Build a Flask app

Prerequisites: make sure you have everything installed from Get Started guide.

1. Install Genkit Flask plugin

   pip install git+https://github.com/firebase/genkit#subdirectory=py/plugins/flask
   

   Or create a requirements.txt file

   genkit-plugin-flask @ git+https://github.com/firebase/genkit#subdirectory=py/plugins/google-genai
   

2. Create main.py file:

   from flask import Flask
   
   from genkit.ai import Genkit
   from genkit.plugins.flask import genkit_flask_handler
   from genkit.plugins.google_genai import (
       GoogleGenai,
       google_genai_name,
   )
   
   ai = Genkit(
       plugins=[GoogleGenai()],
       model=google_genai_name('gemini-2.0-flash'),
   )
   
   app = Flask(__name__)
   
   
   @app.post('/joke')
   @genkit_flask_handler(ai)
   @ai.flow()
   async def joke(name: str, ctx):
       return await ai.generate(
           on_chunk=ctx.send_chunk,
           prompt=f'tell a medium sized joke about {name}',
       )
   

3. Run the app:

   flask --app main.py run
   

   Or with Dev UI:

   genkit start -- flask --app main.py run
   

   You can invoke the flow via HTTP:

   curl -X POST http://127.0.0.1:5000/joke -d '{"data": "banana"}' -H 'content-Type: application/json' -H 'Accept: text/event-stream'
   

   or you can use Genkit client library.

Authorization and custom context

You can do custom authorization and custom context parsing by passing a ContextProvider implementation.

from genkit.types import GenkitError

async def my_context_provider(request):
    return {'username': parse_request_header(request.headers.get('authorization'))}

@app.post('/say_hi')
@genkit_flask_handler(ai, context_provider=my_context_provider)
@ai.flow()
async def say_hi(name: str, ctx):
    if not ctx.context.get('username'):
        raise GenkitError(status='UNAUTHENTICATED', message='user not provided')

    return await ai.generate(
        on_chunk=ctx.send_chunk,
        prompt=f'say hi to {ctx.context.get('username')}',
    )

parse_request_header can be your custom authorization header parsersing/validation.