---
name: super-app
description: Build shared-host, shared-API super apps with tenant-specific UI composition. Use when setting up a base runtime plus custom tenant apps, configuring fixed-core multi-tenancy, reasoning about extends-based runtime lineage, or deciding what tenants can override today.
metadata:
  sources: "host/src/services/tenant-runtime.ts,host/src/services/binding-resolver.ts,host/src/program.ts,host/src/services/federation.server.ts,packages/everything-dev/src/config.ts"
---

# Super Apps

Use this skill for the shared-host pattern where one runtime owns the host, auth, API, and base plugin set, while many descendant runtimes extend that runtime and swap UI-facing pieces per request.

## Mental Model

- `extends` is the lineage edge between runtimes.
- `account` is the tenant namespace root for the currently active runtime.
- `domain` is the public ingress for that runtime, not the lineage key.
- A runtime may be both a child in lineage and a tenant root operationally on its own domain.
- In fixed-core mode, the host, auth, API, and server-side plugins stay fixed to the active base runtime.
- Tenant-specific UI composition is applied per request.

Example mapping:
- `pingpay.io` -> base runtime `bos://pingpayio.near/pingpay.io`
- `pizza.com` -> runtime `bos://pizza.pingpayio.near/pizza.com` that extends `bos://pingpayio.near/pingpay.io`
- `chicago.pizza.com` should resolve inside the `pizza.pingpayio.near` namespace as `bos://chicago.pizza.pingpayio.near/pizza.com`

## What Works Today

Supported tenant overrides in fixed-core mode:
- `app.ui`
- existing `plugins.<id>.ui`
- existing `plugins.<id>.sidebar`

Still fixed to the base runtime:
- `app.host`
- `app.api`
- `app.auth`
- server-side plugin loading and router mounting

Not part of this mode:
- tenant-specific API overrides
- tenant-specific auth overrides
- introducing new plugin IDs dynamically per tenant
- full per-request host/plugin/auth/api hot swap

## Setup Flow

### 1. Create the base runtime

The base runtime owns the shared host and API surface:

```bash
bos init --overrides ui,api,host
```

This app is the one you deploy as the shared host.

### 2. Publish the base runtime

The base runtime must be published before tenants can extend it:

```bash
bos publish --deploy
```

### 3. Create a descendant runtime that extends the base runtime

Child runtime authored config:

```json
{
  "extends": "bos://pingpayio.near/pingpay.io",
  "account": "pizza.pingpayio.near",
  "domain": "pizza.com",
  "repository": "https://github.com/example/pizza-app",
  "app": {
    "ui": {
      "name": "ui",
      "development": "local:ui",
      "production": "https://cdn.example.com/pizza-ui",
      "integrity": "sha384-..."
    }
  }
}
```

This runtime is still a lineage child because it extends the parent, but it is also its own tenant root when served from `pizza.com`.

You can also override existing plugin UIs and sidebar entries for tenant-specific navigation.

## Host Resolution For Tenant Mode

The shared host resolves tenant permissions from the API, not env vars. It fetches the tenant bindings map from the API's `GET /tenants/bindings` endpoint (cached for 30s) and applies DB-backed per-tenant permissions:

- `allow_ui_overrides` controls whether the tenant `ui` override can affect request-scoped composition
- `allow_backend_overrides` controls whether tenant plugin UI overrides (`plugins.<id>.ui`, `plugins.<id>.sidebar`) are applied
- `allow_ssr` controls whether the tenant may use SSR

## Resolution Rules

Design target:
- bare domain serves the active runtime
- subdomains resolve within the active runtime account namespace
- nested labels should compose onto the active runtime account
- a runtime with its own account and domain becomes a new tenant root operationally, even when it extends another runtime

Current implementation limits:
- the shared host still resolves one tenant overlay on top of a process-wide base runtime
- fixed-core mode still only applies UI-facing overrides
- nested label resolution and account-relative tenant derivation are the desired model for future work, not the fully implemented resolver today

The tenant config must:
- exist in FastKV
- extend the base runtime
- resolve to the expected account for that active namespace
- provide integrity for overridden remote UIs

## Security Model

- Tenant UI overrides are integrity-checked before trust is established.
- Integrity verification uses bounded streaming, not full-response buffering.
- Asset requests use stale-while-revalidate verification to avoid latency spikes.
- HTML and SSR requests use blocking verification.
- SSR module cache identity includes `ssrIntegrity`, not just the SSR URL.
- **On integrity failure**: the host rejects the remote entry. HTML and SSR requests block immediately; asset requests fall back. The page renders client-side without the failed remote.

## Tenant Config Caching

The host caches resolved tenant configs in memory. Cache TTL is managed by the tenant runtime service (`host/src/services/tenant-runtime.ts`). After publishing tenant config changes, a host restart is typically required to pick up fresh config unless the cache TTL has expired.

## Debugging Tenant Resolution

If tenant overrides are not applying as expected:

1. **Verify the tenant config exists in FastKV**: The config must be published to `{tenantAccount}/bos/gateways/{gateway}/bos.config.json`
2. **Check extends chain**: The tenant config must extend the base runtime via its `extends` field
3. **Check host logs**: Run `cat .bos/logs/host.log` and look for tenant resolution messages — the host logs which runtime config it resolved for each request
4. **Check tenant permissions**: the tenant record must have the relevant allow flag set in the database (e.g., `allow_ui_overrides` for a `ui` override, `allow_backend_overrides` for plugin UI overrides)
5. **Verify integrity**: If tenant remote URLs have integrity hashes, the host validates them — mismatches cause rejection
6. **Missing tenant config**: If the tenant config is not found in FastKV, the host silently serves the base runtime config without tenant overrides — no error is surfaced to the browser

### Diagnostics

- `bos info` shows the active runtime configuration loaded by the CLI
- The host logs the resolved tenant account per request at startup
- Compare the tenant's published config against the base runtime using `bos info` in the tenant project directory

## Recommended Workflow

For the base runtime:

```bash
bos dev
bos publish --deploy
```

For a shared-host child UI app:

```bash
bos dev --api remote
bos publish --deploy
```

After publishing config changes that affect the base host runtime, restart the host process so it reloads the latest base config snapshot.

## When To Load Other Skills

- Use `everything-dev#init-upgrade` for scaffold/sync/upgrade mechanics.
- Use `everything-dev#extends-config` for deep-merge and resolved-config semantics.
- Use `everything-dev#publish-sync` for publish and deploy steps.
- Use this `super-app` skill when the question is specifically about the shared-host, shared-API multi-tenant architecture.

## The tasks you will actually be given

**"Set up a shared-host tenant."** Base: `bos init --overrides ui,api,host` then `bos publish --deploy`. Child: authored config with `extends` + its own `account`/`domain`, override `app.ui` only, publish it; register the tenant row with the right allow flags in the DB.

**"Tenant overrides are not applying."** Walk the checklist in order: config exists in FastKV → extends the base runtime → tenant record allow flags set → host logs (`cat .bos/logs/host.log`) → integrity hashes on the tenant remotes valid.

**"This tenant needs SSR."** Set `allow_ssr` on the tenant record — the host's BindingResolver reads permissions from `GET /tenants/bindings` (cached 30s); without the flag the tenant falls back to client rendering.

## What comes back when it refuses

| word | do |
|---|---|
| tenant config missing in FastKV | the host silently serves the base runtime — no error surfaces to the browser; verify the published path and the signer namespace |
| `Tenant resolution is unavailable: the API plugin failed to load` | the BindingResolver can't reach `/api/tenants/bindings` — check `GET /api/_health` and the startup plugin-load errors, republish the API |
| integrity rejection of a tenant remote | HTML/SSR requests block immediately, assets fall back — redeploy the tenant bundle and republish so the SRI matches |
| overrides still stale after publishing | the host boots one base snapshot and caches tenant configs — restart the host (or wait out the cache TTL) |