Trait Compactor 

pub trait Compactor:
    Send
    + Sync
    + 'static {
    // Required method
    fn compact<'life0, 'life1, 'life2, 'async_trait>(
        &'life0 self,
        events: &'life1 [GraphEvent],
        budget_chars: usize,
        ctx: &'life2 ExecutionContext,
    ) -> Pin<Box<dyn Future<Output = Result<CompactedHistory>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait,
             'life1: 'async_trait,
             'life2: 'async_trait;
}

Operator-supplied compaction strategy.

Receives the full event log plus a character-budget hint and returns the trimmed view. Async by default so summary-style implementations can dispatch a ChatModel call (SummaryCompactor in entelix-agents is the canonical reference); pure-retention strategies (HeadDropCompactor) simply ignore the future point and return synchronously inside the async fn body.

Implementations must preserve the ToolCall / ToolResult pair invariant — the CompactedHistory return type enforces that structurally; trait authors only need to choose which turns to retain.

Required Methods

fn compact<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, events: &'life1 [GraphEvent], budget_chars: usize, ctx: &'life2 ExecutionContext, ) -> Pin<Box<dyn Future<Output = Result<CompactedHistory>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait,

Compact events to fit within budget_chars. The budget is approximate — implementations measure character length of the rendered text (closest free proxy for token count without pulling a tokenizer dependency). The ExecutionContext carries cancellation + deadline so a long-running summarisation respects the same lifetime as the dispatch that triggered it. Returns Error::Config when the event log violates the pair invariant before compaction (e.g. ToolResult without a preceding ToolCall); a well-formed SessionGraph never hits this path.

Implementors

impl Compactor for HeadDropCompactor