diff --git a/src/buddy.c b/src/buddy.c
index 84c2fb4f..98bf0e37 100644
--- a/src/buddy.c
+++ b/src/buddy.c
@@ -173,6 +173,8 @@ struct buddy_block *buddy_alloc(struct buddy_ctx *ctx, u64 size)
 
     /* TODO: Minimum block size */
 
+    /* TODO: Faster MSB calculation */
+
     u64 desired_block_size = 1;
     u64 desired_level_tier = 0;
     while (desired_block_size < size && desired_level_tier < 64) {
diff --git a/src/buddy.h b/src/buddy.h
index 6294435f..0b79771e 100644
--- a/src/buddy.h
+++ b/src/buddy.h
@@ -16,7 +16,7 @@ struct buddy_block {
 
 struct buddy_level {
     struct buddy_ctx *ctx;
-    b32 backed;     /* Is this level backed by memory in the ctx arena */
+    b32 backed;  /* Signals whether this level is backed by memory in the ctx arena */
     u32 tier;
     u64 size;
     struct buddy_block *first_unused_block;
diff --git a/src/host.c b/src/host.c
index 24715db7..e9895256 100644
--- a/src/host.c
+++ b/src/host.c
@@ -661,7 +661,7 @@ void host_update(struct host *host)
             struct sock_address address = packet->address;
             struct bitbuff bb = bitbuff_from_string(packet->data);
             struct bitbuff_reader br = br_from_bitbuff(&bb);
-            u32 magic = br_read_ubits(&br, 32);
+            u32 magic = br_read_ubits(&br, 32);  /* TODO: implicitly encode magic into crc32 */
             if (magic == PACKET_MAGIC) {
                 /* TODO: Combine kind byte with flags byte */
                 struct host_channel *channel = host_channel_from_address(host, address);
@@ -864,7 +864,7 @@ void host_update(struct host *host)
                         struct host_snd_packet *packet = host_channel_snd_packet_alloc(channel, false);
                         struct bitbuff bb = bitbuff_from_string(STRING_FROM_ARRAY(packet->data));
                         struct bitbuff_writer bw = bw_from_bitbuff(&bb);
-                        bw_write_ubits(&bw, PACKET_MAGIC, 32);
+                        bw_write_ubits(&bw, PACKET_MAGIC, 32);  /* TODO: implicitly encode magic into crc32 */
                         bw_write_ibits(&bw, HOST_PACKET_KIND_TRY_CONNECT, 8);
                         bw_write_ubits(&bw, packet_flags, 8);
                         bw_write_uv(&bw, channel->our_acked_seq);
@@ -877,7 +877,7 @@ void host_update(struct host *host)
                         struct host_snd_packet *packet = host_channel_snd_packet_alloc(channel, false);
                         struct bitbuff bb = bitbuff_from_string(STRING_FROM_ARRAY(packet->data));
                             struct bitbuff_writer bw = bw_from_bitbuff(&bb);
-                        bw_write_ubits(&bw, PACKET_MAGIC, 32);
+                        bw_write_ubits(&bw, PACKET_MAGIC, 32);  /* TODO: implicitly encode magic into crc32 */
                         bw_write_ibits(&bw, HOST_PACKET_KIND_CONNECT_SUCCESS, 8);
                         bw_write_ubits(&bw, packet_flags, 8);
                         bw_write_uv(&bw, channel->our_acked_seq);
@@ -890,7 +890,7 @@ void host_update(struct host *host)
                         struct host_snd_packet *packet = host_channel_snd_packet_alloc(channel, false);
                         struct bitbuff bb = bitbuff_from_string(STRING_FROM_ARRAY(packet->data));
                             struct bitbuff_writer bw = bw_from_bitbuff(&bb);
-                        bw_write_ubits(&bw, PACKET_MAGIC, 32);
+                        bw_write_ubits(&bw, PACKET_MAGIC, 32);  /* TODO: implicitly encode magic into crc32 */
                         bw_write_ibits(&bw, HOST_PACKET_KIND_DISCONNECT, 8);
                         bw_write_ubits(&bw, packet_flags, 8);
                         bw_write_uv(&bw, channel->our_acked_seq);
@@ -922,7 +922,7 @@ void host_update(struct host *host)
                             struct host_snd_packet *packet = host_channel_snd_packet_alloc(channel, is_reliable);
                             struct bitbuff bb = bitbuff_from_string(STRING_FROM_ARRAY(packet->data));
                             struct bitbuff_writer bw = bw_from_bitbuff(&bb);
-                            bw_write_ubits(&bw, PACKET_MAGIC, 32);
+                            bw_write_ubits(&bw, PACKET_MAGIC, 32);  /* TODO: implicitly encode magic into crc32 */
                             bw_write_ibits(&bw, HOST_PACKET_KIND_MSG_CHUNK, 8);
                             bw_write_ubits(&bw, packet_flags, 8);
                             bw_write_uv(&bw, channel->our_acked_seq);
diff --git a/src/phys.c b/src/phys.c
index db19d9ef..38f9af9a 100644
--- a/src/phys.c
+++ b/src/phys.c
@@ -53,7 +53,7 @@ struct phys_collision_data_array phys_create_and_update_contacts(struct arena *a
 
     for (u64 check0_index = 0; check0_index < ss->num_ents_reserved; ++check0_index) {
         struct sim_ent *check0 = &ss->ents[check0_index];
-        if (!sim_ent_is_valid_and_active(check0)) continue;
+        if (!sim_ent_should_simulate(check0)) continue;
         if (!(sim_ent_has_prop(check0, SIM_ENT_PROP_PHYSICAL_DYNAMIC) || sim_ent_has_prop(check0, SIM_ENT_PROP_PHYSICAL_KINEMATIC))) continue;
         if (check0->local_collider.count <= 0) continue;
 
@@ -66,7 +66,7 @@ struct phys_collision_data_array phys_create_and_update_contacts(struct arena *a
         while ((space_entry = space_iter_next(&iter))) {
             struct sim_ent *check1 = sim_ent_from_id(ss, space_entry->ent);
             if (check1 == check0) continue;
-            if (!sim_ent_is_valid_and_active(check1)) continue;
+            if (!sim_ent_should_simulate(check1)) continue;
             if (!(sim_ent_has_prop(check1, SIM_ENT_PROP_PHYSICAL_DYNAMIC) || sim_ent_has_prop(check1, SIM_ENT_PROP_PHYSICAL_KINEMATIC))) continue;
             if (check1->local_collider.count <= 0) continue;
 
@@ -274,7 +274,7 @@ void phys_prepare_contacts(struct phys_step_ctx *ctx, u64 phys_iteration)
 
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *constraint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(constraint_ent)) continue;
+        if (!sim_ent_should_simulate(constraint_ent)) continue;
         if (!sim_ent_has_prop(constraint_ent, SIM_ENT_PROP_CONTACT_CONSTRAINT)) continue;
 
         struct phys_contact_constraint *constraint = &constraint_ent->contact_constraint_data;
@@ -282,7 +282,7 @@ void phys_prepare_contacts(struct phys_step_ctx *ctx, u64 phys_iteration)
         u32 num_points = constraint->num_points;
         struct sim_ent *e0 = sim_ent_from_id(ss, constraint->e0);
         struct sim_ent *e1 = sim_ent_from_id(ss, constraint->e1);
-        if (constraint->last_phys_iteration >= phys_iteration && num_points > 0 && sim_ent_is_valid_and_active(e0) && sim_ent_is_valid_and_active(e1)) {
+        if (constraint->last_phys_iteration >= phys_iteration && num_points > 0 && sim_ent_should_simulate(e0) && sim_ent_should_simulate(e1)) {
             struct v2 normal = constraint->normal;
             struct v2 tangent = v2_perp(normal);
 
@@ -392,7 +392,7 @@ void phys_warm_start_contacts(struct phys_step_ctx *ctx)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *constraint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(constraint_ent)) continue;
+        if (!sim_ent_should_simulate(constraint_ent)) continue;
         if (!sim_ent_has_prop(constraint_ent, SIM_ENT_PROP_CONTACT_CONSTRAINT)) continue;
 
         struct phys_contact_constraint *constraint = &constraint_ent->contact_constraint_data;
@@ -401,7 +401,7 @@ void phys_warm_start_contacts(struct phys_step_ctx *ctx)
         struct sim_ent *e0 = sim_ent_from_id(ss, constraint->e0);
         struct sim_ent *e1 = sim_ent_from_id(ss, constraint->e1);
 
-        if (num_points > 0 && sim_ent_is_valid_and_active(e0) && sim_ent_is_valid_and_active(e1) && !constraint->skip_solve) {
+        if (num_points > 0 && sim_ent_should_simulate(e0) && sim_ent_should_simulate(e1) && !constraint->skip_solve) {
             struct xform e0_xf = sim_ent_get_xform(e0);
             struct xform e1_xf = sim_ent_get_xform(e1);
 
@@ -447,7 +447,7 @@ void phys_solve_contacts(struct phys_step_ctx *ctx, f32 dt, b32 apply_bias)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *constraint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(constraint_ent)) continue;
+        if (!sim_ent_should_simulate(constraint_ent)) continue;
         if (!sim_ent_has_prop(constraint_ent, SIM_ENT_PROP_CONTACT_CONSTRAINT)) continue;
 
         struct phys_contact_constraint *constraint = &constraint_ent->contact_constraint_data;
@@ -461,7 +461,7 @@ void phys_solve_contacts(struct phys_step_ctx *ctx, f32 dt, b32 apply_bias)
         f32 w1 = e1->angular_velocity;
 
         u32 num_points = constraint->num_points;
-        if (num_points > 0 && sim_ent_is_valid_and_active(e0) && sim_ent_is_valid_and_active(e1) && !constraint->skip_solve) {
+        if (num_points > 0 && sim_ent_should_simulate(e0) && sim_ent_should_simulate(e1) && !constraint->skip_solve) {
             struct xform e0_xf = sim_ent_get_xform(e0);
             struct xform e1_xf = sim_ent_get_xform(e1);
 
@@ -578,7 +578,7 @@ void phys_prepare_motor_joints(struct phys_step_ctx *ctx)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *joint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(joint_ent)) continue;
+        if (!sim_ent_should_simulate(joint_ent)) continue;
         if (!sim_ent_has_prop(joint_ent, SIM_ENT_PROP_MOTOR_JOINT)) continue;
 
         struct phys_motor_joint *joint = &joint_ent->motor_joint_data;
@@ -586,7 +586,7 @@ void phys_prepare_motor_joints(struct phys_step_ctx *ctx)
         struct sim_ent *e0 = sim_ent_from_id(ss, joint->e0);
         struct sim_ent *e1 = sim_ent_from_id(ss, joint->e1);
 
-        if (sim_ent_is_valid_and_active(e0) && sim_ent_is_valid_and_active(e1)) {
+        if (sim_ent_should_simulate(e0) && sim_ent_should_simulate(e1)) {
             struct xform e0_xf = sim_ent_get_xform(e0);
             struct xform e1_xf = sim_ent_get_xform(e1);
 
@@ -642,7 +642,7 @@ void phys_warm_start_motor_joints(struct phys_step_ctx *ctx)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *joint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(joint_ent)) continue;
+        if (!sim_ent_should_simulate(joint_ent)) continue;
         if (!sim_ent_has_prop(joint_ent, SIM_ENT_PROP_MOTOR_JOINT)) continue;
 
         struct phys_motor_joint *joint = &joint_ent->motor_joint_data;
@@ -674,7 +674,7 @@ void phys_solve_motor_joints(struct phys_step_ctx *ctx, f32 dt)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *joint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(joint_ent)) continue;
+        if (!sim_ent_should_simulate(joint_ent)) continue;
         if (!sim_ent_has_prop(joint_ent, SIM_ENT_PROP_MOTOR_JOINT)) continue;
 
         struct phys_motor_joint *joint = &joint_ent->motor_joint_data;
@@ -767,12 +767,12 @@ void phys_prepare_mouse_joints(struct phys_step_ctx *ctx)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *joint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(joint_ent)) continue;
+        if (!sim_ent_should_simulate(joint_ent)) continue;
         if (!sim_ent_has_prop(joint_ent, SIM_ENT_PROP_MOUSE_JOINT)) continue;
 
         struct phys_mouse_joint *joint = &joint_ent->mouse_joint_data;
         struct sim_ent *ent = sim_ent_from_id(ss, joint->target);
-        if (sim_ent_is_valid_and_active(ent)) {
+        if (sim_ent_should_simulate(ent)) {
             struct xform xf = sim_ent_get_xform(ent);
 
             /* TODO: Cache this */
@@ -814,12 +814,12 @@ void phys_warm_start_mouse_joints(struct phys_step_ctx *ctx)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *joint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(joint_ent)) continue;
+        if (!sim_ent_should_simulate(joint_ent)) continue;
         if (!sim_ent_has_prop(joint_ent, SIM_ENT_PROP_MOUSE_JOINT)) continue;
 
         struct phys_mouse_joint *joint = &joint_ent->mouse_joint_data;
         struct sim_ent *ent = sim_ent_from_id(ss, joint->target);
-        if (sim_ent_is_valid_and_active(ent)) {
+        if (sim_ent_should_simulate(ent)) {
             f32 inv_m = joint->inv_m;
             f32 inv_i = joint->inv_i;
             struct xform xf = sim_ent_get_xform(ent);
@@ -836,12 +836,12 @@ void phys_solve_mouse_joints(struct phys_step_ctx *ctx, f32 dt)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *joint_ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(joint_ent)) continue;
+        if (!sim_ent_should_simulate(joint_ent)) continue;
         if (!sim_ent_has_prop(joint_ent, SIM_ENT_PROP_MOUSE_JOINT)) continue;
 
         struct phys_mouse_joint *joint = &joint_ent->mouse_joint_data;
         struct sim_ent *ent = sim_ent_from_id(ss, joint->target);
-        if (sim_ent_is_valid_and_active(ent)) {
+        if (sim_ent_should_simulate(ent)) {
             struct v2 v = ent->linear_velocity;
             f32 w = ent->angular_velocity;
 
@@ -923,7 +923,7 @@ void phys_integrate_forces(struct phys_step_ctx *ctx, f32 dt)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(ent)) continue;
+        if (!sim_ent_should_simulate(ent)) continue;
 
         b32 is_dynamic = sim_ent_has_prop(ent, SIM_ENT_PROP_PHYSICAL_DYNAMIC);
         b32 is_kinematic = sim_ent_has_prop(ent, SIM_ENT_PROP_PHYSICAL_KINEMATIC);
@@ -965,7 +965,7 @@ void phys_integrate_velocities(struct phys_step_ctx *ctx, f32 dt)
     struct sim_snapshot *ss = ctx->sim_step_ctx->world;
     for (u64 sim_ent_index = 0; sim_ent_index < ss->num_ents_reserved; ++sim_ent_index) {
         struct sim_ent *ent = &ss->ents[sim_ent_index];
-        if (!sim_ent_is_valid_and_active(ent)) continue;
+        if (!sim_ent_should_simulate(ent)) continue;
         if (!sim_ent_has_prop(ent, SIM_ENT_PROP_PHYSICAL_DYNAMIC) && !sim_ent_has_prop(ent, SIM_ENT_PROP_PHYSICAL_KINEMATIC)) continue;
 
         struct xform xf = get_derived_xform(ent, dt);
@@ -986,7 +986,7 @@ f32 phys_determine_earliest_toi_for_bullets(struct phys_step_ctx *ctx, f32 step_
 
     for (u64 e0_index = 0; e0_index < ss->num_ents_reserved; ++e0_index) {
         struct sim_ent *e0 = &ss->ents[e0_index];
-        if (!sim_ent_is_valid_and_active(e0)) continue;
+        if (!sim_ent_should_simulate(e0)) continue;
         if (!(sim_ent_has_prop(e0, SIM_ENT_PROP_PHYSICAL_DYNAMIC) || sim_ent_has_prop(e0, SIM_ENT_PROP_PHYSICAL_KINEMATIC))) continue;
         if (!sim_ent_has_prop(e0, SIM_ENT_PROP_BULLET)) continue;
         if (e0->local_collider.count <= 0) continue;
@@ -1005,7 +1005,7 @@ f32 phys_determine_earliest_toi_for_bullets(struct phys_step_ctx *ctx, f32 step_
         while ((entry = space_iter_next(&iter))) {
             struct sim_ent *e1 = sim_ent_from_id(ss, entry->ent);
             if (e1 == e0) continue;
-            if (!sim_ent_is_valid_and_active(e1)) continue;
+            if (!sim_ent_should_simulate(e1)) continue;
             if (!(sim_ent_has_prop(e1, SIM_ENT_PROP_PHYSICAL_DYNAMIC) || sim_ent_has_prop(e1, SIM_ENT_PROP_PHYSICAL_KINEMATIC))) continue;
             if (e1->local_collider.count <= 0) continue;
 
diff --git a/src/sim.c b/src/sim.c
index 269131d1..38a09438 100644
--- a/src/sim.c
+++ b/src/sim.c
@@ -10,17 +10,26 @@
  *
  * Client store -> clients -> snapshots -> ents
  *
- * A client store holds clients, which can be retrieved by client handle or by a host channel id (if one is set).
+ * A client store holds clients, which can be retrieved by client handle or by a host channel id (if one is assigned).
  *
- * A client holds snapshots, which can be retrieved by tick (64 bit unsigned int).
+ * A client holds snapshots, which can be retrieved by tick number.
  *   - The snapshots stored in clients & the contents of those snapshots are determined from data transmitted by the client.
- *   - Different kinds of clients will transmit different subsets of snapshot data (e.g. a master client will transmit most/all ent state, while slave clients may just transmit 1 or more cmds)
+ *   - Different kinds of clients will transmit different subsets of snapshot data (e.g. a master client will transmit most ent state, while slave clients may just transmit 1 or more command ents)
  *   - A client will never hold more than one snapshot for the same tick (e.g. a client will never have 2 snapshots at tick 5)
  *
- * A snapshot holds the ent tree for a particular tick, in which ents can be retrieved by ent handle.
+ * A snapshot holds the ent tree for a particular tick, in which ents can be retrieved by ent id.
  *   - A tick is the quantized time step that all clients implicitly conform to.
  *
  * An ent is the smallest unit of simulation state.
+ *   - It is assigned a 128 bit unique identifer generated at allocation time.
+ *       - This id is used to refer to other ents in the tree and to sync ents accross clients.
+ *       - This id is usually random, but can be deterministic under certain conditions.
+ *           - For example, instead of storing a contact constraint lookup table, contact constraints are
+ *             retrieved by searching for the ent with the id resulting from combining the ent ids of the
+ *             two contacting entities (plus a unique 'basis' ent id used for all contact constraints).
+ *   - The ent also implicitly has a 32 bit index, which is just its offset from the start of the entity array in the local snapshot.
+ *       - Since index is based on offset which remains stable regardless of snapshot memory location, it
+ *         is used when working in contexts where id is irrelevant.
  */
 
 #define CLIENT_LOOKUP_BINS 127
@@ -590,7 +599,7 @@ struct sim_snapshot *sim_snapshot_alloc_from_lerp(struct sim_client *client, str
  * ========================== */
 
 /* Syncs entity data between snapshots */
-void sim_snapshot_sync(struct sim_snapshot *local_ss, struct sim_snapshot *remote_ss)
+void sim_snapshot_sync_ents(struct sim_snapshot *local_ss, struct sim_snapshot *remote_ss)
 {
     __prof;
 
diff --git a/src/sim.h b/src/sim.h
index a48d1c58..ea94208f 100644
--- a/src/sim.h
+++ b/src/sim.h
@@ -208,7 +208,7 @@ struct sim_snapshot *sim_snapshot_from_closest_tick_gte(struct sim_client *clien
 struct sim_snapshot *sim_snapshot_alloc_from_lerp(struct sim_client *client, struct sim_snapshot *ss0, struct sim_snapshot *ss1, f64 blend);
 
 /* Sync */
-void sim_snapshot_sync(struct sim_snapshot *local_ss, struct sim_snapshot *remote_ss);
+void sim_snapshot_sync_ents(struct sim_snapshot *local_ss, struct sim_snapshot *remote_ss);
 
 /* Encode / decode */
 void sim_snapshot_encode(struct bitbuff_writer *bw, struct sim_client *receiver, struct sim_snapshot *ss0, struct sim_snapshot *ss1);
diff --git a/src/sim_ent.c b/src/sim_ent.c
index 883166a6..17698b98 100644
--- a/src/sim_ent.c
+++ b/src/sim_ent.c
@@ -151,7 +151,7 @@ void sim_ent_release_all_with_prop(struct sim_snapshot *ss, enum sim_ent_prop pr
      * child entities will be released along with parent anyway) */
     for (u64 i = 0; i < ents_to_release_count; ++i) {
         struct sim_ent *ent = ents_to_release[i];
-        if (ent->is_top && !ent->is_root && ent->valid) {
+        if (ent->valid && !ent->is_root && !sim_ent_has_prop(ent, SIM_ENT_PROP_CMD_CONTROL) && !sim_ent_has_prop(ent, SIM_ENT_PROP_CLIENT)) {
             sim_ent_release(ent);
         }
     }
diff --git a/src/sim_step.c b/src/sim_step.c
index e29ec174..a73ac9cd 100644
--- a/src/sim_step.c
+++ b/src/sim_step.c
@@ -342,6 +342,7 @@ void sim_step(struct sim_step_ctx *ctx)
     struct sim_client *user_input_client = ctx->user_input_client;
     struct sim_client *publish_client = ctx->publish_client;
     struct sim_client *master_client = ctx->master_client;
+    (UNUSED)master_client;
 
     i64 sim_dt_ns = ctx->sim_dt_ns;
 
@@ -361,6 +362,10 @@ void sim_step(struct sim_step_ctx *ctx)
      * Sync remote ents
      * ========================== */
 
+    if (user_input_client->valid) {
+        user_input_client->ent_id = world->local_client_ent;
+    }
+
     {
         for (u64 client_index = 0; client_index < client_store->num_clients_reserved; ++client_index) {
             struct sim_client *client = &client_store->clients[client_index];
@@ -385,15 +390,9 @@ void sim_step(struct sim_step_ctx *ctx)
                 }
 
                 /* Sync ents from client */
-                {
-                    struct sim_snapshot *src_ss = sim_snapshot_from_tick(client, world->tick);
-                    if (src_ss->valid) {
-                        sim_snapshot_sync(world, src_ss);
-                        if (client == master_client) {
-                            world_client->ent_id = src_ss->local_client_ent;
-                            world->local_client_ent = src_ss->local_client_ent;
-                        }
-                    }
+                struct sim_snapshot *src_ss = sim_snapshot_from_tick(client, world->tick);
+                if (src_ss->valid) {
+                    sim_snapshot_sync_ents(world, src_ss);
                 }
             }
         }
@@ -1264,8 +1263,13 @@ void sim_step(struct sim_step_ctx *ctx)
         if (!pub_world->valid) {
             struct sim_snapshot *prev_pub_world = sim_snapshot_from_tick(publish_client, publish_client->last_tick);
             pub_world = sim_snapshot_alloc(publish_client, prev_pub_world, world->tick);
+            /* Sync */
+            sim_snapshot_sync_ents(pub_world, world);
+            pub_world->sim_dt_ns = world->sim_dt_ns;
+            pub_world->sim_time_ns = world->sim_time_ns;
+            pub_world->continuity_gen = world->continuity_gen;
+            pub_world->phys_iteration = world->phys_iteration;
             pub_world->local_client_ent = world->local_client_ent;
-            sim_snapshot_sync(pub_world, world);
         }
     }
 
diff --git a/src/user.c b/src/user.c
index 4410da04..a43749ca 100644
--- a/src/user.c
+++ b/src/user.c
@@ -1982,7 +1982,7 @@ INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(user_local_sim_thread_entry_point, arg)
                                 struct sim_snapshot *base_ss = sim_snapshot_from_tick(client, base_tick);
                                 if (base_ss->tick == base_tick) {
                                     if (is_master) {
-                                        /* Decode incoming slave client snapshots */
+                                        /* Queue incoming slave client snapshot for decoding */
                                         b32 should_decode = tick == client->highest_received_tick + 1 || client->highest_received_tick == 0;
                                         if (should_decode) {
                                             struct sim_ss_decode_node *node = arena_push_zero(scratch.arena, struct sim_ss_decode_node);
@@ -2000,8 +2000,8 @@ INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(user_local_sim_thread_entry_point, arg)
                                                 client->highest_received_tick = tick;
                                             }
                                         }
-                                    } else {
-                                        /* Decode incoming master client snapshots (only the newest one) */
+                                    } else if (client == master_client) {
+                                        /* Decode incoming master client snapshots for decoding (only the newest one) */
                                         b32 should_decode = tick > client->highest_received_tick;
                                         if (should_decode) {
                                             struct sim_ss_decode_node *node = queue.first ? queue.first : arena_push_zero(scratch.arena, struct sim_ss_decode_node);
@@ -2044,9 +2044,12 @@ INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(user_local_sim_thread_entry_point, arg)
                 /* Alloc & decode snapshot */
                 struct sim_snapshot *ss = sim_snapshot_alloc(client, base_ss, tick);
                 sim_snapshot_decode(&br, ss);
+
+                /* Assume all incoming ents want to be sync srcs */
                 for (u64 i = 0; i < ss->num_ents_reserved; ++i) {
                     struct sim_ent *ent = &ss->ents[i];
                     if (ent->valid && sim_ent_has_prop(ent, SIM_ENT_PROP_SYNC_DST)) {
+
                         sim_ent_disable_prop(ent, SIM_ENT_PROP_SYNC_DST);
                         sim_ent_enable_prop(ent, SIM_ENT_PROP_SYNC_SRC);
                     }
@@ -2070,7 +2073,7 @@ INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(user_local_sim_thread_entry_point, arg)
         /* Create user input */
         {
             struct sim_snapshot *prev_user_input_ss = sim_snapshot_from_tick(user_input_client, user_input_client->last_tick);
-            struct sim_snapshot *user_input_ss = sim_snapshot_alloc(user_input_client, prev_user_input_ss, local_client->last_tick + ahead + 1);
+            struct sim_snapshot *user_input_ss = sim_snapshot_alloc(user_input_client, prev_user_input_ss, local_client->last_tick + 1);
             struct sim_ent *user_input_root = sim_ent_from_id(user_input_ss, SIM_ENT_ROOT_ID);
             /* Find / create local control cmd ent */
             struct sim_ent *control_cmd_ent = sim_ent_find_first_match_one(user_input_ss, SIM_ENT_PROP_CMD_CONTROL);
@@ -2138,7 +2141,7 @@ INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(user_local_sim_thread_entry_point, arg)
         }
 
         /* Release unneeded user input snapshots */
-        sim_snapshot_release_ticks_in_range(user_input_client, 0, local_client->last_tick - 1);
+        sim_snapshot_release_ticks_in_range(user_input_client, 0, local_client->first_tick - 1);
 
 
 
@@ -2237,7 +2240,7 @@ INTERNAL SYS_THREAD_ENTRY_POINT_FUNC_DEF(user_local_sim_thread_entry_point, arg)
                 struct bitbuff_writer msg_bw = bw_from_bitbuff(&msg_writer_bb);
 
                 bw_write_uv(&msg_bw, client->highest_received_tick);     /* ack */
-                bw_write_uv(&msg_bw, client->ack);                      /* double ack */
+                bw_write_uv(&msg_bw, client->ack);                       /* double ack */
 
                 struct sim_snapshot *base_ss = sim_snapshot_from_tick(publish_client, client->ack);
                 struct sim_snapshot *publish_ss;