feat: import a Calibre library

Reads metadata.db and copies the books into a library — from a zip uploaded on
the library settings page, or from a path with `litestar calibre-import`. The
source is never touched, and re-running only picks up what is new.

Also names the formats mimetypes does not know: a Calibre library is full of
MOBI and AZW3, and a null content type used to fail the book endpoint.

frontend/AGENTS.md

@@ -167,8 +167,11 @@ Observed in the current tree — don't mistake these for intentional patterns to
   `svelte/no-navigation-without-resolve` on plain `href`s, plus ~59 files Prettier would rewrite
   (mostly vendored shadcn components). Check the files you touched, not the whole tree.
 - `src/routes/api/[...path]/+server.ts` — all four handlers are annotated `RequestHandler` while the
-  import of that type is commented out at line 4. It also buffers whole responses with
-  `arrayBuffer()` and forwards no `Range` header, so book downloads are not streamed.
+  import of that type is commented out at line 4. It also buffers whole **responses** with
+  `arrayBuffer()` and forwards no `Range` header, so book downloads are not streamed. **Requests**
+  are streamed — POST and PATCH pass `request.body` through with `duplex: 'half'` (see `bodyOf`),
+  because a zipped Calibre library upload cannot be held in this process. The response side is
+  still buffered; see `TODO.md`.
 - `src/app.d.ts` — `App.Locals["user"]` is typed from `lucide-svelte`'s `User` _icon_ component
   rather than the `User` interface in `$lib/server/auth`.
 - No CSP, which foliate's README asks for because EPUBs can carry scripts. See `TODO.md` for why it

frontend/src/lib/api/calibre-import.remote.ts

@@ -0,0 +1,51 @@
+import { command, getRequestEvent, query } from '$app/server';
+import { error } from '@sveltejs/kit';
+
+import { stringCoerce } from '$lib/schema/common';
+import type { CalibreImport } from '$lib/schema/library';
+
+/** The backend's own message for a failed response, rather than its JSON envelope. */
+function detailOf(body: string): string {
+	try {
+		const parsed = JSON.parse(body);
+		return typeof parsed?.detail === 'string' ? parsed.detail : body;
+	} catch {
+		return body;
+	}
+}
+
+/**
+ * Where an import has got to.
+ *
+ * A `query` rather than a `command` so it can be refreshed, but it is polled on a timer
+ * rather than cached — the answer changes on its own.
+ *
+ * Starting an import is deliberately **not** here: the archive goes straight to the
+ * backend through the proxy, so it never passes through this process. See the import
+ * screen's `upload`.
+ */
+export const getCalibreImport = query(stringCoerce, async (jobId): Promise<CalibreImport> => {
+	const { locals } = getRequestEvent();
+
+	const response = await locals.api.get(`/libraries/imports/${jobId}`);
+
+	if (!response.ok) error(response.status, detailOf(await response.text()));
+
+	return await response.json();
+});
+
+/**
+ * Ask an import to stop after the book it is on.
+ *
+ * Not an abort: a book abandoned mid-copy would leave files on disk with no row
+ * describing them. Whatever it has imported stays imported.
+ */
+export const cancelCalibreImport = command(stringCoerce, async (jobId): Promise<CalibreImport> => {
+	const { locals } = getRequestEvent();
+
+	const response = await locals.api.delete(`/libraries/imports/${jobId}`);
+
+	if (!response.ok) error(response.status, detailOf(await response.text()));
+
+	return await response.json();
+});

frontend/src/lib/api/index.ts

@@ -2,6 +2,7 @@ export * from './auth.remote';
 export * from './author.remote';
 export * from './book.remote';
 export * from './bookshelf.remote';
+export * from './calibre-import.remote';
 export * from './library.remote';
 export * from './publisher.remote';
 export * from './tag.remote';

frontend/src/lib/schema/library.ts

@@ -19,3 +19,6 @@ export const libraryCreateSchema = z.object({
 
 export type LibraryQuerySchema = typeof libraryQuerySchema;
 export type LibraryCreateSchema = typeof libraryCreateSchema;
+
+export type CalibreImport = components['schemas']['CalibreImportRead'];
+export type ImportFailure = components['schemas']['ImportFailureRead'];

frontend/src/lib/schema/openapi/schema.d.ts

@@ -230,6 +230,24 @@ export interface paths {
         patch?: never;
         trace?: never;
     };
+    "/libraries/imports/{job_id}": {
+        parameters: {
+            query?: never;
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        /** GetImport */
+        get: operations["LibrariesImportsJobIdGetImport"];
+        put?: never;
+        post?: never;
+        /** CancelImport */
+        delete: operations["LibrariesImportsJobIdCancelImport"];
+        options?: never;
+        head?: never;
+        patch?: never;
+        trace?: never;
+    };
     "/libraries": {
         parameters: {
             query?: never;
@@ -248,6 +266,23 @@ export interface paths {
         patch?: never;
         trace?: never;
     };
+    "/libraries/{library_id}/imports/calibre/upload": {
+        parameters: {
+            query?: never;
+            header?: never;
+            path?: never;
+            cookie?: never;
+        };
+        get?: never;
+        put?: never;
+        /** UploadCalibreImport */
+        post: operations["LibrariesLibraryIdImportsCalibreUploadUploadCalibreImport"];
+        delete?: never;
+        options?: never;
+        head?: never;
+        patch?: never;
+        trace?: never;
+    };
     "/access/me": {
         parameters: {
             query?: never;
@@ -791,6 +826,30 @@ export interface components {
             skipped: components["schemas"]["DuplicateFileRead"][];
             possible_duplicates?: components["schemas"]["PossibleDuplicateRead"][];
         };
+        /** CalibreArchiveUpload */
+        CalibreArchiveUpload: {
+            /** Format: binary */
+            archive: string;
+            /** @default false */
+            allow_duplicates: boolean;
+        };
+        /** CalibreImportRead */
+        CalibreImportRead: {
+            id: string;
+            library_id: number;
+            source: string;
+            state: string;
+            total: number;
+            processed: number;
+            created: number;
+            skipped: number;
+            failed: number;
+            current_title?: string | null;
+            failures?: components["schemas"]["ImportFailureRead"][];
+            /** @default 0 */
+            possible_duplicates: number;
+            error?: string | null;
+        };
         /** DuplicateBookGroupRead */
         DuplicateBookGroupRead: {
             books: components["schemas"]["DuplicateBookRead"][];
@@ -831,9 +890,15 @@ export interface components {
             path: string;
             hash: string;
             size: number;
-            content_type: string;
+            content_type?: string | null;
             readonly filename: string;
         };
+        /** ImportFailureRead */
+        ImportFailureRead: {
+            calibre_id: number;
+            title: string;
+            reason: string;
+        };
         /** KosyncDeviceCreate */
         KosyncDeviceCreate: {
             name: string;
@@ -1686,6 +1751,80 @@ export interface operations {
             };
         };
     };
+    LibrariesImportsJobIdGetImport: {
+        parameters: {
+            query?: never;
+            header?: never;
+            path: {
+                job_id: string;
+            };
+            cookie?: never;
+        };
+        requestBody?: never;
+        responses: {
+            /** @description Request fulfilled, document follows */
+            200: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": components["schemas"]["CalibreImportRead"];
+                };
+            };
+            /** @description Bad request syntax or unsupported method */
+            400: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": {
+                        status_code: number;
+                        detail: string;
+                        extra?: null | {
+                            [key: string]: unknown;
+                        } | unknown[];
+                    };
+                };
+            };
+        };
+    };
+    LibrariesImportsJobIdCancelImport: {
+        parameters: {
+            query?: never;
+            header?: never;
+            path: {
+                job_id: string;
+            };
+            cookie?: never;
+        };
+        requestBody?: never;
+        responses: {
+            /** @description Request fulfilled, document follows */
+            200: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": components["schemas"]["CalibreImportRead"];
+                };
+            };
+            /** @description Bad request syntax or unsupported method */
+            400: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": {
+                        status_code: number;
+                        detail: string;
+                        extra?: null | {
+                            [key: string]: unknown;
+                        } | unknown[];
+                    };
+                };
+            };
+        };
+    };
     LibrariesListLibraries: {
         parameters: {
             query?: {
@@ -1772,6 +1911,47 @@ export interface operations {
             };
         };
     };
+    LibrariesLibraryIdImportsCalibreUploadUploadCalibreImport: {
+        parameters: {
+            query?: never;
+            header?: never;
+            path: {
+                library_id: number;
+            };
+            cookie?: never;
+        };
+        requestBody: {
+            content: {
+                "multipart/form-data": components["schemas"]["CalibreArchiveUpload"];
+            };
+        };
+        responses: {
+            /** @description Request accepted, processing continues off-line */
+            202: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": components["schemas"]["CalibreImportRead"];
+                };
+            };
+            /** @description Bad request syntax or unsupported method */
+            400: {
+                headers: {
+                    [name: string]: unknown;
+                };
+                content: {
+                    "application/json": {
+                        status_code: number;
+                        detail: string;
+                        extra?: null | {
+                            [key: string]: unknown;
+                        } | unknown[];
+                    };
+                };
+            };
+        };
+    };
     AccessMeGetUserInfo: {
         parameters: {
             query?: never;

frontend/src/lib/utils.ts

@@ -81,7 +81,10 @@ function isbnDigits(value: string) {
 }
 
 function identifierKey(name: string) {
-	return name.trim().toLowerCase().replace(/[\s_]+/g, '-');
+	return name
+		.trim()
+		.toLowerCase()
+		.replace(/[\s_]+/g, '-');
 }
 
 export function describeIdentifier(name: string, value: string) {
@@ -111,4 +114,17 @@ export function getFileType(filename: string) {
 	return extension.toUpperCase();
 }
 
+/**
+ * The formats there is a reader for. Everything else is download-only.
+ *
+ * A library imported from elsewhere carries MOBI, AZW3 and CBZ files, which are
+ * legitimate to store and to download but have nowhere to open — the reader routes
+ * are `read/epub` and `read/pdf` and there is no third one.
+ */
+const READABLE_FILE_TYPES = ['EPUB', 'PDF'];
+
+export function isReadable(filename: string) {
+	return READABLE_FILE_TYPES.includes(getFileType(filename));
+}
+
 export const pluck = (array: [], key: string) => array.map((obj) => obj?.[key]);

frontend/src/routes/(root)/(library)/book/[bookId]/+page.svelte

@@ -18,7 +18,13 @@
 		PlusIcon,
 		Trash2
 	} from '@lucide/svelte';
-	import { describeIdentifier, formatFileSize, getFileType, sortIdentifiers } from '$lib/utils.js';
+	import {
+		describeIdentifier,
+		formatFileSize,
+		getFileType,
+		isReadable,
+		sortIdentifiers
+	} from '$lib/utils.js';
 	import { getBookOperationsState } from '$lib/state/bookOperations.svelte.js';
 	import { getBookshelfState } from '$lib/state/bookshelf.svelte.js';
 	import { getLibraryState } from '$lib/state/library.svelte.js';
@@ -52,6 +58,11 @@
 		book.progress?.percentage ? Math.round(book.progress.percentage * 100) : 0
 	);
 
+	// Only the files there is a reader for. A book can be stored in a format Chitai
+	// cannot open — a Calibre library is full of MOBI and AZW3 — and offering to read
+	// one opened a window that did nothing at all.
+	const readableFiles = $derived(book.files.filter((file) => isReadable(file.filename)));
+
 	// The primary action states what it will actually do.
 	const readLabel = $derived(
 		book.progress?.completed
@@ -86,6 +97,10 @@
 		'inline-flex items-center gap-2 rounded-lg bg-primary-foreground px-4 py-2 text-sm font-semibold text-primary tabular-nums transition-colors hover:bg-primary-foreground/90';
 	const bandGhost =
 		'inline-flex items-center gap-2 rounded-lg border border-primary-foreground/35 px-4 py-2 text-sm font-medium transition-colors hover:bg-primary-foreground/10';
+
+	// With nothing to read, downloading is the only thing left to do — so it takes the
+	// primary slot rather than leaving the band with no filled button on it.
+	const bandDownload = $derived(readableFiles.length ? bandGhost : bandPrimary);
 </script>
 
 <div class="flex h-full flex-col overflow-y-auto">
@@ -132,9 +147,13 @@
 					</p>
 				{/if}
 
-				<!-- Primary actions live on the band, not in a side rail -->
+				<!--
+					Primary actions live on the band, not in a side rail. Read and Download
+					are counted separately: everything can be downloaded, only EPUB and PDF
+					can be opened, so a book can have two files and one way to read it.
+				-->
 				<div class="mt-5 flex flex-wrap items-center gap-2">
-					{#if book.files.length > 1}
+					{#if readableFiles.length > 1}
 						<DropdownMenu.Root>
 							<DropdownMenu.Trigger class={bandPrimary}>
 								<BookOpenText class="size-4" />
@@ -144,7 +163,7 @@
 								<DropdownMenu.Group>
 									<DropdownMenu.GroupHeading>File formats:</DropdownMenu.GroupHeading>
 									<DropdownMenu.Separator />
-									{#each book.files as file (file.id)}
+									{#each readableFiles as file (file.id)}
 										<DropdownMenu.Item onclick={() => openBookInReader(file)}>
 											{getFileType(file.filename)}
 										</DropdownMenu.Item>
@@ -152,9 +171,20 @@
 								</DropdownMenu.Group>
 							</DropdownMenu.Content>
 						</DropdownMenu.Root>
+					{:else if readableFiles.length === 1}
+						<button
+							type="button"
+							class={bandPrimary}
+							onclick={() => openBookInReader(readableFiles[0])}
+						>
+							<BookOpenText class="size-4" />
+							{readLabel}
+						</button>
+					{/if}
 
+					{#if book.files.length > 1}
 						<DropdownMenu.Root>
-							<DropdownMenu.Trigger class={bandGhost}>
+							<DropdownMenu.Trigger class={bandDownload}>
 								<Download class="size-4" />
 								Download
 							</DropdownMenu.Trigger>
@@ -181,16 +211,7 @@
 					{:else if book.files.length === 1}
 						<button
 							type="button"
-							class={bandPrimary}
-							onclick={() => openBookInReader(book.files[0])}
-						>
-							<BookOpenText class="size-4" />
-							{readLabel}
-						</button>
-
-						<button
-							type="button"
-							class={bandGhost}
+							class={bandDownload}
 							onclick={() =>
 								bookOps.downloadBookFile(book.id, book.files[0].id, book.files[0].filename)}
 						>
@@ -491,7 +512,7 @@
 											>
 											<Table.Cell class="text-right">
 												<div class="flex justify-end gap-1">
-													{#if getFileType(file.filename) === 'EPUB' || getFileType(file.filename) === 'PDF'}
+													{#if isReadable(file.filename)}
 														<Tooltip.Provider>
 															<Tooltip.Root ignoreNonKeyboardFocus>
 																<Tooltip.Trigger

frontend/src/routes/(root)/settings/libraries/[libraryId]/+layout.svelte

@@ -13,14 +13,14 @@
 		libraryState.libraries.find((lib) => String(lib.id) === page.params.libraryId)
 	);
 
-	// Duplicates is the only section today. The strip exists so General and a
-	// danger zone have an obvious place to land; neither is built yet, and an
-	// empty tab is worse than no tab.
+	// The strip exists so General and a danger zone have an obvious place to land;
+	// neither is built yet, and an empty tab is worse than no tab.
 	//
 	// Active state is matched on route id, not pathname, for the reason spelled
 	// out in settings/+layout.svelte.
 	const sections = [
-		{ title: 'Duplicates', routeId: '/(root)/settings/libraries/[libraryId]/duplicates' }
+		{ title: 'Duplicates', routeId: '/(root)/settings/libraries/[libraryId]/duplicates' },
+		{ title: 'Import', routeId: '/(root)/settings/libraries/[libraryId]/import' }
 	] as const;
 </script>
 

frontend/src/routes/(root)/settings/libraries/[libraryId]/import/+page.svelte

@@ -0,0 +1,367 @@
+<script lang="ts">
+	import { page } from '$app/state';
+	import { resolve } from '$app/paths';
+	import { onDestroy } from 'svelte';
+	import { toast } from 'svelte-sonner';
+	import { BookOpen, Loader2, TriangleAlert, Upload } from '@lucide/svelte';
+
+	import * as Card from '$lib/components/ui/card/index.js';
+	import * as Field from '$lib/components/ui/field/index.js';
+	import * as Table from '$lib/components/ui/table/index.js';
+	import { Button } from '$lib/components/ui/button/index.js';
+	import { Input } from '$lib/components/ui/input/index.js';
+	import { Checkbox } from '$lib/components/ui/checkbox/index.js';
+	import { Progress } from '$lib/components/ui/progress/index.js';
+	import { cancelCalibreImport, getCalibreImport } from '$lib/api/calibre-import.remote';
+	import { formatFileSize } from '$lib/utils';
+	import type { CalibreImport } from '$lib/schema/library';
+
+	const libraryId = $derived(page.params.libraryId!);
+
+	let archive = $state<File | null>(null);
+	let allowDuplicates = $state(false);
+
+	let job = $state<CalibreImport | null>(null);
+
+	let busy = $state(false);
+	let problem = $state<string | null>(null);
+
+	/** How much of the archive has reached the server, 0–1, while it is going up. */
+	let uploaded = $state<number | null>(null);
+
+	/** How often a running import is asked where it has got to. */
+	const POLL_MS = 1000;
+	let poll: ReturnType<typeof setInterval> | undefined;
+
+	const running = $derived(job?.state === 'running');
+
+	const percent = $derived(
+		job && job.total > 0 ? Math.round((job.processed / job.total) * 100) : 0
+	);
+
+	function stopPolling() {
+		clearInterval(poll);
+		poll = undefined;
+	}
+
+	onDestroy(stopPolling);
+
+	function pick(event: Event) {
+		const input = event.currentTarget as HTMLInputElement;
+		archive = input.files?.[0] ?? null;
+		problem = null;
+	}
+
+	/**
+	 * The backend's own message for a failed proxied response.
+	 *
+	 * The proxy wraps the upstream body in SvelteKit's error envelope, so the useful
+	 * `detail` is one or two layers down.
+	 */
+	function detailOf(body: string): string {
+		try {
+			const parsed = JSON.parse(body);
+
+			if (typeof parsed?.detail === 'string') return parsed.detail;
+			if (typeof parsed?.message === 'string') return detailOf(parsed.message);
+		} catch {
+			// Not JSON — the raw text is the best there is.
+		}
+
+		return body;
+	}
+
+	/**
+	 * Follow a running import until it lands.
+	 *
+	 * Polled rather than pushed: the job lives on the server, so this survives a reload
+	 * and does not depend on the tab that started it staying open.
+	 */
+	function follow(jobId: string) {
+		stopPolling();
+
+		poll = setInterval(async () => {
+			try {
+				job = await getCalibreImport(jobId);
+			} catch (error) {
+				problem = error instanceof Error ? error.message : 'Lost track of the import';
+				stopPolling();
+				return;
+			}
+
+			if (job.state !== 'running') {
+				stopPolling();
+				announce(job);
+			}
+		}, POLL_MS);
+	}
+
+	function announce(finished: CalibreImport) {
+		const created = `${finished.created} book${finished.created === 1 ? '' : 's'} imported`;
+
+		if (finished.state === 'failed') toast.error(finished.error ?? 'The import failed');
+		else if (finished.state === 'cancelled') toast.info(`Import stopped — ${created}`);
+		else if (finished.failed > 0) toast.warning(`${created}, ${finished.failed} failed`);
+		else toast.success(created);
+	}
+
+	/**
+	 * Send the archive and start the import it becomes.
+	 *
+	 * `XMLHttpRequest` rather than `fetch` for the one thing fetch cannot do: report how
+	 * much of the body has gone up. On a large archive that is the only progress there is
+	 * for minutes at a time.
+	 *
+	 * It goes through the proxy so the browser streams straight to the backend — a remote
+	 * function would put the whole archive through the SvelteKit process first.
+	 */
+	function send(file: File): Promise<CalibreImport> {
+		return new Promise((resolve, reject) => {
+			const request = new XMLHttpRequest();
+
+			request.open('POST', `/api/libraries/${libraryId}/imports/calibre/upload`);
+
+			request.upload.addEventListener('progress', (event) => {
+				if (event.lengthComputable) uploaded = event.loaded / event.total;
+			});
+
+			request.addEventListener('load', () => {
+				if (request.status >= 200 && request.status < 300) {
+					resolve(JSON.parse(request.responseText));
+				} else {
+					reject(new Error(detailOf(request.responseText)));
+				}
+			});
+
+			request.addEventListener('error', () => reject(new Error('The upload failed')));
+			request.addEventListener('abort', () => reject(new Error('The upload was stopped')));
+
+			const body = new FormData();
+			body.append('archive', file);
+			body.append('allow_duplicates', String(allowDuplicates));
+
+			request.send(body);
+		});
+	}
+
+	async function start() {
+		if (!archive) return;
+
+		busy = true;
+		problem = null;
+		uploaded = 0;
+
+		try {
+			job = await send(archive);
+			follow(job.id);
+		} catch (error) {
+			problem = error instanceof Error ? error.message : 'Could not upload the archive';
+		} finally {
+			busy = false;
+			uploaded = null;
+		}
+	}
+
+	async function stop() {
+		if (!job) return;
+
+		try {
+			job = await cancelCalibreImport(job.id);
+		} catch (error) {
+			problem = error instanceof Error ? error.message : 'Could not stop the import';
+		}
+	}
+
+	function reset() {
+		stopPolling();
+		job = null;
+		problem = null;
+		archive = null;
+		uploaded = null;
+	}
+</script>
+
+<div class="flex flex-col gap-4">
+	<Card.Root>
+		<Card.Header>
+			<Card.Title>Import from Calibre</Card.Title>
+			<Card.Description>
+				Zip your Calibre library folder and upload it here. Nothing is taken from the original — the
+				books are copied in, and uploading the same library again only picks up what is new.
+			</Card.Description>
+		</Card.Header>
+
+		<Card.Content class="flex flex-col gap-4">
+			<Field.Field>
+				<Field.Label for="archive">Zipped Calibre library</Field.Label>
+				<!--
+					The native file button inherits the input's own text styling, which leaves
+					"Browse…" looking like the first half of the sentence "Browse… No file
+					selected." The `file:` variants target ::file-selector-button, so it can be
+					made to read as a button without replacing the input with a custom one.
+					Styled here rather than in `ui/input`, which is generated.
+				-->
+				<Input
+					id="archive"
+					type="file"
+					accept=".zip,application/zip"
+					onchange={pick}
+					disabled={running || busy}
+					class="py-1.5 file:mr-3 file:cursor-pointer file:rounded-sm file:border file:border-input file:bg-secondary file:px-2 file:py-0.5 file:text-secondary-foreground file:hover:bg-secondary/80"
+				/>
+				<Field.Description>
+					The zip has to contain <code class="font-mono text-xs">metadata.db</code> — zip the whole Calibre
+					folder rather than just the books.
+				</Field.Description>
+			</Field.Field>
+
+			{#if archive}
+				<p class="text-sm text-muted-foreground">
+					{archive.name} · {formatFileSize(archive.size)}
+				</p>
+			{/if}
+
+			<div class="flex items-center gap-2">
+				<Checkbox id="allow-duplicates" bind:checked={allowDuplicates} disabled={running || busy} />
+				<label for="allow-duplicates" class="text-sm">
+					Import books this library already holds
+				</label>
+			</div>
+
+			{#if uploaded !== null}
+				<div class="flex flex-col gap-1">
+					<Progress value={Math.round(uploaded * 100)} />
+					<p class="text-xs text-muted-foreground">
+						Uploading · {Math.round(uploaded * 100)}%
+					</p>
+				</div>
+			{/if}
+
+			{#if problem}
+				<p class="flex items-center gap-2 text-sm text-destructive">
+					<TriangleAlert class="size-4 shrink-0" />
+					{problem}
+				</p>
+			{/if}
+		</Card.Content>
+
+		<Card.Footer class="gap-2">
+			{#if running}
+				<Button variant="outline" onclick={stop}>Stop after this book</Button>
+			{:else if job}
+				<Button onclick={reset}>Import another</Button>
+			{:else}
+				<!--
+					No preview step: the catalogue cannot be read until the archive is on the
+					server, and by then it has been carried across anyway. Unpacking it is what
+					refuses an archive that is not a Calibre library.
+				-->
+				<Button onclick={start} disabled={busy || !archive}>
+					{#if busy}
+						<Loader2 class="size-4 animate-spin" />
+					{:else}
+						<Upload class="size-4" />
+					{/if}
+					Upload and import
+				</Button>
+			{/if}
+		</Card.Footer>
+	</Card.Root>
+
+	{#if job}
+		<Card.Root>
+			<Card.Header>
+				<Card.Title class="flex items-center gap-2">
+					{#if running}<Loader2 class="size-4 animate-spin" />{/if}
+					{running ? 'Importing' : job.state === 'failed' ? 'Import failed' : 'Import finished'}
+				</Card.Title>
+				<Card.Description>
+					{#if running && job.current_title}
+						{job.processed} of {job.total} · {job.current_title}
+					{:else if job.state === 'cancelled'}
+						Stopped after {job.processed} of {job.total}. Everything imported is complete.
+					{:else if job.state === 'failed'}
+						{job.error ?? 'The import stopped before it finished.'}
+					{:else}
+						{job.processed} of {job.total} books considered.
+					{/if}
+				</Card.Description>
+			</Card.Header>
+
+			<Card.Content class="flex flex-col gap-4">
+				<Progress value={percent} />
+
+				<div class="grid grid-cols-3 gap-3 text-sm">
+					<div>
+						<p class="font-mono text-lg tabular-nums">{job.created}</p>
+						<p class="text-muted-foreground">imported</p>
+					</div>
+					<div>
+						<p class="font-mono text-lg tabular-nums">{job.skipped}</p>
+						<p class="text-muted-foreground">already here</p>
+					</div>
+					<div>
+						<p class="font-mono text-lg tabular-nums">{job.failed}</p>
+						<p class="text-muted-foreground">failed</p>
+					</div>
+				</div>
+
+				{#if job.created > 0}
+					<a
+						href={resolve('/(root)/(library)/library/[libraryId]/view', { libraryId })}
+						class="inline-flex w-fit items-center gap-2 text-sm hover:underline"
+					>
+						<BookOpen class="size-4" />
+						See the books
+					</a>
+				{/if}
+
+				<!--
+					An import into a library that already holds books is the likeliest way to
+					end up with two records for one book, and that screen already handles them.
+				-->
+				{#if job.possible_duplicates > 0}
+					<div class="rounded-lg border p-3 text-sm">
+						<p>
+							{job.possible_duplicates} imported book{job.possible_duplicates === 1 ? '' : 's'}
+							look{job.possible_duplicates === 1 ? 's' : ''} like something this library already had.
+							They were imported all the same — a metadata match is a guess.
+						</p>
+						<a
+							href={resolve('/(root)/settings/libraries/[libraryId]/duplicates', { libraryId })}
+							class="mt-2 inline-block font-medium hover:underline"
+						>
+							Review duplicates
+						</a>
+					</div>
+				{/if}
+
+				{#if job.failures?.length}
+					<div class="flex flex-col gap-2">
+						<p class="text-sm font-medium">Books that could not be imported</p>
+						<div class="overflow-x-auto rounded-lg border">
+							<Table.Root>
+								<Table.Header>
+									<Table.Row>
+										<Table.Head class="w-[80px]">Calibre</Table.Head>
+										<Table.Head>Title</Table.Head>
+										<Table.Head>Reason</Table.Head>
+									</Table.Row>
+								</Table.Header>
+								<Table.Body>
+									{#each job.failures as failure (failure.calibre_id)}
+										<Table.Row>
+											<Table.Cell class="font-mono text-xs">#{failure.calibre_id}</Table.Cell>
+											<Table.Cell>{failure.title}</Table.Cell>
+											<Table.Cell class="font-mono text-xs">{failure.reason}</Table.Cell>
+										</Table.Row>
+									{/each}
+								</Table.Body>
+							</Table.Root>
+						</div>
+					</div>
+				{/if}
+			</Card.Content>
+		</Card.Root>
+	{/if}
+</div>

frontend/src/routes/api/[...path]/+server.ts

@@ -30,6 +30,20 @@ async function handleResponse(response: Response) {
 	}
 }
 
+/**
+ * The body to forward, as fetch init options.
+ *
+ * Passed through as a stream rather than read into memory first: this process should
+ * never hold a whole upload, which for a zipped Calibre library could be many
+ * gigabytes. A request with no body contributes nothing, since `duplex` without a body
+ * is rejected.
+ */
+function bodyOf(request: Request) {
+	if (!request.body) return {};
+
+	return { body: request.body, duplex: 'half' } as RequestInit;
+}
+
 // Shared function to prepare the request with authentication
 function prepareRequest(locals: App.Locals, request: Request) {
 	const token = locals.authToken || 'server-default-token';
@@ -76,13 +90,14 @@ export const POST: RequestHandler = async ({ params, locals, fetch, request, url
 		const backendUrl = `${BACKEND_API_URL}/${path}${queryString}`;
 		const headers = prepareRequest(locals, request);
 
-		// Get the request body
-		const body = await request.arrayBuffer();
-
 		const response = await fetch(backendUrl, {
 			method: 'POST',
 			headers,
-			body
+			// Streamed, not buffered. `arrayBuffer()` held the whole upload in this
+			// process before forwarding a byte of it, which is survivable for one book
+			// and not for a zipped Calibre library. `duplex: 'half'` is required by the
+			// fetch spec whenever the body is a stream.
+			...bodyOf(request)
 		});
 
 		return handleResponse(response);
@@ -100,13 +115,10 @@ export const PATCH: RequestHandler = async ({ params, locals, fetch, request, ur
 		const backendUrl = `${BACKEND_API_URL}/${path}${queryString}`;
 		const headers = prepareRequest(locals, request);
 
-		// Get the request body
-		const body = await request.arrayBuffer();
-
 		const response = await fetch(backendUrl, {
 			method: 'PATCH',
 			headers,
-			body
+			...bodyOf(request)
 		});
 
 		return handleResponse(response);