# Tech stack

## Pinned versions

| Layer          | Tech         | Pinned                          |
| -------------- | ------------ | ------------------------------- |
| Runtime base   | Ubuntu       | 24.04                           |
| Backend        | Python       | 3.13                            |
| Backend        | FastAPI      | 0.121+                          |
| Backend        | Uvicorn      | latest                          |
| Frontend       | Node.js      | 22.13 (build); 22 (LTS) runtime |
| Frontend       | TypeScript   | 5.2+                            |
| Frontend       | React        | 18                              |
| Frontend       | React Flow   | 11                              |
| Frontend       | Tailwind CSS | v4                              |
| Frontend       | Vite         | 5                               |
| Database       | PocketBase   | 0.36.4                          |
| Database       | SQLite       | (bundled with PB)               |
| Reverse proxy  | Nginx        | Alpine 3.22                     |
| Eval framework | DeepEval     | 3.8.4                           |
| MCP runtime    | fastmcp      | latest                          |
| Observability  | Langfuse     | v3 (optional)                   |

## Dockerfile shape

4-stage build:

```mermaid
flowchart LR
    PB[pocketbase-stage<br/>Alpine 3.22] --> Final
    FE[frontend-builder<br/>Node 22.13-slim] --> Final
    BE[backend-builder<br/>Ubuntu 24.04] --> Final
    Final[Final runtime<br/>Ubuntu 24.04 + Nginx]
```

Non-root runtime user. `pocketbase`, frontend bundle, and backend wheels are copied into the final stage; no build tools ship to production.

## Required CI tools

| Tool                                      | Job                | Blocks merge?        |
| ----------------------------------------- | ------------------ | -------------------- |
| Ruff (lint + format)                      | `backend-quality`  | Yes                  |
| Mypy                                      | `backend-quality`  | Yes                  |
| Pytest (≥ 70% coverage)                   | `backend-quality`  | Yes                  |
| tsc                                       | `frontend-quality` | Yes                  |
| ESLint                                    | `frontend-quality` | Yes                  |
| Vitest                                    | `frontend-quality` | Yes                  |
| Vite build                                | `frontend-quality` | Yes                  |
| Gitleaks v8.28+                           | `secret-scan`      | Yes                  |
| pip-audit `--strict`                      | `dependency-audit` | Yes                  |
| npm audit `--audit-level=high --omit=dev` | `dependency-audit` | Yes                  |
| Trivy (HIGH+CRITICAL)                     | `container-scan`   | Yes                  |
| Syft (SPDX-JSON)                          | `sbom`             | Soft (artifact only) |

## External dependencies

| Service                   | Role                         | Required?         |
| ------------------------- | ---------------------------- | ----------------- |
| LLM gateway (your choice) | chat completions, embeddings | **Required**      |
| Langfuse                  | tracing, score dashboards    | Optional          |
| GHCR                      | image distribution           | Required for prod |
| Dependabot                | dep updates                  | Recommended       |

See [Architecture / Security](/architecture/security.md) for the trust-zone view of these dependencies.


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