@pi-unipi/fusion

Devin-style model picker, fusion presets (lead + sidekick), and Local Fusion runtime for UniPi

Packages

Package details

extension

Install @pi-unipi/fusion from npm and Pi will load the resources declared by the package manifest.

npm repohome report
$ pi install npm:@pi-unipi/fusion
Package
@pi-unipi/fusion
Version
3.0.3
Published
Nov 4, 2026
Downloads
3,369/mo · 521/wk
Author
neuron-mr-white
License
MIT
Types
extension
Size
139.4 KB
Dependencies
3 dependencies · 3 peers
Pi manifest JSON
{
  "skills": [],
  "themes": [],
  "prompts": [],
  "extensions": [
    "./src/index.ts"
  ]
}

Security note

Pi packages can execute code and influence agent behavior. Review the source before installing third-party packages.

README

Fusion

Fusion pairs a strong lead model with a lower-cost sidekick model, so the lead plans and the sidekick does the routine work.

@pi-unipi/fusion · part of UniPi

What it does

  • Gives /unipi:model, a keyboard model picker. It shows all available models, their prices and a thinking level for each model.
  • Lets you select one model, or a Fusion pair of a lead and a sidekick.
  • Runs one persistent sidekick for each lead session. The sidekick is a child Pi process. Its context and shells stay between handoffs.
  • Tells the lead to give work to the sidekick. In each turn, the first direct edit or write of the lead gets a reminder. Each 4 non-trivial bash calls of the lead also get a reminder.
  • Shows the estimated savings of the sidekick in /unipi:fusion-stats.

Quick start

  1. Install UniPi: pi install npm:@pi-unipi/unipi. You can also install this package alone: pi install npm:@pi-unipi/fusion.
  2. Open /unipi:settings. Select "Edit fusion presets…". Mark the lead and sidekick models.
  3. Type /unipi:model. Select the Fusion row. Push Enter.
  4. Give the agent a task. The lead calls the sidekick tool.

Commands

Command What it does
/unipi:model Opens the model picker. When you type /model, the picker is the first suggestion.
/unipi:fusion-stats Shows sidekick tokens, costs, savings, handoffs and runtime state.

Picker keys

Key What it does
Up, Down Moves the selection.
Typing Filters the models.
Left, Right Changes the thinking level of the selected row. Fusion keeps the level for each model.
Tab, Shift+Tab On the Fusion row, moves the focus: effort, lead, sidekick.
Space On the Fusion row, selects lead effort or sidekick effort.
Enter Applies the selection.
Alt+Enter Saves the selected row as the startup model.
Esc Closes the picker.

If you change the model with Pi's own /model or Ctrl+P, Fusion mode stops.

Agent tools

Tool What it does
sidekick Gives a message to the sidekick. block: true (default) waits for the report. block: false returns now. The report comes later as a completion notice.
read_subagent Reads or waits for a sidekick handoff.

A call to sidekick while the sidekick works sends the message as an interrupt. It does not start a second sidekick.

Settings

Namespace fusion. Open it with /unipi:settings.

Key Default What it does
startup.model empty Model that Pi opens with. Empty uses Pi's default. Global only.
startup.thinking not set Thinking level that Pi opens with. Global only.
default.lead empty Lead model when you confirm the Fusion row with no change.
default.sidekick empty Sidekick model for the same case.

The preset file holds the model lists, levels, recent models and badges:

  • Global: ~/.unipi/config/fusion/preset.json
  • Project: <project>/.unipi/fusion-preset.json. Its lists replace the global lists. Its objects merge with the global objects.

Add a prices object to the preset file when a provider gives no prices:

{"prices": {"provider/model": {"input": 0.2, "cachedInput": 0.02, "output": 1.2}}}

How it works

The sidekick session file is ~/.unipi/workspace/<id>/sessions/<sid>/fusion/sidekick/<lead-session-id>.jsonl. The sidekick compacts its own context. The child gets UNIPI_FUSION_CHILD=1 and UNIPI_SUBAGENT_CHILD=1, so it does not load Fusion tools or commands.

Read Delegation for the lead and sidekick flow.

See also