@@ -0,0 +1,30 @@
+---
+"@objectstack/lint": minor
+---
+
+fix(lint)!: `os build` and the object save door refuse a `validations[]` rule whose predicate reads `parent` (#24957)
+
+Clause-②: no (narrowing: `os build` and the object save door refuse a `validations[]` rule whose predicate reads `parent`, which the server's rule evaluator never binds)
+Metadata-protocol: narrowed
+
+A `validations[]` rule's predicates are a `script` or `cross_field` rule's `condition`, a `conditional` rule's `when`, and the same slots on the rules nested in its `then` / `otherwise`. The server evaluates them against `record` and `previous` only. The master-detail header is bound as `parent` for a field's own `readonlyWhen` and `requiredWhen` alone, on an object with exactly one `master_detail`. A rule that reads `parent`, such as `parent.status == 'paid'`, faults (`Unknown variable: parent`) on every write it judges, and the server refuses that write as unevaluable, the seed's own rows at boot included.
+
+The build's expression rule (`validateStackExpressions`) reported such a predicate at `warning` (#24720). This entry supersedes that entry's sentence "Nothing new is refused in 18.x" and its plan to refuse in 19.0: the refusal ships now, in this release, and this entry is the current statement. The rule now refuses such a predicate at `error`, at the same location (`object 'NAME' · validation 'RULE'`, `… when`, or the nested rule's label), with the same rule id (`expression-invalid`). The message no longer says it is a warning. The object save door runs the same pass, so its verdict is the build's finding.
+
+**BREAKING — what moves for consumers.**
+
+- `os build`, `os validate` and `os lint` fail on a `validations[]` rule whose predicate reads `parent`. The rule is judged as written, so this also covers a rule marked `active: false`, a rule whose `events` a stack never fires, and a `conditional` branch whose `when` is never true.
+- An object write in publish mode that carries such a rule answered 200, with the finding among its advisories. It now answers `422 INVALID_METADATA`, with an `expression-invalid` issue located at the rule. This covers `PUT /api/v1/meta/object/:name` (and `saveMetaItem` in publish mode), the promotion of a draft (`POST /api/v1/meta/object/:name/publish`, `publishMetaItem`), and a package draft publish (`publishPackageDrafts`).
+
+**Remedy.** To lock or require a field on the header's state, write the predicate on that field's own `readonlyWhen` or `requiredWhen`, where `parent` is bound. To refuse a whole write on the header's state (for example a new line under a paid invoice), use a lifecycle hook (`beforeInsert` / `beforeUpdate` / `beforeDelete`) that reads the header. For any other check, read a column the detail object declares, and denormalise the header value you need onto the detail. Saving the object as a draft (`mode: 'draft'`) is still allowed, because drafts are never gated; publishing that draft is judged.
+
+**Unchanged.**
+
+- The runtime is unchanged: a `validations[]` rule still binds `record` and `previous` and no `parent`, and such a rule already refused every write it judged. If the runtime comes to bind `parent` there, this refusal is withdrawn in that same change.
+- `parent` on a field's own `readonlyWhen` / `requiredWhen` is still accepted with no finding, and so is a `record` column spelled like the root (`record.parent_code`).
+- Stored rows are not migrated, and they are not refused on read. An object stored before this change keeps loading until it is next saved, and that save is judged.
+- `OS_ALLOW_UNLINTED_METADATA_WRITES=1` still turns a refusal into a logged write.
+- No example, template or package object in this repository authors `parent` in a `validations[]` rule.
+- No public export or signature moves.
+
+<!-- adr-0087: not-required (no-migration-prescription) a refusal at `os build` and at the object save door of a validations[] rule predicate that reads `parent`, which the server's rule evaluator never binds: no authorable key, spelling, export or stored shape moves, and no stored row is read, rewritten or converted. A stored object carrying such a rule keeps loading until it is next saved, and the repair is the author's rewrite of the predicate (a field rule, a lifecycle hook, or a denormalised column), which no ledger entry can derive. The other categories are closed on facts: the package publishes (not unpublished); no ADR-0087 id covers this verdict (not already-registered); and the change is a build and door verdict, not a declaration (not runtime-interface-only or type-surface-only). -->
@@ -1715,10 +1715,10 @@ function optionVisibleWhenUserMemberIssue(
 }
 
 /**
- * [#24720] The root verdict for a `validations[]` rule's own predicates — a
+ * [#24720, #24957] The root verdict for a `validations[]` rule's own predicates — a
  * `script` / `cross_field` rule's `condition`, a `conditional` rule's `when`,
  * and the same two slots on every rule nested in its `then` / `otherwise`: a
- * predicate that reads `parent` is reported, at `warning` (18.x).
+ * predicate that reads `parent` is refused, at `error`.
  *
  * ## Why it is reported
  *
@@ -1734,17 +1734,17 @@ function optionVisibleWhenUserMemberIssue(
  * bare-reference check stays silent. The field-rule slots one level up accept
  * the same text, which is what makes it the shape an author copies.
  *
- * ## Why a warning, and when it becomes a refusal
+ * ## Why an error
  *
  * A rule the runtime cannot evaluate must not pass a door (ADR-0049), so the
- * end state is `error`. But refusing it narrows what `os build` and the object
- * save door accept (a rule marked `active: false`, or a `conditional` branch
- * whose `when` is never true, builds and writes today), and no ADR-0087
- * conversion can rewrite a predicate that reads `parent`. Under the standing
- * post-GA ruling (甲), a narrowing no conversion carries ships only its loud
- * half in 18.x: this verdict reports at `warning`, which neither fails
- * `os build` nor refuses a save (the door lists it among its advisories). The
- * refusal — the same finding at `error` — is planned for 19.0.
+ * verdict is `error`: it fails `os build` and the object save door refuses a
+ * publish-mode write that carries it. The rule is judged as written, so a rule
+ * marked `active: false`, a rule whose `events` a stack never fires, and a
+ * `conditional` branch whose `when` is never true are refused too. No ADR-0087
+ * conversion can rewrite a predicate that reads `parent`; the repair is the
+ * author's. The refusal ships without a deprecation window under the standing
+ * ruling (甲, as amended: a protocol narrowing ships as soon as it can, with no
+ * retirement release), which first shipped this verdict at `warning`.
  *
  * ## Why `parent` alone
  *
@@ -1772,8 +1772,7 @@ function validationRuleParentIssue(
     `\`${slot}\` of validation rule '${ruleName}' reads \`parent\`, but the server evaluates a ` +
     `\`validations[]\` rule against \`record\` and \`previous\` only, so \`parent\` is unbound there. ` +
     `The rule can never be evaluated, and the server REFUSES every write it judges — a rule that ` +
-    `cannot be evaluated fails closed, seed rows included. This is a warning today; ` +
-    `\`os build\` and the object save door will refuse it from 19.0. The master-detail header is bound as ` +
+    `cannot be evaluated fails closed, seed rows included. The master-detail header is bound as ` +
     `\`parent\` only for a field's own \`readonlyWhen\` and \`requiredWhen\`, on an object with exactly ` +
     `one \`master_detail\`: to lock or require a field on the header's state, write the predicate on ` +
     `that field's \`readonlyWhen\` or \`requiredWhen\` instead. For any other check, read a column ` +
@@ -2931,8 +2930,8 @@ export function runStackExpressionPasses(stack: AnyRec, options: StackExpression
         const at = p.depth > 0
           ? `object '${objectName}' · ${p.label}`
           : p.slot === 'when' ? `${where} when` : where;
-        // `warning` in 18.x, `error` from 19.0: see the docblock's ruling.
-        issues.push({ where: at, message, source: source!, severity: 'warning' });
+        // `error`: a rule the runtime cannot evaluate must not pass a door; see the docblock.
+        issues.push({ where: at, message, source: source!, severity: 'error' });
       }
       // #4763 — null-guard gate over every predicate the rule carries, nested
       // `then`/`otherwise` branches included.
 
@@ -1,10 +1,10 @@
 // Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
 
 /**
- * #24720 — a `validations[]` rule's predicate that reads `parent` is reported
- * at authoring, at `os validate` / `os build` and at the object save door, at
- * `warning` in 18.x (the standing post-GA ruling 甲: a narrowing no ADR-0087
- * conversion carries ships its loud half first; the refusal comes in 19.0).
+ * #24720, #24957 — a `validations[]` rule's predicate that reads `parent` is
+ * refused at authoring, at `os validate` / `os build` and at the object save
+ * door, at `error`. #24720 shipped the verdict at `warning`; #24957 makes it
+ * the refusal (the standing ruling 甲, as amended: a narrowing ships now).
  *
  * ## The state this closes
  *
@@ -22,7 +22,7 @@
  * ## The verdict
  *
  * One root verdict over every predicate the rule carries, located where
- * `check()` locates the same predicate, reporting `parent` at warning, with the
+ * `check()` locates the same predicate, refusing `parent` at error, with the
  * prescription that is true for it: the field-rule slots where `parent` IS
  * bound, or a denormalised column. The runtime is unchanged.
  */
@@ -78,12 +78,12 @@ const dump = (r: unknown) => JSON.stringify(r, null, 2);
 
 const WHERE = "object 'fx_line' · validation 'paid_lock'";
 
-describe('#24720 — a `validations[]` predicate reading `parent` is reported at authoring', () => {
-  it('⭐ LIT — a `script` rule\'s `condition` reading `parent` is reported at warning, located at the rule', () => {
+describe('#24720 — a `validations[]` predicate reading `parent` is refused at authoring', () => {
+  it('⭐ LIT — a `script` rule\'s `condition` reading `parent` is refused at error, located at the rule', () => {
     const issues = validateStackExpressions(stackOf(header, line([script(PARENT)])));
 
     expect(issues, dump(issues)).toHaveLength(1);
-    expect(issues[0]).toMatchObject({ where: WHERE, severity: 'warning', source: PARENT });
+    expect(issues[0]).toMatchObject({ where: WHERE, severity: 'error', source: PARENT });
     expect(issues[0]!.message).toContain("validation rule 'paid_lock' reads `parent`");
   });
 
@@ -95,15 +95,30 @@ describe('#24720 — a `validations[]` predicate reading `parent` is reported at
     expect(issue!.message).toContain("denormalise the header value you need onto 'fx_line'");
   });
 
-  it('⭐ the `os validate` and `os build` commands both give the finding, at warning: nothing they gate on', () => {
+  it('⭐ the `os validate` and `os build` commands both give the finding at error: the one the command fails on', () => {
     for (const command of ['validate', 'build'] as const) {
       const stack = stackOf(header, line([script(PARENT)]));
       const all = runAuthoringRules(command, { normalized: stack, parsed: stack });
       const found = expressionFindings(all);
       expect(found, `${command}: ${dump(found)}`).toHaveLength(1);
-      expect(found[0]).toMatchObject({ severity: 'warning', where: WHERE });
-      // The 18.x half of the ruling: no `error` anywhere, so the command does not fail.
-      expect(all.filter((f) => f.severity === 'error'), `${command}: ${dump(all)}`).toEqual([]);
+      expect(found[0]).toMatchObject({ severity: 'error', where: WHERE });
+      // It is the ONLY error the stack carries, so it is what fails the command.
+      expect(all.filter((f) => f.severity === 'error'), `${command}: ${dump(all)}`).toEqual(found);
+    }
+  });
+
+  it('⭐ the message promises no later release: it IS the refusal', () => {
+    const [issue] = validateStackExpressions(stackOf(header, line([script(PARENT)])));
+
+    // The retired promise is gone: the finding is the refusal, not a notice of one.
+    expect(issue!.message).not.toMatch(/warning|19\.0/);
+  });
+
+  it('⭐ the rule is judged as written: an inactive rule, or an update-only one, is refused too', () => {
+    for (const extra of [{ active: false }, { events: ['update'] }]) {
+      const issues = validateStackExpressions(stackOf(header, line([{ ...script(PARENT), ...extra }])));
+      expect(issues, `${JSON.stringify(extra)}: ${dump(issues)}`).toHaveLength(1);
+      expect(issues[0]).toMatchObject({ where: WHERE, severity: 'error' });
     }
   });
 
@@ -112,7 +127,7 @@ describe('#24720 — a `validations[]` predicate reading `parent` is reported at
     const issues = validateStackExpressions(stackOf(header, line([rule])));
 
     expect(issues, dump(issues)).toHaveLength(1);
-    expect(issues[0]).toMatchObject({ where: WHERE, severity: 'warning' });
+    expect(issues[0]).toMatchObject({ where: WHERE, severity: 'error' });
   });
 
   it('⭐ a `conditional` rule\'s `when`, and the rules in its `then` / `otherwise`, are judged at their own locations', () => {
@@ -131,7 +146,7 @@ describe('#24720 — a `validations[]` predicate reading `parent` is reported at
       "object 'fx_line' · validation rule 'gate' then → 'inner'",
     ]);
     for (const i of issues) {
-      expect(i.severity).toBe('warning');
+      expect(i.severity).toBe('error');
       expect(i.message).toContain('reads `parent`');
     }
   });
@@ -148,7 +163,7 @@ describe('#24720 — a `validations[]` predicate reading `parent` is reported at
       const issues = validateStackExpressions(stackOf(header, line([script(PARENT)], {}, masters)));
       const here = issues.filter((i) => i.where === WHERE);
       expect(here, `${masters} masters: ${dump(issues)}`).toHaveLength(1);
-      expect(here[0]!.severity).toBe('warning');
+      expect(here[0]!.severity).toBe('error');
     }
   });
 
@@ -175,20 +190,21 @@ describe('#24720 — a `validations[]` predicate reading `parent` is reported at
 });
 
 describe('#24720 — the object door gives the build\'s verdict', () => {
-  it('⭐ LIT — the measured body is ADMITTED at the door with the finding as an advisory, located at the rule', () => {
+  it('⭐ LIT — the measured body is REFUSED at the door with the finding as an error, located at the rule', () => {
     const result = gateObject(line([script(PARENT)]), [header]);
 
     expect(result.rulesRun).toContain('validateStackExpressions');
-    expect(result.errors, dump(result)).toEqual([]);
-    const advs = expressionFindings(result.advisories);
-    expect(advs, dump(result)).toHaveLength(1);
-    expect(advs[0]).toMatchObject({ severity: 'warning', where: WHERE, path: WHERE });
-    expect(advs[0]!.message).toContain("validation rule 'paid_lock' reads `parent`");
+    const errs = expressionFindings(result.errors);
+    expect(errs, dump(result)).toHaveLength(1);
+    expect(errs[0]).toMatchObject({ severity: 'error', where: WHERE, path: WHERE });
+    expect(errs[0]!.message).toContain("validation rule 'paid_lock' reads `parent`");
+    // No longer an advisory: the finding moved, it was not duplicated.
+    expect(expressionFindings(result.advisories), dump(result)).toEqual([]);
   });
 
   it('⭐ PARITY — the door finding IS the build finding', () => {
     const atBuild = commandFindings('build', header, line([script(PARENT)]));
-    const atDoor = expressionFindings(gateObject(line([script(PARENT)]), [header]).advisories);
+    const atDoor = expressionFindings(gateObject(line([script(PARENT)]), [header]).errors);
 
     expect(atBuild, dump(atBuild)).toHaveLength(1);
     expect(atDoor, dump(atDoor)).toEqual(atBuild);