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justin 330543f9ce Fix #215: pluggable LLM + embedding provider abstraction
Adds the vendor-agnostic seam the AI assistant + match-ranking plug into:
- LLMProvider / EmbeddingProvider ABCs (base.py). LLM and embeddings are
  SEPARATE abstractions — Anthropic has no embeddings endpoint, so each is
  configured independently and either can be off.
- NullLLMProvider / NullEmbeddingProvider — the default; fail loud with a clear
  "not configured" error so AI-off deployments don't silently no-op.
- AnthropicLLMProvider — first concrete LLM impl, via the official anthropic SDK
  (default model claude-opus-4-8). A local provider (e.g. Ollama) would be
  another subclass of the same interface.
- Factory in deps.py (get_llm_provider / get_embedding_provider) selects by
  env (MODEL_PROVIDER / EMBEDDING_PROVIDER); documented in .env.example.

Providers are read-only text/vector producers — they never touch the DB, so the
"AI never writes autonomously" invariant (CLAUDE.md #1) holds; writes will go
through ChangeProposal (#214).

Tests: provider selection (null default, anthropic when keyed, fallback without
key) + null providers raise. 81 passed.

Closes #215

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>
2026-06-09 12:51:01 -04:00

37 lines
1.3 KiB
Python

"""Model-provider interfaces — the seam the AI assistant and match ranking plug
into. LLM (text) and embeddings are *separate* abstractions: Anthropic offers no
embeddings endpoint, so the two are configured independently (twelve-factor,
CLAUDE.md #7) and a deployment may run one without the other.
These providers are read-only text/vector producers. They MUST NOT mutate tree
data — the assistant's writes go through a ChangeProposal a human approves
(CLAUDE.md #1). Nothing here touches the database.
"""
from abc import ABC, abstractmethod
class LLMProvider(ABC):
"""Text in, text out. Implementations wrap a chat/completion model."""
@abstractmethod
async def complete(self, *, prompt: str, system: str | None = None) -> str:
"""Return the model's text response to a single user prompt."""
...
class EmbeddingProvider(ABC):
"""Text in, vectors out — for pgvector-backed match ranking."""
#: Dimensionality of the returned vectors (for the pgvector column).
dimensions: int
@abstractmethod
async def embed(self, texts: list[str]) -> list[list[float]]:
"""Return one embedding vector per input text, in order."""
...
class ModelProviderNotConfigured(RuntimeError):
"""Raised when an AI capability is used but no provider is configured."""