@@ -3,9 +3,10 @@
 '@objectstack/service-analytics': minor
 '@objectstack/lint': minor
 '@objectstack/platform-objects': minor
+'@object-ui/app-shell': minor
 ---
 
-feat(spec,analytics,lint,platform-objects): a dataset measure can aggregate the time between two datetime fields of each record
+feat(spec,analytics,lint,platform-objects,app-shell): a dataset measure can aggregate the time between two datetime fields of each record
 
 Clause-②: yes (widening)
 Metadata-protocol: added
@@ -14,5 +15,6 @@ Metadata-protocol: added
 - **`@objectstack/service-analytics`**: the dataset compile refuses a duration column declared anything but `datetime` (`400 DATASET_INVALID`, naming the column and its type). The native-SQL strategy computes the duration as one statement on SQLite, PostgreSQL and MySQL, in double precision on each; SQLite and PostgreSQL are tested live to answer the same number: a record missing either instant is left out, a `to` before its `from` counts as negative, and over a group with no such record `sum` answers `0` and the others `null`. Measure filters, derived measures, ordering and the draft preview serve it. A query the native strategy does not serve (a time dimension bucketed by `granularity`, a field-to-field filter, an object served through engine middleware or an external datasource, a non-SQL datasource) is refused with `400 INVALID_FIELD` naming the measure. Its two columns pass the field-level read gate like any measure's field. The temporal half of the aggregate × field-type refusal now names the duration measure instead of a stored "days open" number.
 - **`@objectstack/lint`**: `os validate` refuses a duration column not declared `datetime` with the new gating rule `measure-duration-field-type-refused` (at `datasets[N].measures[M].duration.from` / `.to`), with an `os explain` entry. `dataset-field-unknown` now also reports a duration column the object does not declare.
 - **`@objectstack/platform-objects`**: the dataset form's new **Duration** row is translated in every shipped locale.
+- **`@object-ui/app-shell`**: changing a dataset's base object in the console's dataset inspector now clears a duration measure along with the other measures that name the old object's fields, instead of keeping it as if it were a plain row count.
 
 What to do: nothing. A dataset without `duration` parses, compiles and answers exactly as before.
@@ -170,6 +170,8 @@ describe('objectChangePatch moves a dataset between objects (objectui#12848)', (
       { name: 'amount_sum', aggregate: 'sum', field: 'amount' },
       { name: 'won_count', aggregate: 'count', filter: { stage: 'won' } },
       { name: 'won_rate', derived: { op: 'ratio', of: ['won_count', 'deal_count'] } },
+      // objectstack#25778: no `field`, yet `from` / `to` name two of the old object's fields.
+      { name: 'avg_days_to_close', aggregate: 'avg', duration: { from: 'created_at', to: 'closed_at', unit: 'days' } },
     ],
   };
 
 
@@ -129,6 +129,7 @@ const CURRENCY_OPTIONS = [
 
 type Dimension = { name?: string; label?: string; field?: string; type?: string; dateGranularity?: string };
 type DerivedSpec = { op?: string; of?: string[] };
+type DurationSpec = { from?: string; to?: string; unit?: string };
 type Measure = {
   name?: string;
   label?: string;
@@ -137,6 +138,8 @@ type Measure = {
   format?: string;
   currency?: string;
   derived?: DerivedSpec;
+  /** Time between two `datetime` fields of a record (`DatasetMeasureSchema.duration`, objectstack#25778). */
+  duration?: DurationSpec;
   filter?: FilterCondition;
 };
 
@@ -361,11 +364,18 @@ function DatasetFilterField({ label, help, value, onCommit, fields, disabled, lo
 /**
  * Whether a measure names none of its object's fields: a plain row count — no
  * `field` (or the row wildcard `'*'`), no measure-scoped `filter` (its keys are
- * fields), and not `derived` (a derived measure combines other measures, which
- * may name fields, and one left pointing at a cleared measure is refused).
+ * fields), not `derived` (a derived measure combines other measures, which
+ * may name fields, and one left pointing at a cleared measure is refused), and
+ * not a `duration` (its `from` / `to` are two fields, with no `field` beside
+ * them — objectstack#25778).
  */
 function measureNamesNoField(m: Measure): boolean {
-  return (isBlankField(m.field) || m.field === '*') && m.filter === undefined && m.derived === undefined;
+  return (
+    (isBlankField(m.field) || m.field === '*') &&
+    m.filter === undefined &&
+    m.derived === undefined &&
+    m.duration === undefined
+  );
 }
 
 /**