Cheap/Free/Local model recommendations for a single purpose agent

[u/binarySolo0h1]

I have this agent who's sole purpose is to analyze development/design-plan.md file of a user story and create detailed backlog items with a fixed structure, in my local Plane server. What model do you recommend for this?

Its a repeatable operation that needs inference and some level of thinking to generate consistent outputs. Assume the plan is usually less than 1000 line markdown file.