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mux can run /compact for you to keep context size manageable. There are two types of automatic compaction:
  • Usage-based: Compacts when your conversation reaches a configurable percentage of the model’s context window
  • Idle-based: Optionally compacts inactive workspaces after a period of time

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Usage-based auto-compaction

When enabled, mux monitors your context usage and:
  1. Shows a subtle warning as you approach the threshold (e.g., “Auto-Compact in 12% usage”)
  2. When you send your next message at or above the threshold, mux runs compaction first, then automatically sends your message as a follow-up

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Configure the threshold

  • Open the Costs sidebar tab and find Context Usage
  • Drag the blue marker to set the percentage
  • The setting is saved per model (and applies to any workspace using that model)
  • Default is 70%
  • Set it to 100% to disable usage-based auto-compaction
mux caps the enabled threshold at 90% to leave a safety buffer before hard context limits.

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Force-compaction during streaming

If a single response pushes context usage above your threshold while streaming, mux may interrupt and compact automatically once you exceed the threshold by an additional buffer (currently +5%). After compaction, mux resumes the conversation automatically. This safety mechanism prevents hitting hard context limits mid-stream.

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Idle-based auto-compaction

Idle-based auto-compaction is off by default. When enabled for a project, mux periodically checks for workspaces that:
  • Have been inactive for the configured number of hours
  • Are not currently streaming
  • Are not already compacted
Eligible workspaces are compacted automatically and marked with the idle-compacted badge (💤📦).

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Configure idle compaction

You can configure idle compaction via the UI or a slash command: Via UI:
  • Click the context usage indicator in the chat input toolbar
  • Enable idle-based auto-compact and set the hours
Via command: 
/idle <hours>
/idle off
Examples: 
/idle 24
Compact workspaces after 24 hours of inactivity. 
/idle off
Disable idle compaction for this project.

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Notes

  • The setting is per project (applies to all workspaces in the project)
  • mux checks roughly once per hour, so compaction may not trigger immediately when the timer expires

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General notes

  • Auto-compaction uses API tokens (same cost model as /compact)
  • Auto-compaction requires known model context limits; if mux can’t determine a model’s context window, usage-based auto-compaction won’t run
  • Both types of auto-compaction use the same summarization logic as manual /compact