callsign

callsign

Unique per-session agent names + iMessage routing for Claude Code and Hermes. Every session self-assigns a memorable name at boot. You address a specific session by speaking to it by name. Replies come back signed.

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The problem

You run several Claude Code (or Hermes) sessions in parallel — one per project. iMessage replies are your remote control:

"Brodie, finish that app."

But which Brodie did you mean? You can't pin a reply to a specific session.

The fix

At session start, callsign tells the model: pick your own name. The model chooses (any single human name — Frank, Vesper, Maverick, anything that fits the agent's vibe), claims it through the registry (callsign claim <name>), introduces itself in chat, and from then on every outbound iMessage is auto-prefixed with that name.

You address whichever session you want:

Frank, push the wellrx fix to staging.
Steven, the flow path isn't working — proceed as you suggested, sir.

A leading-name router resolves each message to the right session.

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Demo

# session boot — the model is told to pick its own name
$ callsign banner
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
┃  CALLSIGN ▸ (awaiting your choice)                 ┃
┃  ⸺ Claude Code session: pick a name for yourself.  ┃
┃  run:  callsign claim <YourName>                   ┃
┃  see suggestions:  callsign suggest                ┃
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

# the agent decides on a name (it can pick ANY single human name) and claims it
$ callsign claim Vesper
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
┃  CALLSIGN ▸ VESPER                                  ┃
┃  ⸺ Claude Code session reporting in, sir.           ┃
┃  reply with 'Vesper, ...' to route iMessages here.  ┃
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

# from now on every outbound iMessage is signed
$ callsign send "patched and pushed, sir."
# delivers: "Vesper: patched and pushed, sir."

# inbound routing — daniel addresses a specific session by name
$ callsign route "Frank, redeploy the worker"
Frank → /Users/daniel/AI/wellrx_REDESIGN
redeploy the worker

# collisions are rejected cleanly
$ callsign claim Vesper          # from a different session
'Vesper' is already in use by another active session — pick a different name
  some unused suggestions: Maeve, Atlas, Sloane, Knox, Aurora

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Install

git clone https://github.com/heyfinal/callsign ~/GIT/callsign
cd ~/GIT/callsign
./install.sh

That writes three launchers into ~/.local/bin:

binary	role
callsign	CLI: assign, list, lookup, retire, route, send, banner, router
imsg-callsign	drop-in imsg send wrapper that auto-prefixes with $CALLSIGN
callsign-router-daemon	long-running incoming-iMessage router (launchd-friendly)

…plus a SessionStart hook at ~/.claude/hooks/callsign_session_start.sh.

Wire it into Claude Code by adding to ~/.claude/settings.json:

{
  "hooks": {
    "SessionStart": [
      {
        "matcher": "startup",
        "hooks": [{
          "type": "command",
          "command": "bash ~/.claude/hooks/callsign_session_start.sh"
        }]
      }
    ]
  }
}

Open a new Claude Code session. You'll see the banner and the model will know its name.

Uninstall: ./install.sh --uninstall.

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How the agent talks back

The SessionStart hook tells the model its callsign and instructs it to use callsign send (or imsg-callsign) for every outbound iMessage. The wrapper prepends {CALLSIGN}: automatically, so the model writes the body naturally — without restating its own name:

right	wrong
callsign send "patched and pushed, sir."	callsign send "Frank here — patched and pushed."
daniel sees Frank: patched and pushed, sir.	daniel sees Frank: Frank here — patched and pushed. (redundant)

The prefix is the identity. The body is just the message.

How addressing works

callsign route accepts the conventions you'd actually type on a phone:

message	resolves to
Frank, do X	Frank
frank: do X	Frank (case-insensitive)
FRANK do X	Frank (single space delimiter)
Frank — do X	Frank (em/en dash)
Hey Frank, do X	Frank (single honorific stripped)
do X	no hit → falls back to the lead session