termcanvas AGENTS.md

A project guide for TermCanvas, a simple Electron app where each canvas node is an interactive terminal. It explains the app’s architecture, terminal sessions, workspace files, and process boundaries.

In plain words
What is it for?
Use it when extending the main Electron process, terminal and tmux sessions, workspace import and watching, canvas data storage, or file dialogs.
Why use it?
It helps coding agents change the app without putting shell processes in the unsafe renderer or breaking terminal-session ownership.

Instructions file for CodexOpenCode

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/lout33/termcanvas/agents-md
Clone the repo
git clone --depth 1 https://github.com/lout33/termcanvas

Made for: Codex, OpenCode.

Per session 1,749 This file is loaded in full into every session.
When invoked 1,749 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 $0.01749 $0.01749
Opus 5 $0.00874 $0.00874
Sonnet 5 $0.00350 $0.00350
Haiku 4.5 $0.00175 $0.00175

Measured 2d ago against content hash 269d4b20c840, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

termcanvas 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 · 270 lines

How it starts

The opening of the file, as written. The whole thing — 270 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AGENTS.md

This file explains the local architecture of the TermCanvas app so future agents can extend it safely.

Product intent

This is a minimal infinite-canvas Electron app for spatial terminal workflows.

Each node is a real interactive terminal, not a text note. The product should stay simple and terminal-first.

Architecture overview

Main process — main.js

Responsibilities:

  • create the Electron window
  • own the terminal session registry
  • spawn PTY clients through node-pty
  • attach PTY clients to long-lived tmux sessions when tmux is available
  • fall back to plain shell PTYs when tmux is unavailable
  • validate that a renderer only talks to its own terminal sessions
  • detach live tmux-backed sessions when a window closes
  • permanently destroy a terminal session when the user closes a node
  • own workspace folder import, refresh, watch, and preview access
  • own app-session file persistence in Electron userData
  • own file dialog and local file read/write for canvas JSON and app-data JSON import/export

Important rule:

Real shell processes belong in main, never in the renderer.

Terminal identity model

The current session store is:

  • Map<terminalId, session>

Important distinction:

  • terminalId is the current renderer-to-main attachment id
  • sessionKey is the stable terminal identity saved in app-session snapshots
  • tmux session names are derived from sessionKey

Each session currently tracks:

  • ownerWebContentsId
  • pty
  • shellName
  • cwd
  • backend ("tmux" or "pty")
  • sessionKey
  • tmuxSessionName
  • isDisposing

Detach semantics matter:

  • closing the app/window should detach from tmux-backed sessions in normal runs
  • clicking a node close button should kill the underlying session permanently
  • smoke-test mode disables persistent relaunch behavior so tests do not leak sessions

App-session persistence

The app now persists a normalized JSON snapshot under Electron userData.

That snapshot includes:

Read the full file on GitHub · 270 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 · 270 lines · 1,749 tokens per session scan A 269d4b20c840

Subscribe to this mod's changes

termcanvas AGENTS.md is an instructions file published in the GitHub repository lout33/termcanvas (24 stars, last pushed 1mo ago), licensed MIT. It adds 1,749 tokens to every session, about $0.0087 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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