# 260614 — Joplin deep dive (SQLite-local, Markdown-on-sync, interchange-format attach)

Date: 2026-06-14

## What this is

A focused study of **Joplin** — the open-source Markdown note app — read through
shard-wiki's lens. Joplin looks like "open-source Obsidian" but is a genuinely different
point in the space: **content is Markdown, the local store is SQLite, and the *sync
representation* is a folder of per-item Markdown+metadata files on a backend you choose**
(filesystem, WebDAV, **Nextcloud**, Dropbox, OneDrive, **S3**, Joplin Server/Cloud). It
also ships **end-to-end encryption** and is itself a **sync layer over heterogeneous
storage**.

Distinctive material:
- **Architecture** — SQLite local store (documented schema); Markdown content;
  notebooks → notes → resources + tags + to-dos; 32-char item IDs; `:/<id>` note links
  (rename-stable, page-level)
- **Sync** — serialized to plain-text items on a chosen target; tombstones; **conflict
  notes** (keep-both) → enables the **"attach the sync mirror, not the app"** pattern on
  WebDAV/Nextcloud/S3
- **E2EE** — items encrypted before leaving the device → **content opacity** (ciphertext
  at rest)
- **Extension surfaces** — a **plugin API** (`joplin.data`/`workspace`/`contentScripts`/
  views) *and* a **local Data API** (REST on `localhost:41184`, token) used by the Web
  Clipper; plus JEX/Markdown/RAW export

## Contents

| Path | Role |
|------|------|
| `findings.md` | Architecture, sync/interchange attach, E2EE/content-opacity, plugin + Data API surfaces, capability profile, INTENT mapping, UC seeds, architecture notes, sources |

## Status

Initial deep dive complete. Two new use cases promoted to `spec/UseCaseCatalog.md`
(UC-60 attach a tool's documented sync/interchange representation on third-party storage
without the app; UC-61 attach an encrypted-at-rest shard with content opacity);
UC-31/36/38/40/51/55 enriched. Logged for `SHARD-WP-0002` (T11, T14): the
interchange/sync-representation attach surface, **content opacity** as a proposed twelfth
capability spectrum, a local-REST attach sub-mode, and format-aware file-store profiles.

**Key takeaways recorded:** the best attach surface is often a tool's **interchange/sync
representation** (offline, app-independent — Joplin items on Nextcloud/WebDAV/S3, the
INTENT-named backends), not its live store or API; **encryption-at-rest** demands a
content-opacity capability so encrypted shards degrade to backup/structure-shell; and
Joplin is the **file-sync-daemon boundary case** — shard-wiki attaches its mirror as
pages and never re-syncs (not-a-sync-daemon).
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