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license: mit
tags:
- fastapi
- gemini
- google-genai
- pydantic
- structured-outputs
- micro-saas
---
# ⚡ FastAPI + Google Gemini 2026 Structured JSON Blueprint (Python 3.13 Ready)
[](https://github.com/RAZIO05/fastapi-gemini-2026-blueprint/actions)
[](https://yahiaoui26.gumroad.com/l/fastapi-gemini-blueprint)
[](https://yahiaoui26.gumroad.com/l/shipai-pro)
[](https://yahiaoui26.gumroad.com/l/shipai-pro)
[](https://yahiaoui26.gumroad.com/l/shipai-pro/LAUNCH20)
<p align="center">
<a href="https://yahiaoui26.gumroad.com/l/shipai-pro/LAUNCH20">
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</a>
</p>
> **Stop fighting unstructured LLM markdown and Python 3.13 `bcrypt` crashes.**
> This reference blueprint shows how to wire **FastAPI**, **Pydantic v2**, and the official **`google-genai` SDK** with native `response_mime_type="application/json"` and 3-model automatic failover.
---
## 🎁 Grab the Free 2026 Architecture Cheat Sheet ($0) or Full Commercial Boilerplate
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---
## 1. Enforcing Strict Pydantic v2 JSON with 3-Model Gemini Failover
```python
import os, json
from google import genai
from pydantic import BaseModel
from typing import List
client = genai.Client(api_key=os.getenv("GEMINI_API_KEY"))
DEFAULT_MODELS = [
os.getenv("GEMINI_MODEL", "gemini-3.5-flash"),
"gemini-flash-lite-latest",
"gemini-3.8-flash",
]
class AIStructuredResponse(BaseModel):
status: str
summary: str
key_points: List[str]
action_items: List[str]
def generate_structured_json(prompt: str, system_instruction: str) -> AIStructuredResponse:
for model_name in DEFAULT_MODELS:
try:
res = client.models.generate_content(
model=model_name,
contents=prompt,
config={
"response_mime_type": "application/json",
"system_instruction": system_instruction,
},
)
return AIStructuredResponse(**json.loads(res.text))
except Exception as err:
if any(code in str(err) for code in ("404", "503", "UNAVAILABLE", "NOT_FOUND")):
continue
raise
```
## 2. Fixing the Python 3.12 / 3.13 `passlib[bcrypt]` 72-Byte Startup Crash
Pin `bcrypt==4.0.1` alongside `passlib[bcrypt]` in `requirements.txt` to avoid the `ValueError: password cannot be longer than 72 bytes` exception during container boot:
```txt
fastapi
uvicorn
google-genai
pydantic[email]
passlib[bcrypt]
bcrypt==4.0.1
python-jose[cryptography]
```
---
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