mailbox-leader

mailbox-leader is a skill for Claude Code, Codex from zach-source/claude-mailbox. It costs 74 tokens per session (442 once invoked), scanned A, original, MIT.

A coordination role for the session leading work across several Claude Code sessions and worktrees. It tracks active sessions, assigns tasks, and manages handoffs.

In plain words
What is it for?
Use it to delegate tasks, monitor session status, answer requests from other sessions, coordinate shared resources, and hand leadership to another session.
Why use it?
It prevents duplicated work and keeps shared changes, such as merges and deployments, coordinated. It also gives secondary sessions a way to request information from the lead.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Claude Code.

Good fit Use it to delegate tasks, monitor session status, answer requests from other sessions, coordinate shared resources, and hand leadership to another session.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/zach-source/claude-mailbox/mailbox-leader
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.

Any agent
npx skills add zach-source/claude-mailbox --skill mailbox-leader
Clone the repo
git clone --depth 1 https://github.com/zach-source/claude-mailbox

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for mailbox-leader

README.md
[![agentmods](https://agentmods.dev/badge/skills/zach-source/claude-mailbox/mailbox-leader/github.svg)](https://agentmods.dev/skills/zach-source/claude-mailbox/mailbox-leader)
Your own site
<a href="https://agentmods.dev/skills/zach-source/claude-mailbox/mailbox-leader"><img src="https://agentmods.dev/badge/skills/zach-source/claude-mailbox/mailbox-leader/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for mailbox-leader

Your own site · 80×15
<a href="https://agentmods.dev/skills/zach-source/claude-mailbox/mailbox-leader"><img src="https://agentmods.dev/badge/skills/zach-source/claude-mailbox/mailbox-leader.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 74 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 442 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00074 $0.00442
Opus 5 $0.00037 $0.00221
Sonnet 5 $0.00015 $0.00088
Haiku 4.5 $0.00007 $0.00044

Measured 9d ago against content hash 0418b867d777, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

mailbox-leader 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 9d 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.

skills/mailbox-leader/SKILL.md · 37 lines

What it actually says

Mailbox leader / orchestrator

You are the leader when get_leader().leader_sid is your session (you're on main). There is at most one leader; if you leave main, release leadership so another main session can take over.

Responsibilities

  1. Know the fieldlist_sessions() to see every active session, its project, worktree, branch, objective, and status. Stale sessions are marked; ignore them.
  2. Delegate instead of doing everythingdelegate(to_sid, title, detail, priority) creates an assigned work item (a mailbox:delegation bead) for a secondary. The open delegation beads ARE your ledger — query/track them rather than keeping state in your head.
  3. Coordinate shared resources — serialize risky shared work (main merges, flake.lock, deploys). Announce plans on broadcast(text, channel="leader") so secondaries hold.
  4. Answer requests — secondaries will request_info/send_dm you before shared actions; poll_inbox() and respond so they aren't blocked.
  5. Hand off cleanly — if you switch off main, release_leadership() (the heartbeat does this automatically when it detects you left main) and broadcast the handoff.

Failover

If the previous leader died, its slot goes stale and the next main session claims it automatically at heartbeat. If leadership is vacant (nobody on main), secondaries proceed autonomously but conservatively — you don't have to force a claim unless the user wants a coordinator.

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. 9d ago First seen · 37 lines · 74 tokens per session scan A 0418b867d777

Subscribe to this mod's changes

mailbox-leader is a skill published in the GitHub repository zach-source/claude-mailbox (1 stars, last pushed 1mo ago), licensed MIT. It adds 74 tokens to every session and 442 once invoked, about $0.0004 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 2026-08-31.

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