yummy

yummy is a Mattermost bot bridge for pi and codex CLIs with:

• single-post progress updates (edits one bot message as work runs)
• stateless resume tokens (/sessions, /resume)
• per-channel and per-thread engine/model/reasoning preferences
• optional OAuth login helpers for OpenAI Codex and GitHub Copilot

Attribution

Credit to the original pi project by Mario Zechner and contributors:

• https://github.com/badlogic/pi-mono

Requirements

• Node.js 20+
• Mattermost bot account + token
• pi and/or codex CLI installed and authenticated

Quick Start

npm ci
npm run build

export YUMMY_URL="https://mattermost.example.com"
export YUMMY_TOKEN="YOUR_BOT_TOKEN"
export YUMMY_DEFAULT_ENGINE="pi"   # pi|codex
export YUMMY_ALLOWED_USERS="alice,bob,@carol"  # strongly recommended

node dist/main.js /var/lib/yummy

YUMMY_URL/YUMMY_TOKEN can also be set as MM_URL/MM_TOKEN.

Configuration

Core:

Variable	Required	Description
YUMMY_URL	yes	Mattermost base URL (for example https://mattermost.example.com)
YUMMY_TOKEN	yes	Mattermost bot token
YUMMY_DEFAULT_ENGINE	no	pi (default) or codex
YUMMY_ALLOWED_USERS	no	Comma/space-separated allowlist of usernames or user IDs

PI runner:

Variable	Required	Description
YUMMY_PI_CMD	no	CLI command path (default pi)
YUMMY_PI_MODEL	no	Default model
YUMMY_PI_PROVIDER	no	Provider passed to pi --provider ...
YUMMY_PI_EXTRA_ARGS	no	Extra CLI args
YUMMY_PI_SESSION_DIR	no	Explicit session directory
YUMMY_PI_THINKING	no	`off
YUMMY_PI_TITLE	no	Display label in progress UI

Codex runner:

Variable	Required	Description
YUMMY_CODEX_CMD	no	CLI command path (default codex)
YUMMY_CODEX_EXTRA_ARGS	no	Extra CLI args (default -c notify=[])
YUMMY_CODEX_TITLE	no	Display label in progress UI
YUMMY_CODEX_MODEL	no	Default model
YUMMY_CODEX_REASONING	no	`none

Mattermost Behavior

• DMs always trigger the bot.
• In channels, mentions trigger by default.
• Replies to bot messages trigger.
• /trigger all can enable non-mention channel messages for a channel/thread scope.
• cancel or /cancel stops the active run for the channel/thread queue.

Command Reference

All commands can be used in-channel or thread-scoped (thread when sent in a thread).

Command	Description
/pi <prompt>	Force pi runner for this message
/codex <prompt>	Force codex runner for this message
/sessions	List recent sessions
/resume [n] [prompt]	Resume session by index or latest
/session [n] [prompt]	Alias for /resume
/agent [pi|codex|clear]	Get/set/clear default engine
/model [pi|codex] <model|clear>	Get/set/clear model override
/reasoning [pi|codex] <off|minimal|low|medium|high|xhigh|clear>	Get/set/clear reasoning override
/trigger [mentions|all|clear]	Get/set/clear trigger mode
/login openai-codex	Start OpenAI Codex OAuth flow
/login github-copilot [enterprise-domain]	Start GitHub Copilot device flow

OAuth Credentials

• Saved to ~/.pi/agent/auth.json (or $PI_CODING_AGENT_DIR/auth.json).
• File permissions are restricted to user-only (0600).
• Do not commit this file.

Data Written in Working Directory

Per channel:

• <channelId>/log.jsonl message log
• <channelId>/attachments/* downloaded files
• <channelId>/sessions.jsonl stored resume lines

Global:

• prefs.json channel/thread defaults and overrides

Use a dedicated directory (for example /var/lib/yummy), not the repo root.

Production Notes

• Run with a dedicated bot account and minimum necessary Mattermost permissions.
• Set YUMMY_ALLOWED_USERS to limit who can invoke the bot.
• Keep runtime data on persistent storage with restricted filesystem ACLs.
• Run under a process manager (systemd, container orchestrator, etc.).
• Monitor logs and rotate/retain log.jsonl based on your policy.

Example systemd unit:

[Unit]
Description=yummy Mattermost bridge
After=network-online.target

[Service]
Type=simple
WorkingDirectory=/opt/yummy
Environment=YUMMY_URL=https://mattermost.example.com
Environment=YUMMY_TOKEN=REPLACE_ME
Environment=YUMMY_DEFAULT_ENGINE=pi
Environment=YUMMY_ALLOWED_USERS=alice,bob
ExecStart=/usr/bin/node /opt/yummy/dist/main.js /var/lib/yummy
Restart=always
RestartSec=3
User=yummy
Group=yummy

[Install]
WantedBy=multi-user.target