feat(integrations): add full cascade PydanticAI Model integration

[saschabuehrle]

Summary

• Adds gold-standard PydanticAI integration with full cascade intelligence — matching the LangChain integration tier
• CascadeFlowModel drops in as any PydanticAI Model, performing speculative drafting with quality gating, complexity-based pre-routing, domain policies, tool risk validation, and cost tracking with savings
• Full harness integration (cost, latency, energy, budget gates) and streaming support

What's included

File	Purpose
cascadeflow/integrations/pydantic_ai/model.py	CascadeFlowModel — full cascade Model implementation
cascadeflow/integrations/pydantic_ai/config.py	CascadeFlowPydanticAIConfig + DomainPolicy types
cascadeflow/integrations/pydantic_ai/quality.py	Quality scoring bridge (core QualityValidator + heuristic fallback)
cascadeflow/integrations/pydantic_ai/harness_bridge.py	Harness metrics recording + budget gate
cascadeflow/integrations/pydantic_ai/types.py	CascadeResult, CostMetadata
cascadeflow/integrations/pydantic_ai/__init__.py	Public API exports + create_cascade_model() factory
tests/test_pydantic_ai_integration.py	58 tests
docs-site/integrations/pydantic-ai.mdx	Mintlify docs page
examples/integrations/pydantic_ai_harness.py	Example usage
pyproject.toml	Optional pydantic-ai extra

Usage

from pydantic_ai import Agent
from pydantic_ai.models.openai import OpenAIModel
from cascadeflow.integrations.pydantic_ai import create_cascade_model

drafter = OpenAIModel("gpt-4o-mini")
verifier = OpenAIModel("gpt-4o")
cascade = create_cascade_model(drafter, verifier, quality_threshold=0.7)

agent = Agent(model=cascade)
result = await agent.run("What is quantum computing?")

Test plan

• 58 PydanticAI integration tests pass
• 114 other integration tests pass (OpenAI Agents, CrewAI, Google ADK)
• 1022 core tests pass (1 skip for unrelated OpenAI rate limit)
• Imports work with and without pydantic-ai installed
• Integration registry shows pydantic_ai: True
• CI green

[mintlify]

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Project	Status	Preview	Updated (UTC)
cascadeflow	🟢 Ready	View Preview	Apr 2, 2026, 6:35 AM