---
description: Step-by-step fake async rule for dev/testing usage without leaking into production flows
alwaysApply: true
---

# Fake Async Rule (Step-by-Step)

Use this when adding temporary async simulation (delay/mock response/loading states).

## Project location guide

- Demo/dev-only UI behavior:
  - `components/pages/**` or feature component files
- API-level fake responses:
  - keep in isolated dev helpers, not inside production `apis/services/**` runtime paths
- Test-level fake async:
  - test files and test utilities only

## 1) Decide if fake async is really needed

- Use fake async only for:
  - development demos
  - temporary backend gap
  - testing scenarios

## 2) Isolate implementation

- Put fake behavior in clearly named helper/function:
  - `fake*`, `mock*`, `dev*`
- Keep fake logic separate from real API call code.

## 3) Gate it explicitly

- Enable fake behavior only in dev/test condition.
- Never run fake async by default in production paths.

## 4) Keep contract shape real

- Even fake responses must follow real API contract shape from `api-contracts.mdc`.
- Avoid fake payloads that differ from expected typed response.

## 5) Add cleanup marker

- If temporary fake async remains, add a TODO with clear context.
- Do not leave fake async in critical user actions (auth, payment, profile save, etc.).

## 6) Final check

- Verify production path still uses real implementation.
- Run lint/format on touched files.