How do I install the Multicodex skill?

Run npx skillmds@latest add vincentkoc/multicodex in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Multicodex safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Multicodex?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Multicodex free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Multicodex?

vincentkoc (@vincentkoc) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Multicodex by vincentkoc — Agent Skill

Name: Multicodex
Author: vincentkoc

Multicodex

Join, coordinate, steer, and attach browser previews to a local-first MultiCodex room. Use when given a MultiCodex invite or host URL, asked to collaborate in a room, steer a lane, or expose a browser preview for work in progress.

vincentkoc 67d9c89 3.0 KB Updated Sep 17, 2026

File contents

MultiCodex

MultiCodex coordinates normal local Codex sessions. The room host and each participant bridge stay on their respective machines. Treat capability URLs as secrets: do not put them in commits, issues, logs, or messages outside the room.

Join a room

Use the invite command supplied by the room owner. A normal participant command looks like:

npx --yes @vincentkoc/multicodex@latest join '<invite-url>' \
  --repo . --name 'Your name' --policy suggest --terminal-mirror

Choose --policy observe, suggest, or steer as the owner requested. --terminal-mirror enables the live terminal view. Add --terminal-control only when the owner and participant explicitly want host typing control.

After connecting, work normally in the local Codex TUI. Room requests appear there as normal instructions or suggestions.

Steer a lane

Only a host capability URL can steer another lane. To send a concise instruction:

npx --yes @vincentkoc/multicodex@latest steer '<host-url>' \
  --lane 'Builder' --text 'Run the focused tests and report the result.'

Use the lane ID when names are ambiguous. Respect the lane policy: the participant remains authoritative for suggestions and steering.

Attach a preview

When the user says attach preview, finish the browser artifact first, then make it reachable and attach it to the current lane. The bridge sets MULTICODEX_LANE_URL to that lane's private view URL.

If no durable dev server is already running, start one in a named tmux window so it survives the agent's one-shot shell command:

tmux new-window -d -n multicodex-preview-<name> \
  "cd <project-dir> && exec <dev-server-command>"

Verify its loopback URL before exposing it. Do not stop or reuse another session's preview window.

npx --yes @vincentkoc/multicodex@latest preview set "$MULTICODEX_LANE_URL" \
  --url 'http://127.0.0.1:5173'

For docs work, serve docs/ with pnpm docs:serve and attach http://127.0.0.1:4173 instead.

Use a URL the room viewer can reach. For a shared Tailscale room, preserve existing Serve routes and use an unused HTTPS port for the preview:

tailscale serve status
tailscale serve --bg --https=8443 http://127.0.0.1:<port>
curl -fsS "https://<machine>.ts.net:8443/"
npx --yes @vincentkoc/multicodex@latest preview set "$MULTICODEX_LANE_URL" \
  --url "https://<machine>.ts.net:8443/"

Do not reset or replace another room's Tailscale Serve configuration. Choose an unused port, verify the preview URL before attaching it, and do not attach URLs with credentials. The room owner opens and refreshes it from the preview pane. Clear it when it is no longer useful:

npx --yes @vincentkoc/multicodex@latest preview set "$MULTICODEX_LANE_URL" --clear

---name: multicodexdescription: Join, coordinate, steer, and attach browser previews to a local-first MultiCodex room. Use when given a MultiCodex invite or host URL, asked to collaborate in a room, steer a lane, or expose a browser preview for work in progress.---# MultiCodexMultiCodex coordinates normal local Codex sessions. The room host and eachparticipant bridge stay on their respective machines. Treat capability URLs assecrets: do not put them in commits, issues, logs, or messages outside the room.## Join a roomUse the invite command supplied by the room owner. A normal participant commandlooks like:```shnpx --yes @vincentkoc/multicodex@latest join '<invite-url>' \ --repo . --name 'Your name' --policy suggest --terminal-mirror```Choose `--policy observe`, `suggest`, or `steer` as the owner requested.`--terminal-mirror` enables the live terminal view. Add `--terminal-control`only when the owner and participant explicitly want host typing control.After connecting, work normally in the local Codex TUI. Room requests appearthere as normal instructions or suggestions.## Steer a laneOnly a host capability URL can steer another lane. To send a concise instruction:```shnpx --yes @vincentkoc/multicodex@latest steer '<host-url>' \ --lane 'Builder' --text 'Run the focused tests and report the result.'```Use the lane ID when names are ambiguous. Respect the lane policy: theparticipant remains authoritative for suggestions and steering.## Attach a previewWhen the user says `attach preview`, finish the browser artifact first, thenmake it reachable and attach it to the current lane. The bridge sets`MULTICODEX_LANE_URL` to that lane's private view URL.If no durable dev server is already running, start one in a named tmux windowso it survives the agent's one-shot shell command:```shtmux new-window -d -n multicodex-preview-<name> \ "cd <project-dir> && exec <dev-server-command>"```Verify its loopback URL before exposing it. Do not stop or reuse anothersession's preview window.```shnpx --yes @vincentkoc/multicodex@latest preview set "$MULTICODEX_LANE_URL" \ --url 'http://127.0.0.1:5173'```For docs work, serve `docs/` with `pnpm docs:serve` and attach`http://127.0.0.1:4173` instead.Use a URL the room viewer can reach. For a shared Tailscale room, preserveexisting Serve routes and use an unused HTTPS port for the preview:```shtailscale serve statustailscale serve --bg --https=8443 http://127.0.0.1:<port>curl -fsS "https://<machine>.ts.net:8443/"npx --yes @vincentkoc/multicodex@latest preview set "$MULTICODEX_LANE_URL" \ --url "https://<machine>.ts.net:8443/"```Do not reset or replace another room's Tailscale Serve configuration. Choose anunused port, verify the preview URL before attaching it, and do not attach URLswith credentials. The room owner opens and refreshes it from the preview pane.Clear it when it is no longer useful:```shnpx --yes @vincentkoc/multicodex@latest preview set "$MULTICODEX_LANE_URL" --clear```

Frequently asked questions