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agent: Account for max_output_tokens in compaction threshold #59469

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Merged
bennetbo merged 1 commit into from
Jun 17, 2026
Merged

agent: Account for max_output_tokens in compaction threshold #59469

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73 changes: 70 additions & 3 deletions crates/agent/src/thread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3970,6 +3970,7 @@ impl Thread {
let model = self.model.as_ref()?;
let auto_compact = AgentSettings::get_global(cx).auto_compact;
let max_tokens = model.max_token_count();
let max_input_tokens = max_tokens.saturating_sub(model.max_output_tokens().unwrap_or(0));
let tokens_before = self
.latest_request_token_usage()
.map(|usage| total_input_tokens(usage).saturating_add(usage.output_tokens));
Expand All @@ -3987,7 +3988,7 @@ impl Thread {
auto_compact_threshold: auto_compact.threshold.to_string(),
auto_compact_threshold_tokens: auto_compact_threshold_token_count(
auto_compact.threshold,
max_tokens,
max_input_tokens,
),
retries: 0,
})
Expand All @@ -4010,9 +4011,11 @@ impl Thread {

let model = self.model.as_ref()?;
let max_token_count = model.max_token_count();
let max_input_tokens =
max_token_count.saturating_sub(model.max_output_tokens().unwrap_or(0));
// Models with a small context window don't leave enough headroom for a
// compaction pass; the UI warns the user about the token limit instead.
if max_token_count < MIN_COMPACTION_CONTEXT_WINDOW {
if max_input_tokens < MIN_COMPACTION_CONTEXT_WINDOW {
return None;
}
let (usage_ix, usage) = {
Expand Down Expand Up @@ -4040,7 +4043,7 @@ impl Thread {

let active_tokens = total_input_tokens(usage).saturating_add(usage.output_tokens);
let compaction_threshold =
auto_compact_threshold_token_count(auto_compact.threshold, max_token_count);
auto_compact_threshold_token_count(auto_compact.threshold, max_input_tokens);
if active_tokens < compaction_threshold {
return None;
}
Expand Down Expand Up @@ -6268,6 +6271,70 @@ mod tests {
});
}

#[gpui::test]
async fn test_compaction_threshold_accounts_for_max_output_tokens(cx: &mut TestAppContext) {
let (thread, _event_stream) = setup_thread_for_test(cx).await;
let model = Arc::new(FakeLanguageModel::default());
model.set_max_output_tokens(Some(32_000));
let user_message_id = UserMessageId::new();

cx.update(|cx| {
thread.update(cx, |thread, cx| {
thread.set_model(model, cx);
thread.messages.push(user_text_message(
user_message_id.clone(),
"near input limit",
));
thread.request_token_usage.insert(
user_message_id.clone(),
language_model::TokenUsage {
input_tokens: 871_199,
..Default::default()
},
);

assert_eq!(thread.compaction_message_target_ix(cx), None);

thread.request_token_usage.insert(
user_message_id.clone(),
language_model::TokenUsage {
input_tokens: 871_200,
..Default::default()
},
);

assert_eq!(thread.compaction_message_target_ix(cx), Some(1));

set_auto_compact_settings(
cx,
agent_settings::AutoCompactSettings {
enabled: true,
threshold: AutoCompactThreshold::TokensRemaining(20_000),
},
);
thread.request_token_usage.insert(
user_message_id.clone(),
language_model::TokenUsage {
input_tokens: 948_000,
..Default::default()
},
);

assert_eq!(thread.compaction_message_target_ix(cx), None);

thread.request_token_usage.insert(
user_message_id.clone(),
language_model::TokenUsage {
input_tokens: 948_001,
..Default::default()
},
);

assert_eq!(thread.compaction_message_target_ix(cx), Some(1));
});
});
}

#[gpui::test]
async fn test_compaction_threshold_respects_enabled_setting(cx: &mut TestAppContext) {
let (thread, _event_stream) = setup_thread_for_test(cx).await;
Expand Down
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