Awakened cohort level

[Genesist]

I am starting at level 7. For the purpose of my character I took leadership at level 6, then got a 4 HD desmodo guard bat as my cohort. It was then trained as a warbeast (MMII). Afterwards Awaken was cast on it. The price of both of these is taken into account.

My question is what level is it? Also when it levels up does it take classes? How does that all work.

 

[Sekhmet]

It'll gain 3 additional HD total, for a total of 7 HD, which puts it in the same region as the other suggested 7th Level or Higher companions in the SRD.
It doesn't take classes, it gains racial hit die (may as well consider them to be the Magical Beast class). You can consider HD to be roughly synonymous with character level, except (in general) the bat won't ever gain HD through gaining EXP.
Some people would argue that, being intelligent, they can take class levels (the Celestial Charger unicorn variant is a level 7 Cleric), but I'd leave that up to the DM's discretion. You'll have to work with your DM to come up with an agreeable LA for your Bat, if that is the case.

Your Bat (as a Magical Beast) will gain the following as it gains HD - d10 HP, BAB equal to it's HD, Good Fort and Reflex saves, and 2+ Int mod skill points. He'll also gain Darkvision 60' and low-light vision.
Every 4th HD, he'll gain a stat point (dumped into his primary), and every 3rd HD he gains a feat. Remember that he has to qualify for feats, just like a PC does.

 

[Genesist]

So is there no hard rule then for determining the level or advancement of an intelligent animal cohort?

 

[Genesist]

Looking at it stat-wise. It has at base 15 stat points above a level 1 base race from MM1. How much LA would you give a race that gain 15 stat points, a good fly speed, and 5 NA?

 

[Sekhmet]

Probably only +2.
Savage Species (ihatethisbook) gives a few good suggestions with creating playable races (or modifying current monsters to be played).
There are some good ideas here ECL Calculator .
The automated version is here http://personal.nbnet.nb.ca/shadows/Handbook/ECLcalc.html .

I got a total of 6.3 ECL, rounding to 6.
The creature is 4HD with 2LA.

Using templates and spell to increase the HD does not increase the LA, so your bat will be 7HD with 2LA.
Please make sure your DM carefully examines your bat's performance over the next few levels to determine if the LA is accurate or not, and adjusts it accordingly. I have a feeling +2 is just fine.