Add set_assistant_id/2 function

Allows the assistant_id to be changed after the agent is started.

lib/gpt_agent.ex

@@ -50,6 +50,7 @@ defmodule GptAgent do
   @callback submit_tool_output(pid(), Types.tool_name(), Types.tool_output()) ::
               Types.result(:invalid_tool_call_id)
   @callback run_in_progress?(pid()) :: boolean()
+  @callback set_assistant_id(pid(), Types.assistant_id()) :: Types.success()
 
   defp noreply(%__MODULE__{} = state), do: {:noreply, state, state.timeout_ms}
   defp noreply(%__MODULE__{} = state, next), do: {:noreply, state, next}
@@ -591,5 +592,10 @@ defmodule GptAgent do
     def run_in_progress?(pid) do
       GenServer.call(pid, :run_in_progress?)
     end
+
+    @impl true
+    def set_assistant_id(pid, assistant_id) do
+      GenServer.cast(pid, {:set_assistant_id, assistant_id})
+    end
   end
 end

mix.exs

@@ -4,7 +4,7 @@ defmodule GptAgent.MixProject do
   def project do
     [
       app: :gpt_agent,
-      version: "6.1.0",
+      version: "6.2.0",
       elixir: "~> 1.16",
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),

test/gpt_agent_test.exs

@@ -1380,4 +1380,21 @@ defmodule GptAgentTest do
       refute GptAgent.run_in_progress?(pid)
     end
   end
+
+  describe "set_assistant_id/2" do
+    test "updates the assistant_id in the agent's state", %{
+      assistant_id: assistant_id,
+      thread_id: thread_id
+    } do
+      {:ok, pid} =
+        GptAgent.connect(thread_id: thread_id, last_message_id: nil, assistant_id: assistant_id)
+
+      assert %GptAgent{assistant_id: ^assistant_id} = :sys.get_state(pid)
+
+      new_assistant_id = UUID.uuid4()
+      :ok = GptAgent.set_assistant_id(pid, new_assistant_id)
+
+      assert %GptAgent{assistant_id: ^new_assistant_id} = :sys.get_state(pid)
+    end
+  end
 end