diff --git a/tests/server/login_flow/conftest.py b/tests/server/login_flow/conftest.py
index d2c47344..d3abb125 100644
--- a/tests/server/login_flow/conftest.py
+++ b/tests/server/login_flow/conftest.py
@@ -544,3 +544,362 @@ async def nc_mcp_login_flow_client_no_custom_scopes(
         client_name="Login Flow MCP No Custom Scopes",
     ):
         yield session
+
+
+# ---------------------------------------------------------------------------
+# Multi-user Login Flow fixtures for permission / isolation tests
+# ---------------------------------------------------------------------------
+
+
+async def _get_login_flow_token_for_user(
+    browser,
+    login_flow_oauth_client_credentials,
+    auth_states: dict,
+    username: str,
+    password: str,
+) -> str:
+    """Get an OAuth token for a specific user targeting the login-flow MCP server.
+
+    Similar to the global ``_get_oauth_token_for_user`` but hard-wires the
+    resource / PRM discovery against port 8004.
+    """
+    nextcloud_host = os.getenv("NEXTCLOUD_HOST")
+    if not nextcloud_host:
+        pytest.skip("Login Flow tests require NEXTCLOUD_HOST")
+
+    client_id, client_secret, callback_url, token_endpoint, authorization_endpoint = (
+        login_flow_oauth_client_credentials
+    )
+
+    # Discover resource identifier from the login-flow server
+    try:
+        resource_metadata = await get_mcp_server_resource_metadata(
+            LOGIN_FLOW_MCP_BASE_URL
+        )
+        resource_id = resource_metadata.get("resource")
+    except Exception:
+        resource_id = None
+
+    state = secrets.token_urlsafe(32)
+
+    scopes_encoded = quote(DEFAULT_FULL_SCOPES, safe="")
+    auth_url = (
+        f"{authorization_endpoint}?"
+        f"response_type=code&"
+        f"client_id={client_id}&"
+        f"redirect_uri={quote(callback_url, safe='')}&"
+        f"state={state}&"
+        f"scope={scopes_encoded}"
+    )
+    if resource_id:
+        auth_url += f"&resource={quote(resource_id, safe='')}"
+
+    context = await browser.new_context(ignore_https_errors=True)
+    page = await context.new_page()
+
+    try:
+        await page.goto(auth_url, wait_until="networkidle", timeout=60000)
+        current_url = page.url
+
+        # Login
+        if "/login" in current_url or "/index.php/login" in current_url:
+            await page.wait_for_selector('input[name="user"]', timeout=10000)
+            await page.fill('input[name="user"]', username)
+            await page.fill('input[name="password"]', password)
+            await page.click('button[type="submit"]')
+            await page.wait_for_load_state("networkidle", timeout=60000)
+
+        # Wait for OIDC redirect chain to settle
+        settle_start = time.time()
+        while time.time() - settle_start < 15:
+            current_url = page.url
+            if "/consent" in current_url or "localhost:8081" in current_url:
+                break
+            await anyio.sleep(0.5)
+
+        # Handle consent screen
+        if "/consent" in page.url:
+            await page.wait_for_load_state("networkidle", timeout=10000)
+            await _handle_oauth_consent_screen(page, username)
+
+        # Wait for callback
+        start_time = time.time()
+        while state not in auth_states:
+            if time.time() - start_time > 30:
+                screenshot_path = f"/tmp/login_flow_oauth_timeout_{username}.png"
+                await page.screenshot(path=screenshot_path)
+                raise TimeoutError(f"Timeout waiting for OAuth callback for {username}")
+            await anyio.sleep(0.5)
+
+        auth_code = auth_states[state]
+    finally:
+        await context.close()
+
+    # Exchange code for token
+    async with httpx.AsyncClient(timeout=30.0) as http_client:
+        token_response = await http_client.post(
+            token_endpoint,
+            data={
+                "grant_type": "authorization_code",
+                "code": auth_code,
+                "redirect_uri": callback_url,
+                "client_id": client_id,
+                "client_secret": client_secret,
+            },
+        )
+        token_response.raise_for_status()
+        return token_response.json()["access_token"]
+
+
+@pytest.fixture(scope="session")
+async def all_login_flow_user_tokens(
+    anyio_backend,
+    browser,
+    login_flow_oauth_client_credentials,
+    test_users_setup,
+    oauth_callback_server,
+) -> dict[str, str]:
+    """Fetch OAuth tokens for all test users in parallel, targeting port 8004."""
+    auth_states, _ = oauth_callback_server
+
+    start_time = time.time()
+    logger.info("Fetching login-flow OAuth tokens for all users in parallel...")
+
+    results: dict[str, str | Exception] = {}
+
+    async def _fetch(username: str, config: dict, delay: float) -> None:
+        if delay > 0:
+            await anyio.sleep(delay)
+        try:
+            token = await _get_login_flow_token_for_user(
+                browser,
+                login_flow_oauth_client_credentials,
+                auth_states,
+                username,
+                config["password"],
+            )
+            results[username] = token
+        except Exception as exc:
+            results[username] = exc
+
+    user_list = list(test_users_setup.items())
+    async with anyio.create_task_group() as tg:
+        for idx, (username, config) in enumerate(user_list):
+            tg.start_soon(_fetch, username, config, idx * 0.5)
+
+    for username, result in results.items():
+        if isinstance(result, Exception):
+            raise result
+
+    elapsed = time.time() - start_time
+    logger.info(
+        f"Fetched {len(results)} login-flow tokens in {elapsed:.1f}s "
+        f"(~{elapsed / len(results):.1f}s per user)"
+    )
+    return results  # type: ignore[return-value]
+
+
+async def _provision_login_flow_mcp_client(
+    token: str,
+    browser,
+    username: str,
+    password: str,
+) -> AsyncGenerator[ClientSession, Any]:
+    """Connect to login-flow MCP server, complete Login Flow v2 provisioning, yield session."""
+    login_url_holder: dict[str, str] = {}
+
+    async def elicitation_callback(
+        context: Any,
+        params: ElicitRequestParams,
+    ) -> ElicitResult:
+        message = params.message
+        for line in message.split("\n"):
+            stripped = line.strip()
+            if stripped.startswith("http") and "/login/v2/" in stripped:
+                login_url_holder["url"] = stripped
+                break
+
+        if "url" in login_url_holder:
+            await _complete_login_flow_v2_as_user(
+                browser, login_url_holder["url"], username, password
+            )
+
+        return ElicitResult(action="accept", content={"acknowledged": True})
+
+    async for session in create_mcp_client_session(
+        url=LOGIN_FLOW_MCP_URL,
+        token=token,
+        client_name=f"Login Flow MCP ({username})",
+        elicitation_callback=elicitation_callback,
+    ):
+        # Provision access
+        provision_result = await session.call_tool(
+            "nc_auth_provision_access", {"scopes": None}
+        )
+        provision_data = json.loads(provision_result.content[0].text)
+
+        if provision_data.get("status") == "login_required":
+            login_url = provision_data.get("login_url")
+            if login_url and "url" not in login_url_holder:
+                await _complete_login_flow_v2_as_user(
+                    browser, login_url, username, password
+                )
+
+        # Poll for completion
+        for attempt in range(15):
+            status_result = await session.call_tool("nc_auth_check_status", {})
+            status_data = json.loads(status_result.content[0].text)
+            if status_data.get("status") == "provisioned":
+                logger.info(
+                    f"Login Flow v2 provisioned for {username}: "
+                    f"{status_data.get('username')}"
+                )
+                break
+            if status_data.get("status") in ("not_initiated", "error"):
+                raise RuntimeError(
+                    f"Login Flow v2 failed for {username}: {status_data.get('message')}"
+                )
+            await anyio.sleep(2)
+        else:
+            raise TimeoutError(
+                f"Login Flow v2 did not complete for {username} after 15 attempts"
+            )
+
+        yield session
+
+
+async def _complete_login_flow_v2_as_user(
+    browser, login_url: str, username: str, password: str
+) -> None:
+    """Complete Nextcloud Login Flow v2 in a browser as a specific user.
+
+    Same steps as ``_complete_login_flow_v2`` but uses the given *username* and
+    *password* instead of reading from environment variables.
+    """
+    login_url = _rewrite_login_flow_url(login_url)
+
+    context = await browser.new_context(ignore_https_errors=True)
+    page = await context.new_page()
+
+    try:
+        logger.info(f"Opening Login Flow v2 URL for {username}: {login_url[:80]}...")
+        await page.goto(login_url, wait_until="networkidle", timeout=60000)
+
+        # Step 1: "Connect to your account" page
+        login_btn = page.get_by_role("button", name="Log in")
+        try:
+            await login_btn.wait_for(timeout=10000)
+            await login_btn.click()
+            await page.wait_for_load_state("networkidle", timeout=30000)
+        except Exception:
+            pass
+
+        # Step 2: Login form
+        user_field = page.locator('input[name="user"]')
+        if await user_field.count() > 0:
+            await user_field.fill(username)
+            await page.locator('input[name="password"]').fill(password)
+            await page.get_by_role("button", name="Log in", exact=True).click()
+            await page.wait_for_load_state("networkidle", timeout=60000)
+
+        # Step 3: "Account access" grant page
+        grant_btn = page.get_by_role("button", name="Grant access")
+        try:
+            await grant_btn.wait_for(timeout=15000)
+            await grant_btn.click()
+        except Exception:
+            pass
+
+        # Step 4: Password confirmation dialog
+        confirm_password = page.get_by_role("dialog").get_by_role(
+            "textbox", name="Password"
+        )
+        try:
+            await confirm_password.wait_for(timeout=10000)
+            await confirm_password.fill(password)
+            confirm_btn = page.get_by_role("dialog").get_by_role(
+                "button", name="Confirm"
+            )
+            await confirm_btn.wait_for(timeout=5000)
+            await confirm_btn.click()
+        except Exception:
+            pass
+
+        # Step 5: Wait for success
+        try:
+            await page.get_by_text("Account connected").wait_for(timeout=15000)
+            logger.info(f"Login Flow v2 completed for {username}")
+        except Exception:
+            await page.wait_for_load_state("networkidle", timeout=10000)
+            logger.info(f"Login Flow v2 done for {username}. URL: {page.url}")
+
+    finally:
+        await context.close()
+
+
+@pytest.fixture(scope="session")
+async def alice_login_flow_mcp_client(
+    anyio_backend,
+    all_login_flow_user_tokens: dict[str, str],
+    test_users_setup,
+    browser,
+) -> AsyncGenerator[ClientSession, Any]:
+    """MCP client authenticated and provisioned as alice (owner role)."""
+    async for session in _provision_login_flow_mcp_client(
+        token=all_login_flow_user_tokens["alice"],
+        browser=browser,
+        username="alice",
+        password=test_users_setup["alice"]["password"],
+    ):
+        yield session
+
+
+@pytest.fixture(scope="session")
+async def bob_login_flow_mcp_client(
+    anyio_backend,
+    all_login_flow_user_tokens: dict[str, str],
+    test_users_setup,
+    browser,
+) -> AsyncGenerator[ClientSession, Any]:
+    """MCP client authenticated and provisioned as bob (viewer role)."""
+    async for session in _provision_login_flow_mcp_client(
+        token=all_login_flow_user_tokens["bob"],
+        browser=browser,
+        username="bob",
+        password=test_users_setup["bob"]["password"],
+    ):
+        yield session
+
+
+@pytest.fixture(scope="session")
+async def charlie_login_flow_mcp_client(
+    anyio_backend,
+    all_login_flow_user_tokens: dict[str, str],
+    test_users_setup,
+    browser,
+) -> AsyncGenerator[ClientSession, Any]:
+    """MCP client authenticated and provisioned as charlie (editor role)."""
+    async for session in _provision_login_flow_mcp_client(
+        token=all_login_flow_user_tokens["charlie"],
+        browser=browser,
+        username="charlie",
+        password=test_users_setup["charlie"]["password"],
+    ):
+        yield session
+
+
+@pytest.fixture(scope="session")
+async def diana_login_flow_mcp_client(
+    anyio_backend,
+    all_login_flow_user_tokens: dict[str, str],
+    test_users_setup,
+    browser,
+) -> AsyncGenerator[ClientSession, Any]:
+    """MCP client authenticated and provisioned as diana (no-access role)."""
+    async for session in _provision_login_flow_mcp_client(
+        token=all_login_flow_user_tokens["diana"],
+        browser=browser,
+        username="diana",
+        password=test_users_setup["diana"]["password"],
+    ):
+        yield session
diff --git a/tests/server/login_flow/test_multi_user_permissions.py b/tests/server/login_flow/test_multi_user_permissions.py
new file mode 100644
index 00000000..a0faee00
--- /dev/null
+++ b/tests/server/login_flow/test_multi_user_permissions.py
@@ -0,0 +1,540 @@
+"""Multi-user permission tests for Login Flow v2 deployment mode.
+
+Tests verify that Nextcloud's sharing / ACL enforcement works correctly
+when resources are accessed through MCP tools by different users, each
+authenticated via Login Flow v2.
+
+Ported from the removed ``tests/server/oauth/test_oauth_*_permissions.py``
+tests.  The underlying assertions are deployment-mode-agnostic; only the
+transport changed (OAuth MCP server -> Login Flow v2 MCP server).
+"""
+
+import json
+import logging
+
+import pytest
+from mcp import ClientSession
+
+logger = logging.getLogger(__name__)
+
+pytestmark = [pytest.mark.integration, pytest.mark.login_flow]
+
+
+# ---------------------------------------------------------------------------
+# WebDAV / Files
+# ---------------------------------------------------------------------------
+
+
+class TestFilePermissions:
+    """Test that MCP file tools respect Nextcloud sharing permissions."""
+
+    async def test_file_share_read_permissions(
+        self,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+        diana_login_flow_mcp_client: ClientSession,
+    ):
+        """Alice shares a file with Bob (read-only).  Bob can read it;
+        Diana (unshared) cannot."""
+        file_path = "/alice_shared_file_read.txt"
+        file_content = "This file is shared with Bob for reading only."
+
+        # Alice creates the file
+        result = await alice_login_flow_mcp_client.call_tool(
+            "nc_webdav_write_file",
+            arguments={"path": file_path, "content": file_content},
+        )
+        assert not result.isError, f"Alice failed to create file: {result.content}"
+
+        share_id = None
+        try:
+            # Alice shares with Bob (read-only, permissions=1)
+            result = await alice_login_flow_mcp_client.call_tool(
+                "nc_share_create",
+                arguments={
+                    "path": file_path,
+                    "share_with": "bob",
+                    "share_type": 0,
+                    "permissions": 1,
+                },
+            )
+            assert not result.isError, f"Share creation failed: {result.content}"
+            share_data = json.loads(result.content[0].text)
+            share_id = share_data["id"]
+
+            # Bob reads the file
+            result = await bob_login_flow_mcp_client.call_tool(
+                "nc_webdav_read_file", arguments={"path": file_path}
+            )
+            assert not result.isError, (
+                f"Bob could not read shared file: {result.content}"
+            )
+            response_data = json.loads(result.content[0].text)
+            assert file_content in response_data["content"]
+
+            # Diana cannot read the file
+            result = await diana_login_flow_mcp_client.call_tool(
+                "nc_webdav_read_file", arguments={"path": file_path}
+            )
+            assert result.isError, "Diana should not be able to read unshared file"
+
+        finally:
+            if share_id:
+                await alice_login_flow_mcp_client.call_tool(
+                    "nc_share_delete", arguments={"share_id": share_id}
+                )
+            await alice_login_flow_mcp_client.call_tool(
+                "nc_webdav_delete_resource", arguments={"path": file_path}
+            )
+
+    async def test_file_share_write_permissions(
+        self,
+        alice_login_flow_mcp_client: ClientSession,
+        charlie_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+    ):
+        """Alice shares a file with Charlie (edit) and Bob (read-only).
+        Charlie can overwrite; Bob cannot."""
+        file_path = "/alice_shared_file_write.txt"
+        file_content = "This file is shared with Charlie for editing."
+
+        result = await alice_login_flow_mcp_client.call_tool(
+            "nc_webdav_write_file",
+            arguments={"path": file_path, "content": file_content},
+        )
+        assert not result.isError
+
+        charlie_share_id = None
+        bob_share_id = None
+        try:
+            # Share with Charlie (read+write, permissions=3)
+            result = await alice_login_flow_mcp_client.call_tool(
+                "nc_share_create",
+                arguments={
+                    "path": file_path,
+                    "share_with": "charlie",
+                    "share_type": 0,
+                    "permissions": 3,
+                },
+            )
+            assert not result.isError
+            charlie_share_id = json.loads(result.content[0].text)["id"]
+
+            # Share with Bob (read-only, permissions=1)
+            result = await alice_login_flow_mcp_client.call_tool(
+                "nc_share_create",
+                arguments={
+                    "path": file_path,
+                    "share_with": "bob",
+                    "share_type": 0,
+                    "permissions": 1,
+                },
+            )
+            assert not result.isError
+            bob_share_id = json.loads(result.content[0].text)["id"]
+
+            # Charlie can write
+            result = await charlie_login_flow_mcp_client.call_tool(
+                "nc_webdav_write_file",
+                arguments={
+                    "path": file_path,
+                    "content": f"{file_content}\nCharlie added this line.",
+                },
+            )
+            assert not result.isError, (
+                f"Charlie should be able to write: {result.content}"
+            )
+
+            # Bob cannot write
+            result = await bob_login_flow_mcp_client.call_tool(
+                "nc_webdav_write_file",
+                arguments={
+                    "path": file_path,
+                    "content": "Bob tries to overwrite this.",
+                },
+            )
+            assert result.isError, "Bob should be denied write access (read-only)"
+
+        finally:
+            for sid in (charlie_share_id, bob_share_id):
+                if sid:
+                    await alice_login_flow_mcp_client.call_tool(
+                        "nc_share_delete", arguments={"share_id": sid}
+                    )
+            await alice_login_flow_mcp_client.call_tool(
+                "nc_webdav_delete_resource", arguments={"path": file_path}
+            )
+
+    async def test_folder_share_permissions(
+        self,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+    ):
+        """Alice shares a folder with Bob; Bob can list and read its contents."""
+        folder_path = "/alice_shared_folder"
+        file_in_folder = f"{folder_path}/document.txt"
+        file_content = "Document in Alice's shared folder"
+
+        result = await alice_login_flow_mcp_client.call_tool(
+            "nc_webdav_create_directory", arguments={"path": folder_path}
+        )
+        assert not result.isError
+
+        result = await alice_login_flow_mcp_client.call_tool(
+            "nc_webdav_write_file",
+            arguments={"path": file_in_folder, "content": file_content},
+        )
+        assert not result.isError
+
+        share_id = None
+        try:
+            result = await alice_login_flow_mcp_client.call_tool(
+                "nc_share_create",
+                arguments={
+                    "path": folder_path,
+                    "share_with": "bob",
+                    "share_type": 0,
+                    "permissions": 1,
+                },
+            )
+            assert not result.isError
+            share_id = json.loads(result.content[0].text)["id"]
+
+            # Bob lists the shared folder
+            result = await bob_login_flow_mcp_client.call_tool(
+                "nc_webdav_list_directory", arguments={"path": folder_path}
+            )
+            assert not result.isError, f"Bob should see shared folder: {result.content}"
+            response_data = json.loads(result.content[0].text)
+            file_names = [f["name"] for f in response_data.get("files", [])]
+            assert "document.txt" in file_names
+
+            # Bob reads the file
+            result = await bob_login_flow_mcp_client.call_tool(
+                "nc_webdav_read_file", arguments={"path": file_in_folder}
+            )
+            assert not result.isError
+            assert file_content in json.loads(result.content[0].text)["content"]
+
+        finally:
+            if share_id:
+                await alice_login_flow_mcp_client.call_tool(
+                    "nc_share_delete", arguments={"share_id": share_id}
+                )
+            await alice_login_flow_mcp_client.call_tool(
+                "nc_webdav_delete_resource", arguments={"path": folder_path}
+            )
+
+    async def test_user_isolation_files(
+        self,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+    ):
+        """Users can only see their own files when nothing is shared."""
+        alice_file = "/alice_private_file.txt"
+        bob_file = "/bob_private_file.txt"
+
+        # Each user creates their own file
+        result = await alice_login_flow_mcp_client.call_tool(
+            "nc_webdav_write_file",
+            arguments={"path": alice_file, "content": "Alice's private file"},
+        )
+        assert not result.isError
+
+        result = await bob_login_flow_mcp_client.call_tool(
+            "nc_webdav_write_file",
+            arguments={"path": bob_file, "content": "Bob's private file"},
+        )
+        assert not result.isError
+
+        try:
+            # Bob lists root — should NOT see Alice's file
+            result = await bob_login_flow_mcp_client.call_tool(
+                "nc_webdav_list_directory", arguments={"path": "/"}
+            )
+            assert not result.isError
+            bob_visible = [
+                f["name"] for f in json.loads(result.content[0].text).get("files", [])
+            ]
+            assert "alice_private_file.txt" not in bob_visible, (
+                "Bob should not see Alice's private file"
+            )
+
+            # Alice lists root — should NOT see Bob's file
+            result = await alice_login_flow_mcp_client.call_tool(
+                "nc_webdav_list_directory", arguments={"path": "/"}
+            )
+            assert not result.isError
+            alice_visible = [
+                f["name"] for f in json.loads(result.content[0].text).get("files", [])
+            ]
+            assert "bob_private_file.txt" not in alice_visible, (
+                "Alice should not see Bob's private file"
+            )
+
+        finally:
+            await alice_login_flow_mcp_client.call_tool(
+                "nc_webdav_delete_resource", arguments={"path": alice_file}
+            )
+            await bob_login_flow_mcp_client.call_tool(
+                "nc_webdav_delete_resource", arguments={"path": bob_file}
+            )
+
+
+# ---------------------------------------------------------------------------
+# Deck
+# ---------------------------------------------------------------------------
+
+
+class TestDeckPermissions:
+    """Test that MCP Deck tools respect board ACL permissions."""
+
+    async def _add_board_acl(
+        self, nc_client, board_id: int, user: str, permission_type: int = 0
+    ) -> int:
+        """Add ACL entry.  permission_type: 0=view, 1=edit, 2=manage."""
+        acl = await nc_client.deck.add_acl_rule(
+            board_id=board_id,
+            type=0,
+            participant=user,
+            permission_edit=permission_type >= 1,
+            permission_share=permission_type >= 2,
+            permission_manage=permission_type >= 2,
+        )
+        return acl.id
+
+    async def test_deck_board_view_permissions(
+        self,
+        nc_client,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+        diana_login_flow_mcp_client: ClientSession,
+    ):
+        """Admin creates a board, adds Bob (view). Bob can see it; Diana cannot."""
+        board = await nc_client.deck.create_board("Shared Board - View Test", "FF0000")
+        board_id = board.id
+        bob_acl_id = None
+
+        try:
+            bob_acl_id = await self._add_board_acl(nc_client, board_id, "bob", 0)
+
+            # Bob can see the board
+            result = await bob_login_flow_mcp_client.call_tool(
+                "deck_get_boards", arguments={}
+            )
+            assert not result.isError
+            board_ids = [
+                b["id"] for b in json.loads(result.content[0].text).get("boards", [])
+            ]
+            assert board_id in board_ids, "Bob should see shared board"
+
+            # Diana cannot see the board
+            result = await diana_login_flow_mcp_client.call_tool(
+                "deck_get_boards", arguments={}
+            )
+            assert not result.isError
+            board_ids = [
+                b["id"] for b in json.loads(result.content[0].text).get("boards", [])
+            ]
+            assert board_id not in board_ids, "Diana should not see board without ACL"
+
+        finally:
+            if bob_acl_id:
+                await nc_client.deck.delete_acl_rule(board_id, bob_acl_id)
+            await nc_client.deck.delete_board(board_id)
+
+    async def test_deck_board_edit_permissions(
+        self,
+        nc_client,
+        charlie_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+    ):
+        """Charlie (edit) can create cards; Bob (view-only) cannot."""
+        board = await nc_client.deck.create_board("Shared Board - Edit Test", "00FF00")
+        board_id = board.id
+        stack = await nc_client.deck.create_stack(board_id, "Test Stack", 1)
+        stack_id = stack.id
+        charlie_acl_id = None
+        bob_acl_id = None
+
+        try:
+            charlie_acl_id = await self._add_board_acl(
+                nc_client, board_id, "charlie", 1
+            )
+            bob_acl_id = await self._add_board_acl(nc_client, board_id, "bob", 0)
+
+            # Charlie creates a card
+            result = await charlie_login_flow_mcp_client.call_tool(
+                "deck_create_card",
+                arguments={
+                    "board_id": board_id,
+                    "stack_id": stack_id,
+                    "title": "Charlie's Card",
+                    "description": "Created by Charlie with edit permission",
+                },
+            )
+            assert not result.isError, f"Charlie should create cards: {result.content}"
+            card_id = json.loads(result.content[0].text).get("id")
+            if card_id:
+                await nc_client.deck.delete_card(board_id, stack_id, card_id)
+
+            # Bob cannot create a card
+            result = await bob_login_flow_mcp_client.call_tool(
+                "deck_create_card",
+                arguments={
+                    "board_id": board_id,
+                    "stack_id": stack_id,
+                    "title": "Bob's Card",
+                    "description": "Bob trying to create a card",
+                },
+            )
+            assert result.isError, "Bob should be denied card creation (view-only)"
+
+        finally:
+            for acl_id in (charlie_acl_id, bob_acl_id):
+                if acl_id:
+                    await nc_client.deck.delete_acl_rule(board_id, acl_id)
+            await nc_client.deck.delete_board(board_id)
+
+    async def test_deck_user_isolation(
+        self,
+        nc_client,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+    ):
+        """Users can only see their own boards when nothing is shared."""
+        alice_board = await nc_client.deck.create_board(
+            "Alice's Private Board", "FF00FF"
+        )
+        bob_board = await nc_client.deck.create_board("Bob's Private Board", "00FFFF")
+
+        try:
+            # Alice should NOT see Bob's board
+            result = await alice_login_flow_mcp_client.call_tool(
+                "deck_get_boards", arguments={}
+            )
+            assert not result.isError
+            board_ids = [
+                b["id"] for b in json.loads(result.content[0].text).get("boards", [])
+            ]
+            assert bob_board.id not in board_ids, (
+                "Alice should not see Bob's private board"
+            )
+
+            # Bob should NOT see Alice's board
+            result = await bob_login_flow_mcp_client.call_tool(
+                "deck_get_boards", arguments={}
+            )
+            assert not result.isError
+            board_ids = [
+                b["id"] for b in json.loads(result.content[0].text).get("boards", [])
+            ]
+            assert alice_board.id not in board_ids, (
+                "Bob should not see Alice's private board"
+            )
+
+        finally:
+            await nc_client.deck.delete_board(alice_board.id)
+            await nc_client.deck.delete_board(bob_board.id)
+
+
+# ---------------------------------------------------------------------------
+# Notes
+# ---------------------------------------------------------------------------
+
+
+class TestNotesPermissions:
+    """Test that MCP Notes tools respect user isolation.
+
+    Nextcloud Notes are inherently single-user (no sharing API). These tests
+    verify that notes created by one user are invisible to others.
+    """
+
+    async def test_user_isolation_notes(
+        self,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+    ):
+        """Notes created by Alice are invisible to Bob and vice versa."""
+        # Alice creates a note
+        result = await alice_login_flow_mcp_client.call_tool(
+            "nc_notes_create_note",
+            arguments={
+                "title": "Alice's Private Note",
+                "content": "This is Alice's private content.",
+                "category": "PermTest",
+            },
+        )
+        assert not result.isError
+        alice_note_id = json.loads(result.content[0].text)["id"]
+
+        # Bob creates a note
+        result = await bob_login_flow_mcp_client.call_tool(
+            "nc_notes_create_note",
+            arguments={
+                "title": "Bob's Private Note",
+                "content": "This is Bob's private content.",
+                "category": "PermTest",
+            },
+        )
+        assert not result.isError
+        bob_note_id = json.loads(result.content[0].text)["id"]
+
+        try:
+            # Alice searches — should NOT see Bob's note
+            result = await alice_login_flow_mcp_client.call_tool(
+                "nc_notes_search_notes", arguments={"query": "PermTest"}
+            )
+            assert not result.isError
+            alice_visible_ids = [
+                n["id"] for n in json.loads(result.content[0].text).get("results", [])
+            ]
+            assert bob_note_id not in alice_visible_ids, (
+                "Alice should not see Bob's private note"
+            )
+
+            # Bob searches — should NOT see Alice's note
+            result = await bob_login_flow_mcp_client.call_tool(
+                "nc_notes_search_notes", arguments={"query": "PermTest"}
+            )
+            assert not result.isError
+            bob_visible_ids = [
+                n["id"] for n in json.loads(result.content[0].text).get("results", [])
+            ]
+            assert alice_note_id not in bob_visible_ids, (
+                "Bob should not see Alice's private note"
+            )
+
+        finally:
+            await alice_login_flow_mcp_client.call_tool(
+                "nc_notes_delete_note", arguments={"note_id": alice_note_id}
+            )
+            await bob_login_flow_mcp_client.call_tool(
+                "nc_notes_delete_note", arguments={"note_id": bob_note_id}
+            )
+
+
+# ---------------------------------------------------------------------------
+# Smoke: all multi-user clients initialised
+# ---------------------------------------------------------------------------
+
+
+class TestMultiUserSmoke:
+    """Quick check that all multi-user MCP clients are functional."""
+
+    async def test_all_clients_can_list_tools(
+        self,
+        alice_login_flow_mcp_client: ClientSession,
+        bob_login_flow_mcp_client: ClientSession,
+        charlie_login_flow_mcp_client: ClientSession,
+        diana_login_flow_mcp_client: ClientSession,
+    ):
+        for name, client in [
+            ("alice", alice_login_flow_mcp_client),
+            ("bob", bob_login_flow_mcp_client),
+            ("charlie", charlie_login_flow_mcp_client),
+            ("diana", diana_login_flow_mcp_client),
+        ]:
+            tools = await client.list_tools()
+            assert len(tools.tools) > 0, f"{name} MCP client has no tools"
+            logger.info(f"{name} MCP client working ({len(tools.tools)} tools)")