The campaign is a folder. The apps just visit.

One folder, several hands

A vault in play looks like this. Every note carries a stable oa_id and names its own generator, so links survive renames and every claim has a source.

your-campaign/
├── campaign.md              GM-owned: calendar, party position, tone
├── regions/<region>/        written by Hexes: gazetteer, hex notes,
│   ├── region.md            travel table, encounter & weather aids
│   └── hexes/
├── settlements/ · sites/   stubs and keyed places
├── npcs/ · factions/      the cast; declared relationships
├── quests/ · sessions/    the running game (spec 0.2: reveals, dates)
├── commissions/             work orders: a stub site → a keyed dungeon
├── player/                  derived player-safe vault (this app writes it)
└── _index/                  compiled ids and relationships (derived)

Who writes what

• Hexes on Automatic writes regions: the gazetteer, hex notes, settlement, site and faction stubs, travel and encounter aids, and a commission envelope per dungeon site.
• Dungeons on Automatic answers the commissions with keyed sites.
• Campaigns on Automatic writes only the derived and sanctioned lanes: the player/ tree, reveal states, the campaign clock, faction goal checkmarks, and tonight's session-note skeleton.
• You own everything else, in any editor. Obsidian gets wikilinks and graph for free.

The rules that keep it safe

• One writer per file. Each note is owned by the app that minted it; nothing else touches it. Cross-app references live in oa_refs frontmatter, never in app state.
• Generated prose sits in fences. Machine text lives between oa:generated markers. Everything you write outside them is never overwritten, by anyone, on any pass.
• Locks freeze what you've settled. Mark a note's content, narrative or geometry with oa_locks and regeneration leaves it alone.
• Reveals are data. Spec 0.2 gives notes, sections and relationship edges a reveal state; the player view and the player/ derivation both follow the same leak rules, so the table sees one consistent world.
• No app required. It's markdown. Git, grep, a text editor and Obsidian all work; the reference validator is the format's gate, not any app.