feat: fetch the next page of books before the reader hits the bottom

The prefetch zone is a viewport deep rather than 200px, and the observer
re-observes after a page lands so a chain of loads is not cut short.

.gitignore

@@ -1,3 +1,4 @@
 .env
 .postgres/
 .venv
+tmp/

AGENTS.md

@@ -73,6 +73,9 @@ pytest tests/                                        # needs Docker (pytest-data
 ruff format src/
 alchemy --config chitai.database.config.config make-migrations
 alchemy --config chitai.database.config.config upgrade
+
+# Import a Calibre library. Copies files; --dry-run reports without writing.
+litestar --app-dir src/chitai/ calibre-import <path> --library <slug>
 ```
 
 Frontend (from `frontend/`):

TODO.md

@@ -242,6 +242,10 @@ so the whole file sits in the node process, per concurrent reader, and the brows
 nothing until it completes. Passing `response.body` straight through restores the stream
 and is a small change.
 
+This is now **responses only**. The request side was fixed for the Calibre archive upload,
+which cannot be held in memory: POST and PATCH pass `request.body` through with
+`duplex: 'half'` (`bodyOf` in the same file). The response side is the same shape of fix.
+
 **Range.** The proxy forwards only `Content-Type`, `Content-Disposition` and
 `Content-Length`. It never sends the client's `Range` upstream, and would drop
 `Accept-Ranges` and `Content-Range` coming back — a 206 without `Content-Range` is

backend/AGENTS.md

@@ -108,6 +108,22 @@ The backend owns files on disk, not just rows:
   if it differs, moves the directory contents and prunes empty parents. Keep that in mind before
   changing metadata handling.
 
+### Content types come from the extension, and null means null
+
+Every ingest path names a file's format with `guess_content_type` (`services/utils.py`), never with
+`mimetypes.guess_type` directly and never with what the client said. Python's built-in map answers
+`None` for `.mobi`, `.azw`, `.prc`, `.fb2`, `.fbz`, `.lit`, `.lrf` and `.cb7` — most of what a
+library imported from elsewhere carries — so `EBOOK_CONTENT_TYPES` fills those in. A browser's
+`application/octet-stream` is discarded rather than used as a fallback: it is the client saying it
+does not know, and storing it is indistinguishable from having determined a format.
+
+When nothing can name the extension the column **stays null**. That is the honest answer, and only
+one consumer cannot take it: OPDS `Link.type` is a required string, so
+`services/opds/opds.py` substitutes `application/octet-stream` at that boundary. Litestar's
+`ASGIFileResponse` already does its own fallback, so `get_file` can pass a null straight through.
+`FileMetadataRead.content_type` is nullable for the same reason — it was once required, which
+turned a stored null into a 500 on a book that was otherwise fine.
+
 ## Duplicate detection
 
 Every ingest path screens incoming files against what is already stored, keyed on
@@ -126,6 +142,7 @@ The policy differs by how deliberate the import is:
 | `create_book` (single, with metadata) | All-or-nothing: raises `DuplicateFilesError`, which `controllers/book.py` renders as a **409** carrying the refused files in `extra`. |
 | `add_files` | A file the book already carries is a no-op; one stored under another book raises `DuplicateFilesError`. |
 | `create_many_from_existing_files` (consume watcher) | Skips, and **moves the file to `CHITAI_DUPLICATE_PATH/<library slug>/`** — nothing is deleted, and it cannot stay put because `watchfiles` only reports additions. That path must stay outside `consume_path` or the watcher re-imports it and tries to read the directory name as a library slug. |
+| `create_many_from_calibre` (Calibre import) | Skips per file, and skips a whole book whose files are all known. Nothing is moved — the source is somebody else's library. This is what makes a re-run a no-op and an interrupted import resumable by running it again. |
 
 `allow_duplicates=true` overrides all of it, on every endpoint. Keep that working — the
 hash is not proof of identity, so a wrong verdict has to be recoverable, and a scripted
@@ -242,6 +259,84 @@ under the new rules, with nothing to show that anything is wrong. Copy
 `normalize_title` learned to strip compact edition markers (`2E`, `5e`). It is
 idempotent and safe to re-run.
 
+## Importing from Calibre
+
+Two pieces, deliberately separated:
+
+- **`services/calibre.py`** reads `metadata.db` and the tree beside it. It knows nothing about
+  `Book`, `BookService` or a session, so it is testable without Postgres, and it reports what
+  Calibre wrote rather than what Chitai wants — identifiers come back keyed by `identifiers.type`
+  verbatim. It also unpacks a zipped library (`extract_calibre_archive`).
+- **`BookService.create_many_from_calibre`** does the ingest, next to the two other ingest paths
+  because it needs the same privates they do (`_reserve_book_path`, `_save_cover_image`,
+  `_screen_for_duplicates`). The CLI in `cli.py` is a thin wrapper over it.
+- **`services/calibre_import.py`** is lifecycle only — the job registry behind the endpoints:
+  state, progress, cancellation, and a session of its own.
+
+`docs/calibre-import.md` is the full brief, including the phases not built yet. What matters here:
+
+- **Files are copied, never moved.** `metadata.db` would go on pointing at files that are gone,
+  which quietly ruins a library somebody still uses. `copy_file` streams rather than using
+  `shutil.copy`, which would block the loop for a 40 MB read.
+- **The extractors are not run.** This is the one ingest path that trusts its input: Calibre's
+  catalogue is curated and its filenames are truncated to ~42 characters, so `data.name` locates a
+  file and the database carries the metadata. The title is stored verbatim for the same reason —
+  no edition split out, no subtitle guessed.
+- **The catalogue is copied before it is read**, and the copy is opened read-write. Calibre may be
+  running; opening the live file either sees a torn state or needs to recover a write-ahead log,
+  which read-only access cannot do. `close()` removes the copy in a `finally`, or a failure leaves
+  a catalogue-sized file in the temp directory.
+- **`check_same_thread=False` plus an `asyncio.Lock`.** Every query runs through
+  `asyncio.to_thread`, which hands out whichever worker is free, so the connection outlives the
+  thread that opened it. The lock is what makes that safe. Removing either one reintroduces
+  `SQLite objects created in a thread can only be used in that same thread`, intermittently —
+  the pool often reuses one thread, so it passes until it does not.
+- **One book never costs the run.** A failure is recorded in `CalibreImportResult.failed`, the
+  session is rolled back so the next book can use it, and the files that book had already copied
+  are deleted — an orphaned directory would make the next attempt reserve `title (2)` and look as
+  though it had worked. A cover that PIL cannot open costs the cover, not the book.
+- **`calibre-uuid`, not `uuid`.** `books.uuid` is stable for the life of the row, so it is the
+  durable link back to the source and worth matching on. `uuid` is the name `normalize_identifier`
+  refuses, because an EPUB regenerates one per build.
+
+### The API takes an uploaded archive; the CLI takes a path
+
+**`POST /libraries/{id}/imports/calibre/upload`** is the only way in over HTTP. It takes a zipped
+Calibre library, answers **202** with a job handle, and unpacks into a temp directory the job owns.
+`GET /libraries/imports/{job_id}` is polled; `DELETE` on the same path stops it.
+
+There is deliberately **no endpoint that imports from a server path**. A desktop Calibre install is
+not on the server, and importing from a path the server can already see is a server-side operation
+— which is what `litestar --app-dir src/chitai/ calibre-import <path> --library <slug>` is for,
+including its `--dry-run`. Do not add the path endpoint back without being asked: it was built,
+then removed on purpose.
+
+- **The registry is in memory, so it assumes one worker process.** That holds today (`litestar run`
+  is single-process, and the consume watcher is already an in-process singleton), but the day
+  `TODO.md`'s "production image runs the development server" item is fixed with a worker count, a
+  poll can land on a worker that never heard of the job. `services/calibre_import.py` says so at
+  the top; an `import_jobs` table is the answer when that happens.
+- **The job opens its own session.** The request that started it is long gone and its session
+  closed with it.
+- **Cancelling is not aborting.** A flag is read between books, never during one, so a cancelled
+  import leaves whole books behind and never half of one. `task.cancel()` would abandon a book
+  mid-copy and leave files with no row describing them.
+- **The job deletes its workspace** — the unpacked archive is a second copy of the whole library,
+  and the books worth keeping have been copied into the library proper by the time it ends. Removed
+  even when the run failed, since nothing will come back for it.
+- **Extraction refuses** an entry pointing outside the archive (zip slip), an archive that will not
+  fit on disk, and one with no `metadata.db` within three levels. All three answer 400 before a job
+  exists, rather than as a job that reports FAILED a moment later.
+- **The upload is streamed both sides.** The archive reaches disk in chunks rather than being read
+  whole, and the SvelteKit proxy passes `request.body` through instead of buffering it — see
+  `frontend/AGENTS.md`.
+
+Things Calibre does that will produce wrong data if you forget them are documented at the top of
+`services/calibre.py` — the `0101-01-01` date sentinel, `|` for a comma in an author name, the
+REAL `series_index` that defaults to 1.0 for every book, HTML in `comments`, the views that need
+SQLite functions Calibre registers from Python, and `books_pages_link` being both recent and
+usually empty. `tests/calibre_fixtures.py` builds a library exercising all of them.
+
 ## KOReader hashing
 
 `services/utils.py` reimplements KOReader's partial-MD5 document identifier: 1 KiB samples at

backend/migrations/versions/2026-08-17_backfill_file_content_types_d2d69065ede3.py

@@ -0,0 +1,114 @@
+"""backfill file content types
+
+Revision ID: d2d69065ede3
+Revises: 49a9e85a0ffc
+Create Date: 2026-08-17 11:37:58.959135
+
+"""
+
+import warnings
+from typing import TYPE_CHECKING
+
+import sqlalchemy as sa
+from alembic import op
+from advanced_alchemy.types import EncryptedString, EncryptedText, GUID, ORA_JSONB, DateTimeUTC, StoredObject, PasswordHash, FernetBackend
+from advanced_alchemy.types.encrypted_string import PGCryptoBackend
+from advanced_alchemy.types.password_hash.argon2 import Argon2Hasher
+from advanced_alchemy.types.password_hash.passlib import PasslibHasher
+from advanced_alchemy.types.password_hash.pwdlib import PwdlibHasher
+from sqlalchemy import Text  # noqa: F401
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+
+__all__ = ["downgrade", "upgrade", "schema_upgrades", "schema_downgrades", "data_upgrades", "data_downgrades"]
+
+sa.GUID = GUID
+sa.DateTimeUTC = DateTimeUTC
+sa.ORA_JSONB = ORA_JSONB
+sa.EncryptedString = EncryptedString
+sa.EncryptedText = EncryptedText
+sa.StoredObject = StoredObject
+sa.PasswordHash = PasswordHash
+sa.Argon2Hasher = Argon2Hasher
+sa.PasslibHasher = PasslibHasher
+sa.PwdlibHasher = PwdlibHasher
+sa.FernetBackend = FernetBackend
+sa.PGCryptoBackend = PGCryptoBackend
+
+# revision identifiers, used by Alembic.
+revision = 'd2d69065ede3'
+down_revision = '49a9e85a0ffc'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", category=UserWarning)
+        with op.get_context().autocommit_block():
+            schema_upgrades()
+            data_upgrades()
+
+def downgrade() -> None:
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", category=UserWarning)
+        with op.get_context().autocommit_block():
+            data_downgrades()
+            schema_downgrades()
+
+def schema_upgrades() -> None:
+    """schema upgrade migrations go here."""
+    pass
+
+def schema_downgrades() -> None:
+    """schema downgrade migrations go here."""
+    pass
+
+def data_upgrades() -> None:
+    """
+    Name the format of every file whose content type was never worked out.
+
+    `create_many_from_existing_files` filled the column from `mimetypes.guess_type`,
+    which answers None for `.mobi`, `.azw`, `.fb2` and `.lit` — so a consume-directory
+    import of any of those stored a null, and the OPDS acquisition link a reader app
+    uses to decide what it can open carried nothing.
+
+    Both write paths now go through `guess_content_type`, which this uses too, so the
+    formats in its table get named retroactively. A row it still cannot name is **left
+    null** rather than filled with a placeholder: null is the truth, the column is
+    nullable, and the one consumer that needs a string substitutes one itself.
+    Idempotent: it only looks at rows that carry nothing.
+    """
+    from chitai.services.utils import guess_content_type
+
+    connection = op.get_bind()
+
+    files = connection.execute(
+        sa.text(
+            "SELECT id, path FROM file_metadata "
+            "WHERE content_type IS NULL OR content_type = ''"
+        )
+    ).fetchall()
+
+    parameters = [
+        {"id": id, "content_type": content_type}
+        for id, path in files
+        if (content_type := guess_content_type(path)) is not None
+    ]
+
+    if not parameters:
+        return
+
+    batch_size = 1000
+    for start in range(0, len(parameters), batch_size):
+        connection.execute(
+            sa.text(
+                "UPDATE file_metadata SET content_type = :content_type WHERE id = :id"
+            ),
+            parameters[start : start + batch_size],
+        )
+
+
+def data_downgrades() -> None:
+    """Add any optional data downgrade migrations here!"""

backend/src/chitai/app.py

@@ -16,6 +16,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 
 from chitai import controllers as c
+from chitai.cli import CalibreCLIPlugin
 from chitai.config import settings
 from chitai.database.config import alchemy
 from chitai.database.models.user import User
@@ -133,7 +134,7 @@ def create_app() -> Litestar:
         ],
         exception_handlers=exception_handlers,
         lifespan=[setup_db_connection, setup_directory_watcher],
-        plugins=[alchemy],
+        plugins=[alchemy, CalibreCLIPlugin()],
         on_app_init=[oauth2_auth.on_app_init],
         openapi_config=OpenAPIConfig(
             title="Chitai",

backend/src/chitai/cli.py

@@ -0,0 +1,186 @@
+# src/chitai/cli.py
+
+"""
+Extra commands on the `litestar` CLI.
+
+Registered through `CalibreCLIPlugin` in `app.py`, so they run as
+`litestar --app-dir src/chitai/ calibre-import …` and get the app's own configuration
+without a second way to load it.
+
+The Calibre import lives here as well as behind an endpoint because the case it exists
+for is a one-time migration of a library that may be hundreds of gigabytes. That should
+not depend on a browser tab staying open.
+"""
+
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+
+import click
+from click import Group
+from litestar.plugins import CLIPluginProtocol
+
+from chitai.config import settings
+from chitai.database.models import Library
+from chitai.services.book import BookService, CalibreImportProgress, CalibreImportResult
+from chitai.services.calibre import CalibreLibrary, CalibreLibraryError
+from chitai.services.library import LibraryService
+
+
+class CalibreCLIPlugin(CLIPluginProtocol):
+    """Adds `calibre-import` to the Litestar CLI."""
+
+    def on_cli_init(self, cli: Group) -> None:
+        cli.add_command(calibre_import)
+
+
+@click.command(name="calibre-import")
+@click.argument(
+    "source",
+    type=click.Path(exists=True, file_okay=False, path_type=Path),
+)
+@click.option(
+    "--library",
+    "library_slug",
+    required=True,
+    help="Slug of the Chitai library to import into.",
+)
+@click.option(
+    "--allow-duplicates",
+    is_flag=True,
+    help="Import books whose files the library already holds.",
+)
+@click.option(
+    "--dry-run",
+    is_flag=True,
+    help="Read the catalogue and report what it holds, without writing anything.",
+)
+def calibre_import(
+    source: Path, library_slug: str, allow_duplicates: bool, dry_run: bool
+) -> None:
+    """
+    Import a Calibre library from SOURCE, the directory holding its metadata.db.
+
+    Files are copied, never moved: the Calibre library is left exactly as it is, and
+    re-running skips whatever is already stored.
+    """
+    asyncio.run(_import(source, library_slug, allow_duplicates, dry_run))
+
+
+async def _import(
+    source: Path, library_slug: str, allow_duplicates: bool, dry_run: bool
+) -> None:
+    try:
+        library_source = CalibreLibrary(source)
+        await library_source.open()
+    except CalibreLibraryError as exc:
+        raise click.ClickException(str(exc)) from exc
+
+    try:
+        if dry_run:
+            await _report(library_source)
+            return
+
+        async with settings.alchemy_config.get_session() as session:
+            library = await _library(session, library_slug)
+
+            result = await BookService(session=session).create_many_from_calibre(
+                library_source,
+                library,
+                allow_duplicates=allow_duplicates,
+                on_progress=_print_progress,
+            )
+    finally:
+        await library_source.close()
+
+    _print_summary(result)
+
+    if result.failed:
+        raise SystemExit(1)
+
+
+async def _library(session: object, slug: str) -> Library:
+    """Resolve the target library, or explain what the options were."""
+    service = LibraryService(session=session)  # type: ignore[arg-type]
+
+    library = await service.get_one_or_none(Library.slug == slug)
+
+    if library is None:
+        available = ", ".join(sorted(item.slug for item in await service.list()))
+        raise click.ClickException(
+            f"No library with slug '{slug}'. Available: {available or 'none'}"
+        )
+
+    # A read-only library is one pointing at a tree Chitai does not own. Copying books
+    # into it would write into somebody else's directory.
+    if library.read_only:
+        raise click.ClickException(
+            f"Library '{slug}' is read-only, so nothing can be imported into it"
+        )
+
+    return library
+
+
+async def _report(source: CalibreLibrary) -> None:
+    """Describe the catalogue without touching the database."""
+    books = await source.books()
+
+    click.echo(f"{len(books)} book(s) in {source.root}\n")
+
+    for book in books:
+        authors = ", ".join(book.authors) or "unknown author"
+        formats = ", ".join(file.format for file in book.files) or "no files"
+        click.echo(f"  #{book.calibre_id:<6} {book.title}")
+        click.echo(f"  {'':<7} {authors} · {formats}")
+
+    missing = [
+        book
+        for book in books
+        if any(not file.path.is_file() for file in book.files) or not book.files
+    ]
+
+    if missing:
+        click.echo(
+            f"\n{len(missing)} book(s) have files the catalogue lists "
+            "but disk does not:"
+        )
+        for book in missing:
+            click.echo(f"  #{book.calibre_id} {book.title}")
+
+
+def _print_progress(progress: CalibreImportProgress) -> None:
+    marker = {"created": "+", "skipped": "-", "failed": "!"}.get(progress.outcome, " ")
+    detail = f" ({progress.detail})" if progress.detail else ""
+
+    click.echo(
+        f"[{progress.processed:>5}/{progress.total}] {marker} {progress.title}{detail}"
+    )
+
+
+def _print_summary(result: CalibreImportResult) -> None:
+    click.echo(
+        f"\n{len(result.created)} created, {len(result.skipped)} skipped, "
+        f"{len(result.failed)} failed, of {result.total}."
+    )
+
+    if result.duplicate_files:
+        click.echo(
+            f"{len(result.duplicate_files)} individual file(s) were already stored and "
+            "were left out of books that imported otherwise."
+        )
+
+    for failure in result.failed:
+        click.echo(f"  failed  #{failure.calibre_id} {failure.title}: {failure.reason}")
+
+    # Imported all the same — a metadata match is a guess, and the duplicates screen is
+    # where these get decided.
+    for possible in result.possible_duplicates:
+        names = ", ".join(
+            f"{candidate.title} (#{candidate.book_id})"
+            for candidate in possible.candidates
+        )
+        click.echo(
+            f"  possible duplicate  {possible.title} (#{possible.book_id}) "
+            f"may already be in the library as: {names}"
+        )

backend/src/chitai/controllers/library.py

@@ -1,12 +1,20 @@
 # src/chitai/controllers/library.py
 
 # Standard library
+import asyncio
+import shutil
+import tempfile
+from pathlib import Path
 from typing import Annotated
 
 # Third-party libraries
+import aiofiles
+from aiofiles import os as aios
 from litestar import Controller, post, get, patch, delete
-from litestar.params import Dependency
+from litestar.enums import RequestEncodingType
+from litestar.params import Body, Dependency
 from litestar.exceptions import HTTPException
+from litestar.status_codes import HTTP_200_OK, HTTP_202_ACCEPTED
 from advanced_alchemy.extensions.litestar.providers import create_service_dependencies
 from advanced_alchemy.service.pagination import OffsetPagination
 from advanced_alchemy.service import FilterTypeT
@@ -14,10 +22,21 @@ from advanced_alchemy.service import FilterTypeT
 # Local imports
 from chitai.database import models as m
 from chitai.services import LibraryService
-from chitai.schemas.library import LibraryCreate, LibraryRead
+from chitai.schemas.library import (
+    CalibreArchiveUpload,
+    CalibreImportRead,
+    LibraryCreate,
+    LibraryRead,
+)
+from chitai.services.calibre import CalibreLibraryError, extract_calibre_archive
+from chitai.services.calibre_import import registry
 from chitai.services.utils import DirectoryDoesNotExist
 
 
+# How much of an uploaded archive is held in memory at a time on its way to disk.
+UPLOAD_CHUNK_SIZE = 262144  # 256 KiB
+
+
 class LibraryController(Controller):
     """Controller for managing library operations."""
 
@@ -74,3 +93,147 @@ class LibraryController(Controller):
         return library_service.to_schema(
             results, total, filters, schema_type=LibraryRead
         )
+
+    @post(
+        path="{library_id:int}/imports/calibre/upload",
+        status_code=HTTP_202_ACCEPTED,
+        request_max_body_size=None,
+    )
+    async def upload_calibre_import(
+        self,
+        library_service: LibraryService,
+        library_id: int,
+        data: Annotated[
+            CalibreArchiveUpload, Body(media_type=RequestEncodingType.MULTI_PART)
+        ],
+    ) -> CalibreImportRead:
+        """
+        Import a zipped Calibre library that was uploaded rather than named on disk.
+
+        For the case where the library is not on the server: zip the Calibre folder and
+        send it. Unpacked into a temp directory the job owns and deletes when it ends —
+        by which time the books worth keeping have been copied into the library proper.
+
+        The server-folder route stays the one for a very large library. This one has to
+        carry the whole archive over HTTP first.
+
+        Path Parameters:
+            library_id: The library to import into.
+
+        Request Body:
+            data: The `.zip` holding the Calibre library.
+
+        Returns:
+            The job, already running.
+
+        Raises:
+            HTTPException: 400 if the archive is not a zip, holds no `metadata.db`,
+                names an entry outside itself, or would not fit on disk; 409 if an
+                import into this library is already running.
+        """
+        library = await self._importable(library_service, library_id)
+
+        if (running := registry.running_for(library_id)) is not None:
+            raise HTTPException(
+                status_code=409,
+                detail="An import into this library is already running",
+                extra={"job_id": running.id},
+            )
+
+        workspace = Path(await asyncio.to_thread(tempfile.mkdtemp))
+
+        try:
+            archive = workspace / "upload.zip"
+            await data.archive.seek(0)
+
+            async with aiofiles.open(archive, "wb") as destination:
+                while chunk := await data.archive.read(UPLOAD_CHUNK_SIZE):
+                    await destination.write(chunk)
+
+            unpacked = workspace / "library"
+            unpacked.mkdir()
+
+            catalogue = await extract_calibre_archive(archive, unpacked)
+
+            # The archive itself is dead weight once unpacked, and the library it
+            # unpacked to can be large.
+            await aios.remove(archive)
+        except CalibreLibraryError as exc:
+            await asyncio.to_thread(shutil.rmtree, workspace, True)
+            raise HTTPException(status_code=400, detail=str(exc))
+        except Exception:
+            await asyncio.to_thread(shutil.rmtree, workspace, True)
+            raise
+
+        job = registry.start(
+            library,
+            catalogue,
+            workspace=workspace,
+            label=data.archive.filename or "uploaded archive",
+            allow_duplicates=data.allow_duplicates,
+        )
+
+        return CalibreImportRead.model_validate(job)
+
+    @get(path="imports/{job_id:str}")
+    async def get_import(self, job_id: str) -> CalibreImportRead:
+        """
+        Report on an import.
+
+        Polled by the client while a run is going. Jobs are held in memory, so this is
+        answered by the process that started it — see `services/calibre_import.py`.
+
+        Path Parameters:
+            job_id: The job to report on.
+
+        Raises:
+            HTTPException: 404 if this process holds no such job.
+        """
+        if (job := registry.get(job_id)) is None:
+            raise HTTPException(status_code=404, detail="No such import")
+
+        return CalibreImportRead.model_validate(job)
+
+    @delete(path="imports/{job_id:str}", status_code=HTTP_200_OK)
+    async def cancel_import(self, job_id: str) -> CalibreImportRead:
+        """
+        Ask an import to stop after the book it is on.
+
+        Deliberately not an abort: a book abandoned mid-copy would leave files on disk
+        with no row describing them. Whatever it has imported stays imported.
+
+        Path Parameters:
+            job_id: The job to stop.
+
+        Raises:
+            HTTPException: 404 if this process holds no such job.
+        """
+        if (job := registry.cancel(job_id)) is None:
+            raise HTTPException(status_code=404, detail="No such import")
+
+        return CalibreImportRead.model_validate(job)
+
+    @staticmethod
+    async def _importable(
+        library_service: LibraryService, library_id: int
+    ) -> m.Library:
+        """
+        The library, if it can be imported into at all.
+
+        Raises:
+            HTTPException: 404 if there is no such library, 400 if it is read-only —
+                a read-only library points at a tree Chitai does not own, so copying
+                books into it would write into somebody else's directory.
+        """
+        library = await library_service.get_one_or_none(m.Library.id == library_id)
+
+        if library is None:
+            raise HTTPException(status_code=404, detail="No such library")
+
+        if library.read_only:
+            raise HTTPException(
+                status_code=400,
+                detail="This library is read-only, so nothing can be imported into it",
+            )
+
+        return library

backend/src/chitai/schemas/book.py

@@ -30,7 +30,11 @@ class FileMetadataRead(BaseModel):
     path: str
     hash: str
     size: int
-    content_type: str
+
+    # Nullable, though every ingest path now writes one through
+    # `guess_content_type`. Rows predating it can hold null, and a required field here
+    # turns one of those into a 500 on a book the reader can otherwise open.
+    content_type: str | None = None
 
     @computed_field
     @property

backend/src/chitai/schemas/library.py

@@ -1,6 +1,7 @@
 from pathlib import Path
 from typing import Annotated
-from pydantic import BaseModel, Field, computed_field
+from pydantic import BaseModel, ConfigDict, Field, SkipValidation, computed_field
+from litestar.datastructures import UploadFile
 from  advanced_alchemy.utils.text import slugify
 
 class LibraryCreate(BaseModel):
@@ -27,6 +28,57 @@ class LibraryRead(BaseModel):
     total: int | None = None
 
 
+class CalibreArchiveUpload(BaseModel):
+    """
+    A zipped Calibre library.
+
+    The only way in through the API: a desktop Calibre install is usually not on the
+    server at all. Importing from a path the server can already see is a server-side
+    operation, and stays one — `litestar calibre-import` does that.
+    """
+
+    archive: Annotated[UploadFile, SkipValidation]
+    allow_duplicates: bool = False
+
+    model_config = ConfigDict(arbitrary_types_allowed=True)
+
+
+class ImportFailureRead(BaseModel):
+    """A book the import could not store."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    calibre_id: int
+    title: str
+    reason: str
+
+
+class CalibreImportRead(BaseModel):
+    """A running or finished import."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: str
+    library_id: int
+    source: str
+    state: str
+
+    total: int
+    processed: int
+    created: int
+    skipped: int
+    failed: int
+
+    current_title: str | None = None
+    failures: list[ImportFailureRead] = Field(default_factory=list)
+
+    # A count, not the records. The library's duplicates screen is what shows them.
+    possible_duplicates: int = 0
+
+    # Set when the run itself broke, as opposed to individual books failing.
+    error: str | None = None
+
+
 class LibraryUpdate(BaseModel):
     name: str | None
     root_path: str | None

backend/src/chitai/services/book.py

@@ -3,7 +3,6 @@
 # Standard library
 from __future__ import annotations
 from collections import defaultdict
-import mimetypes
 
 from collections.abc import Callable, Iterable, Sequence
 from dataclasses import dataclass, field, replace
@@ -51,6 +50,7 @@ from chitai.database.models import (
     Library,
 )
 from chitai.schemas.book import BooksCreateFromFiles
+from chitai.services.calibre import CalibreBook, CalibreLibrary
 from chitai.services.filesystem_library import BookPathGenerator
 from chitai.services.matching import (
     normalize_author,
@@ -58,11 +58,14 @@ from chitai.services.matching import (
     normalize_title,
 )
 from chitai.services.metadata_extractor import Extractor as MetadataExtractor
+from chitai.services.metadata_extractor import parse_identifier
 from chitai.services.utils import (
     cleanup_empty_parent_directories,
+    copy_file,
     delete_file,
     fingerprint_file,
     fingerprint_upload,
+    guess_content_type,
     move_dir_contents,
     move_file,
     save_image,
@@ -85,6 +88,10 @@ Fingerprint = tuple[str, int]
 # How much of a file is held in memory at a time while it is written to disk.
 CHUNK_SIZE = 262144  # 256 KiB
 
+# What Calibre's own `books.uuid` is stored as. Not `uuid`: that name is reserved for
+# the per-build identifier an EPUB carries, which duplicate matching ignores.
+CALIBRE_UUID = "calibre-uuid"
+
 
 @dataclass(frozen=True)
 class DuplicateFile:
@@ -147,6 +154,58 @@ class ImportResult:
     possible_duplicates: list[PossibleDuplicate] = field(default_factory=list)
 
 
+@dataclass(frozen=True)
+class UnimportedBook:
+    """A book in a source catalogue that did not become a Chitai book, and why."""
+
+    calibre_id: int
+    title: str
+    reason: str
+
+    # The book already holding its files, when that is why it was left out.
+    book_id: int | None = None
+
+
+@dataclass(frozen=True)
+class CalibreImportProgress:
+    """One book's outcome, as it happens.
+
+    Reported per book rather than at the end: an import of a real library takes long
+    enough that its progress is the only thing worth looking at while it runs.
+    """
+
+    processed: int
+    total: int
+    title: str
+    outcome: str
+    """`created`, `skipped` or `failed`."""
+
+    detail: str | None = None
+
+
+@dataclass
+class CalibreImportResult:
+    """What importing a Calibre library produced.
+
+    Holds ids rather than `Book` objects: a real catalogue runs to thousands of books,
+    and nothing downstream needs them all in memory at once.
+    """
+
+    total: int = 0
+    created: list[int] = field(default_factory=list)
+    skipped: list[UnimportedBook] = field(default_factory=list)
+    failed: list[UnimportedBook] = field(default_factory=list)
+
+    # Individual files left out of books that were otherwise imported.
+    duplicate_files: list[DuplicateFile] = field(default_factory=list)
+
+    possible_duplicates: list[PossibleDuplicate] = field(default_factory=list)
+
+    # The run gave up before reaching the end of the catalogue, on request. What it did
+    # get through is complete; `processed` is simply short of `total`.
+    stopped: bool = False
+
+
 class DuplicateFilesError(Exception):
     """Raised when an import would store files that are already in the library."""
 
@@ -1246,12 +1305,12 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
                 **kwargs,
             )
             result.books.append(book)
-            await self._record_possible_duplicates(result, book, library)
+            await self._record_possible_duplicates(result.possible_duplicates, book, library)
 
         return result
 
     async def _record_possible_duplicates(
-        self, result: ImportResult, book: Book, library: Library
+        self, into: list[PossibleDuplicate], book: Book, library: Library
     ) -> None:
         """
         Note anything the library already holds that this book might be a copy of.
@@ -1262,7 +1321,9 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
         the same import is a candidate too.
 
         Args:
-            result: The import being assembled, appended to in place.
+            into: The collection to append to, in place. Takes the list rather than the
+                whole result so that every ingest path can use it whatever its own
+                result type is.
             book: The book that was just created.
             library: The library it went into.
         """
@@ -1271,7 +1332,7 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
         )
 
         if candidates:
-            result.possible_duplicates.append(
+            into.append(
                 PossibleDuplicate(
                     book_id=book.id, title=book.title, candidates=candidates
                 )
@@ -1357,7 +1418,6 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
 
             for file in accepted:
                 file_hash, file_size = fingerprints[file.name]
-                content_type, _ = mimetypes.guess_type(file)
 
                 filename = path_gen.generate_filename(data, Path(file.name))
 
@@ -1366,7 +1426,7 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
                         path=str(filename),
                         size=file_size,
                         hash=file_hash,
-                        content_type=content_type,
+                        content_type=guess_content_type(file),
                     )
                 )
 
@@ -1386,12 +1446,280 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
 
             book = await super().create(data)
             result.books.append(book)
-            await self._record_possible_duplicates(result, book, library)
+            await self._record_possible_duplicates(result.possible_duplicates, book, library)
 
             await self.repository.session.commit()
 
         return result
 
+    async def create_many_from_calibre(
+        self,
+        source: CalibreLibrary,
+        library: Library,
+        allow_duplicates: bool = False,
+        on_progress: Callable[[CalibreImportProgress], None] | None = None,
+        should_stop: Callable[[], bool] | None = None,
+    ) -> CalibreImportResult:
+        """
+        Import a Calibre library, **copying** its files rather than taking them.
+
+        Calibre's catalogue is curated and its filenames are truncated, so the metadata
+        is taken from `metadata.db` and the extractors are not run at all — the one
+        ingest path here that trusts what it is given. The title is stored verbatim for
+        the same reason: no edition is split out of it and no subtitle is guessed, since
+        the field is one somebody maintained by hand.
+
+        Files are **copied**, never moved. `metadata.db` would go on pointing at files
+        that were gone, which quietly ruins a library the reader still uses; the source
+        tree is left byte-for-byte alone.
+
+        Re-running is safe and needs no bookkeeping: the same bytes are recognised
+        wherever they sit, so a second pass over one library skips all of it.
+
+        Args:
+            source: An open `CalibreLibrary`.
+            library: The Chitai library to import into.
+            allow_duplicates: Import books whose files are already stored.
+            on_progress: Called once per book, as it is decided.
+            should_stop: Asked before each book whether to give up. Checked between
+                books rather than during one, so a cancelled import leaves whole books
+                behind and never half of one.
+
+        Returns:
+            What was created, left out and flagged. A cancelled run returns what it got
+            through — every book in `created` is committed and complete.
+        """
+        books = await source.books()
+        result = CalibreImportResult(total=len(books))
+
+        for processed, entry in enumerate(books, start=1):
+            if should_stop is not None and should_stop():
+                result.stopped = True
+                break
+
+            try:
+                outcome, detail = await self._import_calibre_book(
+                    entry, library, result, allow_duplicates
+                )
+            except Exception as exc:
+                # One book must never cost the rest of the import. The session is left
+                # unusable by a failed flush, so it is rolled back before the next book
+                # touches it.
+                await self.repository.session.rollback()
+
+                outcome, detail = "failed", f"{type(exc).__name__}: {exc}"
+                result.failed.append(
+                    UnimportedBook(
+                        calibre_id=entry.calibre_id, title=entry.title, reason=detail
+                    )
+                )
+
+            if on_progress is not None:
+                on_progress(
+                    CalibreImportProgress(
+                        processed=processed,
+                        total=result.total,
+                        title=entry.title,
+                        outcome=outcome,
+                        detail=detail,
+                    )
+                )
+
+        return result
+
+    async def _import_calibre_book(
+        self,
+        entry: CalibreBook,
+        library: Library,
+        result: CalibreImportResult,
+        allow_duplicates: bool,
+    ) -> tuple[str, str | None]:
+        """
+        Import one Calibre book, or say why it was left out.
+
+        Args:
+            entry: The book as Calibre describes it.
+            library: The library to import into.
+            result: The import being assembled, appended to in place.
+            allow_duplicates: Store files the library already holds.
+
+        Returns:
+            The outcome — `created` or `skipped` — and a detail for the progress report.
+
+        Raises:
+            Exception: Anything the write path raises, after the files this book had
+                already copied are removed again. An orphaned directory would make the
+                next attempt reserve `title (2)` and look like it had succeeded.
+        """
+        # What the catalogue claims and what is on disk can disagree: Calibre keeps the
+        # row when a file is moved away behind its back.
+        present = [
+            file.path
+            for file in entry.files
+            if await aios.path.isfile(file.path)
+        ]
+
+        if not present:
+            reason = (
+                "no files on disk"
+                if entry.files
+                else "no files in the catalogue"
+            )
+            result.skipped.append(
+                UnimportedBook(
+                    calibre_id=entry.calibre_id, title=entry.title, reason=reason
+                )
+            )
+            return "skipped", reason
+
+        fingerprints = {path.name: await fingerprint_file(path) for path in present}
+
+        if allow_duplicates:
+            accepted, rejected = present, []
+        else:
+            known = await self.find_duplicate_files(fingerprints.values(), library)
+            accepted, rejected = self._screen_for_duplicates(
+                present, fingerprints, known, library
+            )
+
+        if not accepted:
+            held_by = next(
+                (duplicate.book_id for _, duplicate in rejected if duplicate.book_id),
+                None,
+            )
+            result.skipped.append(
+                UnimportedBook(
+                    calibre_id=entry.calibre_id,
+                    title=entry.title,
+                    reason="already stored",
+                    book_id=held_by,
+                )
+            )
+            return "skipped", "already stored"
+
+        # Files this book already has under another name are reported but do not stop
+        # the formats that are new from being imported.
+        result.duplicate_files.extend(duplicate for _, duplicate in rejected)
+
+        data = self._calibre_metadata(entry, library)
+
+        path_gen = BookPathGenerator(library.root_path)
+        parent = await self._reserve_book_path(path_gen.generate_path(data))
+        data["path"] = str(parent)
+
+        copied: list[Path] = []
+        try:
+            await self._attach_calibre_cover(entry, data)
+
+            file_metadata = []
+            for path in accepted:
+                filename = path_gen.generate_filename(data, Path(path.name))
+                destination = _unused_path(parent / filename)
+
+                await copy_file(path, destination)
+                copied.append(destination)
+
+                file_hash, file_size = fingerprints[path.name]
+                file_metadata.append(
+                    FileMetadata(
+                        path=destination.name,
+                        size=file_size,
+                        hash=file_hash,
+                        content_type=guess_content_type(path),
+                    )
+                )
+
+            data["files"] = file_metadata
+
+            book = await self.create(data)
+            result.created.append(book.id)
+
+            await self._record_possible_duplicates(
+                result.possible_duplicates, book, library
+            )
+
+            await self.repository.session.commit()
+        except Exception:
+            for path in copied:
+                await delete_file(path)
+            cleanup_empty_parent_directories(parent, Path(library.root_path))
+            raise
+
+        return "created", None
+
+    def _calibre_metadata(self, entry: CalibreBook, library: Library) -> dict[str, Any]:
+        """
+        Turn one `CalibreBook` into the payload `create` takes.
+
+        Args:
+            entry: The book as Calibre describes it.
+            library: The library it is going into.
+
+        Returns:
+            The metadata dict, with no files or path in it yet.
+        """
+        # Folded onto Chitai's schemes here rather than in the reader, which reports what
+        # Calibre wrote. `parse_identifier` maps `amazon` and `mobi-asin` both onto
+        # `asin`, and a book carrying both would otherwise breach the unique
+        # `(name, book_id)` constraint — so the first one wins, as it does everywhere
+        # else identifiers are merged.
+        identifiers: dict[str, str] = {}
+        for name, value in entry.identifiers.items():
+            if parsed := parse_identifier(value, scheme=name):
+                identifiers.setdefault(*parsed)
+
+        # Deliberately not passed through `parse_identifier`, which would recognise the
+        # shape and file it under `uuid` — a name `normalize_identifier` refuses, since
+        # an EPUB's uuid is regenerated per build. Calibre's is stable for the life of
+        # the row, so it is the one durable link back to the source and worth matching
+        # on when the same library is imported twice.
+        if entry.uuid:
+            identifiers.setdefault(CALIBRE_UUID, entry.uuid)
+
+        return {
+            "library_id": library.id,
+            "title": entry.title or "Unknown",
+            "authors": list(entry.authors),
+            "description": entry.description,
+            "published_date": entry.published_date,
+            "series": entry.series,
+            "series_position": entry.series_position,
+            "tags": list(entry.tags),
+            "publisher": entry.publisher,
+            "language": entry.language,
+            "identifiers": identifiers,
+            "pages": entry.pages,
+        }
+
+    async def _attach_calibre_cover(self, entry: CalibreBook, data: dict) -> None:
+        """
+        Put Calibre's `cover.jpg` on the payload, for `_save_cover_image` to convert.
+
+        Taken from the file Calibre already rendered rather than extracted again from
+        the book: it is the cover the reader chose, and opening every EPUB and rendering
+        the first page of every PDF is the slowest thing an import could do.
+
+        Args:
+            entry: The book as Calibre describes it.
+            data: The payload, modified in place.
+        """
+        if entry.cover is None or not await aios.path.isfile(entry.cover):
+            return
+
+        try:
+            # Copied out of the context manager: the image is saved later, by which time
+            # the file this was opened from is closed.
+            with Image.open(entry.cover) as cover:
+                data["cover_image"] = cover.copy()
+        except OSError:
+            # A truncated or malformed cover.jpg is not a reason to refuse the book. It
+            # is the least important thing in the directory, and one can be added later
+            # from the book page; the files cannot.
+            data.pop("cover_image", None)
+            return
+
+        await self._save_cover_image(data)
+
     @staticmethod
     async def _quarantine_duplicate(
         file: Path, consume_path: Path, library: Library
@@ -1479,7 +1807,12 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
             if not await aios.path.isfile(path):
                 raise ValueError("The file is missing")
 
-            return File(path, media_type=file.content_type)
+            # Rows written before `guess_content_type` existed can hold null here, and
+            # so can `guess_content_type` itself. Litestar fills a null in from the
+            # filename, falling back to `application/octet-stream` on the response.
+            return File(
+                path, media_type=file.content_type or guess_content_type(file.path)
+            )
 
         raise ValueError("No such file for the given book")
 
@@ -1964,7 +2297,10 @@ class BookService(SQLAlchemyAsyncRepositoryService[Book]):
                     path=str(filename),
                     size=file_size,
                     hash=fingerprint[0] if fingerprint else hasher.hexdigest(),
-                    content_type=file.content_type,
+                    # The name outranks what the browser said: it posts
+                    # `application/octet-stream` for every format it does not know,
+                    # which is most of them.
+                    content_type=guess_content_type(file, fallback=file.content_type),
                 )
             )
 

backend/src/chitai/services/calibre.py

@@ -0,0 +1,570 @@
+# src/chitai/services/calibre.py
+
+"""
+Read a Calibre library.
+
+This knows about `metadata.db` and the tree beside it, and nothing about `Book`,
+`BookService` or a database session — it is a file-format reader, and it is testable
+without Postgres or an app. Interpretation belongs to whoever imports what it returns:
+identifiers come back exactly as Calibre wrote them, not folded onto Chitai's schemes.
+
+Things about Calibre that are load-bearing here:
+
+- **Never query the views.** `meta` and the `tag_browser_*` family call SQLite functions
+  Calibre registers from Python at connection time, so `SELECT * FROM meta` fails with
+  `no such function: sortconcat`. Only base tables are touched below.
+- **An unknown date is a sentinel, not a null** — `0101-01-01`, Calibre's
+  `UNDEFINED_DATE`. It parses fine as a date, so nothing complains; it just makes every
+  book without a publication date look like it was published in the year 101.
+- **`data.name` is not the title.** It is the on-disk stem, truncated to Calibre's
+  filename limit and sanitised, so the file is `The Project Gutenberg eBook #33283_
+  Calcul - Silvanus Phillips Thompson.pdf` for a book titled `The Project Gutenberg
+  eBook #33283: Calculus Made Easy, 2nd Edition`. Names locate files; the database
+  carries the metadata.
+- **`authors.name` escapes a comma as `|`**, which Calibre reverses on read
+  (`AuthorsTable.unserialize` in its `db/tables.py`).
+- **`series_index` defaults to 1.0 whether or not the book is in a series**, so a
+  position is only meaningful alongside a series.
+- **`books_pages_link` is recent and often empty.** It is treated as optional both ways:
+  the table may not exist, and where it does the rows are frequently `pages = 0` with
+  `needs_scan = 1`.
+
+Nothing walks the tree: every file is located through `books.path`, which is why
+`.caltrash` — where Calibre keeps deleted books, still on disk — cannot be picked up by
+accident.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import shutil
+import sqlite3
+import tempfile
+import zipfile
+from collections import defaultdict
+from collections.abc import Callable
+from dataclasses import dataclass, field
+from datetime import date, datetime
+from html.parser import HTMLParser
+from pathlib import Path, PurePosixPath
+
+
+METADATA_DB = "metadata.db"
+COVER_FILENAME = "cover.jpg"
+
+# Calibre writes `0101-01-01` for "no date". Any year this early is that sentinel rather
+# than a publication date somebody meant.
+EARLIEST_REAL_YEAR = 1000
+
+# The sidecars a WAL-mode database keeps beside itself. Copied along with it so the
+# snapshot can be recovered, since Calibre may be running while this reads.
+_DATABASE_SIDECARS = ("-wal", "-shm")
+
+
+class CalibreLibraryError(Exception):
+    """The library cannot be read at all — wrong directory, or no catalogue in it."""
+
+
+# How far down an archive to look for `metadata.db`. Zipping a Calibre library gives
+# either the directory itself or its contents, and a file manager may add a wrapper
+# folder on top, so two levels of nesting is normal and more is somebody's backup tree.
+_ARCHIVE_SEARCH_DEPTH = 3
+
+# Extraction is refused unless the destination has the uncompressed size plus this
+# much headroom. Filling the disk would take the whole application down, not just the
+# import.
+_DISK_HEADROOM = 256 * 1024 * 1024  # 256 MiB
+
+
+def _archive_members(archive: zipfile.ZipFile) -> list[zipfile.ZipInfo]:
+    """
+    The entries worth extracting, refusing any that would escape the destination.
+
+    `ZipFile.extract` does sanitise names, but relying on that silently is how the next
+    person to swap the extraction call reintroduces zip-slip. An archive naming
+    `../../etc/anything` is malformed or hostile, and either way there is nothing to
+    salvage by continuing.
+
+    Raises:
+        CalibreLibraryError: If any entry points outside the archive root.
+    """
+    members = []
+
+    for member in archive.infolist():
+        if member.is_dir():
+            continue
+
+        name = PurePosixPath(member.filename)
+
+        if name.is_absolute() or ".." in name.parts:
+            raise CalibreLibraryError(
+                f"The archive contains an entry outside itself: {member.filename!r}"
+            )
+
+        members.append(member)
+
+    return members
+
+
+async def extract_calibre_archive(archive: Path, destination: Path) -> Path:
+    """
+    Unpack a zipped Calibre library and find the catalogue inside it.
+
+    Args:
+        archive: The `.zip` to unpack.
+        destination: An empty directory to unpack into. The caller owns it and is
+            responsible for removing it.
+
+    Returns:
+        The directory holding `metadata.db`, which is what `CalibreLibrary` takes.
+
+    Raises:
+        CalibreLibraryError: If the file is not a zip, names an entry outside itself,
+            would not fit on disk, or holds no `metadata.db`.
+    """
+    return await asyncio.to_thread(_extract_calibre_archive, archive, destination)
+
+
+def _extract_calibre_archive(archive: Path, destination: Path) -> Path:
+    if not zipfile.is_zipfile(archive):
+        raise CalibreLibraryError(
+            "That is not a zip file. A Calibre library has to be zipped, not tarred."
+        )
+
+    with zipfile.ZipFile(archive) as opened:
+        members = _archive_members(opened)
+
+        if not any(
+            PurePosixPath(member.filename).name == METADATA_DB for member in members
+        ):
+            raise CalibreLibraryError(
+                f"The archive holds no {METADATA_DB}, so it is not a Calibre library"
+            )
+
+        # Checked before writing rather than discovered part-way through: a full disk
+        # takes the whole application down, and the number is in the archive already.
+        needed = sum(member.file_size for member in members)
+        free = shutil.disk_usage(destination).free
+
+        if needed + _DISK_HEADROOM > free:
+            raise CalibreLibraryError(
+                f"Unpacking needs {needed // (1024 * 1024)} MiB and only "
+                f"{free // (1024 * 1024)} MiB is free"
+            )
+
+        opened.extractall(destination, members=members)
+
+    return _find_catalogue(destination)
+
+
+def _find_catalogue(root: Path) -> Path:
+    """The shallowest directory under `root` holding a `metadata.db`."""
+    candidates = sorted(
+        (path.parent for path in root.rglob(METADATA_DB) if path.is_file()),
+        key=lambda path: len(path.relative_to(root).parts),
+    )
+
+    for candidate in candidates:
+        if len(candidate.relative_to(root).parts) <= _ARCHIVE_SEARCH_DEPTH:
+            return candidate
+
+    raise CalibreLibraryError(
+        f"No {METADATA_DB} within {_ARCHIVE_SEARCH_DEPTH} levels of the archive root"
+    )
+
+
+@dataclass(frozen=True)
+class CalibreFile:
+    """One row of Calibre's `data` table: a book in one format."""
+
+    path: Path
+    """Absolute path, resolved against the library root. Not checked for existence."""
+
+    format: str
+    """As Calibre stores it, upper case: `EPUB`, `PDF`, `AZW3`."""
+
+    size: int
+    """`data.uncompressed_size` — Calibre's claim, not a fresh stat."""
+
+
+@dataclass(frozen=True)
+class CalibreBook:
+    """One book, with everything Chitai has a column for and nothing it does not."""
+
+    calibre_id: int
+    uuid: str
+    title: str
+    authors: list[str] = field(default_factory=list)
+    description: str | None = None
+    published_date: date | None = None
+    series: str | None = None
+    series_position: str | None = None
+    tags: list[str] = field(default_factory=list)
+    publisher: str | None = None
+    language: str | None = None
+
+    identifiers: dict[str, str] = field(default_factory=dict)
+    """Keyed by `identifiers.type` verbatim — `isbn`, `mobi-asin`, `amazon`."""
+
+    pages: int | None = None
+    cover: Path | None = None
+    files: list[CalibreFile] = field(default_factory=list)
+
+
+class CalibreLibrary:
+    """
+    A Calibre library on disk, opened for reading.
+
+    The catalogue is **copied** before it is read. Calibre may be running and writing,
+    and opening the live file either sees a torn state or needs to recover a write-ahead
+    log, which read-only access cannot do. The copy is small — hundreds of kilobytes for
+    a handful of books, single-digit megabytes for thousands — so this costs nothing and
+    removes the question. The original is never opened by SQLite at all.
+    """
+
+    def __init__(self, root: Path | str) -> None:
+        self.root = Path(root)
+        self._connection: sqlite3.Connection | None = None
+        self._workspace: Path | None = None
+
+        # Every query runs in a worker thread, and `asyncio.to_thread` hands out
+        # whichever one is free — so the connection outlives the thread that opened it
+        # and `check_same_thread` has to be off. The lock is what makes that safe: it
+        # keeps two queries off the connection at once, which is the thing that check
+        # was standing in for.
+        self._lock = asyncio.Lock()
+
+    @property
+    def database(self) -> Path:
+        return self.root / METADATA_DB
+
+    async def open(self) -> None:
+        """
+        Copy the catalogue aside and connect to the copy.
+
+        Raises:
+            CalibreLibraryError: If there is no `metadata.db` under the root.
+        """
+        if self._connection is not None:
+            return
+
+        if not await asyncio.to_thread(self.database.is_file):
+            raise CalibreLibraryError(
+                f"No {METADATA_DB} in '{self.root}' — that is not a Calibre library"
+            )
+
+        self._workspace = Path(await asyncio.to_thread(tempfile.mkdtemp))
+        copy = self._workspace / METADATA_DB
+
+        await asyncio.to_thread(self._copy_database, copy)
+
+        # Read-write on our own copy, deliberately: that is what lets SQLite recover a
+        # write-ahead log the source may have been mid-way through.
+        self._connection = sqlite3.connect(str(copy), check_same_thread=False)
+
+    def _copy_database(self, destination: Path) -> None:
+        shutil.copy2(self.database, destination)
+
+        for suffix in _DATABASE_SIDECARS:
+            sidecar = self.database.with_name(self.database.name + suffix)
+            if sidecar.is_file():
+                shutil.copy2(sidecar, destination.with_name(destination.name + suffix))
+
+    async def close(self) -> None:
+        """
+        Disconnect and remove the copy. Safe to call more than once.
+
+        The copy is removed even if closing the connection fails — otherwise a failure
+        here leaves a catalogue-sized file in the temp directory, and the caller that
+        failed is exactly the one that will not come back to tidy up.
+        """
+        try:
+            if self._connection is not None:
+                async with self._lock:
+                    self._connection.close()
+                    self._connection = None
+        finally:
+            if self._workspace is not None:
+                await asyncio.to_thread(shutil.rmtree, self._workspace, True)
+                self._workspace = None
+
+    async def __aenter__(self) -> CalibreLibrary:
+        await self.open()
+        return self
+
+    async def __aexit__(self, *_exception: object) -> None:
+        await self.close()
+
+    async def count(self) -> int:
+        """How many books the catalogue holds, without reading any of them."""
+        rows = await self._in_thread(lambda: self._execute("SELECT count(*) FROM books"))
+        return int(rows[0][0])
+
+    async def books(self) -> list[CalibreBook]:
+        """
+        Read the whole catalogue.
+
+        One query per table and the joining done in Python, rather than a per-book query
+        across ten tables. Everything Chitai stores about a book is small, so a
+        self-hosted catalogue fits in memory comfortably.
+
+        Returns:
+            Every book, in Calibre id order.
+        """
+        return await self._in_thread(self._read_books)
+
+    async def _in_thread[T](self, work: Callable[[], T]) -> T:
+        """Run one unit of SQLite work off the event loop, and only one at a time."""
+        async with self._lock:
+            return await asyncio.to_thread(work)
+
+    def _execute(self, statement: str) -> list[tuple]:
+        if self._connection is None:
+            raise CalibreLibraryError("The library is not open")
+
+        return self._connection.execute(statement).fetchall()
+
+    def _has_table(self, name: str) -> bool:
+        return bool(
+            self._execute(
+                f"SELECT 1 FROM sqlite_master WHERE type = 'table' AND name = '{name}'"
+            )
+        )
+
+    def _read_books(self) -> list[CalibreBook]:
+        authors = self._grouped(
+            "SELECT bal.book, a.name FROM books_authors_link bal "
+            "JOIN authors a ON a.id = bal.author ORDER BY bal.id"
+        )
+        tags = self._grouped(
+            "SELECT btl.book, t.name FROM books_tags_link btl "
+            "JOIN tags t ON t.id = btl.tag ORDER BY t.name"
+        )
+        # Calibre's link tables are unique per book for these two, so the last write
+        # wins and there is nothing to choose between.
+        series = self._mapped(
+            "SELECT bsl.book, s.name FROM books_series_link bsl "
+            "JOIN series s ON s.id = bsl.series"
+        )
+        publishers = self._mapped(
+            "SELECT bpl.book, p.name FROM books_publishers_link bpl "
+            "JOIN publishers p ON p.id = bpl.publisher"
+        )
+        # A book can carry several languages; Chitai holds one, so the first wins.
+        languages = self._grouped(
+            "SELECT bll.book, l.lang_code FROM books_languages_link bll "
+            "JOIN languages l ON l.id = bll.lang_code ORDER BY bll.item_order"
+        )
+        descriptions = self._mapped("SELECT book, text FROM comments")
+
+        identifiers: dict[int, dict[str, str]] = defaultdict(dict)
+        for book_id, name, value in self._execute(
+            "SELECT book, type, val FROM identifiers"
+        ):
+            if name and value:
+                identifiers[book_id][str(name)] = str(value)
+
+        files: dict[int, list[tuple[str, str, int]]] = defaultdict(list)
+        for book_id, format, name, size in self._execute(
+            "SELECT book, format, name, uncompressed_size FROM data ORDER BY id"
+        ):
+            files[book_id].append((str(format), str(name), int(size or 0)))
+
+        pages: dict[int, int] = {}
+        if self._has_table("books_pages_link"):
+            pages = {
+                book_id: int(count)
+                for book_id, count in self._execute(
+                    "SELECT book, pages FROM books_pages_link WHERE pages > 0"
+                )
+            }
+
+        books = []
+        for row in self._execute(
+            "SELECT id, title, pubdate, series_index, path, uuid, has_cover "
+            "FROM books ORDER BY id"
+        ):
+            book_id, title, pubdate, series_index, path, uuid, has_cover = row
+            directory = self.root / Path(str(path))
+            in_series = series.get(book_id)
+
+            books.append(
+                CalibreBook(
+                    calibre_id=book_id,
+                    uuid=str(uuid or ""),
+                    title=str(title or ""),
+                    authors=[unescape_author(name) for name in authors.get(book_id, [])],
+                    description=strip_html(descriptions.get(book_id)),
+                    published_date=parse_date(pubdate),
+                    series=in_series,
+                    # Meaningless without a series: Calibre defaults the index to 1.0 for
+                    # every book, in a series or not.
+                    series_position=(
+                        format_series_index(series_index) if in_series else None
+                    ),
+                    tags=tags.get(book_id, []),
+                    publisher=publishers.get(book_id),
+                    language=next(iter(languages.get(book_id, [])), None),
+                    identifiers=dict(identifiers.get(book_id, {})),
+                    pages=pages.get(book_id),
+                    cover=directory / COVER_FILENAME if has_cover else None,
+                    files=[
+                        CalibreFile(
+                            path=directory / f"{name}.{format.lower()}",
+                            format=format,
+                            size=size,
+                        )
+                        for format, name, size in files.get(book_id, [])
+                    ],
+                )
+            )
+
+        return books
+
+    def _grouped(self, statement: str) -> dict[int, list[str]]:
+        """Run a `(book, value)` query into one list per book, keeping row order."""
+        grouped: dict[int, list[str]] = defaultdict(list)
+
+        for book_id, value in self._execute(statement):
+            if value is not None:
+                grouped[book_id].append(str(value))
+
+        return grouped
+
+    def _mapped(self, statement: str) -> dict[int, str]:
+        """Run a `(book, value)` query into one value per book."""
+        return {
+            book_id: str(value)
+            for book_id, value in self._execute(statement)
+            if value is not None
+        }
+
+
+def unescape_author(name: str) -> str:
+    """
+    Undo Calibre's comma escaping.
+
+    `authors.name` stores a comma as `|`, and Calibre reverses it on the way out. Left
+    alone, `Doyle, Sir Arthur Conan` comes back as `Doyle| Sir Arthur Conan`.
+    """
+    return name.replace("|", ",").strip()
+
+
+def parse_date(value: object) -> date | None:
+    """
+    Read one of Calibre's timestamps, discarding its "unknown" sentinel.
+
+    Args:
+        value: The stored column, which is text in practice but need not be.
+
+    Returns:
+        The date, or None for a null, an unparseable value, or Calibre's
+        `0101-01-01` placeholder.
+    """
+    if value is None:
+        return None
+
+    if isinstance(value, datetime):
+        parsed = value.date()
+    elif isinstance(value, date):
+        parsed = value
+    else:
+        text = str(value).strip()
+        if not text:
+            return None
+
+        try:
+            parsed = datetime.fromisoformat(text).date()
+        except ValueError:
+            try:
+                parsed = date.fromisoformat(text[:10])
+            except ValueError:
+                return None
+
+    return parsed if parsed.year >= EARLIEST_REAL_YEAR else None
+
+
+def format_series_index(index: object) -> str | None:
+    """
+    Render `series_index` as the string `Book.series_position` holds.
+
+    Calibre stores a REAL, so volume seven arrives as `7.0` — which would be stored
+    verbatim and then compared as a string against the `7` everything else writes.
+    Fractional positions are real and are kept: `1.5` is a novella between two novels.
+    """
+    if index is None:
+        return None
+
+    try:
+        number = float(index)
+    except (TypeError, ValueError):
+        return None
+
+    return str(int(number)) if number.is_integer() else f"{number:g}"
+
+
+class _TextExtractor(HTMLParser):
+    """Flatten markup to text, keeping the line breaks that carried meaning."""
+
+    # Tags whose boundaries are a line break rather than nothing at all. Without these
+    # a description of three paragraphs comes out as one run-on sentence.
+    _BREAKS = frozenset(
+        {
+            "p", "br", "div", "li", "tr", "blockquote", "hr",
+            "h1", "h2", "h3", "h4", "h5", "h6",
+        }
+    )
+
+    def __init__(self) -> None:
+        super().__init__(convert_charrefs=True)
+        self._parts: list[str] = []
+
+    def handle_data(self, data: str) -> None:
+        self._parts.append(data)
+
+    def handle_starttag(self, tag: str, _attrs: object) -> None:
+        self._break(tag)
+
+    def handle_endtag(self, tag: str) -> None:
+        self._break(tag)
+
+    def _break(self, tag: str) -> None:
+        """
+        End the current line, once.
+
+        Both halves of `</p><p>` are a boundary, and the open tag of the very first
+        block is not one at all — so emitting a newline per tag turns two paragraphs
+        into two blank-line-separated ones with a leading gap. One break per boundary
+        is what the plain text wants.
+        """
+        if tag in self._BREAKS and self._parts and not self._parts[-1].endswith("\n"):
+            self._parts.append("\n")
+
+    @property
+    def text(self) -> str:
+        lines = [line.strip() for line in "".join(self._parts).splitlines()]
+
+        return "\n".join(line for line in lines if line).strip()
+
+
+def strip_html(html: str | None) -> str | None:
+    """
+    Turn Calibre's `comments` into plain text.
+
+    `comments.text` is always HTML, and `Book.description` is rendered as text — so the
+    tags would show literally on the book page.
+
+    Args:
+        html: The stored comment, if there is one.
+
+    Returns:
+        The text, or None when there was nothing or nothing survived.
+    """
+    if not html:
+        return None
+
+    parser = _TextExtractor()
+    parser.feed(html)
+    parser.close()
+
+    return parser.text or None

backend/src/chitai/services/calibre_import.py

@@ -0,0 +1,239 @@
+# src/chitai/services/calibre_import.py
+
+"""
+Run a Calibre import in the background and report on it.
+
+The import outlives its request — a real library takes minutes to hours — so the handler
+starts a task and hands back a handle to poll. The work itself is
+`BookService.create_many_from_calibre`; everything here is lifecycle: state, progress,
+cancellation, and a session of its own.
+
+**This registry lives in memory, and therefore assumes one worker process.** That holds
+today: the production `CMD` is `litestar run`, which is single-process, and the consume
+watcher is already an in-process singleton with the same constraint. `TODO.md` records
+that the production image should move to uvicorn with a worker count — the day that
+happens, a poll can land on a worker that has never heard of the job, and this needs an
+`import_jobs` table instead. It is written down here because nothing else will say so.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import shutil
+import uuid
+from dataclasses import dataclass, field
+from enum import StrEnum
+from pathlib import Path
+
+from chitai.config import settings
+from chitai.database.models import Library
+from chitai.services.book import (
+    BookService,
+    CalibreImportProgress,
+    CalibreImportResult,
+    UnimportedBook,
+)
+from chitai.services.calibre import CalibreLibrary
+
+
+class ImportState(StrEnum):
+    """Where a job has got to."""
+
+    RUNNING = "running"
+    FINISHED = "finished"
+
+    # Stopped on request. What it imported is complete.
+    CANCELLED = "cancelled"
+
+    # The run itself broke — an unreadable catalogue, a missing library. Distinct from
+    # individual books failing, which `failures` carries and which never stops the run.
+    FAILED = "failed"
+
+
+@dataclass
+class ImportJob:
+    """One import, running or finished."""
+
+    id: str
+    library_id: int
+    source: str
+
+    state: ImportState = ImportState.RUNNING
+    total: int = 0
+    processed: int = 0
+    created: int = 0
+    skipped: int = 0
+    failed: int = 0
+
+    current_title: str | None = None
+    failures: list[UnimportedBook] = field(default_factory=list)
+
+    # Books imported that look like something the library already had. A count, not the
+    # records: the duplicates screen is what shows them, and a big import would make
+    # this the largest thing in the response for no benefit.
+    possible_duplicates: int = 0
+
+    # Why the whole run stopped, when `state` is FAILED.
+    error: str | None = None
+
+    # The directory the job owns and must delete when it ends: what the uploaded archive
+    # was unpacked into.
+    workspace: Path | None = None
+
+    _stop: bool = False
+
+    @property
+    def finished(self) -> bool:
+        return self.state is not ImportState.RUNNING
+
+    def absorb(self, result: CalibreImportResult) -> None:
+        """Take the final counts from a finished run."""
+        self.total = result.total
+        self.created = len(result.created)
+        self.skipped = len(result.skipped)
+        self.failed = len(result.failed)
+        self.failures = list(result.failed)
+        self.possible_duplicates = len(result.possible_duplicates)
+        self.current_title = None
+
+        self.state = ImportState.CANCELLED if result.stopped else ImportState.FINISHED
+
+
+class CalibreImportRegistry:
+    """
+    The imports this process knows about.
+
+    One instance, held at module scope below. Jobs are kept after they finish so the
+    screen that started one can still read its result; nothing evicts them, which is
+    fine for a handful of one-time migrations and is the other reason a table would be
+    the answer if this ever needed to be durable.
+    """
+
+    def __init__(self) -> None:
+        self._jobs: dict[str, ImportJob] = {}
+
+        # Held only to keep the tasks referenced. Without this the event loop is free to
+        # garbage-collect a running task mid-import.
+        self._tasks: set[asyncio.Task] = set()
+
+    def get(self, job_id: str) -> ImportJob | None:
+        return self._jobs.get(job_id)
+
+    def running_for(self, library_id: int) -> ImportJob | None:
+        """The unfinished import for a library, if it has one."""
+        return next(
+            (
+                job
+                for job in self._jobs.values()
+                if job.library_id == library_id and not job.finished
+            ),
+            None,
+        )
+
+    def cancel(self, job_id: str) -> ImportJob | None:
+        """
+        Ask a job to stop after the book it is on.
+
+        Not `task.cancel()`: that would abandon a book mid-copy, leaving files on disk
+        with no row describing them. The flag is read between books.
+        """
+        job = self._jobs.get(job_id)
+
+        if job is not None and not job.finished:
+            job._stop = True
+
+        return job
+
+    def start(
+        self,
+        library: Library,
+        source: Path,
+        workspace: Path,
+        label: str,
+        allow_duplicates: bool = False,
+    ) -> ImportJob:
+        """
+        Begin importing, and return the handle to poll.
+
+        Args:
+            library: The library to import into.
+            source: The unpacked Calibre library's directory.
+            workspace: A directory the job owns and deletes when it ends — what the
+                uploaded archive was unpacked into. The books have been copied into the
+                library by then, so nothing is lost with it.
+            label: What to report as the source. `source` is a temp directory that would
+                mean nothing to the reader, so this is the archive's own name.
+            allow_duplicates: Import books whose files are already stored.
+
+        Returns:
+            The job, already running.
+        """
+        job = ImportJob(
+            id=str(uuid.uuid4()),
+            library_id=library.id,
+            source=label,
+            workspace=workspace,
+        )
+        self._jobs[job.id] = job
+
+        task = asyncio.create_task(self._run(job, library.id, source, allow_duplicates))
+        self._tasks.add(task)
+        task.add_done_callback(self._tasks.discard)
+
+        return job
+
+    async def _run(
+        self, job: ImportJob, library_id: int, source: Path, allow_duplicates: bool
+    ) -> None:
+        """
+        Do the import, recording everything on the job.
+
+        Opens a **session of its own**: the request that started this is long gone, and
+        its session was closed with it.
+        """
+        from chitai.services.library import LibraryService
+
+        def on_progress(progress: CalibreImportProgress) -> None:
+            job.total = progress.total
+            job.processed = progress.processed
+            job.current_title = progress.title
+
+            if progress.outcome == "created":
+                job.created += 1
+            elif progress.outcome == "skipped":
+                job.skipped += 1
+            else:
+                job.failed += 1
+
+        catalogue = CalibreLibrary(source)
+
+        try:
+            await catalogue.open()
+
+            async with settings.alchemy_config.get_session() as session:
+                library = await LibraryService(session=session).get(library_id)
+
+                result = await BookService(session=session).create_many_from_calibre(
+                    catalogue,
+                    library,
+                    allow_duplicates=allow_duplicates,
+                    on_progress=on_progress,
+                    should_stop=lambda: job._stop,
+                )
+
+            job.absorb(result)
+        except Exception as exc:
+            job.state = ImportState.FAILED
+            job.error = f"{type(exc).__name__}: {exc}"
+        finally:
+            await catalogue.close()
+
+            # An unpacked archive is a second copy of the whole library, and the books
+            # worth keeping have been copied into the library proper by now. Removed
+            # even when the run failed — especially then, since nothing will come back
+            # for it.
+            if job.workspace is not None:
+                await asyncio.to_thread(shutil.rmtree, job.workspace, True)
+
+
+registry = CalibreImportRegistry()

backend/src/chitai/services/filesystem_library.py

@@ -16,6 +16,43 @@ import chitai.database.models as m
 #   - Auto-handle missing values (e.g., skip {series}/ if series is empty)
 
 
+# Characters that cannot survive being interpolated into a path. The forward slash is
+# the one that matters: titles legitimately contain it — "AC/DC", "Him/Her" — and the
+# template writes the title straight into a directory name, so an unsanitised one
+# silently adds a level and puts the book somewhere `book.path` does not describe.
+# Calibre strips these from its own on-disk names and keeps the real title in its
+# database, which is how an import surfaces them.
+_UNSAFE_IN_PATH = re.compile(r"[/\\\x00-\x1f]")
+
+
+def sanitize_path_component(value: str) -> str:
+    """Make one metadata value safe to use as a single directory or file name."""
+    return _UNSAFE_IN_PATH.sub("_", value).strip()
+
+
+def _safe_components(book_data: dict) -> dict:
+    """
+    A shallow copy of the metadata with the values a path is built from sanitised.
+
+    Only strings are touched, and only the fields the default template interpolates. A
+    caller's own template can reach anything else in the dict, which is a reason to keep
+    this conservative rather than to walk the whole structure.
+    """
+    safe = dict(book_data)
+
+    for key in ("title", "series", "series_position"):
+        if isinstance(safe.get(key), str):
+            safe[key] = sanitize_path_component(safe[key])
+
+    if isinstance(safe.get("authors"), list):
+        safe["authors"] = [
+            sanitize_path_component(author) if isinstance(author, str) else author
+            for author in safe["authors"]
+        ]
+
+    return safe
+
+
 default_path_template = """
 /{{book.authors[0] if book.authors else 'Unknown'}}
 {%- if book.series -%}
@@ -101,7 +138,12 @@ class BookPathGenerator:
 
         """
 
-        result = self.root_path / Path(self.path_template.render(book=book_data))
+        # Sanitised per value, never on the rendered result: the separators the template
+        # puts *between* author, series and title are the whole point of it, and only the
+        # values interpolated into it must not contribute any of their own.
+        result = self.root_path / Path(
+            self.path_template.render(book=_safe_components(book_data))
+        )
 
         # Clean up
         result = re.sub(r"/+", "/", str(result))  # Remove consecutive backslashes

backend/src/chitai/services/opds/opds.py

@@ -47,8 +47,13 @@ def convert_book_to_entry(book: m.Book) -> Entry:
         link=[
             ImageLink(href=f"/{book.cover_image}", type="image/webp"),
             *[
+                # The only place a content type has to be a string: `Link.type` is
+                # required, and a null fails the whole feed rather than one entry.
+                # `application/octet-stream` is the registered way to say "opaque
+                # bytes", which is exactly what an unnamed format is.
                 AcquisitionLink(
-                    href=f"/opds/download/{book.id}/{file.id}", type=file.content_type
+                    href=f"/opds/download/{book.id}/{file.id}",
+                    type=file.content_type or "application/octet-stream",
                 )
                 for file in book.files
             ],

backend/src/chitai/services/utils.py

@@ -5,6 +5,7 @@ from __future__ import annotations
 
 import errno
 import hashlib
+import mimetypes
 from pathlib import Path
 import shutil
 from typing import BinaryIO
@@ -238,6 +239,29 @@ async def move_file(src_path: Path, dest_path: Path, create_dirs=True) -> None:
         # all configured separately, so they can easily be separate mounts.
         shutil.move(str(src_path), str(dest_path))
 
+async def copy_file(src_path: Path, dest_path: Path, create_dirs: bool = True) -> None:
+    """
+    Copy a file, streaming it rather than reading it whole.
+
+    `shutil.copy` would block the event loop for as long as the read takes, which for a
+    40 MB ebook — and a few thousand of them in a row — is not acceptable.
+
+    Args:
+        src_path: The file to copy. Left exactly as it is.
+        dest_path: Where the copy goes.
+        create_dirs: Create the destination's parent directories first.
+    """
+    if create_dirs and dest_path.parent:
+        await aios.makedirs(dest_path.parent, exist_ok=True)
+
+    async with (
+        aiofiles.open(src_path, "rb") as source,
+        aiofiles.open(dest_path, "wb") as destination,
+    ):
+        while chunk := await source.read(HASH_CHUNK_SIZE):
+            await destination.write(chunk)
+
+
 async def move_dir_contents(source_dir: Path | str, target_dir: Path | str) -> None:
     """
     Move all contents from source directory to target directory.
@@ -459,6 +483,66 @@ def get_filename(file: Path | str, ext: bool = True) -> str:
     return filename.stem
 
 
+# Content types for the ebook formats `mimetypes` does not know. Python's built-in map
+# covers `.epub`, `.pdf`, `.azw3`, `.cbz`, `.cbr` and `.djvu`, and answers `None` for
+# every format below — so a library imported from elsewhere, which is where MOBI and
+# AZW files come from, stores nothing for them.
+#
+# That matters downstream because an OPDS acquisition link is how a reader app decides
+# whether it can open a file at all.
+
+# What a client sends when it does not know either. Treated as an absence rather than
+# an answer: storing it would be indistinguishable from having determined a format, and
+# it is the value browsers post for every extension they do not recognise.
+_UNSPECIFIED = "application/octet-stream"
+
+EBOOK_CONTENT_TYPES = {
+    "mobi": "application/x-mobipocket-ebook",
+    "prc": "application/x-mobipocket-ebook",
+    "azw": "application/vnd.amazon.ebook",
+    "fb2": "application/x-fictionbook+xml",
+    "fbz": "application/x-zip-compressed-fb2",
+    "lit": "application/x-ms-reader",
+    "lrf": "application/x-sony-bbeb",
+    "cb7": "application/x-cb7",
+}
+
+
+def guess_content_type(
+    file: Path | str | UploadFile, fallback: str | None = None
+) -> str | None:
+    """
+    Name a file's format from its extension.
+
+    The extension is trusted ahead of anything a client said: a browser posts
+    `application/octet-stream` for every format it does not recognise, which is most
+    ebook formats, and that answer is worth less than the `.mobi` on the end of the
+    name.
+
+    Args:
+        file: The file to name, as a path or an upload.
+        fallback: What to use when neither table knows the extension — a client-supplied
+            content type, if there is one. `application/octet-stream` is discarded: it
+            is the client saying it does not know, which is not information.
+
+    Returns:
+        The content type, or None when nothing can name it. Null is the honest answer
+        and the column is nullable: a caller that structurally needs a string should
+        substitute one where it needs it, rather than have an invented value stored.
+    """
+    extension = get_file_extension(file)
+
+    if known := EBOOK_CONTENT_TYPES.get(extension):
+        return known
+
+    guessed, _ = mimetypes.guess_type(get_filename(file))
+
+    if fallback == _UNSPECIFIED:
+        fallback = None
+
+    return guessed or fallback
+
+
 ###############################
 #  ISBN Validation utilities  #
 ###############################

backend/tests/calibre_fixtures.py

@@ -0,0 +1,282 @@
+"""
+Build a Calibre library on disk, for tests to read.
+
+Generated rather than committed as a binary `metadata.db`, because the rows worth
+testing are the awkward ones — the year-101 pubdate, a `|` in an author name, a REAL
+series index, HTML in a comment — and those are clearer written out in Python than
+hidden inside a blob.
+
+The schema below is Calibre's own, copied from a real library's `sqlite_master`, reduced
+to the tables the reader touches. `books_pages_link` is created separately by
+`add_pages`: it is recent, and a library made by an older Calibre will not have it.
+"""
+
+from __future__ import annotations
+
+import shutil
+import sqlite3
+from pathlib import Path
+
+
+SCHEMA = """
+CREATE TABLE books (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    title TEXT NOT NULL DEFAULT 'Unknown' COLLATE NOCASE,
+    sort TEXT COLLATE NOCASE,
+    timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    pubdate TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    series_index REAL NOT NULL DEFAULT 1.0,
+    author_sort TEXT COLLATE NOCASE,
+    path TEXT NOT NULL DEFAULT '',
+    uuid TEXT,
+    has_cover BOOL DEFAULT 0,
+    last_modified TIMESTAMP NOT NULL DEFAULT '2000-01-01 00:00:00+00:00'
+);
+CREATE TABLE authors (
+    id INTEGER PRIMARY KEY, name TEXT NOT NULL COLLATE NOCASE,
+    sort TEXT COLLATE NOCASE, link TEXT NOT NULL DEFAULT '', UNIQUE(name)
+);
+CREATE TABLE books_authors_link (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL, author INTEGER NOT NULL,
+    UNIQUE(book, author)
+);
+CREATE TABLE publishers (
+    id INTEGER PRIMARY KEY, name TEXT NOT NULL COLLATE NOCASE,
+    sort TEXT COLLATE NOCASE, link TEXT NOT NULL DEFAULT '', UNIQUE(name)
+);
+CREATE TABLE books_publishers_link (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL, publisher INTEGER NOT NULL,
+    UNIQUE(book)
+);
+CREATE TABLE tags (
+    id INTEGER PRIMARY KEY, name TEXT NOT NULL COLLATE NOCASE,
+    link TEXT NOT NULL DEFAULT '', UNIQUE (name)
+);
+CREATE TABLE books_tags_link (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL, tag INTEGER NOT NULL,
+    UNIQUE(book, tag)
+);
+CREATE TABLE series (
+    id INTEGER PRIMARY KEY, name TEXT NOT NULL COLLATE NOCASE,
+    sort TEXT COLLATE NOCASE, link TEXT NOT NULL DEFAULT '', UNIQUE (name)
+);
+CREATE TABLE books_series_link (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL, series INTEGER NOT NULL,
+    UNIQUE(book)
+);
+CREATE TABLE languages (
+    id INTEGER PRIMARY KEY, lang_code TEXT NOT NULL COLLATE NOCASE,
+    link TEXT NOT NULL DEFAULT '', UNIQUE(lang_code)
+);
+CREATE TABLE books_languages_link (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL, lang_code INTEGER NOT NULL,
+    item_order INTEGER NOT NULL DEFAULT 0, UNIQUE(book, lang_code)
+);
+CREATE TABLE comments (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL,
+    text TEXT NOT NULL COLLATE NOCASE, UNIQUE(book)
+);
+CREATE TABLE identifiers (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL,
+    type TEXT NOT NULL DEFAULT 'isbn' COLLATE NOCASE,
+    val TEXT NOT NULL COLLATE NOCASE, UNIQUE(book, type)
+);
+CREATE TABLE data (
+    id INTEGER PRIMARY KEY, book INTEGER NOT NULL,
+    format TEXT NOT NULL COLLATE NOCASE, uncompressed_size INTEGER NOT NULL,
+    name TEXT NOT NULL, UNIQUE(book, format)
+);
+"""
+
+# Calibre's own "no date". Stored, never null, and a valid date — which is exactly why
+# it has to be recognised rather than parsed.
+UNDEFINED_DATE = "0101-01-01 00:00:00+00:00"
+
+# What a `cover.jpg` that PIL cannot read looks like. Real libraries hold these, from
+# an interrupted download or a failed conversion.
+CORRUPT_COVER = b"\xff\xd8\xff\xe0 not really a jpeg"
+
+
+def write_cover(path: Path) -> None:
+    """
+    Write a real, readable JPEG.
+
+    Generated with PIL rather than embedded as a hex blob: a hand-rolled JPEG that is
+    subtly malformed fails inside the import as an unrelated error, which is exactly the
+    confusion this avoids.
+    """
+    from PIL import Image
+
+    Image.new("RGB", (2, 3), (10, 20, 30)).save(path, "JPEG")
+
+
+class CalibreFixture:
+    """A Calibre library being assembled under `root`."""
+
+    def __init__(self, root: Path) -> None:
+        self.root = root
+        self.root.mkdir(parents=True, exist_ok=True)
+
+        self.connection = sqlite3.connect(self.root / "metadata.db")
+        self.connection.executescript(SCHEMA)
+
+    def add_pages_table(self) -> None:
+        """Add `books_pages_link`, which only a recent Calibre creates."""
+        self.connection.executescript(
+            """
+            CREATE TABLE books_pages_link (
+                book INTEGER PRIMARY KEY,
+                pages INTEGER DEFAULT 0 NOT NULL,
+                algorithm INTEGER DEFAULT 0 NOT NULL,
+                format TEXT DEFAULT '' NOT NULL COLLATE NOCASE,
+                format_size INTEGER DEFAULT 0 NOT NULL,
+                timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                needs_scan INTEGER NOT NULL DEFAULT 0
+            );
+            """
+        )
+
+    def add_book(
+        self,
+        book_id: int,
+        title: str,
+        *,
+        authors: list[str] | None = None,
+        pubdate: str = UNDEFINED_DATE,
+        series: str | None = None,
+        series_index: float = 1.0,
+        tags: list[str] | None = None,
+        publisher: str | None = None,
+        languages: list[str] | None = None,
+        comment: str | None = None,
+        identifiers: dict[str, str] | None = None,
+        uuid: str | None = None,
+        pages: int | None = None,
+        cover: bool = False,
+        corrupt_cover: bool = False,
+        formats: dict[str, Path] | None = None,
+        directory: str | None = None,
+    ) -> Path:
+        """
+        Add one book, with its files laid out the way Calibre lays them out.
+
+        Args:
+            formats: Format name (`EPUB`) to a real file to copy in. Its on-disk stem is
+                Calibre's, not the title — that is the point of the `data` table.
+            directory: Override the `books.path` value, for testing a row whose
+                directory is not where the convention would put it.
+
+        Returns:
+            The book's directory.
+        """
+        author_names = authors or ["Unknown"]
+        relative = directory or f"{author_names[0]}/{title} ({book_id})"
+        book_directory = self.root / relative
+        book_directory.mkdir(parents=True, exist_ok=True)
+
+        self.connection.execute(
+            "INSERT INTO books (id, title, pubdate, series_index, path, uuid, has_cover) "
+            "VALUES (?, ?, ?, ?, ?, ?, ?)",
+            (
+                book_id,
+                title,
+                pubdate,
+                series_index,
+                relative,
+                uuid or f"uuid-{book_id}",
+                int(cover or corrupt_cover),
+            ),
+        )
+
+        for name in author_names:
+            self._link("authors", "books_authors_link", "author", book_id, name)
+
+        for name in tags or []:
+            self._link("tags", "books_tags_link", "tag", book_id, name)
+
+        if series:
+            self._link("series", "books_series_link", "series", book_id, series)
+
+        if publisher:
+            self._link(
+                "publishers", "books_publishers_link", "publisher", book_id, publisher
+            )
+
+        for order, code in enumerate(languages or []):
+            language_id = self._lookup("languages", "lang_code", code)
+            self.connection.execute(
+                "INSERT INTO books_languages_link (book, lang_code, item_order) "
+                "VALUES (?, ?, ?)",
+                (book_id, language_id, order),
+            )
+
+        if comment is not None:
+            self.connection.execute(
+                "INSERT INTO comments (book, text) VALUES (?, ?)", (book_id, comment)
+            )
+
+        for name, value in (identifiers or {}).items():
+            self.connection.execute(
+                "INSERT INTO identifiers (book, type, val) VALUES (?, ?, ?)",
+                (book_id, name, value),
+            )
+
+        if pages is not None:
+            self.connection.execute(
+                "INSERT INTO books_pages_link (book, pages) VALUES (?, ?)",
+                (book_id, pages),
+            )
+
+        if corrupt_cover:
+            (book_directory / "cover.jpg").write_bytes(CORRUPT_COVER)
+        elif cover:
+            write_cover(book_directory / "cover.jpg")
+
+        for format, origin in (formats or {}).items():
+            # Calibre's on-disk stem: sanitised, truncated, and not the title.
+            stem = f"{title[:40]} - {author_names[0]}".replace(":", "_")
+            destination = book_directory / f"{stem}.{format.lower()}"
+            shutil.copy(origin, destination)
+
+            self.connection.execute(
+                "INSERT INTO data (book, format, uncompressed_size, name) "
+                "VALUES (?, ?, ?, ?)",
+                (book_id, format, destination.stat().st_size, stem),
+            )
+
+        return book_directory
+
+    def add_missing_format(self, book_id: int, format: str, stem: str) -> None:
+        """Record a file in the catalogue without putting one on disk."""
+        self.connection.execute(
+            "INSERT INTO data (book, format, uncompressed_size, name) VALUES (?, ?, ?, ?)",
+            (book_id, format, 1234, stem),
+        )
+
+    def _link(
+        self, table: str, link_table: str, column: str, book_id: int, name: str
+    ) -> None:
+        item_id = self._lookup(table, "name", name)
+        self.connection.execute(
+            f"INSERT INTO {link_table} (book, {column}) VALUES (?, ?)",
+            (book_id, item_id),
+        )
+
+    def _lookup(self, table: str, column: str, value: str) -> int:
+        row = self.connection.execute(
+            f"SELECT id FROM {table} WHERE {column} = ?", (value,)
+        ).fetchone()
+
+        if row:
+            return int(row[0])
+
+        cursor = self.connection.execute(
+            f"INSERT INTO {table} ({column}) VALUES (?)", (value,)
+        )
+        return int(cursor.lastrowid or 0)
+
+    def commit(self) -> Path:
+        """Finish writing and return the library root."""
+        self.connection.commit()
+        self.connection.close()
+        return self.root

backend/tests/integration/test_book.py

@@ -1272,3 +1272,94 @@ class TestFileManagement:
         )
         # Should succeed (idempotent)
         assert response2.status_code == 204
+
+
+@pytest.mark.asyncio
+class TestUnnameableFormats:
+    """
+    A file whose format nothing can name must still round-trip.
+
+    `mimetypes.guess_type` answers None for `.mobi`, `.azw`, `.fb2` and `.lit`, which
+    is most of what a library imported from elsewhere carries alongside its EPUBs.
+    `FileMetadataRead.content_type` used to be a required string, so such a book was
+    created and then failed serialisation on its way back out — a 500 on a book the
+    reader can otherwise download.
+    """
+
+    def upload(self, name: str) -> list[tuple[str, tuple]]:
+        # `application/octet-stream` is what a browser posts for these, and it is not
+        # an answer — the extension is what names the format.
+        return [("files", (name, b"BOOKMOBI\x00 payload", "application/octet-stream"))]
+
+    async def test_a_mobi_is_named_from_its_extension(
+        self, authenticated_client: AsyncClient
+    ) -> None:
+        response = await authenticated_client.post(
+            "/books?library_id=1", files=self.upload("Dune.mobi"), data={"library_id": 1}
+        )
+
+        assert response.status_code == 201
+        book = response.json()
+        assert book["files"][0]["content_type"] == "application/x-mobipocket-ebook"
+
+        detail = await authenticated_client.get(f"/books/{book['id']}")
+        assert detail.status_code == 200
+
+    async def test_an_unknown_extension_stores_no_content_type(
+        self, authenticated_client: AsyncClient
+    ) -> None:
+        """Null, not a placeholder — and the book still serialises either way."""
+        response = await authenticated_client.post(
+            "/books?library_id=1",
+            files=self.upload("Notes.xyzzy"),
+            data={"library_id": 1},
+        )
+
+        assert response.status_code == 201
+        book = response.json()
+        assert book["files"][0]["content_type"] is None
+
+        detail = await authenticated_client.get(f"/books/{book['id']}")
+        assert detail.status_code == 200
+        assert detail.json()["files"][0]["content_type"] is None
+
+    async def test_the_file_downloads(
+        self, authenticated_client: AsyncClient
+    ) -> None:
+        """Litestar supplies its own media type when the row carries none."""
+        created = await authenticated_client.post(
+            "/books?library_id=1",
+            files=self.upload("Notes.xyzzy"),
+            data={"library_id": 1},
+        )
+        book = created.json()
+
+        response = await authenticated_client.get(
+            f"/books/download/{book['id']}/{book['files'][0]['id']}"
+        )
+
+        assert response.status_code == 200
+        assert response.headers["content-type"] == "application/octet-stream"
+
+    async def test_the_opds_feed_survives_a_null_content_type(
+        self, authenticated_client: AsyncClient
+    ) -> None:
+        """
+        The one place the type has to be a string.
+
+        `Link.type` is required, so a null fails the whole feed rather than one entry.
+        OPDS clients speak Basic, not the JWT the rest of the API uses.
+        """
+        await authenticated_client.post(
+            "/books?library_id=1",
+            files=self.upload("Notes.xyzzy"),
+            data={"library_id": 1},
+        )
+
+        feed = await authenticated_client.get(
+            "/opds/acquisition?feed_id=all&feed_title=All+Books",
+            auth=("user1@example.com", "password123"),
+        )
+
+        assert feed.status_code == 200
+        assert 'type="application/octet-stream"' in feed.text

backend/tests/integration/test_calibre_import.py

@@ -0,0 +1,400 @@
+"""
+Tests for the Calibre import endpoints.
+
+The API takes a zipped library and nothing else — a desktop Calibre install is usually
+not on the server, and importing from a path the server can already see stays a
+server-side operation (`litestar calibre-import`).
+"""
+
+import asyncio
+import tempfile
+import zipfile
+from pathlib import Path
+
+import pytest
+from httpx import AsyncClient
+
+from chitai.services.calibre_import import registry
+
+from tests.calibre_fixtures import CalibreFixture
+
+
+EPUB = Path("tests/data_files/Metamorphosis - Franz Kafka.epub")
+OTHER_EPUB = Path("tests/data_files/The Art of War - Sun Tzu.epub")
+
+
+@pytest.fixture(autouse=True)
+def _clear_registry():
+    """The registry is a module-level singleton, so it leaks between tests."""
+    registry._jobs.clear()
+    yield
+    registry._jobs.clear()
+
+
+@pytest.fixture(name="source")
+def fx_source(tmp_path: Path) -> Path:
+    fixture = CalibreFixture(tmp_path / "calibre")
+    fixture.add_book(
+        1,
+        "The Metamorphosis",
+        authors=["Franz Kafka"],
+        tags=["Fiction"],
+        cover=True,
+        formats={"EPUB": EPUB},
+    )
+    fixture.add_book(2, "The Art of War", authors=["Sun Tzu"], formats={"EPUB": OTHER_EPUB})
+    fixture.add_book(3, "Metadata Only", authors=["Nobody"])
+
+    return fixture.commit()
+
+
+def zip_of(root: Path, into: Path, prefix: str = "") -> Path:
+    """Zip a directory the way a file manager would."""
+    into.mkdir(parents=True, exist_ok=True)
+    archive = into / "library.zip"
+
+    with zipfile.ZipFile(archive, "w") as writing:
+        for path in sorted(root.rglob("*")):
+            if path.is_file():
+                writing.write(path, f"{prefix}{path.relative_to(root)}")
+
+    return archive
+
+
+async def upload(
+    client: AsyncClient,
+    archive: Path,
+    library_id: int = 1,
+    allow_duplicates: bool = False,
+) -> tuple[int, dict]:
+    response = await client.post(
+        f"/libraries/{library_id}/imports/calibre/upload",
+        files=[("archive", (archive.name, archive.read_bytes(), "application/zip"))],
+        data={"allow_duplicates": str(allow_duplicates).lower()},
+    )
+
+    return response.status_code, response.json()
+
+
+async def wait_for(client: AsyncClient, job_id: str) -> dict:
+    """Poll until the job is no longer running, the way the screen does."""
+    for _ in range(200):
+        response = await client.get(f"/libraries/imports/{job_id}")
+        assert response.status_code == 200
+
+        job = response.json()
+        if job["state"] != "running":
+            return job
+
+        await asyncio.sleep(0.05)
+
+    raise AssertionError("the import never finished")
+
+
+async def test_an_uploaded_library_imports(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    status, job = await upload(
+        authenticated_client, zip_of(source, tmp_path / "out", prefix="Calibre Library/")
+    )
+
+    assert status == 202
+    assert job["state"] == "running"
+    assert job["library_id"] == 1
+
+    # The archive's name, not the temp directory it was unpacked into.
+    assert job["source"] == "library.zip"
+
+    finished = await wait_for(authenticated_client, job["id"])
+
+    assert finished["state"] == "finished"
+    assert finished["total"] == 3
+    assert finished["created"] == 2
+    assert finished["skipped"] == 1
+    assert finished["failed"] == 0
+    assert finished["error"] is None
+    assert finished["current_title"] is None
+
+    listed = await authenticated_client.get("/books?library_id=1")
+    titles = [book["title"] for book in listed.json()["items"]]
+    assert "The Metamorphosis" in titles
+    assert "The Art of War" in titles
+
+
+async def test_a_library_zipped_without_a_wrapping_folder(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    """Zipping the contents is as common as zipping the folder."""
+    status, job = await upload(authenticated_client, zip_of(source, tmp_path / "out"))
+
+    assert status == 202
+    finished = await wait_for(authenticated_client, job["id"])
+    assert finished["created"] == 2
+
+
+async def test_the_unpacked_copy_is_cleaned_up(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    """
+    An unpacked archive is a second copy of the whole library.
+
+    The books worth keeping have been copied into the library by the time the job ends,
+    so nothing is lost with it — and nothing will come back for it.
+    """
+    status, job = await upload(authenticated_client, zip_of(source, tmp_path / "out"))
+    assert status == 202
+
+    workspace = registry.get(job["id"]).workspace
+    assert workspace is not None
+
+    await wait_for(authenticated_client, job["id"])
+
+    assert not workspace.exists()
+
+
+async def test_uploading_the_same_library_twice_imports_nothing_new(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    """Re-running is safe, which is what makes an interrupted import resumable."""
+    archive = zip_of(source, tmp_path / "out")
+
+    for _ in range(2):
+        _, job = await upload(authenticated_client, archive)
+        finished = await wait_for(authenticated_client, job["id"])
+
+    assert finished["created"] == 0
+    assert finished["skipped"] == 3
+
+
+async def test_allow_duplicates_stores_the_files_again(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    """
+    The one option the screen offers, and it has to reach the import.
+
+    Without it the second pass skips everything, which is the previous test.
+    """
+    archive = zip_of(source, tmp_path / "out")
+
+    _, first = await upload(authenticated_client, archive)
+    await wait_for(authenticated_client, first["id"])
+
+    _, second = await upload(authenticated_client, archive, allow_duplicates=True)
+    finished = await wait_for(authenticated_client, second["id"])
+
+    assert finished["created"] == 2
+    assert finished["skipped"] == 1  # still the book with no files
+
+
+async def test_two_imports_into_one_library_conflict(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    archive = zip_of(source, tmp_path / "out")
+
+    first_status, first = await upload(authenticated_client, archive)
+    assert first_status == 202
+
+    second_status, second = await upload(authenticated_client, archive)
+
+    assert second_status == 409
+    assert second["extra"]["job_id"] == first["id"]
+
+    await wait_for(authenticated_client, first["id"])
+
+
+async def test_a_finished_import_does_not_block_the_next_one(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    archive = zip_of(source, tmp_path / "out")
+
+    _, first = await upload(authenticated_client, archive)
+    await wait_for(authenticated_client, first["id"])
+
+    status, second = await upload(authenticated_client, archive)
+
+    assert status == 202
+    await wait_for(authenticated_client, second["id"])
+
+
+async def test_cancelling_stops_after_the_current_book(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    """
+    Cancelling is not aborting: a book abandoned mid-copy would leave files with no row.
+
+    Whether this cancels before any book, after one, or after the lot is a race — the
+    catalogue is three books long. What must hold either way is that the state is
+    terminal and every book it did import is complete.
+    """
+    _, job = await upload(authenticated_client, zip_of(source, tmp_path / "out"))
+
+    cancelled = await authenticated_client.delete(f"/libraries/imports/{job['id']}")
+    assert cancelled.status_code == 200
+
+    final = await wait_for(authenticated_client, job["id"])
+
+    assert final["state"] in {"cancelled", "finished"}
+
+    listed = await authenticated_client.get("/books?library_id=1")
+    for book in listed.json()["items"]:
+        assert book["files"]
+
+
+async def test_failures_are_reported_on_the_job(
+    authenticated_client: AsyncClient, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """One book failing is recorded and does not stop the run."""
+    fixture = CalibreFixture(tmp_path / "calibre")
+    fixture.add_book(1, "Fine", authors=["A"], formats={"EPUB": EPUB})
+    fixture.add_book(2, "Doomed", authors=["B"], formats={"EPUB": OTHER_EPUB})
+    root = fixture.commit()
+
+    from chitai.services.book import BookService
+
+    original = BookService.create
+
+    async def fail_on_the_second(self, data, *args, **kwargs):
+        if isinstance(data, dict) and data.get("title") == "Doomed":
+            raise RuntimeError("no room on the shelf")
+        return await original(self, data, *args, **kwargs)
+
+    monkeypatch.setattr(BookService, "create", fail_on_the_second)
+
+    _, job = await upload(authenticated_client, zip_of(root, tmp_path / "out"))
+    finished = await wait_for(authenticated_client, job["id"])
+
+    assert finished["state"] == "finished"
+    assert finished["created"] == 1
+    assert finished["failed"] == 1
+    assert finished["failures"][0]["calibre_id"] == 2
+    assert "no room on the shelf" in finished["failures"][0]["reason"]
+
+
+async def test_a_second_copy_is_counted_as_a_possible_duplicate(
+    authenticated_client: AsyncClient, tmp_path: Path
+) -> None:
+    """A count, not the records — the duplicates screen is what shows them."""
+    padded = tmp_path / "padded.epub"
+    padded.write_bytes(EPUB.read_bytes() + b"\0" * 64)
+
+    fixture = CalibreFixture(tmp_path / "calibre")
+    fixture.add_book(1, "The Metamorphosis", authors=["Franz Kafka"], formats={"EPUB": EPUB})
+    fixture.add_book(
+        2, "The Metamorphosis", authors=["Franz Kafka"], formats={"EPUB": padded}
+    )
+    root = fixture.commit()
+
+    _, job = await upload(authenticated_client, zip_of(root, tmp_path / "out"))
+    finished = await wait_for(authenticated_client, job["id"])
+
+    assert finished["created"] == 2
+    assert finished["possible_duplicates"] == 1
+
+
+async def test_polling_an_unknown_job(authenticated_client: AsyncClient) -> None:
+    response = await authenticated_client.get("/libraries/imports/not-a-job")
+    assert response.status_code == 404
+
+
+async def test_cancelling_an_unknown_job(authenticated_client: AsyncClient) -> None:
+    response = await authenticated_client.delete("/libraries/imports/not-a-job")
+    assert response.status_code == 404
+
+
+async def test_importing_into_a_library_that_does_not_exist(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    status, _ = await upload(
+        authenticated_client, zip_of(source, tmp_path / "out"), library_id=999
+    )
+
+    assert status == 404
+
+
+async def test_importing_into_a_read_only_library(
+    authenticated_client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    """A read-only library points at a tree Chitai does not own."""
+    root = tmp_path / "read-only"
+    root.mkdir()
+
+    created = await authenticated_client.post(
+        "/libraries",
+        json={"name": "Read Only", "root_path": str(root), "read_only": True},
+    )
+    assert created.status_code == 201
+
+    status, body = await upload(
+        authenticated_client,
+        zip_of(source, tmp_path / "out"),
+        library_id=created.json()["id"],
+    )
+
+    assert status == 400
+    assert "read-only" in body["detail"]
+
+
+async def test_an_import_needs_authentication(
+    client: AsyncClient, source: Path, tmp_path: Path
+) -> None:
+    status, _ = await upload(client, zip_of(source, tmp_path / "out"))
+
+    assert status == 401
+
+
+class TestRefusedArchives:
+    """Everything wrong with an archive is answered now, not as a job that fails later."""
+
+    async def test_a_hostile_archive(
+        self, authenticated_client: AsyncClient, tmp_path: Path
+    ) -> None:
+        """Zip slip."""
+        archive = tmp_path / "hostile.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("metadata.db", "not really")
+            writing.writestr("../../escaped.txt", "gotcha")
+
+        status, body = await upload(authenticated_client, archive)
+
+        assert status == 400
+        assert "outside itself" in body["detail"]
+        assert registry._jobs == {}
+
+    async def test_something_that_is_not_a_zip(
+        self, authenticated_client: AsyncClient, tmp_path: Path
+    ) -> None:
+        archive = tmp_path / "notes.txt"
+        archive.write_bytes(b"just some text")
+
+        status, body = await upload(authenticated_client, archive)
+
+        assert status == 400
+        assert "not a zip" in body["detail"]
+
+    async def test_an_archive_with_no_catalogue(
+        self, authenticated_client: AsyncClient, tmp_path: Path
+    ) -> None:
+        archive = tmp_path / "books.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("Some Book.epub", "content")
+
+        status, body = await upload(authenticated_client, archive)
+
+        assert status == 400
+        assert "no metadata.db" in body["detail"]
+
+    async def test_a_refusal_leaves_no_temp_files(
+        self, authenticated_client: AsyncClient, tmp_path: Path
+    ) -> None:
+        """Every refusal path removes the workspace it had already made."""
+        before = set(Path(tempfile.gettempdir()).glob("tmp*"))
+
+        archive = tmp_path / "books.zip"
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("Some Book.epub", "content")
+
+        await upload(authenticated_client, archive)
+
+        assert set(Path(tempfile.gettempdir()).glob("tmp*")) == before

backend/tests/unit/test_calibre.py

@@ -0,0 +1,392 @@
+import zipfile
+from datetime import date
+from pathlib import Path
+from types import SimpleNamespace
+
+import pytest
+
+from chitai.services.calibre import (
+    CalibreLibrary,
+    CalibreLibraryError,
+    extract_calibre_archive,
+    format_series_index,
+    parse_date,
+    strip_html,
+    unescape_author,
+)
+
+from tests.calibre_fixtures import UNDEFINED_DATE, CalibreFixture
+
+
+EPUB = Path("tests/data_files/Metamorphosis - Franz Kafka.epub")
+PDF = Path("tests/data_files/Calculus Made Easy - Silvanus Thompson.pdf")
+
+
+@pytest.fixture(name="library_root")
+def fx_library_root(tmp_path: Path) -> Path:
+    """A small Calibre library covering the rows that are easy to read wrongly."""
+    fixture = CalibreFixture(tmp_path / "Calibre Library")
+    fixture.add_pages_table()
+
+    fixture.add_book(
+        1,
+        "The Metamorphosis",
+        authors=["Franz Kafka"],
+        pubdate="1915-10-15 00:00:00+00:00",
+        tags=["Fiction", "Absurdist"],
+        publisher="Kurt Wolff Verlag",
+        languages=["deu", "eng"],
+        comment="<p>A travelling salesman.</p><p>He wakes up <i>changed</i>.</p>",
+        identifiers={"isbn": "978-0-486-29030-0", "amazon": "B01N5IB20Q"},
+        uuid="11111111-2222-3333-4444-555555555555",
+        pages=201,
+        cover=True,
+        formats={"EPUB": EPUB},
+    )
+
+    # Volume seven of a series, and no publication date — the two values most likely to
+    # be carried through verbatim when they should not be.
+    fixture.add_book(
+        2,
+        "Persepolis Rising",
+        # Calibre escapes the comma and nothing else, so the space after it is stored
+        # as-is: `Corey, Jr.` is written `Corey| Jr.`.
+        authors=["Corey| Jr., James S. A."],
+        series="The Expanse",
+        series_index=7.0,
+        formats={"EPUB": EPUB},
+    )
+
+    # A novella between two novels: a fractional position is real and must survive.
+    fixture.add_book(
+        3, "Strange Dogs", series="The Expanse", series_index=6.5, formats={"PDF": PDF}
+    )
+
+    # Every row Calibre will happily hold and Chitai cannot use: no files at all.
+    fixture.add_book(4, "Metadata Only")
+
+    # A catalogue row whose file is not on disk.
+    fixture.add_book(5, "Lost Book")
+    fixture.add_missing_format(5, "EPUB", "Lost Book - Unknown")
+
+    return fixture.commit()
+
+
+async def test_reads_a_book_whole(library_root: Path) -> None:
+    async with CalibreLibrary(library_root) as library:
+        assert await library.count() == 5
+        books = await library.books()
+
+    book = books[0]
+
+    assert book.calibre_id == 1
+    assert book.title == "The Metamorphosis"
+    assert book.authors == ["Franz Kafka"]
+    assert book.published_date == date(1915, 10, 15)
+    assert book.tags == ["Absurdist", "Fiction"]
+    assert book.publisher == "Kurt Wolff Verlag"
+    assert book.pages == 201
+    assert book.uuid == "11111111-2222-3333-4444-555555555555"
+
+    # One language, and the one Calibre put first.
+    assert book.language == "deu"
+
+    # Reported as Calibre wrote them: folding `amazon` onto `asin` is the importer's
+    # job, not the reader's.
+    assert book.identifiers == {"isbn": "978-0-486-29030-0", "amazon": "B01N5IB20Q"}
+
+    assert book.cover is not None
+    assert book.cover.is_file()
+
+    assert len(book.files) == 1
+    assert book.files[0].format == "EPUB"
+    assert book.files[0].path.is_file()
+    # The stem is Calibre's, truncated and sanitised — never the title.
+    assert book.files[0].path.name != f"{book.title}.epub"
+
+
+async def test_the_undefined_date_is_not_a_date(library_root: Path) -> None:
+    """`0101-01-01` parses fine, which is exactly the problem."""
+    async with CalibreLibrary(library_root) as library:
+        books = {book.calibre_id: book for book in await library.books()}
+
+    assert books[2].published_date is None
+
+
+async def test_series_position_is_a_plain_string(library_root: Path) -> None:
+    async with CalibreLibrary(library_root) as library:
+        books = {book.calibre_id: book for book in await library.books()}
+
+    assert books[2].series == "The Expanse"
+    assert books[2].series_position == "7"
+
+    assert books[3].series_position == "6.5"
+
+    # `series_index` defaults to 1.0 for every book, so a position without a series
+    # would invent a volume one out of nothing.
+    assert books[1].series is None
+    assert books[1].series_position is None
+
+
+async def test_author_commas_are_unescaped(library_root: Path) -> None:
+    async with CalibreLibrary(library_root) as library:
+        books = {book.calibre_id: book for book in await library.books()}
+
+    assert books[2].authors == ["Corey, Jr., James S. A."]
+
+
+async def test_comments_come_back_as_text(library_root: Path) -> None:
+    async with CalibreLibrary(library_root) as library:
+        books = {book.calibre_id: book for book in await library.books()}
+
+    assert books[1].description == "A travelling salesman.\nHe wakes up changed."
+    assert books[2].description is None
+
+
+async def test_files_are_reported_whether_or_not_they_exist(library_root: Path) -> None:
+    """
+    The reader says what the catalogue says. Whether the bytes are there is a question
+    for whoever is about to copy them, which stats them anyway.
+    """
+    async with CalibreLibrary(library_root) as library:
+        books = {book.calibre_id: book for book in await library.books()}
+
+    assert books[4].files == []
+
+    assert len(books[5].files) == 1
+    assert not books[5].files[0].path.exists()
+
+
+async def test_a_library_without_the_pages_table_still_reads(tmp_path: Path) -> None:
+    """`books_pages_link` is recent; an older library simply does not have it."""
+    fixture = CalibreFixture(tmp_path / "Old Library")
+    fixture.add_book(1, "Old Book", formats={"EPUB": EPUB})
+    root = fixture.commit()
+
+    async with CalibreLibrary(root) as library:
+        books = await library.books()
+
+    assert books[0].pages is None
+
+
+async def test_the_original_is_never_opened(library_root: Path) -> None:
+    """
+    The catalogue is copied before it is read, and the copy goes away afterwards.
+
+    Calibre may be running and writing; this is what keeps a live library out of it.
+    """
+    before = (library_root / "metadata.db").read_bytes()
+
+    library = CalibreLibrary(library_root)
+    await library.open()
+    workspace = library._workspace
+
+    assert workspace is not None and (workspace / "metadata.db").is_file()
+
+    await library.close()
+
+    assert not workspace.exists()
+    assert (library_root / "metadata.db").read_bytes() == before
+
+
+async def test_closing_twice_is_harmless(library_root: Path) -> None:
+    library = CalibreLibrary(library_root)
+    await library.open()
+    await library.close()
+    await library.close()
+
+
+async def test_a_directory_that_is_not_a_calibre_library(tmp_path: Path) -> None:
+    with pytest.raises(CalibreLibraryError, match="not a Calibre library"):
+        await CalibreLibrary(tmp_path).open()
+
+
+@pytest.mark.parametrize(
+    ("stored", "expected"),
+    [
+        ("2017-12-04 04:00:00+00:00", date(2017, 12, 4)),
+        ("2001-07-02 00:00:00+00:00", date(2001, 7, 2)),
+        ("1999-01-31", date(1999, 1, 31)),
+        # Calibre's sentinel, and anything else implausibly early.
+        (UNDEFINED_DATE, None),
+        ("0101-01-01", None),
+        (None, None),
+        ("", None),
+        ("not a date", None),
+    ],
+)
+def test_parse_date(stored: str | None, expected: date | None) -> None:
+    assert parse_date(stored) == expected
+
+
+@pytest.mark.parametrize(
+    ("index", "expected"),
+    [
+        (7.0, "7"),
+        (1.0, "1"),
+        (6.5, "6.5"),
+        (0.0, "0"),
+        (12.25, "12.25"),
+        (None, None),
+    ],
+)
+def test_format_series_index(index: float | None, expected: str | None) -> None:
+    assert format_series_index(index) == expected
+
+
+@pytest.mark.parametrize(
+    ("stored", "expected"),
+    [
+        ("Doyle| Sir Arthur Conan", "Doyle, Sir Arthur Conan"),
+        ("Franz Kafka", "Franz Kafka"),
+        ("  Herman Melville  ", "Herman Melville"),
+    ],
+)
+def test_unescape_author(stored: str, expected: str) -> None:
+    assert unescape_author(stored) == expected
+
+
+@pytest.mark.parametrize(
+    ("html", "expected"),
+    [
+        ("<p>One.</p><p>Two.</p>", "One.\nTwo."),
+        ("Plain text", "Plain text"),
+        ("<div>A<br>B</div>", "A\nB"),
+        ("<p>Caf&eacute; &amp; bar</p>", "Café & bar"),
+        ("<ul><li>One</li><li>Two</li></ul>", "One\nTwo"),
+        # Markup carrying no text at all is nothing, not an empty description.
+        ("<p></p>", None),
+        ("", None),
+        (None, None),
+    ],
+)
+def test_strip_html(html: str | None, expected: str | None) -> None:
+    assert strip_html(html) == expected
+
+
+class TestArchives:
+    """A Calibre library that arrives zipped rather than as a path."""
+
+    def zipped(self, root: Path, into: Path, prefix: str = "") -> Path:
+        """Zip a directory the way a file manager would."""
+        archive = into / "library.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            for path in sorted(root.rglob("*")):
+                if path.is_file():
+                    writing.write(path, f"{prefix}{path.relative_to(root)}")
+
+        return archive
+
+    async def test_a_library_zipped_at_its_root(
+        self, library_root: Path, tmp_path: Path
+    ) -> None:
+        archive = self.zipped(library_root, tmp_path)
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        catalogue = await extract_calibre_archive(archive, destination)
+
+        assert catalogue == destination
+        async with CalibreLibrary(catalogue) as library:
+            assert await library.count() == 5
+
+    async def test_a_library_zipped_inside_a_folder(
+        self, library_root: Path, tmp_path: Path
+    ) -> None:
+        """Zipping the folder itself is at least as common as zipping its contents."""
+        archive = self.zipped(library_root, tmp_path, prefix="Calibre Library/")
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        catalogue = await extract_calibre_archive(archive, destination)
+
+        assert catalogue == destination / "Calibre Library"
+        async with CalibreLibrary(catalogue) as library:
+            assert await library.count() == 5
+
+    async def test_an_entry_pointing_outside_the_archive_is_refused(
+        self, tmp_path: Path
+    ) -> None:
+        """
+        Zip slip. `ZipFile.extract` sanitises names itself, but relying on that silently
+        is how the next person to change the extraction call reintroduces it.
+        """
+        archive = tmp_path / "hostile.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("metadata.db", "not really")
+            writing.writestr("../../escaped.txt", "gotcha")
+
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        with pytest.raises(CalibreLibraryError, match="outside itself"):
+            await extract_calibre_archive(archive, destination)
+
+        assert not (tmp_path.parent / "escaped.txt").exists()
+
+    async def test_something_that_is_not_a_zip(self, tmp_path: Path) -> None:
+        archive = tmp_path / "not.zip"
+        archive.write_bytes(b"PK-ish, but no")
+
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        with pytest.raises(CalibreLibraryError, match="not a zip file"):
+            await extract_calibre_archive(archive, destination)
+
+    async def test_an_archive_with_no_catalogue(self, tmp_path: Path) -> None:
+        archive = tmp_path / "books.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("Some Book.epub", "content")
+
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        with pytest.raises(CalibreLibraryError, match="no metadata.db"):
+            await extract_calibre_archive(archive, destination)
+
+        # Refused before anything was written.
+        assert list(destination.iterdir()) == []
+
+    async def test_a_catalogue_buried_too_deep(self, tmp_path: Path) -> None:
+        """Somebody's whole backup tree is not a library, however much it contains one."""
+        archive = tmp_path / "backup.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("backups/2026/january/library/metadata.db", "not really")
+
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        with pytest.raises(CalibreLibraryError, match="within 3 levels"):
+            await extract_calibre_archive(archive, destination)
+
+    async def test_an_archive_too_big_for_the_disk(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        """
+        Checked before writing, not discovered part-way through.
+
+        A full disk takes the whole application down, and the size is in the archive
+        already.
+        """
+        archive = tmp_path / "huge.zip"
+
+        with zipfile.ZipFile(archive, "w") as writing:
+            writing.writestr("metadata.db", "not really")
+
+        destination = tmp_path / "unpacked"
+        destination.mkdir()
+
+        monkeypatch.setattr(
+            "chitai.services.calibre.shutil.disk_usage",
+            lambda _path: SimpleNamespace(total=1024, used=1024, free=0),
+        )
+
+        with pytest.raises(CalibreLibraryError, match="only"):
+            await extract_calibre_archive(archive, destination)
+
+        assert list(destination.iterdir()) == []

backend/tests/unit/test_content_type.py

@@ -0,0 +1,64 @@
+from pathlib import Path
+
+import pytest
+
+from chitai.services.utils import guess_content_type
+
+
+@pytest.mark.parametrize(
+    ("filename", "expected"),
+    [
+        # What `mimetypes` already knows, kept here so a host with a thin
+        # /etc/mime.types cannot change the answer without a test noticing.
+        ("Frankenstein.epub", "application/epub+zip"),
+        ("Calculus.pdf", "application/pdf"),
+        ("Persepolis.azw3", "application/vnd.amazon.mobi8-ebook"),
+        ("Watchmen.cbz", "application/vnd.comicbook+zip"),
+        # What it does not, and where a Calibre library's older formats live.
+        ("Dune.mobi", "application/x-mobipocket-ebook"),
+        ("Dune.prc", "application/x-mobipocket-ebook"),
+        ("Dune.azw", "application/vnd.amazon.ebook"),
+        ("Voyna i Mir.fb2", "application/x-fictionbook+xml"),
+        ("Voyna i Mir.fbz", "application/x-zip-compressed-fb2"),
+        ("Reader.lit", "application/x-ms-reader"),
+        ("Reader.lrf", "application/x-sony-bbeb"),
+        ("Watchmen.cb7", "application/x-cb7"),
+        # Case is not part of the answer, and Calibre writes formats uppercase.
+        ("Dune.MOBI", "application/x-mobipocket-ebook"),
+        # Nothing can name these, and None is the answer rather than a placeholder.
+        ("Notes.xyzzy", None),
+        ("README", None),
+    ],
+)
+def test_guess_content_type(filename: str, expected: str | None) -> None:
+    assert guess_content_type(Path(filename)) == expected
+    # A str and a Path must agree, and an upload's `filename` carries its relative
+    # path, so a name with directories in front of it has to resolve the same way.
+    assert guess_content_type(filename) == expected
+    assert guess_content_type(f"Some Author/Some Book/{filename}") == expected
+
+
+def test_fallback_is_used_only_when_the_extension_says_nothing() -> None:
+    """A client's claim fills a gap; it never overrides the name."""
+    assert (
+        guess_content_type(Path("Dune.mobi"), fallback="application/pdf")
+        == "application/x-mobipocket-ebook"
+    )
+    assert (
+        guess_content_type(Path("Notes.xyzzy"), fallback="application/epub+zip")
+        == "application/epub+zip"
+    )
+
+
+def test_an_unspecified_fallback_is_not_an_answer() -> None:
+    """
+    `application/octet-stream` from a client is it saying it does not know.
+
+    Browsers post exactly that for every extension they do not recognise, which is most
+    ebook formats. Storing it would be indistinguishable from having determined a
+    format, so it is discarded and the column keeps its null.
+    """
+    assert (
+        guess_content_type(Path("Notes.xyzzy"), fallback="application/octet-stream")
+        is None
+    )

backend/tests/unit/test_filesystem_library.py

@@ -0,0 +1,69 @@
+"""Tests for BookPathGenerator."""
+
+from pathlib import Path
+
+from chitai.services.filesystem_library import BookPathGenerator, sanitize_path_component
+
+
+ROOT = Path("/library")
+
+
+def path_for(**book) -> Path:
+    return BookPathGenerator(ROOT).generate_path(book)
+
+
+def test_author_and_title() -> None:
+    assert path_for(title="Dune", authors=["Frank Herbert"]) == (
+        ROOT / "Frank Herbert" / "Dune"
+    )
+
+
+def test_a_book_with_no_authors() -> None:
+    assert path_for(title="Beowulf", authors=[]) == ROOT / "Unknown" / "Beowulf"
+
+
+def test_a_series_adds_a_level_and_pads_the_position() -> None:
+    assert path_for(
+        title="Persepolis Rising",
+        authors=["James S. A. Corey"],
+        series="The Expanse",
+        series_position="7",
+    ) == ROOT / "James S. A. Corey" / "The Expanse" / "07 - Persepolis Rising"
+
+
+def test_a_slash_in_a_title_does_not_add_a_directory() -> None:
+    """
+    The separators in the path come from the template, never from the metadata.
+
+    A title with a slash in it — "AC/DC", "Him/Her" — would otherwise put the book one
+    level below where `book.path` says it is, which is what deletes, moves and file
+    lookups all act on. Calibre keeps the real title in its database and strips this
+    from its own directory names, so an import is where they surface.
+    """
+    generated = path_for(title="Back in Black: AC/DC", authors=["Murray Engleheart"])
+
+    assert generated == ROOT / "Murray Engleheart" / "Back in Black: AC_DC"
+    assert generated.relative_to(ROOT).parts == ("Murray Engleheart", "Back in Black: AC_DC")
+
+
+def test_a_slash_in_an_author_or_series_is_handled_too() -> None:
+    assert path_for(title="Split", authors=["A/B Collective"]) == (
+        ROOT / "A_B Collective" / "Split"
+    )
+    assert path_for(
+        title="Volume One", authors=["Someone"], series="Either/Or", series_position="1"
+    ) == ROOT / "Someone" / "Either_Or" / "01 - Volume One"
+
+
+def test_control_characters_are_removed() -> None:
+    assert path_for(title="Line\nBreak", authors=["Someone"]) == (
+        ROOT / "Someone" / "Line_Break"
+    )
+
+
+def test_sanitize_path_component() -> None:
+    assert sanitize_path_component("AC/DC") == "AC_DC"
+    assert sanitize_path_component("back\\slash") == "back_slash"
+    assert sanitize_path_component("  padded  ") == "padded"
+    # Colons and other punctuation are legal in a path and are left alone.
+    assert sanitize_path_component("Title: Subtitle") == "Title: Subtitle"

backend/tests/unit/test_services/test_calibre_import_service.py

@@ -0,0 +1,415 @@
+"""Tests for importing a Calibre library through BookService."""
+
+from pathlib import Path
+
+import pytest
+
+from chitai.config import settings
+from chitai.database import models as m
+from chitai.services import BookService
+from chitai.services.calibre import CalibreLibrary
+
+from tests.calibre_fixtures import CalibreFixture
+
+
+DATA_FILES = Path("tests/data_files")
+EPUB = DATA_FILES / "Metamorphosis - Franz Kafka.epub"
+OTHER_EPUB = DATA_FILES / "The Art of War - Sun Tzu.epub"
+PDF = DATA_FILES / "Calculus Made Easy - Silvanus Thompson.pdf"
+
+
+@pytest.fixture(name="calibre_root")
+def fx_calibre_root(tmp_path: Path) -> Path:
+    """Three books: one plain, one in two formats, one Chitai cannot use."""
+    fixture = CalibreFixture(tmp_path / "source")
+    fixture.add_pages_table()
+
+    fixture.add_book(
+        1,
+        "The Metamorphosis",
+        authors=["Franz Kafka"],
+        pubdate="1915-10-15 00:00:00+00:00",
+        tags=["Fiction", "Absurdist"],
+        publisher="Kurt Wolff Verlag",
+        languages=["deu"],
+        comment="<p>He wakes up <i>changed</i>.</p>",
+        identifiers={"isbn": "978-0-486-29030-0", "amazon": "B01N5IB20Q"},
+        uuid="11111111-2222-3333-4444-555555555555",
+        pages=201,
+        cover=True,
+        formats={"EPUB": EPUB},
+    )
+
+    fixture.add_book(
+        2,
+        "The Art of War",
+        authors=["Sun Tzu"],
+        series="Classics",
+        series_index=3.0,
+        formats={"EPUB": OTHER_EPUB, "PDF": PDF},
+    )
+
+    fixture.add_book(3, "Metadata Only", authors=["Nobody"])
+
+    return fixture.commit()
+
+
+async def library_of(root: Path) -> CalibreLibrary:
+    source = CalibreLibrary(root)
+    await source.open()
+    return source
+
+
+async def test_imports_a_catalogue(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    source = await library_of(calibre_root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    assert result.total == 3
+    assert len(result.created) == 2
+
+    # The book with no files is left out: a record with nothing to read, and a directory
+    # to match, is worse than not importing it.
+    assert [skipped.calibre_id for skipped in result.skipped] == [3]
+    assert result.skipped[0].reason == "no files in the catalogue"
+    assert result.failed == []
+
+    book = await books_service.get(result.created[0])
+
+    assert book.title == "The Metamorphosis"
+    assert [author.name for author in book.authors] == ["Franz Kafka"]
+    assert sorted(tag.name for tag in book.tags) == ["Absurdist", "Fiction"]
+    assert book.publisher is not None and book.publisher.name == "Kurt Wolff Verlag"
+    assert book.published_date is not None and book.published_date.year == 1915
+    assert book.language == "deu"
+    assert book.pages == 201
+    assert book.cover_image is not None
+
+    # The HTML is gone; `Book.description` is rendered as text.
+    assert book.description == "He wakes up changed."
+
+
+async def test_two_formats_are_one_book(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    source = await library_of(calibre_root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    book = await books_service.get(result.created[1])
+
+    assert book.title == "The Art of War"
+    assert sorted(Path(file.path).suffix for file in book.files) == [".epub", ".pdf"]
+
+    # A REAL series index reaches the column as the string everything else writes.
+    assert book.series is not None and book.series.title == "Classics"
+    assert book.series_position == "3"
+
+
+async def test_identifiers_are_folded_onto_chitai_schemes(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    """
+    `amazon` becomes `asin`, a hyphenated ISBN survives, and the Calibre uuid is kept.
+
+    The uuid is deliberately not stored under `uuid`, which duplicate matching ignores
+    because an EPUB regenerates one per build. Calibre's is stable, so it is the durable
+    link back to the row it came from.
+    """
+    source = await library_of(calibre_root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    book = await books_service.get(result.created[0])
+    identifiers = {identifier.name: identifier.value for identifier in book.identifiers}
+
+    assert identifiers["asin"] == "B01N5IB20Q"
+    assert identifiers["isbn-13"] == "9780486290300"
+    assert identifiers["calibre-uuid"] == "11111111-2222-3333-4444-555555555555"
+
+    matching = {
+        identifier.name: identifier.normalized_value for identifier in book.identifiers
+    }
+
+    # Stored under its own name, matched under one scheme for both ISBN forms.
+    assert matching["isbn-13"] == "isbn:9780486290300"
+
+    # And the uuid carries a real matching key, which is the whole reason it is not
+    # filed under `uuid`.
+    assert matching["calibre-uuid"] is not None
+
+
+async def test_the_source_library_is_left_alone(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    """Files are copied. Moving them would leave `metadata.db` pointing at nothing."""
+    before = {
+        path: path.stat().st_mtime_ns
+        for path in sorted(calibre_root.rglob("*"))
+        if path.is_file()
+    }
+
+    source = await library_of(calibre_root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    after = {
+        path: path.stat().st_mtime_ns
+        for path in sorted(calibre_root.rglob("*"))
+        if path.is_file()
+    }
+
+    assert after == before
+
+    # And the copies are really there, under the library's own layout.
+    for book_id in result.created:
+        book = await books_service.get(book_id)
+        for file in book.files:
+            assert (Path(book.path or "") / file.path).is_file()
+
+
+async def test_importing_twice_creates_nothing(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    """
+    Re-running is safe with no bookkeeping: the bytes are recognised wherever they sit.
+
+    This is what makes an interrupted import resumable by simply running it again.
+    """
+    for _ in range(2):
+        source = await library_of(calibre_root)
+        try:
+            result = await books_service.create_many_from_calibre(source, test_library)
+        finally:
+            await source.close()
+
+    assert result.created == []
+    assert sorted(skipped.reason for skipped in result.skipped) == [
+        "already stored",
+        "already stored",
+        "no files in the catalogue",
+    ]
+
+    held_by = [
+        skipped.book_id for skipped in result.skipped if skipped.reason == "already stored"
+    ]
+    assert all(book_id is not None for book_id in held_by)
+
+
+async def test_a_file_the_catalogue_lists_but_disk_does_not(
+    books_service: BookService, test_library: m.Library, tmp_path: Path
+) -> None:
+    """Calibre keeps the row when a file is moved away behind its back."""
+    fixture = CalibreFixture(tmp_path / "source")
+    fixture.add_book(1, "Present", authors=["A"], formats={"EPUB": EPUB})
+    fixture.add_book(2, "Absent", authors=["B"])
+    fixture.add_missing_format(2, "EPUB", "Absent - B")
+    root = fixture.commit()
+
+    source = await library_of(root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    assert len(result.created) == 1
+    assert [(s.calibre_id, s.reason) for s in result.skipped] == [(2, "no files on disk")]
+
+
+async def test_one_broken_book_does_not_stop_the_import(
+    books_service: BookService, test_library: m.Library, tmp_path: Path
+) -> None:
+    """
+    A failure is recorded and the run continues, leaving no files behind for it.
+
+    An orphaned directory would make the next attempt reserve `title (2)` and look as
+    though it had worked.
+    """
+    fixture = CalibreFixture(tmp_path / "source")
+    fixture.add_book(1, "First", authors=["A"], formats={"EPUB": EPUB})
+    fixture.add_book(2, "Doomed", authors=["B"], formats={"EPUB": OTHER_EPUB})
+    fixture.add_book(3, "Third", authors=["C"], formats={"PDF": PDF})
+    root = fixture.commit()
+
+    original = books_service.create
+
+    async def fail_on_the_second(data, *args, **kwargs):
+        if isinstance(data, dict) and data.get("title") == "Doomed":
+            raise RuntimeError("no room on the shelf")
+        return await original(data, *args, **kwargs)
+
+    books_service.create = fail_on_the_second  # type: ignore[method-assign]
+
+    source = await library_of(root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+        books_service.create = original  # type: ignore[method-assign]
+
+    assert len(result.created) == 2
+    assert len(result.failed) == 1
+    assert result.failed[0].calibre_id == 2
+    assert "no room on the shelf" in result.failed[0].reason
+
+    # Nothing of the failed book was left in the library. Checked against the path the
+    # template would have produced, rather than by walking the root — the Calibre source
+    # sits under it in these tests, and its own files are meant to still be there.
+    assert not (Path(test_library.root_path) / "B").exists()
+
+    # And the books either side of it are where they should be.
+    for book_id in result.created:
+        book = await books_service.get(book_id)
+        for file in book.files:
+            assert (Path(book.path or "") / file.path).is_file()
+
+
+async def test_a_cover_that_cannot_be_read_is_not_fatal(
+    books_service: BookService, test_library: m.Library, tmp_path: Path
+) -> None:
+    """
+    A truncated `cover.jpg` costs the cover, not the book.
+
+    Real libraries hold them, from an interrupted download or a failed conversion, and
+    the cover is the one thing in the directory that can be replaced from the book page.
+    """
+    fixture = CalibreFixture(tmp_path / "source")
+    fixture.add_book(
+        1, "Unreadable Cover", authors=["A"], corrupt_cover=True, formats={"EPUB": EPUB}
+    )
+    root = fixture.commit()
+
+    source = await library_of(root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    assert result.failed == []
+    assert len(result.created) == 1
+
+    book = await books_service.get(result.created[0])
+    assert book.cover_image is None
+    assert len(book.files) == 1
+
+
+async def test_shared_authors_and_tags_are_one_row_each(
+    books_service: BookService, test_library: m.Library, tmp_path: Path, session
+) -> None:
+    """Two books by one author must not produce two `Author` rows."""
+    fixture = CalibreFixture(tmp_path / "source")
+    fixture.add_book(
+        1, "One", authors=["Franz Kafka"], tags=["Fiction"], formats={"EPUB": EPUB}
+    )
+    fixture.add_book(
+        2, "Two", authors=["Franz Kafka"], tags=["Fiction"], formats={"EPUB": OTHER_EPUB}
+    )
+    root = fixture.commit()
+
+    source = await library_of(root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    assert len(result.created) == 2
+
+    first, second = [await books_service.get(book_id) for book_id in result.created]
+
+    assert first.authors[0].id == second.authors[0].id
+    assert first.tags[0].id == second.tags[0].id
+
+
+async def test_a_second_copy_is_reported_not_refused(
+    books_service: BookService, test_library: m.Library, tmp_path: Path
+) -> None:
+    """
+    Two catalogue rows for one book, with different bytes, both import.
+
+    File-level dedupe cannot see it — the archives differ — so book-level detection
+    reports the pair and leaves the decision to the reader.
+    """
+    padded = tmp_path / "padded.epub"
+    padded.write_bytes(EPUB.read_bytes() + b"\0" * 64)
+
+    fixture = CalibreFixture(tmp_path / "source")
+    fixture.add_book(
+        1, "The Metamorphosis", authors=["Franz Kafka"], formats={"EPUB": EPUB}
+    )
+    fixture.add_book(
+        2, "The Metamorphosis", authors=["Franz Kafka"], formats={"EPUB": padded}
+    )
+    root = fixture.commit()
+
+    source = await library_of(root)
+    try:
+        result = await books_service.create_many_from_calibre(source, test_library)
+    finally:
+        await source.close()
+
+    assert len(result.created) == 2
+    assert len(result.possible_duplicates) == 1
+    assert result.possible_duplicates[0].candidates[0].book_id == result.created[0]
+
+
+async def test_allow_duplicates_stores_the_same_bytes_again(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    for allow in (False, True):
+        source = await library_of(calibre_root)
+        try:
+            result = await books_service.create_many_from_calibre(
+                source, test_library, allow_duplicates=allow
+            )
+        finally:
+            await source.close()
+
+    assert len(result.created) == 2
+
+
+async def test_duplicate_scope_off_imports_everything(
+    books_service: BookService,
+    test_library: m.Library,
+    calibre_root: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "duplicate_scope", "off")
+
+    for _ in range(2):
+        source = await library_of(calibre_root)
+        try:
+            result = await books_service.create_many_from_calibre(source, test_library)
+        finally:
+            await source.close()
+
+    assert len(result.created) == 2
+
+
+async def test_progress_is_reported_per_book(
+    books_service: BookService, test_library: m.Library, calibre_root: Path
+) -> None:
+    """The import is long enough that its progress is the only thing worth watching."""
+    seen = []
+
+    source = await library_of(calibre_root)
+    try:
+        await books_service.create_many_from_calibre(
+            source, test_library, on_progress=seen.append
+        )
+    finally:
+        await source.close()
+
+    assert [progress.processed for progress in seen] == [1, 2, 3]
+    assert all(progress.total == 3 for progress in seen)
+    assert [progress.outcome for progress in seen] == ["created", "created", "skipped"]
+    assert seen[0].title == "The Metamorphosis"

docs/calibre-import.md

@@ -0,0 +1,407 @@
+# Implementation brief: importing a Calibre library
+
+Written for an agent picking this up cold. Read the repo-root `AGENTS.md` and
+`backend/AGENTS.md` first — this brief assumes both, particularly the **Filesystem behaviour**
+and **Duplicate detection** sections.
+
+Every claim about Calibre's schema and on-disk layout below was checked against a real library at
+`~/Documents/Calibre Library` (6 books, current Calibre). Where a fact came from Calibre's source
+rather than that library, it says so.
+
+## Feasibility: high, and most of the machinery already exists
+
+`metadata.db` is plain SQLite with a schema that has been stable for a decade, and the files sit
+beside it in a predictable tree. Chitai already has every piece an import needs:
+
+| Needed | Already in the tree |
+| --- | --- |
+| Ingest files that are already on disk | `BookService.create_many_from_existing_files` (`services/book.py:1280`) |
+| Deduplicate authors/tags/publishers/series | `_populate_with_unique_relationships` (`services/book.py:1752`), via `as_unique_async` |
+| Generic identifiers with a scheme map | `Identifier`, and `parse_identifier` (`services/metadata_extractor.py:58`) — whose map already covers `isbn`, `amazon`, `mobi-asin`, `google`, `goodreads`, `doi`, `calibre` |
+| Decide where a book lives on disk | `BookPathGenerator`, `_reserve_book_path` (`services/book.py:1066`) |
+| Not import the same book twice | `find_duplicate_files` (`:461`) and `find_duplicate_books` (`:535`) |
+| Store a cover | `_save_cover_image` (`:1994`) |
+
+So this is **a reader, not new ingest machinery**: turn Calibre rows into the metadata dict
+`BookService` already accepts, and hand it to a slightly generalised version of the consume-directory
+path. The parsing is the easy half.
+
+The hard parts are elsewhere, and all three are addressed below:
+
+1. Calibre libraries hold formats Chitai cannot describe, let alone read — and one of them
+   **currently 500s the book detail endpoint** (see prerequisites).
+2. A 5,000-book import is a long-running job, and the app has no job/progress concept.
+3. Whether files are **copied** into the library or **referenced in place** — which is a
+   product decision with a large blast radius, because in-place means Chitai's write paths point
+   at somebody's Calibre library.
+
+## What a Calibre library actually is
+
+```
+Calibre Library/
+├── metadata.db                       the whole catalogue
+├── metadata_db_prefs_backup.json     ignore
+├── .caltrash/  .calnotes/            ignore — deleted books still live in .caltrash
+└── <Author Name>/
+    └── <Title> (<book id>)/          == books.path
+        ├── cover.jpg                 iff books.has_cover
+        ├── metadata.opf              ignore; the db is authoritative
+        └── <data.name>.<format>      one per row in `data`
+```
+
+The tables that matter, and nothing else: `books`, `authors` + `books_authors_link`,
+`publishers` + `books_publishers_link`, `tags` + `books_tags_link`, `series` +
+`books_series_link`, `languages` + `books_languages_link`, `comments`, `identifiers`, `data`,
+`books_pages_link`, `last_read_positions`.
+
+Ten things that will produce wrong data if you do not know them:
+
+- **Never query the views.** `meta`, `tag_browser_*` and friends call SQLite functions Calibre
+  registers from Python at connection time. Verified: `SELECT * FROM meta` fails with
+  `no such function: sortconcat`. Query base tables only.
+
+- **`pubdate` has a sentinel, not a null.** An unknown publication date is stored as
+  `0101-01-01 00:00:00+00:00` (Calibre's `UNDEFINED_DATE`, year 101). It parses fine as a
+  `date`, so nothing will complain — two of the six books in the reference library carry it. Drop
+  any `pubdate` with year < 1000. The same sentinel appears in `timestamp`.
+
+- **`data.name` is lossy and is not the title.** It is the on-disk stem, truncated to Calibre's
+  filename limit and sanitised. Verified in the reference library: the book titled
+  `The Project Gutenberg eBook #33283: Calculus Made Easy, 2nd Edition` is stored as
+  `The Project Gutenberg eBook #33283_ Calcul - Silvanus Phillips Thompson.pdf`. So the file
+  extractors must not be consulted for metadata (see decision 2), and `books.path`/`data.name`
+  are for *locating* files only.
+
+- **`books.title` may contain characters Calibre strips from its own paths** — `:` became `_`
+  above, and titles legitimately contain `/` (`AC/DC`). `BookPathGenerator` interpolates the
+  title straight into a path and only collapses repeated slashes
+  (`services/filesystem_library.py`), so an unsanitised Calibre title can silently add a
+  directory level. Sanitise `/` and control characters out of `title` before path generation.
+
+- **`authors.name` escapes commas as `|`.** Calibre's `AuthorsTable` unserialises with
+  `name.replace('|', ',')` (from Calibre's `db/tables.py`; the reference library has no such
+  name, so this one is unverified locally). Do the same replacement, and pass `authors.name` —
+  **not** `authors.sort`, which is `Melville, Herman`. `format_author_name` would flip the sort
+  form correctly anyway, but there is no reason to hand it the worse input.
+
+- **`series_index` is a REAL.** `7.0` must become `"7"`, not `"7.0"` — `Book.series_position` is
+  a string, and `find_duplicate_books`'s series-position disqualifier compares it as one.
+
+- **`languages.lang_code` is ISO 639-2/B** (`eng`), while `EpubExtractor` stores raw
+  `DC:language` (`en`). Both will coexist in the column. `Book.language` is free text and the
+  edit form is a plain `<input>`, so nothing breaks; normalising to two letters is optional
+  polish, not part of this work.
+
+- **`comments.text` is HTML.** `Book.description` is rendered as plain text by
+  `CollapsibleText`, so `<p>` tags will show literally. Strip to text on import.
+
+- **`books_pages_link` is usually empty of real data.** It carries `needs_scan` and, in the
+  reference library, `pages = 0` for all six books. Only use it when `pages > 0`.
+
+- **`identifiers.type` is free text.** The reference library holds `isbn`, `amazon` and
+  `mobi-asin`, all of which `parse_identifier` already maps. Feed every identifier through it and
+  keep whatever survives; do not filter to a known list.
+
+## Decisions to settle before writing code
+
+1. **Copy files into the library. Do not move, do not reference in place** — for the first
+   version. Moving leaves `metadata.db` pointing at files that are gone, which quietly destroys a
+   library the user still uses. Referencing in place is genuinely desirable (nobody wants two
+   copies of 80 GB) but it points `book.path` at the Calibre tree, and `update_book` **moves
+   directories** while `delete_books` **deletes files** — so a metadata edit in Chitai would
+   rearrange somebody's Calibre library. `Library.read_only` exists but is enforced in exactly one
+   place (`services/library.py:54`, at creation). See phase 3.
+
+2. **Trust Calibre's metadata; do not run the extractors.** Calibre's catalogue is curated, its
+   filenames are truncated garbage, and running `Extractor.extract_metadata` over thousands of
+   files means opening every EPUB and rendering a cover page from every PDF. Take the cover from
+   `cover.jpg` directly. The one exception worth allowing: fill `pages` from the file when
+   Calibre has no useful value, behind a flag, off by default.
+
+3. ~~**The source is a server-side path, not an upload.**~~ **Reversed in review, and the reason
+   this brief was wrong is worth keeping.** The premise — "the library lives on the same host as
+   the backend in every realistic deployment" — is false for the common case: Calibre is a desktop
+   application, and its library is on the desktop. So the split is by *surface*, not by preference:
+
+   - **Over HTTP: an uploaded zip only.** `…/imports/calibre/upload`. There is no endpoint taking a
+     server path; one was built and then removed deliberately.
+   - **On the server: a path only.** `litestar calibre-import <path>`, which is where a very large
+     library or a headless migration belongs — an upload has to carry the whole archive across
+     first.
+
+   A CLI taking a path needs no justification. An *endpoint* taking one would have: it would let any
+   authenticated caller read any directory the backend can, and `TODO.md` records there is no
+   authorization tier at all. Not adding it is one less thing to gate later.
+
+4. **Import into an existing Chitai library**, chosen by the caller. Creating a library is
+   already one action, and the Calibre tree is rewritten by `BookPathGenerator` regardless.
+
+5. **Re-running an import must be safe, and file-level dedupe already makes it so.** The same
+   bytes are recognised by `(hash, size)` whatever their path, so a second run over the same
+   library skips everything. No import bookkeeping is needed for idempotency.
+
+## Prerequisite: a `.mobi` file breaks the book endpoint — **done**
+
+> Landed ahead of the import itself. `guess_content_type` in `services/utils.py` now names every
+> format from its extension, the column keeps a null when nothing can name one, and the OPDS feed
+> substitutes `application/octet-stream` at the one place a string is required. The Read control is
+> driven by `isReadable` rather than by the file count. See the section below for why it mattered,
+> and `backend/AGENTS.md` for the rule as it now stands.
+
+
+`FileMetadataRead.content_type` is a required `str` (`schemas/book.py:33`), but every ingest path
+fills it from `mimetypes.guess_type`, which returns `None` for `.mobi`, `.azw`, `.fb2`, `.lit`
+and `.htmlz` (verified). `FileMetadata.content_type` is nullable in the model, so the row stores
+fine and then fails response validation on the way out — a book whose only file is a MOBI would
+be unreadable through the API.
+
+Nothing in the tree hits this today because the browser upload path is used with EPUBs and PDFs.
+A Calibre library is full of MOBI and AZW3. Fix it first, either way round:
+
+- make the schema field `str | None`, and/or
+- add a small extension→MIME table for the ebook formats `mimetypes` does not know
+  (`application/x-mobipocket-ebook`, `application/vnd.amazon.ebook`, `application/x-fictionbook+xml`).
+
+Do both, in fact: the table is the right answer for OPDS clients, which choose an acquisition link
+by MIME type, and the nullable field is the safety net.
+
+**Related, but not a blocker:** Chitai reads EPUB and PDF only. `openBookInReader`
+(`book/[bookId]/+page.svelte:66`) branches on `getFileType(...) === 'EPUB' | 'PDF'` and does
+nothing for anything else, so an AZW3-only book gets a Read button that silently fails. Importing
+those files is still right — they are downloadable and they are the user's — but the button
+should be disabled for a book with no readable file. One `$derived` on the page, worth doing in
+the same branch.
+
+## Design
+
+### 1. `services/calibre.py` — a pure reader, no Chitai types
+
+```python
+@dataclass(frozen=True)
+class CalibreFile:
+    path: Path          # absolute, resolved against the library root
+    format: str         # "EPUB", as stored
+    size: int           # data.uncompressed_size, for a cheap sanity check
+
+@dataclass(frozen=True)
+class CalibreBook:
+    calibre_id: int
+    uuid: str
+    title: str
+    authors: list[str]
+    ...                 # one field per row of the mapping table below
+    cover: Path | None
+    files: list[CalibreFile]
+
+class CalibreLibrary:
+    def __init__(self, root: Path) -> None: ...
+    async def open(self) -> None: ...          # copy + connect, see below
+    async def books(self) -> AsyncIterator[CalibreBook]: ...
+    async def close(self) -> None: ...
+```
+
+Deliberately knows nothing about `Book`, `BookService` or the session — it is a file-format
+reader, unit-testable against a fixture database with no Postgres and no app.
+
+Two implementation notes:
+
+- **Copy `metadata.db` to a temp file and read the copy.** Calibre may be running and writing;
+  opening the live file read-only either sees a torn state or needs the `-wal` sidecar. The
+  database is small (438 KB for six books, single-digit MB for thousands), so a copy costs
+  nothing and removes the whole problem.
+- **`sqlite3` inside `asyncio.to_thread`, not a new dependency.** The connection is used for a
+  handful of queries. Do not add `aiosqlite` for this.
+
+Read the whole catalogue in **one query per table** and join in Python — six or so `SELECT`s and
+a few dicts, versus a per-book N+1 across ten tables. At self-hosted scale the entire catalogue
+minus descriptions fits in memory comfortably; if `comments.text` for 20k books is a concern,
+fetch that one table per batch.
+
+### 2. The mapping
+
+| Calibre | Chitai | Notes |
+| --- | --- | --- |
+| `books.title` | `title` | Sanitise `/` and control chars for path generation. `Extractor.format_book_title` may still be worth applying to split a subtitle at the second colon — but **do not** run `split_edition`, Calibre's title is the curated one. |
+| `authors.name` via `books_authors_link` | `authors` | `\|` → `,`. Order by `books_authors_link.id`; `Book.author_links` is an `ordering_list`, so insertion order is the displayed order. |
+| `comments.text` | `description` | Strip HTML to text. |
+| `books.pubdate` | `published_date` | Drop the year-101 sentinel. |
+| `series.name`, `books.series_index` | `series`, `series_position` | `7.0` → `"7"`. |
+| `tags.name` | `tags` | |
+| `publishers.name` | `publisher` | `books_publishers_link` is unique per book. |
+| `languages.lang_code` (lowest `item_order`) | `language` | Chitai holds one. |
+| `identifiers.type` / `.val` | `identifiers` | Through `parse_identifier`; keep what survives. |
+| `books.uuid` | `identifiers["calibre-uuid"]` | The one durable link back to the source row. `normalize_identifier` returns a key for it (it is not in `_PER_BUILD_NAMES`), which is *desirable*: a book re-imported from the same Calibre library matches on it exactly. |
+| `books_pages_link.pages` | `pages` | Only when `> 0`. |
+| `cover.jpg` when `has_cover` | `cover_image` | |
+| `data` rows | `files` | |
+| `books.timestamp` | — | `Book.created_at` is audit-managed; do not fight it. |
+| `ratings`, `annotations`, `custom_columns` | — | No home in the model. Out of scope. |
+| `last_read_positions` | `BookProgress` | Phase 2. |
+
+### 3. The ingest
+
+> **As built, this went on `BookService` as `create_many_from_calibre`, not into a separate
+> `services/calibre_import.py`.** The orchestration needs `_reserve_book_path`,
+> `_save_cover_image`, `_screen_for_duplicates` and `_record_possible_duplicates`, and reaching
+> into four privates from another module is worse than one more method in the file where the other
+> two ingest paths already live. `_record_possible_duplicates` was changed to take the list it
+> appends to rather than an `ImportResult`, so every ingest path can share it whatever its own
+> result type is. Two other deviations: `CalibreLibrary.books()` returns a list rather than an
+> async iterator, because the caller needs the total up front anyway; and the reader reports
+> identifiers exactly as Calibre keyed them, with the fold onto Chitai's schemes done by the
+> importer, which keeps the reader free of Chitai imports.
+
+Per book, in this order — it mirrors `create_many_from_existing_files`, which is the closest
+existing shape:
+
+1. `fingerprint_file` each source file (`services/utils.py:164`).
+2. `find_duplicate_files` against the target library. All files known → skip the book entirely,
+   recording it. Some known → import the rest.
+3. Build the metadata dict from the `CalibreBook`.
+4. `_reserve_book_path(path_gen.generate_path(data))`.
+5. **Copy** each file to `parent / _unused_path(...)`, building `FileMetadata` from the
+   fingerprint already computed. `services/utils.py` has `move_file` but no copy — add
+   `copy_file` beside it, streaming through `aiofiles` in `CHUNK_SIZE` blocks like
+   `_save_book_files` does, not `shutil.copy` (a 40 MB blocking read inside the event loop).
+6. Cover: open `cover.jpg` with PIL and hand the `Image` to `_save_cover_image`, which already
+   accepts one and converts to WebP.
+7. `super().create(data)` through `BookService`, then `find_duplicate_books` and record
+   candidates — same as `_record_possible_duplicates` (`services/book.py:1253`).
+8. **Commit per book.** A 5,000-book import inside one transaction is one failure away from
+   nothing, and per-book commits are what lets the library page show books arriving — which is
+   the behaviour commit `85367da` deliberately built.
+
+Report an `ImportResult`-shaped outcome; reuse `ImportResult` itself if it fits, extending it with
+a `failures: list[tuple[int, str]]` keyed by Calibre id. **One book must never fail the run** —
+a missing file, an unreadable cover or a `NOT NULL` violation gets recorded and skipped.
+
+### 4. Progress, and where the import runs
+
+> **As built, the HTTP surface is an uploaded archive and nothing else** — see decision 3.
+>
+> `POST …/imports/calibre/upload` takes a zipped library. The job owns the temp directory it is
+> unpacked into and deletes it when it ends. Extraction refuses zip slip, an archive too big for the
+> disk, and one with no `metadata.db` within three levels — all answered 400 before a job exists.
+>
+> This forced a fix to the SvelteKit proxy, which buffered request bodies with `arrayBuffer()`:
+> survivable for one book, not for a multi-gigabyte archive. POST and PATCH now stream
+> `request.body` through with `duplex: 'half'`.
+>
+> **A preview endpoint was built and then removed with the path route.** It read a server-side
+> catalogue and reported its size before writing anything, which is only useful when the caller
+> named a directory. An upload has already been carried across by the time anything can be read, so
+> unpacking it *is* the validation step — an archive that is not a Calibre library is refused there.
+
+The import outlives its request, so the handler starts it and returns a handle:
+
+- `POST /libraries/{library_id:int}/imports/calibre` — body `{path, copy_files: true}`, returns
+  `{job_id, total}`. 202.
+- `GET /libraries/imports/{job_id}` — `{state, total, processed, created, skipped, failed,
+  current_title, errors}`.
+- `DELETE /libraries/imports/{job_id}` — cancel; the task checks a flag between books.
+
+Keep the registry **in memory**, a `dict[str, ImportJob]` on a module-level singleton, with the
+task created by `asyncio.create_task`. This matches what the app already does — the consume
+watcher is an in-process singleton started from a lifespan hook — and it is roughly thirty lines
+against a model, a migration and a service for the alternative.
+
+State that limitation explicitly in the docstring: **it assumes one worker process.** The
+production `CMD` is `litestar run`, which is single-process, so this holds today; `TODO.md`
+already records that the production image should move to uvicorn with a worker count, and doing
+that would mean a poll landing on a worker that has never heard of the job. The consume watcher
+has the same problem, so this is not a new constraint — but the next person to add workers needs
+to find it written down. If import *history* is ever wanted, that is when an `import_jobs` table
+earns its migration.
+
+**Also add a CLI entry point.** A 200 GB library imported through a browser tab that must stay
+open is a bad experience, and `pyproject.toml` already declares a `chitai` script. A Litestar CLI
+command (`litestar --app-dir src/chitai/ calibre-import <path> --library <slug>`) is ~20 lines
+over the same service and is the right tool for the initial migration, which is the case this
+whole feature exists for. The endpoint is for people who would rather click.
+
+### 5. Frontend
+
+Model it on the duplicates screen, which is the closest precedent in shape and placement:
+
+- Route `(root)/settings/libraries/[libraryId]/import` — beside
+  `settings/libraries/[libraryId]/duplicates`, reached from the library settings page.
+- `getCalibreImport` (a `query`) and `cancelCalibreImport` (a `command`) in
+  `src/lib/api/calibre-import.remote.ts`, re-exported from `src/lib/api/index.ts`. **Starting an
+  import is not a remote function**: the archive goes to the backend through the proxy so the
+  browser streams straight through, where a remote function would put the whole thing through the
+  SvelteKit process first. The screen uses `XMLHttpRequest` for it, which is the only way to get
+  upload progress.
+- A file input, an upload progress bar, then a progress bar polling `getCalibreImport` every second
+  or two, a running count, and the failures listed at the end with their Calibre ids.
+- Finish with a link to the library's duplicates screen. An import into a non-empty library is
+  the single most likely way to produce duplicate books, and that screen already handles them.
+
+Do **not** route this through the upload tray. The tray reports on a client-driven queue it owns
+(`upload-queue.svelte.ts`); this is server-side work whose state survives a page reload, and
+conflating the two would mean teaching the tray to poll.
+
+Regenerate `src/lib/schema/openapi/schema.d.ts` against a backend running **your** branch —
+a stale server silently writes a stale file.
+
+## Testing
+
+The fixture is the interesting part. Build a Calibre library in a `tmp_path` fixture rather than
+committing a binary `metadata.db`: a helper that executes the subset of Calibre's `CREATE TABLE`
+statements (they are in this document's shape, and in any real library's `sqlite_master`), inserts
+a handful of books, and lays out `<Author>/<Title> (id)/` directories containing the existing
+EPUB and PDF fixtures from `backend/tests/data_files/` plus a copy of `cover.jpg`. Generated
+beats committed here because the tests need to assert on *odd* rows — the pubdate sentinel, a
+`|` in an author name, a title with a colon — and those are clearer written in Python than hidden
+in a blob.
+
+- **Unit** (`tests/unit/test_calibre.py`) — the reader alone: field mapping; the year-101 pubdate
+  dropped; `series_index` 7.0 → `"7"`; `|` unescaped in an author name; HTML stripped from
+  `comments`; `pages = 0` ignored; identifiers passed through `parse_identifier`; a `data` row
+  whose file is missing from disk reported rather than raised; `.caltrash` never walked.
+- **Service** (`tests/unit/test_services/test_calibre_import.py`) — a book with two formats lands
+  as one record with two files; the source files still exist afterwards; a second run over the
+  same library creates nothing; a library with one broken book imports the rest; authors and tags
+  shared between two books produce one `Author` / `Tag` row each; `possible_duplicates` reported
+  when the target library already holds the same book.
+- **Integration** (`tests/integration/test_calibre_import.py`) — `POST` returns 202 with a job id,
+  polling reaches a terminal state, and the books are then listable through `GET /books`. A
+  `.mobi`-only book must come back from `GET /books/{id}` without a 500 — that is the
+  prerequisite's regression test.
+
+`pytest` needs Docker (`pytest-databases`).
+
+## Verification
+
+```bash
+nix-shell                                                    # postgres + migrations applied
+cd backend
+pytest tests/                                                # take your own baseline first
+uv run litestar --app-dir src/chitai/ run --port 8001        # for the OpenAPI regeneration
+cd ../frontend && pnpm check                                 # baseline: 30 errors, 1 warning, 8 files
+```
+
+Neither `pnpm check` nor `pnpm lint` is clean on this repo — baseline before assuming an error is
+yours.
+
+End to end, against a real library (`~/Documents/Calibre Library` will do): import into an empty
+Chitai library and confirm the six books arrive with their covers, authors, tags, series
+positions and identifiers intact; that the AZW3 book is listed and downloadable; that the source
+library is byte-for-byte untouched (`diff -r` a copy taken beforehand); and that re-running the
+import creates nothing and reports six skipped books. Then import the same library into a
+library that already holds one of those books by upload, and confirm it lands on the duplicates
+screen rather than as a second copy.
+
+## Phasing
+
+| Phase | Scope |
+| --- | --- |
+| **0** ✅ | The `content_type` prerequisite, plus the Read button. **Done** — see below. |
+| **1** ✅ | `services/calibre.py`, the ingest, the CLI command, copy-only. **Done** — a headless one-time migration works today. |
+| **2** ◐ | The upload endpoint, the job registry and the settings screen — **done**. The HTTP surface is an uploaded zip only; see decision 3, which this reversed. `last_read_positions` → `BookProgress` is **not** done: it needs a Calibre-user → Chitai-user mapping, and the answer differs between the endpoint (which has a `current_user`) and the CLI (which has none). That decision is the next thing to make. |
+| **3** | Reference-in-place import. Its real content is **enforcing `Library.read_only`** across `update_book`, `delete_books`, `add_files` and `remove_files` — which is a feature of its own and should not be smuggled in under an import. |
+
+## Out of scope
+
+Annotations and highlights (no model to put them in), custom columns, ratings, virtual libraries
+and saved searches → bookshelves, format conversion, writing anything back to Calibre, and any
+form of continuing two-way sync. This is a one-way migration.

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/components/view/book-browser.svelte

@@ -29,19 +29,31 @@
 
 	$effect(() => {
 		if (!sentinel || !bookCollection.moreBooks) return;
+		const target = sentinel;
+
 		const observer = new IntersectionObserver(
 			async (entries) => {
-				if (entries[0].isIntersecting && !bookCollection.loading) {
-					await bookCollection.loadMoreBooks();
+				if (!entries[0].isIntersecting) return;
+
+				await bookCollection.loadMoreBooks();
+
+				// A page that does not push the sentinel back out of the prefetch zone
+				// produces no further intersection change, so the observer would sit
+				// idle until the next scroll. Re-observing asks for a fresh reading.
+				if (bookCollection.moreBooks) {
+					observer.unobserve(target);
+					observer.observe(target);
 				}
 			},
 			{
 				root: scrollContainer,
-				rootMargin: '0px 0px 200px 0px' 
+				// One viewport of lead time: the next page is requested a full screen
+				// before the reader reaches the end of the current one.
+				rootMargin: '0px 0px 100% 0px'
 			}
 		);
 
-		observer.observe(sentinel);
+		observer.observe(target);
 
 		return () => {
 			observer.disconnect();
@@ -110,7 +122,7 @@
 
 						{#if bookCollection.moreBooks}
 							<div bind:this={sentinel}>
-								{#if bookCollection.loading}
+								{#if bookCollection.loadingMore}
 									<Spinner />
 								{/if}
 							</div>

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/state/bookCollection.svelte.ts

@@ -28,6 +28,14 @@ export class BookCollectionState {
 	public moreBooks = $state(false);
 	private currentBookPage = $state(1);
 	public loading = $state(false);
+	/** A page append, as opposed to `loading`, which replaces the whole list. */
+	public loadingMore = $state(false);
+
+	/**
+	 * Whether the reader has loaded past the first page. Anything that refetches
+	 * gets page one back, which is a jump to the top from here.
+	 */
+	readonly pastFirstPage = $derived(this.currentBookPage > 1);
 
 	public filterOptions: FilterOption[] = $state([]);
 
@@ -159,22 +167,37 @@ export class BookCollectionState {
 		});
 
 		this.books = [...result.items];
+		this.moreBooks = result.total > result.items.length;
 		this.currentBookPage = 1;
 		this.loading = false;
 	}
 
+	/**
+	 * Prefetching means the trigger can fire again while a page is still in
+	 * flight, so the guard is here rather than in the observer — every caller
+	 * gets it, and a second call is dropped instead of duplicating a page.
+	 */
 	async loadMoreBooks() {
-		const result = await this.ops.listBooks({
-			currentPage: this.currentBookPage + 1,
-			pageSize: 50,
-			sortOrder: this.sortOrder,
-			orderBy: this.orderBy,
-			...this.filters
-		});
+		if (this.loadingMore || !this.moreBooks) return;
 
-		this.books = [...this.books, ...result.items];
-		this.moreBooks = result.total > this.books.length;
-		this.currentBookPage++;
+		this.loadingMore = true;
+		try {
+			const result = await this.ops.listBooks({
+				currentPage: this.currentBookPage + 1,
+				pageSize: 50,
+				sortOrder: this.sortOrder,
+				orderBy: this.orderBy,
+				...this.filters
+			});
+
+			this.books = [...this.books, ...result.items];
+			// An empty page means the count we were given was stale; stop asking
+			// rather than loop on a page that never grows the list.
+			this.moreBooks = result.items.length > 0 && result.total > this.books.length;
+			this.currentBookPage++;
+		} finally {
+			this.loadingMore = false;
+		}
 	}
 
 	updateBooks(books: PaginatedResponse<Book>) {
@@ -187,6 +210,11 @@ export class BookCollectionState {
 		this.moreBooks = books.total > books.items.length;
 		this.filterOptions = this.buildFilterOptions(filterData);
 
+		// The loader hands back the first page, so the counter has to say so —
+		// otherwise loadMoreBooks resumes from wherever the reader had scrolled to
+		// and skips every page in between.
+		this.currentBookPage = 1;
+
 		const urlParams = new URLSearchParams(window.location.search);
 
 		// Re-read sort and filter state from URL

frontend/src/lib/state/upload-queue.svelte.ts

@@ -68,6 +68,9 @@ function warnBeforeUnload(event: BeforeUnloadEvent) {
 /** How long a clean run stays on screen before clearing itself. */
 const DISMISS_AFTER_MS = 6000;
 
+/** How often a run that is still going refreshes the list behind it. */
+const REFRESH_EVERY_MS = 2000;
+
 /**
  * Uploads books one request at a time and keeps the result on screen.
  *
@@ -108,8 +111,15 @@ export class UploadQueueState {
 		)
 	);
 
+	/**
+	 * Set by a list that has loaded past its first page, to keep a mid-run refresh
+	 * from throwing the reader back to the top. See #scheduleRefresh.
+	 */
+	holdRefresh = false;
+
 	#running = false;
 	#dismissTimer: ReturnType<typeof setTimeout> | undefined;
+	#refreshTimer: ReturnType<typeof setTimeout> | undefined;
 	#held = false;
 
 	/** Adds one job per book and starts the runner if it is not already going. */
@@ -177,6 +187,31 @@ export class UploadQueueState {
 		}, DISMISS_AFTER_MS);
 	}
 
+	/**
+	 * Shows the books added so far, without waiting for the rest of the run.
+	 *
+	 * A refetch rather than inserting the created book into the list by hand: the
+	 * server owns the sort, the filters and the paging, so asking it again is what
+	 * makes a part-finished import look the same as a finished one.
+	 *
+	 * Trailing, and at most one refresh per REFRESH_EVERY_MS — a folder of small
+	 * books lands faster than the list can usefully redraw.
+	 */
+	#scheduleRefresh() {
+		if (this.#refreshTimer) return;
+
+		this.#refreshTimer = setTimeout(() => {
+			this.#refreshTimer = undefined;
+
+			// The loaders only ever return the first page, so refreshing under a
+			// reader who has scrolled past it would drop them back to the top. Their
+			// list catches up when the run ends.
+			if (this.holdRefresh) return;
+
+			void invalidate('app:books');
+		}, REFRESH_EVERY_MS);
+	}
+
 	/** Re-queues everything that failed, so one bad book is not a reason to start over. */
 	retryFailed() {
 		this.jobs = this.jobs.map((job) =>
@@ -229,6 +264,8 @@ export class UploadQueueState {
 						// One job is one book, so it has at most one set of candidates.
 						possibleDuplicates: result.possible_duplicates?.[0]?.candidates
 					});
+
+					if (result.created.length > 0) this.#scheduleRefresh();
 				} catch (error) {
 					// One bad book must not take the rest of the queue with it.
 					console.error(`Failed to upload ${this.jobs[index].label}`, error);
@@ -243,6 +280,12 @@ export class UploadQueueState {
 			window.removeEventListener('beforeunload', warnBeforeUnload);
 		}
 
+		// The run is over, so the refresh below is the one that counts — a pending
+		// mid-run one would only repeat it a moment later, and it is the one that
+		// honours holdRefresh.
+		clearTimeout(this.#refreshTimer);
+		this.#refreshTimer = undefined;
+
 		if (created > 0) await invalidate('app:books');
 
 		if (!this.needsAttention) this.#scheduleDismiss();

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)/(library)/library/[libraryId]/view/+page.svelte

@@ -5,6 +5,7 @@
 	import type { PaginatedResponse } from '$lib/schema/common';
 	import { setBookCollectionState } from '$lib/state/bookCollection.svelte';
 	import { getBookOperationsState } from '$lib/state/bookOperations.svelte';
+	import { getUploadQueueState } from '$lib/state/upload-queue.svelte';
 	import { untrack } from 'svelte';
 
 	let {
@@ -23,6 +24,16 @@
 
 	const bookOps = getBookOperationsState();
 	const bookCollection = setBookCollectionState(bookOps, books, filterData);
+	const queue = getUploadQueueState();
+
+	// An upload refreshes this list every couple of seconds so books show up as
+	// they land. That refresh returns the first page, so it waits while the reader
+	// is reading further down. Cleared on the way out: this list is gone, and a
+	// stale hold would stop the next one refreshing at all.
+	$effect(() => {
+		queue.holdRefresh = bookCollection.pastFirstPage;
+		return () => (queue.holdRefresh = false);
+	});
 
 	let skip = $state(true);
 

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);