Implement Symphony according to the following spec:
https://github.com/openai/symphony/blob/main/SPEC.md

git clone https://github.com/openai/symphony.git
cd symphony/elixir

Set up Symphony for my repository based on
https://github.com/openai/symphony/blob/main/elixir/README.md

export OPENAI_API_KEY="sk-..."           # OpenAI API key for Codex
export LINEAR_API_KEY="lin_api_..."      # Linear integration
export GITHUB_TOKEN="ghp_..."           # GitHub PR operations
export SYMPHONY_REPO_PATH="/path/to/repo"  # Target repository

cd elixir
mix deps.get

import Config

config :symphony,
  openai_api_key: System.get_env("OPENAI_API_KEY"),
  linear_api_key: System.get_env("LINEAR_API_KEY"),
  github_token: System.get_env("GITHUB_TOKEN"),
  repo_path: System.get_env("SYMPHONY_REPO_PATH", "./"),
  poll_interval_ms: 30_000,
  max_concurrent_agents: 3

mix symphony.start
# or in IEx for development
iex -S mix

# In your application.ex or directly
defmodule MyApp.Application do
  use Application

  def start(_type, _args) do
    children = [
      Symphony.Supervisor
    ]
    Supervisor.start_link(children, strategy: :one_for_one)
  end
end

defmodule Symphony.Task do
  @type t :: %__MODULE__{
    id: String.t(),
    title: String.t(),
    description: String.t(),
    source: :linear | :manual,
    status: :pending | :running | :completed | :failed,
    branch: String.t() | nil,
    pr_url: String.t() | nil,
    proof_of_work: map() | nil
  }

  defstruct [:id, :title, :description, :source,
             status: :pending, branch: nil,
             pr_url: nil, proof_of_work: nil]
end

defmodule Symphony.AgentRunner do
  @doc """
  Spawns an isolated agent run for a given task.
  Each run gets its own branch and Codex session.
  """
  def run(task) do
    branch = "symphony/#{task.id}-#{slugify(task.title)}"

    with :ok <- Git.create_branch(branch),
         {:ok, result} <- Codex.implement(task, branch),
         {:ok, pr_url} <- GitHub.open_pr(branch, task),
         {:ok, proof} <- ProofOfWork.collect(pr_url) do
      {:ok, %{task | status: :completed, pr_url: pr_url, proof_of_work: proof}}
    else
      {:error, reason} -> {:error, reason}
    end
  end

  defp slugify(title) do
    title
    |> String.downcase()
    |> String.replace(~r/[^a-z0-9]+/, "-")
    |> String.trim("-")
  end
end

defmodule Symphony.Linear.Poller do
  use GenServer

  @poll_interval Application.compile_env(:symphony, :poll_interval_ms, 30_000)

  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  def init(_opts) do
    schedule_poll()
    {:ok, %{processed_ids: MapSet.new()}}
  end

  def handle_info(:poll, state) do
    case Symphony.Linear.Client.fetch_todo_tasks() do
      {:ok, tasks} ->
        new_tasks = Enum.reject(tasks, &MapSet.member?(state.processed_ids, &1.id))
        Enum.each(new_tasks, &Symphony.AgentRunner.run/1)
        new_ids = Enum.reduce(new_tasks, state.processed_ids, &MapSet.put(&2, &1.id))
        schedule_poll()
        {:noreply, %{state | processed_ids: new_ids}}

      {:error, reason} ->
        Logger.error("Linear poll failed: #{inspect(reason)}")
        schedule_poll()
        {:noreply, state}
    end
  end

  defp schedule_poll do
    Process.send_after(self(), :poll, @poll_interval)
  end
end

defmodule Symphony.Linear.Client do
  @linear_api "https://api.linear.app/graphql"

  def fetch_todo_tasks do
    query = """
    query {
      issues(filter: { state: { name: { eq: "Todo" } } }) {
        nodes {
          id
          title
          description
        }
      }
    }
    """

    case HTTPoison.post(@linear_api, Jason.encode!(%{query: query}), headers()) do
      {:ok, %{status_code: 200, body: body}} ->
        tasks =
          body
          |> Jason.decode!()
          |> get_in(["data", "issues", "nodes"])
          |> Enum.map(&to_task/1)
        {:ok, tasks}

      {:error, reason} ->
        {:error, reason}
    end
  end

  defp headers do
    [
      {"Authorization", System.get_env("LINEAR_API_KEY")},
      {"Content-Type", "application/json"}
    ]
  end

  defp to_task(%{"id" => id, "title" => title, "description" => desc}) do
    %Symphony.Task{id: id, title: title, description: desc, source: :linear}
  end
end

defmodule Symphony.ProofOfWork do
  @doc """
  Collects proof of work for a PR before it can be merged.
  Returns a map with CI status, review feedback, and complexity.
  """
  def collect(pr_url) do
    with {:ok, ci_status} <- wait_for_ci(pr_url),
         {:ok, reviews} <- fetch_reviews(pr_url),
         {:ok, complexity} <- analyze_complexity(pr_url) do
      {:ok, %{
        ci_status: ci_status,
        reviews: reviews,
        complexity: complexity,
        collected_at: DateTime.utc_now()
      }}
    end
  end

  defp wait_for_ci(pr_url, retries \\ 30) do
    case GitHub.get_pr_ci_status(pr_url) do
      {:ok, :success} -> {:ok, :success}
      {:ok, :pending} when retries > 0 ->
        Process.sleep(60_000)
        wait_for_ci(pr_url, retries - 1)
      {:ok, status} -> {:ok, status}
      {:error, reason} -> {:error, reason}
    end
  end

  defp fetch_reviews(pr_url), do: GitHub.get_pr_reviews(pr_url)
  defp analyze_complexity(pr_url), do: GitHub.get_pr_diff_complexity(pr_url)
end

# Core symphony loop
def symphony_loop(state) do
  tasks = fetch_new_tasks(state.source)

  tasks
  |> Enum.filter(&(&1.status == :todo))
  |> Enum.each(fn task ->
    Task.async(fn ->
      branch = create_isolated_branch(task)
      invoke_agent(task, branch)         # Codex / Claude / etc.
      proof = collect_proof_of_work(branch)
      present_for_review(task, proof)
    end)
  end)

  Process.sleep(state.poll_interval)
  symphony_loop(state)
end

defmodule Symphony.AgentPool do
  use GenServer

  @max_concurrent 3

  def start_link(_), do: GenServer.start_link(__MODULE__, %{running: 0, queue: []}, name: __MODULE__)

  def submit(task) do
    GenServer.cast(__MODULE__, {:submit, task})
  end

  def handle_cast({:submit, task}, %{running: n} = state) when n < @max_concurrent do
    spawn_agent(task)
    {:noreply, %{state | running: n + 1}}
  end

  def handle_cast({:submit, task}, %{queue: q} = state) do
    {:noreply, %{state | queue: q ++ [task]}}
  end

  def handle_info({:agent_done, _result}, %{running: n, queue: [next | rest]} = state) do
    spawn_agent(next)
    {:noreply, %{state | running: n, queue: rest}}
  end

  def handle_info({:agent_done, _result}, %{running: n} = state) do
    {:noreply, %{state | running: n - 1}}
  end

  defp spawn_agent(task) do
    parent = self()
    spawn(fn ->
      result = Symphony.AgentRunner.run(task)
      send(parent, {:agent_done, result})
    end)
  end
end

# In IEx or a Mix task
Symphony.AgentPool.submit(%Symphony.Task{
  id: "manual-001",
  title: "Add rate limiting to API",
  description: "Implement token bucket rate limiting on /api/v1 endpoints",
  source: :manual
})

# In config/dev.exs
config :symphony, log_level: :debug

# Or at runtime
Logger.put_module_level(Symphony.AgentRunner, :debug)
Logger.put_module_level(Symphony.Linear.Poller, :debug)