fix(mobile): report stalled RPC diagnostics

mobile/app/connection-log.tsx

@@ -12,7 +12,8 @@ import { connectionLogStore } from '../src/transport/connection-log-buffer'
 import { useHostClient } from '../src/transport/client-context'
 import {
   useLastConnectedAt,
-  useReconnectAttempt
+  useReconnectAttempt,
+  useRpcUnresponsiveSince
 } from '../src/transport/client-context-connection-metrics'
 import { buildConnectionDiagnosticsReport } from '../src/diagnostics/connection-diagnostics-report'
 import type { ConnectionLogEntry, HostProfile } from '../src/transport/types'
@@ -49,6 +50,7 @@ export default function ConnectionLogScreen() {
   const { state } = useHostClient(selected?.id)
   const reconnectAttempts = useReconnectAttempt(selected?.id)
   const lastConnectedAt = useLastConnectedAt(selected?.id)
+  const rpcUnresponsiveSince = useRpcUnresponsiveSince(selected?.id)
 
   const subscribe = useCallback(
     (listener: () => void) =>
@@ -71,6 +73,7 @@ export default function ConnectionLogScreen() {
       state,
       reconnectAttempts,
       lastConnectedAt,
+      rpcUnresponsiveSince,
       platform: `${Platform.OS} ${Platform.Version ?? ''}`.trim(),
       appVersion: Constants.expoConfig?.version ?? 'unknown',
       entries
@@ -78,7 +81,7 @@ export default function ConnectionLogScreen() {
     await Clipboard.setStringAsync(report)
     setCopied(true)
     setTimeout(() => setCopied(false), 2000)
-  }, [selected, state, reconnectAttempts, lastConnectedAt, entries])
+  }, [selected, state, reconnectAttempts, lastConnectedAt, rpcUnresponsiveSince, entries])
 
   return (
     <View style={[styles.container, { paddingTop: insets.top + spacing.sm }]}>
@@ -112,7 +115,9 @@ export default function ConnectionLogScreen() {
         <>
           <View style={styles.statusRow}>
             <Text style={styles.statusText}>
-              {state}
+              {state === 'connected' && rpcUnresponsiveSince != null
+                ? 'Connected, not responding'
+                : state}
               {reconnectAttempts > 0 ? ` · attempt ${reconnectAttempts}` : ''}
             </Text>
             <Pressable style={styles.copyButton} onPress={() => void copyDiagnostics()}>

mobile/src/diagnostics/connection-diagnostics-report.test.ts

@@ -52,4 +52,24 @@ describe('buildConnectionDiagnosticsReport', () => {
     expect(report).toContain('Last connected: never this session')
     expect(report).toContain('No connection events recorded this session.')
   })
+
+  it('reports a connected application RPC stall', () => {
+    const report = buildConnectionDiagnosticsReport({
+      hostName: 'Host 3',
+      endpoint: 'ws://100.65.9.106:6768',
+      state: 'connected',
+      reconnectAttempts: 0,
+      lastConnectedAt: NOW - 60_000,
+      rpcUnresponsiveSince: NOW - 30_000,
+      platform: 'ios 26.5.1',
+      appVersion: '0.0.33',
+      entries: [],
+      nowMs: NOW
+    })
+
+    expect(report).toContain(
+      'State: connected, application RPC not responding (reconnect attempts: 0)'
+    )
+    expect(report).toContain('Application RPC stalled: 2026-07-09T21:59:30.000Z (30s ago)')
+  })
 })

mobile/src/diagnostics/connection-diagnostics-report.ts

@@ -11,6 +11,7 @@ export function buildConnectionDiagnosticsReport(args: {
   state: ConnectionState
   reconnectAttempts: number
   lastConnectedAt: number | null
+  rpcUnresponsiveSince?: number | null
   platform: string
   appVersion: string
   entries: readonly ConnectionLogEntry[]
@@ -25,7 +26,16 @@ export function buildConnectionDiagnosticsReport(args: {
   lines.push(
     `Endpoint: ${formatEndpoint(args.endpoint)}${isTailscaleEndpoint(args.endpoint) ? ' (Tailscale)' : ''}`
   )
-  lines.push(`State: ${args.state} (reconnect attempts: ${args.reconnectAttempts})`)
+  const stateLabel =
+    args.state === 'connected' && args.rpcUnresponsiveSince != null
+      ? 'connected, application RPC not responding'
+      : args.state
+  lines.push(`State: ${stateLabel} (reconnect attempts: ${args.reconnectAttempts})`)
+  if (args.rpcUnresponsiveSince != null) {
+    lines.push(
+      `Application RPC stalled: ${new Date(args.rpcUnresponsiveSince).toISOString()} (${formatAgo(now - args.rpcUnresponsiveSince)} ago)`
+    )
+  }
   lines.push(
     args.lastConnectedAt == null
       ? 'Last connected: never this session'