Struct WindowDrop 

pub struct WindowDrop;

Default trim strategy: drops the earliest complete rounds until the remaining sequence fits the budget.

Uses projection semantics (replace: false): lossless — raising the budget restores the trimmed history, and each recomputation is cheap. Guarantees:

• at least the most recent round is kept (kept even when a single round exceeds the budget; nothing more can be trimmed);
• a tool message and its Assistant message share a round and are kept as a pair;
• recorded System messages are treated like any other message and may be trimmed (the system prompt is managed by the Agent layer; Memory does not manage System).

Comparison

When a heavy strategy such as summarization or LLM compaction is needed, inject a custom TrimStrategy that declares materialization (replace: true), trading the materialized zero-recompute for a longer context; light and lossless round-wise dropping is this implementation.

Trait Implementations

impl Clone for WindowDrop

fn clone(&self) -> WindowDrop

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for WindowDrop

impl Debug for WindowDrop

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

Formats the value using the given formatter.

impl Default for WindowDrop

fn default() -> WindowDrop

Returns the “default value” for a type.

impl Eq for WindowDrop

impl PartialEq for WindowDrop

fn eq(&self, other: &WindowDrop) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for WindowDrop

impl TrimStrategy for WindowDrop

fn trim<'life0, 'life1, 'life2, 'life3, 'async_trait>( &'life0 self, messages: &'life1 [Message], budget: &'life2 Budget, counter: &'life3 dyn TokenCounter, ) -> Pin<Box<dyn Future<Output = Result<TrimResult, MemoryError>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, 'life3: 'async_trait,

Trims a message sequence against a budget and counter, returning the trim result (semantics in TrimResult).

fn trim_with_counts<'life0, 'life1, 'life2, 'life3, 'life4, 'async_trait>( &'life0 self, messages: &'life1 [Message], counts: &'life2 [usize], budget: &'life3 Budget, _counter: &'life4 dyn TokenCounter, ) -> Pin<Box<dyn Future<Output = Result<TrimResult, MemoryError>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, 'life3: 'async_trait, 'life4: 'async_trait,

Trims with per-message token counts; the default implementation delegates to trim, so custom strategies need not know about it. WindowDrop overrides it to amortized O(1) — counts are cached by Memory, avoiding per-message recounts inside the strategy (and saving IO with remote counters).