Extend Existing Flow

# Extend Existing Flow

## Recipe

- Category: Implementation
- Recommended mode: Agent Mode
- Risk level: Medium
- Estimated scope: Small to Medium

## Purpose

Extend an existing user flow without breaking its current behavior, contracts, or downstream effects.

This recipe is for adding one new branch, step, state, role, outcome, or integration point to a flow that already works. It emphasizes preserving the original path, understanding the flow end to end, and introducing the extension at the smallest safe boundary.

## Use When

- adding a new step to an existing flow
- adding an alternate path or branch
- extending a form, wizard, checkout, onboarding, approval, booking, or lifecycle flow
- supporting an additional role or state
- adding one new side effect such as notification, export, or provider call
- preserving the original flow is as important as implementing the new behavior

## Do Not Use When

- the flow is fundamentally broken
- the change replaces rather than extends the current behavior
- the state model needs a full redesign
- multiple unrelated flows are involved
- the task requires a broad architecture migration
- the flow is not yet understood
- the extension cannot be delivered without breaking compatibility

## Inputs

- `[FLOW]`: Existing flow to extend
- `[EXTENSION]`: New step, branch, state, role, or outcome
- `[PRIMARY_ACTOR]`: User or system actor
- `[ENTRY_POINT]`: Route, component, event, or trigger
- `[CURRENT_PATH]`: Existing sequence of behavior
- `[NEW_PATH]`: Required extension
- `[PRESERVED_BEHAVIOR]`: Existing behavior that must remain unchanged
- `[ACCEPTANCE_CRITERIA]`: Observable pass/fail conditions
- `[STATE_RULES]`: Relevant statuses and transitions
- `[PERMISSIONS]`: Role, ownership, tenant, or visibility rules
- `[SIDE_EFFECTS]`: Notifications, jobs, billing, exports, or integrations
- `[CONSTRAINTS]`: Technical, product, design, or compatibility limits
- `[OUT_OF_SCOPE]`: Explicit exclusions

## Prompt