Struct ModelContextScan 

pub struct ModelContextScan { /* private fields */ }

Accumulates newest-to-oldest rollout items until they are sufficient to reconstruct the latest model context.

Storage implementations own how they fetch older items. Local JSONL readers and future reverse-paged cloud readers can both feed their items through this scan to share the cutoff rules and chronological replay assembly.

The scan stops once it has both:

• saw_compaction: a CompactedItem with replacement_history and window_number;
• saw_completed_turn_context: a completed user turn with a compatible TurnContextItem.

If the scan reaches the beginning before finding a bounded cutoff, it has already collected the complete replay and so we can return that directly.

TurnContextItem does not identify whether it came from a user turn, so one only counts after the same turn also proves a user-turn boundary: a paginated ItemCompleted(UserMessage) marker, agent message, or inter-agent message. Paginated writers persist that marker for real user turns; older rollouts without it conservatively scan to the beginning. A raw role=user response item is not sufficient because contextual user fragments use that role but do not count as turn boundaries during reconstruction. The compaction restores model-visible items; the turn context restores previous settings (model, comp_hash, and realtime_active) and the reference baseline.

These paginated shapes disable the bounded cutoff:

• compaction without replacement_history or window_number;
• rollback markers;

When one appears, the scanner continues to the beginning and returns the complete replay.

Implementations

impl ModelContextScan

pub fn push(&mut self, item: RolloutItem) -> ModelContextScanProgress

Adds the next newest-to-oldest rollout item and reports whether the reader can stop.

pub fn finish(self, session_meta: SessionMetaLine) -> Vec<RolloutItem>

Returns the collected items in chronological order with canonical head metadata.

Call this after the reader reaches the beginning of its source or after Self::push returns ModelContextScanProgress::Complete.

Trait Implementations

impl Debug for ModelContextScan

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ModelContextScan

fn default() -> ModelContextScan

Returns the “default value” for a type.