diff --git a/‎.changeset/21880-search-companion-field-scope.md‎
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diff --git a/‎packages/objectql/src/search-companion.test.ts‎
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diff --git a/‎packages/objectql/src/search-filter.ts‎
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diff --git a/‎packages/qa/dogfood/package.json‎
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@@ -0,0 +1,11 @@
+---
+'@objectstack/objectql': patch
+---
+
+A field-narrowed `$search` no longer matches through the pinyin search companion of a field outside the search-field set (#21880).
+
+Clause-②: no
+
+- **What changed.** When the optional pinyin search companion is on (`OS_SEARCH_PINYIN_ENABLED`), the engine's search expansion (`expandSearchToFilter`) adds the companion clause only when every field the companion mirrors is inside the effective search-field set: the set `resolveSearchFields` computes, after any `$searchFields` narrowing. The mirrored fields are read from `resolveSearchCompanionSources`, the same function the companion is provisioned and filled from.
+- **What stays the same.** A search with no narrowing keeps the clause whenever the display/name field is in the object's searchable set, so pinyin recall there is unchanged. A CJK term still skips the clause. Deployments with the companion off see no change.
+- **Who notices.** A search narrowed to fields that leave out the display/name field, by a `$searchFields` override, by the narrowing global search applies to the fields a caller may query, or by a declared `searchableFields` that omits it, no longer matches through that field's pinyin form.
@@ -182,6 +182,123 @@ describe('expandSearchToFilter with companion column (query-time, additive)', ()
   });
 });
 
+/**
+ * [#21880] The companion clause follows the effective search-field set.
+ *
+ * The companion is a normalized copy of its source fields, so it may join a
+ * search only when every field it mirrors is inside the set
+ * `resolveSearchFields` computed. A field-narrowed search that leaves a
+ * mirrored field out gets no companion clause; a search with no narrowing
+ * keeps it, so recall is unchanged there.
+ */
+describe('[#21880] the companion clause follows the effective search-field set', () => {
+  // `crm_contact`: the companion mirrors `name` (the derived display field).
+  const fields = provisionSearchCompanion(contact()).fields as any;
+  const companionClause = (term: string) => ({ [SEARCH_COMPANION_FIELD]: { $contains: term } });
+
+  it('premise: the companion is provisioned and mirrors exactly `name`', () => {
+    expect(fields[SEARCH_COMPANION_FIELD]).toBeDefined();
+    expect(resolveSearchCompanionSources({ name: 'crm_contact', fields })).toEqual(['name']);
+  });
+
+  describe('(a) a field-narrowed search that leaves the mirrored field out gets no companion clause', () => {
+    it('a `$searchFields` override without the mirrored field', () => {
+      expect(expandSearchToFilter('zhangwei', { fields, requestedFields: ['email'] })).toEqual({
+        $or: [{ email: { $icontains: 'zhangwei' } }],
+      });
+      // The comma-separated spelling a URL query parameter arrives as.
+      expect(expandSearchToFilter('zhangwei', { fields, requestedFields: 'email,notes' })).toEqual({
+        $or: [{ email: { $icontains: 'zhangwei' } }, { notes: { $icontains: 'zhangwei' } }],
+      });
+    });
+
+    it('the narrowing carried on the search term itself (`{ query, fields }`)', () => {
+      expect(expandSearchToFilter({ query: 'zhangwei', fields: ['notes'] }, { fields })).toEqual({
+        $or: [{ notes: { $icontains: 'zhangwei' } }],
+      });
+    });
+
+    it('a declared `searchableFields` set without the mirrored field', () => {
+      expect(expandSearchToFilter('zhangwei', { fields, searchableFields: ['email'] })).toEqual({
+        $or: [{ email: { $icontains: 'zhangwei' } }],
+      });
+    });
+
+    it('every term of a multi-term search', () => {
+      const filter = expandSearchToFilter('zhang wei', { fields, requestedFields: ['email'] });
+      expect(filter).toEqual({
+        $and: [
+          { $or: [{ email: { $icontains: 'zhang' } }] },
+          { $or: [{ email: { $icontains: 'wei' } }] },
+        ],
+      });
+    });
+
+    it('reads the REAL source: an explicit `nameField` pointer moves what the companion mirrors', () => {
+      // `crm_ticket` names `subject` as its title, so the companion mirrors
+      // `subject` — not `name`, although a `name` field exists.
+      const ticket = provisionSearchCompanion({
+        name: 'crm_ticket',
+        nameField: 'subject',
+        fields: { subject: { type: 'text' }, name: { type: 'text' } },
+      });
+      const ticketFields = ticket.fields as any;
+      expect(resolveSearchCompanionSources(ticket)).toEqual(['subject']);
+
+      const withoutSubject = expandSearchToFilter('zhangwei', {
+        fields: ticketFields, displayField: 'subject', requestedFields: ['name'],
+      });
+      expect(withoutSubject).toEqual({ $or: [{ name: { $icontains: 'zhangwei' } }] });
+
+      const withSubject = expandSearchToFilter('zhangwei', {
+        fields: ticketFields, displayField: 'subject', requestedFields: ['subject'],
+      });
+      expect(withSubject.$or).toContainEqual(companionClause('zhangwei'));
+    });
+  });
+
+  describe('(b) a search with no narrowing keeps the companion clause (recall unchanged)', () => {
+    it('the auto-default set, which leads with the mirrored field', () => {
+      expect(expandSearchToFilter('ZhangWei', { fields })).toEqual({
+        $or: [
+          { name: { $icontains: 'ZhangWei' } },
+          { email: { $icontains: 'ZhangWei' } },
+          { notes: { $icontains: 'ZhangWei' } },
+          companionClause('zhangwei'),
+        ],
+      });
+    });
+
+    it('a narrowed set that still holds the mirrored field', () => {
+      expect(expandSearchToFilter('zw', { fields, requestedFields: ['name'] })).toEqual({
+        $or: [{ name: { $icontains: 'zw' } }, companionClause('zw')],
+      });
+    });
+
+    it('the gate reads the RESOLVED set: a request naming no allowed field falls back to the full set', () => {
+      // `resolveSearchFields` drops unknown names and falls back to the
+      // allowed set when none survives — so the effective set holds `name`.
+      const filter = expandSearchToFilter('zw', { fields, requestedFields: ['no_such_field'] });
+      expect(filter.$or).toContainEqual(companionClause('zw'));
+    });
+  });
+
+  describe('(c) a CJK term still skips the companion clause, as before', () => {
+    it('with and without narrowing', () => {
+      expect(expandSearchToFilter('张伟', { fields })).toEqual({
+        $or: [
+          { name: { $icontains: '张伟' } },
+          { email: { $icontains: '张伟' } },
+          { notes: { $icontains: '张伟' } },
+        ],
+      });
+      expect(expandSearchToFilter('张伟', { fields, requestedFields: ['name'] })).toEqual({
+        $or: [{ name: { $icontains: '张伟' } }],
+      });
+    });
+  });
+});
+
 describe('containsCJK / isCompanionMatchableTerm', () => {
   it('detects Han characters', () => {
     expect(containsCJK('张伟')).toBe(true);
 
@@ -42,6 +42,13 @@
  * `resolveSearchFields` still returns only source fields (the companion is
  * invisible to `$searchFields` overrides and to clients).
  *
+ * [#21880] …and bounded by the same set. The companion is a normalized copy of
+ * named source fields, so its clause is a match on THOSE fields. It joins a
+ * search only when every field it mirrors is inside the effective search-field
+ * set `resolveSearchFields` computed — after any `$searchFields` narrowing — and
+ * a set that leaves a mirrored field out leaves the companion out with it. See
+ * {@link companionWithinSearchFields}.
+ *
  * [#21009] A field the object declares MULTI-VALUED (`isMultiValueField`: a
  * `tags` / `multiselect` / `checkboxes` field, or a `select` / `lookup` /
  * `user` / … declared `multiple: true`) is matched by MEMBERSHIP, `$contains`,
@@ -68,7 +75,12 @@ import {
   type SearchFieldMeta,
   type SearchFieldResolutionOptions,
 } from '@objectstack/spec/data';
-import { SEARCH_COMPANION_FIELD, isCompanionMatchableTerm } from './search-companion.js';
+import {
+  SEARCH_COMPANION_FIELD,
+  isCompanionMatchableTerm,
+  resolveSearchCompanionSources,
+  type CompanionObjectMeta,
+} from './search-companion.js';
 
 export {
   resolveSearchFields,
@@ -147,6 +159,44 @@ function fieldClausesForTerm(field: string, term: string, meta: SearchFieldMeta)
   return [{ [field]: { $icontains: term } }];
 }
 
+/**
+ * [#21880] May the `__search` companion clause join a search over
+ * `searchFields`? Only when every source field the companion mirrors is in
+ * that set.
+ *
+ * The mirrored fields are read from {@link resolveSearchCompanionSources} —
+ * the one function the registry's provisioning seam and plugin-pinyin-search's
+ * populate hook already derive the companion from — over the same `fields` and
+ * the same display-field pointer the engine handed in. So the answer is the
+ * companion's real source, never a second guess at it.
+ *
+ * ⛔ The gate is `searchFields` and nothing else: the set `resolveSearchFields`
+ * already computed, with the declared/auto-default precedence and any
+ * `$searchFields` narrowing applied. No second eligibility rule for the
+ * companion is consulted here — whatever a caller's narrowing removed from the
+ * source columns, it removes from their normalized copy too.
+ *
+ * The companion is ONE column holding the normalized form of its sources, so
+ * the test is "every source is in the set", never "some source is": a clause
+ * over the shared column matches through every field it mirrors at once.
+ * A search whose set holds every mirrored field — any search with no
+ * narrowing, whenever the display/name field is in the object's searchable
+ * set — keeps the clause, so recall there is unchanged.
+ *
+ * An empty source list passes vacuously. The registry never provisions a
+ * companion without a source (`provisionSearchCompanion` returns early on an
+ * empty list), so that case is only an author-declared `__search` column —
+ * an ordinary field the platform does not fill — and it keeps today's answer.
+ */
+function companionWithinSearchFields(searchFields: readonly string[], opts: ExpandSearchOptions): boolean {
+  const sources = resolveSearchCompanionSources({
+    nameField: opts.displayField,
+    fields: opts.fields as CompanionObjectMeta['fields'],
+  });
+  const inSet = new Set(searchFields);
+  return sources.every((f) => inSet.has(f));
+}
+
 /**
  * Expand a `$search` term into a `{ $or: [...] }` (single term) or
  * `{ $and: [{ $or: [...] }, ...] }` (multi-term) filter. Returns `null` when
@@ -177,10 +227,14 @@ export function expandSearchToFilter(raw: unknown, opts: ExpandSearchOptions): a
   // different mechanism from the source-column clauses in
   // `fieldClausesForTerm`, which compare against raw stored text and therefore
   // need `$icontains`. Do not "align" the two.
-  const hasCompanion = !!opts.fields[SEARCH_COMPANION_FIELD];
+  //
+  // [#21880] …and only when the companion mirrors no field outside
+  // `searchFields` — see `companionWithinSearchFields`.
+  const withCompanion = !!opts.fields[SEARCH_COMPANION_FIELD]
+    && companionWithinSearchFields(searchFields, opts);
   const andClauses = terms.map((term) => {
     const clauses = searchFields.flatMap((f) => fieldClausesForTerm(f, term, opts.fields[f] || {}));
-    if (hasCompanion && isCompanionMatchableTerm(term)) {
+    if (withCompanion && isCompanionMatchableTerm(term)) {
       clauses.push({ [SEARCH_COMPANION_FIELD]: { $contains: term.toLowerCase() } });
     }
     return { $or: clauses };
 
@@ -26,6 +26,7 @@
     "@objectstack/plugin-audit": "workspace:*",
     "@objectstack/plugin-auth": "workspace:*",
     "@objectstack/plugin-email": "workspace:*",
+    "@objectstack/plugin-pinyin-search": "workspace:*",
     "@objectstack/plugin-security": "workspace:*",
     "@objectstack/plugin-sharing": "workspace:*",
     "@objectstack/plugin-webhooks": "workspace:*",