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Modular Models

Modular models allows splitting your authorization module across multiple files and modules, improving upon some of the challenges that may be faced when operating an authorization model within a company, such as:

  • A model can grow large and difficult to understand
  • As more teams begin to contribute to a model, the ownership boundaries may not be clear and code review processes might not scale

With modular models, a single model can be split across multiple files in a project. It can be organized in a way that makes sense for the project or teams collaborating on it, and it enables ownership for reviews to be expressed using a feature such as GitHub's, GitLab's or Gitea's code owners.

Key Concepts


The fga.mod is the project file for modular models. This file specifies the schema version for the final combined model and lists the individual files that make up the modular model.

schemaThe schema version to be used for the combined model
contentsThe individual files that make up the modular model


Modules are declared using the module keyword in the DSL, and a module can be written across multiple files. A single file cannot have more than one module.

Currently, modules are stored as metadata but are not used by OpenFGA. Module metadata will be used in upcoming features, such as applying authorization to writing and reading/querying tuples.

Type Extensions

As teams implement features, they might find that core types they are dependent upon might not contain all the relations they need. However, it might not make sense for these relations to be owned by the owner of that type if they aren't needed across the system.

To solve this, individual types can be extended within other modules to implement the relations needed.

In order to allow this, there are certain requirements for type extension:

  • The extended type must exist
  • A single type can only be extended once per file
  • The relations added must not already exist, or be part of another type extension


In this example we'll look at how an authorization model for a SaaS company with an issue tracking and wiki software could implement modular models.


It's likely there will be a core set of types owned by a team that manages the overall identity for the company, this would provide the basics such as users, organizations and groups that can be used by each respective product area.

module core

type user

type organization
define member: [user]
define admin: [user]

type group
define member: [user]

Issue tracking

In the issue tracking software we'd likely separate out the project and issue related types into separate files, we'll also extend the organization type here so that we can add a relation specific to the issue tracking feature, which is the ability to authorize who can create a project.

module issue-tracker

extend type organization
define can_create_project: admin

type project
define organization: [organization]
define viewer: member from organization
module issue-tracker

type ticket
define project: [project]
define owner: [user]


Our wiki model we'll handle in one file for now until it grows some more. Again, we'll also extend the organization type here so that we can add a relation to track who can create a space.

module wiki

extend type organization
define can_create_space: admin

type space
define organization: [organization]
define can_view_pages: member from organization

type page
define space: [space]
define owner: [user]


In order to deploy this model we'll need to create our fga.mod manifest file, in here we'll set our schema version and list the individual module files that make up our model.

schema: '1.2'
- core.fga
- issue-tracker/projects.fga
- issue-tracker/tickets.fga
- wiki.fga

Putting it all together

Now that we have our individual parts of the modular model, we're able to write this model to OpenFGA and then run tests against it.

In order to write our model we need to use the CLI and run:

fga model write --store-id=$FGA_STORE_ID --file fga.mod

We can then write tuples and query this model as you would expect with a singular file authorization model.

await fgaClient.write({
writes: [
}, {
authorization_model_id: "01HVMMBCMGZNT3SED4Z17ECXCA"
Initialize the SDK
// ApiTokenIssuer, ApiAudience, ClientId and ClientSecret are optional.
// import the SDK
const { OpenFgaClient } = require('@openfga/sdk');

// Initialize the SDK with no auth - see "How to setup SDK client" for more options
const fgaClient = new OpenFgaClient({
apiUrl: process.env.FGA_API_URL, // required, e.g. https://api.fga.example
storeId: process.env.FGA_STORE_ID,
authorizationModelId: process.env.FGA_MODEL_ID, // Optional, can be overridden per request

// Run a check
const { allowed } = await fgaClient.check({
user: 'user:anne',
relation: 'can_create_space',
object: 'organization:acme',
}, {
authorization_model_id: '01HVMMBCMGZNT3SED4Z17ECXCA',

// allowed = true

Viewing the model

When viewing the combined model DSL via the CLI with fga model get --store-id=$FGA_STORE_ID, the DSL will be annotated with comments defining the source module and file for types, relations and conditions.

For example, if we look specifically at the organization type we can see that the type is defined in the core.fga file as part of the core module, and then the can_create_project relation is defined in issue-tracker/projects.fga as part of the issuer-tracker module and the can_create_space relation is defined in the wiki.fga file as part of the wiki module.

type organization # module: core, file: core.fga
define admin: [user]
define member: [user] or admin
define can_create_project: admin # extended by: module: issue-tracker, file: issue-tracker/projects.fga
define can_create_space: admin # extended by: module: wiki, file: wiki.fga