Struct TrajectoryRiskAccumulator 

pub struct TrajectoryRiskAccumulator { /* private fields */ }

Per-session trajectory risk accumulator (MAGE spec 004-16).

Maintains a rolling trajectory_risk score in [0.0, 1.0] that accumulates safety signals with exponential temporal decay. Designed to detect multi-turn attacks that evade per-turn controls.

When constructed via new_noop or when config.enabled = false, all methods are zero-cost no-ops — no allocations and current_risk() always returns 0.0.

Implementations

impl TrajectoryRiskAccumulator

pub fn new_noop() -> Self

Construct an accumulator that operates as a zero-cost noop.

Use when shadow memory is disabled or during testing scenarios that do not need risk tracking. No heap allocation is performed.

pub fn new(config: TrajectoryRiskAccumulatorConfig) -> Self

Construct an accumulator from configuration.

When config.enabled = false, delegates to new_noop — no allocation. When enabled, pre-allocates the signal history ring buffer.

pub fn advance_turn(&mut self)

Advance the turn counter and apply exponential decay to the accumulated risk.

Must be called once per turn, before ingest is called for that turn. Decay formula: risk *= exp(-ln(2) / halflife_turns).

No-op when disabled.

pub fn ingest(&mut self, signal_type: AuditSignalType, severity: Severity)

Ingest a safety signal and add its weighted contribution to trajectory_risk.

The raw score is base_weight(signal_type) × severity_multiplier(severity). After addition, trajectory_risk is clamped to [0.0, 1.0]. The event is appended to the signal history ring buffer; the oldest entry is evicted when the buffer is full.

Emits shadow_memory_signals_total{type, severity} counter (NFR-007).

No-op when disabled.

pub fn record_block(&self)

Increment shadow_memory_blocks_total counter (NFR-007).

Call this once when a tool execution is actually blocked due to trajectory risk. Do not call on every is_blocked() query — only when a block action fires.

pub fn record_escalation(&self)

Increment shadow_memory_escalations_total counter (NFR-007).

Call this once when an escalation-to-human-confirmation is triggered.

pub fn current_risk(&self) -> f64

Returns the current accumulated risk score in [0.0, 1.0].

Always returns 0.0 when disabled.

pub fn is_blocked(&self) -> bool

Returns true when trajectory_risk >= risk_threshold and shadow memory is enabled.

Always returns false when disabled.

pub fn should_escalate(&self) -> bool

Returns true when risk is in [escalation_threshold, risk_threshold).

Always returns false when disabled.

pub fn top_signals(&self, n: usize) -> Vec<&SignalEvent>

Returns the top n signals by raw_score descending from recent history.

pub fn reset(&mut self)

Resets trajectory_risk to zero and clears signal history.

Called on context compaction when reset_on_compaction = true. No-op when disabled.

pub fn is_enabled(&self) -> bool

Returns true when shadow memory is enabled (i.e., not in noop mode).

pub fn turn_count(&self) -> u32

Returns the current turn count.