By: Rabbi Ari Enkin
On Purim (and Chanuka) the “al hanissim” prayer is recited as part of the Birkat Hamazon in honor of the holiday. In contrast, however, no mention of Purim is made when one recites the “al hamichya” blessing which follows a snack of mezonot foods, such as cake and cookies. This appears somewhat odd considering that on all other holidays on which there is a special insertion included in the Birkat Hamazon there is an insertion of some sort in the “al hamichya”, as well. This inconsistency has been noted and addressed by several halachic authorities.
One of the explanations for this inconsistency is that it is because the “al hanissim” is a prayer of thanksgiving, which is why it is inserted in the “modim” blessing of the Shemoneh Esrei, as it too is a prayer of thanksgiving in its own right. Similarly, in the Birkat Hamazon, “al hanissim” is inserted in the second section, which includes a number of gifts and miracles that we are thankful for. The “al hamichya” blessing, however, simply does not include a component or section which specifically discusses thanksgiving. As such, “al hanissim” may be essentially incompatible with the content or purpose of “al hamichya” and is therefore not included in it. Related to this is the idea that “al hanissim” is not an independent prayer as most other seasonal insertions are deemed to be, but rather, it is a seasonal-specific continuation of the existing prayers it is inserted to.
Nevertheless, these explanations are weak on several accounts. For example, one who forgot to insert “al hanissim” in the proper place in the Birkat Hamazon can still make-up his omission by reciting it in the concluding “harachaman” section of the Birkat Hamazon. This seems to imply that “al hanissim” is not entirely dependent on any specific section of the Birkat Hamazon. Furthermore, there is indeed some expression of thanksgiving in the “al hamichya”, albeit on a lesser scale than that which is found in the Birkat Hamazon, which should allow for an “al hanissim” insertion of some sort in the course of the prayer.
It might just be that there is simply no authoritative or foolproof explanation for the exclusion of “al hanissim”, or some other reference to Chanuka and Purim, in the “al hamichya”. It is noted that one who unintentionally omitted the “al hanissim” in either the Shemoneh Esrei or the Birkat Hamazon is not required to repeat the prayer. So too, there is no compensational blessing in the Birkat Hamazon for one who omitted “al hanissim” as there are on other occasions when the required insertion was omitted. This seems to convey a sense that the status of the “al hanissim” is on a much lower level of importance than the other seasonal additions for which one is required to repeat the Shemoneh Esrei should one have omitted them. It is also noted that all the insertions which are customarily added to the “al hamichya” are all in honor of holidays which are of Torah origin, whereas Chanuka is of rabbinic origin.
It is interesting to note that there indeed exists an opinion that Chanuka and Purim should be explicitly mentioned in the “al hamichya”, though the halacha is not like this view.  One who accidentally mentioned Chanuka or Purim in the “al hamichya” blessing has discharged his obligation and is not required to repeat the prayer due to the unauthorized insertion.
 OC 208:12.
 Levush, OC 208:12.
 Levush, OC 208:12.
 Tzitz Eliezer 9:33. For much more on this issue see Rivevot Ephraim 2:185:4, 6:359.
 OC 187.
 Aruch Hashulchan, OC 208:7.
 Machatzit Hashekel, OC 208:11.
 Kaf Hachaim, OC 682:3.
 Rivevot Ephraim 8:272:1; Yabia Omer 3:36.