Skip to main content

​
The Flow-First Mindset

When building production AI applications with CrewAI, we recommend starting with a Flow. While it’s possible to run individual Crews or Agents, wrapping them in a Flow provides the necessary structure for a robust, scalable application.

​
Why Flows?

  1. State Management: Flows provide a built-in way to manage state across different steps of your application. This is crucial for passing data between Crews, maintaining context, and handling user inputs.
  2. Control: Flows allow you to define precise execution paths, including loops, conditionals, and branching logic. This is essential for handling edge cases and ensuring your application behaves predictably.
  3. Observability: Flows provide a clear structure that makes it easier to trace execution, debug issues, and monitor performance. We recommend using CrewAI Tracing for detailed insights. Simply run crewai login to enable free observability features.

​
The Architecture

A typical production CrewAI application looks like this:

​
1. The Flow Class

Your Flow class is the entry point. It defines the state schema and the methods that execute your logic. 
from crewai.flow.flow import Flow, listen, start
from pydantic import BaseModel

class AppState(BaseModel):
    user_input: str = ""
    research_results: str = ""
    final_report: str = ""

class ProductionFlow(Flow[AppState]):
    @start()
    def gather_input(self):
        # ... logic to get input ...
        pass

    @listen(gather_input)
    def run_research_crew(self):
        # ... trigger a Crew ...
        pass

​
2. State Management

Use Pydantic models to define your state. This ensures type safety and makes it clear what data is available at each step.
  • Keep it minimal: Store only what you need to persist between steps.
  • Use structured data: Avoid unstructured dictionaries when possible.

​
3. Crews as Units of Work

Delegate complex tasks to Crews. A Crew should be focused on a specific goal (e.g., “Research a topic”, “Write a blog post”).
  • Don’t over-engineer Crews: Keep them focused.
  • Pass state explicitly: Pass the necessary data from the Flow state to the Crew inputs.
    @listen(gather_input)
    def run_research_crew(self):
        crew = ResearchCrew()
        result = crew.kickoff(inputs={"topic": self.state.user_input})
        self.state.research_results = result.raw

​
Control Primitives

Leverage CrewAI’s control primitives to add robustness and control to your Crews.

​
1. Task Guardrails

Use Task Guardrails to validate task outputs before they are accepted. This ensures that your agents produce high-quality results. 
def validate_content(result: TaskOutput) -> Tuple[bool, Any]:
    if len(result.raw) < 100:
        return (False, "Content is too short. Please expand.")
    return (True, result.raw)

task = Task(
    ...,
    guardrail=validate_content
)

​
2. Structured Outputs

Always use structured outputs (output_pydantic or output_json) when passing data between tasks or to your application. This prevents parsing errors and ensures type safety. 
class ResearchResult(BaseModel):
    summary: str
    sources: List[str]

task = Task(
    ...,
    output_pydantic=ResearchResult
)

​
3. LLM Hooks

Use LLM Hooks to inspect or modify messages before they are sent to the LLM, or to sanitize responses. 
@before_llm_call
def log_request(context):
    print(f"Agent {context.agent.role} is calling the LLM...")

​
Deployment Patterns

When deploying your Flow, consider the following:

​
CrewAI Enterprise

The easiest way to deploy your Flow is using CrewAI Enterprise. It handles the infrastructure, authentication, and monitoring for you. Check out the Deployment Guide to get started. 
crewai deploy create

​
Async Execution

For long-running tasks, use kickoff_async to avoid blocking your API.

​
Persistence

Use the @persist decorator to save the state of your Flow to a database. This allows you to resume execution if the process crashes or if you need to wait for human input. 
@persist
class ProductionFlow(Flow[AppState]):
    # ...

​
Summary

  • Start with a Flow.
  • Define a clear State.
  • Use Crews for complex tasks.
  • Deploy with an API and persistence.