Make the first RAG slice executable without risking production data

The Stage 1 foundation now proves provider contracts with mocks and validates PostgreSQL/pgvector ingestion, approval binding, retrieval, reranking, and idempotency using only synthetic data. Live Bailian validation remains gated on rotating the exposed key.

Constraint: The key shown in chat is compromised and cannot be used or committed

Rejected: Mark Stage 1 complete from mock and offline results | real three-model smoke is still required

Confidence: high

Scope-risk: moderate

Reversibility: clean

Directive: Do not enable real-data ingestion until Stage 3 cloud approval and outbound manifest controls are enforced end to end

Tested: make verify; 41 pytest tests; strict mypy; Ruff; Compose config; pinned image build; empty-volume migration; role denial; two idempotent 20-vector seeds; database restart persistence

Not-tested: Live Bailian calls require a newly rotated key; React product UI is not implemented

backend/tests/unit/test_fake_models.py

@@ -0,0 +1,47 @@
+import math
+
+import pytest
+
+from app.adapters.fake import FakeEmbeddingProvider, FakeReranker
+from app.ports.model_providers import ModelProviderError
+
+
+@pytest.mark.asyncio
+async def test_fake_embedding_is_deterministic_normalized_and_1024_dimensional() -> None:
+    provider = FakeEmbeddingProvider()
+
+    first = await provider.embed_documents(["斑岩铜矿 钾化 绢英岩化"])
+    second = await provider.embed_query("斑岩铜矿 钾化 绢英岩化")
+
+    assert first.vectors[0] == second.vectors[0]
+    assert len(first.vectors[0]) == 1024
+    assert math.isclose(sum(value * value for value in first.vectors[0]), 1.0)
+
+
+@pytest.mark.asyncio
+async def test_fake_reranker_preserves_original_candidate_index() -> None:
+    reranker = FakeReranker()
+    documents = ["煤层测井对比", "斑岩铜矿钾化带", "铝土矿含矿层"]
+
+    result = await reranker.rerank("斑岩铜矿的钾化带", documents, top_n=2)
+
+    assert result.items[0].index == 1
+    assert result.items[0].document == documents[1]
+    assert result.items[0].relevance_score >= result.items[1].relevance_score
+
+
+@pytest.mark.asyncio
+async def test_fake_providers_reject_inputs_the_live_contract_rejects() -> None:
+    embedder = FakeEmbeddingProvider()
+    reranker = FakeReranker()
+
+    with pytest.raises(ModelProviderError):
+        await embedder.embed_documents([])
+    with pytest.raises(ModelProviderError):
+        await embedder.embed_documents(["x"] * 11)
+    with pytest.raises(ModelProviderError):
+        await reranker.rerank("", ["document"], top_n=1)
+    with pytest.raises(ModelProviderError):
+        await reranker.rerank("query", [], top_n=1)
+    with pytest.raises(ModelProviderError):
+        await reranker.rerank("query", ["document"], top_n=0)