hustle.Define validates one immutable definition. The definition is a configuration and policy identity. A supported Harness facility binds it to a session; application code does not execute an arbitrary definition directly.

// Every option is explicit. The definition retains no caller-owned slices.
summary, err := hustle.Define(
	hustle.WithName("context.compact"),
	hustle.WithParticipation(hustle.ParticipationBlocking),
	hustle.WithTimeout(5*time.Second),
	hustle.WithLimits(hustle.Limits{InputBytes: 1 << 20, OutputBytes: 1 << 20}),
	hustle.WithCurrentLoopModel(),
	hustle.WithSystemPrompt("Summarize the earlier conversation.", "prompt-v1"),
	hustle.WithPolicyRevision("policy-v1"),
)
if err != nil {
	return fmt.Errorf("define hustle: %w", err)
}
_ = summary

Constructor APIs

API	Purpose
`hustle.Define(opts ...hustle.Option) (hustle.Definition, error)`	Validates and freezes the definition.
`hustle.WithName(hustle.Name) hustle.Option`	Stable registration name; trimmed emptiness and `_looprig.` names are rejected.
`hustle.WithParticipation(hustle.Participation) hustle.Option`	Selects blocking or background lane.
`hustle.WithTimeout(time.Duration) hustle.Option`	Requires a positive per-invocation timeout.
`hustle.WithLimits(hustle.Limits) hustle.Option`	Requires positive serialized input and output byte bounds.
`hustle.WithCurrentLoopModel() hustle.Option`	Resolves the originating Loop model for every invocation.
`hustle.WithNamedInference(inference.Client, model.Model) hustle.Option`	Freezes a validated client and model.
`hustle.WithSystemPrompt(string, string) hustle.Option`	Freezes prompt bytes and a public prompt revision.
`hustle.WithPolicyRevision(string) hustle.Option`	Names parser, policy, and finalization behavior.
`hustle.WithOutputSchema(inference.OutputSchema) hustle.Option`	Freezes optional structured-output policy.
`hustle.WithEvidenceTools(hustle.EvidenceToolPolicy) hustle.Option`	Enables a bounded, read-only evidence loop.
`hustle.WithRetryPolicy(hustle.RetryPolicy) hustle.Option`	Enables the one classified retry only for eligible evidence definitions.

Proof: Hustle options and Define and definition validation tests.

Definition descriptor

Definition.Descriptor() is the secret-free identity used by Rig validation and internal audit. It contains these exact fields:

Field group	Fields
Registration	`Name`, `Participation`, `ModelSource`, `PolicyRevision`, `TimeoutNanos`, `Limits`
Named model	`NamedModelKey`, `NamedModelPolicyRevision`
Prompt and output	`PromptRevision`, `PromptSHA256`, `OutputSchemaName`, `OutputSchemaSHA256`, `StructuredOutputRevision`
Evidence	`EvidenceToolPolicyRevision`, `EvidenceToolDefinitionsSHA256`, `EvidenceProducedToolNamesSHA256`, `EvidenceToolLimits`, `EvidenceToolDefinitionCount`, `StructuredOutputWithTools`
Retry	`RetryPolicy`

The descriptor contains hashes and revisions, not raw prompts, provider clients, endpoints, or output bytes. Definition.PolicyRevision() is the frozen digest of this behavior.

Proof: DefinitionDescriptor and descriptor tests.

Bind before a facility uses it

// package hustle
type Bindings struct {
	Models ModelResolver
}

type BoundDefinition interface {
	Name() Name
	Participation() Participation
	Timeout() time.Duration
	Limits() Limits
	Descriptor() DefinitionDescriptor
	ResolveInference(context.Context, uuid.UUID) (InferenceBinding, error)
	SystemPrompt() string
	OutputSchema() (*inference.OutputSchema, bool)
	EvidenceToolPolicy() (EvidenceToolPolicy, bool)
	RetryPolicy() RetryPolicy
	BindEvidenceTools(context.Context, EvidenceBindings) ([]BoundEvidenceTool, error)
}

Definition.Bind validates context and requires a model resolver for current Loop definitions. The bound view clones mutable model and output policy values. Its sealed interface prevents application implementations from substituting a definition with different policy identity.

Proof: binding interface and clone behavior and binding tests.

Define a Hustle

Constructor APIs

Definition descriptor

Bind before a facility uses it

Source and proof