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arbor

Research agent that grows a hypothesis tree to optimize code against a benchmark

Stars
1.1k
License
Apache-2.0
Last commit
Nov 2026
Last release
Jul 2026
Language
Python
Stars, last 23 weeks+1,147
3 Jun 2026: 0 stars10 Jun 2026: 46 stars17 Jun 2026: 365 stars24 Jun 2026: 720 stars1 Jul 2026: 865 stars8 Jul 2026: 897 stars15 Jul 2026: 925 stars22 Jul 2026: 957 stars29 Jul 2026: 975 stars5 Aug 2026: 987 stars12 Aug 2026: 1,002 stars19 Aug 2026: 1,018 stars26 Aug 2026: 1,037 stars2 Sept 2026: 1,051 stars9 Sept 2026: 1,058 stars16 Sept 2026: 1,071 stars23 Sept 2026: 1,083 stars30 Sept 2026: 1,091 stars7 Oct 2026: 1,096 stars14 Oct 2026: 1,108 stars21 Oct 2026: 1,119 stars28 Oct 2026: 1,130 stars4 Nov 2026: 1,139 stars11 Nov 2026: 1,147 stars

0 on 3 Jun 20261,147 on 11 Nov 2026

From GitHub's daily star counts.

Checked on GitHub.

Overview

Arbor runs a Coordinator and Executor agent loop that proposes hypotheses, edits code in isolated git worktrees, and runs experiments against a user-supplied benchmark. Changes merge into a per-run trunk only if they clear a configurable margin on a held-out test split. It ships as a Python CLI, a keyless MCP server, and a Codex/Claude Code skill suite.

Who it is for: Engineers optimizing a repo or benchmark metric with an autonomous agent loop

Strengths

  • Held-out test split gates merges, with a configurable margin against overfitting
  • Each Executor works in its own git worktree; main is untouched until you merge
  • Keyless mode runs inside Claude Code or Codex using the host model
  • Offline replay demo and a CPU-only NumPy example task need no API key

Weaknesses

  • Needs a runnable eval script, dev/test data, and a clean git repo
  • Native runtime requires an LLM provider key or local model
  • Headline benchmark gains are the authors' own results, not independently checked
  • Keyless MCP server is an optional extra with a separate install

What it needs

  • no GPU
  • Needs Python >=3.10, Git, LLM provider API key or local model (Ollama)
  • Models: Anthropic, OpenAI Responses API, OpenAI-compatible via LiteLLM (DeepSeek, Gemini, Qwen, vLLM, Ollama)
  • port 8765

What changed

From the release notes. No flag means the note does not say so, not that the upgrade is safe.

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