A skill for coding agents that moves a "grilling" design interview out of the terminal and onto a local browser page. The agent asks its questions as cards, each with lettered options and a highlighted recommendation. You answer them in any order, defer or reopen them, discuss any single one in its own thread without losing the rest of the session, and press one button, Send to Agent, to ship everything you staged as a single turn. At the end the agent writes an exhaustive design doc for the topic.

Above: a recommendation accepted on Q3 and a question asked on Q4 go to the agent as one Send, and its reply opens the next round. Then one click on Explore deeper lays out the pros and cons of Q6's options, Visualize draws the design so far as a prototype, and one note in its feedback thread redraws it as v2 with the change asked for. Recorded against a real session by design/record-demo.mjs.

Under the hood it is small on purpose: one Node script and one HTML file, no dependencies, no build step. The agent owns state.json and changes it only through node server.mjs patch, sending just what changed as a small JSON patch that the script merges, validates, and writes atomically; a whole-file rewrite would put the entire state (60 KB by the end of a long grill) into the agent's context on every turn. The page appends one line per Send to events.jsonl; the server that serves the page is also the process whose output a persistent Monitor delivers to the agent. In wait mode the agent must keep its foreground listener active; a page server alone cannot wake an ended agent turn. Submissions made while the agent is not listening remain queued for resume.

The skill is a plain Agent Skills folder (SKILL.md plus one script and one page), so it installs the same way everywhere: put this folder where your agent looks for skills, under the name grill-with-ui. A symlink keeps git pull as the update path; copying the folder works too. Node 20 or newer is the only requirement.

git clone https://github.com/jasonku09/grill-with-ui ~/Projects/grill-with-ui
ln -s ~/Projects/grill-with-ui ~/.claude/skills/grill-with-ui   # Claude Code (Cursor reads it too)
ln -s ~/Projects/grill-with-ui ~/.agents/skills/grill-with-ui   # Codex, Gemini CLI, Cursor, Copilot

Where each agent looks, and how to start a grill once it is there:

Paths are from each product's documentation as of September 2026; /skills (Codex, Gemini CLI) or the agent's skill picker will show whether the install landed. The skill's description names the phrase "grill with ui", so plain language works on every agent.

What the agent needs at run time:

• A shell tool and Node 20+. Claude Code is woken per Send by its persistent Monitor tool. Every other agent uses wait mode, spelled out in SKILL.md: it starts the server detached (or in a harness-managed shell session) and keeps node server.mjs wait active in the foreground. It returns on the next Send or after a bounded timeout, then loops. The agent keeps listening after replies and completed visuals, until the user finishes or explicitly pauses; a running server is not a substitute for that listener.
• Optionally a subagent tool, for Visualize. With one, the visual is drawn in the background while you keep answering. Without one, the agent draws it inline and that turn takes longer.

In any project:

/grill-with-ui <topic you want grilled>

The agent prints a URL. Open it. Answer by clicking an option (the recommended one is outlined) or writing free text; start a discussion in the right-hand panel; use Defer and Reopen on a card when you want to. Everything you do is staged (and survives a reload) until you press Send N to Agent (⌘↩). The one exception is Explore deeper next to a question's title: it goes to the agent the moment you click it, and the pros and cons table for that question's options appears in the discussion panel when the agent is done. The agent answers threads, writes the tables, records your answers, and adds the next round of questions to the page.

Visualize in the header asks the agent for one picture of the design so far: an interactive HTML prototype when the topic is a UI, an architecture or flow diagram otherwise. When the topic is a change to an existing app, the prototype is drawn inside the real page it changes, with the app's own look. It appears in place of the question list and card, with its own feedback thread on the right. Undecided parts are drawn from the recommendations and marked "assumed"; feedback you add there ships with your next Send and redraws it; a note that contradicts an answered question reopens that question rather than silently changing your answer. Ordinary answers and question discussions do not regenerate the visual or delay the next round. When decisions change what it shows, it is marked Out of date; click Regenerate to include the latest decisions. Each requested redraw has a version number and a one-line change note. The agent never writes the file in the grill conversation itself: it briefs a subagent (rules in visual-brief.md) so hundreds of lines of markup stay out of the interview's context. The draw runs in the background, so Send keeps working and the interview goes on while it is drawn; the header says Visualizing… (or the strip says regenerating…) until the new version lands. Finish reconciles and copies the final visual next to the design doc as docs/<topic>-visual.html.

Finish grill sends at once (after an inline confirm), together with anything you had staged; the agent writes the design doc to the path shown in the header (default docs/<topic>-design.md in your project) and stops.

To pick up an unfinished grill, in the same project:

/grill-with-ui resume

If the agent crashed or was closed, sends you made in the meantime are replayed on resume, and the page tab you still have open reconnects on its own.

Session state lives outside your repo, so there is nothing to gitignore:

~/.grill-with-ui/sessions/<project-key>/<YYYYMMDD-HHMMSS>/
  state.json     written only by the agent, through `patch` (questions, recommendations, threads, status)
  events.jsonl   appended only by the page, one line per Send
  server.json    url, port and pid of the running server
  visual.html    the prototype or diagram, drawn by the agent's subagent, served at /visual

<project-key> is the git common root of the project with slashes turned into dashes, so every worktree of a repo sees the same sessions; outside git it is the working directory.

In this repo: server.mjs (the server and CLI), page.html (the page), SKILL.md (the prompt the agent follows), test/, and design/ + docs/design.md (how it was designed). design/record-demo.mjs re-records the GIF above by driving the real page; it needs Playwright and ffmpeg.

node server.mjs new      --topic T [--doc P]                  create a session, print its folder
node server.mjs serve    --session DIR [--port N]             serve the page; print one line per Send
node server.mjs sessions [--all]                               list this project's sessions
node server.mjs pending  --session DIR                         print sends past agent.handled
node server.mjs wait     --session DIR [--after N] [--timeout S]  block until the next send (exit 3 on timeout)
node server.mjs url      --session DIR [--timeout S]           print the running server's url
node server.mjs patch    --session DIR [--file P]              apply a JSON patch (stdin or P) to state.json

patch merges by the rules in SKILL.md ("Patching state.json"). A bad patch exits non-zero and leaves the file untouched; a good one prints one short summary line, never the state.

GRILL_HOME overrides ~/.grill-with-ui.

node --test test/server.test.mjs
PLAYWRIGHT_PKG=/path/to/node_modules/@playwright/test/index.mjs node test/page.e2e.mjs

The page check needs Playwright with Chromium; point PLAYWRIGHT_PKG at an existing install or run it with @playwright/test installed next to the repo. It starts a real server on a throwaway session and drives the page end to end (staging, reload, send, working state, server restart, finished state).