Struct ContextManager 

pub struct ContextManager {
    pub max_tokens: usize,
    pub reserve_ratio: f32,
    pub truncation_ratio: f32,
    pub min_keep_rounds: usize,
    pub token_safety_margin: f32,
    pub max_output_lines: usize,
    pub max_output_bytes: usize,
    pub compression_token_threshold: usize,
    pub compression_enabled: bool,
    pub max_tool_calls_per_turn: usize,
}

Manages the context window, truncating history when approaching token limits.

Fields

max_tokens: usize

Model’s context window size in tokens.

reserve_ratio: f32

Ratio of context window to reserve for LLM response (default 0.2 = 20%).

truncation_ratio: f32

Fraction of max_tokens at which truncation triggers (default 0.7).

min_keep_rounds: usize

Minimum conversation rounds to keep after truncation (default 3).

token_safety_margin: f32

Safety multiplier for token estimates (default 1.3).

max_output_lines: usize

Max output lines for tool results.

max_output_bytes: usize

Max output bytes for tool results.

compression_token_threshold: usize

Token threshold for triggering compression.

compression_enabled: bool

Whether compression is enabled.

max_tool_calls_per_turn: usize

Maximum tool calls per turn (default 30).

Implementations

impl ContextManager

pub fn new(context_window: Option<u64>, config: Option<&ContextConfig>) -> Self

pub fn truncation_threshold(&self) -> usize

Maximum tokens at which truncation is triggered. Uses truncation_ratio (default 0.7) to trigger earlier than the absolute limit, leaving headroom for estimation errors and LLM response.

pub fn available_tokens(&self) -> usize

Maximum tokens available for input (total - reserved for response). Note: this is the absolute upper bound; truncation actually triggers earlier via truncation_threshold().

pub fn truncate_tool_output(&self, content: &str) -> String

Truncate tool output using the configured limits.

pub fn maybe_truncate( &self, messages: &mut Vec<ChatCompletionRequestMessage>, ) -> TruncationResult

Check if history needs truncation and perform it if necessary. Returns TruncationResult with removed messages for async compression.

Strategy:

1. Uses truncation_threshold() (default 70% of max_tokens) as trigger point
2. Removes oldest non-system rounds first
3. Always keeps at least min_keep_rounds recent rounds
4. Applies token_safety_margin to estimates to avoid underestimation