Postbag

Name: Postbag
Author: parasxos

by parasxosversion 2.3.0i★ –iRuns on your computer

Registry nameio.github.parasxos/postbag

Install

Overview

Description from the maker (original English)

Local Claude Code and Codex sessions on one machine exchange letters through native inputs.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Other

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
You fill in yourself: POSTBAG_CODEX

You need

PyPIPython’s uv installed (for the uvx command)

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "postbag": {
      "command": "uvx",
      "args": [
        "postbag",
        "mcp"
      ],
      "env": {
        "POSTBAG_CODEX": "your-value"
      }
    }
  }
}

Run this in your terminal

claude mcp add postbag --env POSTBAG_CODEX=your-value -- uvx postbag mcp

Fill in the empty values before running it.

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "postbag": {
      "command": "uvx",
      "args": [
        "postbag",
        "mcp"
      ],
      "env": {
        "POSTBAG_CODEX": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "postbag": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "postbag",
        "mcp"
      ],
      "env": {
        "POSTBAG_CODEX": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

Values you fill in

POSTBAG_CODEX env
Path to the codex executable for Codex delivery when several are installed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account parasxos, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Otheri

More stars than 0% of the other 32568 servers in this category
Published to the registry more recently than 55% of the other 32568 servers in this category
Basic checks equal to or better than 100% of the other 32568 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Postbag safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (2.3.0) reached the registry 34 days ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Python (uv) on your computer.

What can I use instead?

In the same category: Spec Driven Development, Remote Desktop Commander, FlyDocs

Alternatives

Servers in the same category from other makers, sorted by stars.

Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

Spec Driven Development

by formulahendry

MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.

Runs on your computer★ 440MITUpdated 14 months ago

Install

Remote Desktop Commander

by desktop-commander

Remote Desktop Commander: use files, terminal and processes on your own computers from any AI app.

Runs in the cloud★ 211Updated yesterday

Install

FlyDocs

by flydocs.ai

Spec-driven development workflow: your agent works issues, sessions and the status lifecycle.

Runs on your computerUpdated today

Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

postbag

Let Codex and Claude Code talk to each other.

A local MCP server. Ask Codex to review what Claude Code just wrote, or the other way round. The answer arrives as a new turn. No copying text between windows.

Install

Needs Python 3.10 or later, Claude Code and a recent Codex CLI with codex queue. Run both sessions on one machine with the same postbag version. Delivery is tested on macOS.

pipx install 'postbag[mcp]'

claude mcp add --scope user postbag -- "$(command -v postbag-mcp)" codex mcp add postbag -- "$(command -v postbag-mcp)"

Start a new session in each app, then run /mcp. postbag should list five tools. For uvx and other setups, see MCP setup.

Or ask your agent: *Install postbag using llms-install.md.*

Quick start

A bag is a named conversation. Both agents join the same one. Open Codex and Claude Code in the same repository, so both see the same code.

In Codex:

Join postbag bag "review" as codex.

In Claude Code:

Join postbag bag "review" as claude, then ask codex to review my last commit.

Codex joins first so Claude Code has someone to write to. Approve the postbag tools when asked. Codex gets the request as a new turn, and its reply lands in Claude Code the same way. Either side can end with a final letter, which asks for no reply.

What to use it for

Cross review. Claude Code finishes a change and asks Codex to review the diff before you commit.
Split work. Codex writes the tests while Claude Code writes the implementation. They compare notes by letter.
Second opinion. When one agent is stuck on a bug, it asks the other for a fresh read.

Tools

Your agents call these. You just ask in plain words.

Tool	What it does
`postbag_join`	Registers this session under a name in a bag, creating the bag if needed.
`postbag_send`	Sends a letter to a name in the bag. `final: true` asks for no reply.
`postbag_read`	Pages through the bag's history.
`postbag_bags`	Lists local bags with letter counts and registered names.
`postbag_leave`	Withdraws this session from the bag. History stays.

How it works

Native delivery. Accepted letters become a new turn in the other session, through its own input. postbag adds no delivery daemon, polling or hooks.
No setup prompts. Every letter ends with how to reply, or asks for no reply.
One shared history. Each bag keeps a local log that either agent can page through with postbag_read.

A successful send confirms submission and recording. Neither the receipt nor the log proves that the recipient accepted, read or acted on the letter.

Security

Each letter names its peer and asks the recipient to stay within the human's existing authorization. This is model guidance, not a security boundary. Connect only sessions you trust with the task.
There is no letter limit. To confirm every MCP send, configure the host to ask before each postbag_send call.
Ledgers under ~/.postbag/ hold Claude Code inbox tokens. New files use mode 0600. Never commit or share them.

See SECURITY.md.

MCP setup · Concept · Changelog · Contributing · MIT

Postbag

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

Values you fill in

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Otheri

Common questions

Alternatives

Spec Driven Development

Remote Desktop Commander

FlyDocs

README from the maker

postbag

Install

Quick start

What to use it for

Tools

How it works

Security