Lordaeron SendAddonMessage / CHAT_MSG_ADDON not received between players

[macospeektv]

Realm:
Lordaeron
Client:
WoW 3.3.5a

Description:
Addon messages sent with SendAddonMessage are not being received by other players through CHAT_MSG_ADDON.

Tested with:
- Two characters in the same party/raid
- Both characters online and near each other
- Both clients running the same addon
- Tested WHISPER addon channel
- Tested multiple prefixes: SR335, SOFTRES, SRTEST
- Tested AceComm-3.0 and direct SendAddonMessage
- Normal WHISPER chat messages are delivered correctly

Expected behavior:
When character A sends:

SendAddonMessage("SR335", "PING|test", "WHISPER", "CharacterB")

Character B should receive CHAT_MSG_ADDON with:
prefix = "SR335"
message = "PING|test"
distribution = "WHISPER"
sender = "CharacterA"

Actual behavior:
Character B receives nothing through CHAT_MSG_ADDON.
No addon event fires.
No response can be sent back.

Additional observation:
Normal SendChatMessage(..., "WHISPER", nil, "CharacterB") works correctly.
The addon can synchronize data using visible whisper text, but not through addon messages.

Steps to reproduce:
1. Log in with two characters on two clients.
2. Put both characters in the same party or raid.
3. On both clients, register CHAT_MSG_ADDON event.
4. Register addon prefixes:
- SR335
- SOFTRES
- SRTEST
5. From CharacterA, send:
SendAddonMessage("SR335", "PING|123", "WHISPER", "CharacterB")
6. CharacterB does not receive CHAT_MSG_ADDON.
7. Repeat with PARTY/RAID if needed.

Test addon output:
Both clients show:
- SendAddonMessage available
- Prefixes registered
- AceComm loaded
- ChatThrottleLib loaded

But no PING/PONG is received through CHAT_MSG_ADDON.

Reference:
A similar issue was discussed here:
https://forum.warmane.com/showthread.php?t=481759

[Diabolik01]

this is still an issue

[LazariusWoW]

As mentioned in that thread, that belongs to bugtracker, not the forum. And you already posted a report there which both had a workaround solution and was dismissed as a duplicate, so devs are aware of it:
https://www.warmane.com/bugtracker/report/133789
https://www.warmane.com/bugtracker/report/133537