diff --git a/SIMTEST.txt b/SIMTEST.txt
new file mode 100644
index 0000000..fecb209
--- /dev/null
+++ b/SIMTEST.txt
@@ -0,0 +1,2 @@
+Notes on simulation testing:
+    - Trace the branch coverage of the test and find why some branches are never reached
diff --git a/src/chunk_server.c b/src/chunk_server.c
index eb7b300..6eee73a 100644
--- a/src/chunk_server.c
+++ b/src/chunk_server.c
@@ -146,7 +146,7 @@ static int store_chunk(ChunkStore *store, string data, SHA256 *hash)
     // This is okay as long as we check that the hash
     // is correct while reading back the data.
     Handle fd;
-    if (file_open(path, &fd) < 0)
+    if (file_open(path, &fd) < 0) // TODO: open in overwrite mode
         return -1;
     int copied = 0;
     while (copied < data.len) {
diff --git a/src/client.c b/src/client.c
index 6f662c0..048a00e 100644
--- a/src/client.c
+++ b/src/client.c
@@ -292,12 +292,8 @@ static int get_chunk_server(MouseFS *mfs, Address *addrs, int num_addrs, ByteQue
         if (!have_insertection(addrs, num_addrs, mfs->chunk_servers[i].addrs, mfs->chunk_servers[i].num_addrs))
             continue;
 
-        // It's possible that this chunk server's connection
-        // was dropped but we still didn't process the DISCONNECT
-        // event.
-        int conn_idx = tcp_index_from_tag(&mfs->tcp, found);
-        if (conn_idx < 0)
-            continue;
+        int conn_idx = tcp_index_from_tag(&mfs->tcp, i);
+        assert(conn_idx > -1);
 
         if (output)
             *output = tcp_output_buffer(&mfs->tcp, conn_idx);
@@ -1252,6 +1248,8 @@ static void process_event_for_write(MouseFS *mfs,
                 return;
             }
 
+            mfs->operations[opidx].hashes[i] = hash;
+
             uint32_t num_holders;
             if (!binary_read(&reader, &num_holders, sizeof(num_holders))) {
                 mfs->operations[opidx].result = (MouseFS_Result) { .type=MOUSEFS_RESULT_WRITE_ERROR };
diff --git a/src/metadata_server.c b/src/metadata_server.c
index ce63de0..b2f5324 100644
--- a/src/metadata_server.c
+++ b/src/metadata_server.c
@@ -798,6 +798,8 @@ static int process_chunk_server_sync(MetadataServer *state,
         if (!file_tree_uses_hash(&state->file_tree, hash))
             continue;
 
+        // TODO: execution never reaches this point for some reason
+
         // If the chunk is properly replicated or under-replicated,
         // add it to the ms_add_list.