Photon iMessage platform plugin

This plugin connects Hermes Agent to iMessage (and other Spectrum interfaces) through Photon — a managed service that handles iMessage line allocation, delivery, and abuse-prevention so users don't have to run their own Mac relay.

The free tier uses Photon's shared iMessage line pool and is the path we recommend for everyone who doesn't already pay for a dedicated number.

Architecture

Like Discord and Slack, Photon is a persistent-connection channel — no public URL, no webhook, no signing secret. The spectrum-ts SDK holds a long-lived gRPC stream to Photon for both directions. Because the SDK is TypeScript-only, Hermes runs it inside a small supervised Node sidecar and talks to it over loopback.

                         gRPC (spectrum-ts)
┌─────────────────────────┐ ◄───────────────► ┌──────────────────────┐
│  Photon Spectrum cloud  │   app.messages    │  Node sidecar        │
│  (iMessage line owner)  │   space.send()    │  (plugins/…/sidecar) │
└─────────────────────────┘                   └──────────┬───────────┘
                                       GET /inbound (NDJSON) │  ▲ POST /send
                                       inbound events        ▼  │ /typing
                                              ┌──────────────────────┐
                                              │  PhotonAdapter        │
                                              │  (Python, in gateway) │
                                              └──────────────────────┘

• Inbound: the sidecar consumes the SDK's app.messages gRPC stream, normalizes each message, and streams it to the adapter over a loopback GET /inbound (NDJSON). The adapter dedupes on messageId and dispatches a MessageEvent to the gateway. It reconnects automatically if the stream drops; the sidecar owns the gRPC reconnect to Photon.
• Outbound: send / send_typing are loopback POSTs to the sidecar, authenticated with a shared X-Hermes-Sidecar-Token.

First-time setup

# One-shot setup: device login (opens browser) + project + user + sidecar deps
hermes photon setup --phone +15551234567

# Start the gateway
hermes gateway start --platform photon

hermes photon setup does, in order:

1. Device login (RFC 8628, client_id=photon-cli) — opens https://app.photon.codes/ for approval and stores the bearer token.
2. Find or create the Hermes Agent project on the Photon dashboard.
3. Enable Spectrum, read the project's spectrumProjectId, rotate the project secret, and persist both.
4. Register your phone number as a Spectrum user (idempotent — skipped if a user with that number already exists).
5. Print the assigned iMessage line — the number you text to reach your agent.
6. Install the sidecar deps (spectrum-ts).

There is no separate login command; like every other Hermes channel, onboarding goes through one setup surface. Re-running setup reuses an existing token/project, so it's safe to run again to finish a partial setup. Run hermes photon status to see what's configured.

Credentials

Runtime SDK credentials live in ~/.hermes/.env (the same place every other channel keeps its token), and the adapter reads them from the environment:

PHOTON_PROJECT_ID=<spectrumProjectId>   # the SDK's projectId
PHOTON_PROJECT_SECRET=<projectSecret>

Management metadata lives in ~/.hermes/auth.json under credential_pool:

{
  "credential_pool": {
    "photon": [
      { "access_token": "<device-bearer>", "issued_at": ... }
    ],
    "photon_project": [
      {
        "dashboard_project_id": "<dashboard id>",
        "spectrum_project_id": "<spectrumProjectId>",
        "project_secret": "<projectSecret>",
        "name": "Hermes Agent"
      }
    ]
  }
}

Note on ids. A Photon project has two identifiers: the dashboard id (used for management API calls) and the spectrumProjectId (what the SDK authenticates with). PHOTON_PROJECT_ID is the spectrum id.

Configuration knobs

All env vars are documented in plugin.yaml. The most important:

Attachments & limitations

• Inbound attachments and voice notes are downloaded. The sidecar reads the bytes (content.read()) and base64-inlines them on the NDJSON event; the adapter caches them to the shared media cache and populates media_urls / media_types, so the agent sees the real image/file or can transcribe the voice note — parity with the BlueBubbles iMessage channel. Media larger than PHOTON_MAX_INLINE_ATTACHMENT_BYTES (default 20 MB), or any byte read that fails, falls back to a text marker ([Photon attachment received: …] or [Photon voice received: …]) so the agent still knows something arrived.
• Outbound attachments are supported. Images, voice notes, video, and documents are sent via space.send(attachment(...)) / space.send(voice(...)) through the sidecar's /send-attachment endpoint; a caption is delivered as a separate text bubble after the media.
• Reactions, message effects, polls — supported by spectrum-ts but not yet exposed; the sidecar is the natural place to add them.