Compaction Policy

Compaction is an explicit context policy attached to a loop definition:

type CounterPolicy uint8

const (
	CounterPolicyUnknown CounterPolicy = iota
	CounterPolicyRequireExact
	CounterPolicyAllowConservative
)

type CompactionPolicy struct {
	Automatic        bool
	CounterPolicy    CounterPolicy
	CompactAt        event.BasisPoints
	RearmBelow       event.BasisPoints
	ReservedOutput   content.TokenCount
	SafetyMargin     content.TokenCount
	MaxSummaryTokens content.TokenCount
	CountTimeout     time.Duration
	Hustle           hustle.Name
}

func WithCompaction(policy CompactionPolicy) Option
func (p CompactionPolicy) Validate(capability contextcount.CounterCapability) error

Harness supplies no compaction defaults. The definition must include a nonzero output reservation, summary-token budget, positive count timeout, and a valid registered hustle name. Heuristic counter quality additionally requires a nonzero safety margin.

Automatic validation

Automatic enables threshold-triggered compaction. Then RearmBelow must be nonzero and strictly below CompactAt, CompactAt must be below event.FullScaleBasisPoints, and CounterPolicy must admit the counter quality:

With Automatic false, thresholds and counter policy are not used for the automatic trigger, but the common reservation, summary budget, timeout, hustle, and heuristic-margin checks still apply. WithContextObservation and WithCompaction are mutually exclusive because they represent different admission policies.

policy := loop.CompactionPolicy{
	Automatic:        true,
	CounterPolicy:    loop.CounterPolicyAllowConservative,
	CompactAt:        8_500,
	RearmBelow:       6_000,
	ReservedOutput:   512,
	SafetyMargin:     256,
	MaxSummaryTokens: 256,
	CountTimeout:     2 * time.Second,
	Hustle:           "context.compact",
}
if err := policy.Validate(capability); err != nil {
	var fieldErr *loop.CompactionPolicyError
	if errors.As(err, &fieldErr) {
		log.Println("invalid field", fieldErr.Field)
	}
	return err
}

Identity and summary contract

The policy is part of Definition.PolicyRevision. Request measurement identity uses RequestFingerprintInput, which includes system/tool/runtime revisions, the full model and basis, and both counter capabilities. A compaction result is accepted only when its basis, model, request fingerprint, and output shape match the input. The summary must be one nonempty user text message; malformed transcripts and output are rejected with typed errors that do not render model bytes.

%%{init: {"theme":"dark"}}%%
flowchart LR
    H[context basis + transcript] --> F[RequestFingerprint]
    F --> C[count candidate]
    C --> T{automatic threshold}
    T -->|below| N[next turn request]
    T -->|at/above| U[registered compaction hustle]
    U --> V[validate identity and summary]
    V --> P[publish compacted context]

The Rig must register the named hustle and provide HustleLimits; a loop compaction policy referring to an unregistered or incompatible hustle fails Rig definition.

Source and proof

• Compaction policy, validation, and request fingerprints
• Compaction input/output typed contracts
• Compaction policy tests
• Rig compaction hustle validation