Agens is an Elixir application designed to build multi-agent workflows with language models.
Drawing inspiration from popular tools in the Python ecosystem, such as LangChain/LangGraph and CrewAI, Agens showcases Elixir’s unique strengths in multi-agent workflows. While the ML/AI landscape is dominated by Python, Elixir’s use of the BEAM virtual machine and OTP (Open Telecom Platform), specifically GenServers and Supervisors, makes it particularly well-suited for these tasks. Agens aims to demonstrate how these inherent design features can be leveraged effectively.
By combining Agens with powerful Elixir libraries like Bumblebee and Nx.Serving, along with structured outputs in the OpenAI API and the continuous improvement of open-source language models, the reliance on Python for multi-agent workflows is significantly reduced. This shift allows Elixir’s concurrency model to truly shine.
⚠️ Experimental: v0.1Agens is currently an experimental project. As of version 0.1, it is primarily a proof-of-concept and learning tool.
The next phase of the project focuses on developing real-world examples to uncover potential issues or gaps that the current test suite may not address.
These examples are designed to not only help you get started but also to advance Agens towards becoming a production-ready tool, suitable for integration into new or existing Elixir applications.
Add agens to your list of dependencies in mix.exs:
def deps do
[
{:agens, "~> 0.1.3"}
]
endBuilding a multi-agent workflow with Agens involves a few different steps and core entities:
1. Add the Agens Supervisor to your Supervision tree
This will start Agens as a supervised process inside your application:
children = [
{Agens.Supervisor, name: Agens.Supervisor}
]
Supervisor.start_link(children, strategy: :one_for_one)See Agens.Supervisor for more information
2. Start one or more Servings
A Serving is essentially a wrapper for language model inference. It can be an Nx.Serving struct, either returned by Bumblebee or manually created, or a GenServer that interfaces with the OpenAI API or other language model APIs. Technically, due to GenServer support, a Serving doesn't need to be limited to language models or machine learning—it can also handle regular API calls.
Application.put_env(:nx, :default_backend, EXLA.Backend)
auth_token = System.get_env("HF_AUTH_TOKEN")
repo = {:hf, "mistralai/Mistral-7B-Instruct-v0.2", auth_token: auth_token}
{:ok, model} = Bumblebee.load_model(repo, type: :bf16)
{:ok, tokenizer} = Bumblebee.load_tokenizer(repo)
{:ok, generation_config} = Bumblebee.load_generation_config(repo)
serving = Bumblebee.Text.generation(model, tokenizer, generation_config)
serving_config = %Agens.Serving.Config{
name: :my_serving,
serving: serving
}
{:ok, pid} = Agens.Serving.start(serving_config)See Agens.Serving for more information
3. Create and start one or more Agents
An Agent in the context of Agens is responsible for communicating with Servings and can provide additional context during these interactions.
In practice, Agents typically have their own specialized tasks or capabilities while communicating with the same Serving. Many projects may use a single Serving, such as a language model (LM) or an LM API, but employ multiple Agents to perform different tasks using that Serving.
Additionally, Agents can use modules implementing the Agens.Tool behaviour to extend their capabilities beyond standard LM inference, enabling function-calling and other advanced operations.
agent_config = %Agens.Agent.Config{
name: :my_agent,
serving: :my_serving
}
{:ok, pid} = Agens.Agent.start(agent_config)See Agens.Agent for more information
4. Create and start one or more Jobs
While Agens is designed to be flexible enough to allow direct communication with an Agens.Serving or Agens.Agent, its primary goal is to facilitate a multi-agent workflow that uses various steps to achieve a final result. Each step (Agens.Job.Step) employs an Agent to accomplish its objective, and the results are then passed to the next step in the Job. Conditions can also be used to determine the routing between steps or to conclude the job.
job_config = %Agens.Job.Config{
name: :my_job,
description: "an example job",
steps: [
%Agens.Job.Step{
agent: :my_agent,
objective: "first step objective"
},
%Agens.Job.Step{
agent: :my_agent,
conditions: %{
"__DEFAULT__" => :end
}
}
]
}
{:ok, pid} = Agens.Job.start(job_config)
Agens.Job.run(:my_job, "user input")See Agens.Job for more information
The examples directory includes a single-file Phoenix LiveView application showcasing the basic usage of Agens.
To run the example, use the following command in your terminal:
elixir examples/phoenix.exsThis will start a local Phoenix server, accessible at http://localhost:8080.
Additional options can be passed to Agens.Supervisor in order to override the default values:
opts = [
prefixes: custom_prompt_prefixes
]
children = [
{Agens.Supervisor, name: Agens.Supervisor, opts: opts}
]
Supervisor.start_link(children, strategy: :one_for_one)The following default prompt prefixes can be copied, customized and used for the prefixes option above:
%Agens.Prefixes{
prompt:
{"Agent",
"You are a specialized agent with the following capabilities and expertise"},
identity:
{"Identity",
"You are a specialized agent with the following capabilities and expertise"},
context: {"Context", "The purpose or goal behind your tasks are to"},
constraints:
{"Constraints", "You must operate with the following constraints or limitations"},
examples:
{"Examples",
"You should consider the following examples before returning results"},
reflection:
{"Reflection",
"You should reflect on the following factors before returning results"},
instructions:
{"Tool Instructions",
"You should provide structured output for function calling based on the following instructions"},
objective: {"Step Objective", "The objective of this step is to"},
description:
{"Job Description", "This is part of multi-step job to achieve the following"},
input:
{"Input",
"The following is the actual input from the user, system or another agent"}
}See the Prompting section below or Agens.Prefixes for more information on prompt prefixes.
You can also see Agens.Supervisor for more information on configuration options.
Agens provides a variety of different ways to customize the final prompt sent to the language model (LM) or Serving. A natural language string can be assigned to the entity's specialized field (see below), while nil values will omit that field from the final prompt. This approach allows for precise control over the prompt content.
All fields with values, in addition to user input, will be included in the final prompt. The goal should be to balance detailed prompts with efficient token usage by focusing on relevant fields and using concise language. This approach will yield the best results with minimal token usage, keeping costs low and performance high.
The input value is the only required field for building prompts. This value can be the initial value provided to Agens.Job.run/2, or the final result of a previous step (Agens.Job.Step). Both the input and result are stored in Agens.Message, which can also be used to send messages directly to Agens.Agent or Agens.Serving without being part of an Agens.Job.
Agens.Job.Config uses the description field to configure the prompt for all messages within the Job. This field should be used carefully as it will be sent to the Serving with every prompt.
Agens.Job.Step uses the objective field to customize the final prompt sent to the Serving. This can provide more specific information in the final prompt than the Job description or Agent prompt.
Agens.Agent provides the most advanced prompt capabilities. The prompt field of Agens.Agent.Config accepts either a simple string value, or an Agens.Agent.Prompt struct. The following fields, which are all optional, can be used with the struct approach:
:identity- a string representing the purpose and capabilities of the agent:context- a string representing the goal or purpose of the agent's actions:constraints- a string listing any constraints or limitations on the agent's actions:examples- a list of maps representing example inputs and outputs for the agent:reflection- a string representing any additional considerations or reflection the agent should make before returning results
Keep in mind that a single agent can be used across multiple jobs, so it is best to restrict the agent prompt to specific capabilities and use objective on Agens.Job.Step or description on Agens.Job.Config for Job or Step-specific prompting.
When creating Tools with the Agens.Tool behaviour, the c:Agens.Tool.instructions/0 callback can be used to include specific instructions in the final prompt. These instructions may also include examples, especially for structured output, which can be crucial for designing a Tool that delivers predictable results.
It is important to note that these instructions are provided to the Serving before the Tool is used, ensuring that the language model (LM) supplies the correct inputs to the Tool. After receiving these inputs, the Tool should be able to generate the relevant arguments to make the function call, and finally provide the expected output for the next step of the job.
See Agens.Tool for more information on using Tools.
- User/Agent:
input/result - Job:
description - Agent:
prompt(stringorAgens.Agent.Prompt) - Step:
objective - Tool:
instructions
Note:
Depending on your use case, some fields may be more relevant than others.
It’s often beneficial to be more descriptive at granular levels, such as the
objectiveofAgens.Job.Stepor theinstructionsforAgens.Tool, while taking a more minimal approach with higher-level fields, such as thedescriptionofAgens.Job.Configor thepromptofAgens.Agent.Config.
The name Agens comes from the Latin word for 'Agents' or 'Actors.' It also draws from intellectus agens, a term in medieval philosophy meaning 'active intellect', which describes the mind’s ability to actively process and abstract information. This reflects the goal of the Agens project: to create intelligent, autonomous agents that manage workflows within the Elixir ecosystem.
This project is licensed under the Apache License, Version 2.0. See the LICENSE file for more details.