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Ponytail + Archcore

Cut the code that no project decision needs. Decisions you settle stay in Git as draft ADRs.

How Ponytail + Archcore work together

Ponytail + Archcore lets your agent cut code hard without cutting what a project decision requires. Ponytail pushes each change toward the shortest working diff. Archcore gives the agent the accepted decisions to check first, and a place to save the ones you settle.

Say Ponytail’s review flags a one-implementation interface as dead weight, but an accepted ADR says partner packages implement it. The agent finds the ADR, keeps the interface, and still cuts the unused factory next to it.

See the benchmark note and the recheck note for what was measured. Modes and installation are on the Ponytail project page.

Archcore ↗
Keeps project decisions in Git so the agent checks them before it cuts code and records the ones you settle.
Ponytail ↗
Pushes the agent toward the shortest working change and flags code that can be deleted.

From a simplification to a kept decision

The instructions ask your agent to:

  1. Check decisions before cutting

    Before Ponytail's rules or review remove code, the agent searches Archcore for records that name it.

  2. Keep what a decision requires

    If an accepted record needs the code, it stays, and the agent cites the record. Everything else gets the shortest working diff.

  3. Record what you settle

    If your request settles a decision, like dropping a feature, the agent saves it as a draft ADR (architecture decision record) in .archcore/. The next session finds the reason there, not in chat history.

Both tools must already be set up. Ponytail keeps its rules and review; Archcore keeps the decisions.

See an example → See benefits and limits →

One request, start to finish

Request The owner decided to drop gift wrapping: the supplier contract ended. Remove it from the quotation library, so quote() no longer takes gift_wrap or returns extras. Keep the tests passing.

  1. Archcore: The agent searches Archcore for the touched symbols and finds the integer-cents ADR. The removal does not conflict with it.

  2. Ponytail: Ponytail's rules keep the diff short: the agent deletes the gift-wrap registry, the argument, the extras field and its test.

  3. Agent: The agent runs the tests before it reports.

  4. Archcore: Your request settles a decision, so the agent saves it as .archcore/shop/drop-gift-wrapping.adr.md with your reason.

  5. Agent: A later session that searches for gift wrapping finds the draft ADR. You accept or reject it in review.

This is what the instructions ask for, not a recorded run. The same request passed 30 of 30 benchmark runs across three models; the later-session step was not run.

Connect the two tools

1. Install Archcore and Ponytail

Install Archcore and Ponytail in the agent you use for this project.

2. Add instructions

CLAUDE.md / AGENTS.md / GEMINI.md 
### Archcore + Ponytail

Applies when the session shows Ponytail mode or a `ponytail` skill.

1. Before a ladder rung or a `/ponytail-review` finding, call `search_documents` with `content` naming the affected symbols.
2. If an accepted Archcore record requires the code, keep it and cite the record path.
3. When the request states a decision the owner settled (adopt, drop, replace or defer something), record it in a draft `adr` before reporting the task complete.
4. Create every new `.archcore/**/*.md` record with status `draft`.

3. Check in a new session

Start a new session in this project and ask your agent:

Confirm you can use Archcore and Ponytail, and have read this project’s cooperation instructions.

If the agent reports a missing tool or instruction file, finish that setup before starting work.

Benefits & limits

Cut code without losing project decisions.

With the instructions, the agent kept code an accepted ADR requires and recorded settled decisions as draft ADRs. Without them, it recorded 0 of 15 such decisions.

Ponytail's review meets an accepted decision

The agent kept the interface the ADR requires and cut the unused factory next to it: 20 of 20 runs with claude-sonnet-5, 10 of 10 with claude-sonnet-5-5.

Without the instructions, claude-opus-5-5 kept the interface too, so the gain depends on the model.

You settle a decision in the request

The agent saved the decision as a draft ADR in every run with the instructions, and in none without them.

Decisions made in the middle of a longer conversation were not tested.

Start with Archcore.

Keep your project decisions ready for the next task.

Install Archcore →See how it works

Ponytail + Archcore

Source & verification

Category
Minimal code
Instruction revision
e649d9aa73f4
Source
Landing repository · src/recipes/ponytail/cooperation.md · This revision is not published yet.
Maintainer
Archcore maintainers
Page updated
October 22, 2026

Verification

Date Agent Model Scenario Outcome
October 22, 2026 Claude Code 2.1.306 claude-sonnet-5-5 Over-engineering review with a buried accepted ADR passed
October 22, 2026 Claude Code 2.1.306 claude-sonnet-5-5 A removal the owner settles in the request passed
October 22, 2026 Claude Code 2.1.306 claude-sonnet-5-5 The same removal, reworded passed
October 22, 2026 Claude Code 2.1.306 claude-sonnet-5-5 A free-delivery threshold, with the rejected alternative named passed
October 22, 2026 Claude Code 2.1.306 claude-sonnet-5-5 A rename with no decision to record passed
September 26, 2026 Claude Code 2.1.283 claude-sonnet-5 Over-engineering review with a buried accepted ADR passed
September 26, 2026 Claude Code 2.1.283 claude-sonnet-5 A removal the owner settles in the request passed
September 26, 2026 Claude Code 2.1.283 claude-sonnet-5 The same removal, reworded passed
September 26, 2026 Claude Code 2.1.283 claude-sonnet-5 A free-delivery threshold, with the rejected alternative named passed
September 26, 2026 Claude Code 2.1.283 claude-sonnet-5 A rename with no decision to record passed
September 26, 2026 Claude Code 2.1.283 claude-opus-5-5 A removal the owner settles in the request passed
September 26, 2026 Claude Code 2.1.283 claude-opus-5-5 A free-delivery threshold, with the rejected alternative named passed
September 26, 2026 Claude Code 2.1.283 claude-opus-5-5 Over-engineering review with a buried accepted ADR passed
September 26, 2026 Claude Code 2.1.283 claude-opus-5-5 Five-turn coupon feature with a conflicting request passed
  • Tested with Claude Code 2.1.283 and 2.1.306, Ponytail 4.10.0 and 5.3.2, Archcore 0.10.6 and 0.13.1. Other hosts were not tested.
  • Five single-turn tasks and one five-turn feature on one small Python project.
  • Nothing enforces the instructions. Review the code and the draft ADRs before you accept them.

Update or disconnect

To update, review changes to the instructions before replacing your copy. To disconnect, remove the added instructions from your project file. Both tools and their documents stay in place.