Custom dependencies

By default, skill sub-agents receive SkillRunDeps — a dataclass with state and emit. Skills that integrate external toolsets requiring additional context on the deps object can declare a deps_type — any class that satisfies SkillRunDepsProtocol (must have state: BaseModel | None and emit: Callable) and accepts state and emit as constructor arguments.

The simplest approach is to subclass SkillRunDeps:

from dataclasses import dataclass, field

from haiku.skills import Skill, SkillMetadata, SkillRunDeps


@dataclass
class MyDeps(SkillRunDeps):                # inherits state + emit
    connection: object = field(init=False)

    def __post_init__(self):
        self.connection = open_connection()


skill = Skill(
    metadata=SkillMetadata(name="my-skill", description="Uses a custom connection."),
    instructions="...",
    toolsets=[my_external_toolset],
    deps_type=MyDeps,
)

Inheritance is not required — any class satisfying SkillRunDepsProtocol works, as long as its constructor accepts state and emit keyword arguments.

When deps_type is set, the skill sub-agent is created with MyDeps(state=state, emit=emit) instead of SkillRunDeps(state=state, emit=emit). Any additional attributes are available to toolset tools via ctx.deps.

See Lifespan for a common pairing: a custom deps class whose fields are populated by a lifespan context manager.