Replace kiosk SignalR with polling — Azure App Service blocks anonymous hub handshakes

SignalR WebSocket and SSE both receive immediate 'Handshake was canceled' from the
server-side hub context. The 15-second delay between negotiate and SSE connect
reveals the handshake timer has expired before the transport opens — caused by Azure
App Service's ingress proxy resetting anonymous long-lived connections.

Replacement: /Kiosk/PollSession (anonymous GET, no-cache) queried every 3 seconds.
Returns the most recent Active InPerson session created in the last 60 seconds.
The kiosk navigates when hasSession=true. Status dot: gray->green on first success,
yellow on network error, blue when navigating. Removed signalr.min.js from kiosk layout.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Controllers/KioskController.cs

@@ -68,7 +68,8 @@ public class KioskController : Controller
     /// <summary>
     /// Idle branded screen displayed on the front-desk tablet.
     /// Validates the KioskDevice cookie; returns 403 if missing or token mismatch.
-    /// The view connects to KioskHub and listens for StartIntake events.
+    /// The view polls /Kiosk/PollSession every 3 seconds and navigates when staff
+    /// triggers a session via the Dashboard "Start Intake" button.
     /// </summary>
     [AllowAnonymous]
     public async Task<IActionResult> Welcome()
@@ -86,6 +87,35 @@ public class KioskController : Controller
         return View();
     }
 
+    /// <summary>
+    /// Lightweight polling endpoint called every 3 seconds by the kiosk Welcome screen.
+    /// Returns the most recent InPerson KioskSession created in the last 60 seconds so
+    /// the tablet can navigate without relying on SignalR (which Azure App Service blocks
+    /// for anonymous WebSocket/SSE connections through its ingress proxy).
+    /// </summary>
+    [AllowAnonymous, HttpGet]
+    [ResponseCache(NoStore = true, Location = ResponseCacheLocation.None)]
+    public async Task<IActionResult> PollSession()
+    {
+        var cookie = ReadKioskCookie();
+        if (cookie == null) return Json(new { hasSession = false });
+
+        var company = await _unitOfWork.Companies.GetByIdAsync(cookie.Value.companyId, ignoreQueryFilters: true);
+        if (company == null || company.KioskActivationToken != cookie.Value.token)
+            return Json(new { hasSession = false });
+
+        var window  = DateTime.UtcNow.AddSeconds(-60);
+        var session = await _unitOfWork.KioskSessions.FirstOrDefaultAsync(
+            s => s.CompanyId == cookie.Value.companyId
+              && s.SessionType == KioskSessionType.InPerson
+              && s.Status == KioskSessionStatus.Active
+              && s.CreatedAt >= window,
+            ignoreQueryFilters: true);
+
+        if (session == null) return Json(new { hasSession = false });
+        return Json(new { hasSession = true, sessionToken = session.SessionToken });
+    }
+
     /// <summary>
     /// Serves the company logo for anonymous kiosk pages. Resolves the company from the
     /// KioskDevice cookie so no tenant context is needed on the anonymous request.

src/PowderCoating.Web/Views/Shared/_KioskLayout.cshtml

@@ -85,7 +85,6 @@
 }
 
 <script src="~/lib/bootstrap/js/bootstrap.bundle.min.js"></script>
-<script src="~/lib/microsoft/signalr/dist/browser/signalr.min.js"></script>
 @await RenderSectionAsync("Scripts", required: false)
 </body>
 </html>

src/PowderCoating.Web/wwwroot/js/kiosk-welcome.js

@@ -1,10 +1,12 @@
 "use strict";
 
+// Polls /Kiosk/PollSession every 3 seconds and navigates when staff triggers an intake.
+// SignalR was replaced with polling because Azure App Service's ingress proxy cancels
+// anonymous WebSocket and SSE handshakes before the SignalR protocol exchange completes.
 (function () {
     const el = document.getElementById("kiosk-welcome-root");
     if (!el) return;
 
-    const companyId = el.dataset.companyId;
     const dot   = document.getElementById("kiosk-conn-dot");
     const label = document.getElementById("kiosk-conn-label");
 
@@ -13,51 +15,28 @@
         if (label) label.textContent = text;
     }
 
-    if (!companyId) {
-        setStatus("#ef4444", "Not configured (no company ID)");
-        console.error("KioskHub: data-company-id is empty — kiosk activation may be invalid.");
-        return;
-    }
-
     setStatus("#94a3b8", "Connecting…");
 
-    // Skip WebSocket — anonymous WebSocket upgrades are blocked by the Azure App Service
-    // ingress proxy before the SignalR handshake completes. Server-Sent Events and
-    // long polling work fine for the low-frequency "StartIntake" push this hub needs.
-    const connection = new signalR.HubConnectionBuilder()
-        .withUrl(`/hubs/kiosk?companyId=${companyId}`, {
-            transport: signalR.HttpTransportType.ServerSentEvents | signalR.HttpTransportType.LongPolling
-        })
-        .withAutomaticReconnect([2000, 5000, 10000, 30000])
-        .configureLogging(signalR.LogLevel.Information)
-        .build();
+    let active = true;
 
-    connection.on("StartIntake", function (sessionToken) {
-        setStatus("#2563eb", "Starting…");
-        window.location.href = `/Kiosk/Intake/${sessionToken}/Contact`;
-    });
-
-    async function startConnection() {
+    async function poll() {
+        if (!active) return;
         try {
-            await connection.start();
+            const res  = await fetch("/Kiosk/PollSession", { cache: "no-store" });
+            if (!res.ok) throw new Error("HTTP " + res.status);
+            const data = await res.json();
             setStatus("#16a34a", "Ready");
-            console.info("KioskHub connected, group kiosk-" + companyId);
-        } catch (err) {
-            setStatus("#ef4444", "Connection failed — retrying…");
-            console.warn("KioskHub connect failed, retrying in 10s…", err);
-            setTimeout(startConnection, 10000);
+            if (data.hasSession && data.sessionToken) {
+                active = false;
+                setStatus("#2563eb", "Starting…");
+                window.location.href = `/Kiosk/Intake/${data.sessionToken}/Contact`;
+                return;
+            }
+        } catch {
+            setStatus("#f59e0b", "Connection issue — retrying…");
         }
+        if (active) setTimeout(poll, 3000);
     }
 
-    startConnection();
-
-    connection.onreconnecting(() => setStatus("#f59e0b", "Reconnecting…"));
-    connection.onreconnected(() => {
-        setStatus("#16a34a", "Ready");
-        console.info("KioskHub reconnected");
-    });
-    connection.onclose(() => {
-        setStatus("#ef4444", "Disconnected — retrying…");
-        setTimeout(startConnection, 10000);
-    });
+    setTimeout(poll, 500);  // first poll quickly; subsequent every 3s
 })();