@Jeffrey Ng - Thanks for reaching out.
If you are using trackTrace, there is a message size limit of 32768 characters where as if you are using trackevent's custom property then you will have a limit of 8192.
Can you provide what you are using here?
Also Can you make sure you are using the Trace API because then you should be able to have a message length a lot longer that 8kb.
See Docreference here.
Also please take a look at this doc for more reference on Limit summary
Update :
You should still be able to use TrackTrace for a longer message limit.
See this doc for more reference : api-custom-events-metrics
"The size limit on message is much higher than the limit on properties. An advantage of TrackTrace is that you can put relatively long data in the message.
For example, you can encode POST data there."
Node.js TrackTrace
See the below docs for more reference :
Hope this helps.
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