fix(firmware): upgrade NimBLE to 2.x + DNS fallback for unreliable resolvers

NimBLE-Arduino 1.4.2 had an init/fire race in its FreeRTOS callout porting
layer where os_callout_timer_cb dispatched a queued TimerHandle expiry
against a not-yet-initialized event (NULL fn pointer), causing PC=0
InstrFetchProhibited within ~1s of boot when the camera task starved the
timer service. Confirmed by ets_printf instrumentation. Upgrading to
^2.0.0 rewrites the porting layer and eliminates the race; verified clean
on the customer network for 1+ hour.

Also rolls in DNS-resilience work that surfaced the BLE crash during
provisioning: pin lwIP/esp-netif resolvers to 1.1.1.1/8.8.8.8 across DHCP
renewals, add three-tier resolver fallback in reporter with a hardcoded
IP of last resort, and switch to raw WiFiClient with manual Host header
to bypass HTTPClient's brittle DNS path.

Migration touches for NimBLE 2.x:
- NimBLEAdvertisedDeviceCallbacks -> NimBLEScanCallbacks
- onResult signature now takes const NimBLEAdvertisedDevice*
- setAdvertisedDeviceCallbacks -> setScanCallbacks
- start(0, nullptr, false) -> start(0, false, false)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/superpowers/plans/2026-05-01-ble-nimble-crash.md

@@ -0,0 +1,189 @@
+# BLE / NimBLE Timer-Callout Crash — Handoff
+
+**Date opened:** 2026-05-01
+**Status:** Resolved 2026-05-01 by upgrading `h2zero/NimBLE-Arduino` from `^1.4.2` to `^2.0.0` (`firmware/platformio.ini:24`). BLE scanning re-enabled via `BLE_SCANNING_ENABLED 1` (`firmware/src/main.cpp:30`). Verified clean on customer network for 1+ hour with no panics.
+**Goal:** Re-enable BLE scanning without the device crashing within ~1s of boot.
+
+**Confirmed root cause:** Instrumented `os_callout_timer_cb` with `ets_printf` and observed the very first callout fire on the direct-call path with both `evq=NULL` and `fn=NULL`, while the same `co` address later (post-init) showed valid `evq` and `fn`. Same callout struct reused — classic NimBLE 1.x callout init/fire race where the FreeRTOS `TimerHandle_t` had a queued expiry against a not-yet-initialized event. NimBLE 2.x rewrote the porting layer; the race is gone.
+
+**Migration touches (NimBLE 1.x → 2.x):**
+- `NimBLEAdvertisedDeviceCallbacks` → `NimBLEScanCallbacks`
+- `onResult(NimBLEAdvertisedDevice*)` → `onResult(const NimBLEAdvertisedDevice*)`
+- `setAdvertisedDeviceCallbacks(cb, true)` → `setScanCallbacks(cb, true)`
+- `start(0, nullptr, false)` → `start(0, false, false)` (signature: `duration, isContinue, restart`)
+
+BLE was working before today's customer-site provisioning trip. The crash is reliably reproducible on the current build at the customer location whenever `BLE_SCANNING_ENABLED` is set back to `1`. It may or may not reproduce on a quieter network — the camera task's CPU-starvation pattern is shared, but the crash window's exact trigger is unconfirmed.
+
+---
+
+## Symptom
+
+Within ~1s of boot, after several `cam_hal: EV-VSYNC-OVF` lines from the camera driver:
+
+```
+Guru Meditation Error: Core 0 panic'ed (InstrFetchProhibited). Exception was unhandled.
+
+Core 0 register dump:
+PC      : 0x00000000   PS      : 0x00060630   A0      : 0x8009a9af   A1      : 0x3ffbd6e0
+A2      : 0x3fff1ef8   A3      : 0x00000001   ...
+A8      : 0x800f2ebc   ...
+EXCCAUSE: 0x00000014   EXCVADDR: 0x00000000
+
+Backtrace: 0xfffffffd:0x3ffbd6e0 0x4009a9ac:0x3ffbd700
+```
+
+Decoded with `~/.platformio/packages/toolchain-xtensa-esp32/bin/xtensa-esp32-elf-addr2line -e .pio/build/timercam/firmware.elf -pfiC 0x4009a9ac 0x400f2ebc`:
+
+```
+prvProcessReceivedCommands at freertos/timers.c:852
+  (inlined by) prvTimerTask at freertos/timers.c:600
+os_callout_timer_cb at NimBLE-Arduino/.../npl_os_freertos.c:1742
+```
+
+`PC=0` + `EXCCAUSE=0x14` (InstrFetchProhibited) = jump-to-NULL. The FreeRTOS timer-service task is dispatching a NimBLE callout whose callback function pointer is NULL.
+
+The relevant NimBLE source:
+
+```c
+// firmware/.pio/libdeps/timercam/NimBLE-Arduino/src/nimble/porting/npl/freertos/src/npl_os_freertos.c:1729-1742
+static void
+os_callout_timer_cb(TimerHandle_t timer)
+{
+    struct ble_npl_callout *co;
+
+    co = pvTimerGetTimerID(timer);
+    assert(co);
+
+    if (co->evq) {
+        ble_npl_eventq_put(co->evq, &co->ev);
+    } else {
+        co->ev.fn(&co->ev);   // <-- co->ev.fn is NULL
+    }
+}
+```
+
+Either `co->ev.fn` is genuinely NULL on the direct-call path, OR — given the addr2line frame is a few lines off and the callsite is ambiguous — the FreeRTOS timer's own callback pointer (`pxTimer->pxCallbackFunction`) is NULL inside `prvProcessReceivedCommands`. Both indicate a callout/timer being freed or zeroed while the FreeRTOS timer service still has a command queued for it.
+
+---
+
+## Environment
+
+- Board: M5Stack TimerCam-F (ESP32-D0WDQ6-V3, dual-core 240 MHz, 4MB flash).
+- BLE library: `h2zero/NimBLE-Arduino@^1.4.2` (`firmware/platformio.ini`). 1.4.2 is end-of-life on the 1.x branch; 2.x exists with breaking API changes.
+- Camera: OV3660 via `esp32-camera` driver, 96×96 grayscale @ 5 FPS.
+- BLE scan: passive, low-overhead, hash-collected by `firmware/src/ble_scanner.cpp`.
+- Tasks: `task_camera` (core 1, prio 2, 8KB stack), `task_reporter` (core 0, prio 1, 8KB stack), Arduino loop (default).
+- The camera task triggers `cam_hal: EV-VSYNC-OVF` whenever frame capture overlaps another long operation — this consistently precedes the crash in logs.
+
+---
+
+## What's been ruled out
+
+1. **DNS / network code** — entirely unrelated. DNS path works in production via the new fallback-IP machinery (`firmware/src/reporter.cpp` `resolve_api_ip` and `firmware/src/reporter.h` `REPORTER_API_FALLBACK_IP`). Do not regress this; it shipped with reports working at the customer site.
+2. **Our BLE app code** — the backtrace stays inside the FreeRTOS timer service and NimBLE's own porting layer; nothing in `ble_scanner.cpp` is on the call stack. The bug is in vendored NimBLE.
+3. **Memory corruption from our side** — `A2 = 0x3fff1ef8` is a normal heap address, no obvious overrun pattern. Heap is healthy at the time (we'd see a different fault otherwise).
+4. **Stack overflow** — A1 = 0x3ffbd6e0 is well within the FreeRTOS timer-service task's stack range; no canary smash log.
+
+---
+
+## What changed today
+
+| File | Change | Keep? |
+|---|---|---|
+| `firmware/src/main.cpp` | Added `BLE_SCANNING_ENABLED 0` gate; all `ble_scanner_*` callsites compile out; `BLEHourlyRecord` zero-stubbed when off | Keep until crash fixed; flip to `1` to reproduce |
+| `firmware/src/main.cpp` | Removed verbose `[F]`/`[CV] spawn` per-frame logging; kept entry/exit + heartbeat | Keep |
+| `firmware/src/ble_scanner.cpp` | Removed `[BLE] new device:` per-discovery log | Keep |
+| `firmware/src/reporter.{h,cpp}` | DNS resolution with fallback IP, raw `WiFiClient` HTTP, manual `Host:` header | Keep — production fix |
+| `firmware/lib/net_guard/net_guard.{h,cpp}` | DNS pin to 1.1.1.1/8.8.8.8 at lwIP + esp-netif layers; `net_guard_dump_dns` diagnostic | Keep |
+
+---
+
+## Reproduction
+
+1. `cd firmware && pio run -e timercam`.
+2. Edit `firmware/src/main.cpp`, set `#define BLE_SCANNING_ENABLED 1`. Rebuild.
+3. Flash a TimerCam: `python tools/flash_device.py --port /dev/ttyUSB0 --device-id dc-XXXX --location-id <loc> --hmac-secret <secret> --wifi-ssid "<ssid>" --wifi-password "<pw>"`.
+4. `pio device monitor --port /dev/ttyUSB0 --baud 115200`.
+5. Wait ≤30s. Expect the `Guru Meditation Error: Core 0 panic'ed (InstrFetchProhibited)` traceback above.
+
+Crash is **deterministic** on the customer's network (Elly-Fi). Worth retesting on a quiet desk network — if it doesn't repro there, the trigger is camera-task starvation interacting with NimBLE timers, not a pure NimBLE bug.
+
+To decode any future crash backtrace:
+
+```sh
+~/.platformio/packages/toolchain-xtensa-esp32/bin/xtensa-esp32-elf-addr2line \
+  -e firmware/.pio/build/timercam/firmware.elf -pfiC <addr1> <addr2> ...
+```
+
+---
+
+## Investigation paths, in order of effort/confidence
+
+### 1. Confirm the failing call site (cheap, do this first)
+
+The addr2line line numbers can be off by ±3 due to inlining. Add a temporary `Serial.printf` patch to `npl_os_freertos.c` `os_callout_timer_cb` to log `co`, `co->evq`, `co->ev.fn` on entry. Reproduce. Then we know with certainty whether `co->ev.fn` is NULL on the direct-call path or whether this is an FreeRTOS-level issue (queued command for a deleted timer).
+
+If `evq != NULL` and we still crash, the NULL is in the queued event dispatcher (a different code path; pivot the investigation).
+
+### 2. Try upgrading NimBLE-Arduino to 2.x (medium effort, likely-fix)
+
+`platformio.ini` has `h2zero/NimBLE-Arduino@^1.4.2`. 2.x rewrote the porting layer significantly. Breaking API changes — `NimBLEAdvertisedDeviceCallbacks` was renamed/restructured. Touch points: `firmware/src/ble_scanner.cpp` (the only file that uses NimBLE).
+
+Try: pin `^2.0.0`, fix the API breakage in `ble_scanner.cpp` (it's <100 lines). If 2.x crashes too, the issue is independent of NimBLE version → pivot to (3) or (4).
+
+### 3. Reduce camera-task starvation (cheap, may be sufficient)
+
+The `EV-VSYNC-OVF` lines are the canary. The camera task pins core 1 at priority 2 doing CV processing every 200ms. NimBLE host task runs on core 0 by default but the FreeRTOS timer service task is core-agnostic and may be starved during long CV passes that hold a mutex.
+
+Things to try in `firmware/src/main.cpp`:
+- Lower `CAM_FPS` from 5 to 3, see if VSYNC-OVF still appears.
+- Move CV processing off the capture path (capture into a queue, process at lower priority).
+- Raise FreeRTOS timer-service task priority via `configTIMER_TASK_PRIORITY` (sdkconfig).
+- Confirm NimBLE host task pinning — `CONFIG_BT_NIMBLE_PINNED_TO_CORE` should be 0 or 1 (not unpinned).
+
+### 4. Local NULL-guard patch (last resort, masks the bug)
+
+If upgrade is blocked and starvation reduction isn't enough, patch the vendored source:
+
+```c
+// npl_os_freertos.c:1740
+} else {
+    if (co->ev.fn) co->ev.fn(&co->ev);
+}
+```
+
+This silences the crash but drops the dropped event. The dropped events are likely scan-result deliveries; we'd undercount BLE devices but not crash. Acceptable as a stopgap with a `// TODO: remove when NimBLE upgraded` and a note in this doc.
+
+Caveat: vendored library files in `.pio/libdeps/` get blown away by clean builds. Either copy NimBLE into `firmware/lib/` and pin it (vendored), or use `lib_archive` + a post-install script. Don't ship a build that depends on an unpinned hand-edit.
+
+### 5. Replace BLE stack (high effort)
+
+If 2.x also crashes and starvation reduction doesn't help, switch to the IDF-native bluedroid stack via the Arduino-ESP32 `BLEDevice` API. Larger memory footprint (~30KB more heap) but a different lifecycle model — won't share NimBLE's bug.
+
+---
+
+## Constraints / things not to break
+
+- `firmware/src/reporter.cpp` DNS path with `REPORTER_API_FALLBACK_IP` — production fix, must keep working. Do not regress to `HTTPClient`.
+- `BLE_SCANNING_ENABLED 0` is the **shipping default** until this is resolved. Devices in the field rely on this; flip to `1` only in dev builds.
+- `firmware/lib/net_guard/net_guard.cpp` `net_guard_pin_dns()` is called both at boot and on every WiFi reconnect; if reorganizing net_guard, preserve both call sites.
+- The `ble_scanner` module supports `ble_scanner_pause`/`resume` for OTA — verify it still works after any NimBLE upgrade (`ArduinoOTA.onStart` hook in `main.cpp:248`).
+
+---
+
+## Open questions
+
+- Does the crash repro on a quiet network with no `EV-VSYNC-OVF`? (Determines whether starvation is necessary vs sufficient.)
+- Was BLE working in a previous build, and on which NimBLE version? Earliest BLE-related commit traced to is well before today; binary search across firmware commits with BLE enabled would identify the regression boundary if it's our code.
+- Does the customer site have an unusual RF environment (very dense BLE) that increases the callout-churn rate, making the race more likely? Worth a `nimble_scan_event` count log during a 60s capture window.
+
+---
+
+## Quick verification once you think it's fixed
+
+1. Set `BLE_SCANNING_ENABLED 1`, rebuild, flash.
+2. Run for at least 10 minutes on the customer network — the original crash hit within ~1s, so 10 min with no panic is strong evidence.
+3. Confirm a successful hourly cycle: `[CV] entry/exit`, then `[HTTP] POST .../events/batch ... -> 200`, BLE record with non-zero `unique_devices`.
+4. Run a second device side-by-side; confirm no cross-device interference.
+
+When done, set `BLE_SCANNING_ENABLED 1` as the default and remove the gate (keep the comment block as institutional memory of the bug).

firmware/lib/net_guard/net_guard.cpp

@@ -9,8 +9,66 @@ uint32_t net_guard_next_backoff_ms(uint32_t attempt) {
 #ifdef ARDUINO
 #include "config.h"
 #include <WiFi.h>
+#include <Arduino.h>
+#include <lwip/dns.h>
+#include <esp_netif.h>
 #include "event_log.h"
 
+// Both lwIP's ip_addr_t and esp-netif's esp_ip_addr_t alias the same on-disk
+// layout for IPv4, but the C++ types differ. Take the raw u32 to sidestep it.
+static String fmt_v4(uint32_t addr_be) {
+    if (addr_be == 0) return String("0.0.0.0");
+    char b[16];
+    snprintf(b, sizeof(b), "%u.%u.%u.%u",
+        (unsigned)((addr_be >> 0)  & 0xFF),
+        (unsigned)((addr_be >> 8)  & 0xFF),
+        (unsigned)((addr_be >> 16) & 0xFF),
+        (unsigned)((addr_be >> 24) & 0xFF));
+    return String(b);
+}
+
+void net_guard_dump_dns(const char* tag) {
+    const ip_addr_t* d0 = dns_getserver(0);
+    const ip_addr_t* d1 = dns_getserver(1);
+    Serial.printf("[DNS] %s lwip: %s , %s\n", tag,
+        fmt_v4(d0 ? ip_2_ip4(d0)->addr : 0).c_str(),
+        fmt_v4(d1 ? ip_2_ip4(d1)->addr : 0).c_str());
+
+    esp_netif_t* sta = esp_netif_get_handle_from_ifkey("WIFI_STA_DEF");
+    if (sta) {
+        esp_netif_dns_info_t main_dns{}, backup_dns{};
+        esp_netif_get_dns_info(sta, ESP_NETIF_DNS_MAIN,   &main_dns);
+        esp_netif_get_dns_info(sta, ESP_NETIF_DNS_BACKUP, &backup_dns);
+        Serial.printf("[DNS] %s netif: %s , %s\n", tag,
+            fmt_v4(main_dns.ip.u_addr.ip4.addr).c_str(),
+            fmt_v4(backup_dns.ip.u_addr.ip4.addr).c_str());
+    } else {
+        Serial.printf("[DNS] %s netif: <no STA handle>\n", tag);
+    }
+}
+
+void net_guard_pin_dns() {
+    ip_addr_t d1, d2;
+    IP_ADDR4(&d1, 1, 1, 1, 1);
+    IP_ADDR4(&d2, 8, 8, 8, 8);
+    dns_setserver(0, &d1);
+    dns_setserver(1, &d2);
+
+    // Also push through the esp_netif layer. dns_setserver() writes the
+    // global lwIP table directly; esp_netif_set_dns_info() is what the
+    // DHCP client itself calls, so writing here prevents the next DHCP
+    // event from silently overwriting our pin.
+    esp_netif_t* sta = esp_netif_get_handle_from_ifkey("WIFI_STA_DEF");
+    if (sta) {
+        esp_netif_dns_info_t info{};
+        IP_ADDR4(&info.ip, 1, 1, 1, 1);
+        esp_netif_set_dns_info(sta, ESP_NETIF_DNS_MAIN, &info);
+        IP_ADDR4(&info.ip, 8, 8, 8, 8);
+        esp_netif_set_dns_info(sta, ESP_NETIF_DNS_BACKUP, &info);
+    }
+    net_guard_dump_dns("pinned");
+}
+
 // Shared with the WiFi event task. 32-bit aligned loads/stores are atomic on
 // Xtensa; volatile suffices. Tick re-evaluates every loop iteration, so stale
 // reads self-correct within ~200ms.
@@ -23,6 +81,11 @@ static volatile uint32_t   s_next_retry_ms = 0;
 static void on_wifi_event(WiFiEvent_t event, WiFiEventInfo_t info) {
     switch (event) {
         case ARDUINO_EVENT_WIFI_STA_GOT_IP:
+            // Override DHCP-supplied DNS. Some routers return TC=1 for short
+            // answers (forcing TCP fallback that lwIP can't follow), or hand
+            // out an unreachable resolver. Pin to public resolvers so
+            // hostByName() never depends on the local network's DNS quality.
+            net_guard_pin_dns();
             s_up = true;
             s_attempts = 0;
             s_next_retry_ms = 0;

firmware/lib/net_guard/net_guard.h

@@ -21,4 +21,13 @@ uint8_t net_guard_last_disconnect_reason();
 
 // Non-blocking tick called from loop(); kicks reconnect if due.
 extern "C" void net_guard_tick();
+
+// Override DHCP-supplied DNS with public resolvers (1.1.1.1, 8.8.8.8).
+// Idempotent; safe to call repeatedly. net_guard re-applies on every GOT_IP,
+// but main.cpp must call it once for the boot association (which completes
+// before net_guard_start() registers its event handler).
+void net_guard_pin_dns();
+
+// Diagnostic: print current DNS table state from both lwIP and esp_netif.
+void net_guard_dump_dns(const char* tag);
 #endif

firmware/platformio.ini

@@ -21,7 +21,7 @@ upload_flags = --no-stub
 lib_deps =
     tzapu/WiFiManager@^2.0.17
     bblanchon/ArduinoJson@^7.0.0
-    h2zero/NimBLE-Arduino@^1.4.2
+    h2zero/NimBLE-Arduino@^2.0.0
     espressif/esp32-camera
 
 ; Frame-capture build. Strips WiFi/BLE/CV/reporter; streams raw 96x96 frames

firmware/src/ble_scanner.cpp

@@ -42,8 +42,8 @@ static String sha256_prefix(const String& input) {
     return hex;
 }
 
-class ScanCallback : public NimBLEAdvertisedDeviceCallbacks {
+class ScanCallback : public NimBLEScanCallbacks {
-    void onResult(NimBLEAdvertisedDevice* dev) override {
+    void onResult(const NimBLEAdvertisedDevice* dev) override {
         String mac  = String(dev->getAddress().toString().c_str());
         String hash = sha256_prefix(mac);
         int    rssi = dev->getRSSI();
@@ -51,7 +51,6 @@ class ScanCallback : public NimBLEAdvertisedDeviceCallbacks {
         std::lock_guard<std::mutex> lock(s_mutex);
         auto it = s_seen.find(hash);
         if (it == s_seen.end()) {
-            Serial.printf("[BLE] new device: %s (rssi %d)\n", hash.c_str(), rssi);
             s_seen[hash] = {rssi, 1};
         } else {
             it->second.rssi_sum += rssi;
@@ -68,16 +67,16 @@ static NimBLEScan*  s_scan = nullptr;
 void ble_scanner_start() {
     NimBLEDevice::init("");
     s_scan = NimBLEDevice::getScan();
-    s_scan->setAdvertisedDeviceCallbacks(&s_callback, true); // true = allow duplicates
+    s_scan->setScanCallbacks(&s_callback, true); // true = allow duplicates
     s_scan->setActiveScan(false);   // passive
     s_scan->setInterval(100);
     s_scan->setWindow(99);
     s_scan->setMaxResults(0);       // don't store results — callback-only
-    s_scan->start(0, nullptr, false); // 0 = continuous
+    s_scan->start(0, false, false); // duration=0 (forever), isContinue=false, restart=false
 }
 
 void ble_scanner_pause()  { if (s_scan) s_scan->stop(); }
-void ble_scanner_resume() { if (s_scan) s_scan->start(0, nullptr, false); }
+void ble_scanner_resume() { if (s_scan) s_scan->start(0, false, false); }
 
 void ble_scanner_deinit() {
     if (s_scan) s_scan->stop();

firmware/src/main.cpp

@@ -19,6 +19,15 @@
 #define BUTTON_PIN   37
 #define FACTORY_RESET_HOLD_MS 5000
 
+// BLE scanning disabled in production until the NimBLE-Arduino 1.4.2 timer
+// race is resolved. Symptom: FreeRTOS timer task dispatches an
+// os_callout_timer_cb whose callback fn is NULL, causing PC=0 fetch and
+// Historical note: NimBLE-Arduino 1.4.2 had an init/fire race in its FreeRTOS
+// callout porting layer that caused a NULL-fn dispatch (PC=0,
+// InstrFetchProhibited) within ~1s of boot when the camera task starved the
+// timer service. Fixed by upgrading to 2.x (see platformio.ini).
+#define BLE_SCANNING_ENABLED 1
+
 #define CAM_FPS           5
 #define CAM_INTERVAL_MS   (1000 / CAM_FPS)
 #define REPORT_INTERVAL_S 3600
@@ -67,16 +76,7 @@ static void task_camera(void*) {
         if (camera_capture_96(frame)) {
             if (xSemaphoreTake(s_cv_mutex, pdMS_TO_TICKS(100)) == pdTRUE) {
                 CVResult r = cv_process(g_cv, frame, g_cfg.line_offset);
-                for (const auto& t : g_cv.tracks) {
+                (void)last_logged_track_id;
-                    if (t.id > last_logged_track_id) {
-                        last_logged_track_id = t.id;
-                        Serial.printf("[CV] spawn id=%d y=%.1f\n", t.id, t.spawn_y);
-                    }
-                }
-                if (r.fg_count > 0) {
-                    Serial.printf("[F] n=%d y=%d..%d c=%.1f\n",
-                        r.fg_count, r.fg_min_y, r.fg_max_y, r.fg_centroid_y);
-                }
                 if (r.entries_delta) Serial.printf("[CV] entry +%d (total %d) first=%.1f min=%.1f max=%.1f last=%.1f dur=%d\n",
                     r.entries_delta, g_cv.entries,
                     r.fire_first_c, r.fire_min_c, r.fire_max_c, r.fire_last_c, r.fire_duration);
@@ -119,7 +119,9 @@ static void task_reporter(void*) {
         last_report_ts = now;
 
         // Deinit BLE to free ~25KB heap for SSL handshakes
+#if BLE_SCANNING_ENABLED
         ble_scanner_deinit();
+#endif
         led_set(true); // on = uploading
 
         CameraHourlyRecord cam_rec;
@@ -129,18 +131,26 @@ static void task_reporter(void*) {
             xSemaphoreGive(s_cv_mutex);
         } else {
             // Failed to acquire — skip this cycle, will report next hour
+#if BLE_SCANNING_ENABLED
             ble_scanner_reinit();
+#endif
             led_set(false);
             continue;
         }
 
+#if !BLE_SCANNING_ENABLED
+        BLEHourlyRecord ble_rec = {period_start, period_end, 0, 0};
+#else
         BLEHourlyRecord ble_rec = ble_scanner_collect(period_start, period_end);
+#endif
 
         reporter_submit_camera(g_cfg, cam_rec);
         reporter_submit_ble(g_cfg, ble_rec);
         bool hb_ok = reporter_heartbeat(g_cfg, millis() / 1000, WiFi.RSSI());
 
+#if BLE_SCANNING_ENABLED
         ble_scanner_reinit();
+#endif
         led_set(false);
 
         static uint8_t consecutive_misses = 0;
@@ -202,6 +212,11 @@ void setup() {
         ESP.restart();
     }
 
+    // Boot connect happens before net_guard registers its WiFi event handler,
+    // so the GOT_IP-driven DNS override there won't fire for this association.
+    // Pin DNS now; net_guard re-applies it on every subsequent reconnect.
+    net_guard_pin_dns();
+
     net_guard_start(g_cfg);
     led_set(false); // off = connected
 
@@ -220,17 +235,29 @@ void setup() {
 
     reporter_init();
 
+#if BLE_SCANNING_ENABLED
     ble_scanner_start();
+#endif
 
     // OTA update support
     ArduinoOTA.setHostname(g_cfg.device_id.c_str());
+#if !BLE_SCANNING_ENABLED
+    ArduinoOTA.onStart([]() { });
+#else
     ArduinoOTA.onStart([]() { ble_scanner_pause(); });
+#endif
     ArduinoOTA.onEnd([]()   {
+#if BLE_SCANNING_ENABLED
         ble_scanner_resume();
+#endif
         event_log_write(EVT_REBOOT, REBOOT_OTA, 0);
         ESP.restart();
     });
+#if !BLE_SCANNING_ENABLED
+    ArduinoOTA.onError([](ota_error_t e) { });
+#else
     ArduinoOTA.onError([](ota_error_t e) { ble_scanner_resume(); });
+#endif
     ArduinoOTA.begin();
 
     s_cv_mutex = xSemaphoreCreateMutex();

firmware/src/reporter.cpp

@@ -26,28 +26,107 @@ static uint32_t now_ts() {
     return (uint32_t)time(nullptr);
 }
 
+// Last successfully resolved IP — used as a warm fallback if a subsequent
+// resolution fails. Never takes precedence over a fresh successful resolve.
+static IPAddress s_cached_api_ip;
+
+// Resolve the API host. Tries hostByName first; on failure falls back to the
+// last good resolution, then to the hardcoded fallback IP. Returns the IP via
+// out-param and a label describing where it came from for logging.
+static bool resolve_api_ip(IPAddress& out, const char*& source) {
+    IPAddress ip;
+    uint32_t r0 = millis();
+    bool ok = WiFi.hostByName(REPORTER_API_HOST_NAME, ip);
+    uint32_t elapsed = millis() - r0;
+    if (ok) {
+        s_cached_api_ip = ip;
+        out = ip;
+        source = "dns";
+        Serial.printf("[DNS] %s -> %s (%u ms)\n",
+            REPORTER_API_HOST_NAME, ip.toString().c_str(), (unsigned)elapsed);
+        return true;
+    }
+    Serial.printf("[DNS] %s -> FAIL (%u ms)\n",
+        REPORTER_API_HOST_NAME, (unsigned)elapsed);
+    net_guard_dump_dns("on-fail");
+    net_guard_pin_dns();  // re-assert in case something overwrote the table
+
+    if ((uint32_t)s_cached_api_ip != 0) {
+        out = s_cached_api_ip;
+        source = "cache";
+        return true;
+    }
+    if (out.fromString(REPORTER_API_FALLBACK_IP)) {
+        source = "fallback";
+        return true;
+    }
+    return false;
+}
+
+// Drains and parses the HTTP response status line. Returns the numeric status
+// code, or -1 on read timeout / malformed response.
+static int read_http_status(WiFiClient& client, uint32_t timeout_ms) {
+    uint32_t deadline = millis() + timeout_ms;
+    while (!client.available() && millis() < deadline) vTaskDelay(pdMS_TO_TICKS(10));
+    if (!client.available()) return -1;
+    String line = client.readStringUntil('\n');
+    line.trim();
+    // Format: "HTTP/1.1 200 OK"
+    int sp1 = line.indexOf(' ');
+    if (sp1 < 0) return -1;
+    int sp2 = line.indexOf(' ', sp1 + 1);
+    String code_str = (sp2 > 0) ? line.substring(sp1 + 1, sp2) : line.substring(sp1 + 1);
+    return code_str.toInt();
+}
+
 static bool post_json_once(const DeviceConfig& cfg, const char* path, const String& body) {
     uint32_t ts  = now_ts();
     if (ts < 1700000000UL) return false;
     String   sig = hmac_sign(cfg.hmac_secret, "POST", path, ts, body);
     if (sig.isEmpty()) return false;
 
-    HTTPClient http;
+    IPAddress ip;
-    String url = String(REPORTER_API_HOST) + path;
+    const char* ip_source = "?";
-    http.begin(url);
+    if (!resolve_api_ip(ip, ip_source)) {
-    http.setConnectTimeout(5000);   // DNS + TCP connect
+        Serial.printf("[HTTP] POST %s -> resolve-fail\n", path);
-    http.setTimeout(10000);         // per-transaction response timeout
+        event_log_write(EVT_HTTP_FAIL, event_log_path_hash(path), (uint16_t)-1);
-    http.addHeader("Content-Type", "application/json");
+        return false;
-    http.addHeader("X-Device-Id",  cfg.device_id);
+    }
-    http.addHeader("X-Timestamp",  String(ts));
-    http.addHeader("X-Signature",  sig);
 
     uint32_t t0 = millis();
-    int code = http.POST(body);
+    WiFiClient client;
+    client.setTimeout(10);  // seconds — read timeout
+    if (!client.connect(ip, REPORTER_API_PORT, 5000 /*ms connect timeout*/)) {
+        uint32_t elapsed = millis() - t0;
+        Serial.printf("[HTTP] connect %s:%u (%s) -> failed (%u ms)\n",
+            ip.toString().c_str(), REPORTER_API_PORT, ip_source, (unsigned)elapsed);
+        event_log_write(EVT_HTTP_FAIL, event_log_path_hash(path), (uint16_t)-1);
+        return false;
+    }
+
+    // Manual HTTP/1.1 — gives us full control over the Host header so the
+    // server's vhost routing works even when we connect by IP.
+    client.printf("POST %s HTTP/1.1\r\n", path);
+    client.printf("Host: %s\r\n", REPORTER_API_HOST_NAME);
+    client.print  ("Connection: close\r\n");
+    client.print  ("Content-Type: application/json\r\n");
+    client.printf("Content-Length: %u\r\n", (unsigned)body.length());
+    client.printf("X-Device-Id: %s\r\n", cfg.device_id.c_str());
+    client.printf("X-Timestamp: %u\r\n", (unsigned)ts);
+    client.printf("X-Signature: %s\r\n", sig.c_str());
+    client.print  ("\r\n");
+    client.print(body);
+
+    int code = read_http_status(client, 10000);
+    // Drain so the server can close cleanly.
+    while (client.connected() && client.available()) client.read();
+    client.stop();
+
     uint32_t elapsed = millis() - t0;
-    http.end();
     uint16_t phash = event_log_path_hash(path);
-    Serial.printf("[HTTP] POST %s -> %d (%u ms)\n", url.c_str(), code, (unsigned)elapsed);
+    Serial.printf("[HTTP] POST %s%s (%s %s) -> %d (%u ms)\n",
+        REPORTER_API_HOST_NAME, path, ip_source, ip.toString().c_str(),
+        code, (unsigned)elapsed);
     if (code == 200) {
         event_log_write(EVT_HTTP_OK, phash, (uint16_t)((elapsed > 65535) ? 65535 : elapsed));
         return true;

firmware/src/reporter.h

@@ -12,7 +12,12 @@ struct CameraHourlyRecord {
 };
 
 static const int    REPORTER_MAX_BUFFER     = 24;
-static const char*  REPORTER_API_HOST   = "http://logs.research.bike";
+static const char*  REPORTER_API_HOST_NAME  = "logs.research.bike";
+static const uint16_t REPORTER_API_PORT     = 80;
+// Hardcoded fallback used when DNS fails (some customer networks intercept
+// :53 with a transparent proxy that mangles responses). Update if the
+// server's IP changes — but a successful hostByName() always wins over this.
+static const char*  REPORTER_API_FALLBACK_IP = "5.78.114.131";
 
 void reporter_init();
 void reporter_submit_camera(const DeviceConfig& cfg, const CameraHourlyRecord& rec);