diff --git a/plugins/host_agent/routes.py b/plugins/host_agent/routes.py
index f74b7f8..f5c2221 100644
--- a/plugins/host_agent/routes.py
+++ b/plugins/host_agent/routes.py
@@ -9,7 +9,7 @@ from pathlib import Path
 
 import secrets
 from quart import Blueprint, current_app, jsonify, request, Response, render_template, redirect, url_for, session
-from steward.auth.middleware import require_role
+from steward.auth.middleware import public_route, require_role
 from steward.models.users import UserRole
 from sqlalchemy import select, func, or_, and_
 from datetime import timedelta
@@ -166,6 +166,7 @@ def _error(status: int, code: str, detail: str | None = None) -> tuple[Any, int]
 
 
 @host_agent_bp.post("/ingest")
+@public_route("the agent authenticates with its bearer token")
 async def ingest():
     auth = request.headers.get("Authorization", "")
     if not auth.startswith("Bearer "):
@@ -313,6 +314,7 @@ def _agent_version() -> str:
 
 
 @host_agent_bp.get("/install.sh")
+@public_route("fetched by curl on the host being enrolled; carries an enrolment token")
 async def install_script():
     token = request.args.get("token", "")
     if not token:
@@ -344,6 +346,7 @@ async def install_script():
 
 
 @host_agent_bp.get("/agent.py")
+@public_route("fetched by the installer and by agent self-update; holds no secrets")
 async def agent_source():
     try:
         body = AGENT_SOURCE_PATH.read_text(encoding="utf-8")
@@ -470,6 +473,7 @@ async def _fleet_rows(session) -> list[dict]:
 
 
 @host_agent_bp.get("/widget")
+@require_role(UserRole.viewer)
 async def widget_table():
     """Fleet-glance dashboard widget: one row per monitored host, latest metrics."""
     async with current_app.db_sessionmaker() as session:
@@ -478,6 +482,7 @@ async def widget_table():
 
 
 @host_agent_bp.get("/widget/history")
+@require_role(UserRole.viewer)
 async def widget_history():
     host_id = request.args.get("host_id", "")
     try:
diff --git a/plugins/host_agent/templates/widget_history.html b/plugins/host_agent/templates/widget_history.html
index 1c13783..01e7c5b 100644
--- a/plugins/host_agent/templates/widget_history.html
+++ b/plugins/host_agent/templates/widget_history.html
@@ -22,7 +22,7 @@
     {% endif %}
     <span class="hist-range" style="margin-left:auto;display:inline-flex;border:1px solid var(--border-mid);border-radius:5px;overflow:hidden;">
       {% for opt in [1, 6, 24] %}
-      <button type="button" onclick="histRange({{ wid }}, '{{ host.id }}', {{ opt }})"
+      <button type="button" onclick="histRange({{ wid }}, {{ opt }})"
         style="border:0;cursor:pointer;padding:0.1rem 0.45rem;font-size:0.72rem;
                background:{% if opt == hours %}var(--accent){% else %}transparent{% endif %};
                color:{% if opt == hours %}#fff{% else %}var(--text-muted){% endif %};">{{ opt }}h</button>
@@ -36,11 +36,15 @@
 <script>
 // Live time-range switch. Rewrites the parent cell's hx-get so the choice sticks
 // across polls (htmx re-reads the attribute each poll), then fetches immediately.
-window.histRange = function (wid, hostId, hours) {
+// Only `hours` changes: the rest of the query (host, widget id, a share link's
+// token) is kept, so the switch also works on a shared dashboard.
+window.histRange = function (wid, hours) {
   var cell = document.getElementById("widget-" + wid);
   if (!cell) return;
-  var base = (cell.getAttribute("hx-get") || "").split("?")[0];
-  var url = base + "?host_id=" + encodeURIComponent(hostId) + "&hours=" + hours + "&wid=" + wid;
+  var parts = (cell.getAttribute("hx-get") || "").split("?");
+  var query = new URLSearchParams(parts[1] || "");
+  query.set("hours", hours);
+  var url = parts[0] + "?" + query.toString();
   cell.setAttribute("hx-get", url);
   if (window.htmx) window.htmx.ajax("GET", url, { target: cell, swap: "innerHTML" });
 };
diff --git a/steward/app.py b/steward/app.py
index 7b1041b..7828a80 100644
--- a/steward/app.py
+++ b/steward/app.py
@@ -137,6 +137,9 @@ def create_app(
     app.jinja_env.globals["csrf_token"] = _csrf.csrf_token
     app.jinja_env.globals["csrf_field"] = _csrf.csrf_field
     app.before_request(_csrf.check_request)
+    # Default-deny: a view with neither require_role nor public_route is refused.
+    from .auth.middleware import check_view_is_marked, public_route
+    app.before_request(check_view_is_marked)
 
     # ── 5. Plugin migrations ───────────────────────────────────────────────────
     # Step 3 already applied all plugin migrations via discover_all_plugin_migration_dirs,
@@ -233,33 +236,24 @@ def create_app(
     # ── 11. Share-token middleware ─────────────────────────────────────────────
     @app.before_request
     async def _validate_share_token():
-        """If ?s=<token> is present, validate it and set g.share_viewer."""
+        """A share link's token (?s=) opens, read-only, exactly the widget
+        fragments its own dashboard loads (steward/dashboard/share.py)."""
         from quart import request, g
         raw = request.args.get("s")
-        if not raw:
+        if not raw or request.method != "GET":
             return
         try:
-            import hashlib
-            from datetime import datetime, timezone
-            from sqlalchemy import select
-            from .models.dashboard import DashboardShareToken
-            token_hash = hashlib.sha256(raw.encode()).hexdigest()
+            from .dashboard.share import share_grants
             async with app.db_sessionmaker() as db:
-                result = await db.execute(
-                    select(DashboardShareToken)
-                    .where(DashboardShareToken.token_hash == token_hash)
-                )
-                share = result.scalar_one_or_none()
-            if share:
-                now = datetime.now(timezone.utc)
-                if share.expires_at is None or share.expires_at > now:
+                if await share_grants(db, raw, request.path, request.args):
                     g.share_viewer = True
-                    g.share_dashboard_id = share.dashboard_id
         except Exception:
-            pass  # never block a request due to token validation failure
+            # A failed check grants nothing; the request falls through to login.
+            logging.getLogger(__name__).exception("Share token check failed")
 
     # ── 11. Health check ───────────────────────────────────────────────────────
     @app.get("/health")
+    @public_route("liveness probe for the container")
     async def health():
         return {"status": "ok"}
 
diff --git a/steward/auth/middleware.py b/steward/auth/middleware.py
index 89f9b0d..3ae0855 100644
--- a/steward/auth/middleware.py
+++ b/steward/auth/middleware.py
@@ -77,10 +77,37 @@ def require_role(minimum_role: UserRole):
             if _ROLE_ORDER.index(user_role) < _ROLE_ORDER.index(minimum_role):
                 abort(403)
             return await f(*args, **kwargs)
+        wrapper.steward_role = minimum_role
         return wrapper
     return decorator
 
 
+def public_route(reason: str):
+    """Mark a view that is deliberately reachable without a role — login,
+    the health probe, a bearer-authenticated endpoint. Every other view must
+    carry require_role; check_view_is_marked refuses one that has neither, so
+    a route that forgets its decorator is closed rather than open."""
+    def decorator(f):
+        f.steward_public = reason
+        return f
+    return decorator
+
+
+async def check_view_is_marked() -> Response | None:
+    """before_request hook: default-deny for views with neither require_role
+    nor public_route. Static files and unmatched paths (404) pass through."""
+    from quart import current_app
+    endpoint = request.endpoint
+    if endpoint is None or endpoint == "static" or endpoint.endswith(".static"):
+        return None
+    view = current_app.view_functions.get(endpoint)
+    if view is None or hasattr(view, "steward_role") or hasattr(view, "steward_public"):
+        return None
+    current_app.logger.error("Refused %s: view %r has no require_role or public_route",
+                             request.path, endpoint)
+    abort(403)
+
+
 def login_user(user) -> None:
     """Write user identity into the session, with a fresh CSRF token."""
     from steward.auth.csrf import rotate
diff --git a/steward/auth/routes.py b/steward/auth/routes.py
index 399b0e9..11331ac 100644
--- a/steward/auth/routes.py
+++ b/steward/auth/routes.py
@@ -2,7 +2,7 @@ from __future__ import annotations
 import bcrypt
 from quart import Blueprint, render_template, request, redirect, url_for, session
 from sqlalchemy import select, func
-from steward.auth.middleware import login_user, logout_user, safe_next_url
+from steward.auth.middleware import login_user, logout_user, public_route, safe_next_url
 from steward.models.users import User, UserRole
 
 auth_bp = Blueprint("auth", __name__)
@@ -48,6 +48,7 @@ async def get_user_by_username(app, username: str) -> User | None:
 
 
 @auth_bp.get("/login")
+@public_route("the login page")
 async def login():
     from quart import current_app
     if await get_user_count(current_app) == 0:
@@ -59,6 +60,7 @@ async def login():
 
 
 @auth_bp.post("/login")
+@public_route("the login form")
 async def login_post():
     from quart import current_app
     from steward.core.audit import log_audit
@@ -100,6 +102,7 @@ async def login_post():
 
 
 @auth_bp.get("/login/oidc")
+@public_route("starts SSO login")
 async def login_oidc():
     from quart import current_app
     from steward.auth.oidc import get_discovery, build_authorize_url, generate_state
@@ -125,6 +128,7 @@ async def login_oidc():
 
 
 @auth_bp.get("/login/oidc/callback")
+@public_route("SSO login callback")
 async def login_oidc_callback():
     from quart import current_app
     from steward.auth.oidc import get_discovery, exchange_code, get_userinfo, map_role
@@ -179,12 +183,14 @@ async def login_oidc_callback():
 
 
 @auth_bp.get("/logout")
+@public_route("ends the session")
 async def logout():
     logout_user()
     return redirect(url_for("auth.login"))
 
 
 @auth_bp.get("/setup")
+@public_route("first-run setup (refuses once a user exists)")
 async def setup():
     from quart import current_app
     if await get_user_count(current_app) > 0:
@@ -196,6 +202,7 @@ async def setup():
 
 
 @auth_bp.post("/setup")
+@public_route("first-run setup (refuses once a user exists)")
 async def setup_post():
     from quart import current_app
     from steward.core.audit import log_audit
diff --git a/steward/dashboard/routes.py b/steward/dashboard/routes.py
index 5ce2a73..a4d4788 100644
--- a/steward/dashboard/routes.py
+++ b/steward/dashboard/routes.py
@@ -6,7 +6,7 @@ from datetime import datetime, timezone, timedelta
 from urllib.parse import urlencode
 from quart import Blueprint, render_template, current_app, abort, redirect, request, session
 from sqlalchemy import select, func, update
-from steward.auth.middleware import require_role, current_user_id
+from steward.auth.middleware import public_route, require_role, current_user_id
 from steward.models.users import UserRole
 from steward.models.hosts import Host
 from steward.models.dashboard import Dashboard, DashboardWidget, DashboardShareToken
@@ -513,6 +513,7 @@ async def revoke_share_token(dash_id: int, token_id: int):
 # ── Public share view (no login required) ────────────────────────────────────
 
 @dashboard_bp.get("/share/<raw_token>")
+@public_route("a share link; the token is the credential")
 async def public_share(raw_token: str):
     token_hash = hashlib.sha256(raw_token.encode()).hexdigest()
     now        = datetime.now(timezone.utc)
diff --git a/steward/dashboard/share.py b/steward/dashboard/share.py
new file mode 100644
index 0000000..c0da7d0
--- /dev/null
+++ b/steward/dashboard/share.py
@@ -0,0 +1,58 @@
+"""What a dashboard share link opens.
+
+A share link's page (/share/<token>) loads each of its dashboard's widgets
+from a fragment URL with `&s=<token>` appended. The token opens exactly those
+URLs, read-only: the same path and the same configured parameters (which host,
+which container). Only the time window a viewer can switch on the widget
+itself (VIEW_PARAMS) may differ. Every other page, and the same widget aimed
+at a different host, still needs a login.
+"""
+from __future__ import annotations
+
+import hashlib
+from datetime import datetime, timezone
+from urllib.parse import parse_qsl
+
+from sqlalchemy import select
+
+from steward.models.dashboard import DashboardShareToken
+
+# Parameters a shared widget may change in place: they pick a time window,
+# never which thing is shown.
+VIEW_PARAMS = frozenset({"hours", "range"})
+
+
+def share_allows(widget_urls: list[str], path: str, args) -> bool:
+    """True when `path` + `args` (minus the token) is one of `widget_urls`,
+    allowing only VIEW_PARAMS to differ."""
+    got: dict[str, str] = {}
+    for key in args:
+        if key == "s":
+            continue
+        values = args.getlist(key)
+        if len(values) != 1:
+            return False
+        got[key] = values[0]
+    for url in widget_urls:
+        wpath, _, query = url.partition("?")
+        if wpath != path:
+            continue
+        want = {k: v for k, v in parse_qsl(query, keep_blank_values=True) if k not in VIEW_PARAMS}
+        if all(got.get(k) == v for k, v in want.items()) and set(got) <= set(want) | VIEW_PARAMS:
+            return True
+    return False
+
+
+async def share_grants(db, raw_token: str, path: str, args) -> bool:
+    """True when `raw_token` is a live share token whose dashboard loads this URL."""
+    token_hash = hashlib.sha256(raw_token.encode()).hexdigest()
+    share = (await db.execute(
+        select(DashboardShareToken).where(DashboardShareToken.token_hash == token_hash)
+    )).scalar_one_or_none()
+    if share is None:
+        return False
+    if share.expires_at is not None and share.expires_at <= datetime.now(timezone.utc):
+        return False
+    from .routes import _get_widgets, _resolve_widgets
+    widgets = _resolve_widgets(await _get_widgets(db, share.dashboard_id))
+    return share_allows([w["hx_url"] for w in widgets], path, args)
diff --git a/steward/hosts/routes.py b/steward/hosts/routes.py
index 4f505a2..4208406 100644
--- a/steward/hosts/routes.py
+++ b/steward/hosts/routes.py
@@ -288,7 +288,6 @@ async def uptime_page():
 @hosts_bp.get("/uptime/widget")
 @require_role(UserRole.viewer)
 async def uptime_widget():
-    share_token = request.args.get("s")
     async with current_app.db_sessionmaker() as db:
         result = await db.execute(select(Host).order_by(Host.name))
         hosts = result.scalars().all()
@@ -297,5 +296,4 @@ async def uptime_widget():
         "hosts/uptime_widget.html",
         hosts=hosts,
         uptime=uptime,
-        share_token=share_token,
     )
diff --git a/steward/templates/hosts/uptime_widget.html b/steward/templates/hosts/uptime_widget.html
index a9a79c4..af26dcf 100644
--- a/steward/templates/hosts/uptime_widget.html
+++ b/steward/templates/hosts/uptime_widget.html
@@ -38,7 +38,7 @@
   {% endfor %}
 </div>
 
-{% if share_token %}
+{% if session.user_id %}
 <div style="margin-top:0.5rem;text-align:right;">
   <a href="/hosts/uptime" style="font-size:0.75rem;color:var(--text-muted);">Full SLA →</a>
 </div>
diff --git a/tests/test_route_access.py b/tests/test_route_access.py
new file mode 100644
index 0000000..9c0b4b8
--- /dev/null
+++ b/tests/test_route_access.py
@@ -0,0 +1,74 @@
+"""Who can reach a route: every view carries require_role or public_route,
+an unmarked one is refused, and a share link opens only its own widgets."""
+import ast
+import pathlib
+
+import pytest
+from werkzeug.datastructures import MultiDict
+
+import steward
+from steward.dashboard.share import share_allows
+
+_REPO = pathlib.Path(steward.__file__).parent.parent
+_ROUTE_METHODS = ("get", "post", "put", "patch", "delete", "route", "websocket")
+
+
+def _route_decorated_views():
+    files = [p for root in ("steward", "plugins") for p in (_REPO / root).rglob("*.py")
+             if "migrations" not in p.parts]
+    for path in files:
+        tree = ast.parse(path.read_text())
+        for node in ast.walk(tree):
+            if not isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+                continue
+            decorators = [ast.unparse(d) for d in node.decorator_list]
+            if any(f".{m}('/" in d or f'.{m}("/' in d for d in decorators for m in _ROUTE_METHODS):
+                yield path, node, decorators
+
+
+def test_every_route_says_who_may_reach_it():
+    unmarked = [f"{p.relative_to(_REPO)}:{n.lineno} {n.name}"
+                for p, n, decs in _route_decorated_views()
+                if not any(d.startswith(("require_role(", "public_route(")) for d in decs)]
+    assert not unmarked, "routes with neither require_role nor public_route: " + ", ".join(unmarked)
+
+
+def test_the_scan_sees_routes():
+    names = {n.name for _, n, _ in _route_decorated_views()}
+    assert {"login", "health", "ingest", "widget_table", "public_share"} <= names
+
+
+@pytest.mark.asyncio
+async def test_unmarked_view_is_refused(app, client):
+    async def unmarked():
+        return "open"
+    app.add_url_rule("/__unmarked", "unmarked", unmarked)
+    assert (await client.get("/__unmarked")).status_code == 403
+    assert (await client.get("/health")).status_code == 200
+
+
+WIDGETS = ["/plugins/host_agent/widget/history?host_id=h1&hours=6&wid=7",
+           "/monitors/widget?wid=8"]
+
+
+@pytest.mark.parametrize("path,args,allowed", [
+    ("/plugins/host_agent/widget/history", {"host_id": "h1", "hours": "6", "wid": "7", "s": "t"}, True),
+    ("/plugins/host_agent/widget/history", {"host_id": "h1", "hours": "24", "wid": "7", "s": "t"}, True),
+    ("/monitors/widget", {"wid": "8", "s": "t"}, True),
+    # the same widget aimed at another host
+    ("/plugins/host_agent/widget/history", {"host_id": "h2", "hours": "6", "wid": "7", "s": "t"}, False),
+    # a parameter the widget was not configured with
+    ("/monitors/widget", {"wid": "8", "host_id": "h1", "s": "t"}, False),
+    # a configured parameter left off
+    ("/plugins/host_agent/widget/history", {"hours": "6", "wid": "7", "s": "t"}, False),
+    # any other page
+    ("/hosts/", {"s": "t"}, False),
+    ("/plugins/docker/logs", {"wid": "8", "s": "t"}, False),
+])
+def test_share_opens_only_its_widgets(path, args, allowed):
+    assert share_allows(WIDGETS, path, MultiDict(args)) is allowed
+
+
+def test_share_refuses_a_repeated_parameter():
+    args = MultiDict([("wid", "8"), ("wid", "9"), ("s", "t")])
+    assert not share_allows(WIDGETS, "/monitors/widget", args)