feat: provider abstraction layer — BaseProvider ABC + ProviderFactory [GSoC 2026 Draft]

[vanshjohri09-collab]

GSoC 2026 — Provider Abstraction Layer: Foundation

This draft PR introduces the foundational files for the provider
abstraction layer proposed in my GSoC 2026 application.

What this adds

• app/providers/base.py — BaseProvider ABC with generate(),
  chat(), stream(), health_check() abstract methods
• app/providers/factory.py — get_provider() reading AI_PROVIDER
  from .env, defaulting to huggingface_local (zero regression)
• app/providers/__init__.py — package init

Design decisions

Default is huggingface_local — existing behaviour is fully
preserved. No deployment breaks if AI_PROVIDER is not set.

RAGAgent integration point: app/routes/api.py currently calls
RAGAgent(model=settings.DEFAULT_MODEL). After this project, that
becomes:

provider = get_provider()
agent = RAGAgent(provider=provider)

This PR establishes the interface that makes that change possible.

What comes next (GSoC scope)

• HuggingFaceLocalProvider — wraps existing inference code
• OllamaProvider — local offline inference via /api/generate
• HuggingFaceAPIProvider — Inference API with token
• CustomProvider — any OpenAI-compatible endpoint
• Fallback chain with health_check() caching
• Full pytest + mock test suite (no real API needed in CI)

Related

GSoC 2026 proposal: provider abstraction layer for sugar-ai
Fixes known bug: extract_answer_from_output() breaks with
non-HuggingFace model output format (verified with llama3, mistral)

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Draft — interface design open for mentor feedback before
implementation begins.

[vanshjohri09-collab]

Hi @chimosky I've finalized the BaseProvider ABC and the Factory pattern This forms the foundation for my GSoC proposal Looking forward to your initial feedback on the architecture ,@walterbender @sum2it since you both have a great bird's-eye view of the project, I’d love your thoughts on whether this abstraction fits well with the upcoming UI features Ready for review!

[chimosky]

Seeing as it's a GSoC project idea, I won't review this and would rather it be worked on within GSoC.