The Mattermost plugin's handleAction reads params.replyToId for the
send action, but the message tool passes the reply target as
params.replyTo. The core handleSendAction (message-action-runner.ts)
extracts params.replyTo into a local variable and passes it to
executeSendAction, but never writes it back onto the params object
as replyToId. Since the plugin intercepts before executeSendAction
runs, it always sees replyToId as undefined.
This causes message(replyTo=<id>) to create top-level Mattermost
posts with root_id="" instead of threaded replies.
Fix: check both params.replyToId and params.replyTo in the plugin's
send handler.
Fixes#40924
2f5d68d5f5