TUIC subscription links do not include udp_relay_mode parameter, causing clients to use default behavior with bugs

[zhihaoHappyeveryday]

Describe the bug

When generating TUIC node subscription links (or single node share links) in s-ui, the links do not contain the udp_relay_mode parameter (neither native nor quic).

This forces many TUIC v5 clients (such as Clash Meta / Mihomo, NekoBox, v2rayN, Hiddify, Stash, etc.) to fall back to their own default UDP relay mode. As a result, users encounter the following issues:

• Some clients default to native mode, which performs poorly on unstable/high-packet-loss networks (UDP packet loss, stuttering, screen freezing in games, voice/video call issues, etc.).
• Users who want the more stable quic mode (lossless UDP relay based on QUIC streams) cannot control it through the subscription link and must manually edit the configuration in every client, which is very inconvenient.

To Reproduce

1. Add or edit a TUIC inbound in the s-ui panel (regardless of whether any UDP-related options are set).
2. Generate the subscription link or single node link.
3. Import the link into any TUIC-supporting client.
4. Check the parsed TUIC outbound configuration — the udp_relay_mode parameter is missing.

Expected behavior

s-ui should include the udp_relay_mode parameter in TUIC subscription links by default (for example, &udp_relay_mode=quic or allow the panel to choose native/quic and reflect it in the link).

This would allow users to control the UDP behavior directly via subscription and avoid relying on inconsistent client defaults.

Suggested solution

• Add a setting in the TUIC inbound configuration page for UDP Relay Mode (native / quic).
• Include the selected value in the generated subscription links as &udp_relay_mode=xxx.
• (Optional) Make quic the recommended/default for better stability in most real-world scenarios.

Environment

• s-ui version: [Please fill in your version, e.g. latest / v1.x.x]
• sing-box / Xray core version: [if known]
• Affected clients: Clash Meta, NekoBox, v2rayN, etc.

Additional context

According to the TUIC protocol and sing-box documentation, udp_relay_mode=quic provides reliable (no packet loss) UDP forwarding at the cost of slight extra overhead, while native offers better performance but is prone to packet loss on poor networks.

Many users prefer quic for stability, especially on mobile or international links.

Would you consider adding support for this parameter in TUIC subscription generation?

Thanks for the great panel!