# mesh-sdk

The stable spine a Novox Mesh **module's own code builds against** — the tool it uses to plug
into the mesh, and nothing that belongs to a specific module or to another tier.

It earns its place by **rarely changing** (novox/hq [ADR 0039](https://git.novox.be/novox/hq)).
The test for anything here: *if editing it recompiles unrelated modules and it changes often, it
does not belong.* Per-module code (a service's API client, its tool implementations, its
create-a-resource adapter) lives **in the module**, never here — that coupling is exactly what
turned the old SDK into constant maintenance and made every edit rebuild every module.

## What is in it

Five small areas, each a thing a module's `tools/` or `provisioner/` imports:

### `contracts` — the runtime shapes module code touches
Not the manifest schema (the control plane owns and parses that, in Go). The shapes a module's
*running code* receives and returns: a provisioning **grant** and its credentials, the
**mesh interface** definitions (what an `analytics` grant contains, what an `oidc-client` grant
contains — the contract both a provider and a consumer conform to), and the tool and event types.
These change rarely and deliberately; when one does, a rebuild of everything is *correct*.

### `provisioner` — the reconcile harness every provider shares
The loop is identical for postgres, redis, minio and umami: watch the grants directory, for each
requested grant call the provider's adapter, write the sealed credential, handle withdrawal, and
keep converging (`watch`). That loop lives here. A **module provides only the adapter** — "create
a database", "create a umami site" — which is the volatile, per-service half and belongs in the
module. This is the ADR 0039 line drawn through provisioning: stable loop here, per-service create
in the module.

### `tools` — the tool-serving harness
`registerModuleTools`, the `ToolDefinition` type, and the registry/worker that loads a module's
tools and exposes them through the mesh's command surface. *How* a tool is declared and served is
settled; it does not change when an individual tool does. The tools themselves, and the API client
they call, live in the module.

### `messaging` — the broker and event framework
The broker client (connect, request/reply, publish/subscribe), the event-consumer a module uses to
react to mesh events, and the envelope/routing-key conventions. Transport primitives.

### `primitives` — sealing, semver, resolved-env
Seal/unseal for secrets, semantic version comparison, and the accessor a module uses to read its
own resolved environment.

## What is NOT in it, and where it goes

- **A module's API client and its tool implementations** → in the module. (The Plex client, the
  Umami client, `tools/plex.ts` — all module-local. ADR 0039.)
- **Delivery machinery** — build executor, bundler, dependency resolver, artifact manager, feature
  handlers → **mesh-controller**. It co-evolves with the pipeline.
- **Host synchronisers** — config-sync, ufw config, vhost generation, systemd, health checks →
  **mesh-host**'s apply engine. The host applies these; they are not module code.
- **Domain logic** — tasks, workflows, agents, provider integrations → **tier-2 contexts**.

That is why this stays small: everything volatile has somewhere else to be.

## Using it

A module's tools:

```ts
import { registerModuleTools, ToolDefinition } from "@novox/mesh-sdk/tools";
import { UmamiClient } from "../client.js"; // the client lives in the module, not here

registerModuleTools("umami", (env) => getUmamiTools(new UmamiClient(env.UMAMI_URL)));
```

A provider's provisioner:

```ts
import { runProvisioner, Grant, Credential } from "@novox/mesh-sdk/provisioner";

runProvisioner("analytics", {
  async create(grant: Grant): Promise<Credential> { /* create a umami site, return the grant */ },
  async remove(grant: Grant): Promise<void> { /* delete the site */ },
});
```

The adapter is the only thing the module writes; the watching, sealing and grant-file handling are
the harness's.

## Where the reasoning lives

Design and decisions are in [`novox/hq`](https://git.novox.be/novox/hq):

- `02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md` — the stability rule this repository is
- `02-DECISIONS/0040-what-a-module-is.md` — a module, and why its per-module code lives in the module