LanceDB Hybrid Search Memory Plugin

- **BM25 full-text search** (exact terms)
- Configurable reranking:
  - `rrf` (Reciprocal Rank Fusion, recommended)
  - `linear` (weighted combination)

It is based on (and credits) OpenClaw PR **openclaw/openclaw#7636**.

## What you get

A local plugin (extension) located at:

- `plugin/` → **overrides the built-in plugin id** `memory-lancedb` (adds hybrid search)

Once enabled, it provides the same tools as the bundled LanceDB memory plugin:

- `memory_store`
- `memory_recall`
- `memory_forget`

…but `memory_recall`/auto-recall/forget now use hybrid search when enabled.

## Install / Enable

1) Ensure the skill folder exists (ClawHub install puts it under your workspace):

- `~/.openclaw/workspace/skills/memory-lancedb-hybrid/plugin`

2) Install the plugin dependencies (once):

```bash
cd ~/.openclaw/workspace/skills/memory-lancedb-hybrid/plugin
npm install --omit=dev
```

3) Add the plugin to OpenClaw’s plugin load paths.

This plugin keeps the id `memory-lancedb`, so it will **override** the bundled `memory-lancedb` extension when discovered via `plugins.load.paths` (higher precedence than bundled).

Edit `~/.openclaw/openclaw.json`:

```json5
{
  plugins: {
    load: {
      // Point at the plugin directory inside this skill
      paths: ["~/.openclaw/workspace/skills/memory-lancedb-hybrid/plugin"]
    },

    // Ensure the memory slot points at LanceDB memory
    slots: {
      memory: "memory-lancedb"
    },

    // Configure LanceDB memory (this override adds the `hybrid` config block)
    entries: {
      "memory-lancedb": {
        enabled: true,
        config: {
          embedding: {
            apiKey: "${OPENAI_API_KEY}",
            model: "text-embedding-3-small"
          },

          // Optional
          dbPath: "~/.openclaw/memory/lancedb",

          // Optional
          autoCapture: true,
          autoRecall: true,

          // Hybrid search options
          hybrid: {
            enabled: true,
            reranker: "rrf"

            // If using reranker: "linear", you can also set:
            // vectorWeight: 0.7,
            // textWeight: 0.3,
          }
        }
      }
    }
  }
}
```

4) Restart the Gateway.

Hybrid search needs an FTS index on the `text` column; the plugin will attempt to create it automatically. If FTS setup fails for any reason, the plugin logs a debug message and falls back to vector-only search.

## Config reference

All config lives under `plugins.entries.memory-lancedb.config`.

- `hybrid.enabled` (boolean, default `true`)
- `hybrid.reranker` (`rrf` | `linear`, default `rrf`)
- `hybrid.vectorWeight` (number 0–1, default `0.7`, only used for `linear`)
- `hybrid.textWeight` (number 0–1, default `0.3`, only used for `linear`)

## Notes / troubleshooting

- This plugin does not modify OpenClaw’s install on disk; it **overrides** the bundled `memory-lancedb` at runtime (remove `plugins.load.paths` to revert).
- If you already have LanceDB memory data on disk, you can keep using the same `dbPath`.
- If you see no hybrid effect, make sure `hybrid.enabled` is true and that the FTS index was created (check Gateway logs).

## Files

- `plugin/index.ts` – plugin implementation (hybrid search)
- `plugin/config.ts` – config parsing + UI hints
- `plugin/openclaw.plugin.json` – manifest + JSON Schema (used for strict config validation)