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formats](/docs/extending/extensions/formats/)[Capability methods](/docs/extending/extensions/capabilities/)[Project sections](/docs/extending/extensions/project-sections/)[Server mounts](/docs/extending/extensions/server/)[Connectors](/docs/extending/extensions/connectors/)[Search indexes](/docs/extending/extensions/search/)[Security and secrets](/docs/extending/extensions/security/)[Tutorial: a TOML format](/docs/extending/extensions/tutorial-toml-format/)[Tutorial: a guestbook](/docs/extending/extensions/tutorial-guestbook/)[First-party extensions](/docs/extending/extensions/first-party/)Embedding[Overview](/docs/extending/embedding/)[Hosting the Studio assets](/docs/extending/embedding/hosting/)[Writing a platform adapter](/docs/extending/embedding/platform-adapter/)[The backend protocol](/docs/extending/embedding/backend-protocol/)[Dev server internals](/docs/extending/embedding/dev-server/)[Embedding the runtime in your app](/docs/extending/embedding/runtime-host/)[Writing assistant tools](/docs/extending/embedding/assistant-harness/)UI kit[The Jx UI kit](/docs/extending/ui-kit/)Reference[Protocol routes](/docs/extending/reference/studio-routes/)[Implementation status](/docs/extending/reference/implementation-status/)[Spec changelog](/docs/extending/reference/spec-changelog/)[Standards alignment](/docs/extending/reference/standards/)Contributing[Working in the monorepo](/docs/extending/contributing/monorepo/)[Contributing to these docs](/docs/extending/contributing/docs/)[AI assistant evals](/docs/extending/contributing/ai-evals/) # Server mounts An extension class contributes live routes to a deployed Jx site (and to the dev server) when its descriptor carries a top-level `server` object plus a `mount` capability. That is the whole admission test: no plugin API to register against, no HTTP framework to adopt. The generated site worker and the dev server both discover the block through the [extension registry](/docs/extending/extensions/anatomy) and dispatch requests to the handler your `mount` method returns. This page covers the declaration, the handler contract, how mounts cooperate through the shared context, and the section-owner `deploySchema` hook that lets a mounted section contribute to schema pushes. ## The server block The auth extension's section class, `extensions/auth/src/Auth.class.json`, declares its mount in one line: ```json shiki ``` | Key | Meaning | | ---------- | ------------------------------------------------------------------------------------------------------ | | `basePath` | The route subtree this mount owns. Must be under `/_jx/`. Conflicts are a registry error. | | `order` | Mount order (ascending). Earlier mounts run first and may populate the shared context. | | `module` | Bare specifier the generated worker imports, which survives bundling; falls back to `$implementation`. | Every mount lives under `/_jx/` (the reserved subtree for extension routes on a running site), and each `basePath` has exactly one owner. Two extensions claiming the same subtree fail the registry build instead of shadowing each other. ## The mount capability `mount` is a static [capability method](/docs/extending/extensions/capabilities) with `timing: ["server"]`. It returns a **fetch-style handler**: ```ts shiki ``` You need no HTTP framework: the generated worker wraps each handler itself (`app.all('/*', c => handler(c.req.raw, c.env))`), and the dev server dispatches to it directly. `mount(options, ctx)` receives: - `options`: JSON inlined at generation time, plus host-provided values (the section manifest, resolved class constructors). Because it is baked into the worker, it may carry identifiers only, never secret values. See [Security and secrets](/docs/extending/extensions/security). - `ctx`: the shared server context, described below. Here is the auth extension's real mount, abbreviated from `extensions/auth/src/worker.ts`: ```ts shiki ``` The pattern to copy: set up per-isolate state in the closure, publish anything later mounts need onto `ctx`, and return the handler. Secret values (the signing secret, database URLs) never appear here. They arrive through `env` on each request. ## Mount order and the shared context Each worker isolate creates **one** mutable `JxServerContext` object and passes it to every mount in ascending `order`. Mounts communicate through it: ```ts shiki ``` The first-party extensions demonstrate the choreography: the auth mount (order 10) sets `ctx.auth`; the connector's data mount (order 20) consumes it to evaluate table permission rules. Pick an order above the mounts you depend on: the guestbook example mounts at order 30 so both hooks are already in place. **Fail-closed rule**: a mount that gates writes on authorization must deny everything except explicitly-public rules when `ctx.auth` is absent. The data mount does exactly this. Without the auth extension, only `public` permission rules pass. The connector's data mount is the canonical consumer, serving the wire contract every table rides on: ```text GET /_jx/data/:table ?filter=&sort=&limit=&offset=&include= GET /_jx/data/:table/:id POST /_jx/data/:table PATCH /_jx/data/:table/:id DELETE /_jx/data/:table/:id ``` Note The dev server constructs mounts the same way the generated worker does, so `jx dev` exercises the identical code path, including `ctx` ordering and the fail-closed behavior. See [The dev server](/docs/extending/embedding/dev-server) . ## Section-owner deploySchema Connector classes declare a `deploySchema` capability to sync tables ([Connectors](/docs/extending/extensions/connectors)). A **non-connector**[project-section class](/docs/extending/extensions/project-sections) may declare one too, letting its section contribute steps to the schema push (`jx db push`, the Studio push button). The signature differs, because there is no single connection definition to hand over: ```text deploySchema(sectionValue, projectConfig, { env, dryRun?, connection?, connectors? }) → { steps, applied, warnings, connection } ``` - `steps` are ready push-plan entries (`{ kind, table?, summary, sql?, connection? }`). Hosts append them **after** the connector plan and default each step's `kind` to the contributing section key. The auth extension's Better Auth system-table migration lands as `kind: "auth"` steps this way. - `connectors` carries the same provider stand-ins the mounts receive, so dev pushes hit the `local:` stand-in databases. - When a push is filtered to a `connection` the section does not live on, return empty steps. Hosts stay extension-agnostic throughout: registry dispatch only, no extension imports, no hardcoded section names. `Auth.deploySchema` in `extensions/auth/src/worker.ts` is the working reference. ## Related - [Capability methods](/docs/extending/extensions/capabilities): roles, `timing`, and how hosts invoke statics. - [Security and secrets](/docs/extending/extensions/security): why mount options carry identifiers only. - [Tutorial: a guestbook extension](/docs/extending/extensions/tutorial-guestbook): a mount built end to end. - [Protocol route reference](/docs/extending/reference/studio-routes): the `/__studio/*` routes, a separate surface from `/_jx/*` mounts. ✕ Start here[Overview](/docs/start/)Get started[Install Jx Studio](/docs/start/install/)[Your first project](/docs/start/first-project/)[A tour of Jx Studio](/docs/start/studio-tour/)Tutorials[Tutorial: interactive component](/docs/start/first-component/)[Tutorial: blog with collections](/docs/start/first-collection/)[Video 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search](/docs/framework/site/search/)[Build output and adapters](/docs/framework/site/deployment/)How compilation works[Overview](/docs/framework/build/)[The dev server](/docs/framework/build/dev-server/)[CLI commands](/docs/framework/build/cli/)Working with agents[Overview](/docs/framework/agents/)[Authoring rules for agents](/docs/framework/agents/authoring-rules/)[Machine-readable docs](/docs/framework/agents/machine-readable/)Reference[Overview](/docs/framework/reference/)[Formula catalog](/docs/framework/reference/formulas/)[Operator reference](/docs/framework/reference/operators/)Extending[Overview](/docs/extending/)Extensions[Extension anatomy](/docs/extending/extensions/anatomy/)[Schema composition](/docs/extending/extensions/schema-composition/)[Custom classes](/docs/extending/extensions/classes/)[Custom formats](/docs/extending/extensions/formats/)[Capability methods](/docs/extending/extensions/capabilities/)[Project sections](/docs/extending/extensions/project-sections/)[Server mounts](/docs/extending/extensions/server/)[Connectors](/docs/extending/extensions/connectors/)[Search indexes](/docs/extending/extensions/search/)[Security and secrets](/docs/extending/extensions/security/)[Tutorial: a TOML format](/docs/extending/extensions/tutorial-toml-format/)[Tutorial: a guestbook](/docs/extending/extensions/tutorial-guestbook/)[First-party extensions](/docs/extending/extensions/first-party/)Embedding[Overview](/docs/extending/embedding/)[Hosting the Studio assets](/docs/extending/embedding/hosting/)[Writing a platform adapter](/docs/extending/embedding/platform-adapter/)[The backend protocol](/docs/extending/embedding/backend-protocol/)[Dev server internals](/docs/extending/embedding/dev-server/)[Embedding the runtime in your app](/docs/extending/embedding/runtime-host/)[Writing assistant tools](/docs/extending/embedding/assistant-harness/)UI kit[The Jx UI kit](/docs/extending/ui-kit/)Reference[Protocol routes](/docs/extending/reference/studio-routes/)[Implementation status](/docs/extending/reference/implementation-status/)[Spec changelog](/docs/extending/reference/spec-changelog/)[Standards alignment](/docs/extending/reference/standards/)Contributing[Working in the monorepo](/docs/extending/contributing/monorepo/)[Contributing to these docs](/docs/extending/contributing/docs/)[AI assistant evals](/docs/extending/contributing/ai-evals/) [![Jx Suite](/favicon.svg) Suite](/)The visual IDE for the web. 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