Context Condensing

The Solution: Auto-Compaction

Kilo Code uses a Compaction system to manage context automatically. When your conversation approaches the token limit, compaction kicks in and produces an anchored summary that captures:

• The overall goal of the session
• Constraints and preferences you gave along the way
• Progress, key decisions, and next steps
• Critical context needed to continue
• Relevant files and directories

This summary replaces older conversation history while Kilo keeps the most recent turns verbatim when they fit. If a session has already been compacted, Kilo updates the previous summary instead of starting over, preserving still-relevant details and removing stale ones.

How Compaction Triggers

Automatic trigger

Kilo tracks the total token count for the session — input, output, and cached reads and writes — and compares it to the model's context window. Compaction runs when the total fills the window minus a reserved buffer of headroom kept free for the next turn.

How the buffer is chosen depends on what the model declares. When the model advertises a separate input limit, the buffer defaults to 20,000 tokens (or the model's maximum output size, whichever is smaller). When the model only declares a single context window, Kilo instead reserves the model's full output cap — up to 32,000 tokens.

Custom models that do not declare a context window are not tracked, and auto-compaction does not run for them.

Context Pruning

Between turns, Kilo also runs a lighter prune pass. It walks completed tool outputs outside a 40,000-token recency window and replaces them with "[Old tool result content cleared]". Pruning runs incrementally so large tool outputs don't consume space forever, even before full compaction is needed.

Manual Compaction

You can trigger compaction at any time:

• Slash command: type /compact in chat (also findable by typing smol or condense)
• Task header button: click the compact icon in the active task header
• Settings: toggle auto-compaction in Settings → Context

Defaults

Configuration

Compaction is configured in your kilo.jsonc file:

{
  "compaction": {
    "auto": true, // Enable or disable automatic compaction
    "prune": true, // Enable pruning of old tool outputs beyond the recency window
    "tail_turns": 2, // Recent user turns to keep verbatim during compaction
    "preserve_recent_tokens": 8000, // Maximum token budget for the recent tail
    "reserved": 20000, // Token buffer kept free; smaller = later trigger, larger = earlier trigger
  },
}

Use a different model for compaction

Summarization can use a cheaper or larger-context model than your main agent. Configure a dedicated compaction agent:

{
  "agent": {
    "compaction": {
      "model": "anthropic/claude-haiku-4-5",
    },
  },
}

If no compaction agent is set, the current session's model is used.

Environment overrides