Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add instructions/ndom91/open-plan-annotator/agents-mdgit clone --depth 1 https://github.com/ndom91/open-plan-annotatorWhat 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 | $0.02333 | $0.02333 |
| Opus 5 | $0.01167 | $0.01167 |
| Sonnet 5 | $0.00467 | $0.00467 |
| Haiku 4.5 | $0.00233 | $0.00233 |
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 2d 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.
How it starts
The opening of the file, as written. The whole thing — 127 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 plugin via the @opencode-ai/plugin SDK.
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.
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.
- 2d ago First seen · 127 lines · 2,333 tokens per session scan A 853149615e03
open-plan-annotator AGENTS.md is an instructions file published in the GitHub repository ndom91/open-plan-annotator (90 stars, last pushed 15d ago), licensed MIT. It adds 2,333 tokens to every session, about $0.0117 per session on Opus 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.
Other instructions, from other repositories
nori-skillsets AGENTS.md
Instructions for tilework-tech/nori-skillsets, covering plugin package changes, claude code configuration vs. nori plugin package, skills documentation, style guide and functions and named parameters.
sortie copilot-instructions.md
Instructions for sortie-ai/sortie, covering sortie coding & review standards, 1. layered imports (downward only; violation is critical), 2. concurrency safety, 3. workspace path safety (critical: security boundary) and 4. persistence (sqlite).
copperhead AGENTS.md
Instructions for copperheadhq/copperhead, covering agents.md, repository overview, sources of truth, build and verification and architecture.
copperhead CLAUDE.md
Instructions for copperheadhq/copperhead, covering claude.md, what this repo is, sources of truth, workflow (openspec) and architecture (per spec.md §2).
sortie CLAUDE.md
Instructions for sortie-ai/sortie, covering sortie, commands, gotchas, boundaries and always.
SztuCode CLAUDE.md
Instructions for rojim666/SztuCode, covering claude.md, commands and architecture.