Files
tkmind_go/crates/goose/src/context_mgmt/truncate.rs
T

716 lines
27 KiB
Rust

use crate::message::{Message, MessageContent};
use crate::utils::safe_truncate;
use anyhow::{anyhow, Result};
use mcp_core::{Content, ResourceContents, Role};
use std::collections::HashSet;
use tracing::{debug, warn};
/// Maximum size for truncated content in characters
const MAX_TRUNCATED_CONTENT_SIZE: usize = 5000;
/// Handles messages that are individually larger than the context limit
/// by truncating their content rather than removing them entirely
fn handle_oversized_messages(
messages: &[Message],
token_counts: &[usize],
context_limit: usize,
strategy: &dyn TruncationStrategy,
) -> Result<(Vec<Message>, Vec<usize>), anyhow::Error> {
let mut truncated_messages = Vec::new();
let mut truncated_token_counts = Vec::new();
let mut any_truncated = false;
// Create a basic token counter for re-estimating truncated content
// Note: This is a rough approximation since we don't have access to the actual tokenizer here
let estimate_tokens = |text: &str| -> usize {
// Rough approximation: 1 token per 4 characters for English text
(text.len() / 4).max(1)
};
for (i, (message, &original_tokens)) in messages.iter().zip(token_counts.iter()).enumerate() {
if original_tokens > context_limit {
warn!(
"Message {} has {} tokens, exceeding context limit of {}",
i, original_tokens, context_limit
);
// Try to truncate the message content
let truncated_message = truncate_message_content(message, MAX_TRUNCATED_CONTENT_SIZE)?;
let estimated_new_tokens =
estimate_message_tokens(&truncated_message, &estimate_tokens);
if estimated_new_tokens > context_limit {
// Even truncated message is too large, skip it entirely
warn!("Skipping message {} as even truncated version ({} tokens) exceeds context limit", i, estimated_new_tokens);
any_truncated = true;
continue;
}
truncated_messages.push(truncated_message);
truncated_token_counts.push(estimated_new_tokens);
any_truncated = true;
} else {
truncated_messages.push(message.clone());
truncated_token_counts.push(original_tokens);
}
}
if any_truncated {
debug!("Truncated large message content, now attempting normal truncation");
// After content truncation, try normal truncation if still needed
return truncate_messages(
&truncated_messages,
&truncated_token_counts,
context_limit,
strategy,
);
}
Ok((truncated_messages, truncated_token_counts))
}
/// Truncates the content within a message while preserving its structure
fn truncate_message_content(message: &Message, max_content_size: usize) -> Result<Message> {
let mut new_message = message.clone();
for content in &mut new_message.content {
match content {
MessageContent::Text(text_content) => {
if text_content.text.chars().count() > max_content_size {
let truncated = format!(
"{}\n\n[... content truncated from {} to {} characters ...]",
safe_truncate(&text_content.text, max_content_size),
text_content.text.chars().count(),
max_content_size
);
text_content.text = truncated;
}
}
MessageContent::ToolResponse(tool_response) => {
if let Ok(ref mut result) = tool_response.tool_result {
for content_item in result {
if let Content::Text(ref mut text_content) = content_item {
if text_content.text.chars().count() > max_content_size {
let truncated = format!(
"{}\n\n[... tool response truncated from {} to {} characters ...]",
safe_truncate(&text_content.text, max_content_size),
text_content.text.chars().count(),
max_content_size
);
text_content.text = truncated;
}
}
// Handle Resource content which might contain large text
else if let Content::Resource(ref mut resource_content) = content_item {
if let ResourceContents::TextResourceContents { text, .. } =
&mut resource_content.resource
{
if text.chars().count() > max_content_size {
let truncated = format!(
"{}\n\n[... resource content truncated from {} to {} characters ...]",
safe_truncate(text, max_content_size),
text.chars().count(),
max_content_size
);
*text = truncated;
}
}
}
}
}
}
// Other content types are typically smaller, but we could extend this if needed
_ => {}
}
}
Ok(new_message)
}
/// Estimates token count for a message using a simple heuristic
fn estimate_message_tokens(message: &Message, estimate_fn: &dyn Fn(&str) -> usize) -> usize {
let mut total_tokens = 10; // Base overhead for message structure
for content in &message.content {
match content {
MessageContent::Text(text_content) => {
total_tokens += estimate_fn(&text_content.text);
}
MessageContent::ToolResponse(tool_response) => {
if let Ok(ref result) = tool_response.tool_result {
for content_item in result {
match content_item {
Content::Text(text_content) => {
total_tokens += estimate_fn(&text_content.text);
}
Content::Resource(resource_content) => {
match &resource_content.resource {
ResourceContents::TextResourceContents { text, .. } => {
total_tokens += estimate_fn(text);
}
_ => total_tokens += 5, // Small overhead for other resource types
}
}
_ => total_tokens += 5, // Small overhead for other content types
}
}
}
}
_ => total_tokens += 5, // Small overhead for other content types
}
}
total_tokens
}
/// Truncates the messages to fit within the model's context window.
/// Mutates the input messages and token counts in place.
/// Returns an error if it's impossible to truncate the messages within the context limit.
/// - messages: The vector of messages in the conversation.
/// - token_counts: A parallel vector containing the token count for each message.
/// - context_limit: The maximum allowed context length in tokens.
/// - strategy: The truncation strategy to use. Only option is OldestFirstTruncation.
pub fn truncate_messages(
messages: &[Message],
token_counts: &[usize],
context_limit: usize,
strategy: &dyn TruncationStrategy,
) -> Result<(Vec<Message>, Vec<usize>), anyhow::Error> {
let mut messages = messages.to_owned();
let mut token_counts = token_counts.to_owned();
if messages.len() != token_counts.len() {
return Err(anyhow!(
"The vector for messages and token_counts must have same length"
));
}
// Step 1: Calculate total tokens
let mut total_tokens: usize = token_counts.iter().sum();
debug!("Total tokens before truncation: {}", total_tokens);
// Check if any individual message is larger than the context limit
// First, check for any message that's too large
let max_message_tokens = token_counts.iter().max().copied().unwrap_or(0);
if max_message_tokens > context_limit {
// Try to handle large messages by truncating their content
debug!(
"Found oversized message with {} tokens, attempting content truncation",
max_message_tokens
);
return handle_oversized_messages(&messages, &token_counts, context_limit, strategy);
}
let min_user_msg_tokens = messages
.iter()
.zip(token_counts.iter())
.filter(|(msg, _)| msg.role == Role::User && msg.has_only_text_content())
.map(|(_, &tokens)| tokens)
.min();
// If there are no valid user messages, or the smallest one is too big for the context
if min_user_msg_tokens.is_none() || min_user_msg_tokens.unwrap() > context_limit {
return Err(anyhow!(
"Not possible to truncate messages within context limit: no suitable user messages found"
));
}
if total_tokens <= context_limit {
return Ok((messages, token_counts)); // No truncation needed
}
// Step 2: Determine indices to remove based on strategy
let indices_to_remove =
strategy.determine_indices_to_remove(&messages, &token_counts, context_limit)?;
// Circuit breaker: if we can't remove enough messages, fail gracefully
let tokens_to_remove: usize = indices_to_remove
.iter()
.map(|&i| token_counts.get(i).copied().unwrap_or(0))
.sum();
if total_tokens - tokens_to_remove > context_limit && !indices_to_remove.is_empty() {
debug!(
"Standard truncation insufficient: {} tokens remain after removing {} tokens",
total_tokens - tokens_to_remove,
tokens_to_remove
);
// Try more aggressive truncation or content truncation
return handle_oversized_messages(&messages, &token_counts, context_limit, strategy);
}
if indices_to_remove.is_empty() && total_tokens > context_limit {
return Err(anyhow!(
"Cannot truncate any messages: all messages may be essential or too large individually"
));
}
// Step 3: Remove the marked messages
// Vectorize the set and sort in reverse order to avoid shifting indices when removing
let mut indices_to_remove = indices_to_remove.iter().cloned().collect::<Vec<usize>>();
indices_to_remove.sort_unstable_by(|a, b| b.cmp(a));
for &index in &indices_to_remove {
if index < messages.len() {
let _ = messages.remove(index);
let removed_tokens = token_counts.remove(index);
total_tokens -= removed_tokens;
}
}
// Step 4: Ensure the last message is a user message with TextContent only
while let Some(last_msg) = messages.last() {
if last_msg.role != Role::User || !last_msg.has_only_text_content() {
let _ = messages.pop().ok_or(anyhow!("Failed to pop message"))?;
let removed_tokens = token_counts
.pop()
.ok_or(anyhow!("Failed to pop token count"))?;
total_tokens -= removed_tokens;
} else {
break;
}
}
// Step 5: Check first msg is a User message with TextContent only
while let Some(first_msg) = messages.first() {
if first_msg.role != Role::User || !first_msg.has_only_text_content() {
let _ = messages.remove(0);
let removed_tokens = token_counts.remove(0);
total_tokens -= removed_tokens;
} else {
break;
}
}
debug!("Total tokens after truncation: {}", total_tokens);
// Ensure we have at least one message remaining and it's within context limit
if messages.is_empty() {
return Err(anyhow!(
"Unable to preserve any messages within context limit"
));
}
if total_tokens > context_limit {
return Err(anyhow!(
"Unable to truncate messages within context window."
));
}
debug!("Truncation complete. Total tokens: {}", total_tokens);
Ok((messages, token_counts))
}
/// Trait representing a truncation strategy
pub trait TruncationStrategy {
/// Determines the indices of messages to remove to fit within the context limit.
///
/// - `messages`: The list of messages in the conversation.
/// - `token_counts`: A parallel array containing the token count for each message.
/// - `context_limit`: The maximum allowed context length in tokens.
///
/// Returns a vector of indices to remove.
fn determine_indices_to_remove(
&self,
messages: &[Message],
token_counts: &[usize],
context_limit: usize,
) -> Result<HashSet<usize>>;
}
/// Strategy to truncate messages by removing the oldest first
pub struct OldestFirstTruncation;
impl TruncationStrategy for OldestFirstTruncation {
fn determine_indices_to_remove(
&self,
messages: &[Message],
token_counts: &[usize],
context_limit: usize,
) -> Result<HashSet<usize>> {
let mut indices_to_remove = HashSet::new();
let mut total_tokens: usize = token_counts.iter().sum();
let mut tool_ids_to_remove = HashSet::new();
for (i, message) in messages.iter().enumerate() {
if total_tokens <= context_limit {
break;
}
// Remove the message
indices_to_remove.insert(i);
total_tokens -= token_counts[i];
debug!(
"OldestFirst: Removing message at index {}. Tokens removed: {}",
i, token_counts[i]
);
// If it's a ToolRequest or ToolResponse, mark its pair for removal
if message.is_tool_call() || message.is_tool_response() {
message.get_tool_ids().iter().for_each(|id| {
tool_ids_to_remove.insert((i, id.to_string()));
});
}
}
// Now, find and remove paired ToolResponses or ToolRequests
for (i, message) in messages.iter().enumerate() {
let message_tool_ids = message.get_tool_ids();
// Find the other part of the pair - same tool_id but different message index
for (message_idx, tool_id) in &tool_ids_to_remove {
if message_idx != &i && message_tool_ids.contains(tool_id.as_str()) {
indices_to_remove.insert(i);
// No need to check other tool_ids for this message since it's already marked
break;
}
}
}
Ok(indices_to_remove)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::message::Message;
use anyhow::Result;
use mcp_core::content::Content;
use mcp_core::tool::ToolCall;
use serde_json::json;
// Helper function to create a user text message with a specified token count
fn user_text(index: usize, tokens: usize) -> (Message, usize) {
let content = format!("User message {}", index);
(Message::user().with_text(content), tokens)
}
// Helper function to create an assistant text message with a specified token count
fn assistant_text(index: usize, tokens: usize) -> (Message, usize) {
let content = format!("Assistant message {}", index);
(Message::assistant().with_text(content), tokens)
}
// Helper function to create a tool request message with a specified token count
fn assistant_tool_request(id: &str, tool_call: ToolCall, tokens: usize) -> (Message, usize) {
(
Message::assistant().with_tool_request(id, Ok(tool_call)),
tokens,
)
}
// Helper function to create a tool response message with a specified token count
fn user_tool_response(id: &str, result: Vec<Content>, tokens: usize) -> (Message, usize) {
(Message::user().with_tool_response(id, Ok(result)), tokens)
}
// Helper function to create a large tool response with massive content
fn large_tool_response(id: &str, large_text: String, tokens: usize) -> (Message, usize) {
(
Message::user().with_tool_response(id, Ok(vec![Content::text(large_text)])),
tokens,
)
}
// Helper function to create messages with alternating user and assistant
// text messages of a fixed token count
fn create_messages_with_counts(
num_pairs: usize,
tokens: usize,
remove_last: bool,
) -> (Vec<Message>, Vec<usize>) {
let mut messages: Vec<Message> = (0..num_pairs)
.flat_map(|i| {
vec![
user_text(i * 2, tokens).0,
assistant_text((i * 2) + 1, tokens).0,
]
})
.collect();
if remove_last {
messages.pop();
}
let token_counts = vec![tokens; messages.len()];
(messages, token_counts)
}
#[test]
fn test_handle_oversized_single_message() -> Result<()> {
// Create a scenario similar to the real issue: one very large tool response
let large_content = "A".repeat(50000); // Very large content
let messages = vec![
user_text(1, 10).0,
assistant_tool_request(
"tool1",
ToolCall::new("read_file", json!({"path": "large_file.txt"})),
20,
)
.0,
large_tool_response("tool1", large_content, 100000).0, // Massive tool response
user_text(2, 10).0,
];
let token_counts = vec![10, 20, 100000, 10]; // One message is huge
let context_limit = 5000; // Much smaller than the large message
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
);
// Should succeed by truncating the large content
assert!(
result.is_ok(),
"Should handle oversized message by content truncation"
);
let (truncated_messages, truncated_counts) = result.unwrap();
// Should have some messages remaining
assert!(
!truncated_messages.is_empty(),
"Should have some messages left"
);
// Total should be within limit
let total_tokens: usize = truncated_counts.iter().sum();
assert!(
total_tokens <= context_limit,
"Total tokens {} should be <= context limit {}",
total_tokens,
context_limit
);
Ok(())
}
#[test]
fn test_oldest_first_no_truncation() -> Result<()> {
let (messages, token_counts) = create_messages_with_counts(1, 10, false);
let context_limit = 25;
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
)?;
assert_eq!(result.0, messages);
assert_eq!(result.1, token_counts);
Ok(())
}
#[test]
fn test_complex_conversation_with_tools() -> Result<()> {
// Simulating a real conversation with multiple tool interactions
let tool_call1 = ToolCall::new("file_read", json!({"path": "/tmp/test.txt"}));
let tool_call2 = ToolCall::new("database_query", json!({"query": "SELECT * FROM users"}));
let messages = vec![
user_text(1, 15).0, // Initial user query
assistant_tool_request("tool1", tool_call1.clone(), 20).0,
user_tool_response(
"tool1",
vec![Content::text("File contents".to_string())],
10,
)
.0,
assistant_text(2, 25).0, // Assistant processes file contents
user_text(3, 10).0, // User follow-up
assistant_tool_request("tool2", tool_call2.clone(), 30).0,
user_tool_response(
"tool2",
vec![Content::text("Query results".to_string())],
20,
)
.0,
assistant_text(4, 35).0, // Assistant analyzes query results
user_text(5, 5).0, // Final user confirmation
];
let token_counts = vec![15, 20, 10, 25, 10, 30, 20, 35, 5];
let context_limit = 100; // Force truncation while preserving some tool interactions
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
)?;
let (truncated_messages, truncated_counts) = result;
// Verify that tool pairs are kept together and the conversation remains coherent
assert!(truncated_messages.len() >= 3); // At least one complete interaction should remain
assert!(truncated_messages.last().unwrap().role == Role::User); // Last message should be from user
// Verify tool pairs are either both present or both removed
let tool_ids: HashSet<_> = truncated_messages
.iter()
.flat_map(|m| m.get_tool_ids())
.collect();
// Each tool ID should appear 0 or 2 times (request + response)
for id in tool_ids {
let count = truncated_messages
.iter()
.flat_map(|m| m.get_tool_ids().into_iter())
.filter(|&tool_id| tool_id == id)
.count();
assert!(count == 0 || count == 2, "Tool pair was split: {}", id);
}
// Total should be within limit
let total_tokens: usize = truncated_counts.iter().sum();
assert!(total_tokens <= context_limit);
Ok(())
}
#[test]
fn test_edge_case_context_window() -> Result<()> {
// Test case where we're exactly at the context limit
let (messages, token_counts) = create_messages_with_counts(2, 25, false);
let context_limit = 100; // Exactly matches total tokens
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
)?;
let (mut messages, mut token_counts) = result;
assert_eq!(messages.len(), 4); // No truncation needed
assert_eq!(token_counts.iter().sum::<usize>(), 100);
// Now add one more token to force truncation
messages.push(user_text(5, 1).0);
token_counts.push(1);
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
)?;
let (messages, token_counts) = result;
assert!(token_counts.iter().sum::<usize>() <= context_limit);
assert!(messages.last().unwrap().role == Role::User);
Ok(())
}
#[test]
fn test_multi_tool_chain() -> Result<()> {
// Simulate a chain of dependent tool calls
let tool_calls = vec![
ToolCall::new("git_status", json!({})),
ToolCall::new("git_diff", json!({"file": "main.rs"})),
ToolCall::new("git_commit", json!({"message": "Update"})),
];
let mut messages = Vec::new();
let mut token_counts = Vec::new();
// Build a chain of related tool calls
// 30 tokens each round
for (i, tool_call) in tool_calls.into_iter().enumerate() {
let id = format!("git_{}", i);
messages.push(user_text(i, 10).0);
token_counts.push(10);
messages.push(assistant_tool_request(&id, tool_call, 15).0);
token_counts.push(20);
}
let context_limit = 50; // Force partial truncation
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
)?;
let (truncated_messages, _) = result;
// Verify that remaining tool chains are complete
let remaining_tool_ids: HashSet<_> = truncated_messages
.iter()
.flat_map(|m| m.get_tool_ids())
.collect();
for _id in remaining_tool_ids {
// Count request/response pairs
let requests = truncated_messages
.iter()
.flat_map(|m| m.get_tool_request_ids().into_iter())
.count();
let responses = truncated_messages
.iter()
.flat_map(|m| m.get_tool_response_ids().into_iter())
.count();
assert_eq!(requests, 1, "Each remaining tool should have one request");
assert_eq!(responses, 1, "Each remaining tool should have one response");
}
Ok(())
}
#[test]
fn test_truncation_with_image_content() -> Result<()> {
// Create a conversation with image content mixed in
let messages = vec![
Message::user().with_image("base64_data", "image/png"), // 50 tokens
Message::assistant().with_text("I see the image"), // 10 tokens
Message::user().with_text("Can you describe it?"), // 10 tokens
Message::assistant().with_text("It shows..."), // 20 tokens
Message::user().with_text("Thanks!"), // 5 tokens
];
let token_counts = vec![50, 10, 10, 20, 5];
let context_limit = 45; // Force truncation
let result = truncate_messages(
&messages,
&token_counts,
context_limit,
&OldestFirstTruncation,
)?;
let (messages, token_counts) = result;
// Verify the conversation still makes sense
assert!(messages.len() >= 1);
assert!(messages.last().unwrap().role == Role::User);
assert!(token_counts.iter().sum::<usize>() <= context_limit);
Ok(())
}
#[test]
fn test_error_cases() -> Result<()> {
// Test impossibly small context window
let (messages, token_counts) = create_messages_with_counts(1, 10, false);
let result = truncate_messages(
&messages,
&token_counts,
5, // Impossibly small context
&OldestFirstTruncation,
);
assert!(result.is_err());
// Test unmatched token counts
let messages = vec![user_text(1, 10).0];
let token_counts = vec![10, 10]; // Mismatched length
let result = truncate_messages(&messages, &token_counts, 100, &OldestFirstTruncation);
assert!(result.is_err());
Ok(())
}
}