Survival (Fallout 4)

Survival mode is the most difficult gameplay mode in Fallout 4. It differs significantly from the other gameplay modes. The mode was added to the game for all platforms on March 29, 2016. It replaced the existing Survival difficulty, which was renamed to Very Hard.

Survival mode
Survival mode can be accessed in the options menu. Unlike Hardcore mode used in Fallout: New Vegas, Survival mode can be set before gameplay. This mode also cannot be toggled freely. Once Survival mode is activated, turning it off will permanently disable it from being reactivated for that save file.

List of features
Features in this mode are as follows:
 * Sleeping in any bed for one hour is the only way to save the game, as all other methods of saving are disabled.
 * The exit save can only be loaded once when restarting the game. The save is automatically inaccessible once loaded.
 * Fast travel is disabled.
 * Teleporting out of the Institute works much more differently: the player character can teleport out of the Institute only to the C.I.T. ruins.
 * The Sole Survivor and all other NPCs take and deal double damage.
 * Enemies now yield twice as much experience.
 * Most threats are not visible on the compass.
 * The compass's range of detection for locations of interest has been significantly reduced.
 * A new perk, Adrenaline, is automatically given to the Sole Survivor. It gives the Sole Survivor damage bonuses provided for every two enemies they kill, up to a bonus of 50% extra damage.
 * The Sole Survivor must stay hydrated, eat periodically and have a regular sleep cycle in order to survive. Lack of either of these results in Fatigue, reducing maximum AP.
 * While 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 (or price), i.e, a ribeye steak removes hunger better than a grilled radroach.
 * Sleeping in a bed for less than 7 hours does not heal Hit Points (HP).
 * Illness and antibiotics are introduced.
 * The healing rates of restorative items are significantly slowed.
 * Using Stimpaks, RadAway, and chems can result in thirst and may cause illness.
 * Limbs no longer heal after combat and must be restored with a stimpak, by sleeping in a bed until the Sole Survivor is well rested or by visiting a doctor.
 * Rank 3 of Adamantium Skeleton lifts this effect, as it makes the Sole Survivor's limbs unable to be crippled.
 * Total carry weight is significantly reduced for both the Sole Survivor and their companions.
 * Ammunition has total carry weight, from bullets and cartridges that are light, to mini nukes and missiles that can really tow one down.
 * If the Sole Survivor becomes overencumbered, their Agility and Endurance will drop by 2, they will suffer from Fatigue and they will take constant damage to their legs.
 * Rank 4 of the Strong Back perk, rather than permitting fast travel while overencumbered, simply negates the above effects.
 * Downed companions will not get back up if downed in combat until healed. If left unattended, they will return to their most recent settlement to recover.
 * 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.
 * Locations take 35 in-game days for non-cleared locations and 80 in-game days for cleared locations to repopulate enemies and loot.
 * Stronger enemies now spawn with regularity, making the Commonwealth a dangerous place until very high levels.
 * Use of console commands is disabled.
 * Workshop capacity is reduced, and it may affect the availability of production items.

Gameplay differences


Wellness
There are five stages in each category of wellness that span in-game hours. It does not seem 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, RadAway causing hunger, etc.

Thirst

 * It is possible to drink directly from manual water pumps, water fountains and open water sources such as puddles and rivers. Drinking from irradiated sources has the possibility of afflicting one with an illnesses.
 * The Sole Survivor can fill empty glass containers with dirty or purified water. Dirty water is obtained from sources such as rivers, puddles or ponds. Purified water is obtained from water pumps and water fountains. Among the affected glass containers are beer bottles, empty milk bottles, Gwinnett ale bottles, Gwinnett lager bottles, liquor bottles, Nuka-Cola bottles and vodka bottles. See empty bottle for a complete list.

Hunger

 * Bonuses granted by food are only given if eaten while not currently being hungry, as stated on the game's loading screen. However, eating something that grants a bonus (e.g. the +1 Agility of deathclaw steak) while hungry will remove the bonus if it is already active. For example, eating a deathclaw steak while not hungry to gain the bonus, then becoming Peckish, then eating a second deathclaw steak to become well-fed will negate the +1 Agility bonus and would require eating a third deathclaw steak to regain it.
 * Certain foods, such as soups and certain crops, satisfy both hunger and thirst.
 * Issue #9 of the Wasteland Survival Guide doubles the meat dropped by most animals in the Commonwealth. This can significantly impact the amount of available food, so getting it early on in Sunshine Tidings co-op can be beneficial.

Sleep

 * Sleeping at least one hour on any bed, mattress or sleeping bag will save the game, and remove any Fatigue the player character has developed from being tired.
 * The Sole Survivor cannot sleep more than 3 hours in a sleeping bag and more than 5 hours on a mattress. To sleep for longer amounts of time, it is required to use a real bed.
 * Sleeping seven hours in a full bed ensures being well rested and minimizes risk of illness. For a quick save at a key location, sleep for at least 3 hours. Being only asleep for one hour in any bed, even at a workshop settlement, will still grant a high risk for illness, in particular parasites. Lethargy, insomnia and weakness are also common with not sleeping well.

Note: The in-game / real-time data in the tables above are approximations only.

Illnesses

 * There is a high probability for contracting parasites during melee attacks on infected animals, in particular radroaches and mongrels.
 * All illnesses can be cured by a doctor using the 15 cap "Cure Me" option in their dialogue.

Bugs

 * Starting in Survival mode and later changing the game mode will not change the water production from Water Purifiers.
 * When first joining the Railroad after completing Tradecraft, 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.