---
url: >-
  https://lit-ui-router.dev/reference/ui-router-server/index/interfaces/MountConfig.md
---
[ui-router-server](../../index.md) / [ui-router-server](../index.md) / MountConfig

# Interface: MountConfig\<R>

Defined in: [index.ts:67](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L67)

One mount's routing configuration: its state tree, its redirects, and the
tier that resolves them. `R` is the type of `routes`; an `as const` array
types the router's delegate keys, response states and state names (see
[ServerRouter](ServerRouter.md)).

## Type Parameters

| Type Parameter | Default type |
| ------ | ------ |
|  `R` *extends* readonly [`RouteDeclaration`](../../redirects/interfaces/RouteDeclaration.md)\[] | readonly [`RouteDeclaration`](../../redirects/interfaces/RouteDeclaration.md)\[] |

## Properties

| Property | Type | Description | Defined in |
| ------ | ------ | ------ | ------ |
|  `config?` | [`RouteTableConfig`](../../redirects/interfaces/RouteTableConfig.md) | Url options (defaults: strict, case-sensitive, no squash, slashes as requested); 'simulate' mounts apply all but decodeParams. Hand the same object to [\`applyUrlConfig\`](../../url-config/functions/applyUrlConfig.md) on the client router so both sides compile and format urls alike. Under a `trailingSlash` policy, a url matching a state in the other spelling verdicts as a `308` redirect to the canonical one. | [index.ts:92](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L92) |
|  `ignoreDiagnostics?` | readonly `"bareBaseNotFound"`\[] | Diagnostic kinds this mount means to trip, turned off for it alone: the construction warning skips them and [diagnoseMounts](../functions/diagnoseMounts.md) omits them, so development and CI agree. A kind outside [MountDiagnosticKind](../type-aliases/MountDiagnosticKind.md) throws at construction. **Example** `import type { MountConfig } from 'ui-router-server'; // /api owns its bare base and answers it with a 404 on purpose. const mounts = { '/api': { routes: [{ name: 'item', url: '/items/:id' }], ignoreDiagnostics: ['bareBaseNotFound'], }, } satisfies Record<string, MountConfig>;` | [index.ts:161](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L161) |
|  `otherwise?` | { `state`: `string`; } | Projection of the client's otherwise() rule. `state` references a declared, url-less state (url-less so the unmatched url stays in the address bar, like a server 404 — mirroring the real rule's semantics). When declared, unknown paths under this mount verdict as shell with status 404: the resource genuinely doesn't exist and the shell IS the error page (never 200) — the client boots at the retained path and its own otherwise rule renders the rich notFound state. Redirect rules and route matches take precedence; undeclared keeps the notFound verdict. | [index.ts:122](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L122) |
| `otherwise.state` | `string` | Name of the declared, url-less state unknown paths verdict as. | [index.ts:124](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L124) |
|  `prewarm?` | `number` | Idle headless routers a 'simulate' mount builds once @uirouter/core loads, so its first requests skip the cold build. Default 0: the pool builds on demand. An integer from 0 to 16 (the pool's idle cap); any other value, or a positive count on a 'matcher' mount, throws at construction. A failed prewarm build is dropped silently and requests build on demand. The builds chain onto the import that construction starts, ahead of every request on the mount, so the first request never races them and there is nothing extra to await. In a Cloudflare Worker that constructs its router at module scope, the builds may run during startup: they do no I/O, timers or randomness, so global scope permits them, but their CPU counts toward the Worker's startup time limit. | [index.ts:141](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L141) |
|  `redirects?` | [`RedirectRule`](../../redirects/interfaces/RedirectRule.md)\[] | when()-style pattern rules, evaluated before per-state redirectTo entries. | [index.ts:73](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L73) |
|  `routeIndex?` | [`RouteIndex`](../../redirects/type-aliases/RouteIndex.md) | How a 'matcher' mount looks up the route a pathname matches. Default: a linear scan that tries every route. [routeTrie](../variables/routeTrie.md) walks a segment trie to the few routes whose spelling fits, with the same verdicts, and throws at construction for a route it can't express. Only the index a mount names is bundled. On a 'simulate' mount it throws at construction. **Example** `import { routeTrie } from 'ui-router-server'; import type { MountConfig } from 'ui-router-server'; const app: MountConfig = { routes: [{ name: 'home', url: '' }, { name: 'item', url: '/items/:id' }], routeIndex: routeTrie, };` | [index.ts:111](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L111) |
|  `routes` | `R` | The mount's state tree; dotted names nest, urls append (see [RouteDeclaration](../../redirects/interfaces/RouteDeclaration.md)). | [index.ts:71](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L71) |
|  `strategy?` | `"matcher"` | `"simulate"` | 'matcher' (default): dependency-free pattern matching plus data redirects. 'simulate': replay through a headless @uirouter/core router — the tier where routing that data cannot express (hooks, resolves, redirectTo functions) will live. Those are NOT yet reachable through MountConfig: both strategies consume the same [RouteDeclaration](../../redirects/interfaces/RouteDeclaration.md) data subset today, deliberately, so strategy stays a pure cost knob; the config widens later (e.g. an auth tier). | [index.ts:83](https://github.com/simshanith/lit-ui-router/blob/740888c2b2ba358c4dfa52a122e927df6a604b12/packages/ui-router-server/src/index.ts#L83) |