diff --git a/src/arena.c b/src/arena.c
index 16ebbc11..e9732122 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -51,7 +51,7 @@ void arena_release(struct arena *arena)
 }
 
 /* NOTE: Application will exit if arena fails to commit memory */
-void *_arena_push_bytes(struct arena *arena, u64 size, u64 align)
+void *arena_push_bytes(struct arena *arena, u64 size, u64 align)
 {
     ASSERT(align > 0);
     ASSERT(!arena->readonly);
@@ -101,7 +101,7 @@ void arena_copy_replace(struct arena *dest, struct arena *src)
     arena_reset(dest);
     u64 data_size = src->pos;
     u8 *data_src = src->base;
-    u8 *data_dest = _arena_push_bytes(dest, data_size, 1);
+    u8 *data_dest = arena_push_bytes(dest, data_size, 1);
     MEMCPY(data_dest, data_src, data_size);
 }
 
diff --git a/src/arena.h b/src/arena.h
index 3911761d..b8bf2e53 100644
--- a/src/arena.h
+++ b/src/arena.h
@@ -3,21 +3,19 @@
 
 #include "memory.h"
 
-#define arena_push(a, type) ((type *)_arena_push_bytes((a), sizeof(type), alignof(type)))
-#define arena_push_zero(a, type) ((type *)_arena_push_bytes_zero((a), sizeof(type), alignof(type)))
+#define arena_push(a, type) ((type *)arena_push_bytes((a), sizeof(type), alignof(type)))
+#define arena_push_zero(a, type) ((type *)arena_push_bytes_zero((a), sizeof(type), alignof(type)))
 
-#define arena_push_array(a, type, n) ((type *)_arena_push_bytes((a), (sizeof(type) * (n)), alignof(type)))
-#define arena_push_array_zero(a, type, n) ((type *)_arena_push_bytes_zero((a), (sizeof(type) * (n)), alignof(type)))
+#define arena_push_array(a, type, n) ((type *)arena_push_bytes((a), (sizeof(type) * (n)), alignof(type)))
+#define arena_push_array_zero(a, type, n) ((type *)arena_push_bytes_zero((a), (sizeof(type) * (n)), alignof(type)))
 
-#define arena_pop(a, type, dest) _arena_pop_struct((a), sizeof(type), dest)
-#define arena_pop_array(a, type, n, dest) _arena_pop_struct((a), sizeof(type) * (n), dest)
+#define arena_pop(a, type, dest) arena_pop_struct((a), sizeof(type), dest)
+#define arena_pop_array(a, type, n, dest) arena_pop_struct((a), sizeof(type) * (n), dest)
 
 /* Returns a pointer to where the next allocation would be (at alignment of type).
  * Equivalent arena_push but without actually allocating anything. */
 #define arena_dry_push(a, type) (type *)(_arena_dry_push((a), alignof(type)))
 
-#define arena_align(a, align) (void *)(_arena_align((a), align))
-
 struct temp_arena {
     struct arena *arena;
     u64 start_pos;
@@ -29,15 +27,15 @@ struct temp_arena {
 
 struct arena arena_alloc(u64 reserve);
 void arena_release(struct arena *arena);
-void *_arena_push_bytes(struct arena *arena, u64 size, u64 align);
+void *arena_push_bytes(struct arena *arena, u64 size, u64 align);
 void arena_copy_replace(struct arena *dest, struct arena *src);
 void arena_decommit_unused_blocks(struct arena *arena);
 void arena_set_readonly(struct arena *arena);
 void arena_set_readwrite(struct arena *arena);
 
-INLINE void *_arena_push_bytes_zero(struct arena *arena, u64 size, u64 align)
+INLINE void *arena_push_bytes_zero(struct arena *arena, u64 size, u64 align)
 {
-    void *p = _arena_push_bytes(arena, size, align);
+    void *p = arena_push_bytes(arena, size, align);
     MEMZERO(p, size);
     return p;
 }
@@ -51,7 +49,7 @@ INLINE void arena_pop_to(struct arena *arena, u64 pos)
     arena->pos = pos;
 }
 
-INLINE void _arena_pop_struct(struct arena *arena, u64 size, void *copy_dest)
+INLINE void arena_pop_struct(struct arena *arena, u64 size, void *copy_dest)
 {
     ASSERT(arena->pos >= size);
     ASSERT(!arena->readonly);
@@ -64,7 +62,7 @@ INLINE void _arena_pop_struct(struct arena *arena, u64 size, void *copy_dest)
     arena->pos = new_pos;
 }
 
-INLINE void *_arena_align(struct arena *arena, u64 align)
+INLINE void *arena_align(struct arena *arena, u64 align)
 {
     ASSERT(!arena->readonly);
 
diff --git a/src/buddy.c b/src/buddy.c
new file mode 100644
index 00000000..85d0ce2a
--- /dev/null
+++ b/src/buddy.c
@@ -0,0 +1,200 @@
+#include "buddy.h"
+#include "arena.h"
+
+/* ========================== *
+ * Ctx
+ * ========================== */
+
+struct buddy_ctx *buddy_ctx_alloc(u64 reserve)
+{
+    /* TODO: Determine meta reserve dynamically */
+    struct arena meta_arena = arena_alloc(GIGABYTE(64));
+    struct buddy_ctx *ctx = arena_push_zero(&meta_arena, struct buddy_ctx);
+    ctx->meta_arena = meta_arena;
+    ctx->data_arena = arena_alloc(reserve);
+
+    /* TODO: Minimum block size */
+    ctx->levels = arena_push_array_zero(&ctx->meta_arena, struct buddy_level, 64);
+    for (u64 i = 0; i < 64; ++i) {
+        struct buddy_level *level = &ctx->levels[i];
+        level->ctx = ctx;
+        level->tier = i;
+        level->size = (u64)1 << i;
+    }
+
+
+    return ctx;
+}
+
+void buddy_ctx_release(struct buddy_ctx *ctx)
+{
+    arena_release(&ctx->data_arena);
+    arena_release(&ctx->meta_arena);
+}
+
+/* ========================== *
+ * Block
+ * ========================== */
+
+INTERNAL struct buddy_block *buddy_block_alloc_internal(struct buddy_ctx *ctx)
+{
+    struct buddy_block *block;
+    if (ctx->first_free_block) {
+        block = ctx->first_free_block;
+        ctx->first_free_block = block->next;
+    } else {
+        block = arena_push(&ctx->meta_arena, struct buddy_block);
+    }
+    MEMZERO_STRUCT(block);
+    return block;
+}
+
+INTERNAL void buddy_block_release_internal(struct buddy_ctx *ctx, struct buddy_level *level, struct buddy_block *block)
+{
+    /* Remove from unused list */
+    {
+        struct buddy_block *prev = block->prev;
+        struct buddy_block *next = block->next;
+        if (prev) {
+            prev->next = next;
+        } else {
+            level->first_unused_block = next;
+        }
+        if (next) {
+            next->prev = prev;
+        }
+    }
+
+    block->next = ctx->first_free_block;
+    ctx->first_free_block = block;
+}
+
+INTERNAL struct buddy_block *buddy_block_get_unused(struct buddy_ctx *ctx, struct buddy_level *level)
+{
+    struct buddy_block *block = NULL;
+
+    /* TODO: Tier oob check */
+    if (level->first_unused_block) {
+        block = level->first_unused_block;
+        level->first_unused_block = block->next;
+        if (level->first_unused_block) {
+            level->first_unused_block->prev = NULL;
+        }
+        block->used = true;
+        block->next = NULL;
+        ASSERT(block->memory);
+    } else {
+        if (level->backed) {
+            struct buddy_level *parent_level = &ctx->levels[level->tier + 1];
+            struct buddy_block *parent_block = buddy_block_get_unused(ctx, parent_level);
+            ASSERT(parent_block->memory);
+
+            /* Create left block from parent block */
+            struct buddy_block *left = buddy_block_alloc_internal(ctx);
+            left->used = true;
+            left->level = level;
+            left->parent = parent_block;
+            left->memory = parent_block->memory;
+
+            /* Create right (unused) block from parent block */
+            struct buddy_block *right = buddy_block_alloc_internal(ctx);
+            right->used = false;
+            right->level = level;
+            right->parent = parent_block;
+            right->memory = left->memory + level->size;
+            if (level->first_unused_block) {
+                right->next = level->first_unused_block;
+                level->first_unused_block->prev = right;
+            }
+            level->first_unused_block = right;
+
+            left->sibling = right;
+            right->sibling = left;
+            block = left;
+            ASSERT(block->memory);
+        } else {
+#if 0
+            /* Create left block from arena */
+            struct buddy_block *left = buddy_block_alloc_internal(ctx);
+            left->used = true;
+            left->level = level;
+            left->memory = arena_push_array(&ctx->data_arena, u8, level->size * 2);
+
+            /* Create right (unused) block from arena */
+            struct buddy_block *right = buddy_block_alloc_internal(ctx);
+            right->used = false;
+            right->level = level;
+            right->memory = left->memory + level->size;
+            if (level->first_unused_block) {
+                right->next = level->first_unused_block;
+                level->first_unused_block->prev = right;
+            }
+            level->first_unused_block = right;
+
+            left->sibling = right;
+            right->sibling = left;
+            block = left;
+
+            level->backed = true;
+            ASSERT(block->memory);
+#else
+            /* Create block by growing arena */
+            block = buddy_block_alloc_internal(ctx);
+            block->used = true;
+            block->memory = arena_push_array(&ctx->data_arena, u8, level->size);
+            block->level = level;
+            level->backed = true;
+            ASSERT(block->memory);
+#endif
+        }
+    }
+
+    ASSERT(block->memory);
+    return block;
+}
+
+INTERNAL void buddy_block_mark_unused(struct buddy_block *block)
+{
+    block->used = false;
+    struct buddy_block *sibling = block->sibling;
+    struct buddy_level *level = block->level;
+    if (sibling && !sibling->used) {
+        /* Merge siblings */
+        struct buddy_ctx *ctx = level->ctx;
+        struct buddy_block *parent = block->parent;
+        buddy_block_release_internal(ctx, level, block);
+        buddy_block_release_internal(ctx, level, sibling);
+        if (parent) {
+            buddy_block_mark_unused(parent);
+        }
+    } else {
+        if (level->first_unused_block) {
+            block->next = level->first_unused_block;
+            level->first_unused_block->prev = block;
+        }
+        level->first_unused_block = block;
+    }
+}
+
+struct buddy_block *buddy_alloc(struct buddy_ctx *ctx, u64 size)
+{
+    if (size > 0x00FFFFFFFFFFFFFFULL) {
+        /* TODO: Error */
+    }
+
+    u64 desired_block_size = 1;
+    u64 desired_level_tier = 0;
+    while (desired_block_size < size && desired_level_tier < 64) {
+        desired_block_size <<= 1;
+        ++desired_level_tier;
+    }
+
+    struct buddy_block *block = buddy_block_get_unused(ctx, &ctx->levels[desired_level_tier]);
+
+    return block;
+}
+
+void buddy_release(struct buddy_block *block)
+{
+    buddy_block_mark_unused(block);
+}
diff --git a/src/buddy.h b/src/buddy.h
new file mode 100644
index 00000000..6294435f
--- /dev/null
+++ b/src/buddy.h
@@ -0,0 +1,38 @@
+#ifndef BUDDY_H
+#define BUDDY_H
+
+struct buddy_block {
+    b32 used;
+    struct buddy_level *level;
+    struct buddy_block *parent;
+    struct buddy_block *sibling;
+
+    /* Links to block in level's unused list or in ctx's free list */
+    struct buddy_block *prev;
+    struct buddy_block *next;
+
+    u8 *memory;
+};
+
+struct buddy_level {
+    struct buddy_ctx *ctx;
+    b32 backed;     /* Is this level backed by memory in the ctx arena */
+    u32 tier;
+    u64 size;
+    struct buddy_block *first_unused_block;
+};
+
+struct buddy_ctx {
+    struct arena meta_arena;
+    struct arena data_arena;
+    struct buddy_level *levels;
+    struct buddy_block *first_free_block;
+};
+
+struct buddy_ctx *buddy_ctx_alloc(u64 reserve);
+void buddy_ctx_release(struct buddy_ctx *ctx);
+
+struct buddy_block *buddy_alloc(struct buddy_ctx *ctx, u64 size);
+void buddy_release(struct buddy_block *block);
+
+#endif
diff --git a/src/game.c b/src/game.c
index e0a899a3..1757e110 100644
--- a/src/game.c
+++ b/src/game.c
@@ -1327,7 +1327,7 @@ INTERNAL void game_update(void)
         l.last = &snapshot_event;
         struct string msg = game_string_from_events(temp.arena, l);
 
-        host_queue_write(G.host, HOST_CHANNEL_ID_ALL, msg);
+        host_queue_write(G.host, HOST_CHANNEL_ID_ALL, msg, 0);
 
         arena_temp_end(temp);
     }
diff --git a/src/host.c b/src/host.c
index d5639e50..1d7a059d 100644
--- a/src/host.c
+++ b/src/host.c
@@ -5,6 +5,7 @@
 #include "sys.h"
 #include "util.h"
 #include "log.h"
+#include "buddy.h"
 
 //#define HOST_NETWORK_ADDRESS_STRING(str)
 //#define HOST_NETWORK_ADDRESS_ALL_LOCAL_INTERFACES(port)
@@ -104,13 +105,9 @@ struct host_recv_buffer {
 };
 
 struct host_msg_assembler {
-    struct host *host;
     struct host_channel *channel;
     b32 is_reliable;
 
-    /* TODO: Remove this (testing) */
-    struct arena testarena;
-
     /* Free list */
     struct host_msg_assembler *next_free;
 
@@ -131,8 +128,9 @@ struct host_msg_assembler {
 
     i64 touched_ns;
 
-    u8 *chunks_received_bitmap;
-    u8 *data;
+    struct buddy_block *buddy_block;
+    u8 *chunk_bitmap;
+    u8 *chunk_data;
 };
 
 struct host_msg_assembler_lookup_bucket {
@@ -173,6 +171,11 @@ struct host *host_alloc(u16 listen_port)
     host->cmd_arena = arena_alloc(GIGABYTE(64));
     host->queued_event_arena = arena_alloc(GIGABYTE(64));
     host->channel_arena = arena_alloc(GIGABYTE(64));
+    host->recv_buffer_read = arena_push_zero(&host->arena, struct host_recv_buffer);
+    host->recv_buffer_write = arena_push_zero(&host->arena, struct host_recv_buffer);
+    host->recv_buffer_read->arena = arena_alloc(GIGABYTE(64));
+    host->recv_buffer_write->arena = arena_alloc(GIGABYTE(64));
+    host->buddy = buddy_ctx_alloc(GIGABYTE(64));
 
     host->channels = arena_dry_push(&host->channel_arena, struct host_channel);
 
@@ -182,12 +185,6 @@ struct host *host_alloc(u16 listen_port)
     host->num_msg_assembler_lookup_buckets = NUM_MSG_ASSEMBLER_LOOKUP_BUCKETS;
     host->msg_assembler_lookup_buckets = arena_push_array_zero(&host->arena, struct host_msg_assembler_lookup_bucket, host->num_msg_assembler_lookup_buckets);
 
-
-    host->recv_buffer_read = arena_push_zero(&host->arena, struct host_recv_buffer);
-    host->recv_buffer_write = arena_push_zero(&host->arena, struct host_recv_buffer);
-    host->recv_buffer_read->arena = arena_alloc(GIGABYTE(64));
-    host->recv_buffer_write->arena = arena_alloc(GIGABYTE(64));
-
     host->sock = sock_alloc(listen_port);
 
     host->recv_buffer_write_mutex = sys_mutex_alloc();
@@ -205,6 +202,7 @@ void host_release(struct host *host)
 
     sock_release(host->sock);
 
+    buddy_ctx_release(host->buddy);
     arena_release(&host->recv_buffer_write->arena);
     arena_release(&host->recv_buffer_read->arena);
     arena_release(&host->channel_arena);
@@ -390,19 +388,27 @@ INTERNAL struct host_msg_assembler *host_msg_assembler_alloc(struct host_channel
         ma = arena_push(&host->arena, struct host_msg_assembler);
     }
     MEMZERO_STRUCT(ma);
-    ma->host = channel->host;
     ma->channel = channel;
     ma->msg_id = msg_id;
 
     ma->num_chunks_total = chunk_count;
 
-    /* FIXME: Use buddy allocator or something */
-    u64 data_size = chunk_count * PACKET_MSG_CHUNK_MAX_LEN;
-    u64 bitmap_size = ((chunk_count - 1) / 8) + 1;
-    ma->testarena = arena_alloc(data_size + bitmap_size);
+    u64 chunk_bitmap_size = ((chunk_count - 1) / 8) + 1;
+    if ((chunk_bitmap_size % 16) != 0) {
+        /* Align chunk bitmap to 16 so msg data is aligned */
+        chunk_bitmap_size += 16 - (chunk_bitmap_size % 16);
+    }
+    u64 chunk_data_size = chunk_count * PACKET_MSG_CHUNK_MAX_LEN;
+
+    /* Allocate msg data using buddy allocator since the assembler has
+     * arbitrary lifetime and data needs to stay contiguous for random
+     * access as packets are received */
+    ma->buddy_block = buddy_alloc(host->buddy, chunk_bitmap_size + chunk_data_size);
+    ma->chunk_bitmap = ma->buddy_block->memory;
+    MEMZERO(ma->chunk_bitmap, chunk_bitmap_size);
+    ma->chunk_data = ma->chunk_bitmap + chunk_bitmap_size;
+
     /* FIXME: Ensure chunk_count > 0 */
-    ma->chunks_received_bitmap = arena_push_array_zero(&ma->testarena, u8, bitmap_size);
-    ma->data = arena_push_array(&ma->testarena, u8, data_size);
     ma->is_reliable = is_reliable;
 
     /* Insert into channel list */
@@ -432,11 +438,9 @@ INTERNAL struct host_msg_assembler *host_msg_assembler_alloc(struct host_channel
 
 INTERNAL void host_msg_assembler_release(struct host_msg_assembler *ma)
 {
-    struct host *host = ma->host;
     struct host_channel *channel = ma->channel;
-
-    /* FIXME: Data should be in buddy allocator or something */
-    arena_release(&ma->testarena);
+    struct host *host = channel->host;
+    buddy_release(ma->buddy_block);
 
     /* Release from channel list */
     {
@@ -471,7 +475,6 @@ INTERNAL void host_msg_assembler_release(struct host_msg_assembler *ma)
         }
     }
 
-
     ma->next_free = host->first_free_msg_assembler;
     host->first_free_msg_assembler = ma;
 }
@@ -513,7 +516,7 @@ INTERNAL void host_msg_assembler_touch(struct host_msg_assembler *ma, i64 now_ns
 INTERNAL b32 host_msg_assembler_is_chunk_filled(struct host_msg_assembler *ma, u64 chunk_id)
 {
     if (chunk_id < ma->num_chunks_total) {
-        return (ma->chunks_received_bitmap[chunk_id / 8] & (1 << (chunk_id % 8))) != 0;
+        return (ma->chunk_bitmap[chunk_id / 8] & (1 << (chunk_id % 8))) != 0;
     }
     return false;
 }
@@ -521,7 +524,7 @@ INTERNAL b32 host_msg_assembler_is_chunk_filled(struct host_msg_assembler *ma, u
 INTERNAL void host_msg_assembler_set_chunk_received(struct host_msg_assembler *ma, u64 chunk_id)
 {
     if (chunk_id < ma->num_chunks_total) {
-        ma->chunks_received_bitmap[chunk_id / 8] |= (1 << (chunk_id % 8));
+        ma->chunk_bitmap[chunk_id / 8] |= (1 << (chunk_id % 8));
     }
 }
 
@@ -593,12 +596,13 @@ void host_queue_disconnect(struct host *host, struct host_channel_id channel_id)
     cmd->channel_id = channel_id;
 }
 
-void host_queue_write(struct host *host, struct host_channel_id channel_id, struct string msg)
+void host_queue_write(struct host *host, struct host_channel_id channel_id, struct string msg, u32 flags)
 {
     struct host_cmd *cmd = host_cmd_alloc_and_append(host);
     cmd->kind = HOST_CMD_KIND_WRITE;
     cmd->channel_id = channel_id;
     cmd->write_msg = string_copy(&host->cmd_arena, msg);
+    cmd->write_reliable = flags & HOST_WRITE_FLAG_RELIABLE;
 }
 
 /* ========================== *
@@ -728,7 +732,7 @@ void host_update(struct host *host)
                                     if (!host_msg_assembler_is_chunk_filled(ma, chunk_id)) {
                                         u8 *src = br_seek(&br, data_len);
                                         if (src) {
-                                            u8 *dst = &ma->data[chunk_id * PACKET_MSG_CHUNK_MAX_LEN];
+                                            u8 *dst = &ma->chunk_data[chunk_id * PACKET_MSG_CHUNK_MAX_LEN];
                                             MEMCPY(dst, src, data_len);
                                             if (is_last_chunk) {
                                                 ma->last_chunk_len = data_len;
@@ -743,7 +747,7 @@ void host_update(struct host *host)
                                                 struct string data = ZI;
                                                 data.len = ((chunk_count - 1) * PACKET_MSG_CHUNK_MAX_LEN) + ma->last_chunk_len;
                                                 data.text = arena_push_array(&host->queued_event_arena, u8, data.len);
-                                                MEMCPY(data.text, ma->data, data.len);
+                                                MEMCPY(data.text, ma->chunk_data, data.len);
                                                 queued_event->event.kind = HOST_EVENT_KIND_MSG;
                                                 queued_event->event.msg = data;
                                                 queued_event->event.channel_id = channel->id;
diff --git a/src/host.h b/src/host.h
index 9ba1171d..995fd942 100644
--- a/src/host.h
+++ b/src/host.h
@@ -7,6 +7,7 @@
 #define HOST_CHANNEL_ID_NIL (struct host_channel_id) { .gen = 0, .idx = 0 }
 #define HOST_CHANNEL_ID_ALL (struct host_channel_id) { .gen = U32_MAX, .idx = U32_MAX }
 
+struct buddy_ctx;
 struct host_packet;
 struct host_channel_lookup_bucket;
 struct host_recv_buffer;
@@ -28,6 +29,12 @@ enum host_event_kind {
     HOST_EVENT_KIND_MSG
 };
 
+enum host_write_flag {
+    HOST_WRITE_FLAG_NONE = 0,
+
+    HOST_WRITE_FLAG_RELIABLE = (1 << 0)
+};
+
 struct host_cmd {
     enum host_cmd_kind kind;
     struct host_channel_id channel_id;
@@ -53,6 +60,8 @@ struct host {
     struct arena arena;
     struct sock *sock;
 
+    struct buddy_ctx *buddy;  /* For storing msg assembler data */
+
     struct arena cmd_arena;
     struct host_cmd *first_cmd;
     struct host_cmd *last_cmd;
@@ -108,7 +117,7 @@ void host_queue_connect_to_address(struct host *host, struct sock_address connec
 
 void host_queue_disconnect(struct host *host, struct host_channel_id channel_id);
 
-void host_queue_write(struct host *host, struct host_channel_id channel_id, struct string msg);
+void host_queue_write(struct host *host, struct host_channel_id channel_id, struct string msg, u32 flags);
 
 /* ========================== *
  * Update
diff --git a/src/user.c b/src/user.c
index a9be8b37..61999cf3 100644
--- a/src/user.c
+++ b/src/user.c
@@ -1668,7 +1668,7 @@ INTERNAL void user_update(void)
         struct temp_arena temp = arena_temp_begin(scratch.arena);
 
         struct string cmds_str = game_string_from_cmds(temp.arena, cmd_list);
-        host_queue_write(G.host, HOST_CHANNEL_ID_ALL, cmds_str);
+        host_queue_write(G.host, HOST_CHANNEL_ID_ALL, cmds_str, 0);
 
         arena_temp_end(temp);
     }