🐛 [Bug]: Custom context not carried forward with middleware.

[prasad83]

Bug Description

Issue 1

I had to use the following signature for custom context

type MyContext struct {
	fiber.DefaultCtx
}

app.NewCtxFunc(func(app *fiber.App) fiber.CustomCtx { /* correction: fiber.Ctx is documented */
    return &MyContext{
        DefaultCtx: *fiber.NewDefaultCtx(app), /* correction: Ctx is documented */
    }
})

Issue 2

app := fiber.New()

app.NewCtxFunc(func(app *fiber.App) fiber.CustomCtx {
    return &MyContext{
        DefaultCtx: *fiber.NewDefaultCtx(app),
    }
})

app.Use(logger.New()) /* when used MyContext is not carried forward */

app.Get("/", func(c fiber.Ctx) error {
    myCtx := c.(*MyContext)
}

app.Listen(":8080")

panic: as c here is *DefaultCtx

How to Reproduce

Run and make request http://localhost:8080/

Expected Behavior

myCtx := c.(*MyContext)

this should work even when middleware is used.

Fiber Version

3.0.0-beta4

Code Snippet (optional)

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have checked for existing issues that describe my problem prior to opening this one.
• I understand that improperly formatted bug reports may be closed without explanation.

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[ReneWerner87]

we will check this in the #3296 PR
there we rewrote the custom context initiailisation

[pjebs]

What if embedded Defaultcontext keeps a reference to the custom context so it can refer to it

[Doout]

Is there any update on this? It will be very beneficial to have a custom structure that could be use to store known values and avoid the cost of storing and loading the value from fasthttp UserData

[ReneWerner87]

This has been fixed.

The issue was addressed in #3852 (merged November 2025). The root cause was that the custom context reference wasn't being maintained when the handler chain passed through middleware - the context would fall back to *DefaultCtx instead of preserving your custom type.

What changed:

• The active custom context is now stored on the request context so middleware continuations retain the caller's type
• AcquireCtx sets up the staged custom context before invoking Reset
• nextCustom() properly handles the interface-based routing for custom contexts

Note: The API has changed since beta4. Instead of app.NewCtxFunc(), you now use NewWithCustomCtx as a constructor:

  app := fiber.NewWithCustomCtx(func(app *fiber.App) fiber.CustomCtx {
      return &MyContext{
          DefaultCtx: *fiber.NewDefaultCtx(app),
      }
  })

  app.Use(logger.New()) // works correctly now

  app.Get("/", func(c fiber.Ctx) error {
      myCtx := c.(*MyContext) // no panic, c is *MyContext
      return c.SendString("ok")
  })

There's also a test covering this exact scenario: Test_Ctx_CustomCtx_WithMiddleware in ctx_test.go.

Closing this.