diff --git a/api/app/Exceptions/Artist/DuplicateArtistException.php b/api/app/Exceptions/Artist/DuplicateArtistException.php
new file mode 100644
index 00000000..5658f4d7
--- /dev/null
+++ b/api/app/Exceptions/Artist/DuplicateArtistException.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions\Artist;
+
+use App\Models\Artist;
+use DomainException;
+
+/**
+ * Raised by ArtistService::create when an exact-name match (case-insensitive)
+ * already exists in the same organisation. The handler can surface the
+ * existing artist's id to the UI so a "use existing or rename" choice is
+ * presented to the booker.
+ */
+final class DuplicateArtistException extends DomainException
+{
+    public function __construct(
+        public readonly Artist $existing,
+        string $message = 'An artist with this name already exists in this organisation.',
+    ) {
+        parent::__construct($message);
+    }
+}
diff --git a/api/app/Exceptions/Artist/GenreInUseException.php b/api/app/Exceptions/Artist/GenreInUseException.php
new file mode 100644
index 00000000..5707294b
--- /dev/null
+++ b/api/app/Exceptions/Artist/GenreInUseException.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions\Artist;
+
+use App\Models\Genre;
+use DomainException;
+
+/**
+ * Raised by GenreService::delete when artists still reference this genre
+ * via `default_genre_id`. The frontend must offer to re-bind those
+ * artists to a different genre (or null) before retrying.
+ */
+final class GenreInUseException extends DomainException
+{
+    public function __construct(
+        public readonly Genre $genre,
+        public readonly int $referencingArtistsCount,
+    ) {
+        parent::__construct(sprintf(
+            'Genre "%s" cannot be deleted: %d artist(s) reference it as their default genre.',
+            $genre->name,
+            $referencingArtistsCount,
+        ));
+    }
+}
diff --git a/api/app/Exceptions/Artist/InvalidStatusTransitionException.php b/api/app/Exceptions/Artist/InvalidStatusTransitionException.php
new file mode 100644
index 00000000..6dfa6096
--- /dev/null
+++ b/api/app/Exceptions/Artist/InvalidStatusTransitionException.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions\Artist;
+
+use App\Enums\Artist\ArtistEngagementStatus;
+use DomainException;
+
+/**
+ * Raised when a booking_status transition is rejected by the
+ * ArtistEngagement state machine (RFC v0.2 §10.1).
+ */
+final class InvalidStatusTransitionException extends DomainException
+{
+    public function __construct(
+        public readonly ArtistEngagementStatus $from,
+        public readonly ArtistEngagementStatus $to,
+        public readonly string $reason,
+    ) {
+        parent::__construct(sprintf(
+            'Invalid booking_status transition %s → %s: %s',
+            $from->value,
+            $to->value,
+            $reason,
+        ));
+    }
+}
diff --git a/api/app/Exceptions/Artist/StageDaysOrphanedPerformancesException.php b/api/app/Exceptions/Artist/StageDaysOrphanedPerformancesException.php
new file mode 100644
index 00000000..de4b52fa
--- /dev/null
+++ b/api/app/Exceptions/Artist/StageDaysOrphanedPerformancesException.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions\Artist;
+
+use DomainException;
+
+/**
+ * Raised by StageDayService::replaceDays when the proposed event_ids
+ * would remove a day that still has non-cancelled performances scheduled
+ * on it. The frontend re-prompts the user with a confirmation dialog
+ * and re-submits with `?force_orphan=true` to acknowledge the orphans.
+ *
+ * Controller maps to HTTP 409 with body
+ * `{conflict: 'orphaned_performances', performances_on_removed_events: [...]}`.
+ */
+final class StageDaysOrphanedPerformancesException extends DomainException
+{
+    /**
+     * @param  array<int, string>  $performanceIds
+     * @param  array<int, string>  $removedEventIds
+     */
+    public function __construct(
+        public readonly array $performanceIds,
+        public readonly array $removedEventIds,
+    ) {
+        parent::__construct(sprintf(
+            'Stage-day removal would orphan %d performance(s) on %d event(s).',
+            count($performanceIds),
+            count($removedEventIds),
+        ));
+    }
+}
diff --git a/api/app/Exceptions/Artist/VersionMismatchException.php b/api/app/Exceptions/Artist/VersionMismatchException.php
new file mode 100644
index 00000000..8b53977a
--- /dev/null
+++ b/api/app/Exceptions/Artist/VersionMismatchException.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions\Artist;
+
+use DomainException;
+
+/**
+ * Raised by LaneCascadeService::move when the client-supplied version
+ * does not match the row's current version (RFC v0.2 D14 — optimistic
+ * locking on Performance). Controller maps to HTTP 409 with body
+ * `{conflict: 'version_mismatch', current_version: N, server_data: …}`.
+ */
+final class VersionMismatchException extends DomainException
+{
+    public function __construct(
+        public readonly int $currentVersion,
+        public readonly int $clientVersion,
+    ) {
+        parent::__construct(sprintf(
+            'Performance version mismatch: server=%d, client=%d.',
+            $currentVersion,
+            $clientVersion,
+        ));
+    }
+}
diff --git a/api/app/Services/Artist/ArtistEngagementService.php b/api/app/Services/Artist/ArtistEngagementService.php
new file mode 100644
index 00000000..f9215654
--- /dev/null
+++ b/api/app/Services/Artist/ArtistEngagementService.php
@@ -0,0 +1,214 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Enums\Artist\ArtistEngagementStatus;
+use App\Enums\Artist\BumaHandledBy;
+use App\Exceptions\Artist\InvalidStatusTransitionException;
+use App\Models\Artist;
+use App\Models\ArtistEngagement;
+use App\Models\Event;
+use Illuminate\Support\Facades\DB;
+
+/**
+ * Heart of the artist booking domain. Owns the booking_status state
+ * machine, the deal-info defaults, and the cancellation cascade hook
+ * that the ArtistEngagementObserver relies on (the observer turns a
+ * soft-delete into a performances + advance_sections cascade; this
+ * service composes cancel + delete in one transaction).
+ */
+final class ArtistEngagementService
+{
+    /**
+     * Terminal statuses — no transitions out except an explicit
+     * `allowReopen` flag (currently unused by callers, reserved for
+     * superadmin tooling).
+     */
+    private const TERMINAL = [
+        ArtistEngagementStatus::Cancelled,
+        ArtistEngagementStatus::Rejected,
+        ArtistEngagementStatus::Declined,
+    ];
+
+    /**
+     * @param  array<string, mixed>  $attributes
+     */
+    public function create(Event $event, Artist $artist, array $attributes): ArtistEngagement
+    {
+        return DB::transaction(function () use ($event, $artist, $attributes): ArtistEngagement {
+            $engagement = new ArtistEngagement($attributes);
+            $engagement->artist_id = $artist->id;
+            $engagement->event_id = $event->id;
+
+            // D26 — Buma auto-flip. If artist's agent_company handles
+            // BUMA reporting itself, default the engagement to
+            // BookingAgency; otherwise default to Organisation. Caller
+            // may override via $attributes.
+            if (! array_key_exists('buma_handled_by', $attributes)) {
+                $artist->loadMissing('agentCompany');
+                $engagement->buma_handled_by = ($artist->agentCompany?->handles_buma === true)
+                    ? BumaHandledBy::BookingAgency
+                    : BumaHandledBy::Organisation;
+            }
+
+            $status = $this->coerceStatus($engagement->booking_status ?? ArtistEngagementStatus::Draft);
+            $this->validateInitialStatus($status, $engagement);
+            $engagement->booking_status = $status;
+
+            $engagement->save();
+
+            return $engagement->refresh();
+        });
+    }
+
+    /**
+     * Partial update. Status changes route through transitionStatus so
+     * the state machine fires on every status change regardless of the
+     * other fields in the payload.
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    public function update(ArtistEngagement $engagement, array $attributes): ArtistEngagement
+    {
+        return DB::transaction(function () use ($engagement, $attributes): ArtistEngagement {
+            unset($attributes['organisation_id'], $attributes['artist_id'], $attributes['event_id']);
+
+            if (array_key_exists('booking_status', $attributes)) {
+                $newStatus = $this->coerceStatus($attributes['booking_status']);
+                unset($attributes['booking_status']);
+                $engagement->fill($attributes);
+                $this->transitionStatus($engagement, $newStatus, $attributes);
+                $engagement->save();
+            } else {
+                $engagement->fill($attributes);
+                $engagement->save();
+            }
+
+            return $engagement->refresh();
+        });
+    }
+
+    /**
+     * Atomic transition with full state-machine validation. Throws
+     * InvalidStatusTransitionException on illegal moves.
+     *
+     * @param  array<string, mixed>  $contextAttributes  fields already filled on $engagement
+     */
+    public function transitionStatus(
+        ArtistEngagement $engagement,
+        ArtistEngagementStatus $to,
+        array $contextAttributes = [],
+    ): ArtistEngagement {
+        $from = $this->coerceStatus($engagement->booking_status);
+
+        $this->validateTransition($from, $to, $engagement);
+
+        $engagement->booking_status = $to;
+        $engagement->save();
+
+        return $engagement;
+    }
+
+    /**
+     * Cancel = transition to Cancelled, then soft-delete. Observer
+     * cascades to performances + advance_sections per RFC §5.4.
+     */
+    public function cancel(ArtistEngagement $engagement): ArtistEngagement
+    {
+        return DB::transaction(function () use ($engagement): ArtistEngagement {
+            $from = $this->coerceStatus($engagement->booking_status);
+            if ($from !== ArtistEngagementStatus::Cancelled) {
+                $this->transitionStatus($engagement, ArtistEngagementStatus::Cancelled);
+            }
+            $engagement->delete();
+
+            return $engagement->refresh();
+        });
+    }
+
+    /**
+     * Soft delete only. Observer cascades to children. Use cancel() if
+     * the booking_status should also flip — the API destroy endpoint
+     * routes here directly to keep status untouched (§6.2 — DELETE
+     * /engagements/{id} is "remove the booking", semantically distinct
+     * from "cancel").
+     */
+    public function softDelete(ArtistEngagement $engagement): void
+    {
+        $engagement->delete();
+    }
+
+    private function validateInitialStatus(ArtistEngagementStatus $status, ArtistEngagement $engagement): void
+    {
+        if ($status === ArtistEngagementStatus::Option) {
+            $expires = $engagement->option_expires_at;
+            if ($expires === null || $expires->isPast()) {
+                throw new InvalidStatusTransitionException(
+                    ArtistEngagementStatus::Draft,
+                    $status,
+                    'Option requires option_expires_at in the future.',
+                );
+            }
+        }
+
+        if ($status === ArtistEngagementStatus::Contracted) {
+            $fee = $engagement->fee_amount;
+            if ($fee === null || (float) $fee <= 0) {
+                throw new InvalidStatusTransitionException(
+                    ArtistEngagementStatus::Draft,
+                    $status,
+                    'Contracted requires fee_amount.',
+                );
+            }
+        }
+    }
+
+    private function validateTransition(
+        ArtistEngagementStatus $from,
+        ArtistEngagementStatus $to,
+        ArtistEngagement $engagement,
+    ): void {
+        if ($from === $to) {
+            return;
+        }
+
+        if (in_array($from, self::TERMINAL, true)) {
+            throw new InvalidStatusTransitionException(
+                $from,
+                $to,
+                sprintf('%s is terminal — re-booking creates a new engagement.', $from->value),
+            );
+        }
+
+        if ($to === ArtistEngagementStatus::Option) {
+            $expires = $engagement->option_expires_at;
+            if ($expires === null || $expires->isPast()) {
+                throw new InvalidStatusTransitionException(
+                    $from,
+                    $to,
+                    'Option requires option_expires_at in the future.',
+                );
+            }
+        }
+
+        if ($to === ArtistEngagementStatus::Contracted) {
+            $fee = $engagement->fee_amount;
+            if ($fee === null || (float) $fee <= 0) {
+                throw new InvalidStatusTransitionException(
+                    $from,
+                    $to,
+                    'Contracted requires fee_amount.',
+                );
+            }
+        }
+    }
+
+    private function coerceStatus(ArtistEngagementStatus|string $value): ArtistEngagementStatus
+    {
+        return $value instanceof ArtistEngagementStatus
+            ? $value
+            : ArtistEngagementStatus::from($value);
+    }
+}
diff --git a/api/app/Services/Artist/ArtistService.php b/api/app/Services/Artist/ArtistService.php
new file mode 100644
index 00000000..06a90e07
--- /dev/null
+++ b/api/app/Services/Artist/ArtistService.php
@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Exceptions\Artist\DuplicateArtistException;
+use App\Models\Artist;
+use App\Models\Organisation;
+use Illuminate\Support\Facades\DB;
+
+final class ArtistService
+{
+    /**
+     * Master-create. Detects exact-name duplicates within the
+     * organisation (case-insensitive) and raises DuplicateArtistException
+     * carrying the existing record so the controller can surface a "use
+     * existing or rename" choice. Slug uniqueness is handled by
+     * Artist::booted (Session 1).
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    public function create(Organisation $organisation, array $attributes): Artist
+    {
+        return DB::transaction(function () use ($organisation, $attributes): Artist {
+            $name = (string) $attributes['name'];
+            $existing = Artist::query()
+                ->where('organisation_id', $organisation->id)
+                ->whereRaw('LOWER(name) = ?', [mb_strtolower($name)])
+                ->first();
+
+            if ($existing !== null) {
+                throw new DuplicateArtistException($existing);
+            }
+
+            unset($attributes['organisation_id'], $attributes['slug']);
+            $artist = new Artist($attributes);
+            $artist->organisation_id = $organisation->id;
+            $artist->save();
+
+            return $artist->refresh();
+        });
+    }
+
+    /**
+     * Master-update. Disallows organisation_id mutation (cross-tenant
+     * move is a separate, audited operation we don't expose here).
+     * Slug is not editable post-create either; rename produces a fresh
+     * slug only on Session 4 admin "force-rename" flow if/when added.
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    public function update(Artist $artist, array $attributes): Artist
+    {
+        unset($attributes['organisation_id'], $attributes['slug']);
+
+        $artist->fill($attributes);
+        $artist->save();
+
+        return $artist->refresh();
+    }
+
+    /**
+     * Soft delete. Engagements are intentionally untouched per RFC D27 —
+     * historical engagements survive their master being archived; the
+     * frontend renders a "trashed" banner on the engagement detail.
+     */
+    public function softDelete(Artist $artist): void
+    {
+        $artist->delete();
+    }
+
+    public function restore(Artist $artist): Artist
+    {
+        $artist->restore();
+
+        return $artist->refresh();
+    }
+}
diff --git a/api/app/Services/Artist/GenreService.php b/api/app/Services/Artist/GenreService.php
new file mode 100644
index 00000000..b8994574
--- /dev/null
+++ b/api/app/Services/Artist/GenreService.php
@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Exceptions\Artist\GenreInUseException;
+use App\Models\Artist;
+use App\Models\Genre;
+use App\Models\Organisation;
+use Illuminate\Support\Facades\DB;
+
+final class GenreService
+{
+    /**
+     * @param  array<string, mixed>  $attributes
+     */
+    public function create(Organisation $organisation, array $attributes): Genre
+    {
+        return DB::transaction(function () use ($organisation, $attributes): Genre {
+            $genre = new Genre($attributes);
+            $genre->organisation_id = $organisation->id;
+            $genre->is_active = $attributes['is_active'] ?? true;
+            $genre->save();
+
+            return $genre->refresh();
+        });
+    }
+
+    /**
+     * @param  array<string, mixed>  $attributes
+     */
+    public function update(Genre $genre, array $attributes): Genre
+    {
+        unset($attributes['organisation_id']);
+
+        $genre->fill($attributes);
+        $genre->save();
+
+        return $genre->refresh();
+    }
+
+    /**
+     * Hard delete (genres are config — no soft-delete column on the table).
+     * Blocks if any artist references this genre as `default_genre_id`.
+     */
+    public function delete(Genre $genre): void
+    {
+        $referencingCount = Artist::query()
+            ->where('default_genre_id', $genre->id)
+            ->count();
+
+        if ($referencingCount > 0) {
+            throw new GenreInUseException($genre, $referencingCount);
+        }
+
+        $genre->delete();
+    }
+}
diff --git a/api/app/Services/Artist/LaneCascadeService.php b/api/app/Services/Artist/LaneCascadeService.php
new file mode 100644
index 00000000..a55b14c4
--- /dev/null
+++ b/api/app/Services/Artist/LaneCascadeService.php
@@ -0,0 +1,150 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Exceptions\Artist\VersionMismatchException;
+use App\Models\Performance;
+use App\Models\Stage;
+use Carbon\CarbonImmutable;
+use Illuminate\Support\Facades\DB;
+
+/**
+ * RFC v0.2 D18 — single transactional move algorithm.
+ *
+ * Locks the dragged Performance row (FOR UPDATE), validates the
+ * client's version number against the persisted one, and either parks
+ * the row (stage_id → null) or places it on the target stage with a
+ * cascade-bump of any time-overlapping rows on the same lane. Cascade
+ * is single-level: every performance currently on
+ * (target_stage, target_event, target_lane) whose [start, end] window
+ * overlaps the new placement gets bumped to lane+1. Higher-lane chain
+ * collisions resolve themselves in a subsequent move; the prototype
+ * audit (§5) shows that single-level bumping is sufficient because
+ * collisions are rare and the user is editing one block at a time.
+ *
+ * The PerformanceObserver auto-bumps `version` on save so we don't
+ * need to set it explicitly here.
+ */
+final class LaneCascadeService
+{
+    /**
+     * @return MoveResult moved + (other) cascaded performances
+     *
+     * @throws VersionMismatchException when client version is stale
+     */
+    public function move(
+        Performance $performance,
+        ?Stage $targetStage,
+        ?CarbonImmutable $start,
+        ?CarbonImmutable $end,
+        ?int $targetLane,
+        int $clientVersion,
+    ): MoveResult {
+        return DB::transaction(function () use (
+            $performance,
+            $targetStage,
+            $start,
+            $end,
+            $targetLane,
+            $clientVersion,
+        ): MoveResult {
+            /** @var Performance $locked */
+            $locked = Performance::query()
+                ->whereKey($performance->id)
+                ->lockForUpdate()
+                ->firstOrFail();
+
+            if ((int) $locked->version !== $clientVersion) {
+                throw new VersionMismatchException(
+                    currentVersion: (int) $locked->version,
+                    clientVersion: $clientVersion,
+                );
+            }
+
+            if ($targetStage === null) {
+                $locked->stage_id = null;
+                if ($start !== null) {
+                    $locked->start_at = $start;
+                }
+                if ($end !== null) {
+                    $locked->end_at = $end;
+                }
+                if ($targetLane !== null) {
+                    $locked->lane = $targetLane;
+                }
+                $locked->save();
+
+                return new MoveResult($locked->refresh(), []);
+            }
+
+            if ($start === null || $end === null || $targetLane === null) {
+                throw new \InvalidArgumentException(
+                    'targetStage non-null requires start, end and targetLane.',
+                );
+            }
+
+            $newEventId = $this->resolveEventIdForStageAndStart($targetStage, $start)
+                ?? $performance->event_id;
+
+            // Lock all peer performances on (stage, event, lane) for the
+            // duration of the cascade. The first iteration locks the
+            // already-existing rows; new placements that follow this
+            // transaction wait on these row locks until commit.
+            $existingOnLane = Performance::query()
+                ->where('stage_id', $targetStage->id)
+                ->where('event_id', $newEventId)
+                ->where('lane', $targetLane)
+                ->where('id', '!=', $locked->id)
+                ->lockForUpdate()
+                ->get();
+
+            $cascaded = [];
+            foreach ($existingOnLane as $other) {
+                if ($this->overlaps($start, $end, $other->start_at, $other->end_at)) {
+                    $other->lane = (int) $other->lane + 1;
+                    $other->save();
+                    $cascaded[] = $other->refresh();
+                }
+            }
+
+            $locked->stage_id = $targetStage->id;
+            $locked->event_id = $newEventId;
+            $locked->start_at = $start;
+            $locked->end_at = $end;
+            $locked->lane = $targetLane;
+            $locked->save();
+
+            return new MoveResult($locked->refresh(), $cascaded);
+        });
+    }
+
+    /**
+     * For festivals, `target_start_at` falls inside one of the stage's
+     * sub-events; for flat events, the stage's own event_id is the
+     * answer. Returns null if no stage_day matches — caller falls back
+     * to keeping the performance's existing event_id (validation rules
+     * in the FormRequest already guarantee a valid stage_day exists).
+     */
+    private function resolveEventIdForStageAndStart(Stage $stage, CarbonImmutable $start): ?string
+    {
+        return $stage->stageDays()
+            ->join('events', 'events.id', '=', 'stage_days.event_id')
+            ->where('events.start_at', '<=', $start)
+            ->where('events.end_at', '>=', $start)
+            ->orderBy('events.start_at', 'desc')
+            ->limit(1)
+            ->value('stage_days.event_id');
+    }
+
+    private function overlaps(
+        CarbonImmutable $aStart,
+        CarbonImmutable $aEnd,
+        \DateTimeInterface $bStart,
+        \DateTimeInterface $bEnd,
+    ): bool {
+        return $aStart < CarbonImmutable::instance($bEnd)
+            && CarbonImmutable::instance($bStart) < $aEnd;
+    }
+}
diff --git a/api/app/Services/Artist/MoveResult.php b/api/app/Services/Artist/MoveResult.php
new file mode 100644
index 00000000..2f22ee75
--- /dev/null
+++ b/api/app/Services/Artist/MoveResult.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Models\Performance;
+
+/**
+ * Value object returned by LaneCascadeService::move.
+ *
+ * `moved` is the performance that the user is dragging.
+ * `cascaded` is the list of OTHER performances that the cascade-bump
+ * algorithm shifted to a higher lane to make room (RFC v0.2 D18).
+ *
+ * Both arrays carry already-refreshed Performance models so callers can
+ * map them straight to API resources without an extra DB roundtrip.
+ */
+final class MoveResult
+{
+    /**
+     * @param  array<int, Performance>  $cascaded
+     */
+    public function __construct(
+        public readonly Performance $moved,
+        public readonly array $cascaded,
+    ) {}
+}
diff --git a/api/app/Services/Artist/PerformanceService.php b/api/app/Services/Artist/PerformanceService.php
new file mode 100644
index 00000000..fb39cb3a
--- /dev/null
+++ b/api/app/Services/Artist/PerformanceService.php
@@ -0,0 +1,109 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Models\ArtistEngagement;
+use App\Models\Performance;
+use App\Models\Stage;
+use Carbon\CarbonImmutable;
+use Illuminate\Support\Facades\DB;
+
+/**
+ * Performance CRUD + park/unpark. Placement edits (move-by-drag,
+ * cascade) route through LaneCascadeService to keep the row-locking
+ * and version-bump in one place; this service only handles non-
+ * placement state (notes) plus the binary park/unpark transitions.
+ */
+final class PerformanceService
+{
+    public function __construct(
+        private readonly LaneCascadeService $laneCascade,
+    ) {}
+
+    /**
+     * @param  array<string, mixed>  $attributes
+     */
+    public function create(ArtistEngagement $engagement, array $attributes): Performance
+    {
+        return DB::transaction(function () use ($engagement, $attributes): Performance {
+            $perf = new Performance($attributes);
+            $perf->engagement_id = $engagement->id;
+            $perf->event_id = $attributes['event_id'] ?? $engagement->event_id;
+            $perf->version = 1;
+            $perf->save();
+
+            return $perf->refresh();
+        });
+    }
+
+    /**
+     * Non-placement update only. start_at/end_at/stage_id/lane changes
+     * MUST go through LaneCascadeService::move so the cascade-bump and
+     * optimistic-lock contract are honoured.
+     *
+     * @param  array<string, mixed>  $attributes
+     */
+    public function update(Performance $performance, array $attributes): Performance
+    {
+        unset(
+            $attributes['stage_id'],
+            $attributes['start_at'],
+            $attributes['end_at'],
+            $attributes['lane'],
+            $attributes['version'],
+            $attributes['event_id'],
+            $attributes['engagement_id'],
+        );
+
+        $performance->fill($attributes);
+        $performance->save();
+
+        return $performance->refresh();
+    }
+
+    public function delete(Performance $performance): void
+    {
+        $performance->delete();
+    }
+
+    /**
+     * Move into the wachtrij. lane preserved so the user can drag back
+     * to roughly the same visual position (D12 — wachtrij is just
+     * stage_id=null, no separate table).
+     */
+    public function park(Performance $performance, int $clientVersion): Performance
+    {
+        $result = $this->laneCascade->move(
+            performance: $performance,
+            targetStage: null,
+            start: null,
+            end: null,
+            targetLane: null,
+            clientVersion: $clientVersion,
+        );
+
+        return $result->moved;
+    }
+
+    public function unpark(
+        Performance $performance,
+        Stage $targetStage,
+        CarbonImmutable $start,
+        CarbonImmutable $end,
+        int $targetLane,
+        int $clientVersion,
+    ): Performance {
+        $result = $this->laneCascade->move(
+            performance: $performance,
+            targetStage: $targetStage,
+            start: $start,
+            end: $end,
+            targetLane: $targetLane,
+            clientVersion: $clientVersion,
+        );
+
+        return $result->moved;
+    }
+}
diff --git a/api/app/Services/Artist/StageDayService.php b/api/app/Services/Artist/StageDayService.php
new file mode 100644
index 00000000..92fdf4cf
--- /dev/null
+++ b/api/app/Services/Artist/StageDayService.php
@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Enums\Artist\ArtistEngagementStatus;
+use App\Exceptions\Artist\StageDaysOrphanedPerformancesException;
+use App\Models\Performance;
+use App\Models\Stage;
+use App\Models\StageDay;
+use Illuminate\Support\Facades\DB;
+
+/**
+ * RFC §10.5 — atomic stage_days matrix replacement.
+ *
+ * Each event_id submitted must be either equal to `stage.event_id`
+ * (flat-event case) or a child of it via `parent_event_id` (festival
+ * sub-event case). Validation of that constraint lives in the
+ * FormRequest; this service trusts a vetted list and operates atomically.
+ */
+final class StageDayService
+{
+    /**
+     * @param  array<int, string>  $eventIds
+     * @return array{added: array<int, string>, removed: array<int, string>}
+     */
+    public function replaceDays(Stage $stage, array $eventIds, bool $forceOrphan = false): array
+    {
+        return DB::transaction(function () use ($stage, $eventIds, $forceOrphan): array {
+            $current = $stage->stageDays()->pluck('event_id')->all();
+            $proposed = array_values(array_unique($eventIds));
+
+            $added = array_values(array_diff($proposed, $current));
+            $removed = array_values(array_diff($current, $proposed));
+
+            if ($removed !== [] && ! $forceOrphan) {
+                $orphanIds = Performance::query()
+                    ->where('stage_id', $stage->id)
+                    ->whereIn('event_id', $removed)
+                    ->whereHas('engagement', function ($q): void {
+                        $q->whereNotIn('booking_status', [
+                            ArtistEngagementStatus::Cancelled->value,
+                            ArtistEngagementStatus::Rejected->value,
+                            ArtistEngagementStatus::Declined->value,
+                        ]);
+                    })
+                    ->pluck('id')
+                    ->all();
+
+                if ($orphanIds !== []) {
+                    throw new StageDaysOrphanedPerformancesException($orphanIds, $removed);
+                }
+            }
+
+            if ($removed !== []) {
+                StageDay::query()
+                    ->where('stage_id', $stage->id)
+                    ->whereIn('event_id', $removed)
+                    ->delete();
+            }
+
+            foreach ($added as $eventId) {
+                StageDay::query()->create([
+                    'stage_id' => $stage->id,
+                    'event_id' => $eventId,
+                ]);
+            }
+
+            return ['added' => $added, 'removed' => $removed];
+        });
+    }
+}
diff --git a/api/app/Services/Artist/StageService.php b/api/app/Services/Artist/StageService.php
new file mode 100644
index 00000000..e96d8d15
--- /dev/null
+++ b/api/app/Services/Artist/StageService.php
@@ -0,0 +1,84 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Artist;
+
+use App\Models\Event;
+use App\Models\Performance;
+use App\Models\Stage;
+use Illuminate\Support\Facades\DB;
+
+final class StageService
+{
+    /**
+     * @param  array<string, mixed>  $attributes
+     */
+    public function create(Event $event, array $attributes): Stage
+    {
+        return DB::transaction(function () use ($event, $attributes): Stage {
+            $stage = new Stage($attributes);
+            $stage->event_id = $event->id;
+            if (! isset($attributes['sort_order'])) {
+                $stage->sort_order = (int) Stage::query()->where('event_id', $event->id)->max('sort_order') + 1;
+            }
+            $stage->save();
+
+            return $stage->refresh();
+        });
+    }
+
+    /**
+     * @param  array<string, mixed>  $attributes
+     */
+    public function update(Stage $stage, array $attributes): Stage
+    {
+        unset($attributes['event_id']);
+
+        $stage->fill($attributes);
+        $stage->save();
+
+        return $stage->refresh();
+    }
+
+    /**
+     * Hard delete (stages have no SoftDeletes trait — they are config-
+     * level structure, not event-history). Performances on this stage
+     * are cascade-parked: stage_id → null, lane preserved so they re-
+     * appear in the wachtrij with their previous lane index for visual
+     * continuity. Caller wraps the cascade count into the activity log
+     * (Step 9, RFC §8 stage.deleted entry).
+     */
+    public function delete(Stage $stage): int
+    {
+        return DB::transaction(function () use ($stage): int {
+            $parkedCount = Performance::query()
+                ->where('stage_id', $stage->id)
+                ->update(['stage_id' => null]);
+
+            $stage->stageDays()->delete();
+            $stage->delete();
+
+            return $parkedCount;
+        });
+    }
+
+    /**
+     * Persist a new stage order. The request layer validates that
+     * `$orderedStageIds` is a permutation of all stage ids on
+     * `$event` — here we trust that and just write the new sort_order.
+     *
+     * @param  array<int, string>  $orderedStageIds
+     */
+    public function reorder(Event $event, array $orderedStageIds): void
+    {
+        DB::transaction(function () use ($event, $orderedStageIds): void {
+            foreach ($orderedStageIds as $position => $stageId) {
+                Stage::query()
+                    ->where('event_id', $event->id)
+                    ->where('id', $stageId)
+                    ->update(['sort_order' => $position]);
+            }
+        });
+    }
+}