrap();
+        s.execute("edit.undo", &json!({})).unwrap();
+        let doc = s.doc.clone();
+        let undo = s.undo.clone();
+        let redo = s.redo.clone();
+        let before = (s.is_dirty(), s.revision, s.evaluations, s.model.is_stale(), s.camera, s.selection.clone());
+        let card = json!({"schema_version":1,"designation":"Synthetic empty card","family":"other","sources":[],"properties":[]});
+        let result = s.execute("material.properties.validate", &json!({"card":card})).unwrap();
+        assert_eq!(result["validation"]["analysis_solver_available"], false);
+        for p in [json!({}), json!({"card":card,"assign":true}), json!({"card":{"schema_version":9}})] {
+            assert!(s.execute("material.properties.validate", &p).is_err());
+        }
+        assert!(Arc::ptr_eq(&doc, &s.doc));
+        assert_eq!(before, (s.is_dirty(), s.revision, s.evaluations, s.model.is_stale(), s.camera, s.selection.clone()));
+        for (a, b) in [(&undo, &s.undo), (&redo, &s.redo)] {
+            assert_eq!(a.len(), b.len());
+            for (a, b) in a.iter().zip(b) {
+                assert!(Arc::ptr_eq(&a.doc, &b.doc));
+            }
+        }
+    }
+
+    #[test]
+    fn validation_does_not_settle_live_geometry() {
+        let mut s = Session::default();
+        for (id, p) in [
+            ("sketch.create", json!({"plane":"XY"})),
+            ("sketch.rectangle.two_point", json!({"p0":[5,5],"p1":[25,20]})),
+            ("sketch.dimension", json!({"entities":["l1"],"value":20})),
+            ("sketch.dimension", json!({"entities":["l2"],"value":15})),
+            ("sketch.finish", json!({})),
+            ("solid.extrude", json!({"distance":5})),
+            ("sketch.edit", json!({"sketch":"Sketch1"})),
+            ("sketch.drag", json!({"entity":"l1.start","from":[5,5],"to":[4,5],"live":true})),
+        ] {
+            s.execute(id, &p).unwrap();
+        }
+        assert!(s.model.is_stale());
+        let doc = s.doc.clone();
+        let before = (s.revision, s.evaluations, s.active_sketch, s.undo.len(), s.redo.len());
+        let card = json!({"schema_version":1,"designation":"Synthetic","family":"other","sources":[],"properties":[]});
+        s.execute("material.properties.validate", &json!({"card":card})).unwrap();
+        assert!(s.execute("material.properties.validate", &json!({"card":false})).is_err());
+        assert!(Arc::ptr_eq(&doc, &s.doc));
+        assert!(s.model.is_stale());
+        assert_eq!(before, (s.revision, s.evaluations, s.active_sketch, s.undo.len(), s.redo.len()));
+    }
+}
diff --git a/crates/engine/src/cmd/mod.rs b/crates/engine/src/cmd/mod.rs
index f8b9ed7e..dd39bb56 100644
--- a/crates/engine/src/cmd/mod.rs
+++ b/crates/engine/src/cmd/mod.rs
@@ -38,6 +38,7 @@ mod config;
 mod file;
 mod inspect;
 pub(crate) mod joints;
+mod material_properties;
 mod materials;
 mod measure_sel;
 mod mesh;
@@ -248,6 +249,7 @@ pub fn command_specs() -> Vec<&'static CommandSpec> {
     v.extend(file::COMMANDS.iter());
     v.extend(inspect::COMMANDS.iter());
     v.extend(materials::COMMANDS.iter());
+    v.extend(material_properties::COMMANDS.iter());
     v.extend(section::COMMANDS.iter());
     v.extend(view_navigation::COMMANDS.iter());
     v.extend(diagnostics::COMMANDS.iter());
diff --git a/docs/features.md b/docs/features.md
index 242d104a..f5df4b7c 100644
--- a/docs/features.md
+++ b/docs/features.md
@@ -1,6 +1,6 @@
 # Features
 
-SolidCraft's commands by area, generated by `cargo xtask features` from the command registry (`solidcraft-cli commands`). **343 commands.** Planned (registered, not built yet): 6. Every command runs the same way from the toolbar, a script, `solidcraft-cli exec <id> '<json>'`, the control channel and MCP; parameters are in the [command reference](book/src/reference/commands.md) (`cargo xtask book`). Status and plans: [ROADMAP](../ROADMAP.md).
+SolidCraft's commands by area, generated by `cargo xtask features` from the command registry (`solidcraft-cli commands`). **344 commands.** Planned (registered, not built yet): 6. Every command runs the same way from the toolbar, a script, `solidcraft-cli exec <id> '<json>'`, the control channel and MCP; parameters are in the [command reference](book/src/reference/commands.md) (`cargo xtask book`). Status and plans: [ROADMAP](../ROADMAP.md).
 
 ## Sketch (99)
 
@@ -432,7 +432,7 @@ SolidCraft's commands by area, generated by `cargo xtask features` from the comm
 |---|---|---|
 | Delete Face | `face.delete` | SOLID › MODIFY |
 
-## `material.*` (5)
+## `material.*` (6)
 
 | Command | Id | Toolbar |
 |---|---|---|
@@ -441,6 +441,7 @@ SolidCraft's commands by area, generated by `cargo xtask features` from the comm
 | New Physical Material | `material.create` | – |
 | Edit Physical Material | `material.edit` | – |
 | Delete Physical Material | `material.delete` | – |
+| Validate Physical Material Data | `material.properties.validate` | – |
 
 ## `mesh.*` (1)
 
diff --git a/docs/physical-material-cards.md b/docs/physical-material-cards.md
new file mode 100644
index 00000000..f9294972
--- /dev/null
+++ b/docs/physical-material-cards.md
@@ -0,0 +1,127 @@
+# Physical material data cards
+
+`material.properties.validate {card}` checks a caller-supplied candidate record,
+without assigning it, saving it in the design, reading files, fetching sources or
+changing history, selection, camera or live geometry. This is phase 1 of #923/#922,
+building towards #785. Existing `material.create/edit` and their density/appearance
+behavior are unchanged. The design format is unchanged.
+
+Validation means numerical and structural consistency. It does not authenticate
+sources, approve redistribution, certify design values, provide a solver or enable
+advanced rendering. The result reports `analysis_solver_available: false` and
+`rendering_properties_available: false`. Missing properties remain unknown.
+
+## Contract (standalone card schema 1)
+
+A card has `schema_version: 1`, `designation`, `family` (`wood`, `polymer`, `glass`,
+`metal`, `other`), `sources` and `properties`. Source IDs are exact, case-sensitive
+local references. Each source has `id`, `title`, `kind` (`user_supplied`,
+`measurement`, `public_reference`, `illustrative`), optional `license` and
+`reference` strings. These strings are metadata supplied by the caller; even a
+declared open license remains in `source_review_required`. Nothing is downloaded.
+
+Every property has `data`, `source_id` and optional `conditions`. Conditions are
+`temperature_k`, `moisture_dry_basis_kg_kg`, `strain_rate_per_s` and a free-text
+`state` (grade, temper, processing or specimen condition). Conditions belong to
+the property, not an assumed global room temperature. An elastic block represents
+constants measured under the same conditions and source; mixed-condition curves
+and independently sourced constants need a later representation.
+
+| `data.kind` | Explicit SI fields |
+|---|---|
+| `density` | `kg_m3` |
+| `elasticity` | `model`, described below |
+| `tensile_strength`, `compressive_strength`, `yield_strength`, `shear_strength` | `pa` |
+| `thermal_conductivity` | `w_m_k: [k1,k2,k3]`, `axes` |
+| `thermal_expansion` | `per_k: [a1,a2,a3]`, `axes` |
+| `specific_heat` | `j_kg_k` |
+
+Directional values use `axes: material123` (material-local 1/2/3) or `wood_lrt`
+(longitudinal/radial/tangential). These labels do not assign a frame to a body or
+infer mechanical orientation from texture rotation. Equal directional values can
+describe an isotropic thermal property. Thermal expansion may be zero or negative.
+
+An isotropic elastic model has `symmetry: isotropic`, `young_modulus_pa` and
+`poisson_ratio`. Stability requires E > 0 and -1 < nu < 0.5. Valid auxetic values
+are accepted. The result derives G = E/[2(1+nu)] and K = E/[3(1-2nu)], in Pa.
+
+An orthotropic model has `symmetry: orthotropic`, `axes`,
+`young_moduli_pa: [E1,E2,E3]`, `shear_moduli_pa: [G12,G23,G31]` and
+`poisson_ratios: [nu12,nu23,nu31]`. Here nu_ij = -eps_j/eps_i under stress along i;
+reciprocity supplies nu_ij/Ei = nu_ji/Ej. The normal compliance is symmetric with
+diagonal 1/Ei and off-diagonal -nu_ij/Ei. Diagonal scaling produces unit diagonal;
+Sylvester's criterion checks its positive definiteness. All three shear moduli
+must be positive. General orthotropic Poisson ratios are not capped at 0.5.
+Moduli whose reciprocals cannot be represented finitely are rejected; the
+isotropic derived response and its reciprocals must also remain finite/positive.
+
+Moisture is kg water / kg dry material and can exceed one. It is not a wet-mass
+fraction. Unspecified temperature/state, wood moisture or polymer strain rate are
+reported in `unspecified_conditions`; they are not guessed or replaced by zero.
+The family label does not certify that a chosen constitutive model fits a material.
+Scalar strengths are individual measurements, not a three-dimensional failure
+envelope. Typed strength directions and test methods remain a separate extension.
+
+## Admission limits
+
+Before cloning/deserializing JSON: at most 2,048 nodes, depth 12, 32 array entries
+or object fields and a 256 KiB conservative accounting budget (32 bytes per node
+plus string/key bytes). The typed record allows 32 sources and 16 properties;
+duplicate source IDs or property kinds and unknown fields are rejected.
+
+Text limits in UTF-8 bytes: designation/title 256, source ID 128, license 512,
+reference 2,048 and state 1,024; controls and blank text are rejected. All numeric
+values must be finite. Positive-value upper admission limits are density 1e6
+kg/m³, moduli/strengths 1e15 Pa, conductivity 1e9 W/(m K), heat capacity 1e9
+J/(kg K), temperature 20,000 K and strain rate 1e12 /s. Expansion is within ±1 /K,
+dry-basis moisture within [0,1e6] (also accommodating highly hydrated polymers),
+orthotropic Poisson ratios within ±1e6 in addition
+to the compliance stability test. These are generous technical admission limits,
+not measured applicability ranges or a conditioning guarantee for a future solver.
+
+## Original synthetic example
+
+These deliberately invented constants demonstrate validation, not a real grade:
+
+```json
+{
+  "card": {
+    "schema_version": 1,
+    "designation": "Synthetic elastic example — not design data",
+    "family": "other",
+    "sources": [{
+      "id": "example",
+      "title": "Original synthetic example",
+      "kind": "illustrative",
+      "license": "MIT OR Apache-2.0"
+    }],
+    "properties": [{
+      "data": {
+        "kind": "elasticity",
+        "model": {"symmetry": "isotropic", "young_modulus_pa": 12000000000, "poisson_ratio": 0.25}
+      },
+      "source_id": "example"
+    }]
+  }
+}
+```
+
+The result has G = 4.8e9 Pa, K = 8e9 Pa, unspecified conditions and source review
+still required. No assigned mass, saved material or appearance changes.
+
+## Next phases and references
+
+Persistence/library integration needs a separately reviewed document migration,
+atomic edits, undo/redo and offline reopening, coordinated with #863. Curves,
+uncertainty, hardness scales, viscoelasticity and failure criteria remain later work.
+Visual PBR/texture/environment consumption uses the renderer contract requested
+in #813, with #909/#837 input utilities; accepting physical data advertises none
+of those capabilities.
+
+The [USDA Wood Handbook](https://research.fs.usda.gov/fpl/wood-handbook), including
+[chapter 4's dry-mass moisture definition](https://research.fs.usda.gov/download/treesearch/62243.pdf), is a public
+scientific reference for moisture, mechanical behavior and the distinction between
+specimen properties and graded design values. No handbook data/table is bundled.
+The [Khronos PBR material model](https://www.khronos.org/gltf/pbr) is a reference for
+the separate optical track. No third-party code, engineering dataset or asset is
+added by this implementation.