diff --git a/.claude/CLAUDE.md b/.claude/CLAUDE.md
index b67ef96..b2d8930 100644
--- a/.claude/CLAUDE.md
+++ b/.claude/CLAUDE.md
@@ -66,6 +66,7 @@ enlace/
 ├── util.py        # Pure helpers: derive_display_name, derive_route_prefix, is_skippable
 ├── discover.py    # ConventionDiscoverer: walks apps/, reads app.toml, detects types
 ├── compose.py     # build_backend(): mounts ASGI sub-apps, proxy routes, static files
+├── access.py      # can_see_app / is_user_allowed: the ONE visibility predicate (launcher + auth gate)
 ├── proxy.py       # Lightweight ASGI reverse proxy for process/external backends (httpx)
 ├── supervise.py   # Dev-mode asyncio process supervisor (health checks, restart, logs)
 ├── diagnose.py    # diagnose_app(): scan an app dir for enlace compatibility issues
diff --git a/enlace/access.py b/enlace/access.py
new file mode 100644
index 0000000..2b3dee2
--- /dev/null
+++ b/enlace/access.py
@@ -0,0 +1,105 @@
+"""Who may reach an app: the one predicate the gate and the launcher both call.
+
+Two code paths answer "may this user reach this app": the request-time gate
+(``enlace_auth``'s ``PlatformAuthMiddleware``) and the ``/_apps`` launcher (which
+hides what the caller could not open). When each carried its own copy of the
+answer they drifted — the gate honoured runtime grants and the launcher did not,
+so a granted user could open an app they could never find
+(https://github.com/i2mint/enlace/issues/35). This module is the single copy;
+both sides call it, so they cannot disagree.
+
+enlace core still enforces nothing — enforcement is ``enlace_auth``'s job. The
+launcher uses this module to *filter*, the gate to *deny*.
+
+Runtime grants reach enlace core through one dependency-injection slot on the
+root app's state, :data:`GRANTS_STATE_ATTR`: a callable ``app_id -> iterable of
+emails`` of currently active grants, installed by the auth plugin (the same
+callable its gate consults). Absent it, only the static ``allowed_users`` count.
+"""
+
+import logging
+from typing import Callable, Iterable, Optional
+
+_logger = logging.getLogger("enlace.access")
+
+#: The root app's ``state`` attribute an auth plugin sets to its grants resolver.
+GRANTS_STATE_ATTR = "dynamic_allowed_users"
+
+GrantsResolver = Callable[[str], Iterable[str]]
+
+
+def granted_users(resolver: Optional[GrantsResolver], app_id: str) -> frozenset[str]:
+    """The lowercased emails holding an active runtime grant for ``app_id``.
+
+    Called per request, never cached: expiry is evaluated by the resolver at call
+    time, so the gate and the launcher expire a grant at the same instant.
+
+    A failing resolver yields no grants (fail closed for grant-based access,
+    static ``allowed_users`` still work): a grants-store hiccup must never break
+    auth or the listing. It is logged, not raised.
+    """
+    if resolver is None:
+        return frozenset()
+    try:
+        return frozenset(e.lower() for e in (resolver(app_id) or ()))
+    except Exception as exc:  # noqa: BLE001 - see the fail-closed note above
+        # One line per failure, traceback at DEBUG: the launcher resolves every
+        # protected app per /_apps call, so a broken store would otherwise emit
+        # a traceback per app per page load.
+        _logger.warning(
+            "dynamic grants lookup failed for app_id=%r (%s: %s); "
+            "falling back to config allowed_users only",
+            app_id,
+            type(exc).__name__,
+            exc,
+        )
+        _logger.debug("grants lookup traceback", exc_info=True)
+        return frozenset()
+
+
+def is_user_allowed(
+    user_id: Optional[str],
+    user_email: Optional[str],
+    *,
+    allowed_users: Iterable[str] = (),
+    granted: Iterable[str] = (),
+) -> bool:
+    """Whether an authenticated user passes a ``protected:user`` app's allowlist.
+
+    The allowlist is the static ``allowed_users`` ∪ the active runtime
+    ``granted`` emails, compared case-insensitively. An empty union means the
+    app is open to any authenticated user. An unauthenticated caller
+    (``user_id is None``) never passes.
+    """
+    if user_id is None:
+        return False
+    allowed = {e.lower() for e in allowed_users} | {e.lower() for e in granted}
+    if not allowed:
+        return True
+    return (user_email or user_id).lower() in allowed
+
+
+def can_see_app(
+    access: str,
+    user_id: Optional[str],
+    user_email: Optional[str],
+    *,
+    allowed_users: Iterable[str] = (),
+    granted: Iterable[str] = (),
+) -> bool:
+    """Whether the ``/_apps`` launcher shows an app of this access level.
+
+    - ``public`` / ``local`` → always.
+    - ``protected:shared`` → always: it is gated when opened, not when listed,
+      so users know the app exists and can ask for the password.
+    - ``protected:user`` → exactly when :func:`is_user_allowed` — the gate's own
+      predicate, so a user sees precisely the apps they can open.
+    - anything else → never (deny by default).
+    """
+    if access in ("public", "local", "protected:shared"):
+        return True
+    if access == "protected:user":
+        return is_user_allowed(
+            user_id, user_email, allowed_users=allowed_users, granted=granted
+        )
+    return False
diff --git a/enlace/base.py b/enlace/base.py
index b8efdc4..4e21c44 100644
--- a/enlace/base.py
+++ b/enlace/base.py
@@ -6,7 +6,7 @@
 don't see entries they couldn't open anyway. That makes the access string
 vocabulary part of enlace's contract — the values
 ``"public" | "local" | "protected:shared" | "protected:user"`` are the
-ones ``compose._can_access`` understands; anything else is treated as
+ones ``enlace.access.can_see_app`` understands; anything else is treated as
 deny-by-default.
 
 The fields are otherwise opaque to enlace: enforcement, session lookup,
diff --git a/enlace/compose.py b/enlace/compose.py
index 3d4269c..021e5a2 100644
--- a/enlace/compose.py
+++ b/enlace/compose.py
@@ -508,31 +508,30 @@ def _stamp_updated_at(
         app.updated_at = manifest.app_source.committed_at or manifest.deployed_at
 
 
-def _can_access(
-    access: str,
-    user_id: Optional[str],
-    user_email: Optional[str],
-    allowed_users: list[str],
-) -> bool:
-    """Whether a request can see an app of this access level in /_apps.
-
-    `public` / `local` → always.
-    `protected:user`   → only if authenticated AND (no allowed_users list, or
-                         the user's email is in it).
-    `protected:shared` → visible either way (gated at open-time, not
-                         discovery-time — users should know the app exists
-                         so they can ask for the password).
+def _can_access(app: AppConfig, request: Request) -> bool:
+    """Whether the caller of ``request`` may see ``app`` in /_apps.
+
+    Delegates to :func:`enlace.access.can_see_app` — the same allowlist
+    predicate the auth gate calls — with the runtime grants the auth plugin
+    injected (see :data:`enlace.access.GRANTS_STATE_ATTR`), resolved per
+    request so a grant appears, and expires, in the launcher exactly when it
+    does at the gate.
     """
-    if access in ("public", "local", "protected:shared"):
-        return True
-    if access == "protected:user":
-        if user_id is None:
-            return False
-        if allowed_users:
-            who = user_email or user_id
-            return who in allowed_users
-        return True
-    return False
+    from enlace import access
+
+    resolver = getattr(request.app.state, access.GRANTS_STATE_ATTR, None)
+    granted = (
+        access.granted_users(resolver, app.name)
+        if app.access == "protected:user"
+        else ()
+    )
+    return access.can_see_app(
+        app.access,
+        getattr(request.state, "user_id", None),
+        getattr(request.state, "user_email", None),
+        allowed_users=app.allowed_users,
+        granted=granted,
+    )
 
 
 def _app_launch(app: AppConfig) -> tuple[bool, Optional[str]]:
@@ -656,7 +655,7 @@ async def apps_listing(request: Request) -> dict:
         for app in apps:
             if app.name == landing_name:
                 continue
-            if not _can_access(app.access, user_id, user_email, app.allowed_users):
+            if not _can_access(app, request):
                 continue
             items.append(
                 build_launcher_item(app, config, _overlay_entry(request, app.name))
@@ -676,9 +675,7 @@ def _visible_app(name: str, request: Request) -> Optional[AppConfig]:
         app = apps_by_name.get(name)
         if app is None or app.name == landing_name:
             return None
-        user_id = getattr(request.state, "user_id", None)
-        user_email = getattr(request.state, "user_email", None)
-        if not _can_access(app.access, user_id, user_email, app.allowed_users):
+        if not _can_access(app, request):
             return None
         return app
 
@@ -767,11 +764,15 @@ def _icon_response(body: bytes, content_type: str, token: str, cache: str) -> Re
 
 
 def _add_index_route(parent: FastAPI, config: PlatformConfig) -> None:
-    """Add a GET / route that lists all discovered apps as a simple HTML page."""
-    apps = config.apps
+    """Add a GET / route listing, as a simple HTML page, the apps the caller may see.
+
+    Filtered by the same predicate as ``/_apps`` (:func:`_can_access`), so the
+    built-in index never names an app the caller could not open.
+    """
 
     @parent.get("/", response_class=HTMLResponse)
-    async def index():
+    async def index(request: Request):
+        apps = [a for a in config.apps if _can_access(a, request)]
         items = []
         for app in apps:
             has_frontend = app.frontend_dir and app.frontend_dir.is_dir()
diff --git a/enlace/tests/test_access.py b/enlace/tests/test_access.py
new file mode 100644
index 0000000..9125b36
--- /dev/null
+++ b/enlace/tests/test_access.py
@@ -0,0 +1,182 @@
+"""The launcher and the auth gate share one visibility predicate (issue #35).
+
+A user holding a runtime grant for a ``protected:user`` app could open it (the
+gate unions static ``allowed_users`` with live grants) but never see it in
+``/_apps`` (the launcher did not). These tests pin the property that matters —
+the launcher's verdict equals the gate's predicate for every combination of
+static-only, grant-only, both and neither — not merely "a granted user sees it",
+which a hard-coded ``True`` would pass.
+"""
+
+import itertools
+
+import pytest
+from starlette.testclient import TestClient
+
+from enlace import access
+from enlace.base import AppConfig, PlatformConfig
+from enlace.compose import build_backend
+
+STATIC = "static@x.com"
+GRANTED = "granted@x.com"
+BOTH = "both@x.com"
+NEITHER = "neither@x.com"
+
+
+class _FakeSession:
+    """Stand-in for the auth plugin's session middleware: identity from a header."""
+
+    def __init__(self, app):
+        self.app = app
+
+    async def __call__(self, scope, receive, send):
+        if scope["type"] == "http":
+            email = dict(scope["headers"]).get(b"x-test-user")
+            state = scope.setdefault("state", {})
+            state["user_id"] = email.decode() if email else None
+            state["user_email"] = email.decode() if email else None
+        await self.app(scope, receive, send)
+
+
+def _gated_app(allowed_users=(STATIC, BOTH)):
+    return AppConfig(
+        name="gated",
+        route_prefix="/api/gated",
+        app_type="frontend_only",
+        access="protected:user",
+        allowed_users=list(allowed_users),
+    )
+
+
+def _client(apps, grants):
+    """A backend whose injected grants resolver reads the mutable ``grants`` dict."""
+    backend = build_backend(PlatformConfig(apps=apps))
+    backend.add_middleware(_FakeSession)
+    setattr(
+        backend.state, access.GRANTS_STATE_ATTR, lambda app_id: grants.get(app_id, ())
+    )
+    return TestClient(backend)
+
+
+def _listed(client, user):
+    headers = {"x-test-user": user} if user else {}
+    return [a["name"] for a in client.get("/_apps", headers=headers).json()["apps"]]
+
+
+@pytest.mark.parametrize("user", [STATIC, GRANTED, BOTH, NEITHER, None])
+def test_launcher_verdict_equals_the_gate_predicate(user):
+    """For every kind of user, listed in /_apps ⟺ allowed by the gate's predicate."""
+    grants = {"gated": {GRANTED, BOTH}}
+    app = _gated_app()
+    client = _client([app], grants)
+    gate_says = access.is_user_allowed(
+        user,
+        user,
+        allowed_users=app.allowed_users,
+        granted=access.granted_users(lambda a: grants.get(a, ()), "gated"),
+    )
+    assert ("gated" in _listed(client, user)) is gate_says
+    # And the concrete expectations, so a predicate that is wrong on both
+    # sides cannot pass by agreeing with itself.
+    assert gate_says is (user in (STATIC, GRANTED, BOTH))
+
+
+def test_grant_appears_and_expires_without_restart():
+    """The resolver is consulted per request: no startup snapshot to go stale."""
+    grants: dict = {}
+    client = _client([_gated_app()], grants)
+    assert _listed(client, GRANTED) == []
+    grants["gated"] = {GRANTED}
+    assert _listed(client, GRANTED) == ["gated"]
+    del grants["gated"]
+    assert _listed(client, GRANTED) == []
+
+
+def test_granted_user_gets_the_icon_too():
+    """The icon route shares the verdict — a listed app never has a broken icon."""
+    client = _client([_gated_app()], {"gated": {GRANTED}})
+    assert client.get("/_apps/gated/icon", headers={"x-test-user": GRANTED}).is_success
+    assert (
+        client.get("/_apps/gated/icon", headers={"x-test-user": NEITHER}).status_code
+        == 404
+    )
+
+
+def test_matching_is_case_insensitive_on_both_sources():
+    """The gate lowercases both sides; the launcher must as well."""
+    app = _gated_app(allowed_users=["Static@X.com"])
+    client = _client([app], {"gated": {"Granted@X.COM"}})
+    assert _listed(client, "static@x.com") == ["gated"]
+    assert _listed(client, "GRANTED@x.com") == ["gated"]
+
+
+def test_failing_resolver_falls_back_to_static_allowlist():
+    """A grants-store hiccup hides grant-only access but never breaks the listing."""
+
+    def broken(app_id):
+        raise OSError("grants store unavailable")
+
+    backend = build_backend(PlatformConfig(apps=[_gated_app()]))
+    backend.add_middleware(_FakeSession)
+    setattr(backend.state, access.GRANTS_STATE_ATTR, broken)
+    client = TestClient(backend)
+    assert _listed(client, STATIC) == ["gated"]
+    assert _listed(client, GRANTED) == []
+
+
+def test_no_resolver_means_static_allowlist_only():
+    """Without an auth plugin there are no grants; behaviour is unchanged."""
+    backend = build_backend(PlatformConfig(apps=[_gated_app()]))
+    backend.add_middleware(_FakeSession)
+    client = TestClient(backend)
+    assert _listed(client, STATIC) == ["gated"]
+    assert _listed(client, GRANTED) == []
+
+
+@pytest.mark.parametrize(
+    "static, granted",
+    list(itertools.product([(), ("a@x.com",)], [(), ("a@x.com",), ("b@x.com",)])),
+)
+def test_is_user_allowed_truth_table(static, granted):
+    """Empty union ⇒ open to any signed-in user; otherwise membership in the union."""
+    union = set(static) | set(granted)
+    expected = (not union) or ("a@x.com" in union)
+    assert (
+        access.is_user_allowed(
+            "a@x.com", "a@x.com", allowed_users=static, granted=granted
+        )
+        is expected
+    )
+    assert (
+        access.is_user_allowed(None, None, allowed_users=static, granted=granted)
+        is False
+    )
+
+
+@pytest.mark.parametrize(
+    "level, expected",
+    [
+        ("public", True),
+        ("local", True),
+        ("protected:shared", True),
+        ("protected:user", False),
+        ("something-else", False),
+    ],
+)
+def test_can_see_app_by_access_level_for_anonymous(level, expected):
+    """Anonymous callers see open and shared-password apps, never user-gated ones."""
+    assert access.can_see_app(level, None, None) is expected
+
+
+def test_builtin_index_lists_only_what_the_caller_may_open():
+    """The HTML index (no landing app) uses the launcher's predicate too."""
+    public = AppConfig(
+        name="open_one",
+        route_prefix="/api/open_one",
+        app_type="frontend_only",
+        access="public",
+    )
+    client = _client([public, _gated_app()], {"gated": {GRANTED}})
+    assert "Gated" not in client.get("/").text
+    assert "Open One" in client.get("/").text
+    assert "Gated" in client.get("/", headers={"x-test-user": GRANTED}).text