A plugin that validates LLM responses and retries with reflection feedback when they don't meet quality criteria.

Configuration

# Basic — retries on error events only (default behaviour)
ADK.Plugin.register({ADK.Plugin.ReflectRetry, max_retries: 3})

# With custom validation — retries when validator returns {:error, reason}
ADK.Plugin.register({ADK.Plugin.ReflectRetry,
  max_retries: 3,
  validator: fn events ->
    text = events |> Enum.map_join("\n", &ADK.Event.text/1)
    if String.contains?(text, "I don't know"),
      do: {:error, "Response was evasive — provide a concrete answer"},
      else: :ok
  end
})

# With custom reflection template
ADK.Plugin.register({ADK.Plugin.ReflectRetry,
  max_retries: 2,
  validator: &MyApp.validate_response/1,
  reflection_template: "Attempt {attempt}/{max}: {reason}\n\nPlease revise your response."
})

How it works

In after_run/3, this plugin:

1. Checks for error events (events with non-nil :error field)
2. If no errors and a :validator function is configured, calls it with the events
3. If validation fails (or errors found), builds a reflection message and re-runs the agent
4. Repeats up to :max_retries times
5. Returns whatever the last attempt produced if retries are exhausted

Validator function

The validator receives the list of events and must return:

• :ok — response is acceptable
• {:error, reason} — response failed validation; reason is included in reflection

Reflection template

The template string supports these placeholders:

• {attempt} — current attempt number (1-based)
• {max} — max retries configured
• {reason} — the error/validation failure reason

Default: "[Reflect & Retry — Attempt {attempt}/{max}] {reason}\n\nPlease try again, adjusting your approach."