bambuddy/backend/app/api/routes/print_queue.py

"""API routes for print queue management."""

import json
import logging
import zipfile
from datetime import datetime, timezone
from pathlib import Path

import defusedxml.ElementTree as ET
from fastapi import APIRouter, Depends, HTTPException, Query
from sqlalchemy import and_, func, inspect, or_, select, update
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from backend.app.api.routes.library_variants import normalize_model_name, resolve_variant_model
from backend.app.core.auth import RequirePermissionIfAuthEnabled, require_ownership_permission
from backend.app.core.config import settings
from backend.app.core.database import get_db
from backend.app.core.permissions import Permission
from backend.app.models.archive import PrintArchive
from backend.app.models.library import LibraryFile
from backend.app.models.print_batch import PrintBatch, PrintBatchPlate
from backend.app.models.print_queue import PrintQueueItem, PrintQueueVariant
from backend.app.models.printer import Printer
from backend.app.models.project import Project
from backend.app.models.user import User
from backend.app.schemas.print_queue import (
    PrintBatchCreate,
    PrintBatchDispatchRequest,
    PrintBatchPlateProgress,
    PrintBatchPlateTarget,
    PrintBatchResponse,
    PrintBatchUngroupResponse,
    PrintBatchUpdate,
    PrintQueueBulkUpdate,
    PrintQueueBulkUpdateResponse,
    PrintQueueItemCreate,
    PrintQueueItemResponse,
    PrintQueueItemUpdate,
    PrintQueueReorder,
    QueueVariantCreate,
    QueueVariantSummary,
)
from backend.app.services.filament_deficit import compute_deficit_for_queue_item
from backend.app.services.filament_requirements import overrides_for_plate
from backend.app.services.notification_service import notification_service
from backend.app.services.print_batch import (
    BatchDispatchError,
    dispatch_remaining,
    load_progress,
    refresh_batch_status,
)
from backend.app.utils.printer_models import (
    is_gcode_compatible,
)
from backend.app.utils.threemf_tools import (
    extract_plate_metadata_from_3mf,
    extract_print_time_from_3mf,
)

logger = logging.getLogger(__name__)

router = APIRouter(prefix="/queue", tags=["queue"])


def _variant_summaries(item: PrintQueueItem) -> list[QueueVariantSummary]:
    """Cross-model candidates for display (#671), or [] if they weren't loaded.

    Every route that builds a queue response eager-loads ``variants``. Reading
    the attribute unguarded would still be a landmine for the next one that
    doesn't: a lazy load on an async session raises rather than degrading, so a
    forgotten ``selectinload`` would turn a card render into a 500.
    """
    if "variants" in inspect(item).unloaded:
        return []
    return [
        QueueVariantSummary(
            library_file_id=v.library_file_id,
            filename=v.library_file.filename if v.library_file else "",
            target_model=v.target_model,
            position=v.position,
        )
        for v in item.variants
    ]


def _extract_filament_types_from_3mf(file_path: Path, plate_id: int | None = None) -> list[str]:
    """Extract unique filament types from a 3MF file.

    Args:
        file_path: Path to the 3MF file
        plate_id: Optional plate index to filter for (for multi-plate files)

    Returns:
        List of unique filament types (e.g., ["PLA", "PETG"])
    """
    types: set[str] = set()

    try:
        with zipfile.ZipFile(file_path, "r") as zf:
            if "Metadata/slice_info.config" not in zf.namelist():
                return []

            content = zf.read("Metadata/slice_info.config").decode()
            root = ET.fromstring(content)

            if plate_id is not None:
                # Find the plate element with matching index
                for plate_elem in root.findall(".//plate"):
                    plate_index = None
                    for meta in plate_elem.findall("metadata"):
                        if meta.get("key") == "index":
                            try:
                                plate_index = int(meta.get("value", "0"))
                            except ValueError:
                                pass  # Skip plate with unparseable index
                            break

                    if plate_index == plate_id:
                        for filament_elem in plate_elem.findall("filament"):
                            filament_type = filament_elem.get("type", "")
                            used_g = filament_elem.get("used_g", "0")
                            try:
                                used_grams = float(used_g)
                            except (ValueError, TypeError):
                                used_grams = 0
                            if used_grams > 0 and filament_type:
                                types.add(filament_type)
                        break
            else:
                # No plate_id specified - extract all filaments with used_g > 0
                for filament_elem in root.findall(".//filament"):
                    filament_type = filament_elem.get("type", "")
                    used_g = filament_elem.get("used_g", "0")
                    try:
                        used_grams = float(used_g)
                    except (ValueError, TypeError):
                        used_grams = 0
                    if used_grams > 0 and filament_type:
                        types.add(filament_type)

    except Exception as e:
        logger.warning("Failed to extract filament types from %s: %s", file_path, e)

    return sorted(types)


# Local alias kept so existing call sites stay compact; the implementation lives
# in utils/threemf_tools.py so the notification path (main.py) can reuse it
# without importing from a routes module (#1785).
_extract_print_time_from_3mf = extract_print_time_from_3mf


def _assert_can_queue_archive(archive: PrintArchive, current_user: User | None) -> None:
    """Gate turning *archive* into a print. Raises rather than returning a verdict.

    Shared by every route that creates queue items from an archive, so a new
    one can't quietly become a weaker door to the same action than
    ``POST /queue/`` is.

    Two separate checks:

    * IDOR fix (maziggy/bambuddy-security #2): without this, a caller with
      QUEUE_CREATE could queue any user's archive even without ARCHIVES_READ on
      it — Landon's PoC enumerated this on admin's archives as operator1. Gate
      on ARCHIVES_READ_ALL OR ownership. 404 (not 403) so we don't leak "this
      id exists but you can't queue it" for enumeration.
    * Reprint perm gate (#1625): the legacy ``/archives/{id}/reprint`` endpoint
      required ARCHIVES_REPRINT_OWN/ALL, and every route that replaces it must
      keep that gate or an operator with QUEUE_CREATE could reprint via a
      direct API call even when explicitly denied reprint perm. Mirrors the
      frontend ``canModify('archives', 'reprint', ...)`` helper: REPRINT_ALL
      allows any archive, REPRINT_OWN allows own only, ownerless archives
      require REPRINT_ALL (fail-closed).
    """
    if current_user is None:
        return
    if not current_user.has_permission(Permission.ARCHIVES_READ_ALL.value) and archive.created_by_id != current_user.id:
        raise HTTPException(404, "Archive not found")
    owns_archive = archive.created_by_id is not None and archive.created_by_id == current_user.id
    has_reprint = current_user.has_permission(Permission.ARCHIVES_REPRINT_ALL.value) or (
        owns_archive and current_user.has_permission(Permission.ARCHIVES_REPRINT_OWN.value)
    )
    if not has_reprint:
        raise HTTPException(
            status_code=403,
            detail="Permission archives:reprint_own or archives:reprint_all required",
        )


def _assert_can_queue_library_file(library_file: LibraryFile, current_user: User | None) -> None:
    """Gate turning *library_file* into a print — LIBRARY_READ_ALL or ownership."""
    if current_user is None:
        return
    if (
        not current_user.has_permission(Permission.LIBRARY_READ_ALL.value)
        and library_file.created_by_id != current_user.id
    ):
        raise HTTPException(404, "Library file not found")


async def _assert_can_dispatch_batch_sources(db: AsyncSession, batch_id: int, current_user: User | None) -> None:
    """Apply the ``POST /queue/`` source-file gates to everything a dispatch would print.

    Dispatching clones existing queue items, so without this it would be a
    weaker door to the same outcome: a caller holding QUEUE_CREATE and
    QUEUE_UPDATE_ALL but explicitly denied ``archives:reprint_*`` could start
    prints through an order that ``POST /queue/`` would have refused them.

    Every distinct source among the batch's items is checked, including the
    library files behind cross-model variants — those get cloned too, and any
    one of them may be the file that actually runs.
    """
    archive_ids = set(
        (
            await db.execute(
                select(PrintQueueItem.archive_id)
                .where(PrintQueueItem.batch_id == batch_id)
                .where(PrintQueueItem.archive_id.is_not(None))
                .distinct()
            )
        )
        .scalars()
        .all()
    )
    library_file_ids = set(
        (
            await db.execute(
                select(PrintQueueItem.library_file_id)
                .where(PrintQueueItem.batch_id == batch_id)
                .where(PrintQueueItem.library_file_id.is_not(None))
                .distinct()
            )
        )
        .scalars()
        .all()
    )
    library_file_ids |= set(
        (
            await db.execute(
                select(PrintQueueVariant.library_file_id)
                .join(PrintQueueItem, PrintQueueVariant.queue_item_id == PrintQueueItem.id)
                .where(PrintQueueItem.batch_id == batch_id)
                .distinct()
            )
        )
        .scalars()
        .all()
    )

    for archive_id in archive_ids:
        archive = (await db.execute(select(PrintArchive).where(PrintArchive.id == archive_id))).scalar_one_or_none()
        # A deleted source can't be printed; dispatch will fail on it anyway.
        if archive is not None:
            _assert_can_queue_archive(archive, current_user)

    for library_file_id in library_file_ids:
        library_file = (
            await db.execute(LibraryFile.active().where(LibraryFile.id == library_file_id))
        ).scalar_one_or_none()
        if library_file is not None:
            _assert_can_queue_library_file(library_file, current_user)


async def _resolve_source_path(db: AsyncSession, item: PrintQueueItem) -> Path | None:
    """Resolve an existing queue item's source 3MF on disk, or None."""
    if item.archive_id:
        result = await db.execute(select(PrintArchive).where(PrintArchive.id == item.archive_id))
        archive = result.scalar_one_or_none()
        if archive:
            return settings.base_dir / archive.file_path
    elif item.library_file_id:
        result = await db.execute(LibraryFile.active().where(LibraryFile.id == item.library_file_id))
        library_file = result.scalar_one_or_none()
        if library_file:
            lib_path = Path(library_file.file_path)
            return lib_path if lib_path.is_absolute() else settings.base_dir / library_file.file_path
    return None


def _enrich_response(item: PrintQueueItem) -> PrintQueueItemResponse:
    """Add nested archive/printer/library_file info to response."""
    # Parse ams_mapping from JSON string BEFORE model_validate
    ams_mapping_parsed = None
    if item.ams_mapping:
        try:
            ams_mapping_parsed = json.loads(item.ams_mapping)
        except json.JSONDecodeError:
            ams_mapping_parsed = None

    # Parse required_filament_types from JSON string
    required_filament_types_parsed = None
    if item.required_filament_types:
        try:
            required_filament_types_parsed = json.loads(item.required_filament_types)
        except json.JSONDecodeError:
            required_filament_types_parsed = None

    # Parse filament_overrides from JSON string
    filament_overrides_parsed = None
    if item.filament_overrides:
        try:
            filament_overrides_parsed = json.loads(item.filament_overrides)
        except json.JSONDecodeError:
            filament_overrides_parsed = None

    # Parse nozzle_mapping from JSON string (#1780 — H2C rack slicer-pick
    # preservation). Nullable opaque JSON blob stored verbatim from
    # BambuStudio's project_file; surface it parsed for the response model
    # and any future "edit print → nozzle" UI.
    nozzle_mapping_parsed = None
    if item.nozzle_mapping:
        try:
            nozzle_mapping_parsed = json.loads(item.nozzle_mapping)
        except json.JSONDecodeError:
            nozzle_mapping_parsed = None

    nozzles_info_parsed = None
    if item.nozzles_info:
        try:
            nozzles_info_parsed = json.loads(item.nozzles_info)
        except json.JSONDecodeError:
            nozzles_info_parsed = None

    # Create response with parsed ams_mapping
    item_dict = {
        "id": item.id,
        "printer_id": item.printer_id,
        "target_model": item.target_model,
        "target_location": item.target_location,
        "required_filament_types": required_filament_types_parsed,
        "filament_overrides": filament_overrides_parsed,
        "waiting_reason": item.waiting_reason,
        "archive_id": item.archive_id,
        "library_file_id": item.library_file_id,
        "position": item.position,
        "scheduled_time": item.scheduled_time,
        "require_previous_success": item.require_previous_success,
        "auto_off_after": item.auto_off_after,
        "manual_start": item.manual_start,
        "filament_short": bool(item.filament_short),
        "skip_filament_check": bool(item.skip_filament_check),
        "ams_mapping": ams_mapping_parsed,
        "plate_id": item.plate_id,
        "bed_levelling": item.bed_levelling,
        "flow_cali": item.flow_cali,
        "vibration_cali": item.vibration_cali,
        "layer_inspect": item.layer_inspect,
        "timelapse": item.timelapse,
        "use_ams": item.use_ams,
        "nozzle_offset_cali": item.nozzle_offset_cali,
        "preheat_override": item.preheat_override,
        "preheat_chamber_target_override": item.preheat_chamber_target_override,
        "status": item.status,
        "started_at": item.started_at,
        "completed_at": item.completed_at,
        "error_message": item.error_message,
        "created_at": item.created_at,
        # User tracking (Issue #206)
        "created_by_id": item.created_by_id,
        "created_by_username": item.created_by.username if item.created_by else None,
        # Batch grouping
        "batch_id": item.batch_id,
        "batch_name": item.batch.name if item.batch else None,
        # SJF scheduling
        "been_jumped": item.been_jumped,
        # Auto-print G-code injection
        "gcode_injection": item.gcode_injection,
        # H2C rack-swap nozzle pick (#1780)
        "nozzle_mapping": nozzle_mapping_parsed,
        "nozzles_info": nozzles_info_parsed,
        "cleanup_library_after_dispatch": item.cleanup_library_after_dispatch,
        # Cross-model alternatives (#671). Guarded rather than read directly:
        # every route that reaches here eager-loads the relationship, but a
        # caller that forgets would trigger a lazy load, and a lazy load on an
        # async session raises rather than degrading. An empty list is the
        # correct answer for the ordinary item this would most likely be.
        "variants": _variant_summaries(item),
    }
    response = PrintQueueItemResponse(**item_dict)
    if item.archive:
        # Soft-deleted archive: files are gone from disk but the row stays
        # (its filament/cost contribution still flows into stats per #1343).
        # Suppress the archive-derived UI surface so the queue page doesn't
        # 404-storm the thumbnail / plates / plate-thumbnail endpoints — the
        # frontend's existing truthy gate on archive_thumbnail covers it
        # (#1348 follow-up). The archive_deleted flag lets the UI render a
        # "source deleted" badge on these rows.
        if item.archive.deleted_at is not None:
            response.archive_deleted = True
        else:
            response.archive_name = item.archive.print_name or item.archive.filename
            response.archive_thumbnail = item.archive.thumbnail_path
            response.print_time_seconds = item.archive.print_time_seconds
            response.filament_used_grams = item.archive.filament_used_grams
            response.filament_type = item.archive.filament_type
            response.filament_color = item.archive.filament_color
            response.layer_height = item.archive.layer_height
            response.nozzle_diameter = item.archive.nozzle_diameter
            response.sliced_for_model = item.archive.sliced_for_model
            response.bed_type = item.archive.bed_type
            # Marks history/reprint rows whose archive carries the slicer's own
            # live-resolved AMS-slot pick (extra_data.slicer_ams_mapping) — see
            # `_extract_slicer_ams_mapping_json` in virtual_printer/manager.py.
            #
            # Only when the saved mapping was resolved against *this* row's
            # printer: a global tray ID means nothing on another printer, so
            # that's the exact condition under which the mapping is reused. A
            # badge on a row where nothing gets reused would be a lie (#2700
            # review). Model-based rows (printer_id None) never match, which is
            # correct — the mapping is not reused there either.
            extra = item.archive.extra_data if isinstance(item.archive.extra_data, dict) else {}
            saved_mapping = extra.get("slicer_ams_mapping")
            response.archive_has_slicer_ams_mapping = (
                isinstance(saved_mapping, dict)
                and isinstance(saved_mapping.get("mapping"), list)
                and item.printer_id is not None
                and saved_mapping.get("printer_id") == item.printer_id
            )
            if item.plate_id:
                archive_path = settings.base_dir / item.archive.file_path
                if archive_path.exists():
                    # One cached parse for all three per-plate overrides (#2573).
                    plate_meta = extract_plate_metadata_from_3mf(archive_path, item.plate_id)
                    if plate_meta.print_time_seconds is not None:
                        response.print_time_seconds = plate_meta.print_time_seconds
                    if plate_meta.filament_used_grams > 0:
                        response.filament_used_grams = plate_meta.filament_used_grams
                    if plate_meta.bed_type:
                        response.bed_type = plate_meta.bed_type
    if item.library_file:
        response.library_file_name = (
            item.library_file.file_metadata.get("print_name") if item.library_file.file_metadata else None
        )
        if not response.library_file_name:
            response.library_file_name = item.library_file.filename
        response.library_file_thumbnail = item.library_file.thumbnail_path
        # Get metadata from library file if no archive
        if not item.archive and item.library_file.file_metadata:
            response.print_time_seconds = item.library_file.file_metadata.get("print_time_seconds")
            response.filament_used_grams = item.library_file.file_metadata.get("filament_used_grams")
            response.filament_type = item.library_file.file_metadata.get("filament_type")
            response.filament_color = item.library_file.file_metadata.get("filament_color")
            response.layer_height = item.library_file.file_metadata.get("layer_height")
            response.nozzle_diameter = item.library_file.file_metadata.get("nozzle_diameter")
            response.sliced_for_model = item.library_file.file_metadata.get("sliced_for_model")
            response.bed_type = item.library_file.file_metadata.get("bed_type")
        if item.plate_id:
            lib_path = Path(item.library_file.file_path)
            library_file_path = lib_path if lib_path.is_absolute() else settings.base_dir / item.library_file.file_path
            if library_file_path.exists():
                # One cached parse for all three per-plate overrides (#2573).
                plate_meta = extract_plate_metadata_from_3mf(library_file_path, item.plate_id)
                if plate_meta.print_time_seconds is not None:
                    response.print_time_seconds = plate_meta.print_time_seconds
                if plate_meta.filament_used_grams > 0:
                    response.filament_used_grams = plate_meta.filament_used_grams
                if plate_meta.bed_type:
                    response.bed_type = plate_meta.bed_type
    if item.printer:
        response.printer_name = item.printer.name
    return response


@router.get("/", response_model=list[PrintQueueItemResponse])
async def list_queue(
    printer_id: int | None = Query(None, description="Filter by printer (-1 for unassigned)"),
    status: str | None = Query(None, description="Filter by status"),
    target_model: str | None = Query(
        None, description="Filter by target model (also includes model-based items when combined with printer_id)"
    ),
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_READ_ALL,
            Permission.QUEUE_READ_OWN,
        )
    ),
):
    """List all queue items, optionally filtered by printer or status."""
    user, can_read_all = auth_result
    query = (
        select(PrintQueueItem)
        .options(
            selectinload(PrintQueueItem.archive),
            selectinload(PrintQueueItem.printer),
            selectinload(PrintQueueItem.library_file),
            selectinload(PrintQueueItem.created_by),
            selectinload(PrintQueueItem.batch),
            # Cross-model candidates (#671) and their files, for the card label.
            selectinload(PrintQueueItem.variants).selectinload(PrintQueueVariant.library_file),
        )
        .order_by(PrintQueueItem.printer_id.nulls_first(), PrintQueueItem.position)
    )
    if user is not None and not can_read_all:
        query = query.where(PrintQueueItem.created_by_id == user.id)

    if printer_id is not None:
        if printer_id == -1:
            # Special value: filter for unassigned items
            query = query.where(PrintQueueItem.printer_id.is_(None))
        else:
            # Resolve effective model: prefer explicit param, fall back to printer's DB model.
            # This ensures model-based "Any X" items are returned even when the frontend
            # doesn't send target_model (e.g. printer.model is NULL on the client side).
            effective_model = target_model
            if not effective_model:
                printer_row = (
                    await db.execute(select(Printer.model).where(Printer.id == printer_id))
                ).scalar_one_or_none()
                effective_model = printer_row

            if effective_model:
                # Include both printer-specific items AND model-based (unassigned) items
                query = query.where(
                    or_(
                        PrintQueueItem.printer_id == printer_id,
                        and_(
                            PrintQueueItem.printer_id.is_(None),
                            func.lower(PrintQueueItem.target_model) == effective_model.lower(),
                        ),
                    )
                )
            else:
                query = query.where(PrintQueueItem.printer_id == printer_id)
    elif target_model:
        query = query.where(func.lower(PrintQueueItem.target_model) == target_model.lower())
    if status:
        query = query.where(PrintQueueItem.status == status)

    result = await db.execute(query)
    items = result.scalars().all()
    return [_enrich_response(item) for item in items]


async def _resolve_queue_variants(
    db: AsyncSession,
    specs: list[QueueVariantCreate],
    current_user: User | None,
) -> list[tuple[QueueVariantCreate, LibraryFile, str]]:
    """Validate a cross-model candidate set and pair each file with its model (#671).

    Validated as a set, not file by file, because the failure modes are about the
    set: two candidates for the same printer give the resolver no basis to choose,
    and a set where nothing can ever run is a job that waits forever.

    At least one candidate must have an active printer — the rest may not, which
    is deliberate. Grouping the H2C slice before the H2C arrives is a reasonable
    thing to do, and refusing the whole queue action over it would be worse than
    letting that candidate simply never match.
    """
    file_ids = [s.library_file_id for s in specs]
    if len(set(file_ids)) != len(file_ids):
        raise HTTPException(400, "The same file cannot be listed twice as a variant")

    rows = (await db.execute(LibraryFile.active().where(LibraryFile.id.in_(file_ids)))).scalars().all()
    by_id = {f.id: f for f in rows}

    resolved: list[tuple[QueueVariantCreate, LibraryFile, str]] = []
    seen_models: dict[str, str] = {}
    any_active_printer = False

    for spec in specs:
        library_file = by_id.get(spec.library_file_id)
        # Same IDOR posture as the single-file path: a file the caller cannot read
        # is reported as missing rather than forbidden.
        if not library_file or (
            current_user
            and not current_user.has_permission(Permission.LIBRARY_READ_ALL.value)
            and library_file.created_by_id != current_user.id
        ):
            raise HTTPException(404, f"Library file not found: {spec.library_file_id}")

        from backend.app.utils.filename import InvalidFilenameError, validate_print_filename

        try:
            validate_print_filename(library_file.filename)
        except InvalidFilenameError as e:
            raise HTTPException(400, str(e)) from e

        model = resolve_variant_model(library_file, spec.target_model)
        if not model:
            raise HTTPException(
                400,
                f"{library_file.filename} does not say which printer it was sliced for — "
                "set its target model explicitly",
            )

        # Cross-model safety gate (#2578), per candidate. A set is only as safe as
        # its worst member, and model-based dispatch has no human in the loop.
        sliced_for = (library_file.file_metadata or {}).get("sliced_for_model")
        if not is_gcode_compatible(sliced_for, model):
            raise HTTPException(
                400,
                f"{library_file.filename} was sliced for {sliced_for} and cannot be dispatched to {model} printers",
            )

        if model in seen_models:
            raise HTTPException(
                400,
                f"{library_file.filename} and {seen_models[model]} are both for {model} — "
                "variants must target different printers",
            )
        seen_models[model] = library_file.filename

        has_printer = (
            (
                await db.execute(
                    select(Printer).where(Printer.model == model).where(Printer.is_active == True)  # noqa: E712
                )
            )
            .scalars()
            .first()
        )
        any_active_printer = any_active_printer or bool(has_printer)

        resolved.append((spec, library_file, model))

    if not any_active_printer:
        raise HTTPException(400, f"No active printers for any of: {', '.join(seen_models)}")

    return resolved


def _variant_values(
    spec: QueueVariantCreate,
    library_file: LibraryFile,
    model: str,
    position: int,
) -> dict:
    """Column values for one candidate, extracted from its own 3MF.

    Each candidate is a different slice, so its filament requirements and print
    time come from its own file rather than being inherited from the item.

    Returns values rather than a row so a quantity>1 batch can build one row per
    copy without re-opening the 3MF for each.
    """
    lib_path = Path(library_file.file_path)
    file_path = lib_path if lib_path.is_absolute() else settings.base_dir / library_file.file_path

    required_types = None
    filament_overrides_json = None
    print_time = (library_file.file_metadata or {}).get("print_time_seconds")

    if file_path.exists():
        types = _extract_filament_types_from_3mf(file_path, spec.plate_id)
        if types:
            required_types = json.dumps(types)
        if spec.plate_id:
            plate_time = _extract_print_time_from_3mf(file_path, spec.plate_id)
            if plate_time is not None:
                print_time = plate_time
        if spec.filament_overrides:
            plate_overrides = overrides_for_plate(spec.filament_overrides, file_path, spec.plate_id)
            if plate_overrides:
                filament_overrides_json = json.dumps(plate_overrides)
                override_types = sorted({o["type"] for o in plate_overrides if "type" in o})
                if override_types:
                    existing = set(json.loads(required_types)) if required_types else set()
                    required_types = json.dumps(sorted(existing | set(override_types)))

    return {
        "position": position,
        "library_file_id": library_file.id,
        "target_model": model,
        "plate_id": spec.plate_id,
        "ams_mapping": json.dumps(spec.ams_mapping) if spec.ams_mapping else None,
        "nozzle_mapping": json.dumps(spec.nozzle_mapping) if spec.nozzle_mapping else None,
        "filament_overrides": filament_overrides_json,
        "required_filament_types": required_types,
        "print_time_seconds": print_time,
    }


@router.post("/", response_model=PrintQueueItemResponse)
async def add_to_queue(
    data: PrintQueueItemCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_CREATE),
):
    """Add an item to the print queue."""
    # Normalize target_model (e.g., "Bambu Lab X1E" / "C13" -> "X1E").
    # normalize_model_name resolves internal codes first: the previous
    # `normalize_printer_model(x) or normalize_printer_model_id(x)` chain never
    # reached the code map, because the first call returns unknown input
    # unchanged — so a "C13" target stayed "C13", matched no printer row and
    # left the item waiting forever. Identical result for every other spelling.
    target_model_norm = normalize_model_name(data.target_model)

    # Cross-model alternatives (#671): several sliced files, whichever printer
    # frees up first. The whole candidate set is validated before anything is
    # written — a half-valid set would produce a job that can only reach some of
    # the printers the user asked for, with nothing to say which.
    variant_specs: list[tuple[QueueVariantCreate, LibraryFile, str]] = []
    if data.variants:
        if data.printer_id:
            raise HTTPException(
                400, "Cannot specify both printer_id and variants — pick a printer or offer alternatives"
            )
        if data.archive_id or data.library_file_id:
            raise HTTPException(
                400, "Cannot combine variants with archive_id or library_file_id — the variants are the files"
            )
        variant_specs = await _resolve_queue_variants(db, data.variants, current_user)
        # Mirror the first candidate onto the item so the queue listing, the SJF
        # grouping and the "Any H2S" label have something before a printer is
        # picked. Resolution overwrites it with whichever candidate actually runs.
        target_model_norm = variant_specs[0][2]

    # Validate that either archive_id or library_file_id is provided.
    # A cross-model item deliberately holds neither: its files live on the
    # variant rows. Pointing library_file_id at one of them would be worse than
    # useless — that FK is ON DELETE CASCADE, so deleting a single alternative
    # would take the whole queue item with it.
    if not data.archive_id and not data.library_file_id and not data.variants:
        raise HTTPException(400, "Either archive_id or library_file_id must be provided")

    # Cannot specify both printer_id and target_model
    if data.printer_id and target_model_norm:
        raise HTTPException(400, "Cannot specify both printer_id and target_model")

    # Validate printer exists (if assigned)
    if data.printer_id is not None:
        result = await db.execute(select(Printer).where(Printer.id == data.printer_id))
        if not result.scalar_one_or_none():
            raise HTTPException(400, "Printer not found")

    # Validate target_model has active printers. Skipped for cross-model items:
    # target_model there is just the first candidate, and _resolve_queue_variants
    # has already required that *some* candidate has a printer.
    if target_model_norm and not data.variants:
        result = await db.execute(
            select(Printer).where(Printer.model == target_model_norm).where(Printer.is_active == True)  # noqa: E712
        )
        if not result.scalars().first():
            raise HTTPException(400, f"No active printers for model: {target_model_norm}")

    # Validate archive exists (if provided) and get it for filament extraction
    archive = None
    if data.archive_id:
        result = await db.execute(select(PrintArchive).where(PrintArchive.id == data.archive_id))
        archive = result.scalar_one_or_none()
        if not archive:
            raise HTTPException(400, "Archive not found")
        _assert_can_queue_archive(archive, current_user)

    # Validate library file exists (if provided) and get it for filament extraction
    library_file = None
    if data.library_file_id:
        result = await db.execute(LibraryFile.active().where(LibraryFile.id == data.library_file_id))
        library_file = result.scalar_one_or_none()
        if not library_file:
            raise HTTPException(400, "Library file not found")
        _assert_can_queue_library_file(library_file, current_user)
        # Bambu SD card is FAT32/exFAT — illegal filename chars would 553 at
        # FTP upload time (#1540). Reject at queue time so the user gets the
        # actionable error before waiting in queue.
        from backend.app.utils.filename import InvalidFilenameError, validate_print_filename

        try:
            validate_print_filename(library_file.filename)
        except InvalidFilenameError as e:
            raise HTTPException(400, str(e)) from e

    # Cross-model safety gate (#2578): a G-code 3MF sliced for one model must
    # not be queued for dispatch to an incompatible model. The UI can no longer
    # produce such rows, but API-created rows must be rejected here too — the
    # scheduler assigns model-based items to hardware with no human in the loop.
    if target_model_norm:
        sliced_for = None
        if archive:
            sliced_for = archive.sliced_for_model
        elif library_file and library_file.file_metadata:
            sliced_for = library_file.file_metadata.get("sliced_for_model")
        if not is_gcode_compatible(sliced_for, target_model_norm):
            raise HTTPException(
                400,
                f"File was sliced for {sliced_for} and cannot be dispatched to {target_model_norm} printers",
            )

    # Extract filament types for model-based assignment (used by scheduler for validation)
    required_filament_types = None
    file_path = None
    if target_model_norm:
        # Get file path from archive or library file
        if archive:
            file_path = settings.base_dir / archive.file_path
        elif library_file:
            lib_path = Path(library_file.file_path)
            file_path = lib_path if lib_path.is_absolute() else settings.base_dir / library_file.file_path

        if file_path and file_path.exists():
            filament_types = _extract_filament_types_from_3mf(file_path, data.plate_id)
            if filament_types:
                required_filament_types = json.dumps(filament_types)
                logger.info("Extracted filament types for model-based queue: %s", filament_types)

    # If filament overrides are provided, update required_filament_types to match override types
    filament_overrides_json = None
    if data.filament_overrides and target_model_norm:
        plate_overrides = overrides_for_plate(data.filament_overrides, file_path, data.plate_id)
        if plate_overrides:
            filament_overrides_json = json.dumps(plate_overrides)
            # Update required_filament_types from overrides so scheduler validates against overridden types
            override_types = sorted({o["type"] for o in plate_overrides if "type" in o})
            if override_types:
                # Merge with existing types (overrides may only cover some slots)
                existing_types = set(json.loads(required_filament_types)) if required_filament_types else set()
                # Replace types for overridden slots, keep others
                all_types = existing_types | set(override_types)
                required_filament_types = json.dumps(sorted(all_types))

    # Validate quantity
    quantity = max(1, data.quantity)

    # Validate batch_id if provided. Client passes batch_id when adding items
    # into a pre-created batch (multi-plate auto-batch or "Group as batch" flow).
    # 404 keeps the existing-id leak surface low.
    batch = None
    batch_id = None
    if data.batch_id is not None:
        result = await db.execute(select(PrintBatch).where(PrintBatch.id == data.batch_id))
        existing_batch = result.scalar_one_or_none()
        if not existing_batch:
            raise HTTPException(404, "Batch not found")
        if existing_batch.status != "active":
            raise HTTPException(400, "Cannot add items to a non-active batch")
        if (
            current_user is not None
            and existing_batch.created_by_id is not None
            and existing_batch.created_by_id != current_user.id
            and not current_user.has_permission(Permission.QUEUE_UPDATE_ALL.value)
        ):
            raise HTTPException(404, "Batch not found")
        batch = existing_batch
        batch_id = existing_batch.id

    # Create batch if quantity > 1 and no batch_id provided
    if batch_id is None and quantity > 1:
        # Derive batch name from source file
        batch_name_base = "Batch"
        if archive:
            batch_name_base = archive.print_name or archive.filename or "Batch"
        elif library_file:
            if library_file.file_metadata:
                batch_name_base = library_file.file_metadata.get("print_name") or library_file.filename
            else:
                batch_name_base = library_file.filename
        batch_name_base = batch_name_base.replace(".gcode.3mf", "").replace(".3mf", "")

        batch = PrintBatch(
            name=f"{batch_name_base} ×{quantity}",
            archive_id=data.archive_id,
            library_file_id=data.library_file_id,
            quantity=quantity,
            status="active",
            created_by_id=current_user.id if current_user else None,
        )
        db.add(batch)
        await db.flush()  # Get batch.id before creating items
        batch_id = batch.id

    # Get queue scope for this printer (or for unassigned/model-based items).
    if data.printer_id is not None:
        queue_scope = (
            PrintQueueItem.printer_id == data.printer_id,
            PrintQueueItem.status == "pending",
        )
    else:
        # For unassigned/model-based items, scope across all unassigned.
        queue_scope = (
            PrintQueueItem.printer_id.is_(None),
            PrintQueueItem.status == "pending",
        )

    # Serialize concurrent queue inserts to the same scope (#1625-followup).
    # The race: two concurrent ASAP inserts both compute MAX(position) before
    # either commits; in an empty scope, both INSERT at position 1 (duplicate).
    # In a non-empty scope, Postgres's row-level locks on the UPDATE shift
    # serialize naturally, but the empty-scope path has no rows to lock.
    # A transaction-scoped advisory lock keyed on the printer_id closes that
    # window; the lock is released automatically at commit/rollback. Different
    # printers don't contend. SQLite serializes writes implicitly so this is a
    # no-op there.
    #
    # Dialect is checked against the actual session binding, NOT the
    # `is_sqlite()` helper, because the test fixture overrides `get_db` with a
    # SQLite engine while `settings.database_url` still points at Postgres
    # (the helper reads settings). Inspecting the connection directly is the
    # right shape for any code that mutates SQL based on the live dialect.
    from sqlalchemy import text

    bind = db.get_bind()
    if bind.dialect.name == "postgresql":
        scope_key = data.printer_id if data.printer_id is not None else 0
        # 1625 namespaces the lock so it can't collide with other advisory
        # locks elsewhere in the codebase.
        await db.execute(text("SELECT pg_advisory_xact_lock(1625, :k)"), {"k": scope_key})

    insert_position = max(1, data.insert_position or 1)
    if data.insert_at_top or data.insert_position is not None:
        result = await db.execute(select(func.max(PrintQueueItem.position)).where(*queue_scope))
        max_pos = result.scalar() or 0
        insert_position = min(insert_position, max_pos + 1)
        await db.execute(
            update(PrintQueueItem)
            .where(*queue_scope)
            .where(PrintQueueItem.position >= insert_position)
            .values(position=PrintQueueItem.position + quantity)
        )
        start_position = insert_position
    else:
        result = await db.execute(select(func.max(PrintQueueItem.position)).where(*queue_scope))
        max_pos = result.scalar() or 0
        start_position = max_pos + 1

    # Resolve print_time_seconds for SJF scheduling (cache on item at creation)
    cached_print_time = None
    if archive:
        cached_print_time = archive.print_time_seconds
        if data.plate_id:
            archive_path = settings.base_dir / archive.file_path
            if archive_path.exists():
                plate_time = _extract_print_time_from_3mf(archive_path, data.plate_id)
                if plate_time is not None:
                    cached_print_time = plate_time
    elif library_file:
        if library_file.file_metadata:
            cached_print_time = library_file.file_metadata.get("print_time_seconds")
        if data.plate_id:
            lib_path = Path(library_file.file_path)
            library_file_path = lib_path if lib_path.is_absolute() else settings.base_dir / library_file.file_path
            if library_file_path.exists():
                plate_time = _extract_print_time_from_3mf(library_file_path, data.plate_id)
                if plate_time is not None:
                    cached_print_time = plate_time

    # Validate project exists before insert so a bogus ID yields 404, not an FK-constraint 500
    if data.project_id is not None:
        project_result = await db.execute(select(Project).where(Project.id == data.project_id))
        if not project_result.scalar_one_or_none():
            raise HTTPException(status_code=404, detail="Project not found")

    ams_mapping_json = json.dumps(data.ams_mapping) if data.ams_mapping else None
    # Reprint fallback: the caller didn't specify an explicit ams_mapping (no
    # per-slot filament-mapping edit was made), but the archive carries the
    # slicer's own live-resolved AMS-slot pick from the original print (see
    # `extra_data.slicer_ams_mapping`, written by the VP-queue path via
    # `_extract_slicer_ams_mapping_json`). Reuse it so the reprint dispatches
    # to the exact same physical spool instead of the scheduler re-deriving a
    # (possibly ambiguous) mapping from just the file's static type/color.
    #
    # Global tray IDs only mean something relative to the specific printer
    # they were resolved against, so this only fires when the reprint targets
    # that exact printer (`extra_data.slicer_ams_mapping.printer_id`) — never
    # for a model-based dispatch (data.printer_id is None) or a reprint aimed
    # at a different printer, where the same tray number can hold a
    # completely different spool (#2700 review).
    #
    # It also stands down when the request carries force-color-match overrides:
    # those are the caller asking the scheduler to match strictly against the
    # printer's live trays, and they are only ever applied inside
    # `_compute_ams_mapping_for_printer` — the function a stored mapping makes
    # the scheduler skip. Same precedence as the VP-side toggle pair (#2700
    # review).
    #
    # Note this is otherwise unconditional — it applies regardless of whether
    # the physical spool in that slot has changed since the original print.
    # #1308 covers re-verifying a stored mapping against live AMS state at
    # dispatch time; that check is a separate PR and, once merged, will also
    # catch a stale slot inherited through this fallback.
    wants_live_color_match = any(
        isinstance(o, dict) and o.get("force_color_match") for o in (data.filament_overrides or [])
    )
    if (
        ams_mapping_json is None
        and not wants_live_color_match
        and archive
        and archive.extra_data
        and data.printer_id is not None
    ):
        saved = archive.extra_data.get("slicer_ams_mapping")
        if (
            isinstance(saved, dict)
            and saved.get("printer_id") == data.printer_id
            and isinstance(saved.get("mapping"), list)
            and saved["mapping"]
        ):
            ams_mapping_json = json.dumps(saved["mapping"])
    items = []
    for i in range(quantity):
        item = PrintQueueItem(
            printer_id=data.printer_id,
            target_model=target_model_norm,
            target_location=data.target_location,
            required_filament_types=required_filament_types,
            filament_overrides=filament_overrides_json,
            archive_id=data.archive_id,
            library_file_id=data.library_file_id,
            scheduled_time=data.scheduled_time,
            require_previous_success=data.require_previous_success,
            auto_off_after=data.auto_off_after,
            manual_start=data.manual_start,
            skip_filament_check=data.skip_filament_check,
            ams_mapping=ams_mapping_json,
            plate_id=data.plate_id,
            bed_levelling=data.bed_levelling,
            flow_cali=data.flow_cali,
            vibration_cali=data.vibration_cali,
            layer_inspect=data.layer_inspect,
            timelapse=data.timelapse,
            use_ams=data.use_ams,
            nozzle_offset_cali=data.nozzle_offset_cali,
            preheat_override=data.preheat_override,
            preheat_chamber_target_override=data.preheat_chamber_target_override,
            gcode_injection=data.gcode_injection,
            cleanup_library_after_dispatch=data.cleanup_library_after_dispatch,
            project_id=data.project_id,
            position=start_position + i,
            status="pending",
            created_by_id=current_user.id if current_user else None,
            batch_id=batch_id,
            print_time_seconds=cached_print_time,
        )
        db.add(item)
        items.append(item)

    if variant_specs:
        variant_values = [
            _variant_values(spec, library_file, model, position)
            for position, (spec, library_file, model) in enumerate(variant_specs)
        ]
        # SJF orders pending items before any printer is known, so the row carries
        # the shortest candidate's estimate. Resolution replaces it with the one
        # that actually runs.
        estimates = [v["print_time_seconds"] for v in variant_values if v["print_time_seconds"]]
        for item in items:
            # Each copy in a quantity>1 batch gets its own candidate rows —
            # attempt counts are per-item, and two copies must be free to land on
            # different printers.
            item.variants.extend(PrintQueueVariant(**values) for values in variant_values)
            item.print_time_seconds = min(estimates) if estimates else None

    await db.commit()

    # Refresh the first item for the response
    item = items[0]
    await db.refresh(item)
    await db.refresh(item, ["archive", "printer", "library_file", "created_by", "batch"])

    source_name = f"archive {data.archive_id}" if data.archive_id else f"library file {data.library_file_id}"
    target_desc = data.printer_id or (f"model {target_model_norm}" if target_model_norm else "unassigned")
    qty_desc = f" (×{quantity})" if quantity > 1 else ""
    logger.info("Added %s to queue for %s%s", source_name, target_desc, qty_desc)

    # MQTT relay - publish queue job added
    try:
        from backend.app.services.mqtt_relay import mqtt_relay

        await mqtt_relay.on_queue_job_added(
            job_id=item.id,
            filename=item.archive.filename if item.archive else "",
            printer_id=item.printer_id,
            printer_name=item.printer.name if item.printer else None,
        )
    except Exception:
        pass  # Don't fail queue add if MQTT fails

    # Send notification for job added
    try:
        job_name = (
            item.archive.filename
            if item.archive
            else item.library_file.filename
            if item.library_file
            else f"Job #{item.id}"
        )
        job_name = job_name.replace(".gcode.3mf", "").replace(".3mf", "")
        if quantity > 1:
            job_name = f"{job_name} ×{quantity}"
        target = (
            item.printer.name if item.printer else (f"Any {item.target_model}" if target_model_norm else "Unassigned")
        )
        await notification_service.on_queue_job_added(
            job_name=job_name,
            target=target,
            db=db,
            printer_id=item.printer_id,
            printer_name=item.printer.name if item.printer else None,
        )
    except Exception:
        pass  # Don't fail queue add if notification fails

    return _enrich_response(item)


@router.patch("/bulk", response_model=PrintQueueBulkUpdateResponse)
async def bulk_update_queue_items(
    data: PrintQueueBulkUpdate,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_UPDATE_ALL,
            Permission.QUEUE_UPDATE_OWN,
        )
    ),
):
    """Bulk update multiple queue items with the same values.

    Only pending items can be updated. Non-pending items are skipped.
    Items not owned by the user are also skipped (unless user has *_all permission).
    """
    user, can_modify_all = auth_result

    if not data.item_ids:
        raise HTTPException(400, "No item IDs provided")

    # Get fields to update (exclude item_ids and unset fields)
    update_data = data.model_dump(exclude={"item_ids"}, exclude_unset=True)
    if not update_data:
        raise HTTPException(400, "No fields to update")

    # Validate printer_id if being changed
    if "printer_id" in update_data and update_data["printer_id"] is not None:
        result = await db.execute(select(Printer).where(Printer.id == update_data["printer_id"]))
        if not result.scalar_one_or_none():
            raise HTTPException(400, "Printer not found")

    # Fetch all items
    result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.id.in_(data.item_ids)))
    items = result.scalars().all()

    updated_count = 0
    skipped_count = 0

    for item in items:
        # Skip non-pending rows and rows a dispatch worker has claimed (#2615) —
        # editing a claimed row mid-upload would split it from the in-flight
        # dispatch, so it's excluded from the bulk change (cancel to move it).
        if item.status != "pending" or item.dispatching_at is not None:
            skipped_count += 1
            continue

        # Ownership check
        if not can_modify_all and item.created_by_id != user.id:
            skipped_count += 1
            continue

        for field, value in update_data.items():
            setattr(item, field, value)
        updated_count += 1

    await db.commit()

    logger.info("Bulk updated %s queue items, skipped %s", updated_count, skipped_count)
    return PrintQueueBulkUpdateResponse(
        updated_count=updated_count,
        skipped_count=skipped_count,
        message=f"Updated {updated_count} items"
        + (f", skipped {skipped_count} non-pending/not-owned" if skipped_count else ""),
    )


# --- Batch endpoints ---


def _validate_plate_targets(
    plates: list[PrintBatchPlateTarget] | None,
) -> list[PrintBatchPlateTarget] | None:
    """Reject duplicate plates and orders that ask for nothing at all.

    A duplicate would violate the (batch_id, plate_id) unique constraint at
    flush time — and on SQLite/PostgreSQL a NULL plate_id slips past that
    constraint entirely, so the check has to happen here to catch two
    "whole file" rows in one order.
    """
    if plates is None:
        return None
    if not plates:
        raise HTTPException(400, "plates must contain at least one plate")

    seen: set[int | None] = set()
    for target in plates:
        if target.plate_id in seen:
            label = target.plate_id if target.plate_id is not None else "whole file"
            raise HTTPException(400, f"Duplicate plate in order: {label}")
        seen.add(target.plate_id)

    if all(target.quantity_target == 0 for target in plates):
        raise HTTPException(400, "Order must request at least one print")
    return plates


async def _validate_batch_project(db: AsyncSession, project_id: int | None, current_user: User | None) -> None:
    """404 on a bogus project id rather than letting the FK blow up as a 500."""
    if project_id is None:
        return
    result = await db.execute(select(Project).where(Project.id == project_id))
    if not result.scalar_one_or_none():
        raise HTTPException(404, "Project not found")


async def _load_batch_for_write(
    db: AsyncSession, batch_id: int, current_user: User | None, permission: Permission
) -> PrintBatch:
    """Fetch a batch the caller is allowed to modify, or 404.

    404 rather than 403 on the ownership miss, matching the rest of this
    module: a 403 would confirm the id exists to someone enumerating.
    """
    result = await db.execute(
        select(PrintBatch).options(selectinload(PrintBatch.plates)).where(PrintBatch.id == batch_id)
    )
    batch = result.scalar_one_or_none()
    if not batch:
        raise HTTPException(404, "Batch not found")
    if (
        current_user is not None
        and batch.created_by_id is not None
        and batch.created_by_id != current_user.id
        and not current_user.has_permission(permission.value)
    ):
        raise HTTPException(404, "Batch not found")
    return batch


@router.post("/batches", response_model=PrintBatchResponse)
async def create_batch(
    data: PrintBatchCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_CREATE),
):
    """Create a batch.

    Two modes:
    * ``item_ids`` provided: assign the listed pending queue items to a new
      batch ("Group as batch" UI action).
    * ``item_ids`` omitted/empty: create an empty batch so the client can
      pass the returned ``id`` on subsequent ``POST /queue/`` calls. Used by
      the multi-plate auto-batch flow in PrintModal.

    ``plates`` turns the batch into an order with per-plate targets (#342):
    progress is then measured against what was asked for rather than against
    what happened to be queued, so a failed run still counts as owed. Omitting
    it keeps the pre-#342 behaviour exactly.
    """
    if not data.name or not data.name.strip():
        raise HTTPException(400, "Batch name is required")

    plate_targets = _validate_plate_targets(data.plates)
    await _validate_batch_project(db, data.project_id, current_user)

    batch = PrintBatch(
        name=data.name.strip()[:255],
        archive_id=data.archive_id,
        library_file_id=data.library_file_id,
        quantity=len(data.item_ids) if data.item_ids else 1,
        status="active",
        created_by_id=current_user.id if current_user else None,
        project_id=data.project_id,
        due_date=data.due_date,
        notes=data.notes,
    )
    db.add(batch)
    await db.flush()  # Need batch.id before assigning to items

    if plate_targets is not None:
        for target in plate_targets:
            db.add(
                PrintBatchPlate(
                    batch_id=batch.id,
                    plate_id=target.plate_id,
                    plate_name=target.plate_name,
                    quantity_target=target.quantity_target,
                    sort_order=target.sort_order,
                )
            )
        # The legacy `quantity` column is display-only; keep it meaningful for
        # anything still reading it by making it the order's total.
        batch.quantity = max(1, sum(t.quantity_target for t in plate_targets))

    assigned = 0
    if data.item_ids:
        result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.id.in_(data.item_ids)))
        items = result.scalars().all()
        for item in items:
            if item.status != "pending":
                continue
            if item.batch_id is not None:
                continue
            if (
                current_user is not None
                and item.created_by_id != current_user.id
                and not current_user.has_permission(Permission.QUEUE_UPDATE_ALL.value)
            ):
                continue
            item.batch_id = batch.id
            assigned += 1
        batch.quantity = max(assigned, 1)

    await db.commit()
    await db.refresh(batch)

    logger.info("Created batch %s '%s' with %s assigned items", batch.id, batch.name, assigned)
    return await _build_batch_response(db, batch)


@router.patch("/batches/{batch_id}", response_model=PrintBatchResponse)
async def update_batch(
    batch_id: int,
    data: PrintBatchUpdate,
    db: AsyncSession = Depends(get_db),
    current_user: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_UPDATE_OWN),
):
    """Edit an order's header or its per-plate targets while it runs (#342).

    Production requirements change mid-run, so targets are editable. Lowering a
    target below what has already been dispatched is allowed and simply leaves
    ``remaining`` at zero — cancelling the surplus queue items is a separate,
    explicit action, because silently deleting queued work on a number change
    would be a nasty surprise.
    """
    batch = await _load_batch_for_write(db, batch_id, current_user, Permission.QUEUE_UPDATE_ALL)

    plate_targets = _validate_plate_targets(data.plates)
    if data.project_id is not None:
        await _validate_batch_project(db, data.project_id, current_user)

    if data.name is not None:
        if not data.name.strip():
            raise HTTPException(400, "Batch name is required")
        batch.name = data.name.strip()[:255]
    if data.project_id is not None:
        batch.project_id = data.project_id
    if data.due_date is not None:
        batch.due_date = data.due_date
    if data.notes is not None:
        batch.notes = data.notes
    if data.status is not None:
        batch.status = data.status

    if plate_targets is not None:
        existing = {row.plate_id: row for row in batch.plates}
        for target in plate_targets:
            row = existing.pop(target.plate_id, None)
            if row is None:
                db.add(
                    PrintBatchPlate(
                        batch_id=batch.id,
                        plate_id=target.plate_id,
                        plate_name=target.plate_name,
                        quantity_target=target.quantity_target,
                        sort_order=target.sort_order,
                    )
                )
            else:
                row.quantity_target = target.quantity_target
                row.sort_order = target.sort_order
                if target.plate_name is not None:
                    row.plate_name = target.plate_name
        # Plates absent from the payload are dropped — the list is the order.
        for orphan in existing.values():
            await db.delete(orphan)
        batch.quantity = max(1, sum(t.quantity_target for t in plate_targets))

    await db.flush()
    await db.refresh(batch)
    # Raising a target on a finished order reopens it; lowering one on a
    # running order can complete it.
    await refresh_batch_status(db, batch)
    await db.commit()
    await db.refresh(batch)

    logger.info("Updated batch %s", batch.id)
    return await _build_batch_response(db, batch)


@router.post("/batches/{batch_id}/dispatch", response_model=PrintBatchResponse)
async def dispatch_batch(
    batch_id: int,
    data: PrintBatchDispatchRequest,
    db: AsyncSession = Depends(get_db),
    current_user: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_CREATE),
):
    """Queue the runs this order still owes (#342).

    Each new item is cloned from the most recent item for the same plate in
    this batch, so it inherits the printer/model target, AMS mapping, filament
    overrides and print options the user already chose — and the validation
    those went through at creation time.
    """
    batch = await _load_batch_for_write(db, batch_id, current_user, Permission.QUEUE_UPDATE_ALL)
    if batch.status == "cancelled":
        raise HTTPException(400, "Cannot dispatch a cancelled batch")

    # Dispatch starts prints, so it must not be a weaker door than POST /queue/.
    await _assert_can_dispatch_batch_sources(db, batch.id, current_user)

    try:
        created = await dispatch_remaining(
            db,
            batch,
            plate_id=data.plate_id,
            only_plate=data.only_plate,
            limit=data.limit,
            created_by_id=current_user.id if current_user else None,
        )
    except BatchDispatchError as exc:
        raise HTTPException(400, str(exc)) from exc

    await db.commit()
    await db.refresh(batch)

    logger.info("Batch %s dispatched %d item(s)", batch.id, len(created))
    return await _build_batch_response(db, batch)


@router.post("/batches/{batch_id}/ungroup", response_model=PrintBatchUngroupResponse)
async def ungroup_batch(
    batch_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_UPDATE_OWN),
):
    """Disband a batch: clear batch_id from all members and delete the batch row.

    Items stay in the queue. Only ungroups items the caller owns (unless they
    hold QUEUE_UPDATE_ALL). A batch with all members ungrouped is deleted.
    """
    result = await db.execute(select(PrintBatch).where(PrintBatch.id == batch_id))
    batch = result.scalar_one_or_none()
    if not batch:
        raise HTTPException(404, "Batch not found")

    can_modify_all = current_user is None or current_user.has_permission(Permission.QUEUE_UPDATE_ALL.value)
    if not can_modify_all and batch.created_by_id != (current_user.id if current_user else None):
        raise HTTPException(404, "Batch not found")

    result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.batch_id == batch_id))
    items = result.scalars().all()
    ungrouped = 0
    remaining = 0
    for item in items:
        if not can_modify_all and item.created_by_id != (current_user.id if current_user else None):
            remaining += 1
            continue
        item.batch_id = None
        ungrouped += 1

    # Delete the batch row only when all members were ungrouped — otherwise it
    # still owns the items the caller couldn't touch.
    if remaining == 0:
        await db.delete(batch)

    await db.commit()

    logger.info("Ungrouped batch %s (%s items)", batch_id, ungrouped)
    return PrintBatchUngroupResponse(
        ungrouped_count=ungrouped,
        message=f"Ungrouped {ungrouped} item(s)",
    )


@router.get("/batches", response_model=list[PrintBatchResponse])
async def list_batches(
    status: str | None = Query(None, description="Filter by status (active, completed, cancelled)"),
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_READ_ALL,
            Permission.QUEUE_READ_OWN,
        )
    ),
):
    """List print batches with progress stats.

    Batches with neither queue items nor per-plate targets are omitted. Those
    are empty shells — a grouping whose items were deleted with their source
    archive, or a create that never got as far as adding any — and they carry
    nothing to show, track or dispatch. A brand-new order is still listed
    before its first dispatch, because its targets say what it owes.
    """
    current_user, can_read_all = auth_result
    query = (
        select(PrintBatch)
        .where(
            select(PrintQueueItem.id).where(PrintQueueItem.batch_id == PrintBatch.id).exists()
            | select(PrintBatchPlate.id).where(PrintBatchPlate.batch_id == PrintBatch.id).exists()
        )
        .order_by(PrintBatch.created_at.desc())
    )
    if status:
        query = query.where(PrintBatch.status == status)
    if current_user is not None and not can_read_all:
        query = query.where(PrintBatch.created_by_id == current_user.id)
    result = await db.execute(query)
    batches = result.scalars().all()

    # Resolve creator names in one query rather than one per batch.
    creator_ids = {b.created_by_id for b in batches if b.created_by_id is not None}
    usernames: dict[int, str] = {}
    if creator_ids:
        rows = await db.execute(select(User.id, User.username).where(User.id.in_(creator_ids)))
        usernames = {row[0]: row[1] for row in rows.all()}

    return [await _build_batch_response(db, batch, usernames=usernames) for batch in batches]


@router.get("/batches/{batch_id}", response_model=PrintBatchResponse)
async def get_batch(
    batch_id: int,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_READ_ALL,
            Permission.QUEUE_READ_OWN,
        )
    ),
):
    """Get a print batch with progress stats."""
    current_user, can_read_all = auth_result
    result = await db.execute(select(PrintBatch).where(PrintBatch.id == batch_id))
    batch = result.scalar_one_or_none()
    if not batch:
        raise HTTPException(404, "Batch not found")
    if (
        current_user is not None
        and not can_read_all
        and (batch.created_by_id is None or batch.created_by_id != current_user.id)
    ):
        raise HTTPException(404, "Batch not found")
    return await _build_batch_response(db, batch)


@router.delete("/batches/{batch_id}")
async def cancel_batch(
    batch_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_DELETE_ALL),
):
    """Cancel all pending items in a batch and mark batch as cancelled."""
    result = await db.execute(select(PrintBatch).where(PrintBatch.id == batch_id))
    batch = result.scalar_one_or_none()
    if not batch:
        raise HTTPException(404, "Batch not found")

    # Cancel all pending queue items in this batch
    result = await db.execute(
        select(PrintQueueItem).where(and_(PrintQueueItem.batch_id == batch_id, PrintQueueItem.status == "pending"))
    )
    pending_items = result.scalars().all()
    cancelled_count = 0
    for item in pending_items:
        item.status = "cancelled"
        cancelled_count += 1

    batch.status = "cancelled"
    await db.commit()

    return {"message": f"Batch cancelled, {cancelled_count} pending items cancelled"}


async def _build_batch_response(
    db: AsyncSession, batch: PrintBatch, *, usernames: dict[int, str] | None = None
) -> PrintBatchResponse:
    """Build a batch response with per-plate progress derived from queue items.

    ``usernames`` lets the list endpoint resolve every creator in one query
    instead of one per batch.
    """
    progress = await load_progress(db, batch)

    created_by_username = None
    if batch.created_by_id:
        if usernames is not None:
            created_by_username = usernames.get(batch.created_by_id)
        else:
            result = await db.execute(select(User).where(User.id == batch.created_by_id))
            user = result.scalar_one_or_none()
            if user:
                created_by_username = user.username

    return PrintBatchResponse(
        id=batch.id,
        name=batch.name,
        archive_id=batch.archive_id,
        library_file_id=batch.library_file_id,
        quantity=batch.quantity,
        status=batch.status,
        created_at=batch.created_at,
        completed_at=batch.completed_at,
        created_by_id=batch.created_by_id,
        created_by_username=created_by_username,
        project_id=batch.project_id,
        due_date=batch.due_date,
        notes=batch.notes,
        pending_count=progress.pending,
        printing_count=progress.printing,
        completed_count=progress.completed,
        failed_count=progress.failed,
        cancelled_count=progress.cancelled,
        skipped_count=progress.skipped,
        has_targets=progress.has_targets,
        target_count=progress.target,
        remaining_count=progress.remaining,
        actual_cost=progress.actual_cost,
        estimated_remaining_cost=progress.estimated_remaining_cost,
        filament_used_grams=progress.filament_used_grams,
        print_time_seconds=progress.print_time_seconds,
        plates=[
            PrintBatchPlateProgress(
                plate_id=plate.plate_id,
                plate_name=plate.plate_name,
                quantity_target=plate.quantity_target,
                dispatched=plate.dispatched,
                remaining=plate.remaining,
                pending_count=plate.pending,
                printing_count=plate.printing,
                completed_count=plate.completed,
                failed_count=plate.failed,
                cancelled_count=plate.cancelled,
                skipped_count=plate.skipped,
                actual_cost=plate.actual_cost,
                estimated_remaining_cost=plate.estimated_remaining_cost,
                filament_used_grams=plate.filament_used_grams,
                print_time_seconds=plate.print_time_seconds,
            )
            for plate in progress.plates
        ],
    )


@router.get("/{item_id}", response_model=PrintQueueItemResponse)
async def get_queue_item(
    item_id: int,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_READ_ALL,
            Permission.QUEUE_READ_OWN,
        )
    ),
):
    """Get a specific queue item."""
    current_user, can_read_all = auth_result
    result = await db.execute(
        select(PrintQueueItem)
        .options(
            selectinload(PrintQueueItem.archive),
            selectinload(PrintQueueItem.printer),
            selectinload(PrintQueueItem.library_file),
            selectinload(PrintQueueItem.created_by),
            selectinload(PrintQueueItem.batch),
            # Cross-model candidates (#671) and their files, for the card label.
            selectinload(PrintQueueItem.variants).selectinload(PrintQueueVariant.library_file),
        )
        .where(PrintQueueItem.id == item_id)
    )
    item = result.scalar_one_or_none()
    if not item:
        raise HTTPException(404, "Queue item not found")
    if (
        current_user is not None
        and not can_read_all
        and (item.created_by_id is None or item.created_by_id != current_user.id)
    ):
        raise HTTPException(404, "Queue item not found")
    return _enrich_response(item)


@router.patch("/{item_id}", response_model=PrintQueueItemResponse)
async def update_queue_item(
    item_id: int,
    data: PrintQueueItemUpdate,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_UPDATE_ALL,
            Permission.QUEUE_UPDATE_OWN,
        )
    ),
):
    """Update a queue item."""
    user, can_modify_all = auth_result

    result = await db.execute(
        select(PrintQueueItem)
        # Needed by the cross-model guard below, and by the response builder —
        # without it _variant_summaries falls back to [] and a PATCH would strip
        # the alternatives out of the payload it echoes back.
        .options(selectinload(PrintQueueItem.variants).selectinload(PrintQueueVariant.library_file))
        .where(PrintQueueItem.id == item_id)
    )
    item = result.scalar_one_or_none()
    if not item:
        raise HTTPException(404, "Queue item not found")

    # Ownership check
    if not can_modify_all:
        if item.created_by_id != user.id:
            raise HTTPException(403, "You can only update your own queue items")

    if item.status != "pending":
        raise HTTPException(400, "Can only update pending items")

    # Dispatch claim (#2615): the row is pending but a scheduler worker has
    # already claimed it and is uploading to its printer. Editing now (e.g.
    # reassigning printer_id) would split the queue row from the in-flight
    # archive/expected-print/physical command. Reject until dispatch finishes;
    # to move it, cancel first (the coordinated escape) and re-queue.
    if item.dispatching_at is not None:
        raise HTTPException(409, "Item is being dispatched — cancel it first to make changes")

    update_data = data.model_dump(exclude_unset=True)

    # Normalize target_model if being updated (see add_to_queue for why the
    # code map has to run first).
    if "target_model" in update_data and update_data["target_model"]:
        update_data["target_model"] = normalize_model_name(update_data["target_model"])

    # A cross-model item (#671) owns its own printer decision: each candidate
    # carries its model, and the resolver folds the winner onto the row at
    # dispatch. Assigning a printer here would leave a row with variants *and* a
    # printer_id, and the fixed-printer branch of the scheduler wins that race —
    # so it would dispatch a row whose library_file_id is still null and die in
    # the upload. Narrowing target_model is refused for the same reason: it
    # would silently discard every alternative the user queued.
    #
    # Compared against the current value rather than merely present, because the
    # edit dialog re-sends target_model unchanged on every save.
    if item.variants:
        for field in ("printer_id", "target_model"):
            if field in update_data and update_data[field] != getattr(item, field):
                raise HTTPException(
                    400,
                    "This job has printer alternatives — remove them before assigning a printer or model",
                )

    # Cannot specify both printer_id and target_model
    new_printer_id = update_data.get("printer_id", item.printer_id)
    new_target_model = update_data.get("target_model", item.target_model)
    if new_printer_id and new_target_model:
        raise HTTPException(400, "Cannot specify both printer_id and target_model")

    # Validate new printer_id if being changed (and not None)
    if "printer_id" in update_data and update_data["printer_id"] is not None:
        result = await db.execute(select(Printer).where(Printer.id == update_data["printer_id"]))
        if not result.scalar_one_or_none():
            raise HTTPException(400, "Printer not found")

    # Validate target_model has active printers
    if "target_model" in update_data and update_data["target_model"]:
        result = await db.execute(
            select(Printer).where(Printer.model == update_data["target_model"]).where(Printer.is_active == True)  # noqa: E712
        )
        if not result.scalars().first():
            raise HTTPException(400, f"No active printers for model: {update_data['target_model']}")

        # Cross-model safety gate (#2578) — same check as the create route, so
        # a mismatched target can't be introduced by editing either.
        sliced_for = None
        if item.archive_id:
            result = await db.execute(select(PrintArchive.sliced_for_model).where(PrintArchive.id == item.archive_id))
            sliced_for = result.scalar_one_or_none()
        elif item.library_file_id:
            result = await db.execute(select(LibraryFile).where(LibraryFile.id == item.library_file_id))
            lib = result.scalar_one_or_none()
            if lib and lib.file_metadata:
                sliced_for = lib.file_metadata.get("sliced_for_model")
        if not is_gcode_compatible(sliced_for, update_data["target_model"]):
            raise HTTPException(
                400,
                f"File was sliced for {sliced_for} and cannot be dispatched to {update_data['target_model']} printers",
            )

    # Serialize ams_mapping to JSON for TEXT column storage
    if "ams_mapping" in update_data:
        update_data["ams_mapping"] = json.dumps(update_data["ams_mapping"]) if update_data["ams_mapping"] else None

    # Serialize filament_overrides to JSON for TEXT column storage, keeping only
    # the slots this item's plate actually prints (#2551 — same shared-override
    # list the create path narrows).
    if "filament_overrides" in update_data:
        overrides = update_data["filament_overrides"]
        if overrides:
            overrides = overrides_for_plate(
                overrides,
                await _resolve_source_path(db, item),
                update_data.get("plate_id", item.plate_id),
            )
        update_data["filament_overrides"] = json.dumps(overrides) if overrides else None

    # Serialize H2C rack-swap nozzle pick (#1780) to JSON for TEXT column
    # storage; same Text-as-opaque-blob convention as ams_mapping above.
    if "nozzle_mapping" in update_data:
        update_data["nozzle_mapping"] = (
            json.dumps(update_data["nozzle_mapping"]) if update_data["nozzle_mapping"] else None
        )

    # Re-check the dispatch claim right before mutating (#2615). Several awaited
    # validations ran since the guard above, and a scheduler worker may have
    # claimed the row in that gap. A fresh read (item isn't dirty yet, so no
    # autoflush races the check) narrows the window to effectively nothing.
    claimed = (
        await db.execute(select(PrintQueueItem.dispatching_at).where(PrintQueueItem.id == item_id))
    ).scalar_one_or_none()
    if claimed is not None:
        raise HTTPException(409, "Item is being dispatched — cancel it first to make changes")

    for field, value in update_data.items():
        setattr(item, field, value)

    await db.commit()
    await db.refresh(item, ["archive", "printer", "library_file", "created_by", "batch"])

    logger.info("Updated queue item %s", item_id)
    return _enrich_response(item)


@router.delete("/{item_id}")
async def delete_queue_item(
    item_id: int,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_DELETE_ALL,
            Permission.QUEUE_DELETE_OWN,
        )
    ),
):
    """Remove an item from the queue."""
    user, can_modify_all = auth_result

    result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.id == item_id))
    item = result.scalar_one_or_none()
    if not item:
        raise HTTPException(404, "Queue item not found")

    # Ownership check
    if not can_modify_all:
        if item.created_by_id != user.id:
            raise HTTPException(403, "You can only delete your own queue items")

    if item.status == "printing":
        raise HTTPException(400, "Cannot delete item that is currently printing")

    await db.delete(item)
    await db.commit()

    logger.info("Deleted queue item %s", item_id)
    return {"message": "Queue item deleted"}


@router.post("/reorder")
async def reorder_queue(
    data: PrintQueueReorder,
    db: AsyncSession = Depends(get_db),
    _: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_UPDATE_ALL),
):
    """Bulk update positions for queue items."""
    for reorder_item in data.items:
        result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.id == reorder_item.id))
        item = result.scalar_one_or_none()
        if item and item.status == "pending":
            item.position = reorder_item.position

    await db.commit()
    logger.info("Reordered %s queue items", len(data.items))
    return {"message": f"Reordered {len(data.items)} items"}


@router.post("/printer/{printer_id}/resume")
async def resume_queue_after_failure(
    printer_id: int,
    db: AsyncSession = Depends(get_db),
    _: User | None = RequirePermissionIfAuthEnabled(Permission.QUEUE_UPDATE_ALL),
):
    """Clear the previous-success gate for a printer and restore skipped items.

    Single atomic op (#1818):

    * Sets ``gate_acknowledged=True`` on every ``failed`` / ``aborted`` queue
      item for this printer that's still in the scheduler's lookback window,
      so the next ``_check_previous_success`` call ignores them.
    * Restores ``skipped`` items whose ``error_message`` matches the
      scheduler's exact "Previous print failed or was aborted" gate string
      back to ``pending`` (clears ``error_message`` + ``completed_at``).

    Returns counts so the UI can render a precise toast. No-op endpoint
    (zero counts) when called against a printer with no gate to clear.
    """
    result = await db.execute(select(Printer).where(Printer.id == printer_id))
    printer = result.scalar_one_or_none()
    if not printer:
        raise HTTPException(404, "Printer not found")

    ack_result = await db.execute(
        select(PrintQueueItem)
        .where(PrintQueueItem.printer_id == printer_id)
        .where(PrintQueueItem.status.in_(["failed", "aborted"]))
        .where(PrintQueueItem.gate_acknowledged == False)  # noqa: E712
    )
    to_ack = ack_result.scalars().all()
    for failed_item in to_ack:
        failed_item.gate_acknowledged = True

    restore_result = await db.execute(
        select(PrintQueueItem)
        .where(PrintQueueItem.printer_id == printer_id)
        .where(PrintQueueItem.status == "skipped")
        .where(PrintQueueItem.error_message == "Previous print failed or was aborted")
    )
    to_restore = restore_result.scalars().all()
    for skipped_item in to_restore:
        skipped_item.status = "pending"
        skipped_item.error_message = None
        skipped_item.completed_at = None

    await db.commit()

    logger.info(
        "Resume after failure on printer %s: acknowledged %d failure(s), restored %d skipped item(s)",
        printer_id,
        len(to_ack),
        len(to_restore),
    )
    return {"acknowledged": len(to_ack), "restored": len(to_restore)}


@router.post("/{item_id}/cancel")
async def cancel_queue_item(
    item_id: int,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_UPDATE_ALL,
            Permission.QUEUE_UPDATE_OWN,
        )
    ),
):
    """Cancel a pending queue item."""
    user, can_modify_all = auth_result

    result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.id == item_id))
    item = result.scalar_one_or_none()
    if not item:
        raise HTTPException(404, "Queue item not found")

    # Ownership check
    if not can_modify_all:
        if item.created_by_id != user.id:
            raise HTTPException(403, "You can only cancel your own queue items")

    if item.status not in ("pending",):
        raise HTTPException(400, f"Cannot cancel item with status '{item.status}'")

    item.status = "cancelled"
    item.completed_at = datetime.now(timezone.utc)
    await db.commit()

    logger.info("Cancelled queue item %s", item_id)
    return {"message": "Queue item cancelled"}


@router.post("/{item_id}/stop")
async def stop_queue_item(
    item_id: int,
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_UPDATE_ALL,
            Permission.QUEUE_UPDATE_OWN,
        )
    ),
):
    """Stop an actively printing queue item.

    Ownership-scoped (#1625-followup): callers with QUEUE_UPDATE_OWN can stop
    their own items; callers with QUEUE_UPDATE_ALL can stop any item. Mirrors
    the /cancel shape. Pre-fix this required QUEUE_UPDATE_ALL — Operators
    holding only _OWN saw the Stop button in the queue UI but got 403 on click.
    """

    from backend.app.services.printer_manager import printer_manager

    user, can_modify_all = auth_result

    result = await db.execute(select(PrintQueueItem).where(PrintQueueItem.id == item_id))
    item = result.scalar_one_or_none()
    if not item:
        raise HTTPException(404, "Queue item not found")

    # Ownership check — mirrors /cancel. Ownerless items (created_by_id IS NULL)
    # require _ALL: stop is destructive and an _OWN holder can't claim "they
    # own it" the way /start does (#1670).
    if not can_modify_all and user is not None:
        if item.created_by_id is None or item.created_by_id != user.id:
            raise HTTPException(403, "You can only stop your own queue items")

    if item.status != "printing":
        raise HTTPException(400, f"Can only stop items that are printing, current status: '{item.status}'")

    # Capture values we need for background task
    printer_id = item.printer_id
    auto_off_after = item.auto_off_after

    # Try to send stop command to printer
    stop_sent = False
    try:
        stop_sent = printer_manager.stop_print(printer_id)
        if not stop_sent:
            logger.warning("stop_print returned False for printer %s - printer may not be connected", printer_id)
    except Exception as e:
        logger.error("Error sending stop command for queue item %s: %s", item_id, e)

    # Mark this printer as user-stopped BEFORE the first await so that if the
    # MQTT on_print_complete callback fires during the db.commit() yield the flag
    # is already set and the "failed" status will be correctly overridden to
    # "cancelled" (preventing a spurious "print failed" notification).
    try:
        from backend.app.main import mark_printer_stopped_by_user

        mark_printer_stopped_by_user(printer_id)
    except Exception as _mark_err:
        logger.warning("Failed to mark printer %s as user-stopped: %s", printer_id, _mark_err)

    # Update queue item status regardless - if printer is off, print is already stopped
    item.status = "cancelled"
    item.completed_at = datetime.now(timezone.utc)
    item.error_message = "Stopped by user" if stop_sent else "Stopped by user (printer was offline)"

    # Reconcile the linked archive when the printer is offline (#2603). When the
    # stop command reaches the printer it later reports the stop over MQTT and
    # on_print_complete flips the archive to cancelled/failed. When the printer is
    # offline no such event ever arrives, so the archive would stay "printing"
    # forever (queue row cancelled, archive still printing — the reporter's
    # archive 436). Close it out here, mirroring what the MQTT path would have
    # done. Only touch a still-"printing" archive so we never overwrite a real
    # completion that raced in.
    if not stop_sent and item.archive_id:
        archive = await db.get(PrintArchive, item.archive_id)
        if archive and archive.status == "printing":
            archive.status = "cancelled"
            archive.completed_at = datetime.now(timezone.utc)
            archive.failure_reason = "Stopped by user (printer was offline)"

    await db.commit()

    logger.info("Stopped printing queue item %s (stop command sent: %s)", item_id, stop_sent)

    # Schedule power-off if the queue item opted in. Delegates to the smart-plug
    # manager so the off honours each plug's configured strategy (time delay or
    # temperature threshold), is cancelled if the printer starts printing again,
    # and never cuts power on a loaded print (#1890). Previously an inline block
    # hardcoded a 50°C / 600s cooldown wait and powered off on the timeout
    # regardless of print state.
    if auto_off_after:
        from backend.app.services.smart_plug_manager import smart_plug_manager

        try:
            await smart_plug_manager.schedule_off_after_queue_job(printer_id, db)
        except Exception as e:
            logger.warning("Auto-off: Failed to schedule power-off for printer %s: %s", printer_id, e)

    return {"message": "Print stopped" if stop_sent else "Queue item cancelled (printer was offline)"}


@router.post("/{item_id}/start")
async def start_queue_item(
    item_id: int,
    skip_filament_check: bool = Query(default=False),
    db: AsyncSession = Depends(get_db),
    auth_result: tuple[User | None, bool] = Depends(
        require_ownership_permission(
            Permission.QUEUE_UPDATE_ALL,
            Permission.QUEUE_UPDATE_OWN,
        )
    ),
):
    """Manually start a staged (manual_start) queue item.

    Ownership-scoped (#1625-followup): callers with QUEUE_UPDATE_OWN can
    start their own items + claim ownership of NULL-owner items (VP-uploaded
    items arrive unattributed per #1670). Callers with QUEUE_UPDATE_ALL can
    start any item. Pre-fix this required QUEUE_UPDATE_OWN with no ownership
    check, so _OWN holders could start anyone's queue items via direct API.

    Clears the manual_start flag so the scheduler picks it up. When
    ``skip_filament_check`` is false (the default) the live filament
    deficit (#1496) is checked first — if the assigned spool can't satisfy
    a slot's required grams, the route returns ``409`` with the deficit
    payload so the caller can show a confirm dialog and retry with
    ``skip_filament_check=true``.
    """
    user, can_modify_all = auth_result

    result = await db.execute(
        select(PrintQueueItem)
        .options(
            selectinload(PrintQueueItem.archive),
            selectinload(PrintQueueItem.printer),
            selectinload(PrintQueueItem.library_file),
            selectinload(PrintQueueItem.batch),
            selectinload(PrintQueueItem.variants).selectinload(PrintQueueVariant.library_file),
        )
        .where(PrintQueueItem.id == item_id)
    )
    item = result.scalar_one_or_none()
    if not item:
        raise HTTPException(404, "Queue item not found")

    # Ownership check — softer than /cancel because /start is the entry point
    # for #1670's VP-import flow: an unowned item is claimable by the first
    # _OWN holder who clicks ▶, and the route below credits them as owner.
    # An item with a DIFFERENT owner → 403.
    if not can_modify_all and user is not None:
        if item.created_by_id is not None and item.created_by_id != user.id:
            raise HTTPException(403, "You can only start your own queue items")

    if item.status != "pending":
        raise HTTPException(400, f"Can only start pending items, current status: '{item.status}'")

    # Live deficit check — re-evaluated against current spool state, so a
    # spool swap between scheduler flagging and the user clicking ▶ clears
    # the block automatically.
    if not skip_filament_check:
        deficit = await compute_deficit_for_queue_item(db, item)
        if deficit:
            raise HTTPException(
                status_code=409,
                detail={
                    "code": "insufficient_filament",
                    "deficit": [d.to_dict() for d in deficit],
                },
            )

    # Print Anyway / no deficit: clear the flags and let the scheduler dispatch.
    item.manual_start = False
    item.filament_short = False
    # Persist the user's "Print Anyway" decision so the scheduler does not
    # immediately re-flag this item on the next tick (#1698-followup). The
    # pre-fix behaviour bounced between "user said anyway" and
    # "scheduler re-blocked on same deficit" forever.
    if skip_filament_check:
        item.skip_filament_check = True
    # Credit the clicker as the item's owner when no prior owner is set —
    # VP-uploaded queue items arrive over FTP unattributed, so without this
    # the print log's User column stays blank even when auth is on
    # (#1670). An item that already has a creator (UI-added queue items)
    # keeps that attribution; the dispatcher is not promoted over the
    # original uploader.
    if user is not None and item.created_by_id is None:
        item.created_by_id = user.id
    await db.commit()
    await db.refresh(item, ["archive", "printer", "library_file", "created_by", "batch"])

    logger.info(
        "Manually started queue item %s (cleared manual_start; skip_filament_check=%s)",
        item_id,
        skip_filament_check,
    )
    return _enrich_response(item)