Message Protocol

Message

%Message{
  id: "uuid",
  parent_id: nil | "uuid",    # forms a tree
  role: :user | :assistant | :system,
  content: [content_block],
  timestamp: DateTime.t(),
  metadata: %{}
}

Content Blocks

{:text, "hello"}
{:thinking, "let me reason..."}
{:tool_use, %{id: "tc_1", name: "shell", arguments: %{"command" => "ls"}}}
{:image, mime_type, base64_data}

Tool Call

%ToolCall{
  id: "tc_1",
  name: "shell",
  arguments: %{"command" => "ls -la"}
}

Tool Result

%ToolResult{
  tool_call_id: "tc_1",
  name: "shell",
  content: "total 42\ndrwxr-xr-x ...",
  is_error: false
}

Streaming Deltas

{:text_delta, "partial text"}
{:thinking_delta, "partial thinking"}
{:tool_call_start, id, name}
{:tool_call_delta, id, json_fragment}
{:tool_call_end, id}
{:usage, %{input: 1234, output: 567}}

Tool call JSON fragments are buffered until tool_call_end, then decoded with Jason.decode!/1.