Fallout 4 files have been combed through and information pertaining to the Survival Mode overhaul extracted.
According to the files found by reddit user ShaneD53, both quick and manual saving has been disabled for Survival mode. The only way to save is to sleep in a bed. The length of time players will be able to sleep will depend upon the bed. Sleeping bags won't allow the player s=to sleep for a full night, but one can be used to save the game.
Fast travel has also been disabled which means you will have to foot it across the map. Should the player come upon a previously cleared location, they will find enemies have re-spawned, and contain less loot so keep that in mind when traversing the map. Also, limb injuries will no longer auto-heal, so players will need to make sure they have a Stimpak handy.
As with most Survival-type modes, enemies will be tougher and players will take more damage. Enemies will not appear on the game compass either and distance is shortened for areas of interest.
One bonus to engaging the enemy is the Adrenaline perk is automatically applied. This will help the player dole out more damage considering their enemies do too. Adrenaline rank increases with kills, but will be lowered when sleeping for more than one hour.
During battle, companions downed by enemies won't jump back into the fray. Instead, they will go home if they are abandoned and haven't been healed.
Ammo will have weight applied to it an it will vary depending on the caliber size. This applies to mini nukes and other weapons.
The updated Survival difficulty will also come with a new Wellness feature. Players will to eat, drink and rest or else SPECIAL stats will diminish and Fatigue will increase, affecting the player's combat prowess across the board.
Players can also get sick and when infected by a disease, eating bad meat or using Chems. When the player becomes sick, a message will pop up on the screen. At this point, the player will need to craft antibiotics or buy them from a physician in order to be cured.
Obviously, Bethesda will reveal more on the new Survival Mode features soon, so consider this information an outline of what to expect instead of gospel for the time being.
Mod support for Fallout 4 is also slated for PC as early as April.