# Replace Apollo Router with Cosmo Router, no subgraph changes required

Full Federation v1 and v2 compatibility means your existing subgraphs and clients keep working. Fetch the router config from Cosmo and deploy Cosmo Router in minutes.

Zero subgraph changes. Zero client updates. Gradual traffic migration supported.

## The problem

## Router migration feels too risky to attempt

Compatibility unknowns, potential subgraph changes, and client coordination all add up to a project that seems harder than it is.

### Directive compatibility is unknown before you commit

Teams cannot risk a router swap if they are unsure whether Federation v1 and v2 directives behave the same way. Uncertainty about compatibility blocks migration planning entirely.

### Subgraph modification risk is too high

If the new router requires changes to subgraph schemas or resolvers, the migration scope expands from a router deployment into a multi-team schema rewrite.

### Client-side changes cannot be coordinated across consumers

Changing how GraphQL clients connect to the router requires coordinating updates across every consumer of the API. Teams need the router swap to be transparent to clients.

## Our solution

## A drop-in replacement for Apollo Router

Cosmo Router implements the Federation specification and supports the same directives as Apollo Router. After migrating your graph configuration, fetch the router config from Cosmo and deploy. No subgraph code changes, no client updates.

### From Apollo Router to Cosmo Router

1. Complete the Apollo GraphOS graph migration (or set up Cosmo manually).
2. Deploy Cosmo Router using the router config available in Cosmo after migration. Fetch it with: `npx wgc federated-graph fetch <graph-name>`.
3. Update your load balancer or API gateway to route traffic to Cosmo Router.
4. Cosmo Router handles query planning, subgraph orchestration, and response aggregation.
5. No changes are required in your subgraphs or GraphQL clients. For a detailed breakdown of how Cosmo handles [Apollo Router compatibility](/content/blog/cosmo-compatibility-mode-for-apollo-router-and-gateway/index.html), see the compatibility post.
6. Access Cosmo Studio immediately for observability, analytics, and schema management.

Deploy once. Existing subgraphs and clients keep working.

## Apollo Router Migration

## Before & After

| Before Cosmo                                      | With Cosmo                                               |
|---------------------------------------------------|---------------------------------------------------------|
| Concerns about Federation directive compatibility   | Full support for Federation v1 and v2 directives       |
| Manual router configuration required                | Router config available in Cosmo after migration        |
| Subgraph modification risk                          | Zero subgraph changes required                          |
| Client updates needed after router swap            | Clients continue working without changes                 |

## Immediate gains

### Cosmo Studio from day one

- **Advanced observability**: Real-time metrics, request tracing, and schema analytics are available in Cosmo Studio the moment the router is live.
- **Schema management**: Manage subgraphs, view composition results, and track schema changes across all environments from a single interface.

## How Apollo Router migration works

### 01 Migrate

Use the Apollo GraphOS migration tool to bring your graph configuration into Cosmo. After migration, fetch the router config with `npx wgc federated-graph fetch <graph-name>`. Manual Cosmo setup is also supported.

### 02 Deploy

Deploy Cosmo Router to your infrastructure using the router config fetched with `npx wgc federated-graph fetch <graph-name>`. The router runs as a binary, in Docker, or on Kubernetes. Subgraph endpoints do not change.

### 03 Route

Update your load balancer or API gateway to direct GraphQL traffic to Cosmo Router. The router handles query planning and subgraph orchestration compatibly with Apollo Router behavior.

### 04 Monitor

Access Cosmo Studio for real-time observability, schema analytics, and federated graph management. These capabilities are available from the moment the router is live.

## What's included

### Everything you need for the router swap

Available on Free, Pro, and Enterprise.

### Federation v1 and v2 support

All standard Federation v1 and v2 directives through version 2.5 are supported. Existing subgraph schemas work without modification.

### Router config ready after migration

After migration, fetch the router config with `npx wgc federated-graph fetch <graph-name>`. No manual configuration is needed.

### Zero subgraph changes

Cosmo Router communicates with subgraphs using the same HTTP/GraphQL protocols as Apollo Router. Existing subgraph code, resolvers, and schemas need no changes.

### Client compatibility

GraphQL clients continue working after the router swap. The router endpoint and response format remain compatible, so no client-side updates are required.

## Switch to Cosmo Router today

Migrate your graph from Apollo GraphOS, fetch the router config, and deploy Cosmo Router.

## FAQ

### Apollo Router Migration FAQ

- Will my GraphQL queries still work after the router swap?
- Do I need to update my subgraphs?
- Do GraphQL clients need to update?
- What about custom directives?
- Can I migrate gradually rather than all at once?
- Do I need to complete the GraphOS migration first?

Full details in the [migration documentation](https://cosmo-docs.wundergraph.com/studio/migrate-from-apollo).