Add modern FastAPI integration example with dependency injection

[Jacob-hash999]

Add Modern FastAPI Integration Example (2026)

Summary

Updated FastAPI example to use current Instructor API (from_provider) instead of deprecated dsl module. Added dependency injection, async patterns, and proper error
handling.

Problem

The existing examples/fastapi_app/main.py uses the deprecated DSL API:

• Uses dsl.ChatCompletion, ResponseSchema (no longer documented)
• Not using current instructor.from_provider() pattern
• Confusing for new users following the README

Solution

Created examples/modern-fastapi-integration/modern_fastapi_example.py showing 2026 best practices:

Before (old API):

task = (
    dsl.ChatCompletion(name="...")
    | dsl.SystemTask(task="...")
    | SearchRequest
)
return await task.acreate()

After (new API):
client = instructor.from_provider("openai/gpt-4o-mini")
result = client.chat.completions.create(
    response_model=List[SearchQuery],
    messages=[...],
)
return SearchResponse(queries=result)

Features

- ✅ Modern API: Uses instructor.from_provider()
- ✅ Dependency Injection: FastAPI best practice for sharing clients
- ✅ Async: Proper async/await patterns
- ✅ Error Handling: HTTPException with informative messages
- ✅ Type Safety: Full type hints for IDE support
- ✅ Production Ready: Includes health check endpoint

Testing

python examples/modern-fastapi-integration/modern_fastapi_example.py

# Then test:
curl -X POST http://localhost:8000/search \
     -H "Content-Type: application/json" \
     -d '{"text": "Find ML engineers with Python experience"}'

Why This Matters

I use Instructor daily in production and the DSL example was confusing when I started. This example follows the README patterns and will help new users get started faster.