codex - 💡(How to fix) Fix Suggestion: improve local compaction handoff

let user_messages = collect_user_messages(&pre_compaction_history_items);
let recent_tail = collect_recent_context_tail(&pre_compaction_history_items);

let mut new_history = build_compacted_history_with_recent_tail(
    Vec::new(),
    &user_messages,
    &summary_text,
    recent_tail,
);

---

const COMPACT_RECENT_OUTPUT_ITEMS_MAX: usize = 16;
const COMPACT_RECENT_OUTPUT_MAX_TOKENS: i64 = 20_000;

fn collect_recent_context_tail(items: &[ResponseItem]) -> Vec<ResponseItem> {
    let Some(last_user_index) = items
        .iter()
        .enumerate()
        .rev()
        .find_map(|(index, item)| real_user_message_text(item).is_some().then_some(index))
    else {
        return Vec::new();
    };

    let mut selected_outputs = Vec::new();
    let mut remaining_tokens = COMPACT_RECENT_OUTPUT_MAX_TOKENS;
    for item in items[last_user_index + 1..].iter().rev() {
        if !is_recent_output_item(item) {
            continue;
        }
        if selected_outputs.len() >= COMPACT_RECENT_OUTPUT_ITEMS_MAX {
            break;
        }

        let item_tokens =
            approx_tokens_from_byte_count_i64(estimate_response_item_model_visible_bytes(item));
        if item_tokens > remaining_tokens {
            break;
        }
        remaining_tokens = remaining_tokens.saturating_sub(item_tokens.max(0));
        selected_outputs.push(item.clone());
    }
    selected_outputs.reverse();
    let selected_outputs = retain_complete_tool_pairs(selected_outputs);

    let mut recent_tail = Vec::with_capacity(selected_outputs.len() + 1);
    recent_tail.push(items[last_user_index].clone());
    recent_tail.extend(selected_outputs);
    recent_tail
}

---

just fmt
just fix -p codex-core
RUST_MIN_STACK=8388608 cargo test -p codex-core compact::tests
RUST_MIN_STACK=8388608 cargo test -p codex-core --test all suite::compact::
cargo build -p codex-cli