4pda App Stops Connecting on 0.16.16+

[DmitryN71]

exclave_backup_1764602067996.json

Bug Report: Connectivity Regression for Specific App (4pda) in v0.16.16+
Severity: High (Functional Regression)
​Summary
​The "4pda" Android application fails to establish a connection when using Exclave versions 0.16.16 and 0.16.17. The exact same configuration works perfectly on version 0.16.15. This indicates a regression in the routing or split-tunneling logic introduced in 0.16.16.
​Environment
​App Name: Exclave
​Affected Versions: 0.16.16, 0.16.17
​Last Working Version: 0.16.15
​OS: Android
​Target App: 4pda (Package: ru.4pda.app / Domain: 4pda.to, 4pda.ru)
​Configuration Details (from attached backup)
​DNS Strategy: Remote & Direct set to https://dns.adguard-dns.com/dns-query
​Routing Strategy: Domain Strategy: AsIs
​Tun Implementation: Mixed/System (Value: 1)
​Split Tunneling: Enabled (individual list populated with ~100+ RU apps).
​Note: The 4pda app is not present in the exclusion list, meaning it should be routed through the proxy (tunneled).
​Rules: Explicit rules exist for 4pda:
​Rule: 4pda IP (108.181.60.131)
​Rule: 4pda (Domain: 4pda.to, 4pda.ru)
​Symptoms
​On v0.16.15, the 4pda app loads content normally via the configured proxy.
​Upon updating to v0.16.16 or v0.16.17, the app shows connection errors (timeout/no network).
​Global connectivity check (e.g., cp.cloudflare.com) occasionally shows context deadline exceeded in the profile logs, but other apps in the exclusion list appear to function or are unaffected.
​Steps to Reproduce
​Install Exclave v0.16.16 or v0.16.17.
​Import the attached configuration file (exclave_backup_1764602067996.json).
​Launch the 4pda application.
​Result: Connection fails.
​Downgrade to v0.16.15.
​Result: Connection succeeds.

[DmitryN71]

PS: both mentioned rules for the app are turned off.

[DmitryN71]

Update: Root Cause Isolation (XTLS-Vision + IMAPS)
​I have performed further analysis and isolated the specific cause of the regression. The issue is not the app itself, but how XTLS-Vision handles IMAPS traffic in the new core.
​Technical Findings:
​Protocol: VLESS + Reality
​Critical Factor: flow: xtls-rprx-vision
​Traffic Type: The affected app (4pda) initiates a connection via IMAPS (IMAP over TLS, likely Port 993).
​Behavior:
In v0.16.16+, when xtls-rprx-vision is enabled, IMAPS traffic triggers a context cancellation immediately.

Log output:
I/v2ray-core: app/proxyman/outbound: failed to process outbound traffic > proxy/vless/outbound: connection ends > context canceled

Workaround / Confirmation:
If I edit the server/client configuration to remove flow: xtls-rprx-vision (leaving just VLESS+Reality), the connection succeeds immediately. This confirms the regression lies specifically in the implementation of the Vision flow in the recent core update.

[dyhkwong]

suspicious change: XTLS/Xray-core@c6afcd5

Can you confirm Xray-core 25.12.1 also has this bug?

PS. there is no Exclave 0.16.17?

[dyhkwong]

Reverted "XTLS Vision: Check TLS record isComplete", please try https://github.com/dyhkwong/Exclave/actions/runs/19839918451 (for 0.16.16) or https://github.com/dyhkwong/Exclave/actions/runs/19840029257 (for 0.17.0)

[DmitryN71]

Reverted "XTLS Vision: Check TLS record isComplete", please try https://github.com/dyhkwong/Exclave/actions/runs/19839918451 (for 0.16.16) or https://github.com/dyhkwong/Exclave/actions/runs/19840029257 (for 0.17.0)

Wow! You're fast, thanks!
I confirm the issue is fixed in this build of 0.16.16. I haven't tried the 0.17.0 build, but I guess it's also good :)

[dyhkwong]

0.17.1 and 0.16.17 has been released to address this.
This bug was introduced in XTLS/Xray-core#5179 and I copied that code as is, I don't have the condition to reproduce this, if you can reproduce this with Xray-core 25.12.1, please also report to them so this can be fixed.

[dyhkwong]

Xray pushed a new fix for vision but it is for server side CPU consumption, not for the client. I don't understand Russian verification code so I can't test 4PDA myself.

This build contains the change of XTLS/Xray-core#5365, can you test if it works or it is still broken?

[DmitryN71]

I don't understand Russian verification code so I can't test 4PDA myself.

Thanks. I will test it, but it seems it hasn't been published by you yet.
And you don't need to speak Russian to reproduce this; you can just test it on any app that connects via IMAPS.

[dyhkwong]

Thanks. I will test it, but it seems it hasn't been published by you yet.

Okay now.

[DmitryN71]

Xray pushed a new fix for vision but it is for server side CPU consumption, not for the client. I don't understand Russian verification code so I can't test 4PDA myself.

This build contains the change of XTLS/Xray-core#5365, can you test if it works or it is still broken?

Confirm as fixed in this build, too! :)

[dyhkwong]

That's strange. Will hold it until those Xray Android clients release new version and it gets wider testing.

[DmitryN71]

Are you saying it's strange that it's working? :)
Anyway, what build do you recommend to use now?