diff --git a/nextcloud_mcp_server/auth/browser_oauth_routes.py b/nextcloud_mcp_server/auth/browser_oauth_routes.py
index cb0b33e9..58bb3d95 100644
--- a/nextcloud_mcp_server/auth/browser_oauth_routes.py
+++ b/nextcloud_mcp_server/auth/browser_oauth_routes.py
@@ -407,11 +407,11 @@ async def oauth_login_callback(request: Request) -> RedirectResponse | HTMLRespo
         else:
             # Integrated mode (Nextcloud OIDC)
             discovery_url = oauth_config.get("discovery_url")
-            async with nextcloud_httpx_client() as http_client:
-                response = await http_client.get(discovery_url)
-                response.raise_for_status()
-                discovery = response.json()
-                token_endpoint = discovery["token_endpoint"]
+            # Use the shared 5-minute discovery cache; oauth_login() above
+            # has already populated it for this discovery_url so the
+            # callback should hit the cache rather than re-fetching.
+            discovery = await get_oidc_discovery(discovery_url)
+            token_endpoint = discovery["token_endpoint"]
 
             token_params = {
                 "grant_type": "authorization_code",
diff --git a/nextcloud_mcp_server/auth/oauth_routes.py b/nextcloud_mcp_server/auth/oauth_routes.py
index 2f6de955..db55cb3f 100644
--- a/nextcloud_mcp_server/auth/oauth_routes.py
+++ b/nextcloud_mcp_server/auth/oauth_routes.py
@@ -38,6 +38,7 @@ from nextcloud_mcp_server.auth.client_registry import get_client_registry
 from nextcloud_mcp_server.auth.storage import RefreshTokenStorage
 from nextcloud_mcp_server.auth.token_utils import (
     IdTokenVerificationError,
+    get_oidc_discovery,
     verify_id_token,
 )
 from nextcloud_mcp_server.config import get_settings
@@ -91,6 +92,7 @@ class ASProxySession:
     code_challenge: str
     code_challenge_method: str
     requested_scopes: str
+    nonce: str = ""
     created_at: float = field(default_factory=time.time)
     expires_at: float = field(default_factory=lambda: time.time() + 600)
 
@@ -103,10 +105,6 @@ class ASProxySession:
 _proxy_codes: dict[str, ProxyCodeEntry] = {}
 _as_proxy_sessions: dict[str, ASProxySession] = {}
 
-# OIDC discovery document cache (URL → (expires_at, data))
-_discovery_cache: dict[str, tuple[float, dict[str, Any]]] = {}
-_DISCOVERY_CACHE_TTL = 300  # 5 minutes
-
 # DCR rate limiting (IP → [timestamps])
 _dcr_rate_limit: dict[str, list[float]] = {}
 _DCR_RATE_LIMIT_MAX = 10  # max requests
@@ -138,26 +136,6 @@ def _transform_scopes_for_idp(scopes: str, resource_server_id: str) -> str:
     )
 
 
-async def _get_cached_discovery(url: str) -> dict[str, Any]:
-    """Fetch OIDC discovery document with caching (5-minute TTL).
-
-    Follows redirects so the configured discovery URL works against Nextcloud
-    instances without pretty URLs enabled, where ``/.well-known/openid-configuration``
-    issues a 301 to ``/index.php/.well-known/openid-configuration``.
-    """
-    now = time.time()
-    if url in _discovery_cache:
-        expires_at, data = _discovery_cache[url]
-        if now < expires_at:
-            return data
-    async with nextcloud_httpx_client(follow_redirects=True) as http_client:
-        response = await http_client.get(url)
-        response.raise_for_status()
-        data = response.json()
-    _discovery_cache[url] = (now + _DISCOVERY_CACHE_TTL, data)
-    return data
-
-
 def _cleanup_expired_proxy_codes() -> None:
     """Remove expired proxy codes and sessions."""
     now = time.time()
@@ -316,6 +294,10 @@ async def oauth_authorize(request: Request) -> RedirectResponse | JSONResponse:
     # We do NOT forward PKCE to Nextcloud — the MCP server is a confidential client.
     server_state = secrets.token_urlsafe(32)
 
+    # OIDC nonce binds the IdP's ID token to THIS authorization request,
+    # blocking ID-token replay across flows (PR #758 round-2 finding 2).
+    server_nonce = secrets.token_urlsafe(32)
+
     requested_scope = request.query_params.get("scope", "")
     default_scopes = "openid profile email"
     resource_scopes = oauth_config.get("scopes", "")
@@ -333,6 +315,7 @@ async def oauth_authorize(request: Request) -> RedirectResponse | JSONResponse:
         code_challenge=code_challenge,
         code_challenge_method=code_challenge_method,
         requested_scopes=scopes,
+        nonce=server_nonce,
     )
 
     # Use MCP server's own client_id with Nextcloud
@@ -359,7 +342,7 @@ async def oauth_authorize(request: Request) -> RedirectResponse | JSONResponse:
             status_code=500,
         )
 
-    discovery = await _get_cached_discovery(discovery_url)
+    discovery = await get_oidc_discovery(discovery_url)
     authorization_endpoint = discovery["authorization_endpoint"]
 
     # Replace internal Docker hostname with public URL for browser access
@@ -395,6 +378,7 @@ async def oauth_authorize(request: Request) -> RedirectResponse | JSONResponse:
         "response_type": "code",
         "scope": idp_scope_str,
         "state": server_state,
+        "nonce": server_nonce,
         "prompt": "consent",
         "resource": f"{mcp_server_url}/mcp",  # MCP server audience
     }
@@ -469,7 +453,7 @@ async def oauth_authorize_nextcloud(
         # supporting the offline_access scope.
         discovery_url = oauth_config.get("discovery_url")
         if discovery_url:
-            disc = await _get_cached_discovery(discovery_url)
+            disc = await get_oidc_discovery(discovery_url)
             scopes_supported = disc.get("scopes_supported")
             if scopes_supported is None or "offline_access" in scopes_supported:
                 scopes += " offline_access"
@@ -506,7 +490,7 @@ async def oauth_authorize_nextcloud(
             status_code=500,
         )
 
-    discovery = await _get_cached_discovery(discovery_url)
+    discovery = await get_oidc_discovery(discovery_url)
     authorization_endpoint = discovery["authorization_endpoint"]
 
     # Fix internal hostname for browser access
@@ -623,7 +607,7 @@ async def oauth_callback_nextcloud(request: Request):
             status_code=500,
         )
 
-    discovery = await _get_cached_discovery(discovery_url)
+    discovery = await get_oidc_discovery(discovery_url)
     token_endpoint = discovery["token_endpoint"]
 
     # Build token exchange params
@@ -917,7 +901,7 @@ async def _oauth_callback_as_proxy(
             status_code=500,
         )
 
-    discovery = await _get_cached_discovery(discovery_url)
+    discovery = await get_oidc_discovery(discovery_url)
     token_endpoint = discovery["token_endpoint"]
 
     # Exchange auth code with Nextcloud (server-side, confidential client, no PKCE)
@@ -959,12 +943,18 @@ async def _oauth_callback_as_proxy(
     # transport could plant arbitrary identity claims into the proxy code
     # entry that gets handed back to the MCP client. Mirrors the
     # verification done in oauth_callback_nextcloud.
+    #
+    # ``expected_nonce`` is the per-request nonce we forwarded to the IdP
+    # in oauth_authorize (PR #758 round-2 finding 2); falsy → skip nonce
+    # check for backward compatibility with sessions stored before the
+    # nonce field was added.
     id_token = nc_token_response.get("id_token")
     try:
         await verify_id_token(
             id_token,
             discovery_url=discovery_url,
             expected_audience=mcp_server_client_id,
+            expected_nonce=session.nonce or None,
         )
     except IdTokenVerificationError as e:
         logger.error("AS proxy: ID token verification failed: %s", e)
@@ -1252,7 +1242,7 @@ async def _token_refresh(request: Request, form) -> JSONResponse:
             status_code=500,
         )
 
-    discovery = await _get_cached_discovery(discovery_url)
+    discovery = await get_oidc_discovery(discovery_url)
     token_endpoint = discovery["token_endpoint"]
 
     # Proxy refresh request to Nextcloud
@@ -1341,7 +1331,7 @@ async def oauth_register_proxy(request: Request) -> JSONResponse:
     registration_endpoint = None
     if discovery_url:
         try:
-            discovery = await _get_cached_discovery(discovery_url)
+            discovery = await get_oidc_discovery(discovery_url)
             registration_endpoint = discovery.get("registration_endpoint")
         except Exception:
             logger.warning("Failed to fetch OIDC discovery for DCR endpoint")
diff --git a/nextcloud_mcp_server/auth/token_utils.py b/nextcloud_mcp_server/auth/token_utils.py
index 7903ac34..95364ab0 100644
--- a/nextcloud_mcp_server/auth/token_utils.py
+++ b/nextcloud_mcp_server/auth/token_utils.py
@@ -21,10 +21,11 @@ from ..http import nextcloud_httpx_client
 logger = logging.getLogger(__name__)
 
 
-# OIDC discovery + JWKS caches keyed by URL → (expires_at, data). Mirrors the
-# pattern in oauth_routes._get_cached_discovery so that ID-token verification
-# during the OAuth callback doesn't make two extra round-trips per login (PR
-# #758 finding 4). 5-minute TTL matches oauth_routes.
+# OIDC discovery + JWKS caches keyed by URL → (expires_at, data). Single
+# source of truth for the codebase: oauth_routes / browser_oauth_routes both
+# go through ``get_oidc_discovery`` which reads/writes _discovery_cache, so
+# the first discovery fetch primes the cache for all later callers (PR #758
+# round-2 nit 3). 5-minute TTL.
 _discovery_cache: dict[str, tuple[float, dict[str, Any]]] = {}
 _jwks_cache: dict[str, tuple[float, dict[str, Any]]] = {}
 _OIDC_CACHE_TTL = 300
@@ -35,16 +36,26 @@ class IdTokenVerificationError(Exception):
 
 
 async def _get_cached(
-    cache: dict[str, tuple[float, dict[str, Any]]], url: str
+    cache: dict[str, tuple[float, dict[str, Any]]],
+    url: str,
+    *,
+    follow_redirects: bool = False,
 ) -> dict[str, Any]:
-    """Return cached JSON response for *url* or fetch + cache on miss/expiry."""
+    """Return cached JSON response for *url* or fetch + cache on miss/expiry.
+
+    ``follow_redirects`` is forwarded to ``nextcloud_httpx_client``: discovery
+    fetches against Nextcloud without pretty URLs need it (the configured
+    ``/.well-known/openid-configuration`` path issues a 301), but JWKS
+    fetches deliberately stay strict — the URL came from the discovery
+    document we already trust, so a redirect there would be suspicious.
+    """
     now = time.time()
     entry = cache.get(url)
     if entry is not None:
         expires_at, data = entry
         if now < expires_at:
             return data
-    async with nextcloud_httpx_client() as http_client:
+    async with nextcloud_httpx_client(follow_redirects=follow_redirects) as http_client:
         response = await http_client.get(url)
         response.raise_for_status()
         data = response.json()
@@ -57,10 +68,13 @@ async def get_oidc_discovery(discovery_url: str) -> dict[str, Any]:
 
     Shares the 5-minute discovery cache used by `verify_id_token`, so a
     callback that does discovery → token-exchange → ID-token verification
-    reuses one HTTP round-trip instead of three. Public alias for `_get_cached`
-    against `_discovery_cache` (PR #758 nits 5 & 6).
+    reuses one HTTP round-trip instead of three. The fetch follows
+    redirects because Nextcloud without pretty URLs returns 301 from
+    ``/.well-known/openid-configuration`` to ``/index.php/.well-known/...``.
+    Single source of truth for OIDC discovery in the codebase
+    (PR #758 round-2 nit 3).
     """
-    return await _get_cached(_discovery_cache, discovery_url)
+    return await _get_cached(_discovery_cache, discovery_url, follow_redirects=True)
 
 
 async def verify_id_token(
@@ -103,7 +117,7 @@ async def verify_id_token(
         raise IdTokenVerificationError("ID token missing from token response")
 
     try:
-        discovery = await _get_cached(_discovery_cache, discovery_url)
+        discovery = await get_oidc_discovery(discovery_url)
 
         issuer = discovery.get("issuer")
         jwks_uri = discovery.get("jwks_uri")
diff --git a/nextcloud_mcp_server/server/oauth_tools.py b/nextcloud_mcp_server/server/oauth_tools.py
index 1ae62e79..ea7ee0b0 100644
--- a/nextcloud_mcp_server/server/oauth_tools.py
+++ b/nextcloud_mcp_server/server/oauth_tools.py
@@ -105,8 +105,12 @@ async def get_provisioning_status(ctx: Context, user_id: str) -> ProvisioningSta
             status = await astrolabe.get_background_sync_status(user_id)
 
             if status.get("has_access"):
-                logger.info(
-                    f"  get_provisioning_status: ✓ App password FOUND for user_id={user_id}"
+                # Demoted to debug (PR #758 round-2 nit 4): user_id ends up
+                # in log aggregation on every call, which is noise in a
+                # multi-tenant deployment.
+                logger.debug(
+                    "  get_provisioning_status: app password FOUND for user_id=%s",
+                    user_id,
                 )
                 provisioned_at_str = status.get("provisioned_at")
                 return ProvisioningStatus(
@@ -115,28 +119,28 @@ async def get_provisioning_status(ctx: Context, user_id: str) -> ProvisioningSta
                     credential_type="app_password",
                 )
         except Exception as e:
-            logger.debug(f"  App password check failed for {user_id}: {e}")
+            logger.debug("  App password check failed for %s: %s", user_id, e)
 
     # Check for OAuth refresh token (fallback)
-    logger.info(
-        f"  get_provisioning_status: Looking up refresh token for user_id={user_id}"
+    logger.debug(
+        "  get_provisioning_status: looking up refresh token for user_id=%s", user_id
     )
     storage = await get_shared_storage()
 
     token_data = await storage.get_refresh_token(user_id)
 
     if not token_data:
-        logger.info(
-            f"  get_provisioning_status: ✗ No credentials found for user_id={user_id}"
+        logger.debug(
+            "  get_provisioning_status: no credentials found for user_id=%s", user_id
         )
         return ProvisioningStatus(is_provisioned=False)
 
-    logger.info(
-        f"  get_provisioning_status: ✓ Refresh token FOUND for user_id={user_id}"
-    )
-    logger.info(f"    flow_type: {token_data.get('flow_type')}")
-    logger.info(
-        f"    provisioning_client_id: {token_data.get('provisioning_client_id', 'N/A')}"
+    logger.debug(
+        "  get_provisioning_status: refresh token FOUND for user_id=%s "
+        "flow_type=%s provisioning_client_id=%s",
+        user_id,
+        token_data.get("flow_type"),
+        token_data.get("provisioning_client_id", "N/A"),
     )
 
     # Convert timestamp to ISO format if present
@@ -370,18 +374,22 @@ async def check_logged_in(ctx: Context, user_id: str) -> str:
         "yes" if logged in, or elicitation prompting for login
     """
     try:
-        # Check if already logged in
-        logger.info(f"Checking provisioning status for user_id: {user_id}")
+        # Demoted to debug (PR #758 round-2 nit 4): per-user logging at INFO
+        # ends up in log aggregation on every check_logged_in call, which is
+        # noise in a hosted multi-tenant deployment.
+        logger.debug("Checking provisioning status for user_id=%s", user_id)
         status = await get_provisioning_status(ctx, user_id)
-        logger.info(f"  Provisioning status: is_provisioned={status.is_provisioned}")
+        logger.debug(
+            "  Provisioning status for %s: is_provisioned=%s",
+            user_id,
+            status.is_provisioned,
+        )
 
         if status.is_provisioned:
-            logger.info(f"✓ User {user_id} is already logged in - returning 'yes'")
-            logger.info("=" * 60)
+            logger.debug("User %s already logged in", user_id)
             return "yes"
 
-        logger.info(f"✗ User {user_id} is NOT logged in - triggering elicitation")
-        logger.info("=" * 60)
+        logger.debug("User %s NOT logged in — triggering elicitation", user_id)
 
         # Not logged in - generate OAuth URL for Flow 2
         # Use settings (handles both ENABLE_BACKGROUND_OPERATIONS and ENABLE_OFFLINE_ACCESS)
@@ -462,8 +470,11 @@ async def check_logged_in(ctx: Context, user_id: str) -> str:
             scopes=scopes,
         )
 
-        # Use elicitation to prompt user to login
-        logger.info(f"Eliciting login for user {user_id} with URL: {auth_url}")
+        # Use elicitation to prompt user to login. Logged at debug (PR #758
+        # round-2 nit 4): the auth URL contains the per-request ``state``
+        # token, which is sensitive enough that it shouldn't land in
+        # multi-tenant log aggregation by default.
+        logger.debug("Eliciting login for user %s (URL omitted)", user_id)
 
         result = await ctx.elicit(
             message=f"Please log in to Nextcloud at the following URL:\n\n{auth_url}\n\nAfter completing the login, check the box below and click OK.",
@@ -472,10 +483,15 @@ async def check_logged_in(ctx: Context, user_id: str) -> str:
 
         if result.action == "accept":
             # Check if login was successful by looking for refresh token
-            # Strategy: Try multiple lookup methods to handle both flows
-            logger.info("User accepted login prompt, checking for refresh token")
-            logger.info(f"  State parameter: {state[:16]}...")
-            logger.info(f"  User ID: {user_id}")
+            # Strategy: Try multiple lookup methods to handle both flows.
+            # Demoted to debug (PR #758 round-2 nit 4): user_id + state
+            # appear here on every elicitation accept.
+            logger.debug(
+                "User accepted login prompt; looking up refresh token "
+                "(user_id=%s state=%s...)",
+                user_id,
+                state[:16],
+            )
 
             # First, try to find token by provisioning_client_id (Flow 2 from elicitation)
             refresh_token_data = (
@@ -483,45 +499,39 @@ async def check_logged_in(ctx: Context, user_id: str) -> str:
             )
 
             if refresh_token_data:
-                logger.info("✓ Refresh token found via provisioning_client_id lookup")
-                logger.info(
-                    f"  Flow type: {refresh_token_data.get('flow_type', 'unknown')}"
-                )
-                logger.info(
-                    f"  Provisioned at: {refresh_token_data.get('provisioned_at', 'unknown')}"
+                logger.debug(
+                    "Refresh token found via provisioning_client_id lookup "
+                    "(flow_type=%s provisioned_at=%s)",
+                    refresh_token_data.get("flow_type", "unknown"),
+                    refresh_token_data.get("provisioned_at", "unknown"),
                 )
                 return "yes"
 
             # Fallback: Try to find token by user_id (browser login or any other flow)
-            logger.info(f"✗ No token found with provisioning_client_id={state[:16]}...")
-            logger.info(f"  Trying fallback lookup by user_id: {user_id}")
+            logger.debug(
+                "No token via provisioning_client_id=%s...; falling back to user_id=%s",
+                state[:16],
+                user_id,
+            )
 
             refresh_token_data = await storage.get_refresh_token(user_id)
 
             if refresh_token_data:
-                logger.info("✓ Refresh token found via user_id lookup")
-                logger.info(
-                    f"  Flow type: {refresh_token_data.get('flow_type', 'unknown')}"
-                )
-                logger.info(
-                    f"  Provisioned at: {refresh_token_data.get('provisioned_at', 'unknown')}"
-                )
-                logger.info(
-                    f"  Provisioning client ID: {refresh_token_data.get('provisioning_client_id', 'NULL')}"
-                )
-                logger.info(
-                    "  Note: This token was created via browser login or different flow"
+                logger.debug(
+                    "Refresh token found via user_id lookup "
+                    "(flow_type=%s provisioned_at=%s provisioning_client_id=%s)",
+                    refresh_token_data.get("flow_type", "unknown"),
+                    refresh_token_data.get("provisioned_at", "unknown"),
+                    refresh_token_data.get("provisioning_client_id", "NULL"),
                 )
                 return "yes"
 
             # No token found by either method
-            logger.warning(f"✗ No refresh token found for user {user_id}")
             logger.warning(
-                f"  Checked provisioning_client_id={state[:16]}... - NOT FOUND"
-            )
-            logger.warning(f"  Checked user_id={user_id} - NOT FOUND")
-            logger.warning(
-                "  This may indicate the user completed login but token wasn't stored"
+                "No refresh token found for user_id=%s (checked provisioning_client_id=%s... and user_id) — "
+                "user completed elicitation but token wasn't stored",
+                user_id,
+                state[:16],
             )
 
             return (
diff --git a/tests/unit/test_browser_oauth_xss.py b/tests/unit/test_browser_oauth_xss.py
index 13903dcf..8b82b483 100644
--- a/tests/unit/test_browser_oauth_xss.py
+++ b/tests/unit/test_browser_oauth_xss.py
@@ -15,6 +15,7 @@ import httpx
 import pytest
 from cryptography.fernet import Fernet
 
+from nextcloud_mcp_server.auth import token_utils
 from nextcloud_mcp_server.auth.browser_oauth_routes import oauth_login_callback
 from nextcloud_mcp_server.auth.storage import RefreshTokenStorage
 
@@ -24,6 +25,14 @@ pytestmark = pytest.mark.unit
 XSS_PAYLOAD = "<script>alert(1)</script>"
 
 
+@pytest.fixture(autouse=True)
+def _clear_oidc_discovery_cache():
+    """Reset the shared discovery cache between tests."""
+    token_utils._discovery_cache.clear()
+    yield
+    token_utils._discovery_cache.clear()
+
+
 @pytest.fixture
 async def storage():
     with tempfile.TemporaryDirectory() as tmpdir:
@@ -109,9 +118,18 @@ async def test_callback_escapes_idp_http_error_body(storage):
         },
     )
 
-    with patch(
-        "nextcloud_mcp_server.auth.browser_oauth_routes.nextcloud_httpx_client",
-        side_effect=fake_client,
+    # Discovery now goes through token_utils.get_oidc_discovery (PR #758
+    # round-2 nit 3); token-exchange POST still uses browser_oauth_routes'
+    # httpx client.
+    with (
+        patch(
+            "nextcloud_mcp_server.auth.browser_oauth_routes.nextcloud_httpx_client",
+            side_effect=fake_client,
+        ),
+        patch(
+            "nextcloud_mcp_server.auth.token_utils.nextcloud_httpx_client",
+            side_effect=fake_client,
+        ),
     ):
         response = await oauth_login_callback(request)
 
diff --git a/tests/unit/test_dcr_proxy.py b/tests/unit/test_dcr_proxy.py
index 07eed461..621ef299 100644
--- a/tests/unit/test_dcr_proxy.py
+++ b/tests/unit/test_dcr_proxy.py
@@ -42,7 +42,7 @@ async def test_registration_not_supported_when_no_endpoint():
     }
 
     with patch(
-        "nextcloud_mcp_server.auth.oauth_routes._get_cached_discovery",
+        "nextcloud_mcp_server.auth.oauth_routes.get_oidc_discovery",
         new_callable=AsyncMock,
         return_value=discovery_doc,
     ):
diff --git a/tests/unit/test_oauth_callback_session_cleanup.py b/tests/unit/test_oauth_callback_session_cleanup.py
index 1f84f678..7ad2efbe 100644
--- a/tests/unit/test_oauth_callback_session_cleanup.py
+++ b/tests/unit/test_oauth_callback_session_cleanup.py
@@ -109,7 +109,7 @@ async def test_callback_deletes_oauth_session_after_reading_verifier(storage):
 
     with (
         patch(
-            "nextcloud_mcp_server.auth.oauth_routes._get_cached_discovery",
+            "nextcloud_mcp_server.auth.oauth_routes.get_oidc_discovery",
             new=AsyncMock(return_value=fake_discovery),
         ),
         patch(
@@ -165,7 +165,7 @@ async def test_callback_no_session_row_does_not_crash(storage):
 
     with (
         patch(
-            "nextcloud_mcp_server.auth.oauth_routes._get_cached_discovery",
+            "nextcloud_mcp_server.auth.oauth_routes.get_oidc_discovery",
             new=AsyncMock(return_value=fake_discovery),
         ),
         patch(
@@ -242,7 +242,7 @@ async def test_as_proxy_rejects_invalid_id_token():
 
     with (
         patch(
-            "nextcloud_mcp_server.auth.oauth_routes._get_cached_discovery",
+            "nextcloud_mcp_server.auth.oauth_routes.get_oidc_discovery",
             new=AsyncMock(return_value=fake_discovery),
         ),
         patch(
@@ -264,3 +264,66 @@ async def test_as_proxy_rejects_invalid_id_token():
     assert _proxy_codes == {}
     # And the session has been popped (one-time use).
     assert server_state not in _as_proxy_sessions
+
+
+async def test_as_proxy_passes_session_nonce_to_verify_id_token():
+    """The session-bound nonce must be forwarded as ``expected_nonce``.
+
+    Pins PR #758 round-2 finding 2: ``oauth_authorize`` generates a nonce
+    and stores it on the ``ASProxySession``; the callback must pass it to
+    ``verify_id_token`` so an ID token harvested from a parallel auth
+    request can't be replayed inside the AS-proxy flow.
+    """
+    server_state = "as-proxy-state-with-nonce"
+    server_nonce = "nonce-bound-to-this-request"
+    _as_proxy_sessions[server_state] = ASProxySession(
+        client_id="mcp-client",
+        client_redirect_uri="http://127.0.0.1:9999/callback",
+        client_state="client-state",
+        code_challenge="challenge",
+        code_challenge_method="S256",
+        requested_scopes="openid",
+        nonce=server_nonce,
+    )
+    _proxy_codes.clear()
+
+    request = _build_as_proxy_request(code="auth-code", state=server_state)
+
+    fake_discovery = {
+        "token_endpoint": "https://idp.example.com/token",
+        "issuer": "https://idp.example.com",
+    }
+    fake_token_response = MagicMock(status_code=200)
+    fake_token_response.json.return_value = {
+        "access_token": "ac",
+        "id_token": "id-tok",
+        "token_type": "Bearer",
+    }
+    fake_http = MagicMock()
+    fake_http.post = AsyncMock(return_value=fake_token_response)
+    fake_http.__aenter__ = AsyncMock(return_value=fake_http)
+    fake_http.__aexit__ = AsyncMock(return_value=None)
+
+    verify_mock = AsyncMock(return_value={"sub": "alice"})
+
+    with (
+        patch(
+            "nextcloud_mcp_server.auth.oauth_routes.get_oidc_discovery",
+            new=AsyncMock(return_value=fake_discovery),
+        ),
+        patch(
+            "nextcloud_mcp_server.auth.oauth_routes.nextcloud_httpx_client",
+            return_value=fake_http,
+        ),
+        patch(
+            "nextcloud_mcp_server.auth.oauth_routes.verify_id_token",
+            new=verify_mock,
+        ),
+    ):
+        await _oauth_callback_as_proxy(request, server_state)
+
+    verify_mock.assert_awaited_once()
+    kwargs = verify_mock.await_args.kwargs
+    assert kwargs.get("expected_nonce") == server_nonce, (
+        "AS-proxy callback must forward session.nonce to verify_id_token"
+    )
diff --git a/tests/unit/test_oidc_discovery.py b/tests/unit/test_oidc_discovery.py
index c2459f25..0212e318 100644
--- a/tests/unit/test_oidc_discovery.py
+++ b/tests/unit/test_oidc_discovery.py
@@ -1,12 +1,12 @@
-"""Unit tests for OIDC discovery fetch in oauth_routes."""
+"""Unit tests for the shared OIDC discovery fetch in token_utils."""
 
 from unittest.mock import patch
 
 import httpx
 import pytest
 
-from nextcloud_mcp_server.auth import oauth_routes
-from nextcloud_mcp_server.auth.oauth_routes import _get_cached_discovery
+from nextcloud_mcp_server.auth import token_utils
+from nextcloud_mcp_server.auth.token_utils import get_oidc_discovery
 
 pytestmark = pytest.mark.unit
 
@@ -14,9 +14,9 @@ pytestmark = pytest.mark.unit
 @pytest.fixture(autouse=True)
 def _clear_discovery_cache():
     """Reset the in-memory discovery cache between tests."""
-    oauth_routes._discovery_cache.clear()
+    token_utils._discovery_cache.clear()
     yield
-    oauth_routes._discovery_cache.clear()
+    token_utils._discovery_cache.clear()
 
 
 async def test_discovery_follows_redirect_to_index_php():
@@ -26,7 +26,8 @@ async def test_discovery_follows_redirect_to_index_php():
     redirect ``/.well-known/openid-configuration`` to
     ``/index.php/.well-known/openid-configuration``. Without follow_redirects
     the OAuth authorize handler raises HTTPStatusError and returns 500
-    (see oauth_routes._get_cached_discovery).
+    (PR #758 round-2 nit 3 consolidated the discovery cache; see
+    ``token_utils.get_oidc_discovery``).
     """
 
     pretty_url = "https://nx.example.com/.well-known/openid-configuration"
@@ -51,10 +52,10 @@ async def test_discovery_follows_redirect_to_index_php():
         return httpx.AsyncClient(**kwargs)
 
     with patch(
-        "nextcloud_mcp_server.auth.oauth_routes.nextcloud_httpx_client",
+        "nextcloud_mcp_server.auth.token_utils.nextcloud_httpx_client",
         side_effect=fake_client,
     ) as factory:
-        result = await _get_cached_discovery(pretty_url)
+        result = await get_oidc_discovery(pretty_url)
 
     assert result == discovery_doc
     factory.assert_called_once()