[Bug]: Electrum config connect ANR in isValidURL regex on main thread

[piotr-iohk]

What happened?

On production 2.3.1 (build 184), Play Vitals reports 1 ANR (1 user, 1 event) with stack:

Input dispatching timed out
  at kotlin.text.Regex.matches (Regex.kt:108)
  at to.bitkit.ui.settings.advanced.ElectrumConfigViewModel.isValidURL (ElectrumConfigViewModel.kt:209)
  at to.bitkit.ui.settings.advanced.ElectrumConfigViewModel.validateInput (ElectrumConfigViewModel.kt:189)
  at to.bitkit.ui.settings.advanced.ElectrumConfigViewModel$onClickConnect$1.invokeSuspend (ElectrumConfigViewModel.kt:249)
  at to.bitkit.ui.settings.advanced.ElectrumConfigViewModel.onClickConnect (ElectrumConfigViewModel.kt:248)

User tapped Connect on the Electrum server settings screen. URL validation runs a hostname Regex.matches() call via ICU native matcher (libicui18n.so), blocking the main thread long enough to trigger an ANR.

Expected behavior

Tapping Connect should validate host/port quickly and either show a validation toast or proceed to connect — without freezing the UI.

Steps to Reproduce

1. Open Settings → Advanced → Electrum server (custom server config).
2. Enter a host string that may stress the hostname regex (exact production input unknown; likely long/malformed host before port).
3. Tap Connect.
4. UI hangs; ANR dialog may appear.

Code path: onClickConnect() → viewModelScope.launch (Main) → validateInput() → isValidURL() → hostname.matches(Regex(...)) at line 209.

Likely fix direction: move validation off main thread and/or replace regex with URI parsing (see RgsServerViewModel.isValidURL pattern).

Logs / Screenshots / Recordings

• Play Vitals screenshot (2026-07-13 weekly report)
• Stack trace above (Play Console ANR details)

Bitkit Version

2.3.1 (build 184) — production mainnet

Device / OS

Motorola moto g - 2025, Android 16 (SDK 36). Occurred ~4 days before report (Play Vitals sample).

Reproducibility

Rarely (once or twice) — 1 user / 1 event on 2.3.1 since Jun 29 rollout.

Additional context

• Play Vitals week of Jul 6–13: 9 crashes, 1 ANR on 2.3.1 (184). This ANR is the only ANR cluster this week.
• [Bug]: Node.listBalances ANR in receive flow #1036 (LDK listBalances/listPeers ANRs) and [Bug]: CoreService$init$1.invokeSuspend — UniFFI API checksum mismatch (bitkit-core, Play 2.2.0) #983 (CoreService init) not seen on 2.3.1 this week.
• [Bug]: Production SIGABRT in arm64 native code (Play 2.2.0 / build 181) #982 SIGABRT still dominant (7/9 crash events).
• Tracked under epic [Epic] Play production crashes — mainnet 2.2.0 (build 181) vitals triage #986.