Architectural guidelines for managing context across multi-package monorepos in Cursor

Guides
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When working in larger monorepos or multi-service projects, Composer often pulls context from the wrong package or mixes up frontend and backend conventions.

Here is a 3-step configuration that solves cross-package bleeding:

  1. Root vs. Package Scoping:
    Place lightweight .cursorrules in individual subpackages rather than one massive root file. Cursor Composer prioritizes the rule file closest to the active open file.

  2. Strict File Invariants:
    In your backend service .cursorrules:

- Backend: FastAPI / Python 3.11
- Scope: Inbound requests must extract authentication from Authorization header. Never accept tenant_id from body.

In your frontend .cursorrules:

- Frontend: Next.js 14 App Router
- Rule: Server components by default. Add 'use client' only when state hooks (useState, useEffect) are strictly required.
  1. Terminal Context Isolation:
    When prompting Composer, reference relative file paths explicitly (@packages/api/src/...) rather than relying on fuzzy semantic search across the entire workspace. This keeps the prompt budget focused on the active package’s AST.