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Engineering Jun 2026 7 min read

How we built repo-grounded AI

A practical look at indexing, planning, and verification loops for agents that need to work inside real repositories.

The architecture behind BuildStax understanding your codebase before writing a single line.

Context starts before the prompt

Most coding agents treat the prompt as the primary source of truth. BuildStax treats the repository as the source of truth. Before a model writes code, the agent builds a local map of files, symbols, package scripts, tests, and recent changes so the prompt can be grounded in the shape of the actual project.

  • Incremental file indexing keeps startup fast.
  • Symbol search narrows edits to relevant modules.
  • Git status is checked before modifying files so unrelated work is not touched.

Plans become constrained edits

The planner produces a small set of intended file changes, then the editor applies the smallest correct patch. This keeps the agent from rewriting broad areas of the codebase when the task only needs a targeted fix.

Verification closes the loop

After editing, BuildStax runs the narrowest useful verification command it can identify. That might be a unit test, a type check, a formatter, or a production build. The key is that verification is part of the workflow, not an optional final step.

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