Function truncate_messages 

pub fn truncate_messages(
    messages: &[Message],
    keep: usize,
    preserve_system: bool,
) -> Vec<Message>

Truncate message history, keeping recent messages

Always preserves the system prompt (if present) and keeps the most recent N messages. This is a simple truncation - it does NOT attempt to preserve tool chains or important context.

Arguments

• messages - List of messages to truncate
• keep - Number of recent messages to keep (default: 10)
• preserve_system - Keep system message if present (default: true)

Returns

Truncated message list (new Vec, original unchanged)

Examples

use open_agent::{Message, Client, truncate_messages, estimate_tokens};

// Manual truncation when needed
let tokens = estimate_tokens(client.history());
if tokens > 28000 {
    let truncated = truncate_messages(client.history(), 10, true);
    *client.history_mut() = truncated;
}

Note

This is a SIMPLE truncation. For domain-specific needs (e.g., preserving tool call chains, keeping important context), implement your own logic or use this as a starting point.

Warning: Truncating mid-conversation may remove context that the model needs to properly respond. Use judiciously at natural breakpoints.