msg

A command-line tool for communication between separate coding-agent sessions, including agents running in tmux panes.

In plain words
What is it for?
Registering sessions, sending direct or group messages, reading incoming messages, listing agents, and checking communication status.
Why use it?
It gives agents a shared way to register, send messages, read replies, and check which agents are available.

Skill for Claude CodeCodex

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 skills/pchalasani/claude-code-tools/msg
Any agent
npx skills add pchalasani/claude-code-tools --skill msg
Clone the repo
git clone --depth 1 https://github.com/pchalasani/claude-code-tools

Made for: Claude Code, Codex.

Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 333 The whole file, excluding the scripts and references it only reads on demand.
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 $0.00037 $0.00333
Opus 5 $0.00018 $0.00167
Sonnet 5 $0.00007 $0.00067
Haiku 4.5 $0.00004 $0.00033

Measured 2d ago against content hash 5318481c279d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

msg 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.

plugins/msg/skills/msg/SKILL.md · 75 lines

What it actually says

msg: Inter-Agent Communication

You can communicate with other coding agent sessions (Claude Code or Codex CLI) using the msg CLI tool.

Registration

Before sending or receiving messages, register yourself:

msg register <your-name>

This auto-detects your tmux pane. You only need to do this once per session.

Sending Messages

Send a message directly to another agent:

msg send <agent-name> "Your message here"

Send to multiple agents:

msg send agent1,agent2 "Message for both of you"

Replying

msg reply <agent-name> "Your reply here"

Receiving Messages

Check your inbox:

msg inbox

This shows all unread messages grouped by thread and marks them as read.

Other Commands

msg list          # List registered agents
msg threads       # List active threads
msg status        # Check system health

Guidelines

  • Keep messages concise -- they consume context in the receiving agent's session.
  • When replying, include enough context that the recipient understands without re-reading the full thread.
  • If you need to share code or file paths, reference them in the message text rather than pasting large blocks.
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 · 75 lines · 37 tokens per session scan A 5318481c279d

Subscribe to this mod's changes

msg is a skill published in the GitHub repository pchalasani/claude-code-tools (1,989 stars, last pushed 2d ago), licensed MIT. It adds 37 tokens to every session and 333 once invoked, about $0.0002 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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