Rhai Reference

Conditions, scripts, and sequences all share one engine, so beyond what’s listed here they are plain Rhai: arithmetic, strings, if, let, loops, functions.

The variable store

It’s a simple map that is available everywhere. See Variables. You can access it and modify it in the following ways:

Syntax	What it does
`vars["Name"]`	Reads a variable. Unknown names are an error, so typos surface as warnings.
`vars["Name"] = value`	Writes a variable, creating it if needed. Holds bools, numbers, and text.
`vars.has("Name")`	Whether the variable exists.

Numbers are floats on the script side, but Rhai mixes integers and floats freely: vars["Gold"] >= 10 works.

Built-in cues

Available in sequences, you can schedule cues instead of running on the spot.

Call	What it schedules
`wait(seconds)`	A simple wait to make a step in your cutscene to take as long as you need.
`emit("message")`	Fires a named message. Other cues can start `.after` it.

Constant	Value
`line_end`	The estimated reading time of the line being presented, from `SequencerSettings`.

An entry with no sequence plays the default one, wait(line_end) unless you change it in SequencerSettings.

Timing methods

There are some built-in methods you can use for timing:

Method	Effect
`.at(seconds)`	Starts the cue that many seconds into the sequence.
`.after("message")`	Holds the cue until that message fires.
`.emits("message")`	Fires a message when the cue finishes.
`.required()`	Still runs when the line is skipped, for cleanup and state that must land.

An example:

shake_camera(0.5);
play_anim("draw").at(1.5).emits("drawn");
play_sound("gasp").after("drawn");
reset_camera().required();
wait(line_end)

Your game’s functions

You register your own Bevy systems so dialogue runners can call them by name. There are two ways to register one, because there are two different things a call can mean:

Registration	It’s a…	The call in Rhai	What that means
`app.add_dialogue_system("has_item", system)`	function	`has_item("sword")`	Runs right away and gives back an answer.
`app.add_sequencer_command("play_anim", system)`	stage direction	`play_anim("draw").at(1.5)`	Doesn’t run yet when a runner reads the sequence. It’s staged for later, with a `.at`/`.after`/`.emits`/`.required` on when.

Both kinds are callable everywhere: conditions, scripts, and sequences. That’s why a sequence can mix them, if has_item("lute") { play_anim() }: checking has_item happens immediately, while play_anim() gets scheduled to play out.

Both take up to four arguments of bool, i64, f64, f32, String, or Dynamic.

Where each field runs

Entry field	Mode	Runs	Good for
`condition`	Expression only — one expression returning a bool	When the runner checks whether the entry can be reached	Gating branches: `vars["Gold"] >= 10 && has_item("sword")`
`script`	Full Rhai	Once per presentation; never on resume	Changing the game: `vars["Gold"] -= 10; guard_bribed()`
`sequence`	Full Rhai, calls schedule cues	Every presentation, including resume	Showing the game: `play_anim("bow"); wait(line_end)`

Broken logic never blocks dialogue: a condition that fails to compile or errors at runtime passes with a warning, a failing script is reported and skipped.