Surfaces prompt-cache hit rate on the Insights page so cache-efficiency
(a key cost-optimisation signal) is visible at a glance.
Backend (api/routes.py, _handle_insights):
- Aggregate cache_read_tokens per model and per day, plus a total.
- Graceful fallback for older agent state.db schemas lacking the
cache_read_tokens column (COALESCE + OperationalError second query).
- New response fields: total_cache_read_tokens, total_cache_hit_percent,
per-model cache_read_tokens + cache_hit_percent, per-day cache_read_tokens.
Frontend:
- Models table gains a Cache column (panels.js + style.css 6-col grid).
- Daily bar tooltip includes the bounded cache hit rate.
- New i18n keys insights_model_cache / insights_cache_hit in all 13 locales.
Correctness fix (maintainer-flagged on #3912): the original computed
hit-rate as cache_read / input_tokens (reads-over-misses), which EXCEEDS
100% on cache-heavy sessions. This uses the FULL prompt total as the
denominator -- cache_read / (input_tokens + cache_read) -- via the shared
api.usage.prompt_cache_hit_percent helper, so it is bounded 0-100% and
means "% of the prompt served from cache". Returns None (rendered as a
muted dash) when there are no cache reads.
Tests (tests/test_insights.py):
- Updated existing assertions for the new response shape.
- Added a non-vacuous <=100% boundary test: a cache-heavy case
(cache_read=9900, input=100) where the OLD formula reports 9900% but the
bounded denominator yields 99%. Verified the test FAILS under the old
formula and PASSES under the fix.
Salvage note: PR #3912's diff was ~99 releases stale (mostly re-derived old
code, illusory +5405). This ports ONLY the real ~190-line feature fresh
onto current master.
Closes#3911
Co-authored-by: TomBanksAU <TomBanksAU@users.noreply.github.com>
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