Trait ContextCompaction 

pub trait ContextCompaction: Send + Sync {
    // Required methods
    fn compact<'life0, 'life1, 'life2, 'async_trait>(
        &'life0 self,
        session_id: &'life1 SessionId,
        messages: &'life2 [ChatMessage],
    ) -> Pin<Box<dyn Future<Output = Option<Vec<ChatMessage>>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait,
             'life1: 'async_trait,
             'life2: 'async_trait;
    fn token_count_hint(&self, session_id: &SessionId) -> Option<usize>;
}

Trait for inline context compaction within the react loop.

Implemented by agent-works’s ContextCompactor. agent-base defines the trait to avoid circular dependencies (agent-works depends on agent-base).

The react loop calls compact after tool execution when the estimated token count exceeds a configurable threshold. This prevents context window overflow without requiring the LLM call to fail first.

Required Methods

fn compact<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, session_id: &'life1 SessionId, messages: &'life2 [ChatMessage], ) -> Pin<Box<dyn Future<Output = Option<Vec<ChatMessage>>> + Send + 'async_trait>>

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

Compact a message history.

Takes the current messages and returns Some(compacted_messages) if compaction was performed. Returns None if compaction was skipped (below threshold, too few messages, or disabled).

The react loop handles reading/writing the session — the compactor only transforms the message list.

fn token_count_hint(&self, session_id: &SessionId) -> Option<usize>

Estimate current token count for the session.

Returns None if the implementation cannot estimate (falls back to ContextWindowManager::estimate_tokens on the react loop side).

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors