message-claude

A communication tool for sending a plain-text message to a running Claude Code session on the same computer.

In plain words
What is it for?
Use it to list Claude sessions, select one by name or other details, and send it a short message. It supports macOS, Linux, and WSL 2, but not native Windows.
Why use it?
It lets scripts, hooks, long-running jobs, and Codex sessions report information to Claude without manual copying. It also helps you choose the correct session when several are registered.

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/heapy/kortex/message-claude
Any agent
npx skills add Heapy/kortex --skill message-claude
Clone the repo
git clone --depth 1 https://github.com/Heapy/kortex

Made for: Claude Code, Codex.

Per session 123 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 752 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 $0.00123 $0.00752
Opus 5 $0.00062 $0.00376
Sonnet 5 $0.00025 $0.00150
Haiku 4.5 $0.00012 $0.00075

Measured 2d ago against content hash 244c544e79c7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

message-claude 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.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/message_claude.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/heapy/skills/message-claude/SKILL.md · 68 lines

How it starts

The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Message Claude

Find the exact Claude Code session and send it one plain-text message.

For the opposite direction, use Message Codex.

If ListAgents and SendMessage are available, use them. Do not use the raw inbox to bypass a permission rule that denied either tool. The workflow below is for external callers such as a standalone Codex session, Codex launched by Claude, a hook, or a script.

The bundled helper supports macOS, Linux, and WSL 2. Native Windows uses a named pipe and is not implemented here.

Send a message

Resolve scripts/message_claude.py from this skill's directory.

  1. List the registered sessions:

    python3 <skill-dir>/scripts/message_claude.py --list
    
  2. Select the target by its exact name. If names repeat, narrow with --cwd or --pid. Never guess between multiple matches.

  3. Send a short message:

    python3 <skill-dir>/scripts/message_claude.py \
      --name the-session-name \
      --message 'codex: the migration finished; tenant_id is the new column'
    

    Omit --message to read arbitrary or multiline text from stdin.

The helper uses --config-dir, then CLAUDE_CONFIG_DIR, then ~/.claude. Pass --config-dir when Claude uses a custom directory that the caller did not inherit.

What the helper guarantees

  • Reads <config-dir>/sessions/*.json and refuses zero or multiple target matches.
  • Reads the target's peerToken without printing it. The key filename hashes messagingSocketPath exactly as recorded; it does not resolve /tmp to /private/tmp.
  • JSON-encodes the complete auth and message payload before connecting, so quotes, newlines, and backslashes in the message remain valid.
  • Reports a successful socket write, not guaranteed delivery. The receiving session may still hold or refuse the message through crossSessionInbound.

Failures

  • No matching session: list again and check name, cwd, pid, and --config-dir.
  • Connection failure: the registry entry may be stale; list again instead of retrying blindly.
  • Permission error: the Codex sandbox may block that Unix socket. Report the socket path and ask for a grant scoped to its directory; do not bypass the sandbox.
  • Missing peerToken: stop and verify the config directory and target rather than sending an unauthenticated message.

Read the full file on GitHub · 68 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 68 lines · 123 tokens per session scan A 244c544e79c7

Subscribe to this mod's changes

message-claude is a skill published in the GitHub repository Heapy/kortex (6 stars, last pushed 4d ago), licensed Apache-2.0. It adds 123 tokens to every session and 752 once invoked, about $0.0006 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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