What is open-plan-annotator AGENTS.md?

Instructions for a local tool that opens a browser page when an AI coding assistant finishes making a plan, so a person can review and annotate it before coding starts.

Reviewing and annotating plans in Claude Code or OpenCode, installing the needed runtime, and starting the local review page.

It gives developers a visual way to inspect and comment on a plan before code is written, while handling the tool's local runtime and browser server.

How ndom91/open-plan-annotator configures Claude Code and Codex

Reuse

Borrowing it

Nothing to install: this file belongs to ndom91/open-plan-annotator. 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/ndom91/open-plan-annotator/main/AGENTS.md

Clone the repo

git clone --depth 1 https://github.com/ndom91/open-plan-annotator

Made for: Claude Code, Codex, OpenCode.

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/ndom91/open-plan-annotator/agents-md/github.svg)](https://agentmods.dev/instructions/ndom91/open-plan-annotator/agents-md)

Your own site

<a href="https://agentmods.dev/instructions/ndom91/open-plan-annotator/agents-md"><img src="https://agentmods.dev/badge/instructions/ndom91/open-plan-annotator/agents-md/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/ndom91/open-plan-annotator/agents-md"><img src="https://agentmods.dev/badge/instructions/ndom91/open-plan-annotator/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 2,422 This file is loaded in full into every session.

When invoked 2,422 The same file — it is already loaded in full.

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.

Model	Per session	Once invoked
Fable 5.1	$0.02422	$0.02422
Opus 5.5	$0.00969	$0.00969
Sonnet 5.5	$0.00484	$0.00484
Haiku 4.5	$0.00242	$0.00242

Measured 20d ago against content hash 14e57383cbcf, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

open-plan-annotator AGENTS.md 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 20d 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.

AGENTS.md · 128 lines

How it starts

The opening of the file, as written. The whole thing — 128 lines — stays where its author put it; the contents beside it link to each section on GitHub.

open-plan-annotator: Development Guide

What This Is

A fully local Claude Code plugin that intercepts ExitPlanMode hook events and opens a browser UI for reviewing and annotating plans before code is written. Ships as a package-managed platform runtime binary (compiled via bun build --compile) that embeds the React UI. Also works as an OpenCode V2 plugin with a stable default export (id + setup()).

Architecture

Claude Code path:
  SessionStart hook fires
    → scripts/install-runtime.mjs   (Node: ensures per-platform runtime binary is present)
      → If missing: fetches @open-plan-annotator/runtime-<platform>-<arch>@<version>
        tarball from the npm registry, verifies dist.integrity, extracts the
        compiled Bun binary into packages/runtime-<platform>-<arch>/bin/.
      → If present: exits 0 immediately (fast path).

  ExitPlanMode hook fires
    → bin/open-plan-annotator.mjs   (Node wrapper: buffers stdin, resolves runtime package, delegates)
      → packages/runtime-<platform>-<arch>/bin/open-plan-annotator  (compiled Bun binary)
        → Reads hook JSON from stdin
        → Starts HTTP server on ephemeral port
        → Opens browser to the UI
        → Blocks until user approves/denies
        → Writes hook response JSON to stdout

OpenCode path:
  Agent calls annotate_plan tool
    → opencode/index.js             (OpenCode plugin entry, loaded via package.json "main")
      → opencode/bridge.js          (constructs fake HookEvent, spawns binary)
        → bin/open-plan-annotator.mjs → binary (same as above)
      → Parses HookOutput, returns approval/feedback to agent

The OpenCode plugin bridges to the same binary by constructing a Claude-format HookEvent payload and parsing the HookOutput response. This means there is only one server/UI codepath.

Runtime distribution

The main npm package (open-plan-annotator) is small and ships no compiled binary. Per-platform binaries live in their own runtime packages (@open-plan-annotator/runtime-darwin-arm64, -darwin-x64, -linux-arm64, -linux-x64), each compiled with bun build --compile --target=bun-<platform>. These are listed as optionalDependencies so npm install picks the right one automatically.

Read the full file on GitHub · 128 lines

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.

20d ago Changed · +1 lines · +89 tokens per session 14e57383cbcf
2mo ago First seen · 127 lines · 2,333 tokens per session scan A 853149615e03

Subscribe to this mod's changes

open-plan-annotator AGENTS.md is an instructions file published in the GitHub repository ndom91/open-plan-annotator (100 stars, last pushed 21d ago), licensed MIT. It adds 2,422 tokens to every session, about $0.0097 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.

Planning agentic-ai ai claude-code-plugin coding-agent opencode-plugin plan-mode

open-plan-annotator AGENTS.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
open-plan-annotator AGENTS.mdndom91/open-plan-annotator	Instructions file	100	21d ago	MIT	A	2,422	Claude Code, Codex, OpenCode
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	9,719	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	today	MIT	A	7,461	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	5,516	GitHub Copilot
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	today	MIT	A	4,680	Codex, OpenCode
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	275k	3d ago	MIT	A	4,313	Codex, OpenCode

open-plan-annotator: Instructions file for Claude Code