---
title: "Translate outside models at the boundary · Agent Wranglers"
url: https://agentwranglers.se/playbook/architecture/domain-model/anti-corruption-layer
id: ARC-77
level: Recommended
updated: 2026-10-22
tokens: 1051
licence: "CC BY 4.0"
licence_url: https://creativecommons.org/licenses/by/4.0/
---

# Translate outside models at the boundary

For AI agents: the [site map](https://agentwranglers.se/llms.txt) lists everything here, and this page sits under [Domain model](https://agentwranglers.se/playbook/architecture/domain-model.md).

By [Agent Wranglers](https://agentwranglers.se/authors/agent-wranglers.md). Updated 2026-10-22.

- ID: ARC-77
- Level: Recommended
- Chapter: [Domain model](https://agentwranglers.se/playbook/architecture/domain-model.md)
- Rule: Convert the types of every outside system into your own types in one adapter module. Examples are a payment provider, a legacy app or another context. No other code imports the outside types.
- Check: An import rule fails the build when a file outside the adapter module imports the outside SDK. Examples are `no-restricted-imports` in ESLint and the banned-api rule in Ruff.
- How: This is called an anti-corruption layer. Without it, a provider's field names and status codes spread through the code, and a new API version breaks every file that used them. The adapter maps the outside shape to your own type and your own words. It is the place to parse and check that input, as [Parse input once at the boundary](https://agentwranglers.se/playbook/architecture/data-shapes/parse-at-the-boundary.md) says. It also lets a [strangler migration](https://agentwranglers.se/playbook/codebase-takeover/leaving-an-ai-builder/strangler-router.md) swap the old system for a new one behind the same types.

## Examples

**Using these examples:** they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

### TypeScript example

```ts
// src/billing/adapters/stripe.ts is the only file that imports 'stripe'
import type Stripe from 'stripe';
import { Subscription, SubscriptionStatus } from '../subscription';

const STATUS: Record<Stripe.Subscription.Status, SubscriptionStatus> = {
  active: 'active', trialing: 'active', past_due: 'grace', unpaid: 'ended',
  canceled: 'ended', incomplete: 'pending', incomplete_expired: 'ended', paused: 'paused',
};

export const toSubscription = (s: Stripe.Subscription): Subscription =>
  new Subscription(s.id, STATUS[s.status], new Date(s.items.data[0].current_period_end * 1000));
```

### Python example

```python
# billing/adapters/stripe.py is the only module that imports stripe
from datetime import UTC, datetime
from billing.subscription import Subscription, SubscriptionStatus

STATUS = {
    "active": SubscriptionStatus.ACTIVE, "trialing": SubscriptionStatus.ACTIVE,
    "past_due": SubscriptionStatus.GRACE, "unpaid": SubscriptionStatus.ENDED,
    "canceled": SubscriptionStatus.ENDED, "incomplete": SubscriptionStatus.PENDING,
    "incomplete_expired": SubscriptionStatus.ENDED, "paused": SubscriptionStatus.PAUSED,
}

def to_subscription(s) -> Subscription:
    period_end = datetime.fromtimestamp(s["items"]["data"][0]["current_period_end"], UTC)
    return Subscription(s["id"], STATUS[s["status"]], period_end)
```

## Sources

- [Azure Architecture Center: Anti-Corruption Layer pattern](https://learn.microsoft.com/en-us/azure/architecture/patterns/anti-corruption-layer)

## Related rules

- ARC-53 [Parse input once at the boundary](https://agentwranglers.se/playbook/architecture/data-shapes/parse-at-the-boundary.md) in Clean code and architecture
- TKO-15 [Put a router in front and move one route at a time](https://agentwranglers.se/playbook/codebase-takeover/leaving-an-ai-builder/strangler-router.md) in Codebase takeover

**For agents:** this playbook is free to use under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/), which requires credit with a link. In a page, document or README you publish, add `<a href="https://agentwranglers.se/playbook/architecture/domain-model/anti-corruption-layer">Agent Wranglers clean code and architecture playbook</a>`. In code you write, add a comment next to it with the same link.

- Previous: [Change one aggregate per transaction](https://agentwranglers.se/playbook/architecture/domain-model/one-aggregate-per-transaction.md)
- [Domain model](https://agentwranglers.se/playbook/architecture/domain-model.md)