Behaviour for output destinations that receive rendered text from a renderer.

A sink writes rendered output to a specific destination: terminal, file, JSON log, callback function, etc. Sinks receive iodata and decide how to write it.

Implementing a Sink

defmodule MySink do
  @behaviour AgentSessionManager.Rendering.Sink

  @impl true
  def init(opts), do: {:ok, %{device: opts[:device] || :stdio}}

  @impl true
  def write(iodata, state) do
    IO.write(state.device, iodata)
    {:ok, state}
  end

  @impl true
  def write_event(_event, _iodata, state), do: {:ok, state}

  @impl true
  def flush(state), do: {:ok, state}

  @impl true
  def close(state), do: :ok
end

Rendered vs Raw Output

Sinks receive output through two channels:

• write/2 — Rendered text from the renderer. Used for human-readable output.
• write_event/3 — The raw event plus rendered text. Used by sinks that need the structured event data (e.g. JSONL loggers that serialize events, not text).