iOS: auto-load the scoped gateway canvas with safe fallback (#40282)

Merged via squash.

- mb-server validation: `swift test --package-path apps/shared/OpenClawKit --filter GatewayNodeSessionTests`
- mb-server validation: `pnpm build`
- Scope note: top-level `RootTabs` shell change was intentionally removed from this PR before merge

apps/ios/Sources/Model/NodeAppModel+Canvas.swift

@@ -1,9 +1,24 @@
 import Foundation
 import Network
 import OpenClawKit
-import os
+
+enum A2UIReadyState {
+    case ready(String)
+    case hostNotConfigured
+    case hostUnavailable
+}
 
 extension NodeAppModel {
+    func resolveCanvasHostURL() async -> String? {
+        guard let raw = await self.gatewaySession.currentCanvasHostUrl() else { return nil }
+        let trimmed = raw.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty, let base = URL(string: trimmed) else { return nil }
+        if let host = base.host, LoopbackHost.isLoopback(host) {
+            return nil
+        }
+        return base.appendingPathComponent("__openclaw__/canvas/").absoluteString
+    }
+
     func _test_resolveA2UIHostURL() async -> String? {
         await self.resolveA2UIHostURL()
     }
@@ -19,22 +34,14 @@ extension NodeAppModel {
     }
 
     func showA2UIOnConnectIfNeeded() async {
-        guard let a2uiUrl = await self.resolveA2UIHostURL() else {
-            await MainActor.run {
-                self.lastAutoA2uiURL = nil
-                self.screen.showDefaultCanvas()
-            }
-            return
-        }
         let current = self.screen.urlString.trimmingCharacters(in: .whitespacesAndNewlines)
         if current.isEmpty || current == self.lastAutoA2uiURL {
-            // Avoid navigating the WKWebView to an unreachable host: it leaves a persistent
-            // "could not connect to the server" overlay even when the gateway is connected.
-            if let url = URL(string: a2uiUrl),
+            if let canvasUrl = await self.resolveCanvasHostURLWithCapabilityRefresh(),
+               let url = URL(string: canvasUrl),
                await Self.probeTCP(url: url, timeoutSeconds: 2.5)
             {
-                self.screen.navigate(to: a2uiUrl)
-                self.lastAutoA2uiURL = a2uiUrl
+                self.screen.navigate(to: canvasUrl)
+                self.lastAutoA2uiURL = canvasUrl
             } else {
                 self.lastAutoA2uiURL = nil
                 self.screen.showDefaultCanvas()
@@ -42,11 +49,46 @@ extension NodeAppModel {
         }
     }
 
+    func ensureA2UIReadyWithCapabilityRefresh(timeoutMs: Int = 5000) async -> A2UIReadyState {
+        guard let initialUrl = await self.resolveA2UIHostURLWithCapabilityRefresh() else {
+            return .hostNotConfigured
+        }
+        self.screen.navigate(to: initialUrl)
+        if await self.screen.waitForA2UIReady(timeoutMs: timeoutMs) {
+            return .ready(initialUrl)
+        }
+
+        // First render can fail when scoped capability rotates between reconnects.
+        guard await self.gatewaySession.refreshNodeCanvasCapability() else { return .hostUnavailable }
+        guard let refreshedUrl = await self.resolveA2UIHostURL() else { return .hostUnavailable }
+        self.screen.navigate(to: refreshedUrl)
+        if await self.screen.waitForA2UIReady(timeoutMs: timeoutMs) {
+            return .ready(refreshedUrl)
+        }
+        return .hostUnavailable
+    }
+
     func showLocalCanvasOnDisconnect() {
         self.lastAutoA2uiURL = nil
         self.screen.showDefaultCanvas()
     }
 
+    private func resolveA2UIHostURLWithCapabilityRefresh() async -> String? {
+        if let url = await self.resolveA2UIHostURL() {
+            return url
+        }
+        guard await self.gatewaySession.refreshNodeCanvasCapability() else { return nil }
+        return await self.resolveA2UIHostURL()
+    }
+
+    private func resolveCanvasHostURLWithCapabilityRefresh() async -> String? {
+        if let url = await self.resolveCanvasHostURL() {
+            return url
+        }
+        guard await self.gatewaySession.refreshNodeCanvasCapability() else { return nil }
+        return await self.resolveCanvasHostURL()
+    }
+
     private static func probeTCP(url: URL, timeoutSeconds: Double) async -> Bool {
         guard let host = url.host, !host.isEmpty else { return false }
         let portInt = url.port ?? ((url.scheme ?? "").lowercased() == "wss" ? 443 : 80)

apps/ios/Sources/Model/NodeAppModel.swift

@@ -882,16 +882,17 @@ final class NodeAppModel {
         let command = req.command
         switch command {
         case OpenClawCanvasA2UICommand.reset.rawValue:
-            guard let a2uiUrl = await self.resolveA2UIHostURL() else {
+            switch await self.ensureA2UIReadyWithCapabilityRefresh(timeoutMs: 5000) {
+            case .ready:
+                break
+            case .hostNotConfigured:
                 return BridgeInvokeResponse(
                     id: req.id,
                     ok: false,
                     error: OpenClawNodeError(
                         code: .unavailable,
                         message: "A2UI_HOST_NOT_CONFIGURED: gateway did not advertise canvas host"))
-            }
-            self.screen.navigate(to: a2uiUrl)
-            if await !self.screen.waitForA2UIReady(timeoutMs: 5000) {
+            case .hostUnavailable:
                 return BridgeInvokeResponse(
                     id: req.id,
                     ok: false,
@@ -899,7 +900,6 @@ final class NodeAppModel {
                         code: .unavailable,
                         message: "A2UI_HOST_UNAVAILABLE: A2UI host not reachable"))
             }
-
             let json = try await self.screen.eval(javaScript: """
             (() => {
               const host = globalThis.openclawA2UI;
@@ -908,6 +908,7 @@ final class NodeAppModel {
             })()
             """)
             return BridgeInvokeResponse(id: req.id, ok: true, payloadJSON: json)
+
         case OpenClawCanvasA2UICommand.push.rawValue, OpenClawCanvasA2UICommand.pushJSONL.rawValue:
             let messages: [OpenClawKit.AnyCodable]
             if command == OpenClawCanvasA2UICommand.pushJSONL.rawValue {
@@ -924,16 +925,17 @@ final class NodeAppModel {
                 }
             }
 
-            guard let a2uiUrl = await self.resolveA2UIHostURL() else {
+            switch await self.ensureA2UIReadyWithCapabilityRefresh(timeoutMs: 5000) {
+            case .ready:
+                break
+            case .hostNotConfigured:
                 return BridgeInvokeResponse(
                     id: req.id,
                     ok: false,
                     error: OpenClawNodeError(
                         code: .unavailable,
                         message: "A2UI_HOST_NOT_CONFIGURED: gateway did not advertise canvas host"))
-            }
-            self.screen.navigate(to: a2uiUrl)
-            if await !self.screen.waitForA2UIReady(timeoutMs: 5000) {
+            case .hostUnavailable:
                 return BridgeInvokeResponse(
                     id: req.id,
                     ok: false,