disler GitHub avatar

fusion-harness

disler

A harness for the Pi coding agent that runs two frontier models (architect and builder) in parallel, fuses their outputs with attribution, and optionally auto-validates builds via a gate loop.

Stars

232

7-day growth

+65

Forks

50

Open issues

0

License

MIT

Last updated

2026-07-27

AI repository intelligence
FR-AI / ANALYSIS

Why it is worth attention

It implements the 'architect/editor' fusion pattern as a first-class, on-camera-clear workflow with hard-labeled roles, a gate-first validation loop, and per-line provenance, allowing engineers to combine compute instead of choosing a single model.

Who it is for

  • Developers using AI coding agents (Claude Code, Pi) who want to leverage multiple models
  • Teams evaluating frontier models for coding tasks and needing a systematic comparison mechanism
  • Engineers building multi-agent workflows or extending agentic coding harnesses
  • Researchers and practitioners interested in agentic engineering and model fusion patterns

Use cases

  • Get two independent model perspectives on a coding question (/opinion)
  • Fuse plans or code from two models into a single, attributed result (/fusion)
  • Automatically validate a build against a pre-designed acceptance gate (/auto-validate)
  • Chain opinion, fusion, and validation to run a micro-software development lifecycle in one session

Strengths

  • Concrete three-command value ladder (opinion, fusion, auto-validate) on the same two agents
  • Clean-room child processes with no skills, extensions, or context files for deterministic behavior
  • Gate-first validation loop that designs acceptance criteria before building, preventing self-grading
  • Per-line provenance and attribution (Consensus & Divergence) in fused outputs

Considerations

  • Requires specific external tools and API keys (Pi, just, jq, uv, Anthropic/OpenAI keys)
  • Parallel workers can clobber files if asked to write the same path without using identity-in-filename
  • Stale persistent architect sessions may need manual reset (/fh-reset), and Anthropic usage-policy false positives can occur on fable-5 with long transcripts

README quick start

fusion-harness

Fuse frontier models instead of racing them. AND, not OR. A standalone Pi coding agent extension harness for two-model agentic engineering.

📺 Watch this video to get the full breakdown of this codebase: GPT-5.6 Sol vs Fable 5 Is the Wrong Question (Fusion) on YouTube

"Which model is best" is a benchmark question, not an engineering question. One model plans, another builds, and the results fuse: you combine compute instead of selecting it. Aider called the pattern architect/editor (the original fusion); Devin calls it fusion; OpenRouter calls it model fusion. This repo makes the pattern a first-class, on-camera-clear workflow: two hard-labeled agents, a gate-first validation loop, and attributed fusion. You don't have to pick a winner when you can hire both.


Install

Agentic Install

claude "/install"   # runs the /install slash command in Claude Code (or Pi, or your favorite agentic coding tool)

The /install command lives at .claude/commands/install.md and handles toolchain checks, key checks, and project-specific setup.

Manual Install

Prereqs: pi, just, jq, uv.

npm install -g @earendil-works/pi-coding-agent    # the Pi coding agent
brew install just jq uv                           # task runner, json inspection, gate runner
printf 'ANTHROPIC_API_KEY=sk-ant-...\nOPENAI_API_KEY=sk-...\n' >> .env   # architect + builder keys
just fh-workhorse                                 # launch on the cheap test pair

Why this exists

Every frontier release restarts the same argument: GPT-5.6 Sol or Fable 5? Benchmarks crown a winner, teams switch, and next quarter the crown moves. Meanwhile the two models are genuinely different animals: one plans and critiques with more depth, the other ships working diffs faster. Picking one means losing the other's edge on every single task.

The deeper problem is review, the second constraint of agentic engineering. A single unchecked agent drif

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