Error API

Reference for TaggedError, exhaustive and partial matching, UnhandledException, codec errors, and Panic.

`TaggedError(tag)`

Factory for a generic Error subclass:

class NotFound extends TaggedError("NotFound")<{
  id: string;
  message: string;
}> {}

Instances expose _tag, declared properties, native Error fields, toJSON(), exhaustive .match(handlers), and generator iterator behavior. Concrete classes expose .is(value).

Guards

API	Narrows to
`TaggedError.is(value)`	`AnyTaggedError`
`isTaggedError(value)`	`AnyTaggedError`
`ConcreteError.is(value)`	the concrete subclass
`Panic.is(value)`	`Panic`
`isPanic(value)`	`Panic`

Matching

API	Behavior
`error.match(handlers)`	Exhaustive instance match over every `_tag`
`matchError(error, handlers)`	Exhaustive standalone match over every `_tag`
`matchError(handlers)(error)`	Data-last exhaustive match
`matchErrorPartial(error, handlers)`	Handle selected tags; return others unchanged
`matchErrorPartial(error, handlers, fallback)`	Handle selected tags; transform others with fallback
`matchErrorPartial(handlers, fallback)(error)`	Data-last partial match

Handler return types are inferred as a union when they differ. If an exhaustive .match() or matchError handler throws, the operation throws Panic with the original exception as cause. matchErrorPartial retains its fallback and handler exception behavior.

The match property name is reserved on TaggedError payloads; TypeScript also rejects incompatible subclass members with that name.

Built-in error classes

`UnhandledException`

Returned by Result.try and Result.tryPromise when no custom catch translator is supplied.

Property	Type
`_tag`	`"UnhandledException"`
`cause`	`unknown`
`message`	`string`

`ResultSerializationError`

Returned when a selected serialization schema reports validation issues. serializeUnsafe throws Panic with this error as its cause instead of returning it.

Property	Type
`_tag`	`"ResultSerializationError"`
`value`	`unknown`
`issues`	optional readonly Standard Schema issues

`ResultDeserializationError`

Returned for an invalid serialized envelope or when a selected payload schema reports issues. deserializeUnsafe throws Panic with this error as its cause while preserving valid decoded domain Err values.

Property	Type
`_tag`	`"ResultDeserializationError"`
`value`	`unknown`
`issues`	optional readonly Standard Schema issues; absent for an invalid envelope

`Panic`

Thrown for defects. Exposes _tag: "Panic", message, optional cause, toJSON(), static .is, and generator iterator behavior.

`panic(message, cause?)`

Throws a new Panic and returns never at the type level.