Struct ContextWindow 

pub struct ContextWindow {
    pub max_chars: usize,
    pub total_dropped: usize,
    pub truncation_count: usize,
}

Context window configuration — controls conversation budget.

Characters are used as a proxy for tokens. A rough heuristic: ~4 characters ≈ 1 token (English text average).

The budget covers only conversation history messages, not the system prompt (which is always sent separately).

Fields

max_chars: usize

Maximum characters allowed in conversation history. 0 means unlimited.

total_dropped: usize

Total messages dropped across all truncations in this unit.

truncation_count: usize

Number of truncation events.

Implementations

impl ContextWindow

pub fn new() -> Self

Create with default budget (100k chars).

pub fn with_budget(max_chars: usize) -> Self

Create with a custom character budget. 0 = unlimited.

pub fn unlimited() -> Self

Create with unlimited budget (no truncation).

pub fn enforce(&mut self, history: &mut ConversationHistory) -> usize

Enforce the budget on a conversation history. Returns the number of messages dropped (0 if within budget).

pub fn was_truncated(&self) -> bool

Whether any truncation has occurred.

pub fn estimate_tokens(chars: usize) -> usize

Estimated token count from character count (~4 chars/token).

Trait Implementations

impl Clone for ContextWindow

fn clone(&self) -> ContextWindow

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ContextWindow

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

Formats the value using the given formatter.