# Hermes Mobile Direct Gateway Architecture

Hermes Mobile is pivoting to a native Android client that talks directly to a remote upstream Hermes Agent gateway/API server. The `apps/companion` TypeScript server is legacy compatibility code and must not be required by Android or future releases.

## Architecture

```text
Android app
  Kotlin/Compose UI
  connection/auth storage
  transport DTOs
  domain repositories
        |
        | HTTPS, bearer token when configured
        v
Upstream Hermes Agent gateway/API server
  auth/session authority
  chat/completion authority
  streaming/tool/artifact authority
  provider credentials and Hermes runtime
```

The Android app remains a thin client. It may store server profiles, non-provider UI preferences, selected session IDs, and Android-secured bearer tokens. It must not embed provider credentials, clone Hermes backend behavior, or make the legacy companion server part of the release path.

## Documented Upstream Surface

The current repository/context documents these upstream Hermes API-server endpoints:

| Endpoint | Status | Mobile contract |
| --- | --- | --- |
| `GET /health` | Documented | Primary reachability and compatibility probe. Response shape beyond a successful JSON response is treated as server-specific. |
| `GET /v1/models` | Documented | Authenticated compatibility probe for bearer-token connections and future model picker source. |
| `POST /v1/chat/completions` | Documented | Baseline OpenAI-compatible chat path. Mobile must assume this may not expose Hermes session IDs or structured tool events. |
| `POST /v1/responses` | Documented | Preferred future request/streaming path if upstream exposes richer response events. Exact Hermes event mapping is not yet verified. |

These are the only upstream API-server routes currently treated as documented by this repository. Any route not listed here must be labeled provisional until checked against official Hermes Agent docs or a running gateway.

## Unverified Assumptions

The following are useful design assumptions, not confirmed contracts:

- Bearer authentication is accepted through an `Authorization: Bearer <token>` header on `/v1/*`.
- `/health` returns a stable `status` field.
- `/v1/responses` can provide enough streaming metadata to preserve Hermes sessions, tool lifecycle, artifacts, cancellation, and reconnect state.
- Hermes session listing, creation, continuation, and deletion have stable direct HTTP endpoints.
- Tool result and artifact listing/download have stable direct HTTP endpoints.
- Cancellation has a stable direct HTTP endpoint.
- Error payloads consistently include `message` or `error`.

Android contracts may model these needs, but implementation must keep them capability-gated until verified.

## Compatibility Policy

- Direct gateway routes are the default target for all new Android transport work.
- Legacy companion routes such as `/api/health`, `/api/auth/validate`, `/api/chat`, `/api/files/*`, and `/api/terminal/*` are temporary compatibility only.
- UI and domain terminology should say "gateway", "server", or "upstream Hermes" unless explicitly describing legacy companion behavior.
- The transport/domain model exposes direct gateway capabilities first. `legacyCompanionAdapter` exists only to identify old adapters during migration.
- Backend behavior belongs upstream in Hermes Agent. Hermes Mobile may add client adapters and mappers, not server-side replacements.

## Android Contract Milestones

1. Auth and connection: validate URL, store bearer tokens securely, probe `GET /health`, and use `GET /v1/models` as the first authenticated check.
2. Sessions: keep repository interfaces for list/create/select/continue, but mark route mapping provisional until upstream session docs are verified.
3. Streaming: support final response and token delta reduction now; gate structured tool/artifact/session events behind server capabilities.
4. Companion removal: after direct gateway chat/session/streaming works end to end, remove legacy companion UI routes and then deprecate install/docs around `apps/companion`.