# 03 — Architecture Overview

A one-page mental model. For details follow the cross-links.

## Topology

```
                         ┌────────────────┐
   voice / typing ──────▶│     Memos      │◀──── Nexa replies as comments
                         │  (interface)   │
                         └───────┬────────┘
                                 │ webhook (- [ ] / #nexa:*)
                                 ▼
                         ┌────────────────┐
   IMAP / RSS / NC  ────▶│      n8n       │◀──── workflows live in
   Karakeep / Bluesky    │  (logic)       │      ./nexa-core/n8n-workflows
                         └───┬────────┬───┘
                  classify ▲ │        │ ▲ retrieve
                           │ ▼        ▼ │
                       ┌──────────┐  ┌──────────┐
                       │  SAIA    │  │  Qdrant  │
                       │ LiteLLM  │  │  vector  │
                       └──────────┘  └────┬─────┘
                                          │ optional
                                          ▼
                                     ┌──────────┐
                                     │  Graph   │  (Neo4j or Ontotext —
                                     │   DB     │   see open questions)
                                     └──────────┘
                                 │
                                 ▼ writes
                  ┌──────────────────────────────┐
                  │  Nextcloud (Tasks, Calendar, │
                  │  Mail, Files / Obsidian)     │
                  └──────────────────────────────┘
```

## Components

| Component | Role | Where it runs (today) |
|-----------|------|-----------------------|
| **Memos** | Interface, voice input, webhook source | docker host LXC 104 → `memos.nuclide.systems` |
| **n8n** | Workflow / logic engine | docker host LXC 104 → `n8n.nuclide.systems` |
| **SAIA / LiteLLM** | Model gateway, embeddings, classification | docker host LXC 104 → `ai.nuclide.systems` (LiteLLM internal :4000) |
| **Qdrant** | Vector memory (semantic recall) | docker host LXC 104 (existing `qdrant_scientific` may be reused — see [11](./11-open-questions.md)) |
| **Graph DB** | Structural memory (deferred) | not yet deployed |
| **Nextcloud** | Tasks, calendar, mail, files | dedicated LXC 105 → `nc.nuclide.systems` |
| **ntfy** | Push channel for system alerts | docker host → `ntfy.nuclide.systems` |
| **Backrest** | Backup orchestration | LXC 103 |
| **Zoraxy** | Reverse proxy + TLS | LXC 108 (`192.168.1.4:8000`) |
| **AdGuard DNS** | Internal name resolution | LXC 102 |
| **Home Assistant** | Voice + house automation | VM 100 (HAOS) |

## Two-pillar memory

- **Qdrant** answers *"what is similar / relevant?"* (cosine search over embeddings).
- **Graph DB** answers *"who, what depends on what, how is it structured?"* (Cypher / SPARQL).

Both pillars are queried in parallel for `#nexa:ask` and merged before SAIA generates the final answer. See [08 — GraphRAG architecture](./08-graphrag-architecture.md).

## Dual-context routing

Every input is classified `work` or `personal` before any side effect (task creation, calendar write). See [04 — Integration matrix](./04-integration-matrix.md) and [06 — Classification logic](./06-classification-logic.md).