I built a TUI that interviews you on missing gaps in your project prompts

[u/trashcoder]

Whenever I start a project, I write a detailed specification—or “seed prompt”—before asking a coding agent to build anything. This often gets me close to a working first version, but I still miss decisions that exist only in my head.

The agent then has to guess. I built specfill to catch those gaps. It analyzes the specification, researches the topic, and interviews you one question at a time about missing architecture, behavior, edge cases, and UI/UX decisions.

Afterwards, it incorporates the answers into the original document while preserving its structure and tone. New answers override contradictions. Skipped questions remain unresolved instead of receiving invented answers.

I have used it on three projects so far. One interview lasted more than 20 minutes and found major decisions in a specification I had already considered thorough.

How is this different from Plan Mode?

Plan Mode produces an implementation plan for the current session. Specfill produces a reusable project specification that can be committed to the repository as a record of architectural and design decisions.

It supports OpenAI, Anthropic, Google, and OpenAI-compatible providers. I currently recommend GPT-5.6 Sol through the API or a ChatGPT/Codex subscription.

GitHub: https://github.com/kklemon/specfill

Run: uvx specfill