A facade for boilerplate-less semantic search, corpus indexing, and RAG-plug-in readiness.

ef makes the modern embedding pipeline — corpus → segment → embed → vector store → retrieve — usable with progressive disclosure: the light case (a list of strings, search in one or two lines) and the heavy case (huge corpora, many segmentations and embedders, varied sources and vector DBs) share one facade. ef is not a RAG framework — it returns ranked context; you bring your own LLM.

import ef

index = ef.ingest([
    "The cat sat on the mat",
    "Dogs are loyal companions",
    "Neural networks learn from data",
])

for hit in index.search("loyal dogs", limit=2):
    print(hit.score, hit.segment["text"])

That is the whole light path — no configuration, no install beyond ef itself. ingest returns a SearchableCorpus ready to search.

pip install ef                       # core: search, indexing, refresh, eval
pip install "ef[openai]"             # OpenAI embeddings
pip install "ef[sentence-transformers]"  # local sentence-transformers embeddings
pip install "ef[explore]"            # the L5 explore layer (UMAP, HDBSCAN)
pip install "ef[imbed]"              # imbed-backed components & cluster labelling

The core install needs only numpy (plus dol, i2, vd). The default embedder is dependency-free — feature hashing, lexical not semantic; for real semantic search pass a sentence-transformers or provider embedder (see below).

ef is a facade, not a framework. It owns the schemas (Segment, Embedder, Segmenter, Corpus), the indexing core, refresh, and the RAG-plug-in surface — and it stops there: no agent loops, no prompt templating, no answer synthesis. "Bring your own LLM, your own agent framework, your own UI."

It is built on five layers, the same facade covering all of them:

L0 Sources    Corpus = MutableMapping[source_id, Source]   (dol store: fs/S3/API/RAM)
L1 Parse      pluggable text extraction
L2 Segment    Segmenter facade (chunkers)
L3 Embed      Embedder facade (provider / local adapters)
L4 Index      vd.Collection  (ef writes; vd owns the index)
L5 Derive     project / cluster / label   ("explore the corpus")
──────────────────────────────────────────────────────────────
   Search     search(query) -> ranked SearchHits
   RAG plug   retrieve(query) -> list[Segment]  handed to your LLM/agent

ingest and SourceManager take an embedder= — a string, a callable, a URL, or an Embedder. The as_embedder seam normalizes all of them:

from ef import as_embedder, openai_embedder, sentence_transformers_embedder

index = ef.ingest(corpus, embedder=sentence_transformers_embedder("all-MiniLM-L6-v2"))
index = ef.ingest(corpus, embedder=openai_embedder("text-embedding-3-small"))
index = ef.ingest(corpus, embedder=as_embedder("cohere:embed-v4.0"))   # also voyage:/gemini:
index = ef.ingest(corpus, embedder=as_embedder(my_callable, model_id="custom@768"))

Hosted-API adapters: openai_embedder (needs ef[openai]) plus cohere_embedder, voyage_embedder and gemini_embedder — the latter three speak their providers' REST endpoints directly, so they need only an API key, no SDK. Each translates ef's canonical input_type (query / document / classification / clustering) to the vendor's own task name. Local options: sentence_transformers_embedder, http_embedder (any TEI-style service), and the dependency-free HashingEmbedder default.

An Embedder is just a batch callable Iterable[str] -> ndarray(n, dim) with a little metadata. Composition wrappers — CachedEmbedder, RetryingEmbedder, MultiEmbedder, NormalizingEmbedder — each wrap an inner embedder.

For large or changing corpora, multiple segmentations/embedders, and explicit control, use SourceManager. Configs that share a pipeline step share its artifacts for free — the indexing core is a content-addressed producer graph, so a second embedder or segmenter re-uses everything upstream of it.

from ef import SourceManager

manager = SourceManager(corpus, store="my_vectors")
manager.ingest(segmenter="recursive", embedder="openai:text-embedding-3-small")
index = manager.searchable()

As sources change, an index drifts. SourceManager diagnoses and repairs it:

report = manager.diagnose()        # the four staleness conditions
manager.refresh(mode="incremental")  # none | incremental | full | scoped_full
manager = SourceManager(corpus, store="my_vectors", auto_refresh=True)  # live

ef hands a corpus to your RAG/agent framework and measures retrieval quality — it does not synthesize answers.

segments = index.retrieve("how do neural networks learn?", limit=5)
context = "\n\n".join(s["text"] for s in segments)   # feed context to your LLM

from ef import evaluate_retrieval, evaluate_rag
retrieval = evaluate_retrieval(index.retrieve, qrels, queries)  # BEIR-shaped, NDCG@10
rag = evaluate_rag(samples)                          # deterministic lexical metrics

retrieve() returns plain Segments (provenance preserved in metadata["source"]); search() returns scored SearchHits. with_reranker adds a two-stage reranking pass. as_ragas_dataset bridges to Ragas for LLM-judged metrics.

The secondary "see the shape of the corpus" surface — ef's visualization heritage, the backend an app_ef corpus map consumes. Three functions, each taking a corpus or a vector matrix:

coords = ef.project(index, dims=2)          # PCA -> UMAP, 2-D coordinates
labels = ef.cluster(index, n_clusters=8)    # k-means (or method="hdbscan")
titles = ef.label_clusters(segments, labels)  # LLM-titled clusters (via imbed)

project and cluster import numpy-only; their default paths (PCA, k-means) need no extra. method="umap", method="hdbscan" and label_clusters use the ef[explore] / ef[imbed] extras, imported lazily.

No agent loops, no tool-calling, no conversation memory, no prompt templating, no LLM answer synthesis, no bundled UI, no global config singleton. The RAG-plug-in surface is the boundary: ef returns retrieve(query) -> list[Segment]; the application (or srag / raglab / LangGraph) takes it from there.

• GitHub: https://github.com/thorwhalen/ef
• vd (vector-store interface): https://github.com/i2mint/vd
• imbed (heavy embedding/clustering implementations): https://github.com/thorwhalen/imbed

ef ships a developer agent skill — install it into your agent host with gh skill (don't have it? install gh) before working in this repo:

gh skill install thorwhalen/ef ef-architecture --agent claude-code

MIT