diff --git a/src/inputs/EventsWhereInput.ts b/src/inputs/EventsWhereInput.ts
index 0ada45f..0875769 100644
--- a/src/inputs/EventsWhereInput.ts
+++ b/src/inputs/EventsWhereInput.ts
@@ -65,9 +65,9 @@ export class EventsWhereInput {
         this.partnerCode ? { partners: { some: { partnerCode: { equals: this.partnerCode, mode: 'insensitive' } } } } : {},
         this.mine ? {
           OR: [
-            { mentors: { some: { username: auth.username || '' } } },
-            { mentors: { some: { managerUsername: auth.username || '' } } },
-            { students: { some: { username: auth.username || '' } } },
+            { mentors: { some: { OR: [{ id: auth.id }, { username: auth.username }] } } },
+            { students: { some: { OR: [{ id: auth.id }, { username: auth.username }] } } },
+            ...(auth.username ? [{ mentors: { some: { managerUsername: auth.username } } } as Prisma.EventWhereInput] : []),
           ],
         } : {},
       ],
diff --git a/tests/testEventsWhereInput.ts b/tests/testEventsWhereInput.ts
new file mode 100644
index 0000000..65f2e31
--- /dev/null
+++ b/tests/testEventsWhereInput.ts
@@ -0,0 +1,239 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { sign as jwtSign } from 'jsonwebtoken';
+
+// src/config.ts validates ~28 env vars at import time; set them before importing
+// anything under src/. Static `import` declarations are hoisted, so the src
+// modules are loaded via `require()` AFTER these assignments run (require is a
+// function call, not hoisted). This keeps the file CommonJS-clean (no TLA).
+const REQUIRED_ENV: Record<string, string> = {
+  DATABASE_URL: 'postgresql://noop',
+  ELASTIC_URL: 'noop',
+  ELASTIC_INDEX: 'noop',
+  AUTH_SECRET: 'testsecret',
+  AUTH_AUDIENCE: 'testaud',
+  EMAIL_HOST: 'noop',
+  EMAIL_PORT: '25',
+  EMAIL_USER: 'noop',
+  EMAIL_PASS: 'noop',
+  EMAIL_INBOUND_DOMAIN: 'noop',
+  GEOCODIO_API_KEY: 'noop',
+  OPENAI_API_KEY: 'noop',
+  OPENAI_ORGANIZATION: 'noop',
+  WEBHOOK_KEY: 'noop',
+  BADGR_USERNAME: 'noop',
+  BADGR_PASSWORD: 'noop',
+  BADGR_ISSUER: 'noop',
+  SHOPIFY_API_TOKEN: 'noop',
+  SHOPIFY_API_KEY: 'noop',
+  SHOPIFY_API_SECRET_KEY: 'noop',
+  SHOPIFY_STORE_DOMAIN: 'noop',
+  LINEAR_API_KEY: 'noop',
+  LINEAR_TEAM_ID: 'noop',
+  LINEAR_PROBLEM_LABEL_ID: 'noop',
+  METRICS_KEY: 'noop',
+  PLACID_API_TOKEN: 'noop',
+  ATTIO_API_TOKEN: 'noop',
+  ATTIO_ALUMNI_LIST: 'noop',
+};
+for (const [k, v] of Object.entries(REQUIRED_ENV)) process.env[k] ||= v;
+
+// reflect-metadata must be loaded before any type-graphql @InputType/@Field
+// decorators run (which happens at module load of EventsWhereInput).
+require('reflect-metadata');
+const { EventsWhereInput } = require('../src/inputs/EventsWhereInput') as typeof import('../src/inputs/EventsWhereInput');
+const { AuthContext, AuthRole, AuthByTarget } = require('../src/context') as typeof import('../src/context');
+const { signTokenUser } = require('../src/utils/signToken') as typeof import('../src/utils/signToken');
+
+// Helper: build an EventsWhereInput with only `mine` set.
+function mineInput(mine = true): InstanceType<typeof EventsWhereInput> {
+  const input = new EventsWhereInput();
+  input.mine = mine;
+  return input;
+}
+
+// Helper: the mine clause is the 4th AND element of toQuery's output.
+function mineClause(auth: AuthContext): { OR?: unknown[] } {
+  const query = mineInput(true).toQuery(auth);
+  return (query.AND as unknown[])[3] as { OR?: unknown[] };
+}
+
+// Per the bug report: every mentor/student token ever issued in this repo is
+// ID-target (tgt: AuthByTarget.ID, sid: <user-id>) via signTokenUser, for which
+// AuthContext.id is set and AuthContext.username is undefined.
+const mentorToken = signTokenUser({ id: 'mentor-id-1', eventId: 'event-1', maxWeeks: 6 } as any);
+const studentToken = signTokenUser({ id: 'student-id-1', eventId: 'event-1' } as any);
+
+// A username-target manager token is the designed-for (validate() admits
+// managers with username, not id) but no in-repo issuer mints it; we mint one
+// directly to exercise that path.
+const managerToken = jwtSign(
+  { typ: AuthRole.MANAGER, tgt: AuthByTarget.USERNAME, sid: 'mgr1', evt: 'event-1' },
+  process.env.AUTH_SECRET!,
+  { audience: process.env.AUTH_AUDIENCE!, noTimestamp: true },
+);
+const unameMentorToken = jwtSign(
+  { typ: AuthRole.MENTOR, tgt: AuthByTarget.USERNAME, sid: 'alice', evt: 'event-1' },
+  process.env.AUTH_SECRET!,
+  { audience: process.env.AUTH_AUDIENCE!, noTimestamp: true },
+);
+
+test('ID-target mentor token carries auth.id and not auth.username (bug premise)', () => {
+  const auth = new AuthContext(mentorToken);
+  assert.equal(auth.isMentor, true);
+  assert.equal(auth.id, 'mentor-id-1');
+  assert.equal(auth.username, undefined);
+});
+
+test('mine:true for an ID-target mentor matches by id, never by empty username', () => {
+  const auth = new AuthContext(mentorToken);
+  const clause = mineClause(auth);
+  assert.ok(clause.OR, 'mine clause present');
+
+  // deepEqual ignores undefined-valued own properties, mirroring Prisma's
+  // behavior of stripping undefined keys (verified empirically with Prisma 3).
+  assert.deepEqual(clause.OR, [
+    { mentors: { some: { OR: [{ id: 'mentor-id-1' }, { username: undefined }] } } },
+    { students: { some: { OR: [{ id: 'mentor-id-1' }, { username: undefined }] } } },
+  ]);
+
+  // The manager branch must NOT be emitted for an ID-target caller (auth.username
+  // is undefined): otherwise it would collapse to {mentors:{some:{}}} and match
+  // every event that has any mentor.
+  assert.equal(clause.OR!.length, 2);
+
+  const json = JSON.stringify(mineInput(true).toQuery(auth));
+  assert.match(json, /"id":"mentor-id-1"/);
+  assert.doesNotMatch(json, /"username":""/);
+  assert.doesNotMatch(json, /"managerUsername":""/);
+  assert.doesNotMatch(json, /"managerUsername"/);
+});
+
+test('mine:true for an ID-target student matches by id', () => {
+  const auth = new AuthContext(studentToken);
+  assert.equal(auth.isStudent, true);
+  assert.equal(auth.id, 'student-id-1');
+  assert.equal(auth.username, undefined);
+
+  const clause = mineClause(auth);
+  assert.deepEqual(clause.OR, [
+    { mentors: { some: { OR: [{ id: 'student-id-1' }, { username: undefined }] } } },
+    { students: { some: { OR: [{ id: 'student-id-1' }, { username: undefined }] } } },
+  ]);
+  assert.equal(clause.OR!.length, 2);
+
+  const json = JSON.stringify(mineInput(true).toQuery(auth));
+  assert.match(json, /"id":"student-id-1"/);
+  assert.doesNotMatch(json, /"username":""/);
+  assert.doesNotMatch(json, /"managerUsername"/);
+});
+
+test('mine:true for a username-target mentor matches by username and includes the manager branch', () => {
+  const auth = new AuthContext(unameMentorToken);
+  assert.equal(auth.isMentor, true);
+  assert.equal(auth.id, undefined);
+  assert.equal(auth.username, 'alice');
+
+  const clause = mineClause(auth);
+  // Because auth.username is defined, the manager branch IS emitted.
+  assert.deepEqual(clause.OR, [
+    { mentors: { some: { OR: [{ id: undefined }, { username: 'alice' }] } } },
+    { students: { some: { OR: [{ id: undefined }, { username: 'alice' }] } } },
+    { mentors: { some: { managerUsername: 'alice' } } },
+  ]);
+  assert.equal(clause.OR!.length, 3);
+
+  const json = JSON.stringify(mineInput(true).toQuery(auth));
+  assert.match(json, /"username":"alice"/);
+  assert.match(json, /"managerUsername":"alice"/);
+  assert.doesNotMatch(json, /"username":""/);
+  assert.doesNotMatch(json, /"managerUsername":""/);
+});
+
+test('mine:true for a username-target manager matches managed mentors by username', () => {
+  const auth = new AuthContext(managerToken);
+  assert.equal(auth.isManager, true);
+  assert.equal(auth.id, undefined);
+  assert.equal(auth.username, 'mgr1');
+
+  const clause = mineClause(auth);
+  assert.deepEqual(clause.OR, [
+    { mentors: { some: { OR: [{ id: undefined }, { username: 'mgr1' }] } } },
+    { students: { some: { OR: [{ id: undefined }, { username: 'mgr1' }] } } },
+    { mentors: { some: { managerUsername: 'mgr1' } } },
+  ]);
+  assert.equal(clause.OR!.length, 3);
+
+  const json = JSON.stringify(mineInput(true).toQuery(auth));
+  assert.match(json, /"managerUsername":"mgr1"/);
+  assert.doesNotMatch(json, /"managerUsername":""/);
+  assert.doesNotMatch(json, /"username":""/);
+});
+
+test('mine:true for an unauthenticated caller does not emit a username:"" leak and omits the manager branch', () => {
+  const auth = new AuthContext(undefined);
+  assert.equal(auth.isAuthenticated, false);
+  assert.equal(auth.id, undefined);
+  assert.equal(auth.username, undefined);
+
+  const clause = mineClause(auth);
+  // No manager branch (auth.username undefined), so the OR has two participants
+  // branches whose {id}/{username} are all undefined — Prisma strips undefined
+  // keys, leaving OR:[{},{}] which matches nothing (verified empirically).
+  assert.equal(clause.OR!.length, 2);
+  assert.deepEqual(clause.OR, [
+    { mentors: { some: { OR: [{ id: undefined }, { username: undefined }] } } },
+    { students: { some: { OR: [{ id: undefined }, { username: undefined }] } } },
+  ]);
+
+  const json = JSON.stringify(mineInput(true).toQuery(auth));
+  // No empty-string fallback anywhere (the original bug).
+  assert.doesNotMatch(json, /"username":""/);
+  assert.doesNotMatch(json, /"managerUsername":""/);
+  // No manager branch at all, so no {mentors:{some:{}}} "any mentor" leak.
+  assert.doesNotMatch(json, /"managerUsername"/);
+  // No identifying id/username value — i.e. the predicate matches no one.
+  assert.doesNotMatch(json, /"id":"[^"]/);
+  assert.doesNotMatch(json, /"username":"[^"]/);
+});
+
+test('mine:false/unset produces no mine clause', () => {
+  const auth = new AuthContext(mentorToken);
+  const query = new EventsWhereInput().toQuery(auth);
+  // The mine slot of the AND array is {} when mine is not set.
+  assert.deepEqual((query.AND as unknown[])[3], {});
+});
+
+test('mine:true composes with the other filters without losing them', () => {
+  const auth = new AuthContext(mentorToken);
+  const input = new EventsWhereInput();
+  input.mine = true;
+  input.public = true;
+  input.partnerCode = 'CODE';
+  const query = input.toQuery(auth) as any;
+  const and = query.AND as unknown[];
+  assert.equal(and.length, 4);
+  assert.deepEqual(and[0], { partnersOnly: false });          // public
+  assert.deepEqual(and[1], {});                              // dateFilter (no state)
+  assert.deepEqual(and[2], {
+    partners: { some: { partnerCode: { equals: 'CODE', mode: 'insensitive' } } },
+  });
+  assert.ok((and[3] as any).OR, 'mine OR present');
+});
+
+test('no toQuery output across scenarios contains the buggy `username:""`/`managerUsername:""` fallback', () => {
+  const scenarios: AuthContext[] = [
+    new AuthContext(mentorToken),
+    new AuthContext(studentToken),
+    new AuthContext(unameMentorToken),
+    new AuthContext(managerToken),
+    new AuthContext(undefined),
+  ];
+  for (const auth of scenarios) {
+    assert.doesNotMatch(
+      JSON.stringify(mineInput(true).toQuery(auth)),
+      /"username":""|{"username":""}|"managerUsername":""/,
+      `empty-string fallback leaked for auth id=${auth.id} username=${auth.username}`,
+    );
+  }
+});