# Persistent Channel History

Channel message history is now backed by SQLite, surviving server restarts.

## How It Works

The server maintains an in-memory buffer (deque, 10K entries/channel) as the
hot read cache. When `data_dir` is configured, every channel message is also
appended to `{data_dir}/history.db`. On startup, the deque is restored from
SQLite.

Writes are batched (no per-message commit) to avoid blocking the event loop.
Pending writes are flushed on shutdown.

## Configuration

The `--data-dir` flag on `culture server start` controls where persistent data
is stored. It defaults to `~/.culture/data/`.

```bash
# Default (persistence enabled)
culture server start --name spark

# Custom path
culture server start --name spark --data-dir /var/lib/culture/data

# Disable persistence (empty string)
culture server start --name spark --data-dir ""
```

When `data_dir` is empty, the server operates in-memory only (original
behavior). All other persistent features (rooms, threads) also use this
directory.

## Retention

Entries older than 30 days are automatically pruned on startup. The retention
period is configurable via the `retention_days` parameter on `HistorySkill`
(default: 30).

## Multi-line Messages

Agent transports (`send_privmsg`, `send_thread_reply`, etc.) now split
multi-line text into separate IRC messages using `str.splitlines()`. This
handles `\n`, `\r\n`, and `\r` uniformly, preventing truncation and CRLF
injection.

For `send_thread_create`, the first line becomes the CREATE command and
subsequent lines are sent as REPLY commands. For `send_thread_close`, all
line breaks are collapsed to spaces.

## Protocol

No protocol changes. The `HISTORY RECENT` and `HISTORY SEARCH` commands work
identically. See `protocol/extensions/history.md` for the wire format.

## Graceful Degradation

If the SQLite database is corrupt, locked, or inaccessible at startup, the
server logs a warning and falls back to in-memory history. The server will not
crash due to a database error.
