feat: implement FParkan architecture foundation

Add the modular fparkan workspace, domain crates, adapters, apps, xtask policy/CI, acceptance evidence, and licensed corpus gates for the macOS-focused roadmap foundation.

crates/fparkan-world/src/lib.rs

@@ -0,0 +1,840 @@
+#![forbid(unsafe_code)]
+//! Deterministic world identity, queue, lifecycle, and snapshots.
+
+use std::collections::VecDeque;
+
+/// Object handle with generation.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub struct ObjectHandle {
+    /// Generation.
+    pub generation: u32,
+    /// Slot.
+    pub slot: u32,
+}
+
+/// Original mission object id.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub struct OriginalObjectId(pub u32);
+
+/// Owner id.
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub struct OwnerId(pub u16);
+
+/// Tick.
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
+pub struct Tick(pub u64);
+
+/// State hash.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct StateHash(pub [u8; 32]);
+
+/// World phase.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum WorldPhase {
+    /// Idle.
+    Idle,
+    /// Calculating.
+    Calculating,
+    /// Applying deferred operations.
+    ApplyingDeferred,
+    /// Publishing snapshot.
+    PublishingSnapshot,
+}
+
+/// Object draft.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct ObjectDraft {
+    /// Original id.
+    pub original_id: Option<OriginalObjectId>,
+}
+
+/// Distinct object identity metadata.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct IdentityMetadata {
+    /// Original mission object id.
+    pub original_id: Option<OriginalObjectId>,
+    /// Mirrored original id.
+    pub mirror_id: Option<OriginalObjectId>,
+    /// Local owner id.
+    pub owner_id: Option<OwnerId>,
+}
+
+/// World command.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct WorldCommand {
+    /// Sequence.
+    pub sequence: u64,
+    /// Target.
+    pub target: Option<ObjectHandle>,
+}
+
+/// World event.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct WorldEvent {
+    /// Sequence.
+    pub sequence: u64,
+    /// Target object, if any.
+    pub target: Option<ObjectHandle>,
+}
+
+/// Input snapshot.
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub struct InputSnapshot;
+
+/// World snapshot.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct WorldSnapshot {
+    /// Tick.
+    pub tick: Tick,
+    /// Live object handles.
+    pub objects: Vec<ObjectHandle>,
+    /// Commands processed during this step.
+    pub events: Vec<WorldEvent>,
+    /// State hash.
+    pub hash: StateHash,
+}
+
+/// World configuration.
+#[derive(Clone, Debug, Default, Eq, PartialEq)]
+pub struct WorldConfig;
+
+/// Fixed-step clock state.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct FixedStepClock {
+    accumulated_millis: u64,
+    tick: Tick,
+    paused: bool,
+    platform_event_collections: u64,
+}
+
+/// Fixed-step configuration.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct FixedStepConfig {
+    /// Milliseconds per simulation tick.
+    pub step_millis: u32,
+}
+
+impl Default for FixedStepConfig {
+    fn default() -> Self {
+        Self { step_millis: 16 }
+    }
+}
+
+/// Shutdown ordering report.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct ShutdownReport {
+    /// Object handles released before managers.
+    pub released_objects: Vec<ObjectHandle>,
+    /// Whether managers were released after objects.
+    pub managers_released: bool,
+}
+
+#[derive(Clone, Debug)]
+struct Slot {
+    generation: u32,
+    live: bool,
+    registered: bool,
+    original_id: Option<OriginalObjectId>,
+    owner_id: Option<OwnerId>,
+    mirror_id: Option<OriginalObjectId>,
+    registration_sequence: Option<u64>,
+}
+
+/// World.
+#[derive(Clone, Debug)]
+pub struct World {
+    slots: Vec<Slot>,
+    queue: VecDeque<WorldCommand>,
+    deferred_delete: Vec<ObjectHandle>,
+    phase: WorldPhase,
+    tick: Tick,
+    next_sequence: u64,
+    next_registration_sequence: u64,
+}
+
+/// World error.
+#[derive(Debug, Eq, PartialEq)]
+pub enum WorldError {
+    /// Invalid handle.
+    InvalidHandle,
+    /// Stale handle.
+    StaleHandle,
+    /// Object already deleted.
+    Deleted,
+    /// Duplicate original object id.
+    DuplicateOriginalObjectId(OriginalObjectId),
+    /// Invalid fixed-step configuration.
+    InvalidFixedStep,
+}
+
+impl std::fmt::Display for WorldError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+
+impl std::error::Error for WorldError {}
+
+/// Creates a world.
+#[must_use]
+pub fn new(_config: WorldConfig) -> World {
+    World {
+        slots: Vec::new(),
+        queue: VecDeque::new(),
+        deferred_delete: Vec::new(),
+        phase: WorldPhase::Idle,
+        tick: Tick(0),
+        next_sequence: 0,
+        next_registration_sequence: 0,
+    }
+}
+
+/// Constructs an object without registering it.
+///
+/// # Errors
+///
+/// Returns [`WorldError::InvalidHandle`] if the slot index cannot be
+/// represented by an [`ObjectHandle`].
+pub fn construct_object(world: &mut World, draft: ObjectDraft) -> Result<ObjectHandle, WorldError> {
+    let slot = u32::try_from(world.slots.len()).map_err(|_| WorldError::InvalidHandle)?;
+    let handle = ObjectHandle {
+        generation: 1,
+        slot,
+    };
+    world.slots.push(Slot {
+        generation: 1,
+        live: true,
+        registered: false,
+        original_id: draft.original_id,
+        owner_id: None,
+        mirror_id: None,
+        registration_sequence: None,
+    });
+    Ok(handle)
+}
+
+/// Registers a constructed object.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if the handle is stale, deleted, or out of range.
+pub fn register_object(world: &mut World, handle: ObjectHandle) -> Result<(), WorldError> {
+    let original_id = checked_slot(world, handle)?.original_id;
+    if let Some(original_id) = original_id {
+        let duplicate = world.slots.iter().enumerate().any(|(idx, slot)| {
+            u32::try_from(idx).is_ok_and(|slot_index| slot_index != handle.slot)
+                && slot.live
+                && slot.registered
+                && slot.original_id == Some(original_id)
+        });
+        if duplicate {
+            return Err(WorldError::DuplicateOriginalObjectId(original_id));
+        }
+    }
+    let sequence = world.next_registration_sequence;
+    world.next_registration_sequence = world.next_registration_sequence.saturating_add(1);
+    let slot = checked_slot_mut(world, handle)?;
+    slot.registered = true;
+    slot.registration_sequence = Some(sequence);
+    Ok(())
+}
+
+/// Attaches local ownership metadata to an object.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if the handle is stale, deleted, or out of range.
+pub fn set_owner(
+    world: &mut World,
+    handle: ObjectHandle,
+    owner_id: Option<OwnerId>,
+) -> Result<(), WorldError> {
+    checked_slot_mut(world, handle)?.owner_id = owner_id;
+    Ok(())
+}
+
+/// Attaches mirror metadata to an object without changing its original id.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if the handle is stale, deleted, or out of range.
+pub fn set_mirror_original(
+    world: &mut World,
+    handle: ObjectHandle,
+    mirror_id: Option<OriginalObjectId>,
+) -> Result<(), WorldError> {
+    checked_slot_mut(world, handle)?.mirror_id = mirror_id;
+    Ok(())
+}
+
+/// Returns registration sequence for a live object.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if the handle is stale, deleted, or out of range.
+pub fn registration_sequence(
+    world: &World,
+    handle: ObjectHandle,
+) -> Result<Option<u64>, WorldError> {
+    Ok(checked_slot(world, handle)?.registration_sequence)
+}
+
+/// Returns object identity metadata.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if the handle is stale, deleted, or out of range.
+pub fn identity_metadata(
+    world: &World,
+    handle: ObjectHandle,
+) -> Result<IdentityMetadata, WorldError> {
+    let slot = checked_slot(world, handle)?;
+    Ok(IdentityMetadata {
+        original_id: slot.original_id,
+        mirror_id: slot.mirror_id,
+        owner_id: slot.owner_id,
+    })
+}
+
+/// Requests deletion.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if the handle is stale, deleted, or out of range.
+pub fn request_delete(world: &mut World, handle: ObjectHandle) -> Result<(), WorldError> {
+    checked_slot(world, handle)?;
+    if world.phase == WorldPhase::Calculating {
+        if !world.deferred_delete.contains(&handle) {
+            world.deferred_delete.push(handle);
+        }
+        Ok(())
+    } else {
+        delete_now(world, handle)
+    }
+}
+
+/// Enqueues a command.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] when a targeted command references an invalid
+/// handle.
+pub fn enqueue(world: &mut World, mut command: WorldCommand) -> Result<(), WorldError> {
+    if let Some(handle) = command.target {
+        checked_slot(world, handle)?;
+    }
+    command.sequence = world.next_sequence;
+    world.next_sequence = world.next_sequence.saturating_add(1);
+    world.queue.push_back(command);
+    Ok(())
+}
+
+/// Advances one deterministic step.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if a queued command references a stale, deleted, or
+/// out-of-range handle.
+pub fn step(world: &mut World, input: &InputSnapshot) -> Result<WorldSnapshot, WorldError> {
+    step_with_handler(world, input, |_, _| Ok(()))
+}
+
+/// Advances one deterministic step with a command callback.
+///
+/// The callback runs while the world is in the calculating phase, which allows
+/// tests and adapters to exercise deferred deletion semantics without exposing
+/// mutable slot internals.
+///
+/// # Errors
+///
+/// Returns [`WorldError`] if a queued command references a stale, deleted, or
+/// out-of-range handle, or if the callback reports a world error.
+pub fn step_with_handler<F>(
+    world: &mut World,
+    _input: &InputSnapshot,
+    mut handler: F,
+) -> Result<WorldSnapshot, WorldError>
+where
+    F: FnMut(&mut World, &WorldCommand) -> Result<(), WorldError>,
+{
+    world.phase = WorldPhase::Calculating;
+    let mut events = Vec::new();
+    while let Some(command) = world.queue.pop_front() {
+        if let Some(handle) = command.target {
+            if world.deferred_delete.contains(&handle) {
+                continue;
+            }
+            checked_slot(world, handle)?;
+        }
+        handler(world, &command)?;
+        events.push(WorldEvent {
+            sequence: command.sequence,
+            target: command.target,
+        });
+    }
+    world.phase = WorldPhase::ApplyingDeferred;
+    let deletes = std::mem::take(&mut world.deferred_delete);
+    for handle in deletes {
+        let _ = delete_now(world, handle);
+    }
+    world.tick.0 = world.tick.0.saturating_add(1);
+    world.phase = WorldPhase::PublishingSnapshot;
+    let snapshot = WorldSnapshot {
+        tick: world.tick,
+        objects: live_registered(world),
+        events,
+        hash: canonical_state_hash(world),
+    };
+    world.phase = WorldPhase::Idle;
+    Ok(snapshot)
+}
+
+/// Computes canonical state hash.
+#[must_use]
+pub fn canonical_state_hash(world: &World) -> StateHash {
+    let mut state = 0xcbf2_9ce4_8422_2325_u64;
+    hash_u64(&mut state, world.tick.0);
+    for (idx, slot) in world.slots.iter().enumerate() {
+        hash_u64(&mut state, idx as u64);
+        hash_u64(&mut state, u64::from(slot.generation));
+        hash_u64(&mut state, u64::from(u8::from(slot.live)));
+        hash_u64(&mut state, u64::from(u8::from(slot.registered)));
+        hash_u64(&mut state, slot.original_id.map_or(0, |id| u64::from(id.0)));
+        hash_u64(&mut state, slot.mirror_id.map_or(0, |id| u64::from(id.0)));
+        hash_u64(&mut state, slot.owner_id.map_or(0, |id| u64::from(id.0)));
+        hash_u64(&mut state, slot.registration_sequence.unwrap_or(u64::MAX));
+    }
+    let mut out = [0; 32];
+    out[..8].copy_from_slice(&state.to_le_bytes());
+    out[8..16].copy_from_slice(&state.rotate_left(13).to_le_bytes());
+    out[16..24].copy_from_slice(&state.rotate_left(29).to_le_bytes());
+    out[24..32].copy_from_slice(&state.rotate_left(47).to_le_bytes());
+    StateHash(out)
+}
+
+/// Creates a fixed-step clock.
+///
+/// # Errors
+///
+/// Returns [`WorldError::InvalidFixedStep`] when the configured step is zero.
+pub fn fixed_step_clock(config: FixedStepConfig) -> Result<FixedStepClock, WorldError> {
+    if config.step_millis == 0 {
+        return Err(WorldError::InvalidFixedStep);
+    }
+    Ok(FixedStepClock {
+        accumulated_millis: 0,
+        tick: Tick(0),
+        paused: false,
+        platform_event_collections: 0,
+    })
+}
+
+/// Records platform event collection independently of game time.
+pub fn collect_platform_events(clock: &mut FixedStepClock) {
+    clock.platform_event_collections = clock.platform_event_collections.saturating_add(1);
+}
+
+/// Sets pause state.
+pub fn set_paused(clock: &mut FixedStepClock, paused: bool) {
+    clock.paused = paused;
+}
+
+/// Advances fixed-step game time.
+///
+/// Returns the number of simulation ticks that should be executed.
+///
+/// # Errors
+///
+/// Returns [`WorldError::InvalidFixedStep`] when the configured step is zero.
+pub fn advance_fixed_step(
+    clock: &mut FixedStepClock,
+    config: FixedStepConfig,
+    elapsed_millis: u64,
+) -> Result<u32, WorldError> {
+    if config.step_millis == 0 {
+        return Err(WorldError::InvalidFixedStep);
+    }
+    if clock.paused {
+        return Ok(0);
+    }
+    clock.accumulated_millis = clock.accumulated_millis.saturating_add(elapsed_millis);
+    let step = u64::from(config.step_millis);
+    let mut ticks = 0_u32;
+    while clock.accumulated_millis >= step {
+        clock.accumulated_millis -= step;
+        clock.tick.0 = clock.tick.0.saturating_add(1);
+        ticks = ticks.saturating_add(1);
+    }
+    Ok(ticks)
+}
+
+/// Returns fixed-step clock tick.
+#[must_use]
+pub fn fixed_step_tick(clock: &FixedStepClock) -> Tick {
+    clock.tick
+}
+
+/// Returns platform event collection count.
+#[must_use]
+pub fn platform_event_collections(clock: &FixedStepClock) -> u64 {
+    clock.platform_event_collections
+}
+
+/// Runs end-frame callbacks in stable sequence order.
+#[must_use]
+pub fn end_frame_callback_order(mut callbacks: Vec<WorldEvent>) -> Vec<u64> {
+    callbacks.sort_by_key(|event| event.sequence);
+    callbacks.into_iter().map(|event| event.sequence).collect()
+}
+
+/// Releases live objects before managers.
+#[must_use]
+pub fn shutdown(mut world: World) -> ShutdownReport {
+    let released_objects = live_registered(&world);
+    for slot in &mut world.slots {
+        slot.live = false;
+        slot.registered = false;
+        slot.generation = slot.generation.saturating_add(1);
+    }
+    ShutdownReport {
+        released_objects,
+        managers_released: true,
+    }
+}
+
+fn hash_u64(state: &mut u64, value: u64) {
+    for byte in value.to_le_bytes() {
+        *state ^= u64::from(byte);
+        *state = state.wrapping_mul(0x0000_0100_0000_01b3);
+    }
+}
+
+fn checked_slot(world: &World, handle: ObjectHandle) -> Result<&Slot, WorldError> {
+    let slot = world
+        .slots
+        .get(handle.slot as usize)
+        .ok_or(WorldError::InvalidHandle)?;
+    if slot.generation != handle.generation {
+        return Err(WorldError::StaleHandle);
+    }
+    if !slot.live {
+        return Err(WorldError::Deleted);
+    }
+    Ok(slot)
+}
+
+fn checked_slot_mut(world: &mut World, handle: ObjectHandle) -> Result<&mut Slot, WorldError> {
+    let slot = world
+        .slots
+        .get_mut(handle.slot as usize)
+        .ok_or(WorldError::InvalidHandle)?;
+    if slot.generation != handle.generation {
+        return Err(WorldError::StaleHandle);
+    }
+    if !slot.live {
+        return Err(WorldError::Deleted);
+    }
+    Ok(slot)
+}
+
+fn delete_now(world: &mut World, handle: ObjectHandle) -> Result<(), WorldError> {
+    let slot = checked_slot_mut(world, handle)?;
+    slot.live = false;
+    slot.generation = slot.generation.saturating_add(1);
+    Ok(())
+}
+
+fn live_registered(world: &World) -> Vec<ObjectHandle> {
+    world
+        .slots
+        .iter()
+        .enumerate()
+        .filter_map(|(idx, slot)| {
+            let slot_index = u32::try_from(idx).ok()?;
+            (slot.live && slot.registered).then_some(ObjectHandle {
+                generation: slot.generation,
+                slot: slot_index,
+            })
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn construct_register_and_hash_are_stable() {
+        let mut world = new(WorldConfig);
+        let handle = construct_object(&mut world, ObjectDraft { original_id: None }).expect("obj");
+        let before = step(&mut world, &InputSnapshot).expect("step");
+        assert!(before.objects.is_empty());
+        register_object(&mut world, handle).expect("register");
+        let after = step(&mut world, &InputSnapshot).expect("step");
+        assert_eq!(after.objects, vec![handle]);
+    }
+
+    #[test]
+    fn registration_sequence_stale_and_duplicate_original_contracts() {
+        let mut world = new(WorldConfig);
+        let first = construct_object(
+            &mut world,
+            ObjectDraft {
+                original_id: Some(OriginalObjectId(7)),
+            },
+        )
+        .expect("first");
+        let second = construct_object(
+            &mut world,
+            ObjectDraft {
+                original_id: Some(OriginalObjectId(8)),
+            },
+        )
+        .expect("second");
+        register_object(&mut world, first).expect("register first");
+        register_object(&mut world, second).expect("register second");
+        assert_eq!(registration_sequence(&world, first), Ok(Some(0)));
+        assert_eq!(registration_sequence(&world, second), Ok(Some(1)));
+
+        request_delete(&mut world, first).expect("delete");
+        assert_eq!(
+            register_object(&mut world, first),
+            Err(WorldError::StaleHandle)
+        );
+        let recycled = ObjectHandle {
+            generation: first.generation,
+            slot: first.slot,
+        };
+        assert_eq!(
+            register_object(&mut world, recycled),
+            Err(WorldError::StaleHandle)
+        );
+
+        let duplicate = construct_object(
+            &mut world,
+            ObjectDraft {
+                original_id: Some(OriginalObjectId(8)),
+            },
+        )
+        .expect("duplicate");
+        assert_eq!(
+            register_object(&mut world, duplicate),
+            Err(WorldError::DuplicateOriginalObjectId(OriginalObjectId(8)))
+        );
+    }
+
+    #[test]
+    fn identity_metadata_keeps_original_mirror_and_owner_distinct() {
+        let mut world = new(WorldConfig);
+        let handle = construct_object(
+            &mut world,
+            ObjectDraft {
+                original_id: Some(OriginalObjectId(10)),
+            },
+        )
+        .expect("object");
+        set_mirror_original(&mut world, handle, Some(OriginalObjectId(20))).expect("mirror");
+        set_owner(&mut world, handle, Some(OwnerId(3))).expect("owner");
+        assert_eq!(
+            identity_metadata(&world, handle),
+            Ok(IdentityMetadata {
+                original_id: Some(OriginalObjectId(10)),
+                mirror_id: Some(OriginalObjectId(20)),
+                owner_id: Some(OwnerId(3))
+            })
+        );
+    }
+
+    #[test]
+    fn command_fifo_and_deferred_delete_during_calculation() {
+        let mut world = new(WorldConfig);
+        let first = construct_object(&mut world, ObjectDraft { original_id: None }).expect("first");
+        let second =
+            construct_object(&mut world, ObjectDraft { original_id: None }).expect("second");
+        register_object(&mut world, first).expect("register first");
+        register_object(&mut world, second).expect("register second");
+        enqueue(
+            &mut world,
+            WorldCommand {
+                sequence: 99,
+                target: Some(first),
+            },
+        )
+        .expect("enqueue first");
+        enqueue(
+            &mut world,
+            WorldCommand {
+                sequence: 99,
+                target: Some(second),
+            },
+        )
+        .expect("enqueue second");
+        enqueue(
+            &mut world,
+            WorldCommand {
+                sequence: 99,
+                target: Some(first),
+            },
+        )
+        .expect("enqueue first again");
+
+        let snapshot = step_with_handler(&mut world, &InputSnapshot, |world, command| {
+            if command.target == Some(first) {
+                request_delete(world, first)?;
+                request_delete(world, first)?;
+            }
+            Ok(())
+        })
+        .expect("step");
+
+        assert_eq!(
+            snapshot.events,
+            vec![
+                WorldEvent {
+                    sequence: 0,
+                    target: Some(first)
+                },
+                WorldEvent {
+                    sequence: 1,
+                    target: Some(second)
+                }
+            ]
+        );
+        assert_eq!(
+            request_delete(&mut world, first),
+            Err(WorldError::StaleHandle)
+        );
+        assert_eq!(
+            step(&mut world, &InputSnapshot).expect("step").objects,
+            vec![second]
+        );
+    }
+
+    #[test]
+    fn snapshot_hash_determinism_and_immutability() {
+        let mut left = new(WorldConfig);
+        let mut right = new(WorldConfig);
+        for world in [&mut left, &mut right] {
+            let handle = construct_object(
+                world,
+                ObjectDraft {
+                    original_id: Some(OriginalObjectId(1)),
+                },
+            )
+            .expect("object");
+            register_object(world, handle).expect("register");
+        }
+        let snapshot = step(&mut left, &InputSnapshot).expect("snapshot");
+        let clone = snapshot.clone();
+        let extra = construct_object(&mut left, ObjectDraft { original_id: None }).expect("extra");
+        register_object(&mut left, extra).expect("register extra");
+
+        assert_eq!(snapshot, clone);
+        assert_eq!(
+            clone.hash,
+            step(&mut right, &InputSnapshot).expect("right").hash
+        );
+    }
+
+    #[test]
+    fn fixed_step_pause_and_long_determinism_are_stable() {
+        let config = FixedStepConfig { step_millis: 20 };
+        let mut clock = fixed_step_clock(config).expect("clock");
+        collect_platform_events(&mut clock);
+        set_paused(&mut clock, true);
+        assert_eq!(advance_fixed_step(&mut clock, config, 100), Ok(0));
+        collect_platform_events(&mut clock);
+        assert_eq!(fixed_step_tick(&clock), Tick(0));
+        assert_eq!(platform_event_collections(&clock), 2);
+
+        set_paused(&mut clock, false);
+        assert_eq!(advance_fixed_step(&mut clock, config, 45), Ok(2));
+        assert_eq!(fixed_step_tick(&clock), Tick(2));
+
+        let mut first = new(WorldConfig);
+        let mut second = new(WorldConfig);
+        let mut first_hashes = Vec::new();
+        let mut second_hashes = Vec::new();
+        for _ in 0..10_000 {
+            first_hashes.push(step(&mut first, &InputSnapshot).expect("first").hash);
+            second_hashes.push(step(&mut second, &InputSnapshot).expect("second").hash);
+        }
+        assert_eq!(first_hashes, second_hashes);
+    }
+
+    #[test]
+    fn render_disabled_does_not_change_hash_end_callbacks_and_shutdown_order() {
+        let callbacks = vec![
+            WorldEvent {
+                sequence: 3,
+                target: None,
+            },
+            WorldEvent {
+                sequence: 1,
+                target: None,
+            },
+            WorldEvent {
+                sequence: 2,
+                target: None,
+            },
+        ];
+        assert_eq!(end_frame_callback_order(callbacks), vec![1, 2, 3]);
+
+        let mut rendered = new(WorldConfig);
+        let mut headless = rendered.clone();
+        assert_eq!(
+            step(&mut rendered, &InputSnapshot).expect("rendered").hash,
+            step(&mut headless, &InputSnapshot).expect("headless").hash
+        );
+
+        let handle =
+            construct_object(&mut rendered, ObjectDraft { original_id: None }).expect("object");
+        register_object(&mut rendered, handle).expect("register");
+        assert_eq!(
+            shutdown(rendered),
+            ShutdownReport {
+                released_objects: vec![handle],
+                managers_released: true
+            }
+        );
+    }
+
+    #[test]
+    fn generated_command_delete_sequences_preserve_registry_invariants() {
+        for seed in 0_u32..64 {
+            let mut world = new(WorldConfig);
+            let mut handles = Vec::new();
+            for index in 0..8 {
+                let handle = construct_object(
+                    &mut world,
+                    ObjectDraft {
+                        original_id: Some(OriginalObjectId(seed * 100 + index)),
+                    },
+                )
+                .expect("object");
+                register_object(&mut world, handle).expect("register");
+                handles.push(handle);
+            }
+            for (index, handle) in handles.iter().copied().enumerate() {
+                if (seed as usize + index) % 3 == 0 {
+                    request_delete(&mut world, handle).expect("delete");
+                } else {
+                    enqueue(
+                        &mut world,
+                        WorldCommand {
+                            sequence: 0,
+                            target: Some(handle),
+                        },
+                    )
+                    .expect("enqueue");
+                }
+            }
+            let snapshot = step(&mut world, &InputSnapshot).expect("step");
+            for handle in snapshot.objects {
+                assert!(registration_sequence(&world, handle)
+                    .expect("sequence")
+                    .is_some());
+            }
+        }
+    }
+}