We add in the special prayer עננו on fast days. It is added in two different locations. (1) as a separate brocho between גואל and רופא and (2) as an addition into the brocho of שמע קולנו.
In (1) the closing phrase which begins כי אתה is needed before the closing brocho.
In (2) it seems to me that that closing phrase is in a sense duplicated by the closing phrase of שמע קולנו which also begins כי אתה.
Are there any nuschaos which drop one of the closing phrases when עננו is said in שמע קולנו?
R Yitzchak Abadi writes (Or Yitzchak 65) that indeed one should not say כי אתה...צרה וצוקה when reciting Aneinu in the fourth to last Bracha of Shmoneh Esrei. If one did accidentally say it he writes that one should not continue with כי אתה שומע... from the end of the regular text, but amend it to ואתה שומע... and not say כי twice.
Haghot Minhagim (Tirnau) (Iyar #32) says not to finish with both כי phrases. The Rambam too (Siddur HaTefillah 18) only includes one כי phrase.
That said Tosfot (Ta'anit 13b) clearly says to include both.
I remembered that there is a principle that the brocho must end with a summary of the ending close to the ending. שצריך לומר מעין חתימה סמוך לחתימה
From a search for “ma’ain chasimo” in Bar Ilan , I found many sources for this (see for example Sefer Avudraham Purim).
The two different phrases which conclude the brochos are “summaries” for the two different brochos. When עננו is alone, we need a conclusion which fits the brocho “ho’oneh be’ais tzoro” but when עננו is in the brocho of שמע קולנו we need a conclusion which fits the brocho of “shomei’a tefilloh”.
That's why we do not find any nuschaos which drop one of the closing phrases when עננו is said in שמע קולנו.
