Hex packages requirements are specified in gleam.toml in the dependencies and dev-dependencies tables.
[dependencies]
gleam_stdlib = ">= 0.60.0 and < 2.0.0"
gleam_time = ">= 1.3.0 and < 2.0.0"
[dev-dependencies]
gleeunit = ">= 1.0.0"
Dependencies requirements can also be added with the gleam add lustre@4 terminal command.
Gleam will automatically download the missing required dependencies when running any command that needs them, such as gleam run or gleam test.