# `Runic.IncompatiblePortError`
[🔗](https://github.com/zblanco/runic/blob/main/lib/runic/exceptions.ex#L63)

Raised when connecting two components with incompatible port contracts.

This occurs when `Workflow.add/3` detects that a producer's output ports
are not type-compatible with a consumer's input ports.

## Example

    require Runic
    alias Runic.Workflow

    int_step = Runic.step(fn x -> x + 1 end,
      name: :int_producer,
      outputs: [out: [type: :integer]]
    )

    string_consumer = Runic.step(fn x -> String.upcase(x) end,
      name: :string_consumer,
      inputs: [in: [type: :string]]
    )

    # This raises IncompatiblePortError
    Workflow.new()
    |> Workflow.add(int_step)
    |> Workflow.add(string_consumer, to: :int_producer)

## Solutions

1. Ensure output types match expected input types
2. Use `type: :any` for flexible ports
3. Pass `validate: :off` to bypass validation during prototyping

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*Consult [api-reference.md](api-reference.md) for complete listing*