keystone: Agent for Claude Code

.claude/agents/keystone-planner.md

keystone-planner is an agent for Claude Code from tacoda/keystone. It costs 26 tokens per session (202 once invoked), scanned A, original, MIT.

A planning agent that examines the project's current codebase notes and the relevant local coding patterns before proposing implementation steps. It includes a verification check for each step.

In plain words
What is it for?
Use it before making a change when you need to identify affected areas, applicable rules, matching code patterns, and tests to run.
Why use it?
It reduces out-of-scope planning and helps ensure the proposed work follows the conventions already used in the affected code.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: model in frontmatter.

This is tacoda/keystone's own configuration. It tells Claude Code how to work on keystone itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything keystone configures →

Reuse

Borrowing it

Nothing to install: this file belongs to tacoda/keystone. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/tacoda/keystone/main/.claude/agents/keystone-planner.md
Clone the repo
git clone --depth 1 https://github.com/tacoda/keystone

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for keystone-planner

README.md
[![agentmods](https://agentmods.dev/badge/agents/tacoda/keystone/keystone-planner/github.svg)](https://agentmods.dev/agents/tacoda/keystone/keystone-planner)
Your own site
<a href="https://agentmods.dev/agents/tacoda/keystone/keystone-planner"><img src="https://agentmods.dev/badge/agents/tacoda/keystone/keystone-planner/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for keystone-planner

Your own site · 80×15
<a href="https://agentmods.dev/agents/tacoda/keystone/keystone-planner"><img src="https://agentmods.dev/badge/agents/tacoda/keystone/keystone-planner.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 202 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00026 $0.00202
Opus 5.5 $0.00010 $0.00081
Sonnet 5.5 $0.00005 $0.00040
Haiku 4.5 $0.00003 $0.00020

Measured 2mo ago against content hash 52d93a2904dc, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

keystone-planner scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/keystone-planner.md · 36 lines

What it actually says

Planner

You read .charter/corpus/state/CODEBASE_STATE.md, identify the touched region(s), load the globs-matched idioms, and emit a step-by-step plan with one verification check per step.

Posture

  • Concrete: every step names a file, a function, or a test.
  • Scoped: do not load idioms for stacks this task does not touch.
  • Cite the rule paths your plan depends on.

Output

## Touched region(s)
- <region>: <stacks>

## Loaded idioms
- <rule id>

## Plan
1. <step> → verify: <check>
2. <step> → verify: <check>
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2mo ago First seen · 36 lines · 26 tokens per session scan A 52d93a2904dc

Subscribe to this mod's changes

keystone-planner is an agent published in the GitHub repository tacoda/keystone (44 stars, last pushed 3mo ago), licensed MIT. It adds 26 tokens to every session and 202 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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