Can i see full chat history?

To my knowledge, it's not possible to get a full chat log in Steam. It only displays the last few messages.

you may be able to see a few more lines if you use the web chat instead of the client's chat window - no guarantee though.

No, chat history isn't supported by the (shitty) Steam client nor by the Enhanced Steam add-on.
However I'm not aware of which basis they're using to clean everyone's chat history.

Yes, ask steam support for the full conversation :D

Steam support would probably give you the log it is, after all, public information.

:( would be useful eg as gave away gift & user said all good in chat but now it's marked as not received

I just discovered this recently, but the Steam iOS app tends to show a long list of recently sent/received messages.

Has anything changed in the year or so since this was posted? Any workaround?

http://www.steamgifts.com/giveaway/wsPPM/I-need-my-chat-history