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+---
+---
+
+Test-only (objectui#6823): the console deprecation notice and the machine-readable
+`deprecated.replacement` a deprecated type declares are now asserted to offer the same
+set of replacement types, one case per renderer (`div`, `span`).
+
+Since objectui#6674 a deprecated type's migration guidance is stated twice — the notice
+string literal in the renderer, and the `deprecated.replacement` on its registration,
+transcribed from the notice by hand. Nothing held them together, so a reword of either
+left the other stale, and the stale copy is the one an automated gate reads and repeats
+to authors. There is no `tsc` here to notice one string literal drifting from another.
+
+`packages/components/src/__tests__/deprecation-guidance-agreement.test.tsx` extracts the
+double-quoted type names from each side — the notice's guidance BULLETS, and the
+declaration's replacement line — and asserts set equality. Nothing about the guidance
+text is restated in the test; a third copy of the sentence is the defect one layer up,
+and per triage it is the signal to stop rather than the way to write this.
+
+Shape ruled by triage (2026-08-29): assert the agreement, do not converge the two texts.
+The notice wording is pinned byte-for-byte by four existing tests, and those pins are
+themselves objectui#4000's ruling — converging would trade one ruled invariant for
+another. No pin is touched here, and no published behaviour changes.
diff --git a/packages/components/src/__tests__/deprecation-guidance-agreement.test.tsx b/packages/components/src/__tests__/deprecation-guidance-agreement.test.tsx
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+/**
+ * ObjectUI
+ * Copyright (c) 2024-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * A deprecated type's migration guidance is stated TWICE, and this file is the
+ * only thing holding the two statements together (objectui#6823).
+ *
+ * 1. the human-facing console notice — `DIV_DEPRECATION_NOTICE` /
+ *    `SPAN_DEPRECATION_NOTICE`, string literals inside the renderers, and
+ * 2. the machine-readable `deprecated.replacement` on the same file's
+ *    registration, which objectui#6674 added so a gate can tell an author what
+ *    to write instead.
+ *
+ * Both say the same thing today, in different words, because the second was
+ * transcribed from the first by hand. Nothing asserted they still agree, so a
+ * reword of either left the other stale — and the stale one is the copy an
+ * automated gate reads and repeats to authors, at a scale no console notice
+ * reaches. This is the shape objectui#4580 ruled about and objectui#6067 /
+ * #5671 / #5893 executed three times since; the unit here is a sentence rather
+ * than a type, and unlike those it fails SILENTLY, because there is no `tsc` to
+ * notice a string literal drifting away from another string literal.
+ *
+ * ## Why this ASSERTS the agreement instead of deriving one text from the other
+ *
+ * Deriving the notice's guidance line from the declaration is the direction
+ * that class of ruling usually takes, and triage weighed it here and ruled
+ * against it (2026-08-29, on objectui#6823). Those precedents were about TYPES,
+ * enforced by `tsc`, with no competing ruling on their wording. This sentence
+ * is pinned BYTE-FOR-BYTE by four existing tests —
+ * `div-deprecation-provenance`, `div-deprecation-warn-once`,
+ * `span-deprecation-provenance`, `span-deprecation-warn-once` — and those pins
+ * are themselves a deliberate maintainer ruling: objectui#4000 records that the
+ * guidance is "byte-for-byte what it was." Converging the two statements means
+ * MOVING those pins, i.e. trading one ruled invariant for another, which is a
+ * judged change of its own and not a rider on a drift-prevention card.
+ *
+ * The assertion below buys the whole drift protection without touching
+ * objectui#4000 at all.
+ *
+ * ## What is compared, and why it is EXTRACTED rather than restated
+ *
+ * Restating either text here would be a THIRD copy of the sentence — the very
+ * defect, one layer up, and the point at which this file would have to stop and
+ * escalate instead. So nothing below spells out any guidance text. Both
+ * statements are reduced, mechanically, to the thing they are both about: the
+ * set of component type names offered as the replacement, read out of each text
+ * as its double-quoted runs. That convention is one both texts already follow —
+ * a replacement type is named in double quotes on both sides — and it is the
+ * half that has to agree: prose framing may differ (the notice explains WHEN to
+ * reach for each, the declaration is one line for a gate to repeat), the
+ * alternatives on offer may not.
+ *
+ * Set equality, not containment, and that is deliberate: containment one way
+ * catches a name added to the declaration but not the notice, and misses the
+ * reverse. Drift has no preferred direction, so both directions are asserted at
+ * once.
+ *
+ * ## Scope — the notice's SCOPE sentence is deliberately not read here
+ *
+ * The `surfaces` / `isHtmlTierNode` half is already pinned to itself by
+ * objectui#6674, in the two provenance tests. Extraction below is confined to
+ * the notice's guidance BULLETS, so this file cannot start failing because that
+ * sentence was reworded — the bullets are what `deprecated.replacement`
+ * restates, and their layout is itself part of what objectui#4000's four pins
+ * hold in place.
+ */
+
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { render } from '@testing-library/react';
+import { ComponentRegistry } from '@object-ui/core';
+// Registers the renderers at module scope, NOT inside a `beforeAll` — there the
+// cold transform is billed to `hookTimeout`. See
+// object-ui/no-dynamic-import-in-test-hook (objectui#3010/#3021).
+import '../renderers';
+
+/**
+ * The component type names a piece of guidance offers: its double-quoted runs.
+ *
+ * Deliberately not a list of names kept here. A hard-coded list would be the
+ * third copy this file exists to avoid, and would go stale in exactly the way
+ * the two statements it compares can.
+ */
+function offeredTypeNames(guidance: string): Set<string> {
+  return new Set([...guidance.matchAll(/"([^"]+)"/g)].map((match) => match[1]));
+}
+
+/**
+ * The notice's migration guidance: its bullet lines, and only those.
+ *
+ * Everything else in the notice — the header naming the type, the SCOPE
+ * sentence objectui#6674 already pins elsewhere, the docs link — is out of
+ * scope for this comparison, and reading past the bullets is how this file
+ * would acquire a coupling to text that is not its business.
+ */
+function guidanceBullets(notice: string): string {
+  return notice
+    .split('\n')
+    .filter((line) => line.trimStart().startsWith('- '))
+    .join('\n');
+}
+
+/**
+ * Render one JSON-authored node of `type` and return the deprecation notices it
+ * emitted.
+ *
+ * The notice literal is module-private, as it should be — exporting it to test
+ * it would widen the package's surface for a test's convenience. It is read the
+ * way every reader reads it: off the console. The warn-once guard
+ * (objectui#3965) is a module-level Set per renderer module, so each type may be
+ * rendered in exactly one case of this file; the count assertion in each case is
+ * what would catch that rule being broken later.
+ */
+function deprecationNoticesFor(type: string): string[] {
+  const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});
+  const Component = ComponentRegistry.get(type);
+  if (!Component) throw new Error(`Component "${type}" is not registered`);
+  render(<Component schema={{ type }} />);
+  const deprecation = new RegExp(`The "${type}" component is deprecated`);
+  return warn.mock.calls
+    .map((args: unknown[]) => String(args[0]))
+    .filter((message) => deprecation.test(message));
+}
+
+/**
+ * One case's body, shared so both renderers are held to the identical check and
+ * a third deprecated type joins them in one line rather than by transcription —
+ * which is the failure mode this whole file is about.
+ */
+function expectGuidanceAndDeclarationAgree(type: string): void {
+  const notices = deprecationNoticesFor(type);
+  // Control FIRST: an agreement between two texts proves nothing if one of them
+  // was never produced. Zero notices (a renderer that stopped warning, a type
+  // that stopped resolving) would otherwise read as a pass on empty sets.
+  expect(notices).toHaveLength(1);
+
+  const bullets = guidanceBullets(notices[0]);
+  // Control: the notice really carries bullet guidance. A reflow that dissolves
+  // the bullets is a reword of the guidance, and it has to come back through
+  // here rather than silently emptying the comparison.
+  expect(bullets).not.toBe('');
+
+  const declared = ComponentRegistry.deprecationFor(type, 'json')?.replacement;
+  // Control: the declaration objectui#6674 added is still there and still says
+  // something. Without this, deleting `replacement` would turn this case green.
+  expect(declared).toBeTruthy();
+
+  const fromDeclaration = offeredTypeNames(declared as string);
+  // Control: the comparison is not vacuous. Guidance rewritten without quoted
+  // names on the declaration side would otherwise satisfy an empty-vs-empty
+  // equality while saying nothing at all.
+  expect(fromDeclaration.size).toBeGreaterThan(0);
+
+  const fromNotice = offeredTypeNames(bullets);
+
+  // The whole point: the alternatives the human is offered and the alternatives
+  // a gate would repeat are the same set. Reword either side's list — add,
+  // drop or rename one — and this goes red.
+  expect([...fromNotice].sort()).toEqual([...fromDeclaration].sort());
+}
+
+describe('deprecation guidance — the console notice and `deprecated.replacement` agree (#6823)', () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('div: the notice offers exactly the alternatives the declaration names', () => {
+    expectGuidanceAndDeclarationAgree('div');
+  });
+
+  it('span: the notice offers exactly the alternatives the declaration names', () => {
+    expectGuidanceAndDeclarationAgree('span');
+  });
+});