docs(research): investigate LiteLLM knowledgebase/vector_store feature for #23

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/research/litellm-knowledgebase.md

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+# Research: LiteLLM vector store / knowledgebase feature (for Gitea issue #23)
+
+**Question:** Can LiteLLM's built-in "knowledgebase" / vector store feature be
+used to load two Markdown fact files (`data/memory.md`,
+`data/claude-legacy-memory.md`) into a queryable knowledge base, and if so,
+what does that require from this stack (config shape, backend, embedding
+model, ingestion mechanism)?
+
+**Bottom line: no, not against this stack's existing Qdrant instance, and not
+without adding a dedicated embedding model.** LiteLLM's vector store feature
+is a *routing/registry* layer over a small set of natively-integrated
+backends (Bedrock Knowledge Bases, OpenAI Vector Stores, Azure
+Vector/AI-Search, Vertex AI RAG/Search, Gemini File Search, RAGFlow) plus one
+self-hosted option — Postgres+pgvector, via a **separate companion service**
+(`BerriAI/litellm-pgvector`), not Qdrant. There is no Qdrant provider at all.
+Ingesting the two fact files would also require running a dedicated
+embedding-capable model, which this stack doesn't currently have (the one
+llama.cpp instance serves a chat model, not started with `--embeddings`).
+
+## 1. Config shape in `config.yaml`
+
+Top-level block is **`vector_store_registry`** (this is the current key name;
+an earlier PR that introduced the feature used `vector_stores` — see
+Provenance note below), a list of entries:
+
+```yaml
+vector_store_registry:
+  - vector_store_name: "my-knowledgebase"      # optional friendly name
+    litellm_params:
+      vector_store_id: "T37J8R4WTM"             # required, provider's own ID
+      custom_llm_provider: "bedrock"            # required — selects backend
+      vector_store_description: "..."           # optional
+      vector_store_metadata: {}                 # optional
+      litellm_credential_name: "..."            # optional, reuse a named credential
+      embedding_model: "..."                    # backend-dependent — see §3
+```
+
+Source: [docs.litellm.ai/docs/completion/knowledgebase](https://docs.litellm.ai/docs/completion/knowledgebase)
+(fetched directly). Earlier shape (same idea, older field names) documented
+in [BerriAI/litellm PR #10448](https://github.com/BerriAI/litellm/pull/10448)
+("[Feat] Vector Stores/KnowledgeBases - Allow defining Vector Store Configs"):
+
+```yaml
+vector_stores:
+  - vector_store_name: "bedrock-litellm-website-knowledgebase"
+    litellm_params:
+      custom_llm_provider: "bedrock"
+      id: "T37J8R4WTM"
+```
+
+This is a **registry of pointers to knowledge bases that already exist on
+the backend provider** — it is not itself a vector database. `model_list`
+entries are not where a store is attached; `vector_store_registry` is its
+own top-level sibling of `model_list`.
+
+### Referencing a vector store from a request
+
+Not via a `model_list` entry — via the **`tools`** array of a
+`/chat/completions` (or `/v1/responses`) request, OpenAI Assistants-style
+`file_search` tool:
+
+```json
+{
+  "model": "gpt-4o",
+  "messages": [...],
+  "tools": [
+    {
+      "type": "file_search",
+      "vector_store_ids": ["T37J8R4WTM"]
+    }
+  ]
+}
+```
+
+LiteLLM intercepts the tool call, looks up the referenced ID in
+`vector_store_registry`, calls that backend's native search, and injects the
+retrieved chunks into the prompt before calling the target model. Source:
+[docs.litellm.ai/docs/completion/knowledgebase](https://docs.litellm.ai/docs/completion/knowledgebase).
+
+There are also direct, OpenAI-compatible proxy endpoints for managing/using a
+store outside of a chat completion — see §4.
+
+## 2. Backend providers — Qdrant is NOT one of them
+
+Per the official docs page and the PR that introduced the feature, the
+natively-supported `custom_llm_provider` values are:
+
+| Provider | `custom_llm_provider` value | Notes |
+|---|---|---|
+| AWS Bedrock Knowledge Bases | `bedrock` | Original/reference implementation ([PR #10448](https://github.com/BerriAI/litellm/pull/10448)) |
+| OpenAI Vector Stores | `openai` | Wraps OpenAI's own vector store API |
+| Azure Vector Stores | `azure` | Assistants-API-only per docs |
+| Azure AI Search | `azure_ai_search` (vector search capability) | |
+| Vertex AI RAG Engine | `vertex_ai` | Added in [PR #15781](https://github.com/BerriAI/litellm/pull/15781) |
+| Vertex AI Search API | `vertex_ai/search_api` | |
+| Gemini File Search | — | |
+| RAGFlow Datasets | — | Dataset mgmt only; search unsupported per docs |
+| Postgres + pgvector | `pg_vector` (via a **separate** connector service) | See below — not built into the litellm proxy image |
+
+Source: [docs.litellm.ai/docs/completion/knowledgebase](https://docs.litellm.ai/docs/completion/knowledgebase),
+cross-checked against [PR #12595](https://github.com/BerriAI/litellm/pull/12595)
+("[Feat] Vector Stores - Add Vertex RAG Engine API as a provider") and
+[PR #15781](https://github.com/BerriAI/litellm/pull/15781) ("(feat) Vector
+Stores: support Vertex AI Search API").
+
+**Qdrant is not listed anywhere** in the knowledgebase docs, the vector
+store provider PRs, or the pgvector connector's own README. LiteLLM does use
+Qdrant in one unrelated feature — **semantic response caching**
+(`docs.litellm.ai/docs/caching/all_caches`, `qdrant_api_base` /
+`qdrant_api_key` / `qdrant_collection_name` config) — but that is a cache for
+LLM *responses*, not the vector-store/knowledgebase (RAG) feature, and shares
+no config or code path with `vector_store_registry`. It would not let
+LiteLLM search Qdrant-held documents as a knowledge base.
+
+### The pgvector option is a separate microservice, not a built-in backend
+
+[`BerriAI/litellm-pgvector`](https://github.com/BerriAI/litellm-pgvector) is
+its own repo/container: a FastAPI app that exposes OpenAI-compatible vector
+store endpoints backed by Postgres with the `pgvector` extension, calling
+back out to a LiteLLM proxy's `/embeddings` endpoint to generate embeddings.
+It is registered into `vector_store_registry` like any other backend (with
+`custom_llm_provider: pg_vector` pointed at this companion service's URL),
+but it is **not Qdrant** and **not part of the main `litellm` proxy image**
+already running in this stack — it would mean deploying and operating a
+fourth service (on top of `litellm`, `litellm-db`, and `llama-server`), with
+its own Postgres database using the pgvector extension (the existing
+`litellm-db` Postgres image, `postgres:16-alpine`, does not have pgvector
+installed).
+
+### Verdict on the existing Qdrant instance
+
+**LiteLLM's knowledgebase/vector_store feature cannot point at this repo's
+existing standalone `qdrant` service.** There is no Qdrant provider type for
+`vector_store_registry`. To use LiteLLM's native feature at all, this stack
+would need to either integrate with a cloud-native backend (Bedrock/Vertex/
+Azure/OpenAI — none of which apply, this stack is local-only) or stand up
+the separate `litellm-pgvector` + pgvector-enabled Postgres stack — an
+entirely different vector store technology from the Qdrant already running
+for Open WebUI. The existing Qdrant collection Open WebUI uses for its own
+RAG/Memory feature is unrelated to and unreachable from LiteLLM's
+knowledgebase feature.
+
+## 3. Embedding model requirement
+
+LiteLLM's vector store feature **does call an embedding endpoint itself**
+when a backend needs one (pgvector explicitly; the managed cloud backends
+handle embedding server-side). The field is `embedding_model` inside a
+`vector_store_registry` entry's `litellm_params`, confirmed in
+[BerriAI/litellm issue #23980](https://github.com/BerriAI/litellm/issues/23980)
+("[Bug]: Vector store creation fails when using model mapping public model
+name for embedding_model"), which shows:
+
+```json
+"litellm_params": {
+  "vector_bucket_name": "my-embeddings",
+  "index_name": "test-index",
+  "aws_region_name": "us-east-1",
+  "embedding_model": "test-vector-store/bedrock/amazon.nova-2-multimodal-embeddings-v1:0"
+}
+```
+
+For the pgvector connector specifically, the embedding model is configured
+via its own env vars (not `vector_store_registry`, since it's a separate
+service): `EMBEDDING__MODEL`, `EMBEDDING__BASE_URL` (pointed at a LiteLLM
+proxy), `EMBEDDING__API_KEY`, `EMBEDDING__DIMENSIONS` — e.g.
+`EMBEDDING__MODEL=text-embedding-ada-002`,
+`EMBEDDING__BASE_URL=http://litellm:4000`. Source:
+[BerriAI/litellm-pgvector README](https://github.com/BerriAI/litellm-pgvector/blob/main/README.md).
+This confirms: **yes, the embedding model must be reachable as a model
+LiteLLM's proxy can call** — i.e. it needs its own `model_list` entry with
+`mode: embedding` (LiteLLM's standard way of declaring an embedding-capable
+model — see [docs.litellm.ai/docs/embedding/supported_embedding](https://github.com/BerriAI/litellm/blob/main/docs/my-website/docs/embedding/supported_embedding.md)),
+so the pgvector service (or LiteLLM itself for backends that embed
+internally) can call `POST /embeddings` against it through the proxy.
+
+### Does llama.cpp (this repo's model server) support `/embeddings`?
+
+Yes, but not enabled as currently configured, and not well-suited to the
+model already loaded. llama.cpp's server (`tools/server`, the same
+`ghcr.io/ggml-org/llama.cpp:server-rocm` image this repo uses per
+`docker-compose.yml`) exposes an OpenAI-compatible `POST /v1/embeddings`
+route (and a native `/embedding` route), **but only when started with the
+`--embeddings` flag** — source:
+[ggml-org/llama.cpp tools/server/README.md](https://github.com/ggml-org/llama.cpp/blob/master/tools/server/README.md).
+This repo's `llama-server` command in `docker-compose.yml` (lines 16–22) does
+not pass `--embeddings`, so the currently-running instance does not serve
+embeddings at all.
+
+Even if the flag were added, llama.cpp loads **one model per server
+process** — the flag would make the already-loaded Qwen3.8-27B **chat**
+model (per `litellm-config.yaml`, `qwen3.8-27b-local` /
+`Qwen3.8-27B-UD-Q4_K_XL.gguf`) emit pooled hidden-state vectors as
+"embeddings," but a generalist instruction-tuned chat model is not what
+that's trained for — embedding quality from a non-embedding-trained model is
+materially worse than a purpose-trained embedding model (e.g. BGE, Nomic
+Embed, mxbai-embed, gte). **A separate, dedicated embedding model/server
+would be needed** — either a second `llama-server` container loaded with a
+small GGUF embedding model (`--embeddings` flag on), or a different
+embedding-serving stack — and it would need its own `model_list` entry in
+`litellm-config.yaml` with `mode: embedding` for LiteLLM/litellm-pgvector to
+call it.
+
+## 4. How documents actually get ingested
+
+Two ingestion paths exist depending on backend, both are HTTP APIs — there
+is no admin-UI "add document" flow beyond store *creation*, and no CLI:
+
+**a) OpenAI-compatible vector-store file API** (used for the `openai`
+backend, and shown as the general pattern in the docs):
+
+- `POST /v1/vector_stores` — create a store. Body:
+  ```json
+  {
+    "name": "My Document Store",
+    "file_ids": ["file-abc123"],
+    "chunking_strategy": {
+      "type": "static",
+      "static": {"max_chunk_size_tokens": 800, "chunk_overlap_tokens": 400}
+    },
+    "metadata": {"key": "value"}
+  }
+  ```
+  Requires files already uploaded through a separate Files API to obtain
+  `file_id`s first — the docs page does not show a files-upload endpoint
+  under the vector-store docs directly (this is OpenAI's own two-step
+  upload-then-attach flow, proxied through). Source:
+  [docs.litellm.ai/docs/vector_stores/create](https://docs.litellm.ai/docs/vector_stores/create).
+- `POST /v1/vector_stores/{vector_store_id}/search` — query it:
+  ```json
+  {
+    "query": "What is the capital of France?",
+    "filters": {"file_ids": ["file-abc123"]},
+    "max_num_results": 5,
+    "ranking_options": {"score_threshold": 0.7},
+    "rewrite_query": true
+  }
+  ```
+  Source: [docs.litellm.ai/docs/vector_stores/search](https://docs.litellm.ai/docs/vector_stores/search).
+- `GET /vector_store/list` — list registered stores. Source:
+  [docs.litellm.ai/docs/completion/knowledgebase](https://docs.litellm.ai/docs/completion/knowledgebase).
+- LiteLLM Admin UI: **Experimental → Vector Stores → Create Vector Store**
+  exists for registering/creating stores, and the **Logs** page shows
+  vector-store search queries/scores after use — but this is store
+  management and observability, not a bulk document-ingestion UI. Source:
+  [docs.litellm.ai/docs/completion/knowledgebase](https://docs.litellm.ai/docs/completion/knowledgebase).
+
+**b) `litellm-pgvector` connector's own embeddings API** (only path relevant
+if this repo went the self-hosted pgvector route, since Qdrant isn't
+supported at all): direct chunk-level ingestion, no file upload step —
+
+- `POST /v1/vector_stores/{id}/embeddings` — single chunk:
+  ```json
+  {"content": "...", "embedding": [/* optional, else computed server-side */], "metadata": {}}
+  ```
+- `POST /v1/vector_stores/{id}/embeddings/batch` — array of the same shape,
+  for bulk loading.
+
+Source: [BerriAI/litellm-pgvector README](https://github.com/BerriAI/litellm-pgvector/blob/main/README.md).
+
+For a follow-up ticket that wants to programmatically load
+`data/memory.md` / `data/claude-legacy-memory.md` (dated fact lists) into a
+knowledge base, the realistic path through LiteLLM's native feature would be
+the pgvector connector's batch-embeddings endpoint (chunk the Markdown into
+facts/sections client-side, POST each as a batch) — **but that requires
+first standing up**: (1) a pgvector-enabled Postgres, (2) the
+`litellm-pgvector` service, and (3) a dedicated embedding model server
+registered in `litellm-config.yaml`. None of that reuses the Qdrant instance
+already running in this stack.
+
+## 5. Repo context read for this research
+
+- `litellm-config.yaml` — current config has one `model_list` entry
+  (`qwen3.8-27b-local`, chat-only, via llama.cpp), `router_settings`
+  (priority scheduling), `general_settings.master_key`. No
+  `vector_store_registry` block exists yet.
+- `docker-compose.yml` — confirms `qdrant` service (image `qdrant/qdrant`,
+  network `ai-stack`, no host port, only `open-webui` currently consumes it
+  via `VECTOR_DB=qdrant` / `QDRANT_URI=http://qdrant:6333`); confirms
+  `llama-server` command has no `--embeddings` flag and loads a single GGUF
+  (`Qwen3.8-27B-UD-Q4_K_XL.gguf`); confirms `litellm-db` is plain
+  `postgres:16-alpine` (no pgvector extension installed).
+- `CLAUDE.md` — points to `docs/agents/issue-tracker.md` (Gitea issues via
+  `tea`) and `docs/agents/domain.md` (domain docs convention).
+- `docs/agents/domain.md` — says to check `CONTEXT.md` and `docs/adr/` at
+  repo root before exploring, but "if any of these files don't exist,
+  proceed silently." Neither `CONTEXT.md` nor `docs/adr/` exist in this repo
+  yet, so there's no glossary/ADR conflict to flag.
+- `docs/research/` — repeated existing precedent (e.g.
+  `docs/research/proxy-shadow-pricing.md`, `docs/research/voidllm-evaluation.md`,
+  `docs/research/qwen3.8-27b-tool-calling.md`) confirms this is the
+  established location and Markdown format for this kind of investigation;
+  this file follows that convention.
+
+## Provenance note on the top-level config key name
+
+The docs page fetched live (`docs.litellm.ai/docs/completion/knowledgebase`)
+shows `vector_store_registry` as the current top-level key. The original
+feature PR ([#10448](https://github.com/BerriAI/litellm/pull/10448)) used
+`vector_stores` in its example YAML. If implementing against a specific
+pinned LiteLLM version, verify the exact key against that version's docs/
+source rather than assuming either name — this repo's `docker-compose.yml`
+pins `ghcr.io/berriai/litellm:main-stable`, a rolling tag, so the schema in
+whatever image is actually pulled should be spot-checked (e.g. `GET /openapi.json`
+against the running proxy, or grepping the image's installed
+`litellm/types/router.py` / proxy schema) before writing config against it.