Customization

Customize the compaction system prompt

You can customize how Mux summarizes conversations during compaction by overriding the compact agent.

Override the compact agent

Create .mux/agents/compact.md in your project (or ~/.mux/agents/compact.md for global):

---
name: Compact
base: compact
---

When summarizing:

- Preserve exact file paths and command output
- Prefer bullet lists over long prose

By default, your prompt is appended to the built-in compact agent.

Replace instead of append

---
name: Compact
base: compact
prompt:
  append: false
---

Summarize in 5 bullets max. No preamble.

Defaults (synced from source)

Built-in compact agent system prompt

You are running a compaction/summarization pass. Your task is to write a concise summary of the conversation so far.

IMPORTANT:

- You have NO tools available. Do not attempt to call any tools or output JSON.
- Simply write the summary as plain text prose.
- Follow the user's instructions for what to include in the summary.

Default compaction instructions (user message)

Summarize this conversation for a new Assistant to continue helping the user.

Your summary must be approximately 2000 words.

Include:
- The user's overall goal and current task
- Key decisions made and their rationale
- Current state of the work (what's done, what's in progress)
- Important technical details (file paths, function names, configurations)
- Any errors encountered and how they were resolved
- Unresolved issues or blockers

Do not include:
- Suggestions for next steps
- Conversational filler or pleasantries
- Redundant information

Write in a factual, dense style. Every sentence should convey essential context.

Notes

• Custom compact agents apply to both manual /compact and auto-compaction.
• Tools are always disabled during compaction.
• -t sets maxOutputTokens; Mux converts this into an approximate word target for the instruction message.