BoardSimple

Eesti keeles

A simple, free board for giving feedback on UIs created by coding agents.

If you don't need all the tools Paper offers and just want a board to review your agent's UI proposals, BoardSimple is a lightweight option. Put HTML screens side by side, mark what should change, and let your agent read the feedback from a local file. No account or subscription is required.

BoardSimple is an early-stage local tool. It works with HTML files your agent creates; it does not embed a running application's URL. It is an independent project, unaffiliated with Paper.

Install

Needs Node.js 24+. No npm dependencies.

npm install -g boardsimple

Or run it once without installing, inside your project folder:

npx boardsimple

Keep the terminal running while you use the board; press Ctrl+C to stop the server. On Windows, if PowerShell blocks npm scripts, use npm.cmd, npx.cmd and boardsimple.cmd.

The demo ships in this repository. To try it, you also need Git:

git clone https://github.com/hallikkristjan-code/boardsimple.git
cd boardsimple
boardsimple examples/demo-en

Give feedback to your agent

1. Ask your coding agent to create self-contained HTML screens in your project's screens/ folder. Copy the agent guide into the project's AGENTS.md or CLAUDE.md.
2. Run boardsimple ./my-project from its parent folder, or boardsimple inside the project.
3. Compare the screens, draw a ring, box, line or arrow, and write what should change.
4. When your agent is listening, click Send to agent. Otherwise click Copy command for agent and paste it into the chat.
5. Let the agent read .canvas/annotations.json and update the HTML. The board refreshes automatically.

Annotations stay in the project's .canvas/ folder. Include that folder in your backups; add it to your project's .gitignore if the feedback is private. BoardSimple stores feedback locally; the HTML screens you load may still request external assets.

Send directly to an agent

Ask your agent to run boardsimple wait in the project folder (the agent guide tells it to). The command opens the board if needed and waits. The notes panel shows whether an agent is listening; while it is, Send to agent hands it the open notes and the agent starts working in its conversation. Each send saves a snapshot in .canvas/feedback-<id>.json, so later edits do not change what was sent. Sending does not mark notes done, commit changes or publish anything.

Tested on Windows with Claude Code run through T3 Code and with the Codex app. Other agents and systems are untested, and some agents stop long-running commands early; Copy command for agent always works.

A board started by boardsimple wait runs without a terminal and stops by itself after 30 minutes with no board window open and no agent waiting. A board you start by hand runs until Ctrl+C.

Usage

boardsimple                 # current folder
boardsimple ./my-project
boardsimple --port 5000 --no-open
boardsimple wait            # for agents: open the board and wait for "Send to agent"

The canvas opens in its own window (Chrome, Edge, Chromium or Brave in --app mode): it has its own taskbar entry, shows up in Alt+Tab and does not get lost among tabs. The window keeps its own profile (~/.boardsimple/chrome-profile), so its size and position are remembered. A canvas link clicked elsewhere lands in a normal tab; when no board window is open, the tab opens one and closes itself, otherwise it stays a working canvas. Without any of those browsers it opens in your default browser.

Try the demo from a clone of this repository: boardsimple examples/demo-en.

• Screens: screens/<group>/<name>.html, sized with <meta name="artboard" content="width=390,height=844">.
• Tools: Select (V) — click and scroll inside a screen · Hand (H or Space) — pan · Ring (O), Box (B), Line (P), Arrow (A) — mark. A line closes if you finish near its start; otherwise it stays an underline. The color applies to the next marks.
• Zoom: mouse wheel or pinch; "Fit all" (Shift+1).
• For the agent: notes are saved to .canvas/annotations.json right away; a deleted note can be undone for a few seconds. Send the open notes to a waiting agent (boardsimple wait), or copy the command into the chat.
• Language: the app follows your browser (Estonian if it is listed, otherwise English). The ET/EN button next to the theme toggle switches it and remembers the choice. The command line follows the system language; BOARDSIMPLE_LANG=en or et overrides it.
• Troubleshooting: when the GPU process crashes or resets, a line is added to .canvas/client.log. Missing graphics tiles do not show up there.

Agent guide for a project's CLAUDE.md: AGENTS-BOARDSIMPLE.en.md.

The server listens on 127.0.0.1 only and refuses requests with a foreign Origin or Host header. Screens use a separate read-only loopback origin in sandbox frames: their own scripts, local modules and fonts can run, but cannot access the board's DOM or agent controls. Screen browser storage belongs to that separate origin. Geometry and annotation hit-tests use a limited message bridge.

Development

npm test                      # node tests
python -I test/e2e/e2e.py     # browser e2e (pip install playwright && playwright install chromium)
python -I test/e2e/marks.py   # marking tools and colors
python -I test/e2e/agents.py  # listening status, send to a waiting agent, screen isolation
python -I test/e2e/a11y.py    # keyboard use, undo and contrast
python -I test/e2e/touch.py   # one and two fingers, narrow window
python -I test/e2e/window.py  # hand-over from a tab to the app window
python -I test/e2e/load.py    # 146-page load test; BOARDSIMPLE_E2E_GPU=1 adds a GPU memory limit on Windows

CI runs all of them (node tests on Ubuntu and Windows, e2e and load test on Ubuntu). It does not check the GPU limit, because it has no real GPU.

License

MIT. Free to use, modify and share.