I find this confusing. Is there any way to know when a noun in the "ki-" class will take a vowel-stem adjective inflected as "k-" and when it will be "ch-"? (Why "kingi" but "chekundu"?)
The lesson tips for 'More adjectives' (are we in that lesson?) suggest "kingi is a special case:
-ingi and -engi mean many, a lot, or plenty, but the agreements differ according to the noun classes they modify. Usually, this adjective only occurs in the plural form, though some classes do take singular agreements.
I see - thanks, killearn!
I just found this good explanation for agreements in the KI-VI noun class: https://tinyurl.com/yckndtrn
It confirms your suggestion. In summary:
For possessives it is always ch-/vy- (e.g. "kiti changu" = my chair)
For adjectives starting with 'e' it is ch-/vy- (e.g. "kiti cheupe" = white chair)
For all other adjectives it is ki-/vi- (e.g. "kiti kingine" = another chair)
The question "Chakula kingi" demonstrates that this rule is unaffected by whether the class 7 noun begins with ki- (as in "kiti") or ch- (as in "chakula").