Query Layer

Query Layer Patterns

Reference Repositories

• TanStack Query: async state management for data fetching

Upstream Grounding

When TanStack Query behavior, Svelte adapter types, cache invalidation semantics, optimistic updates, or mutation lifecycle callbacks affect correctness, ask DeepWiki a narrow question against TanStack/query before relying on memory. Use it to orient, then verify decisive details against local installed types, source, or official docs before changing code.

Skip DeepWiki for stable basics and repo-local patterns already documented below.

The query layer is the reactive bridge between UI components and the service layer. It wraps service functions or observable operations with caching, mutation lifecycle state, invalidation, and direct imperative access using TanStack Query and Wellcrafted factories.

Related Skills: See services-layer for the service layer these queries consume. See svelte for Svelte-specific TanStack Query patterns. See error-handling for toast/report patterns after Results reach the UI boundary.

Core Architecture

Copy code
┌─────────────┐     ┌─────────────┐     ┌──────────────┐
│     UI      │ --> │    Query    │ --> │   Services   │
│ Components  │     │    Layer    │     │  (UI-free)   │
└─────────────┘     └─────────────┘     └──────────────┘
      ↑                    │
      └────────────────────┘
         Reactive Updates

Query Layer Responsibilities:

• Call services with injected settings/configuration
• Preserve typed service and operation errors unless the adapter introduces a new local failure
• Manage TanStack Query cache for optimistic updates
• Provide hook-ready .options for shared definitions and explicit imperative APIs where they exist
• Own shared cache identity through exported *Keys maps

Wellcrafted Query API Shape

Use resultQueryOptions and resultMutationOptions at one hook call site when a Result-returning function needs to enter TanStack's data/error channels and no imperative API or shared query identity is needed.

The adapters unwrap internally (Ok.data is returned, Err.error is thrown). Pass the Result-returning function; do not unwrap first.

Use defineQuery and defineMutation in shared $lib/queries modules.

Queries expose .options, .fetch(), and .ensure(). They are not callable.

Mutations expose .options and are callable. They do not expose .execute().

Canonical Whispering Query Module Shape

The Whispering query modules these examples came from were removed when Whispering became a standalone file-folder app with no query layer. The shape is still the convention for a $lib/queries module in an app that has one.

For Whispering-style $lib/queries modules, keep source-of-truth declarations close to the work they describe. Factories receive the session-owned runtime explicitly:

typescriptCopy code
export const audioKeys = defineKeys({
	availability: (id: string, blobId: string, uploadedAt: string | null) =>
		['audio', 'availability', id, blobId, uploadedAt] as const,
});

export function createAudioQueries({ defineQuery }: WhisperingQueryRuntime) {
	return {
		availability: (recording: Accessor<Recording>) =>
			defineQuery({
				queryKey: audioKeys.availability(
					recording().id,
					recording().audioBlobId,
					recording().uploadedAt,
				),
				queryFn: () => getRecordingAudioAvailability(recording()),
			}),
	};
}

Rules:

• Export *Keys = defineKeys({ ... }) beside the adapter or state module that owns the work.
• Static keys do not need as const; key factories use as const when literal positions matter.
• Keep keys in the owning module unless another layer needs the same fallback identity.
• Inline small single-use input objects. Name an input type only when it is reused, exported, large enough to obscure the function, or carries domain meaning. Put named input types immediately before the adapter namespace that uses them.
• Keep adapter-local defineErrors namespaces local unless another module needs to name that exact union.

Adapter Boundary: Queries vs Operations

Use $lib/queries as the shared TanStack observation surface. It may wrap a direct service/state call, or a $lib/operations entry point when UI needs shared mutation identity: multiple consumers, cache invalidation, optimistic updates, useIsMutating, or a named mutation key over that operation.

Keep orchestration in $lib/operations: delivery, sounds, analytics, clipboard writes, and multi-step workflows. A reusable operation returns its outcome; a terminal interaction controller may also report it. Do not promote a one-component operation into $lib/queries merely to observe local pending state. The svelte skill owns the component's choice between local createMutation and direct await.

Dependency Direction

txtCopy code
UI -> operations/* -> services/* + state/* + $lib/tauri
UI -> queries/*    -> services/* or operations/*, plus narrow state reads/writes for observed lifecycle

Query modules receive the session-owned query runtime and import services, state, or operations. They do not import sibling query modules just to sequence work; cross-adapter coordination belongs in operations.

Error Flow

In Whispering, service and operation errors are already tagged errors. Query adapters pass them through. The UI/report boundary decides how to present them.

txtCopy code
Service / Operation       ->  Query Adapter     ->  UI / Report
TaggedError<'Name'>           same error            report.error({ cause: error })

Only define a query-local error when the adapter itself discovers a failure that no lower layer can own, such as a missing recording lookup before calling an operation.

Reactive And Imperative Use

Query-layer adapters provide reactive hook usage and explicit imperative usage.

Reactive Interface: .options

Shared query adapters expose .options as a static object. Svelte hooks read it inside an accessor:

svelteCopy code
<script lang="ts">
	import { createQuery, createMutation } from '@tanstack/svelte-query';
	import { getWhisperingQueries } from '$lib/whispering/context';

	const queries = getWhisperingQueries();
	const availability = createQuery(() =>
		queries.audio.availability(() => recording).options,
	);

	const transcribeRecording = createMutation(
		() => queries.transcription.transcribeRecording.options,
	);
</script>

{#if availability.isPending}
	<Spinner />
{:else if availability.error !== null}
	<Error message={availability.error.message} />
{:else}
	<AvailabilityBadge value={availability.data} />
{/if}

Imperative Interface: Queries Choose Cache Policy, Mutations Are Callable

Use outside component context, or whenever the caller needs a direct Result:

typescriptCopy code
// In an event handler or workflow
async function handleDownload(recording: Recording) {
	const { error } = await queries.download.downloadRecording(recording);
	if (error !== null) {
		report.error({ cause: error });
		return;
	}
	report.success({ title: 'Recording downloaded' });
}

// In a sequential workflow
async function stopAndTranscribe(toastId: string) {
	const { data: url, error: playbackUrlError } =
		await queries.audio.availability(() => recording).fetch();

	if (playbackUrlError !== null) {
		report.error({ cause: playbackUrlError });
		return;
	}

	// Continue with transcription...
}

Use .fetch() when TanStack should evaluate the query's normal staleness policy: fresh cached data may still be returned without a request. Use .ensure() when any cached data is acceptable and fetching is only required when the cache is empty.

When to Use Each

For local component operation placement and lifecycle decisions, use the svelte skill's mutation guidance.

Key Rules

1. Use defineKeys for shared cache identity - Export the key map beside the owner
2. Use .options (no parentheses) - It's a static object, wrap in accessor for Svelte
3. Do not translate tagged errors by default - Pass service/operation errors through to the report boundary
4. Services receive explicit app inputs - The consuming edge injects settings and device config
5. Keep component lifecycle policy in svelte - This skill owns shared adapter shape and cache behavior
6. Update cache deliberately - Use optimistic writes only when the cache owner and rollback path are explicit; otherwise invalidate or refetch

References

Load these on demand based on what you're working on:

• If working with error pass-through examples and anti-patterns, read references/error-transformation-patterns.md

• If working with runtime dependency injection and service selection, read references/runtime-dependency-injection.md

• If working with cache management, query definitions, RPC namespace, or notify coordination, read references/advanced-query-patterns.md

• See the services-layer skill for how services are implemented

• See the error-handling skill for trySync/tryAsync patterns and toast-on-error conventions