Samsung Internet v29.x fails requestPostMessageChannel - reproducible on official demo

[maciejrozanski]

I am reporting a regression in Samsung Internet Browser v29.x. The method requestPostMessageChannel fails to establish a communication channel due to a service binding failure ("Unable to start service... not found").

This issue:

• Works perfectly on Samsung Internet v28.x and Chrome/Firefox/Brave.
• Is reproducible on the official Google twa-post-message demo.

Affected Method [CustomTabsService#requestPostMessageChannel]

Environment

• Device: Android (Checked on Android 14)
• Samsung Internet (FAIL): v29.0.2.76, v29.0.1.12
• Samsung Internet (SUCCESS): v28.0.5.9
• Chrome (SUCCESS): Latest Stable
• Library: android-browser-helper (latest)

Reproduction Steps To rule out project-specific issues, I verified this using the official demo:

1. Cloned demos/twa-post-message.
2. Updated applicationId to match my domain's assetlinks.json (to ensure DAL validation passes).
3. Ran the demo on Samsung Internet v29.x.

Result: requestPostMessageChannel returns false.

Comparative Log Analysis Below are the logs from the exact same demo app running on Chrome vs. Samsung v29.

1. Chrome (SUCCESS) Chrome correctly validates the relationship and establishes the channel.

D/PostMessageDemo: Requested Post Message Channel: true
D/PostMessageDemo: Relationship result: true
D/PostMessageDemo: Message channel ready.

2. Samsung Internet v29.x (FAIL) Samsung v29 attempts to bind to the service but fails to resolve the Intent.

I/CustomTabs...ionService: requestPostMessageChannel() session:H.y@ec31a6a
I/ClientManager: bindToPostMessageServiceForSession()
W/ActivityManager: Unable to start service Intent { xflg=0x4 cmp=com.demo.app/H.B } U=0: not found
W/PostMessageServConn: Could not bind to PostMessageService in client.
W/CustomTabsConnection: requestPostMessageChannel() with origin ... =false
D/PostMessageDemo: Requested Post Message Channel: false

Impact
This regression breaks postMessage communication for TWA applications running on the latest Samsung Internet Browser.

Can anyone confirm the issue?