agentmods.dev

PlainTab AGENTS.md

A set of instructions for coding agents working on PlainTab, a Chrome and Edge new-tab extension that can also run as a standalone webpage. It explains which project rules take priority and what the project must avoid.

In plain words
What is it for?
Use it when changing PlainTab to find the required rule files, follow startup and storage guidance, and keep the extension based on plain JavaScript, CSS, and static assets.
Why use it?
It prevents changes that conflict with the repository’s constraints, such as adding build tools, frameworks, testing systems, or large dependencies.

Instructions file for CodexOpenCode

88 3mo ago A scan 1,043 tokens original MIT
View the source file kaininx/PlainTab
Install

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.

agentmods
npx agentmods add instructions/kaininx/plaintab/agents-md
Clone the repo
git clone --depth 1 https://github.com/kaininx/PlainTab

Made for: Codex, OpenCode.

Per session 1,043 This file is loaded in full into every session.
When invoked 1,043 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
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 $0.01043 $0.01043
Opus 5 $0.00522 $0.00522
Sonnet 5 $0.00209 $0.00209
Haiku 4.5 $0.00104 $0.00104

Measured 2d ago against content hash a6559de01d13, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

PlainTab 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.

AGENTS.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md

Shared instructions for AI agents working on PlainTab.

PlainTab is a Chrome/Edge Manifest V3 new-tab extension. It is also able to run as a standalone web page by opening index.html directly.

Rule Priority

Use this order when instructions conflict:

  1. .claude/rules/00-core.md
  2. The matching file under .claude/rules/
  3. This AGENTS.md
  4. Tool-specific adapters such as CLAUDE.md
  5. Reference docs and task notes

Before changing core behavior, read 00-core.md and the relevant module rule. Use .claude/rules/README.md as the rule map.

Project Constraints

Do not introduce:

  • Build tools
  • npm or package.json
  • Frontend frameworks
  • Lint or test frameworks
  • Large runtime dependencies

Use vanilla JavaScript, native CSS, and static browser extension assets.

Required Rule Files

  • Rule map: .claude/rules/README.md
  • Core behavior: .claude/rules/00-core.md
  • Storage, IndexedDB, localStorage, migrations: .claude/rules/10-storage.md
  • Wallpaper rendering, first paint, image lifecycle: .claude/rules/20-wallpaper.md
  • Language detection and fallback: .claude/rules/30-language.md
  • Startup flow and global interactions: .claude/rules/40-runtime.md
  • Search behavior: .claude/rules/50-search.md
  • Settings panel UI and state: .claude/rules/60-settings.md
  • Command palette: .claude/rules/70-command-palette.md

Startup Invariants

index.html loading order is part of the zero-white-flash design:

  1. #wallpaperBack exists first
  2. js/preload.js runs synchronously
  3. #wallpaperFront exists
  4. Other DOM follows
  5. js/languages.js
  6. Main runtime scripts

Do not move preload.js, make it async, or add network work to the first-paint path.

Wallpaper And Storage Safety

The wallpaper system uses a stable back layer and a transition front layer. At least one layer must always have visible content.

Storage safety rules:

  • Write large data before writing references
  • Remove references before deleting large data
  • Access IndexedDB through the storage module, not from unrelated UI code
  • Revoke Blob URLs when they are no longer needed
  • Preserve localStorage key compatibility unless a migration exists

Read the full file on GitHub · 135 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.

  1. 2d ago First seen · 135 lines · 1,043 tokens per session scan A a6559de01d13

Subscribe to this mod's changes

PlainTab AGENTS.md is an instructions file published in the GitHub repository kaininx/PlainTab (88 stars, last pushed 3mo ago), licensed MIT. It adds 1,043 tokens to every session, about $0.0052 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.

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