diff --git a/changes/unreleased/query-feature-outcomes.changed.md b/changes/unreleased/query-feature-outcomes.changed.md
new file mode 100644
index 0000000000..5e6acd2f2f
--- /dev/null
+++ b/changes/unreleased/query-feature-outcomes.changed.md
@@ -0,0 +1 @@
+- `Project` and `WhereFeature` reading a feature an element row lacks now fail with a `missing-feature` error naming the element and the features it does have (`Target`, `Property`, `Candidates`), instead of leaving the cell empty, and carry the QVTS outcome record (`Feature(<name>)` step, the element and its features as frontier); a property no row carries stays `unknown-property`. The new `tolerate = true` argument on both operations keeps the empty cell for sources that mix element kinds (the cookbook's `MassTable` uses it). Metadata paths (`Tag::key`) are unaffected.
diff --git a/docs/internals/design/query-outcomes.md b/docs/internals/design/query-outcomes.md
index cd9ad1bf50..b43bcb7dee 100644
--- a/docs/internals/design/query-outcomes.md
+++ b/docs/internals/design/query-outcomes.md
@@ -28,7 +28,8 @@ to `∅` is the ambiguity QVTS exists to remove.
 | `Named` | the element | `unknown-element`: the longest prefix that resolves, the segment it lacks, the nearest spellings; an alias that denotes nothing | `ambiguous-element`: the elements, by qualified name |
 | `WhereType`, `WhereMetadata` | the selected rows | `unknown-classification` | — |
 | `RelatedElements` | the neighbours, possibly none | `unknown-relationship` | — |
-| `Project`, `WhereFeature` on a feature the element lacks | *today an empty cell* `(none)` | *to do:* a path error per element, with the features reachable on it | — |
+| `Project`, `WhereFeature` on a feature the element lacks | an empty cell, with `tolerate = true` | `missing-feature`: the element (`Target`), the feature (`Property`), the features it does have (`Candidates`); `unknown-property` when no row carries it | — |
+| `Project`, `WhereFeature` on a metadata path (`Tag::key`) the element lacks | *today an empty cell* | *to do:* decide whether an absent annotation is a path error | — |
 | `Project` on a `[1]` feature with two values | *today the first value* | — | *to do:* `multiplicity` |
 
 `Error` carries the frontier in `Target` (the namespace that resolved), `Expected` (the segment it
@@ -38,7 +39,7 @@ QVTS record itself (`internal/doc/queryexec/outcome.go`), field for field with
 `lean/QVTS/Outcome.lean`: a `PathError` is a list of `Failure{Step, Expected, Frontier}`, a
 `ModelError` a list of `Finding{Step, Element, Constraint, Observed}` plus the path failures of the
 same fan-out; `Frontier` carries `At`, `Members (name, metaclass)`, `Features (name, type)`, `Kinds`
-and `Nearest`. `Named` fills it today. The surfaces that show it: `-run-query` prints it under the
+and `Nearest`. `Named` and the `missing-feature` outcome of `Project`/`WhereFeature` fill it today. The surfaces that show it: `-run-query` prints it under the
 error line and `-json` writes it as `checks[].outcome` in the shape `qvts/sparql/expected/*.json`
 records (`outcome`, `step`, `failures` | `findings` + `pathFailures`); `%run-query` prints the same
 lines; the gRPC service attaches it to the failed call as a `QueryOutcome` error detail. The
diff --git a/docs/manual/examples/cookbook.sysml b/docs/manual/examples/cookbook.sysml
index fd271af497..7e148a41b6 100644
--- a/docs/manual/examples/cookbook.sysml
+++ b/docs/manual/examples/cookbook.sysml
@@ -164,7 +164,8 @@ package Cookbook {
 		in root : Element;
 		Project(
 			source = PartsByMass(root = root),
-			properties = ("name", "mass", "qualifiedName")
+			properties = ("name", "mass", "qualifiedName"),
+			tolerate = true  // opticalPath and dataPath declare no mass
 		)
 	}
 
@@ -173,6 +174,7 @@ package Cookbook {
 		Project(
 			source = PartsByMass(root = root),
 			properties = ("name", "mass"),
+			tolerate = true,
 			columns = (
 				Column(name = "massLbs", cell = { in row : Subsystem; (row.mass ?? 0.0) * 2.2 }),
 				Column(name = "label", expression = "part: " + Element::name)
diff --git a/docs/manual/query-cookbook.md b/docs/manual/query-cookbook.md
index a88832567d..8671f338d3 100644
--- a/docs/manual/query-cookbook.md
+++ b/docs/manual/query-cookbook.md
@@ -101,7 +101,8 @@ calc def MassTable :> Query {
 	in root : Element;                 // entry parameters, bound by the caller
 	Project(                            // operations compose inside-out
 		source = PartsByMass(root = root),  // ... and queries invoke queries
-		properties = ("name", "mass", "qualifiedName")
+		properties = ("name", "mass", "qualifiedName"),
+		tolerate = true                 // an element lacking a property gets an empty cell
 	)
 }
 ```
@@ -550,7 +551,8 @@ calc def MassTable :> Query {
 	in root : Element;
 	Project(
 		source = PartsByMass(root = root),
-		properties = ("name", "mass", "qualifiedName")
+		properties = ("name", "mass", "qualifiedName"),
+		tolerate = true  // opticalPath and dataPath declare no mass
 	)
 }
 ```
@@ -581,8 +583,22 @@ $ sysml cookbook.sysml -run-query "Cookbook::MassTable root=Cookbook::telescope"
     qualifiedName = "Cookbook::telescope::dataPath"
 ```
 
-A cell for a property the element lacks is empty (`(none)` in the CLI's row
-listing, an empty table cell in a document). A feature whose declared value
+`opticalPath` and `dataPath` are connections: they declare no `mass`. Reading
+a feature of an element that has none so named is by default an error that
+names the element and the features it does have — a path error, telling a
+query that left the model apart from a feature that is present and empty:
+
+```console
+$ sysml cookbook.sysml -run-query "Cookbook::MassTable root=Cookbook::telescope"   # without tolerate = true
+error: query Cookbook::MassTable reads feature mass of Cookbook::telescope::opticalPath, which has no such feature
+```
+
+`tolerate = true` on `Project` (and on `WhereFeature`) accepts the mixed rows
+and leaves the cell empty (`(none)` in the CLI's row listing, an empty table
+cell in a document). A property no row carries at all is an unknown property
+whichever way — that is a misspelling, not a mixed source. A metadata path
+(`Properties::key`) is always tolerated: an annotation is optional by nature.
+A feature whose declared value
 names an element of the model — an enumeration literal, a part, a unit — holds
 that element, printed by name like `general`, whether the value is written on
 the feature or bound by a redefinition (`attribute :>> beam = Beam::'650mm';`);
@@ -785,6 +801,7 @@ calc def MassBudget :> Query {
 	Project(
 		source = PartsByMass(root = root),
 		properties = ("name", "mass"),
+		tolerate = true,
 		columns = (
 			Column(name = "massLbs", cell = { in row : Subsystem; (row.mass ?? 0.0) * 2.2 }),
 			Column(name = "label", expression = "part: " + Element::name)
diff --git a/docs/project/api-json-differential-baseline.json b/docs/project/api-json-differential-baseline.json
index 54a3616203..8c97952981 100644
--- a/docs/project/api-json-differential-baseline.json
+++ b/docs/project/api-json-differential-baseline.json
@@ -65,7 +65,7 @@
         "dir": "examples",
         "origin": "ours",
         "files": 52,
-        "digest": "sha256:cd33a6f84a9998e255f6dc8d1b2cb374dce50e930e015f67f990303c8157558a"
+        "digest": "sha256:ba2e49098c36879a3a944f37a56cdb39f0dde31f3c75dd8817ce333d6ba226c1"
       },
       {
         "name": "probes",
@@ -79,14 +79,14 @@
         "dir": "docs/manual/examples",
         "origin": "ours",
         "files": 11,
-        "digest": "sha256:817bcc10d912772ed88d34c1fb500161d00a1e940adca71b72885b6866e4a5c6"
+        "digest": "sha256:46abb05dbfef90d395cbccb7f1c278f95a4495d0e16770ec5e20df001bd9be7d"
       },
       {
         "name": "opensysml-libraries",
         "dir": "internal/workspace/libs/stdlib/OpenSysML Libraries",
         "origin": "ours",
         "files": 16,
-        "digest": "sha256:82e35230165a3d95d831330f21c3290cca8b9519f5b494d341e0a866a0e373a5"
+        "digest": "sha256:ac6a1e3b3376227415fa16aec5bf1918312a69cad0d8d63b6adcda799a44c9b3"
       }
     ],
     "recorded": "2026-10-27"
@@ -111,26 +111,26 @@
     "oursUnconvertible": 0,
     "oursColliding": 28,
     "pilotFailed": 59,
-    "pilotLibraryElements": 35490,
+    "pilotLibraryElements": 35864,
     "elements": {
-      "matched": 92455,
+      "matched": 92491,
       "oursOnly": 18479,
-      "pilotOnly": 37766,
+      "pilotOnly": 37775,
       "pilotOnlyImplied": 0,
       "typeMismatch": 1729
     },
     "properties": {
-      "presentEqual": 1121587,
-      "presentDifferent": 27497,
-      "oursMissing": 1074012,
-      "pilotMissing": 68257,
-      "absentBoth": 1973372,
+      "presentEqual": 1122005,
+      "presentDifferent": 27547,
+      "oursMissing": 1074516,
+      "pilotMissing": 68275,
+      "absentBoth": 1974074,
       "indeterminate": 26286,
       "pilotNondeterministic": 514
     },
     "rows": 11728,
-    "unkeyedReferences": 111949,
-    "extensionProperties": 159941,
+    "unkeyedReferences": 111976,
+    "extensionProperties": 159959,
     "duplicateElements": {
       "ours": 527,
       "pilot": 82631
@@ -371,20 +371,20 @@
       "oursRefused": 0,
       "pilotFailed": 0,
       "oursColliding": 3,
-      "pilotLibraryElements": 13888,
+      "pilotLibraryElements": 14020,
       "elements": {
-        "matched": 26974,
+        "matched": 27002,
         "oursOnly": 6046,
-        "pilotOnly": 15072,
+        "pilotOnly": 15079,
         "pilotOnlyImplied": 0,
         "typeMismatch": 186
       },
       "properties": {
-        "presentEqual": 333478,
-        "presentDifferent": 8320,
-        "oursMissing": 322802,
-        "pilotMissing": 20056,
-        "absentBoth": 599839,
+        "presentEqual": 333821,
+        "presentDifferent": 8341,
+        "oursMissing": 323194,
+        "pilotMissing": 20070,
+        "absentBoth": 600385,
         "indeterminate": 9869,
         "pilotNondeterministic": 162
       },
@@ -443,20 +443,20 @@
       "files": 11,
       "oursRefused": 0,
       "pilotFailed": 0,
-      "pilotLibraryElements": 16846,
+      "pilotLibraryElements": 17088,
       "elements": {
-        "matched": 7191,
+        "matched": 7199,
         "oursOnly": 920,
-        "pilotOnly": 2108,
+        "pilotOnly": 2110,
         "pilotOnlyImplied": 0,
         "typeMismatch": 0
       },
       "properties": {
-        "presentEqual": 88704,
-        "presentDifferent": 2005,
-        "oursMissing": 89489,
-        "pilotMissing": 4812,
-        "absentBoth": 150077,
+        "presentEqual": 88779,
+        "presentDifferent": 2034,
+        "oursMissing": 89601,
+        "pilotMissing": 4816,
+        "absentBoth": 150233,
         "indeterminate": 2170,
         "pilotNondeterministic": 36
       },
@@ -36442,7 +36442,7 @@
       0,
       0,
       0,
-      10180,
+      10189,
       0,
       0
     ],
@@ -36451,7 +36451,7 @@
       43,
       130,
       6,
-      9782,
+      9791,
       24,
       0
     ],
@@ -36487,7 +36487,7 @@
       0,
       0,
       0,
-      9255,
+      9264,
       0,
       0
     ],
@@ -36496,7 +36496,7 @@
       0,
       0,
       0,
-      10180,
+      10189,
       0,
       0
     ],
@@ -36514,7 +36514,7 @@
       0,
       4,
       0,
-      10176,
+      10185,
       0,
       0
     ],
@@ -36523,12 +36523,12 @@
       0,
       622,
       0,
-      9558,
+      9567,
       0,
       0
     ],
     "Feature.direction": [
-      8602,
+      8611,
       192,
       4,
       101,
@@ -36550,7 +36550,7 @@
       0,
       21,
       0,
-      10159,
+      10168,
       0,
       0
     ],
@@ -36559,7 +36559,7 @@
       0,
       55,
       0,
-      10125,
+      10134,
       0,
       0
     ],
@@ -36575,7 +36575,7 @@
     "Feature.feature": [
       0,
       0,
-      10174,
+      10183,
       0,
       6,
       0,
@@ -36584,7 +36584,7 @@
     "Feature.featureMembership": [
       0,
       0,
-      10174,
+      10183,
       0,
       6,
       0,
@@ -36593,7 +36593,7 @@
     "Feature.featureTarget": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36602,7 +36602,7 @@
     "Feature.featuringType": [
       67,
       0,
-      9878,
+      9887,
       0,
       234,
       1,
@@ -36613,14 +36613,14 @@
       0,
       15,
       0,
-      10165,
+      10174,
       0,
       0
     ],
     "Feature.inheritedFeature": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36629,7 +36629,7 @@
     "Feature.inheritedMembership": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36640,7 +36640,7 @@
       0,
       437,
       0,
-      9743,
+      9752,
       0,
       0
     ],
@@ -36649,7 +36649,7 @@
       0,
       3,
       0,
-      10177,
+      10186,
       0,
       0
     ],
@@ -36672,7 +36672,7 @@
       0
     ],
     "Feature.isAbstract": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36681,7 +36681,7 @@
       0
     ],
     "Feature.isComposite": [
-      10146,
+      10155,
       34,
       0,
       0,
@@ -36692,14 +36692,14 @@
     "Feature.isConjugated": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
       0
     ],
     "Feature.isConstant": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36717,7 +36717,7 @@
       0
     ],
     "Feature.isDerived": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36726,7 +36726,7 @@
       0
     ],
     "Feature.isEnd": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36735,7 +36735,7 @@
       0
     ],
     "Feature.isImpliedIncluded": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36755,14 +36755,14 @@
     "Feature.isLibraryElement": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
       0
     ],
     "Feature.isOrdered": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36771,7 +36771,7 @@
       0
     ],
     "Feature.isPortion": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36789,7 +36789,7 @@
       0
     ],
     "Feature.isSufficient": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36798,7 +36798,7 @@
       0
     ],
     "Feature.isUnique": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36807,7 +36807,7 @@
       0
     ],
     "Feature.isVariable": [
-      9079,
+      9088,
       0,
       75,
       0,
@@ -36836,7 +36836,7 @@
     "Feature.member": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36845,7 +36845,7 @@
     "Feature.membership": [
       0,
       0,
-      10180,
+      10189,
       0,
       0,
       0,
@@ -36863,7 +36863,7 @@
     "Feature.name": [
       190,
       0,
-      9570,
+      9579,
       0,
       0,
       0,
@@ -36874,7 +36874,7 @@
       0,
       453,
       0,
-      9727,
+      9736,
       0,
       0
     ],
@@ -36883,7 +36883,7 @@
       0,
       0,
       0,
-      10180,
+      10189,
       0,
       0
     ],
@@ -36910,7 +36910,7 @@
       0,
       4,
       0,
-      10176,
+      10185,
       0,
       0
     ],
@@ -36919,14 +36919,14 @@
       0,
       3,
       0,
-      10177,
+      10186,
       0,
       0
     ],
     "Feature.ownedElement": [
       0,
       0,
-      4917,
+      4926,
       0,
       5263,
       0,
@@ -36937,7 +36937,7 @@
       0,
       1,
       0,
-      10179,
+      10188,
       0,
       0
     ],
@@ -36946,7 +36946,7 @@
       4,
       568,
       0,
-      9481,
+      9490,
       6,
       0
     ],
@@ -36955,7 +36955,7 @@
       0,
       121,
       6,
-      9782,
+      9791,
       0,
       0
     ],
@@ -36964,7 +36964,7 @@
       0,
       7,
       0,
-      10173,
+      10182,
       0,
       0
     ],
@@ -36973,7 +36973,7 @@
       1,
       568,
       0,
-      9481,
+      9490,
       0,
       0
     ],
@@ -36982,7 +36982,7 @@
       0,
       0,
       0,
-      10165,
+      10174,
       0,
       0
     ],
@@ -36991,21 +36991,21 @@
       0,
       3,
       0,
-      10177,
+      10186,
       0,
       0
     ],
     "Feature.ownedMember": [
       119,
       104,
-      4671,
+      4680,
       0,
       5278,
       8,
       0
     ],
     "Feature.ownedMembership": [
-      4296,
+      4305,
       569,
       37,
       94,
@@ -37016,7 +37016,7 @@
     "Feature.ownedRedefinition": [
       280,
       0,
-      653,
+      662,
       0,
       9247,
       0,
@@ -37033,7 +37033,7 @@
     ],
     "Feature.ownedRelationship": [
       4163,
-      1421,
+      1430,
       137,
       90,
       4369,
@@ -37043,7 +37043,7 @@
     "Feature.ownedSpecialization": [
       873,
       20,
-      682,
+      691,
       34,
       8571,
       0,
@@ -37052,7 +37052,7 @@
     "Feature.ownedSubsetting": [
       371,
       8,
-      665,
+      674,
       6,
       9130,
       0,
@@ -37063,7 +37063,7 @@
       0,
       70,
       0,
-      10110,
+      10119,
       0,
       0
     ],
@@ -37072,7 +37072,7 @@
       0,
       29,
       28,
-      9463,
+      9472,
       0,
       0
     ],
@@ -37081,12 +37081,12 @@
       0,
       7,
       0,
-      10173,
+      10182,
       0,
       0
     ],
     "Feature.owner": [
-      10180,
+      10189,
       0,
       0,
       0,
@@ -37097,14 +37097,14 @@
     "Feature.owningFeatureMembership": [
       0,
       0,
-      9529,
+      9538,
       0,
       0,
       0,
       0
     ],
     "Feature.owningMembership": [
-      9560,
+      9569,
       356,
       6,
       0,
@@ -37115,14 +37115,14 @@
     "Feature.owningNamespace": [
       1133,
       0,
-      8789,
+      8798,
       0,
       0,
       0,
       0
     ],
     "Feature.owningRelationship": [
-      9817,
+      9826,
       363,
       0,
       0,
@@ -37133,7 +37133,7 @@
     "Feature.owningType": [
       0,
       0,
-      9529,
+      9538,
       0,
       0,
       0,
@@ -37189,14 +37189,14 @@
       0,
       0,
       0,
-      10180,
+      10189,
       0,
       0
     ],
     "Feature.type": [
       346,
       14,
-      9647,
+      9656,
       0,
       0,
       173,
@@ -37207,7 +37207,7 @@
       0,
       7,
       0,
-      10173,
+      10182,
       0,
       0
     ],
@@ -39466,7 +39466,7 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
@@ -39475,7 +39475,7 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
@@ -39484,7 +39484,7 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
@@ -39493,12 +39493,12 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
     "FeatureValue.featureWithValue": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39507,7 +39507,7 @@
       0
     ],
     "FeatureValue.isDefault": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39516,7 +39516,7 @@
       0
     ],
     "FeatureValue.isImplied": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39525,7 +39525,7 @@
       0
     ],
     "FeatureValue.isImpliedIncluded": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39534,7 +39534,7 @@
       0
     ],
     "FeatureValue.isInitial": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39545,14 +39545,14 @@
     "FeatureValue.isLibraryElement": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
       0
     ],
     "FeatureValue.memberElement": [
-      6870,
+      6879,
       307,
       0,
       0,
@@ -39563,14 +39563,14 @@
     "FeatureValue.memberElementId": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
       0
     ],
     "FeatureValue.membershipOwningNamespace": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39583,7 +39583,7 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
@@ -39592,12 +39592,12 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
     "FeatureValue.ownedMemberElement": [
-      6870,
+      6879,
       307,
       0,
       0,
@@ -39608,14 +39608,14 @@
     "FeatureValue.ownedMemberElementId": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
       0
     ],
     "FeatureValue.ownedRelatedElement": [
-      6870,
+      6879,
       307,
       0,
       0,
@@ -39628,7 +39628,7 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
@@ -39636,13 +39636,13 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0
     ],
     "FeatureValue.owningRelatedElement": [
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39655,14 +39655,14 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
     "FeatureValue.relatedElement": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39671,7 +39671,7 @@
     "FeatureValue.source": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39680,7 +39680,7 @@
     "FeatureValue.target": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
@@ -39691,12 +39691,12 @@
       0,
       0,
       0,
-      7177,
+      7186,
       0,
       0
     ],
     "FeatureValue.value": [
-      6870,
+      6879,
       307,
       0,
       0,
@@ -39707,7 +39707,7 @@
     "FeatureValue.visibility": [
       0,
       0,
-      7177,
+      7186,
       0,
       0,
       0,
@@ -51729,8 +51729,8 @@
       0
     ],
     "InvocationExpression.argument": [
-      446,
-      4,
+      439,
+      11,
       0,
       14,
       16,
@@ -51891,8 +51891,8 @@
       0
     ],
     "InvocationExpression.input": [
-      385,
-      79,
+      368,
+      96,
       1,
       0,
       15,
@@ -52314,8 +52314,8 @@
       0
     ],
     "InvocationExpression.parameter": [
-      399,
-      81,
+      382,
+      98,
       0,
       0,
       0,
@@ -55108,14 +55108,14 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.behavior": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55126,7 +55126,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55135,7 +55135,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55144,7 +55144,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55153,14 +55153,14 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.directedFeature": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55171,7 +55171,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55180,7 +55180,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55189,14 +55189,14 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.feature": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55205,7 +55205,7 @@
     "LiteralBoolean.featureMembership": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55214,7 +55214,7 @@
     "LiteralBoolean.featureTarget": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55223,7 +55223,7 @@
     "LiteralBoolean.featuringType": [
       0,
       0,
-      92,
+      101,
       0,
       294,
       0,
@@ -55232,7 +55232,7 @@
     "LiteralBoolean.function": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55243,14 +55243,14 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.inheritedFeature": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55259,7 +55259,7 @@
     "LiteralBoolean.inheritedMembership": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55270,7 +55270,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55279,12 +55279,12 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.isAbstract": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55293,7 +55293,7 @@
       0
     ],
     "LiteralBoolean.isComposite": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55304,14 +55304,14 @@
     "LiteralBoolean.isConjugated": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
       0
     ],
     "LiteralBoolean.isConstant": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55320,7 +55320,7 @@
       0
     ],
     "LiteralBoolean.isDerived": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55329,7 +55329,7 @@
       0
     ],
     "LiteralBoolean.isEnd": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55338,7 +55338,7 @@
       0
     ],
     "LiteralBoolean.isImpliedIncluded": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55349,7 +55349,7 @@
     "LiteralBoolean.isLibraryElement": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55358,14 +55358,14 @@
     "LiteralBoolean.isModelLevelEvaluable": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
       0
     ],
     "LiteralBoolean.isOrdered": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55374,7 +55374,7 @@
       0
     ],
     "LiteralBoolean.isPortion": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55383,7 +55383,7 @@
       0
     ],
     "LiteralBoolean.isSufficient": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55392,7 +55392,7 @@
       0
     ],
     "LiteralBoolean.isUnique": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55401,7 +55401,7 @@
       0
     ],
     "LiteralBoolean.isVariable": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55412,7 +55412,7 @@
     "LiteralBoolean.member": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55421,7 +55421,7 @@
     "LiteralBoolean.membership": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55430,7 +55430,7 @@
     "LiteralBoolean.output": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55441,7 +55441,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55450,7 +55450,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55459,7 +55459,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55468,7 +55468,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55477,7 +55477,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55486,7 +55486,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55495,7 +55495,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55504,7 +55504,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55513,7 +55513,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55522,7 +55522,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55531,7 +55531,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55540,7 +55540,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55549,7 +55549,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55558,7 +55558,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55567,7 +55567,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55576,7 +55576,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55585,7 +55585,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55594,7 +55594,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55603,7 +55603,7 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
@@ -55612,12 +55612,12 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.owner": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55626,7 +55626,7 @@
       0
     ],
     "LiteralBoolean.owningMembership": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55637,14 +55637,14 @@
     "LiteralBoolean.owningNamespace": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
       0
     ],
     "LiteralBoolean.owningRelationship": [
-      386,
+      395,
       0,
       0,
       0,
@@ -55655,7 +55655,7 @@
     "LiteralBoolean.parameter": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55664,7 +55664,7 @@
     "LiteralBoolean.result": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55675,14 +55675,14 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.type": [
       0,
       0,
-      386,
+      395,
       0,
       0,
       0,
@@ -55693,12 +55693,12 @@
       0,
       0,
       0,
-      386,
+      395,
       0,
       0
     ],
     "LiteralBoolean.value": [
-      386,
+      395,
       0,
       0,
       0,
@@ -68644,7 +68644,7 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
@@ -68653,7 +68653,7 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
@@ -68662,7 +68662,7 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
@@ -68671,12 +68671,12 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
     "ParameterMembership.isImplied": [
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68685,7 +68685,7 @@
       0
     ],
     "ParameterMembership.isImpliedIncluded": [
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68696,14 +68696,14 @@
     "ParameterMembership.isLibraryElement": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
       0
     ],
     "ParameterMembership.memberElement": [
-      4222,
+      4231,
       213,
       0,
       0,
@@ -68714,7 +68714,7 @@
     "ParameterMembership.memberElementId": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68723,14 +68723,14 @@
     "ParameterMembership.memberName": [
       0,
       0,
-      4419,
+      4428,
       0,
       0,
       0,
       0
     ],
     "ParameterMembership.membershipOwningNamespace": [
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68743,7 +68743,7 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
@@ -68752,12 +68752,12 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
     "ParameterMembership.ownedMemberElement": [
-      4222,
+      4231,
       213,
       0,
       0,
@@ -68768,14 +68768,14 @@
     "ParameterMembership.ownedMemberElementId": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
       0
     ],
     "ParameterMembership.ownedMemberFeature": [
-      4218,
+      4227,
       213,
       4,
       0,
@@ -68786,14 +68786,14 @@
     "ParameterMembership.ownedMemberName": [
       0,
       0,
-      4419,
+      4428,
       0,
       0,
       0,
       0
     ],
     "ParameterMembership.ownedMemberParameter": [
-      4222,
+      4231,
       213,
       0,
       0,
@@ -68802,7 +68802,7 @@
       0
     ],
     "ParameterMembership.ownedRelatedElement": [
-      4222,
+      4231,
       213,
       0,
       0,
@@ -68815,7 +68815,7 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
@@ -68823,13 +68823,13 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0
     ],
     "ParameterMembership.owningRelatedElement": [
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68842,14 +68842,14 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
     "ParameterMembership.owningType": [
       70,
       0,
-      4365,
+      4374,
       0,
       0,
       0,
@@ -68858,7 +68858,7 @@
     "ParameterMembership.relatedElement": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68867,7 +68867,7 @@
     "ParameterMembership.source": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68876,7 +68876,7 @@
     "ParameterMembership.target": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
@@ -68887,14 +68887,14 @@
       0,
       0,
       0,
-      4435,
+      4444,
       0,
       0
     ],
     "ParameterMembership.visibility": [
       0,
       0,
-      4435,
+      4444,
       0,
       0,
       0,
diff --git a/docs/project/pilot-differential-baseline.json b/docs/project/pilot-differential-baseline.json
index f58d4efc99..8f3fbc2184 100644
--- a/docs/project/pilot-differential-baseline.json
+++ b/docs/project/pilot-differential-baseline.json
@@ -69,7 +69,7 @@
         "dir": "examples",
         "origin": "ours",
         "files": 52,
-        "digest": "sha256:cd33a6f84a9998e255f6dc8d1b2cb374dce50e930e015f67f990303c8157558a"
+        "digest": "sha256:ba2e49098c36879a3a944f37a56cdb39f0dde31f3c75dd8817ce333d6ba226c1"
       },
       {
         "name": "probes",
@@ -83,10 +83,10 @@
         "dir": "internal/workspace/libs/stdlib/OpenSysML Libraries",
         "origin": "ours",
         "files": 16,
-        "digest": "sha256:82e35230165a3d95d831330f21c3290cca8b9519f5b494d341e0a866a0e373a5"
+        "digest": "sha256:ac6a1e3b3376227415fa16aec5bf1918312a69cad0d8d63b6adcda799a44c9b3"
       }
     ],
-    "recorded": "2026-10-26"
+    "recorded": "2026-10-27"
   },
   "totals": {
     "files": 920,
@@ -17898,7 +17898,7 @@
           "openSysMLOnly": [],
           "pilotOnly": [
             {
-              "line": 542,
+              "line": 543,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18028,12 +18028,6 @@
           "severityMismatch": [],
           "openSysMLOnly": [],
           "pilotOnly": [
-            {
-              "line": 187,
-              "severity": "warning",
-              "category": "kind-mismatch",
-              "count": 1
-            },
             {
               "line": 193,
               "severity": "warning",
@@ -18041,13 +18035,13 @@
               "count": 1
             },
             {
-              "line": 208,
+              "line": 199,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 222,
+              "line": 214,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18059,19 +18053,19 @@
               "count": 1
             },
             {
-              "line": 239,
+              "line": 234,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 246,
+              "line": 245,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 256,
+              "line": 252,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18083,13 +18077,13 @@
               "count": 1
             },
             {
-              "line": 267,
+              "line": 268,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 277,
+              "line": 273,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18101,7 +18095,7 @@
               "count": 1
             },
             {
-              "line": 297,
+              "line": 289,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18113,19 +18107,19 @@
               "count": 1
             },
             {
-              "line": 314,
+              "line": 309,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 324,
+              "line": 320,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 334,
+              "line": 330,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18143,7 +18137,7 @@
               "count": 1
             },
             {
-              "line": 360,
+              "line": 352,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18155,13 +18149,13 @@
               "count": 1
             },
             {
-              "line": 381,
+              "line": 372,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 395,
+              "line": 387,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18179,13 +18173,13 @@
               "count": 1
             },
             {
-              "line": 414,
+              "line": 413,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 452,
+              "line": 420,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
@@ -18197,25 +18191,31 @@
               "count": 1
             },
             {
-              "line": 468,
+              "line": 464,
+              "severity": "warning",
+              "category": "kind-mismatch",
+              "count": 1
+            },
+            {
+              "line": 474,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 481,
+              "line": 487,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
             },
             {
-              "line": 481,
+              "line": 487,
               "severity": "warning",
               "category": "unmapped",
               "count": 18
             },
             {
-              "line": 487,
+              "line": 493,
               "severity": "warning",
               "category": "kind-mismatch",
               "count": 1
diff --git a/examples/analysis-results-demo/README.md b/examples/analysis-results-demo/README.md
index 0eca74718d..1645af00a5 100644
--- a/examples/analysis-results-demo/README.md
+++ b/examples/analysis-results-demo/README.md
@@ -76,7 +76,9 @@ part scoutRun : FuelBudgetRun {
 Two limitations shape the record. The annotation's attribute values are
 not projectable — `Project(properties = ("runAt"))` reports
 `unknown property` — so `command` is also carried as a plain attribute on
-`DemoRun` for the provenance table to show; the `@AnalysisRecords::RecordedRun`
+`DemoRun` for the provenance table to show (a run `-record-run` writes has no
+such attribute, so the table's `Project` says `tolerate = true` to leave its
+cell empty rather than fail); the `@AnalysisRecords::RecordedRun`
 metadata still answers `WhereMetadata` filters and keeps the provenance
 machine-readable. And the library's untyped `'subject'` ref cannot drive the
 `liveFuelLeft` formula, so `FuelBudgetRun` keeps a typed `lander` ref and each
diff --git a/examples/analysis-results-demo/lander-results.sysml b/examples/analysis-results-demo/lander-results.sysml
index 74c4c01054..f66d268269 100644
--- a/examples/analysis-results-demo/lander-results.sysml
+++ b/examples/analysis-results-demo/lander-results.sysml
@@ -448,7 +448,8 @@ package Reporting {
     calc def Provenance :> Query {
         Project(
             source = WhereMetadata(source = Descendants(source = Named(qualifiedName = "Records"), maxDepth = 1), 'metadata' = "AnalysisRecords::RecordedRun"),
-            properties = ("name", "kind", "caseName", "command"))
+            properties = ("name", "kind", "caseName", "command"),
+            tolerate = true)  // a run -record-run writes carries command in its metadata only
     }
 
     // The trade-study record.
diff --git a/examples/self-model/document.sysml b/examples/self-model/document.sysml
index 7a737d72af..a6cda88de4 100644
--- a/examples/self-model/document.sysml
+++ b/examples/self-model/document.sysml
@@ -33,6 +33,7 @@ package OpenSysMLDocument {
         in root : Element;
         Project(
             source = WhereFeature(
+                tolerate = true,
                 source = WhereType(
                     source = OwnedElements(source = DefinitionOf(root = root)),
                     type = "PartUsage"
@@ -63,6 +64,7 @@ package OpenSysMLDocument {
         in root : Element;
         Project(
             source = WhereFeature(
+                tolerate = true,
                 source = WhereType(
                     source = OwnedElements(source = DefinitionOf(root = root)),
                     type = "PartUsage"
@@ -81,6 +83,7 @@ package OpenSysMLDocument {
         in root : Element;
         Project(
             source = WhereFeature(
+                tolerate = true,
                 source = WhereType(
                     source = OwnedElements(source = DefinitionOf(root = root)),
                     type = "PartUsage"
@@ -111,6 +114,7 @@ package OpenSysMLDocument {
         in root : Element;
         Project(
             source = WhereFeature(
+                tolerate = true,
                 source = WhereType(
                     source = OwnedElements(source = DefinitionOf(root = root)),
                     type = "PartUsage"
@@ -129,6 +133,7 @@ package OpenSysMLDocument {
         in root : Element;
         Project(
             source = WhereFeature(
+                tolerate = true,
                 source = WhereType(
                     source = OwnedElements(source = DefinitionOf(root = root)),
                     type = "PartUsage"
@@ -146,6 +151,7 @@ package OpenSysMLDocument {
         in root : Element;
         Project(
             source = WhereFeature(
+                tolerate = true,
                 source = WhereType(
                     source = OwnedElements(source = DefinitionOf(root = root)),
                     type = "PartUsage"
diff --git a/internal/doc/queryexec/derived_test.go b/internal/doc/queryexec/derived_test.go
index d4d035b2ba..249da27cd5 100644
--- a/internal/doc/queryexec/derived_test.go
+++ b/internal/doc/queryexec/derived_test.go
@@ -64,7 +64,8 @@ calc def Vehicles :> Query {
 	in root : Element[1];
 	Project(
 		source = WhereType(source = Descendants(source = root, maxDepth = 1), type = "PartUsage"),
-		properties = ("name", "liftoffMass", "engineCount", "topMass")
+		properties = ("name", "liftoffMass", "engineCount", "topMass"),
+		tolerate = true
 	)
 }
 `
diff --git a/internal/doc/queryexec/errors.go b/internal/doc/queryexec/errors.go
index adfce6e1b7..57c12a8921 100644
--- a/internal/doc/queryexec/errors.go
+++ b/internal/doc/queryexec/errors.go
@@ -29,8 +29,11 @@ const (
 	ErrorUnknownElement        ErrorKind = "unknown-element"
 	// ErrorAmbiguousElement: Named was given a name several elements carry — a
 	// finding about the model, where ErrorUnknownElement is one about the query.
-	ErrorAmbiguousElement      ErrorKind = "ambiguous-element"
-	ErrorUnknownRelationship   ErrorKind = "unknown-relationship"
+	ErrorAmbiguousElement    ErrorKind = "ambiguous-element"
+	ErrorUnknownRelationship ErrorKind = "unknown-relationship"
+	// ErrorMissingFeature: Project or WhereFeature read a feature an element row
+	// lacks — a path error about that element; ErrorUnknownProperty: no row had it.
+	ErrorMissingFeature        ErrorKind = "missing-feature"
 	ErrorUnevaluableFeature    ErrorKind = "unevaluable-feature"
 	ErrorUnknownInvocation     ErrorKind = "unknown-invocation"
 	ErrorInvocationCycle       ErrorKind = "invocation-cycle"
@@ -143,6 +146,32 @@ func (e *Error) unknownElementMessage() string {
 	return suggest.With(msg, e.Expected, e.Candidates)
 }
 
+// missingFeatureMessage names the element lacking the feature and the features
+// it does have, so the reader sees where the path left the model.
+func (e *Error) missingFeatureMessage() string {
+	msg := fmt.Sprintf("query %s reads feature %s of %s, which has no such feature", e.Query, e.Property, e.Target)
+	if e.Actual != "" {
+		msg = fmt.Sprintf("query %s reads feature %s of %s, but the path stops at %s", e.Query, e.Property, e.Target, e.Actual)
+	}
+	if len(e.Candidates) == 0 {
+		return msg
+	}
+	msg += ": its features are " + strings.Join(e.Candidates, ", ")
+	if len(e.Candidates) <= 3 {
+		return msg
+	}
+	return suggest.With(msg, e.missingSegment(), e.Candidates)
+}
+
+// missingSegment is the segment the record says names nothing: the failed step's
+// argument, so a path that repeats a name cannot misdirect the suggestion.
+func (e *Error) missingSegment() string {
+	if e.Outcome != nil && e.Outcome.Path != nil && len(e.Outcome.Path.Failures) == 1 {
+		return e.Outcome.Path.Failures[0].Step.Argument
+	}
+	return e.Property
+}
+
 // column names the projected column an error arose in, when it did in one.
 func (e *Error) column() string {
 	if e.Property == "" {
@@ -188,6 +217,8 @@ func (e *Error) Error() string {
 		return fmt.Sprintf("query %s references unknown property %s", e.Query, e.Property)
 	case ErrorUnknownClassification:
 		return fmt.Sprintf("query %s references unknown classification %s", e.Query, e.Actual)
+	case ErrorMissingFeature:
+		return e.missingFeatureMessage()
 	case ErrorUnknownElement:
 		return e.unknownElementMessage()
 	case ErrorAmbiguousElement:
diff --git a/internal/doc/queryexec/memberpath.go b/internal/doc/queryexec/memberpath.go
index a3f8252207..e73f6f2500 100644
--- a/internal/doc/queryexec/memberpath.go
+++ b/internal/doc/queryexec/memberpath.go
@@ -31,3 +31,17 @@ func (e *executor) memberPathValues(sym *symbols.Symbol, segments []string) ([]V
 	member, _ := e.context.Model.LookupMember(current, segments[len(segments)-1])
 	return values, true, member, nil
 }
+
+// memberPathStop walks a member path as memberPathValues does and reports where
+// it stopped: the last member reached and the segment that names no member there.
+func (e *executor) memberPathStop(sym *symbols.Symbol, segments []string) (*symbols.Symbol, string) {
+	current := sym
+	for _, segment := range segments {
+		member, ok := e.context.Model.LookupMember(current, segment)
+		if !ok || member == nil {
+			return current, segment
+		}
+		current = member
+	}
+	return current, segments[len(segments)-1]
+}
diff --git a/internal/doc/queryexec/memberpath_test.go b/internal/doc/queryexec/memberpath_test.go
index e9e57fc2ea..908f2bddbe 100644
--- a/internal/doc/queryexec/memberpath_test.go
+++ b/internal/doc/queryexec/memberpath_test.go
@@ -251,7 +251,8 @@ calc def Runs :> Query {
 	in root : Element;
 	Project(
 		source = Descendants(source = root, maxDepth = 1),
-		properties = ("name", "stat.runs")
+		properties = ("name", "stat.runs"),
+		tolerate = true
 	)
 }`)
 	result := memberPathRows(t, fixture, "Runs")
diff --git a/internal/doc/queryexec/missing_feature_test.go b/internal/doc/queryexec/missing_feature_test.go
new file mode 100644
index 0000000000..b6688cd61d
--- /dev/null
+++ b/internal/doc/queryexec/missing_feature_test.go
@@ -0,0 +1,118 @@
+package queryexec
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+// TestExecuteMissingFeatureIsAPathErrorUnlessTolerated: reading a feature an
+// element lacks names that element and the features it has; tolerate = true
+// keeps the empty cell, and only a property no row carries is then unknown.
+func TestExecuteMissingFeatureIsAPathErrorUnlessTolerated(t *testing.T) {
+	fixture := loadExecutionFixture(t, `
+part def Heavy { attribute mass : ScalarValues::Real; }
+part root {
+	part a : Heavy { attribute :>> mass = 1.0; }
+	part b { attribute volume = 2.0; attribute mas = 3.0; }
+}
+calc def Masses :> Query {
+	in source : Element;
+	Project(source = OwnedElements(source = source), properties = ("mass"))
+}
+calc def ToleratedMasses :> Query {
+	in source : Element;
+	Project(source = OwnedElements(source = source), properties = ("mass"), tolerate = true)
+}
+calc def ToleratedAbsent :> Query {
+	in source : Element;
+	Project(source = OwnedElements(source = source), properties = ("absent"), tolerate = true)
+}
+calc def HeavyOnes :> Query {
+	in source : Element;
+	WhereFeature(source = OwnedElements(source = source), 'feature' = "mass", operator = ">", value = "0.5")
+}
+calc def ToleratedHeavyOnes :> Query {
+	in source : Element;
+	WhereFeature(source = OwnedElements(source = source), 'feature' = "mass", operator = ">", value = "0.5", tolerate = true)
+}
+`)
+	bindings := Bindings{"source": {ElementValue(fixture.symbol(t, "root"))}}
+	var executionError *Error
+	for _, query := range []string{"Masses", "HeavyOnes"} {
+		_, err := fixture.execute(t, query, bindings, Options{})
+		if !errors.As(err, &executionError) || executionError.Kind != ErrorMissingFeature {
+			t.Fatalf("%s: error = %v, want missing-feature", query, err)
+		}
+		if executionError.Target != "Observatory::root::b" || executionError.Property != "mass" {
+			t.Fatalf("%s: names %s.%s, want Observatory::root::b.mass", query, executionError.Target, executionError.Property)
+		}
+		if got := strings.Join(executionError.Candidates, ","); got != "mas,volume" {
+			t.Fatalf("%s: frontier = %q, want the features of root::b", query, got)
+		}
+		if msg := executionError.Error(); !strings.HasSuffix(msg, "of Observatory::root::b, which has no such feature: its features are mas, volume") {
+			t.Fatalf("%s: message = %q", query, msg)
+		}
+		outcome := executionError.Outcome
+		if outcome == nil || outcome.Kind() != "pathError" || len(outcome.Path.Failures) != 1 {
+			t.Fatalf("%s: outcome = %+v, want one path failure", query, outcome)
+		}
+		failure := outcome.Path.Failures[0]
+		if failure.Step.Label() != "Feature(mass)" || failure.Expected != "a feature named mass on the element" || failure.Frontier.At != "Observatory::root::b" || failure.Frontier.Nearest != "mas" {
+			t.Fatalf("%s: failure = %+v", query, failure)
+		}
+		if len(failure.Frontier.Features) != 2 || failure.Frontier.Features[0].Name != "mas" || failure.Frontier.Features[1].Name != "volume" {
+			t.Fatalf("%s: frontier features = %+v", query, failure.Frontier.Features)
+		}
+	}
+	tolerated, err := fixture.execute(t, "ToleratedMasses", bindings, Options{})
+	if err != nil {
+		t.Fatalf("ToleratedMasses: %v", err)
+	}
+	if len(tolerated.Rows()) != 2 || len(tolerated.Rows()[0].Cells()[0].Values()) != 1 || len(tolerated.Rows()[1].Cells()[0].Values()) != 0 {
+		t.Fatalf("ToleratedMasses: rows = %+v, want a's mass and an empty cell for b", tolerated.Rows())
+	}
+	kept, err := fixture.execute(t, "ToleratedHeavyOnes", bindings, Options{})
+	if err != nil || len(kept.Rows()) != 1 {
+		t.Fatalf("ToleratedHeavyOnes: rows = %v, err = %v, want a alone", kept.Rows(), err)
+	}
+	_, err = fixture.execute(t, "ToleratedAbsent", bindings, Options{})
+	if !errors.As(err, &executionError) || executionError.Kind != ErrorUnknownProperty {
+		t.Fatalf("ToleratedAbsent: error = %v, want unknown-property", err)
+	}
+}
+
+// TestExecuteMissingFeatureOnAMemberPathStopsAtTheMemberReached: a dotted
+// property whose segment names no member reports the member the path reached,
+// with that member's features as the frontier, not the row's.
+func TestExecuteMissingFeatureOnAMemberPathStopsAtTheMemberReached(t *testing.T) {
+	fixture := loadExecutionFixture(t, `
+part root {
+	part x { part stat { attribute count = 1; attribute runs = 2; } }
+	part y { part stat { attribute count = 3; attribute run = 4; } }
+}
+calc def Runs :> Query {
+	in source : Element;
+	Project(source = OwnedElements(source = source), properties = ("stat.runs"))
+}
+`)
+	bindings := Bindings{"source": {ElementValue(fixture.symbol(t, "root"))}}
+	var executionError *Error
+	_, err := fixture.execute(t, "Runs", bindings, Options{})
+	if !errors.As(err, &executionError) || executionError.Kind != ErrorMissingFeature {
+		t.Fatalf("error = %v, want missing-feature", err)
+	}
+	if executionError.Target != "Observatory::root::y" || executionError.Actual != "Observatory::root::y::stat" {
+		t.Fatalf("names %s stopping at %s, want root::y stopping at root::y::stat", executionError.Target, executionError.Actual)
+	}
+	if msg := executionError.Error(); !strings.HasSuffix(msg, "reads feature stat.runs of Observatory::root::y, but the path stops at Observatory::root::y::stat: its features are count, run") {
+		t.Fatalf("message = %q", msg)
+	}
+	failure := executionError.Outcome.Path.Failures[0]
+	if failure.Step.Label() != "Feature(runs)" || failure.Frontier.At != "Observatory::root::y::stat" || failure.Frontier.Nearest != "run" {
+		t.Fatalf("failure = %+v", failure)
+	}
+	if len(failure.Frontier.Features) != 2 || failure.Frontier.Features[0].Name != "count" || failure.Frontier.Features[1].Name != "run" {
+		t.Fatalf("frontier features = %+v", failure.Frontier.Features)
+	}
+}
diff --git a/internal/doc/queryexec/objects_test.go b/internal/doc/queryexec/objects_test.go
index 52fa8f38ea..d1cf558de4 100644
--- a/internal/doc/queryexec/objects_test.go
+++ b/internal/doc/queryexec/objects_test.go
@@ -33,7 +33,8 @@ calc def Held :> Query {
 	in root : Element;
 	Project(
 		source = Descendants(source = root, maxDepth = 3),
-		properties = ("qualifiedName", "name", "pressure")
+		properties = ("qualifiedName", "name", "pressure"),
+		tolerate = true
 	)
 }
 calc def Direct :> Query {
diff --git a/internal/doc/queryexec/operations.go b/internal/doc/queryexec/operations.go
index 97a15b0750..801d2cbeed 100644
--- a/internal/doc/queryexec/operations.go
+++ b/internal/doc/queryexec/operations.go
@@ -4,6 +4,7 @@ import (
 	"errors"
 	"math"
 	"regexp"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -11,6 +12,7 @@ import (
 	"github.com/Open-MBEE/OpenSysML/internal/ir/queryplan"
 	"github.com/Open-MBEE/OpenSysML/internal/semantic/query"
 	"github.com/Open-MBEE/OpenSysML/internal/semantic/semantics"
+	"github.com/Open-MBEE/OpenSysML/internal/semantic/suggest"
 	"github.com/Open-MBEE/OpenSysML/internal/semantic/symbols"
 )
 
@@ -396,17 +398,25 @@ func (e *executor) evaluateWhereFeature(expression queryplan.Expression) (sequen
 		}
 		return sequence{}, e.operatorError(expression, operator)
 	}
+	tolerate, err := e.tolerateArgument(expression)
+	if err != nil {
+		return sequence{}, err
+	}
 	if len(source.values) == 0 {
 		return source, nil
 	}
 	result := filtered(source)
 	known := false
+	var missing error
 	columnIndex := projectedColumn(source, property)
 	for i := range source.values {
 		values, present, valueErr := e.featureValues(expression, source, i, property, columnIndex)
 		if valueErr != nil {
 			return sequence{}, valueErr
 		}
+		if !present && !tolerate && missing == nil {
+			missing = e.missingFeature(expression, property, source.values[i])
+		}
 		known = known || present
 		for _, actual := range values {
 			match, compareErr := e.compareValue(actual, operator, expected)
@@ -425,6 +435,9 @@ func (e *executor) evaluateWhereFeature(expression queryplan.Expression) (sequen
 	if !known {
 		return sequence{}, e.unknownProperty(expression, property)
 	}
+	if missing != nil {
+		return sequence{}, missing
+	}
 	return result, nil
 }
 
@@ -609,6 +622,10 @@ func (e *executor) evaluateProject(expression queryplan.Expression) (sequence, e
 	if total == 0 {
 		return sequence{}, e.invalidArgument(expression, "properties", "empty")
 	}
+	tolerate, err := e.tolerateArgument(expression)
+	if err != nil {
+		return sequence{}, err
+	}
 	seen := make(map[string]bool, total)
 	for _, property := range properties {
 		seen[property] = true
@@ -633,6 +650,7 @@ func (e *executor) evaluateProject(expression queryplan.Expression) (sequence, e
 		result.columns[len(properties)+i] = Column{name: column.name, origin: column.origin.Origin()}
 	}
 	tracker := newPropertyTracker()
+	missing := make([]error, len(properties))
 	for row, value := range source.values {
 		result.cells[row] = make([]Cell, total)
 		for column, property := range properties {
@@ -640,6 +658,9 @@ func (e *executor) evaluateProject(expression queryplan.Expression) (sequence, e
 			if valueErr != nil {
 				return sequence{}, e.unevaluable(expression, property, value, valueErr)
 			}
+			if !present && !tolerate && missing[column] == nil {
+				missing[column] = e.missingFeature(expression, property, value)
+			}
 			known[column] = known[column] || present
 			result.cells[row][column] = Cell{
 				values: values,
@@ -663,6 +684,13 @@ func (e *executor) evaluateProject(expression queryplan.Expression) (sequence, e
 				return sequence{}, e.unknownProperty(expression, property)
 			}
 		}
+		// A property some rows carry and an element row lacks is a path error
+		// about that element, unless tolerated; one no row carries is unknown.
+		for _, err := range missing {
+			if err != nil {
+				return sequence{}, err
+			}
+		}
 		if property, missing := tracker.missing(); missing {
 			return sequence{}, e.unknownProperty(expression, property)
 		}
@@ -1169,6 +1197,74 @@ func (e *executor) operatorError(expression queryplan.Expression, operator strin
 	}
 }
 
+// tolerateArgument reads Project's and WhereFeature's tolerate: by default an
+// element lacking the feature is a path error; true keeps the cell empty.
+func (e *executor) tolerateArgument(expression queryplan.Expression) (bool, error) {
+	if !hasArgument(expression, "tolerate") {
+		return false, nil
+	}
+	return e.booleanArgument(expression, "tolerate")
+}
+
+// missingFeature reports a feature the element row lacks, its own features as
+// the frontier; nil for a non-element row or a metamodel property every element answers.
+func (e *executor) missingFeature(expression queryplan.Expression, property string, row Value) error {
+	sym, isElement := row.Element()
+	if !isElement || sym == nil || isQueryableProperty(property) || strings.Contains(property, "::") {
+		// A metadata path names an annotation the element may simply not carry.
+		return nil
+	}
+	reached, segment, nested := sym, property, ""
+	if segments, ok := parseMemberPath(property); ok {
+		reached, segment = e.memberPathStop(sym, segments)
+		if reached != sym {
+			nested = symbols.FQNOf(reached)
+		}
+	}
+	features := e.features(reached)
+	names := make([]string, 0, len(features))
+	for _, f := range features {
+		names = append(names, f.Name)
+	}
+	return &Error{
+		Kind:       ErrorMissingFeature,
+		Query:      e.definition.Name(),
+		Operation:  expression.Operation(),
+		Property:   property,
+		Target:     symbols.FQNOf(sym),
+		Actual:     nested,
+		Candidates: names,
+		Origin:     expression.Origin(),
+		Outcome: &Outcome{Path: &PathError{Failures: []Failure{{
+			Step:     Step{Kind: StepFeature, Argument: segment},
+			Expected: "a feature named " + segment + " on the element",
+			Frontier: Frontier{At: symbols.FQNOf(reached), Features: features, Nearest: first(suggest.Nearest(segment, names))},
+		}}}},
+	}
+}
+
+// features lists, in name order, the features an element has from the model's own
+// declarations (inherited ones included; library ones are noise) with their declared type.
+func (e *executor) features(sym *symbols.Symbol) []FeatureRef {
+	out := []FeatureRef{}
+	for _, member := range e.context.Model.MembersOf(sym) {
+		if member == nil || !member.IsFeature() || e.context.Index.IsLibraryDocument(member.DocName) {
+			continue
+		}
+		name := symbols.LastSegment(member.Name)
+		if name == "" {
+			continue
+		}
+		ref := FeatureRef{Name: name}
+		if types, ok := e.reader.Values(member, query.PropertyType); ok && len(types) > 0 {
+			ref.Type = types[0]
+		}
+		out = append(out, ref)
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
+	return slices.CompactFunc(out, func(a, b FeatureRef) bool { return a.Name == b.Name })
+}
+
 func (e *executor) unknownProperty(expression queryplan.Expression, property string) error {
 	return &Error{
 		Kind:      ErrorUnknownProperty,
diff --git a/internal/frontend/repl/docrender_test.go b/internal/frontend/repl/docrender_test.go
index 15ec849842..416272b593 100644
--- a/internal/frontend/repl/docrender_test.go
+++ b/internal/frontend/repl/docrender_test.go
@@ -69,7 +69,8 @@ const docDiagramModel = `package Imaging {
 		in root : Element;
 		Project(
 			source = WhereType(source = OwnedElements(source = root), type = "PartUsage"),
-			properties = ("name", "mass")
+			properties = ("name", "mass"),
+			tolerate = true  // the connection link is a part usage with no mass
 		)
 	}
 
diff --git a/internal/ir/queryplan/columns_test.go b/internal/ir/queryplan/columns_test.go
index 3f1839040c..7341313359 100644
--- a/internal/ir/queryplan/columns_test.go
+++ b/internal/ir/queryplan/columns_test.go
@@ -395,7 +395,7 @@ func TestCompilePositionalSurplusArgumentsAreTyped(t *testing.T) {
 	fixture := loadQueryFixture(t, computedFixture+`
 calc def Bad :> Query {
 	in root : Element;
-	Project(Descendants(source = root, maxDepth = 1), ("name"), null, null)
+	Project(Descendants(source = root, maxDepth = 1), ("name"), null, false, null)
 }
 `)
 	_, err := Compile(fixture.index, fixture.model, fixture.resolver, fixture.symbol(t, "Bad"))
diff --git a/internal/workspace/libs/extensions-project/.meta.json b/internal/workspace/libs/extensions-project/.meta.json
index 655f6a72d1..0ca5e582e6 100644
--- a/internal/workspace/libs/extensions-project/.meta.json
+++ b/internal/workspace/libs/extensions-project/.meta.json
@@ -14,7 +14,7 @@
     },
     "libraries/DocumentQueries.sysml": {
       "algorithm": "SHA256",
-      "value": "aa60929736008efde216af31a14482817abc221a67e53c337173f53b59d63322"
+      "value": "370b6f880bb2dc375b534f388e3c802c5820cc45e13977c38b3d36a9d1710233"
     },
     "libraries/IdentityMetadata.sysml": {
       "algorithm": "SHA256",
@@ -69,7 +69,7 @@
       "value": "9e00f049209584092dc8bcb398b736c08e6a39b1db667a8a744de3df72a543bf"
     }
   },
-  "created": "2026-10-25T17:57:00Z",
+  "created": "2026-10-27T13:19:03Z",
   "index": {
     "AnalysisRecords": "libraries/AnalysisRecords.sysml",
     "DiagramLayout": "libraries/DiagramLayout.sysml",
diff --git a/internal/workspace/libs/stdlib.snapshot b/internal/workspace/libs/stdlib.snapshot
index 120d45dafe..ecaa9bb75d 100644
Binary files a/internal/workspace/libs/stdlib.snapshot and b/internal/workspace/libs/stdlib.snapshot differ
diff --git a/internal/workspace/libs/stdlib/OpenSysML Libraries/DocumentQueries.sysml b/internal/workspace/libs/stdlib/OpenSysML Libraries/DocumentQueries.sysml
index 69413e1e19..6f7022adb2 100644
--- a/internal/workspace/libs/stdlib/OpenSysML Libraries/DocumentQueries.sysml	
+++ b/internal/workspace/libs/stdlib/OpenSysML Libraries/DocumentQueries.sysml	
@@ -179,6 +179,8 @@ library package DocumentQueries {
 		in 'feature' : String[1];
 		in operator : String[1];
 		in value : String[1];
+		/* As for Project: an element lacking the feature is a path error unless tolerated. */
+		in tolerate : Boolean[1] default false;
 		return result : Element[0..*] ordered;
 	}
 
@@ -235,6 +237,11 @@ library package DocumentQueries {
 		in source : Element[0..*] ordered;
 		in properties : String[0..*] ordered default null;
 		in columns : ColumnSpec[0..*] ordered default null;
+		/* A property an element row lacks — a feature name, or a dotted member path
+		 * whose segment names no member on that row — is a path error naming the
+		 * element and the features it does have; tolerate = true keeps the empty
+		 * cell. A Column path is a computed cell and stays absent, as documented above. */
+		in tolerate : Boolean[1] default false;
 		return result : Element[0..*] ordered;
 	}
 
diff --git a/scripts/extension-libraries-pin.sh b/scripts/extension-libraries-pin.sh
index f3ec9c497a..196576ba0d 100755
--- a/scripts/extension-libraries-pin.sh
+++ b/scripts/extension-libraries-pin.sh
@@ -8,4 +8,4 @@
 # verifies, because a ref is mutable. Change them together.
 EXTENSIONS_REPO="${EXTENSIONS_REPO:-https://github.com/Open-MBEE/OpenSysML-Extensions-Library.git}"
 EXTENSIONS_REF="${EXTENSIONS_REF:-main}"
-EXTENSIONS_COMMIT="${EXTENSIONS_COMMIT:-b36b361f85af4764de8e2817cbae62fb9e74ffdb}"
+EXTENSIONS_COMMIT="${EXTENSIONS_COMMIT:-745963b151f925e4543b03d5bb09b978aa492e12}"