Restate

Restate is a lightweight durable execution runtime with first-class support for AI agents. The Pydantic AI integration is provided via the Restate Python SDK.

Visit the Restate documentation for more information.

Durable Execution

Restate makes your agent durable by recording every step of its execution in a journal. If your process crashes mid-execution, Restate replays the journal, skips completed steps, and resumes from exactly where it left off.

Your agent runs in a regular HTTP handler inside a Restate service. The Restate Server sits in front of your application and manages orchestration, journaling, and retries. Services run like regular Docker containers or serverless functions.

A durable agent has three building blocks:

1. The handler: your agent logic, exposed as an HTTP endpoint in a Restate service.
2. LLM calls: persisted so responses are not re-fetched on recovery — saving cost and time.
3. Tool executions: wrapped in durable steps so side effects are not duplicated.

                  Clients
              (HTTP, Kafka, etc.)
                     |
                     v
            +---------------------+
            |   Restate Server    |      (Journals execution,
            +---------------------+       retries on failure,
                     ^                    manages state)
                     |
        Journal      |   Replay on
        steps,       |   recovery,
        retries      |   schedule calls
                     v
+------------------------------------------------------+
|               Application Process                    |
|   +----------------------------------------------+   |
|   |         Restate Service Handler              |   |
|   |           (Agent Run Loop)                   |   |
|   |    [ Durable Steps (Tool, MCP, Model) ]      |   |
|   +----------------------------------------------+   |
|         |           |                |               |
+------------------------------------------------------+
          |           |                |
          v           v                v
      [External APIs, services, databases, etc.]

See the Restate documentation for more information.

Durable Agent

Any Pydantic AI agent can be made durable by wrapping it with RestateAgent from the Restate SDK and running it inside a Restate service handler.

Install the Restate SDK:

pip

Terminal

pip install pydantic-ai restate_sdk[serde]

uv

Terminal

uv add pydantic-ai restate_sdk[serde]

Here is a complete example of a durable Pydantic AI agent with Restate:

restate_agent.py

import restate
from pydantic_ai import Agent, RunContext
from restate.ext.pydantic import RestateAgent, restate_context

weather_agent = Agent(  # (1)
  'openai:gpt-5.2',
  system_prompt='You are a helpful agent that provides weather updates.',
)


@weather_agent.tool()
async def get_weather(_run_ctx: RunContext[None], city: str) -> dict:
  """Get the current weather for a given city."""

  # Do durable tool steps using the Restate context
  async def call_weather_api(city: str) -> dict:
      return {'temperature': 23, 'description': 'Sunny and warm.'}

  return await restate_context().run_typed(  # (2)
      f'Get weather {city}', call_weather_api, city=city
  )


restate_agent = RestateAgent(weather_agent)  # (3)

agent_service = restate.Service('WeatherAgent')


@agent_service.handler()
async def run(_ctx: restate.Context, prompt: str) -> str:  # (4)
  result = await restate_agent.run(prompt)
  return result.output


app = restate.app(services=[agent_service])  # (5)

if __name__ == "__main__":  # (6)
  import hypercorn
  import asyncio
  conf = hypercorn.Config()
  conf.bind = ["0.0.0.0:9080"]
  asyncio.run(hypercorn.asyncio.serve(app, conf))

Define your agent and tools as you normally would with Pydantic AI.

Use restate_context() actions inside tools to make their execution durable. The result is persisted and retried until it succeeds. Side effects won't be duplicated on recovery.

RestateAgent wraps the agent so every LLM response is saved in the Restate Server and replayed during recovery.

The Restate service handler gives the agent a durable execution context and exposes it as an HTTP endpoint.

restate.app() creates the application that can be served.

Run the application with an ASGI server like Hypercorn.

See the Restate agent quickstart to learn how to run the agent.