Concentration Notifier

This is a module for dnd5e helping Dungeon Masters and players track concentration. At its core, a chat message will notify all active clients when an actor starts concentrating on an item or loses concentration on an item.

• An active effect is created on the actor when they use an item that has the Concentration component (for spells), and for other items a field has been supplied next to the Duration for non-spell items that should require concentration.
• An actor who is concentrating on something and takes damage will receive a message with two buttons; one for rolling a saving throw to maintain concentration, and one button for convenience to remove the concentration effect (the deletion button will prompt the user; the prompt can be skipped by holding Shift).
• The message also has a link to the item and shows the DC for the saving throw (standard calculation of half the damage taken, rounded down, to a minimum of 10).
• The active effect used to track concentration is named after the item, e.g., 'Bless' or 'Concentration - Bless'. The format can be toggled in the settings.
• If an actor who is already concentrating on an item uses a different item that requires concentration (or the same item but at a different level for spells), the active effect will get swapped. The effects otherwise have a duration equal to the item's duration, as set in the details of the item.

Additionally, when a scroll is made from a spell that requires concentration, that will also be tagged as requiring concentration.

Character Flags

The module supplies new fields (found under Special Traits). These fields work with Active Effects.

• flags.dnd5e.concentrationAbility: Change the ability that is used for the actor's concentration saves. For example, use Wisdom instead of Constitution by putting wis in this field.
• flags.dnd5e.concentrationAdvantage: Set the default of concentration saves to be rolled with advantage.
• flags.dnd5e.concentrationBonus: Give an actor a bonus to Concentration saves, such as @abilities.int.mod or 1d6. Good for Wizard Bladesingers. This field respects roll data.
• flags.dnd5e.concentrationReliable: Change concentration saves such that rolls on the d20s cannot go below 10.
• flags.dnd5e.concentrationUnfocused: Prevent an actor from starting concentration. If the 'Ability Use Warnings' setting is enabled, the actor will also be given a warning in the AbilityUseDialog that their item cannot be concentrated on.

Helper Functions

The Actor document is supplied with the new function Actor#rollConcentrationSave, which accepts the usual arguments (same as rollAbilitySave) but makes use of the above flags automatically.

Additionally, these functions are found in the global namespace CN (here caster refers to a token placeable, token document, or an actor document):

• CN.isActorConcentrating(caster): returns the effect if the actor is concentrating on any item, otherwise false.
• CN.isActorConcentratingOnItem(caster, item): returns the effect if the actor is concentrating on the given item, otherwise false.
• CN.isEffectConcentration(effect): returns true or false if the effect is a concentration effect.
• CN.breakConcentration(caster, {message=true}={}): ends all concentration effects on the actor. Returns the array of deleted effects. Set message to false to suppress notifications.
• CN.waitForConcentrationStart(caster, {item, max_wait=10000}={}): will wait for the actor to receive any concentration effect (or specific to the item, if provided). Useful for halting scripts in edge cases. The optional integer denotes the maximum number of ms to wait for. Returns the effect if one exists, otherwise false.
• CN.redisplayCard(caster): displays the chat card of the item being concentrated on, at the level it was cast.
• CN.extendModule(status, require): (detailed below.)

Effect Flags

The effect placed on an actor to denote concentration contains some useful data, intended to make script writing easier for persistently active spells such as call lightning or moonbeam:

• flags.concentrationnotifier.data.itemData, with all the details of the item being concentrated on.
• flags.concentrationnotifier.data.castData, with the item's base level, the level at which it was cast, and its uuid.

Using a macro to set the flag unbreakable within castData to true will prevent automatically prompting the caster for saving throws to maintain concentration when they take damage. Useful in rare instances where a feature lets you have unbreakable concentration on a particular spell.

Extending the Module

If you want to support other 'groupings' of concentration, this is quite simple to do. For example, if you want to support concentration on Hex for the Witch class from Valda's Spire of Secrets, which are tracked separately from spells, you would run this script in a module or world script.

Hooks.once("setup", () => CN.extendModule("hex-concentration", function itemRequiresConcentration(item) {
  if (item.type !== "feat") return false;
  const type = item.system.type;
  const units = item.system.duration?.units in CONFIG.DND5E.scalarTimePeriods;
  const flags = !!item.flags.concentrationnotifier?.data.requiresConcentration;
  return units && flags && (type.value === "class") && (type.subtype === "witchHex");
}));

This assumes the existence of 'witchHex' added as a custom class feature type.

The extendModule function takes the new status (a string, which must be different from 'concentration' or 'concentrating') and a synchronous function that is run to determine whether an item being used is requiring this type of concentration. In the above example, a hex requires concentration if it has a duration, is set by this module to require concentration, and is a class feature with the 'witchHex' subtype.

Here is another example, which causes the module to track concentration separately for all spells that are cast at 9th level or higher.

Hooks.once("setup", () => CN.extendModule("nine-concentration", function itemRequiresConcentration(item) {
  return (item.type === "spell") && (item.system.level >= 9) && item.system.components.concentration;
}));