# Route one call path to the replacement, reversibly

One call path moved to the replacement behind a flag, with both paths tested and the switch reversible.

Category: Architecture and boundaries
Source: https://letsship.ai/use-cases/take-one-strangler-step
Published: 2026-08-25

## Goal

Route one call path to the new implementation behind a reversible switch.

## Acceptance criteria

- Both the old and the new path are covered by tests
- The switch is a flag that can be reverted without a deploy
- Behaviour is identical on both paths, proven by a comparison test
- The plan states which path comes next

## What lands as proof

A comparison test asserting both paths produce the same result, which is what makes the switch safe to flip.

## Prompt

Copy this to an agent to open the ticket:

```text
Create a Linear issue in my team and assign it to the SHIP agent.

Title: Route {path} to the new implementation

Description: Route one call path to the new implementation behind a reversible switch.

Acceptance criteria:
- Both the old and the new path are covered by tests
- The switch is a flag that can be reverted without a deploy
- Behaviour is identical on both paths, proven by a comparison test
- The plan states which path comes next

Before you create the issue, identify a migration this repository is part-way through and replace {path} with the next call path to move.
```

## Questions

### What does the agent actually change?

The ticket is scoped to one outcome: route one call path to the new implementation behind a reversible switch. Work that serves that outcome is in scope, and anything outside it is left for a separate ticket, so the pull request stays reviewable.

### How do I know the work is done?

The pull request carries the evidence, not only the diff. Here that means both paths under test, the switch documented and reversible, so a reviewer can confirm the result without reproducing the work locally.

### How much oversight does this need?

The run stops for the plan, and the review bar is raised afterwards so that smaller suggestions block the merge too, not only serious findings.