The durable runtime for swarm intelligence

# A durable agent: the consistency boundary.
# Pure decide/evolve over an event stream — no I/O, no clock.
defmodule Bank.Account do
  use Z8.Agent, snapshot: [every: 100]

  defstruct account_id: nil, balance: 0, status: :new

  # decide: current state + command -> events (+ optional reply)
  def decide(%__MODULE__{status: :new}, %OpenAccount{} = cmd, _ctx),
    do: %Z8.Write.Decision{
      events: [%AccountOpened{account_id: cmd.account_id}],
      reply: :opened
    }

  def decide(%__MODULE__{balance: b}, %Withdraw{amount: a}, _ctx) when a > b,
    do: {:error, :insufficient_funds}

  # evolve: fold an event back into state. Runs on every replay, forever.
  def evolve(acc, %AccountOpened{} = e),
    do: %__MODULE__{acc | account_id: e.account_id, status: :open}
end

# An AI agent. Its event stream IS the run record;
# replay never re-calls the model.
defmodule Support.Triage do
  use Z8.AI.Agent,
    model: :fast,
    prompt: "You are a support triage assistant.",
    tools: [Support.Actions.LookupCustomer],
    max_iterations: 4
end

# Dispatch a run, then await the answer.
:ok = App.dispatch(%Support.Triage.StartRun{run_id: id, query: "double charged"})
{:ok, answer} = Z8.AI.await(App, id)

# Route commands to agents, then start the application.
defmodule Bank.Router do
  use Z8.Dispatch.Router
  middleware Z8.Dispatch.Middleware.Validate

  identify Bank.Account, by: :account_id, prefix: "account-"
  dispatch [OpenAccount, Deposit, Withdraw], to: Bank.Account
end

defmodule Bank.App do
  use Z8.Application, otp_app: :bank
  router Bank.Router
end

# Strong consistency blocks until the :strong handlers ack.
{:ok, _} = Bank.App.start_link()
:ok = Bank.App.dispatch(%Deposit{account_id: "A", amount: 50}, consistency: :strong)