@@ -2,17 +2,17 @@
 '@objectstack/spec': patch
 ---
 
-fix(spec)!: `EngineQueryOptionsSchema.fields` and the RPC request's `select` declare the projection their transport siblings declare, instead of any list (#26954)
+fix(spec)!: the engine-side projection declarations (`EngineQueryOptionsSchema.fields`, the RPC request's `select`, the legacy `DataEngineQueryOptionsSchema.select` and the vector-find request's `fields`) declare the projection their transport siblings declare, instead of any list (#26954)
 
-Clause-②: no (narrowing) — the published engine-side declarations of a read's projection (`EngineQueryOptionsSchema.fields`, and the deprecated `select` of the RPC query options reached through `DataEngineFindRequestSchema`, `DataEngineFindOneRequestSchema` and `DataEngineRequestSchema`) refuse a list naming no field, which they admitted before. Nothing is widened and no key is added, removed or renamed.
+Clause-②: no (narrowing) — the published engine-side declarations of a read's projection (`EngineQueryOptionsSchema.fields`; the deprecated `select` of the RPC query options reached through `DataEngineFindRequestSchema`, `DataEngineFindOneRequestSchema` and `DataEngineRequestSchema`; the deprecated `DataEngineQueryOptionsSchema.select`; and `DataEngineVectorFindRequestSchema.fields`, also an arm of `DataEngineRequestSchema`) refuse a list naming no field, which they admitted before. Nothing is widened and no key is added, removed or renamed.
 Metadata-protocol: none
 
 <!-- adr-0087: not-required (no-migration-prescription) No key of any schema is added, removed, renamed or re-shaped and no metadata type or stored shape moves: these are engine and RPC request declarations, never stored, and no metadata type embeds them. A caller names at least one field or leaves the projection out; there is nothing for a migration to rewrite and no tombstone. -->
 
-**BREAKING** accept-set narrowing of published declarations (`@objectstack/spec/data`). No runtime in this repository parses either member, so no request served here changes; what can break is code outside it that parses with these exported schemas, or a client generated from their JSON Schema, and sent an empty projection.
+**BREAKING** accept-set narrowing of published declarations (`@objectstack/spec/data`). No runtime in this repository parses any of these members, so no request served here changes; what can break is code outside it that parses with these exported schemas, or a client generated from their JSON Schema, and sent an empty projection.
 
-- **Before.** `EngineQueryOptionsSchema.fields` and the RPC query's `select` admitted any list of strings: `[]`, and a list with a blank or whitespace-only name.
-- **Now.** A list must hold at least one name, and no name may be blank (JSON Schema `minItems: 1`, and a non-blank pattern on each name). Both read this rule from the same declaration as `QueryTransportParamsSchema.select` / `$select` and `GetDataRequestSchema.select`, so the refusal messages are the same.
+- **Before.** `EngineQueryOptionsSchema.fields`, the RPC query's `select`, `DataEngineQueryOptionsSchema.select` and `DataEngineVectorFindRequestSchema.fields` admitted any list of strings: `[]`, and a list with a blank or whitespace-only name.
+- **Now.** A list must hold at least one name, and no name may be blank (JSON Schema `minItems: 1`, and a non-blank pattern on each name). All four read this rule from the same declaration as `QueryTransportParamsSchema.select` / `$select` and `GetDataRequestSchema.select`, so the refusal messages are the same.
 - **Unchanged.** The inferred types (`string[]`), a named projection, and leaving the projection out. The in-process ObjectQL engine does not parse its options with this schema: `engine.find(object, { fields: [] })` still reads every column, as before.
 
 **The remedy.** Name at least one field, or leave `fields` / `select` out to read every column.
@@ -1311,4 +1311,36 @@ describe('the engine-side projection declarations admit exactly what their trans
       expect(parsed.query).toEqual({ fields: value });
     });
   }
+
+  // The legacy options bag's `select` and the vector-find request's `fields`
+  // are `z.string()` lists, so their sibling is the bare `select`.
+  it.each(REFUSED)('DataEngineQueryOptionsSchema.select refuses %s, naming the path, as the bare `select` does', (_name, value, tail) => {
+    const parsed = DataEngineQueryOptionsSchema.safeParse({ select: value });
+    expect(parsed.success).toBe(false);
+    const issue = parsed.success ? undefined : parsed.error.issues[0];
+    expect(issue?.path).toEqual(['select', ...tail]);
+    expect(issue?.message).toBe(sibling('select', value)?.message);
+  });
+
+  it.each(KEPT)('DataEngineQueryOptionsSchema.select keeps %s, unchanged', (_name, value) => {
+    expect(DataEngineQueryOptionsSchema.parse({ select: value }).select).toEqual(value);
+  });
+
+  for (const [label, schema] of [
+    ['DataEngineVectorFindRequestSchema', DataEngineVectorFindRequestSchema],
+    ['DataEngineRequestSchema', DataEngineRequestSchema],
+  ] as const) {
+    it.each(REFUSED)(`${label}: vectorFind fields refuses %s, naming the path, as the bare \`select\` does`, (_name, value, tail) => {
+      const parsed = schema.safeParse({ method: 'vectorFind', object: 'doc', vector: [0.1, 0.2], fields: value });
+      expect(parsed.success).toBe(false);
+      const issue = parsed.success ? undefined : parsed.error.issues[0];
+      expect(issue?.path).toEqual(['fields', ...tail]);
+      expect(issue?.message).toBe(sibling('select', value)?.message);
+    });
+
+    it.each(KEPT)(`${label}: vectorFind fields keeps %s, unchanged`, (_name, value) => {
+      const parsed = schema.parse({ method: 'vectorFind', object: 'doc', vector: [0.1, 0.2], fields: value }) as { fields?: string[] };
+      expect(parsed.fields).toEqual(value);
+    });
+  }
 });
@@ -96,8 +96,10 @@ export const BaseEngineOptionsSchema = lazySchema(() => z.object({
  * rule cannot drift apart.
  *
  * [#26954] The engine-side declarations of the same projection —
- * `EngineQueryOptionsSchema.fields` and `RpcQueryOptionsSchema.select` — take
- * the array arm from here too. It is declared ahead of both because
+ * `EngineQueryOptionsSchema.fields`, `RpcQueryOptionsSchema.select`, the
+ * legacy `DataEngineQueryOptionsSchema.select` and
+ * `DataEngineVectorFindRequestSchema.fields` — take the array arm from here
+ * too. It is declared ahead of both because
  * `RpcQueryOptionsSchema` extends `EngineQueryOptionsSchema` at module load,
  * which runs the lazy factory before any later `const` exists.
  */
@@ -212,8 +214,8 @@ export const EngineQueryOptionsSchema = lazySchema(() => BaseEngineOptionsSchema
 export const DataEngineQueryOptionsSchema = lazySchema(() => BaseEngineOptionsSchema.extend({
   /** @deprecated Use `where` (EngineQueryOptionsSchema) */
   filter: DataEngineFilterSchema.optional(),
-  /** @deprecated Use `fields` (EngineQueryOptionsSchema) */
-  select: z.array(z.string()).optional(),
+  /** @deprecated Use `fields` (EngineQueryOptionsSchema) — the same projection rule (#26954) */
+  select: transportProjectionArray(z.string()).optional(),
   /** @deprecated Use `orderBy` (EngineQueryOptionsSchema) */
   sort: DataEngineSortSchema.optional(),
   limit: z.number().int().min(1).optional(),
@@ -1519,8 +1521,8 @@ export const DataEngineVectorFindRequestSchema = lazySchema(() => z.object({
   vector: z.array(z.number()),
   /** Optional pre-filter (Metadata filtering) — standard QueryAST `where` */
   where: z.union([z.record(z.string(), z.unknown()), FilterConditionSchema]).optional(),
-  /** Fields to retrieve — standard QueryAST `fields` */
-  fields: z.array(z.string()).optional(),
+  /** Fields to retrieve — standard QueryAST `fields`; the same projection rule (#26954) */
+  fields: transportProjectionArray(z.string()).optional(),
   /** Number of results */
   limit: z.number().int().default(5).optional(),
   /** Minimum similarity score (0-1) or distance threshold */