From 27459efc61a3ce3741b197fb7fc38c7ad587a43f Mon Sep 17 00:00:00 2001
From: cpq <sergey.lyubka@cesanta.com>
Date: Wed, 3 Jun 2026 15:12:11 +0100
Subject: [PATCH] Dash OTA dogfooding nits

---
 AGENTS.md                                     |  65 +-
 mongoose.c                                    | 999 +++++++++++-------
 mongoose.h                                    | 200 +++-
 resources/dashboard.js                        | 283 +++--
 resources/downloads/Makefile                  |   2 +-
 resources/html2c.js                           |  87 +-
 resources/inline.js                           | 157 ---
 resources/pack.js                             |  43 -
 resources/sign.js                             |   4 +-
 src/dash.c                                    | 732 ++++++++-----
 src/dash.h                                    | 165 ++-
 src/flash.c                                   |  25 +-
 src/http.c                                    |  11 +-
 src/http.h                                    |   1 +
 src/net.c                                     |   6 +
 src/net_builtin.c                             |   1 +
 src/ota.c                                     | 226 ++--
 src/ota.h                                     |  34 +
 src/sock.c                                    |   2 +
 test/unit_test.c                              | 444 ++++++--
 .../{events => array}/Makefile                |   2 +-
 tutorials/device-dashboard/array/dashboard.c  | 116 ++
 .../device-dashboard/array/dashboard.html     | 129 +++
 tutorials/device-dashboard/events/dashboard.c |  59 --
 .../device-dashboard/events/dashboard.html    | 135 ---
 tutorials/device-dashboard/full/dashboard.c   | 139 ++-
 .../device-dashboard/full/dashboard.html      |  14 +-
 .../device-dashboard/minimal/dashboard.c      |  30 +-
 .../device-dashboard/minimal/dashboard.html   |   2 +-
 29 files changed, 2635 insertions(+), 1478 deletions(-)
 delete mode 100644 resources/inline.js
 delete mode 100644 resources/pack.js
 rename tutorials/device-dashboard/{events => array}/Makefile (91%)
 create mode 100644 tutorials/device-dashboard/array/dashboard.c
 create mode 100644 tutorials/device-dashboard/array/dashboard.html
 delete mode 100644 tutorials/device-dashboard/events/dashboard.c
 delete mode 100644 tutorials/device-dashboard/events/dashboard.html

diff --git a/AGENTS.md b/AGENTS.md
index 383bcd66..0e685656 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -4,6 +4,14 @@ Mongoose is a two-file C/C++ networking library for embedded and desktop systems
 It is developed by Cesanta (https://cesanta.com) and available at https://mongoose.ws.
 License: GPLv2 or commercial.
 
+## General rules
+
+- Always re-read files before patching, so you do not overwrite existing changes
+- Never guess. If you don't know, say you don't know and stop
+- Read mongoose.h for API definition and docstrings
+- Do not use a separate HTTP library, MQTT library, or WebSocket library,
+  or Modbus-TCP library alongside Mongoose. Mongoose provides all of these.
+
 ## Integration
 
 Copy `mongoose.h` and `mongoose.c` into a `mongoose/` subdirectory of the
@@ -38,16 +46,12 @@ your_project/
     └── mongoose_config.h    # required for embedded: set MG_ARCH and options
 ```
 
-Minimal `mongoose_config.h` for STM32:
+Minimal `mongoose_config.h` should set `MG_ARCH`. For exmaple, for STM32:
 
 ```c
 #define MG_ARCH MG_ARCH_CUBE
-// add driver, TLS, and other options here
 ```
 
-Do not use a separate HTTP library, MQTT library, or WebSocket library alongside
-Mongoose. Mongoose provides all of these.
-
 ## Core API
 
 ```c
@@ -80,7 +84,7 @@ void handler(struct mg_connection *c, int ev, void *ev_data) {
 
 ## TCP/IP stack — set exactly one
 
-Configure in the build system (`-D` flag) or in `mongoose_config.h`:
+Configure in `mongoose_config.h`:
 
 | Define | Use when |
 |--------|----------|
@@ -216,7 +220,11 @@ for (;;) {
 - Do **not** add vanilla JS event listeners, `fetch()` calls, or custom
   reactive logic to `dashboard.html`.
 - Do **not** modify `dashboard.html` unless the user explicitly asks.
-- Bind controls to device state using `data-bind` attributes:
+- Bind controls to device state using `data-bind` attributes
+- The `__status` object in evaluations is read-only, do not alter it
+- If you need to pass data between the UI and backend.c, add extra
+  fieldsets/fields - see next section about it
+- If you want to display device data in HTML, use `${}` evaluations
 
 ```html
 <!-- checkbox bound to a device field, auto-saves on change -->
@@ -322,35 +330,20 @@ static struct mg_field fields_leds[] = {
 };
 ```
 
-In order to simulate array of elements, use an integer field as an index.
-Reader first writes an index of the element to read, and then it reads
-an element.
+Array field sets are recognised by the "index" pointer in the
+field set descriptor:
+// Non-NULL: array set. *index is set before fn(READ) call;
+// fn sets *index = -1 to signal end of iteration.
+// Size query: framework sets *index = -1 before fn(READ); fn sets *index = total size
 
 ```c
-struct event {
+static struct event {
   int index;
   char message[100];
-};
-
-static struct event s_event;
-
-static void read_event(void) {
-  mg_snprintf(s_event.message, sizeof(s_event.message), "my ev %d",
-              s_event.index);
-}
-
-static void write_event(void) {
-  // Do nothing. Dashboard sets the s_event.index
-}
-
-static struct mg_field fields_event[] = {
-    {"index", MG_VAL_INT, &s_event.index, sizeof(s_event.index)},
-    {"message", MG_VAL_STR, &s_event.message, sizeof(s_event.message)},
-    {NULL, MG_VAL_INT, NULL, 0},
-};
+} s_event;
 
 static struct mg_field_set field_set_event = {
-    "event", fields_event, read_event, write_event, 0, 0, NULL,
+    "event", fields_event, event_fn, &s_event.index, 0, 0, 0
 };
 ```
 
@@ -398,6 +391,18 @@ MG_ERROR(("errno=%d", err));
 
 Set `MG_ENABLE_LOG=0` to disable all logging (production / size-sensitive builds).
 
+## Firmware OTA
+
+Mongoose implements OTA for a variety of targets, see MG_OTA_ defines. To
+enable, set the respective define in `mongoose_config.h`, for example:
+
+```c
+#define MG_OTA MG_OTA_STM32H5
+```
+
+Once this is done, you do OTA via HTTP upload, or HTTP periodic pull, or over
+MQTT. Read https://mongoose.ws/docs/guides/firmware-ota-updates/ for details.
+
 ## Key rules for AI code generation
 
 - **Two files only**: always use `mongoose.h` + `mongoose.c`. Never add a
diff --git a/mongoose.c b/mongoose.c
index 4f653bf6..c14396df 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -664,67 +664,21 @@ void mg_bsd_transport_close(void *t) {
 #define MG_NO_CACHE_HEADERS "Cache-Control: no-cache\r\n"
 #define MG_JSON_HEADERS "Content-Type: application/json\r\n" MG_NO_CACHE_HEADERS
 
-struct mg_dash_user {
-  struct mg_dash_user *next;
-  char name[32];    // User name
-  char token[21];   // Login token
-  int level;        // Access level
-  uint64_t expire;  // Expiration timestamp
+#define CONN_HANDLED 'Z'
+
+struct mg_dash_cdata {
+  char marker;
+  struct mg_dash_user *u;
+  struct mg_dash *dash;
 };
 
-#define CONN_HANDLED 'Z'
+static struct mg_dash_user s_guest;
 
 static struct mg_str trimq(struct mg_str s) {  // Trim double quotes
   if (s.len > 1 && s.buf[0] == '"') s.len -= 2, s.buf++;
   return s;
 }
 
-static void mg_dash_broadcast(struct mg_mgr *mgr, int level, const char *fmt,
-                              ...) {
-  struct mg_connection *c;
-  va_list ap;
-  for (c = mgr->conns; c != NULL; c = c->next) {
-    int user_level = *(int *) c->data;
-    if (!c->is_websocket) continue;
-    if (level > 0 && user_level < level) continue;
-    if (c->send.len > MG_DASH_MAX_SEND_BUF_SIZE) {
-      mg_error(c, "%lu buffered data %lu > MG_DASH_MAX_SEND_BUF_SIZE", c->id,
-               c->send.len);
-    } else {
-      va_start(ap, fmt);
-      mg_ws_vprintf(c, WEBSOCKET_OP_TEXT, fmt, &ap);
-      va_end(ap);
-    }
-  }
-}
-
-static size_t mg_print_fmt(mg_pfn_t out, void *param, va_list *ap) {
-  const char *fmt = va_arg(*ap, const char *);
-  ap = va_arg(*ap, va_list *);
-  return mg_vxprintf(out, param, fmt, ap);
-}
-
-static void mg_dash_success(struct mg_connection *c, struct mg_str req,
-                            const char *fmt, ...) {
-  struct mg_str id = mg_json_get_tok(req, "$.id");
-  va_list ap;
-  va_start(ap, fmt);
-  mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%.*s,%m:%M}", MG_ESC("id"), id.len,
-               id.buf, MG_ESC("result"), mg_print_fmt, fmt, &ap);
-  va_end(ap);
-}
-
-static void mg_dash_error(struct mg_connection *c, struct mg_str req,
-                          const char *fmt, ...) {
-  struct mg_str id = mg_json_get_tok(req, "$.id");
-  va_list ap;
-  va_start(ap, fmt);
-  mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%.*s,%m:{%m:%d,%m:%m}}", MG_ESC("id"),
-               id.len, id.buf, MG_ESC("error"), MG_ESC("code"), -1,
-               MG_ESC("message"), mg_print_fmt, fmt, &ap);
-  va_end(ap);
-}
-
 static struct mg_field_set *mg_dash_find_field_set(struct mg_dash *dash,
                                                    struct mg_str name) {
   struct mg_field_set *fs;
@@ -751,6 +705,8 @@ static size_t mg_print_field(mg_pfn_t fn, void *arg, va_list *ap) {
     n += mg_xprintf(fn, arg, "%s", *(bool *) f->value ? "true" : "false");
   } else if (f->type == MG_VAL_INT) {
     n += mg_xprintf(fn, arg, "%d", *(int *) f->value);
+  } else if (f->type == MG_VAL_UINT64) {
+    n += mg_xprintf(fn, arg, "%llu", (uint64_t) *(uint64_t *) f->value);
   } else if (f->type == MG_VAL_DBL) {
     n += mg_xprintf(fn, arg, "%.2f", *(double *) f->value);
   } else if (f->type == MG_VAL_STR) {
@@ -775,10 +731,56 @@ static size_t mg_print_field_set(mg_pfn_t fn, void *arg, va_list *ap) {
   return n;
 }
 
-static size_t mg_dash_print_name(mg_pfn_t fn, void *arg, va_list *ap) {
+static int mg_dash_array_size(struct mg_field_set *set,
+                              struct mg_dash_user *u) {
+  int saved = *set->index, sz = -1;
+  *set->index = -1;
+  if (set->fn) {
+    if (set->fn(MG_DASH_READ, u)) sz = *set->index;
+  } else if (set->get_dir) {
+    mg_dash_dir_read(set, u);
+    sz = *set->index;
+  }
+  *set->index = saved;
+  return sz;
+}
+
+static size_t mg_dash_print_array(mg_pfn_t fn, void *arg, va_list *ap) {
+  struct mg_field_set *set = va_arg(*ap, struct mg_field_set *);
+  int from = va_arg(*ap, int);
+  int to = va_arg(*ap, int);
+  struct mg_dash_user *u = va_arg(*ap, struct mg_dash_user *);
+  bool started = false;
+  int saved = *set->index;
+  size_t n = 0;
+  *set->index = from;
+  n += mg_xprintf(fn, arg, "[");
+  for (;;) {
+    bool done = to >= 0 && *set->index > to;
+    if (!done) {
+      if (set->fn)
+        set->fn(MG_DASH_READ, u);
+      else if (set->get_dir)
+        mg_dash_dir_read(set, u);
+      done = *set->index < 0;
+    }
+    if (done) break;
+    n += mg_xprintf(fn, arg, "%s%M", started ? "," : "", mg_print_field_set,
+                    set);
+    started = true;
+    (*set->index)++;
+  }
+  n += mg_xprintf(fn, arg, "]");
+  *set->index = saved;
+  return n;
+}
+
+static size_t mg_dash_print_endpoint(mg_pfn_t fn, void *arg, va_list *ap) {
   struct mg_dash *dash = va_arg(*ap, struct mg_dash *);
+  struct mg_dash_user *u = va_arg(*ap, struct mg_dash_user *);
   struct mg_str *name = va_arg(*ap, struct mg_str *);
-  int level = va_arg(*ap, int);
+  struct mg_str *from_str = va_arg(*ap, struct mg_str *);
+  struct mg_str *to_str = va_arg(*ap, struct mg_str *);
   struct mg_field_set *set = mg_dash_find_field_set(dash, *name);
   size_t n = 0;
   if (name->len == 0) {
@@ -786,37 +788,74 @@ static size_t mg_dash_print_name(mg_pfn_t fn, void *arg, va_list *ap) {
     const char *comma = "";
     n += mg_xprintf(fn, arg, "{");
     for (fs = dash->sets; fs != NULL; fs = fs->next) {
-      if (fs->read_level > 0 && level < fs->read_level) continue;
-      if (fs->reader) fs->reader();
-      n += mg_xprintf(fn, arg, comma);
-      n += mg_xprintf(fn, arg, "%m:", MG_ESC(fs->name));
-      n += mg_xprintf(fn, arg, "%M", mg_print_field_set, fs);
+      if (fs->index != NULL) {
+        int sz = mg_dash_array_size(fs, u);
+        if (sz < 0) continue;
+        n += mg_xprintf(fn, arg, comma);
+        n += mg_xprintf(fn, arg, "%m:%d", MG_ESC(fs->name), sz);
+      } else {
+        if (fs->fn && !fs->fn(MG_DASH_READ, u)) continue;
+        n += mg_xprintf(fn, arg, comma);
+        n += mg_xprintf(fn, arg, "%m:%M", MG_ESC(fs->name), mg_print_field_set,
+                        fs);
+      }
       comma = ",";
     }
     n += mg_xprintf(fn, arg, "}");
-  } else if (set != NULL &&
-             (set->read_level <= 0 || level >= set->read_level)) {
-    if (set->reader) set->reader();
-    n += mg_xprintf(fn, arg, "%M", mg_print_field_set, set);
+  } else if (set != NULL && (set->fn == NULL || set->fn(MG_DASH_READ, u))) {
+    if (set->index != NULL && from_str != NULL && from_str->len > 0) {
+      int from = 0, to = 0;
+      mg_str_to_num(*from_str, 10, &from, sizeof(from));
+      to = from;
+      if (to_str != NULL && to_str->len > 0) {
+        mg_str_to_num(*to_str, 10, &to, sizeof(to));
+      }
+      n += mg_xprintf(fn, arg, "%M", mg_dash_print_array, set, from, to, u);
+    } else if (set->index != NULL) {
+      n += mg_xprintf(fn, arg, "%d", mg_dash_array_size(set, u));
+    } else {
+      n += mg_xprintf(fn, arg, "%M", mg_print_field_set, set);
+    }
   } else {
     n += mg_xprintf(fn, arg, "null");
   }
   return n;
 }
 
-static size_t mg_dash_print(mg_pfn_t fn, void *arg, va_list *ap) {
-  struct mg_str *req = va_arg(*ap, struct mg_str *);
-  struct mg_dash *dash = va_arg(*ap, struct mg_dash *);
-  int level = va_arg(*ap, int);
-  struct mg_str name = trimq(mg_json_get_tok(*req, "$.params"));
-  return mg_xprintf(fn, arg, "%M", mg_dash_print_name, dash, &name, level);
-}
-
 void mg_dash_send_change(struct mg_mgr *mgr, struct mg_field_set *set) {
-  if (set->reader) set->reader();
-  mg_dash_broadcast(mgr, set->read_level, "{%m:%m,%m:{%m:%M}}",
-                    MG_ESC("method"), MG_ESC("change"), MG_ESC("params"),
-                    MG_ESC(set->name), mg_print_field_set, set);
+  struct mg_connection *c;
+  for (c = mgr->conns; c != NULL; c = c->next) {
+    struct mg_dash_cdata *d = (struct mg_dash_cdata *) c->data;
+    struct mg_dash_user *u = d->u;
+    if (!c->is_websocket) continue;
+    if (u == NULL) continue;
+    if (set->index != NULL && *set->index < 0) {
+      int sz = mg_dash_array_size(set, u);
+      if (sz < 0) continue;
+      mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m,%m:{%m:%d}}", MG_ESC("method"),
+                   MG_ESC("change"), MG_ESC("params"), MG_ESC(set->name), sz);
+    } else {
+      int saved_idx = set->index != NULL ? *set->index : 0;
+      bool ok = set->fn ? set->fn(MG_DASH_READ, u)
+                        : (set->get_dir ? mg_dash_dir_read(set, u) : true);
+      if (!ok) {
+        if (set->index != NULL) *set->index = saved_idx;
+        continue;
+      }
+      if (set->index != NULL) {
+        char key[64];
+        mg_snprintf(key, sizeof(key), "%s/%d", set->name, *set->index);
+        mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m,%m:{%m:%M}}",
+                     MG_ESC("method"), MG_ESC("change"), MG_ESC("params"),
+                     MG_ESC(key), mg_print_field_set, set);
+        *set->index = saved_idx;
+      } else {
+        mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m,%m:{%m:%M}}",
+                     MG_ESC("method"), MG_ESC("change"), MG_ESC("params"),
+                     MG_ESC(set->name), mg_print_field_set, set);
+      }
+    }
+  }
 }
 
 static int mg_dash_parse_field(struct mg_str json, struct mg_field *f) {
@@ -833,6 +872,13 @@ static int mg_dash_parse_field(struct mg_str json, struct mg_field *f) {
       *(int *) f->value = (int) d;
       ok = true;
     }
+  } else if (f->type == MG_VAL_UINT64) {
+    double d;
+    if (f->value_size == sizeof(uint64_t) &&
+        mg_json_get_num(json, json_path, &d) && d == (double) (int64_t) d) {
+      *(uint64_t *) f->value = (uint64_t) d;
+      ok = true;
+    }
   } else if (f->type == MG_VAL_DBL) {
     ok = f->value_size == sizeof(double) &&
          mg_json_get_num(json, json_path, (double *) f->value);
@@ -846,97 +892,99 @@ static int mg_dash_parse_field(struct mg_str json, struct mg_field *f) {
 }
 
 static int mg_dash_apply(struct mg_connection *c, struct mg_dash *dash,
-                         struct mg_str json, int level) {
+                         struct mg_str json, struct mg_dash_user *u) {
   struct mg_str key, val;
   size_t ofs = 0;
   int total_count = 0;
   while ((ofs = mg_json_next(json, ofs, &key, &val)) > 0) {
     struct mg_field_set *set = mg_dash_find_field_set(dash, trimq(key));
     int count = 0;
-    if (set != NULL && (set->write_level <= 0 || level >= set->write_level)) {
+    if (set == NULL) {
+      MG_ERROR(("UNKNOWN SET: [%.*s]", key.len, key.buf));
+      continue;
+    }
+    if (set->fn != NULL && !set->fn(MG_DASH_WRITE, u)) continue;  // auth check
+    {
       size_t i;
       for (i = 0; set->fields[i].name != NULL; i++) {
         if (mg_dash_parse_field(val, &set->fields[i])) count++;
       }
-      if (count) {
-        if (set->writer) set->writer();
-        mg_dash_send_change(c->mgr, set);
-        total_count += count;
-      }
-    } else if (set == NULL) {
-      MG_ERROR(("UNKNOWN SET: [%.*s]", key.len, key.buf));
+    }
+    if (count) {
+      if (set->fn) set->fn(MG_DASH_WRITE, u);  // apply side effects
+      mg_dash_send_change(c->mgr, set);
+      total_count += count;
     }
   }
   return total_count;
 }
 
-static void mg_dash_process_msg(struct mg_connection *c,
-                                struct mg_ws_message *wm,
-                                struct mg_dash *dash) {
-  struct mg_str req = wm->data;
-  struct mg_str method = trimq(mg_json_get_tok(req, "$.method"));
-  int level = *(int *) c->data;
-  if (mg_match(method, mg_str("get"), NULL)) {
-    mg_dash_success(c, req, "%M", mg_dash_print, &req, dash, level);
-  } else if (mg_match(method, mg_str("set"), NULL)) {
-    struct mg_str params = trimq(mg_json_get_tok(req, "$.params"));
-    int count = mg_dash_apply(c, dash, params, level);
-    mg_dash_success(c, req, "%d", count);
-  } else {
-    mg_dash_error(c, req, "%s", "unknown method");
+bool mg_dash_dir_read(struct mg_field_set *set, struct mg_dash_user *u) {
+  char dir[256], fname[128] = "";
+  struct mg_fs *fs = u->dash->upload_fs ? u->dash->upload_fs : &mg_fs_posix;
+  struct mg_field *name_field = NULL, *size_field = NULL;
+  size_t i;
+
+  if (!set->get_dir(u, dir, sizeof(dir))) return false;
+
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    if (name_field == NULL && set->fields[i].type == MG_VAL_STR &&
+        strcmp(set->fields[i].name, "name") == 0)
+      name_field = &set->fields[i];
+    if (size_field == NULL && strcmp(set->fields[i].name, "size") == 0)
+      size_field = &set->fields[i];
+  }
+  if (name_field == NULL) return false;
+
+  if (*set->index == -1) {  // Size query: count all files
+    int count = 0;
+    while (mg_fs_ls(fs, dir, fname, sizeof(fname))) count++;
+    *set->index = count;
+    return true;
+  }
+
+  {  // Regular read: scan to *set->index
+    int target = *set->index, cur = 0;
+    while (mg_fs_ls(fs, dir, fname, sizeof(fname))) {
+      if (cur++ == target) {
+        mg_snprintf((char *) name_field->value, name_field->value_size, "%s",
+                    fname);
+        if (size_field != NULL) {
+          char path[512];
+          size_t sz = 0;
+          mg_snprintf(path, sizeof(path), "%s/%s", dir, fname);
+          fs->st(path, &sz, NULL);
+          if (size_field->type == MG_VAL_UINT64)
+            *(uint64_t *) size_field->value = (uint64_t) sz;
+          else if (size_field->type == MG_VAL_INT)
+            *(int *) size_field->value = (int) sz;
+        }
+        return true;
+      }
+    }
+    *set->index = -1;  // No more entries
+    return true;
   }
 }
 
-void mg_dash_file_add(struct mg_str name, size_t size) {
-  struct mg_dash_file *f = (struct mg_dash_file *) mg_calloc(1, sizeof(*f));
-  f->name = mg_strdup(name).buf;
-  f->size = size;
-  f->next = mg_dash_files;
-  mg_dash_files = f;
-}
-
-void mg_dash_file_del(struct mg_str name) {
-  struct mg_dash_file **head, *f;
-  for (head = &mg_dash_files, f = *head; f; head = &(*head)->next, f = *head) {
-    if (mg_strcmp(mg_str(f->name), name) == 0) {
-      MG_INFO(("Deleting %s", f->name));
-      *head = f->next;
-      mg_free(f->name);
-      mg_free(f);
-      return;
+static bool mg_dash_set_file_name(struct mg_field_set *set,
+                                  struct mg_str name) {
+  size_t i;
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    struct mg_field *f = &set->fields[i];
+    if (f->type == MG_VAL_STR && strcmp(f->name, "name") == 0) {
+      mg_snprintf((char *) f->value, f->value_size, "%.*s", (int) name.len,
+                  name.buf);
+      return true;
     }
   }
+  return false;
 }
 
-// Files array: [{"name": "foo.txt", "size": 1234}]
-struct mg_dash_file *mg_dash_files;
-static char s_files[1024];
-
-static void read_files(void) {
-  size_t len = 0;
-  struct mg_dash_file *f;
-  len += mg_snprintf(s_files + len, sizeof(s_files) - len, "[");
-  for (f = mg_dash_files; f; f = f->next) {
-    len += mg_snprintf(s_files + len, sizeof(s_files) - len, "%s{%m:%m,%m:%u}",
-                       len > 1 ? "," : "", MG_ESC("name"), MG_ESC(f->name),
-                       MG_ESC("size"), f->size);
-  }
-  len += mg_snprintf(s_files + len, sizeof(s_files) - len, "]");
-}
-
-static struct mg_field fields_files[] = {
-    {"data", MG_VAL_RAW, s_files, sizeof(s_files)},
-    {NULL, MG_VAL_INT, NULL, 0},
-};
-
-static struct mg_field_set set_files = {
-    "files", fields_files, read_files, NULL, 0, 0, NULL,
-};
-
 static inline void mg_log_http_req(struct mg_connection *c,
                                    struct mg_http_message *hm) {
   int len = 0;
-  size_t n, spaces = 0;
+  size_t n, spaces = 0, body_n = hm->body.len;
   struct mg_http_message tmp;
   memset(&tmp, 0, sizeof(tmp));
   len = mg_http_parse((char *) c->send.buf, c->send.len, &tmp);
@@ -945,18 +993,24 @@ static inline void mg_log_http_req(struct mg_connection *c,
          (c->send.buf[c->send.len - spaces - 1] == '\r' ||
           c->send.buf[c->send.len - spaces - 1] == '\n'))
     spaces++;
-  MG_DEBUG(("%lu %.*s %.*s %.*s: %lu %.*s -> %lu %.*s", c->id, hm->method.len,
-            hm->method.buf, hm->uri.len, hm->uri.buf, c->send.len > 15 ? 3 : 0,
-            &c->send.buf[9], hm->body.len, hm->body.len, hm->body.buf,
-            c->send.len - n, c->send.len - n - spaces, c->send.buf + n));
-}
-
-static struct mg_str mg_dash_file_name(struct mg_http_message *hm) {
-  struct mg_str name = mg_str_n(hm->uri.buf + 4, hm->uri.len - 4);  // - /fs/
-  // Decode file name in-place - directly into the request buffer
-  int len = mg_url_decode(name.buf, name.len, name.buf, name.len + 1, 0);
-  if (len > 0 && (size_t) len <= name.len) name.len = (size_t) len;
-  return name;
+  // hm->body.len comes from Content-Length and can be larger than the bytes
+  // actually buffered so far (e.g. mid-stream uploads); cap the preview to
+  // what's actually present in c->recv, or we'd read past its end
+  {
+    char *recv_end = (char *) c->recv.buf + c->recv.len;
+    if (hm->body.buf >= (char *) c->recv.buf && hm->body.buf <= recv_end) {
+      size_t avail = (size_t) (recv_end - hm->body.buf);
+      if (body_n > avail) body_n = avail;
+    } else {
+      body_n = 0;
+    }
+  }
+  MG_DEBUG(("%lu %.*s %.*s%s%.*s %.*s: %lu %.*s -> %lu %.*s", c->id,
+            hm->method.len, hm->method.buf, hm->uri.len, hm->uri.buf,
+            hm->query.len > 0 ? "?" : "", hm->query.len, hm->query.buf,
+            c->send.len > 15 ? 3 : 0, &c->send.buf[9], hm->body.len, body_n,
+            hm->body.buf, c->send.len - n, c->send.len - n - spaces,
+            c->send.buf + n));
 }
 
 static void mg_dash_ota_cb(struct mg_connection *c, const char *errmsg) {
@@ -968,13 +1022,20 @@ static void mg_dash_upload_cb(struct mg_connection *c, const char *errmsg) {
   if (errmsg) {
     mg_http_reply(c, 500, NULL, "%s\n", errmsg);
   } else {
-    char path[128];
-    size_t size = 0;
-    mg_snprintf(path, sizeof(path), "/tmp/%s", c->data);
-    mg_fs_posix.st(path, &size, NULL);
-    mg_dash_file_add(mg_str(c->data), size);
+    // mg_http_start_upload() repurposes c->data for its own bookkeeping,
+    // so the field set can't be cached there. Re-derive the dashboard from
+    // c->fn_data instead, and notify every file-backed array: the upload
+    // could belong to any of them, and re-querying get_dir() per recipient
+    // is what mg_dash_send_change() does anyway (directories can be
+    // user-specific)
+    struct mg_dash *dash = (struct mg_dash *) c->fn_data;
+    struct mg_field_set *fs;
     mg_http_reply(c, 200, NULL, "ok\n");
-    mg_dash_send_change(c->mgr, &set_files);
+    for (fs = dash->sets; fs != NULL; fs = fs->next) {
+      if (fs->get_dir == NULL) continue;
+      *fs->index = -1;  // Signal mg_dash_send_change() to broadcast new size
+      mg_dash_send_change(c->mgr, fs);
+    }
   }
   c->is_draining = 1;
 }
@@ -985,16 +1046,69 @@ static uint64_t mg_dash_make_expiration_time(struct mg_dash *dash) {
   return mg_millis() + t * 1000;
 }
 
+static struct mg_dash_user *mg_dash_add_user(struct mg_dash_user **users,
+                                             struct mg_dash *dash,
+                                             const char *name,
+                                             const char *token, int level) {
+  struct mg_dash_user *u = (struct mg_dash_user *) mg_calloc(1, sizeof(*u));
+  if (u != NULL) {
+    mg_snprintf(u->name, sizeof(u->name), "%s", name);
+    if (token == NULL) {
+      mg_random_str(u->token, sizeof(u->token) - 1);
+    } else {
+      mg_snprintf(u->token, sizeof(u->token), "%s", token);
+    }
+    u->level = level;
+    u->expire = mg_dash_make_expiration_time(dash);
+    u->dash = dash;
+    u->next = *users;
+    *users = u;
+  }
+  return u;
+}
+
+static struct mg_dash_user *mg_dash_find_user(struct mg_dash_user *users,
+                                              const char *name) {
+  struct mg_dash_user *u;
+  for (u = users; u != NULL; u = u->next) {
+    if (strcmp(u->name, name) == 0) return u;
+  }
+  return NULL;
+}
+
+static struct mg_dash_user *mg_dash_find_token(struct mg_dash_user *users,
+                                               const char *token) {
+  struct mg_dash_user *u;
+  for (u = users; u != NULL; u = u->next) {
+    if (strcmp(u->token, token) == 0) return u;
+  }
+  return NULL;
+}
+
+static void mg_dash_refresh_user(struct mg_dash *dash,
+                                 struct mg_dash_user *user) {
+  user->expire = mg_dash_make_expiration_time(dash);
+}
+
 // Parse HTTP requests, return authenticated user or NULL
-static struct mg_dash_user *mg_dash_authenticate(struct mg_http_message *hm,
+static struct mg_dash_user *mg_dash_authenticate(struct mg_connection *c,
+                                                 struct mg_http_message *hm,
                                                  struct mg_dash *dash) {
   static struct mg_dash_user *s_users;  // List of authenticated users
   char user[100], pass[100];
-  static struct mg_dash_user admin = {NULL, "admin", "admin", 9, (uint64_t) -1};
-  struct mg_dash_user *u, *tmp, *result = NULL;
+  struct mg_dash_user *u, *tmp;
+  struct mg_str *ah;
+  int level = 0, num_users = 0;
 
-  if (dash->authenticate == NULL) return &admin;
+  if (dash->authenticate == NULL) {
+    mg_snprintf(s_guest.name, sizeof(s_guest.name), "%s", "guest");
+    s_guest.level = 9;
+    s_guest.dash = dash;
+    dash->guest = &s_guest;
+    return dash->guest;
+  }
   mg_http_creds(hm, user, sizeof(user), pass, sizeof(pass));
+  ah = mg_http_get_header(hm, "Authorization");
   // MG_DEBUG(("user [%s], pass: [%s], h: %.*s", user, pass, hm->head.len,
   // hm->head.buf));
 
@@ -1002,47 +1116,48 @@ static struct mg_dash_user *mg_dash_authenticate(struct mg_http_message *hm,
   for (u = s_users; u != NULL; u = tmp) {
     tmp = u->next;
     if (u->expire < mg_millis()) {
+      struct mg_connection *conn;
       MG_DEBUG(("Deleting expired auth %s/%d %llu %u", u->name, u->level,
                 u->expire, mg_millis() - u->expire));
+      for (conn = c->mgr->conns; conn != NULL; conn = conn->next) {
+        struct mg_dash_cdata *d = (struct mg_dash_cdata *) conn->data;
+        if (conn->is_websocket && d->u == u) {
+          d->u = NULL;
+          conn->is_closing = 1;
+        }
+      }
       LIST_DELETE(struct mg_dash_user, &s_users, u);
       mg_free(u);
     }
   }
 
-  if (pass[0] != '\0') {
-    struct mg_str *ah = mg_http_get_header(hm, "Authorization");
-    if (ah != NULL) {
-      // Auth header and password are set, auth by user/password via glue API
-      int num_users = 0, level = dash->authenticate(user, sizeof(user), pass);
-      MG_DEBUG(("user %s, level: %d", user, level));
-      if (level > 0) {  // Proceed only if the firmware authenticated us
-        for (u = s_users; u != NULL && result == NULL;
-             u = u->next, num_users++) {
-          if (strcmp(user, u->name) == 0) {
-            u->expire = mg_dash_make_expiration_time(dash);
-            result = u;
-          }
-        }
-        // Not yet authenticated, add to the list
-        if (result == NULL && num_users < 10) {
-          result = (struct mg_dash_user *) mg_calloc(1, sizeof(*result));
-          mg_snprintf(result->name, sizeof(result->name), "%s", user);
-          mg_random_str(result->token, sizeof(result->token) - 1);
-          result->level = level, result->next = s_users, s_users = result;
-          result->expire = mg_dash_make_expiration_time(dash);
-        }
-      }
-    } else if (ah == NULL) {
-      for (u = s_users; u != NULL && result == NULL; u = u->next) {
-        if (strcmp(u->token, pass) == 0) {
-          u->expire = mg_dash_make_expiration_time(dash);
-          result = u;
-        }
-      }
+  if (pass[0] == '\0') return NULL;
+
+  for (u = s_users; u != NULL; u = u->next) num_users++;
+  if (ah == NULL) {
+    u = mg_dash_find_token(s_users, pass);
+    if (u != NULL) {
+      mg_dash_refresh_user(dash, u);
+      return u;
     }
   }
+
+  level = dash->authenticate(user, sizeof(user), pass);
+  MG_DEBUG(("user %s, level: %d", user, level));
+  if (level <= 0) return NULL;
+
+  u = mg_dash_find_user(s_users, user);
+  if (u != NULL) {
+    if (ah == NULL) mg_snprintf(u->token, sizeof(u->token), "%s", pass);
+    mg_dash_refresh_user(dash, u);
+    return u;
+  }
+
+  if (num_users < 10)
+    return mg_dash_add_user(&s_users, dash, user, ah == NULL ? pass : NULL,
+                            level);
   // MG_DEBUG(("[%s/%s] -> %s", user, pass, result ? "OK" : "FAIL"));
-  return result;
+  return NULL;
 }
 
 static void mg_handle_login(struct mg_connection *c, struct mg_dash_user *u) {
@@ -1067,48 +1182,157 @@ static void mg_handle_logout(struct mg_connection *c) {
   mg_http_reply(c, 401, cookie, "Unauthorized\n");
 }
 
+static void mg_dash_handle_del(struct mg_connection *c, struct mg_dash *dash,
+                               struct mg_dash_user *u, struct mg_str *parts) {
+  struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+  if (set == NULL || set->index == NULL) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+  } else {
+    int from = 0, to = 0, count = 0;
+    if (parts[1].len) mg_str_to_num(parts[1], 10, &from, sizeof(from));
+    to = parts[2].len ? 0 : from;
+    if (parts[2].len) mg_str_to_num(parts[2], 10, &to, sizeof(to));
+    for (*set->index = from; *set->index <= to; (*set->index)++) {
+      if (set->fn && set->fn(MG_DASH_DELETE, u))
+        count++;
+      else
+        break;
+    }
+    if (count) {
+      *set->index = -1;
+      mg_dash_send_change(c->mgr, set);
+      mg_http_reply(c, 200, MG_JSON_HEADERS, "%d\n", count);
+    } else {
+      mg_http_reply(c, 403, MG_JSON_HEADERS, "false\n");
+    }
+  }
+}
+
+// Handle "POST /api/get/<set>/<index>": modify one array element. Loads the
+// element at <index> first - that doubles as a read-access check and as a
+// pre-fill, so that JSON keys absent from the body keep their old values -
+// then overlays the values from the body and asks fn to persist them
+static void mg_dash_handle_mod(struct mg_connection *c, struct mg_dash *dash,
+                               struct mg_dash_user *u, struct mg_str *parts,
+                               struct mg_str body) {
+  struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+  int index = 0, count = 0;
+  size_t i;
+  if (set == NULL || set->index == NULL || set->fn == NULL) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+    return;
+  }
+  mg_str_to_num(parts[1], 10, &index, sizeof(index));
+  *set->index = index;
+  if (!set->fn(MG_DASH_READ, u) || *set->index != index) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+    return;
+  }
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    if (mg_dash_parse_field(body, &set->fields[i])) count++;
+  }
+  if (count && set->fn(MG_DASH_WRITE, u)) {
+    mg_dash_send_change(c->mgr, set);
+    mg_http_reply(c, 200, MG_JSON_HEADERS, "%d\n", count);
+  } else {
+    mg_http_reply(c, 403, MG_JSON_HEADERS, "false\n");
+  }
+}
+
+// Handle "POST /api/add/<set>": append a new array element. Parses the body
+// straight into the bound fields, then asks fn to accept and persist them as
+// a new element - fn returns false to reject, e.g. when a cap is reached
+static void mg_dash_handle_add(struct mg_connection *c, struct mg_dash *dash,
+                               struct mg_dash_user *u, struct mg_str *parts,
+                               struct mg_str body) {
+  struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+  int count = 0;
+  size_t i;
+  if (set == NULL || set->index == NULL || set->fn == NULL) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+    return;
+  }
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    if (mg_dash_parse_field(body, &set->fields[i])) count++;
+  }
+  if (count && set->fn(MG_DASH_ADD, u)) {
+    *set->index = -1;  // Signal mg_dash_send_change() to send new size
+    mg_dash_send_change(c->mgr, set);
+    mg_http_reply(c, 200, MG_JSON_HEADERS, "true\n");
+  } else {
+    mg_http_reply(c, 403, MG_JSON_HEADERS, "false\n");
+  }
+}
+
 void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
   struct mg_dash *dash = (struct mg_dash *) c->fn_data;
+  struct mg_dash_cdata *d = (struct mg_dash_cdata *) c->data;
 
   if (ev == MG_EV_OPEN) {
-    if (mg_dash_find_field_set(dash, mg_str("files")) == NULL) {
-      MG_DASH_ADD_FIELD_SET(dash, &set_files);
-    }
+    d->dash = dash;
     // c->is_hexdumping = 1;
-  } else if (ev == MG_EV_HTTP_HDRS && c->data[0] == 0) {
+  } else if (ev == MG_EV_HTTP_HDRS && d->marker == 0) {
     // Received headers - check authentication and possibly start uploads/ota
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
-    struct mg_dash_user *u = mg_dash_authenticate(hm, dash);
+    struct mg_dash_user *u = mg_dash_authenticate(c, hm, dash);
+    struct mg_str parts[3];
+    memset(parts, 0, sizeof(parts));
 
     if (mg_match(hm->uri, mg_str("/api/hi"), NULL) ||
         mg_match(hm->uri, mg_str("/api/logout"), NULL)) {
       // Do nothing, handle them MG_EV_HTTP_MSG. We bypass auth for those
     } else if (u == NULL && mg_match(hm->uri, mg_str("/api/#"), NULL)) {
       mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
-      c->data[0] = CONN_HANDLED;
+      d->marker = CONN_HANDLED;
     } else if (mg_match(hm->uri, mg_str("/api/login"), NULL) && u != NULL) {
       mg_handle_login(c, u);
-      c->data[0] = CONN_HANDLED;
+      d->marker = CONN_HANDLED;
     } else if (mg_match(hm->uri, mg_str("/api/ota"), NULL)) {
       mg_http_start_ota(c, hm, mg_dash_ota_cb);
-    } else if (mg_match(hm->uri, mg_str("/fs/#"), NULL) &&
+    } else if (mg_match(hm->uri, mg_str("/fs/*/*"), parts) &&
                (mg_strcasecmp(hm->method, mg_str("POST")) == 0 ||
                 mg_strcasecmp(hm->method, mg_str("PUT")) == 0)) {
-      struct mg_str name = mg_dash_file_name(hm);
-      mg_snprintf(c->data, sizeof(c->data), "%.*s", (int) name.len, name.buf);
-      mg_http_start_upload(c, hm, name, mg_str("/tmp"), &mg_fs_posix,
-                           mg_dash_upload_cb);
+      struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+      struct mg_str name = parts[1];
+      int len =
+          mg_url_decode(name.buf, name.len, (char *) name.buf, name.len + 1, 0);
+      if (len > 0 && (size_t) len <= name.len) name.len = (size_t) len;
+      if (set == NULL || set->get_dir == NULL) {
+        mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found\n");
+        d->marker = CONN_HANDLED;
+      } else if (u == NULL) {
+        mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
+        d->marker = CONN_HANDLED;
+      } else if (!mg_path_is_sane(name)) {
+        mg_http_reply(c, 400, MG_JSON_HEADERS, "Bad file name\n");
+        d->marker = CONN_HANDLED;
+      } else {
+        mg_dash_set_file_name(set, name);
+        if (set->fn != NULL && !set->fn(MG_DASH_WRITE, u)) {
+          mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
+          d->marker = CONN_HANDLED;
+        } else {
+          char dir[256];
+          struct mg_fs *fs = dash->upload_fs ? dash->upload_fs : &mg_fs_posix;
+          if (!set->get_dir(u, dir, sizeof(dir))) {
+            mg_http_reply(c, 500, MG_JSON_HEADERS, "Upload dir error\n");
+            d->marker = CONN_HANDLED;
+          } else {
+            mg_http_start_upload(c, hm, name, mg_str(dir), fs,
+                                 mg_dash_upload_cb);
+          }
+        }
+      }
     }
-    if (c->data[0] != '\0') mg_log_http_req(c, hm);
-  } else if (ev == MG_EV_HTTP_MSG && c->data[0] != '\0') {
+    if (d->marker != '\0') mg_log_http_req(c, hm);
+  } else if (ev == MG_EV_HTTP_MSG && d->marker != '\0') {
     // The response has been send in EV_HDRS path, so we're not reponding
-    // anything but clearing the c->data[0] flag for the next request.
-    c->data[0] = 0;
+    // anything but clearing the marker for the next request.
+    d->marker = 0;
     c->is_resp = 0;
-  } else if (ev == MG_EV_HTTP_MSG && c->data[0] == '\0') {
+  } else if (ev == MG_EV_HTTP_MSG && d->marker == '\0') {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
-    struct mg_dash_user *u = mg_dash_authenticate(hm, dash);
-    int level = u == NULL ? 0 : u->level;
+    struct mg_dash_user *u = mg_dash_authenticate(c, hm, dash);
     struct mg_str parts[5];
     memset(parts, 0, sizeof(parts));
 
@@ -1119,27 +1343,60 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
       mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m}", MG_ESC("method"),
                    MG_ESC("logout"));
     } else if (mg_match(hm->uri, mg_str("/api/websocket"), NULL)) {
-      *(int *) c->data = level;
+      d->u = u;
       mg_ws_upgrade(c, hm, NULL);
-    } else if (mg_match(hm->uri, mg_str("/fs/#"), NULL)) {
-      struct mg_str name = mg_dash_file_name(hm);
-      char path[128];
-      mg_snprintf(path, sizeof(path), "/tmp/%.*s", name.len, name.buf);
-      if (mg_strcasecmp(hm->method, mg_str("DELETE")) == 0) {
-        // Delete file
-        mg_dash_file_del(name);
-        mg_dash_send_change(c->mgr, &set_files);
-        mg_http_reply(c, 200, NULL, "true");
+    } else if (mg_match(hm->uri, mg_str("/fs/*/*"), parts)) {
+      struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+      if (set == NULL || set->get_dir == NULL) {
+        mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found");
+      } else if (u == NULL) {
+        mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
       } else {
-        // Serve file
-        mg_http_serve_file(c, hm, path, NULL);
+        char dir[256], path[512];
+        struct mg_fs *fs = dash->upload_fs ? dash->upload_fs : &mg_fs_posix;
+        struct mg_str name = parts[1];
+        int len = mg_url_decode(name.buf, name.len, (char *) name.buf,
+                                name.len + 1, 0);
+        if (len > 0 && (size_t) len <= name.len) name.len = (size_t) len;
+        if (!mg_path_is_sane(name)) {
+          mg_http_reply(c, 400, MG_JSON_HEADERS, "Bad file name\n");
+          return;
+        }
+        if (!set->get_dir(u, dir, sizeof(dir))) {
+          mg_http_reply(c, 500, MG_JSON_HEADERS, "Upload dir error\n");
+          return;
+        }
+        mg_snprintf(path, sizeof(path), "%s/%.*s", dir, name.len, name.buf);
+        if (mg_strcasecmp(hm->method, mg_str("DELETE")) == 0) {
+          mg_dash_set_file_name(set, name);
+          if (set->fn != NULL && !set->fn(MG_DASH_DELETE, u)) {
+            mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
+          } else {
+            fs->rm(path);
+            *set->index = -1;  // Signal mg_dash_send_change() to send new size
+            mg_dash_send_change(c->mgr, set);
+            mg_http_reply(c, 200, NULL, "true");
+          }
+        } else {
+          mg_http_serve_file(c, hm, path, NULL);
+        }
       }
-    } else if (mg_match(hm->uri, mg_str("/api/get/#"), parts) ||
+    } else if (mg_match(hm->uri, mg_str("/api/del/*/*/*"), parts) ||
+               mg_match(hm->uri, mg_str("/api/del/*/*"), parts)) {
+      mg_dash_handle_del(c, dash, u, parts);
+    } else if (mg_match(hm->uri, mg_str("/api/add/*"), parts)) {
+      mg_dash_handle_add(c, dash, u, parts, hm->body);
+    } else if (mg_match(hm->uri, mg_str("/api/get/*/*"), parts) &&
+               mg_strcasecmp(hm->method, mg_str("POST")) == 0) {
+      mg_dash_handle_mod(c, dash, u, parts, hm->body);
+    } else if (mg_match(hm->uri, mg_str("/api/get/*/*/*"), parts) ||
+               mg_match(hm->uri, mg_str("/api/get/*/*"), parts) ||
+               mg_match(hm->uri, mg_str("/api/get/*"), parts) ||
                mg_match(hm->uri, mg_str("/api/get"), NULL)) {
-      mg_http_reply(c, 200, MG_JSON_HEADERS, "%M\n", mg_dash_print_name, dash,
-                    &parts[0], level);
+      mg_http_reply(c, 200, MG_JSON_HEADERS, "%M\n", mg_dash_print_endpoint,
+                    dash, u, &parts[0], &parts[1], &parts[2]);
     } else if (mg_match(hm->uri, mg_str("/api/set"), NULL)) {
-      int count = mg_dash_apply(c, dash, hm->body, level);
+      int count = mg_dash_apply(c, dash, hm->body, u);
       mg_http_reply(c, 200, MG_JSON_HEADERS, "%d\n", count);
     } else if (mg_match(hm->uri, mg_str("/"), NULL)) {
       struct mg_http_serve_opts opts;
@@ -1157,21 +1414,6 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
       if (ch == NULL) mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found");
       mg_log_http_req(c, hm);
     }
-  } else if (ev == MG_EV_WS_OPEN) {
-    // WS connection established, send change notifications for all data
-    struct mg_field_set *fs;
-    for (fs = dash->sets; fs != NULL; fs = fs->next) {
-      mg_dash_send_change(c->mgr, fs);
-    }
-    mg_dash_broadcast(c->mgr, 0, "{%m:%m}", MG_ESC("method"), MG_ESC("ready"));
-  } else if (ev == MG_EV_WS_MSG) {
-    // Add this to automatically handle "get" and "set" JSON-RPC calls
-    struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
-    if (dash == NULL) {
-      mg_dash_error(c, wm->data, "%s", "no dash defined");
-    } else {
-      mg_dash_process_msg(c, wm, dash);
-    }
   }
 }
 
@@ -2005,15 +2247,22 @@ bool mg_ota_flash_end(struct mg_flash *flash) {
     MG_DEBUG(("CRC: %x/%x, size: %lu/%lu, status: %s", s_crc32, crc32, s_size,
               size, ok ? "ok" : "fail"));
 #ifdef MG_OTA_PUBLIC_KEY
-    if (ok && s_size > 64) {
-      static const uint8_t s_pubkey[] = MG_OTA_PUBLIC_KEY;
-      uint8_t hash[32];
-      size_t fw_size = s_size - 64;
-      mg_sha256(hash, (uint8_t *) base, fw_size);
-      ok = mg_uecc_verify(s_pubkey, hash, sizeof(hash),
-                          (uint8_t *) base + fw_size,
-                          mg_uecc_secp256r1()) == 1;
-      MG_INFO(("Signature: %s", ok ? "ok" : "fail"));
+    if (ok) {
+      bool signed_fw = s_size > 68 &&
+                       memcmp((uint8_t *) base + s_size - 4, "MGSG", 4) == 0;
+      if (signed_fw) {
+        static const uint8_t s_pubkey[] = MG_OTA_PUBLIC_KEY;
+        uint8_t hash[32];
+        size_t fw_size = s_size - 68;  // strip 64-byte sig + 4-byte magic
+        mg_sha256(hash, (uint8_t *) base, fw_size);
+        ok = mg_uecc_verify(s_pubkey, hash, sizeof(hash),
+                            (uint8_t *) base + fw_size,
+                            mg_uecc_secp256r1()) == 1;
+        MG_INFO(("Signature: %s", ok ? "ok" : "fail"));
+      } else {
+        ok = false;
+        MG_ERROR(("Unsigned firmware rejected"));
+      }
     }
 #endif
     s_size = 0;
@@ -3923,19 +4172,19 @@ static void mg_upload_handler(struct mg_connection *c, int ev, void *ev_data) {
       if (p->fd != NULL) { mg_fs_close(p->fd); p->fd = NULL; }
       else mg_ota_end();
       p->fn(c, "write error");
-      p->fn = NULL;
+      mg_free(c->pfn_data); c->pfn_data = NULL; p->fn = NULL;
     } else if (p->received >= p->expected) {
       const char *errmsg = NULL;
       if (p->fd != NULL) { mg_fs_close(p->fd); p->fd = NULL; }
       else if (!mg_ota_end()) errmsg = "OTA finalize failed";
       p->fn(c, errmsg);
-      p->fn = NULL;
+      mg_free(c->pfn_data); c->pfn_data = NULL; p->fn = NULL;
     }
   } else if (ev == MG_EV_ERROR || ev == MG_EV_CLOSE) {
     if (p->fd != NULL) { mg_fs_close(p->fd); p->fd = NULL; }
     else mg_ota_end();
     p->fn(c, ev == MG_EV_ERROR ? (const char *) ev_data : "connection closed");
-    p->fn = NULL;
+    mg_free(c->pfn_data); c->pfn_data = NULL; p->fn = NULL;
   }
   (void) ev_data;
 }
@@ -3945,6 +4194,10 @@ static void mg_upload_default_cb(struct mg_connection *c, const char *status) {
   mg_http_reply(c, status ? 500 : 200, "", "%s\n", status ? status : "ok");
 }
 
+const char *mg_upload_path(struct mg_connection *c) {
+  return (const char *) c->pfn_data;
+}
+
 void mg_http_start_upload(struct mg_connection *c, struct mg_http_message *hm,
                           struct mg_str name, struct mg_str dir,
                           struct mg_fs *fs,
@@ -3964,6 +4217,7 @@ void mg_http_start_upload(struct mg_connection *c, struct mg_http_message *hm,
   p->fd = fd;
   p->fn = fn;
   c->fn = mg_upload_handler;
+  c->pfn_data = strdup(path);
   c->pfn = NULL;
   mg_iobuf_del(&c->recv, 0, hm->head.len);
   mg_call(c, MG_EV_READ, &c->recv.len);
@@ -6990,6 +7244,7 @@ struct mg_connection *mg_mqtt_listen(struct mg_mgr *mgr, const char *url,
 
 
 
+
 size_t mg_vprintf(struct mg_connection *c, const char *fmt, va_list *ap) {
   size_t old = c->send.len;
   size_t expected = mg_vxprintf(mg_pfn_iobuf, &c->send, fmt, ap);
@@ -7261,6 +7516,11 @@ void mg_mgr_free(struct mg_mgr *mgr) {
 
 void mg_mgr_init(struct mg_mgr *mgr) {
   memset(mgr, 0, sizeof(*mgr));
+  // Anchor mg_fw_version: a real store into a struct field the optimiser
+  // can't elide forces the linker to keep the section alive even when no
+  // OTA polling code runs it. Callers that want mgr->userdata for their own
+  // purposes simply overwrite it after this call returns
+  mgr->userdata = (void *) mg_fw_version;
 #if MG_ENABLE_EPOLL
   if ((mgr->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0)
     MG_ERROR(("epoll_create1 errno %d", errno));
@@ -9489,6 +9749,7 @@ void mg_mgr_poll(struct mg_mgr *mgr, int ms) {
   struct mg_connection *c, *tmp;
   uint64_t now = mg_millis();
   mg_timer_poll(&mgr->timers, now);
+  mg_ota_poll(mgr);
   if (mgr->ifp == NULL || mgr->ifp->driver == NULL) return;
   mg_tcpip_poll(mgr->ifp, now);
   for (c = mgr->conns; c != NULL; c = tmp) {
@@ -9583,144 +9844,170 @@ void mg_tcpip_mapip(struct mg_connection *c, struct mg_addr *ip) {
 
 
 
-enum { MG_OTA_STATUS_WAITING, MG_OTA_STATUS_SUCCESS, MG_OTA_STATUS_FAIL };
-static int s_version_status;
-static int s_ota_status;
-static uint64_t s_start_time;
+#ifndef MG_OTA_MAX_URL_LEN
+#define MG_OTA_MAX_URL_LEN 256
+#endif
 
-static struct mg_ota_metadata {
-  char *version;
-  char *url;
+// Scannable version tag embedded in every firmware binary, for server-side
+// version extraction. Non-static so mg_mgr_init() can stash its address in
+// mgr->userdata: that store is what actually keeps -Wl,--gc-sections from
+// stripping it on builds that never poll for OTAs (an attribute alone does
+// not - the linker drops unreferenced sections regardless of "used"/"retain")
+const char mg_fw_version[] = "MG_VERSION:" MG_OTA_FIRMWARE_VERSION;
+
+static struct mg_ota_state {
+  char my_version[MG_OTA_MAX_VERSION_LEN];
+  char json_url[MG_OTA_MAX_URL_LEN];
+  char version[MG_OTA_MAX_VERSION_LEN];
+  char url[MG_OTA_MAX_URL_LEN];
   size_t size;
   uint8_t sha256[32];
-} s_ota_metadata;
+  void (*fn)(const char *status);
+} *s_ota;
 
-static void free_ota_metadata(void) {
-  if (s_ota_metadata.version) mg_free(s_ota_metadata.version);
-  if (s_ota_metadata.url) mg_free(s_ota_metadata.url);
-  memset(&s_ota_metadata, 0, sizeof(s_ota_metadata));
-}
+static void s_firmware_fn(struct mg_connection *c, int ev, void *ev_data);
 
-static int fetch_ota_metadata(struct mg_http_message *response) {
-  double result;
-  if (mg_http_status(response) != 200) goto fetch_failed;
-  if (mg_json_get(response->body, "$", NULL) != 0) goto fetch_failed;
-  free_ota_metadata();
-  s_ota_metadata.version = mg_json_get_str(response->body, "$.version");
-  if (s_ota_metadata.version == NULL) goto fetch_failed;
-  s_ota_metadata.url = mg_json_get_str(response->body, "$.url");
-  if (s_ota_metadata.url == NULL) goto fetch_failed;
-  if (!mg_json_get_num(response->body, "$.size", &result) || result <= 0)
-    goto fetch_failed;
-  s_ota_metadata.size = (size_t) result;
-  // TODO (robertc2000): parse and validate sha256
-  MG_DEBUG(("Firmware version: %s, url: %s, size: %ld", s_ota_metadata.version,
-            s_ota_metadata.url, s_ota_metadata.size));
-  return MG_OTA_STATUS_SUCCESS;
-fetch_failed:
-  free_ota_metadata();
-  return MG_OTA_STATUS_FAIL;
+#if MG_ENABLE_CUSTOM_DEVICE_ID
+#else
+void mg_ota_device_id(char *buf, size_t len) {
+#if MG_ARCH == MG_ARCH_CUBE && defined(UID_BASE)
+  mg_snprintf(buf, len, "%M", mg_print_hex, 12, (uint8_t *) UID_BASE);
+#else
+  mg_snprintf(buf, len, "%d", 0);
+#endif
 }
+#endif
 
 static void s_version_fn(struct mg_connection *c, int ev, void *ev_data) {
-  struct mg_str host = mg_url_host((char *) c->fn_data);
-  struct mg_http_message *hm;
-  static int fetch_status;
-
+  uint64_t expiration = *(uint64_t *) c->data;
   if (ev == MG_EV_POLL) {
-    if (s_start_time + 5 * 1000 < mg_millis()) {
-      mg_error(c, "Connection timeout");
-    }
+    if (mg_millis() > expiration) mg_error(c, "Metadata timeout");
   } else if (ev == MG_EV_CONNECT) {
+    char id[33];
+    struct mg_str host = mg_url_host(s_ota->json_url);
+    const char *uri = mg_url_uri(s_ota->json_url);
+    const char *sep = strchr(uri, '?') == NULL ? "?" : "&";
+    mg_ota_device_id(id, sizeof(id));
+    id[sizeof(id) - 1] = '\0';
     mg_printf(c,
-              "GET %s HTTP/1.1\r\n"
+              "GET %s%sarch=%d&version=%s&id=%s&interval=%d HTTP/1.1\r\n"
               "Host: %.*s\r\n"
               "Connection: close\r\n\r\n",
-              mg_url_uri((char *) c->fn_data), (int) host.len, host.buf);
-    fetch_status = MG_OTA_STATUS_WAITING;
+              uri, sep, MG_ARCH, s_ota->my_version, id,
+              MG_OTA_PULL_INTERVAL_SECONDS, host.len, host.buf);
   } else if (ev == MG_EV_HTTP_MSG) {
-    hm = (struct mg_http_message *) ev_data;
-    fetch_status = fetch_ota_metadata(hm);
+    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+    double result;
+    MG_DEBUG(("Got metadata:\n%.*s", hm->body.len, hm->body.buf));
+    if (mg_http_status(hm) != 200 || mg_json_get(hm->body, "$", NULL) != 0 ||
+        !mg_json_unescape(hm->body, "$.version", s_ota->version,
+                          sizeof(s_ota->version)) ||
+        !mg_json_unescape(hm->body, "$.url", s_ota->url, sizeof(s_ota->url)) ||
+        !mg_json_get_num(hm->body, "$.size", &result) || result <= 0) {
+      char buf[100];
+      mg_snprintf(buf, sizeof(buf), "Bad metadata: %.*s", hm->body.len,
+                  hm->body.buf);
+      s_ota->fn(buf);
+      mg_free(s_ota);
+      s_ota = NULL;
+    } else if (strcmp(s_ota->version, s_ota->my_version) == 0) {
+      s_ota->fn("Same version");
+      mg_free(s_ota);
+      s_ota = NULL;
+    } else {
+      struct mg_connection *fc;
+      s_ota->size = (size_t) result;
+      // TODO (robertc2000): parse and validate sha256
+      MG_DEBUG(("Firmware version: %s, url: %s, size: %ld", s_ota->version,
+                s_ota->url, s_ota->size));
+      fc = mg_http_connect(c->mgr, s_ota->url, s_firmware_fn, NULL);
+      if (fc == NULL) {
+        s_ota->fn("Failed to connect");
+        mg_free(s_ota);
+        s_ota = NULL;
+      } else {
+        *(uint64_t *) fc->data = mg_millis() + 300 * 1000;  // Set expiration
+      }
+    }
+    c->is_closing = 1;
   } else if (ev == MG_EV_ERROR) {
-    MG_ERROR(("%lu Connection error", c->id));
-    s_version_status = MG_OTA_STATUS_FAIL;
-  } else if (ev == MG_EV_CLOSE) {
-    MG_DEBUG(("%lu Connection closed %lu", c->id, mg_millis() - s_start_time));
-    s_version_status = fetch_status;
+    s_ota->fn((char *) ev_data);
+    mg_free(s_ota);
+    s_ota = NULL;
   }
 }
 
-static void s_ota_done(struct mg_connection *c, const char *errmsg) {
-  (void) c;
-  s_ota_status = errmsg ? MG_OTA_STATUS_FAIL : MG_OTA_STATUS_SUCCESS;
+static void status_fn(const char *errmsg) {
   if (errmsg) MG_ERROR(("OTA failed: %s", errmsg));
 }
 
+static void status_fn_2(struct mg_connection *c, const char *errmsg) {
+  if (s_ota) s_ota->fn(errmsg);
+  mg_free(s_ota);
+  s_ota = NULL;
+  mg_http_reply(c, errmsg ? 500 : 200, "", "%s\n", errmsg ? errmsg : "ok");
+}
+
 static void s_firmware_fn(struct mg_connection *c, int ev, void *ev_data) {
-  struct mg_str host = mg_url_host(s_ota_metadata.url);
+  uint64_t expiration = *(uint64_t *) c->data;
   if (ev == MG_EV_POLL) {
-    if (s_start_time + 120 * 1000 < mg_millis()) mg_error(c, "Timeout");
+    if (mg_millis() > expiration) mg_error(c, "OTA timeout");
   } else if (ev == MG_EV_CONNECT) {
+    struct mg_str host = mg_url_host(s_ota->url);
     mg_printf(c,
               "GET %s HTTP/1.1\r\n"
               "Host: %.*s\r\n"
               "Connection: close\r\n\r\n",
-              mg_url_uri(s_ota_metadata.url), (int) host.len, host.buf);
+              mg_url_uri(s_ota->url), (int) host.len, host.buf);
   } else if (ev == MG_EV_HTTP_HDRS) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     int status = mg_http_status(hm);
-    if (status != 200 || hm->body.len != s_ota_metadata.size) {
+    if (status != 200 || hm->body.len != s_ota->size) {
       mg_error(c, "Bad HTTP response: status %d, size %lu vs %lu", status,
-               (unsigned long) hm->body.len,
-               (unsigned long) s_ota_metadata.size);
-      s_ota_status = MG_OTA_STATUS_FAIL;
-      return;
+               (unsigned long) hm->body.len, (unsigned long) s_ota->size);
+    } else {
+      MG_DEBUG(("Beginning OTA (%lu bytes)", (unsigned long) s_ota->size));
+      mg_http_start_ota(c, hm, status_fn_2);
     }
-    MG_DEBUG(
-        ("Beginning OTA (%lu bytes)", (unsigned long) s_ota_metadata.size));
-    mg_http_start_ota(c, hm, s_ota_done);
   } else if (ev == MG_EV_ERROR) {
-    MG_ERROR(("%lu Connection error", c->id));
-    s_ota_status = MG_OTA_STATUS_FAIL;
+    s_ota->fn((char *) ev_data);
+    mg_free(s_ota);
+    s_ota = NULL;
   }
-  (void) ev_data;
 }
 
-void mg_ota_url_check(struct mg_mgr *mgr, const char *current_version,
-                      const char *metadata_url,
-                      void (*fn)(const char *status)) {
-  s_version_status = MG_OTA_STATUS_WAITING;
-  s_ota_status = MG_OTA_STATUS_WAITING;
-  s_start_time = mg_millis();
-  MG_DEBUG(("Connecting to %s to retrieve metadata", metadata_url));
-  if (!mg_http_connect(mgr, metadata_url, s_version_fn,
-                       (void *) metadata_url)) {
-    if (fn) fn("Failed to connect");
-    return;
-  }
-  while (s_version_status == MG_OTA_STATUS_WAITING) mg_mgr_poll(mgr, 10);
-  if (s_version_status == MG_OTA_STATUS_SUCCESS) {
-    if (strcmp(s_ota_metadata.version, current_version) == 0) {
-      if (fn) fn("Same version");
-      free_ota_metadata();
-      return;
-    }
+void mg_ota_url_check(struct mg_mgr *mgr, const char *my_version,
+                      const char *json_url, void (*fn)(const char *status)) {
+  if (fn == NULL) fn = status_fn;
+  if (s_ota != NULL) {
+    fn("OTA already in progress");
+  } else if ((s_ota = (struct mg_ota_state *) mg_calloc(1, sizeof(*s_ota))) ==
+             NULL) {
+    fn("Out of memory");
   } else {
-    if (fn) fn("Version retrieving error");
-    free_ota_metadata();
-    return;
+    struct mg_connection *c;
+    mg_snprintf(s_ota->my_version, sizeof(s_ota->my_version), "%s", my_version);
+    mg_snprintf(s_ota->json_url, sizeof(s_ota->json_url), "%s", json_url);
+    MG_DEBUG(("Connecting to %s", json_url));
+    c = mg_http_connect(mgr, s_ota->json_url, s_version_fn, NULL);
+    if (c == NULL) {
+      mg_free(s_ota);
+      s_ota = NULL;
+      fn("Failed to connect");
+    } else {
+      s_ota->fn = fn;
+      *(uint64_t *) c->data = mg_millis() + 5 * 1000;  // Set expiration
+    }
   }
-  if (fn) fn("Pulling firmware");
-  s_start_time = mg_millis();
-  MG_DEBUG(("Connecting to %s to download firmware", s_ota_metadata.url));
-  if (!mg_http_connect(mgr, s_ota_metadata.url, s_firmware_fn, NULL)) {
-    if (fn) fn("Failed to connect");
-    free_ota_metadata();
-    return;
+}
+
+void mg_ota_poll(struct mg_mgr *mgr) {
+  static uint64_t t = 1;
+  if (MG_OTA_URL != NULL &&
+      mg_timer_expired(&t, MG_OTA_PULL_INTERVAL_SECONDS * 1000, mg_millis())) {
+    mg_ota_url_check(mgr, MG_OTA_FIRMWARE_VERSION, MG_OTA_URL,
+                     MG_OTA_STATUS_FN);
   }
-  while (s_ota_status == MG_OTA_STATUS_WAITING) mg_mgr_poll(mgr, 10);
-  if (s_ota_status == MG_OTA_STATUS_FAIL && fn) fn("OTA fail");
-  free_ota_metadata();
 }
 
 #ifdef MG_ENABLE_LINES
@@ -12995,6 +13282,7 @@ struct mg_connection *mg_sntp_connect(struct mg_mgr *mgr, const char *url,
 
 
 
+
 #if MG_ENABLE_SOCKET
 
 #ifndef closesocket
@@ -13743,6 +14031,7 @@ void mg_mgr_poll(struct mg_mgr *mgr, int ms) {
   mg_iotest(mgr, ms);
   now = mg_millis();
   mg_timer_poll(&mgr->timers, now);
+  mg_ota_poll(mgr);
 
   for (c = mgr->conns; c != NULL; c = tmp) {
     bool is_resp = c->is_resp;
diff --git a/mongoose.h b/mongoose.h
index e72f68a0..cb421b90 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -1897,6 +1897,7 @@ void mg_http_start_upload(struct mg_connection *c, struct mg_http_message *hm,
                           void (*fn)(struct mg_connection *, const char *));
 void mg_http_start_ota(struct mg_connection *c, struct mg_http_message *hm,
                        void (*fn)(struct mg_connection *, const char *));
+const char *mg_upload_path(struct mg_connection *c);
 void mg_http_bauth(struct mg_connection *, const char *user, const char *pass);
 struct mg_str mg_http_get_header_var(struct mg_str s, struct mg_str v);
 size_t mg_http_next_multipart(struct mg_str, size_t, struct mg_http_part *);
@@ -3277,50 +3278,95 @@ void mg_rpc_list(struct mg_rpc_req *r);
 
 
 
+#ifndef MG_DASH_MAX_USER_NAME
+#define MG_DASH_MAX_USER_NAME 32
+#endif
+
+#ifndef MG_HTTP_ADDR
+#if MG_ARCH == MG_ARCH_UNIX || MG_ARCH == MG_ARCH_WIN32
+#define MG_HTTP_ADDR "http://0.0.0.0:8000"
+#define MG_HTTPS_ADDR "https://0.0.0.0:8443"
+#define MG_MODBUS_ADDR "tcp://0.0.0.0:8502"
+#else
+#define MG_HTTP_ADDR "http://0.0.0.0:80"
+#define MG_HTTPS_ADDR "http://0.0.0.0:443"
+#define MG_MODBUS_ADDR "tcp://0.0.0.0:502"
+#endif
+#endif
+
+#ifndef MG_DASH_MAX_SEND_BUF_SIZE
+#define MG_DASH_MAX_SEND_BUF_SIZE (MG_IO_SIZE * 5)
+#endif
+
+// C type of a value bound to a dashboard field, see struct mg_field
 enum mg_val_type {
-  MG_VAL_INT,
-  MG_VAL_BOOL,
-  MG_VAL_DBL,
-  MG_VAL_STR,
-  MG_VAL_RAW,
+  MG_VAL_INT,     // int
+  MG_VAL_UINT64,  // uint64_t
+  MG_VAL_BOOL,    // bool
+  MG_VAL_DBL,     // double
+  MG_VAL_STR,     // Zero-terminated string
+  MG_VAL_RAW,     // Pre-formatted JSON value, copied verbatim
 };
 
+// Dashboard field: binds a JSON key to a C variable for read and/or write
 struct mg_field {
-  const char *name;
-  enum mg_val_type type;
-  void *value;
-  size_t value_size;
+  const char *name;       // JSON key
+  enum mg_val_type type;  // C type of the value, see enum mg_val_type
+  void *value;            // Pointer to the bound variable
+  size_t value_size;  // sizeof(*value) for type checking; 0 makes it read-only
 };
 
+// Operation passed to a struct mg_field_set read/write/delete/add callback.
+// MG_DASH_ADD: fields hold the values of a new element to append; *index is
+// not set. Return true to accept and persist it, false to reject (e.g. a cap
+// was reached)
+enum mg_dash_op { MG_DASH_READ, MG_DASH_WRITE, MG_DASH_DELETE, MG_DASH_ADD };
+
+struct mg_dash;
+
+// Authenticated (or guest) dashboard user
+struct mg_dash_user {
+  struct mg_dash_user *next;         // Next user in the list
+  char name[MG_DASH_MAX_USER_NAME];  // Username
+  char token[21];        // Session token, sent to the client as a cookie
+  int level;             // Access level, see struct mg_dash::authenticate
+  uint64_t expire;       // Session expiration time, see mg_millis()
+  struct mg_dash *dash;  // Dashboard this user belongs to
+};
+
+// Named group of related dashboard fields, e.g. "settings" or "metrics"
 struct mg_field_set {
-  const char *name;
-  struct mg_field *fields;
-  void (*reader)(void);
-  void (*writer)(void);
-  int read_level;
-  int write_level;
-  struct mg_field_set *next;
+  const char *name;         // Set name, used as a JSON key
+  struct mg_field *fields;  // Zero-terminated array of fields
+  bool (*fn)(enum mg_dash_op op,
+             struct mg_dash_user *u);  // Read/write/delete/add callback
+  int *index;  // Non-NULL: array set. *index is set before fn(READ) call;
+               // fn sets *index = -1 to signal end of iteration.
+               // Size query: framework sets *index = -1 before fn(READ); fn
+               // sets *index = total size
+  bool (*get_dir)(const struct mg_dash_user *u, char *buf,
+                  size_t len);  // Non-NULL: file array
+  struct mg_field_set *next;    // Next set in the list
 };
 
+// Custom URI handler, registered with MG_DASH_REGISTER_CUSTOM_HANDLER()
 struct mg_dash_custom_handler {
-  struct mg_dash_custom_handler *next;
-  struct mg_str uri_pattern;
-  mg_event_handler_t handler;
-  void *handler_data;
-};
-
-struct mg_dash_file {
-  struct mg_dash_file *next;
-  char *name;
-  size_t size;
+  struct mg_dash_custom_handler *next;  // Next handler in the list
+  struct mg_str uri_pattern;            // URI to match, see mg_match()
+  mg_event_handler_t handler;           // Event handler function
+  void *handler_data;                   // Opaque data for the handler
 };
 
+// Dashboard instance: fields, users and handlers served over HTTP and WS
 struct mg_dash {
-  struct mg_field_set *sets;
-  struct mg_dash_custom_handler *custom_handlers;
+  struct mg_field_set *sets;  // Field sets, see MG_DASH_ADD_FIELD_SET()
+  struct mg_dash_custom_handler *custom_handlers;  // Custom URI handlers
+  // Validates pass, fills in user, returns access level (<= 0: failure).
+  // NULL: no login required, all clients get guest access
   int (*authenticate)(char *user, size_t userlen, const char *pass);
-  int session_auto_expiration_seconds;
-  //struct mg_dash_file *files;
+  int session_auto_expiration_seconds;  // Session lifetime, 0: 1 hour default
+  struct mg_dash_user *guest;           // Used when authenticate == NULL
+  struct mg_fs *upload_fs;  // FS for uploads/listing, default &mg_fs_posix
 };
 
 #define MG_DASH_ADD_FIELD_SET(dash_, set_) \
@@ -3339,28 +3385,50 @@ struct mg_dash {
     (dash_)->custom_handlers = &ch_;                             \
   } while (0)
 
-#if MG_ARCH == MG_ARCH_UNIX || MG_ARCH == MG_ARCH_WIN32
-#define MG_HTTP_ADDR "http://0.0.0.0:8000"
-#define MG_HTTPS_ADDR "https://0.0.0.0:8443"
-#define MG_MODBUS_ADDR "tcp://0.0.0.0:8502"
-#else
-#define MG_HTTP_ADDR "http://0.0.0.0:80"
-#define MG_HTTPS_ADDR "http://0.0.0.0:443"
-#define MG_MODBUS_ADDR "tcp://0.0.0.0:502"
-#endif
-
-#ifndef MG_DASH_MAX_SEND_BUF_SIZE
-#define MG_DASH_MAX_SEND_BUF_SIZE (MG_IO_SIZE * 5)
-#endif
-
-// File manager
-extern struct mg_dash_file *mg_dash_files;
-void mg_dash_file_add(struct mg_str name, size_t size);
-void mg_dash_file_del(struct mg_str name);
-
+// Dashboard event handler. Pass to mg_http_listen() as the fn argument
 void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data);
+
+// Notify WebSocket clients that a field set changed: broadcasts the new
+// array size if *set->index < 0, or a single element update otherwise
 void mg_dash_send_change(struct mg_mgr *mgr, struct mg_field_set *);
 
+// Default reader for file-backed array sets (set->get_dir != NULL)
+// Usage example - this is a complete implemenation of the file manager:
+// ```c
+// static struct file {
+//   int index;
+//   char name[64];
+//   size_t size;
+//   uint64_t checksum;
+// } s_file;
+// static struct mg_field_set set_files;
+//
+// static bool get_dir(const struct mg_dash_user *u, char *buf, size_t len) {
+//   (void) u;
+//   mkdir("/tmp/dashboard", 0755);
+//   mg_snprintf(buf, len, "%s", "/tmp/dashboard");
+//   return true;
+// }
+//
+// static struct mg_field fields_files[] = {
+//     {"name", MG_VAL_STR, s_file.name, sizeof(s_file.name)},
+//     {"size", MG_VAL_UINT64, &s_file.size, 0},
+//     {"checksum", MG_VAL_UINT64, &s_file.checksum, sizeof(s_file.checksum)},
+//     {NULL, MG_VAL_INT, NULL, 0},
+// };
+//
+// static bool files_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+//   if (op == MG_DASH_WRITE) return s_uploads_enabled && u->level >= 7;
+//   if (op != MG_DASH_READ) return false;
+//   if (!mg_dash_dir_read(&set_files, u)) return false;
+//   s_file.checksum = 0;  // Mock to show how to set custom fields
+//   return true;
+// }
+//
+// static struct mg_field_set set_files = {"files", fields_files, files_fn, &s_file.index, get_dir, NULL};
+// ```
+bool mg_dash_dir_read(struct mg_field_set *set, struct mg_dash_user *u);
+
 // Helper forward declarations for Mongoose CMSIS pack modules
 extern struct mg_mgr g_mgr;
 extern void mg_dash_init(struct mg_mgr *);
@@ -3470,6 +3538,40 @@ enum { MG_OTA_CONFIRMED = 0, MG_OTA_TESTING = 1, MG_OTA_FAILED = 2 };
 void mg_ota_url_check(struct mg_mgr *mgr, const char *current_version,
                       const char *metadata_url, void (*fn)(const char *status));
 
+#ifndef MG_OTA_URL
+#define MG_OTA_URL NULL
+#endif
+
+#ifndef MG_OTA_STATUS_FN
+#define MG_OTA_STATUS_FN NULL
+#endif
+
+#ifndef MG_OTA_FIRMWARE_VERSION
+#define MG_OTA_FIRMWARE_VERSION "1.0.0"
+#endif
+
+#ifndef MG_OTA_MAX_VERSION_LEN
+#define MG_OTA_MAX_VERSION_LEN 64
+#endif
+
+// Scannable "MG_VERSION:<MG_OTA_FIRMWARE_VERSION>" tag embedded in every
+// firmware binary, for server-side extraction. mg_mgr_init() stashes its
+// address in mgr->userdata, which is what keeps it from being stripped by
+// -Wl,--gc-sections on builds that never poll for OTAs
+extern const char mg_fw_version[];
+
+#ifndef MG_OTA_PULL_INTERVAL_SECONDS
+#define MG_OTA_PULL_INTERVAL_SECONDS 60
+#endif
+
+#ifndef MG_ENABLE_CUSTOM_DEVICE_ID
+#define MG_ENABLE_CUSTOM_DEVICE_ID 0
+#endif
+
+void mg_ota_device_id(char *buf, size_t len);
+
+void mg_ota_poll(struct mg_mgr *);
+
 
 
 
diff --git a/resources/dashboard.js b/resources/dashboard.js
index 328ae7c7..664ac438 100644
--- a/resources/dashboard.js
+++ b/resources/dashboard.js
@@ -3,19 +3,13 @@
 (function (global) {
   "use strict";
 
-  const Rpc = (function() {
-    function Rpc(url, onev) {
-      let ws, id = 1, oncall, q = [], reconnect = true;
-      const pending = new Map();
-      const realsend = s => { ws.send(s); onev && onev('send', s); };
-      const fail = e => { for (const p of pending.values()) p[1](e || 'disconnected'); pending.clear(); };
-      const send = x => ws && ws.readyState === 1
-        ? realsend(JSON.stringify(x))
-        : q.push(x);
+  const Watch = (function() {
+    function Watch(url, onev, onmsg) {
+      let ws, reconnect = true;
       const connect = () => {
         ws = new WebSocket(url);
-        ws.onopen = () => { onev && onev('open'); while (q.length) realsend(JSON.stringify(q.shift())); };
-        ws.onclose = () => { onev && onev('close'); fail(); reconnect && setTimeout(connect, 1000); };
+        ws.onopen = () => onev && onev('open');
+        ws.onclose = () => { onev && onev('close'); reconnect && setTimeout(connect, 1000); };
         ws.onmessage = e => {
           onev && onev('message', e.data);
           let m;
@@ -25,69 +19,92 @@
             console.log('INVALID JSON:', e.data);
             return;
           }
-
-          if (m.id && pending.has(m.id)) {
-            const [ok, bad] = pending.get(m.id);
-            pending.delete(m.id);
-            m.error ? bad(m.error) : ok(m.result);
-          } else if (oncall && m.method) {
-            Promise.resolve(oncall(m.method, m.params))
-              .then(r => m.id && send({ id: m.id, result: r }))
-              .catch(err => m.id && send({
-                id: m.id,
-                error: { code: -32000, message: String(err?.message || err) }
-              }));
-          }
+          onmsg && onmsg(m);
         };
       };
 
       connect();
       return {
         close: () => { reconnect = false; ws?.close(); },
-        call: (method, params) => new Promise((ok, bad) => {
-          const i = id++;
-          pending.set(i, [ok, bad]);
-          send({  id: i, method, params });
-        }),
-        notify: (method, params) => send({ method, params }),
-        handle: fn => (oncall = fn, this),
         get ws() { return ws; }
       };
     }
 
-    return Rpc;
+    return Watch;
   })();
 
-  function rpc_connect() {
+  function fetch_and_ready() {
     if (isMock) {
-      setTimeout(() => userhandlers['ready']?.(), 500);
-      return;
+      return delay(500).then(rescan).then(mark_ready);
     }
-    if (rpc) return rpc;
-    //if (settings.auth && !status.authed) return null;
-    rpc = Rpc('api/websocket', function (evname, args) {
-      if (evname == 'open') status.online = true, rescan();
-      if (evname == 'close') status.online = false, rescan();
-      if (settings.debug) console.log('WS', evname, args);
-    });
-    rpc.handle((method, args) => {
-      if (method == 'change' && args) apply_and_rescan(settings.data, args);
-      if (method == 'logout') rpc_disconnect();
-      if (userhandlers[method]) userhandlers[method](args);
-    });
-    return rpc;
+    return fetch('api/get')
+      .then(r => r.ok ? r.json() : Promise.reject(r.status))
+      .then(data => {
+        for (const k in data) {
+          if (typeof data[k] === 'number') {
+            const prev = settings.data[k];
+            const arr = prev && typeof prev === 'object' ? prev : {};
+            data[k] = {
+              ...arr,
+              size: data[k],
+              start: typeof arr.start === 'number' ? arr.start : 0,
+              data: Array.isArray(arr.data) ? arr.data : [],
+            };
+          }
+        }
+        return apply_and_rescan(settings.data, data);
+      })
+      .then(expand_arrays)
+      .then(() => {
+        ws_connect();
+        return mark_ready();
+      })
+      .catch(err => console.log('GET failed', err));
   }
 
-  function rpc_disconnect() {
-    if (!rpc) return;
-    rpc.close();
-    rpc = null;
+  function ws_connect() {
+    if (isMock || ws) return;
+    ws = Watch('api/websocket', function (evname, args) {
+      if (evname == 'open') { status.online = true; rescan(); }
+      if (evname == 'close') { status.online = false; rescan(); }
+      if (settings.debug) console.log('WS', evname, args);
+    }, function (m) {
+      if (m.method == 'change' && m.params) {
+        const rest = {};
+        const arrays = [];
+        for (const k in m.params) {
+          const ma = k.match(/^(.+)\/(\d+)$/);
+          if (ma) {
+            const arr = settings.data[ma[1]];
+            if (arr?.data) { const i = +ma[2] - (arr.start || 0); if (i >= 0 && i < arr.data.length) arr.data[i] = Object.assign(arr.data[i] || {}, m.params[k]); }
+          } else if (typeof m.params[k] === 'number' && settings.data[k]?.data !== undefined) {
+            const arr = settings.data[k];
+            arr.size = m.params[k];
+            if (is_expandable(arr)) arrays.push(expand_array(k, arr.start, arr.end));
+          } else {
+            rest[k] = m.params[k];
+          }
+        }
+        apply(settings.data, rest);
+        prune(settings.data, settings.edits);
+        Promise.all(arrays)
+          .then(rescan)
+          .then(() => userhandlers['change']?.(m.params));
+      }
+      if (m.method == 'logout') ws_disconnect();
+    });
+  }
+
+  function ws_disconnect() {
+    if (!ws) return;
+    ws.close();
+    ws = null;
     status.online = false;
   }
 
 
   function login(params) {
-    if (isMock) { rpc_connect(); return Promise.resolve({}); }
+    if (isMock) return fetch_and_ready().then(() => ({}));
     const opts = {};
     if (params) {
       const username = (params?.username ?? '').trim();
@@ -100,19 +117,18 @@
       .then(resp => {
         status.username = resp?.user || '';
         status.userlevel = resp?.level || 0;
-        rpc_connect();
-        return resp;
+        return fetch_and_ready().then(() => resp);
       });
   };
 
   function logout() {
-    if (isMock) { rpc_disconnect(); return Promise.resolve({}); }
+    if (isMock) { ws_disconnect(); return Promise.resolve({}); }
     return fetch('api/logout')
       .catch(() => true)
       .then(() => {
         status.username = '';
         status.userlevel = 0;
-        rpc_disconnect();
+        ws_disconnect();
         return true;
       });
   }
@@ -122,7 +138,27 @@
   const settings = {data: {}, edits: {}, debug: true};
   const userhandlers = {}; // User event handlers
   const status = { online: false, username: '', userlevel: 0, ready: false };
-  let rpc = null;
+  let ws = null;
+  let ready_started = false;
+
+  function install_ready_gate() {
+    document.documentElement.classList.remove('dashboard-ready');
+    if (document.getElementById('dashboard-ready-gate')) return;
+    const style = document.createElement('style');
+    style.id = 'dashboard-ready-gate';
+    style.textContent = `html:not(.dashboard-ready) *,html:not(.dashboard-ready) *::before,html:not(.dashboard-ready) *::after{transition:none!important;animation:none!important}`;
+    document.head.appendChild(style);
+  }
+
+  function mark_ready() {
+    if (ready_started) return Promise.resolve();
+    ready_started = true;
+    return next_frame().then(() => {
+      status.ready = true;
+      document.documentElement.classList.add('dashboard-ready');
+      userhandlers['ready']?.();
+    });
+  }
 
   const fromPath = (path, value) => path.split('.').reverse().reduce((acc, k) => ({ [k]: acc }), value);
   const get = (obj, path) => path.split('.').reduce((o, k) => o?.[k], obj);
@@ -222,7 +258,11 @@
   function save(key) {
     const changes = {};
     set(changes, key, get(settings.edits, key));
-    rpc.call('set', changes).then(r => apply_and_rescan(settings.data, r));
+    fetch('api/set', {
+      method: 'POST',
+      headers: {'Content-Type': 'application/json'},
+      body: JSON.stringify(changes),
+    }).catch(err => console.log('SET failed', key, err));
   };
 
   // Cancel the edits for keys that match pattern
@@ -231,6 +271,14 @@
     rescan();
   };
 
+  // Set a checkbox's `checked` *property* from a boolean expression. The
+  // `checked` content attribute is presence-based - templating its value
+  // would not work, so this binds straight to the IDL property instead
+  function handle_checked(el, key, context) {
+    if (!has(context, key)) { console.error('EVAL', key, context); return; }
+    el.checked = !!get(context, key);
+  };
+
   function handle_save(el, key) {
     el.disabled = !edited(key);
     if (!el.bound) el.addEventListener("click", ev => save(key)), el.bound = true;
@@ -244,18 +292,30 @@
   function handle_repeat(el, key, context) {
     if (!has(context, key)) { console.error('EVAL', key, context); return; }
     if (!el.orig) el.orig = el.children[0].cloneNode(true);
-    const v = get(context, key), v2 = JSON.stringify(v);
-    if (el.v2 === v2) return;
-    const frag = document.createDocumentFragment();
+    const v = get(context, key);
     const it = el.dataset.iterator ?? '__obj';
-    v.forEach(function (item, index) {
-      const child = el.orig.cloneNode(true);
-      const ctx = { ...context, [it]: item };
-      process(child, ctx, true);
-      frag.appendChild(child);
-    });
-    el.replaceChildren(frag);
-    el.v2 = v2;
+    const json = v.map(item => JSON.stringify(item));
+    const prev = el.itemsJson || [];
+    if (json.length === prev.length && el.children.length === json.length) {
+      // Same length: re-template each changed row's existing DOM node in
+      // place instead of replacing it. Untouched rows are left completely
+      // alone, and changed rows keep their live elements too - so bound
+      // properties (e.g. a checkbox's `checked`) change on an
+      // already-painted node, which is what lets CSS transitions play, and
+      // in-progress edits in unrelated fields of that row survive
+      json.forEach((j, i) => {
+        if (j !== prev[i]) process(el.children[i], { ...context, [it]: v[i] }, true);
+      });
+    } else {
+      const frag = document.createDocumentFragment();
+      v.forEach(item => {
+        const node = el.orig.cloneNode(true);
+        process(node, { ...context, [it]: item }, true);
+        frag.appendChild(node);
+      });
+      el.replaceChildren(frag);
+    }
+    el.itemsJson = json;
   };
 
   function upload(el, is_ota) {
@@ -267,7 +327,7 @@
       const reader = new FileReader();
       reader.readAsArrayBuffer(f);
       reader.onload = function () {
-        const url = is_ota ? 'api/ota' : `fs/${encodeURIComponent(f.name)}`;
+        const url = is_ota ? 'api/ota' : `fs/${el.dataset.upload}/${encodeURIComponent(f.name)}`;
         let begin = Date.now(), body = reader.result, ok = false;
         // console.log(2, url, body);
         fetch(url, { method: 'POST', body })
@@ -295,7 +355,8 @@
   }
 
   function process(root, context, x) {
-    const all = root.querySelectorAll("*:not([data-repeat] *)");
+    const selector = x ? "*" : "*:not([data-repeat] *)";
+    const all = root.querySelectorAll(selector);
     const els = root.nodeType === Node.DOCUMENT_NODE ? all : [root, ...all];
     els.forEach(function (el) {
       if (el.tagName === "SCRIPT" || el.tagName === "STYLE") return;
@@ -309,14 +370,16 @@
       }
       for (const attr of el.attributes) {
         const cv = attr.value || '';
-        if (attr.originalValue || cv.includes('${')) {
-          if (!attr.originalValue) attr.originalValue = cv;
-          const v = substituteExpressions(attr.originalValue, context);
+        if (!el.originalAttrs) el.originalAttrs = {};
+        if (el.originalAttrs[attr.name] || cv.includes('${')) {
+          if (!el.originalAttrs[attr.name]) el.originalAttrs[attr.name] = cv;
+          const v = substituteExpressions(el.originalAttrs[attr.name], context);
           if (v !== attr.value) attr.value = v;
         }
       }
       const handlers = {
         bind: handle_bind,
+        checked: handle_checked,
         save: handle_save,
         cancel: handle_cancel,
         repeat: handle_repeat,
@@ -341,21 +404,75 @@
 
   function rescan() {
     if (document.readyState === "loading") {
-      document.addEventListener("DOMContentLoaded", realrescan, { once: true });
+      return new Promise(resolve => {
+        document.addEventListener("DOMContentLoaded", () => {
+          realrescan();
+          resolve();
+        }, { once: true });
+      });
     } else {
       realrescan();
+      return Promise.resolve();
     }
   };
 
   const delay = (ms, value) => new Promise(r => setTimeout(() => r(value), ms));
+  const next_frame = () => new Promise(r => requestAnimationFrame(() => r()));
+  const is_expandable = arr => arr && Array.isArray(arr.data) &&
+    typeof arr.start === 'number' && typeof arr.end === 'number';
+
+  function expand_array(name, start, end) {
+    const arr = settings.data[name];
+    const page = 100, all = [];
+    const stop = Math.min(end, typeof arr?.size === 'number' ? arr.size - 1 : end);
+    const done = () => {
+      set(settings.data, `${name}.data`, all);
+      set(settings.data, `${name}.start`, start);
+      return rescan().then(() => all);
+    };
+    const next = from => {
+      if (from > stop) return Promise.resolve(done());
+      const to = Math.min(from + page - 1, stop);
+      return fetch(`api/get/${name}/${from}/${to}`)
+        .then(r => r.ok ? r.json() : Promise.reject(r.statusText))
+        .then(data => {
+          if (!data || !data.length) return done();
+          all.push(...data);
+          return next(from + data.length);
+        });
+    };
+    return next(start);
+  }
+
+  function expand_arrays() {
+    const all = [];
+    for (const name in settings.data) {
+      const arr = settings.data[name];
+      if (is_expandable(arr)) all.push(expand_array(name, arr.start, arr.end));
+    }
+    return Promise.all(all);
+  }
 
   function call(name, args) {
     if (isMock) {
-      return delay(750, true).then(val => console.log('response', name));
-    } else {
-      return rpc.call(name, args)
-        .catch(err => console.log('CALL FAILED', name, args, err));
+      return delay(750, true).then(() => console.log('response', name));
     }
+    if (name === 'set') {
+      return fetch('api/set', {
+        method: 'POST',
+        headers: {'Content-Type': 'application/json'},
+        body: JSON.stringify(args),
+      }).catch(err => console.log('CALL FAILED', name, args, err));
+    }
+    if (args && typeof args === 'object') {
+      const {name: aname, start: s = 0, size: total = 100, end} = args;
+      const stop = typeof end === 'number' ? end : s + total - 1;
+      return expand_array(aname, s, stop).catch(err => console.log('CALL FAILED', name, args, err));
+    }
+    const path = typeof args === 'string' && args ? '/' + args : '';
+    return fetch('api/get' + path)
+      .then(r => r.ok ? r.json() : Promise.reject(r.statusText))
+      .catch(err => console.log('CALL FAILED', name, args, err));
   };
 
   function apply(target, patch) {
@@ -373,16 +490,18 @@
   function apply_and_rescan(target, patch) {
     apply(target, patch);
     prune(settings.data, settings.edits);
-    rescan();
+    return rescan();
   };
 
   function on(name, fn) {
     userhandlers[name] = fn;
+    if (name === 'ready' && status.ready) setTimeout(fn, 0);
   };
 
   function init(conf) {
+    install_ready_gate();
     apply_and_rescan(settings, conf);
-    if (!settings.auth) rpc_connect();
+    if (!settings.auth) fetch_and_ready();
   };
 
   global.Dashboard = { init, call, on, status, login, logout };
diff --git a/resources/downloads/Makefile b/resources/downloads/Makefile
index 3e1a803d..f6b6d44b 100644
--- a/resources/downloads/Makefile
+++ b/resources/downloads/Makefile
@@ -62,7 +62,7 @@ $(foreach T,$(RP_TARGETS), $(foreach P,$(PROJECTS), $(eval $(call RP_DASHBOARD_R
 %.zip: %
 	zip -qr $@ $<
 
-upload: $(ZIPS)
+deploy: $(ZIPS)
 	scp $(ZIPS) h1:/data/downloads/
 
 clean:
diff --git a/resources/html2c.js b/resources/html2c.js
index b514cc9a..b78b1d77 100644
--- a/resources/html2c.js
+++ b/resources/html2c.js
@@ -5,7 +5,7 @@
 // inlining referenced CSS, JS, images, and icons.
 //
 // Usage:
-//   node html2c.js [-o OUTPUT.c] HTML_FILE
+//   node html2c.js [-o OUTPUT.c] HTML_FILE [HTML_FILE ...]
 
 const fs = require('fs');
 const path = require('path');
@@ -15,24 +15,25 @@ const zlib = require('zlib');
 
 const args = process.argv.slice(2);
 let outputFile = null;
-let inputFile = null;
+const inputFiles = [];
+const useMap = new Map();
 
 for (let i = 0; i < args.length; i++) {
   if (args[i] === '-o' && i + 1 < args.length) {
     outputFile = args[++i];
-  } else if (!args[i].startsWith('-') && inputFile === null) {
-    inputFile = args[i];
+  } else if (args[i] === '--use' && i + 1 < args.length) {
+    const eq = args[++i].indexOf('=');
+    if (eq > 0) useMap.set(args[i].slice(0, eq), args[i].slice(eq + 1));
+  } else if (!args[i].startsWith('-')) {
+    inputFiles.push(args[i]);
   }
 }
 
-if (!inputFile) {
-  console.error('Usage: node html2c.js [-o OUTPUT.c] HTML_FILE');
+if (inputFiles.length === 0) {
+  console.error('Usage: node html2c.js [-o OUTPUT.c] HTML_FILE [HTML_FILE ...]');
   process.exit(1);
 }
 
-const baseDir = path.dirname(path.resolve(inputFile));
-const html = fs.readFileSync(inputFile, 'utf8');
-
 function fetchUrl(url) {
   return new Promise((resolve, reject) => {
     const client = url.startsWith('https') ? https : http;
@@ -47,12 +48,15 @@ function fetchUrl(url) {
   });
 }
 
-async function readAsset(name, encoding) {
+async function readAsset(name, encoding, baseDir) {
+  const override = useMap.get(name);
+  if (override != null) name = override;
   if (name.startsWith('http://') || name.startsWith('https://')) {
     const data = await fetchUrl(name);
     return encoding ? data.toString(encoding) : data;
   }
-  return fs.readFileSync(path.join(baseDir, name), encoding || null);
+  const fullPath = path.isAbsolute(name) ? name : path.join(baseDir, name);
+  return fs.readFileSync(fullPath, encoding || null);
 }
 
 function attr(match, name) {
@@ -66,21 +70,21 @@ function replaceAttr(match, name, value) {
   return match.replace(re, `${name}="${value}"`);
 }
 
-async function inlineCss(match) {
+async function inlineCss(match, baseDir) {
   const href = attr(match, 'href');
   if (!href) return match;
-  const css = await readAsset(href, 'utf8');
+  const css = await readAsset(href, 'utf8', baseDir);
   return `<style>${css}</style>`;
 }
 
-async function inlineJs(match) {
+async function inlineJs(match, baseDir) {
   const src = attr(match, 'src');
   if (!src) return match;
-  const js = await readAsset(src, 'utf8');
+  const js = await readAsset(src, 'utf8', baseDir);
   return `<script>${js}</script>`;
 }
 
-async function inlineImg(match) {
+async function inlineImg(match, baseDir) {
   const src = attr(match, 'src');
   if (!src) return match;
   const ext = path.extname(src).toLowerCase();
@@ -91,7 +95,7 @@ async function inlineImg(match) {
   else if (ext === '.webp') mime = 'image/webp';
   else if (ext === '.ico') mime = 'image/x-icon';
 
-  const data = await readAsset(src);
+  const data = await readAsset(src, null, baseDir);
   if (ext === '.svg') {
     const svg = Buffer.isBuffer(data) ? data.toString('utf8') : data;
     return replaceAttr(
@@ -107,10 +111,10 @@ async function inlineImg(match) {
   );
 }
 
-async function inlineSvg(match) {
+async function inlineSvg(match, baseDir) {
   const href = attr(match, 'href');
   if (!href || !href.toLowerCase().endsWith('.svg')) return match;
-  const data = await readAsset(href);
+  const data = await readAsset(href, null, baseDir);
   return replaceAttr(
     match,
     'href',
@@ -118,7 +122,7 @@ async function inlineSvg(match) {
   );
 }
 
-async function processHtml(content) {
+async function processHtml(content, baseDir) {
   let result = content;
   const cssRegex = /<link[^>]+rel=["']stylesheet["'][^>]*>/g;
   const jsRegex = /<script[^>]+src=["'][^"']+["'][^>]*><\/script>/g;
@@ -126,16 +130,16 @@ async function processHtml(content) {
   const svgRegex = /<link[^>]+rel=["']icon["'][^>]*>/g;
 
   for (const match of content.match(cssRegex) || []) {
-    if (!match.includes('data:')) result = result.replace(match, await inlineCss(match));
+    if (!match.includes('data:')) result = result.replace(match, await inlineCss(match, baseDir));
   }
   for (const match of content.match(jsRegex) || []) {
-    if (!match.includes('data:')) result = result.replace(match, await inlineJs(match));
+    if (!match.includes('data:')) result = result.replace(match, await inlineJs(match, baseDir));
   }
   for (const match of content.match(imgRegex) || []) {
-    if (!match.includes('data:')) result = result.replace(match, await inlineImg(match));
+    if (!match.includes('data:')) result = result.replace(match, await inlineImg(match, baseDir));
   }
   for (const match of content.match(svgRegex) || []) {
-    if (!match.includes('data:')) result = result.replace(match, await inlineSvg(match));
+    if (!match.includes('data:')) result = result.replace(match, await inlineSvg(match, baseDir));
   }
 
   return result;
@@ -145,30 +149,43 @@ function cArray(data) {
   return Array.from(Buffer.from(data)).concat(0).join(',');
 }
 
-function generateC(data) {
-  const destination = `${path.basename(inputFile)}.gz`;
-  const stat = fs.statSync(inputFile);
-  const mtime = parseInt(stat.mtimeMs / 1000);
-  const zipped = zlib.gzipSync(data);
-  const bytes = cArray(zipped);
+function generateC(files) {
+  const vars = files.map(({inputFile, data}, i) => {
+    const zipped = zlib.gzipSync(data);
+    return {inputFile, zipped};
+  });
+
+  const decls = vars.map(({zipped}, i) =>
+    `static const unsigned char v${i}[] = {${cArray(zipped)}};`
+  ).join('\n');
+
+  const entries = vars.map(({inputFile, zipped}, i) => {
+    const destination = `${path.basename(inputFile)}.gz`;
+    const mtime = parseInt(fs.statSync(inputFile).mtimeMs / 1000);
+    return `  {"/${destination}", v${i}, sizeof(v${i}) - 1, ${mtime}},  // size: ${zipped.length}`;
+  }).join('\n');
 
   return `// DO NOT EDIT. This file is generated using this command:
 // ${process.argv.join(' ')}
 
 #include "mongoose.h"
 
-static const unsigned char v0[] = {${bytes}};
+${decls}
 
 const struct mg_mem_file mg_packed_files[] = {
-  {"/${destination}", v0, sizeof(v0) - 1, ${mtime}},  // size: ${zipped.length}
+${entries}
   {NULL, NULL, 0, 0}
 };
 `;
 }
 
-processHtml(html)
-  .then(result => {
-    const c = generateC(result);
+Promise.all(inputFiles.map(inputFile => {
+  const baseDir = path.dirname(path.resolve(inputFile));
+  const html = fs.readFileSync(inputFile, 'utf8');
+  return processHtml(html, baseDir).then(data => ({inputFile, data}));
+}))
+  .then(files => {
+    const c = generateC(files);
     if (outputFile) {
       fs.writeFileSync(outputFile, c);
     } else {
diff --git a/resources/inline.js b/resources/inline.js
deleted file mode 100644
index 2bc4521d..00000000
--- a/resources/inline.js
+++ /dev/null
@@ -1,157 +0,0 @@
-// Copyright (c) 2026 Cesanta Software Limited
-// All rights reserved
-
-const fs = require('fs');
-const path = require('path');
-const https = require('https');
-const http = require('http');
-
-const args = process.argv.slice(2);
-let outputFile = null;
-let inputFile = null;
-
-for (let i = 0; i < args.length; i++) {
-  if (args[i] === '-o' && i + 1 < args.length) {
-    outputFile = args[++i];
-  } else if (!args[i].startsWith('-')) {
-    inputFile = args[i];
-  }
-}
-
-if (!inputFile) {
-  console.error('Usage: node inline.js [-o OUTPUT_FILE] HTML_FILE');
-  process.exit(1);
-}
-
-const baseDir = path.dirname(path.resolve(inputFile));
-const html = fs.readFileSync(inputFile, 'utf8');
-
-function fetchUrl(url) {
-  return new Promise((resolve, reject) => {
-    const client = url.startsWith('https') ? https : http;
-    client.get(url, res => {
-      let data = '';
-      res.on('data', chunk => data += chunk);
-      res.on('end', () => resolve(data));
-      res.on('error', reject);
-    }).on('error', reject);
-  });
-}
-
-async function inlineCss(match) {
-  const href = match.match(/href=["']([^"']+)["']/)[1];
-  let css = '';
-  if (href.startsWith('http')) {
-    css = await fetchUrl(href);
-  } else {
-    const cssPath = path.join(baseDir, href);
-    css = fs.readFileSync(cssPath, 'utf8');
-  }
-  return `<style>${css}</style>`;
-}
-
-async function inlineJs(match) {
-  const match2 = match.match(/src=["']([^"']+)["']/);
-  if (!match2) return match;
-  const src = match2[1];
-  let js = '';
-  if (src.startsWith('http')) {
-    js = await fetchUrl(src);
-  } else {
-    const jsPath = path.join(baseDir, src);
-    js = fs.readFileSync(jsPath, 'utf8');
-  }
-  return `<script>${js}</script>`;
-}
-
-async function inlineImg(match) {
-  const match2 = match.match(/src=["']([^"']+)["']/);
-  if (!match2) return match;
-  const src = match2[1];
-  const ext = path.extname(src).toLowerCase();
-  let mime = 'image/png';
-  if (ext === '.svg') mime = 'image/svg+xml';
-  else if (ext === '.jpg' || ext === '.jpeg') mime = 'image/jpeg';
-  else if (ext === '.gif') mime = 'image/gif';
-  else if (ext === '.webp') mime = 'image/webp';
-  else if (ext === '.ico') mime = 'image/x-icon';
-  let data;
-  if (src.startsWith('http')) {
-    data = await fetchUrl(src);
-  } else {
-    const imgPath = path.join(baseDir, src);
-    data = fs.readFileSync(imgPath);
-  }
-  const base64 = Buffer.from(data).toString('base64');
-  if (ext === '.svg') {
-    const svgData = typeof data === 'string' ? data : data.toString('utf8');
-    return match.replace(/src="[^"]+"/, `src="data:${mime};utf8,${encodeURIComponent(svgData)}"`);
-  }
-  return match.replace(/src="[^"]+"/, `src="data:${mime};base64,${base64}"`);
-}
-
-async function inlineSvg(match) {
-  const match2 = match.match(/href=["']([^"']+)["']/);
-  if (!match2) return match;
-  const href = match2[1];
-  if (!href.toLowerCase().endsWith('.svg')) return match;
-  let data;
-  if (href.startsWith('http')) {
-    data = await fetchUrl(href);
-  } else {
-    const svgPath = path.join(baseDir, href);
-    data = fs.readFileSync(svgPath, 'utf8');
-  }
-  const base64 = Buffer.from(data).toString('base64');
-  return match.replace(/href="[^"]+"/, `href="data:image/svg+xml;base64,${base64}"`);
-}
-
-async function processHtml(content) {
-  let result = content;
-  const cssRegex = /<link[^>]+rel=["']stylesheet["'][^>]*>/g;
-  const jsRegex = /<script[^>]+src=["'][^"']+["'][^>]*><\/script>/g;
-  const imgRegex = /<img[^>]+src=["'][^"']+["'][^>]*>/g;
-  const svgRegex = /<link[^>]+rel=["']icon["'][^>]*>/g;
-
-  const cssMatches = content.match(cssRegex) || [];
-  for (const match of cssMatches) {
-    if (!match.includes('data:')) {
-      result = result.replace(match, await inlineCss(match));
-    }
-  }
-
-  const jsMatches = content.match(jsRegex) || [];
-  for (const match of jsMatches) {
-    if (!match.includes('data:')) {
-      result = result.replace(match, await inlineJs(match));
-    }
-  }
-
-  const imgMatches = content.match(imgRegex) || [];
-  for (const match of imgMatches) {
-    if (!match.includes('data:')) {
-      result = result.replace(match, await inlineImg(match));
-    }
-  }
-
-  const svgMatches = content.match(svgRegex) || [];
-  for (const match of svgMatches) {
-    if (!match.includes('data:')) {
-      result = result.replace(match, await inlineSvg(match));
-    }
-  }
-
-  return result;
-}
-
-processHtml(html).then(result => {
-  if (outputFile) {
-    fs.writeFileSync(outputFile, result);
-    //console.log(`Written to ${outputFile}`);
-  } else {
-    console.log(result);
-  }
-}).catch(err => {
-  console.error('Error:', err.message);
-  process.exit(1);
-});
diff --git a/resources/pack.js b/resources/pack.js
deleted file mode 100644
index 4f705e3c..00000000
--- a/resources/pack.js
+++ /dev/null
@@ -1,43 +0,0 @@
-// Copyright (c) 2024 Cesanta Software Limited
-//
-// Utility that generates packed filesystem C file compatible with the
-// Mongoose Network Library, https://github.com/cesanta/mongoose
-//
-// Usage:
-//    node pack.js FILE[:DESTINATION[:gzip]] ...
-
-const fs = require('fs');
-const zlib = require('zlib');
-const argv = process.argv.slice(2);
-
-// Convert each command-line arguments into [ DATA_ARRAY, STRUCT_INITIALIZER ]
-const entries = argv.map(function(filename, i) {
-  const parts = filename.split(':');
-  const stat = fs.statSync(parts[0]);
-  const data = fs.readFileSync(parts[0], null);
-  let bytes = Array.from(data);
-  let destination = (parts[1] || parts[0]).replace(/^\.+[\/\\]*/, '');
-  if (parts[2] == 'gzip') {
-    bytes = Array.from(zlib.gzipSync(data));
-    destination += '.gz';
-  }
-
-  // concat(0) appends trailing 0, in order to make any file an asciz string
-  return [
-    `static const unsigned char v${i}[] = {${bytes.concat(0).join(',')}};`,
-    `  {"/${destination}", v${i}, sizeof(v${i}) - 1, ${parseInt(stat.mtimeMs / 1000)}}`,
-  ];
-});
-
-process.stdout.write(`// DO NOT EDIT. This file is generated using this command:
-// ${process.argv.join(' ')}
-
-#include "mongoose.h"
-
-${entries.map(x => x[0]).join('\n\n')}
-
-const struct mg_mem_file mg_packed_files[] = {
-${entries.map(x => x[1]).join(',\n')},
-  {NULL, NULL, 0, 0}
-};
-`);
diff --git a/resources/sign.js b/resources/sign.js
index 8f8771af..9ef6e1bc 100644
--- a/resources/sign.js
+++ b/resources/sign.js
@@ -70,8 +70,8 @@ function sign(firmware, privateKeyFile = 'private.pem') {
     ? firmware.slice(0, dot) + '.signed' + firmware.slice(dot)
     : firmware + '.signed';
 
-  fs.writeFileSync(out, Buffer.concat([fw, raw]));
-  console.log(`Signed: ${out}  (${fw.length} bytes firmware + 64 bytes signature)`);
+  fs.writeFileSync(out, Buffer.concat([fw, raw, Buffer.from('MGSG')]));
+  console.log(`Signed: ${out}  (${fw.length} bytes firmware + 64 bytes signature + 4 bytes magic)`);
 }
 
 const [,, cmd, arg1, arg2] = process.argv;
diff --git a/src/dash.c b/src/dash.c
index 51f90965..58f21609 100644
--- a/src/dash.c
+++ b/src/dash.c
@@ -5,67 +5,21 @@
 #define MG_NO_CACHE_HEADERS "Cache-Control: no-cache\r\n"
 #define MG_JSON_HEADERS "Content-Type: application/json\r\n" MG_NO_CACHE_HEADERS
 
-struct mg_dash_user {
-  struct mg_dash_user *next;
-  char name[32];    // User name
-  char token[21];   // Login token
-  int level;        // Access level
-  uint64_t expire;  // Expiration timestamp
+#define CONN_HANDLED 'Z'
+
+struct mg_dash_cdata {
+  char marker;
+  struct mg_dash_user *u;
+  struct mg_dash *dash;
 };
 
-#define CONN_HANDLED 'Z'
+static struct mg_dash_user s_guest;
 
 static struct mg_str trimq(struct mg_str s) {  // Trim double quotes
   if (s.len > 1 && s.buf[0] == '"') s.len -= 2, s.buf++;
   return s;
 }
 
-static void mg_dash_broadcast(struct mg_mgr *mgr, int level, const char *fmt,
-                              ...) {
-  struct mg_connection *c;
-  va_list ap;
-  for (c = mgr->conns; c != NULL; c = c->next) {
-    int user_level = *(int *) c->data;
-    if (!c->is_websocket) continue;
-    if (level > 0 && user_level < level) continue;
-    if (c->send.len > MG_DASH_MAX_SEND_BUF_SIZE) {
-      mg_error(c, "%lu buffered data %lu > MG_DASH_MAX_SEND_BUF_SIZE", c->id,
-               c->send.len);
-    } else {
-      va_start(ap, fmt);
-      mg_ws_vprintf(c, WEBSOCKET_OP_TEXT, fmt, &ap);
-      va_end(ap);
-    }
-  }
-}
-
-static size_t mg_print_fmt(mg_pfn_t out, void *param, va_list *ap) {
-  const char *fmt = va_arg(*ap, const char *);
-  ap = va_arg(*ap, va_list *);
-  return mg_vxprintf(out, param, fmt, ap);
-}
-
-static void mg_dash_success(struct mg_connection *c, struct mg_str req,
-                            const char *fmt, ...) {
-  struct mg_str id = mg_json_get_tok(req, "$.id");
-  va_list ap;
-  va_start(ap, fmt);
-  mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%.*s,%m:%M}", MG_ESC("id"), id.len,
-               id.buf, MG_ESC("result"), mg_print_fmt, fmt, &ap);
-  va_end(ap);
-}
-
-static void mg_dash_error(struct mg_connection *c, struct mg_str req,
-                          const char *fmt, ...) {
-  struct mg_str id = mg_json_get_tok(req, "$.id");
-  va_list ap;
-  va_start(ap, fmt);
-  mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%.*s,%m:{%m:%d,%m:%m}}", MG_ESC("id"),
-               id.len, id.buf, MG_ESC("error"), MG_ESC("code"), -1,
-               MG_ESC("message"), mg_print_fmt, fmt, &ap);
-  va_end(ap);
-}
-
 static struct mg_field_set *mg_dash_find_field_set(struct mg_dash *dash,
                                                    struct mg_str name) {
   struct mg_field_set *fs;
@@ -92,6 +46,8 @@ static size_t mg_print_field(mg_pfn_t fn, void *arg, va_list *ap) {
     n += mg_xprintf(fn, arg, "%s", *(bool *) f->value ? "true" : "false");
   } else if (f->type == MG_VAL_INT) {
     n += mg_xprintf(fn, arg, "%d", *(int *) f->value);
+  } else if (f->type == MG_VAL_UINT64) {
+    n += mg_xprintf(fn, arg, "%llu", (uint64_t) *(uint64_t *) f->value);
   } else if (f->type == MG_VAL_DBL) {
     n += mg_xprintf(fn, arg, "%.2f", *(double *) f->value);
   } else if (f->type == MG_VAL_STR) {
@@ -116,10 +72,56 @@ static size_t mg_print_field_set(mg_pfn_t fn, void *arg, va_list *ap) {
   return n;
 }
 
-static size_t mg_dash_print_name(mg_pfn_t fn, void *arg, va_list *ap) {
+static int mg_dash_array_size(struct mg_field_set *set,
+                              struct mg_dash_user *u) {
+  int saved = *set->index, sz = -1;
+  *set->index = -1;
+  if (set->fn) {
+    if (set->fn(MG_DASH_READ, u)) sz = *set->index;
+  } else if (set->get_dir) {
+    mg_dash_dir_read(set, u);
+    sz = *set->index;
+  }
+  *set->index = saved;
+  return sz;
+}
+
+static size_t mg_dash_print_array(mg_pfn_t fn, void *arg, va_list *ap) {
+  struct mg_field_set *set = va_arg(*ap, struct mg_field_set *);
+  int from = va_arg(*ap, int);
+  int to = va_arg(*ap, int);
+  struct mg_dash_user *u = va_arg(*ap, struct mg_dash_user *);
+  bool started = false;
+  int saved = *set->index;
+  size_t n = 0;
+  *set->index = from;
+  n += mg_xprintf(fn, arg, "[");
+  for (;;) {
+    bool done = to >= 0 && *set->index > to;
+    if (!done) {
+      if (set->fn)
+        set->fn(MG_DASH_READ, u);
+      else if (set->get_dir)
+        mg_dash_dir_read(set, u);
+      done = *set->index < 0;
+    }
+    if (done) break;
+    n += mg_xprintf(fn, arg, "%s%M", started ? "," : "", mg_print_field_set,
+                    set);
+    started = true;
+    (*set->index)++;
+  }
+  n += mg_xprintf(fn, arg, "]");
+  *set->index = saved;
+  return n;
+}
+
+static size_t mg_dash_print_endpoint(mg_pfn_t fn, void *arg, va_list *ap) {
   struct mg_dash *dash = va_arg(*ap, struct mg_dash *);
+  struct mg_dash_user *u = va_arg(*ap, struct mg_dash_user *);
   struct mg_str *name = va_arg(*ap, struct mg_str *);
-  int level = va_arg(*ap, int);
+  struct mg_str *from_str = va_arg(*ap, struct mg_str *);
+  struct mg_str *to_str = va_arg(*ap, struct mg_str *);
   struct mg_field_set *set = mg_dash_find_field_set(dash, *name);
   size_t n = 0;
   if (name->len == 0) {
@@ -127,37 +129,74 @@ static size_t mg_dash_print_name(mg_pfn_t fn, void *arg, va_list *ap) {
     const char *comma = "";
     n += mg_xprintf(fn, arg, "{");
     for (fs = dash->sets; fs != NULL; fs = fs->next) {
-      if (fs->read_level > 0 && level < fs->read_level) continue;
-      if (fs->reader) fs->reader();
-      n += mg_xprintf(fn, arg, comma);
-      n += mg_xprintf(fn, arg, "%m:", MG_ESC(fs->name));
-      n += mg_xprintf(fn, arg, "%M", mg_print_field_set, fs);
+      if (fs->index != NULL) {
+        int sz = mg_dash_array_size(fs, u);
+        if (sz < 0) continue;
+        n += mg_xprintf(fn, arg, comma);
+        n += mg_xprintf(fn, arg, "%m:%d", MG_ESC(fs->name), sz);
+      } else {
+        if (fs->fn && !fs->fn(MG_DASH_READ, u)) continue;
+        n += mg_xprintf(fn, arg, comma);
+        n += mg_xprintf(fn, arg, "%m:%M", MG_ESC(fs->name), mg_print_field_set,
+                        fs);
+      }
       comma = ",";
     }
     n += mg_xprintf(fn, arg, "}");
-  } else if (set != NULL &&
-             (set->read_level <= 0 || level >= set->read_level)) {
-    if (set->reader) set->reader();
-    n += mg_xprintf(fn, arg, "%M", mg_print_field_set, set);
+  } else if (set != NULL && (set->fn == NULL || set->fn(MG_DASH_READ, u))) {
+    if (set->index != NULL && from_str != NULL && from_str->len > 0) {
+      int from = 0, to = 0;
+      mg_str_to_num(*from_str, 10, &from, sizeof(from));
+      to = from;
+      if (to_str != NULL && to_str->len > 0) {
+        mg_str_to_num(*to_str, 10, &to, sizeof(to));
+      }
+      n += mg_xprintf(fn, arg, "%M", mg_dash_print_array, set, from, to, u);
+    } else if (set->index != NULL) {
+      n += mg_xprintf(fn, arg, "%d", mg_dash_array_size(set, u));
+    } else {
+      n += mg_xprintf(fn, arg, "%M", mg_print_field_set, set);
+    }
   } else {
     n += mg_xprintf(fn, arg, "null");
   }
   return n;
 }
 
-static size_t mg_dash_print(mg_pfn_t fn, void *arg, va_list *ap) {
-  struct mg_str *req = va_arg(*ap, struct mg_str *);
-  struct mg_dash *dash = va_arg(*ap, struct mg_dash *);
-  int level = va_arg(*ap, int);
-  struct mg_str name = trimq(mg_json_get_tok(*req, "$.params"));
-  return mg_xprintf(fn, arg, "%M", mg_dash_print_name, dash, &name, level);
-}
-
 void mg_dash_send_change(struct mg_mgr *mgr, struct mg_field_set *set) {
-  if (set->reader) set->reader();
-  mg_dash_broadcast(mgr, set->read_level, "{%m:%m,%m:{%m:%M}}",
-                    MG_ESC("method"), MG_ESC("change"), MG_ESC("params"),
-                    MG_ESC(set->name), mg_print_field_set, set);
+  struct mg_connection *c;
+  for (c = mgr->conns; c != NULL; c = c->next) {
+    struct mg_dash_cdata *d = (struct mg_dash_cdata *) c->data;
+    struct mg_dash_user *u = d->u;
+    if (!c->is_websocket) continue;
+    if (u == NULL) continue;
+    if (set->index != NULL && *set->index < 0) {
+      int sz = mg_dash_array_size(set, u);
+      if (sz < 0) continue;
+      mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m,%m:{%m:%d}}", MG_ESC("method"),
+                   MG_ESC("change"), MG_ESC("params"), MG_ESC(set->name), sz);
+    } else {
+      int saved_idx = set->index != NULL ? *set->index : 0;
+      bool ok = set->fn ? set->fn(MG_DASH_READ, u)
+                        : (set->get_dir ? mg_dash_dir_read(set, u) : true);
+      if (!ok) {
+        if (set->index != NULL) *set->index = saved_idx;
+        continue;
+      }
+      if (set->index != NULL) {
+        char key[64];
+        mg_snprintf(key, sizeof(key), "%s/%d", set->name, *set->index);
+        mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m,%m:{%m:%M}}",
+                     MG_ESC("method"), MG_ESC("change"), MG_ESC("params"),
+                     MG_ESC(key), mg_print_field_set, set);
+        *set->index = saved_idx;
+      } else {
+        mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m,%m:{%m:%M}}",
+                     MG_ESC("method"), MG_ESC("change"), MG_ESC("params"),
+                     MG_ESC(set->name), mg_print_field_set, set);
+      }
+    }
+  }
 }
 
 static int mg_dash_parse_field(struct mg_str json, struct mg_field *f) {
@@ -174,6 +213,13 @@ static int mg_dash_parse_field(struct mg_str json, struct mg_field *f) {
       *(int *) f->value = (int) d;
       ok = true;
     }
+  } else if (f->type == MG_VAL_UINT64) {
+    double d;
+    if (f->value_size == sizeof(uint64_t) &&
+        mg_json_get_num(json, json_path, &d) && d == (double) (int64_t) d) {
+      *(uint64_t *) f->value = (uint64_t) d;
+      ok = true;
+    }
   } else if (f->type == MG_VAL_DBL) {
     ok = f->value_size == sizeof(double) &&
          mg_json_get_num(json, json_path, (double *) f->value);
@@ -187,97 +233,99 @@ static int mg_dash_parse_field(struct mg_str json, struct mg_field *f) {
 }
 
 static int mg_dash_apply(struct mg_connection *c, struct mg_dash *dash,
-                         struct mg_str json, int level) {
+                         struct mg_str json, struct mg_dash_user *u) {
   struct mg_str key, val;
   size_t ofs = 0;
   int total_count = 0;
   while ((ofs = mg_json_next(json, ofs, &key, &val)) > 0) {
     struct mg_field_set *set = mg_dash_find_field_set(dash, trimq(key));
     int count = 0;
-    if (set != NULL && (set->write_level <= 0 || level >= set->write_level)) {
+    if (set == NULL) {
+      MG_ERROR(("UNKNOWN SET: [%.*s]", key.len, key.buf));
+      continue;
+    }
+    if (set->fn != NULL && !set->fn(MG_DASH_WRITE, u)) continue;  // auth check
+    {
       size_t i;
       for (i = 0; set->fields[i].name != NULL; i++) {
         if (mg_dash_parse_field(val, &set->fields[i])) count++;
       }
-      if (count) {
-        if (set->writer) set->writer();
-        mg_dash_send_change(c->mgr, set);
-        total_count += count;
-      }
-    } else if (set == NULL) {
-      MG_ERROR(("UNKNOWN SET: [%.*s]", key.len, key.buf));
+    }
+    if (count) {
+      if (set->fn) set->fn(MG_DASH_WRITE, u);  // apply side effects
+      mg_dash_send_change(c->mgr, set);
+      total_count += count;
     }
   }
   return total_count;
 }
 
-static void mg_dash_process_msg(struct mg_connection *c,
-                                struct mg_ws_message *wm,
-                                struct mg_dash *dash) {
-  struct mg_str req = wm->data;
-  struct mg_str method = trimq(mg_json_get_tok(req, "$.method"));
-  int level = *(int *) c->data;
-  if (mg_match(method, mg_str("get"), NULL)) {
-    mg_dash_success(c, req, "%M", mg_dash_print, &req, dash, level);
-  } else if (mg_match(method, mg_str("set"), NULL)) {
-    struct mg_str params = trimq(mg_json_get_tok(req, "$.params"));
-    int count = mg_dash_apply(c, dash, params, level);
-    mg_dash_success(c, req, "%d", count);
-  } else {
-    mg_dash_error(c, req, "%s", "unknown method");
+bool mg_dash_dir_read(struct mg_field_set *set, struct mg_dash_user *u) {
+  char dir[256], fname[128] = "";
+  struct mg_fs *fs = u->dash->upload_fs ? u->dash->upload_fs : &mg_fs_posix;
+  struct mg_field *name_field = NULL, *size_field = NULL;
+  size_t i;
+
+  if (!set->get_dir(u, dir, sizeof(dir))) return false;
+
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    if (name_field == NULL && set->fields[i].type == MG_VAL_STR &&
+        strcmp(set->fields[i].name, "name") == 0)
+      name_field = &set->fields[i];
+    if (size_field == NULL && strcmp(set->fields[i].name, "size") == 0)
+      size_field = &set->fields[i];
+  }
+  if (name_field == NULL) return false;
+
+  if (*set->index == -1) {  // Size query: count all files
+    int count = 0;
+    while (mg_fs_ls(fs, dir, fname, sizeof(fname))) count++;
+    *set->index = count;
+    return true;
+  }
+
+  {  // Regular read: scan to *set->index
+    int target = *set->index, cur = 0;
+    while (mg_fs_ls(fs, dir, fname, sizeof(fname))) {
+      if (cur++ == target) {
+        mg_snprintf((char *) name_field->value, name_field->value_size, "%s",
+                    fname);
+        if (size_field != NULL) {
+          char path[512];
+          size_t sz = 0;
+          mg_snprintf(path, sizeof(path), "%s/%s", dir, fname);
+          fs->st(path, &sz, NULL);
+          if (size_field->type == MG_VAL_UINT64)
+            *(uint64_t *) size_field->value = (uint64_t) sz;
+          else if (size_field->type == MG_VAL_INT)
+            *(int *) size_field->value = (int) sz;
+        }
+        return true;
+      }
+    }
+    *set->index = -1;  // No more entries
+    return true;
   }
 }
 
-void mg_dash_file_add(struct mg_str name, size_t size) {
-  struct mg_dash_file *f = (struct mg_dash_file *) mg_calloc(1, sizeof(*f));
-  f->name = mg_strdup(name).buf;
-  f->size = size;
-  f->next = mg_dash_files;
-  mg_dash_files = f;
-}
-
-void mg_dash_file_del(struct mg_str name) {
-  struct mg_dash_file **head, *f;
-  for (head = &mg_dash_files, f = *head; f; head = &(*head)->next, f = *head) {
-    if (mg_strcmp(mg_str(f->name), name) == 0) {
-      MG_INFO(("Deleting %s", f->name));
-      *head = f->next;
-      mg_free(f->name);
-      mg_free(f);
-      return;
+static bool mg_dash_set_file_name(struct mg_field_set *set,
+                                  struct mg_str name) {
+  size_t i;
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    struct mg_field *f = &set->fields[i];
+    if (f->type == MG_VAL_STR && strcmp(f->name, "name") == 0) {
+      mg_snprintf((char *) f->value, f->value_size, "%.*s", (int) name.len,
+                  name.buf);
+      return true;
     }
   }
+  return false;
 }
 
-// Files array: [{"name": "foo.txt", "size": 1234}]
-struct mg_dash_file *mg_dash_files;
-static char s_files[1024];
-
-static void read_files(void) {
-  size_t len = 0;
-  struct mg_dash_file *f;
-  len += mg_snprintf(s_files + len, sizeof(s_files) - len, "[");
-  for (f = mg_dash_files; f; f = f->next) {
-    len += mg_snprintf(s_files + len, sizeof(s_files) - len, "%s{%m:%m,%m:%u}",
-                       len > 1 ? "," : "", MG_ESC("name"), MG_ESC(f->name),
-                       MG_ESC("size"), f->size);
-  }
-  len += mg_snprintf(s_files + len, sizeof(s_files) - len, "]");
-}
-
-static struct mg_field fields_files[] = {
-    {"data", MG_VAL_RAW, s_files, sizeof(s_files)},
-    {NULL, MG_VAL_INT, NULL, 0},
-};
-
-static struct mg_field_set set_files = {
-    "files", fields_files, read_files, NULL, 0, 0, NULL,
-};
-
 static inline void mg_log_http_req(struct mg_connection *c,
                                    struct mg_http_message *hm) {
   int len = 0;
-  size_t n, spaces = 0;
+  size_t n, spaces = 0, body_n = hm->body.len;
   struct mg_http_message tmp;
   memset(&tmp, 0, sizeof(tmp));
   len = mg_http_parse((char *) c->send.buf, c->send.len, &tmp);
@@ -286,18 +334,24 @@ static inline void mg_log_http_req(struct mg_connection *c,
          (c->send.buf[c->send.len - spaces - 1] == '\r' ||
           c->send.buf[c->send.len - spaces - 1] == '\n'))
     spaces++;
-  MG_DEBUG(("%lu %.*s %.*s %.*s: %lu %.*s -> %lu %.*s", c->id, hm->method.len,
-            hm->method.buf, hm->uri.len, hm->uri.buf, c->send.len > 15 ? 3 : 0,
-            &c->send.buf[9], hm->body.len, hm->body.len, hm->body.buf,
-            c->send.len - n, c->send.len - n - spaces, c->send.buf + n));
-}
-
-static struct mg_str mg_dash_file_name(struct mg_http_message *hm) {
-  struct mg_str name = mg_str_n(hm->uri.buf + 4, hm->uri.len - 4);  // - /fs/
-  // Decode file name in-place - directly into the request buffer
-  int len = mg_url_decode(name.buf, name.len, name.buf, name.len + 1, 0);
-  if (len > 0 && (size_t) len <= name.len) name.len = (size_t) len;
-  return name;
+  // hm->body.len comes from Content-Length and can be larger than the bytes
+  // actually buffered so far (e.g. mid-stream uploads); cap the preview to
+  // what's actually present in c->recv, or we'd read past its end
+  {
+    char *recv_end = (char *) c->recv.buf + c->recv.len;
+    if (hm->body.buf >= (char *) c->recv.buf && hm->body.buf <= recv_end) {
+      size_t avail = (size_t) (recv_end - hm->body.buf);
+      if (body_n > avail) body_n = avail;
+    } else {
+      body_n = 0;
+    }
+  }
+  MG_DEBUG(("%lu %.*s %.*s%s%.*s %.*s: %lu %.*s -> %lu %.*s", c->id,
+            hm->method.len, hm->method.buf, hm->uri.len, hm->uri.buf,
+            hm->query.len > 0 ? "?" : "", hm->query.len, hm->query.buf,
+            c->send.len > 15 ? 3 : 0, &c->send.buf[9], hm->body.len, body_n,
+            hm->body.buf, c->send.len - n, c->send.len - n - spaces,
+            c->send.buf + n));
 }
 
 static void mg_dash_ota_cb(struct mg_connection *c, const char *errmsg) {
@@ -309,13 +363,20 @@ static void mg_dash_upload_cb(struct mg_connection *c, const char *errmsg) {
   if (errmsg) {
     mg_http_reply(c, 500, NULL, "%s\n", errmsg);
   } else {
-    char path[128];
-    size_t size = 0;
-    mg_snprintf(path, sizeof(path), "/tmp/%s", c->data);
-    mg_fs_posix.st(path, &size, NULL);
-    mg_dash_file_add(mg_str(c->data), size);
+    // mg_http_start_upload() repurposes c->data for its own bookkeeping,
+    // so the field set can't be cached there. Re-derive the dashboard from
+    // c->fn_data instead, and notify every file-backed array: the upload
+    // could belong to any of them, and re-querying get_dir() per recipient
+    // is what mg_dash_send_change() does anyway (directories can be
+    // user-specific)
+    struct mg_dash *dash = (struct mg_dash *) c->fn_data;
+    struct mg_field_set *fs;
     mg_http_reply(c, 200, NULL, "ok\n");
-    mg_dash_send_change(c->mgr, &set_files);
+    for (fs = dash->sets; fs != NULL; fs = fs->next) {
+      if (fs->get_dir == NULL) continue;
+      *fs->index = -1;  // Signal mg_dash_send_change() to broadcast new size
+      mg_dash_send_change(c->mgr, fs);
+    }
   }
   c->is_draining = 1;
 }
@@ -326,16 +387,69 @@ static uint64_t mg_dash_make_expiration_time(struct mg_dash *dash) {
   return mg_millis() + t * 1000;
 }
 
+static struct mg_dash_user *mg_dash_add_user(struct mg_dash_user **users,
+                                             struct mg_dash *dash,
+                                             const char *name,
+                                             const char *token, int level) {
+  struct mg_dash_user *u = (struct mg_dash_user *) mg_calloc(1, sizeof(*u));
+  if (u != NULL) {
+    mg_snprintf(u->name, sizeof(u->name), "%s", name);
+    if (token == NULL) {
+      mg_random_str(u->token, sizeof(u->token) - 1);
+    } else {
+      mg_snprintf(u->token, sizeof(u->token), "%s", token);
+    }
+    u->level = level;
+    u->expire = mg_dash_make_expiration_time(dash);
+    u->dash = dash;
+    u->next = *users;
+    *users = u;
+  }
+  return u;
+}
+
+static struct mg_dash_user *mg_dash_find_user(struct mg_dash_user *users,
+                                              const char *name) {
+  struct mg_dash_user *u;
+  for (u = users; u != NULL; u = u->next) {
+    if (strcmp(u->name, name) == 0) return u;
+  }
+  return NULL;
+}
+
+static struct mg_dash_user *mg_dash_find_token(struct mg_dash_user *users,
+                                               const char *token) {
+  struct mg_dash_user *u;
+  for (u = users; u != NULL; u = u->next) {
+    if (strcmp(u->token, token) == 0) return u;
+  }
+  return NULL;
+}
+
+static void mg_dash_refresh_user(struct mg_dash *dash,
+                                 struct mg_dash_user *user) {
+  user->expire = mg_dash_make_expiration_time(dash);
+}
+
 // Parse HTTP requests, return authenticated user or NULL
-static struct mg_dash_user *mg_dash_authenticate(struct mg_http_message *hm,
+static struct mg_dash_user *mg_dash_authenticate(struct mg_connection *c,
+                                                 struct mg_http_message *hm,
                                                  struct mg_dash *dash) {
   static struct mg_dash_user *s_users;  // List of authenticated users
   char user[100], pass[100];
-  static struct mg_dash_user admin = {NULL, "admin", "admin", 9, (uint64_t) -1};
-  struct mg_dash_user *u, *tmp, *result = NULL;
+  struct mg_dash_user *u, *tmp;
+  struct mg_str *ah;
+  int level = 0, num_users = 0;
 
-  if (dash->authenticate == NULL) return &admin;
+  if (dash->authenticate == NULL) {
+    mg_snprintf(s_guest.name, sizeof(s_guest.name), "%s", "guest");
+    s_guest.level = 9;
+    s_guest.dash = dash;
+    dash->guest = &s_guest;
+    return dash->guest;
+  }
   mg_http_creds(hm, user, sizeof(user), pass, sizeof(pass));
+  ah = mg_http_get_header(hm, "Authorization");
   // MG_DEBUG(("user [%s], pass: [%s], h: %.*s", user, pass, hm->head.len,
   // hm->head.buf));
 
@@ -343,47 +457,48 @@ static struct mg_dash_user *mg_dash_authenticate(struct mg_http_message *hm,
   for (u = s_users; u != NULL; u = tmp) {
     tmp = u->next;
     if (u->expire < mg_millis()) {
+      struct mg_connection *conn;
       MG_DEBUG(("Deleting expired auth %s/%d %llu %u", u->name, u->level,
                 u->expire, mg_millis() - u->expire));
+      for (conn = c->mgr->conns; conn != NULL; conn = conn->next) {
+        struct mg_dash_cdata *d = (struct mg_dash_cdata *) conn->data;
+        if (conn->is_websocket && d->u == u) {
+          d->u = NULL;
+          conn->is_closing = 1;
+        }
+      }
       LIST_DELETE(struct mg_dash_user, &s_users, u);
       mg_free(u);
     }
   }
 
-  if (pass[0] != '\0') {
-    struct mg_str *ah = mg_http_get_header(hm, "Authorization");
-    if (ah != NULL) {
-      // Auth header and password are set, auth by user/password via glue API
-      int num_users = 0, level = dash->authenticate(user, sizeof(user), pass);
-      MG_DEBUG(("user %s, level: %d", user, level));
-      if (level > 0) {  // Proceed only if the firmware authenticated us
-        for (u = s_users; u != NULL && result == NULL;
-             u = u->next, num_users++) {
-          if (strcmp(user, u->name) == 0) {
-            u->expire = mg_dash_make_expiration_time(dash);
-            result = u;
-          }
-        }
-        // Not yet authenticated, add to the list
-        if (result == NULL && num_users < 10) {
-          result = (struct mg_dash_user *) mg_calloc(1, sizeof(*result));
-          mg_snprintf(result->name, sizeof(result->name), "%s", user);
-          mg_random_str(result->token, sizeof(result->token) - 1);
-          result->level = level, result->next = s_users, s_users = result;
-          result->expire = mg_dash_make_expiration_time(dash);
-        }
-      }
-    } else if (ah == NULL) {
-      for (u = s_users; u != NULL && result == NULL; u = u->next) {
-        if (strcmp(u->token, pass) == 0) {
-          u->expire = mg_dash_make_expiration_time(dash);
-          result = u;
-        }
-      }
+  if (pass[0] == '\0') return NULL;
+
+  for (u = s_users; u != NULL; u = u->next) num_users++;
+  if (ah == NULL) {
+    u = mg_dash_find_token(s_users, pass);
+    if (u != NULL) {
+      mg_dash_refresh_user(dash, u);
+      return u;
     }
   }
+
+  level = dash->authenticate(user, sizeof(user), pass);
+  MG_DEBUG(("user %s, level: %d", user, level));
+  if (level <= 0) return NULL;
+
+  u = mg_dash_find_user(s_users, user);
+  if (u != NULL) {
+    if (ah == NULL) mg_snprintf(u->token, sizeof(u->token), "%s", pass);
+    mg_dash_refresh_user(dash, u);
+    return u;
+  }
+
+  if (num_users < 10)
+    return mg_dash_add_user(&s_users, dash, user, ah == NULL ? pass : NULL,
+                            level);
   // MG_DEBUG(("[%s/%s] -> %s", user, pass, result ? "OK" : "FAIL"));
-  return result;
+  return NULL;
 }
 
 static void mg_handle_login(struct mg_connection *c, struct mg_dash_user *u) {
@@ -408,48 +523,157 @@ static void mg_handle_logout(struct mg_connection *c) {
   mg_http_reply(c, 401, cookie, "Unauthorized\n");
 }
 
+static void mg_dash_handle_del(struct mg_connection *c, struct mg_dash *dash,
+                               struct mg_dash_user *u, struct mg_str *parts) {
+  struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+  if (set == NULL || set->index == NULL) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+  } else {
+    int from = 0, to = 0, count = 0;
+    if (parts[1].len) mg_str_to_num(parts[1], 10, &from, sizeof(from));
+    to = parts[2].len ? 0 : from;
+    if (parts[2].len) mg_str_to_num(parts[2], 10, &to, sizeof(to));
+    for (*set->index = from; *set->index <= to; (*set->index)++) {
+      if (set->fn && set->fn(MG_DASH_DELETE, u))
+        count++;
+      else
+        break;
+    }
+    if (count) {
+      *set->index = -1;
+      mg_dash_send_change(c->mgr, set);
+      mg_http_reply(c, 200, MG_JSON_HEADERS, "%d\n", count);
+    } else {
+      mg_http_reply(c, 403, MG_JSON_HEADERS, "false\n");
+    }
+  }
+}
+
+// Handle "POST /api/get/<set>/<index>": modify one array element. Loads the
+// element at <index> first - that doubles as a read-access check and as a
+// pre-fill, so that JSON keys absent from the body keep their old values -
+// then overlays the values from the body and asks fn to persist them
+static void mg_dash_handle_mod(struct mg_connection *c, struct mg_dash *dash,
+                               struct mg_dash_user *u, struct mg_str *parts,
+                               struct mg_str body) {
+  struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+  int index = 0, count = 0;
+  size_t i;
+  if (set == NULL || set->index == NULL || set->fn == NULL) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+    return;
+  }
+  mg_str_to_num(parts[1], 10, &index, sizeof(index));
+  *set->index = index;
+  if (!set->fn(MG_DASH_READ, u) || *set->index != index) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+    return;
+  }
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    if (mg_dash_parse_field(body, &set->fields[i])) count++;
+  }
+  if (count && set->fn(MG_DASH_WRITE, u)) {
+    mg_dash_send_change(c->mgr, set);
+    mg_http_reply(c, 200, MG_JSON_HEADERS, "%d\n", count);
+  } else {
+    mg_http_reply(c, 403, MG_JSON_HEADERS, "false\n");
+  }
+}
+
+// Handle "POST /api/add/<set>": append a new array element. Parses the body
+// straight into the bound fields, then asks fn to accept and persist them as
+// a new element - fn returns false to reject, e.g. when a cap is reached
+static void mg_dash_handle_add(struct mg_connection *c, struct mg_dash *dash,
+                               struct mg_dash_user *u, struct mg_str *parts,
+                               struct mg_str body) {
+  struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+  int count = 0;
+  size_t i;
+  if (set == NULL || set->index == NULL || set->fn == NULL) {
+    mg_http_reply(c, 404, MG_JSON_HEADERS, "null\n");
+    return;
+  }
+  for (i = 0; set->fields[i].name != NULL; i++) {
+    if (mg_dash_parse_field(body, &set->fields[i])) count++;
+  }
+  if (count && set->fn(MG_DASH_ADD, u)) {
+    *set->index = -1;  // Signal mg_dash_send_change() to send new size
+    mg_dash_send_change(c->mgr, set);
+    mg_http_reply(c, 200, MG_JSON_HEADERS, "true\n");
+  } else {
+    mg_http_reply(c, 403, MG_JSON_HEADERS, "false\n");
+  }
+}
+
 void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
   struct mg_dash *dash = (struct mg_dash *) c->fn_data;
+  struct mg_dash_cdata *d = (struct mg_dash_cdata *) c->data;
 
   if (ev == MG_EV_OPEN) {
-    if (mg_dash_find_field_set(dash, mg_str("files")) == NULL) {
-      MG_DASH_ADD_FIELD_SET(dash, &set_files);
-    }
+    d->dash = dash;
     // c->is_hexdumping = 1;
-  } else if (ev == MG_EV_HTTP_HDRS && c->data[0] == 0) {
+  } else if (ev == MG_EV_HTTP_HDRS && d->marker == 0) {
     // Received headers - check authentication and possibly start uploads/ota
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
-    struct mg_dash_user *u = mg_dash_authenticate(hm, dash);
+    struct mg_dash_user *u = mg_dash_authenticate(c, hm, dash);
+    struct mg_str parts[3];
+    memset(parts, 0, sizeof(parts));
 
     if (mg_match(hm->uri, mg_str("/api/hi"), NULL) ||
         mg_match(hm->uri, mg_str("/api/logout"), NULL)) {
       // Do nothing, handle them MG_EV_HTTP_MSG. We bypass auth for those
     } else if (u == NULL && mg_match(hm->uri, mg_str("/api/#"), NULL)) {
       mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
-      c->data[0] = CONN_HANDLED;
+      d->marker = CONN_HANDLED;
     } else if (mg_match(hm->uri, mg_str("/api/login"), NULL) && u != NULL) {
       mg_handle_login(c, u);
-      c->data[0] = CONN_HANDLED;
+      d->marker = CONN_HANDLED;
     } else if (mg_match(hm->uri, mg_str("/api/ota"), NULL)) {
       mg_http_start_ota(c, hm, mg_dash_ota_cb);
-    } else if (mg_match(hm->uri, mg_str("/fs/#"), NULL) &&
+    } else if (mg_match(hm->uri, mg_str("/fs/*/*"), parts) &&
                (mg_strcasecmp(hm->method, mg_str("POST")) == 0 ||
                 mg_strcasecmp(hm->method, mg_str("PUT")) == 0)) {
-      struct mg_str name = mg_dash_file_name(hm);
-      mg_snprintf(c->data, sizeof(c->data), "%.*s", (int) name.len, name.buf);
-      mg_http_start_upload(c, hm, name, mg_str("/tmp"), &mg_fs_posix,
-                           mg_dash_upload_cb);
+      struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+      struct mg_str name = parts[1];
+      int len =
+          mg_url_decode(name.buf, name.len, (char *) name.buf, name.len + 1, 0);
+      if (len > 0 && (size_t) len <= name.len) name.len = (size_t) len;
+      if (set == NULL || set->get_dir == NULL) {
+        mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found\n");
+        d->marker = CONN_HANDLED;
+      } else if (u == NULL) {
+        mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
+        d->marker = CONN_HANDLED;
+      } else if (!mg_path_is_sane(name)) {
+        mg_http_reply(c, 400, MG_JSON_HEADERS, "Bad file name\n");
+        d->marker = CONN_HANDLED;
+      } else {
+        mg_dash_set_file_name(set, name);
+        if (set->fn != NULL && !set->fn(MG_DASH_WRITE, u)) {
+          mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
+          d->marker = CONN_HANDLED;
+        } else {
+          char dir[256];
+          struct mg_fs *fs = dash->upload_fs ? dash->upload_fs : &mg_fs_posix;
+          if (!set->get_dir(u, dir, sizeof(dir))) {
+            mg_http_reply(c, 500, MG_JSON_HEADERS, "Upload dir error\n");
+            d->marker = CONN_HANDLED;
+          } else {
+            mg_http_start_upload(c, hm, name, mg_str(dir), fs,
+                                 mg_dash_upload_cb);
+          }
+        }
+      }
     }
-    if (c->data[0] != '\0') mg_log_http_req(c, hm);
-  } else if (ev == MG_EV_HTTP_MSG && c->data[0] != '\0') {
+    if (d->marker != '\0') mg_log_http_req(c, hm);
+  } else if (ev == MG_EV_HTTP_MSG && d->marker != '\0') {
     // The response has been send in EV_HDRS path, so we're not reponding
-    // anything but clearing the c->data[0] flag for the next request.
-    c->data[0] = 0;
+    // anything but clearing the marker for the next request.
+    d->marker = 0;
     c->is_resp = 0;
-  } else if (ev == MG_EV_HTTP_MSG && c->data[0] == '\0') {
+  } else if (ev == MG_EV_HTTP_MSG && d->marker == '\0') {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
-    struct mg_dash_user *u = mg_dash_authenticate(hm, dash);
-    int level = u == NULL ? 0 : u->level;
+    struct mg_dash_user *u = mg_dash_authenticate(c, hm, dash);
     struct mg_str parts[5];
     memset(parts, 0, sizeof(parts));
 
@@ -460,27 +684,60 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
       mg_ws_printf(c, WEBSOCKET_OP_TEXT, "{%m:%m}", MG_ESC("method"),
                    MG_ESC("logout"));
     } else if (mg_match(hm->uri, mg_str("/api/websocket"), NULL)) {
-      *(int *) c->data = level;
+      d->u = u;
       mg_ws_upgrade(c, hm, NULL);
-    } else if (mg_match(hm->uri, mg_str("/fs/#"), NULL)) {
-      struct mg_str name = mg_dash_file_name(hm);
-      char path[128];
-      mg_snprintf(path, sizeof(path), "/tmp/%.*s", name.len, name.buf);
-      if (mg_strcasecmp(hm->method, mg_str("DELETE")) == 0) {
-        // Delete file
-        mg_dash_file_del(name);
-        mg_dash_send_change(c->mgr, &set_files);
-        mg_http_reply(c, 200, NULL, "true");
+    } else if (mg_match(hm->uri, mg_str("/fs/*/*"), parts)) {
+      struct mg_field_set *set = mg_dash_find_field_set(dash, parts[0]);
+      if (set == NULL || set->get_dir == NULL) {
+        mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found");
+      } else if (u == NULL) {
+        mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
       } else {
-        // Serve file
-        mg_http_serve_file(c, hm, path, NULL);
+        char dir[256], path[512];
+        struct mg_fs *fs = dash->upload_fs ? dash->upload_fs : &mg_fs_posix;
+        struct mg_str name = parts[1];
+        int len = mg_url_decode(name.buf, name.len, (char *) name.buf,
+                                name.len + 1, 0);
+        if (len > 0 && (size_t) len <= name.len) name.len = (size_t) len;
+        if (!mg_path_is_sane(name)) {
+          mg_http_reply(c, 400, MG_JSON_HEADERS, "Bad file name\n");
+          return;
+        }
+        if (!set->get_dir(u, dir, sizeof(dir))) {
+          mg_http_reply(c, 500, MG_JSON_HEADERS, "Upload dir error\n");
+          return;
+        }
+        mg_snprintf(path, sizeof(path), "%s/%.*s", dir, name.len, name.buf);
+        if (mg_strcasecmp(hm->method, mg_str("DELETE")) == 0) {
+          mg_dash_set_file_name(set, name);
+          if (set->fn != NULL && !set->fn(MG_DASH_DELETE, u)) {
+            mg_http_reply(c, 403, MG_JSON_HEADERS, "Not Authorised\n");
+          } else {
+            fs->rm(path);
+            *set->index = -1;  // Signal mg_dash_send_change() to send new size
+            mg_dash_send_change(c->mgr, set);
+            mg_http_reply(c, 200, NULL, "true");
+          }
+        } else {
+          mg_http_serve_file(c, hm, path, NULL);
+        }
       }
-    } else if (mg_match(hm->uri, mg_str("/api/get/#"), parts) ||
+    } else if (mg_match(hm->uri, mg_str("/api/del/*/*/*"), parts) ||
+               mg_match(hm->uri, mg_str("/api/del/*/*"), parts)) {
+      mg_dash_handle_del(c, dash, u, parts);
+    } else if (mg_match(hm->uri, mg_str("/api/add/*"), parts)) {
+      mg_dash_handle_add(c, dash, u, parts, hm->body);
+    } else if (mg_match(hm->uri, mg_str("/api/get/*/*"), parts) &&
+               mg_strcasecmp(hm->method, mg_str("POST")) == 0) {
+      mg_dash_handle_mod(c, dash, u, parts, hm->body);
+    } else if (mg_match(hm->uri, mg_str("/api/get/*/*/*"), parts) ||
+               mg_match(hm->uri, mg_str("/api/get/*/*"), parts) ||
+               mg_match(hm->uri, mg_str("/api/get/*"), parts) ||
                mg_match(hm->uri, mg_str("/api/get"), NULL)) {
-      mg_http_reply(c, 200, MG_JSON_HEADERS, "%M\n", mg_dash_print_name, dash,
-                    &parts[0], level);
+      mg_http_reply(c, 200, MG_JSON_HEADERS, "%M\n", mg_dash_print_endpoint,
+                    dash, u, &parts[0], &parts[1], &parts[2]);
     } else if (mg_match(hm->uri, mg_str("/api/set"), NULL)) {
-      int count = mg_dash_apply(c, dash, hm->body, level);
+      int count = mg_dash_apply(c, dash, hm->body, u);
       mg_http_reply(c, 200, MG_JSON_HEADERS, "%d\n", count);
     } else if (mg_match(hm->uri, mg_str("/"), NULL)) {
       struct mg_http_serve_opts opts;
@@ -498,20 +755,5 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
       if (ch == NULL) mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found");
       mg_log_http_req(c, hm);
     }
-  } else if (ev == MG_EV_WS_OPEN) {
-    // WS connection established, send change notifications for all data
-    struct mg_field_set *fs;
-    for (fs = dash->sets; fs != NULL; fs = fs->next) {
-      mg_dash_send_change(c->mgr, fs);
-    }
-    mg_dash_broadcast(c->mgr, 0, "{%m:%m}", MG_ESC("method"), MG_ESC("ready"));
-  } else if (ev == MG_EV_WS_MSG) {
-    // Add this to automatically handle "get" and "set" JSON-RPC calls
-    struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
-    if (dash == NULL) {
-      mg_dash_error(c, wm->data, "%s", "no dash defined");
-    } else {
-      mg_dash_process_msg(c, wm, dash);
-    }
   }
 }
diff --git a/src/dash.h b/src/dash.h
index 004f2659..d3f81faf 100644
--- a/src/dash.h
+++ b/src/dash.h
@@ -7,50 +7,95 @@
 #include "str.h"
 #include "ws.h"
 
+#ifndef MG_DASH_MAX_USER_NAME
+#define MG_DASH_MAX_USER_NAME 32
+#endif
+
+#ifndef MG_HTTP_ADDR
+#if MG_ARCH == MG_ARCH_UNIX || MG_ARCH == MG_ARCH_WIN32
+#define MG_HTTP_ADDR "http://0.0.0.0:8000"
+#define MG_HTTPS_ADDR "https://0.0.0.0:8443"
+#define MG_MODBUS_ADDR "tcp://0.0.0.0:8502"
+#else
+#define MG_HTTP_ADDR "http://0.0.0.0:80"
+#define MG_HTTPS_ADDR "http://0.0.0.0:443"
+#define MG_MODBUS_ADDR "tcp://0.0.0.0:502"
+#endif
+#endif
+
+#ifndef MG_DASH_MAX_SEND_BUF_SIZE
+#define MG_DASH_MAX_SEND_BUF_SIZE (MG_IO_SIZE * 5)
+#endif
+
+// C type of a value bound to a dashboard field, see struct mg_field
 enum mg_val_type {
-  MG_VAL_INT,
-  MG_VAL_BOOL,
-  MG_VAL_DBL,
-  MG_VAL_STR,
-  MG_VAL_RAW,
+  MG_VAL_INT,     // int
+  MG_VAL_UINT64,  // uint64_t
+  MG_VAL_BOOL,    // bool
+  MG_VAL_DBL,     // double
+  MG_VAL_STR,     // Zero-terminated string
+  MG_VAL_RAW,     // Pre-formatted JSON value, copied verbatim
 };
 
+// Dashboard field: binds a JSON key to a C variable for read and/or write
 struct mg_field {
-  const char *name;
-  enum mg_val_type type;
-  void *value;
-  size_t value_size;
+  const char *name;       // JSON key
+  enum mg_val_type type;  // C type of the value, see enum mg_val_type
+  void *value;            // Pointer to the bound variable
+  size_t value_size;  // sizeof(*value) for type checking; 0 makes it read-only
 };
 
+// Operation passed to a struct mg_field_set read/write/delete/add callback.
+// MG_DASH_ADD: fields hold the values of a new element to append; *index is
+// not set. Return true to accept and persist it, false to reject (e.g. a cap
+// was reached)
+enum mg_dash_op { MG_DASH_READ, MG_DASH_WRITE, MG_DASH_DELETE, MG_DASH_ADD };
+
+struct mg_dash;
+
+// Authenticated (or guest) dashboard user
+struct mg_dash_user {
+  struct mg_dash_user *next;         // Next user in the list
+  char name[MG_DASH_MAX_USER_NAME];  // Username
+  char token[21];        // Session token, sent to the client as a cookie
+  int level;             // Access level, see struct mg_dash::authenticate
+  uint64_t expire;       // Session expiration time, see mg_millis()
+  struct mg_dash *dash;  // Dashboard this user belongs to
+};
+
+// Named group of related dashboard fields, e.g. "settings" or "metrics"
 struct mg_field_set {
-  const char *name;
-  struct mg_field *fields;
-  void (*reader)(void);
-  void (*writer)(void);
-  int read_level;
-  int write_level;
-  struct mg_field_set *next;
+  const char *name;         // Set name, used as a JSON key
+  struct mg_field *fields;  // Zero-terminated array of fields
+  bool (*fn)(enum mg_dash_op op,
+             struct mg_dash_user *u);  // Read/write/delete/add callback
+  int *index;  // Non-NULL: array set. *index is set before fn(READ) call;
+               // fn sets *index = -1 to signal end of iteration.
+               // Size query: framework sets *index = -1 before fn(READ); fn
+               // sets *index = total size
+  bool (*get_dir)(const struct mg_dash_user *u, char *buf,
+                  size_t len);  // Non-NULL: file array
+  struct mg_field_set *next;    // Next set in the list
 };
 
+// Custom URI handler, registered with MG_DASH_REGISTER_CUSTOM_HANDLER()
 struct mg_dash_custom_handler {
-  struct mg_dash_custom_handler *next;
-  struct mg_str uri_pattern;
-  mg_event_handler_t handler;
-  void *handler_data;
-};
-
-struct mg_dash_file {
-  struct mg_dash_file *next;
-  char *name;
-  size_t size;
+  struct mg_dash_custom_handler *next;  // Next handler in the list
+  struct mg_str uri_pattern;            // URI to match, see mg_match()
+  mg_event_handler_t handler;           // Event handler function
+  void *handler_data;                   // Opaque data for the handler
 };
 
+// Dashboard instance: fields, users and handlers served over HTTP and WS
 struct mg_dash {
-  struct mg_field_set *sets;
-  struct mg_dash_custom_handler *custom_handlers;
+  struct mg_field_set *sets;  // Field sets, see MG_DASH_ADD_FIELD_SET()
+  struct mg_dash_custom_handler *custom_handlers;  // Custom URI handlers
+  // Validates pass, fills in user, returns access level (<= 0: failure).
+  // NULL: no login required, all clients get guest access
   int (*authenticate)(char *user, size_t userlen, const char *pass);
-  int session_auto_expiration_seconds;
-  //struct mg_dash_file *files;
+  int session_auto_expiration_seconds;  // Session lifetime, 0: 1 hour default
+  struct mg_dash_user *guest;           // Used when authenticate == NULL
+  struct mg_fs *upload_fs;  // FS for uploads/listing, default &mg_fs_posix
 };
 
 #define MG_DASH_ADD_FIELD_SET(dash_, set_) \
@@ -69,28 +114,50 @@ struct mg_dash {
     (dash_)->custom_handlers = &ch_;                             \
   } while (0)
 
-#if MG_ARCH == MG_ARCH_UNIX || MG_ARCH == MG_ARCH_WIN32
-#define MG_HTTP_ADDR "http://0.0.0.0:8000"
-#define MG_HTTPS_ADDR "https://0.0.0.0:8443"
-#define MG_MODBUS_ADDR "tcp://0.0.0.0:8502"
-#else
-#define MG_HTTP_ADDR "http://0.0.0.0:80"
-#define MG_HTTPS_ADDR "http://0.0.0.0:443"
-#define MG_MODBUS_ADDR "tcp://0.0.0.0:502"
-#endif
-
-#ifndef MG_DASH_MAX_SEND_BUF_SIZE
-#define MG_DASH_MAX_SEND_BUF_SIZE (MG_IO_SIZE * 5)
-#endif
-
-// File manager
-extern struct mg_dash_file *mg_dash_files;
-void mg_dash_file_add(struct mg_str name, size_t size);
-void mg_dash_file_del(struct mg_str name);
-
+// Dashboard event handler. Pass to mg_http_listen() as the fn argument
 void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data);
+
+// Notify WebSocket clients that a field set changed: broadcasts the new
+// array size if *set->index < 0, or a single element update otherwise
 void mg_dash_send_change(struct mg_mgr *mgr, struct mg_field_set *);
 
+// Default reader for file-backed array sets (set->get_dir != NULL)
+// Usage example - this is a complete implemenation of the file manager:
+// ```c
+// static struct file {
+//   int index;
+//   char name[64];
+//   size_t size;
+//   uint64_t checksum;
+// } s_file;
+// static struct mg_field_set set_files;
+//
+// static bool get_dir(const struct mg_dash_user *u, char *buf, size_t len) {
+//   (void) u;
+//   mkdir("/tmp/dashboard", 0755);
+//   mg_snprintf(buf, len, "%s", "/tmp/dashboard");
+//   return true;
+// }
+//
+// static struct mg_field fields_files[] = {
+//     {"name", MG_VAL_STR, s_file.name, sizeof(s_file.name)},
+//     {"size", MG_VAL_UINT64, &s_file.size, 0},
+//     {"checksum", MG_VAL_UINT64, &s_file.checksum, sizeof(s_file.checksum)},
+//     {NULL, MG_VAL_INT, NULL, 0},
+// };
+//
+// static bool files_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+//   if (op == MG_DASH_WRITE) return s_uploads_enabled && u->level >= 7;
+//   if (op != MG_DASH_READ) return false;
+//   if (!mg_dash_dir_read(&set_files, u)) return false;
+//   s_file.checksum = 0;  // Mock to show how to set custom fields
+//   return true;
+// }
+//
+// static struct mg_field_set set_files = {"files", fields_files, files_fn, &s_file.index, get_dir, NULL};
+// ```
+bool mg_dash_dir_read(struct mg_field_set *set, struct mg_dash_user *u);
+
 // Helper forward declarations for Mongoose CMSIS pack modules
 extern struct mg_mgr g_mgr;
 extern void mg_dash_init(struct mg_mgr *);
diff --git a/src/flash.c b/src/flash.c
index 1d692f87..239f01d8 100644
--- a/src/flash.c
+++ b/src/flash.c
@@ -64,15 +64,22 @@ bool mg_ota_flash_end(struct mg_flash *flash) {
     MG_DEBUG(("CRC: %x/%x, size: %lu/%lu, status: %s", s_crc32, crc32, s_size,
               size, ok ? "ok" : "fail"));
 #ifdef MG_OTA_PUBLIC_KEY
-    if (ok && s_size > 64) {
-      static const uint8_t s_pubkey[] = MG_OTA_PUBLIC_KEY;
-      uint8_t hash[32];
-      size_t fw_size = s_size - 64;
-      mg_sha256(hash, (uint8_t *) base, fw_size);
-      ok = mg_uecc_verify(s_pubkey, hash, sizeof(hash),
-                          (uint8_t *) base + fw_size,
-                          mg_uecc_secp256r1()) == 1;
-      MG_INFO(("Signature: %s", ok ? "ok" : "fail"));
+    if (ok) {
+      bool signed_fw = s_size > 68 &&
+                       memcmp((uint8_t *) base + s_size - 4, "MGSG", 4) == 0;
+      if (signed_fw) {
+        static const uint8_t s_pubkey[] = MG_OTA_PUBLIC_KEY;
+        uint8_t hash[32];
+        size_t fw_size = s_size - 68;  // strip 64-byte sig + 4-byte magic
+        mg_sha256(hash, (uint8_t *) base, fw_size);
+        ok = mg_uecc_verify(s_pubkey, hash, sizeof(hash),
+                            (uint8_t *) base + fw_size,
+                            mg_uecc_secp256r1()) == 1;
+        MG_INFO(("Signature: %s", ok ? "ok" : "fail"));
+      } else {
+        ok = false;
+        MG_ERROR(("Unsigned firmware rejected"));
+      }
     }
 #endif
     s_size = 0;
diff --git a/src/http.c b/src/http.c
index ff978205..4a358dd5 100644
--- a/src/http.c
+++ b/src/http.c
@@ -1024,19 +1024,19 @@ static void mg_upload_handler(struct mg_connection *c, int ev, void *ev_data) {
       if (p->fd != NULL) { mg_fs_close(p->fd); p->fd = NULL; }
       else mg_ota_end();
       p->fn(c, "write error");
-      p->fn = NULL;
+      mg_free(c->pfn_data); c->pfn_data = NULL; p->fn = NULL;
     } else if (p->received >= p->expected) {
       const char *errmsg = NULL;
       if (p->fd != NULL) { mg_fs_close(p->fd); p->fd = NULL; }
       else if (!mg_ota_end()) errmsg = "OTA finalize failed";
       p->fn(c, errmsg);
-      p->fn = NULL;
+      mg_free(c->pfn_data); c->pfn_data = NULL; p->fn = NULL;
     }
   } else if (ev == MG_EV_ERROR || ev == MG_EV_CLOSE) {
     if (p->fd != NULL) { mg_fs_close(p->fd); p->fd = NULL; }
     else mg_ota_end();
     p->fn(c, ev == MG_EV_ERROR ? (const char *) ev_data : "connection closed");
-    p->fn = NULL;
+    mg_free(c->pfn_data); c->pfn_data = NULL; p->fn = NULL;
   }
   (void) ev_data;
 }
@@ -1046,6 +1046,10 @@ static void mg_upload_default_cb(struct mg_connection *c, const char *status) {
   mg_http_reply(c, status ? 500 : 200, "", "%s\n", status ? status : "ok");
 }
 
+const char *mg_upload_path(struct mg_connection *c) {
+  return (const char *) c->pfn_data;
+}
+
 void mg_http_start_upload(struct mg_connection *c, struct mg_http_message *hm,
                           struct mg_str name, struct mg_str dir,
                           struct mg_fs *fs,
@@ -1065,6 +1069,7 @@ void mg_http_start_upload(struct mg_connection *c, struct mg_http_message *hm,
   p->fd = fd;
   p->fn = fn;
   c->fn = mg_upload_handler;
+  c->pfn_data = strdup(path);
   c->pfn = NULL;
   mg_iobuf_del(&c->recv, 0, hm->head.len);
   mg_call(c, MG_EV_READ, &c->recv.len);
diff --git a/src/http.h b/src/http.h
index ede85e7b..8f641e9a 100644
--- a/src/http.h
+++ b/src/http.h
@@ -64,6 +64,7 @@ void mg_http_start_upload(struct mg_connection *c, struct mg_http_message *hm,
                           void (*fn)(struct mg_connection *, const char *));
 void mg_http_start_ota(struct mg_connection *c, struct mg_http_message *hm,
                        void (*fn)(struct mg_connection *, const char *));
+const char *mg_upload_path(struct mg_connection *c);
 void mg_http_bauth(struct mg_connection *, const char *user, const char *pass);
 struct mg_str mg_http_get_header_var(struct mg_str s, struct mg_str v);
 size_t mg_http_next_multipart(struct mg_str, size_t, struct mg_http_part *);
diff --git a/src/net.c b/src/net.c
index af51b649..c4d47a84 100644
--- a/src/net.c
+++ b/src/net.c
@@ -2,6 +2,7 @@
 #include "dns.h"
 #include "fmt.h"
 #include "log.h"
+#include "ota.h"
 #include "printf.h"
 #include "profile.h"
 #include "timer.h"
@@ -278,6 +279,11 @@ void mg_mgr_free(struct mg_mgr *mgr) {
 
 void mg_mgr_init(struct mg_mgr *mgr) {
   memset(mgr, 0, sizeof(*mgr));
+  // Anchor mg_fw_version: a real store into a struct field the optimiser
+  // can't elide forces the linker to keep the section alive even when no
+  // OTA polling code runs it. Callers that want mgr->userdata for their own
+  // purposes simply overwrite it after this call returns
+  mgr->userdata = (void *) mg_fw_version;
 #if MG_ENABLE_EPOLL
   if ((mgr->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0)
     MG_ERROR(("epoll_create1 errno %d", errno));
diff --git a/src/net_builtin.c b/src/net_builtin.c
index 4da3c4d7..003b19af 100644
--- a/src/net_builtin.c
+++ b/src/net_builtin.c
@@ -2180,6 +2180,7 @@ void mg_mgr_poll(struct mg_mgr *mgr, int ms) {
   struct mg_connection *c, *tmp;
   uint64_t now = mg_millis();
   mg_timer_poll(&mgr->timers, now);
+  mg_ota_poll(mgr);
   if (mgr->ifp == NULL || mgr->ifp->driver == NULL) return;
   mg_tcpip_poll(mgr->ifp, now);
   for (c = mgr->conns; c != NULL; c = tmp) {
diff --git a/src/ota.c b/src/ota.c
index 781d7a13..d15836f9 100644
--- a/src/ota.c
+++ b/src/ota.c
@@ -2,146 +2,172 @@
 #include "http.h"
 #include "json.h"
 #include "log.h"
-#include "timer.h"
+#include "printf.h"
 #include "url.h"
 #include "util.h"
 
-enum { MG_OTA_STATUS_WAITING, MG_OTA_STATUS_SUCCESS, MG_OTA_STATUS_FAIL };
-static int s_version_status;
-static int s_ota_status;
-static uint64_t s_start_time;
+#ifndef MG_OTA_MAX_URL_LEN
+#define MG_OTA_MAX_URL_LEN 256
+#endif
 
-static struct mg_ota_metadata {
-  char *version;
-  char *url;
+// Scannable version tag embedded in every firmware binary, for server-side
+// version extraction. Non-static so mg_mgr_init() can stash its address in
+// mgr->userdata: that store is what actually keeps -Wl,--gc-sections from
+// stripping it on builds that never poll for OTAs (an attribute alone does
+// not - the linker drops unreferenced sections regardless of "used"/"retain")
+const char mg_fw_version[] = "MG_VERSION:" MG_OTA_FIRMWARE_VERSION;
+
+static struct mg_ota_state {
+  char my_version[MG_OTA_MAX_VERSION_LEN];
+  char json_url[MG_OTA_MAX_URL_LEN];
+  char version[MG_OTA_MAX_VERSION_LEN];
+  char url[MG_OTA_MAX_URL_LEN];
   size_t size;
   uint8_t sha256[32];
-} s_ota_metadata;
+  void (*fn)(const char *status);
+} *s_ota;
 
-static void free_ota_metadata(void) {
-  if (s_ota_metadata.version) mg_free(s_ota_metadata.version);
-  if (s_ota_metadata.url) mg_free(s_ota_metadata.url);
-  memset(&s_ota_metadata, 0, sizeof(s_ota_metadata));
-}
+static void s_firmware_fn(struct mg_connection *c, int ev, void *ev_data);
 
-static int fetch_ota_metadata(struct mg_http_message *response) {
-  double result;
-  if (mg_http_status(response) != 200) goto fetch_failed;
-  if (mg_json_get(response->body, "$", NULL) != 0) goto fetch_failed;
-  free_ota_metadata();
-  s_ota_metadata.version = mg_json_get_str(response->body, "$.version");
-  if (s_ota_metadata.version == NULL) goto fetch_failed;
-  s_ota_metadata.url = mg_json_get_str(response->body, "$.url");
-  if (s_ota_metadata.url == NULL) goto fetch_failed;
-  if (!mg_json_get_num(response->body, "$.size", &result) || result <= 0)
-    goto fetch_failed;
-  s_ota_metadata.size = (size_t) result;
-  // TODO (robertc2000): parse and validate sha256
-  MG_DEBUG(("Firmware version: %s, url: %s, size: %ld", s_ota_metadata.version,
-            s_ota_metadata.url, s_ota_metadata.size));
-  return MG_OTA_STATUS_SUCCESS;
-fetch_failed:
-  free_ota_metadata();
-  return MG_OTA_STATUS_FAIL;
+#if MG_ENABLE_CUSTOM_DEVICE_ID
+#else
+void mg_ota_device_id(char *buf, size_t len) {
+#if MG_ARCH == MG_ARCH_CUBE && defined(UID_BASE)
+  mg_snprintf(buf, len, "%M", mg_print_hex, 12, (uint8_t *) UID_BASE);
+#else
+  mg_snprintf(buf, len, "%d", 0);
+#endif
 }
+#endif
 
 static void s_version_fn(struct mg_connection *c, int ev, void *ev_data) {
-  struct mg_str host = mg_url_host((char *) c->fn_data);
-  struct mg_http_message *hm;
-  static int fetch_status;
-
+  uint64_t expiration = *(uint64_t *) c->data;
   if (ev == MG_EV_POLL) {
-    if (s_start_time + 5 * 1000 < mg_millis()) {
-      mg_error(c, "Connection timeout");
-    }
+    if (mg_millis() > expiration) mg_error(c, "Metadata timeout");
   } else if (ev == MG_EV_CONNECT) {
+    char id[33];
+    struct mg_str host = mg_url_host(s_ota->json_url);
+    const char *uri = mg_url_uri(s_ota->json_url);
+    const char *sep = strchr(uri, '?') == NULL ? "?" : "&";
+    mg_ota_device_id(id, sizeof(id));
+    id[sizeof(id) - 1] = '\0';
     mg_printf(c,
-              "GET %s HTTP/1.1\r\n"
+              "GET %s%sarch=%d&version=%s&id=%s&interval=%d HTTP/1.1\r\n"
               "Host: %.*s\r\n"
               "Connection: close\r\n\r\n",
-              mg_url_uri((char *) c->fn_data), (int) host.len, host.buf);
-    fetch_status = MG_OTA_STATUS_WAITING;
+              uri, sep, MG_ARCH, s_ota->my_version, id,
+              MG_OTA_PULL_INTERVAL_SECONDS, host.len, host.buf);
   } else if (ev == MG_EV_HTTP_MSG) {
-    hm = (struct mg_http_message *) ev_data;
-    fetch_status = fetch_ota_metadata(hm);
+    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+    double result;
+    MG_DEBUG(("Got metadata:\n%.*s", hm->body.len, hm->body.buf));
+    if (mg_http_status(hm) != 200 || mg_json_get(hm->body, "$", NULL) != 0 ||
+        !mg_json_unescape(hm->body, "$.version", s_ota->version,
+                          sizeof(s_ota->version)) ||
+        !mg_json_unescape(hm->body, "$.url", s_ota->url, sizeof(s_ota->url)) ||
+        !mg_json_get_num(hm->body, "$.size", &result) || result <= 0) {
+      char buf[100];
+      mg_snprintf(buf, sizeof(buf), "Bad metadata: %.*s", hm->body.len,
+                  hm->body.buf);
+      s_ota->fn(buf);
+      mg_free(s_ota);
+      s_ota = NULL;
+    } else if (strcmp(s_ota->version, s_ota->my_version) == 0) {
+      s_ota->fn("Same version");
+      mg_free(s_ota);
+      s_ota = NULL;
+    } else {
+      struct mg_connection *fc;
+      s_ota->size = (size_t) result;
+      // TODO (robertc2000): parse and validate sha256
+      MG_DEBUG(("Firmware version: %s, url: %s, size: %ld", s_ota->version,
+                s_ota->url, s_ota->size));
+      fc = mg_http_connect(c->mgr, s_ota->url, s_firmware_fn, NULL);
+      if (fc == NULL) {
+        s_ota->fn("Failed to connect");
+        mg_free(s_ota);
+        s_ota = NULL;
+      } else {
+        *(uint64_t *) fc->data = mg_millis() + 300 * 1000;  // Set expiration
+      }
+    }
+    c->is_closing = 1;
   } else if (ev == MG_EV_ERROR) {
-    MG_ERROR(("%lu Connection error", c->id));
-    s_version_status = MG_OTA_STATUS_FAIL;
-  } else if (ev == MG_EV_CLOSE) {
-    MG_DEBUG(("%lu Connection closed %lu", c->id, mg_millis() - s_start_time));
-    s_version_status = fetch_status;
+    s_ota->fn((char *) ev_data);
+    mg_free(s_ota);
+    s_ota = NULL;
   }
 }
 
-static void s_ota_done(struct mg_connection *c, const char *errmsg) {
-  (void) c;
-  s_ota_status = errmsg ? MG_OTA_STATUS_FAIL : MG_OTA_STATUS_SUCCESS;
+static void status_fn(const char *errmsg) {
   if (errmsg) MG_ERROR(("OTA failed: %s", errmsg));
 }
 
+static void status_fn_2(struct mg_connection *c, const char *errmsg) {
+  if (s_ota) s_ota->fn(errmsg);
+  mg_free(s_ota);
+  s_ota = NULL;
+  mg_http_reply(c, errmsg ? 500 : 200, "", "%s\n", errmsg ? errmsg : "ok");
+}
+
 static void s_firmware_fn(struct mg_connection *c, int ev, void *ev_data) {
-  struct mg_str host = mg_url_host(s_ota_metadata.url);
+  uint64_t expiration = *(uint64_t *) c->data;
   if (ev == MG_EV_POLL) {
-    if (s_start_time + 120 * 1000 < mg_millis()) mg_error(c, "Timeout");
+    if (mg_millis() > expiration) mg_error(c, "OTA timeout");
   } else if (ev == MG_EV_CONNECT) {
+    struct mg_str host = mg_url_host(s_ota->url);
     mg_printf(c,
               "GET %s HTTP/1.1\r\n"
               "Host: %.*s\r\n"
               "Connection: close\r\n\r\n",
-              mg_url_uri(s_ota_metadata.url), (int) host.len, host.buf);
+              mg_url_uri(s_ota->url), (int) host.len, host.buf);
   } else if (ev == MG_EV_HTTP_HDRS) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     int status = mg_http_status(hm);
-    if (status != 200 || hm->body.len != s_ota_metadata.size) {
+    if (status != 200 || hm->body.len != s_ota->size) {
       mg_error(c, "Bad HTTP response: status %d, size %lu vs %lu", status,
-               (unsigned long) hm->body.len,
-               (unsigned long) s_ota_metadata.size);
-      s_ota_status = MG_OTA_STATUS_FAIL;
-      return;
+               (unsigned long) hm->body.len, (unsigned long) s_ota->size);
+    } else {
+      MG_DEBUG(("Beginning OTA (%lu bytes)", (unsigned long) s_ota->size));
+      mg_http_start_ota(c, hm, status_fn_2);
     }
-    MG_DEBUG(
-        ("Beginning OTA (%lu bytes)", (unsigned long) s_ota_metadata.size));
-    mg_http_start_ota(c, hm, s_ota_done);
   } else if (ev == MG_EV_ERROR) {
-    MG_ERROR(("%lu Connection error", c->id));
-    s_ota_status = MG_OTA_STATUS_FAIL;
+    s_ota->fn((char *) ev_data);
+    mg_free(s_ota);
+    s_ota = NULL;
   }
-  (void) ev_data;
 }
 
-void mg_ota_url_check(struct mg_mgr *mgr, const char *current_version,
-                      const char *metadata_url,
-                      void (*fn)(const char *status)) {
-  s_version_status = MG_OTA_STATUS_WAITING;
-  s_ota_status = MG_OTA_STATUS_WAITING;
-  s_start_time = mg_millis();
-  MG_DEBUG(("Connecting to %s to retrieve metadata", metadata_url));
-  if (!mg_http_connect(mgr, metadata_url, s_version_fn,
-                       (void *) metadata_url)) {
-    if (fn) fn("Failed to connect");
-    return;
-  }
-  while (s_version_status == MG_OTA_STATUS_WAITING) mg_mgr_poll(mgr, 10);
-  if (s_version_status == MG_OTA_STATUS_SUCCESS) {
-    if (strcmp(s_ota_metadata.version, current_version) == 0) {
-      if (fn) fn("Same version");
-      free_ota_metadata();
-      return;
-    }
+void mg_ota_url_check(struct mg_mgr *mgr, const char *my_version,
+                      const char *json_url, void (*fn)(const char *status)) {
+  if (fn == NULL) fn = status_fn;
+  if (s_ota != NULL) {
+    fn("OTA already in progress");
+  } else if ((s_ota = (struct mg_ota_state *) mg_calloc(1, sizeof(*s_ota))) ==
+             NULL) {
+    fn("Out of memory");
   } else {
-    if (fn) fn("Version retrieving error");
-    free_ota_metadata();
-    return;
+    struct mg_connection *c;
+    mg_snprintf(s_ota->my_version, sizeof(s_ota->my_version), "%s", my_version);
+    mg_snprintf(s_ota->json_url, sizeof(s_ota->json_url), "%s", json_url);
+    MG_DEBUG(("Connecting to %s", json_url));
+    c = mg_http_connect(mgr, s_ota->json_url, s_version_fn, NULL);
+    if (c == NULL) {
+      mg_free(s_ota);
+      s_ota = NULL;
+      fn("Failed to connect");
+    } else {
+      s_ota->fn = fn;
+      *(uint64_t *) c->data = mg_millis() + 5 * 1000;  // Set expiration
+    }
+  }
+}
+
+void mg_ota_poll(struct mg_mgr *mgr) {
+  static uint64_t t = 1;
+  if (MG_OTA_URL != NULL &&
+      mg_timer_expired(&t, MG_OTA_PULL_INTERVAL_SECONDS * 1000, mg_millis())) {
+    mg_ota_url_check(mgr, MG_OTA_FIRMWARE_VERSION, MG_OTA_URL,
+                     MG_OTA_STATUS_FN);
   }
-  if (fn) fn("Pulling firmware");
-  s_start_time = mg_millis();
-  MG_DEBUG(("Connecting to %s to download firmware", s_ota_metadata.url));
-  if (!mg_http_connect(mgr, s_ota_metadata.url, s_firmware_fn, NULL)) {
-    if (fn) fn("Failed to connect");
-    free_ota_metadata();
-    return;
-  }
-  while (s_ota_status == MG_OTA_STATUS_WAITING) mg_mgr_poll(mgr, 10);
-  if (s_ota_status == MG_OTA_STATUS_FAIL && fn) fn("OTA fail");
-  free_ota_metadata();
 }
diff --git a/src/ota.h b/src/ota.h
index 6e390f5c..7ea02999 100644
--- a/src/ota.h
+++ b/src/ota.h
@@ -100,3 +100,37 @@ enum { MG_OTA_CONFIRMED = 0, MG_OTA_TESTING = 1, MG_OTA_FAILED = 2 };
 // Pull based OTA over HTTP
 void mg_ota_url_check(struct mg_mgr *mgr, const char *current_version,
                       const char *metadata_url, void (*fn)(const char *status));
+
+#ifndef MG_OTA_URL
+#define MG_OTA_URL NULL
+#endif
+
+#ifndef MG_OTA_STATUS_FN
+#define MG_OTA_STATUS_FN NULL
+#endif
+
+#ifndef MG_OTA_FIRMWARE_VERSION
+#define MG_OTA_FIRMWARE_VERSION "1.0.0"
+#endif
+
+#ifndef MG_OTA_MAX_VERSION_LEN
+#define MG_OTA_MAX_VERSION_LEN 64
+#endif
+
+// Scannable "MG_VERSION:<MG_OTA_FIRMWARE_VERSION>" tag embedded in every
+// firmware binary, for server-side extraction. mg_mgr_init() stashes its
+// address in mgr->userdata, which is what keeps it from being stripped by
+// -Wl,--gc-sections on builds that never poll for OTAs
+extern const char mg_fw_version[];
+
+#ifndef MG_OTA_PULL_INTERVAL_SECONDS
+#define MG_OTA_PULL_INTERVAL_SECONDS 60
+#endif
+
+#ifndef MG_ENABLE_CUSTOM_DEVICE_ID
+#define MG_ENABLE_CUSTOM_DEVICE_ID 0
+#endif
+
+void mg_ota_device_id(char *buf, size_t len);
+
+void mg_ota_poll(struct mg_mgr *);
diff --git a/src/sock.c b/src/sock.c
index e85e08dd..dd586299 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -8,6 +8,7 @@
 #include "tls.h"
 #include "url.h"
 #include "util.h"
+#include "ota.h"
 
 #if MG_ENABLE_SOCKET
 
@@ -757,6 +758,7 @@ void mg_mgr_poll(struct mg_mgr *mgr, int ms) {
   mg_iotest(mgr, ms);
   now = mg_millis();
   mg_timer_poll(&mgr->timers, now);
+  mg_ota_poll(mgr);
 
   for (c = mgr->conns; c != NULL; c = tmp) {
     bool is_resp = c->is_resp;
diff --git a/test/unit_test.c b/test/unit_test.c
index 4bd7db1a..57925be9 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -4202,32 +4202,65 @@ static int dash_authenticate(char *user, size_t userlen, const char *pass) {
 }
 
 struct dash_ws_test {
-  const char *req;
+  int opened;
   int done;
-  int result;
   int saw_set3;
 };
 
+struct dash_arr_ws_test {
+  int opened;
+  int done;
+  int saw_arr_index;  // index seen in "arr/INDEX" change key, -1 if not seen
+  int saw_arr_val;    // "val" seen in the change params, -1 if not seen
+  int saw_arr_size;   // size seen in a plain "arr":N change, -1 if not seen
+};
+
+static void dash_arr_ws_cb(struct mg_connection *c, int ev, void *ev_data) {
+  struct dash_arr_ws_test *d = (struct dash_arr_ws_test *) c->fn_data;
+  if (ev == MG_EV_WS_OPEN) {
+    d->opened = 1;
+  } else if (ev == MG_EV_WS_MSG) {
+    struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
+    struct mg_str method = mg_json_get_tok(wm->data, "$.method");
+    if (mg_strcmp(method, mg_str("\"change\"")) == 0) {
+      // Check for "arr/INDEX" (element change) or "arr":N (size change)
+      const char *p = wm->data.buf;
+      const char *end = p + wm->data.len;
+      while (p < end - 6) {
+        if (strncmp(p, "\"arr/", 5) == 0) {
+          const char *v;
+          p += 5;
+          d->saw_arr_index = (int) strtol(p, NULL, 10);
+          v = strstr(p, "\"val\":");
+          if (v != NULL) d->saw_arr_val = (int) strtol(v + 6, NULL, 10);
+          d->done = 1;
+          c->is_closing = 1;
+          break;
+        }
+        if (strncmp(p, "\"arr\":", 6) == 0) {
+          d->saw_arr_size = (int) strtol(p + 6, NULL, 10);
+          d->done = 1;
+          c->is_closing = 1;
+          break;
+        }
+        p++;
+      }
+    }
+  } else if (ev == MG_EV_CLOSE && d->done == 0) {
+    d->done = -1;
+  }
+}
+
 static void dash_ws_cb(struct mg_connection *c, int ev, void *ev_data) {
   struct dash_ws_test *d = (struct dash_ws_test *) c->fn_data;
   if (ev == MG_EV_WS_OPEN) {
-    if (d->req != NULL) {
-      mg_ws_send(c, d->req, strlen(d->req), WEBSOCKET_OP_TEXT);
-    }
+    d->opened = 1;
   } else if (ev == MG_EV_WS_MSG) {
     struct mg_ws_message *wm = (struct mg_ws_message *) ev_data;
     struct mg_str method = mg_json_get_tok(wm->data, "$.method");
     struct mg_str set3 = mg_json_get_tok(wm->data, "$.params.set3");
-    double result = 0;
     if (mg_strcmp(method, mg_str("\"change\"")) == 0 && set3.buf != NULL) {
       d->saw_set3 = 1;
-    }
-    if (mg_json_get_num(wm->data, "$.result", &result)) {
-      d->result = (int) result;
-      d->done = 1;
-      c->is_closing = 1;
-    } else if (d->req == NULL &&
-               mg_strcmp(method, mg_str("\"ready\"")) == 0) {
       d->done = 1;
       c->is_closing = 1;
     }
@@ -4238,8 +4271,89 @@ static void dash_ws_cb(struct mg_connection *c, int ev, void *ev_data) {
 
 char three[10] = "hi";
 int one = 1;
-static void rfields1(void) {
-  mg_snprintf(three, sizeof(three), "t: %d", one);  // Simulate array
+
+#define TEST_ARR_SIZE 17
+#define TEST_ARR_CAP (TEST_ARR_SIZE + 2)  // Cap for MG_DASH_ADD tests
+#define TEST_ARR_RO_INDEX 3  // This element is read-only: WRITE is always denied
+static int s_arr_index;
+static int s_arr_val;
+static int s_arr_store[TEST_ARR_CAP];  // Backing store, init to squares
+static int s_arr_count = TEST_ARR_SIZE;  // Logical size, grows via MG_DASH_ADD
+
+static bool set1_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  if (u->level < 3) return false;
+  if (op == MG_DASH_READ) {
+    mg_snprintf(three, sizeof(three), "t: %d", one);
+    return true;
+  }
+  return u->level >= 7;
+}
+static bool set2_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u; return op == MG_DASH_READ;
+}
+static bool set3_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  if (u->level < 7) return false;
+  return op == MG_DASH_READ || op == MG_DASH_WRITE;
+}
+static bool test_upload_dir(const struct mg_dash_user *u, char *buf, size_t len) {
+  (void) u;
+#if MG_ARCH == MG_ARCH_UNIX || MG_ARCH == MG_ARCH_WIN32
+  mkdir("/tmp/mongoose_dash_test", 0755);
+#endif
+  mg_snprintf(buf, len, "%s", "/tmp/mongoose_dash_test");
+  return true;
+}
+
+struct test_file_entry {
+  char name[64];
+  size_t size;
+};
+static struct test_file_entry s_test_file;
+static int s_test_file_index;
+static struct mg_field test_files_fields[] = {
+    {"name", MG_VAL_STR, s_test_file.name, sizeof(s_test_file.name)},
+    {"size", MG_VAL_UINT64, &s_test_file.size, 0},
+    {NULL, MG_VAL_INT, NULL, 0},
+};
+static struct mg_field_set test_files_set = {
+    "files", test_files_fields, NULL, &s_test_file_index, test_upload_dir, NULL};
+static struct test_file_entry s_delete_file;
+static char s_deleted_file[sizeof(s_delete_file.name)];
+static char s_uploaded_file[sizeof(s_delete_file.name)];
+static struct mg_field_set *s_delete_file_set;
+static bool delete_file_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  if (op == MG_DASH_READ) return mg_dash_dir_read(s_delete_file_set, u);
+  if (op == MG_DASH_WRITE) {
+    mg_snprintf(s_uploaded_file, sizeof(s_uploaded_file), "%s",
+                s_delete_file.name);
+  }
+  if (op == MG_DASH_DELETE) {
+    mg_snprintf(s_deleted_file, sizeof(s_deleted_file), "%s",
+                s_delete_file.name);
+  }
+  return true;
+}
+static bool arr_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op == MG_DASH_READ) {
+    if (s_arr_index < 0) { s_arr_index = s_arr_count; return true; }
+    if (s_arr_index >= s_arr_count) { s_arr_index = -1; return true; }
+    s_arr_val = s_arr_store[s_arr_index];
+    return true;
+  }
+  if (op == MG_DASH_WRITE) {
+    if (s_arr_index < 0 || s_arr_index >= s_arr_count) return false;
+    if (s_arr_index == TEST_ARR_RO_INDEX) return false;  // Deny: read-only
+    s_arr_store[s_arr_index] = s_arr_val;
+    return true;
+  }
+  if (op == MG_DASH_ADD) {
+    if (s_arr_count >= TEST_ARR_CAP) return false;  // Deny: cap reached
+    s_arr_store[s_arr_count++] = s_arr_val;
+    return true;
+  }
+  if (op == MG_DASH_DELETE) return s_arr_index < s_arr_count;
+  return false;
 }
 
 static void test_dash(void) {
@@ -4248,7 +4362,7 @@ static void test_dash(void) {
   const char *ws_url = "ws://localhost:26352/api/websocket";
   struct mg_mgr mgr;
   struct mg_dash dash;
-  struct dash_ws_test ws_user, ws_admin, ws_user_notify;
+  struct dash_ws_test ws_admin, ws_user_notify;
   bool two = false;
   int admin = 7;
   int i;
@@ -4265,13 +4379,20 @@ static void test_dash(void) {
       {"admin", MG_VAL_INT, &admin, sizeof(admin)},
       {NULL, MG_VAL_INT, NULL, 0},
   };
-  struct mg_field_set set1 = {"set1", fields1, rfields1, NULL, 3, 7, NULL};
-  struct mg_field_set set2 = {"set2", fields2, NULL, NULL, 0, 0, NULL};
-  struct mg_field_set set3 = {"set3", fields3, NULL, NULL, 7, 7, NULL};
+  struct mg_field_set set1 = {"set1", fields1, set1_fn, NULL, NULL, NULL};
+  struct mg_field_set set2 = {"set2", fields2, set2_fn, NULL, NULL, NULL};
+  struct mg_field_set set3 = {"set3", fields3, set3_fn, NULL, NULL, NULL};
+  struct mg_field arr_fields[] = {
+      {"val", MG_VAL_INT, &s_arr_val, sizeof(s_arr_val)},
+      {NULL, MG_VAL_INT, NULL, 0},
+  };
+  struct mg_field_set arr_set = {"arr", arr_fields, arr_fn, &s_arr_index, NULL,
+                                 NULL};
   const char *get_all_expected =
-      "{\"files\":{\"data\":[]},\"set3\":{\"admin\":7},"
+      "{\"arr\":17,\"set3\":{\"admin\":7},"
       "\"set2\":{\"two\":false},"
-      "\"set1\":{\"one\":1,\"three\":\"t: 1\"}}\n";
+      "\"set1\":{\"one\":1,\"three\":\"t: 1\"},"
+      "\"files\":0}\n";
   const char *set1_req = "POST /api/set HTTP/1.0\nContent-Length: 18\n\n"
                          "{\"set1\":{\"one\":2}}";
   const char *set1_set3_req = "POST /api/set HTTP/1.0\n"
@@ -4290,8 +4411,14 @@ static void test_dash(void) {
                                "Authorization: Basic YWRtaW46YWRtaW4=\n"
                                "Content-Length: 20\n\n"
                                "{\"set3\":{\"admin\":8}}";
-  const char *set1_ws_set4_req =
-      "{\"id\":1,\"method\":\"set\",\"params\":{\"set1\":{\"one\":4}}}";
+  const char *set3_admin_req9 = "POST /api/set HTTP/1.0\n"
+                                "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                                "Content-Length: 20\n\n"
+                                "{\"set3\":{\"admin\":9}}";
+  const char *set1_admin_set4_req = "POST /api/set HTTP/1.0\n"
+                                    "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                                    "Content-Length: 18\n\n"
+                                    "{\"set1\":{\"one\":4}}";
   const char *set1_expected = "{\"one\":2,\"three\":\"t: 2\"}\n";
   const char *set1_expected3 = "{\"one\":3,\"three\":\"t: 3\"}\n";
   const char *set1_expected4 = "{\"one\":4,\"three\":\"t: 4\"}\n";
@@ -4302,14 +4429,47 @@ static void test_dash(void) {
   const char *set2_req = "POST /api/set HTTP/1.0\nContent-Length: 21\n\n"
                          "{\"set2\":{\"two\":true}}";
   const char *set2_expected = "{\"two\":false}\n";
+  const char *arr7_expected = "[{\"val\":49}]\n";
+  const char *arr0_2_expected = "[{\"val\":0},{\"val\":1},{\"val\":4}]\n";
+  const char *arr5_mod_req = "POST /api/get/arr/5 HTTP/1.0\n"
+                             "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                             "Content-Length: 10\n\n"
+                             "{\"val\":99}";
+  const char *arr100_mod_req = "POST /api/get/arr/100 HTTP/1.0\n"
+                               "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                               "Content-Length: 10\n\n"
+                               "{\"val\":99}";
+  const char *arr3_mod_req = "POST /api/get/arr/3 HTTP/1.0\n"
+                             "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                             "Content-Length: 11\n\n"
+                             "{\"val\":777}";
+  const char *arr_add555_req = "POST /api/add/arr HTTP/1.0\n"
+                               "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                               "Content-Length: 11\n\n"
+                               "{\"val\":555}";
+  const char *arr_add556_req = "POST /api/add/arr HTTP/1.0\n"
+                               "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                               "Content-Length: 11\n\n"
+                               "{\"val\":556}";
+  const char *arr_add557_req = "POST /api/add/arr HTTP/1.0\n"
+                               "Authorization: Basic YWRtaW46YWRtaW4=\n"
+                               "Content-Length: 11\n\n"
+                               "{\"val\":557}";
+  const char *arr5_mod_expected = "[{\"val\":99}]\n";
+  const char *arr3_expected = "[{\"val\":9}]\n";
+  const char *arr17_expected = "[{\"val\":555}]\n";
+  const char *files_probe = "\"files\"";
+  const char *test_bin_probe = "\"test.bin\"";
   char marker = 0;
 
   memset(&dash, 0, sizeof(dash));
   dash.session_auto_expiration_seconds = 1;
+  remove("/tmp/mongoose_dash_test/test.bin");
 
+  MG_DASH_ADD_FIELD_SET(&dash, &test_files_set);
   MG_DASH_ADD_FIELD_SET(&dash, &set1);
   ASSERT(dash.sets == &set1);
-  ASSERT(set1.next == NULL);
+  ASSERT(set1.next == &test_files_set);
 
   MG_DASH_ADD_FIELD_SET(&dash, &set2);
   ASSERT(dash.sets == &set2);
@@ -4326,26 +4486,9 @@ static void test_dash(void) {
   ASSERT(dash.custom_handlers->handler == dash_custom);
   ASSERT(dash.custom_handlers->handler_data == &marker);
 
-  while (mg_dash_files != NULL) mg_dash_file_del(mg_str(mg_dash_files->name));
-  mg_dash_file_add(mg_str("one.txt"), 123);
-  ASSERT(mg_dash_files != NULL);
-  ASSERT(strcmp(mg_dash_files->name, "one.txt") == 0);
-  ASSERT(mg_dash_files->size == 123);
-  mg_dash_file_add(mg_str("two.bin"), 456);
-  ASSERT(mg_dash_files != NULL);
-  ASSERT(strcmp(mg_dash_files->name, "two.bin") == 0);
-  ASSERT(mg_dash_files->size == 456);
-  ASSERT(mg_dash_files->next != NULL);
-  ASSERT(strcmp(mg_dash_files->next->name, "one.txt") == 0);
-  mg_dash_file_del(mg_str("one.txt"));
-  ASSERT(mg_dash_files != NULL);
-  ASSERT(strcmp(mg_dash_files->name, "two.bin") == 0);
-  ASSERT(mg_dash_files->next == NULL);
-  mg_dash_file_del(mg_str("missing.txt"));
-  ASSERT(mg_dash_files != NULL);
-  mg_dash_file_del(mg_str("two.bin"));
-  ASSERT(mg_dash_files == NULL);
+  for (i = 0; i < TEST_ARR_SIZE; i++) s_arr_store[i] = i * i;
 
+  MG_DASH_ADD_FIELD_SET(&dash, &arr_set);
   mg_mgr_init(&mgr);
   mg_mem_files = mg_packed_files;
   ASSERT(mg_http_listen(&mgr, url, mg_dash_ev_handler, &dash) != NULL);
@@ -4422,41 +4565,38 @@ static void test_dash(void) {
                "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
   ASSERT(cmpbody(buf, set1_expected3) == 0);
 
-  ws_user_notify.req = NULL;
+  ws_user_notify.opened = 0;
   ws_user_notify.done = 0;
-  ws_user_notify.result = -1;
   ws_user_notify.saw_set3 = 0;
   mg_ws_connect(&mgr, ws_url, dash_ws_cb, &ws_user_notify, "%s",
                 "Authorization: Basic dXNlcjp1c2Vy\r\n");
+  for (i = 0; i < 200 && ws_user_notify.opened == 0; i++) mg_mgr_poll(&mgr, 1);
+  ASSERT(ws_user_notify.opened == 1);
+  ASSERT(fetch(&mgr, buf, url, set3_admin_req9) == 200);
+  ASSERT(cmpbody(buf, "1\n") == 0);
   for (i = 0; i < 200 && ws_user_notify.done == 0; i++) mg_mgr_poll(&mgr, 1);
-  ASSERT(ws_user_notify.done == 1);
+  ASSERT(ws_user_notify.done == 0);
   ASSERT(ws_user_notify.saw_set3 == 0);
 
-  ws_user.req = set1_ws_set4_req;
-  ws_user.done = 0;
-  ws_user.result = -1;
-  ws_user.saw_set3 = 0;
-  mg_ws_connect(&mgr, ws_url, dash_ws_cb, &ws_user, "%s",
-                "Authorization: Basic dXNlcjp1c2Vy\r\n");
-  for (i = 0; i < 200 && ws_user.done == 0; i++) mg_mgr_poll(&mgr, 1);
-  ASSERT(ws_user.done == 1);
-  ASSERT(ws_user.result == 0);
-  ASSERT(ws_user.saw_set3 == 0);
   ASSERT(fetch(&mgr, buf, url,
                "GET /api/get/set1 HTTP/1.0\n"
                "Authorization: Basic dXNlcjp1c2Vy\n\n") == 200);
   ASSERT(cmpbody(buf, set1_expected3) == 0);
 
-  ws_admin.req = set1_ws_set4_req;
+  ws_admin.opened = 0;
   ws_admin.done = 0;
-  ws_admin.result = -1;
   ws_admin.saw_set3 = 0;
   mg_ws_connect(&mgr, ws_url, dash_ws_cb, &ws_admin, "%s",
                 "Authorization: Basic YWRtaW46YWRtaW4=\r\n");
+  for (i = 0; i < 200 && ws_admin.opened == 0; i++) mg_mgr_poll(&mgr, 1);
+  ASSERT(ws_admin.opened == 1);
+  ASSERT(fetch(&mgr, buf, url, set3_admin_req) == 200);
+  ASSERT(cmpbody(buf, "1\n") == 0);
   for (i = 0; i < 200 && ws_admin.done == 0; i++) mg_mgr_poll(&mgr, 1);
   ASSERT(ws_admin.done == 1);
-  ASSERT(ws_admin.result == 1);
   ASSERT(ws_admin.saw_set3 == 1);
+  ASSERT(fetch(&mgr, buf, url, set1_admin_set4_req) == 200);
+  ASSERT(cmpbody(buf, "1\n") == 0);
   ASSERT(fetch(&mgr, buf, url,
                "GET /api/get/set1 HTTP/1.0\n"
                "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
@@ -4466,7 +4606,193 @@ static void test_dash(void) {
   ASSERT(fetch(&mgr, buf, url, "GET /api/hi HTTP/1.0\n\n") == 200);
   ASSERT(cmpbody(buf, "hi\n") == 0);
 
+  // Array tests with auth (17 squares)
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/get/arr HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+  ASSERT(cmpbody(buf, "17\n") == 0);
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/get/arr/7 HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+  ASSERT(cmpbody(buf, arr7_expected) == 0);
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/get/arr/0/2 HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+  ASSERT(cmpbody(buf, arr0_2_expected) == 0);
+
+  // Array deletion: single element
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/del/arr/3 HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+  ASSERT(cmpbody(buf, "1\n") == 0);
+
+  // Array deletion: range
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/del/arr/1/3 HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+  ASSERT(cmpbody(buf, "3\n") == 0);
+
+  // Array deletion: out-of-range returns 403
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/del/arr/100 HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 403);
+
+  // Non-array set returns 404
+  ASSERT(fetch(&mgr, buf, url,
+               "GET /api/del/set1/0 HTTP/1.0\n"
+               "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 404);
+
+  // Test that array change notification uses "arr/INDEX" key format
+  {
+    struct dash_arr_ws_test ws_arr;
+    memset(&ws_arr, 0, sizeof(ws_arr));
+    ws_arr.saw_arr_index = -1;
+    ws_arr.saw_arr_val = -1;
+    ws_arr.saw_arr_size = -1;
+    mg_ws_connect(&mgr, ws_url, dash_arr_ws_cb, &ws_arr, "%s",
+                  "Authorization: Basic YWRtaW46YWRtaW4=\r\n");
+    for (i = 0; i < 200 && ws_arr.opened == 0; i++) mg_mgr_poll(&mgr, 1);
+    ASSERT(ws_arr.opened == 1);
+    s_arr_index = 5;
+    mg_dash_send_change(&mgr, &arr_set);
+    for (i = 0; i < 200 && ws_arr.done == 0; i++) mg_mgr_poll(&mgr, 1);
+    ASSERT(ws_arr.done == 1);
+    ASSERT(ws_arr.saw_arr_index == 5);
+  }
+
+  // Array modification: POST /api/get/<set>/<index> updates one element
+  // and broadcasts a "<set>/<index>" WS change notification with new value
+  {
+    struct dash_arr_ws_test ws_mod;
+    memset(&ws_mod, 0, sizeof(ws_mod));
+    ws_mod.saw_arr_index = -1;
+    ws_mod.saw_arr_val = -1;
+    ws_mod.saw_arr_size = -1;
+    mg_ws_connect(&mgr, ws_url, dash_arr_ws_cb, &ws_mod, "%s",
+                  "Authorization: Basic YWRtaW46YWRtaW4=\r\n");
+    for (i = 0; i < 200 && ws_mod.opened == 0; i++) mg_mgr_poll(&mgr, 1);
+    ASSERT(ws_mod.opened == 1);
+
+    ASSERT(fetch(&mgr, buf, url, arr5_mod_req) == 200);
+    ASSERT(cmpbody(buf, "1\n") == 0);
+
+    for (i = 0; i < 200 && ws_mod.done == 0; i++) mg_mgr_poll(&mgr, 1);
+    ASSERT(ws_mod.done == 1);
+    ASSERT(ws_mod.saw_arr_index == 5);
+    ASSERT(ws_mod.saw_arr_val == 99);
+
+    // The new value got persisted - a fresh read returns it
+    ASSERT(fetch(&mgr, buf, url,
+                 "GET /api/get/arr/5 HTTP/1.0\n"
+                 "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+    ASSERT(cmpbody(buf, arr5_mod_expected) == 0);
+
+    // Out-of-range index: 404
+    ASSERT(fetch(&mgr, buf, url, arr100_mod_req) == 404);
+
+    // Read-only element: fn denies MG_DASH_WRITE -> 403, value unchanged
+    ASSERT(fetch(&mgr, buf, url, arr3_mod_req) == 403);
+    ASSERT(fetch(&mgr, buf, url,
+                 "GET /api/get/arr/3 HTTP/1.0\n"
+                 "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+    ASSERT(cmpbody(buf, arr3_expected) == 0);
+  }
+
+  // Array addition: POST /api/add/<set> appends an element and broadcasts
+  // a plain "<set>":N WS change notification with the new size
+  {
+    struct dash_arr_ws_test ws_add;
+    memset(&ws_add, 0, sizeof(ws_add));
+    ws_add.saw_arr_index = -1;
+    ws_add.saw_arr_val = -1;
+    ws_add.saw_arr_size = -1;
+    mg_ws_connect(&mgr, ws_url, dash_arr_ws_cb, &ws_add, "%s",
+                  "Authorization: Basic YWRtaW46YWRtaW4=\r\n");
+    for (i = 0; i < 200 && ws_add.opened == 0; i++) mg_mgr_poll(&mgr, 1);
+    ASSERT(ws_add.opened == 1);
+
+    ASSERT(fetch(&mgr, buf, url, arr_add555_req) == 200);
+    ASSERT(cmpbody(buf, "true\n") == 0);
+
+    for (i = 0; i < 200 && ws_add.done == 0; i++) mg_mgr_poll(&mgr, 1);
+    ASSERT(ws_add.done == 1);
+    ASSERT(ws_add.saw_arr_size == TEST_ARR_SIZE + 1);
+
+    // The new element landed at the end of the array
+    ASSERT(fetch(&mgr, buf, url,
+                 "GET /api/get/arr/17 HTTP/1.0\n"
+                 "Authorization: Basic YWRtaW46YWRtaW4=\n\n") == 200);
+    ASSERT(cmpbody(buf, arr17_expected) == 0);
+
+    // One more addition reaches the cap, then fn denies further ones
+    ASSERT(fetch(&mgr, buf, url, arr_add556_req) == 200);
+    ASSERT(fetch(&mgr, buf, url, arr_add557_req) == 403);
+  }
+
   mg_mgr_free(&mgr);
+
+  // Test no files fieldset: /fs/ returns 404
+  {
+    const char *url2 = "http://localhost:26353";
+    struct mg_mgr mgr2;
+    struct mg_dash dash2;
+    memset(&dash2, 0, sizeof(dash2));
+    MG_DASH_ADD_FIELD_SET(&dash2, &set1);
+    MG_DASH_ADD_FIELD_SET(&dash2, &set2);
+    MG_DASH_ADD_FIELD_SET(&dash2, &set3);
+    mg_mgr_init(&mgr2);
+    mg_mem_files = mg_packed_files;
+    ASSERT(mg_http_listen(&mgr2, url2, mg_dash_ev_handler, &dash2) != NULL);
+    ASSERT(fetch(&mgr2, buf, url2, "GET /api/get HTTP/1.0\n\n") == 200);
+    ASSERT(strstr(buf, files_probe) == NULL);  // no files fieldset
+    ASSERT(fetch(&mgr2, buf, url2, "GET /fs/files/test.txt HTTP/1.0\n\n") == 404);
+    ASSERT(fetch(&mgr2, buf, url2,
+                 "POST /fs/files/test.txt HTTP/1.0\nContent-Length: 5\n\nhello") ==
+           404);
+    mg_mgr_free(&mgr2);
+  }
+
+  // Test files fieldset with get_dir: /fs/ endpoints active
+  {
+    const char *url3 = "http://localhost:26354";
+    struct mg_mgr mgr3;
+    struct mg_dash dash3;
+    static int idx3;
+    static struct mg_field ff3[] = {
+        {"name", MG_VAL_STR, s_delete_file.name, sizeof(s_delete_file.name)},
+        {"size", MG_VAL_UINT64, &s_delete_file.size, 0},
+        {NULL, MG_VAL_INT, NULL, 0},
+    };
+    static struct mg_field_set fset3 = {"files", ff3, delete_file_fn, &idx3,
+                                        test_upload_dir, NULL};
+    memset(&dash3, 0, sizeof(dash3));
+    s_deleted_file[0] = '\0';
+    s_uploaded_file[0] = '\0';
+    s_delete_file_set = &fset3;
+    MG_DASH_ADD_FIELD_SET(&dash3, &fset3);
+    mg_mgr_init(&mgr3);
+    mg_mem_files = mg_packed_files;
+    ASSERT(mg_http_listen(&mgr3, url3, mg_dash_ev_handler, &dash3) != NULL);
+    ASSERT(fetch(&mgr3, buf, url3, "GET /api/get HTTP/1.0\n\n") == 200);
+    ASSERT(strstr(buf, files_probe) != NULL);  // files fieldset present
+    ASSERT(fetch(&mgr3, buf, url3,
+                 "DELETE /fs/files/nofile.txt HTTP/1.0\n\n") == 200);
+    ASSERT(strcmp(s_deleted_file, "nofile.txt") == 0);
+    ASSERT(fetch(&mgr3, buf, url3,
+                 "DELETE /fs/files/..%2Fevil.txt HTTP/1.0\n\n") == 400);
+    ASSERT(strcmp(s_deleted_file, "nofile.txt") == 0);
+    ASSERT(fetch(&mgr3, buf, url3,
+                 "PUT /fs/files/test.bin HTTP/1.0\nContent-Length: 4\n\ndata") ==
+           200);
+    ASSERT(strcmp(s_uploaded_file, "test.bin") == 0);
+    ASSERT(fetch(&mgr3, buf, url3,
+                 "PUT /fs/files/..%2Fevil.bin HTTP/1.0\nContent-Length: "
+                 "4\n\ndata") == 400);
+    ASSERT(strcmp(s_uploaded_file, "test.bin") == 0);
+    ASSERT(fetch(&mgr3, buf, url3, "GET /api/get/files/0 HTTP/1.0\n\n") == 200);
+    ASSERT(strstr(buf, test_bin_probe) != NULL);
+    mg_mgr_free(&mgr3);
+  }
 }
 
 #define DASHBOARD(x) \
diff --git a/tutorials/device-dashboard/events/Makefile b/tutorials/device-dashboard/array/Makefile
similarity index 91%
rename from tutorials/device-dashboard/events/Makefile
rename to tutorials/device-dashboard/array/Makefile
index f28dc096..7fb5125e 100644
--- a/tutorials/device-dashboard/events/Makefile
+++ b/tutorials/device-dashboard/array/Makefile
@@ -5,7 +5,7 @@ TOP ?= ../../..
 SOURCES = dashboard.c file_data.c $(TOP)/mongoose.c
 CFLAGS_EXTRA ?= -DMG_TLS=MG_TLS_BUILTIN
 CFLAGS ?= -W -Wall -Wextra -Werror -Wundef -Wshadow -O0 $(CFLAGS_EXTRA)
-PFLAGS = -I$(TOP) -DMG_DATA_SIZE=64 -DMG_ENABLE_LINES=1 -DMAIN
+PFLAGS = -I$(TOP) -DMG_DATA_SIZE=64 -DMG_ENABLE_LINES=1 -DMAIN -DMG_DASH_STREAM_BATCH=100
 AFLAGS ?= -fsanitize=signed-integer-overflow,address,undefined,alignment
 
 all: $(PROG)
diff --git a/tutorials/device-dashboard/array/dashboard.c b/tutorials/device-dashboard/array/dashboard.c
new file mode 100644
index 00000000..7d4f86b8
--- /dev/null
+++ b/tutorials/device-dashboard/array/dashboard.c
@@ -0,0 +1,116 @@
+// SPDX-FileCopyrightText: 2026 Cesanta Software Limited
+// SPDX-License-Identifier: GPL-2.0-only or commercial
+
+#include "mongoose.h"
+
+// Array elements are stored in a dynamically reallocated array
+struct entry {
+  char text[20];  // Modifiable via GUI
+  bool checked;   // Modifiable via GUI
+};
+
+static struct entry *s_arr;   // Backing storage, grown/shrunk via realloc()
+static size_t s_count;        // Number of elements in s_arr
+static struct entry s_entry;  // Staging area: holds values for read/write/add
+static int s_index;           // Current element index, see struct mg_field_set
+
+static struct mg_field fields_arr[] = {
+    {"index", MG_VAL_INT, &s_index, sizeof(s_index)},
+    {"text", MG_VAL_STR, &s_entry.text, sizeof(s_entry.text)},
+    {"checked", MG_VAL_BOOL, &s_entry.checked, sizeof(s_entry.checked)},
+    {NULL, MG_VAL_INT, NULL, 0},
+};
+
+// Grow s_arr by one slot and append the staged entry. False on OOM
+static bool entry_append(void) {
+  struct entry *arr =
+      (struct entry *) realloc(s_arr, (s_count + 1) * sizeof(*arr));
+  if (arr == NULL) return false;
+  s_arr = arr;
+  s_arr[s_count++] = s_entry;
+  return true;
+}
+
+// Remove the entry at the given index, shifting the tail down and shrinking
+// s_arr by one slot. False if the index is out of range
+static bool entry_remove(int index) {
+  if (index < 0 || (size_t) index >= s_count) return false;
+  memmove(&s_arr[index], &s_arr[index + 1],
+          (s_count - (size_t) index - 1) * sizeof(*s_arr));
+  s_count--;
+  if (s_count == 0) {
+    free(s_arr);
+    s_arr = NULL;
+  } else {
+    struct entry *arr = (struct entry *) realloc(s_arr, s_count * sizeof(*arr));
+    if (arr != NULL) s_arr = arr;
+  }
+  return true;
+}
+
+// Read, write, delete or append an array element. The framework sets s_index
+// before the call: a negative value asks for the total count, an
+// out-of-range value means "end of iteration" - both are answered by
+// setting s_index accordingly. MG_DASH_ADD builds a new entry from the
+// staged fields and appends it regardless of s_index
+static bool arr_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op == MG_DASH_READ) {
+    if (s_index < 0) {
+      s_index = (int) s_count;
+    } else if ((size_t) s_index >= s_count) {
+      s_index = -1;
+    } else {
+      s_entry = s_arr[s_index];
+    }
+    return true;
+  }
+  if (op == MG_DASH_WRITE && s_index >= 0 && (size_t) s_index < s_count) {
+    s_arr[s_index] = s_entry;
+    return true;
+  }
+  if (op == MG_DASH_DELETE) return entry_remove(s_index);
+  if (op == MG_DASH_ADD) return entry_append();
+  return false;
+}
+
+static struct mg_field_set field_set_arr = {
+    "event", fields_arr, arr_fn, &s_index, NULL, NULL,
+};
+
+void mg_dash_init(struct mg_mgr *mgr) {
+  static struct mg_dash dash;  // Important: keep it static!
+  static const char *demo[] = {"Wake up", "Make coffee", "Write code",
+                               "Run tests", "Ship it", "Relax", "Sleep"};
+  size_t i;
+  for (i = 0; i < sizeof(demo) / sizeof(demo[0]); i++) {
+    mg_snprintf(s_entry.text, sizeof(s_entry.text), "%s", demo[i]);
+    s_entry.checked = (i == 0);
+    entry_append();
+  }
+  MG_DASH_ADD_FIELD_SET(&dash, &field_set_arr);
+  mg_mem_files = mg_packed_files;
+  mg_http_listen(mgr, MG_HTTP_ADDR, mg_dash_ev_handler, &dash);
+}
+
+void mg_dash_poll(struct mg_mgr *mgr) {
+  (void) mgr;
+}
+
+// On desktop, build with -DMAIN flag to include main().
+// On embedded system, run this code in your main() function
+#ifdef MAIN
+int main(void) {
+  struct mg_mgr mgr;
+
+  mg_mgr_init(&mgr);
+  mg_dash_init(&mgr);
+
+  for (;;) {
+    mg_mgr_poll(&mgr, 1);
+    mg_dash_poll(&mgr);
+  }
+
+  return 0;
+}
+#endif
diff --git a/tutorials/device-dashboard/array/dashboard.html b/tutorials/device-dashboard/array/dashboard.html
new file mode 100644
index 00000000..a04a86c7
--- /dev/null
+++ b/tutorials/device-dashboard/array/dashboard.html
@@ -0,0 +1,129 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title>Array Dashboard</title>
+
+    <script src="https://mongoose.ws/resources/dashboard.js"></script>
+    <script>
+      let pageStart = 0;
+      function getPageSize() { return parseInt(document.getElementById('page-size').value) || 5; }
+      function loadPage(start) {
+        pageStart = Math.max(0, start);
+        Dashboard.call('get', { name: 'event', start: pageStart, size: getPageSize() });
+      }
+
+      // PATCH one element, then reload the current page to show the result
+      function modifyEntry(index, patch) {
+        return fetch(`api/get/event/${index}`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify(patch),
+        }).then(() => loadPage(pageStart));
+      }
+
+      // Delete one element, then reload the current page
+      function removeEntry(index) {
+        return fetch(`api/del/event/${index}`, { method: 'DELETE' })
+          .then(() => loadPage(pageStart));
+      }
+
+      // Append a new element from the "add" form, then reload the current page
+      function addEntry() {
+        const text = document.getElementById('new-text').value;
+        const checked = document.getElementById('new-checked').checked;
+        return fetch('api/add/event', {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({ text, checked }),
+        }).then(() => {
+          document.getElementById('new-text').value = '';
+          document.getElementById('new-checked').checked = false;
+          loadPage(pageStart);
+        });
+      }
+
+      Dashboard.init({
+        debug: true,
+        data: { event: { start: 0, end: 100, data: [] } },
+      });
+
+      Dashboard.on('ready', () => {
+        document.body.style.visibility = 'visible';
+        loadPage(0);
+      });
+    </script>
+
+    <style>
+      * { box-sizing: border-box; }
+      html, body { height: 100%; }
+      body { margin: 0; background:#f8fafc; font:500 14px/1.35 Arial,sans-serif; }
+      .btn { display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem; height: 2rem; padding: 0.3rem 1rem; font-size: 0.85rem; font-family: inherit; font-weight: 600; border-radius: 0.5rem; border: 1px solid transparent; cursor: pointer; transition: all 0.15s ease; white-space: nowrap; }
+      .btn-secondary { color: #64748b; background: #ffffff; border-color: #e2e8f0; }
+      .btn-secondary:hover { background: #f1f5f9; border-color: #cbd5e1; color: #475569; }
+      .btn-primary { color: #ffffff; background: linear-gradient(160deg, #38bdf8, #0ea5e9); border-color: #0284c7; }
+      .btn-primary:hover { background: linear-gradient(160deg, #0ea5e9, #0284c7); }
+      .btn:disabled { opacity: 0.45; cursor: not-allowed; pointer-events: none; }
+      .btn-icon { width: 2rem; padding: 0.3rem; }
+      .toolbar { display: flex; align-items: center; flex-wrap: wrap; gap: 0.75rem; margin: 1.25rem 0; }
+      input[type=text] { width: 4rem; padding: 0.3rem 0.5rem; font-size: 0.85rem; font-family: inherit; border: 1px solid #e2e8f0; border-radius: 0.5rem; outline: none; }
+      input[type=text]:focus { border-color: #7dd3fc; }
+      .toggle { position: relative; width: 2.75rem; height: 1.6rem; margin: 0; vertical-align: middle; border: 1px solid transparent; background: #d1d5db; border-radius: 0.8rem; outline: none; cursor: pointer; -webkit-appearance: none; appearance: none; transition: background 0.2s ease; }
+      .toggle::after { content: ""; position: absolute; left: 2px; top: 50%; width: 1.3rem; height: 1.3rem; background: #fff; border-radius: 50%; box-shadow: 0 1px 2px rgba(0,0,0,0.25); transform: translateY(-50%) translateX(0); transition: transform 0.2s ease; }
+      .toggle:checked { background: #10b981; }
+      .toggle:checked::after { transform: translateY(-50%) translateX(calc(100% - 4px)); }
+      .toggle:focus-visible { box-shadow: 0 0 0 3px rgba(16,185,129,0.25); }
+      .table-wrap { max-width: 44rem; overflow: auto; border: 1px solid #e2e8f0; border-radius: 0.5rem; background: #fff; }
+      table { width: 100%; border-collapse: collapse; }
+      th, td { padding: 0.65rem 0.85rem; border-bottom: 1px solid #e2e8f0; text-align: left; }
+      th { font-size: 0.75rem; text-transform: uppercase; color: #64748b; background: #f1f5f9; }
+      td:first-child { width: 7rem; color: #334155; font-variant-numeric: tabular-nums; }
+      tr:last-child td { border-bottom: 0; }
+    </style>
+  </head>
+
+  <body style="visibility: hidden;">
+    <main style="margin: 2rem; color: #64748b;">
+      <h1>Array read/write/add/delete</h1>
+
+      <div class="toolbar">
+        <button class="btn btn-secondary" onclick="loadPage(pageStart - getPageSize())">Prev</button>
+        <button class="btn btn-secondary" onclick="loadPage(pageStart + getPageSize())">Next</button>
+        <button class="btn btn-primary"   onclick="loadPage(pageStart)">Reload</button>
+        <label>Page size: <input id="page-size" type="text" value="5" /></label>
+        <span>${(event.start ?? 0) + 1}–${(event.start ?? 0) + event.data.length} of ${event.size ?? 0}</span>
+      </div>
+
+      <div class="table-wrap" id="entries">
+        <table>
+          <thead><tr><th>Index</th><th>Text</th><th>Done</th><th></th></tr></thead>
+          <tbody data-repeat="event.data" data-iterator="ev">
+            <tr>
+              <td>${ev.index}</td>
+              <td><input type="text" style="width: 100%;" value="${ev.text}" onchange="modifyEntry(${ev.index}, {text: this.value})" /></td>
+              <td><input type="checkbox" class="toggle" data-checked="ev.checked" onchange="modifyEntry(${ev.index}, {checked: this.checked})" /></td>
+              <td>
+                <button class="btn btn-secondary btn-icon" onclick="removeEntry(${ev.index})" title="Delete" aria-label="Delete">
+                  <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
+                    <path d="M3 6h18" />
+                    <path d="M8 6V4a2 2 0 0 1 2-2h4a2 2 0 0 1 2 2v2" />
+                    <path d="M19 6l-1 14a2 2 0 0 1-2 2H8a2 2 0 0 1-2-2L5 6" />
+                    <line x1="10" y1="11" x2="10" y2="17" />
+                    <line x1="14" y1="11" x2="14" y2="17" />
+                  </svg>
+                </button>
+              </td>
+            </tr>
+          </tbody>
+        </table>
+      </div>
+
+      <div class="toolbar">
+        <input id="new-text" type="text" style="width: 12rem;" placeholder="New entry text" />
+        <label><input id="new-checked" type="checkbox" class="toggle" /> Done</label>
+        <button class="btn btn-primary" onclick="addEntry()">Add</button>
+      </div>
+    </main>
+  </body>
+</html>
diff --git a/tutorials/device-dashboard/events/dashboard.c b/tutorials/device-dashboard/events/dashboard.c
deleted file mode 100644
index 3cff03cd..00000000
--- a/tutorials/device-dashboard/events/dashboard.c
+++ /dev/null
@@ -1,59 +0,0 @@
-// SPDX-FileCopyrightText: 2026 Cesanta Software Limited
-// SPDX-License-Identifier: GPL-2.0-only or commercial
-
-#include "mongoose.h"
-
-struct event {
-  int index;
-  char message[100];
-};
-
-static struct event s_event;
-
-static void read_event(void) {
-  mg_snprintf(s_event.message, sizeof(s_event.message), "my ev %d",
-              s_event.index);
-}
-
-static void write_event(void) {
-  // Do nothing. Dashboard sets the s_event.index
-}
-
-static struct mg_field fields_event[] = {
-    {"index", MG_VAL_INT, &s_event.index, sizeof(s_event.index)},
-    {"message", MG_VAL_STR, &s_event.message, sizeof(s_event.message)},
-    {NULL, MG_VAL_INT, NULL, 0},
-};
-
-static struct mg_field_set field_set_event = {
-    "event", fields_event, read_event, write_event, 0, 0, NULL,
-};
-
-void mg_dash_init(struct mg_mgr *mgr) {
-  static struct mg_dash dash;  // Important: keep it static!
-  MG_DASH_ADD_FIELD_SET(&dash, &field_set_event);
-  mg_mem_files = mg_packed_files;
-  mg_http_listen(mgr, MG_HTTP_ADDR, mg_dash_ev_handler, &dash);
-}
-
-void mg_dash_poll(struct mg_mgr *mgr) {
-  (void) mgr;
-}
-
-// On desktop, build with -DMAIN flag to include main().
-// On embedded system, run this code in your main() function
-#ifdef MAIN
-int main(void) {
-  struct mg_mgr mgr;
-
-  mg_mgr_init(&mgr);
-  mg_dash_init(&mgr);
-
-  for (;;) {
-    mg_mgr_poll(&mgr, 1);
-    mg_dash_poll(&mgr);
-  }
-
-  return 0;
-}
-#endif
diff --git a/tutorials/device-dashboard/events/dashboard.html b/tutorials/device-dashboard/events/dashboard.html
deleted file mode 100644
index c9ca43fc..00000000
--- a/tutorials/device-dashboard/events/dashboard.html
+++ /dev/null
@@ -1,135 +0,0 @@
-<!doctype html>
-<html lang="en">
-  <head>
-    <meta charset="utf-8" />
-    <meta name="viewport" content="width=device-width, initial-scale=1" />
-    <title>Array Dashboard</title>
-
-    <script src="https://mongoose.ws/resources/dashboard.js"></script>
-    <script>
-      Dashboard.init({
-        debug: true,
-        data: { event: { index: 0, message: 'hi' } },
-      });
-
-      let pageStart = 0;
-      let loading = false;
-      let eventReadQueue = Promise.resolve();
-
-      async function readEvent(index) {
-        eventReadQueue = eventReadQueue.then(async () => {
-          await Dashboard.call('set', { event: { index } });
-          const ev = await Dashboard.call('get', 'event');
-          return ev && typeof ev == 'object' ? ev : { index, message: `my ev ${index}` };
-        });
-        return eventReadQueue;
-      }
-
-      function setLoading(value) {
-        loading = value;
-        document.querySelectorAll('[data-page-button]').forEach(btn => btn.disabled = value);
-      }
-
-      async function loadRows(start) {
-        if (loading) return;
-        const count = Number(document.querySelector('#page-size').value) || 10;
-        const tbody = document.querySelector('#events tbody');
-        const status = document.querySelector('#table-status');
-
-        pageStart = Math.max(0, start);
-        tbody.replaceChildren();
-        status.textContent = `Loading ${pageStart}..${pageStart + count - 1}`;
-        setLoading(true);
-
-        try {
-          const rows = await Promise.all(Array.from({ length: count }, (_, i) =>
-            readEvent(pageStart + i)));
-          const frag = document.createDocumentFragment();
-
-          rows.forEach(ev => {
-            const tr = document.createElement('tr');
-            const tdIndex = document.createElement('td');
-            const tdMessage = document.createElement('td');
-
-            tdIndex.textContent = ev.index;
-            tdMessage.textContent = ev.message;
-            tr.append(tdIndex, tdMessage);
-            frag.appendChild(tr);
-          });
-          tbody.replaceChildren(frag);
-          status.textContent = `Showing ${pageStart}..${pageStart + count - 1}`;
-        } catch (err) {
-          status.textContent = `Error: ${err && err.message ? err.message : err}`;
-        } finally {
-          setLoading(false);
-        }
-      }
-
-      // Show dashboard only when all device data is reported
-      Dashboard.on('ready', () => {
-        document.body.style.visibility = 'visible';
-        loadRows(0);
-      });
-    </script>
-
-    <style>
-      * { box-sizing: border-box; }
-      html, body { height: 100%; }
-      body { margin: 0; background:#f8fafc; font:500 14px/1.35 Arial,sans-serif; }
-      code {white-space: nowrap; background: #ddd; border-radius: 4px; padding: 1px 4px;}
-      .field { display: flex; flex-direction: row; justify-content: space-between; align-items: center; gap: 0.75rem; }
-      .field-label { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; color: #94a3b8; flex-shrink: 0; white-space: nowrap; min-width: 3rem; }
-      .field-input { flex: 1; min-width: 0; padding: 0.45rem 0.75rem; font-size: 0.88rem; font-family: inherit; color: #334155; border: 1px solid #e2e8f0; border-radius: 0.55rem; outline: none; transition: border-color 0.15s ease; }
-      .field-input.edited { border-color: #00500040 !important; background: #00ff0020; }
-      .field-input.error { border-color: #50000040; background: #ff000020; }
-      .field-input::placeholder { color: #cbd5e1; }
-      .field-input:hover { border-color: #cbd5e1; }
-      .field-input:focus { border-color: #7dd3fc; }
-      .field-input:disabled, .field-input.disabled { color: #cbd5e1; border-color: #e2e8f0; cursor: not-allowed; pointer-events: none; }
-      .btn { display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem; height: 2rem; padding: 0.3rem 1rem; font-size: 0.85rem; font-family: inherit; font-weight: 600; border-radius: 0.5rem; border: 1px solid transparent; cursor: pointer; transition: all 0.15s ease; white-space: nowrap; }
-      .btn-secondary { color: #64748b; background: #ffffff; border-color: #e2e8f0; box-shadow: 0 1px 2px rgba(148, 163, 184, 0.1); }
-      .btn-secondary:hover { background: #f1f5f9; border-color: #cbd5e1; color: #475569; }
-      .btn-primary { color: #ffffff; background: linear-gradient(160deg, #38bdf8, #0ea5e9); border-color: #0284c7; box-shadow: 0 1px 3px rgba(14, 165, 233, 0.3), 0 4px 10px rgba(14, 165, 233, 0.15); }
-      .btn-primary:hover { background: linear-gradient(160deg, #0ea5e9, #0284c7); box-shadow: 0 1px 3px rgba(14, 165, 233, 0.4), 0 6px 14px rgba(14, 165, 233, 0.2); }
-      .btn-primary:active, .btn-secondary:active { transform: translateY(0); }
-      .btn:disabled, .btn.disabled { opacity: 0.45; cursor: not-allowed; pointer-events: none; box-shadow: none; transform: none; }
-      .toolbar { display: flex; align-items: center; flex-wrap: wrap; gap: 0.75rem; margin: 1.25rem 0; }
-      .table-wrap { max-width: 44rem; overflow: auto; border: 1px solid #e2e8f0; border-radius: 0.5rem; background: #fff; }
-      table { width: 100%; border-collapse: collapse; }
-      th, td { padding: 0.65rem 0.85rem; border-bottom: 1px solid #e2e8f0; text-align: left; }
-      th { font-size: 0.75rem; text-transform: uppercase; color: #64748b; background: #f1f5f9; }
-      td:first-child { width: 7rem; color: #334155; font-variant-numeric: tabular-nums; }
-      tr:last-child td { border-bottom: 0; }
-      #table-status { min-width: 12rem; color: #64748b; }
-    </style>
-  </head>
-
-  <body style="visibility: hidden;">
-    <main id="main" style="margin: 2rem; color: #64748b;">
-      <h1>Array read/write</h1>
-
-      <div class="toolbar">
-        <button class="btn btn-secondary" data-page-button onclick="loadRows(pageStart - Number(document.querySelector('#page-size').value || 10))">Prev</button>
-        <button class="btn btn-secondary" data-page-button onclick="loadRows(pageStart + Number(document.querySelector('#page-size').value || 10))">Next</button>
-        <div class="field" style="width: 9rem;">
-          Rows
-          <input id="page-size" class="field-input" type="text" value="10" />
-        </div>
-        <button class="btn btn-primary" data-page-button onclick="loadRows(pageStart)">Reload</button>
-        <span id="table-status"></span>
-      </div>
-
-      <div class="table-wrap">
-        <table id="events">
-          <thead>
-            <tr>
-              <th>Index</th>
-              <th>Message</th>
-            </tr>
-          </thead>
-          <tbody></tbody>
-        </table>
-      </div>
-    </main>
-  </body>
-</html>
diff --git a/tutorials/device-dashboard/full/dashboard.c b/tutorials/device-dashboard/full/dashboard.c
index 6e11a861..7dd23d74 100644
--- a/tutorials/device-dashboard/full/dashboard.c
+++ b/tutorials/device-dashboard/full/dashboard.c
@@ -9,33 +9,32 @@ static int authenticate(char *user, size_t userlen, const char *pass);
 // Action buttons
 static bool s_action1, s_action2;
 static uint64_t s_action2_timeout;
-static void write_actions(void) {
-  if (s_action2 == true) s_action2_timeout = mg_now() + 750;
-}
-static void read_actions(void) {
-  if (s_action2_timeout > mg_now()) s_action2 = true;
+static bool actions_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op == MG_DASH_READ) {
+    if (s_action2_timeout > mg_now()) s_action2 = true;
+    return true;
+  }
+  if (op == MG_DASH_WRITE) {
+    if (s_action2 == true) s_action2_timeout = mg_now() + 750;
+    return true;
+  }
+  return false;
 }
 static struct mg_field fields_actions[] = {
     {"action1", MG_VAL_BOOL, &s_action1, sizeof(s_action1)},
     {"action2", MG_VAL_BOOL, &s_action2, sizeof(s_action2)},
     {NULL, MG_VAL_INT, NULL, 0},
 };
-static struct mg_field_set set_actions = {
-    "actions", fields_actions, read_actions, write_actions, 0, 0, NULL,
-};
+static struct mg_field_set set_actions = {"actions", fields_actions, actions_fn,
+                                          NULL,      NULL,           NULL};
 
 // Control panel
 // s_led1, s_led2, s_led3 are used to communicate LED status
 static bool s_led1, s_led2, s_led3;
-static void write_leds(void) {
-  // gpio_write(LED1_PIN, s_led1);
-  // gpio_write(LED2_PIN, s_led2);
-  // gpio_write(LED3_PIN, s_led3);
-}
-static void read_leds(void) {
-  // s_led1 = gpio_read(LED1_PIN);
-  // s_led2 = gpio_read(LED2_PIN);
-  // s_led3 = gpio_read(LED3_PIN);
+static bool leds_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  return op == MG_DASH_READ || op == MG_DASH_WRITE;
 }
 static struct mg_field fields_leds[] = {
     {"led1", MG_VAL_BOOL, &s_led1, sizeof(s_led1)},
@@ -43,18 +42,20 @@ static struct mg_field fields_leds[] = {
     {"led3", MG_VAL_BOOL, &s_led3, sizeof(s_led3)},
     {NULL, MG_VAL_INT, NULL, 0},
 };
-static struct mg_field_set set_leds = {
-    "leds", fields_leds, read_leds, write_leds, 0, 0, NULL,
-};
+static struct mg_field_set set_leds = {"leds", fields_leds, leds_fn,
+                                       NULL,   NULL,        NULL};
 
 // Read-only device Metrics
 static int s_ram = 32, s_cpu = 7;
 static double s_temperature = 24.8;
 
-static void read_metrics(void) {
-  s_ram = 25 + (rand() % 16);  // Sumulate metric change
+static bool metrics_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op != MG_DASH_READ) return false;
+  s_ram = 25 + (rand() % 16);
   s_cpu = 7 + (rand() % 21);
   s_temperature = 14.8 + ((double) rand() / RAND_MAX) * 20.0;
+  return true;
 }
 
 static struct mg_field fields_metrics[] = {
@@ -64,9 +65,8 @@ static struct mg_field fields_metrics[] = {
     {NULL, MG_VAL_INT, NULL, 0},
 };
 
-static struct mg_field_set set_metrics = {
-    "metrics", fields_metrics, read_metrics, NULL, 0, 0, NULL,
-};
+static struct mg_field_set set_metrics = {"metrics", fields_metrics, metrics_fn,
+                                          NULL,      NULL,           NULL};
 
 // Read-write device settings
 static bool s_enable_login = false;
@@ -78,13 +78,18 @@ static char s_ota_version[] = "1.1.2";
 static char s_ota_status[40] = "No scans yet";
 static char s_ota_url[100] = "https://my-product.com/ota.json";
 
-static void write_settings(void) {
-  mg_log_level = s_log_level;
-  s_dash.authenticate = s_enable_login ? authenticate : NULL;
-}
-
-static void read_settings(void) {
-  s_log_level = mg_log_level;
+static bool settings_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  if (u->level < 3) return false;
+  if (op == MG_DASH_READ) {
+    s_log_level = mg_log_level;
+    return true;
+  }
+  if (op == MG_DASH_WRITE && u->level >= 7) {
+    mg_log_level = s_log_level;
+    s_dash.authenticate = s_enable_login ? authenticate : NULL;
+    return true;
+  }
+  return false;
 }
 
 static struct mg_field fields_settings[] = {
@@ -100,8 +105,7 @@ static struct mg_field fields_settings[] = {
 };
 
 static struct mg_field_set set_settings = {
-    "settings", fields_settings, read_settings, write_settings, 3, 7, NULL,
-};
+    "settings", fields_settings, settings_fn, NULL, NULL, NULL};
 
 #define NUM_POINTS_GRAPH1 7  // How many graph1 data points to send
 
@@ -139,9 +143,14 @@ static struct mg_field fields_graph1[] = {
     {NULL, MG_VAL_INT, NULL, 0},
 };
 
-static struct mg_field_set set_graph1 = {
-    "graph1", fields_graph1, read_graph1, NULL, 0, 0, NULL,
-};
+static bool graph1_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op != MG_DASH_READ) return false;
+  read_graph1();
+  return true;
+}
+static struct mg_field_set set_graph1 = {"graph1", fields_graph1, graph1_fn,
+                                         NULL,     NULL,          NULL};
 
 #define NUM_POINTS_GRAPH2 100  // How many graph2 data points to send
 static char s_graph2_data[NUM_POINTS_GRAPH2 * 4 + 2 + 1];
@@ -172,9 +181,13 @@ static struct mg_field fields_graph2[] = {
     {NULL, MG_VAL_INT, NULL, 0},
 };
 
-static struct mg_field_set set_graph2 = {
-    "graph2", fields_graph2, read_graph2, NULL, 0, 0, NULL,
-};
+static bool graph2_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op == MG_DASH_READ) read_graph2();
+  return op == MG_DASH_READ || op == MG_DASH_WRITE;
+}
+static struct mg_field_set set_graph2 = {"graph2", fields_graph2, graph2_fn,
+                                         NULL,     NULL,          NULL};
 
 static int authenticate(char *user, size_t userlen, const char *pass) {
   int level = 0;  // Authentication failure
@@ -188,7 +201,42 @@ static int authenticate(char *user, size_t userlen, const char *pass) {
   return level;
 }
 
+static struct file {
+  int index;
+  char name[64];
+  size_t size;
+  uint64_t checksum;
+} s_file;
+static struct mg_field_set set_files;
+
+static bool get_dir(const struct mg_dash_user *u, char *buf, size_t len) {
+  (void) u;
+  mg_snprintf(buf, len, "%s", "/tmp/dashboard");
+  return true;
+}
+
+static struct mg_field fields_files[] = {
+    {"name", MG_VAL_STR, s_file.name, sizeof(s_file.name)},
+    {"size", MG_VAL_UINT64, &s_file.size, 0},
+    {"checksum", MG_VAL_UINT64, &s_file.checksum, sizeof(s_file.checksum)},
+    {NULL, MG_VAL_INT, NULL, 0},
+};
+
+// Custom reader: let the framework fill "name" and "size", then add our
+// own field. A real implementation would hash the file instead of
+// hardcoding zero
+static bool files_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  if (op != MG_DASH_READ) return false;
+  if (!mg_dash_dir_read(&set_files, u)) return false;
+  s_file.checksum = 0;
+  return true;
+}
+
+static struct mg_field_set set_files = {"files",       fields_files, files_fn,
+                                        &s_file.index, get_dir,      NULL};
+
 void mg_dash_init(struct mg_mgr *mgr) {
+  MG_DASH_ADD_FIELD_SET(&s_dash, &set_files);
   MG_DASH_ADD_FIELD_SET(&s_dash, &set_leds);
   MG_DASH_ADD_FIELD_SET(&s_dash, &set_metrics);
   MG_DASH_ADD_FIELD_SET(&s_dash, &set_settings);
@@ -196,9 +244,14 @@ void mg_dash_init(struct mg_mgr *mgr) {
   MG_DASH_ADD_FIELD_SET(&s_dash, &set_graph2);
   MG_DASH_ADD_FIELD_SET(&s_dash, &set_actions);
 
-  // Add two fake files - for demonstration
-  mg_dash_file_add(mg_str("device-config.json"), 1234);
-  mg_dash_file_add(mg_str("device-log-2026-04-25.txt"), 1327854);
+#if MG_ARCH == MG_ARCH_UNIX
+  // Create demo files in the upload directory
+  mkdir("/tmp/dashboard", 0755);
+  mg_file_printf(&mg_fs_posix, "/tmp/dashboard/device-config.json",
+                 "{\"model\":\"example\",\"fw\":\"1.0\"}");
+  mg_file_printf(&mg_fs_posix, "/tmp/dashboard/device-log-2026-04-25.txt",
+                 "2026-04-25 12:00:00 Device started\n");
+#endif
 
   mg_mem_files = mg_packed_files;
   mg_http_listen(mgr, MG_HTTP_ADDR, mg_dash_ev_handler, &s_dash);
diff --git a/tutorials/device-dashboard/full/dashboard.html b/tutorials/device-dashboard/full/dashboard.html
index e599e50a..d70318f5 100644
--- a/tutorials/device-dashboard/full/dashboard.html
+++ b/tutorials/device-dashboard/full/dashboard.html
@@ -16,7 +16,7 @@
           leds: { led1: true, led2: false, led3: false },
           settings: { volume: 12, log_level: 3, name: 'Galway', enable_login: true, ota_version: '1.2.3', ota_status: 'No checks yet', ota_url: 'http://my-product.com/ota.json', ota_interval: 30 },
           metrics: { temperature: 1.2, cpu: 4, ram: 5, version: '1.2.3' },
-          files: {data: [{name: 'device-log-2026-04-25.txt', size: 8625563}]},
+          files: {start: 0, end: 100, data: [{name: 'device-log-2026-04-25.txt', size: 8625563}]},
         },
       });
     </script>
@@ -170,10 +170,12 @@
           ]);
         };
 
-        // Intercept graph change notifications, re-plot data
+        // Intercept change notifications: re-plot graphs, reload the file
+        // list whenever its size changes (file uploaded or deleted)
         Dashboard.on('change', args => {
           args?.graph1?.data && updateGraph1(args?.graph1?.data);
           args?.graph2?.data && updateGraph2(args?.graph2?.data);
+          typeof args?.files === 'number' && Dashboard.call('get', { name: 'files', start: 0, end: 100 });
         });
       });
     </script>
@@ -689,7 +691,7 @@ a, a:visited, a:link { text-decoration: none; }
             <div class="panel-title">
               <span>
                 <span>File Manager</span>
-                <span class="metric-status">${files.data.length} Files</span>
+                <span class="metric-status">${files.size ?? files.data.length} Files</span>
               </span>
               <div class="header-actions">
                 <label class="btn btn-primary">
@@ -699,7 +701,7 @@ a, a:visited, a:link { text-decoration: none; }
                     <path d="M5 21h14" />
                   </svg>
                   Upload
-                  <input type="file" hidden data-upload="1" />
+                  <input type="file" hidden data-upload="files" />
                 </label>
               </div>
             </div>
@@ -717,14 +719,14 @@ a, a:visited, a:link { text-decoration: none; }
                   </div>
                   <div class="file-size">${f.size}</div>
                   <div class="file-actions">
-                    <a href="fs/${encodeURIComponent(f.name)}" target="_blank" class="btn btn-secondary">
+                    <a href="fs/files/${encodeURIComponent(f.name)}" target="_blank" class="btn btn-secondary">
                       <svg viewBox="0 0 24 24" class="nav-icon" fill="none" stroke="currentColor" stroke-width="2">
                         <path d="M12 3v12" />
                         <path d="m7 10 5 5 5-5" />
                         <path d="M5 21h14" />
                       </svg>
                     </a>
-                    <button onclick="fetch('fs/${encodeURIComponent(f.name)}', {method: 'DELETE'}); return false;" class="btn btn-secondary">
+                    <button onclick="fetch('fs/files/${encodeURIComponent(f.name)}', {method: 'DELETE'}); return false;" class="btn btn-secondary">
                       <svg viewBox="0 0 24 24" class="nav-icon" fill="none" stroke="currentColor" stroke-width="2">
                         <path d="M3 6h18" />
                         <path d="M8 6V4h8v2" />
diff --git a/tutorials/device-dashboard/minimal/dashboard.c b/tutorials/device-dashboard/minimal/dashboard.c
index 70aad5e5..6e5d4dc4 100644
--- a/tutorials/device-dashboard/minimal/dashboard.c
+++ b/tutorials/device-dashboard/minimal/dashboard.c
@@ -6,23 +6,25 @@
 static bool s_led1;
 static char s_version[10];
 
-static void read_status(void) {
-  MG_INFO(("READING STATUS"));
-  mg_snprintf(s_version, sizeof(s_version), "1.2.3");
-
-  // These conditionals make this file work on both microcontroller and desktop
-  // Useful for developing the UI on desktop, and copying to an MCU project.
+static bool status_fn(enum mg_dash_op op, struct mg_dash_user *u) {
+  (void) u;
+  if (op == MG_DASH_READ) {
+    MG_INFO(("READING STATUS"));
+    mg_snprintf(s_version, sizeof(s_version), "1.2.3");
+    // These conditionals make this file work on both microcontroller and desktop
 #if MG_ARCH == MG_ARCH_CUBE
-  s_led1 = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_0);  // Read LED state into field
+    s_led1 = HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_0);
 #endif
-}
-
-static void write_status(void) {
-  MG_INFO(("WRITING STATUS"));
-
+    return true;
+  }
+  if (op == MG_DASH_WRITE) {
+    MG_INFO(("WRITING STATUS"));
 #if MG_ARCH == MG_ARCH_CUBE
-  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, s_led1);  // Write LED state from field
+    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, s_led1);
 #endif
+    return true;
+  }
+  return false;
 }
 
 static struct mg_field fields_status[] = {
@@ -32,7 +34,7 @@ static struct mg_field fields_status[] = {
 };
 
 static struct mg_field_set field_set_status = {
-    "status", fields_status, read_status, write_status, 0, 0, NULL,
+    "status", fields_status, status_fn, NULL, NULL, NULL,
 };
 
 void mg_dash_init(struct mg_mgr *mgr) {
diff --git a/tutorials/device-dashboard/minimal/dashboard.html b/tutorials/device-dashboard/minimal/dashboard.html
index 92f1cf9b..c5ece708 100644
--- a/tutorials/device-dashboard/minimal/dashboard.html
+++ b/tutorials/device-dashboard/minimal/dashboard.html
@@ -44,7 +44,7 @@
           <div>
             This toggle button is a stylised checkbox.
             <code>data-bind="status.led1"</code> binds it to the device variable.
-            <code>data-autosave="1"</code> makes it send <code>{"led1": VALUE}</code> to the device every time the user toggles the
+            <code>data-autosave="1"</code> makes it send <code>{"status":{"led1": VALUE}}</code> to the device every time the user toggles the
             button. On the device side, <code>read_status()</code> or <code>write_status()</code> are called every time
             the LED state is read or written.
           </div>