# Phase 0B — Experiment B: Open Dungeon history model

Driven live on `127.0.0.1:3111` against Ollama through the "custom"
OpenAI-compatible provider (`http://127.0.0.1:11434/v1`, `qwen2.5:0.5b`), with
its own SQLite file.

## B1. Schema — no lineage exists

`src/lib/db.ts` creates four tables: `chats`, `messages`, `characters`,
`app_settings`. The message row is:

```sql
CREATE TABLE messages (
  id TEXT PRIMARY KEY,
  chat_id TEXT NOT NULL REFERENCES chats(id) ON DELETE CASCADE,
  role TEXT CHECK (role IN ('user','assistant')),
  content TEXT NOT NULL,
  attachments_json ..., image_request_json ..., generated_image_json ...,
  created_at TEXT NOT NULL
);
CREATE INDEX idx_messages_chat_created ON messages(chat_id, created_at);
```

No `parent_id`, no branch, no take, no depth, no checkpoint table. Order is
`created_at` (a TEXT timestamp), with ties broken by id.

## B2. Retry / Edit / Erase — all destructive, measured

```
BEFORE (5 rows)
  a504cb34 assistant "Oh, Vale, you're just sitting in that rundown ..."
  e349d8b9 user      "I pocket a brass key from the ashtray."
  9984692b assistant "You find a worn, faded brass key on the tabletop..."
  bb1ceb3f user      "I drive to the address on its tag."
  a6e11115 assistant "Yes, you keep going. There, you can call your ..."

EDIT e349d8b9 in place  → PATCH /api/chats/{id}/messages/{id}
  original text "brass key from the ashtray" still anywhere in DB? False

DELETE a6e11115?after=1 (what BOTH Retry and Erase call)
  rows 5 → 4

Scan of every column of every table for the deleted tail
or the pre-edit text: none
```

- **Edit** is `UPDATE messages SET content = ? WHERE id = ?`. The prior text is
  unrecoverable.
- **Retry** (`retryLastTurn`, `page.tsx`) deletes the last assistant message and
  everything after it, then regenerates. The discarded attempt is gone.
- **Erase** (`eraseLastTurn`) deletes the last exchange and the tail.
- Old future turns are therefore always deleted, never retained.

## B3. What depends on the linear model

1. **`db.ts`** — 20 exported functions. `addMessage`, `updateMessageContent`,
   `deleteMessageAndAfter` and `getChat` are the history four.
   `getChat` returns a flat `messages` array and must become a lineage query.
2. **`story-prompt.ts`** — windows by array index:
   `for (let i = messages.length - 1; ...)`, `messages.slice(dropped)`,
   `messages.slice(0, dropped)`. Becomes an ancestry walk.
3. **The summary watermark is positional — the cost Phase 0A missed.**
   `chats.story_summary_count` records "how many of the chat's oldest messages
   the summary already covers", and `api/story/route.ts` compares
   `evicted.length > stored.coveredCount`, then summarizes
   `evicted.slice(stored.coveredCount)`. "The first N messages" is meaningless on
   a branch. Summaries must be re-anchored to a turn id and made per-lineage.
4. **`page.tsx` is 3,991 lines** in one component; `api/story/route.ts` is 1,196.
   Retry/erase/edit live there as array slicing (`messages.slice(0, cutFrom)`).
   There is no take stepper, branch panel or tree view to build on.
5. **No tests.** All of the above would be changed with no regression net.

## B4. Invasiveness estimate

To reach parent-linked turns, an active head, retained abandoned history, named
checkpoints and lineage-safe summaries, Open Dungeon needs: a schema migration,
a rewrite of its persistence read/write path, a rewrite of context assembly, a
redesign of summarization, and new branch UI — with a test suite written first
to make any of it safe. This is a from-scratch implementation of the hardest
part of the specification, not a retrofit.

By comparison AI-DnD already has all of it except a non-destructive undo, and
its reads funnel through one chokepoint (`lineage.Path.clause`).

## B5. Worth reusing as reference

- The reading experience: serif prose, prose-size control, the composer's
  Do/Say/Story modes.
- Inline scene images driven by a narrator tool call (`generate_image`), with a
  local FLUX worker on `127.0.0.1:7869` or a user's ComfyUI on `8188`.
- Character portraits reused as reference images for visual continuity, and fed
  back to the narrator as vision context. This is the most valuable idea here for
  `MEDIA-EXTENSION-CONTRACT.md`.
- The worker HTTP protocol may be portable even though none of the UI is —
  Open Dungeon is Next.js, AI-DnD is React + FastAPI.

## B6. Other findings

- The `local` provider hard-codes five Gemma 4 QAT builds
  (`src/lib/text-models.ts`, `LOCAL_TEXT_MODELS`) and `/api/health` reports only
  those as installed. Any other local Ollama model must be reached through the
  "custom" provider. A genre-agnostic app wanting "pick any installed model"
  must lift this.
- Next.js telemetry is enabled by default and printed its notice on first start.
- 335 npm packages; `npm audit` reports 6 high, 1 low.