Incompatible with Express 5

[roni45]

Problem Description
When using openapi-ts-router with Express v5, the application throws the following error at runtime:

TypeError: Missing parameter name at 2: https://git.new/pathToRegexpError

This error originates from the internal path-to-regexp logic used by Express when setting up routes provided by openapi-ts-router.

Environment
openapi-ts-router: 0.2.14
express: ^5.1.0,
Node.js: v22.12.0
OS: (Windows)
pnpm:9.15.2

Observations
When switching back to Express v4, everything works as expected.

[bennobuilder]

The issue has two parts:

1. Router mounting: Use app.use(router) instead of app.get('/*', router)
2. Express 5 compatibility: req.query and req.params are now read-only

Two Options for Express 5 compatibility:

Option 1: Remove parsing middleware entirely

• Parameter parsing happens only in validators (e.g. string -> number conversion)
• Use validators like z.coerce.number() or v.pipe(v.string(), v.transform(Number))

Option 2: Use parsed data approach

• Store parsed data in req.parsed.query and req.parsed.params (e.g. const { petId } = req.parsed.params;)

Which approach do you prefer?

I think it's better to remove the parsing middleware and handle string -> number conversion directly in validators using e.g. z.coerce.number() or similar. This keeps things simpler and leverages the validation library's built-in coercion features.

Temporary workaround: Use parseParams: false in your route config.

[bennobuilder]

We now store parsed/validated data in req.valid:

// Before
const { petId } = req.params; // Read-only in Express 5

// After  
const { petId } = req.valid.params; // Parsed & typed

New Access Pattern

• req.valid.params - Parsed path parameters (string to number/boolean)
• req.valid.query - Parsed query parameters
• req.params - Raw strings (read-only)
• req.query - Raw strings (read-only)

Migration

Update your handlers:

handler: (req, res) => {
  const { id } = req.valid.params;    // number
  const { limit } = req.valid.query;  // number
}