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fix: avoid projecting token measurements past latest usage

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This commit is contained in:
Keisuke Hirata 2026-06-01 17:29:58 +09:00
parent 28447466ca
commit 342f194c87
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2 changed files with 27 additions and 36 deletions
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59
crates/llm-worker/src/token_counter.rs
View File

@ -6,8 +6,8 @@
//! # 方針
//!
//! - ローカルトークナイザは持たない。実測値があればそれを採用し、
//! measurement 間はバイト数で按分、最新 measurement より先は測定済みの増分 rate
//! または byte/4 fallback で外挿する
//! measurement 間はバイト数で按分、最新 measurement より先は byte/4
//! fallback で外挿する
//! - 推定の出どころは [`EstimateSource`] で呼び出し側に明示する。
//! 課金判断には使えないが、compact / prune / memory extract trigger 等の
//! 閾値判定には十分な精度
@ -22,7 +22,7 @@ pub enum EstimateSource {
Measured,
/// 連続する 2 つの measurement の間をバイト按分で計算
Interpolated,
/// 最後の measurement より新しい区間を最終 rate で外挿
/// 最後の measurement より新しい区間を byte/4 fallback で外挿
Extrapolated,
/// measurement が 1 件も無く、バイト数のみのフォールバック
NoData,
@ -122,33 +122,8 @@ pub fn tokens_at(
let at_bytes = prefix[index];
let delta_bytes = at_bytes.saturating_sub(lo_bytes);
let mut measured_span = None;
for pair in records.windows(2) {
let older = &pair[0];
let newer = &pair[1];
if newer.history_len > lo.history_len {
break;
}
let older_bytes = prefix[older.history_len.min(cap)];
let newer_bytes = prefix[newer.history_len.min(cap)];
let span_bytes = newer_bytes.saturating_sub(older_bytes);
let span_tokens = newer
.input_total_tokens
.saturating_sub(older.input_total_tokens);
if span_bytes > 0 && span_tokens > 0 {
measured_span = Some((span_tokens, span_bytes));
}
}
let delta_tokens = if let Some((span_tokens, span_bytes)) = measured_span {
(delta_bytes as u128 * span_tokens as u128 / span_bytes as u128) as u64
} else {
delta_bytes / 4
};
TokenEstimate {
tokens: lo.input_total_tokens.saturating_add(delta_tokens),
tokens: lo.input_total_tokens.saturating_add(delta_bytes / 4),
source: EstimateSource::Extrapolated,
}
}
@ -255,7 +230,7 @@ mod tests {
}
#[test]
fn extrapolation_prefers_latest_measured_incremental_span_rate() {
fn extrapolation_after_multiple_measurements_uses_byte_fallback_for_unmeasured_delta() {
let history = vec![
msg("first"),
msg(&"measured increment ".repeat(20)),
@ -263,15 +238,31 @@ mod tests {
];
let records = vec![record(1, 10_000), record(2, 10_200)];
let prefix = prefix_bytes(&history);
let measured_bytes = prefix[2].saturating_sub(prefix[1]);
let delta_bytes = prefix[3].saturating_sub(prefix[2]);
let expected_delta = (delta_bytes as u128 * 200_u128 / measured_bytes as u128) as u64;
let est = total_tokens(&history, &records);
assert_eq!(est.source, EstimateSource::Extrapolated);
assert_eq!(est.tokens, 10_200 + expected_delta);
assert_ne!(est.tokens, 10_200 + delta_bytes / 4);
assert_eq!(est.tokens, 10_200 + delta_bytes / 4);
}
#[test]
fn extrapolation_does_not_reuse_measured_rate_after_context_projection() {
let compacted_span = msg("x");
let projected = vec![
msg("first"),
msg("summary only"),
compacted_span,
msg("new user input"),
];
let records = vec![record(1, 10_000), record(3, 30_000)];
let prefix = prefix_bytes(&projected);
let delta_bytes = prefix[4].saturating_sub(prefix[3]);
let est = total_tokens(&projected, &records);
assert_eq!(est.source, EstimateSource::Extrapolated);
assert_eq!(est.tokens, 30_000 + delta_bytes / 4);
}
#[test]

4
crates/pod/src/compact/token_counter.rs
View File

@ -9,7 +9,7 @@
//! # 方針
//!
//! - ローカルトークナイザは持たない。実測値があればそれを採用し、
//! measurement 間はバイト数で按分、最新 measurement より先は最終 rate で外挿する
//! measurement 間はバイト数で按分、最新 measurement より先は byte/4 で外挿する
//! - Compact の retained split では、request-time pruning / projection 後の
//! `UsageRecord` を persisted history prefix の単調系列として扱わない。
//! 現在の prompt occupancy 推定を raw serialized bytes に配分し、末尾の
@ -245,7 +245,7 @@ pub(crate) fn savings_for_prune_impl(
impl<C: LlmClient, St: Store> Pod<C, St> {
/// 現在の history 全体の推定トークン数。
///
/// 最後の measurement と、その後に追加された未測定分のバイト按分／外挿。
/// 最後の measurement と、その後に追加された未測定分の byte/4 外挿。
pub fn total_tokens(&self) -> TokenEstimate {
let usage = self.usage_history();
llm_worker::token_counter::total_tokens(self.history(), &usage)