Context Window & Compaction

Every model has a context window (max tokens it can see). Long-running chats accumulate messages and tool results; once the window is tight, Kurahi compacts older history to stay within limits.

What compaction is

Compaction summarizes older conversation into a compact summary entry and keeps recent messages intact. The summary is stored in the session history, so future requests use:

• The compaction summary
• Recent messages after the compaction point

Compaction persists in the session’s JSONL history.

Configuration

See Compaction config & modes for the agents.defaults.compaction settings.

Auto-compaction (default on)

When a session nears or exceeds the model’s context window, Kurahi triggers auto-compaction and may retry the original request using the compacted context.

You’ll see:

• 🧹 Auto-compaction complete in verbose mode
• /status showing 🧹 Compactions: <count>

Before compaction, Kurahi can run a silent memory flush turn to store durable notes to disk. See Memory for details and config.

Manual compaction

Use /compact (optionally with instructions) to force a compaction pass:

/compact Focus on decisions and open questions

Context window source

Context window is model-specific. Kurahi uses the model definition from the configured provider catalog to determine limits.

Compaction vs pruning

• Compaction: summarises and persists in JSONL.
• Session pruning: trims old tool results only, in-memory, per request.

See /concepts/session-pruning for pruning details.

Tips

• Use /compact when sessions feel stale or context is bloated.
• Large tool outputs are already truncated; pruning can further reduce tool-result buildup.
• If you need a fresh slate, /new or /reset starts a new session id.