diff --git a/CLAUDE.md b/CLAUDE.md
index cc0149c..6c6df3d 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -14,6 +14,7 @@ pytest tests/ -k "test_name"          # single test by name
 **Run dev server:**
 ```bash
 export DATA_DIR=/tmp/imptune_data
+export COOKIE_SECURE=false  # plain HTTP — omit if serving behind TLS
 uvicorn imptune.main:app --reload --port 8000
 ```
 
@@ -33,18 +34,21 @@ pip install -r requirements.txt -r requirements-dev.txt
 ImpTune make printer deploy packages (`.intunewin` for Intune, `.zip` for NinjaRMM) from Windows driver ZIPs + web UI. No external services — single FastAPI + SQLite + Docker volume.
 
 **Request flow:**
-1. Driver upload → `api/drivers.py` → `services/inf_parser.py` parse INF → `storage/driver_store.py` store by SHA256 → Peewee `Driver` record
-2. Printer config → `api/printers.py` → `db/models.py` `Printer` record (links Driver FK)
+1. Driver upload → `api/drivers.py` → `services/inf_parser.py` parse INF → `storage/driver_store.py` store by SHA256 → Peewee `Driver` record (shared/global — visible to every Owner)
+2. Printer config → `api/printers.py` → `db/models.py` `Printer` record (links Driver FK, scoped to `request.state.owner`)
 3. Icon upload → `api/icons.py` → Pillow validate PNG 256×256 → SHA256 storage → `Icon` record
 4. Package export → `api/packages.py` → `generators/script_generator.py` render Jinja2 PS1 templates → `generators/intunewin_builder.py` encrypt ZIP (AES-256-CBC + HMAC-SHA256)
 
 **Key modules:**
-- `imptune/config.py` — `DATA_DIR`, `DB_PATH`, `DRIVERS_DIR`, `ICONS_DIR` from env
-- `imptune/db/database.py` — SQLite WAL mode + `foreign_keys=1`; all models inherit `BaseModel`
+- `imptune/config.py` — `DATA_DIR`, `DB_PATH`, `DRIVERS_DIR`, `ICONS_DIR`, `COOKIE_SECURE` from env
+- `imptune/db/database.py` — SQLite WAL mode + `foreign_keys=1`; all models inherit `BaseModel`; `init_db()` also backfills `owner_id` on pre-per-owner-scoping DBs into a synthetic legacy `Owner` (key written to `{DATA_DIR}/legacy_owner_key.txt`)
+- `imptune/services/session.py` — `OwnerSessionMiddleware` resolves `request.state.owner` from the `imptune_owner_key` cookie, creating one on first visit (skips `/health`)
 - `imptune/services/inf_parser.py` — auto-detect encoding (UTF-16/UTF-8/cp1252), resolve `%TOKEN%` from `[Strings]`, handle multi-model INFs
 - `imptune/generators/intunewin_builder.py` — Python-native `.intunewin` (ZIP-in-ZIP); IV 16 bytes (not 32); match reference tool `1.8.6.0` output
 - `imptune/templates/scripts/` — Jinja2 templates for `install.ps1`, `uninstall.ps1`, `detect.ps1`
 
+**Per-owner storage:** `Printer`/`Client` (groups) are scoped to an `Owner` identified by an opaque bearer key in a cookie — no accounts. `Driver` stays global/shared. Every route taking a `printer_id`/`client_id` must filter/check `.owner == request.state.owner` (404, not 403, on mismatch) — printer IDs are small sequential ints, so a list-only filter isn't enough. Onboarding modal (`templates/base.html`, gated on `request.state.is_new_owner`) offers "download backup key" (`GET /session/key/download`, marks `Owner.is_permanent`) vs. temporary; `/session/restore` re-attaches a browser to a previously downloaded key. In tests, use the `owner` fixture (`tests/conftest.py`) when creating `Printer`/`Client` rows directly via the ORM so the `client` fixture's cookie-scoped requests can see them.
+
 **UI stack:** Pico CSS + HTMX 2 + Alpine.js 3 + Jinja2 server-side templates.
 
 **HTMX pattern:** Forms `hx-post`, swap `#driver-list` / `#printer-list` / `#client-list` targets. Errors return inline HTML fragments (HTTP 400/409) via `_error_response()`. Success return partials from `templates/partials/`.
@@ -64,4 +68,5 @@ ImpTune make printer deploy packages (`.intunewin` for Intune, `.zip` for NinjaR
 | Var | Default | Purpose |
 |-----|---------|---------|
 | `DATA_DIR` | `/data` | Storage root (DB + drivers + icons) |
-| `PORT` | `8000` | Server port |
\ No newline at end of file
+| `PORT` | `8000` | Server port |
+| `COOKIE_SECURE` | `true` | Owner-session cookie `Secure` flag. Set `false` for local plain-HTTP dev (`uvicorn --reload`) or the browser drops the cookie and a new Owner is created on every request. |
\ No newline at end of file
diff --git a/imptune/api/clients.py b/imptune/api/clients.py
index db40556..785985d 100644
--- a/imptune/api/clients.py
+++ b/imptune/api/clients.py
@@ -27,7 +27,7 @@ def _error_response(message: str, status_code: int = 400) -> HTMLResponse:
 
 def _render_client_list(request: Request) -> HTMLResponse:
     """Render the client list partial for HTMX swap."""
-    clients = list(Client.select().order_by(Client.name))
+    clients = list(Client.select().where(Client.owner == request.state.owner).order_by(Client.name))
     return templates.TemplateResponse(
         request=request,
         name="partials/client_list.html",
@@ -47,7 +47,7 @@ def create_client(request: Request, name: str = Form(...)) -> HTMLResponse:
         return _error_response("Client name is required.")
 
     try:
-        Client.create(name=name)
+        Client.create(name=name, owner=request.state.owner)
     except IntegrityError:
         return _error_response(f"Client '{name}' already exists.", status_code=409)
 
diff --git a/imptune/api/icons.py b/imptune/api/icons.py
index af123da..8c25c13 100644
--- a/imptune/api/icons.py
+++ b/imptune/api/icons.py
@@ -5,7 +5,7 @@ import hashlib
 import io
 from pathlib import Path
 
-from fastapi import APIRouter, UploadFile
+from fastapi import APIRouter, Request, UploadFile
 from fastapi.responses import HTMLResponse
 from PIL import Image
 
@@ -18,7 +18,7 @@ MAX_ICON_BYTES = 750 * 1024  # 750 KB
 
 
 @router.post("/{printer_id}/icon", response_class=HTMLResponse)
-def upload_icon(printer_id: int, file: UploadFile) -> HTMLResponse:
+def upload_icon(request: Request, printer_id: int, file: UploadFile) -> HTMLResponse:
     """Accept a printer icon PNG, validate it, store it, and update the Icon record.
 
     Validation rules:
@@ -29,8 +29,10 @@ def upload_icon(printer_id: int, file: UploadFile) -> HTMLResponse:
     Replaces any previously uploaded icon for this printer.
     Returns an HTMX-friendly HTML fragment.
     """
-    # Check printer exists
-    printer = Printer.get_or_none(Printer.id == printer_id)
+    # Check printer exists and belongs to this owner
+    printer = Printer.get_or_none(
+        (Printer.id == printer_id) & (Printer.owner == request.state.owner)
+    )
     if printer is None:
         return HTMLResponse(
             content="<p>Printer not found.</p>",
diff --git a/imptune/api/packages.py b/imptune/api/packages.py
index 0d321ac..ec7b6e1 100644
--- a/imptune/api/packages.py
+++ b/imptune/api/packages.py
@@ -6,11 +6,11 @@ import shutil
 import tempfile
 import zipfile
 
-from fastapi import APIRouter
+from fastapi import APIRouter, Request
 from fastapi.responses import PlainTextResponse, Response
 
 import imptune.config as cfg
-from imptune.db.models import Icon, Printer
+from imptune.db.models import Icon, Owner, Printer
 from imptune.generators.intunewin_builder import build_intunewin
 from imptune.generators.script_generator import render_detect, render_install, render_uninstall
 from imptune.storage.driver_store import DriverStore
@@ -18,9 +18,9 @@ from imptune.storage.driver_store import DriverStore
 router = APIRouter(prefix="/printers")
 
 
-def _get_printer_and_driver(printer_id: int):
-    """Fetch printer and validate driver — returns (printer, driver, driver_name) or PlainTextResponse error."""
-    printer = Printer.get_or_none(Printer.id == printer_id)
+def _get_printer_and_driver(printer_id: int, owner: Owner):
+    """Fetch printer (scoped to owner) and validate driver — returns (printer, driver, driver_name) or PlainTextResponse error."""
+    printer = Printer.get_or_none((Printer.id == printer_id) & (Printer.owner == owner))
     if printer is None:
         return None, PlainTextResponse("Printer not found", status_code=404)
 
@@ -48,9 +48,9 @@ def _get_driver_zip_path(driver) -> str:
 
 
 @router.get("/{printer_id}/packages/ninja")
-def get_ninja_package(printer_id: int):
+def get_ninja_package(request: Request, printer_id: int):
     """Download a NinjaRMM-ready ZIP containing install.ps1 and the driver files."""
-    result, error = _get_printer_and_driver(printer_id)
+    result, error = _get_printer_and_driver(printer_id, request.state.owner)
     if error is not None:
         return error
 
@@ -96,9 +96,9 @@ def get_ninja_package(printer_id: int):
 
 
 @router.get("/{printer_id}/packages/intunewin")
-def get_intunewin_package(printer_id: int):
+def get_intunewin_package(request: Request, printer_id: int):
     """Download a Microsoft Intune .intunewin deployment package."""
-    result, error = _get_printer_and_driver(printer_id)
+    result, error = _get_printer_and_driver(printer_id, request.state.owner)
     if error is not None:
         return error
 
diff --git a/imptune/api/pages.py b/imptune/api/pages.py
index e069db4..593ab04 100644
--- a/imptune/api/pages.py
+++ b/imptune/api/pages.py
@@ -17,12 +17,16 @@ templates = Jinja2Templates(directory=str(Path(__file__).parent.parent / "templa
 def dashboard(request: Request):
     from imptune.db.models import Printer
 
+    owner = request.state.owner
     recent_printers = list(
-        Printer.select().order_by(Printer.created_at.desc()).limit(5)
+        Printer.select()
+        .where(Printer.owner == owner)
+        .order_by(Printer.created_at.desc())
+        .limit(5)
     )
     recent_packages = list(
         Printer.select()
-        .where(Printer.driver.is_null(False))
+        .where((Printer.owner == owner) & Printer.driver.is_null(False))
         .order_by(Printer.created_at.desc())
         .limit(5)
     )
@@ -56,9 +60,11 @@ def drivers_page(request: Request):
 def printers_page(request: Request):
     from imptune.db.models import Client, Driver, Printer
 
+    owner = request.state.owner
     query = (
         Printer.select(Printer, Client)
         .join(Client, JOIN.LEFT_OUTER)
+        .where(Printer.owner == owner)
         .order_by(Client.name, Printer.name)
     )
     grouped: dict[str, list] = defaultdict(list)
@@ -66,7 +72,7 @@ def printers_page(request: Request):
         client_name = p.client.name if p.client_id else "Unassigned"
         grouped[client_name].append(p)
 
-    clients = list(Client.select().order_by(Client.name))
+    clients = list(Client.select().where(Client.owner == owner).order_by(Client.name))
 
     all_drivers = list(Driver.select().order_by(Driver.uploaded_at.desc()))
     driver_data = []
@@ -89,7 +95,7 @@ def printers_page(request: Request):
 def printers_new_page(request: Request):
     from imptune.db.models import Client, Driver
 
-    clients = list(Client.select().order_by(Client.name))
+    clients = list(Client.select().where(Client.owner == request.state.owner).order_by(Client.name))
     all_drivers = list(Driver.select().order_by(Driver.uploaded_at.desc()))
     driver_data = [
         {"driver": d, "names": json.loads(d.driver_desc) if d.driver_desc else []}
@@ -111,7 +117,7 @@ def printer_detail(request: Request, printer_id: int):
         .join(Client, JOIN.LEFT_OUTER)
         .switch(Printer)
         .join(Driver, JOIN.LEFT_OUTER)
-        .where(Printer.id == printer_id)
+        .where((Printer.id == printer_id) & (Printer.owner == request.state.owner))
         .first()
     )
     if printer is None:
@@ -148,7 +154,7 @@ def printer_detail(request: Request, printer_id: int):
 def clients_page(request: Request):
     from imptune.db.models import Client
 
-    clients = list(Client.select().order_by(Client.name))
+    clients = list(Client.select().where(Client.owner == request.state.owner).order_by(Client.name))
     return templates.TemplateResponse(
         request=request,
         name="clients.html",
@@ -160,7 +166,8 @@ def clients_page(request: Request):
 def client_detail(request: Request, client_id: int):
     from imptune.db.models import Client, Driver, Printer
 
-    client = Client.get_or_none(Client.id == client_id)
+    owner = request.state.owner
+    client = Client.get_or_none((Client.id == client_id) & (Client.owner == owner))
     if client is None:
         return HTMLResponse(
             content="<h1>404 Not Found</h1><p>Client not found.</p>",
@@ -170,12 +177,12 @@ def client_detail(request: Request, client_id: int):
     query = (
         Printer.select(Printer, Client)
         .join(Client, JOIN.LEFT_OUTER)
-        .where(Printer.client == client_id)
+        .where((Printer.client == client_id) & (Printer.owner == owner))
         .order_by(Printer.name)
     )
     grouped = {client.name: list(query)}
 
-    clients = list(Client.select().order_by(Client.name))
+    clients = list(Client.select().where(Client.owner == owner).order_by(Client.name))
     all_drivers = list(Driver.select().order_by(Driver.uploaded_at.desc()))
     driver_data = [
         {"driver": d, "names": json.loads(d.driver_desc) if d.driver_desc else []}
@@ -203,7 +210,7 @@ def packages_page(request: Request):
         .join(Client, JOIN.LEFT_OUTER)
         .switch(Printer)
         .join(Driver, JOIN.LEFT_OUTER)
-        .where(Printer.driver.is_null(False))
+        .where((Printer.owner == request.state.owner) & Printer.driver.is_null(False))
         .order_by(Printer.name)
     )
     return templates.TemplateResponse(
diff --git a/imptune/api/printers.py b/imptune/api/printers.py
index 2e88a56..0af007e 100644
--- a/imptune/api/printers.py
+++ b/imptune/api/printers.py
@@ -33,9 +33,11 @@ def _render_printer_list(request: Request) -> HTMLResponse:
     """Query printers with LEFT JOIN on client and render grouped partial."""
     import json
 
+    owner = request.state.owner
     query = (
         Printer.select(Printer, Client)
         .join(Client, JOIN.LEFT_OUTER)
+        .where(Printer.owner == owner)
         .order_by(Client.name, Printer.name)
     )
     grouped: dict[str, list[Printer]] = defaultdict(list)
@@ -43,7 +45,7 @@ def _render_printer_list(request: Request) -> HTMLResponse:
         client_name = p.client.name if p.client_id else "Unassigned"
         grouped[client_name].append(p)
 
-    clients = list(Client.select().order_by(Client.name))
+    clients = list(Client.select().where(Client.owner == owner).order_by(Client.name))
     all_drivers = list(Driver.select().order_by(Driver.uploaded_at.desc()))
     driver_data = [
         {"driver": d, "names": json.loads(d.driver_desc) if d.driver_desc else []}
@@ -94,8 +96,13 @@ def create_printer(
     color_mode_bool = color_mode == "on"
     collate_bool = collate == "on"
 
-    # Resolve optional FK IDs
+    owner = request.state.owner
+
+    # Resolve optional FK IDs — client must belong to this owner
     client_fk = int(client_id) if client_id.strip() else None
+    if client_fk is not None:
+        if Client.get_or_none((Client.id == client_fk) & (Client.owner == owner)) is None:
+            return _error_response(f"Client {client_fk} not found.", status_code=404)
     driver_fk = int(driver_id) if driver_id.strip() else None
 
     Printer.create(
@@ -106,6 +113,7 @@ def create_printer(
         color_mode=color_mode_bool,
         paper_size=paper_size,
         collate=collate_bool,
+        owner=owner,
         client=client_fk,
         driver=driver_fk,
     )
@@ -116,7 +124,11 @@ def create_printer(
 @router.delete("/{printer_id}", response_class=HTMLResponse)
 def delete_printer(request: Request, printer_id: int) -> HTMLResponse:
     """Delete a printer by ID. Returns updated printer list partial."""
-    deleted = Printer.delete().where(Printer.id == printer_id).execute()
+    deleted = (
+        Printer.delete()
+        .where((Printer.id == printer_id) & (Printer.owner == request.state.owner))
+        .execute()
+    )
     if not deleted:
         return _error_response(f"Printer {printer_id} not found.", status_code=404)
 
@@ -140,7 +152,8 @@ def update_printer(
     """Update an existing printer configuration in-place."""
     from datetime import UTC, datetime
 
-    printer = Printer.get_or_none(Printer.id == printer_id)
+    owner = request.state.owner
+    printer = Printer.get_or_none((Printer.id == printer_id) & (Printer.owner == owner))
     if printer is None:
         return _error_response(f"Printer {printer_id} not found.", status_code=404)
 
@@ -159,6 +172,11 @@ def update_printer(
     if paper_size not in _VALID_PAPER:
         return _error_response(f"Invalid paper size: {paper_size}.")
 
+    client_fk = int(client_id) if client_id.strip() else None
+    if client_fk is not None:
+        if Client.get_or_none((Client.id == client_fk) & (Client.owner == owner)) is None:
+            return _error_response(f"Client {client_fk} not found.", status_code=404)
+
     printer.name = name
     printer.ip_address = ip_address
     printer.port_name = port_name
@@ -166,7 +184,7 @@ def update_printer(
     printer.color_mode = color_mode == "on"
     printer.paper_size = paper_size
     printer.collate = collate == "on"
-    printer.client = int(client_id) if client_id.strip() else None
+    printer.client = client_fk
     printer.driver = int(driver_id) if driver_id.strip() else None
     printer.updated_at = datetime.now(UTC).replace(tzinfo=None)
     printer.save()
diff --git a/imptune/api/scripts.py b/imptune/api/scripts.py
index cbc53e1..0b16b12 100644
--- a/imptune/api/scripts.py
+++ b/imptune/api/scripts.py
@@ -1,18 +1,18 @@
 """Script download endpoints — generates and serves PowerShell scripts for a printer."""
 import json
 
-from fastapi import APIRouter
+from fastapi import APIRouter, Request
 from fastapi.responses import PlainTextResponse
 
-from imptune.db.models import Printer
+from imptune.db.models import Owner, Printer
 from imptune.generators.script_generator import render_detect, render_install, render_uninstall
 
 router = APIRouter(prefix="/printers")
 
 
-def _get_printer_and_driver(printer_id: int):
-    """Fetch printer and validate driver — returns (printer, driver_name) or PlainTextResponse error."""
-    printer = Printer.get_or_none(Printer.id == printer_id)
+def _get_printer_and_driver(printer_id: int, owner: Owner):
+    """Fetch printer (scoped to owner) and validate driver — returns (printer, driver_name) or PlainTextResponse error."""
+    printer = Printer.get_or_none((Printer.id == printer_id) & (Printer.owner == owner))
     if printer is None:
         return None, PlainTextResponse("Printer not found", status_code=404)
 
@@ -35,8 +35,8 @@ def _get_printer_and_driver(printer_id: int):
     return (printer, driver, driver_name), None
 
 
-def _install_response(printer_id: int):
-    result, error = _get_printer_and_driver(printer_id)
+def _install_response(printer_id: int, owner: Owner):
+    result, error = _get_printer_and_driver(printer_id, owner)
     if error is not None:
         return error
     printer, driver, driver_name = result
@@ -57,8 +57,8 @@ def _install_response(printer_id: int):
     )
 
 
-def _uninstall_response(printer_id: int):
-    result, error = _get_printer_and_driver(printer_id)
+def _uninstall_response(printer_id: int, owner: Owner):
+    result, error = _get_printer_and_driver(printer_id, owner)
     if error is not None:
         return error
     printer, driver, driver_name = result
@@ -73,8 +73,8 @@ def _uninstall_response(printer_id: int):
     )
 
 
-def _detect_response(printer_id: int):
-    result, error = _get_printer_and_driver(printer_id)
+def _detect_response(printer_id: int, owner: Owner):
+    result, error = _get_printer_and_driver(printer_id, owner)
     if error is not None:
         return error
     printer, driver, driver_name = result
@@ -86,36 +86,36 @@ def _detect_response(printer_id: int):
 
 
 @router.get("/{printer_id}/scripts/install")
-def get_install_script(printer_id: int):
+def get_install_script(request: Request, printer_id: int):
     """Download the PowerShell install script for a printer."""
-    return _install_response(printer_id)
+    return _install_response(printer_id, request.state.owner)
 
 
 @router.get("/{printer_id}/scripts/install.ps1")
-def get_install_script_ps1(printer_id: int):
+def get_install_script_ps1(request: Request, printer_id: int):
     """Download the PowerShell install script for a printer (.ps1 alias)."""
-    return _install_response(printer_id)
+    return _install_response(printer_id, request.state.owner)
 
 
 @router.get("/{printer_id}/scripts/uninstall")
-def get_uninstall_script(printer_id: int):
+def get_uninstall_script(request: Request, printer_id: int):
     """Download the PowerShell uninstall script for a printer."""
-    return _uninstall_response(printer_id)
+    return _uninstall_response(printer_id, request.state.owner)
 
 
 @router.get("/{printer_id}/scripts/uninstall.ps1")
-def get_uninstall_script_ps1(printer_id: int):
+def get_uninstall_script_ps1(request: Request, printer_id: int):
     """Download the PowerShell uninstall script for a printer (.ps1 alias)."""
-    return _uninstall_response(printer_id)
+    return _uninstall_response(printer_id, request.state.owner)
 
 
 @router.get("/{printer_id}/scripts/detect")
-def get_detect_script(printer_id: int):
+def get_detect_script(request: Request, printer_id: int):
     """Download the PowerShell detection script for a printer."""
-    return _detect_response(printer_id)
+    return _detect_response(printer_id, request.state.owner)
 
 
 @router.get("/{printer_id}/scripts/detect.ps1")
-def get_detect_script_ps1(printer_id: int):
+def get_detect_script_ps1(request: Request, printer_id: int):
     """Download the PowerShell detection script for a printer (.ps1 alias)."""
-    return _detect_response(printer_id)
+    return _detect_response(printer_id, request.state.owner)
diff --git a/imptune/api/session.py b/imptune/api/session.py
new file mode 100644
index 0000000..18e7682
--- /dev/null
+++ b/imptune/api/session.py
@@ -0,0 +1,73 @@
+"""Owner session routes — backup-key download and restore-on-new-browser."""
+from __future__ import annotations
+
+from pathlib import Path
+
+from fastapi import APIRouter, Form, Request
+from fastapi.responses import HTMLResponse, PlainTextResponse, RedirectResponse
+from fastapi.templating import Jinja2Templates
+
+import imptune.config as cfg
+from imptune.db.models import Owner
+from imptune.services.session import COOKIE_MAX_AGE, COOKIE_NAME, is_same_origin
+
+router = APIRouter(prefix="/session")
+
+templates = Jinja2Templates(
+    directory=str(Path(__file__).parent.parent / "templates")
+)
+
+
+@router.get("/key/download")
+def download_key(request: Request) -> PlainTextResponse:
+    """Mark the current owner permanent and hand back its key as a backup file."""
+    owner: Owner = request.state.owner
+    if not owner.is_permanent:
+        owner.is_permanent = True
+        owner.save()
+
+    return PlainTextResponse(
+        content=owner.key,
+        headers={"Content-Disposition": 'attachment; filename="imptune-backup-key.txt"'},
+    )
+
+
+@router.get("/restore", response_class=HTMLResponse)
+def restore_page(request: Request, error: str = "") -> HTMLResponse:
+    return templates.TemplateResponse(
+        request=request,
+        name="session_restore.html",
+        context={"error": error},
+    )
+
+
+@router.post("/restore")
+def restore_session(request: Request, key: str = Form(...)):
+    """Re-associate this browser with a previously downloaded backup key."""
+    if not is_same_origin(request):
+        return templates.TemplateResponse(
+            request=request,
+            name="session_restore.html",
+            context={"error": "Request rejected — please submit this form directly from this site."},
+            status_code=403,
+        )
+
+    owner = Owner.get_or_none(Owner.key == key.strip())
+    if owner is None:
+        return templates.TemplateResponse(
+            request=request,
+            name="session_restore.html",
+            context={"error": "Key not found."},
+            status_code=404,
+        )
+
+    response = RedirectResponse(url="/", status_code=303)
+    response.set_cookie(
+        COOKIE_NAME,
+        owner.key,
+        max_age=COOKIE_MAX_AGE,
+        httponly=True,
+        samesite="lax",
+        secure=cfg.COOKIE_SECURE,
+    )
+    return response
diff --git a/imptune/config.py b/imptune/config.py
index 125792a..dfac5d7 100644
--- a/imptune/config.py
+++ b/imptune/config.py
@@ -7,6 +7,8 @@ load_dotenv()
 
 DATA_DIR = os.environ.get("DATA_DIR", "/data")
 PORT = int(os.environ.get("PORT", "8000"))
+# Set to "false" for local plain-HTTP dev — browsers drop Secure cookies over HTTP.
+COOKIE_SECURE = os.environ.get("COOKIE_SECURE", "true").lower() != "false"
 
 DB_PATH = str(Path(DATA_DIR) / "imptune.db")
 DRIVERS_DIR = str(Path(DATA_DIR) / "drivers")
diff --git a/imptune/db/database.py b/imptune/db/database.py
index b3d19a1..e7e8f47 100644
--- a/imptune/db/database.py
+++ b/imptune/db/database.py
@@ -16,7 +16,7 @@ def init_db() -> None:
     Closes any existing connection before re-initializing so that test
     fixtures can monkeypatch DB_PATH between test runs.
     """
-    from imptune.db.models import Client, Driver, Printer, Icon
+    from imptune.db.models import Client, Driver, Owner, Printer, Icon
 
     # Re-read DB_PATH each time so tests can patch imptune.config.DB_PATH
     import imptune.config as cfg
@@ -33,4 +33,39 @@ def init_db() -> None:
         },
     )
     db.connect(reuse_if_open=True)
-    db.create_tables([Client, Driver, Printer, Icon], safe=True)
+    db.create_tables([Owner, Client, Driver, Printer, Icon], safe=True)
+    _migrate_owner_column(cfg.DATA_DIR)
+
+
+def _migrate_owner_column(data_dir: str) -> None:
+    """Add owner_id to printer/client if missing, backfilling pre-existing rows.
+
+    Runs against a DB created before per-owner scoping existed. Idempotent:
+    a no-op once the column exists and no rows are left with a NULL owner_id.
+    """
+    from pathlib import Path
+
+    from imptune.db.models import Client, Owner, Printer
+    from imptune.services.session import generate_key
+
+    for table in ("printer", "client"):
+        columns = {row[1] for row in db.execute_sql(f"PRAGMA table_info({table})")}
+        if "owner_id" not in columns:
+            db.execute_sql(
+                f"ALTER TABLE {table} ADD COLUMN owner_id INTEGER REFERENCES owner (id)"
+            )
+
+    orphaned = Printer.select().where(Printer.owner.is_null()).count() or Client.select().where(
+        Client.owner.is_null()
+    ).count()
+    if not orphaned:
+        return
+
+    legacy_owner = Owner.create(key=generate_key(), is_permanent=True)
+    Printer.update(owner=legacy_owner.id).where(Printer.owner.is_null()).execute()
+    Client.update(owner=legacy_owner.id).where(Client.owner.is_null()).execute()
+
+    key_path = Path(data_dir) / "legacy_owner_key.txt"
+    key_path.write_text(legacy_owner.key, encoding="utf-8")
+    print(f"[imptune] Pre-existing printers/clients migrated to a legacy owner. "
+          f"Restore key written to {key_path} — paste it into /session/restore to reclaim them.")
diff --git a/imptune/db/models.py b/imptune/db/models.py
index c68eb2b..3fdd432 100644
--- a/imptune/db/models.py
+++ b/imptune/db/models.py
@@ -24,14 +24,27 @@ class BaseModel(Model):
         database = db
 
 
-class Client(BaseModel):
-    """Represents a deployment target (AD client / OU)."""
+class Owner(BaseModel):
+    """Cookie-scoped identity — no accounts, just an opaque bearer key."""
 
-    name = CharField(unique=True)
+    key = CharField(unique=True, index=True)
+    is_permanent = BooleanField(default=False)
+    created_at = DateTimeField(default=_utcnow)
+
+    class Meta:
+        table_name = "owner"
+
+
+class Client(BaseModel):
+    """Represents a deployment target (AD client / OU), scoped to an Owner."""
+
+    name = CharField()
+    owner = ForeignKeyField(Owner, backref="clients")
     created_at = DateTimeField(default=_utcnow)
 
     class Meta:
         table_name = "client"
+        indexes = ((("owner", "name"), True),)
 
 
 class Driver(BaseModel):
@@ -56,6 +69,7 @@ class Printer(BaseModel):
     name = CharField()
     ip_address = CharField()
     port_name = CharField()
+    owner = ForeignKeyField(Owner, backref="printers")
     client = ForeignKeyField(Client, null=True, backref="printers")
     driver = ForeignKeyField(Driver, null=True, backref="printers")
     duplex_mode = CharField(default="OneSided")
diff --git a/imptune/main.py b/imptune/main.py
index 71d15b5..a6dfb16 100644
--- a/imptune/main.py
+++ b/imptune/main.py
@@ -5,9 +5,10 @@ from pathlib import Path
 from fastapi import FastAPI
 from fastapi.staticfiles import StaticFiles
 
-from imptune.api import clients, drivers, health, icons, pages, packages, printers, scripts
+from imptune.api import clients, drivers, health, icons, pages, packages, printers, scripts, session
 from imptune.config import DATA_DIR, DRIVERS_DIR, ICONS_DIR
 from imptune.db.database import db, init_db
+from imptune.services.session import OwnerSessionMiddleware
 
 
 @asynccontextmanager
@@ -23,6 +24,7 @@ async def lifespan(app: FastAPI):
 
 
 app = FastAPI(title="ImpTune", lifespan=lifespan)
+app.add_middleware(OwnerSessionMiddleware)
 
 # Serve baked-in static assets (pico.min.css, htmx.min.js, alpine.min.js)
 _static_dir = Path(__file__).parent / "static"
@@ -37,3 +39,4 @@ app.include_router(clients.router)
 app.include_router(scripts.router)
 app.include_router(packages.router)
 app.include_router(icons.router)
+app.include_router(session.router)
diff --git a/imptune/services/session.py b/imptune/services/session.py
new file mode 100644
index 0000000..b1ffe5c
--- /dev/null
+++ b/imptune/services/session.py
@@ -0,0 +1,84 @@
+"""Cookie-scoped Owner session — opaque bearer key, no accounts."""
+from __future__ import annotations
+
+import secrets
+
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette.requests import Request
+
+import imptune.config as cfg
+from imptune.db.models import Owner
+
+COOKIE_NAME = "imptune_owner_key"
+COOKIE_MAX_AGE = 10 * 365 * 24 * 60 * 60  # 10 years
+
+
+def generate_key() -> str:
+    return secrets.token_urlsafe(32)
+
+
+def is_same_origin(request: Request) -> bool:
+    """Origin/Referer check — the CSRF guard for /session/restore.
+
+    Restoring a key re-points the cookie at a *different* Owner, so unlike
+    the rest of the app's unprotected POSTs (which only ever mutate the
+    caller's own data), a forged cross-site POST here is a login-CSRF /
+    session-fixation vector: an attacker who knows their own key can force
+    a victim's browser onto the attacker's Owner. Browsers always send
+    Origin (and usually Referer) on form POSTs, same-site or not, so
+    requiring a match — and rejecting when both are absent — blocks a plain
+    auto-submitting HTML form without needing a token.
+    """
+    expected = f"{request.url.scheme}://{request.url.netloc}"
+
+    origin = request.headers.get("origin")
+    if origin is not None:
+        return origin == expected
+
+    referer = request.headers.get("referer")
+    if referer:
+        from urllib.parse import urlparse
+
+        parsed = urlparse(referer)
+        return f"{parsed.scheme}://{parsed.netloc}" == expected
+
+    return False
+
+
+class OwnerSessionMiddleware(BaseHTTPMiddleware):
+    """Resolves request.state.owner from a cookie, creating one on first visit."""
+
+    async def dispatch(self, request: Request, call_next):
+        if request.url.path == "/health":
+            return await call_next(request)
+
+        key = request.cookies.get(COOKIE_NAME)
+        owner = Owner.get_or_none(Owner.key == key) if key else None
+        is_new = owner is None
+        if owner is None:
+            owner = Owner.create(key=generate_key(), is_permanent=False)
+
+        request.state.owner = owner
+        request.state.is_new_owner = is_new
+
+        response = await call_next(request)
+
+        # Routes like /session/restore intentionally set this cookie themselves
+        # (to a *different* owner than the one this middleware just minted) —
+        # don't clobber that with the auto-provisioned one.
+        route_already_set_cookie = any(
+            header.lower() == b"set-cookie" and value.startswith(f"{COOKIE_NAME}=".encode())
+            for header, value in response.raw_headers
+        )
+
+        if is_new and not route_already_set_cookie:
+            response.set_cookie(
+                COOKIE_NAME,
+                owner.key,
+                max_age=COOKIE_MAX_AGE,
+                httponly=True,
+                samesite="lax",
+                secure=cfg.COOKIE_SECURE,
+            )
+
+        return response
diff --git a/imptune/templates/base.html b/imptune/templates/base.html
index 3bea785..35efdef 100644
--- a/imptune/templates/base.html
+++ b/imptune/templates/base.html
@@ -315,6 +315,10 @@
         <li><a href="/packages" {% if request.url.path == "/packages" %}class="active"{% endif %}
                x-data x-text="$store.i18n.t('packages')">Packages</a></li>
       </ul>
+      <ul class="sidebar-nav sidebar-nav-footer">
+        <li><a href="/session/key/download">Download backup key</a></li>
+        <li><a href="/session/restore" {% if request.url.path == "/session/restore" %}class="active"{% endif %}>Restore from backup key</a></li>
+      </ul>
     </nav>
     <div class="main-wrapper">
       <header class="topbar">
@@ -333,6 +337,20 @@
         </div>
       </header>
       <main class="main-content">
+        {% if request.state.is_new_owner %}
+        <dialog open id="session-choice-modal">
+          <article>
+            <h3>Keep your printers?</h3>
+            <p>Your printers, configs, and groups are private to this browser
+            (drivers stay shared with everyone). If you clear your cookies
+            without a backup key, they're gone for good.</p>
+            <footer>
+              <a role="button" href="/session/key/download">Store permanently (download backup key)</a>
+              <button class="secondary" onclick="this.closest('dialog').close()">Keep temporary, this browser only</button>
+            </footer>
+          </article>
+        </dialog>
+        {% endif %}
         {% block content %}{% endblock %}
       </main>
     </div>
diff --git a/imptune/templates/session_restore.html b/imptune/templates/session_restore.html
new file mode 100644
index 0000000..807081d
--- /dev/null
+++ b/imptune/templates/session_restore.html
@@ -0,0 +1,20 @@
+{% extends "base.html" %}
+
+{% block content %}
+<h1>Restore backup key</h1>
+
+<p>Paste the key from your <code>imptune-backup-key.txt</code> backup file to
+recover your printers, configs, and groups on this browser.</p>
+
+{% if error %}
+<div class="error"><p>{{ error }}</p></div>
+{% endif %}
+
+<form method="post" action="/session/restore">
+  <label>
+    Backup key
+    <input type="text" name="key" placeholder="paste your key here" required autofocus>
+  </label>
+  <button type="submit">Restore</button>
+</form>
+{% endblock %}
diff --git a/tests/conftest.py b/tests/conftest.py
index 8d8cdf8..f4f993d 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -12,6 +12,21 @@ def client(tmp_data_dir):
         yield c
 
 
+@pytest.fixture
+def owner(client):
+    """The Owner the `client` fixture's cookie jar is scoped to.
+
+    Triggers the session middleware (any non-/health request creates the
+    cookie), then resolves the Owner record so tests can create Printer/Client
+    rows directly via the ORM that the same `client` can then see over HTTP.
+    """
+    from imptune.db.models import Owner
+    from imptune.services.session import COOKIE_NAME
+
+    client.get("/")
+    return Owner.get(Owner.key == client.cookies[COOKIE_NAME])
+
+
 @pytest.fixture
 def tmp_data_dir(tmp_path, monkeypatch):
     """Set DATA_DIR to a temp directory so tests don't write to /data."""
diff --git a/tests/e2e/conftest.py b/tests/e2e/conftest.py
index c3ac40e..8caf68b 100644
--- a/tests/e2e/conftest.py
+++ b/tests/e2e/conftest.py
@@ -34,6 +34,10 @@ def live_server(tmp_path_factory):
     os.makedirs(cfg.DRIVERS_DIR, exist_ok=True)
     os.makedirs(cfg.ICONS_DIR, exist_ok=True)
 
+    # Plain HTTP loopback server — Secure-flagged cookies would be dropped
+    # inconsistently across browser engines, so disable that flag for E2E.
+    cfg.COOKIE_SECURE = False
+
     # Also set env var so lifespan handler picks up correct dirs
     os.environ["DATA_DIR"] = str(data_dir)
 
@@ -68,3 +72,31 @@ def live_server(tmp_path_factory):
 
     server.should_exit = True
     thread.join(timeout=2.0)
+
+
+@pytest.fixture(scope="session")
+def _e2e_owner_key(live_server):
+    """One Owner shared by every E2E browser context.
+
+    E2E specs cover unrelated UI (theme, i18n, port autofill); without a
+    pre-existing cookie each fresh Playwright context would be treated as a
+    first-time visitor and blocked by the onboarding modal (a real <dialog>
+    that intercepts all pointer events until dismissed).
+    """
+    from imptune.services.session import COOKIE_NAME
+
+    resp = httpx.get(f"{live_server}/")
+    return resp.cookies[COOKIE_NAME]
+
+
+@pytest.fixture(autouse=True)
+def _seed_owner_cookie(page, live_server, _e2e_owner_key):
+    """Pre-seed the owner cookie so the first-visit modal never appears in specs unrelated to onboarding."""
+    from urllib.parse import urlparse
+
+    from imptune.services.session import COOKIE_NAME
+
+    hostname = urlparse(live_server).hostname
+    page.context.add_cookies(
+        [{"name": COOKIE_NAME, "value": _e2e_owner_key, "domain": hostname, "path": "/"}]
+    )
diff --git a/tests/e2e/test_printer_edit.py b/tests/e2e/test_printer_edit.py
index 25ab4b5..a52c752 100644
--- a/tests/e2e/test_printer_edit.py
+++ b/tests/e2e/test_printer_edit.py
@@ -4,12 +4,16 @@ from __future__ import annotations
 import pytest
 
 
-def test_printer_edit_modal_open_and_prefill(page, live_server: str) -> None:
+def test_printer_edit_modal_open_and_prefill(page, live_server: str, _e2e_owner_key: str) -> None:
     """Edit button opens modal with printer's current name pre-filled."""
     import httpx
 
-    # Create a printer via API
-    with httpx.Client(base_url=live_server, follow_redirects=True) as api:
+    from imptune.services.session import COOKIE_NAME
+
+    # Create a printer via API, under the same owner the page's cookie is seeded with
+    with httpx.Client(
+        base_url=live_server, follow_redirects=True, cookies={COOKIE_NAME: _e2e_owner_key}
+    ) as api:
         api.post(
             "/printers",
             data={
@@ -30,11 +34,15 @@ def test_printer_edit_modal_open_and_prefill(page, live_server: str) -> None:
     assert name_val == "EditTest Printer"
 
 
-def test_printer_edit_submit_updates_list(page, live_server: str) -> None:
+def test_printer_edit_submit_updates_list(page, live_server: str, _e2e_owner_key: str) -> None:
     """Submitting the edit form updates the printer name in the list (no page reload)."""
     import httpx
 
-    with httpx.Client(base_url=live_server, follow_redirects=True) as api:
+    from imptune.services.session import COOKIE_NAME
+
+    with httpx.Client(
+        base_url=live_server, follow_redirects=True, cookies={COOKIE_NAME: _e2e_owner_key}
+    ) as api:
         resp = api.post(
             "/printers",
             data={
diff --git a/tests/test_db.py b/tests/test_db.py
index e99ee1a..7d6836c 100644
--- a/tests/test_db.py
+++ b/tests/test_db.py
@@ -43,6 +43,7 @@ def test_create_tables(db_env):
     init_db()
 
     tables = db.get_tables()
+    assert "owner" in tables
     assert "client" in tables
     assert "driver" in tables
     assert "printer" in tables
diff --git a/tests/test_icon_upload.py b/tests/test_icon_upload.py
index f87b237..67cd363 100644
--- a/tests/test_icon_upload.py
+++ b/tests/test_icon_upload.py
@@ -28,7 +28,7 @@ def _make_jpeg(width: int = 256, height: int = 256) -> bytes:
     return buf.getvalue()
 
 
-def _create_printer(client):
+def _create_printer(owner):
     """Create a test Printer record and return it."""
     from imptune.db.models import Printer
 
@@ -36,15 +36,16 @@ def _create_printer(client):
         name="Test Printer",
         ip_address="10.0.0.1",
         port_name="IP_10.0.0.1",
+        owner=owner,
     )
 
 
 class TestIconUpload:
-    def test_upload_valid_png(self, client, tmp_data_dir):
+    def test_upload_valid_png(self, client, owner, tmp_data_dir):
         """POST a valid 256x256 PNG returns 200 and Icon record created."""
         from imptune.db.models import Icon
 
-        printer = _create_printer(client)
+        printer = _create_printer(owner)
         png_data = _make_png(256, 256)
         response = client.post(
             f"/printers/{printer.id}/icon",
@@ -65,9 +66,9 @@ class TestIconUpload:
         icon_file = Path(tmp_data_dir) / "icons" / sha256
         assert icon_file.exists()
 
-    def test_reject_non_png(self, client, tmp_data_dir):
+    def test_reject_non_png(self, client, owner, tmp_data_dir):
         """POST with a JPEG file returns 422 with PNG format error."""
-        printer = _create_printer(client)
+        printer = _create_printer(owner)
         jpeg_data = _make_jpeg(256, 256)
         response = client.post(
             f"/printers/{printer.id}/icon",
@@ -76,9 +77,9 @@ class TestIconUpload:
         assert response.status_code == 422
         assert "PNG" in response.text
 
-    def test_reject_oversized(self, client, tmp_data_dir):
+    def test_reject_oversized(self, client, owner, tmp_data_dir):
         """POST with PNG > 750KB returns 422 with 750 KB error."""
-        printer = _create_printer(client)
+        printer = _create_printer(owner)
         # Craft oversized data: valid PNG bytes followed by padding
         png_bytes = _make_png(256, 256)
         oversized = png_bytes + b"\x00" * (750 * 1024 + 1 - len(png_bytes))
@@ -89,9 +90,9 @@ class TestIconUpload:
         assert response.status_code == 422
         assert "750" in response.text
 
-    def test_reject_wrong_dimensions(self, client, tmp_data_dir):
+    def test_reject_wrong_dimensions(self, client, owner, tmp_data_dir):
         """POST with 128x128 PNG returns 422 with 256x256 error."""
-        printer = _create_printer(client)
+        printer = _create_printer(owner)
         png_data = _make_png(128, 128)
         response = client.post(
             f"/printers/{printer.id}/icon",
@@ -100,11 +101,11 @@ class TestIconUpload:
         assert response.status_code == 422
         assert "256x256" in response.text
 
-    def test_replace_existing_icon(self, client, tmp_data_dir):
+    def test_replace_existing_icon(self, client, owner, tmp_data_dir):
         """Second upload for same printer replaces the Icon record."""
         from imptune.db.models import Icon
 
-        printer = _create_printer(client)
+        printer = _create_printer(owner)
 
         # First upload
         png1 = _make_png(256, 256)
diff --git a/tests/test_packages.py b/tests/test_packages.py
index 0c53125..5e5dcdc 100644
--- a/tests/test_packages.py
+++ b/tests/test_packages.py
@@ -22,7 +22,7 @@ def driver_zip_bytes():
 
 
 @pytest.fixture
-def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes):
+def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes, owner):
     """Create Driver record (with ZIP on disk) and Printer record linked to it."""
     import hashlib
     import os
@@ -50,6 +50,7 @@ def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes):
         ip_address="192.168.1.100",
         port_name="IP_192.168.1.100",
         driver=driver,
+        owner=owner,
         duplex_mode="OneSided",
         color_mode=True,
         paper_size="A4",
@@ -59,7 +60,7 @@ def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes):
 
 
 @pytest.fixture
-def printer_no_driver(tmp_data_dir):
+def printer_no_driver(tmp_data_dir, owner):
     """Create Printer record with no driver assigned."""
     from imptune.db.models import Printer
 
@@ -68,6 +69,7 @@ def printer_no_driver(tmp_data_dir):
         ip_address="10.0.0.1",
         port_name="IP_10.0.0.1",
         driver=None,
+        owner=owner,
     )
 
 
diff --git a/tests/test_printer_crud.py b/tests/test_printer_crud.py
index 507c21a..c46b068 100644
--- a/tests/test_printer_crud.py
+++ b/tests/test_printer_crud.py
@@ -189,7 +189,7 @@ def test_create_printer_invalid_ip(client: TestClient) -> None:
     assert resp.status_code == 400
 
 
-def test_printer_detail_shows_driver(client: TestClient) -> None:
+def test_printer_detail_shows_driver(client: TestClient, owner) -> None:
     """GET /printers/{id} returns 200 with all printer fields and driver name."""
     from imptune.db.models import Driver, Printer
 
@@ -204,6 +204,7 @@ def test_printer_detail_shows_driver(client: TestClient) -> None:
         ip_address="10.0.1.1",
         port_name="IP_10_0_1_1",
         driver=driver_obj,
+        owner=owner,
     )
 
     resp = client.get(f"/printers/{printer.id}")
@@ -220,7 +221,7 @@ def test_printer_detail_not_found(client: TestClient) -> None:
     assert resp.status_code == 404
 
 
-def test_printer_detail_no_driver(client: TestClient) -> None:
+def test_printer_detail_no_driver(client: TestClient, owner) -> None:
     """GET /printers/{id} for printer with no driver returns 200 with 'No driver assigned'."""
     from imptune.db.models import Printer
 
@@ -229,6 +230,7 @@ def test_printer_detail_no_driver(client: TestClient) -> None:
         ip_address="10.0.1.2",
         port_name="IP_10_0_1_2",
         driver=None,
+        owner=owner,
     )
 
     resp = client.get(f"/printers/{printer.id}")
@@ -311,7 +313,7 @@ def test_printers_library_no_form(client: TestClient) -> None:
     assert 'action="/printers" method="post"' not in html
 
 
-def test_patch_printer(client: TestClient) -> None:
+def test_patch_printer(client: TestClient, owner) -> None:
     """PATCH /printers/{id} with updated name returns 200, updated name in response, DB updated."""
     from imptune.db.models import Printer
 
@@ -319,6 +321,7 @@ def test_patch_printer(client: TestClient) -> None:
         name="Original Name",
         ip_address="10.0.2.1",
         port_name="IP_10_0_2_1",
+        owner=owner,
     )
 
     resp = client.patch(
@@ -339,18 +342,19 @@ def test_patch_printer_not_found(client: TestClient) -> None:
     assert resp.status_code == 404
 
 
-def test_client_detail_returns_200(client: TestClient) -> None:
+def test_client_detail_returns_200(client: TestClient, owner) -> None:
     """GET /clients/{id} returns 200 with client name and assigned printer name."""
     from imptune.db.models import Client, Printer
 
     # Create client
-    cl = Client.create(name="Detail Client")
+    cl = Client.create(name="Detail Client", owner=owner)
     # Create printer assigned to that client
     Printer.create(
         name="Client Printer",
         ip_address="10.0.3.1",
         port_name="IP_10_0_3_1",
         client=cl,
+        owner=owner,
     )
 
     resp = client.get(f"/clients/{cl.id}")
@@ -366,7 +370,7 @@ def test_client_detail_not_found(client: TestClient) -> None:
     assert resp.status_code == 404
 
 
-def test_client_links_in_printer_list(client: TestClient) -> None:
+def test_client_links_in_printer_list(client: TestClient, owner) -> None:
     """GET /printers with a printer assigned to a client contains href to client detail."""
     from imptune.db.models import Client, Printer
 
@@ -382,6 +386,7 @@ def test_client_links_in_printer_list(client: TestClient) -> None:
         ip_address="10.0.4.1",
         port_name="IP_10_0_4_1",
         client=cl,
+        owner=owner,
     )
 
     resp = client.get("/printers")
diff --git a/tests/test_script_download.py b/tests/test_script_download.py
index 0fb5aec..de4b556 100644
--- a/tests/test_script_download.py
+++ b/tests/test_script_download.py
@@ -22,7 +22,7 @@ def driver_zip_bytes():
 
 
 @pytest.fixture
-def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes):
+def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes, owner):
     """Create Driver record (with ZIP on disk) and Printer record linked to it."""
     import hashlib
     import os
@@ -49,6 +49,7 @@ def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes):
         ip_address="192.168.1.100",
         port_name="IP_192.168.1.100",
         driver=driver,
+        owner=owner,
         duplex_mode="OneSided",
         color_mode=True,
         paper_size="A4",
@@ -58,7 +59,7 @@ def setup_printer_with_driver(tmp_data_dir, driver_zip_bytes):
 
 
 @pytest.fixture
-def printer_no_driver(tmp_data_dir):
+def printer_no_driver(tmp_data_dir, owner):
     """Create Printer record with no driver assigned."""
     from imptune.db.models import Printer
 
@@ -67,6 +68,7 @@ def printer_no_driver(tmp_data_dir):
         ip_address="10.0.0.1",
         port_name="IP_10.0.0.1",
         driver=None,
+        owner=owner,
     )
 
 
diff --git a/tests/test_script_generator.py b/tests/test_script_generator.py
index 2175ecd..736cb08 100644
--- a/tests/test_script_generator.py
+++ b/tests/test_script_generator.py
@@ -3,7 +3,7 @@ import pytest
 from imptune.generators.script_generator import render_detect, render_install, render_uninstall
 
 
-def _create_test_driver_and_printer():
+def _create_test_driver_and_printer(owner):
     """Helper: create a Driver + Printer for integration tests."""
     from imptune.db.models import Driver, Printer
 
@@ -19,6 +19,7 @@ def _create_test_driver_and_printer():
         ip_address="10.0.0.1",
         port_name="IP_10.0.0.1",
         driver=driver,
+        owner=owner,
         duplex_mode="LongEdge",
         color_mode=True,
         paper_size="A4",
@@ -149,25 +150,25 @@ def test_render_detect():
 # ---------------------------------------------------------------------------
 
 
-def test_install_endpoint(client):
+def test_install_endpoint(client, owner):
     """GET /printers/{id}/scripts/install returns 200 with pnputil in content."""
-    _driver, printer = _create_test_driver_and_printer()
+    _driver, printer = _create_test_driver_and_printer(owner)
     response = client.get(f"/printers/{printer.id}/scripts/install")
     assert response.status_code == 200
     assert "pnputil" in response.text
 
 
-def test_uninstall_endpoint(client):
+def test_uninstall_endpoint(client, owner):
     """GET /printers/{id}/scripts/uninstall returns 200 with Remove-Printer in content."""
-    _driver, printer = _create_test_driver_and_printer()
+    _driver, printer = _create_test_driver_and_printer(owner)
     response = client.get(f"/printers/{printer.id}/scripts/uninstall")
     assert response.status_code == 200
     assert "Remove-Printer" in response.text
 
 
-def test_detect_endpoint(client):
+def test_detect_endpoint(client, owner):
     """GET /printers/{id}/scripts/detect returns 200 with Write-Output in content."""
-    _driver, printer = _create_test_driver_and_printer()
+    _driver, printer = _create_test_driver_and_printer(owner)
     response = client.get(f"/printers/{printer.id}/scripts/detect")
     assert response.status_code == 200
     assert "Write-Output" in response.text
@@ -179,7 +180,7 @@ def test_script_endpoint_missing_printer(client):
     assert response.status_code == 404
 
 
-def test_script_endpoint_no_driver(client):
+def test_script_endpoint_no_driver(client, owner):
     """GET /printers/{id}/scripts/install returns 422 when no driver assigned."""
     from imptune.db.models import Printer
 
@@ -188,6 +189,7 @@ def test_script_endpoint_no_driver(client):
         ip_address="10.0.0.2",
         port_name="IP_10.0.0.2",
         driver=None,
+        owner=owner,
         duplex_mode="OneSided",
         color_mode=True,
         paper_size="A4",
diff --git a/tests/test_session.py b/tests/test_session.py
new file mode 100644
index 0000000..b6350de
--- /dev/null
+++ b/tests/test_session.py
@@ -0,0 +1,127 @@
+"""Tests for per-owner cookie-scoped session — first visit, isolation, restore."""
+from fastapi.testclient import TestClient
+
+from imptune.services.session import COOKIE_NAME
+
+
+def test_first_visit_sets_cookie_and_new_owner_flag(client):
+    resp = client.get("/")
+    assert resp.status_code == 200
+    assert COOKIE_NAME in client.cookies
+    assert "session-choice-modal" in resp.text
+
+    # Second visit — cookie already present, modal must not reappear
+    resp2 = client.get("/")
+    assert "session-choice-modal" not in resp2.text
+
+
+def test_printers_are_isolated_between_owners(tmp_data_dir):
+    from imptune.main import app
+
+    with TestClient(app) as client_a, TestClient(app) as client_b:
+        client_a.post(
+            "/printers",
+            data={"name": "Owner A Printer", "ip_address": "10.0.0.1", "port_name": "IP_A"},
+            follow_redirects=False,
+        )
+
+        page_a = client_a.get("/printers")
+        page_b = client_b.get("/printers")
+
+        assert "Owner A Printer" in page_a.text
+        assert "Owner A Printer" not in page_b.text
+
+
+def test_owner_b_cannot_reach_owner_a_printer_by_id(tmp_data_dir):
+    from imptune.main import app
+
+    with TestClient(app) as client_a, TestClient(app) as client_b:
+        client_a.post(
+            "/printers",
+            data={"name": "Private Printer", "ip_address": "10.0.0.2", "port_name": "IP_B"},
+            follow_redirects=False,
+        )
+        from imptune.db.models import Printer
+
+        printer_id = Printer.get(Printer.name == "Private Printer").id
+
+        assert client_b.get(f"/printers/{printer_id}").status_code == 404
+        assert client_b.patch(f"/printers/{printer_id}", data={"name": "Hijacked"}).status_code == 404
+        assert client_b.delete(f"/printers/{printer_id}").status_code == 404
+        assert client_b.get(f"/printers/{printer_id}/scripts/install").status_code == 404
+        assert client_b.get(f"/printers/{printer_id}/packages/ninja").status_code == 404
+
+
+def test_download_key_marks_permanent_and_returns_key(client):
+    from imptune.db.models import Owner
+
+    client.get("/")
+    resp = client.get("/session/key/download")
+    assert resp.status_code == 200
+    assert "attachment" in resp.headers["content-disposition"]
+    assert "imptune-backup-key.txt" in resp.headers["content-disposition"]
+
+    key = resp.text
+    assert len(key) > 20
+
+    owner = Owner.get(Owner.key == key)
+    assert owner.is_permanent is True
+
+
+def test_restore_with_valid_key_reattaches_owner_data(tmp_data_dir):
+    from imptune.main import app
+
+    with TestClient(app) as client_a:
+        client_a.get("/")
+        client_a.post(
+            "/printers",
+            data={"name": "Backed Up Printer", "ip_address": "10.0.0.3", "port_name": "IP_C"},
+            follow_redirects=False,
+        )
+        key = client_a.get("/session/key/download").text
+
+    with TestClient(app) as client_new:
+        restore_resp = client_new.post(
+            "/session/restore",
+            data={"key": key},
+            headers={"origin": "http://testserver"},
+            follow_redirects=False,
+        )
+        assert restore_resp.status_code == 303
+
+        page = client_new.get("/printers")
+        assert "Backed Up Printer" in page.text
+
+
+def test_restore_with_invalid_key_shows_error(client):
+    resp = client.post(
+        "/session/restore",
+        data={"key": "not-a-real-key"},
+        headers={"origin": "http://testserver"},
+    )
+    assert resp.status_code == 404
+    assert "Key not found" in resp.text
+
+
+def test_restore_rejects_cross_origin_post(client):
+    """CSRF guard: a forged cross-site form POST must not be able to re-point
+    the victim's cookie at an attacker-known key (login-CSRF / session fixation)."""
+    resp = client.post(
+        "/session/restore",
+        data={"key": "irrelevant"},
+        headers={"origin": "https://attacker.example"},
+    )
+    assert resp.status_code == 403
+
+    resp_no_header = client.post("/session/restore", data={"key": "irrelevant"})
+    assert resp_no_header.status_code == 403
+
+
+def test_health_endpoint_does_not_create_owner_rows(client):
+    from imptune.db.models import Owner
+
+    before = Owner.select().count()
+    for _ in range(5):
+        client.get("/health")
+    after = Owner.select().count()
+    assert after == before
diff --git a/tests/test_static.py b/tests/test_static.py
index 8331da9..9d68e32 100644
--- a/tests/test_static.py
+++ b/tests/test_static.py
@@ -53,7 +53,7 @@ def test_theme_toggle_present(client):
     assert "cycle" in response.text or "store.theme" in response.text
 
 
-def test_dashboard_shows_recent_printers(client):
+def test_dashboard_shows_recent_printers(client, owner):
     """Dashboard renders names of recently-created printers from DB."""
     from imptune.db.models import Printer
 
@@ -61,11 +61,13 @@ def test_dashboard_shows_recent_printers(client):
         name="TestPrinter-Alpha",
         ip_address="10.0.0.1",
         port_name="IP_10.0.0.1",
+        owner=owner,
     )
     Printer.create(
         name="TestPrinter-Beta",
         ip_address="10.0.0.2",
         port_name="IP_10.0.0.2",
+        owner=owner,
     )
 
     response = client.get("/")
@@ -85,7 +87,7 @@ def test_theme_toggle_present(client):
     assert "cycle" in response.text or "store.theme" in response.text
 
 
-def test_dashboard_shows_recent_packages(client):
+def test_dashboard_shows_recent_packages(client, owner):
     """Dashboard recent-packages section shows only printers with a driver assigned."""
     from imptune.db.models import Driver, Printer
 
@@ -100,11 +102,13 @@ def test_dashboard_shows_recent_packages(client):
         ip_address="10.0.0.2",
         port_name="IP_10.0.0.2",
         driver=driver,
+        owner=owner,
     )
     Printer.create(
         name="PkgPrinter-NoDriver",
         ip_address="10.0.0.3",
         port_name="IP_10.0.0.3",
+        owner=owner,
     )
 
     response = client.get("/")
diff --git a/tests/test_upload_export_roundtrip.py b/tests/test_upload_export_roundtrip.py
index a951441..16c4182 100644
--- a/tests/test_upload_export_roundtrip.py
+++ b/tests/test_upload_export_roundtrip.py
@@ -18,7 +18,7 @@ def driver_zip_bytes():
 
 
 def test_upload_then_ninja_export_finds_driver_on_disk(
-    client, tmp_data_dir, driver_zip_bytes
+    client, tmp_data_dir, driver_zip_bytes, owner
 ):
     from imptune.db.models import Client, Driver, Printer
 
@@ -33,13 +33,14 @@ def test_upload_then_ninja_export_finds_driver_on_disk(
     driver.driver_desc = json.dumps(["HP LaserJet Pro"])
     driver.save()
 
-    tenant = Client.create(name="Acme Corp")
+    tenant = Client.create(name="Acme Corp", owner=owner)
     printer = Printer.create(
         name="Round Trip Printer",
         ip_address="192.168.1.50",
         port_name="IP_192.168.1.50",
         client=tenant,
         driver=driver,
+        owner=owner,
     )
 
     resp = client.get(f"/printers/{printer.id}/packages/ninja")