diff --git a/src/backend/api/routers/auth.py b/src/backend/api/routers/auth.py
index 4dd8369..a2b4ea1 100644
--- a/src/backend/api/routers/auth.py
+++ b/src/backend/api/routers/auth.py
@@ -1,5 +1,6 @@
 """Authentication router - login, logout, profile."""
 from fastapi import APIRouter, Depends, HTTPException, Request, status
+from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.backend.database import get_db
@@ -8,10 +9,17 @@ from src.backend.models.orm.user import User
 from src.backend.models.api.user import (
     LoginRequest,
     LoginResponse,
+    PinLoginRequest,
+    PinUserItem,
     UserProfileUpdate,
     UserResponse,
 )
-from src.backend.services.auth_service import authenticate_user, login_user, logout_user
+from src.backend.services.auth_service import (
+    authenticate_pin,
+    authenticate_user,
+    login_user,
+    logout_user,
+)
 
 router = APIRouter(prefix="/api/auth", tags=["auth"])
 
@@ -32,6 +40,35 @@ async def login(data: LoginRequest, db: AsyncSession = Depends(get_db)):
     )
 
 
+@router.get("/pin-users", response_model=list[PinUserItem])
+async def pin_users(db: AsyncSession = Depends(get_db)):
+    """Utenti che possono entrare con PIN (#59): attivi, non admin, con PIN.
+
+    Pubblico per costruzione (serve prima del login): espone solo id e nome.
+    """
+    result = await db.execute(
+        select(User).where(
+            User.active == True,  # noqa: E712
+            User.is_admin == False,  # noqa: E712
+            User.pin_hash.is_not(None),
+        )
+    )
+    items = [
+        PinUserItem(id=u.id, display_name=u.display_name or u.username)
+        for u in result.scalars().all()
+    ]
+    items.sort(key=lambda i: i.display_name.casefold())
+    return items
+
+
+@router.post("/login-pin", response_model=LoginResponse)
+async def login_pin(data: PinLoginRequest, db: AsyncSession = Depends(get_db)):
+    """Login con user_id e PIN a 4 cifre (#59); stessa risposta del login."""
+    user = await authenticate_pin(db, data.user_id, data.pin)
+    api_key = await login_user(db, user)
+    return LoginResponse(user=UserResponse.model_validate(user), api_key=api_key)
+
+
 @router.post("/logout", status_code=status.HTTP_204_NO_CONTENT)
 async def logout(
     request: Request,
diff --git a/src/backend/api/routers/measurements.py b/src/backend/api/routers/measurements.py
index 73d8314..4e631b6 100644
--- a/src/backend/api/routers/measurements.py
+++ b/src/backend/api/routers/measurements.py
@@ -147,6 +147,7 @@ async def authorise_measurement(
 
     supervisor = await auth_service.authorise_supervisor(
         db, action.supervisor_username, action.supervisor_password,
+        user_id=action.supervisor_user_id, pin=action.supervisor_pin,  # #59
     )
     measurement = await measurement_service.authorise_measurement(
         db, measurement, supervisor,
diff --git a/src/backend/api/routers/production.py b/src/backend/api/routers/production.py
index 2a4f8c6..f21c018 100644
--- a/src/backend/api/routers/production.py
+++ b/src/backend/api/routers/production.py
@@ -163,6 +163,7 @@ async def pause_production_run(
     run = await production_service.get_run(db, run_id)
     supervisor = await auth_service.authorise_supervisor(
         db, action.supervisor_username, action.supervisor_password,
+        user_id=action.supervisor_user_id, pin=action.supervisor_pin,  # #59
     )
     run = await production_service.pause_run(db, run, user, supervisor, note=action.note)
     return await _as_response(db, run)
@@ -179,6 +180,7 @@ async def resume_production_run(
     run = await production_service.get_run(db, run_id)
     supervisor = await auth_service.authorise_supervisor(
         db, action.supervisor_username, action.supervisor_password,
+        user_id=action.supervisor_user_id, pin=action.supervisor_pin,  # #59
     )
     run = await production_service.resume_run(db, run, user, supervisor, note=action.note)
     return await _as_response(db, run)
@@ -195,6 +197,7 @@ async def close_production_run(
     run = await production_service.get_run(db, run_id)
     supervisor = await auth_service.authorise_supervisor(
         db, action.supervisor_username, action.supervisor_password,
+        user_id=action.supervisor_user_id, pin=action.supervisor_pin,  # #59
     )
     run = await production_service.close_run(db, run, user, supervisor, note=action.note)
     return await _as_response(db, run)
diff --git a/src/backend/api/routers/users.py b/src/backend/api/routers/users.py
index 94ae584..0ab4d9b 100644
--- a/src/backend/api/routers/users.py
+++ b/src/backend/api/routers/users.py
@@ -6,8 +6,14 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from src.backend.database import get_db
 from src.backend.api.middleware.api_key import require_admin_user
 from src.backend.models.orm.user import User
-from src.backend.models.api.user import UserCreate, UserPasswordChange, UserResponse, UserUpdate
-from src.backend.services.auth_service import create_user, hash_password, regenerate_api_key, revoke_all_keys
+from src.backend.models.api.user import PinSet, UserCreate, UserPasswordChange, UserResponse, UserUpdate
+from src.backend.services.auth_service import (
+    create_user,
+    hash_password,
+    regenerate_api_key,
+    revoke_all_keys,
+    set_user_pin,
+)
 
 router = APIRouter(prefix="/api/users", tags=["users"])
 
@@ -151,6 +157,30 @@ async def change_user_password(
     return {"message": f"Password changed for user {user.username}"}
 
 
+@router.put("/{user_id}/pin", status_code=status.HTTP_200_OK)
+async def change_user_pin(
+    user_id: int,
+    data: PinSet,
+    admin: User = Depends(require_admin_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Imposta o toglie (pin null) il PIN di un utente (admin, #59/#51).
+
+    422 se l'utente e' admin. Il PIN non si restituisce mai.
+    """
+    result = await db.execute(select(User).where(User.id == user_id))
+    user = result.scalar_one_or_none()
+    if user is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
+    if user.is_admin:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail="Admin users cannot have a PIN",
+        )
+    await set_user_pin(db, user, data.pin)
+    return {"message": f"PIN {'set' if data.pin else 'removed'} for user {user.username}"}
+
+
 @router.delete("/{user_id}", status_code=status.HTTP_204_NO_CONTENT)
 async def deactivate_user(
     user_id: int,
diff --git a/src/backend/migrations/versions/017_user_pin.py b/src/backend/migrations/versions/017_user_pin.py
new file mode 100644
index 0000000..8881a4d
--- /dev/null
+++ b/src/backend/migrations/versions/017_user_pin.py
@@ -0,0 +1,34 @@
+"""users: PIN a 4 cifre per login rapido e capoturno (#59)
+
+pin_hash (bcrypt, mai in chiaro), contatore errori consecutivi e fine blocco.
+
+Revision ID: 017_user_pin
+Revises: 016_vision_recipe_dir
+Create Date: 2026-10-07
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '017_user_pin'
+down_revision: Union[str, None] = '016_vision_recipe_dir'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # batch: SQLite non sa fare DROP COLUMN nativo su tutte le versioni
+    with op.batch_alter_table('users') as batch:
+        batch.add_column(sa.Column('pin_hash', sa.String(255), nullable=True))
+        batch.add_column(sa.Column(
+            'pin_failed_count', sa.Integer(), nullable=False, server_default='0'))
+        batch.add_column(sa.Column('pin_locked_until', sa.DateTime(), nullable=True))
+
+
+def downgrade() -> None:
+    with op.batch_alter_table('users') as batch:
+        batch.drop_column('pin_locked_until')
+        batch.drop_column('pin_failed_count')
+        batch.drop_column('pin_hash')
diff --git a/src/backend/models/api/measurement.py b/src/backend/models/api/measurement.py
index 00a5f2e..11ec194 100644
--- a/src/backend/models/api/measurement.py
+++ b/src/backend/models/api/measurement.py
@@ -2,7 +2,7 @@
 from src.backend.models.api.tipi import UtcDateTime, UtcNaiveInput
 from typing import Optional
 
-from pydantic import BaseModel, ConfigDict, Field
+from pydantic import BaseModel, ConfigDict, Field, model_validator
 
 
 class MeasurementCreate(BaseModel):
@@ -71,8 +71,21 @@ class MeasurementListResponse(BaseModel):
 class MeasurementAuthorisation(BaseModel):
     """Credentials of the supervisor allowing an out-of-tolerance value to stand."""
 
-    supervisor_username: str = Field(..., min_length=1)
-    supervisor_password: str = Field(..., min_length=1)
+    # #59: o username+password, oppure supervisor_user_id+supervisor_pin
+    supervisor_username: Optional[str] = Field(None, min_length=1)
+    supervisor_password: Optional[str] = Field(None, min_length=1)
+    supervisor_user_id: Optional[int] = Field(None, gt=0)
+    supervisor_pin: Optional[str] = Field(None, pattern=r"^[0-9]{4}$")
+
+    @model_validator(mode="after")
+    def _one_credential_pair(self):
+        by_password = self.supervisor_username and self.supervisor_password
+        by_pin = self.supervisor_user_id and self.supervisor_pin
+        if not (by_password or by_pin):
+            raise ValueError(
+                "supervisor credentials required: username+password or user_id+pin"
+            )
+        return self
 
 
 class TaskProgressResponse(BaseModel):
diff --git a/src/backend/models/api/production.py b/src/backend/models/api/production.py
index f382ddb..eae838a 100644
--- a/src/backend/models/api/production.py
+++ b/src/backend/models/api/production.py
@@ -2,7 +2,7 @@
 from src.backend.models.api.tipi import UtcDateTime
 from typing import Literal, Optional
 
-from pydantic import BaseModel, ConfigDict, Field
+from pydantic import BaseModel, ConfigDict, Field, model_validator
 
 
 class ProductionRunCreate(BaseModel):
@@ -64,8 +64,21 @@ class ProductionRunWithEventsResponse(ProductionRunResponse):
 class SupervisorAction(BaseModel):
     """Credentials of the supervisor authorising a line stop or a close."""
 
-    supervisor_username: str = Field(..., min_length=1)
-    supervisor_password: str = Field(..., min_length=1)
+    # #59: o username+password, oppure supervisor_user_id+supervisor_pin
+    supervisor_username: Optional[str] = Field(None, min_length=1)
+    supervisor_password: Optional[str] = Field(None, min_length=1)
+    supervisor_user_id: Optional[int] = Field(None, gt=0)
+    supervisor_pin: Optional[str] = Field(None, pattern=r"^[0-9]{4}$")
+
+    @model_validator(mode="after")
+    def _one_credential_pair(self):
+        by_password = self.supervisor_username and self.supervisor_password
+        by_pin = self.supervisor_user_id and self.supervisor_pin
+        if not (by_password or by_pin):
+            raise ValueError(
+                "supervisor credentials required: username+password or user_id+pin"
+            )
+        return self
     note: Optional[str] = None
 
 
diff --git a/src/backend/models/api/user.py b/src/backend/models/api/user.py
index eb022ac..fab403e 100644
--- a/src/backend/models/api/user.py
+++ b/src/backend/models/api/user.py
@@ -50,6 +50,8 @@ class UserResponse(BaseModel):
     active: bool
     created_at: UtcDateTime
     last_login: Optional[UtcDateTime] = None
+    # #59: solo il fatto che il PIN esista, mai l'hash
+    has_pin: bool = False
 
 
 class UserPasswordChange(BaseModel):
@@ -68,3 +70,21 @@ class LoginResponse(BaseModel):
     user: UserResponse
     api_key: str
     message: str = "Login successful"
+
+
+class PinUserItem(BaseModel):
+    """Voce dell'elenco pubblico per il login con PIN (#59): solo id e nome."""
+    id: int
+    display_name: str
+
+
+class PinLoginRequest(BaseModel):
+    """Login con PIN (#59)."""
+    user_id: int
+    pin: str = Field(..., pattern=r"^[0-9]{4}$")
+
+
+class PinSet(BaseModel):
+    """Imposta (4 cifre) o toglie (null) il PIN di un utente (#59)."""
+    pin: Optional[str] = Field(None, pattern=r"^[0-9]{4}$")
+
diff --git a/src/backend/models/orm/user.py b/src/backend/models/orm/user.py
index e5ba358..7a47de2 100644
--- a/src/backend/models/orm/user.py
+++ b/src/backend/models/orm/user.py
@@ -22,6 +22,13 @@ class User(Base):
     # Admin flag separate from roles
     is_admin: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
 
+    # PIN a 4 cifre (#59): solo l'hash; contatore errori e fine blocco per il lockout
+    pin_hash: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
+    pin_failed_count: Mapped[int] = mapped_column(
+        Integer, nullable=False, default=0, server_default="0"
+    )
+    pin_locked_until: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)
+
     # User preferences
     language_pref: Mapped[str] = mapped_column(
         Enum("it", "en", name="language_enum"), nullable=False, default="it"
@@ -39,6 +46,11 @@ class User(Base):
     )
     last_login: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)
 
+    @property
+    def has_pin(self) -> bool:
+        """True se l'utente ha un PIN impostato (#59); serve a UserResponse.has_pin."""
+        return self.pin_hash is not None
+
     def has_role(self, role: str) -> bool:
         """Check if user has a specific role."""
         return role in (self.roles or [])
diff --git a/src/backend/services/auth_service.py b/src/backend/services/auth_service.py
index 3da2328..50a1311 100644
--- a/src/backend/services/auth_service.py
+++ b/src/backend/services/auth_service.py
@@ -54,7 +54,79 @@ async def authenticate_user(
     return user
 
 
-async def authorise_supervisor(db: AsyncSession, username: str, password: str) -> User:
+# #59: PIN a 4 cifre. Hash identico alle password (bcrypt); 5 errori -> blocco 15 minuti.
+PIN_MAX_FAILURES = 5
+PIN_LOCK_MINUTES = 15
+
+
+async def set_user_pin(db: AsyncSession, user: User, pin: str | None) -> None:
+    """Imposta o toglie (None) il PIN; azzera contatore e blocco. Admin esclusi (#59)."""
+    if pin is not None and user.is_admin:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail="Admin users cannot have a PIN",
+        )
+    user.pin_hash = hash_password(pin) if pin is not None else None
+    user.pin_failed_count = 0
+    user.pin_locked_until = None
+    await db.flush()
+
+
+async def authenticate_pin(db: AsyncSession, user_id: int, pin: str) -> User:
+    """Verifica user_id+PIN con blocco dopo 5 errori consecutivi (#59).
+
+    401 PIN errato (o utente non idoneo: stessa risposta, niente enumerazione),
+    423 utente bloccato. Il contatore va committato prima di sollevare: get_db fa
+    rollback su eccezione e l'errore andrebbe perso.
+    """
+    result = await db.execute(
+        select(User).where(User.id == user_id, User.active == True)  # noqa: E712
+    )
+    user = result.scalar_one_or_none()
+    if user is None or user.is_admin or user.pin_hash is None:
+        verify_password(pin, _DUMMY_PASSWORD_HASH)  # stesso costo di un PIN errato
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid PIN"
+        )
+    now = utcnow()
+    if user.pin_locked_until is not None:
+        if user.pin_locked_until > now:
+            raise HTTPException(
+                status_code=status.HTTP_423_LOCKED,
+                detail="PIN locked until "
+                + user.pin_locked_until.strftime("%Y-%m-%d %H:%M:%S")
+                + " UTC",
+            )
+        # blocco scaduto: si riparte da zero
+        user.pin_locked_until = None
+        user.pin_failed_count = 0
+    if verify_password(pin, user.pin_hash):
+        if user.pin_failed_count:
+            user.pin_failed_count = 0
+            await db.flush()
+        return user
+    user.pin_failed_count += 1
+    locked = user.pin_failed_count >= PIN_MAX_FAILURES
+    if locked:
+        user.pin_locked_until = now + timedelta(minutes=PIN_LOCK_MINUTES)
+    await db.commit()
+    if locked:
+        raise HTTPException(
+            status_code=status.HTTP_423_LOCKED,
+            detail="PIN locked until "
+            + user.pin_locked_until.strftime("%Y-%m-%d %H:%M:%S")
+            + " UTC",
+        )
+    raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid PIN")
+
+
+async def authorise_supervisor(
+    db: AsyncSession,
+    username: str | None = None,
+    password: str | None = None,
+    user_id: int | None = None,
+    pin: str | None = None,
+) -> User:
     """Check the credentials of the supervisor authorising something.
 
     Used wherever the shop floor needs a capoturno: a line stop, a closure, an
@@ -65,7 +137,16 @@ async def authorise_supervisor(db: AsyncSession, username: str, password: str) -
     Uses authenticate_user rather than a full login: logging in would issue a
     needless API key for the supervisor.
     """
-    supervisor = await authenticate_user(db, username, password)
+    if user_id is not None and pin is not None:
+        # #59: via PIN, stesso blocco del login con PIN (401/423 sollevati da li')
+        supervisor = await authenticate_pin(db, user_id, pin)
+    elif username is not None and password is not None:
+        supervisor = await authenticate_user(db, username, password)
+    else:
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
+            detail="Supervisor credentials required",
+        )
     if supervisor is None:
         raise HTTPException(
             status_code=status.HTTP_401_UNAUTHORIZED,
diff --git a/src/backend/tests/test_migrations.py b/src/backend/tests/test_migrations.py
index 3938829..64e9664 100644
--- a/src/backend/tests/test_migrations.py
+++ b/src/backend/tests/test_migrations.py
@@ -149,3 +149,22 @@ class TestVisionRecipeDirMigration:
         assert "vision_recipe_dir" not in cols()
         command.upgrade(cfg, "head")  # e di nuovo su
         assert "vision_recipe_dir" in cols()
+
+
+class TestUserPinMigration:
+    """017_user_pin: users.pin_hash / pin_failed_count / pin_locked_until, su e giu (#59)."""
+
+    def test_017_upgrade_and_downgrade(self, sqlite_database_url):
+        db_path, _ = sqlite_database_url
+        cfg = _alembic_config()
+        new = {"pin_hash", "pin_failed_count", "pin_locked_until"}
+
+        def cols():
+            return {c["name"] for c in _inspect(db_path).get_columns("users")}
+
+        command.upgrade(cfg, "head")
+        assert new <= cols()
+        command.downgrade(cfg, "016_vision_recipe_dir")
+        assert not (new & cols())
+        command.upgrade(cfg, "head")  # e di nuovo su
+        assert new <= cols()
diff --git a/src/backend/tests/test_pin.py b/src/backend/tests/test_pin.py
new file mode 100644
index 0000000..7f78206
--- /dev/null
+++ b/src/backend/tests/test_pin.py
@@ -0,0 +1,167 @@
+"""PIN a 4 cifre: login rapido, blocco, capoturno via PIN (#59)."""
+from datetime import timedelta
+
+import pytest
+from fastapi import HTTPException
+from httpx import AsyncClient
+from sqlalchemy import select
+
+from src.backend.models.orm.user import User
+from src.backend.services import auth_service
+from src.backend.tests.conftest import _create_user, auth_headers
+from src.backend.tests.test_production_runs import (
+    _open, _recipe_with_interval, _station,
+)
+from src.backend.utils.tempo import utcnow
+
+
+async def _pin_user(db_session, username="operaio", pin="1234", **kw) -> User:
+    user = await _create_user(db_session, username=username, **kw)
+    await auth_service.set_user_pin(db_session, user, pin)
+    await db_session.commit()
+    return user
+
+
+async def _login_pin(client, user_id, pin):
+    return await client.post("/api/auth/login-pin", json={"user_id": user_id, "pin": pin})
+
+
+async def test_login_pin_ok_same_shape_as_login(client: AsyncClient, db_session):
+    user = await _pin_user(db_session)
+    resp = await _login_pin(client, user.id, "1234")
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["user"]["username"] == "operaio"
+    assert data["user"]["has_pin"] is True
+    assert data["api_key"]
+    assert "pin_hash" not in data["user"]
+    # la api_key vale davvero
+    me = await client.get("/api/auth/me", headers={"X-API-Key": data["api_key"]})
+    assert me.status_code == 200
+
+
+async def test_login_pin_wrong_is_401(client: AsyncClient, db_session):
+    user = await _pin_user(db_session)
+    assert (await _login_pin(client, user.id, "9999")).status_code == 401
+
+
+async def test_login_pin_format_422(client: AsyncClient, db_session):
+    user = await _pin_user(db_session)
+    for bad in ("123", "12345", "12a4", ""):
+        assert (await _login_pin(client, user.id, bad)).status_code == 422
+
+
+async def test_lock_after_five_errors_even_with_right_pin(client: AsyncClient, db_session):
+    user = await _pin_user(db_session)
+    for _ in range(4):
+        assert (await _login_pin(client, user.id, "0000")).status_code == 401
+    resp = await _login_pin(client, user.id, "0000")  # 5 errore: scatta il blocco
+    assert resp.status_code == 423
+    assert "locked until" in resp.json()["detail"]
+    assert (await _login_pin(client, user.id, "1234")).status_code == 423
+
+
+async def test_lock_expires_and_counter_resets(client: AsyncClient, db_session):
+    user = await _pin_user(db_session)
+    for _ in range(5):
+        await _login_pin(client, user.id, "0000")
+    row = (await db_session.execute(select(User).where(User.id == user.id))).scalar_one()
+    await db_session.refresh(row)
+    assert row.pin_locked_until > utcnow() + timedelta(minutes=14)
+    # tempo simulato: il blocco e scaduto un secondo fa
+    row.pin_locked_until = utcnow() - timedelta(seconds=1)
+    await db_session.commit()
+    assert (await _login_pin(client, user.id, "1234")).status_code == 200
+    await db_session.refresh(row)
+    assert row.pin_failed_count == 0 and row.pin_locked_until is None
+
+
+async def test_success_resets_failed_counter(client: AsyncClient, db_session):
+    user = await _pin_user(db_session)
+    for _ in range(3):
+        await _login_pin(client, user.id, "0000")
+    assert (await _login_pin(client, user.id, "1234")).status_code == 200
+    for _ in range(4):  # il contatore e ripartito da zero: 4 errori non bloccano
+        assert (await _login_pin(client, user.id, "0000")).status_code == 401
+
+
+async def test_admin_cannot_have_pin_or_login_with_it(client: AsyncClient, admin_user, db_session):
+    resp = await client.put(
+        f"/api/users/{admin_user.id}/pin", headers=auth_headers(admin_user), json={"pin": "1234"},
+    )
+    assert resp.status_code == 422
+    # anche un admin con pin_hash scritto a mano non entra da login-pin
+    admin_user.pin_hash = auth_service.hash_password("1234")
+    await db_session.commit()
+    assert (await _login_pin(client, admin_user.id, "1234")).status_code == 401
+    listed = (await client.get("/api/auth/pin-users")).json()
+    assert all(u["id"] != admin_user.id for u in listed)
+
+
+async def test_put_pin_set_and_remove(client: AsyncClient, admin_user, db_session):
+    user = await _create_user(db_session, username="senzapin")
+    await db_session.commit()
+    h = auth_headers(admin_user)
+    assert (await client.put(f"/api/users/{user.id}/pin", headers=h, json={"pin": "4321"})).status_code == 200
+    assert (await _login_pin(client, user.id, "4321")).status_code == 200
+    assert (await client.put(f"/api/users/{user.id}/pin", headers=h, json={"pin": "12"})).status_code == 422
+    assert (await client.put(f"/api/users/{user.id}/pin", headers=h, json={"pin": None})).status_code == 200
+    assert (await _login_pin(client, user.id, "4321")).status_code == 401
+    assert (await client.put("/api/users/99999/pin", headers=h, json={"pin": "1234"})).status_code == 404
+    # non admin: 403
+    assert (await client.put(
+        f"/api/users/{user.id}/pin", headers=auth_headers(user), json={"pin": "1234"},
+    )).status_code == 403
+
+
+async def test_pin_users_list(client: AsyncClient, db_session):
+    a = await _pin_user(db_session, username="zeta", display_name="Zeta Rossi", pin="1111")
+    b = await _pin_user(db_session, username="alfa", display_name="Alfa Bianchi", pin="2222")
+    await _create_user(db_session, username="nopin")
+    await _pin_user(db_session, username="inattivo", pin="3333", active=False)
+    await db_session.commit()
+    resp = await client.get("/api/auth/pin-users")  # senza autenticazione
+    assert resp.status_code == 200
+    data = resp.json()
+    assert [u["display_name"] for u in data] == ["Alfa Bianchi", "Zeta Rossi"]
+    assert all(set(u) == {"id", "display_name"} for u in data)
+    assert {u["id"] for u in data} == {a.id, b.id}
+
+
+async def test_supervisor_via_pin(client: AsyncClient, measurement_tec_user, admin_user, db_session):
+    station = await _station(db_session, admin_user.id, code="ST-PIN")
+    recipe = await _recipe_with_interval(db_session, admin_user.id, 10, code="REC-PIN")
+    run_id = (await _open(client, measurement_tec_user, station, recipe)).json()["id"]
+    capo = await _pin_user(db_session, username="capo-pin", pin="5555", roles=["Supervisor"])
+    h = auth_headers(measurement_tec_user)
+
+    bad = await client.post(
+        f"/api/production-runs/{run_id}/pause", headers=h,
+        json={"supervisor_user_id": capo.id, "supervisor_pin": "0000"},
+    )
+    assert bad.status_code == 401
+    ok = await client.post(
+        f"/api/production-runs/{run_id}/pause", headers=h,
+        json={"supervisor_user_id": capo.id, "supervisor_pin": "5555"},
+    )
+    assert ok.status_code == 200
+    # nessuna coppia di credenziali: 422
+    none = await client.post(f"/api/production-runs/{run_id}/resume", headers=h, json={})
+    assert none.status_code == 422
+
+
+async def test_supervisor_pin_role_still_checked(db_session):
+    plain = await _pin_user(db_session, username="non-capo", pin="6666", roles=["Maker"])
+    with pytest.raises(HTTPException) as e:
+        await auth_service.authorise_supervisor(db_session, user_id=plain.id, pin="6666")
+    assert e.value.status_code == 403
+
+
+async def test_supervisor_pin_lockout(db_session):
+    capo = await _pin_user(db_session, username="capo-lock", pin="7777", roles=["Supervisor"])
+    codes = []
+    for pin in ["0000"] * 5 + ["7777"]:
+        with pytest.raises(HTTPException) as e:
+            await auth_service.authorise_supervisor(db_session, user_id=capo.id, pin=pin)
+        codes.append(e.value.status_code)
+    assert codes == [401, 401, 401, 401, 423, 423]