Survival (Fallout 4)

Survival mode is the most difficult gameplay mode in Fallout 4. It differs significantly from the other gameplay modes.

Survival mode
Survival mode can be accessed in the options menu. Unlike Hardcore modes in previous Fallout games, Survival mode can be set before gameplay. This mode also cannot be toggled freely. Once Survival mode is activated, turning it off will prevent you from turning it back on for that save file.

Features in this mode are as follows:
 * Manual saving, quicksaving, and autosaving (with the exception of autosaving after sleeping) are disabled. The only way to save is to sleep in any bed for at least one hour.
 * In Survival mode, the exit save is automatically inaccessible once it is loaded. System crashes will allow you to return to your last exit save.
 * Fast travel is disabled.
 * The Sole Survivor takes but also deals more damage.
 * Most threats are not visible on the compass.
 * Locations of interest are harder to detect.
 * A new perk, Adrenaline, is automatically given to the Sole Survivor.
 * The Sole Survivor must stay hydrated, eat periodically, and have a regular sleep cycle in order to survive.
 * If the Sole Survivor is hungry, all foods lose their healing properties and do not regain them until enough is consumed to make the survivor "well-fed." The amount of food that must be eaten to do this is relative to its quality, i.e, brahim steak removes hunger better than grilled radroach.
 * Fatigue damage reduces Action points (AP).
 * Sleeping in a bed for less than 7 hours does not heal Hit points (HP).
 * Illness and antibiotics are introduced.
 * The healing rates of RadAway, stimpaks, and other healing items are significantly reduced.
 * RadAway and chems can negatively affect the immune system.
 * Limbs no longer heal after combat and must be restored with a stimpak, sleeping in a bed until well rested, or by visiting a doctor.
 * Ammunition has weight and total carry weight is significantly reduced for both the Sole Survivor and their companions.
 * Companions will not get back up if downed in combat until healed. If left unattended, they will return home.
 * Robotic companions created in the Automatron add-on, excluding NPC robots like Ada and Jezebel, will now be destroyed if not repaired after being downed in combat.
 * Cleared locations (both those marked as "[Cleared]" or otherwise) take much longer to repopulate enemies and loot.
 * Normally non-"[cleared]" locations take 7 in-game days and "[cleared]" locations take 20 in-game days to start respawning. In survival mode, these are increased to 35 in-game days and 80 in-game days, respectively.
 * Perhaps as a consequence of fewer respawned enemies, enemies now yield twice as much experience. (This change is not explicitly mentioned by the help notes for survival mode.)
 * Enemies that usually spawn at higher levels will now spawn with regularity.
 * Ability to access the game console (the tilde key) and use console commands is disabled.

Gameplay differences


Wellness
There are five stages in each category of wellness that span in-game hours. It doesn't appear that the thresholds are linear. For example, it takes about 6 hours to go from well-fed to peckish to hungry, then 12 hours to go from hungry to famished. The following table shows the approximate times that it takes for a character to go from completely satisfied to the listed condition in each area. In-game time is expressed in "hours" and real-time is expressed in "minutes". These effects can be sped up when using certain items. Stimpaks and other drugs inducing dehydration, Rad-Away causing hunger, etc.

''Note: The In-game / real-time data in this table are approximations only. The time expressed is not truly accurate. This table may be incomplete''.

Bugs

 * If you start in Survival mode and later change the game mode, your water production from Water Purifiers will not change.
 * When you first join The Railroad, the message "You can now fast travel to and from Railroad HQ" still appears, despite the fact that fast travel is disabled in Survival mode.