Tearing my hair out on this Take Lanes.  Don't know what I did but now and then I see clips get splitted to line up with a 'selected' clip.  My clips are almost always overlapping each other as when I do punch in, I always give some lead and end duration then cross fade them.  This auto mute/split causing me to have to go back and undo (delete every 'remnants' clips.  Then I can not resize the Left or Right ends of a clip, it shows a 'crossfade' tool, and then occasionally somehow the'left or right ' bracket' symbol is back  which allows me to extend the left or right border of the clip.  Looks like this is the way that it supposes to work but can someone explain what is going on here as I'm at a lost.  Thanks

What you're seeing is the function of the Comping tool (icon looks like three horizontal lines representing multiple takes) which is the default mode of the Smart tool when used in the lower half of clips in take lanes. It can't be turned off so you'll just need to stay away from the bottom half of clips when editing in take lanes and making manual splits and crossfades. But you might want to look into Comp recording/editing functions as they're designed to facilitate the process of comping takes/punches together.
 
If you do inadvertently split clips with the comp tool, you can Undo it (Ctrl+Z) immediately or "heal" it at any time by selecting adjacent clips in one of lanes and Ctrl+clicking one of them with the Comp tool.

When editing what condition causing it to split like that?  so I can watch and preventing it.  I cant undo b/c I don't know when it does that, and I can mot see all  the lanes at once (vertically)

Right click the Global Record button. From there you should select any option apart from "Comping Mode"

I strongly suggest watching a tutorial on X3 speed comping on YouTube. It will change your life. At least the bits of it that include Sonar :)

Thanks for the replies.  After spending an evening reading, figuring things out, I think that this function (speed comping) although a good idea, for my workflow it's actually causing me to spend more time rather than less to edit clips.
Actually I rarely do 'true' comping, i.e., clip a note/word from different phrases/lines.  And when I do this, it's at most between two or three clips.  If I really need to patch a bunch of notes/words to comp a phrase, it never really work out for me (sounding natural and fluid),  for this situation I would re-track that line/phrase.
 
What I do most of the time is selecting between a bunch of short phrases (clips), phrases with some clear break point like a line of a verse or a guitar runs.  I also have bunch of alternative takes to see if something fits better.  For this, this implementation of comping doesn't fit.  It would auto split all my alternative takes and I have to 'heal' each clips.  Once a clip is trimmed, why not just discard the end bits, I have to lasso the bits and delete them manually as they cluttered up the view.
 
Maybe for future release this can be considered as 2 types of comping, first level is for selecting clip among many and a second level for going in to slice and dice (what it's designed to do now).
 

Why would you have to heal clips?

Sanderxpander
Why would you have to heal clips?

When I want to hear the clip in it entirety. After some comping a comped clip might not have the fluidity of a less than perfect take, but now all clips are clipped to bit.
Perhaps a good solution would be for you to be able to select the clips that you want to comp and leave the rest alone.

I see. I usually just click the parts I want to hear. Are you making very many very small comps?

+1 to watching a tutorial on the comping feature. The comping mode is designed for full phrases, specifically where you can split at a zero-crossing (no audio, or where the envelope drops to zero). This also makes the crossfades between clips much more seamless. Although comping at other places is definitely possible, it is not the ideal use of comping's intent.
 
As mentioned above, it is important to watch the cursor's "look" when using the smart tool. There are hot spots at various places on the waveform, and the look of that cursor lets you know what mode it is in. It seems like you are unintentionally splitting clips. The hot spots for the comping tool are at this link: https://www.cakewalk.com/Documentation?product=SONAR%20X3&language=3&help=Tools.09.html
 
One of the quickest "down and dirty" tutorials (6 minutes), is here: https://youtu.be/TPi1BkBhEvE