High cache-hit decimal display
高缓存命中率的小数显示
The Web conversation stats line rounded every non-empty cache-hit ratio to an integer. Once the actual ratio passed 99%, the display hid further progress, and a ratio of at least 99.5% appeared as 100% even while uncached input or cache writes remained. Users therefore could not distinguish a nearly complete cache hit from a true full hit.
English
Problem
The Web conversation stats line rounded every non-empty cache-hit ratio to an integer. Once the actual ratio passed 99%, the display hid further progress, and a ratio of at least 99.5% appeared as 100% even while uncached input or cache writes remained.
Users therefore could not distinguish a nearly complete cache hit from a true full hit.
Decision
StatsLine continues to derive the ratio from the whole-session tokenUsage projection owned by @deepseek-ai/dsh-token-meter; the projection remains the only owner of the uncached-input, cache-read, cache-write, and output counts (projection decision). The presentation layer changes only the text inserted into the existing stats.cacheHit locale template.
| Actual ratio | Display |
|---|---|
| No billed input | Cache-hit group omitted |
| Integer rounding is below 100% | Rounded integer |
| Non-full ratio whose current rounding is 100% | Minimum decimal precision whose rounded result is below 100% |
| 100% | 100% |
Every non-empty ratio starts at zero decimal places. A non-full ratio increases precision one place at a time only while rounding would produce 100%, so 99.1% and 99.49% remain 99%, while 99.5%, 99.95%, and 99.995% retain one, two, and three decimal places respectively. StatsLine uses exact small-factor comparisons over the safe-integer token counts, then scales the near-full gap only while the intermediate remains within that range. This avoids floating-point tie errors without imposing a precision cap or substitute label. A full hit does not carry a redundant decimal. The same derived string feeds the inline row and its overflow tooltip.
Ownership and lifecycle
Token-meter continues to fold usage from the complete durable session log. StatsLine performs a synchronous display derivation whenever the standard projection value changes. It introduces no setting, stored percentage, event, wire field, client state, or recovery path.
Live updates, reload replay, and reconnect recovery all restore the same tokenUsage counts and run the same display function. A missing projection still omits every token group, and a zero input denominator still omits only the cache-hit group.
Verification
The component spec pins the zero denominator, ordinary integer rounding, half-step rounding at several decimal precisions, each precision boundary through three decimal places, a near-full cumulative sample that needs fourteen decimal places, the true 100% result, both locales, and equality between inline and tooltip values. The assembled lifecycle-chrome replay sidecar selects 9,950 / 10,000 = 99.5% as a deterministic ratio that integer rounding would misreport as 100% while the base session fixture remains recordable; the live assertion and post-reload browser snapshot both display 99.5% without another model call.
Alternatives considered
Keep integer rounding for every ratio. Rejected because it hides all movement above 99% and still reports some non-full hits as 100%.
Truncate the high band to one decimal. Rejected because 99.95%, 99.995%, and still closer ratios all collapse to 99.9% instead of retaining the minimum precision that distinguishes them from a full hit.
Cap precision and use a substitute such as <100%. Rejected because the exact cumulative counts can produce the required numeric result, and a cap would make display behavior depend on an arbitrary presentation limit.
Show one decimal at every ratio. Rejected because the additional low-band motion adds noise and changes the established display where integer precision is sufficient.
Persist a display percentage in token-meter. Rejected because the projection already carries the exact counts, while presentation precision belongs to the Web stats line. A second stored value would duplicate derivable state and expand replay and wire responsibilities.
Consequences
High cache-hit sessions remain visually stable until integer rounding would falsely report a full hit, then expose only the decimal places needed to preserve that distinction. Extremely close non-full ratios can therefore produce long decimal strings; this is the accepted cost of having no arbitrary precision cap or nonnumeric fallback. Every delivery and recovery path stays on the existing durable projection lifecycle.
中文
问题
Web 会话统计行会把所有非空缓存命中率舍入为整数。真实比率超过 99% 后，显示会隐藏后续提升；比率达到 99.5% 时，即使仍有未缓存输入或缓存写入，也会显示为 100%。
用户因此无法区分接近完整的缓存命中与真实满命中。
决策
StatsLine 继续从 @deepseek-ai/dsh-token-meter 所拥有的完整会话 tokenUsage 投影派生比率；该投影仍是未缓存输入、缓存读取、缓存写入与输出计数的唯一所有方（投影决策）。展示层只改变插入现有 stats.cacheHit locale 模板的文本。
| 真实比率 | 显示结果 |
|---|---|
| 没有计费输入 | 省略缓存命中分组 |
| 整数舍入结果低于 100% | 舍入后的整数 |
| 当前舍入结果为 100% 的非满命中 | 舍入结果低于 100% 所需的最少小数位 |
| 100% | 100% |
所有非空比率都从零位小数开始。非满命中只有在舍入结果会成为 100% 时才逐位增加精度，因此 99.1% 与 99.49% 仍显示为 99%，而 99.5%、99.95% 与 99.995% 分别保留一位、两位与三位小数。StatsLine 对安全整数 token 计数执行精确的小因子比较，并且只在中间值仍处于该范围内时缩放接近满命中的差值。该算法既避开浮点临界值误差，也不设置精度上限或替代文案。真实满命中不会携带多余的小数。同一份派生字符串同时用于行内统计与溢出 tooltip。
归属与生命周期
token-meter 继续从完整持久会话日志折叠用量。标准投影值变化时，StatsLine 同步派生显示文本。本决策不引入设置、持久百分比、事件、协议字段、客户端状态或恢复路径。
实时更新、刷新回放与重连恢复都会还原同一组 tokenUsage 计数，并运行同一个显示函数。投影缺失时仍会省略全部 token 分组；输入分母为零时仍只省略缓存命中分组。
验证
组件测试固定了零分母、普通整数舍入、多个小数精度上的半步舍入、直至三位小数的各个精度边界、需要十四位小数的近满累计样本、真实 100%、两种 locale，以及行内值与 tooltip 值的一致性。组装后的 lifecycle-chrome replay sidecar 将 9,950 / 10,000 = 99.5% 选作确定性测试输入；该比率按整数舍入会误报为 100%，同时基础会话 fixture 仍可重录。活跃页面断言与刷新后的浏览器快照都会显示 99.5%，且不会产生额外模型调用。
备选方案
对所有比率继续使用整数舍入。 不予采纳，因为它会隐藏 99% 以上的全部变化，并继续把部分非满命中显示为 100%。
把高位区间向下截取到一位小数。 不予采纳，因为 99.95%、99.995% 以及更接近满命中的比率都会坍缩为 99.9%，无法保留区分真实满命中所需的最少精度。
限制精度并使用 <100% 等替代文案。 不予采纳，因为精确累计计数能够产生所需的数值结果，而精度上限会让显示行为依赖任意的展示限制。
所有比率都显示一位小数。 不予采纳，因为低位区间的额外变化会增加无效抖动，并改变整数精度已经足够的既有显示。
在 token-meter 中持久化显示百分比。 不予采纳，因为投影已经携带精确计数，而展示精度属于 Web 统计行。第二个持久值会复制可派生状态，并扩大回放与协议职责。
后果
高缓存命中率会保持稳定的整数显示，直到整数舍入会错误地报告满命中；此时界面只展示维持区分所需的小数位。极接近满命中的非满比率可能因此产生较长的小数字符串，这是不设置任意精度上限或非数值回退所接受的代价。所有交付与恢复路径继续沿用既有持久投影生命周期。