diff --git a/.changeset/import-protocol-implementor-typed.md b/.changeset/import-protocol-implementor-typed.md
new file mode 100644
index 0000000000..4cb5cf8fe0
--- /dev/null
+++ b/.changeset/import-protocol-implementor-typed.md
@@ -0,0 +1,13 @@
+---
+"@objectstack/plugin-auth": patch
+---
+
+fix(plugin-auth): let `ImportProtocolLike` type the admin import protocol's members (#17422)
+
+`admin-import-users.ts` is the only hand-written in-repo implementor of the runner's `ImportProtocolLike`, and it annotated all three required members `args: any`. An explicit parameter annotation wins over the contextual type, so #16952's newly declared request dialect held every implementor except this one — the one with a demonstrated history: before #16950 this file read `args?.query?.$filter ?? {}`, the runner moved to the canonical spelling, the read went `undefined`, and the `?? {}` default degraded the import's duplicate probe into match-everything, so `POST /api/v1/auth/admin/import-users` updated the wrong users without a sound.
+
+The three annotations are deleted, so `findData` / `createData` / `updateData` are typed by the contract they implement. Measured: with the annotations gone, reading a retired wire alias (`args.query?.$filter`) is `TS2339 Property '$filter' does not exist on type 'QueryInput'`; with `args: any` restored the identical probe type-checks at exit 0.
+
+`FindDataRequest` declares `query` optional, so `findData` now states its refusal in code — a thrown `Error` carrying the already-registered `INVALID_REQUEST` code — instead of relying on an incidental `TypeError` from a property read on `undefined`. No `??` fallback and no optional chaining were added: both spell match-everything, which is the defect this closes.
+
+No API, request body, response shape or exported signature changes. A caller that reaches `findData` through `runImport` always supplies `query`, so no supported call moves; only a protocol call that was already failing now fails with a code attached.
diff --git a/packages/plugins/plugin-auth/src/admin-import-users.test.ts b/packages/plugins/plugin-auth/src/admin-import-users.test.ts
index 592925a75a..59cb105460 100644
--- a/packages/plugins/plugin-auth/src/admin-import-users.test.ts
+++ b/packages/plugins/plugin-auth/src/admin-import-users.test.ts
@@ -1,12 +1,18 @@
 // Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
 
 import { describe, it, expect, vi } from 'vitest';
+import { readFileSync } from 'node:fs';
+import { dirname, resolve } from 'node:path';
+import { fileURLToPath } from 'node:url';
 import { assertEngineUpdateDispatch } from '@objectstack/objectql';
 import { runAdminImportUsers, IMPORT_USERS_MAX_ROWS, type IdentityImportDeps } from './admin-import-users.js';
 import type { AdminActor } from './admin-user-endpoints.js';
 
 const ACTOR: AdminActor = { id: 'admin-1', email: 'admin@example.com' };
 
+const HERE = dirname(fileURLToPath(import.meta.url));
+const IMPORT_USERS_SOURCE = readFileSync(resolve(HERE, 'admin-import-users.ts'), 'utf8');
+
 function makeRequest(body: unknown): Request {
   return new Request('http://localhost/api/v1/auth/admin/import-users', {
     method: 'POST',
@@ -624,3 +630,33 @@ describe('runAdminImportUsers — CSV payloads', () => {
     expect(m.createUser.mock.calls.map((c) => c[0].body.email).sort()).toEqual(['c1@x.co', 'c2@x.co']);
   });
 });
+
+/**
+ * [#17422] The IMPLEMENTOR half of #16952's contract.
+ *
+ * `ImportProtocolLike` types the three required members, but an EXPLICIT
+ * parameter annotation wins over a contextual type — so `findData(args: any)`
+ * opts this file back out of the contract while `tsc --noEmit` stays green.
+ * Measured on #17422 in this package: with the annotation restored, a probe
+ * reading the retired wire alias (`args.query?.$filter` — the pre-#16950 read
+ * whose `?? {}` default degraded the duplicate probe into match-everything)
+ * type-checks at exit 0; with the annotation gone the same probe is
+ * `TS2339 Property '$filter' does not exist on type 'QueryInput'`.
+ *
+ * ⇒ Nothing else in the repo can see that difference. The behavioural upsert
+ * tests above discriminate the CONSEQUENCE (ablated to the historical read,
+ * two of them go red) but not the opt-out itself: re-annotating the parameter
+ * leaves every one of them green and every gate green. This is that guard.
+ */
+describe('[#17422] the import protocol literal is typed BY `ImportProtocolLike`', () => {
+  it('binds the literal to the exported contract', () => {
+    expect(IMPORT_USERS_SOURCE).toContain('const protocol: ImportProtocolLike = {');
+  });
+
+  for (const member of ['findData', 'createData', 'updateData'] as const) {
+    it(`leaves \`${member}\`'s parameter unannotated, so the contract types it`, () => {
+      expect(IMPORT_USERS_SOURCE).toContain(`async ${member}(args) {`);
+      expect(IMPORT_USERS_SOURCE).not.toMatch(new RegExp(`async\\s+${member}\\s*\\(\\s*args\\s*:`));
+    });
+  }
+});
diff --git a/packages/plugins/plugin-auth/src/admin-import-users.ts b/packages/plugins/plugin-auth/src/admin-import-users.ts
index a557f3ca47..a371c6d7c7 100644
--- a/packages/plugins/plugin-auth/src/admin-import-users.ts
+++ b/packages/plugins/plugin-auth/src/admin-import-users.ts
@@ -362,17 +362,34 @@ export async function runAdminImportUsers(
     // to `{}` stops constraining anything, so the duplicate probe matches rows
     // it was given no key for and the upsert updates the WRONG user. One
     // dialect, read straight — a request that arrives without a `query` is a
-    // caller defect and costs a loud TypeError, not a silent match-everything.
-    async findData(args: any) {
-      const where = args.query.where;
-      const limit = args.query.limit;
+    // caller defect and is refused loudly, not softened into match-everything.
+    //
+    // [#17422] The parameter is deliberately UNANNOTATED: `ImportProtocolLike`
+    // types it, and an explicit annotation here would win over that contextual
+    // type and opt this implementor back out of the contract (the runner's own
+    // docblock says so). `FindDataRequest` declares `query` OPTIONAL, so the
+    // contract makes this file write its refusal down instead of leaving it as
+    // an incidental TypeError from a property read on `undefined`.
+    // ⛔ Not `args.query ?? {}` and ⛔ not `args.query?.where`: both spell
+    // match-everything, which is the exact regression this protocol's history
+    // is about.
+    async findData(args) {
+      const query = args.query;
+      if (!query) {
+        throw Object.assign(
+          new Error('import-users: findData was called without a query — refusing to match every user'),
+          { code: 'INVALID_REQUEST' },
+        );
+      }
+      const where = query.where;
+      const limit = query.limit;
       return engine.find(args.object, { where, limit, context: SYSTEM_CTX } as any);
     },
 
     // One better-auth create per row — hashing + credential sys_account.
     // Deliberately NO createManyData: there is no safe bulk primitive for
     // identities, and scrypt dominates the cost anyway.
-    async createData(args: any) {
+    async createData(args) {
       const data: Record<string, any> = args?.data ?? {};
       const email: string = typeof data.email === 'string' && data.email.length > 0
         ? data.email
@@ -431,7 +448,7 @@ export async function runAdminImportUsers(
 
     // Upsert updates touch PROFILE fields only — never email, never anything
     // credential- or system-managed. An empty filtered patch is a no-op.
-    async updateData(args: any) {
+    async updateData(args) {
       const patch: Record<string, any> = {};
       for (const [k, v] of Object.entries(args?.data ?? {})) {
         if (UPDATE_ALLOWED_FIELDS.has(k) && v !== undefined && v !== null && v !== '') patch[k] = v;