diff --git a/.changeset/default-value-literal-gate-prefers-rename.md b/.changeset/default-value-literal-gate-prefers-rename.md
new file mode 100644
index 0000000000..563e0c9a6c
--- /dev/null
+++ b/.changeset/default-value-literal-gate-prefers-rename.md
@@ -0,0 +1,13 @@
+---
+"@objectstack/spec": patch
+---
+
+The authoring-time `defaultValue` gate now prescribes the key rename an author actually made, instead of a type error about a member they never wrote.
+
+`checkLiteralDefaultValue` — the shared core of the field gate (`FieldSchema.defaultValue`) and the action-param gate (`ActionParamSchema.defaultValue`) — read a value-contract rejection positionally, `result.error.issues[0]`. zod reports per-member issues before the object-level `unrecognized_keys` one, so on a default whose keys were **renamed** the actionable message sorted last and was discarded. An `address` default authored as `{ street: 5, postal_code: '98101' }` answered `Invalid input: expected string, received number`, and a `location` default authored as the legacy `{ latitude, longitude }` pair answered `Invalid input: expected number, received undefined` — while `AddressValueSchema` and `LocationValueSchema` had each built the rename prescription and thrown it away. Which of the two the author got depended on whether some unrelated member happened to also be wrong: nobody chose that, and nobody could see it.
+
+The gate now prefers the undeclared-key issue when the rejection carries one. `LiteralDefaultValueVerdict.detail` keeps its name, its type and its documented meaning — "the 'why' a refusal carries verbatim"; what changes is which of several already-reachable messages it carries.
+
+⛔ No verdict moves. Exactly the same defaults are accepted and refused, on the same evidence — only the refusal text changes.
+
+Scoped by measurement rather than inherited: the sixteen classes `valueSchemaFor(def, 'stored')` covers were swept again on this function, at both arities. Only `location` and `address` can emit `unrecognized_keys` at all, because only they are backed by a key-closed object schema — for the other fourteen the preference cannot change a single character. Both classes it does reach curate the alias map that makes the undeclared key the more actionable half of the rejection.
diff --git a/packages/spec/src/data/default-value-shape.test.ts b/packages/spec/src/data/default-value-shape.test.ts
index 140ddfcea9..2672ae31a4 100644
--- a/packages/spec/src/data/default-value-shape.test.ts
+++ b/packages/spec/src/data/default-value-shape.test.ts
@@ -118,4 +118,60 @@ describe('#7127 checkLiteralDefaultValue — the shared stored-form literal chec
   it('stays open where the contract is deliberately open (json)', () => {
     expect(checkLiteralDefaultValue({ type: 'json' }, { anything: ['at', 'all'] }).ok).toBe(true);
   });
+
+  // ── #16077: `detail` is the ACTIONABLE issue, not `issues[0]` ─────────────
+  //
+  // zod sorts per-member issues ahead of the object-level `unrecognized_keys`
+  // one, so a positional read handed an author who RENAMED a key a
+  // missing-member type error about a member they never wrote — and which of
+  // the two they got depended on whether some unrelated member happened to
+  // also be wrong. Each case below asserts BOTH halves: the prescription is
+  // present, AND the half that was being shown instead is gone. Without the
+  // second the pin cannot see a regression back to the positional read.
+  it('#16077 prefers the rename over a MISSING-member type error (location)', () => {
+    const v = checkLiteralDefaultValue({ type: 'location' }, { latitude: 1, longitude: 2 });
+    expect(v.ok).toBe(false);
+    // Positionally this rejection reads
+    // `[invalid_type(lat), invalid_type(lng), unrecognized_keys]`.
+    expect(v.detail).toContain('`latitude` \u2192 `lat`');
+    expect(v.detail).toContain('`longitude` \u2192 `lng`');
+    expect(v.detail).not.toContain('expected number, received undefined');
+    // Edit distance cannot reach `latitude` -> `lat`; the curated `aliases`
+    // map is the only thing that can, which is why discarding it cost the
+    // author the whole prescription.
+  });
+
+  it('#16077 prefers the rename over a WRONG-TYPED-member error (address)', () => {
+    const v = checkLiteralDefaultValue({ type: 'address' }, { street: 5, postal_code: '98101' });
+    expect(v.ok).toBe(false);
+    // Every member of `address` is optional, which rules out a MISSING-member
+    // error but says nothing about a wrong-typed declared one — it sorts ahead
+    // just the same. This is the case that made the defect look location-only.
+    expect(v.detail).toContain('`postal_code` \u2192 `postalCode`');
+    expect(v.detail).not.toContain('expected string, received number');
+  });
+
+  it('#16077 leaves the already-correct case exactly as it was (the asymmetry is gone)', () => {
+    // No member error to sort ahead, so this one was always right. Pinning it
+    // beside the two above is what states the property: the diagnosis no
+    // longer depends on whether an unrelated member happened to also be wrong.
+    const lucky = checkLiteralDefaultValue({ type: 'address' }, { postal_code: '98101' });
+    const unlucky = checkLiteralDefaultValue({ type: 'address' }, { street: 5, postal_code: '98101' });
+    expect(lucky.ok).toBe(false);
+    expect(lucky.detail).toContain('`postal_code` \u2192 `postalCode`');
+    expect(unlucky.detail).toContain('`postal_code` \u2192 `postalCode`');
+  });
+
+  it('#16077 is a NO-OP for a class that cannot emit `unrecognized_keys`', () => {
+    // The sweep over all sixteen classes `valueSchemaFor(def, 'stored')`
+    // covers found only `location` and `address` backed by a `strictObject`,
+    // so only they can emit the issue the preference looks for. For the other
+    // fourteen the selected message is `issues[0]` exactly as before — this
+    // pin is the one that goes red if the preference ever starts reordering
+    // a class it has no business reordering.
+    const v = checkLiteralDefaultValue({ type: 'datetime' }, '2026-08-10T15:00');
+    expect(v.ok).toBe(false);
+    expect(v.detail).toContain('ISO-8601 instant');
+    expect(v.detail).not.toContain('Unrecognized key');
+  });
 });
diff --git a/packages/spec/src/data/default-value-shape.ts b/packages/spec/src/data/default-value-shape.ts
index b73b487f17..71867fd33f 100644
--- a/packages/spec/src/data/default-value-shape.ts
+++ b/packages/spec/src/data/default-value-shape.ts
@@ -96,13 +96,59 @@ export function discriminateDefaultValueShape(dv: unknown): DefaultValueShape {
   return 'literal';
 }
 
-/** Verdict of {@link checkLiteralDefaultValue}: `ok`, or the first contract violation. */
+/** Verdict of {@link checkLiteralDefaultValue}: `ok`, or the contract violation to act on. */
 export interface LiteralDefaultValueVerdict {
   ok: boolean;
-  /** First issue message from the value contract — the "why" a refusal carries verbatim. */
+  /**
+   * The ACTIONABLE issue message from the value contract — the "why" a refusal
+   * carries verbatim. Selected by {@link actionableValueIssueMessage}, not read
+   * positionally; the field's name, type and meaning are what they always were.
+   */
   detail?: string;
 }
 
+/**
+ * The one parse issue an author can act on, out of everything zod reported for
+ * this literal's value-shape rejection.
+ *
+ * NOT `issues[0]`. zod reports per-member issues before the object-level
+ * `unrecognized_keys` one, so on a default whose keys were RENAMED the
+ * actionable message sorts LAST and a positional read discards it. An
+ * `address` default authored as `{ street: 5, postal_code: '98101' }` reports:
+ *
+ *     [0] invalid_type          street   Invalid input: expected string, received number
+ *     [1] unrecognized_keys              ... Did you mean `postal_code` -> `postalCode`? ...
+ *
+ * The rename IS the prescription, and edit distance cannot reach it
+ * (`latitude` -> `lat`), which is exactly why `LocationValueSchema` and
+ * `AddressValueSchema` curate an `aliases` map. Reading positionally built that
+ * hint and threw it away, handing the author a missing-member type error about
+ * a member they never wrote — and which of the two they got depended on whether
+ * some unrelated member happened to also be wrong, which nobody chose and
+ * nobody can see.
+ *
+ * The preference is a NO-OP for every other class rather than merely harmless
+ * to it, which is what makes it safe as a blanket rule. Swept on THIS function
+ * over all sixteen classes `valueSchemaFor(def, 'stored')` covers, at both
+ * arities: only `location` and `address` can emit `unrecognized_keys` at all,
+ * because only they are backed by a `strictObject`. The string, numeric,
+ * boolean, calendar-date, instant, clock-time, option, reference and
+ * file-reference classes are scalars; `composite` / `record` / `repeater` /
+ * `vector` are open records and arrays; the open fallback is `z.unknown()`. For
+ * the other fourteen this cannot change a single character.
+ *
+ * The stored-value scan reached the same reading from the other side
+ * (objectql `record-validator.ts`'s `valueShapeDetail`). Two readings of one
+ * rejection, one per surface — deliberately not shared, because `packages/spec`
+ * is upstream of `objectql` and this gate answers a metadata AUTHOR while that
+ * one answers an operator running a migration.
+ */
+function actionableValueIssueMessage(
+  issues: ReadonlyArray<{ code: string; message: string }>,
+): string {
+  return (issues.find((i) => i.code === 'unrecognized_keys') ?? issues[0])?.message ?? 'invalid value';
+}
+
 /**
  * Check a LITERAL default against its owner's own stored-form value contract
  * (`valueSchemaFor(def, 'stored')` — ADR-0104 D1). The shared core of the
@@ -117,7 +163,7 @@ export interface LiteralDefaultValueVerdict {
 export function checkLiteralDefaultValue(def: ValueShapeFieldDef, dv: unknown): LiteralDefaultValueVerdict {
   const result = valueSchemaFor(def, 'stored').safeParse(dv);
   if (result.success) return { ok: true };
-  return { ok: false, detail: result.error.issues[0]?.message ?? 'invalid value' };
+  return { ok: false, detail: actionableValueIssueMessage(result.error.issues) };
 }
 
 /* ────────────────────────────────────────────────────────────────────────────
diff --git a/packages/spec/src/data/field-default-value.test.ts b/packages/spec/src/data/field-default-value.test.ts
index b671593ebc..e2b89c7188 100644
--- a/packages/spec/src/data/field-default-value.test.ts
+++ b/packages/spec/src/data/field-default-value.test.ts
@@ -34,6 +34,11 @@ type Case = {
   accepted: boolean;
   /** Substrings the refusal message must carry (rejection rows only). */
   contains?: string[];
+  /**
+   * Substrings the refusal message must NOT carry — the wrong half of a
+   * rejection that a positional issue read would have selected (#16077).
+   */
+  notContains?: string[];
 };
 
 const CASES: Case[] = [
@@ -86,6 +91,26 @@ const CASES: Case[] = [
     accepted: false,
     contains: ['`heading`'],
   },
+  // #16077 — the two rows above are the LUCKY half: their other members are
+  // well-typed, so nothing sorted ahead of the object-level issue and the
+  // rename surfaced by accident. These two are the unlucky half, where a
+  // positional `issues[0]` read handed the author a type error about a member
+  // they never wrote. `notContains` names the half that was shown instead —
+  // without it the row cannot see a regression back to the positional read.
+  {
+    label: '#16077 location + the RENAMED legacy pair (a missing-member error sorts ahead)',
+    field: { type: 'location', defaultValue: { latitude: 37.77, longitude: -122.42 } },
+    accepted: false,
+    contains: ['`latitude` \u2192 `lat`', '`longitude` \u2192 `lng`'],
+    notContains: ['expected number, received undefined'],
+  },
+  {
+    label: '#16077 address + a renamed key beside a WRONG-TYPED declared one',
+    field: { type: 'address', defaultValue: { street: 5, postal_code: '98101' } },
+    accepted: false,
+    contains: ['`postal_code` \u2192 `postalCode`'],
+    notContains: ['expected string, received number'],
+  },
 
   // ── Literal branch: valid literals stay accepted ──────────────────────────
   { label: 'VALID number', field: { type: 'number', defaultValue: 7 }, accepted: true },
@@ -227,7 +252,7 @@ const CASES: Case[] = [
 ];
 
 describe('#7127 FieldSchema.defaultValue — three shapes, each judged on its own terms', () => {
-  for (const { label, field, accepted, contains } of CASES) {
+  for (const { label, field, accepted, contains, notContains } of CASES) {
     it(`${accepted ? 'accepts' : 'rejects'}: ${label}`, () => {
       const issue = defaultValueIssue(field);
       if (accepted) {
@@ -243,6 +268,9 @@ describe('#7127 FieldSchema.defaultValue — three shapes, each judged on its ow
       for (const fragment of contains ?? []) {
         expect(issue!.message).toContain(fragment);
       }
+      for (const fragment of notContains ?? []) {
+        expect(issue!.message).not.toContain(fragment);
+      }
     });
   }
 
diff --git a/packages/spec/src/ui/action-param-default-value.test.ts b/packages/spec/src/ui/action-param-default-value.test.ts
index a5d61e3dff..0802e9341d 100644
--- a/packages/spec/src/ui/action-param-default-value.test.ts
+++ b/packages/spec/src/ui/action-param-default-value.test.ts
@@ -143,6 +143,26 @@ describe('#6970 ActionParamSchema.defaultValue — authored defaults meet the pa
     });
   }
 
+  it('#16077 carries the rename, not a member type error, on a renamed structured default', () => {
+    // The action-param gate and the field gate share ONE core
+    // (`checkLiteralDefaultValue`), so the positional issue read cost this
+    // surface the same prescription. Pinned here as well as at the core
+    // because this consumer composes `verdict.detail` into its own message:
+    // a core fix that never reached the composed text would be invisible to a
+    // core-only pin.
+    const issue = defaultValueIssue({
+      name: 'site',
+      type: 'location',
+      defaultValue: { latitude: 37.77, longitude: -122.42 },
+    })!;
+    expect(issue).not.toBeNull();
+    expect(issue.path).toEqual(['defaultValue']);
+    expect(issue.message).toContain('`latitude` \u2192 `lat`');
+    expect(issue.message).toContain('`longitude` \u2192 `lng`');
+    // The half a positional `issues[0]` read selected instead.
+    expect(issue.message).not.toContain('expected number, received undefined');
+  });
+
   it("names the author's default as the cause, not just the param", () => {
     const issue = defaultValueIssue({ name: 'start', type: 'datetime', defaultValue: '2026-08-10T15:00' })!;
     // The underlying reason is carried verbatim from the shared value contract,