Struct BudgetContextPolicy 

pub struct BudgetContextPolicy { /* private fields */ }

Keeps the newest whole turns that fit ContextConfig’s budget and replaces older history with one bounded summary note.

A turn group is a user message and everything after it up to the next user message, so an assistant tool call is never separated from its result.

Implementations

impl BudgetContextPolicy

pub fn new(config: ContextConfig) -> Result<Self, ContextError>

A policy for config, which must leave room for history.

Trait Implementations

impl ContextPolicy for BudgetContextPolicy

fn select( &self, history: &[Message], system_prompt: &str, tools: &[ToolSpec], ) -> Result<ContextSelection, ContextError>

The budget for history is the window minus the system prompt, the tool schemas, the output reserve, and the safety margin. Selection then:

1. keeps the newest turn group, failing if it alone is over budget;
2. walks older groups from newest to oldest, keeping each while it fits, and stops at the first that does not (so the kept history is always one contiguous suffix);
3. if anything was left out, puts one summary note of the left-out prefix in front. When the note does not fit beside the kept groups, the oldest kept group joins the summarized prefix and the note is rebuilt; with only the newest group left, the note is cut to the room that remains.