Issue Creation Checklist

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Bug Description

ModelStatic TypeScript type looses custom satic methods.

Reproducible Example

const sequelize = ...; // Your Sequelize instance

class Foo extends Model {
  static myHelper(): Promise<Foo[]> {
    return this.findAll(...); // Custom logic, custom options, etc.
  }
}

Foo.init({}, { sequelize });

const F = sequelize.model('Foo') as ModelStatic<Foo>;

F.myHelper(); // TS2339: Property myHelper does not exist on type ModelStatic<Foo>

As a workaround you can type the return of sequelize.model) as typeof M instead.

What do you expect to happen?

The static helpers are kept in the ModelStatic type, and available.

What is actually happening?

The static helpers aren't available on the ModelStatic type.

Environment

• Sequelize version: 6.37.8
• Node.js version: 24.11.1
• If TypeScript related: TypeScript version: 6.0.2
• Database & Version: MySQL 8
• Connector library & Version: mysql2@3.20.0

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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